OUR LEISURE -TIME PROJECT GUIDE FOR 101 NIGHTS …€¦ · "555" Loudspeaker "555" Switch Hitter Wrong -Way Battery Protector Old Crowbar Add An Antenna Trimmer Adjustable Crowbar

1978 EDITION$1.50

SURE-REOGIRCOTSVIINCItat.

FOR1NE3

BEGINNERMilD

PRO

Solid State'WarnersAttacie Alarm

Wet Basement SquealerHighway Nightfall AlertPhotoelectric Tattletale

Lots more build 'emprojec7s for workbench,

home and car!

0

IGe 02 7?

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OUR LEISURE -TIME PROJECT GUIDE FOR 101 NIGHTS

!ELECTRONICPROJECTS By the Editors of

Elementary Elect-onics

For Under $15-A11 Easy To Build

Square Wave GeneratorWide -Range OscillatorStaircase Generator

DC Controlled Oscillator

Signal Operated SwitchPoor Man's Hold Switch

The Light TouchTurn -On Delay

Penny -Pinchers AmplifierCeramic Cartridge Preamp

Dynamic Mike AmplifierBroadband ,etmplif er

Construction

Channel ChangerSuper DXer Signal BoosterAdd Tone to Your Phone

See -Through Crystal Radio

Logic ProbeQuick Diode Checker

Transistor TesterContinuity Checker

SWL's Super CalibratorGroove Booster

SCA Adaptor

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WE PACKAGED IT ALL! Build one, two, three or more projects without solderingor damaging components. V/hen you are done, unplug theparts and set them aside for your next building session.Interconnections between components made with #24PVC -covered solid hookup wire, again without soldering.Easy-fast-simple-have fun with electronics withoutburning your fingers or your dining room table! Continental Specialties Corporation Model

EXP350 Experimertor^" Socket solderlessAfter you have mastered the 101 Projects, use the breadboard included free with your order

components and solderless breadboard to bring your ownideas and designs to life.Order today, and your 101 Projects kit will be on its way toyou in 24 hours or less. 203-467-5590

BankAmericard/VISA and Master Charge9 A.M. to 5 P.M. (EST).

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101 ELECTRONIC PROJECTSFOR UNDER $15

1 Signal Operated Switch2 Logic Probe3 Simple Squealer4 Quick Draw Game #15 Pierce Crystal Oscillator6 CB Saver7 Ceramic Cartridge Preamplifier8 Dynamic Mike Amplifier9 Quick Draw Game #2

10 Make Your VOM a FSM11 Pulsing CB Saver12 High Performance Transistor

Radio13 LED Bar Graph Display 2114 Multivibrator Tone Hummer 2215 High Impedance Mike Amplifier 2216 Plant Moisture Monitor17 Switch Contact Debouncer18 Square Wave Generator19 Tone Control Network20 Voltage Controlled Audio

Oscillator21 Wide Range Oscillator22 Weirdly Wailing Oscillator23 Quick Continuity Tester24 Poor Man's Hold Switch25 LED Simple Signaller26 Spark Probe27 Cheapskate's Light Show28 Broad Band Amplifier29 Super Vibrato30 Penny Pincher's Utility

Amplifier31 Easy Headlight -On Warning32 Wet Basement Alarm

17 33 Metal Detector 29 6817 34 Nulling Stereo Balance Checker 29 6918 35 Quick Diode Checker 29 7018 36 Speaker System Expander 30 7118 37 Watch That Modulation 30 7219 38 Wire Wringer 30 7319 39 Wide Range Voltage Pilot 31 7419 40 The Light Touch 31 7520 41 A Touchy Gamble 31 7620 42 Transistor Squelch 32 7720 43 IF Amplifier 32 78

44 Make Your VOM a Tachometer 33 7921 45 Transistor Checker 33 80

46 Photoelectric Tattletale 37 8147 Highway Nightfall Alert 37 8248 Level Detector 37 83

22 49 Sensitive Squelch 38 8423 50 Idiot's Delight 38 8523 51 SWL's Low Band Converter 39 8624 52 Staircase Generator 39 87

53 Side Tone Oscillator 40 8824 54 Overvoltage 40 8924 55 Cigar Lighter 40 9025 56 Two -Transistor Radio 41 9125 57 Fox Hunt Transmitter 41 9225 58 Mike Clipper 42 9326 59 Conference Mike Mixer 42 9426 60 Nine Volt Neon 42 9526 61 Low Impedance Mike Mixer 43 9627 62 Blinking Neon Night Light 43 9727 63 Low -Power Light Blinker 44 98

64 Three -Way Switch Demonstrator 44 9928 65 Audio Utility Amp 45 10028 66 VOM Thermometer 45 10128 67 Logical OR Demonstrator 46

ADDED

IC1 SWL's Super CalibratorIC2 Lie DetectorIC3 CB Mobile -to -Base Power UnitIC4 CB Channel BoosterIC5 5V/3A for Digital ProjectsIC6 Bi-Polar Power SupplyIC7 Bi-Polar Power AmpIC8 Groove BoosterIC9 Photo Timer

IC10 Bargain Tape Preamp

CheckerboardAdd Tone to Your PhoneSuper DXerChannel Changer

New ProductsAsk Hank, He'KnowsIntroduction

Logical NAND DemonstratorEasy Instrument CalibratorLogical AND DemonstratorLogical NOR Demonstrator"555" Loudspeaker"555" Switch HitterWrong -Way Battery ProtectorOld CrowbarAdd An Antenna TrimmerAdjustable CrowbarNoise GeneratorLet There Be LightAttache AlarmGotcha GeneratorThe BamboozlerTurn -On DelaySWL's Simple Squelch29C Mag. Phone FilterSlide Show StopperAdd -A -TweeterFlash TesterBasic Color OrganPhoto Print MeterAuto Ignition MazeCrystal CheckerFM Overload FilterDoorknob Security AlarmRemote Flash TriggerAngler's Bite BoosterNifty Night LightLED Telephone Ring IndicatorCurrent TattletaleTelephone Dial BlinkerFlashlight Remote Control

BONUS -30 INTEGRATED CIRCUIT PROJECTS

59 IC11 Mighty Mite Signal Tracer59 IC12 100X Instrument Amp60 IC13 C Booster60 IC14 Notch Filter Oscillator61 IC15 Electric Butler Intercom61 IC16 Ultimate Talk Power62 IC17 Tape Head Preamp62 IC18 Stereo Balancer63 IC19 The Basic Amplifier63 IC20 Versatile Hi -Pass Filter

64 IC21 Cigar -Size Amplifier64 IC22 Protect -a -Volt65 IC23 Hi -Level 4 -Channel Mixer65 IC24 SCA Adaptor65 IC25 Stereo Mike Preanp66 IC26 Comm -Press Log Amp66 IC27 Porta-Groove Amp67 IC28 Record Remote Amplifier67 IC29 Far Out Gain Control

IC30 No -Noise Mike Preamp72

TEN TRIED AND TRUE PROJECTS7779 Flashmate82 Measure the Wind85 Thunderbolt

88 Color Analyzer91 FRAG-Audio Generator96 Custom Switches

REGULAR DEPARTMENTS AND FEATURES

8 Computer New Products13 Readers Service Card14 CB New Products

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4 101 ELECTRONIC PROJECTS 1978

The mostimportantpiece ofelectronicequipmentyou'll ever own.

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INCLUDES ALL THE LATESTTERMINOLOGY FOR SUCH FIELDS AS: Communications Reliability Microelectronics Computers Fiberoptics Medical Semi -conductors ElectronicsLOOK at all the valuable "extras" this onehandy reference volume contains: Hundreds of easy -to -grasp ILLUSTRA-

TIONS AND DIAGRAMS-positionedwith the terms they depict-and clearlycaptioned for quick understanding.

CROSS-REFERENCED to aid you inlocating those terms which you mightlook for in more than one place. Ex-ample: When looking up "Esaki diode"you'll be referred to "tunnel diode:'

Helpful PRONUNCIATION GUIDE ofmore than 1100 often -mispronouncedelectronic terms showing syllabic divi-sion as well as the newest, most -accep-ted pronunciation of each term.

A newly -revised list of SEMI -CONDUC-TOR SYMBOLS AND ABBREVIATIONSfor use in semiconductor device datasheets and specifications.

Clearly -illustrated SCHEMATICSYMBOLS.

GREEK ALPHABET. A special tablelists the letters along with technicalterms for which these letters are usedas symbols (Name and Designates).

819 Pages of crystal-clear definitions.Over 18,500 terms defined and alpha-betically arranged. Size: 5-1/2 x 8-1/2.

Authoritative ComprehensiveBE OUR GUEST. Examine theMODERN DICTIONARY OF ELECTRONICSfree for 15 days. Discover whybook reviewers and some of themost demanding electronics ex-perts around are calling it the mostcomplete, up-to-date, authorita-tive dictionary ever compiled forthis exacting field. And get a FREE$4.95 bonus book.Since rolling off the presses thisgiant reference is already beinghailed as THE dictionary of theindjstry by thousands of elec-tronic engineers, technicians, ex-perimenters and hobbyists fromcoast to coast. So don't be sur-prised if it becomes one of ther

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Users tell us that one of the thingsthat sets it head and shouldersabove other electronic dictionariesis all the valuable extra informationit contains. But see for yourself.Send for the MODERN DICTIONARYDF ELECTRONICS today. If you don'tagree it's one of the most importantpieces of electronic "equipment"you could own, simply return itwithin 15 days and owe nothing.And no matter what you decide,you'll get a free copy of "How toRead Schematic Diagrams" tokeep...as our "thank you" gift.

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P.C. BOARD The 4 x 4 5.1/16 inch board is made of glass Coated EPDXY Lamina..and features solder coated I or copper pads. The board has provisionfor 22/44 two sided edge connector. with contacts on standard .156spacing Edge contacts re no...dedicated for maximum flexibility.The board contains a matrix of .040 in diameter holes on .100 inchcenters. The component side contains 76 two hole pads that can accommodate any DIP sae from 640 pins, as well as discrete componentsTypical density is II of 14.Pin or 16 Pin DIP... Components may besoldered directly to the board or intermediate sockets may be used to,soldering or wire -wrapping.Two independent bus systems are provided for voltage end ground onboth sides of the board. In addition. the component side contains 14individual busses running the full length of the board for complete weiring fuaibilitr. These busses enable access from edge contacts to distantcomponents These busses tan also serve to augment the voltage orground busses, and may A. cut to length for particular applications

Hobby Board H PCB -1 154.99

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WHO'S WHO ONELECTRONIC PROJECTS

FOR UNDER $15

THE STAFF

Editor -in -Chief andElectronics Group Coordinator

Julian S. Martin, WA2COLManaging Editor

Alan H. Rose, K2RHK

Technical EditorNeil Shapiro, WB2KOI, KAFA7222

Associate EditorGordon Sell, KBDA1464

Citizens Band EditorKathi Martin, KGK3916

Workbench EditorHank ScottArt Director

Ralph Rubino

Assistant Art DirectorDavid Pindar

Cover Art DirectorIrving BernsteinArt Assistants

Caroline ImparatoRobert ModeroMichael VessioTerri Czeczko

Advertising DirectorDavid J. Miller, KCX1268

Advertising. Research AssociateJyll Holzman, KAKZ1490

Production DirectorCarl Bartee

Production ManagerCarole Dixon

Assistant Production Manager:.Mary Carfagno

Newsstand CirculationDirector

Don GabreeSubscription Circulation &

Marketing DirectorRobert V. Enlow

Subscription Circulation ManagerEugene S. SlawsonDirector of Market

DevelopmentJames C. Weakley

President and PublisherJoel Davis

Vice President andGeneral ManagerLeonard F. Pinto

Vice President and TreasurerVictor C. Stabile, KBP0681

101 ELECTRONIC PROJECTS is publishedannually by Davis Publications, Inc. Editorialand business offices: 229 Park Avenue South,New York, New York 10003. Advertising offices:New York. 229 Park Avenue South, 212 -OR3-1300; Chicago, 520 N. Michigan Ave., 312-527-0330; Los Angeles: J. E. Publishers' Rep.Co., 8732 Sunset Blvd. 213-659-3810.EDITORIAL CONTRIBUTIONS must be accom-panied by return postage and will be handledwith reasonable care: however, publisher as-sumes no responsibility for return or safety ofmanuscripts, artwork, or photographs. All con-tributions should be addressed to the Editor -in -Chief, 101 ELECTRONIC PROJECTS, 229Park Avenue South, New York, N.Y. 10003.

Copyright 1978 byDavis Publications, Inc.

New ProdtictsTriggered Oscilloscope

VIZ has introduced a high -caliber trig-gered oscilloscope, the WO -527A. Thescope is five inches in diameter withvertical -amplifier frequency response to15 MHz; the bandwidth of the horizontalamplifier is from DC to 1 MHz. Front -panel pushbutton switches make the dis-play -mode and sweep -function selectionfast and easy. The scope has a trigger -level adjustment system that uses LEDsto indicate trigger polarity at a glance.Horizontal -amplifier input impedance is1 megohm shunted for trace expansionby 30 pF. A special TV line selector func-tion permits line -by-line display of video

) C.) 0


frames. The triggered sweep system pro-vides calibrated time bases from 0.5usec/cm to 0.5 sec/cm, and a 10Xsweep magnifier provides sweep speedsup to 50 nsec for trace expansion. Otherfeatures include preset TV, vertical andhorizontal sweep settings for stable,automatic TV video waveform lockin; a0.4-V peak -to -peak square -wave calibrat-ing signal for convenient voltage mea-surement and probe compensation at afront -panel terminal; choice of AC or DCvertical amplifier coupling; selection ofadjustable or automatic trigger mode;AC, DC, or ground reference for the in-put signal; and a divide -by -ten triggersource function to ensure stable lock -in.The WO -527A scope is available at VIZdistributors at the dealer -optional priceof $479.00. For more information, writeto VIZ Mfg. Co., 335 E. Price Street,Philadelphia, PA 19144.

Electronic KeyerHam Radio Center's new ElectronicKeyer, Model HK -5A, features a trimcabinet colored -keyed to match mostmodern amateur radio equipment withall front mounted controls (speed,weight, tone and volume) and jacks forexternal paddle and/or keyer, plus ex-ternal power. Inside, this battery oper-ated unit has an iambic circuit forsqueeze keying, self -completing dots and


dashes, a dot memory, built-in tonemonitor and grid block and direct key-ing. Batteries not included. Also, it canbe used as a code aractice oscillatorwith a straight key. Sells for $69.95. Formore information about Model HK -5A,write Ham Radio Center, Inc., 8340-42Olive Boulevard, P.O. Box 28271, St.Louis, MO 63132.

The Beam BoxB.I.C. introduced an irdoor FM antennawhich they call The Beam Box. It is actu-ally a new type of high fidelity com-ponent, specially designed to be perma-nently positioned alongside, above, orbeneath the other components in a musicsystem. In describing The Beam Box,Andrew Carduner, Vice-president of B.I.C.explained, "Most owners of FM receiversand tuners never realize or enjoy thefull reception capability of their equip-ment simply because the antenna is un-able to deliver a proper signal to theantenna terminals of the set. The wire -dipole antenna generally used with mostFM receivers cannot easily be orientedin the proper direction to pick-up re -


flection-free, strong signals from all thestations in a given area. Outdoor an-tennas are costly to install, impractical orprohibited for apartment dwellers andrequire a rotator in order to receive ade-quate signals from more than one direc-tion. The Beam Box solves these prob-lems and more." The Beam box isequipped with a passive electronic cir-cuit that directs its sensitivity patterntowards any one of four geographicquadrants at the turn of a switch, with-out the antenna itself ever having tomove. Unlike a wire dipole, it is able toreceive optimum signals from any direc-tion. By electronically directing its recep-tion pattern towards the signals youwant, multipath signals are suppressedso that stereo separation and signal-to-noise performance are improved. TheBeam Box carries a suggested retailprice of $89.95. For more info, write toB.I.C., Westbury, NY 11590.

FM on 2 -MetersA solid-state, fully -synthesized 800 -chan-nel 144-148 mHz two -meter FM trans-ceiver, Model FT -227R by Yaesu, featuresa memory circuit to pJt you on anypreset channel with a flip of the memoryswitch; it has been designated the YaesuMemorizer. Frequency readout is by


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Send for your Heathkit Mail OrderCatalog today! It's filled with large.clear illustrations and comalete de-

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FREEYou can get a FREE retailca'alog by redeemingthis coupon in person atani of the 50 HeathkitElectronic Centers (Units

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CIRCLE 1 ON READER SERVICE COUPON ELECTRONICS HOBBYIST/Spring-Summer 1978

NewProducts

CIRCLE 47 ON READER SERVICE COUPONmeans of four large LED's. Optical sens-ing eliminates switch problems in fre-quency selection. PLL techniques areused for fully synthesized frequency con-trol in 5 kHz steps, and a special memorycircuit allows instant return to any pre-selected frequency within the twometerband. Offsets of ±600 kHz, plus any oddsplit within the two -meter band can beachieved using the memory circuit. Thenew FT -227R has automatic final pro-tection, PLL unlock protection and abusy -channel indicator. It provides built-in tone burst, plus optional squelch -decoder and selectable ten- or one -wattoutput. The FT -227R requires 800 mA,on receive and 2.5 A on transmit at 13.8VDC. Priced at under $300. Available atall authorized Yaesu dealers. For moreinfo, write to Yaesu Electronics Corp.,15954 Downey Avenue, P.O. Box 498,Paramount, CA 90723.

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1001 BARGAINS INSPEAKERS - PARTS -TUBES - HIGH FIDELIW

COMPONENTS-RECORD CHANGERSTape Recorders-Kits-Everything in Electronics1901 McGee Street, Kansas City, Missouri 64108

Solderless CardsAP Products' new version of their popu-lar Unicards are reuseable solderlesscards for a modular approach to systemsbreadboarding. These new versions util-ize AP Terminal Strips with double rowsof terminals each having 5 tie -points.This configuration is ideal for breadboarding LSI integrated circuits. TheseUnicards provide solderless, plug-in tie -

points on a universal .1 -in. x .1 -in.


matrix and require no special patchcords. They plug into standard 51/4 -in.card racks and are compatible with APextender cards. The new version of Uni-card I has 960 tie -points (192 terminalseach with 5 points) while Unicard IIoffers 1,620 tie -points (324 terminalseach with 5 points). The continuous ma-trix of terminals on .100 -in. centersaccepts all DIP's, TO -5's or discrete components with lead diameters up to .032-

PARTS! (0eA

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OF -1 OSCILLATOR

$425ea.

The OF -I oscillator is aresistor/capacitor circuit

providing oscillation over a range of frequen-cies by inserting the desired crystal.2 to 22 MHz, OF-1LO. Cat No 035108 18 to 60 MHz.OF -1 HI. Cat No 035109 Specify when ordering

MXX-1 Transistor RF Mixer3 to 20 MHz. Cat. No. 03510620 to 170 MHz, Cat. No. 035106 $5.50 es.SAX -1 Transistor RF Amp3 to 20 MHz. Cat. No. 03510220 to 170 MHz Cat. No. 035103 $5.50 es.SAX -1 Broadband Amp20 Hz to 150 MHz Cat No 035107 $5.75 Si.

O2° Calibration ToleranceEXPERIMENTER

CRYSTALS(HC 6/U Holder)

$475eaCat. No. Specifications ll031300 3 to 20 MHz - For use in OF -IL OSC

Specify when ordering.031310 20 to 60 MHz - For use in OF -1H OSC

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Enclose payment with order no COD) Shippingand postage (inside U S Canada and Mexico only)will be prepaid by International Prices quoted forU S Canada and Mexico orders only Orders forshipment to other countries win be quoted on re-quest Price subtect to change Address orders to

M/S Dept PO Box 32497Oklahoma City Oklahoma 73132

WRITE FOR BROCHURE

International Crystal Mfg. Co., Inc.10 North Lee Oklahoma City. Oklahoma 73102

in. As many as four.een 12 -pin DIPScan be accommodated on Unicard I,twenty-two 14 pin DIPS on Unicard II orany mix of packages or components.Prices start at $31.50 for the Unicard I.For more complete information, write toAP Products, 72 Corwin Drive, Box 110,Painesville, OH 44077.

Highway TimeAn electronic quartz LED digital clock bySparkomatic is reported to be accurateto within a one -minute variance per year.Solid-state technology has eliminated theneed for moving parts. Hour and minutebuttons on the front display windowpermit easy time setting, while theclock's highly illuminated digital numer-


als, which can be read in any light, showthe hours and minutes concurrently.The new clock can be installed in anycar, camper, van, pickup, boat or othervehicle and it can be mounted on -dash,in -dash, or underdash to produce a fac-tory equipment look. Sells for $19.95.For more details, write to SparkomaticCorp., Milford, PA 18327.

Heavy -Duty RotatorThe Beam Master antenna rotor was de-signed specifical!y for CB beam antennaswith up to 5 square feet of wind loadingarea and large TV antenna arrays. It fea-tures a heavy-duty tocl steel gear sys-tem; strong, weatherprotected housingwith a snaplock cover for easy installa-tion; and a contemporary, low -profilerotor control unit. Beam Master canwithstand 8,400 -in. lbs. of vertical force.

CIRCLE 64 ONREADER SERVICE COUPON

It has a built-in thrust Dearing that canhandle loads up to 250 lbs. The mastsupport can accommodate masting from1- to 2 -in. outside diameters and comesequipped with all stainless steel hard-ware. Beam Master's rotor control unitcombines smoother, quiet action withpinpoint positioning, and uses synchro-nized motors for on -target accuracy inthe desired direction. The console has amodern, easy -to -read faceplate and com-

10CIRCLE 11 ON READER SERVICE COUPON

101 ELECTRONIC PROJECTS 1978

Lab TestElementaryElectronics

ForYourself

Get switched -on with themagazine for electronicsfans and hobbyists

Ementary, TesIkk

sr-eq:

In case you're not all that familiar withus,we're not a publication for electricalengineers and other wizards. No way.ELEMENTARY ELECTRONICS is ex-pressly for people who like to build theirown projects and gadgets-and maybeget a little knee-deep in tape, solder andwire clippings in the process.In fact, we have a sneaking suspicionthat our readers like us because theythink we're just as bug-eyed and down-right crazy over great new project ideasas they are. And I guess they're right!

E E thinks of you who dig electronics asthe last of a special breed. It's more thanjust the "do-it-yourself" angle-it's alsothe spirit of adventure. In this pre-packaged, deodorized world, buildingyour own stereo system, shortwavereceiver, darkroom timer or CB outfit islike constructing a fine-tuned littleuniverse all your own. And when it allworks perfectly-it really takes you toanother world.

ELEMENTARY ELECTRONICSknows the kinds of projectsyou like-and we bring 'emto you by the truckload!

Ever hanker to build a sharp -lookingdigital clock radio? Or to hook up anelectronic game to your TV? Or aneasy -to -build photometer that makesperfect picture enlargements? Or aspace-age Lite-Com so you and thefamily can talk to each other on a lightbeam? We've got it all to get youstarted.

WHEN IT COMES TO REPAIRSE/E can save you time, troubleand a pile of money!

Has your sound system gone blooeyjust when the party's going great? Doyou shudder when your friendly neigh-borhood electrician hands you the bill?E/E can help.Of course, we can't make you a masterelectrician overnight. But we can showyou the fundamentals of repair plusmaintenance tips.IF YOU'RE NEW TO ELECTRONICSYOU GET A "BASIC COURSE"!That's right! It's a regular feature. And

AND

it gives you the complete, ground -floorlowdown on a variety of importantelectronics subjects. For example-Understanding Transistors ... HowRadio Receivers Pull in Signals ...Cathode Ray Tubes Explained ... HowCapacitors Work ... Using Magnet.smin Electronics. And more!

ENJOY GREAT ARTICLESLIKE THESE How to Build Your Own Transformer How to Select the Right Shortwave

Receiver The Burgeoning World of Micro-

computers Quickdraw Rickshaw -The Electric

Car that Really Gets Around What's Really Wrong with FM

Radio? How to Power -Up Your Antique

Radio The Vanishing Vacuum Tube How to Customize Your CB Antenna Those Incredible TV Sets of the

Future Listening in on the Forgotten

Continent DXing Endangered Species Sandbagging -CB Fun Without a

License The World's Worst Hi-Fi Com-

ponents

TRY A FEW ISSUESEVALUATE OUR ...IP. GREAT PROJECT IDEAS. Simulatespace flight with our computer analogproject. Build your own audio visualdarkroom timer. Restore your old carradio. Construct a see-through crystalradio.10. HOW -TO -DO -IT HELP. Tips cndpointers that add up to money saved.For example-tuning up your tapeplayer ... all about radios ... whys andhows of turntables ... care and feedingof speakers.10. NO-NONSENSE TESTS. The scoopon Pioneer's TP.900 FM stereo car radio... How well dces GE's NiCad chargerpep up your pooped batteries? ...What's I,c, eyour best bet in video games? Plus + ..* 41

e e ,,<0.(-%1help in making buying decisions. e s... py"..- ,.( e 62

Q - -)or"..** --4 e-'x, r), 40so

0 A

-0\0`,6 0)-

%Q .0 ,c e ecy J

--teFe <eyy.1e.0

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11

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pws wx g10.-00~1010.. 6,044

wimigar 00.14.0,femaihMiddIN

131 , .00or, Mb. ,10..-

TERs imPEATERs.mcitasrat Now Fuv

frorimay.

EXCITING DISCOVERIES. What-ever your particular interest in elec-tronics, you'll be entering a world ofdiscovery in the pages of ELEMENTARYELECTRONICS.

ELEMENTARY ELECTRONICSis regularly $6.95 for 6 issues (oneyear).

But with this special introductory offeryou can enjoy a full year for only $3.98.

.**..

NewProductspact, low -profile design. It comes with astrip guide for easy installation, plus,terminal barriers, a strain -relief, andfurniture -protecting base pads. BeamMaster provides plenty of torque for all -season performance even under theheaviest of ice -load conditions. The ro-tor's brake system has a built-in storm -load safety feature to prevent drive -traindamage and protect the rotor's gear sys-tem. Beam Master is available in 115volt AC (Model 9515) or 220 Volt AV(Model 9508). The Model 9515 sug-gested retail price is $89.95. For moreinformation, write to Channel Master,Ellenville, NY 12428.

Starter Instrument PackageFive new test instrument kits by Heathcomprise a "starter" test bench orientedprimarily toward the electronics new-comer. The IT -5283 Signal Tracer pro-vides AF and RF signal tracing, audiblevolt/ohm indication and substitutespeaker functions for general radio andhi-fi servicing. The 1M-5284 Multimetermeasures AC and DC voltage to 1000volts, DC current flow to 1000 mA andhas four ranges for impedance measure-ments to 100 meg. Output of from 310kHz to 110 MHz, divided into five bands,and usable to 220 MHz with harmonics,is the feature of the IG-5280 RF Oscilla-tor. The IG-5282 Audio Generator fea-

CIRCLE 31 ON

READER SERVICE

COUPON

tures sine and square wave functions andswitchable ranges from 10 Hz to 100kHz. Separate resistance, inductance andcapacitance ranges are all features of theIB-5281 RCL bridge. Power requirementsfor each of the five units are met by aninternal battery supply (two nine volt bat-teries are required plus one "C" cell forthe IM -5284) or by the IPA -5280-1 powersupply. This power supply operates froman AC outlet and five separate outputsallow simultaneous operation of all fiveinstruments. For further information onthese units, mail-order priced at $37.95each (IPA -5280-1 power supply is

$24.95), write for a free catalog toHeath Company, Dept. 350-500, BentonHarbor, MI 49022.

12

New Slinky DipoleThe Slinky Dipole model SWL-1 is anew ultra -broadband adjustable lengthshort wave antenna that may be usedin either the tuned or un-tuned mode.In many cases, even the untuned modeis reported to give excellent perform-ance, and the tuned mode will furtherpeak the antenna efficiency right atyour desired band. The special Slinkycoils, which form the heart of the an-tenna, are used as the arms of the di-pole. These giant coils look like the toy


coils, but are five times the size andcontain 335 feet of conductor. When inuse, the.spiral arms of the dipole pro-vide the special distributed helical load-ing. This acts like distributed inductance,enabling the electrical length to be asmuch as five times the physical length.Complete Slinky Dipole Kit, Model SWL-1,mail-order priced at $39.95 postpaid.The Slinky may also be used for trans-mitting on the ham bands. Order fromTeletron Corp., Suite 602, Box 84, KingsPark, NY 11754.

Mini -ShopA new self-contained mini -shop that af-fords organization and easy access totools is now available from Penco Prod-ucts Inc., Oaks, PA. Called Shoperafters,the mini -shop can be used by homecraftsmen, electronic hobbyists, and do-it-yourselfers. The mini -shop is composedof two sections: Section A includes awork bench with drawer and a peg -boardback for hanging tools; section B in-cludes standard accessories-rollablemachine cabinet, drawer case with 18 -drawer insert, work stool and an extrashelf. The two sections are attachedside -by -side so that all tools can bestored easily within arms' reach. Ma-chine cabinet and drawer case alloworganization of tools and other equip-ment, to avoid time-consuming searches


over the odd -sized tables, drawers andshelves that comprise most homeowners'tool storage facilities. The two workunits are each 75 -in. high, 48 -in. across,and 24 -in. deep. The shelves and work-benches can be easily adjusted verticallyon 2 -in. increments. The mini -shop listsfor $413.00 with indiv dual parts soldseparately. For further information, con-tact Penco Products Inc., Oaks, PA

19456..

Audio Load KitHeath has introduced an Audio LoadKit for service technicians and audio-philes. The ID -5252 provides audio loadsof 2, 4, 8, 16 and 32 ohms for amplifiertesting according to the specificationsof the manufacturer and the Institute ofHigh Fidelity Manufacturers (IHFM). Aseries of five -way binding posts allow itto handle up to 240 wa:ts mono or four60 watt inputs, both into 8 ohms. Inaddition to the various resistor values,

CIRCLE 31 ON READERthere are jacks for connecting a volt-meter, oscilloscope or other instrumentat the load in use. The ID -5252 includesfour 3 -foot =12 gauge leads with spadelugs. The kit is mail-order priced at$44.95. For further information, writefor a free catalog to the Heath Company,Dept. 350-21, Benton Harbor, MI 49022.

SERVICE COUPON

Cartridge Maintenance KitRobins Industries has introduced their"Stylee" Phono Stylus and CartridgeMaintenance Kit. The kit includes every-thing needed for the audiophile to in-spect, maintain, install and replace deli-cate needles and cartridges. The integralkit components are: precision stylushand-held microscope, screwdriver,tweezers, and stylus cleaning fluid andbrush, all packaged in plastic storage


case. The nucleus of the "Stylee Kit"is its unique hand-held microscope. Itsespecially designed lens is of sufficientlyhigh powered magnification to thoroughlyexamine all styli for imperfections andwear points, yet is purposely limited in

(Continued on page 115)


ASK HANK,

4 HE KNOWS!

Got a question r a problem with a project-askHank! Please remember that Hank's column islimited to answering specific electronic projectquestions that you send to him. Personal repliescannot be made. Sorry, he isn't offering a circuitdesign service. Write to:

Hank Scott, Workshop Editor

101 ELECTRONIC PROJECTS229 Park Avenue SouthNew York, NY 10003

Racing With the AmpI see a lot of raceways in buildings that

add wiring on the internal wall. Is this agood practice?

-A.M., Silver Springs, MD

You bet it is! It may not look good inyour living room, but in the office, garage,shop, and maybe the kitchen, it's alright.The raceway is a metal conduit that issecured to the wall. It is an inexpensiveway to add outlets without breaking upwalls and floors. Raceways can also beused to cheaply interconnect air condi-tioners to the main fuse panel.

One Score and Four Years AgoHank, what happened to the good old

days? My old Dual turntable bit the dustafter 12 years of faithful service, andwhile looking for a new one I must haveseen over 100 different models. How cana guy chose?

-Li., Elmwood Park, NJ

My dad had a 1927 Ford that lasted upuntil World War IL when he sold it be-cause he couldn't get gas. You know whathe bought after the war? That's right, aFord. Once you like a brand, and itsproducts are still very competitive andhigh in quality, why gamble and change.

Antenna Blues/ have a Kenwood KR -77 with quite a

few years on it. We have cable TV hereand I am not too thrilled with theirchoice of FM stations. So, I put an omni-directional antenna up on the roof-thebest I could find. I still have difficulty"bringing in" some of the few stations Ithink worth listening to. Can I piggy -backan additional FM directional' antenna onthe omni I now have and direct the newantenna toward the few stations I thinkare super up here in the mountains ofwestern North Carolina? Will this improveeither or both? Should I go the whole wayand get a rotor?

-J. C., Hendersonville, NC

You can piggy -back an FM directionalantenna, but use an antenna switch toreduce the multipath reception the omniwould be adding to the signal. A rotator?I would prefer it, but before you try it,install an MATV system (it works for FMsignals, too!). Maybe your directional an-tenna is broad beam enough to be pullingthose hill signals and get signal boostingby the MATV amplifier. If not, go rotator.I suggest you write to The Finney Com-pany, 34 West Interstate Street. Bedford,OH 44146: They're hotshots in MATV andtheir literature may offer a better solu-tion to your problem. As for that Ken -

wood KR -77, it's a good unit, but have itchecked out for it may need a front endalignment.

Meters LieOn my hi-fi receiver, when tuning FM,

the signal strength is not at maximumposition when the tuning indicator is

centered. For maximum signal, the tuningindicator is about 1/32 -in. to the left ofzero. What should I do?

-W.D., Chatsworth, CAYou didn't say a thing about how the

unit sounds! Tune for minimum distortion.I think you'll discover this occurs when thetuning meter is centered. If the sound ispoor, then alignment is necessary. I knowthis should not happen, but it is fairlycommon.

Lost TVI hooked up an unamplified MATV sys-

tem in my house. These are long runs ofRG-59/U cables. Can you tell me the kindof losses I will experience.

Van Nuys, CALet me give you the dB losses for both

RG-59/U and RG-59/U Foam (or lowloss cable) per 100 feet of run.

TV ChannelsCable 2 6 7 13 14 47 83

RG-59/U 2.8 3.6 5.3 5.9 9.3 11.8 13.0RG-59/U -Foam 1.8 2.4 3.8 4.0 5.9 7.9 8.6

RG-11/U has slightly less loss but becauseof its price and thickness, I find it un-suitable for most home installations. Yourbest bet may be to install a remote ampli-fier near the antenna.

Match MakerWhat is the "matchbox" I hear CBers

talk about?-B.M., Blacksburg, VA

They are talking about an antennamatcher that electrically matches the an-tenna impedance with the transmitters im-pedance for maximum power transfer.Effectively, the matchbox is an impedancematching transformer that helps to reducethe SWR to near 1:1.

Loop the TapeWhere can 1 get a surplus or inexpen-

sive tape transport for making short -looptape machines? I want to build my owntelephone answering machine.

-LS., Cleveland, OHPoly Paks is offering an 8 -track trans-

port for under $13.00. See their ad inELEMENTARY ELECTRONICS. Also, look tothe cheap cassette players that are avail-able-it may be the cheapest way outconsidering the cost of electronics that isincluded.

Lightning's Too FastThis may sound stupid, but can you

use the thunderbolt sound -activated flashswitch to take pictures of lightning whenthunder sounds?

-H.F., Gainsville, FL

No, because by the time you hear thethunder, lightning is long gone. Soundtravels 1100 feet per second, approxi-mately. Lightning one mile away createsthunder that is heard about 5 secondslater, which is much too late to take thepicture. Actually, what you need is a lightactuated switch-a circuit very much likea photographic slave that will trip yourcamera when a flash of light trips it. Nowthat is a project worth designing.

ShockingMy electronics shop teacher says I

have to install an isolation transformerin my three -transistor, AC operated receiv-er before I can bring it to school. Is it thatimportant?

Washington, DC

I assume that you are dropping the ACline voltage through a resistor, then recti-fying it for some low level DC supply. Ifthis is so, half the time the set's groundwill be connected directly to the hot sideof the AC line. This is dangerous. A 1:1time ratio power transformer will isolatethe set from the AC line and reduce possi-ble shock. Listen to your teacher and askhim to explain next time.

Tte FM Noise KillerWhy pre -emphasis, and then de -emphasis,

in FM transmissions in hi-fi?-A.M., Santa Barbara, CA

Nr;se levels increase for higher -fre-quency audio signals. If the level of theaudio signal is raised as frequency in-creases, the level of audio above thenoise remains high enough to insure ade-quate signal-to-noise ratios. That's whypre -emphasis at the transmitter occurs. Atthe home FM receiver, the signal goesthrough a process of de -emphasis to pro-vide a flat frequency response. Whenthis is done, the high frequencies are re-duced (as much as 17 dB at 15,000 Hertz)also reducing the noise to a level belowthat produced by the receiver. Thus, trans-mission noise is effectively reduced.

Why D.C. AmpsWhat is the advantage of a direct -

coupled amplifier?-H.L., Reston, VA

A coupling capacitor has a varying re-actance for different frequencies that isquite noticeable at an amplifier's lowerfrequency limit. In fact, the coupling ca-pacitor size determines the lower frequencylimit. Direct coupled amplifier circuits usea copper wire or a direct connection, effec-tively reducing the lower frequency limitto zero. This type of circuit is simple todesign when using complementary pnp andnpn transistors down the signal amplifi-cation line. Direct coupled amplifiers arenow common in audio components wherelow frequency reproduction without phase -shift is important.


101 ELECTRONIC PROJECTS 1978 13

1978 EDITION

101 ELECTRONIC PROJECTS

FOR UNDER $15 ALL EASY TO BUILD

WI THINK YOU'RE GOING to find thisyear's 101 ELECTRONIC PROJECTSthe most interesting edition yet.

We've added scores of useful new cir-cuits and weeded out many of the dog-eared old veterans. We've added aseries of informative logic demonstra-tors, a number of exciting telephoneaccessories, a smattering of alarm cir-cuits, a bunch of useful automotivecircuits, and a wealth of other projects.

And we've made these the easiest -to -build projects ever.

Plug -and -Chug Projects. Throughoutthese pages, you'll see many of theseprojects actually built up on solderlessbreadboards. These make our projectssimpler to build and easier to under-stand.

If you've never tried solderless bread-boards before, you'll find a treat instore for you. Components plug rightinto them. Inside, spring clips connecteach row of five "holes" together. Sim-ple hookup wire jumpers then completethe circuit. And long "bus" connectorsalong each edge are naturals for carry-ing supply (battery) voltages.

So, everything hooks together in afew minutes. You can try different partvalues immediately. Checking out dif-ferent transistors, for example, is evenquicker to do than it is to talk about.

The solderless breadboard we usedis the Continental Specialties Corpora -14

tion ExperimentorTM Socket modelEXP350. It's very versatile and very in-expensive. You can order one fromCSC or buy one from one of theirdealers. Other suitable solderless bread-boards are available from Radio Shackor from GC Electronics (Calectro)dealers.

Or, if you wish, you can build yourprojects following the more traditionalmethods, like printed circuits.

Surprise-A 101 ELECTRONIC PRO-JECTS Kit. We've made special arrange-ments to offer a kit of all the partsyou'll need to build any of the 101ELECTRONIC PROJECTS in this edition.The inside front cover has the details.

Or, you can buy your parts throughany of the traditional sources. We'vemade a special effort to design our cir-cuits so that, in many cases, substitutingclose but wrong part values, or differ-ent transistors (of a type-NPN, PNP.PFET, UJT, etc.), will still result in aworking circuit. Some of the parts wetried were bought in plastic bags athamfest flea markets-and they worked.

The electronics dealers who advertiseregularly in the back of ELEMENTARYELECTRONICS and other leading elec-tronic hobby magazines are good sour-ces for parts. So are your local elec-tronic and radio parts stores. In manycases, you can get parts from your own"junkbox" after stripping them off old,

broken equipment. Chances are a localTV repair shop can give you a junkerto start you on your way.

A Plug for Safety. One thing that's dif-ferent about this year's 101 ELECTRON-IC PROJECTS is that none of our projectsattach to the AC power line. Instead,they're powered by battery, by yourcar, by the phone line or by a signal.

This doesn't mean that you're com-pletely free from trouble, it just reducesthe chance of an accident. But, thereare still a few procedures to follow toavoid trouble.

For one, always check across thepower leads with an 0.1mmeter beforeyou connect power. If it reads less than20-30 Ohms, you're going to be draw-ing too much current. That can drainyour battery, blow your car's fuse, burnout your stereo's output or mess up thephone company lines all around you,depending on the project.

Don't attach anything to the phonelines unless and until you're very sureit won't disturb service. Make sure yourparts can withstand a several -hundred -volt de-icing surge, and never leave any-thing attached for more than a fewminutes.

New Devices. One of the best aspectsof these projects is that they representa great opportunity to gain hands-onexperience with a variety of differentelectronic components.


JFETS (Junction Field Effect Tran-sistors) are more sensitive than stand-ard bipolar transistors. They respond tovoltage changes at very small currents(in other words, they offer a high inputimpedance), and operate much morelike vacuum tubes than transistors. Yet,they are small, easy to work with, andvery versatile.

SCRS (Silicon Controlled Rectifiers),the solid state equivalent of a latchingrelay, can be thought of as a transistorwith a built in "gotcha." Bring anSCR's gate voltage to its turn -on pointand you'll have to open the circuit toturn it off again.

Phototransistors let light (sometimesvoltages too) control their output. Youcan use them to detect light, signal withlight, and more.

UJTs (Unijunction Transistors) arenatural-born relaxation oscillators. Thisis due to an unusual quality they pos-sess called "negative resistance."They're small, inexpensive, and easy towork with.

Beep -beep, hoop-boop, some of the soundsyou know and love from out of the mouthsof 555 chips. But, to really hear it all, you'llneed this 555 Loudspeaker for sure.

Zener diodes work like regular diodeswhen hooked "frontwards" (forwardbiased), but act as voltage regulatorswhen hooked "backwards." This canlead to interesting applications, as you'llsee on the pages that follow.

And, you'll find many new ways toapply transistors, LEDs, diodes, switch-es, relays and more.

Secret Formulas for Success. Just forthe record, here are a few of the formu-las that tell you how much a partvalue can change and what that willdo to circuit operation.

E=IR. This is Ohm's law. E is Volt-age in Volts, I is current in Amps, R isresistance in Ohms. You can figure anyone when you know the other two:

E=IR I=E/R R=E/IP=EI. This is Watt's law. It says

that the power in Watts is the productof the current in Amps and the Volt-age. If you use it to figure resistorwattage, add a 50% safety margin. Youcan also combine it with Ohm's law:

P=EI=I2R=E2/RI=P/E-VP/RE=P 'I=VPR


The Bamboozler blinkstwo lights, but does itwith style. It's up toyou to tell your friendswhy. Don't worry,you'll come up withsome explanation.

This PhotoelectricSomething's There Tat-tletale will serve youin many ways. It usesa phototransistor to doyour spying for you.

r . .

4......

Idiot's Delight? Well, itturns those idiot lightson your dashboard in-to delightful little buz-zers. It has a built-indelay so you can startthe car without noise.

Transistor Checker willmake it pushbuttoneasy to check on thosetransistors you havefloating in your junkbox. Do it before youbuild that transistorproject, not after whenit's too late-all youneed is right here.

15

Here's a Logic Probe to help you mind yourl's and 0's. It's sensitive enough to be of areal help around the home workshop.

T RC. This will help you figure outthe speed of timer circuits and the fre-quency of R -C oscillater circuits. Thetime delay in seconds is roughly theproduct of the resistance in Ohms andthe capacitance in Farads. (1 micro-farad=1/1,000,000 of a Farad; 1 pico-farad = 1/1,000,000,000,000 Farad).And since R (frequency in Hertz) isthe reciprocal of T (period in seconds):F=1/T T RC F 1/RC

Buy Cheap. There's really no reasonto get super critical about the parts inthese projects We grabbed whateverwas handy when we built them, and socan you. Besides-and more important-when you don't have too mucll, in-vested it's easier to experiment withvariations and not worry too muchabout blowing out a part.

Don't be afraid to combine these cir-cuits with each other. The worst thingthat can happen is they won't work to-gether. The best that can happen is

you'll learn something.And don't worry too much about

part values. If the circuit calls for an8 -Ohm speaker, for example, chancesare anything from 4 to 40 Ohms willdo. A 22 microfarad capaciter canprobably be any value from 10 to 50.

Take what you've got and give it a

shot.Discovery Is The Name of The Game.

And, like a game should be, its fun.You'll find ways to use your VOM asa field strength meter or thermometer.

You'll find instant insight into AND,OR, NAND, NOR and EXCLUSIVENOR logic gates-and learn how yourhome's two-way switch works.

You'll build an LED bargraph, anLED null meter, and use an LED aspart of a switch.

You'll listen to radio stations, walkietalkies and your plants. You'll buildsound changers that electronic instru-mentalists love. And more.

It's all just a turn of the page away. g

Turn your VOM into aField Strength Meter.The sensitivity of thecircuit is determinedby the type of diode.

A LED Bar Graph takes any kinds of lightemitting diode and turns it into an inter-esting display to monitor the range of volt-age imsented al the Graph's input.

Add this Quick Draw Game #1 to your oldhomestead for laugh -a -minute action. Lightyour light before opponent outdraws you.

Okay tightwad-thisPenny Pincher's UtilityAmplifier is for you!There are over a hun-dred uses and forabout a penny a use!

It won't help you to win .he Indy 500, butturning your VOM into a Tachometer willhelp you to do your own tuneups. So saveon money and gas with this project.

Overvoltage Protector wo:ks hard so thatyour circuits can be protected against toomuch voltage just as a circuit breaker willprotect them against too much current.

16 '01 ELECTRONI, ri,vJ C;TS 1978

101 ELECTRONIC PROJECTSFOR UNDER $15

1 Signal Operated Switch111 If a VOX is a voice operatedswitch, is this signal operated switcha SOX?

You can take a signal, like the ear-phone jack output from a radio ortape player, and use it to trigger therelay operation. If used with an FMwireless mike, an FM radio and acassette recorder, for example, thiscircuit could start the recorder when-ever the FM radio receives the wire-less mike signal. DI -RI -CI form anR -C delay network that delays theturn-off of the relay until some time(the number of seconds of delay isroughly the number of ohms of R1times the number of microfarads ofCl divided by a million) after thesignal stops.

The sgnal charges Cl through DI,which keeps it from discharging backthrough the signal source. CI thenholds the base of 01 high until it dis-

PARTS LIST FORSIGNAL OPERATED SWITCH

B1-6.15 VDCC1-2.2-150-uF capacitor01-Silicon diode (1N914 or

equiv.)K1-Small, sensitive relay (reed re-

lays are ideal); voltage compati-ble with Bl; coil impedancegreater than 131 voltage by Q1collector current rating

Q1-NPN switching transistor; col-lector current rating greaterthan relay current (2N2222handles 800 mA and most smallrelays)

R1 -4700 -470,000 -ohm resistor,1/2 -watt

charges enough through RI and thebase -emitter circuit of 01 to reach aturn-off point. Q1 completes the cir-cuit for K l's coil, and you can do

whatever you want with the contacts(turn on a light, start a motor, honka horn, fire up a computer, light upyour TV).

2 Logic Probe111 While not as sophisticated as someof the very sensitive and much moreexpensive professional logic probes,you'll be able to see the l's and 0'sin your logic.circuits as you probe.The probe tip is connected to the baseof 01 through resistor R3. When theprobe tip is reading a high, or "1"signal, the transistor will conduct.turning on LED1. It will also con-duct the current from R2 through Dand Q1, effectively shorting outLED2.

If the probe tip is connected toground (a logical low or "0"), tran-sistor 01 will not conduct, so LEDIwill not light. The R2 current willthen be "steered" into LED2 insteadof DI and Q1, lighting LED2. Somelogic families switch states in circuitswith "1" and "0" levels very close to-gether, near a value of half the sup-ply voltage; this probe may not workwith those families. For TTL and

most CMOS circuits, you should getgood results. The probe is poweredby the circuit under test.

One more caution: if you find thisprobe loading the lines in a CMOS

cr other low -power logic circuit, tryeither increasing the value of R3, oradding an additional logic buffer be-tween the probe and the circuit youwish to monitor.

PARTS LIST FOR LOGIC PROBE

Di-Silicon signal or switchingdiode (1N914 or equiv.)

LED 1, LED 2- Light emittingdiodes

Q1-General purpose NPN transis-tor (2N2222, 2N3904 or equiv.)

R1 -100 -180 -ohm resistor, 1/2 -wattR2 -150 -330 -ohm resistor, 1/2 -wattR3 -1000 -3300 -ohm resistor, 1/2 -

wattS1-SPST (may not be needed)


3 Simple Squealer Back when transistors were brandnew and everybody wanted to seehow they worked, one of the favoritecircuits was very similar to this one.It put out an ear -piercing squeal. Theonly way anybody could put up withit was to use it with a telegraph keyas a code practice oscillator, oftenin a very large room. The compo-nents you choose will have a greateffect on the output of this circuit,and you can take it from a whine toa whisper, from a ticking to a squeal.

Just one precaution: it's possiblethat the components you use couldallow too much current to passthrough 01 or 02. So if the case ofeither transistor becomes too hot totouch, replace it with a transistor

SI

= - 131

m

RI

01

e

e

02

CI

PARTS LIST FORSIMPLE SQUEALER

B1-3-15 VDC batteryC1-.005-.05-uFQ1-NPN silicon transistor

(2N3904 or equiv.)Q2-PNP transistor (2N3906 ur

equiv.)R1 -82,000 -120,000 -ohm resistor,

1/2 -wattS1-SPST switch or telegraph keySPKR-4-16-ohm spea ter

with a higher collector current rating,even a power transistor if you wish.

The editors can not be held respon-

sible for the sanity of you or yourneighbors after prolonged experimen-tation with this circuit.

4 Quick Draw Game"1 Okay, podner, the fust one to pushthe button lights the light on his side,and blocks the other light from turn-ing on.

You can yell "draw"But instead of a switch, you can finda trickier way of closing the contacts.

Try rolling a steel ball baringdown a channel with the contacts onthe bottom. When the ball completesthe circuit, go for your trigger but-tons. Or you can just leave SI closed.Once both "triggers" (S2 and S3)are released, this game is automati-cally set to be played again.

PARTS LIST FORQUICK DRAW GAME #1

B1-6-15 VDC battery.LED1, LED2-Light emitting diodesQl, Q2-NPN transistors (2N2222

or similar)R1, R4 -150 -390 -ohms resistors,

1/2 -wattR2, R3 -22,000 -56,000 -ohm re-

sistors, 1/2 -wattS1-SPST switch (see text)S2, S3-Normally open momentary,

or micro, switches

5 Pierce Crystal Oscillator This JFET Pierce oscillator is verystable, very simple, and can provevery useful. With a suitable crystal,this oscillator can be the clock of amicroprocessor, a digital timepiece ora calculator. With a probe attachedat the output, it can be used as aprecise injection oscillator for trouble-shooting. You can attach a smalllength of wire at the output to act asan antenna and use this circuit as amicropower transmitter. With suitablecrystals it can then provide referencemarker frequencies for short wave lis-tening, receiver tuneup, tv repairs andmore. Transistor Q1 can be a Sili-conix 2N5458, a Motorola MPF102or similar.18

PARTS LIST FORPIERCE CRYSTAL OSCILLATOR

B1-6-15 VDC batteryC1-.001-.01-uF capacitorC2-100-pF-.001-uF capacitorQ1-N-channel JFET (Junction

Field Effect Transistor) (2N5458or equiv.)

R1-1-2.2 Megohm resistor, 1/2 -

wattRFC1-Radio frequency choke, 2.5-

mHS1-SPST switchXTAL-Crystal

C2

RFC I

CI

X TAL


6 CB SaverD Here's a simple little trick to blowthe whistle on a would-be purloinerof your car's under -dash radio or tapeplayer, as well as any Citizens Bandit.Most thieves, in order to keep theirderring-do as brief as possible, simplycut all the wires attached to whateverit is they wish to steal. Unknown tothem, one of the wires in the bundlehas been keeping the SCR in yourCB Saver from firing. No sooner isthe wire cut than resistor R I pulls thegate of the SCR high and allows it toconduct, which pulls in the horn re-lay and honks your hooter until youcome and stop it, by opening SI.

To be fair, if left honking for toolong, your horn can burn out or yourbattery can die. But if, like most of

+12 VDC

GATEATTACH TO CASEGROUND OFEQUIPMENT

TO HORN RINGCONTACT ON HORNRELAY

ANODE

)SCRi

CATHODE

Si

PARTS LIST FOR CB SAVER

R1 -820 -1800 -ohm resistor, 1/2 -

wattSCR1 - Silicon -controlled -rectifier,

20 -volts or more at 1 -amp. ormore

S1-SPST switch (hidden defeatswitch)

us, you're never too far from your car,this inexpensive circuit can save youvaluable time in knowing that some-thing's awry.

A number of CB Savers can behooked up independently of eachother to protect all of your equipment.If you like, they can all share the

same hidden defeat switch. Anothernice trick is to connect a fender -mounted normally closed switch be-tween the "case" terminal andground. Then if a burglar tries to pickthe keyswitch or cut the wires to theswitch, he'll set off your horn imme-diately.

7 Ceramic Cartridge Preamplifier Here's the answer to how to marrythat old ceramic cartridge phono-graph with the amplifier that isn'tquite hot enough to be able to acceptit. It's a common enough problem,found by a lot of people when they at-tempt to upgrade a system. Here's thesolution.

The circuit is really acting as animpedance converter, converting ahigh impedance input, such as a cer-amic cartridge, into a low impedance.Choose an input resistor (R1) tomatch the impedance of your phonocartridge; the circuit's output impe-dance will be very close to the valueof R2.

This same circuit, of course, can

HI3H IMPEDANCE

(CARTRIDGE)SHIELDED INPUT

O

PARTS LIST FOR CERAMIC CARTRIDGE PREAMPB1-6-15 VDC batteryC1-5.15-uF capacitorQ1-N-channel JFET (Junction

Fielc Effect Transistor) (2N5458or equiv.)

177

R1-1-10 Megohm resistor, 1/2 -wattR2 -820 -150 -ohm resistor (see

text), 1/2 -wattS1-SPST switch

be put to other uses involving mag-netic tape heads or piezoelectrictransducers (used in ultrasonics), for

example, or other high impedancesources. If installed inside the ampli-fier, B I and SI may not be necessary.

8 Dynamic Mike AmplifierPARTS LIST FOR DYNAMIC MIKE AMPB1-6-15 VDC batteryC1-5-25-uF capacitorC2-50-250-uF capacitorC3-2-15-uF capacitorQ1-NPN transistor (2N2222, 2N-

3904 or equiv.)R1 -33,000 -68,000 -ohm resistor,

1/2 -wattR2 -2700 -5600 -ohm resistor, 1/2. -

wattR3 -82 -150 -ohm resistor, 1/2 -wattMIC-Low impedance microphone,

8 -600 -ohms


This simple one -transistor preampwill get a little more signal out of evena tired old microphone. And the cir-cuit is small enough to build rightinto a microphone, if you want to. Ifyou use this circuit at the microphone,it will let you use a longer run of

cable to the input of your cassette re-corder, for example, or whateveryou're using. The added amplificationof this circuit should more than offsetthe additional line losses.

If your microphone includes apush -to -talk switch, you might want

to investigate making it do doubtduty as a power switch as well. Inmost cases, this will be easier if youinclude Si in the negative battery con-nection rather than the positive, asshown here.

9 Quick Draw Game #2PARTS LIST FOR

QUICK DRAW GAME #2

B1-6.15 VDC batteryI 1 , I2-Pilot lights (see text)R1, R2 -1000.3900 -ohm resistorsSCR1, SCR2-Silicon controlled

rectifiers (see text)S1-SPST switchS2, S3-Normally open pushbutton,

or micro, switch

SI0

SCRI

12 ©

SCR2

Here our Quick Draw Game goesHollywood. The bright, incandescentpilot lights can be used with colorfuljewels, and the SCRs give the gamea "memory." Choose a lamp type for

II and 12 that is compatible with thevoltage you select for B I. And selectan SCR type for SCR1 and SCR2that is compatible with both the volt-age of B 1 (or greater) and the cur-

rent requirements of I1 and 12 (orgreater). SI turns the game on. Thenthe first player to push his "trigger"switch will light his lamp and blockhis opponent. To reset, turn Si off.

10 Make Your VOM a FSM "I his simple RF (radio frequency)detector circuit will permit you tomeasure RF on any meter that canmeasure a few volts. The antentra canbe a length of wire, a telescoping whipor a real antenna. A foot or so of stiffwire should do for most purposes.The sensitivity of the circuit is de-termined mostly by the forward volt-age drop of the detector diode Dl.Silicon is worst, germanium (such asthe inexpensive 1N34) better, hotcarrier diodes better still. In a strongRF field, you can even use an LEDand watch the RF make it glow.

Cl can be a broadcast tuning ca-pacitor or almost any variable capaci-

ANTDI

RFC I CONNECT TO VOMOR VOLTMETER

PARTS LIST FORVOM INTO FSM

ANT-Antenna (see text)C1-205-pF variable or trimmer ca-

pacitor (see text)DI-Signal diode (1N34 or similar),

or silicon diode (1N914 orsimilar)

RFS1-RF choke, approx. 2.5 mH

tance of a couple of hundred pf range.In operation, tune Cl for the largestswing on your meter. Adjusting thelength of the antenna may help, too.Then watch the reading change aseither you or the transmitter moves.

You can use this device with asimple chart to mark down your read-ings at different points around a sig-nal source. The chart can then showthe RF pattern characteristic of theantenna transmitting the signal.

11 Pulsing CB Saver If there's anything that will attractattention better than a honking carhorn, it's an intermittently honkingcar horn. This circuit is an adaptationof the CB Saver that interrupts thehorn relay contact with a flasher cart-ridge. Make sure you get the multiple -load flasher, as others require toomuch current to operate.

Notice there is no hidden defeatswitch. There are two ways to defeat -

20

TO HORN RELAYHORN RING CONTACT

TO CASEGROUND ONEQUIPMENT

PARTS LIST FORPULSING CB SAVER

R1 -820 -1800 -ohm resistor, 1/2 -

wattSCR1 - Silicon -controlled -rectifier,

20 -volts or more at 1 -amp. ormore

FL1-Multiple load turn signalflasher cartridge


this alarm. You can either regroundthe protection lead, or pull the flasherout of its socket (assuming you use

a socket). If you want to protect sev-eral pieces of equipment, use sepa-rate protection leads, resistors and

SCRs for each, and parallel all of theSCR anodes at the SCR end of theflasher.

12 High Performance Transistor Radio Here's a neat way to update yourcrystal set, assuming you can still findit. Or use these few inexpensive partsto build from scratch. Instead ofusing a cat's whisker or a diode, thisradio uses the very sensitive junctionof a junction FET as its detector.This makes it a very "hot," very sen-sitive high impedance detector. Thenthe JFET does double duty by con-

verting the high input impedance to alower output impedance-low enoughand with enough drive to power a setof high impedance headphones or ahigh impedance earphone (about 1Kor so).

The antenna coil is one of thosesimple loopsticks you've seen at theparts stores. (Or you might want towind your own on an oatmeal box).

The broadcast variable capacitor isone of the tuning capacitors takenfrom an old, defunct radio. You canuse any long wire for the antenna, butif you string it outdoors, be sure touse a lightning arrestor. You can alsoclip an alligator clip to your bed-spring, a windowscreen, or the metalpart of a telephone.

PARTS LIST FORHIGH PERFORMANCETRANSISTOR RADIO

B1-6-15 VDC batteryCl-Approx. 356-pF broadcast -

type variable capacitorC2-300.600-pF capacitorC3-.05-.5-uF capacitorC4-.22-1.0-uF capacitorL1/L2-Ferrite Ioopstick, or ferrite -

bar BCB antenna coilQ1-N-channel JFET (Junction

Field Effect Transistor) (2N-5458, MPF102 or equiv.)

ANT

LI; L2 C

0I

HE ADPHONESC3 K)

C2T RI VOLR2UME

R1 -18,000 -47,000 -ohm resistor,1/2 -watt

R2 -20,000 -100,00 -ohm poten-

R 3

C4

SI

BI

/77

tiometerR3 -4700 -10,000 -ohm resistor,

1/2 -watt

13 LED Bar Graph Display This circuit takes advantage of theforward voltage drop exhibited bysilicon diodes. Each leg of the circuitshows a light emitting diode in serieswith a current limiting resistor and adifferent number of diode voltagedrops, from 0 to 5. You may use anykind of diode you wish, including ger-

manium, silicon, even expensive hotcarrier types (although they won'texhibit quite as much drop, they'revery expensive, and too large a cur-rent could burn them out).

Depending on the diodes youchoose, each will exhibit a forwardvoltage drop between 0.3 and 0.7

volts. For consistency, stay with di-odes of the same type, or at least thesame family. Those twenty -for -a -dol-lar "computer" diodes will do justfine. To expand the range of this LED"meter," use two resistors as a volt-age divider at the input. Connect oneacross the and - terminals, the

0

RI //LED I

eia414LED2

1-5 VDC

/diLED 3

R4 LED 4

R5 + 6LED 5

6

1:1Y

D21r 03 Y PARTS LIST FORLED BAR GRAPH DISPLAY

D4 i D5 Y D6 D1-15-Silicon diodes (such as1N914)

+ R1, R2, R3, R4, R5, R6 -120.270 -07 It 08 1 D9? DIO ohm resistors, 1/2 -watt

LED1, LED2, LED3, LED4, LED5,LED6-Light emitting diodes

DI t DI2 i DI3 i DI4 i DI5

0


PARTS LIST FORHIGH IMPEDANCEMIKE AMPLIFIER

R3

other from the + terminal to thevoltage being measured. The LEDswill then be monitoring a range de-termined by the ratio of those resis-

tors, as determined by this formula:The voltage across the input equals

the resistance across the output, di-vided by the sum of the resistances

and multiplied by the voltage beingmeasured. Or:

RinEin = Em x Rsum

14 Multivibrator Tone Hummer[1] This multivibrator produces anaudio tone rich in harmonics. If youwere to look at the output on anoscilloscope, you would see it is asquare wave. Because it is so rich inharmonics, you can use this circuit asa signal injector for tracing signals inaudio, if (intermediate frequency),

and even some rf stages. Just howhigh the harmonics will go dependson the particular transistors youchoose, the voltage you operate themat, and the specific values of theother components.

You can also use this circuit to pro-vide very fast clock pulses to logic

circuits, with pulse width in the frac-tion -of -a -millisecond range, if youlike. Remember, the higher in pitchthe tone that you heir, the shortereach pulse width. You can also usethis as a signal injector or signalsource in setting up stereo or inter-com systems.

PARTS LIST FORMULTIVIBRATOR TONE HUMMER

B1-6-15 VDCCl, C2-.05-.5-uF capacitors121, R4 -2200 -4700 -ohm resistors,

1/2 -wattR2, R3 -4700 -100,000 -ohm resis-

tors, 1/2 -wattSI -SPST switchQl, Q2-NPN transistor (2N2222,

2N3904 or equiv.)

15 High Impedance Mike AmplifierCI This high -to -low impedanceconverter will let you use a-highimpedance crystal, ceramic or dy-namic microphone with conventional(around 5K) microphone inputs. Itwill also let you use a high impe-dance mike over a longer run ofcable with less danger of introducing

hum.01 is a general purpose N -channel

JFET, like the Siliconix 2N5458,Motorola MPF102 or similar. ChooseRI to match the impedance of yourmicrophone.

If you choose to mount this circuitin or near the microphone case

(where it will do the most good),and the microphone is a push -to -talktype, investigate using the PTT switchin place of S1. This may work betterif S1 is placed in the negative batterylead rather than the positive (asshown).

M IC CI

B1-6-15 VDC batteryCl, C3-.001-.01-uF capacitorsC2-25-100-uFQ1-N-channel JFET (Junction

Field Effect Transistor) (2N5458or similar)

R1-1-10 Megohm resistor, 1/2 -watt31 R2 -1800.330 -ohm resistor, 1/2 -

wattR3 -4700 -10,000 -ohm resistor, 1/2.

wattS1-SPST switch (see text)

16 Plant Moisture Monitor Some people don't believe thatplants can listen, talk, sing and playmusical instruments. But you canprove, at least, that they sing out

22

when you water them. This circuitlets you use the soil near your plantsas a variable resistor that changesvalue as you add more water to it.

Just stick the metal spikes into thesoil, a few inches from each other.For best results, cut flat, skinnywedges out of thin copper or alumi-


num or out of printed circuit boardstock. Depending on the soils resist-ance, the sound will vary from slowclicking noises to a high pitchedshriek.

V VMETAL SPIKE

PROBES

PARTS LIST FORPLANT MOISTURE MINDER

81-6-18 VDCC1-5.25 uF capacitor

/77

R1 -2200 -5600 -ohm resistor, 1/2 -

wattR2 -3300 -5600 -ohm resistor, 1/2 -

wattR3 -82 -120 -ohm resistor, 1/2 -wattQ1-Unijunction (UJT) transistor

(2N2646 or equiv.)Q2-NPN transistor (2N2222, 2N-

3904 or equiv.)S1-SPST switchSPKR-4.32-ohm speaker

17 Switch Contact Debouncer Today's logic circuits are so quickthat even the fast, tiny bouncing ofswitch contacts can be counted asseparate switching events. This simplecircuit adds a tiny delay to the switch-ing to keep those bounces from reach-ing your logic. It gets its power rightfrom the logic circuit you're using itwith. Most logic requires switchingbetween some input and ground. Forthose cases, use the circuit the wayit's shown. It goes in the lead fromthe ungrounded side of the switch tothe logic input (which is then con-nected to the Output shown).

Should your application require

PARTS LIST FORSWITCH CONTACT DEBOUNCER

C1-.5-2.2-uF capacitor, electro-lytic, (VDC greater than yourpower supply)

R 1 -10,000 -56,000 -ohm resistor,1/2 -watt

R2 -270.1000 -ohm resistor, 1/2 -

wattS1-SPST (switch to be debounced)Q1-NPN transistor (2N2222, 2N

3904 or equiv.

switching to the positive supply (as-suming ground is negative above),simply swap the -1- and - leads andmake 01 a PNP transistor (2N3906,

for example). Also, if the capacitoryou're using for CI is polarized, anelectiolytic, for example, reverse itspolarity as well.

18 Square Wave Generator

t I t2 t3

OUTPUT A

OUTPUT B

OUTPUT C

t l = 12 = t3 WHEN RI = R2 = R3

CI C2 C3 AND R4 = R5 R6

RI

OUTPUT A

R4e

CI

0I

P5

TC2

R2

e

02

R3

OUTPUT B OUTPUT C

R61Ar-

TC3

03e BI

T

EJ Here is a versatile square wavegenerator capable of surprising per-formance. It can deliver clock orswitching pulses, act as a signalsource, and more. And because theoutputs take turns switching, it canbe used as a simple sequence gen-erator or as a multiple -phase clock.

The component values indicatedwill support a range of output fre-quencies from a few pulses per secondup into the high audio range. Andthis square wave ouput is rich in har-monics. If you use a 5 -volt powersupply, this circuit can trigger TTLlogic directly.

PARTS LIST FORSQUARE WAVE GENERATOR

B1-6-15 VDC batteryCl, C2, C3-.5-uF capacitorQI, Q2, Q3-NPN general purpose

transistor (2N2222, 2N3904 orequiv.)

RI, R2, R3 -500 -2700 -ohm resis-tors, 1/2 -watt

R4, R5, R6 -10,000 -47,000 -ohmresistor, 1/2 -watt

Sl-SPST switch


19 Tone Control Network Since there are no active devicesin this circuit, like transistors or ICs,it can provide no amplification on itsown to offset the very lossy character-istics of these networks. Fortunately,most audio systems have more thanenough oomph to accommodate thisnetwork loss.

Once you have learned, by experi-

menting with the effects of variouscomponent values, just how you canalter the characteristics of these net-works, you may want to constructyour own graphic equalizer. Just in-clude more stages similar to the twobasic types of filters you see here: R1,R2, R3, R4, Cl, C2 and C3 form oneof the filters, the rest of the compo-

nents the other. Just remember, themore stages of passive filtering youadd, the more loss yon introduce intoyour system. For that reason, mostcommercial graphic equalizers includebuilt-in amplifiers. And, of course,you will have to duplicate your fil-ter(s) for each channel if you'reworking in four or more tracks.

INPUT FROM PR EAMP OUTPUT TO POWER AMP0 PARTS LIST FOR0

TONE CONTROL NETWORK_1_ Cl, C5-.068-.2-uF capacitorsCI

C41 C2-.033-.068-uF capacitorRI C3-.33-.68-uF capacitor

C2 R4 R5 C4-.005-.02-uF capacitorR1, R4, R5 -1500 -oh -n resistors.

R2

R3

BASSTREBLE

R6 1/2 -wattR2, R6 -50,000 -200,000 -ohm po-

tentiometer, logarithmic or audioraper

R3, R7 -820 -1500 -ohm resistors,C3 R7

C5 1/2 -watt

/77

20 Voltage Controlled Audio Oscillator Unijunction transistors are veryinteresting. They love to be uud inoscillators, and it doesn't take toomany parts or very much coaxing toget their sawtooth outputs going. Thislittle squealer will tell you how muchvoltage it's connected to. The higherthe voltage, the lower frequency out-put you'll hear. 5 or 6 Volts shouldstart its high squeal going; 25 or 30volts and it'll be ticking like a metro-nome. You can take advantage of thisvoltage to frequency conversion anduse this circuit as an audible volt-meter. Or, with a resistor across theinput, it can be an audible current

PARTS LIST FORVOLTAGE CONTROLLED

OSCI LLATOR

C1-.5-2.2-uF capacitorR1 -10,000 -47,000 -ohm resistor,

1/2 -wattR2 -82 -150 -ohm resistor, 1/2 -wattQ1-unijunction transistor (2N-

2646 or equiv.)SPKR-8-40-ohms

meter.For a slightly stranger effect, con-

nect a large value capacitor (say 50-100 uF with a voltage rating largerthan the voltages you intend to ap-

ply). You'll hear a swooping effect.Many different components can beplaced across the input for differenteffects when voltage :s applied. Ex-periment and have fun.

21 Wide Range OscillatorPARTS LIST FOR

WIDE RANGE OSCILLATOR

81-6.15 VDCC1-5-25-uF capacitorQ1-Unijunction (UJT) transistor

(2N2646 or equiv.)Q2-NPN transistor (2N2222, 2N-

3904 or equiv.)R1 -2200 -5600 -ohm resistor, 1/2 -

watt

R2-500,000-5 Megohm potentio-meter

R3 -3300 -5600 -ohm resistor, 1/2 -

wattR4 -82 -120 -ohm resistor, 1/2 -wattS1-SPST switchSPKR-4-32-ohm speake


You may need an audio signal forany of a number of reasons: as awarning tone, as a test oscillator tocheck microphones and recorders, aspart of a toy, as an annunciator oras one of an endless list of things.

This circuit will give you the tones

you need, even tones above and belowfrequencies you would expect. It willproduce the steady click -click -clickingof a metronome, for example. Then,with a twist of the control and a re-sponsive enough speaker, you can useit to silently call your dog.

The frequency of the sawtoothwaveform this circuit produces de-pends mostly on the value of Cl, the.battery voltage, and the combinedseries value of RI and R2. TransistorQ2 acts as a speaker driver and iso-lates the UJT from speaker loading.

22 Weirdly Wailing Oscillator Once you hear the nifty soundeffect this tiny circuit puts out, you'llbe dreaming up places to use it. Thecombination of Cl and C2 causes thisoscillator to work at two widely sepa-rated frequencies at once. One, de-termined mostly by C2, determinesthe basic tone the oscillator will pro-duce. The other, determined mostlyby Cl, governs the number of timesper second the basic tone will be in-terrupted.

The output sounds very much likea pumping whistle-it's a sound effectassociated with toy ray guns, tv and

RI

the movies. If you wishas a toy, try using a momentary switchor microswitch for SI.

to build this

PARTS LIST FORWEIRDLY WAILING OSCILLATOR

B1-6.15 VDCCI-100.500-uF capacitorC2-.1-.5-uF capacitorC1-NPN transistor (2N2222, 2N-

3904 or equiv.)R1 -15 -27 -ohm resistor, 1/2 -wattR2 -8200 -15,000 -ohm resistor, 1/2 -

wattS1-SPST switch (see text)T1 -250 -1000 -ohm primary, center

tapped; 4 -16 -ohm secondary

23 Quick Continuity Checker There are times when just knowing -whether or not a complete circuit ispresent, whether a particular path isan open or a short, can provide thesolution to a nasty troubleshootingchore. Here, the buzzer tells all. Theuse of two transistors in a Darlingtonconfiguration, as this circuit arrange-

ment is called, provides more gainthan could a single transistor.

As a result, this checker is sensi-tive enough to indicate continuityeven when substantial resistance ispresent. Diode DI protects the tran-sistors frcm the potentially lethal (totransistors) inductive kickback of the

buzzer. In much the same fashion asthe single coil in a car's ignition cancreate a high voltage from a lowone, the surges of current throughthe uuzzer can destroy a transistorurf ess some protection is afforded.DI shorts this inductive kickback out.

PARTS LIST FORQUICK CONTINUITY CHECKER

B1-9VDC battery TEST SI0

D1-aode, 1N914 or equiv. POINTS

QI, Q2-NPN transistor, 2N2222) 02

RI

or equiv. 81R1 -1000 -ohm resistor, 1/2 -watt DI A BUZZERS1-SPST switch

24 Poor Man's Hold Switch This is just one step more sophis-ticated than holding your hand overthe telephone mouthpiece. We allfind occasions when we would liketo discuss something with the peoplein the room without sharing it withthe party on the phone. This circuitprpvides dc continuity for the phoneline to keep from losing a call when101 ELECTRONIC PROJECTS 1978

you hang the phone up. There issome danger, though, of putting thephone on "terminal holt," if youforget. Because as long as you areswitched to hold, it's just like leavinga phone off the hook: no one cancall in, you can't call out.

Only two of the lines that reachyour telephone are really part of the

phone line, and these are most oftenthe red and green wires that are inthe cable between your phone andthe wall. Other wires in the cablemay carry power for lighting yourphone, or may carry nothing. Checkcarefully. Also understand that ifyou make a connection to the phoneline that inhibits the phone com-

25

pany's ability to provide service, theyhave the right to disconnect you foras long as they like. This is a proven,simple. circuit that should cause nodifficulty. But be careful.

TELEPHONE

LINES

PARTS LIST FOR POOR MAN'SPHONE HOLD SWITCH

R1 -650 -ohm resistor, 1/2 -wattS1-DPDT switch

NORMAL

HOLD

RI

25 LED Simple Signaller Here's a tricky way to send threedifferent codes down just two wires.You can signal LED1 only, LED2only, or neither. It all depends onthe polarity of the voltage to theright of S2, which S2 controls, andwhether or not S1 is on.

You can also omit the two LEDsfrom the circuit and use it as a LEDchecker. Just connect the LED youwant to check where LED1 andLED2 are shown. Then one or theother position of S2 will cause a goodLED to light.

You can even add a fourth mode

PARTS LIST FORLED SIMPLE SIGNALER

B1-9VDC batteryLED1, LED2-Light emitting diodesR1 -470 -ohm resistor, 1/2 -wattS1-SPST switchS2-DPDT switch

of operation by substituting avoltage ac supply, like the plug-insmall transformer variety. This willcause both LEDs to light. If you

low substitute a signal source for thebattery, the relative brightness ofthe LEDs will give same indicationof the duty cycle of the waveform.

26 Spark Probe Interested in a bright °rang,- lightyou can turn on without batteries ora power supply? This gadget and yoursweater on a dry winter's day cando it. Because the tiny currents andhigh voltage, static electricity caneasily light this neon gas dischargelamp. So can the high voltage onthe face of your TV's picture tube.The spark high voltage near yourcar's spark plug wires. The RF poten-tial near a transmitter or antenna.And a lot more things you'll havefun finding.

In many cases, especially wheredirect contact and electronic sources

PROBE

CLIP

PARTS LIST FOR SPARK PROBE

I1-NE-2 neon bulbMISC-alligator clip; insulated

probe

of high voltage (such as power sup-plies and ignition circuits) can beavoided, you can attach the alligatorclip to your watchband as you bringthe probe near your sweater, yourcomb, or the face of your picture

tube. For other applications, attachthe clip to ground and make sureyour probe is a very good insulatorand thick enough to keep the highvoltages from conducting throughyou.

27 Cheapskate's Light Show171 Here's one for small spenders. Ittakes the sounds that just about any-thing will turn out, through speakerterminals, headphone jacks or almostLny audio output, and turns them intoa bright, pulsating orange glow on aninexpensive neon lamp.

Transformer T1 can be almost anyinterstage transformer. The primary26


SPEAKER LEADS PARTS LIST FORCHEAPSKATE'S LIGHT SHOW

I1-NE-2 neon bulbT1 -1000:10,000 -ohm transformer

must be a small fraction of thesecondary's impedance. You may beable to check this by looking at theDC resistance of the primary and

secondary of almost any junk boxtransformer with your ohmmeter. TImultiplies the audio outpu: voltage toa value high enough tc light the

NE -2. Be careful, the voltage acrossthe NE -2 is high enough to give youquite a kick if you touch it.

28 Broadband Amplifier This simple one -transistor ampli-fier is capable of handily boostingsignals from audio through high fre-quency RF.

The design is stable, well -bypassed,and a neat little performer. And itsapplications are endless. Connect it

to a crystal checker, for example, adda short length of wire at the outputfor a flea -power marker signalsource. Use it as a preamp to yourfrequency counter or oscilloscopewith a short length of wire at theinput to observe signals you couldn't

see before. Hams can use it as abuilding block to simple ORP trans-ceivers. SWLs can use it to pep uptired receivers. The circuit is fairlystraightforward and trouble -free. Youcan help keep it trouble free by lay-ing it out as the schematic.

CI

R2C2

PARTS LIST FORBROADBAND AMPLIFIER

B1-9VDC batteryCl, C3, C4-.01-uF capacitorC2-100-pf capacitorQ1-NPN transistor, 2N2222 or

equiv.R1 -10,000 -ohm potentiometer

0IrR4

C

RFC I R6

SI

INPUT

R I

0OJTPUT

BI R2 -100,000 -ohm resistor, 1/2 -wattC4

R3 R3 -10,000 -ohm resistor, 1/2 -wattR4 -4700 -ohm resistor, 112 -watt

R5 C3 R5 -470 -ohm resistor, 1/2 -wattR6 -100 -ohm resistor, 1/2 -wattRFC1-2.5-mH chokeS1-SPST switch

29 Super Vibrato This professional -sounding circuitadds vibrato to almost any electronicmusical instrument. Now you can playall the vibrato effects the big, Top 40groups have been using on their albumsand singles for years. 01, R2-5, andCl-3 form a phase shift oscillator.Speed control R2 varies its outputfrequency, which is coupled throughC4, R6 and R7 to 02. Q2 and R8then amplitude modulate the signal inthe line between the instrument andthe amplifier. The amount of modu-lation applied is varied by Depthcontrol R6.

You may also want to try thiscircuit out between a mike and yourtape recorder to experiment withstrange vocal effects. If driven hardenough, it can even make you soundas if you're talking under water. Ifthe range of R6 doesn't permit this,try either adding a third battery orreducing the value of R8. You maydecide to make Si a momentary orpush -push foot pedal switch andbuild this entire circuit into the footpedal housing.101 ELECTRONIC PROJECTS 1978

SI

BI

B2

INPUT FROM INSTRUMENT RI

c2

R2

SPEED

R3

C4

R7

DEPTH

R4

PARTS LIST FOR SUPER VIBRATO

Bi, B2-9VDC batteryC1-.5-uF capacitorC2-2.3-uF capacitorC3-5-uF, 25VDC electrolytic ca-

pacitorC4-.05-uF capacitorQl - \IPN transistor, 2N2222,

2N3904, or equiv.Q2-PNP transistor, 2N3906 or

equiv.

OUTPUT TO AMP

02

R8 -100,000 -ohm resistor, V2 -watt

R2 -10,000 -ohm potentiometerR3 -2700 -ohm resistor, 1/2 -wattR4 -3300 -ohm resistor, V2 -wattR5 -560,000 -ohm resistor, 1/2 -wattR6 -500,000 -ohm pote.ntiometerR7 -470 -ohm resistor, 1/2 -wattR9 -4700 -ohm resistor, 1/2 -wattSl-SPST switch

27

30 Penny Pincher's Utility Amplifier Here's high gain with just a hand-ful of parts for a zillion audio appli-cations. 01 and 02 are Darlingtonconnected to deliver a lot of gainand make this a really hot circuit.Transformer T1 reduces the loading

on the transistors to help assure astrong, clean output. This amplifierhas many test bench applications,from signal tracing to loudness boost-ing to checking out new sound ef-fects.

Add it to an inexpensive record ortape player for a quick and easycheckout. Or tie a high output crystalmike to the input and use it as anelectronic stethoscope.

CI

RI

R2

C2

b

01

02

T

SPKR

BI

SI

PARTS LIST FOR PENNYPINCHER'S UTILITY AMPLIFIER

BI-9VDC batteryCl, C2-.1-uF capacitorQ1-PNP transistor, 2N3904 or

equiv.Q2-PNP transistor, 2N2222 or

equiv.RI - 1-Megohm potentiometer,

audio taperR2-1.8-Megohm resistor, 1/2 -watt

S1-SPST switchSPKR-8-ohm speakerT1 -500:8 -ohm transformerJ1-RCA phono jack (or any two -

conductor jack)

31 Easy Headlight -On Warning Nobody has to tell you about thetime and money you can get stuckgoing through if you forget and leaveyour headlights on when yoti. leaveyour car. This circuit reminds youyour lights are on the instant youturn your key off. The Detroit warn-ing circuits wait until you open thedoor. You can connect to the volt-ages you need right at the fuseblock.Try the "radio" fuse for the ignition

PART,S LIST FOREASY HEADLIGHT -ON WARNING

DI, D2-Diode, 1N914 or equiv.R1 -150 -ohm resistor, 112 -watt

circuit, the "instrument" fuse con-nects you to the dashboard nightlights, on whenever the headlightsare on.

D2

32 Wet Basement Alarm For those of us with basementsplagued by dampness, an early warn-ing of wetness is our best, first line ofdefense. This tiny circuit monitorsfor wetness between its two metalprobes. When it senses the wet, it

pulls in relay KI.Relay K1 can be connected to

buzzers, bells, pumps, whatever yoursituation demands. Just make sure therelay contacts are rated for the loadyou wish to use.

Where actual liquids are to besensed, the probes can be simplemetal spikes driven into the mostmoisture -prone section of the base-ment floor. To monitor for dampness,etch or scrape a zigzag pattern

PARTS LIST FORWET BASEMENT ALARM 0

B1-12VDC batteryKI

Dl-Diode, 1N914 or equiv. Di

K1-SPDT relay, 12VDCQ1-NPN transistor, 2N3904 or

equiv. BI

R1 -2700 -ohm resistor, 1/2 -watt

S1-SPST switch01

PROBES

through the middle of a blank cop-per -coated pc board and connect toeach isolated area. Position the boardalong the floor or wall you wish tomonitor.


33 Metal DetectorE This not only demonstrates howmetal detectors work, it actually willdetect metal-with the help of a tran-sistor radio.

The search coil, Cl and C2 forma tuned circuit for oscillator 01,which can be tuned to operate nearthe center of the broadcast band.Tune your portable radio to a sta-

tion near the middle of the hand,then turn on the metal detector andtune C2 until you hear a squeal asthe two signals mix to produce abeat (heterodyne) note.

Metal near the search coil will de -tune the circuit slightly, changing thepitch of the squeal. The spot that ex-hibits the biggest change is where

cu dig for your treasure. The searchcoil is 20 turns of number 30 enam-eled wire, wound on a 6"x8" woodor plastic form. It is affixed at theend of a 30" to 40" wooden pole,and connected to the remainder ofthe metal detector circuit through acoaxial cable.

PARTS LIST FORMETAL DETECTOR

B1-9VDC batteryC1-500-pf capacitorC2-365-pf variable capacitorC3-47-pf capacitorC4-120-pf capacitorJ1-S0239 jackPL1-PL239 plugQ1-FET (Field Effect Transistor),

2N5458 or equiv.R1 -5600 -ohm resistor, 1/2 -wattS1-SPST switchMISC-#30 enameled wire, 6" x

8" wood or plastic form, 30"to 40" wooden pole, coaxialcable

8" X 6' COIL

0" - 40" POLE

9

PL I

01

51

JI

CI

C2 FREQUENCY

C3

C4

RI

34 Nulling Stereo Balance Checker11 Ever get frustrated trying to guesswhere the center of your stereo's bal-ance control really was? A few com-ponents and a few minutes of timecan take the guesswork out of it.

Set your stereo on MONO, putsomething on and you're ready. Nowadjust the balance control from sideto side. You'll see first one LEDlight, then the other. When you getnear the transition point, go slowly.At some point, both LEDs will beoff. This is the center balance posi-

LEFT CHANNEL

DI

RIGHT CHANNEL

D2

PARTS LIST FOR NULLINGSTEREO BALANCE CHECKER

D1, D2-Diode, 1N914 or equiv.LED1, LED2-Light emitting diodeRI, R2 -1000 -ohm resistor, 1/2 -

watt

tion. This circuit may also he adaptedto finding zero beat for hams andSWLs. Omit DI and D2 and connect

the leads of R1 and R2 across thereceiver's speaker terminals. At zerobeat, both LEDs will be dark.

35 Quick Diode Checker

PARTS LIST FORQUICK DIODE CHECKER

B1-9VDC batteryLED1-Light emitting diodeR1 -470 -ohm resistor, 1/2 -wattS1-DPDT switch

HI

BI9V

LED I(:/.,cp

1 TESTSI TERMINALS

0


This not only tells you whether ornot a diode is good, it checks thepolarity for you as fast as you canflick a switch.

The diode under test completes thecircuit through B1, RI and the LED

when inserted in the proper polarity.Switch Si reverses the polarity of thediode under test. A good diode willlight the LED only in one switchposition. An open diode will notlight it in either position. A shorted

diode will light it in both positions.To use the circuit as a polarity indi-cator, connect the diode to the testterminals. The diagrams above referto the polarity of the diode when theLED lights in the switch posilions.

36 Speaker System Expander This neat arrangement lets youconnect multiple speakers to yoursystem's speaker terminals withoutupsetting the impedance match. Thisseries -parallel arrangement of speak-ers exhibits the same impedance as asingle speaker, assuming all speakersare of equal impedance and individ-ually match the rating of the system.

And inasmuch as the bass response ofarrayed speakers is somewhat addi-tive, you will find more bottom toyour sound than any one of thespeakers could have delivered alone.Of course, it takes more power todrive an array than a single speaker,but most modern music systems haveplenty to spare.

37 Watch That Modulation If you own a transmitter and anoscilloscope, this will let you see whatyour signal looks like. A short whipantenna, about the size of a walkietalkie whip (30" or so) picks up asampling of your transmitted signal.DI acts as a detector and couples thedemodulated RF (in other words,your modulation without the carrier)through a coaxial cable to you, oscil-loscope's vertical input.

Resistor RI acts as a variable loadon the signal to control its level as itfeeds to your scope. For an excellentdiscussion of how to read the mean-ing of the pattern that appears onyour oscilloscope with this circuit,

PARTS LIST FORWATCH THAT MODULATION

Cl, C2-.001-uF capac torDl-D:ode, 1N914 or equiv.R1 -50,000 -ohm potentiometer

COAX CABLE PLUG TOMATCH SCOPE

see the Radio Amateur's Handbook,published by the American Radio

Relay League and available in manyelectronics stores.

38 Wire Wringer

SI RI

-BILED I

R2 R3 RS

01

CI

R402

C2

R6

EARPHONES

rd

4CABLE

PARTS LIST FOR WIRE WRINGER

B1-9VDC batteryC1-10-uF, 15VDC electrolytic ca-

pacitorC2-.001-uF, 15VDC electrolytic

capacitorLED1-Light emitting diodeQl, Q2-FET (Field Effect Transis-

tor), 2N2646 or equiv.R1, R2, R5, R6 -470 -ohm resistor,

1/2 -wattR3, R7 -47 -ohm resistor, 1/2 -watt

R4 -220,000 -ohm resistor, 1/2 -wattSl-SPST switch


There you are with your millionconductor un-color-coded cable re-sisting the temptation to hang your-self with it because you can't matchthe ends.

This should make it easier. Usingone long lead of its own or one wire

you've already identified in the cable.clip its other lead to the next wirein the bundle.

Then, with a simple utility ampli-fier or even just a high impedanceearphone at the other end of thecable, listen for the characteristic be -

be -be -beep of the twin UJT relaxa-tion oscillators. Oscillator 01 runs atabout 2 beats a second; oscillator Q2at about 2000 Hz. In addition toringing wires, this novel tone gener-ator can be used as an audio signalinjector for troubleshooting.

39 Wide Range Voltage PilotEl Believe it or not, this simple testerwill verify voltages between 2 and120 Volts, AC or DC-and tell youwhich!

It's easy to understand if you canthink of the filament of a small night -light bulb as being a wirewound re-sistor. It provides the current limitingthat LED 1 and LED 2 need to op-erate safely. And, of course, whenthe voltage at the probe tips is highenough, I1 lights as well.

You can choose different colorsfor LED 1 and LED 2 and the probetips for very quick polarity indica-tions in the case of DC voltages. Andseeing both LEDs glow is quick con-firmation of an AC voltage.

PARTS LIST FORWIDE RANGE VOLTAGE PILOT

11-Bulb, 71/2 watts at 120 -voltsLED1, LED2-Light emitting diode

0

11

LED I

+ LED2

40 The Light TouchEj Here's an intriguing substitute forthat light you're always flicking onfor just a second, then right off again.This touch -actuated switch stays ononly for as long as you need it, justas long as you keep your finger onthe touch plate.

R1 sets the input impedance of thevery sensitive JFET G1 to a very

high 10 Megohms. 01 picks up straysignals coupled through your body tothe touch plate and amplifies to turnon Q2, which turns on lamp driver03. Lamp 11 is any small 12 Voltlamp, such as are found in auto dash-boards.

R4 and CI add a small amount ofhysteresis (delay) to keep the light

from constantly flickering. If a lightisn't what you need to switch thisway, try substituting a relay for II.You may want to raise B1 to 12 or15 Volts.

0SI

81

TOUCHPLATE

RI

01

R2

PARTS LIST FORTHE LIGHT TOUCH

B1-9VDC batteryC1-15-uF capacitorI 1-Any 12 volt lampQ1-FET (Field Effect Transistor),

2N458 or equiv.Q2-NPN transistor, 2N2222,

2N3904 or equiv.Q3-PNP transistor, 2N3906 or

equiv.R1-10-Megohm resistor, 1/2 -wattR2 -47,000 -ohm resistor, 1/2 -wattR3 -120,000 -ohm resistor, 1/2 -wattR4 -470 -ohm resistor, 1/2 -wattS1-SPST switch

41 A Touchy GambleE] Any bets on whether the LEDwinds up on or off when you takeyour finger off the touch plate? Theodds are even with this little bandit.101 ELECTRONIC PROJECTS 1978

Your body acts as an antenna,picking up power line hum and otherstray signals and coupling themthrough your fingertip to the touch-

plate and the input of high pin Darl-ington transistor pair Q1 -Q2. Theiroutput starts bistable multivibrator03-04 flip-flopping faster than the

31

eye can follow. Because it's sym-metrical, the chances of stoppingwith Q3 on or off are equal.

When the multivibrating stopswith Q3 on, it lights the LED. WhenQ3 is off, so is the LED. Now that

you can let an LED call heads ortails for you, you can save your pen-nies for the gum machine.

SI

81

_=_ 9V

TOUCHPLATE

RI R2

SCI

R3

01

b

02

R4

R6 R7

e 03R5

DI i iD2

Re

04

C2

R9

PARTS LIST FORA TOUCHY GAMBLE

B1-9VDCC1-2.2-uF capacitorC2, C3-.01-uF capacitorDI, D2-Diode, 1N914 or equiv.LED1-Light emitting diodeQl, Q2, Q3, Q4-NPN transistor,

2N3904 or equiv.RI, R2-2.2-Megohn resistor, 1/2 -

wattR3 -10,000 -ohm resistor, 1/2 -watt

R4, R8 -1000 -ohm resistor, 1/2 -

wattR5, R9-47,000-ohn resistor, %-

CO wattR6, R7-22,000-ohn resistor, 1/2 -

wattS1-SPST switch

42 Transistor Squelch0 Here's a simple squelch circuit youcan add on to most radios and it'sas versatile as any.

Transistor 01 acts as a noise am-plifier, operating on signals from thereceiver IF. The noise signal is am-plified, then detected by Dl. The re-sultant voltage appears across R3,which acts as a voltage dividernt theinput of switch Q2. When enough

signal -derived voltage reaches 02'sbase, it turns on, switching off thereceiver audio output.

This audio squelching can be ac-complished simply by connecting theinput terminal of the receiver's audiostage to the R5 connection. This isa noise -operated squelch best suitedfor use with FM communications sys-tems. On FM, signals tend to quiet

the ever-present noise, and FM IFsare designed with noise outputs.

For use with AM systems, use theIF or detector signal output as thesquelch input. Locate the -V connec-tion of your receiver's first audio am-plifier, break it, and connect it so thetop of R5. Then increasing signalwill enable receiver audio, and that'swhat squelches are sipposed to do.

+v0

FROMIF CI

RI

R2

C3

THRESHOLDR4

TO

R5

AUD'O PARTS LIST FOR0 TRANSISTOR SQUELCH

Cl, C3-.1-uF capacitorC2-.01-uF capacitorC4-33-uF capacitorC5-47-uF capacitorDl-Diode, 1N914 or equiv.

01

R3

o- I (

QI, Q2-NPN transistor, 2N390402 or equiv.

DI C4 C5R1 -180,000 -ohm resistor, 1/2 -mattR2, R3-10,000-ohn resistor, 1/2 -

wattC2

R4 -680 -ohm potentiometer-v R5 -330 -ohm resistor, 1/2 -watt0

43 IF Amplifier0 This IF module doesn't offer anyselectivity, but it has a tubful of gainto offer, so it's perfect for followingmechanical filters or other highly se-lective stages.

01 through Q5 act as individual32

gain stages, providing a great deal ofoverall gain for the system. R1, Cl.C2 and RFC1 keep the supply lineclearly filtered and by passed to avoidannoying parasitics and other buga-boos of high gain receivers. You can

also use this circuit as a preamplifierfor your test equipment. Oscillo-scopes, counters and the like can be-come supersensitive to help you digeven the really weak signals out ofthe 455 kHz jungles.


+V RIO-O-AAAr-

CI ' C2,-'

FROMFIRSTIFSO

0-v

R3

RFC I

R7

R3 R5

R4

C3

01

C4

02

R6

be

R8

CS

03

Cb

R9

TIO

?RIO R13

C6

e

R11

04

R12

e

05

C70

OUTPUTTO

DETECTOR

OUTPUTTO SQUELCH

C9T NOISE AMP

PARTS LIST FOR IF AMPLIFIERCl, C2, C7, C8, C9-.1-uF capaci-

torC3, C4, C5, C6-.001-uF capacitorC10-.01-uF capacitorQl, Q2, Q3, Q4, G5-NPN transis-

tor, 2N3904 or equiv.R1 -47 -ohm resistor, 1/2 -wattR2, R4, R6, R9, R11 -180,000 -

ohm resistor, 1/2 -wattR3, R5, R8-27000R3, R5, R8 -27,000 -ohm resistor.

1/2 -wattR7 -680 -ohm resistor, 1/2 -wattR10 -10,000 -ohm resistor, 1/2 -wattR12 -6800 -ohm resistor, 1/2 -wattR13 -2200 -ohm resistor, 1/2 -wattRFC1-2.5-mH choke

44 Make Your VOM a TachometerMost of us don't need dashboard

tachometers to drive by. But a tach-ometer can be invaluable as a tune-up aid. And it's a lot handier to haveunder the hood when you need itthere than behind the wheel whereyou can't see it.

But is a tach worth the investment?With this arrangement, there isn't

enough investment to worry about.Pulses from the distributor points

are amplified by 01, limited by DI,coupled by C2, rectified by D2 andD3, and impressed as a voltageacross R5. You could use R5 tocalibrate this circuit to one of yourVOM's voltage ranges, but that oftenisn't necessary. Much of the time, we

arc looking more for changes in en-gine speed than for a specific enginespeed. If you do need to know spe-cific speeds, of course, you can al-ways borrow a known -good tach andcalibrate with R5.

This same circuit can also be ap-plied as a frequency to voltage con-verter for many other purposes.

R 1fahBATTERYPOSITIVE

POINTS-4

R2Syr

R3w.

CI^ R4

e

01

C2

I(

D31,4

DI lt D2 R5

-oVOM-0

BATTERYNEGATIVE

PARTS LIST FORVOM INTO TACHOMETER

C1-2.2-uF capacitorC2-.47-uF capacitorDl-Zener Diode, 9.1V at 1/4 -wattD2, D3-Diodes, 1N914 or equiv.Q1-NPN transistor, 2N3904 or

equiv.R1 -390 -ohm resistor, 1/2 -wattR2, R3 -220 -ohm resistorR4 -1800 -ohm resistor, 1/2 -wattR5 -1000 -ohm potentiometer

45 Transistor Checker

PARTS LIST FORTRANSISTOR CHECKER

131-9 VDC batteryLED1, LED2-Light emitting diodeR1 -1000 -ohm resistor, 1/2 -wattR2 -470 -ohm resistor, 1/2 -wattSl-DPDT switchS2-Momentary push button

switchS01-Transistor socket

81

- 9V

f N PN1

OSI

PNP

RI

S2

Sol

R2

LED I

LED 2 +

NPN PNP

0111L3)


It's pushbutton -easy to check tran-sistors with this tiny marvel. Just plugthe transistor in and push S2. If it'sgood and you set the PNP-NPN switchSi properly, the appropriate LED

will light.Don't know the type? That's okay.

Plug it in and try both Si switchpositions while you watch for theappropriate LED to light. You can

even test diodes using the collector -emitter leads on the socket. The col-lector -emitter leads can also be usedto check continuity.

46 Photoelectric Tattletale How would you like to knowwhether or not the postal personbrought you any post? Or how abouta circuit to start something goingwhenever you put a card in a slot?That's what this little photorelay isall about. Whenever the phototran-sistor sees the LED, it pulls up thebase of relay driver Q2 and pulls inthe relay. Stick something betweenthe LED and Q1 and the relay re-leases. Dl shunts out the relay's in-ductive kickback.

If you point the LED and Q1 inthe same direction, they will act to-gether as a reflective sensor. Then ifanything comes close enough to

PARTS LIST FORPHOTOELECTRIC SOMETHING'S

THERE TATTLETALE

B1-12VDC battery1N914 or equiv.

K1-SPDT relay, 12VDCLED1-Light emitting diodeQ1-Phototransistor, FPT100 or

equiv.Q2-NPN transistor, 2N2222 or

equiv.R1 -150 -ohm resistor, 1/2 -watt

R2 -2700 -ohm resistor, 1/2 -wattS1-SPST switch

bounce the light from the LED backinto 01 (assuming both are kept inthe dark-any light will trigger Q1),

the relay will pull in. The circuit canalso be used without RI and LED1as a light- or no -light -operated alarm.

47 Highway Nightfall Alert When it gets dark out, you don'talways notice the change. So it isn'thard to get caught driving in the darkwithout your headlights on. This littleproject buzzes a friendly reminderuntil you turn the lights on, turn the

car off, or morning comes.K1 turns on with your headlights.

When it's on, it disables the rest ofthe circuit. So a warning can onlysound with your headlights off. Aslong as light strikes 01, Q2 remains

on, holding Q3 off. Voltage dividerR5 -R7 -R8 determines the tarn -onpoint for Q3. Q3 drives K2, whichtriggers a buzzer or other sigiallingdevice. A photoconductor may besubstituted for RI -Q1, if desired.

PARTS LIST FORHIGHWAY NIGHTFALL ALERT

D1, D2-diode, 1N914 or equiv.K1-SPDT relay, 12VDCK2-SPST relay, 12VDCQl-Phototransistor, FPT100 or



eq u iv.

RI, R4, R7 -4700 -ohm resistor,1/2 -watt

R2 -560 -ohm resistor, 1/2 -wattR3, R5, R8 -10,000 -ohm resistor,

1/2 -wattR6 -220 -ohm resistor, 1/2 -watt

48 Level Detector There are times when voltages areallowed to vary widely in a givensystem, so long as they do not exceedsome preset limit. This might happen34

in speed or temperature controls, forexample, or even simple R -C timers.

This circuit is based upon a two -transistor comparator. An input volt-

age (which must not exceed B1 ineither positive or negative value) at03 is compared to a preset dividerR3 -R4 at Q2. When the input volt -


IL

0

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101 ELECTRONIC PROJECTS 1978CIRCLE 8 ON READER SERVICE COUPON 37

age equals or exceeds the preset volt-age, 01 turns on, driving pilot lampII on. Resistor RI permits the use ofa #47 type lamp with a standard 9volt battery.

PARTS LIST FORLEVEL DETECTOR

B1-9VDC batteryC1-.1-uF capacitorDI-Diode, 1N914 or equiv.11-Bulb, #47 -typeQ1-NPN transistor, 2N2222 or

equiv.Q2, Q3-PNP transistor, 2N3906

or equiv.R1 -27 -ohm resistor, 1/2 -wattR2 -5600 -ohm resistor, 1/2 -wattR3 -100,000 -ohm resistor, 1/2 -watt

OSI

81

RI

II

DI

02b

R2

R5

R3

R4LEVEL 03

R6

CI

R4-1-Megohm potentiometerR5 -3300 -ohm resistor, 1/2 -watt

1 NPUT0

R6 -1000 -ohm resistor, 1/2 -wattS1-SPST switch

49 Sensitive SquelchD The high sensitivity of this circuitis due to the use of a JFET at 01.With R2 at just 47K, the high impe-dance input JFET is just loafingalong. (If you need more sensitivity,try values up to 10 Megohms forR2). The signal input from a detectoror other audio signal or noise sourcewithin your circuit is applied though

voltage divider RI and Cl to the gateof 01. 01 amplifies this signal andpasses it through C2 to D1 -D2, whichconvert it to a DC voltage. This isused to drive switch Q2 on, with adelayed turn-off provided by R7-05.R6-05 delay turn -on. These delaysprevent picket -fencing.

FM squelches are noise operated,

where the more noise there s, theless signal. So an FM squelch mustdisable with increasing input. In anFM system, 02 would shunt theaudio signal to ground at the firstaudio stage. An AM system would bedesigned to enable with increasinginput. In an AM system, Q2 wouldbe used.

PARTS LIST FORSENSITIVE SQUELCH

C1-33-pF capacitorC2-.05-uF capacitorC3-4.7-uF capacitorC4-10-uF capacitorC5-.22-uF capacitorD1, D2-Diode, 1N914 or equiv.Ql-FET (Field Effect Transistor),

2N5458 or equiv.Q2-NPN transistor, 2N2222 or

equiv.R1 -100,000 -ohm potentiometerR2 -47,000 -ohm resistor, 1/2 -wattR3 -12,000 -ohm resistor, 1/2 -wattR4 -3300 -ohm resistor, 1/2 -wattR5-3.3-Megohm resistor, 1/2 -wattR6, R7 -1000 -ohm resistor, 1/2 -

waft

+ V 0

SIGNAL INO-

CI

RISQUELCH

LEVEL

V 0

R3

C2

SWITCHOUTPUT

D2 0IN914

R

R

C4

DI11.4914

5

R6

02

R7

C8

50 Idiot's Delight Sometimes the dashboard idiotlights aren't warning enough thatsomething's gone awry. Bright sun -38

light, a burned -out lamp or simplya lack of attention can obviate De-troit's brilliant efforts. But this sim-

ple gizmo adds a buzz to their blink,plus a luxurious extra. 121, Cl and01 give you about 7 seconds when


you first get into the car to get your-self going and let the idiot lightsdouse before the buzzer can sound.

D1 -D5 can be added to or sub-tracted from to fit the number ofdashboard dimwits on your car. Youcan use something other than a buz-zer, if you wish, to help you keepfrom getting confused about yourdoor being ajar, your key being in,your lights being left on, or your seatbelt being unfastened.

PARTS UST FORIDIOT'S DELIGHT

C1-15-uF capacitorDI, D2, D3, D4, D5, D6-Diode,

1N914 or equiv.Q1-FET (Field Effect Transistor),

2N5458 or equiv.R1 -470,000 -ohm resistor, 1/2 -watt

TOUNGROUNDEDSIDE CFDASHBOARDIDIOT LIGHTS

51 S111L's Low Band ConverterEver listened in on the long waves,

from 25-500 kHz? It's easy with thissimple converter. It'll put those longwaves between 3.5 and 4.0 MHz onyour SWL receiver.

01 acts as a 3.5 MHz crystal oscil-

lator, mixing the crystal frequencywith the long wave input from theantenna and forwarding the mix toyour receiver.

Ll is a standard broadcast loop -stick antenna coil. The crystal is

available from many companies bymail order, or is likely to be at aham radio store near you. You couldalso use a 3.58 MHz TV color crystal.

Adjust the slug of L1 for your bestsignal after tuning to a strong station.

XTAL

C5

)H0 OUTPUT TO RECEIVERUSE COAX.

PARTS LIST FORSWL'S LOW BAND CONVERTER

B1-9VDC batteryCl, C4-470-pf capacitorC2-.1-uF capacitorC3-.001-uF capacitorC5-50-pf capacitorLl-Loopstick coilQ1-PNP transistor, 2N3906 or

R1 -470,000 -ohm resistor, 1/2 -wattRFC -2.5 mH chokeS1-SPST switchXTAL-3.5 MHz crystal

52 Staircase Generator This circuit can be used as a stair-case generator, a ramp generator, ora primitive frequency -to -voltage con-verter. Each pulse appearing at theinput adds to the voltage at the out-put in step fashion, the height of thestep being about the height (voltageamplitude) of the input pulse.

The pulses are passed through Q1and Q2 and integrated in C2. Thistype of circuit can be used to set alevel, based on the length of a con-stant -amplitude pulse train at its in-put. In this fashion, it lends itself toremote control applications.

OUTPUT

PARTS LIST FOR STAIRCASE GENERATORCl, C2-2.2-uF capacitor or equiv.QI, Q2-NPN transistor, 2N2222 R1 -10,000 -ohm resistor, 1/2 -watt


53 Sidetone Oscillator CW (continuous wave, the form ofmodulation involving a simple turn-ing on and off of the RF carrier) isthe simplest way for a beginning hamto transmit to his fellow hams. Andthe famous Morse Code is how hegets his message across. But Morse is

a lot easier to send if you can hearwhat you're sending. This circuit letsyou do just that.

A short length of wire near thetransmitter picks up RF as it's trans-mitted and acts as the antenna for ourcircuit. This RF is detected by D1,

smoothed by C2, and used to turn 01on and off, following the transmittedsignal exactly. 01 switches the posi-tive supply through R2 to beep os-cillator Q2 through the center tap ofTI. The values shown produce apleasant, easily distinguishable tone.

CI

ANT

01+

RFCI

C2

BI

TONE e

RI

R2

R3

0C 3 C4

R4

e

02

RS

TI

SPKR

PARTS LIST FORSIDETONEOSCILLATOR

B1-9VDC batteryC1-50-pf capacitorC2-470-pf capacitorC3, C4-.01-uF capacitorDI-Diode, 1N914Ql, Q2-NPN transistor, 2N2222

or equiv.R1 -470,000 -ohm resistor, 1/2 -wattR2 -5000 -ohm potentiometerR3 -4700 -ohm resistcr, 1/2 -wattR4 -100,000 -ohm resistor, 1/2 -wattR5 -100 -ohm resistor, 1/2 -wattRFC1-2.5-mH chokeT1-1000; 8 -ohm transformer,

centertappedSPKR-8-ohm speaker

54 Overvoltage Protector Too high a voltage can damageany number of electronic compo-nents. Many other components canwithstand high voltages, but only fora limited time. This circuit provideseither protection against too muchvoltage in much the same way a cir-cuit breaker protects against toomuch current, or a warning that anovervoltage condition is occurring.

In the Breaker position, power isapplied to the protected circuit onlyso long as relay K I is not energized.K1 will energize whenever the inputvoltage exceeds the Zener voltage ofdiode DI, because above its zenervoltage, a reverse -biased Zener diodelike this one will conduct. In theBuzzer position, power remains ap-plied to the circuit through the relayitself. When an overvoltage is present,

POWERSI

BUZZER

BREAKER

DI

+ POWERo TO

CIRCUIT

PARTS LIST FOROVERVOLTAGE PROTECTOR

Dl-Zener diode; 9.1 Volt at 1/4 -

wattD2-Diode, 1N914 cr equiv.K1-Relay; 12 -volt, coil at least

600 -ohmS1-SPDT switch

the relay pulls in, disconnecting itself,which allows it to release and re-es-tablish connection, which causes it topull in and break connection and soon-exactly the action of a buzzer.

And that's exactly the sound the relaywill make-with enough noise gener-ated to carry the buzz into the audioand IF circuits of almost anythingconnected or nearby.

55 Cigar Lighter Power When you want to run your radioor some other low -power 9 volt de-vice in your car, here's a way you cando it and save on batteries. This is asimple shunt regulator using a 2N-2222 and 9.1 Volt Zener. With a

2N2222, you can power devices re-quiring as much as 800 ma; to drivedevices requiring more current, use a2N3055. With either device, unlessthe equipment you are driving is verylow power, use a heat sink.

There are two easy ways to deter-mine how much current your transis-tor radio or whatever draws (more tothe point, whether or not the amountof current it draws will necessitateheat sinking). One is to connect your


VOM in series between one of thebattery posts and its associated clipconnector. You will want to checkthe maximum amount of currentdrawn. Another way is to connectthis circuit for only a few secondsand touch 01 with your finger. If itgets too hot to hold your finger on,use a heat sink. You may want to usea heat sink in any case. You may alsowant to include a small fuse (try 1/2amp).

PARTS LIST FORCIGAR LIGHTER POWER

C1 -100-u F capacitorDl-Zener diode, 9.1 V at 1/4 -watt

Q1-NPN transistor, 2N2222 orequiv.


+11-16FROMCAR REGULATED 9

VOLTSOUT

56 Two Transistor Radio[ Crystal sets are a lot of fun. Trou-ble is, their little earphones aren't.This is a nice little compromise, aloudspeaking crystal set.

L I is a standard broadcast loop -stick antenna, Cl a standard broad-cast band variable capacitor. Chan-ces are you can pull both parts fromthe carcass of an old radio. For anantenna, try attaching a length of

wire with an alligator clip to any ex-posed metal part on a telephone, like

-the finger stop of a dial phone. Youcan also try window frames, bed-springs or bed frames.

(If you do construct any kind ofoutdoor antenna, keep far away frompower and telephone lines and installa good lightning arrestor with a soundground lead. It's also a good idea to

ground the antenna when you're notusing ,it, and not to use it in badweather.) LI and Cl form the tunedcircuit that tunes the radio. Diode DIacts as a detector. For better per-formance, substitute a germaniumdiode (such as a IN34 or IN60) ora hot carrier diode. 01 and Q2 pro-vide the amplification needed to drivethe speaker.

PARTS LIST FORTWO -TRANSISTOR RADIO

B1-9 VDC batteryC1-365-pF variable capacitorC2-.1-uF capacitorDl-Diode, 1N914 or equiv.Ll-Standard broadcast loopstick

antennaQ1-NPN transistor, 2N3904 or


equip.R1 -100,000 -ohm resistor, 1/2 -wattR2 -4700 -ohm resistor, 1/2 -wattSI-SPST switchT1 -500:8 -ohm matching trans-

formerSPKR-8-ohm speaker

ANT

LI

C2

TUNE

CI

RIR2

e

01

e

02

C

TI

SPKR

SI

B

57 Fox Hunt TransmitterPARTS LIST FOR

FOX HUNT TRANSMITTER

B1-9 VDC batteryCl, C3-.001-uF capacitorC2-260-pF variable capacitorQ1-NPN transistor, 2N2222 or

equiv.R1 -10,000 -ohm resistor, 1/2 -wattR2 -470 -ohm resistor, 1/2 -wattR3 -47,000 -ohm resistor, 1/2 -wattRFC1-2.5 mH radio frequency

chokeSI-SPST switchXTAL-crystal cut for the 49 MHz

band

1

RI

X TA L

SCI

b

e

ANT

01

R2

RFC I

C 2

FRED

0

0 SI

-C3 81

R3


El Ever been to a radio foxhunt?Everyone brings a portable radio anda very directional antenna and triesto find where a small transmitter hasbeen hidden. First one to find it wins.And here's just the transmitter tobring this old ham radio game to therest of us. Transistor 01 acts as a

crystal oscillator in the new 49 MHzwalkie-talkie band. The output of thisoscillator is very low, and no licenseis required if you keep your antennadown to just a few inches in length. Trimmer capacitor C2 lets you

tweak the frequency of this transmit-ter right into the middle of the chan-

nel. Use a walkie talkie and listen forcarrier; when you hear it best, you'reon frequency. This same circuit canbe used as a wireless mike. Connecta carbon microphone, like an oldtelephone handset mike, in series withR2 and ground.

58 Mike Clipper0 If you were to look at your voiceon an oscilloscope, you would see avery ragged waveform with a lot of"hot" peaks. These peaks are notvery valuable in terms of gettingacross the words you're saying, butthey can affect the average poWer ofyour voice. This circuit lets you in-crease the amount of 'sock (voicepower) in your voice when placedbetween the first and second mikeamp stages of a PA or transmitter.

PARTS LIST FOR MIKE CLIPPER

C1-100-uF capacitorC2-.1-uF capacitor81, 82-Diode. 1 N914 or equivR1 -10,000 -ohm potentiometer

Clipping control R1 sets the levelat which clipping begins. DI and D2then knock out the most positive andmost negative half volt of voice sig-nal, killing the peaks.

C2

RI

INPUTFROMMIKEPREAMP

59 Conference Mike MixerD After trying for several years, Ifinally came to the conclusion thatthere's no way to tape record a con-ference or roundtable discussion withone mike. This scheme allows four,and can be expanded.

JFET transistor 01 is used ...Is a

high -to -low impedance converter. Theinput of the amplifier -impedance con-verter is between about 1/2 and 1

Megohm as shown, but can be in-creased by increasing R5-8 to 10Megohms if necessary. The output isabout 1000 ohms impedance, but can

be increased or decreased by chang-ing the value of R9. Use 560, 620 or680 Ohms, for example, to feed a600 Ohm input; use 100K-1 Meg fora high impedance input. You willwant to use shielded cable on all in-put and output leads, of course.

CI

0 )I LEVEL

MIC I

RI M0- R5

C2

0- )F1 LEVEL

R2MIC 20

MIC 30

R3

R6

LEVEL

C4

R7

0 )1 LEVEL

MIC 4 R41-. vv.O R8

9

01

C6

C

/77

R10

Si

0

cr °131

/77

PARTS LIST FORCONFERENCE MIKE MIXER

B1-9 VDC batteryCl, C2, C3, C4-.1-uF capacitorC5, C6-10-uF capacitorRI, R2, R3, R4-1-Megohm poten-

tiometer, audio taperR5, R6, R7, R8-2.7-Megohm

resistorR9-10-Megohm resistorR10 -1000 -ohm resistorQ1-FET (Field Effect Transistor),

2N5458 or equiv.S1-SPST switch

60 Nine Volt Neon0 Wait a minute! Don't neon lampsneed ninety volts to fire? Neon lamp11 gets that kind of voltage-possiblymore, depending on the state of yourbattery and the actual value of T1.Because T1 and Q1 act together toform a DC -to -AC converter.42

R1 and CI set the frequency ofUJT oscillator Q1 to about 1000Hertz. Actually, any frequency nearthe middle of the audio range (300-5,000 Hz) would be okay, so, feelfree to take some liberties with R1and Cl's values. That's because those

are the frequencies that are easiest tohandle for Ti, a transistor -type inter -stage transformer. You may findsomething suitable in one of your oldjunker radios or amplifier boards.

TI acts as a step-up transformer,raising the input voltage to a level


where it can fire the NE -2. You maynot need R3, but it limits the amountof current that 11 has to handle. Foran interesting variation, use a largeelectrolytic capacitor between about

10 and 1000 microfarads for Cl, orincrease the value of R1 to 1-19Megohms (this won't work with everyUJT you try). This will cause theUJT oscillator to pulse at a rate some-

where between a few pulses a secondand a pulse every few seconds. You'llknow because Il will flash with everypulse.

PARTS LIST FORNINE VOLT NEON

B1-9 VDC batteryC1-.1-uF capacitor11-Neon bulb, NE -2 typeQ1-UJT (Unijunction Transistor),

2N2646 or equiv.R1 -10,000 -ohm resistor, 1/2 -wattR2 -100 -ohm resistor, 1/2 -wattR3 -470,000 -ohm resistorS1-SPST switchT1-Transformer, 10,000 -ohm pri-

mary and 100,000 -ohm second-ary

SI

61 Low Impedance Mike Mixer There's no reason to limit yourselfto using just one mike at a time whenyou have this circuit to help you withyour recording-or any other purpose.You can set up a small microphonemixing console. For pizzazz, you

could use slide -style controls for RI -4; for miniaturization, you could usetiny trimmer resistors.

Each control adjusts the level of itsassociated microphone as they aremixed together. This gives you the

veriatility of making one mike louderor softer without upsetting the levelof any of the others. Transistor 01provides a bit of amplification to com-pensate for losses in mixing, and toassure good level at the input.

CI

LEVELCS

O

PARTS LIST FORLOW IMPEDANCE MIKE MIXER

B1-9 VDC batteryCl. C2, C3, C4-.1-uF capacitorC5-10-uF capacitor

0-

MIC I

)

R5

LEVEL

C2R90

MIC 2 R2R6 Q1-PNP transistor, 2N3904 or

C30I equiv.

LEVEL 81 R2, R3, R4-1-Megohm po-0MIC 3 -.entiometer, audio taperR3

R7 R5, R6, R7, R8 -100,000 -ohm re-sistor, 1/2 -watt

C4

LEVEL/77 R9 -15,000 -ohm resistor, 1/2 -watt

S1-SPST switch0MIC 4 R4

R8

62 Blinking Neon Night Light UJT oscillator 01 feeds a tone ofabout 2000 Hz to transistor trans-former Ti, which steps it up to alevel where it can fire a neon lamp,11. But the circuitry to the right ofT1 does something a little more in-teresting. Diode Dl (which makesthis circuit a true DC -to -DC con-verter) rectifies the AC signal and ap-plies it to C2. Resistor R3 limits the101 ELECTRONIC PROJECTS 1978

rate at which C2 can charge. WhenC2 finally reaches a voltage highenough to allow 11 to light, I1 firesand discharges C2, starting the ac-tion over again.

Use a 200 PIV diode for DI anda 250 Volt (or more) capacitor forC2, or just make sure both are ratedfor more voltage than appears acrossthe secondary of T I. DI, C2, R3 and

II form a circuit called a relaxationoscillator. Interestingly, that is ex-actly the kind of oscillator 01 is.

Both rely on some R -C combinationcharging a capacitor at a restrictedrate, then discharging it at some de-termined time. Just as you can mul- tiply the values of RI and Cl to geta fix on the frequency of 01 (f =1/R ICI, more or less), you can mul-

43

PARTS LIST FORBLINKING NEON NIGHT LIGHT

SI

- BI

RI

CI

T

01

B1-9 VDC batteryC1-.05-uF capacitorC2-.5-uF electrolytic capacitor,

R2 450 VDCDI-Diode, 1N4001 or equiv.Q1-UJT (Unijunction Transistor),

b I 2N2646 or equiv.

b2

R1 -10,000 -ohm resistor, 1/2 -wattR2 -100 -ohm resistorR3 -470,000 -ohm resistor, 172 -

wattS1-SPST switchT1-Transformer, 10,000 -ohm pri-

mary and 100,000 -ohm second-ary

tiply R3 and C2 to determine thatthe NE -2 will blink about four timesa second. You can also connect thecircuit to the right of T1 to 110 Volthousehold power tc see the sameaction.

63 Low -Power Light Blinker[1] Need a flashing pilot light insomething? A blinking warning lightfor when some special condition oc-curs? Here's an easy way to addblinking action to a #47 lamp.

UJT 01 is used as a relaxationoscillator delivering pulses at speeds

varying from about five per second toabout 11/4 seconds -per pulse. 02 and03 are arranged in a Darlington con-figuration to reduce loading on Qwhile providing drive for Il. ResistorR4 serves several purposes. It dropsthe voltage across II, a 6 -volt lamp,

permitting it to be used with a 9 Voltbattery. It limits the current throughI1 and the system, prolonging bothbattery and bulb life. For a brighterblink, reduce the value of R4. For aslower blink rate range, increase thevalues of either R2 or Cl.

PARTS LIST FORLOW -POWER LIGHT BLINKER

B1-9 VDC batteryC1-100-uF capacitor11-Pilot light, #47 typeQ1-UJT (Unijunction Transistor),

RI

R2

2N2646 or equiv. R3

Q2, Q3-PNP transistor,or equiv.

2N39060 1

R1, R2 -2200 -ohm resistor, 1/2 -

wattR3 -10,000 -ohm resistor, 1/2 -wattR4 -27 -ohm resistor, 1/2 -wattS1-SPST switch

bl

b2

02

CI

03 SI

co

R4

64 Three -Way Switch Demonstrator

PARTS LIST FOR THREE-WAYSWITCH DEMONSTRATOR

SI S2

RI

81B1-9VDC batteryLEDI-Light emitting diodeR1 -470 -ohm resistor, 1/2 -watt

SI S2

EXCLUSIVE NORLED (IzON, z OFF

00

0I

1

0Si, S2-SPDT switch LED I O1

1

0I

0


If you live in a house with a stair-way, you've probably experiencedthis circuit before. If the light is on,flicking either switch will turn it off.If the lights is off, flicking eitherswitch will turn it on. Usually, in a

home, one switch will be at the bot-tom of a stairway, the other at thetop. The switches then operate a parof lights, in tandem.

In logic, his configuration is calledan Exclusive nor. It does the oppo-

site of what an exclusive or circuitwould do. In an exclusive or circuit,the output is true (=1=on) if eitherbut not both inputs (the switches)are true. The chart shows the TruthTable for an exclusive nor circuit.

65 Audio Utility Amp[1] This circuit may look familiar ifyou're in the habit of glancing at theschematics of your portable radiosand recorders. This is a very popularway of getting a signal to a speaker.Transistor 01 acts as a driver forcomplementary pair Q2 and 03. Q2and 03 take turns conducting as theyfollow the input signal, so they candeliver a healthy signal through C2 to

T1. T1 is suggested to reduce theloading that a low speaker impedancewould cause if connected directly be-tween C2 and ground; a higher im-pedance speaker or headphone couldconnect directly.

You can also use this c rcuit as asignal tracer to listen in on what'shappening inside some of the othercircuits on these pages. Just clip a

lead between the minus leads of bothprojects and use one lead of a .01microfarad capacitor in series with theinput as a probe.

PARTS LIST FORAUDIO UTILITY AMP

B1-9 VDC batteryC1-15-uF electrolytic capacitor,

15 VDC (or greater thanneeded)

C2-100-uF electrolytic capacitor,15 VDC (or greater thanneeded)

Ql, Q2-NPN transistor, 2N3906or equiv.

Q3-PNP transistor, 2N3906 orequiv.

R1-1-Megohm potentiometerR2 -270,000 -ohm resistor, 1/2 -wattR3 -1200 -ohm resistor, 112 -watt


Sl-SPST switchT1 -500:8 -ohm matching trans-

formerSPKR-8-ohm speaker

66 A VOM Thermometer Almost all electronic componentschange characteristics as temperatureschange. In the case of silicon diodes,like the 1N914, the characteristic thatchanges is the amount of forwardvoltage drop.

Diodes aren't perfect conductors,you see, because they must take ad-vantage of the bias (voltage) acrossa semiconductor junction (the placewhere the two different kinds of semi-conductor material, p and n, meet)in order to operate.

Almost every semiconductor deviceshows a junction voltage drop ofabout 1/2 Volt when forward biased,as the diodes here are. But the exactamount of that voltage drop changeswith temperature.

So if you string eight diodes inseries, like these, and measure thevoltage across the string on the 5 Voltscale of your VOM, you'll see thevoltage varying up and down around4 Volts as you change the tempera -101 ELECTRONIC PROJECTS 1978

ture the diodes are exposed to.You could calibrate a separate

meter to give you actual degree read-ings, but for many purposes, justknowing the temperature is changingis enough.

PARTS LIST FORA VOM THERMOMETER

B1-9 VDC batteryD1, D2, D3, D4, D5, D6, D7, D8,

D9-Diode, 1N914 or equiv.R1 -4700 -ohm resistor, 1/2 -watt

S1-SPST switch

VOM5 VOLT RANGE

DI

D2

D3D4

05

D6

D7

08

45

67 Logical OR Demonstrator In digital logic, an OR statementis true if any one of the statementsleading to it is true. Parallel switchesare a good analogy for the OR logicfunction. If any of the parallelswitches are on (=true="1"), theL.E.D. turns on. While this circuit

demonstrates the operation of a "two -input OR gate," you may add asmany parallel switches as you like todemonstrate the action of "wider" ORgates.

OR gates are very widely used inalarm circuits, for example, where an

81

SI

S2

OFF = 0ON= I

ORSI S2 LED LED 1 4-

00

0 0

RI

alarm should be sounded wheneveranything occurs at any one of theseveral inputs. The chart of numbersis known as a "Truth Table." Thecolumns at the left identify the statesof the various inputs, the column atthe right the state of the output.Compare the results (right column)of this Truth Table with the resultsof other types of logic and you willsee why digital logic systems can beso versatile.

The nice thing about this circuit isthat it's so visual. You'll find that it'sso much easier to understand digitallogic when you can watch what's hap-pening rather than reading about it.

PARTS LIST FORLOGICAL "OR" DEMONSTRATOR

B1-9 VDC batteryLED1-Light emitting diodeR1 -470 -ohm resistor, 1/2 -wattSi, S2-SPST switch

68 Logical NAND DemonstratorL NAND is logic shorthand for "NotAnd." So a NAND gate has an out-put of 1 only when an AND gatewould not. Compare the right column(results, or output) of an AND gatetruth table to that for the NAND gateabove and you will see that they areexactly opposite.

Here, the L.E.D. will turn on onlyif the two switches are not bothturned on. Be careful that the seriescombination of SI and S2 can shortout only the L.E.D. and not RI aswell or your battery will not last morethan a few seconds. R I limits the cur-rent drain on the battery to about 20milliamps.

PARTS LIST FORLOGICAL "NAND"DEMONSTRATOR

B1-9 VDC battery RI -470 -ohm resistor, 1/2 -wattLED1-Light emitting diode Si, S2-SPST switch

NANDSI S2 LED

0 0 I

0 I 1

I 0 I

I I 0

69 Easy Instrument CalibratorL How accurate is your VOM? Youroscilloscope? Your other voltage -measuring test gear? You can find outin seconds with just these two parts.

You can use any Zener you haveon hand. Of course, the calibrator isonly as accurate as your Zener, andyour input voltage has to be greaterthan your Zener voltage. For a wider46


PARTS LIST FORR

OUTPUTEASY INSTRUMENT CALIBRATORZENERDl-Zener diode; 9.1 -volt at 1/4 - INPUT I VOLTAGE

watt 10 -18 VOLTS

R1 -1000 -ohm resistor, 112 -watt 0

range of input voltages, use Ohm'sLaw to calculate the maximum safeZener current (I=P/E, but use only

about half the rated I) and the valueof R 1 (The maximum input voltageminus the zener voltage, all divided

by the Zener current). You'll know ina flash how your meters are doing, andyou'll be glad you do.

70 Logical AND DemonstratorU In digital logic, an AND statementis true only if all parts of the logicleading to it (its inputs) are all true.If we take "true" to mean "on", alogic state we define as "1" (and nottrue = off = 0), we can see that aseries switch configuration is a goodway to illustrate the AND logicalstatement.

In integrated circuit logic, insteadof actual mechanical switches, tran-sistors are used as switches. Speci-fically, this circuit demonstrates theaction on a "two -input AND gate."Only if both switches are on will theL.E.D. turn on. Similarly, you canexpand the demonstrator to demon-strate as many inputs to an AND gateas you have switches to connect inseries.

BI

Si

ANDSi 52 LED

00

0 000

Once again, we present the "truthtable" of this particular circuit whichwill tell you exactly what's happeningand when. Truth tables are often usedin digital design, and can be indispens-able. Depending on the device they canbe quite long.

PARTS LIST FOR_OGICAL "AND" DEMONSTRATOR

B1-9VDC batteryLED1-Light emitting diodeR1 -470 -ohm resistor. 1/2 -watt

Si, S2-SPST switch

71 Logical NOR Demonstrator Just as the output of a NAND gateis the opposite of that for an ANDgate, this NOR gate produces resultsopposite those of an OR gate.

LED1 will turn on when neither Sinor S2 are on.

A NOR gate is a good way tohandle a failsafe system in which acircuit cannot operate unless all sys-tems are "go"; in other words, if anyof the inputs are on, the system can-not be.

This truth table compares the op-eration of different types of logicgates:Think of 0=off=not true,1 =on=trueDigital logic is certainly in the fore-

front of modern electronics. Circuits

BINOR

SI S2 LED

o 0 I

o I 0I 0 0I 0 0

such as this NOR Demonstrator canhelp to prepare you in understandingcomplex circuitry. The principles youlearn remain the same as in actualdigital circuitry-only the methodof achieving demonstrable resultschanges.

PARTS LIST FORLOGICAL "NOR"DEMONSTRATORB1-9 VDC batteryLED1-Light emitting diodeR1 -470 -ohm resistor, 12 wattSi, S2-SPST switch

72 "555" Loudspeaker Uncontested champ of the beep.and boop brigade is the beautifullyversatile "555" series of timer ICs.For clicks, squeaks and squawks,more and more circuits ask for them,and more and more experimenters en-joy playing with them in new designs.But, by itself, the 555 doesn't put outas much signal as many of us wouldlike, requiring a boost somewhere be101 ELECTRONIC PROJECTS 1978

PARTS LIST FOR"555" LOUDSPEAKER

Q1-PNP transistor, 2N3906 orequiv.

R1 -5C00 -ohm trimmer poten-tiometer

SPKR-8-ohm speaker

0555

OUTPUT(PIN 3:

47

fore it can drive a speaker. Here, theboost and the speaker come together.

01 acts as an amplifier and

speaker driver, working directly fromthe 555 output (pin 3) through alevel control, RI. You may wish to

substitute a fixed value or eliminateR I entirely.

73 "555" Switch Hitter,L1 The "555" is a very versatile timerwhen you need a time delay or anykind of regular timed event. But ifyou try to draw more than 100 or200 milliamps through it, you'll soonbe drawing a blank and a new 555from your parts drawer. With thesesimple additions, you can draw asmany amps as your relay's contactswill carry. 01 acts as a relay driver,triggered by the output of the 555(pin 3) through a 1000 Ohm re-sistor (R I ). Relay K I can he drivenfrom the 555's power supply (choosean appropriate coil voltage for K1)or from a separate positive powersupply if the 555's supply can't

PARTS LIST FOR"555" SWITCH HITTER

V-0A---0

DI-Diode, 1N914 or equiv. DI KIQ1-NPN transistor, 2N2222 or

equiv.555

R1 -1000 -ohm resistor, I/2 -watt OUTPUT (PIN 3)K1-Relay, (rated at least equal to

system voltage)01

RI 46.

0

handle the extra load. Q2 can handleup to 800 milliamps itself, so anyrelay coil that draws less than that

(100this)loads

Ohms or so more than satisfieswill work fine. Similarly, othercan be substituted for Kl-Dl.

74 Wrong -WayBattery Protectorri Want to ruin an expensive pieceof solid state equipment? Just hookthe battery or supply up backwards.But by adding these four diodes toyour equipment, you can say goodbyeto backwards forever. This diode ar-rangement is one you may recognizeas a full wave bridge. In power sup-plies, it's used to rectify both halvesof the AC waveform.

Here, it makes sure that no matterwhich way you connect the battery,the positive and negative supply ter-

PARTS LIST FORWRONG -WAY BATTERY

PROTECTOR

DI, D2, D3, D4-Diode, 1N914 orequiv.

minals in your equipment get the are introduced, your equipment will choose your diodes so they're ratedright polarity voltage. Remember, be getting about a volt less than your for all the current your circuit willsince the forward bias of two diodes battery is delivering. And remember, draw.

75 Old Crowbarr11 Fuses protect your circuits by re-acting to too much current. A crow-bar is a special kind of protectivecircuit that blows your fuse whenthere's too much voltage. It puts astop to everything, including potentialdamage. This crowbar works by us-ing the SCR as a dead short across

the supply leads, which blows thefuse. Your SCR should be rated fora little more current than the fuseis rated for.

When a voltage over the rating ofZener DI occurs, capacitor Cl quick-ly charges to trigger SCR1 into con-duction (turn it on), which shorts

PARTS LIST FOR OLD CROWBAR

C1-22-uF, 16 VDC electrolytic ca-pacitor

Dl-Zener diode, 9.1 -volt, 1/4 -wattSCR1-See text 0

FUSE

SCR

DI

cl

0


the supply and blows the fuse. Un- curate as the components, and it however, for many applications, itfortunately, the circuit is only as ac - isn't easy to change the trip point; can save a lot of grief.

76 Add An AntennaTrimmer One part? That's all, but it canmake a big difference in your short-wave listening. The American RadioRelay League's ARRL Handbook,the ham operator's "bible," can helpyou understand the complex natureof radio waves and how this circuit(is one part a circuit?) helps yourantenna match your receiver at anygiven frequency.

But for right now, all you need toknow is that when you add this trim-

mer (or connect it to these leadsthrough coax, but only a very shortlength), you can adjust it to makeyour receiver really hot wherever it's

tuned. It works by helping your re-ceiver take advantage of all the sig-nal your antenna can pick up. Tryit and see.

PARTS LIST FORADD AN ANTENNA TRIMMER

77 Adjustable Crowbar This crowbar circuit takes advan-tage of the electrically well-definedswitching point of UJT (unijunctiontransistor) 01. Q1's actual trip pointvoltage is set by trimmer R4. The01 circuit is isolated from the loadby DI. When Q1 conducts, it trig-

gers SCR1, shorting the supply andblowing the fuse. Choose SCR1 tohandle more than the rated fuse cur-rent at the maximum supply voltage.

To test for your trip point (whensetting it, for example), disconnectthe LOAD. Substitute a lamp of the

proper voltage (the supply voltage ora little more) for the fuse. Set thevoltage at the supply voltage termi-nals for the trip point you desire,then adjust R4 until the test lamp justlights.

PARTS LIST FORADJUSTABLE CROWBAR

C1-.02-uF capacitorC2-2.2-uF capacitorDl-Diode, 1N914 or equiv.R1 -47 -ohm resistor, 1/2 -watt

FUSE

R2 -330 -ohm resistor, 1/2 -wattR3 -3300 -ohm resistor, 1/2 -wattR4 -10,000 -ohm trimmer poten-

tiometerSCR I

Q1-UJT (Unijunction Transistor),2N2646 or equiv.

SCR1-See textSUPPLY

0

DI

R2

bI

b2LI

RIIITCI

R3

C2

R4ADJ.

TO LOAD

0

78 Noise GeneratorPARTS LIST FOR

NOISE GENERATOR

B1-9 VDC batteryC1-.05-uF capacitorC2-220-uF capacitorC3-.005-uF capacitorR1-1-Megohm resistor, 1/2 -wattR2-1.8-Megohm resistor, 112 -watt

R3, R5 -150 -ohm resistor, I/2 -wattR4 -120,000 -ohm resistor, 112 -wattR6 -56,000 -ohm resistor, 1/2 -wattQl, Q2-NPN transistor, 2N3904

cr equiv.S1-SPST switch


Audio buffs often refer to theirsystems as having color or tempera-ture. One that is rich in low endresponse is said to be warm and red;a bright high end on a system meansit's cool and blue.

The mixture of all these character-istic colors is white, and white noisegenerators produce a whooshing

shound that is randomly distributedthroughout the spectrum. Likewise,pink noise generators are just a bitwarmer. This simple noise generatoris one we might call off-white. Ittakes advantage of the junction noisegenerated in a reverse -biased semi-conductor junction (here, a base -to-emitter junction in NPN transistor

01).The noise generated by current

through Q1 is amplified by Q2 andmade available at the output. For asimple demonstration of tonal color-ing, patch this noise into your soundsystem and see how manipulatingyour tone controls alters the natureof the noise your hear.

79 Let There Be Light Whether or not this makes sensefor you depends on you. This is apilot light that you can use with bat-tery operated equipment. Connect itjust after the power switch and it willbe on whenever the equipment is on.Of course, this adds about 20 milli -amp additional current drain to a cir-cuit powered by a 9 Volt battery, andthat could shorten your battery life.

But if you tend to forget that thingsare on-especially silent battery -oper-ated things-the light could remind

PARTS LIST FORLET THERE BE LIGHT

LED1-Light emitting diodeR1 -470 -ohm resistor, 1/2 -watt

you and help save your battery. Youwill find other places in a circuitwhere adding these two parts can beuseful or interesting. Go ahead andlook.

80 Attache Alarm Who knows what evils lurk, readyto pilfer the Twinkies out of yourattache case when you're not looking?This squealer does. Because whenyou arm the alarm by turning orl SI,the lightest touch will set it off. More

accurately, the touch of light. Lightstriking 01 turns on transistor switchQ2, which energizes oscillator Q3-04.And that blows the whistle on thebad guy.

SI

RI

e

0I

CI

04b

SPEAKER

PARTS LIST FOR ATTACHE ALARM

B1-9 VDC batteryC1-.01-uF capacitorQ1-Photoelectric transistor, FPT

100 or equiv.Q2-NPN transistor, 2N2222 or



equiv.R1 -2200 -ohm resistor, 1/2 -wattR2 -100,00 -ohm resistor, 1/2 -wattS1-SPST switchSPKR-8-ohm speaker

81 Gotcha GeneratorPARTS LIST FOR

GOTCHA GENERATOR

B1-9 VDC batteryC1-.1-uF capacitorQ1-UJT (Unijunction transistor),

2N2646 or equiv.R1 -10,000 -ohm resistor, 1/2 -wattR2 -100 -ohm resistor, 1/2 -wattR3 -470,000 -ohm resistor, 1/2 -wattS1-SPST switchTl-Transformer, 10,000:100,000 -

ohm

DOUBLE SIDEDPRINTED CIRCUIT

BOARD STOCK


Want to play a game of Hot Po-tato with a double sided printed cir-cuit board stock? Just add this andyou could be putting just under ahundred volts across it-but at only afew hundred microamps of current.(Change R3 to 10 Meg for just under10 microamps of current). Trans-formers can be used to step up volt-age.% as you know. That's the way

power transformers are designed. Butpower transformers have to be ableto handle a great deal of current atonly 60 Hertz, which requires a bulkypackage.

The AC supply for this t-ansformeris generated by Unijunction transistoroscillator 01. It only has to supplycurrent in the milliamp range, andworks at about 1000 Hertz so we can

use a small "transistor" interstagetransformer for Ti. A blank piece ofcopper coated double sided pc boardstock is a good way to keep thestepped -up AC signal from shortingwhile close-one lead is attached toeach face of the board. Bet a friendhe can't hold it in his hand for aminute, then throw the switch.

82 The Bamboozler11 Officially, this is a slow speedastable multivibrator with state -indi-cating photo -optic outputs. Unoffi-cially, it's just a circuit to alternatelyflash two L.E.D.s. But you don'thave to tell anybody that. Tell themit's counting Ekno Rays from theplanet Nerd. Or it remotely controlsyour pacemaker. Or it can tell aperson's innermost secrets. Or you'llthink of something. R3 limits thecurrent the whole circuit can draw.If you find the flashing too dim orunreliable, reduce the value of R3to 150, 100 or 47 Ohms. If youcould handle even dimmer blinks, in-crease R3 to a maximum of about100 Ohms.

You could also use different colorLEDs, add a magnetic reed switch inseries with each capacitor, and hidea magnet between your fingers. Then,by careful positioning, you can con-trol whether both flash, one stays onor both stay on.

PARTS LIST FORTHE BAMBOOZLER

B1-9 VDC batteryCl, C2-10-uF capacitorLED1, LED2-Light emitting diodeQl, Q2-PNP transistor, 2N3906

or equiv.

R1, R2 -47,000 -ohm resistor, 1/2 -

wattR3 -220 -ohm resistor, 1/2 -wattS1-SPST switch

ei

R3

LED I

b

Of

CI

0 RI

b

02

C2

R2

LED 2

83 Turn -On Delay Turn the switch on and the cir-cuit you're controlling (LOAD)won't turn on until 10 seconds laterwith this UJT delay. The SCR is the"switch" that eventually permits cur-rent to flow through the load. But theSCR won't turn on until the UJTtimer circuit delivers a pulse to itsgate. This happens after a time delaydetermined by the product.

Choose a value for SCR1 that caneasily handle the maximum currentthe load will draw, plus a margin forsafety, and the voltage of the powersupply, plus a margin for safety. Fora 9-12 Volt circuit drawing up to 1/2amp or so, a 20 Volt 1 Amp SCRshould do nicely. Since SI, whenturned off, interrupts the flow of cur-rent through the SCR, turn-off forthe load happens immediately.101 ELECTRONIC PROJECTS 1978 51

PARTS LIST FOR TURN -ON DELAY

C1-220-uF capacitorQ1-UJT (Unijunction Transistor),

2N2646 or equiv.R1 -47,000 -ohm resistor, V2 -watt

Si+V 0

-v 0

R2 -22 -ohm resistor, 1/2 -wattSCRI-See textSI-SPST

RI

CI

DI

2

oi

(+1LOAD.THE CIRCUITYOU ADD THISTO.

SCRI

R2

84 SWL's Simple SquelchE It's almost a universal rule thattwo-way radios have a squelch con-trol, a device that mutes the back-ground noise until a station is re-ceived. Even public service radiosnow include a squelch, so why put upwith ear -jarring noise when listeningon your SWL receiver. Just a coupleof #47 pilot lamps scrounged fromold tube radios and two resistors areall that's needed to squelch your SWreceiver. And if you can't scroungethe lamps, they're available at justabout every radio parts distributorand service shop. Switch SI is neededonly to bypass the squelch for very

TO RECEIVERSPEAKEROUTPUT

TO A 4 TO8 OMMSPE As E R

PARTS LIST FORSWL'S SIMPLE SQUELCH

11,12-#47 pilot lampR1, R2-4 to 6 -ohm resistor, 1 -watt,

10 percentS1-Dpdt switch

weak signals.In many instances, the circuit will

provide a basic attenuation of thenoise background, not completesquelch. But it's a substantial squelch

considering the low cost and ease ofconstruction. Just about any enclo-sure, plastic or metal. can be used.The components can even lie on thetable.

85 290 Mag. Phone Filter If you're tired of copying CW sig-nals through the grind without a Q -multiplier on your receiver, the 29eMag. Phone Filter is the next bestanswer. It's the cheapest route togreater selectivity.

Capacitor Cl plus the inductanceof a magnetic headset form a par-allel resonant circuit at approximatelyI kHz. All other signals are shin -plyattenuated so you hear mainly thesignal you want. Resistor R I isolatesthe resonant circuit to prevent a re -

RI

RECEIVERSPEAKER

OUTPUTTERMINALS

CI

PARTS LIST FOR290 MAG. PHONE FILTER

C1-0.005-.05-uF capacitor (seetext

E1 -2000 -ohm magnetic headset

R1 -100,00 -ohm, 1/2 -watt resistor

ceiver's low output impedance fromreducing the "Q" of the headset cir-cuit.

The exact value of Cl depends on

the particular headset. Try differentvalues in the range shown until thedesired resonant frequency or peak-ing action is obtained.

86 Slide Show StopperE] Soundless slide shows are dull,dull, dull! But a stereo recorder canautomate the whole show so slideschange automatically in step withthe commentary.

Record your commentary on theleft track. At the instant you wantslides to change, record a one -secondnoise or tone burst on the right track.Connect the programmer between therecorder's right speaker output andthe projector's remote control cable.Make a test run to determine theright -track volume setting to makenoise or tone bursts activate relay K1.No fancy tone generators needed here.Just give a hearty Bronx cheer intothe mike of the left channel only!

Then start the tape from the begin-ning. The audience will hear your

52

commentary or spectacular music -and -sound reproduction through a

speaker connected to the recorder'sleft channel, while the signal on theright channel automatically changesthe slides.

DI

TO

RECORDERSPEAKEROUT PUT

PARTS LIST FORSLIDE SHOW STOPPER

C1-25-uF, 50-VDC electrolyticcapacitor

D1, D2 -1-A '400-P'V siliconrectifier, Motorola 1N4004

K1 -2500 -ohm coil plate -typerelay

T1 -5000 -ohm CT audio outputtransformer

-0 TOt °PROJECTORCONTROL

K1


87 Add -A -Tweeter

0 Any single -voice coil speaker ishard pressed to handle both low andhigh frequencies simultaneously-andit's the highs that suffer most. Amuch cleaner sound can usually beobtained from speakers 6 inches orlarger if the highs are pumpedthrough a tweeter. It can be any smallspeaker rated 4 to 6 ohms of approx-imately 2 to 3 inches in diameter.

The back-to-back capacitors, Cland C2, permit only the highs from

about 1500 Hz up to pass into thetweeter. By keeping the lows out ofthe tweeter, the highs come out clean-er, and there's no chance of the great-er low frequency power "blowing"the tweeter. Potentiometer RI is usedto match the tweeter's output levelto that of the woofer-because smallspeakers are generally much moreefficient than large speakers. If youeliminate R1, the highs will literallyscream in your ears.

EXISTINGWOOFER

NEWTWEETER

PARTS LIST FORAD D -A -TWEETER

C1, C2-22-uF electrolyticcapacitor, 50 VDC

R1 -50 -ohm wireboundpotentiometer, 1 or 2 watts.

Misc.-Cone type tweeters aresuitable for use with this circuit.

88 FlashTester Even if you spend $18 or $20 fora super-duper professional remoteflash tripper, you'll get little morethan this two -component circuit. Priceis important if the results are equal.

Transistor 01 is a light -activatedsilicon -controlled rectifier (LASCR).The gate is tripped by light entering asmall lens built into the top cap.

To operate, provide a 6 -in. lengthof stiff wire for the anode and cathodeconnections and terminate the wiresin a polarized power plug that match-

es the sync terminals on your elec-tronic flashgun (strobelight). Makecertain the anode lead connects tothe positive sync terminal.

When using the device, bend theconnecting wires so the LASCR lensfaces the main flash. This will fire theremote unit.

No reset switch is needed. Voltageat the flash's sync terminals falls be-low the LASCR's holding voltagewhen the flash is fired, thereby turningoff the LASCR.

PARTS LIST FORREMOTE FLASH TRIGGER

Q1 -200-V light -activated silicon -controlled rectifier (LASCR)

R1 -47,000 -ohm, 1/2 -watt resistor

RITO SYNCTERMINALS

89 Basic Color Organ

D This simple color organ is certainto keep your party from becoming adrag. Connected to your hi-fi ampli-fier's speaker output (across thespeaker terminals) it will throb intime to the music. Paint the bulb redor deep blue and your party roomwill take on the atmosphere of a rockclub.

Transformer TI can be any match-ing transistor type in the range of500 '500 to 2500 2500 ohms. Notethat none of the connections fromSCR I or its components are connect-ed to ground. For safety's sake, youmust keep the 117 -volt line voltagefrom the amplifier connections-that'sthe reason for T1. To adjust, set po-


tentiometer R I "off" and adjust theamplifier volume control for a normallistening level. Then adjust RI untillamp I1 starts to throb in step withthe beat.

TI

AUDIOINPUT 5

PARTS LIST FORBASIC COLOR ORGAN

11-117V lamp, not to exceed 40watts.

R1-Potentiometer, 500 to 5000ohms

SCR1-Si I icon ControlledRectifier, HEP R1218

T1-Transistor output transformer,see text

SCR I

LAMP

117 VAC

53

90 Photo Print Meter0 Every print a good print! That'swhat you get with the photo printmeter.

Meter M I can be just about any-thing up to 0-1 DC mA. But if youprefer low light levels and long ex-posures, install a sensitive meter of500 uA or less.

When light from the enlarger fallson the solar cell (PC1), a voltage isgenerated that is in proportion to theamount of light. Sensitivity controlRI allows the user to set the meterindication to a convenient value.

To use the meter, first make agood normal print in your normalmanner from a No. 2 or No. 3 nega-

tive. Then, do not disturb the en-larger setting, but integrate the lightby placing a diffusing disc or opalglass under the olens. Place the solarcell on the easel and adjust RI for aconvenient meter reading, say, fullscale. The meter is now calibrated.

When using it, focus the enlarger,use the diffuser, and adjust the lensdiaphragm until you get the referencemeter reading. Then use the exposuretime previously found for the calibra-tion print. Suggested reading: IlfordManual of Photography, obtainablefrom any photo store. Also, checkKodak publications available at thesame place.

MI

RI

PARTS LIST FORPHOTO PRINT METER

M1-100, 250, or 500-uA DC meterPCI-Solar cell (Caleciro J4-801)R1 -5000 -ohm potentiometer linear

taper

91 Auto Ignition Maze0 Install a combination lock on yourcar's dashboard and a thief wouldhave a better chance playing Russianroulette.

Switches SI through S5 are spdtrather than spst only to keep all ex-ternal switch markings the same.

Tracing the circuit will show thatonly if switches S2 and S4 are downis the siren disabled. The siren soundsif any other switch is down or if S2

or S4 is up when the ignition isturned on. A simple wiring changelets you set any combination.

The switches can be "sporty" autoaccessory switches sold individuallyor in switch banks such as G.C. 35-916. Provide labels such as "Car-buretor Heater," "Window Washer,"etc. and no one will know the car iswired for "sound."

92 Crystal Checker0 A fast way to see if the crystal fromyour transmitter or receiver is proper -y "active" is to compare its output

PARTS LIST FORCRYSTAL ACTIVITY CHECKER

B1 -9 -volt transistor radio batteryC1-50-pF disc capacitor,

100 VDC or betterC2-0.005-uF disc capacitor,

25 VDC or betterC3-33-pF disc or mica capacitor,

100 VDC or betterD1-Diode, 1N60M1-Meter, 0-1 mA DCPB 1-Normally open push button

switchQ1-NPN transistor, HEP-50

(Radio Shack 276-2009)R1 -100,000 -ohm, 1/2 -watt resistorR2 -10,000 -ohm, 1/2 -watt resistorRFC-2.5-mH RF chokeS01-Socket to match crystals,

see text

against that of a known good crystal.This crystal checker will handle bothfundamental and overtone type crys-tals. Socket SO1 should match thepins on your crystals. If you use morethan one type of crystal, install two(or more) sockets in parallel. Theunit can be assembled in any type ofcabinet.

To test a crystal's activity, first plugin a known good crystal, depress pushbutton switch PB1 and note the me-ter reading. Then install the ques-tionable crystal, press ?B I and noteits meter reading; if it's good its out-put should approximate that of thereference crystal. Take care that youdon't compare apples with oranges;

RI100K

RFC P8181

9VDC

01 I I


the reference crystal should be the tested. If good crystals drive the meter 10 percent resistor in series withexact same type as the crystal to be off scale, install a 1000 -ohm, 1/2 -watt, meter MI.

93 FM Overload Filter0 A simple filter is all it takes toremove a strong, local FM signal thatis blocking or cross modulating otherFM stations. The filter connects inseries with the FM antenna's down -lead. Just be sure to use the shortestpossible length between the filter'soutput and the receiver.

The filter must be assembled in ametal cabinet with 1/4 -in. access holesso you can adjust the trimmer tuningcapacitors. The metal cabinet isgrounded to the receiver's chassis.Switch SI by-passes the filter for nor-mal operation. If your antenna's

downlead is coaxial cable, only onefilter is installed-in series with thecenter (hot) conductor. To adjust,

PARTS LIST FORFM OVERLOAD FILTER

C1, C2-40-pF trimmer capacitorRFC1, RFC2-0.22-uH RF choke,

any typeS1-Dpst slide switchMisc-300-ohm twinlead, metal

cabinet

TOANTENNA

RFCI

300 OHMTWIN LEAD SIDI

RFC2

TORECEIVER

VERYSHORT

tune in the offending station and use adjust trimmer capacitors Cl andan insulated alignment screwdriver to C2 for minimum signal strength.

94 Doorknob Security Alarm0 Here's security for the traveler.Just connect this alarm to the door-knob of your motel room and a loudbuzzer will sound if anyone touchesthe doorknob.

PARTS LIST FORDOORKNOB SECURITY ALARM

B1 -6 -volt battery, Burgess Z4or equiv.

BP1-Binding postBU1-6-volt buzzerCI, C2-0.05-uF disc capacitor,

25 VDC or betterC3-47-pF silver mica capacitor

(Allied Electronics 782-0860)C4-300-pF trimmer capacitorC5-0.05-uF, 25 VDC capacitorC6-50-uF electrolytic capacitor,

25 VDC or betterD1, D2-Diode, 1N60D3-Diode, 1N914

CI.054F

C2.051,

-C3 :BPI50pF

IllCS

1 0111F

NZ54'f -250pF

R31K

DI1N60

L1-15-uH adjustable RF coil(Miller 4205, or equiv.)

PB1-Pushbutton switch (reset)Q1 -2N3394Q2 -2N3391R1 -47,000 -ohm, 1/2 -watt resistorR2 -10,000 -ohm, V2 -watt resistor

R456011

D2IN6C

022N3391

- BI6v

S

A

Pet

C6

T 513"F

R3, R6 -1000 -ohm, 1/2 -watt resistorR4 -560 -ohm, 1/2 -watt resistorR5 -5600 -ohm, 1/2 -watt resistorS1-Switch, spst (on -off)SCR1-800-mA/30-V silicon

controlled rectifier, HEP R1001

Transistor circuit 01 is an oscilla-tor with a connection through bind-ing post BPI to the doorknob. Aslong as 01 oscillates, its rectified out-put is applied to Q2 which holds theSCR1 gate almost at ground poten-tial. When someone touches the door-knob, hand capacitance "kills" theoscillator, thereby removing that cut-

off (holding) bias from the SCR1gate; the SCR conducts and soundsalarm buzzer BU1. The alarm canonly be turned off by opening resetswitch PB1.

The alarm should be assembled ina small metal cabinet with insulatedbinding post BPI at the top. A smallwire loop attached to BP1 secures the

alarm to the doorknob-the alarmactually hangs on the knob. To adjust,carefully set C4 in small incrementsuntil touching your finger to BP1causes the buzzer to sound. If C4 isoveradjusted, hand capacitance willnct "kill" the oscillator. Best opera-tion is obtained if the door is made ofwood.


95 Remote FlashTriggerD The way film and flashbulb pricesare going these days, if your flashfails to fire you're stuck with almosthalf a buck in wasted polaroid film,and if you fire a flash to check theflashgun battery you've just burnedup at least 25 -cents worth of flash.But worse, if the flash fails to fire youmight have missed the picture of alifetime.

You can't check a flash batterywith a voltmeter because the meterdoesn't apply the heavy surge cur-rent needed by the flashbulb, and justabout any fully dead battery that

isn't leaking acid will check okaywhen tested without load.

This little flash tester you canprobably build from junk -box partswill give you a quick load -check onflashgun batteries. T1 can be any6.3 -volt filament transformer ratedfrom 300-mA up. NL-1 is just aboutany neon lamp of the NE -2 or NE -86 variety. Solder Ti's terminals tothose of a used flashbulb or flashcube.

To check the battery, just plug inthe flash tester and trip the camerashutter (cover the lens if the camerahas film). Lamp NL-1 will flash if the

battery is okay (T1 requires a highinrush current, as does the flashbulb).

TO FLASH 1TERMINALSTHROUGHFLASHBULBBASE ( SEETEXT)

6.3V300ma

TI

NL-I

PARTS LIST FOR FLASH TESTER71 -6.3 -volt filament transformerNL-1-Neon lamp, see textMisc.-Used flashbulb base.

96 Angler's Bite Booster

El Click -click might not sound likemuch to you but to a fish it's thedinner bell. That's the lure of thiselectronic circuit. Shove the wholeworks in a watertight container, low-

the side, and wait for thefish to hit the hooks.

For proper operation T1 must besubminiature type about half asjargeas your thumb. El must be a crystalheadphone.

ON -OFFSI 131 82

0_11_1

TI

,NOT

MEP -20111

USED

El

30

C2

RI

CI

PARTS LIST FORANGLER'S BITE BOOSTERB1, B2 -1.5-V AAA batteryC1, C2-50-uF, 12-VDC electrolytic

capacitorE1-Crystal earphoneQ1-Motorola HEP-230 pnp

transistorR1 -5000 -ohm potR2 -27,000 -ohm, 1/4 -watt resistorSI -Spst switch, part of R1T1-Subminiature transistor output

transformer; 500 -ohm centertapped primary to 3 -ohmsecondary

97 Nifty Night Light It's automatic! Let the face of 01get dark, and 11 turns on. Phototran-sistor 01 turns on buffer switch Q2 -Q3, which activates Darlington switchpair 04 and 05 to turn on II. II iscurrent limited by R4 to deliver longlife and reduce the circuit's overall

current drain.Don't make the mistake a brilliant

engineering school made years ago.They installed a sophisticated systembased on a circuit much like this. Itwas designed to turn their area lightson at dusk, off. at sunrise, and had

delays built in to keep the lamps fromflickering when a cloud, for example,temporarily blocked the sun. The mis-take came when they placed the cir-cuit at the bottom of the light poles.

BI

SIo

RI

e

01

e

04

R4

I

05

PARTS LIST FORNIFTY NIGHT LIGHT

B1-9 VDC batteryII-Bulb, #47 -typeQ1-Photoelectric transistor, FPT-

100 or equiv.Q2, Q3-NPN transislor, 2N3904

or equiv.Q4, Q5-PNP transislor, 2N3906

or equiv.R1-10-Megohm resistor, 1/2 -wattR2 -1000 -ohm resistcr, 1/2 -wattR3 -100,00 -ohm resistor, 1/2 -wattR4 -27 -ohm resistor, 1/2 -wattSI-SPST switch


The first night, the lights came on took them for sunlight and turned whole process over and had thefine, but after a delay the circuit mis- them of! again. Which started the campus blinking all night.

98 LED Telephone Ring Indicator Know what makes your phonering? A 20 Hertz AC signal at any-where from 60 to 120 Volts, depend-ing on your phone company. Thatsame bell -ringing signal can be usedto light an LED with the circuitshown here, without significantlyloading the telephone line. Cl pro-vides DC isolation to help foolproofthis project. The .1 value shownworks, but you may want to increaseit to .5 microfarads. Use a mylarcapacitor (like the Sprague "OrangeDrop" series) rated at 250-450 work-ing volts or more.

Why so high? The telephone com-pany keeps its lines clear of ice andtrouble by daily sweeping a pulse ofhigh voltage throughout the system.Too low a working voltage couldmean trouble for them, and that isabsolutely the last thing you want to

cause. We might even suggest con-necting to the telephone lines onlytemporarily to verify circuit opera-tion. This will help avoid accidentsand trouble. DI through D4 act as afull wave bridge to deliver the ACringing voltage as DC to LED1. R1limits the current through the circuit.

PARTS LIST FORLED TELEPHONE RING

INDICATOR

C1-.1-uF capacitorD1, D2, D3, D4-Diode, 1N914 or

equiv.LED1-Light emitting diodeR1 -82,000 -ohm resistor, 1/2 -watt

99 Current Tattletale Ever have to check a line to seewhether or not any current was flow-ing within it, and which way? Here'san easy answer. Any current flowhere will build up a voltage in RI.If the voltage in' RI is more thanabout 2 volts, one or the other (orboth, if AC) of the LEDs will light.

Different systems may require dif-ferent values for RI. Use Ohm's Lawto calculate RI. For example, if wewanted to know whether or not acar's taillight bulb had burned out,we could connect this circuit in serieswith the lamp's supply lead. Assumethe particular lamp requires typically1/2 Amp to light. We then need to

know what value for R1 will providea 2 Volt drop.

Using Ohm's Law, E=IXR, orR=E /1=2+1/2 = 4 Ohms (you wouldwant to use a 4 or 5 Watt resistor tocomfortably handle this 1 Watt power

dissipation).In a 100 Volt B+ supply drawing

100 ma, R=E/I=2/.100 = 20 Ohms.The circuit drawn above is sensi-

tive enough to detect a few milliam-peres of current flow.

RI

PARTS LIST FORCURRENT TATTLETALE

LED1, LED2-Light emitting diodeR1, R2, R3 -470 -ohm resistor, V2 -

wattLED2

100 Telephone Dialing BlinkerL] It's fun watching each dial pulseflash the LED on this simple circuit.And it may lead you to experimenting

with sonic remote control ideas.When yolir phone is off the hook,roughly 50 VDC appears across the

phone lines. This is interrupted dur-ing dialing, once for each value (forexample, 7 times when you dial a

PARTS LIST FORTELEPHONE DIALING BLINKER

RI

C1-33-uF capacitor TO TELEPHONE LINESDl-Diode, 1N914 or equiv.LED1-Light emitting diode

(RED -GREEN, IN MOSTCASES), ON INSTRUMENTSIDE OF HANG -UP

CI R2 DI

R1 -2700 -ohm resistor, 1/2 -watt HOOKSWITCH LED IR2 -180 -ohm resistor, 1/2 -watt 0


"7") of the number you dial. R1 andR2 act as a voltage divider (and cur-rent limiter) to place a few voltsacross LED1. Cl acts as a filter.

Try using LED1 with a photoelec-

tric switch circuit to turn the blinkinglight back into a digital signal. Youcan then devise a counter or otherdevice to accept dialing input as data.This can lead to a versatile telephone

intercom system, independent of thetelephone company's lines and equip-ment. If you use a :ower DC linevoltage for your private system, re-duce the value of RI accordingly.

101 Flashlight Remote Control

This is the kind of circuit that hasalways been called a TV commercialkiller, but I happen to like TV com-mercials, so I put it to work doingother things. Whenever a beam froma flashlight hits 01 (mounted in ashort piece of plastic or cardboardtube to keep ambient light from af-fecting it), it conducts, pulling upthe base of Q2. This turns Q2 onand pulls in the relay.

The relay can be hooked to anynumber of things. You can use it tostart and stop a cassette machine,buzz someone into your apartmentbuilding, or answer a speakerphone.If you use it to turn on a lamp andlet 01 "see" the lamp, the lamp will

PARTS LIST FORFLASHLIGHT REMOTE CONTROL

B1-12 VDC batteryD1-Diode, 1N914 or equiv.Q1-Phototransistor, FPT100 or

equiv.Q2-NPN Transistor, 2N2222 or

equiv.K1-Relay, 12 VDCR1 -2200 -ohm resistor, 1/2 -wattS1-SPST switch

stay on until you pass something overthe lens of Q1 to shut the light out.Or attach a noisemaker or radio and

let it point out your window for anelectronic cock's crew that soundswhen the sun comes up.

Old Crowbarsee page

48

Low -Power Light Blinker-see page 44

Simple Squealer-see page 18

Signal OperatedSveiteh-see

p

Weir

ge 17

watot-see 9age 2


30 INTEGRATEDCIRCUIT PROJECTSIC1 SWL's Super Calibrator[1 Providing WWV referenced out-puts at 1 MHz, 100 kHz, 10 kHz andI kHz, this super calibrator looksquite difficult to assemble, but if youlay it out for a printed circuit boardyou'll find it's one of the easiest pro-jects to build and get working be-cause there's very little that can gowrong if the ICs and the crystal areokay.

ICI serves as both the oscillatorand buffer amplifier. Another bufferamplifier is used for the output am-plifier (terminals 11, 12 and 13),

ICI's output at pin 8 is a buffered 1MHz. ICs 2, 3 and 4 are divide by 10frequency dividers providing outputsof 100 kHz, 10 kHz and 1 kHz. Sinceall outputs are square waveform, alloutput signals are rich in harmonicsand so can be used to calibrate re-ceiver dials to well above 60 MHz forthe 1 MHz output and to at least 30MHz for the 100 KHz and 10 kHzoutputs. The 1 kHz harmonics canrange up to 30 MHz depending onyour receiver's sensitivity. The cali-brator's output at jack .11 can be con-

nected directly to the receiver's an-tenna input terminals without affect-ing the calibrator's output frequency.

The unit is set to zero -beat withWWV with trimmer capacitor C4. Itcan be assembled in any type of cabi-net, but a PC board is specificallyrecommended for circuit stability.

Power must come from a 5 -voltregulated source and we recommendthe LM340 5 -volt three -terminal reg-Llator for this project. Make certaincapacitor Cl is installed as close aspossible to IC 1 pin 14.

5REGULATED

OUTPUT

VDC

'II C2 SI

I kHz

PARTS LIST FORSWL'S SUPER CALIBRATOR

R1, R2 -220 -ohms, 1/2 -watt, 10%,resistor

C1, C2, C3-0.01-uF, 10-VDC orhigher, capacitor

10 kHz

100 kHz

I MHz

c

I14 III 12 13 C4-5-50-pF trimmer capacitor

ICI8 511 14

IC22 3 6 7 10

11 14

IC 32 3 6 7 10

12 1

5 11:C4

2 3 6

14

7 10

X1 -1 -MHz crystal, Calectro J4-1900 or equiv.

"4.

RI

IC1-Integrated circuit typeSN7400I.

5

IC2, IC3, IC4-Integrated circuitC3type SN7490

R2 S1-SP4T switchC4 J 1-Output jack (phono type

suggested)XI 1MHZ

IC2 Lie Detector0 When a person is under mentalstress one of the physiological changesincludes a lowering of the body'sskin resistance, and one of the char-acteristics measured by the modernlie detector is skin resistance.

Our "lie detector" works the sameway: it measures the body's skin re-sistance. In typical use you would

connect one test probe, actually alength of non -insulated wire taped tothe skin, to each hand, arm, or wrist,adjust control R2 for a meter null(zero meter reading), and then askyour questions. If a question causesthe subject mental stress you will usu-ally see this stress indicated by an in-crease in the meter reading

Potentiometer R4 serves as a sen-sitivity control. To avoid pinning themeter start with R4 at about the midposition: increasing the resistance in-creases the gain, while decreasing theresistance reduces the gain and themeter reading.

If you want to avoid taping theprobes to your subject you can use


the inexpensive, less -than -$1 -a -pairbicycle clips available in most depart-ment and sporting goods stores. Solderthe test probe wires to the clips andthen bend the clips so they hold ontothe hand or arm gently but firmly.Wiping the area under the clips withalcohol will improve overall sensi-tivity.

If long test probes are used, say inexcess of 3 -feet, shielded wire is

suggested, with the shield for eachtest probe wire connected to thechassis ground-the junction betweenswitches S1 a and Slb. You can alsouse two -wire shielded cable (twowires in one shield) and fan the wiresout a foot or so from under the probeend.

TESTPROBES

PARTS LIST FOR LIE DETECTOR

Resistors 1/2- or 1/4 -watt, 10%,unless otherwise specified

R1, R5 -10,000 -ohmsR2, R4-1-megohm potentiometerR3, R6 -1,000 -ohmsR7 -560 -ohmsC1, C2-0.01-uF, 25 VDC or higher

ICI-Operational amplif er, type741

S1-Switch, DPSTB1, B2-6 volt battery, Burgess Z4

or equiv.MI-Meter, 0-1 mA DC

IC3 CB Mobile -to -Base Power Unit CB mobile transceivers and 3 to5 -watt CB handie-talkies are easilyconverted to base station operationwith this 13.8 volt regulated powerunit. Transformers T1 and T2 shouldbe rated 2 amperes. When T1 andT2's secondaries are connected, testthe transformer(s) output voltagewith an AC voltmeter. If the meterindicates approximately 6.3 volts,reverse the connections of eithertransformer's primary or secoary,but not both. The meter will then

read about 18 VAC. Complete therest of this project only after you arecertain the output voltage from thetransformer(s) is about 18 VAC.

ICI must be heat sinked to thecabinet. Note that ICI's tab is a "hot"terminal; make certain it is insulatedfrom the cabinet with a power tran-sistor insulator or a mica washer.Coat both sides of the insulator(washer) with silicon heat sinkgrease. And make certain the mount-ing screw is insulated from the

cabinet; use fiber shoulder washersunder the screw.

Connect rectifier D2 exactly whereshown in the circuit. D2 should berated at least 50 PIV at 3 amperes.Bridge rectifier DI is rated 50 PIV at6 amperes. Do not substitute a 3ampere bridge rectifier for D1 unlessyou heat sink it to the chassis. (Heatsinking for D1 is suggested for boththe 3 and 6 ampere types.)

PARTS LIST FORCB MOBILE -TO -BASE POWER UNIT

C1-2000-uF, 25-VDC electrolyticcapacitor

C2-0.1-uF Mylar capacitorC3-500-uF, 25-VDC electrolytic

capacitorD1-Bridge rectifier, see text02-Silicon rectifier, 50 PIV, 3

amperesIC1-Voltage regulator, LM -340-15

(T -package)T1 -12 -volt, 2 -ampere filament

transformer72 -6.3 -volt, 2 -ampere filament

transformer

117 VAC

T I

BRIDGERECTIFIER

HEAT SINK'Cl

2JI

13.8 VDC OUTPUT / IA

ro<

I 2 3ICI

TAB ISALSO 3

IC4 CB Channel Booster Connect the CB Channel Pullerahead of a low cost receiver, andyou'll hear CB signals as if they werecoming from your backyard. Using

no tuned circuits, this CB signalbooster delivers approximately 15dBoverall gain-that's about 3 S -units!Only restriction is that this little rf

amplifier be used with a communi-cations -type receiver having an an-tenna trimmer. It cannot be used infront of a low -impedance -input type


CS

CB transceiver. Seems the low im-pedance antenna input common toCB units will sharply reduce thebooster's gain.

Typical of all RF amplifiers, thebooster requires very short connect-ing leads. In particular, solder ca-pacitor C3 right at pin 4. Integratedcircuit IC1 can be soldered directlyinto the circuit or a socket can beused. Battery B1 is a 6V Z4 type orlarger.

FROM52 OH M

ANTENNA

00IyF

J1

CI10OpF

BOTTOMVIEW

OF ICI

C2100pr

OUTPUT(SEE TEXT)

SI131

6VDC

PARTS LIST FORCB CHANNEL BOOSTER

B1 -6V batteryC1, C2-100-pF, 15 VDC capacitorC3-0.001-uF, 15 VDC capacitorIC1-HEP 590 (Motorola)

J2

11,12-Phono or coaxial jackR1 -52 -ohms, 1/2 -watt resistorR2 -1,500 -ohms, 1/2 -watt resistorS1-SPST switch

IC5 5V/3A for Digital Projects The 5 -volt power supply is almostthe universal power source for digitalprojects. Only problem is the 5 voltsmust be highly regulated, for a powerline transient riding through the sup-ply can zap a board full of ICs. Thissupply gives you full protectionagainst transients, as well as provid-ing tight regulation. The entire regu-lator is contained in ICI; no othercomponents other than the filter ca-pacitor and rectifier are needed. Forfull 5 ampere output ICI requires a

heat sink of 30 square inches; but ifyou use a metal cabinet 3 x 4 x 5inches or larger the cabinet itselfserves as the heat sink. Since pin 3 onIC1 is grounded (to the cabinet), allyou need is some silicon heat sinkgrease between the IC and the cab-inet-no insulator.

Power transformer T1 must berated for the maximum current youwill use or need. If you want the full5 amperes Ti must be rated 5 am-peres. But if you will need less cur-

rent, say 2 amperes, TI can be rated2 amperes.

Rectifiers 01 through 02 are avail-able with ratings up to 3 amperes inthe standard coaxial mounting. Forgreater current capacity the rectifiersmust be heat-sinked (electrically iso-lated) to the cabinet, or other sink.A 10 -ampere bridge rectifier such assold by Calectro and Radio Shackcan be substituted, but make certainit is heat sinked to the chassis.

PARTS LIST FOR5V/3A FOR DIGITAL PROJECTS

C1-3000-uF, 25 VDC electrolyticcapacitor

C2-0.1-uF Mylar capacitorC3-500-uF, 10 VDC electrolytic

capacitor131 -D4-See textF1-1/4 ampere, 3AGIC1-5-volt regulator, LM223 or

LM323S1-Spst slide or toggle switchT1- see text

117VAC

SI

02HEAT SINK(SEE TEXT)

ALTERNATE POWER SOURCE

30 Sy inHEAT SINK

ICI

TO I:I

3500#,A.F

+5 VDCREGULATED

3 ISCASE

ICIBOTTOM VIEW

IC6 Bi-Polar Power SupplyD Most IC circuits require a Bi-Polarpower supply. That is, a power sourcewith two outputs-one positive withrespect to ground and the other nega-tive with respect to ground. A stand-ard bridge rectifier circuit will providea Bi-Polar output if the transformer'ssecondary is center -tapped to ground.

Filter capacitors Cl and C2 shouldbe at least 1000 uF (2000 uF pre-ferred) at a voltage rating at leastequal to the supply's output voltage.

The supply's output voltage isequal to 1.4 times Es. Voltage Esequals one-half Transformer Ti'speak secondary voltage. For exam-

ple, assume that Ti's secondary volt-age is 24 volts (rms) center -tapped;the voltage on each side of the center -tap (Es) is 12. The supply's outputvoltage is therefore 12 x 1.4 or ±16.8 VDC. Always remember thateach Bi-Polar output is derived fromhalf Ti's secondary voltage.


PARTS LIST FORBI -POLAR POWER SUPPLY

C1, C2-1000 or 2000-uF capacitorat the supply's output voltage

SR 1 -SR4-Silicon rectifiers PIVrated to at least twice thesupply's output voltage

T1-Power transformer withcenter -tapped secondary(Calectro D1-752)

117 VAC +16.8VDC

-16.8VDC

COMMONORGROUND

C21000pF

1C7 Bi-Polar Power AmplifierCI It is incovenient when workingwith IC preamplifiers requiring bi-polar power sources to convert to asingle -ended power source for thepower amplifier. Our Bi-Polar Amp,however, can be driven from a bi-polar power supply. One of the bene-fits enjoyed by Bi-Polar Amp is that a

large, expensive output coupling ca-pacitor isn't needed. Since the deviceresponds well into the high frequencyrange, capacitors C2 and C3 must beplaced directly at the IC terminals toprevent high frequency oscillation.While capacitor CI can be an electro-lytic type, a non -polarized 1 uF is

suggested.The amplifier's input impedance is

10,000 ohms, a suitable value forsolid-state projects. Voltage gain is36. If less overall gain is required(say, 10X), disconnect pins 2 and 4and connect pin 5 to ground throughcapacitor C5.

C2.10F

ICIBOTTOM VIEW

INPUT

NOTE I LEAD 7 OF ICI ISCONNECTED TO CASE

+8VDCC4

RI101)

C5 C610uF I 01),JF

PARTS LIST FORBI -POLAR POWER AMP

C1-1-uF, voltage rating at leastequal to peak input voltagefrom preceding stage, capacitor

spKi C2, C3-0.1-uF, 10 VDC capacitor161? C4-39-pF, 100 VDC cisc capacitor

C5-10-uF, 10 VDC capacitorC6-0.01-uF, 25 VDC capacitorICI-Motorola MC -1554GR1 -10 -ohms,'/: -watt resistorSPK1-16-ohm speaker

1C8 Groove Booster

P Using a dual operational amplifierIC, the Groove Booster will providea fully equalized 1 V rms output fromstandard phono magnetic pickups.The terminal numbers which are cir-cled on the schematic are the connec-tions for one of the two independentstereo amplifiers on the single IC chip.

The uncircled numbers are the ter-minals for the stereo second IC.Power supply terminals #14 and #7are common to both stereo amplifiers.Note that the power supply is -±-12

volts to ground. Two 6 -volt batteriesin series can be used for each side ofthe power supply. If batteries areused, connect 25-uF capacitors frompins 7 and 14 to ground-and gettheir polarity correct.62

CI.1yF

FROM 4'MAGNETICPHONO = R3CARTRIDGE 1K

RI R247K 100K

C225pF

PARTS LIST FORGROOVE BOOSTER

C3

C4.006mF

C1-0.1-uF, 3 VDC capacitorC2-25-uF, 3 VDC capacitorC3-820-pF, 500V VDC disc

capacitorC4-0.006-uF, 100V VDC disc

capacitorC5-0.0015-uF, 100V VDC disc

14

401

12 12 II 10 9 8

2 3 4 5 6 7

IC( TOP VIEW)

C6 OUTPUT LEADSmF 10K OR HIGHER

IC5

.00150F

capacitorC6-5-uF, 25 VDC capacitorICI-Motorola MC1303LR1 -47,000 -ohms, 1/2 -watt resistorR2 -100,000 -ohms, 1/2 -watt resistorR3 -1,000 -ohms, 1/2 -watt resistorR4 -750,000 -ohms, 1/2 -watt resistorR5 -51,000 -ohms, 1/2 -watt resistor


1C9 Photo Timer

[j] You can spend $50 to $125 for aphoto -enlarger timer but chances areyou're not going to get more than afancy version of this easy -to -buildcircuit. If you use a DPDT relay, asshown, your safelights can be wiredto turn on when the enlarger turnsoff and vice versa.

If R2 is 1-megohm the timer'srange is about 1 to 110 seconds. IfR2 is 1.5-megohms the timer's rangeis approximately 1 to 16 seconds.The precise range will be determinedprimarily by C2's accuracy, so use areasonably good quality capacitor forC2, but don't get a precision or MIL -spec part; it's not necessary.

If you use a low current relay forRY1, say less than 100-mA at 6-VDC, you can eliminate Q1 and con-nect the relay directly from IC termi-nal 3 to ground. If you use a heavy-duty relay, as high as 300-mA at6 -volts, use 01. The power inputshould be 6 -volts (doesn't have to beregulated) at 300-mA, or 500-mA fora heavy-duty relay. We suggest anypopular -brand low cost relay, such asP&B, Magnacraft or Calectro.

6V3 TO 5A >--1

SEE TEXT CI

C2

PARTS LIST FORResistors V2 watt, 10%, unless

otherwise specified.R1 -10,000 -ohmsR2-1.0- or 1.5-megohm linear

taper potentiometer (see text)R3 -22,000 -ohmsR4 -560 -ohmsCapacitors rated 6-VDC or higherC1-100-uF electrolyticC2-100-uF electrolytic (see text)

TO SAFELIGHT (N.C)#

1 TO ENLARGER (Na).1

RV 1

(6V,300 MA MAX)

01

E

hie ;50

PHOTO TIMERC3-0.01-uF capacitorIC'!-Integrated circuit timer type

555 (any package)Q1-NPN transistor, Radio Shack

276-2030 or equiv.D1-Silicon rectifier, 1N4003,

equiv. or higher PIV rating.RY1-6-VDC relay, see textS1-N.O. push-button or momentary

contact switch.

Potentiometer R2 should be lineartaper. After the timer is assembledattach a large pointer knob to RI'sshaft, and using an electric clock witha sweep second hand as a reference,calibrate timing control R2.

If the unit is assembled in a metalcabinet use a three -wire linecord toground the cabinet. If you use an allplastic cabinet with no exposed metalhardware that can be touched you canuse a two -wire linecord.

IC10 Bargain Tape PreamplifierI: From time to time you'll find bar-gains at dealers selling tape and cas-sette deck mechanisms at rock bottomprices-often less than $20! Completewith heads, these decks need only theelectronics to get them working. Thepreamp provides both the amplifica-tion and equalization. You can feedits output directly into an amplifier'sauxiliary input. Overall frequency re-

sponse is suitable for cassettes and33/4 IPS reel-to-reel tapes. Since theactual required equalization is deter-mined partially by the playback headcharacteristics, it might be necessaryto modify Dr "tailor" the equalization;this is done by small changes in thevalue of capacitor C3 and resistor R5.

If assembled on a small printedcircuit board, the preamp can be

tucked under the tape mechanism'sbase plate. The power supply can beanything from 9 to 18 volts at ap-proximately 3 mA. Transistor typeradio batteries will do; if batteries areused they must be bypassed with a25-uF capacitor. And, be sure youobserve proper battery polarity.

PARTS LIST FORBARGAIN TAPE PREAMP

Cl, C2-25-uF, 6 VDC capacitorC3-0.005-uF capacitorC4-10-uF, 20 VDC capacitorC5-0.001-uF capacitor1C1-Motorola MFC-4010121, R4-3,900 ohms, 1/2 -watt

resistorR2 -39,000 -ohms, V2 -watt resistorR3 -560,000 -ohms, V2 -watt resistorR5 -56,000 -ohms, 1/2 -watt resistor

ICITOP VIEW

DOT

FROMTAPEHEAD

R5 C3

+9-I8VDC

C4101.1F

®TO AMPAUXILIARYINPUT


IC11 Mighty Mite Signal Tracer

Featuring extremely high gainsuitable for tracing signals directlyfrom microphones and magnetic pick-ups, our Mighty Mite signal tracercan be made small enough to sit di-rectly on ,the back of the speakermagnet. Though intended for check-ing transistor circuits, Mighty Mitecan be used with tubed equipment ifcapacitor Cl has a 600 VDC mini-mum rating, and if volume control RIis always started from its off position.Regardless of the size speaker used,Mighty Mite's speaker impedancemust be 16 ohms minimum, thoughhigher impedances work better. Poweroutput is approximately 250 mW;more than sufficient output level froma solid-state signal tracer smallenough to hide oh the back of aspeaker magnet.

I

INPUT

I

CIIVF

RI50K

C2I1jF

47K

01

C30050 -

R3

100K

PARTS LIST FORMIGHTY MITE SIGNAL TRACER

C1-0.1-uF, 600 VDC capacitor(see text)

C2-0.1-uF, 10 VDC capacitorC3, C4-.005-uF, 10 VDC capacitorC5-100-uF, 3 VDC capacitorC6-100-uF, 10 VDC capacitor

(250 uF for better low -frequencyresponse with large speakers)

ICI-Motorola MFC-4000

15

C5_L100 pF

Wbr, OIBOTTOM

VII w

C6100 yF

FIAT

SPKI1611

ICITOP VIEW

DOT

R1-Potentiometer, 50,000 -ohms,audio taper resistor

R2 -47,000 -ohms, 1/2 -watt resistorR3 -100,000 -ohms, 1/2 -watt resistorR4 -15 -ohms, 1/2 -watt resistorR5 -4,700 -ohms, 1/2 -watt resistorR6 -1,000 -ohms, 1/2 -watt resistorQ1-PNP transistor, Radio Shack

276-2021SPK1-16-ohm speaker (see text)

IC12 1013X Instrument Amplifier When voltages drop too low to beindicated on your scope or VTVM,just connect our 100X Instrt"rnentAmplifier ahead of your test gear andyou get full -screen or full-scale read-ings. With an input impedance of 1

megohm, and a flat frequency re-sponse from DC to 20 kHz and be-yond, the 100X Instrument Amplifierprovides a gain of exactly 100 whenpotentiometer R2's wiper is at the top(full gain).

Connected ahead of a VTVM, the100X Instrument Amplifier will con-vert, for example, a 10 mV DC levelinto 1 V. Here's a value that can beread on your VTVM! Similarly, ifconnected ahead of a scope's verticalinput, the amp boosts a signal thatwill just cause a wiggle on the CRTto almost a full screen trace. Themaximum input signal level for un-distorted output is 100 mV peak -to-

peak. Naturally, higher input signals

can be used because of the attenua-tion provided by sensitivity controlR2.

After you've completed the 100XInstrument Amplifier, connect aVTVM across the output, adjust R4for a zero DC meter reading. Fromtime to time check the DC output; if ithas drifted off zero, simply readjustR4. It might happen that changingR2's setting over a wide range mightcause the output to drift off zero; if

INPUT

ICIBOTTOM VIEW

+12VDC

RIK)K

PARTS LIST FOR100X INSTRUMENT AMPLIFIER

B1, B2-Battery, 12VC1, C2-100-uF, 15 VDC capacitorICI-Motorola MC -1456GR1 -10,000 -ohms, 1/2 -watt, 5%

resistorR2-Potentiometer, 1 megohmR3-1 megohm, 1/2 -watt, 5% resistorR4-Potentiometer, 10,000 -ohms

linear taperR5 -10,000 -ohms, 1/2 -watt resistor

so, simply readjust R4. If you areprimarily concerned with AC mea-

surements, the output DC zero drift itor can be connected between theis unimportant, and a 0.1-uF capac- 100X and your VTVM or scope.


IC13 C BoosterSuppose you needed a 10,000-uF

capacitor; do you think it couldsqueeze on your project's printed cir-cuit board? The answer is yes becauseit need be no larger than a transistor.By using a capacitance amplifier, thevalue of any capacitor can be boostedby a factor of 1000X. Capacitor Cxis the value to be boosted; the effec-tive capacity appears at the terminalsindicated C. If Cx is 10 uF the effec-tive capacity that appears at the out-

put terminals is 1000 x 10 uF or10,000 uF. Almost any capacity valuecan be used for Cx.

PARTS LIST FOR C BOOSTER

C1-250-pF disc capacitor, 50 VDCor better

IC1-SE537 Integrated Circuit(Signetics)

R1, R3-10-megohm, 1/2 -wattresistor

R2 -1000 -ohm, 1/2 -watt resistor

IC14 Notch Filter Oscillator Every experimenter's spare partsbox has the necessary components forour Notch Filter 1 kHz Oscillator. It'ssuitable for testing audio equipment,signal tracing or tape recorder biasadjustments. Integrated circuit IC1can be just about any operational am-plifier sold through "surplus dealers."The 1 kHz "notch filter" from theamplifier output to the inverting ornegative (-) input determines the

output frequency. Notch Filter Oscil-lator's non -inverting or positive (+)input is grounded.

The power supply is bi-polar; useany voltage up to ±15 VDC. Whileresistor R5 is not needed in manyinstances, its use insures your NotchFilter Oscillator project's success.Potentiometer R I sets the outputlevel; its maximum value will ap-proach the total power supply volt-

age. If fine output control is desired,add potentiometer R6.

When your Notch Filter Oscillatoris connected to a DC circuit, connecta DC blocking capacitor in series withR6's wiper arm. If the oscillator is todrive circuits of less than 10K ohmimpedance, substitute a 1-uF non -polarized capacitor for C4, rated tothe power supply's voltage.

R2 R3

C4 r-- R6IbiF 1 100K

FINECONTROLLEDOUTPUT

1-41)OUTPUT

I

PARTS LIST FORNOTCH FILTER OSCILLATOR

C1, C2, C3-0.005-uF, 75 VDCcapacitor

C4-0.1-uF (see text) capacitorIC1-741-type operational amplifier

R1-10,000 ohmspot

R2, R3 -47,000 -ohms, 1/2 -wattresistor

R4 -3,900 -ohms, V2 -watt resistorR5 -10,000 -ohms, 1/2 -watt resistor

:see text)R6-Potentiometer, 100,000 -ohms,

audio taper (see text)

1C15 Electric Butler Intercom Using a miniature 1 watt IC poweramplifier, our Electric Butler providesvery high sensitivity and a loud, cleanoutput. Wiring and layout is not criti-cal as long as capacitors C4 and C5are installed directly at ICI's termi-nals. Capacitor C6 can be as low as100 uF if you want to cut costs andare willing to give up a little bassresponse. While SI can be a standard101 ELECTRONIC PROJECTS 1978

DPDT switch, a spring -return typewill keep the Master station alwaysmonitoring the Remote.

The speakers can be any "intercomtype" rated from 20 to 45 ohms.Though miniature 16 ohm speakerscan be used, they do not have thepower handling capacity of the "inter-com" speaker. If there appears to besome high frequency instability, use

a shielded wire between Si and RI;make a single -shield ground at R 1.

If an AC power supply is used, itmust be rated for at least 100 mAdrain. If a battery supply is used,figure the 10 mA idling current; thebatteries will be able to deliver the100 mA maximum output peak cur-rent. Solder a 1 inch square tin heatsink to ICI's tab during construction.

65

PARTS LIST FORELECTRIC BUTLER INTERCOM

C1-0.2-uF, 3 VDC capacitorC2-0.02-uF, 3 VDC capacitorC3-100-uF, 25 VDC capacitorC4-0.05-uF, 75 VDC capacitorC5-0.001-uF, 10 VDC capacitorC6-200-uF, 25 VDC capacitor (see

text)IC1-General Electric PA -234Q1-NPN transistor 2N3391

(H EP 726)R1-Potentiometer, 5,000 -ohms,

audio taper resistorR2-2.2 megohms, 1/2 -watt resistorR3 -22,000 -ohms, 1/2 -watt resistorR4, R6 -100,000 -ohms, 1/2 -watt

0IBOTTOM VIEW

FLAT

BASE MASTERSTATION

EMITTERCOLLECTOR

R2

01

CI E 2N3391

R3

.02pF 100K

R710

RI5K

10mo IDLE+22VDC 100mA PEAK

SPKI20-450

C5.00IpF

R5IM

R6100 K

LISTEN

TALKSI

resistorR5-1 megohm, 1/2 -watt resistorR7 -10 -ohms, 1/2 -watt resistor

REMOTESTATION

SPK 2

4520-0

7 5 3 I

/ 8 10 12 14

HEAT SINK TAB TOP VIEW

SPK1, SPK2-Speaker, 20 to 45ohms, (see text)

S1-Switch, DPDT (see text)

1C16 Ultimate Talk Power

0 Operating directly from micro-phone level and providing a nominalI V output, this compressor delivers20 dB of compression (essentiallydistortion -free limiting) and will giveultimate talk -power to P.A. systemsand ham or CB transmitters. Fact is,some sideband transmitters might notbe able to handle the almost continu-ous "peak power" output of ourcompressor!

The only restriction on its use isthat the microphone, DM1, must bethe dynamic type: any impedancefrom 50 to 50,000 ohms will work.If DM1 can be permanently con-nected to the circuit, components R2and C3 can be eliminated. But theymust be used if there is any possibilityDM I will be disconnected. No sub-stitution can be made for transistorQl.

Capacitors C6 and C8 must be in-stalled directly at the IC terminals forinstability suppression. Capacitors CSand C9 can be installed anywherethat's convenient. A bi-polar 12Vsupply (well filtered) is required.Power can be provided by batteries

.25pF I

BOTTOM VIEW

C2

)1+10pF

012N3820

Cl2 _L.002 -

pF

RIVIPS100K

10

DMCII 1

50pF

R5

IM

C3

1

.1pF

ICI

0 C5+I2VDC 1021

100PF C4

R3 .-±-1 -.1pF

DI

14

100K

MCI433G2

R247K

-12VDC

3

.1uF

5

C7

50pF

.1pF

C9100pF

PARTS LIST FORULTIMATE TALK -POWER

C1-0.25-uF, 10 VDC capacitorC2-10-uF, 10 VDC capacitorC3, C4, C6, C8, C10-0.1-uF, 75

VDC capacitorC5, C9-100-uF, 15 VDC capacitorC7, C11-50-pF, 75 VDC disc

capacitorC12-0.002-uF, 25 VDC capacitorIC1 -Motorola MC -1433GR1 -100,000 -ohms, 1/2 -watt resistor

R44700

CIO

ICIBOTTOM VIEW

I I-0.1pF OUTPUT APPROX

IV. 50K OR HIGHERLEVEL

R2 -47,000 -ohms, 1/2 -watt resistorR3 -100 -ohms, V2-wa-1 resistorR4 -4,700 -ohms, 1/2 -watt resistorR5-1 megohm, 1/2 -watt resistorDM1-Dynamic microphone (see

text)01, D2-Germanium diode, 1N60

or equiv.Q1-FET transistor, type 2N3820

(Texas Instruments)

(for total hum -free operation) be-cause the current requirement is ap-

proximately 15 mA. Any gain controlsmust come after the output at C10.

IC17 Tape Head Preamplifier0 Is it worth about $20 to have an-other tape or cassette player? Fromtime to time surplus dealers offercomplete tape or cassette mechanisms-everything ready -to -go except for

the electronics, and at rock -bottomprices of $10, $15 or $20. All themechanism needs is this equalizedtape head preamplifier. Though thepower supply is rated at ±15 VDC,

almost optimum results will be ob-tained with supply voltages as low as

VDC. Two ordinary 9 -volt tran-sistor radio batteries will power thepreamp for many hours.


The op amp, ICI, is internally com-pensated and no special wiring prac-tices are needed; the preamp can bebuilt in just about any enclosure,though the connecting wire from thetape head should be shielded. R Iconnects to the non -inverting ( +1input of the IC, R2 between the out-put and the inverting (-) input. Nopin connections are given because theIC is available in many different pinconfigurations.

PARTS LIST FORTAPE HEAD PREAMP

C1-22-uF electrolytic capacitor,25 VDC or better (CalectroA1-128)

C2-0.005-uF disc capacitor, 25VDC or better

C3-0.01-uF disc capacitor, 25VDC or better

IC1-Type 741 op ampR1 -100 -ohms, 1/z -watt resistorR2 -100,000 -ohms, 1/z -watt resistor

C3OluF

IC18 Stereo BalancerP By comparing the difference be-tween channel outputs when feedinga mono signal, this differential stereobalancer meter allows you to set yourstereo amplifier for precise electricalbalance. Wiring is not critical; thecircuitry can very easily be batterypowered using a bi-polar battery con-nection as shown.

To use, set your sterec amplifier tomono-then adjust the balance controluntil meter Ml indicates a null (mini-mum reading). If you cannot obtaina null it indicates there is a phasereversal-which should be corrected-between the signal input and thespeaker terminals. This circuit workson the differential principle. When an

amplifier is in perfect balance there isno difference in mono output voltagebetween channels. So our differentialamplifier indicates zero difference onThe meter.

14 13 12 11 10 9 8

N OTC H

O1 2 3 4 5 6 7 RI

ICI (TOP VIEW) SSS,1 100K

R3INPUTS FROM LEFT 10KSPEAKERTERMINALS RIGHT1 =.

--- R2

100K

R510

2

5

+9VDC

-9VDC

ifC2500F

R73600

IOK

C350yF

-9v

9VDC

B2

PARTS LIST FORSTEREO BALANCER

61, B2-Battery, 9V, type 2U6C1-0.05-uF, 50 VDC capacitorC2, C3-47-uF, 50 VDC capacitorC4-50-pf, 100 VDC capacitorIC1 -Motorola MC -1433P'41 -VU meter (Calectro D1-958)R1, R2, R6 -100,000 -ohms, 1/2 -watt

resistorR3, R4 -10,000 -ohms, 1/2 -watt

resistorR5 -10 -ohms, 1/2 -watt resistorR7-3,600 ohms (usually with VU

meter) resistor

1C19 The Basic Amplifier

This general purpose amplifier fea-tures a power gain of 100 (20dB)and can be used as a preamplifier fora microphone, receiver, signal tracer,etc. The IC is internally compensated,providing stable performance with aflat frequency response to about 10kHz with a gradual roll -off to 20kHz. The overall gain can be reducedto 10 by increasing the value of R2to 100,000 -ohms. ICI is available inseveral different packages; use the onemost convenient for your particularcomponent layout. R3 connects to the101 ELECTRONIC PROJECTS 1978

PARTS LIST FORTHE BASIC AMPLIFIER

C1-0.1-uF Mylar capacitor, 25 VDCIC1-Type 741 operational amplifierR1, R3-1 megohm, 1/z -watt resistorR2 -10,000 -ohm, 1/z -watt resistor,

(see text)

RIMEG

non -inverting (+) input ofRI between the output andverting ( - ) input. No pin

the IC,the in-connec-

tions are given because the IC isavailable in many different configura-tions.

67

COMPUTER FIEW PROOLETSHere in one place the editors of 101 ELECTRONIC PROJECTS present

for you the latest in home and hobby computers

4rCiHigh Speed Logic Probe-ContinentalSpecialties claims to have broken aspeed limit with this LP -3 High SpeedLogic probe which is capable of de-tecting pulses as fast as 10 nanosec-onds. The pulse detector can read bothpositive and negative -going leadingedges. The pulse stretcher then length-ens the pulse to a tenth of a second. Asingle pulse causes a single blink ofthe Pulse LED. A pulse train causes itto flash at a 10 Hz rate. With the Pulse/Memory switch in the memory position,a pulse will latch the LED on indefi-nitely. The high and low LEDs may alsocome into play during pulse trains, per-

mitting an easy estimation of the pulse duty cycle. High and low logic statesare read independently by separate dual threshold window comparators to permitfull logic state analysis. A slide switch selects suitable threshold levels for eitherTTL/DTL or CMOS/HTL logic families. Since power is derived from the circuitunder test, no phantom logic state readings are possible. Input impedance is 550K,and input is protected against 117VAC overloads for up to 15 seconds. Inter-changeable power leads and replaceable- probe tips and accessories are avail-able. Price of the LP -3 is $69.95. Circle 57 on Reader Service Coupon.

Power Supply/CPU Board-PAiA Elec-tronics' 8700 Computer/Controller, anOEM micro -processor development sys-tem, is based on the popular 650X fam-ily of processors. Its fully socketed,plated through board provides space for1K bytes of RAM in 256 byte increments(2112) and 1K bytes of PROM also in256 byte increments (2112), five 8 -bitparallel input ports and one 8 -bit paral-lel output port. Several connectors arefor system expansion and the imple-mentation of more complex I/O struc-tures. A unique microdiagnostic featureprovides simple system check-out byfloating the MPU data buss while forcing the execution of an address -increment-ing NOP instruction. The PAiA 8700 is available in kit or assembled form at pricesstarting at $90. Currently available options include a PS -87 Power Supply pricedat $24.95 (shown), and CS -87 Cassette Interface ($22.50) which also provideson -board software and hardware relay drivers for tape motion control. A variey oflow-cost (under $40) video display options for the 8700 including 80 x 16 Upperand Upper/Lower case ASCII and 128 and 256 color and B/W graphics displaysare scheduled for near -future release. Circle 55 on Reader Service Coupon formore information about this product from PAiA Electronics.

110 OW /1994).111.6 'Stk.

.......board selectable. Functions carried

Math Board-Developed by PetrotechLavalin and available from WoodtronLtd. in Canada or La Porte Electronicsin Texas, this math board reduces thesize of RAM required to compute stand-ard math functions and operates withmicrocomputers such as the MotorolaM6800 or Intel 8080. That math boardoperates as a block of memory occupy-ing 16 address states which are on

out on the math board are trigonometric,logarithmic, ex, square roots, and many more. In addition, 16 address and eightdata line boosters are provided along with two RS 232 receiver channels. Theseboards are available in kit form, which consists of printed 93/4 -in. x 51/2 -in circuitboard, instructions, and a software package of input-output routines for an M6800.Price: $72.80. Circle 50 on Reader Service Coupon for more information aboutthis product from Petrotech Lavalin.

Mitt

5 -Volt, 8K EPROM-Inte 's 2758 5 -volt,8 -kilobit EPROM (erasable programmableread-only memory) is claimed to providesignificant advantages in microcomputersystem designs. Operation on a single+5 -volt TTL power supply eliminatesspecial MOS supplies from systemsbased on 5 -volt microprocessors, andalso minimizes costs in other systems.The 2758 is directly uperadable to 16Kmasked ROM. There's complete freedomto change system storage capacity in 1K -byte increments with no design changes.Reduced power and cooling costs be-cause the 2758 reduces active power dis-sipation by more than fifty percent, anda new standby mode can be used to re-duce dissipation by more than eighty per-cent. Programming rates two to 2,000times faster, depending on the numberof bytes stored at a time. Easily pro-grammed in a system; tiis feature canbe used in new designs to save socket-ing and to automate updates of programs.The 2758 stores 1024 x 6 bits (1K byte),is TTL-compatible in all modes-activeoperation, standby and programming-and has a maximum access time of 450nanoseconds. Price: $40. Circle 48 onReader Service Coupon fcr more informa-tion from Intel about this product.

High -density Memory Bcards-Intel hascome up with three Multibus high -densitymemory expansion boards for SBC-80single board computers. Designated asSBC 032, SBC 048 and SBC 064 RAMMemory Expansion Boards, they respec-



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- a free service to all whowant more information and lit-erature on products and serv-ices advertised in this issue.

Simply tear out the perforated card,carefully print your name andaddress (and zip), then circle thenumbers corresponding to the num-bers below the advertisement or thenumbers identifying products men-tioned in columns and articles thatinterest you. No postage, no chargeat all-for you- convenience andinformation.

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magazine that covers- In every 100 -page issue at least

3 expertly written articles on thelatest CB equ pment. proceduresand regulations-keeping youfully abreast of all CB develop-ments.

The entire area of radiocommunication.

Action Bands-police, fire,marine, air traffic control, etc.Many CBers tune in on thesebands.

Shortwave racio-listen in toplaces like Papeete, Kuwait.Kinshasa and ether distant,exotic parts of the globe.

How to build all kinds of usefuland fun gadgets for home, car.your CB, your iarkroom.

Basic Courses that help youmaster some important aspect ofelectricity or e ectronics so youmay fully understand, forexample, how your CB works.

elementary.ElectronicsSUBSCRIPTIONORDERCARD

C-7-"e 101 Electronic Projects looks at some of the newest transceivers,

La..

antennas and accessories for you to use in CB contacts this year!

PR UC

Voice Activated CB HeadsetFor use with any two-way communica-tions system, Speak Easy is easily in-stalled in home or vehicle CB rig. WithSpeak Easy you no longer have to holdand key a microphone to be heard.Simply speak and it will automaticallytransmit your message. A powerful minia-turized pre -amp delivers your voice to itsdestination. Dual red/green LEDs tellyou when you're on the air. Fully ad-justable sensitivity gives you total soundcontrol. Speak Easy comes with two


miniaturized microphones built in toboost modulation and effectively elimi-nate background noise. Made with a

durable and lightweight aluminum boommike, Speak Easy is both rugged andcomfortable. Suggested retail price is$79.95. For more information, write toChase Western Product Sales, 11526Burbank Blvd., Suite 17, North Holly-wood, CA 91601.

Silent Vehicle AlarmThe Page Alert 101 Silent Vehicle Alarmalerts you with a pocket pager "beepbeep" signal when your mobile CB rig, oreven your car, is in the process of beingripped off. The system consists of asmall transmitter that sends out an indi-vidually coded radio signal when thedoors, hood or trunk of your vehicle areopened. This signal is received by a

small pocket pager, much like the kinddoctors use, conveniently worn on yourbelt or carried in your pocket or purse.A "crime -in -progress" telephone call canbe made to the police after hearing yourpocket pager's warning "beep." The


Page Alert 101's pocket pager can becarried more than V2 mile from the ve-hicle. No special installation beyond theusual car alarm system is required toinstall the Page Alert 101 transmitter.The solid-state transmitter is powered bythe vehicle's 12 -volt battery and thepocket page uses batteries. There areover 60,000 individual tone codes sothat there is no chance of anothertransmitter signalling the wrong re-ceiver. Although compatible with anyexisting horn or bell audible alarm, usedalone the Page Alert 101 is a silentvehicle alarm device. The complete PageAlert 101 (sells for $189.50) along withinstallation accessories is available fromPage Alert Systems, Inc., 23840 MadisonStreet, Torrance CA 90505.

Absorbtive TVI FilterThe CPI FL -1, according to the manufa.:-turer, attenuates all 27 MHz harmonicfrequencies by 90 dB or better, withouttroublesome tuning for optimum har-monic rejection. The FL -1 has up to 10watts power dissipation capability, so allCB harmonics will be absorbed ratherthan reflected back to the transceiverwhere they could radiate off the coaxial


cable or from the set. The unit has apower -through rating of 650 watts. Inaddition, the TVI filter also serves as anantenna -transceiver matchbox. Input and

oLtput tuning controls in the CPI FL -1filter will match a 3:1 antenna SWridown to 1:1 at 50 ohms. Insertion lossis reduced to only 0.3 dB. Priced to sellat $49.95. Further information on theCPI FL -1 TVI filter, and the completelire of the company's high technology,American -made communications gear, isavailable from Communications Power,Inc., 2407 Charleston Road, MountainView, CA 94043.

Magnetic Mount AntennaA new, 40 -channel mobile CB antennasystem has been announced by AvantiResearch & Development, Inc. Featuringa powerful magnetic mount for roof ortrunk locations. Model AV -727 permitsinstant removal for hideaway or carwash. A mylar pad protects the vehiclefinish. Other features includes a hermeti-cally seated coil to maintain antenna im-

CIRCLE 51 ONREADER SERVICE

COUPON

pedance and eliminate internal surfaceleakage, a ribbed base to provide a longleakage path, and a 48 -in. whip. Thesystem, complete with an 18 -ft. coaxialcable, is 'priced at $32.95. Avanti Re-search & Development, Inc., 340 StewartAvenue, Addison, IL 60101.

All Stainless Steel Bumper Mount"Bumper Mate" (Model #HWM-19) isanother new addition to the line of CBartennas and accessories from Anixter-Mark. The makers says that this is thefirst all stainless steel antenna bumpermount. Motorists can not only put anend to rusty bumper mounts, but thismount will probably outlast chromedbumpers. It's fully adjustable and fitspractically all bumpers. The perforatedstrap allows the antenna mount to beplaced anywhere on the bumper. Thefull adjustment allows compensation forthe angle of the mounting surface of thebumper. Clamp the mount on anybumper, tighten the bolts and it's readyto go. The Anixter-Mark "Bumper Mate"will accept any antenna with a 3/8-4124



IC20 Versatile Hi -Pass Filter A high pass filter is a handy de-vice to have around. Depending onthe corner (turnover) frequency youselect it can serve as a hum filter,distortion meter or highly -selectiveaudio equalizer. The values of Cl,C2, C3 and R1 provide a corner fre-quency of 1000 Hz. The IC has in-ternal compensation so special wiringtechniques are unnecssary. No pinconnections are given because the 741IC is available in many different pinconfigurations. Check the manufac-turer's specs for the particular IC

used. R2 connects to the non -invert-ing (+) input of the IC, R1 between

the output and the inverting (-)input.

PARTS LIST FORVERSATILE HI -PASS FILTER

C1, C2, C3-470-pF, disc capacitor,50 VDC or better

IC1-741-type operationalamplifier

R1, R2-10 megohms, 1/2 -wattresistor

R3 -10,000 -ohms, 1/2 -watt resistor

1C21 Cigar -Size Amplifier Using an IC no larger than a fly,Cigar -Size Amplifier delivers almost250 mW into a 16 -ohm speaker. A50 mV input signal coming from asource whose output impedance is1000 ohms or lower is required formaximum output. The power supply

can be a 9 volt type 2U6 battery; theidling current is no higher than 6mA. Best way to keep things small isto use a printed circuit board as-sembly or a mini -mount as shown.

Cigar -size amplifier can serve as ageneral utility amplifier for checking

out low-level audio projects, or it canserve as a monitoring amplifier fortape and cassette decks.

IKINPUTIMPEDANCEI

10K

C42500F+

16 -OHMOUTPUT

ICITOP VIEW

DOT

PARTS LIST FORCIGAR -SIZE AMPLIFIER

C1-5-uF, 10 VDC capacitorC2-0.005-uF, 10 VDC capacitorC3-0.003-uF, 10 VDC capacitorC4-250-uF, 10 VDC capacitorC5-50-uF, 10 VDC capacitorICI-Motorola MFC 4000R1 -1,000 -ohms, 1/2 -watt resistorR2 -4,700 -ohms, 1/2 -watt resistorR3 -10,000 -ohms, 1/2 -watt resistor

IC22 Protect -A -VoltO A simple turn of a knob sets Pro-tect -a -Volt's output voltage anywherein the 3 to 20 -volt range-and with

full short circuit protection! Shouldthere be a wiring error in the poweredproject, this supply automatically

SRI

ICI BOTTOM VIEW

PARTS LIST FORPROTECT -A -VOLT

C1-2000-uF, 25 VDC capacitor(see text)

C2, C3-0.1-uF, 75 VDC disc orMylar capacitor

IC1-Motorola MC -1461RR1 -50,000 -ohms potR2 -6,800 -ohms, V2 -watt resistorR3 -3 -ohms, 1/2 -watt resistorR4 -27 -ohms, 1/2 -watt resistorSRI, SR2-Silicon rectifier, 50

PIV, 1AT1-Power transformer; 117 VAC

primary, 30 VC.T.: 200 mAsecondary (see text)


shuts down the output voltage untilthe overload is removed. The maxi-mum output current (short circuitprotection) has been established byresistor R3's value to 200 mA. Powertransformer Ti's rating should notexceed 200 mA as extra current ca-pacity could not be handled by the

integrated circuit.To make this project easy to build,

and to sharply reduce total cost, itwas necessary to eliminate a fully off,or zero output, setting for VoltageAdjust control R1. The minimumoutput voltage is 3V. The maximumvoltage from Ti's secondary must be

30V rms if the secondary is center -tapped; 15V rms if there is no center -tap and a bridge -rectifier is substi-tuted for silicon rectifiers SRI andSR2. Capacitor Cl's voltage ratingmust be 25 volts minimum. Do noteliminate high -frequency -compensa-tion network components R4/C3.

IC23 Hi -Level 4 -Channel MixerD Best signal to noise ratio in amicrophone mixer is always obtainedif amplification is provided ahead ofthe loss in the mixer network. Youcan easily put this idea to work withour mixer-a full -fidelity, professional -grade microphone mixer that con-tains four independent amplifierswithin the integrated circuit.

For simplification, our schematicshows only the connections for oneof the four amplifiers; the others areidentical to the first.

Note that the power supply is a

single -ended 12 VDC (negativegrounded ); it must be well filtered,or, use a battery supply. The currentrequirements are approximately 30mA total. The power supply is inter-nally connected to the amplifiers.

To prevent high frequency oscilla-tion, components C3, R2 and C5must be installed directly at the IC'sterminals.

Any 50 to 50,000 ohm dynamicmicrophone can be used. However,crystal and ceramic mikes won't workwith Pro -Mix; the medium imped-

INPUT

I

NOTCH

(16 15 14 13 12 II 10 9

h 1 Al 1 I IL 11

CI

.10F

C22000F

1 2 3 4 5 6 7ICI

TOP VIEW

8

PARTS LIST FOR HI -LEVEL MIXER

C1-0.1-uF, 3 VDC capacitorC2-200-uF, 3 VDC capacitorC3-0.05-uF, 75 VDC disc capacitorC4-1-uF, 15 VDC capacitorC5-0.1-uF, 15 VDC capacitor

IC1-RCA CA 3052R1 -100 -ohms, 1/2 -watt resistorR2-, -.7 -ohms, 1/2 -watt resistorR3-Potentiometer, 10,000 -ohms

audio taperR4 -10,000 -ohms, 1/2 -watt resistor

ante IC's medium input impedancewill excessively load down a high im-

pedance mike, resulting in sharp, low -frequency attenuation.

IC24 SCA AdaptorEl This simple but very effective SCAAdaptor can be assembled on a sec-tion of perfboard about 2 -in. x 3 -in.

in size. All components should befirmly soldered to push -in terminals.

R7

TO FMDETECTORBEFOREDE -EMPHASISCIRCUIT

R6

8 10

IC INE565A

9

C3

7

4

PARTS LIST FOR THESCA ADAPTOR

C1, C2-510-pF, 500 VDC ceramicdisc capacitor

/4.10 TO\ +24 VDC C3, C7-0.001-uF, 75 V Mylar

capacitorC4, C6-0.018-uF, 500 VDC

C6 ceramic disc or Mylar capacitorC41

CS

C5-0.047-uF, 75 VDC Mylarcapacitor

R8 R9 RIO JI IC1-Signetics NE565AOUTPUT J1-Phono jack

R1, R2, R3, R4 -4700 -ohm, V2 -watt14 13 12 II 10 9 resistorI I Illl R5 -10,000 -ohm, I/2 -watt resistor

ICI R6 -1800 -ohm, 1/2 -watt resistorTOP VIEW

R7 -5000 -ohm potentiometer1 1 1 1 1 1 R8, R9, R10 -1000 -ohm, V2 -watt1 2 3 4 5 6

resistor


The input must connect to the FMreceiver's detector output before thede -emphasis network. The SCA out-put at J1 can be connected to anyrelatively high -gain amplifier-the out-put level is about equal to that of acrystal microphone.

The FM receiver must be tuned toa station you know has SCA pro-gramming. Then adjust potentiometerR7 for a clean SCA audio output.Potentiometer R7's adjustment is notcritical-the subcarrier is pulled inwhen R7's adjustment is near the

correct setting. A metal cabinet is sug-gested. If desired, a pre de -emphasisoutput jack can be installed on theFM receiver or tuner so that the nor-mal (after de -emphasis) output canfeed the hi-fi system independent ofthe SCA output.

1C25 Stereo Mike Preamplifier A dual IC gives hi-fi amplificationfor a stereo microphone pair. Lowdistortion and full -fidelity frequencyresponse characterize this mike pre -amp. With resistors R1 and R2 pro-viding a center -tap for the powersupply, the IC can be powered froma standard single -ended power supply,or series connected batteries.

Be very careful to observe the cor-

rect polarity for capacitors C2 andC3. In the event the unit motorboats(low frequency oscillation), install a0.1 uF capacitor from pin 14 toground.

The connections for one of the twoamplifiers is shown circled; the con-nections for the second amplifier areuncircled. Pins 7 and 14 are commonto both amplifiers. Capacitor Cx's

value is determined ly the load im-pedance. It should be of such valueas to provide the desired overall lowfrequency response; 0.1 uF is sug-gested for high impedance outputloads (100K and higher), while 10uF is suggested for low impedanceloads.

MICROPHONEINPUT

CI.1pF

f_11.C2= 25mP

C3

25pF IK 100K

24-26VDC

C5I 50yF14

CK

14 13 12 11 10 9 8

1 2 3 4 5 6 7

ICI( TOP VIEW )

OUTPUT LEADI0K12 OR HIGHER

PARTS LIST FORSTEREO MIKE PREAMP

Cl -0.1-uF, 100 VDC capacitorC2, C3-25-uF, 25 VDC capacitorC4-680-pF disc capacitorC5-50-uF, 25 to 50 VDC capacitorC6-33-pF disc capacitorCx-See textICI-Motorola MC1303LJ1-Microphone jackRI, R2 -2,200 -ohms, E% resistorR3, R5 -100,000 -ohms resistorR4 -1,000 -ohms resistor

1C26 Comm -Press Log Amplifier A log amplifier is a device thattakes a large change in input signaland converts it to a small change inoutput. Hook one into a communica-tions system and both low and loudsounds come out at almost the samelevel giving you a lot more talk power;it sounds just like the hard -sell com-mercials on TV. The input levelshould be about 0.1 volt peak for an

output voltage of about 1 volt peak.Since this is a high frequency de-

vice, lead dress and good power sup-ply bypassing at the power supplyterminals are required. Keep theground leads short. If a microphonepreamplifier is used before the logamplifier, connect a volume controlbefore the log amp's input.

Some experimentation will be

needed for optimum P.A. operation.Because of the much higher averagevoice power, a P.A. system using alog amp compressor might appear tobe more sensitive to acoustic feed-back (howling). Ac:ually, you willhave much more voice output beforethe howling starts.

+ 6 VDC

INPUT

OUTPUT

PARTS LIST FORTHE COMM-PRESS LOG AMP



C3-0.1-uF, 75 VDC Mylar capacitor01, D2-Diode, Silicon, 1N914IC1-Signetics SE501R1-510-ohm,'/2-watt resistor

74 101 ELECTRONIC PROJECTS 1978 '

IC27 Porta-Groove AmplifierEl Just add a battery -powered motorto our Porta-Groove Amp, and you'vemade a portable phonograph of con-siderably better quality than you canbuy. Phono pickup X1 must be theceramic type-either the usual highimpedance or so-called low imped-ance (actually several thousandohms) ceramic type can be used.

Transformer T1 should have a pri-mary impedance anywhere from 150to 300 ohms center -tapped. The sec-ondary should match the speaker im-pedance. Do not use a sub -miniatureTl; for good sound quality Ti musthave sufficient "iron," so make cer-tain it can handle approximately 25mA average current.

A 6 -inch speaker will deliver re-markably good sound quality, at leastthe equal of a good quality tableradio. Two 6V lantern batteries oreight D cells easy give Porta-GrooveAmp enough oomph. Do not use C orAA cells; they cannot give even rea-sonable life with the 20 mA idlingdrain, 140 mA peak power drain.

PARTS LIST FORPORTA-GROOVE AMP

Cl, C2, C4-5-uF, 6 VDCC3-0.01-uF, 10 VDCC5-50-uF, 15 VDCC6-.005-uF, 15 VDCR 1-Potentiometer, 1 megohm

audio taperR2 -470,000 -ohms, 1/2 -watt resistorR3-Potentiometer, 3 megohmsR4 -510,000 -ohms, 1/2 -watt resistorR5 -1,000 -ohms, 1/2 -watt resistorSPK1-Speaker, 3.2, 4 or 6-8 ohmsT1-Output transformer, 150 to 300

-E-C)5R2 50V1

4701(

VOLUME

C6005

OF

ICIBOTTOMVIEW 4700

ohms center -tapped primarycoil to speaker impedance (seetext) (Ca'ectro D1-729 or equiv.)

TI

03 C4Oluf I

9 I2VDC

SPX

IC1-RCA CA3020 or CA3020AX1-Ceramic phono pickup (see

text-Calectro S2-288 or equiv.)

1C28 Record Remote Amplifier Here's a professional performancerecord remote amplifier suitable forthe hobbyist, amateur recordist orprofessional broadcast engineer. Theinput is any microphone with an out-put impedance up to 50,000 ohms, orfor professional use, the input can beat line level. Output is 500 -ohms atline level with a bulit-in VU meterindicating output level. When the dis-tance between the remote amplifier

and its associated equipment is lessthan 25 feet the amplifier can be con-nected to any hi-fi type, high imped-ance input (10,000 -ohms or higher).

For long line or professional ap-plications, connect a 500/500 linematching transformer to output jackJ2. Capacitor C4 is 0.1 tiF for all ap-plications except when used with aline matching transformer. When atransformer is used C4 is 25 uF. Bet-

ter results can be obtained with a linematc' ing transformer if the trans-former primary replaces R4 (elimi-nating C4).

M1 is a standard VU meter whoseinternal rectifier has been removed(open the case and unsolder the recti-fier). Total current drain is less than5 mA and the bi-polar power supplycan consist of two transistor radiotype 9 -volt batteries.

INPUTJI

OUTPUTJ2

15

8 7

ICIBOTTOM VIEW

PARTS LIST FORRECORD REMOTE AMPLIFIER


C2, C3-47-uF, 50 VDC electrolyticcapacitor

C4-0.1-uF or 25-uF, 12 VDCcapacitor (see text)

D1, D2, D3, D4 -1N60ICI-Type 741 operational amplifier11, J2-Shielded jacksMI-VU meter with internal rectifier

removed (Calectro D1-930 orequiv.)

R1 -50,000 -ohm audio taperpotentiometer

R2 -100 -ohm, 1/2 -watt resistorR3 -15,000 -ohm, V2 -watt resistorR4 -560 -ohm, Y2 -watt resistor


1C29 Far Out Gain Control12 One of the problems of locating avolume control in a remote location isthaPof hum and noise pickup; as ageneral rule, the greater the wirelength the greater the hum and noisepicked up. With an electronic attenu-ator the entire problem is eliminated,for the volume control wires carryonly a DC control voltage whichcauses an integrated circuit ampli-fier's gain to vary by as much as 90dB. Hum and noise picked up in theDC control wires are not impressedon the amplified audio signal.

No layout precautions are requiredand any type of assembly can be used.If desired, the amplifier gain can bevoltage controlled by eliminating po-

tentiometer R 1 and applying 3.5 to6 volts DC directly to pin 2. With3.5 VDC the amplifier works at fullgain. The attenuation increases to amaximum of 90 dB as the controlvoltage is increased to 6 VDC.

PARTS LIST FORTHE FAR OUT GAIN CONTROL

C1-0.47-uF, 25 VDC capacitorC2-50-uF, 25 VDC capacitorC3-680-pF, 500 VDC ceramic disc

capacitor 5

C4-0.1-uF, 75 VDC Mylar capacitorIC1-Motorola MFC 6040R1 -50,000 -ohm potentiometer

CI

INPUT -1

6-4 -

ICI -TOP VIEW

+ 9- 20 VDC

4ICI

3 MFC6040

3

C4

Ft...OUTPUT

C3

RI

REMOTELYLOCATEDPOTENT IOME TER

1C30 No -Noise Mike Preamplifier+ 30 VDC

C

INPUT

R R2

R4

R3

C4

PARTS LIST FORTHE NO -NOISE MIKE PREAMP


C2-100-uF, 12 VDC electrolyticCS

I 1----IPOUT PUT capacitorC3-0.047-uF Mylar capacitorC4, C5-0.1-uF Mylar capacitorIC1-Motorola MFC 8040R1 -75,000 -ohm, 1/2 -watt resistor4

32- 5

67 R2 -270,000 -ohm, 1/2 -watt resistor0

R3 -110,000 -ohm, 1/2 -watt resistorICI

VIEWTOP R4 -100 -ohm, 1/2 -watt resistor

1:1 Packing a walloping 60 dB gainwith a 7 volt output, this mike preampnevertheless is almost dead quiet. Theinput impedance is about 75,000 -ohms; output impedance about 100 -

ohms. Actual maximum output volt-age depends upon the load resistance,ranging from 7 volts output into a10,000 -ohm load to 4 volts outputinto a 1000 -ohm load. Parts layout is

not critical and any type of assemblycan be used. The power supply cur-rent is approximately 8 mA, with amaximum of 12 mA.


BUILD CHEdERBOAlb FOR QUIEK ERIN

andful of parts plugged into solderless breadboard make a testerfor crystals, diodes, LEDs and lots m ,re.

by Marlireinstein

I built a crystal tester several yearsago and had an accident. Two of theconnections were accidentally shortedtogether when I soldered the parts to-gether. As a result, I soon discoveredthat my crystal tester was also good asa diode tester, a LED tester, a con-tinuity tester, an electrolytic tester andmore.

Now that's what I call a happy acci-dent!

The whole circuit was built onto ascrap of printed circuit board andmounted in a small plastic box. I'veused it for years, and it's come in handydozens of times. Recently, while chat-ting with a couple of ELECTRONICSHOBBYIST editors it occurred to us thatsome of you might enjoy this handylittle gadget. So I rebuilt it one eveningon a small, inexpensive solderless bread-board. And now I can pass the secretsof this marvelous little Checker Boardon to you.

What It Can Do. Checker Boardstarted out as a crystal tester, with thedesired action that a good crystal lightsthe LED and that a bad crystal won't.You can also use it to check out somany other components with just assimple an indication. These are someof the things you can test with yourChecker Board: lamps, switches, diodes,LEDs, cables, capacitors, crystals.printed circuit traces, connectors andmore. You can even use Checker Boardto test itself!

How It Works, Part One. Transistor

QI and the parts near it, R1, R2, Cl,and C2, work together with the crystalyou connect into the circuit as a simplecrystal oscillator. Without a good crys-tal, the circuit will not oscillate. Whenit does oscillate, a signal appears atthe emitter of Ql.

Capacitor C3 passes this signal todiodes DI and D2, which are connectedas a rectifier. They convert the signal(which is a high -frequency AC signal,at the frequency of the crystal) to abumpy DC signal. C4 smoothes outmost of the blimps. As result, the signalthat leaves Q1 arrives at Q2 as a smallDC voltage. Q2 then acts as a switch.When the DC voltage appears at itsbase, it completes the circuit from thebattery and switch, through R3 andthe LED, to ground. When this hap-pens, the LED turns on.

With no signal coming out of QI,no voltage appears at the base of Q2 soit doesn't turn on, and neither does the*LED. R3 limits the current that cango through the LED to keep it fromburning out and to help gibe it a verylong life. It also lengthens CheckerBoard's battery's life.

And that's how Checker Boardchecks crystals.

How It Works, Part Two. Take agood look at R4. It acts as a kind ofcheater, connecting the cathode endof the LED to the red clip. So, whenthere's no crystal in the circuit, R3,R4 and D3 are the only parts of thecircuit actually connected to the clips,

the switch and the battery. The equiva-lent circuit is shown nearby. As youcan see, whatever you connect to thealligator clips then completes the cir-cuit to light the LED. The purpose ofR4, here, is to keep this mode of op-eration from interfering with CheckerBoar,"s performance as a crystal tester,since that's why we built it.

Building Checker Board. Use anyconstruction technique you feel com-fortable with. Nothing is very critical,and you can try lots of other values forany given component and still have aChecker Board that works.

The Checker Board you see here wasbuilt on a small solderless breadboardfrom AP Products. It's fully describedin the Parts List. You can use any sizewire from #20 to #28 to make theconnections between terminals, andmost components' leads plug right in.

You can help the switches, batteryleads and alligator clip leads plug rightin, too, if you use AP Headers. They'resmall contact posts embedded in a plas-tic strip at precise 1/10 -inch intefvals,so they can plug right into the bread-board. Just break off the number ofposts you need from the rest of thestrip, solder your connection to theshort end and plug the long end intothe breadboard.

I used small U-shaped pieces of barewire plugged into several holes in a rowto form a contact pad area, connectedto each clip lead. This makes testinglarger components as easy as touching


CHECKERBOARDtheir leads to the hare wires.

You can use either a momentaryswitch, like a pushbutton, or any spstswitch, or both for SI. It depends onwhether you prefer on -off or push -to -test operation.

If you have trouble relating the sche-matic to the solderless breadboard, itshould clear up quickly once you under-stand how the solderless breadboardis arranged.

There are 17 rows of five holes eachon each side of the center of the bread-board, a total of 34 rows in all. Under-neath each row of five holes is a con-necting spring clip. The clip holds ontowhatever lead you push through thehole. And all the leads you've insertedin any one row (on each side of cen-ter, independently) are connected to-gether.

In other words, there are 34 placeswhere you can tie up to 5 leads to-gether, 17 on each side of the center.

Once you know that, you can cus-tom -design a circuit in just a few min-utes, working directly from your ideaonto one of these breadboards. Or youcan translate a circuit like CheckerBoard into a solderless breadboard lay-out very, very quickly indeed. You cansolder switches and cable leads to head-ers, like these from AP products, andplug them right into either solcrlessbreadboards or female headers, thedarker strips near the center of thephoto. Headers come in rows of 36contact posts, and either cut or can bebroken to length. A single row of maleheaders, widely available, costs less

than a dollar.Using Checker Board. Follow the

instructions below as you test each com-ponent. Generally, components can ei-ther be clipped -to with the alligatorclips, plugged directly into the solder -


,fR 30RICjII)OR

If you use Checkerboard circuit to testcapacitors (electrolytics, tantalums, etc.) ordiodes, LEDs, or switches, here's the actualworking circuit, simplified from the cornplete Checkerboard circuit, which cancheck crystals.

Top view of Checker-board tester assembledon solderless breadboardshows where the parts goif you use this method ofassembly.

Prototype Checkerboard was built on AP Products' solderless breadboard for easeof construction and flexibility in layout. Perf board can also be used.

SINORMALLYOPEN

RED CLIPBLACK CLIP

9VBI

R3220

C3001 D2

( 0

R4470NAA,

DI

CDD3

2

C4005

PARTS LIST FOR CHECKER BOARD

Cl, 3-.001-uF capacitorC2-100-pF capacitorC4-.005-uF capacitor01, 2-1N914 or other general-purpose, rapid -

response silicon diodeD3-LED (light -emitting diode)

2-General-purpose, small -signal NPN

transistor, 2N3904 or similarR1 -3300 -ohm, 1/2 -watt resistorR2 -1000 -ohm, 1/2 -watt resistorR3 -220 -ohm, 1/2 -watt resistorR4 -470 -ohm, 1/2 -watt resistor

S1-SPST toggle switch, or normally -openpushbutton. Use either, or both in paral-lel, as desired.

Misc.-Solderless breadboard (AP Products,Inc. distribution strip part number923273 -for AP dealer see end of PartsList); headers (AP Products), alligator clipswith pastic covers, 9-V battery connector,9-VDC transistor radio batte-y, hookup wire,solder, etc.

For name of dealer nearest you who carriesAP Products telephone 80C-321-9668 tollfree.

The 470 ohm resistor (R4) is included to keep the continuity tester from interferingwith the crystal checker. In the crystal tester mode, the crystal being tested plusC1, R1, R2 and Q1 act as a simple oscillator circuit. If the crystal is good asignal will appear at the emitter of Q1 and be rectified by D1 and D2 into a bumpyDC that will turn on Q2. If the crystal is bad nothing will get past Q1 and, therefore,there will be nothing to turn on Q2 and light LED 1.


ADD TONE TO YOUR PHONEWith your own Touch Tone Pad you can key a phone, computer, or transceiver for peanuts.

One of the most popular hobbyistitems-appealing to hams, experiment-ers, phone phreaks and thousands ofother experimenters-is the Touch -TonePad or Encoder, that two-tone generat-ing device used on Touch -Tone Tele-phones. It seems the uses for theTouch -Tone signals are almost endless:hams use them to activate and useautopatches that permit telephone callsfrom a mobile transceiver to a land -line, experimenters use them in con-junction with the Signetics touch-tonedecoder ICs for remote control appli-cations, and phone phreaks use themto help make "free" (though illegal)long distance calls. Some people usethem to access hobby and time sharedcomputers, and others simply connectthem to standard dial phones to get ad-ditional Touch -Tone service withoutpaying Ma Bell a lifetime's worth ofextra charges for a relatively inexpen-sive extension phone.

In actual fact there is a differencebetween a Touch -Tone Pad and anEncoder. Though they eventually dothe same thing you can be stuck forsome rather expensive, unusable hard-ware if you can't get them straight. Theoriginal telephone pad, the one used inTouch -Tone phones, generates a two-tone signal when a key is depressed andis called a Touch -Tone Pad. On theother hand, when a keyboard deviceresembling the telephone keyboard isused to control an electronic tone gen-erator-usually an integrated circuit pur-

chased as an independent component-the keyboard is also called a Touch -Tone Pad but it is really only a switch-ing matrix; it does not generate anytones. When this keyboard is combinedwith an electronic circuit that generatesthe tones-usually at a signal levelslightly higher than normal microphonelevel-the entire device is called aTouch -Tone Encoder.

The encoder is a rather small, some-what fragile device generally used byradio amateurs for controlling auto -patch repeaters. The pad-which ismade by Western Electric and othertelephone equipment manufacturers-isbuilt like a battleship, produces a rela-tively high level output. that can be usedfor just about any;hing, and until re -

This is what you can get from the surplusdealers: a Western Electric Touch -Tonepad and plastic housing.

cently the only way to get one was togo directly to a telephone equipmentdealer and pay list price, or hope onefell off the back of a truck.

But now the telephone -type Touch -Tone Pad has flooded the surplus mar-ket and anyone can pick one up forbetween $8 and somewhat less than $20,depending on condition. For an extracouple of dollars you can also get abeige plastic cabinet pre -punched to fitthe pad. About the only problem you'llhave is that some of the pads have onlynumerals, not letters; but this shouldcreate no problems since most touch-tone coding, and even telephone num-bers, are now predominantly numerals.

Probably the most flexible pad is theWestern Electric type shown in the pho-


TONE TO PHONEtographs. This model is available fromseveral surplus dealers.

Wiring. The Western Electric padcomes jam packed with attached colorcoded wires which are generally usedfor connecting into telephones. Formany hobbyist uses most of these wiresare simply ignored. There is some varia-tion in color coding between differentmodels of Western Electric pads, butmost models are very similar and somegeneral color coding can be used. Also,most reliable suppliers will send con-necting instructions and so specify intheir ads.

In fact, before undertaking this pro-ject, you might want to check yourability to discern colors. It often hap-pens that people who ordinarily wouldhave no trouble seeing colors find it dif-ficult to distinguish between color -codedwires in electronic equipment. A prob-lem in this area could make it impossibleto wire the Touch Tone Pad properly.So why not compare your reading of thewires with one or two friends', just tomake sure.

The schematics show the hobbyistconnections for the Western Electrictype 35N I A and 35N3A pads-or dialsas they are called by Western Electric-the most common type of pads avail-able. The circuit shown in Fig.J, canbe connected directly across the tele-phone terminals of a telephone wheretouch-tone is already provided by thelocal telephone company. You will hearthe tones in the receiver (handset). Ifyou don't hear a tone simply reverse theconnections to the line.

A normally open switch which isbuilt into the pad is closed each time akey is pressed. This switch closes thecircuit between the pad and the line,simultaneously applying power from theline to the pad (an external powersupply isn't needed). If you want thepad connected only when the handsetis off the hook connect the pad afterthe line switch terminals; usually ter-minals F and C on the phone network(repeat coil or transformer).

Figure 2 shows the connections forusing the pad with an FM transceiverfor autopatch. Potentiometer RI setsthe level into the modulator and isnormally adjusted for 5 kHz deviation.Some phase modulated transceivers re-quire a frequency correcting networkwhen using a touch-tone pad and in-structions for a simple resistor -capacitor(R/C) equalizer are generally given inthe transceiver's instruction manual.

VIOLETa BLUE (+)

GREENI TONEPAD

TO TELEPHONECIRCUITS 6 40VDC

GREEN 8 WHITE

Figure 1

ORANGE8 BLACK(-)

GREEN

GREEN a WHITE

VIOLETa BLUE

ORANGEACK0.I mF

TOAUTOPATCH

RIINPUT

500- CONNECTION

OHM

+12-I3.BVX

ADJUST RI FOR 5KHzPANS

The circuit in Fig. 2 requires thetransceiver's PTT (push to talk) beheld down when the tones are keyed in.We will show later how to modify apad so it also provides automatic trans-mitter keying each time a tone is keyed.

Mounting the pad. The best way tomount and wire a pad is in one of theplastic cases usually available from thesame dealer who supplies the pad. Asshown in the photographs there's plentyof room inside the cabinet for a ter-minal strip and associated components.To avoid short circuits clip the unusedpad leads short, or tape the lugs on theend of each wire. The pad wires arestandard stranded type-not litz silkwound-so you can clip off the lugs,strip the insulation and solder just asyou would any other stranded hook-upwire.

If you need or want automaticor control circuit switching each timea pad key is depressed, you can easilymodify the pad to provide the circuitcontrol shown in Fig. 4. Note thatswitch SI is the normally open switch

4- WIRECABLE

that is part of the pad and applies thepower to the pad as well as connectingthe pad's output signal. Switch S2 is themodification and can be wired directlyacross a PTT switch, or used as controlwires for a keying or switching circuit.

First step is to remove the plasticcovers of the pad. They snap right off.Remove the front one first, the oneover the keys. Then remove the rearcover taking care to snake the wirescarefully through the opening in theplastic cover. You wil find the rear ofthe pad looks like the photograph, witha set of multi -switch terminals at theupper left. If you look carefully at theswitch you'll find almost all the sec-tions are normally closed, opening whena pad key is depressed. But two sets ofcontacts are normally open and closeonly when a key is depresesd. The bot-tom set of contacts is SI and should notbe disturbed. Counting down from thetop, the second set of contacts is alsonormally open and usually ,is the onlyset of contacts to which no wires areconnected. (Note that some pads might

4 -TERMINALSTRIP

KEYS

BASE

With the pad installed in the cabinet mount there's plenty of room in the back for aterminal strip and some components. This 4 -terminal strip installation provides the con-nections shown in Figs. 1 and 2 through a 4 -wire cable. The user s mply selects theright set of color -coded wires.


GREEN

GREEN 8WHITE

VIOLET aBLUE

ORANGEa BLACK 500

OHM

100_ mF

9-40VDC

- xTI

500 -OHM

Y

ISOLATEDOUTPUT

have one wire connected to one of thenormally open terminals, and the wireis generally brown. Simply cut the wireoff at the terminal and leave it alone.)

Carefully cut off the unused wiresfrom the top set of normally closedcontacts and move them to the normal-ly open contacts using a very smallsoldering iron (about 20 watts) and aslittle heat as is possible. Use a tinydrop of solder to prevent a solderbridge. If you don't want to cut thewires from the top contacts use #22stranded wire for the normally openconnections.

Carefully slip the plastic cover overthe wires, seat it on the pad and theninstall the front plastic cover. You nowhave a touch-tone pad with an extraset of normally open switch contacts.

Get Out the Grinder. For some un-accountable reason a few of the plastictouch-tone pad cabinets do not makeallowance for pointed projections onthe mounting ear located on each sideof the pad. Each ear has two projec-tions with a mounting screw in between.

x'OPTIONAL LEVEL CONTROL

-OHM500 VARIABLE LEVEL

Y_ ISOLATED OUTPUT

The plastic cabinet has been pre -formedto accommodate the screw and one pro-jection; the remaining projection getsin the way and can result in damage tcthe cabinet when the mounting screw istightened. For best results use a handgrinder or file and remove the projec-tion towards the bottom when the padis held upright. When the pad is install-ed in the cabinets don't tighten the twomounting screws; let the pad float onits mount. When the top of the cabinetis secured with the four mountingscrews provided, the pad will be rigidlylocked in position without damage tothe cabinet.

Correct Voltages. The Western Elec-tric touch-tone pad will work with anapplied voltage between 6 and 40 VDCat the orange/black and violet/blue ter-minals. If the voltage is less than 6volts the oscillator won't "start," or theoutput signal will be highly distotted.Keep in mind that if you use the cir-cuits shown in Figs. 2 and 3, there is avoltage drop across RI and T1, andless than the applied voltage arrives at

MULTI -CONTACT SWITCH (REFER TO TEXT)

PAD CHASSIS IS WITH PLASTIC GUARD REMOVED

Switch arrangement to secure the control function shown in Fig. 4. Switch S1 is partof the pad wiring and controls both the power and pad connection. The set of contactslabeled S2 is the second down from the top and can be connected as in Fig. 4 toprovide an isolated control circuit.

TONE PAD

S I rd VIOLET a BLUEORANGE a BLACK

S2)4 CONTROL

SWITCH

Fig'. re 4. Power switch S1 is part of the padand is connected in series with the violet -blue (positive power) lead. It automaticallycloses each time a key is pressed. Switch S2is connected to S1's operating lever but isnot normally used in the pad. You canconnect a pair of wires, as shown, to pro-vide a set of isolated control terminals. S2'sterminals can be used to operate the PTTswitch of a transceiver whenever a key isdepressed, or to lift the 500 -ohm poten-tiometer off a microphone circuit with con-nection shown in Fig. 2 or the optional cir-cuit that is included in Fig. 3.

the pad. In Fig. 2 about 3 volts ,is drop-ped across RI; you can normally getgood operation if the voltage appliedto the power supply end of RI is noless than 9 VDC. Of course, if Fig. 2 isused for an autopatch the normal trans-ceiver power supply of 12 to 13.8 VDCis available and you'll have no prob-lems.

The transformer shown in Fig. 3 hasless ^c a voltage drop than the resistorload of Fig. 2, so the applied voltagecan be closer to 6 volts and still insureproper operation of the pad.

The pad has build -in Zener diodevoltage regulation so the output voltageis more or less constant over the powersupply. The maximum output voltagemeasured across R1 in Fig. 2 is nom-inally 0.77 volts RMS when indicatedby a standard VOM; 3.5 volts peak -to -peak when measured by an oscilloscope.If you plug these values into a calcu-lator nothing comes out the way youexpect because two tones are involved.


PARTS LIST

I-0.1-uF capacitor (Radio Shack 272-135 orequiv.)

1-100-uF, 50-VDC electrolytic capacitor (Ra-dio Shack 272-1044 or equiv.)

1 -500 -ohm adjust potentiometer (RadioShack 271-226 or equiv.)

1-Isolating transformer, primary 500.600 -ohms, secondary 500 -1000 -ohms (Calectro

01-728 or similar) Calectro-GC Electron.ics, Rockford, IL 61101.

Touch tone pads can be purchased from:Telephone Equipment Co., P.O. Box 596,Leesburg, FL 32748.


CAN YOU REMEMBER the early daysof TV-back to the mid- and late-1940s-when the Joneses, who had

the only TV in the neighborhood, wouldstrain to clean up a snowy, flickeringpicture by adjusting a "booster" that saton the top of their 12 -in. phosphorcyclops?

Well, more often than not those out-board boxes, with their 6J6s in push-pull tunable circuits, didn't amount tothe proverbial hill -of -beans. ThoseWorld War II vintage tubes were notat all well suited to the new-fangledwide -band requirements of TV. Butlater on as the technology advanced,and more powerful transmitterseowerebuilt, good, solid pictures became therule.

Unlike the old TV boosters, today agood booster for short wave receivers-apreselector-can be designed with allthe advantages of the latest solid-statedevices; and, to boot, it can be simpleand very easy to build. It's the easiestway to turn any receiver into an evenhotter signal sniffer. You use a booster(a very high gain RF amplifier) be-tween the antenna and the receiverantenna terminals. A good one will alsoprovide sharp image rejection by addinga relatively high -Q circuit to the re -

Our outboard rig makes QSL waves-adds20dB minimum gain to any shortwavereceiver

ceiver input. Image signals (which oftentake the pleasure out of receivers withlow frequency single -conversion IF am-plifiers by jamming desired signals)vanish as if by magic when passedthrough a high -Q booster or preselector.In short, a top quality super boostersuch as the SUPER DXER, will add an-other dimension of performance to anyshortwave receiver.

What It Can Do. The SUPER DXERprovides from 20 to 40 dB of signalboost-the exact amount is determinedby the particular input characteristics ofyour receiver. Figuring on 6 dB per S -unit, that's an increase of better than 3to 6 S -units. In plain terms, the SUPER

DXER will bring in stations where allyour receiver will pick up running bare-foot is its own noise.

The SUPER DXER's input is a diodeprotected FET (field effect transistor);the protection diodes are built into theFET so that excessively strong inputsignals, and even static discharges, willnot destroy Q1. Since the FET's inputimpedance is many thousands of meg-ohms, there is virtually no loading ofthe LI 'C1 tuning circuit; its "Q" re-mains high and provides a very highdegree of image -signal attenuation.

The SUPER DXER output circuit is a

Add an extra 20+ dB gain to your short-wave receiver. Simple kit -of -parts is avail-able. You supply the outer case and knob.Note: Wrap ft ground wire as shown above.

low impedance emitter follower, and itwill match, with a reasonable degree ofperformance, just about any receiverinput impedance. As long as your re-ceiever has two antenna terminals, one"hot" and one ground, you can use theSUPER DXER.

Optimum performance will be ob-tained if your receiver is equipped withan antenna trimmer. Just as the antennatrimmer peaks the receiver for use withany type of antenna, it also adds some-thing extra when matching the SUPER

DX12.Set Bandpass. The SUPER DXER

has a tuning range of slightly morethan 3 -to -1 between 5 and 21 MHz.That means if the low end is set to 5MHz, the upper limit will be slightlyhigher than 15 MHz (3 times 5). Ifthe lower limit is set at 7 MHz, theupper frequency limit will be slightlyhigher than 21 MHz. Since the slug intuning coil LI is adjustable, you canselect any operating range between 5and 21 MHz.

SUPER DXER, though a very highgain device, is absolutely stable if builtexactly as shown and described. Therewill be no spurious cscillations or re-sponse. It is possible that changes in thecomponent layout or construction willresult in self -oscillation at certain fre-quencies; hence, make no modificationsor substitutions unless you are qualified.

Getting Started. Your first step is toprepare the printed circuit board. Usingsteel wool and a strong householdcleanser such as Ajax or Comet, thor-oughly scrub the copper surface of a21/4 -in. x 31/4 -in. copper -clad board.Any type will do-epoxy or fiberglass;the type of board is unimportant. Rinsethe board under running water anddry thoroughly.

Cover the copper with a piece ofcarbon paper-carbon side against the


copper-and place under the full-scaletemplate we have provided. Secure thePC board in position with masking tape.Using a sharp pointed tool such as anice pick, indent the copper foil at eachcomponent mounting hole by pressingthe point of the tool through the tem-plate and carbon paper. Next, using aball point pen and firm pressure, tracethe foil outlines on the template.

After all foil outlines have beentraced, remove the PC hoard from un-der the template and, using a resist pen,fill in all the desired copper foil areaswith resist. Make certain you place adot of resist over the indents at each ofthe corner mounting holes. Pour aboutone inch of etchant into a small con-tainer and float the PC board-copperfoil down-on top of the etchant. Everyfive minutes or so gently rock the con-tainer to agitate the etchant. After 15or twenty minutes check the PC boardto see if all the undesired copper hasbeen removed. When .every trace of theundesired copper is gone, rinse theboard under running' water, and thenremove the resist with steel wool or aresist "stripper."

Continue. Drill out all the mountingholes marked by an indent with a X57,58, or 59 bit-this includes the cornermounting and Cl mounting holes. Thendrill the corner mounting holes for a06 screw, and use a 5 16 -in. bit for theCl mounting hole.

Install tuning capacitor Cl first. Tun-ing capacitor Cl should be the typeprovided in the kit of parts. It has aplastic dust cover and a long shaft. Donot use the type supplied with a short

L1

1

11

IIyBPI II` 0

II11

113

C2 --I-001

91

92

Ct01-N 365 pF

C3.001

0140822 C

SI

B

9V022N3394

R34.7K

C4.001

PARTS LIST FOR SUPER DXER

B1 -9 -volt battery (Eveready 216 or equal) andconnector

BPI -insulatedbinding postC1-365-pF subminiature tuning capacitorC2, C3, C4-0.001-uF, 25-VDC or better ceramic

disc11-RCA-type phono jackL1-5 to 20 -MHz antenna coil, Custom Com-

ponents SW -520Ql-MOSFET, RCA 40822

BOTTOMVIEWS

01SOURCE DRAIN

GATE 2 GATE I

EMITTER02

BASE

REDDOT

COLLECTOR

2END VIEW

Q2-npn transistor, 2N3394R2, R3 -4700 -ohm, 1/2 -watt resistor

S1-spst switch (power on -off)

The Frinted circuit board for the Super DXer isavailable from Electronics Hobby Shop, Box 192,Brooklyn, NY 11235 for only $4.95. US ordersadd $1.50 for postage and handling: Canadianorders add $3.00. No foreign orders, please.Postal money orders will speed delivery; other-wise allow 6-8 weeks for delivery.

shaft to which a tuning dial for thebroadcast band can be attached. Removethe mounting nut and ground washerfrom Cl's shaft. Then make certainthe shaft's retaining nut is tight. It is

usually supplied loose. Discard theground washer and secure Cl to the PCboard with the mounting nut. Then in-stall tuning coil LI. Make note of twothings about LI: the terminal end of LIhas a large red dot (ignore any othermarks); LI must be positioned so the

Exact PC board size. Transfer image topaper. This is the bottom (copper)

to the front panel with 1/4 -in. spacersmounting screw. Secure the battery to

copper -clad board using carbonside of your board. Mount it

between board and panel at eachthe back of the cabinet with tape

red dot faces the bottom edge of thePC board-the edge closest to the coil.Also note that the lug connected to thetop of the fine -wire primary is adjacentto :he bottom of the heavy -wire second-ary. When the red dot is facing the edgeof the PC board, both these lugs areagainst the board. Solder the lugs to thematching holes in the PC board. Usethe -hortest possible length of wire toconnect the remaining primary (fine -wire) terminal to the antenna inputprinted foil. Connect the remaining LIterminal (heavy wire) to its matchinghole with solid, insulated wire-form arig:it angle bend in the wire so it doesn'ttouch LI. Now mount the remainingcomponents.

Orienting Q. Note that QI is posi-tioned properly when the small tab onthe case faces the nearest edge of thePC board. Also note that the roundedge of Q2 faces the nearest edge of thePC board. The flat edge of Q2's caseshculd face Cl.

Because the printed copper foil facesthe front panel when the assembly ismounted in the case, and is thereforeinaccessible for soldering, the connect-ing wires to front panel componentsshculd be installed at this time. Solder6 -in. solid, insulated wires to the an-tenna, output, and output ground, and+9V foils. Solder the negative (usuallyblack) wire from the battery connectorto the ground foil.

The SUPER DXER is mounted in a

standard plastic or Bakelite case ap-proximately 63/4 -in. x 3 3/16 -in. x 1% -


SUPER DXER

in. The front panel must be aluminum.If the cabinet is not supplied with analuminum panel, obtain an optional oraccessory metal panel. Do not use aplastic panel.

Drill a Vs -in. hole in the center of thefront panel. Position the PC assemblyover the hole with Cl's shaft fully in-serted through the hole, and mark thelocations for the four PC board mount-ing screws. Drill the panel and tem-porarily secure the PC board to thepanel. Then locate the positions forpower switch Si, antenna input bindingpost BP1, and output jack J1. Makecertain .11 is as close to the PC boardoutput terminals as is possible-within11/2 inches.

Remove the PC board and drill theholes for the panel components. Powerswitch SI can be any inexpensive spsttype such as a slide switch. Install thepanel components and then the PCboard. To prevent the copper foil on theunderside of the PC board from short-ing to the panel, place a 3/4 -in. plastic ormetal spacer, Or a stack of washers, be-tween the PC board and the panel ateach mounting screw. Connect the panelcomponents to the appropriate %API'S. ex-tending from the PC board and theSUPER DXER is ready for alignment.

Alignment. Prepare a length of 50or 52 -ohm coaxial cable (such as RG-58) that will reach from the SUPERDXER's output jack to the receiver an-tenna input terminals. Solder a stand-ard phono plug to one end. Take carethat you do not use ordinary shieldedcable such as used to interconnect hi-fiequipment; coaxial cable is a must.

Connect the coax between the SUPERDXER and your receiver. Rotate the Clshaft fully counterclockwise and installa pointer knob so that the pointer ex-tends to the left (9 o'clock position).Connect your antenna to binding postBPI. Then, set Ll's slug so that thebottom of the screwdriver slot is levelwith the very top of LI. This will pro-vide a frequency range of approximate-ly 5 to 15 MHz. If you back out theslug Va inch, the frequency coveragewill be from approximately 7 to 21MHz. You can use any in-between slugadjustment.

Turn on the receiver and booster, andset the receiver tuning to 5 MHz, orwhatever frequency you selected for the

"bottom end." Adjust CI for maximumreceived signal or noise and mark thepanel accordingly. Repeat the procedureat approximately 7, 10, 14, and 15 (or20) HMz. The panel markings are im-portant because the SUPER DXER'S tun-ing is so sharp it must be preset to nearthe desired frequency or you'll receivenothing-neither signal nor noise. Thepanel markings complete the adjust-ments.

Pull 'em In. To prevent self -oscilla-tion, you must keep the antenna wire asfar as possible from the coaxial outputcable. To receive a signal, set Cl to theapproximate desired frequency,and thentune in the signal on the receiver. Final-ly, peak Cl's adjustment for maximumsignal strength as indicated on your re-ceiver's S -meter, or listen carefully foran increase in speaker volume. Keep in

mind that, if the signal is sufficientlystrong to begin with, the receiver AVCwill "absorb" the SUPER DXER's boost,and the speaker volume will probablyremain the same, thcugh the S -meterreading will increase. SUPER DXER'Sboost will be most apparent on very weaksignals, digging out those signals belowthe receiver's usual threshold sensitiv-ity, making them perfectly readable.

Don't worry about strong signalsoverloading your SUPER DXER; it isvirtually immune to overload even fromexcessively strong signals. However, thebooster's output can be so high as tooverload the input of some budget re-ceivers. If this occurs simply reduce thebooster's output by detuning CI justenough to drop the overall signalstrength below the receiver's overloadvalue. Happy DXing!

TO BI(+)THRU SI

TO JICENTER

TERMINAL

TO JIOUTER

TERMINAL

C2

C4

R2

G2 \C3 RI

111"11--- To 8

TO BPI

For exact part placement on PC board, see diagram above. View is fom component(top) side of your Super DXer board. Layout below shows a completed Super DXer.

Pins 3 and 4 of the dual winding coil 1.1 are shown in an end view for clarity.

C2

C4

R3

LI

02 R2

CI

01


0 With today's increasing crime rate,and the increasing need for security,many police departments are expand-ing the number of frequencies on whichthey transmit information. In mostscanners you can only fit either eightor ten different frequencies, and thetask of changing crystals when theones you have installed are temporarilyout of use, is bothersome, especially ina mobile unit!

Of course, instead of changing cryst-als you could always buy one of thesixteen -channel synthesized units, andpay in excess of $300! Or you couldsolve the problem of changing crystalsby building and installing the "Channel -Changer." It's small and easily installson either a mobile or base scanner, andrequires no external power source. Itprovides you with capability of chang-ing crystals at the flip of a switch. Forthis project I used a Realistic Patrol-man PRO -14, but the principle can beeasily adapted to work with most majorcrystal -controlled scanning monitors.

What it Does. The Channel -Changeris a low-cost switching device whichperforms the task of changing crystalsin a Scanner. It does this by using a12 -position, single pole, rotary switchto change from one crystal to another.This gives a maximum of 12 possiblefrequencies for .one crystal position inthe scanner. The only limitation is thatall crystals in the Channel -Changermust be in the same frequency band,i.e., all frequencies installed in the de-vice must be either in the 30-50 MHz(VHF low), 150-174 MHz (VHFhigh) or 450-512 MHz (UHF) range.Do not install several crystals fromone of these bands and several fromanother band in the Channel -Changerat the same time, as this may damagethe crystal, the scanner, or both. Thisrule of thumb only applies to thecrystals installed in the Channel -Changer itself; the other nine crystalsockets in the scanner may be usedwith crystals in any frequency band.

Construction. All components aremounted in a metal utility cabinet usingthe base of the box as the chassis.

This back view of the Changer shows thebarrier terminal strip and its two intercon-nection points to connect to the scanner.

1,0 Id 'sr, . OOOOO

.1101

000003111

CHANNEL

CHANGER

SoupsUp YourScanner

Add the versatility andexcitement of extra

frequencies

to your Public ServiceBand monitoring.

by Louis A. Smith II

First mount Si, the crystal -selectorswitch,, on the front panel of the case.Exact placement isn't critical, but itshould be mounted near the center ofthe panel.

Next comes the crystal holder. Forthis purpose I utilized a 22 -pin edgecard connector. The edge card con-nector is excellent for this purpose be-cause firm contact with the crystalsis essential. Before mounting the con-nector on the chassis, some wiring must.be done. Connect the first twelve ter-minals on one side of the connectortogether, using #20 gauge wire. Afterthis wiring has been completed, theconnector may be mounted in the cen-ter of the chassis base, parallel withthe front and back panels. It shouldbe mounted on one -inch aluminumspacers, with the side with the ter-minals connected facing the back panelof the case.

Lastly, mount the 2 -terminal barrierstrip on the outer side of the backpanel, near the center. Drill two 1/4 -inch holes in the back panel, one aboveeach terminal.

Now attach some type of indicatorknob on the shaft of SI. I used acommunication knob. The shaft of Siwill have to be shortened to accom-modate such a knob.

Wiring the Changer. When the com-ponents are mounted, it is time to fin-ish the construction by wiring the proj-ect.

The first step in wiring is to connecta wire from the common (innermost)terminal on SI to terminal 1 on thebarrier strip.

Next SI must be wired to the edgecard connector (crystal holder). Whenlooking at S1 from a rear view, chooseone of the 12 outside terminals whichis approximately at the 6 o'clock posi-tion. Connect a wire from this terminalon SI to the first terminal on the edgecard'connector, (that is, the terminalfacing the leftmost of the twelve whichwere previously wired together.) Thiswill be the connection for crystal sock-et =1 in Channel -Changer. Continuearound the rotary switch wiring the

Wire the first twelve terminals of an edge -card connector together, as shown above.Some of the terminals opposite those wired are bent down for greater clarity.


CHANGERnext terminal on SI to the next terminalon the connector, going from left toright on the connector, and clockwisearound SI. Continue wiring in this man-ner until all twelve positions on SIhave been wired to the correspondingtwelve terminals of the crystal holder.

The final connection to be made inwiring is to connect a wire from oneof the twelve terminals on the con-nector which were wired together, toterminal 2 on the barrier strip. Con-sult the schematic diagram.

Interfacing with the Scanner. Afterthe wiring is finished, install up totwelve crystals in the twelve wired posi-tions in the edge card connector. Theposition furthest to the left will beposition #1, the next, position #2, andso on. Although Channel -Changer hasthe capability to hold 12 crystals, it

may be used to switch any numberfrom 2 through 12. Now the Changeris ready to be attached to the PRO -14.

First, remove the crystal compart-ment cover, located on top of the scan-ner. Choose the channel to which youwant to connect the device and removea crystal, if one is already present inthe socket. Next, move the "Band Se-lect Switch" for that channel to thespecific band in which all the crystalsin the Channel -Changer are. If thechannel you selected is chan.el 1

through 5, connect a wire (#20 gauge)from terminal 1 on the barrier strip tothe lower pin in the socket. If the se-lected channel is 6 through 10, con -

1 **/..

Here's ChannelChanger ready foraction! With it, youcan add twelve morechannels of excite-ment to your scanner.It's both easy to build,fun to use.

nect a wire from terminal 1 on the bar-rier strip to the upper pin in the crystalsocket. Instead of inserting a plain wireinto the crystal socket, it is better touse some type of metallic terminal.The pins on these terminals are .042inches in diameter, so I recommendpinching them slightly with long -nosedpliers to fit in the crystal socketswhich are made to accommodate thepins on a crystal which are approxi-mately .038 inches in diameter. (Secschematic diagram for definition of up-per and lower pins in the socket.)

Next connect a wire to terminal 2on the barrier strip and fasten theother end of this wire to the outsideof the crystal compartment cover withelectricians tape. Strip about 1/4 -inchof the plastic covering on this wire offthe end which is attached to the com-partment cover. These two wires run-ning from terminals I & 2 on the bar-rier strip to the crystal compartment ofthe PRO -14 can be of any length, butit is best to keep them short to avoidpossible interference with the FMbroadcast hand.

After these connections have beenmade in the compartment, the cover

can be replaced. Be careful not totighten the cover screws too much asthis may cut the wire running fromterminal 1 on the barrier strip to theinside of the scanner, and thus shortout the connection.

A few final construction hints: It isadvisable to label the positions of Sion the front panel, so that it can beeasily seen which crystal is connectedto the scanner at any given time. Label-ing should be done before replacingthe cover of the utility case, while look-ing at the back of SI to see whichcrystal is connected when SI is in anyof its twelve positions. Dry -transfer let-tering works well on the surface of theutility case.

Testing it Out. When construction iscompleted, Channel -Changer is readyto be tested out. Before turning powerin the scanner on, check all wiringagainst the schematic diagram, and cor-rect any errors.

With a National Weather Servicecrystal, (or any other continuous broad-casting crystal in your area, such asmobile telephone, etc.', installed in thechanger, set SI so that this continuousbroadcasting crystal Is connected in

12 CRYSTALS 0 0

This extremely simple circuit can be puttogether in an evening with a minimum ofeffort. Wire up the switch and terminalsin sequence so that the wiring is neat andorderly, and mark the front panel care-fully to align with the switch positions.

Flo 0

S 1

0 0

TO TERMINAL 2 ON BARRIER STRIP

0 od

TO TERMINAL I ON BAPRIER STRIP

PARTS LIST FOR CHANNEL CHANGER

SI - Rotary switch, single -pole, 12 -position,

shorting

XTAL holder Edge card connector, madeto accommodate 22 -pin card

Misc. -aluminum spacers, barrier terminalstrip, 2 terminal, communications knob,crystals, see text for options, dry -transferlettering, hook-up wire, gauge 20, metalutility cabinet, metalic terminals


RADIOTELEPHONE(RCC) FREQUENCIES

These VHF and UHF frequencies areused by mobile telephone systemsacross the country.

VHF "High" Band

ChannelReceive Transmit Designator152.03 158.49 1

152.06 158.52 3152.09 158.55 5

152.12 158.58 7152.15 158.61 9152.18 158.64 11

152.21 158.67 13

UHF Band

454.025 459.025 21454.050 459.050 22454.075 459.075 23

454.100 459.100 24454.125 459.125 25454.150 459.150 26

454.175 459.175 27454.200 459.200 28454.225 459.225 29

454.250 459.250 30454.275 459.275 31454300 459.300 32

454.325 459.325 33454.350 459.350 34

Thanks to Channel Changer, you're going tohave a lot of extra frequency requirementsin your scanner. The radiotelephone bandscan make for some real exciting listening.Here's the lowdown-our compliments.

the circuit. Turn the scanner on, andmanually stop the scanner on the chan-nel to which the Changer is connected.The scanner should now be receivingthe frequency of the continuous broad-casting crystal. If reception is poor, ordoesn't exist at all, switch the connec-tions at :he terminals on the barrio.strip. If this doesn't correct the prob-lem, a bit more of the plastic coveringshould be removed from the wire whichwas taped to the crystal compartmentcover. Also, make sure that the wire inthe crystal socket is securely in place.'This should improve reception.

Installing the Changer. Channel -Changer can be easily mounted ineither a base or mobile installation. Itshould be kept in mind that the twoleads extending from the terminals ofthe barrier strip should be kept as shortas possible.

To install Channel -Changer on abase insta lation, it can be set either ontop or beside the scanner after the wir-ing between the Changer and the Scan-ner has been completed.

If you want to install the Changerin a vehicle, it can easily be boltedunder the dash board next -.0 the scan-ner after all interconnections have beenmade.

Channel -Changer is very useful forscanner -owners who live in major met-ropolitan areas, or in areas in whichpolice departments have several fre-quencies, but who primarily use onefor general communications, and hold

CRYSTALSOCKET

BARRIERSTRIP

SI

Here's the inside storyon Channel Changer,you can see how easyand quick constructionwill be. Up tO twelvecrystals may be in-stalled, only the firstone is shown here.The other eleven havebeen omitted toshow the edge -cardconnector.

If you're interfacing Channel Changer onycur scanner's channels 1 through 5 (inclu-sive) connect a wire from terminal one onthe barrier strip to the lower pin in thesocket. If to channels 6 through 10(inclusive) then the wire goes from theterminal to the upper pin in the socketMake certain you don't do it backwards.

the others in reserve for special oremergency messages. It is also usefulwhen installed on a mobile unit, forpeople who commute from one area toanother, because the crystals of thepolice or fire departments of anotherlocality could be installed in the Chang-er. nd switched to only when youdrive within receiving range.

Operation. After the PRO -14 scanneris turned on, set the control knob (S1)on the Changer to the desired crystalposition. The scanner will scan 9crystals installed in the scanner itselfplus the one crystal in the desiredposition of the Changer. The PRO -14will not scan all twelve crystals in theChanger at the same time, but onlythe one to which SI is set. When atransmission is received on the selectedcrystal in the Changer, the channel in-dicator light on the PRO -14 will lightcorresponding to the channel in thescanner to which the Changer is con-nected.

As an example if the Channel -Chang-er is connected to channel 3 on thescanner, the indicator light for channel3 will light when a transmission is re-ce ved on the crystal selected in theChanger. The Changer can be cut outof the scanning circuit altogether bysimply locking out the channel on thescanner to which it is connected.

Now that you've built the Channel -Changer, you've solved your crystalchange problem! Happy PSB listen-ing!


Any photographer, amateur or pro,will tell you the biggest bane of his lifes figuring exposures for electronic flashphotography. If you know the manu-facturer's guide number for your flashunit, and if that number is close enoughto being accurate for your productionline unit, and if you can remember itfrom one shooting session to another,and if you remember how to use it, andif your flash is fully charged, and ifyou use straight, harsh flash instead ofPouncing it, and if. . . . Well, flashphotography is very often iffy.

Theoretically, you divide the guidenumber by the number of feet betweenthe flash and subject, and the answeryou get is the f-stop. This has to befigured for every shot, if you move be-tween shots and this guide numrer isonly good for one film type. Again, itgets pretty iffy. There are, to be sure,flash meters on the market, but the leastexpensive one I know of costs nearly$100, and they are all rather bulky.

The answer to these problems isFlash -Mate. It's smaller than an Insta-matic camera, inexpensive to build, re-liable and accurate, and easy to build,with readily -available parts. It takes allthe IF variables in stride, and givesyou the right f-stop for any flash at anydistance and for any film type fromASA 10 to ASA 400. Flash -mate canbe either of two basic types of meters.One, called an ambient light meter,measures the light output of your flash,aimed right at it. The other type, formeasuring reflected, light, is aimed atthe subject and reads the light reflectedby the subject. Your Flash -Mate canbe calibrated for either type, as youchoose.

How Circuit Works. The siliconphototransistor used as the light -sensingelement in Flash -Mate has a very highresistance to ambient light, thereforethe unit will work effectively under awide range of lighting conditions, even

FLASHMATE-THE PHOTOGRAPHER'S

DREAMPhotoflash problems vanish

with this easy -readout solid-state meter.Frank I. Gilpin

including sunlight. The sudden lightprovided by the electronic flash causesa sudden drop in the phototransistor'sresistance. This sudden drop in resis-tance pulses the trigger circuit of Q2 -Q3. This pulse allows Q3 to chargecapacitor C2 to a value proportionateto the intensity of the energy -producinglight striking Ql. The value of thischarge on C2 is then measured by FETQ4, and indicated on the meter. Be-cause of the high input resistance ofthe FET, C2 does not discharge forseveral minutes and you have plenty oftime to take a reading.

A discharge path for the meter andC2 is provided by R4 and S1. Theswitch turns the unit off and simultane-ously discharges C2, leaving it readyfor another reading, in about two sec-onds.

Sensitivity adjustments for variousfilm types are effected by adjusting R8.A rotary switch could be used to con-nect a different trimmer resistor to themeter for each ASA number, but thatwould boost the cost, increase the sizeof the unit and limit the number ofASA numbers for which Flash -Matecan be calibrated.

Potentiometer R8 can be calibratedfor any ASA value, and as many as youwant. You can even add more calibra-tions later. The only drawback to this

compromise is that you must take careto set the pot directly on the referencemarks before taking readings for agiven ASA. If you exercise care andpatience when calibrating the unit, thiswill present no problems in later use.

The two PNP transistors Q2 and Q3are audio signal types and almost anyhigh gain experimenter grade units willdo. There are, however, few substitutesfor Ql. It has a very high resistance toambient light, has a reaction time onthe order of 2.8 microseconds and hasa wide range of illumination sensitivity.You can use a HEP-312, or a ClairexCL902, which also have the necessaryreaction times and ambient light resis-tances required to keep the trigger cir-cuit biased off until a bright, suddenlight is sensed. The FET, Q4, is a P -channel, small signal unit and there area number of substitutions possible, suchas 2N5461 through 2N5465.

Assembly Options. You have achoice of assembly methods. YourFlash -Mate can be assembled on aperforated board using point-to-pointwiring, or on a printed circuit board,for which the foil pattern is shown.Layout is not overly critical and youcan vary the arrangement. Q1 is madewith a clear epoxy lens which is quitedurable, but an extra measure of pro-tection can be provided by covering it

Flash -Mate, a gadget thatphotographers have dreamedof for years, is here-waiting for you to build!

It's notexpensiveand it'squick andeasy toassemble.


The layout of Flash -Mate's perf (or PC)board is uncritical and the arrangements ofthe components may vary. The roominessof the box allows for a clean layout

To calibrate Flash -Mate you will need anaccurate electronic flash with an f-stopcomputer disc. Calibration can be doneeither for ambient light or bounce flash.

01e

OFF -RESET

9VBATTERYCLIP

TO TOSIB SIC

3 -LUG MOUNTINGSTRIP

The foil side of Flash -Mate's board is quicklyetched, especially if youuse this full-size pattern.You could reduce or en-large this as size andlayout are not critical inthis circuit.

TOR8

C3 Here's the componentside of Flash -Mate's PCboard. The layout is sim-ple and straightforward,which helps keep assem-bly time to a minimum.Flash -Mate is a greatweekend project; accu-rate, unique, and goestogether easily.

with a clear pilot light lens or otherclear plastic dome. The phototransistorcan be mounted in several ways. Youcan press -fit it through a rubber grom-met in the front panel of the cabinet,epoxy it through a hole, or it can bemounted on the chassis board so thatit is rigidly suspended behind a hole inthe front panel.

After all components are mountedand wired to the chassis board andconnected to Ml, R8, Q1 and SI onthe front panel, check to make sure allpolarities are correct. Remember thatwhen the chassis board is mounted inthe cabinet, you have to be able toreach RIO to make adjustments. If theshaft is slotted you can drill a small

hole in the cabinet facing the adjust-ment slot in the trimmer.

Some potentiometers have a knurledplastic wheel for adjustment which canbe manually roated regardless of itsmounting position.

When you are sure all is in order andyou have double checked your wiring,apply power to the unit with Si. TurnR8 fully clockwise for least resistanceand adjust RIO until the meter needlerests on zero. After this one internaladjustment, you can close the cabinet,screw down the front panel and preparefor the calibration procedure. You'llneed a tape measure, a tripod and aflash unit.

To calibrate Flash -Mate either for

ambient readings, or the reflected lightreading mode, you will need a reliableelectronic flash with an f-stop computerdisc. You should also be sure the unitis charged fully, or has fresh batteries.

Ambient Light Reading Calibration.Set the flash computer to ASA 400.Determine the distance -from -subjectnecessary for an f-stop of f22. For in-s..ance, if your computer says a distanceof three feet for fl 1, two and a halffeet for f16 and 18 inches for f22,place the meter on a table and theflash mounted on a tripod exactly 18inches in front of it. Carefully removethe clear plastic meter cover. Turn onthe meter and set R8 fully clockwiseand after a few seconds to stabilize, firethe flash. The meter needle shouldtravel all the way upscale. Adjust R8until the needle rests exactly on theuppermost reference mark of the meterscale. Label this spot "f22." Reset themeter with SI and consult your flashcomputer once more to determine thedistance for f16. Measure off this dis-tance, set the flash at that spot and fireit at the flash meter. The needle shouldrest at a spot lower than the first. Markthis spot on the meter scale "f16."Take care not to disturb the setting ofR8 during this calibration step.

Follow this procedure all the waythrough the scale to f2, remembering torer-t the meter after each reading.When you've finished this step, replacethe cover on the meter face and labelthe panel adjacent to R8's indicatorknob "400."

This completes the calibration of themeter scale for all ASA values and thecalibration of R8 for ASA 400. Selectthe next highest ASA on the computerand find the distance for an apertureof f16. Set the flash that distance fromthe meter and fire it. Adjust R8 untilthe needle rests exactly on the previ-ously established mark for f16. Nowmark the panel adjacent to R8's indi-cator knob and label it for the ASAnumber used to determine the distance.The meter is now calibrated for thatASA. Repeat this step for each ASAvalue desired. I have my meter cali-brated for 25, 64, 80, 125 and 400, thefive films I use most, but I can easilyadd more at some later date by using areliable flash and the above procedure.

Reflected Light Calibration. Thebest situation is to find any wall whichis an 18 percent gray, but any neutralcolor wall, or off-white bedsheet will do.In this procedure, the wall (or a sheettacked up on a wall) becomes your"subject." Using the reference Wash


FLASHMATEunit's computer to determine the firstdistance for f22 at ASA 400, place themeter and flash this distance from thewall. Both the flash and meter areaimed at the same spot on the wall.Fire the flash from just above and afew inches behind the meter to avoid"blinding" it with a strong sidelightfrom the flash. Mark the meter face forf22 and continue moving the meter andflash farther from the wall until f2 iscalibrated. Repeat for other ASAs asin the previous step.

Using Flash -Mate. For the ambientlight reading model, the procedure fortaking a reading is as follows: PlaceFlash -Mate at the same location as thesubject, facing the flash, and set R8 forthe ASA of the film you're using andturn it on. Place the flash where youwant it and fire it using the open flashbutton. Read the f-stop from Flash -Mate and set your camera to that f-

stop.To use Flash -Mate calibrated for re-

flected light readings, place it facing thesubject in the same position as the flash.Fire the flash, take the reading fromFlash -Mate and set your lens to thatf-stop.

Personally, I prefer the direct, orambient reading mode of calibration.For me, it offers more versatility. Forexample, your model need not be.; -res-ent to take a reading in advance. Ifyou were going to shoot portraits usingdirect flash, bounce flash, or the popu-lar umbrella reflector technique, youneed only set up the flash and selectwhere the model will sit or stand forthe picture. Place Flash -Mate at thatposition, take a reading and set yourcamera lens. When the model arrives,all you need do is focus and shoot withno wasted time and wow, will you ap-pear professional with no fumblingover f-stop computations or camerafiddling. If you plan to shoot from sev-eral positions during the session, thesespots and their readings can be de-termined beforehand and noted. Apiece of masking tape on the floorwith the appropriate f-stop marked onit will remind you of the correct set-ting for that position. This technique isalso handy for those special awardsluncheons, handshakes, weddings,graduations, or any other plannedevents. You can go a little early beforethe event and take your readings andpick your spots from which to shootand when that once -in -a -lifetime eventoccurs, you'll have a perfect exposureof it.

Flash -Mate is one usefulgadget -bag stuffer. Forgetabout computing f-stopsand concentrate on com-posing theme pictures. Thephoto -sensitive transistor(above the meter) meas-ures the light, and themeter read; directly in f-stops. The snit can be cali-brated to read eitherambient light or forbounce flash photography,depending on your ownartistic pre cerences.

BI SI

0ON RESET/OFF

9VSchematic for Flashmate circuitry. Be sure when wiring in the tansistorsthat you carefully observe lead keying, and always avoid allowing them toheat too much.

RIO50K

C3\

ICOuF

b (NOT USED)

01.PHOTOTRANSISTOR

P -CHANNELFE-, 04

PARTS LIST FOR FLASH MATE

Cl -.02-uF capacitorC2, 3-100-uF, 16-VDC electrolytic capacitorM1-0-50 microampere DC panel meterIll -Photo -sensitive transistor HEP-312 or

Clairex CL902Q2, 3-General-purpose PNP silicon transis-

tor, 2N5139 or HEP-51Q4-Field-effect transistor, P -channel, 2N-

5460 or 2N5461R1 -4700 -ohm, 1/4 -watt resistorR2-47 or 50 -ohm, 1/4 -watt resistorR3 -10,000 -ohm, 1/4 -watt resistorR4 -1000 -ohm, 1/4 -watt resistorR5-20-megohm, 1/4 -watt resistorR6 -150 -ohm, 1/4 -watt resistorFlashmate can be built either with the printed circuit board layout presented withthe article, or you could just use a perfboard and point-to-point wiring as thelayout is not critical. A few final reminders: Once all components are mounted tothe chassis, and wired, check to make certain you have not reversed any polarities;reall that you have to reach R10 to make adjustments so don't forget the smallhole in the cabinet facing that trimmer's adjustment slot. The phototransistor,Q1, is made with a clear epoxy lens which is fairly durable and should Mold upunder most circumstances. If, however, you seek a measure of extra ruggedness,cover the phototransistor lens with a clear pilot light lens or any other clearplastic dome. Properly built and cared for your Flashmate will be calculatingF-stops for you for years of parties, weddings, or just plain shutterbugging.

02, 03

R7, 9 -2 7 , 0 00-o h m, 1/4 -watt resistorR8 -100,000 -ohm printed circuit board -mount-

ing potentiometerR10 -50,000 -ohmprinted circuit board -mount-

ing potentiometerSt-Single-pole, double -throw switch

Misc.-Printed-circuit board kit cabinet 61/4 -in. x 31/4 -in. x 2 -in. or larger; knob;

hookup wire, hardware, sclder, etc.

Note: If you use construction such as perfboard, axial -lead capacitors will be moreconvenient to mount.


MEASURE THE WINDEasy -to -wire, accurate, anemometer uses ICs and LED -readout.

Increasing energy costs have driven many people tothinking of alternate sources of power, such as solarenergy and water power. But the technology for these

natural energy sources is still quite expensive and com-plicated to install. It'll be at least several years beforethe cost of most natural energy systems comes downenough and the parts are easy enough for most peopleto install. Wind power for generating electricity, on theother hand, has been available for many years. Forseveral decades farmers and others in rural areas haveused windmill generators as standby electricity and insome cases, as their main power supply. Windmills andwind -driven electrical generators can be bought off theshelf by anyone, and require no expertise other than theusual home mechanic skills to set up.

Have you wondered if there's enough wind where youlive to drive a windmill electrical generator? Do youknow if there's enough wind to fly that big kite you'veoften thought of constructing? Is there enough windcoming over the hIlls near your area so you can get intohang-gliding? Or do you live in an area where tornadoesor hurricanes sometimes strike? If so, it could literallybe a matter of life -and -death for you to read the wind -

speed easily, with an accurate, easy -to -install anemome-ter (windspeed meter). That's what the Digital Wind -

speed Meter is-an accurate anemometer using the

latest digital TTL (transistor -transistor logic) integratedcircuits.

Though this project isn't recommended for someonewho s never built any solid-state projects before, itshould be easy enough for anyone who has built oneor two simpler projects such as most of those publishedin Electronics Hobbyist.

In addition, it's the sort of project which will get youstarted easily in digital logic circuitry, the circuits andcomaonents which are the basic building blocks ofcomauters and most other advanced electronics today.

How Anemometers Work. There are two types of elec-tronic anemometers in general use. One type uses aircups or a wind turbine to turn a tiny electric generatorwhose output is directly connected to a milliammeter.The faster the wind blows, the faster the generatorturns and the higher the meter reads. This type ofanemometer is simple and reliable but it usually is notaccurate.

A more sophistica:ed type uses air cups to turn ashaft to produce electric pulses. The pulses are inte-grated by a capacito and related circuitry to producea DC voltage whose magnitude is directly proportionalto the wind speed. This voltage is aso displayed on ameter. This method is easier to calibrate, and thus ismore accurate than the simple generator method. By


DIGITALWINDSPEEDMETERusing state-of-the-art digital electronics,improvement can be made upon thismethod of measuring the wind's speed.Instead of the round -about method ofadding up the electric pulses by chargingup a capacitor, why not just count themdirectly? The digital anemometer de-scribed here does just that. The result isa more accurate sophisticated instru-ment that is easier to read and cheaperto build.

How It Works. The theory behindthe digital anemometer is simple. SeeFig. 1. The wind turns a shaft whichhas streamlined plastic cups attached toit. On one rod that holds two oppositelydirected cups are placed two small mag-nets. A reed switch is mounted on thestationary base beneath the rotating cupsso that it will be operated by the ro-tating magnets above. Each time thecups make a full revolution, the reedswitch opens and closes twice. Thepulses generated by this reed switch trig-ger a one-shot multivibrator (TTL-7412)

TTLONE-SHOT

which cleans up the pulses, eliminatingcontact -bounce and other error pulses.The cleaned -up pulses are then fed toa TTL NAND gate which is controlledby the 555 one-shot multivibrator. The555's one-shot output pulse is manuallyadjustable to let us calibrate the ane-mometer. Another 555 astable multi -vibrator provides automatic triggeringpulses for the 555 one-shot as well assupplying reset and blanking pulses forthe counters and decoders. The result-ing controlled and cleaned up pulses(which originated in the reed switch)are counted on two TTL decade count-ers and displayed on two LED displays.

Construction. The rotating wind sen-sor is made up of 4 plastic cups,mounted with %2 -in. or Vs -in. rods to aslot -car motor or similar cheap andreadily available bearing. (The brushesof the motor can be removed if de-sired.) The egg -shaped containers inwhich Leggs nylons are sold are idealfor the plastic cups which catch thewind.

The rods which support the cups canbe steel welding rods or (better) copperor brass. One rod should be one foot

HAND

4,4.044 _n_ru ULMCALIBRATION

55ONE-SH5OT

555ASTABLE

L

_ILFLE1

7490COUNTERS

7447DECODERS

LEDDISPLAYS

Fig. 1-Block diagram for digital anemometer. As the calibration control is variedit changes the duration of the pulse put out by the 555 one-shot. This acts as avariable window for the pulses coming from the windspeed sensor permittingaccurate readout of the LEDs.

MECHANICAL(CASE) SUPPORT

POWERTRANSFORMER

POWER ON/OFFSWITCH

SIGNALINPUT JACK

MAIN P.C. BOARD(COMPONENTS MTD. ON OTHER SIDE)

FUSE

ONE-SHOTSIGNALPROCESSORP.C. BOARD

long and the other two should be sixinches long.

Next, obtain a small cylindrical pieceof a solid metal that is easily solderable-brass or copper is best. Drill two holes,using bits the same size as the rods, atright angles to each other through thiscylinder of metal as shown in Fig. 2.

Now center the 12-ir. rod in thecylinder. Insert the two shorter rods inthe remaining two open holes in thecylinder, as shown in Fig. 3. Using acid -flux, solder the rods to the cylinder.

Mount the motor, which is used asthe bearing, in a 2 -in. long piece of two-by-four. To mount the motor, drill andfile a hole in the wood large enoughto take the motor. Cover the motor'scase with epoxy glue and insert it in thehole as shown in Fig. 4.

Using a bit as close to the diameterof the motor's shaft as possible drill ahole about 1/2 -in. deep in the bottomof the cylinder (see Fig. 3) which nowhas rods soldered to it. Insert the motorshaft into this hole and solder it, usingacid -core flux.

(If steel is used, secure with epoxyglue.)

TI -IN

1/2-IN.H

TWO HOLESDRILLEDTHROUGH, ATRIGHT ANGLES

SOLID CYLINDER,BRASS ORCOPPER

Fig. 2-Centerpiece of windspeed sensor.

INSERT 2" ROD FIRST

Fig. 3-Assembly of rods and centerpieceto form rotor.

Fig. 4-Wood block mount with bearing.


Now mount the four plastic cups tothe rod, taking care to correctly orientthe cups. Drill holes in the cups and in-sert the rods in the holes. Keep the cupsin place with epoxy or other good glue.

Next we mount the magnets on therods. If copper or brass rods are used,great, just solder or glue the magnets tothe undersides of two opposite rods,centering them one inch from the pivot.The reed switch is then mounted on thewood base so the magnets pass a quarterof an inch above it.

If the rod is iron or steel, we have aproblem because it will distort the mag-net's magnetic field. This problem isovercome by using a non-magneticspacer between the magnet and the rod-1/4 -in. is enough space. A 1/4 -in. x 1 -

in. piece of wood is glued to the rod andthen the magnet glued to the wood.Since there is very little weight involved,a good glue will hold the magnet fine.This completes the construction of thewind sensor.

Circuit Assembly.. To build the cir-

Fig. 5-Rotor in place on bearing.

MAGNETNO 2

NOT VISIBLE)

REED SWITCH

OUTPUT JACK

Fig. 6-Completed unit. Adjust height ofreed switch so magnets pass about 1/4 -in.over it or less.

2 .rt , I WATT

6V 5VFig. 7-Temporary battery power supply foruse when calibrating the instrument in anautomobile.

REED SWITCHMOUNTED ONWIND SENSOR 39K R1

SI PI

R410K

+5V

2M

R3

->- -4

+5V C1

39K.47u F

R214 II

C 1 74 21

4 5 6 7

7 6IC5 551 2 3

C4 .01uF

4

C2

luF

1/4 I CE1

+5v7402

150K(SEE

TEXT)

R610K

25uF

C6

C3

.OIuF

0

+5V +5V

114

2

1740/4 IC0 2 =

1412 5

6

117°

I I

IC3 7490

12 9

+51V

12

P 2

3 3

1/4 IC87402

2

5V

6

118176 5IC9 5551 2 3 4

NOTCH

C5

.01

(TOP VIEW)

16 15 14 3 12 11 10 9

5V14

7+5V

16

4

4IC 4 7490

12 9 8 1

6

.;--

V

I 2 6

T 7I 2 6

16106 744 7 81 8 IC7 7447

13 121110 915 14 4-131211 1095 14[41

R7R13

270n

I 13 108 7 2 11

LED/DISI

14

R 14 -R20

270.rt

1 13 10 8 7 2 II

LED/DIS2

+5V

PINCONNECTIONS

1 2 3 4 5 6 7 8 FOR 7447

2 3 4 5 .6 7(TOP VIEW)

PINCONNECTIONSFOR 7490,74121, 7400AND 74C2

234567

(TOP VIEW)

f9

encd

141312

11

10

98

14

PIN CONNECTIONSSLA -7 AS WELL AS MOSTLED DISPLAYS

Be very careful when inserting IC into their respectivesockets. Be sure right types are inserted and oriented

so that IC half-moon keys align correctly with sockets.

PARTS LIST FOR DIGITAL WINDSPEED METER

C1-0.47.uF, 50-VDC capacitorC2-1.0-uF, 50-VDC capacitorC3, C4, C5-0.01-uF, 50-VDC capacitorC6-25-uF, 35-VDC or more electrolytic capac-

itorLED1, LED2--LED display numerals (Radio

Shack 276-053 or equiv.)IC1-74121 monstable multivibrator integrated

circuit, TTL typeIC2-7400 NAND gate integrated circuit, TTL

type

IC3, IC4--7490 decade counter integrated cir-cuit, TTL type

IC5, IC9-NE555 integrated circuitIC6, IC7-7447 BCD -to -Decimal decoder, TTL

typeIC13-74C2 NOR gate, TTL typeP1 -2 -connector jack (8 matching plug for ca-

ble) RCA -type phono plug recommendedR1, R2 -39,000 -ohm, 1/4 -watt resistorR3-2-megohrif printed circuit board -mounting

potentiometer (Allied Radio 854.6287 orequiv.I

R4, R6 -10,000 -ohm, 1/4 -watt resistorR5-150 000 -ohm, 1/4 -watt resistorR7-R20-270-ohm, 1/4 -watt resistor (14

needed)

Si - Miniature reed switch (Radio Shack 275-)33 or equiv.)

Misc.-Four plastic cups such as the contain.ers Leggs stockings come in. Two smallmagnets such as the "Magic" magnetsmost hardware stores carry. One I2 -in. andtwo 6 -in. pieces of copper or brasss rod,Vs- or 3/32 -in. diameter. One slot car motoror equiv.), for use as bearing. One piece ofcopper or brass rod about 1 -in. long, 1/2 -in.diameter (solid). One 2 -in. piece of woodtwo-by-four. Epoxy glue, solder, mountingbrackets (two) for wood block, screws. TenIC sockets.

POWER SUPPLYThe Digital Windspeed Meter requires a regu-lated five -volt DC power supply. The easiestway to do this is to hook a 2 -ohm resistorin series with a six -volt battery. This is alsothe safest power.


DIGITALWINDSPEEDMETER

The pictorial shows the loca-tion of compenents as seenfrom the bottom (the compo-nents are on the far side of theboard, from the viewers per-spective) with the foil -side up.It is best to secure the ICs byusing IC sockets, although youcan solder them directly byusing a low -wattage solderingiron (25 watts would be good).You might use sockets whenmounting the display socketsto allow easy replacement ifnecessary. Since the location ofcomponents isn't critical, thiscircuit can be assembled onperf board if that's easier.

Vcr, WO

cuit use any convenient layout on a perfboard. The position of the componentsis not critical. If you haven't workedwith ICs before you'll be better offsoldering IC sockets in place on the perfboard, and connecting the, other com-ponents to the pins of the IC sockets. Ifyou've had a fair amount of experie-fzeand can solder ICs directly into a circuitwithout overheating the pins (using apair of long -nose pliers as a heat sinkwhile soldering to each pin), do it thatway.

The main job in wiring the anemom-eter lies in making the printed circuitboard. The pattern shown can be madeby using the simple resist method. Sim-ply draw the pattern with a felt -tippedresist pen on the foil side of the printedcircuit board, place in etching solutionfor an hour or so and drill the holesmarked. The somewhat more sophis-ticated, yet still easy, non -camera photomethod can also be used.

If a small 25 -watt soldering iron isused, the ICs can be soldered directlyto the board, although IC sockets areless risky. Be sure to orient the notchon the ICs as shown in the componentlayout diagram. It is always wise touse IC sockets when mounting displayLEDs. Be sure to either bend back orcut off pin 12 on the socket which isused to mount Display No. 1.

Unless double sided PC boards areused, jumpers made up of hookup orbare wire are needed. Place jumpers be-

tween the two J1s, J2s, J3s, J4s, J5sand J6s. In addition, interconnect the+5 VDC points on the PC board withjumpers (6 needed).

Connect the two leads from the re-mote mounted reed switch to pointsP1 and to one of the two GNDs.

Connect the plus power supply leadto the +5 point at the top of the board.Connect the other supply lead to theother GND point which is also locatedat the top of the board.

The 5 -volt regulated TTL power sup-ply described by Herb Friedman onpage 61 of this issue of ElectronicsHobbyist is ideal for this project.This power supply is compact enoughto easily fit in the same case asthe logic unit.

The entire circuit can be mounted inany convenient size bakelite or alu-minum case with aluminum panel. Fora smart appearance, spray paint thepanel with some auto -touch-up whitelacquer. Use dry transfer decals for thelettering.

Cut a slot in the panel so the twodigit LED display can be readily seen.If desired, the switch to turn on thepower can be an inexpensive slide switchbut a toggle switch is more reliable andeasier to mount. The circuit board andall other components should be mountedto the back of the front panel for easeof accessibility.

If one desires a longer display time,increase R5 from the recommended

150k to 220k or even 270k.Any type of two -conductor connect-

ing jack can be mounted on the frontpanel (I used an RCA -type jack) aslong as the appropriate plug is used. Thetwo wire cable which connects the ro-tary wind sensor to the electrical unitmust be long enough to reach from theroof to the place in your home whereyou want to keep the display unit. Anykind of shielded cable, including audiocable or microphone cable is OK. Coaxsuch as RG-59/U is fine, but don't buyit special for this job because it costsmuch more than other (audio) cable.

Calibation. This anemometer iseasily calibrated since there is just onepot to adjust. As an initial test, plug theunit in and connect the wind sensor tothe display unit. After a few secondswarmup the unit should show 00 thengo momentarily blank. Turn the cupsby hand and a number should appearon the display for a second or two andthen disappear for a second. Now turnthe cups as fast as you can by hand andadjust the calibration pot to read asclose as possible to 20. If everything sofar works OK, it is time to take the ane-mometer for a ride. If not, go back toSquare One and check your wiring andthe seating of the LED display modules.

The anemometer should be calibratedagainst an accurate automobile's speed-ometer. Since the anemometer will beaway from the regular house supply,you will have to take along a 5 -volt

(Cooliturell on page 100)

94mnl Fl FCTRONIC PROJECTS 1978

battery supply. In order to drop thevoltage to the required 5 VDC, youmust connect a 2 ohm resistor in serieswith a 6 volt battery.

With someone else driving, take theunit in an auto on a nearly calm dayand drive as steadily as possible at acertain definite speed, say 30 mph.Drive up and down a quiet road, withthe wind sensor held out the windowand adjust the calibration pot so thedisplay will read an average value of 30.

Use. The wind sensor should bemounted on a roof or other locationwhere there are few obstructions. Be-cause of the one-shot ahead of the

NAND gate, the anemometer may sud-denly go blank. when winds are of hur-ricane speed. So if the display oneminute shows 75 mph and the nextminute 00, don't stick your head outthe window to see if something hap-.pened to the wind sensor on your roof,a tree might just be sailing by.

A simple way of checking your speed-ometer is to drive down an expresswayat 55 and have someone time you be-twen two mileposts. Then get yourhand calculator out and divide 3600 bythe number of seconds it took you totravel the mile. The result is your truespeed.

The key to building a successful Digital Windspeed Meter is the making of an accurateprinted circuit board. As you can see, many of the foil strips are in close proximity toeach other. Be sure not to let any of the lines touch where they aren't supposed to;the resulting short circuit would probably damage one of the integrated circuit chips.Probably the best method for this circuit, if you are not equipped to use a photo -etchingtechnique, is to use a resist type felt tipped pen and sketch the patterns on the copper -plated board. The board is then soaked in an acid etching solution for an hour or so.After the pattern is reproduced in copper you should drill all the holes. If you havea small drill -press, use it-a hand-held drill is likely to slip and damage the circuit.

TurnSignalsfrom

SideMarkerlights

D Side clearance lights are the lampsusually mounted on the front and rearfenders. These lights can be made toprovide additional driving safety byadapting them to flash in unison withthe directional flashers if the auto doesnot now have rear flashers.

The circuit diagram shows how thepresent auto or pick-up electric wiringis modified so the side lights will alsoflash. A 24 ohm resistor is added inseries with each side -clearance lampbulb filament. This reduces the bril-liance of the side bulb to about half ofwhat it was originally. An epoxy diodeis used to isolate the parking lamp fila-ment from the flashing light circuit.

A separate wire lead is run from theside lamp to the directional flasherlamp on the same side of the auto. Theside clearance lamp will then flash inunison with the front directional flasherlamp. A second diode is used to isolatethe flasher filament from the parkinglight circuit so that it will not turn onwhen the parking light turns on.

Make good electrical connections byusing instant auto electric connectors orsoldering with a good soldering iron.Wrap all connections and componentswith a good amount of black plasticelectrical tape so that they will with-stand the weather. The side clearancelights will now flash not only with thedirectional signals but also when theemergency 4 -way flasher is turned on.

+12 VOLTS

DIRECTIONALFLASHER

DI

124.2

+12 VOLTS L RIFRJM PARKINGLAMP SWITCH

D2 I

FRONTFLASHERLAMP

---- ADDEDCIRCUITRY

SIDEFENDER -MOUNTEDBULB

PARTS LIST FOR ADD-ON TURN SIGNALS

D1, D2-Diode 1 amp, 50 PIV or better (Radioshack 276-1135 or equiv.)

R1 -24 -ohms, 1 -watt resistor (Radio Shack 271-1000 or equiv.)

Misc.-wire, electrical tape.


THUNDERBOLT-For Stop-ActionPhotosQuick as lightning, this sound -activated flash switch respondsto get your picture.

by Frank I. Gilpin

HOW WOULD YOU LIKE TO CAPTUREthe sphere -capped minaret of adrop of water at the precise mo-

ment it strikes the surface of a pool, ora bursting balloon with the piercingdart still in mid-air? All you need is thiseasily -constructed, sound -activated, elec-tronic flash-Thunderbolt.

Sound -activated switches have beenaround a long time. The first one Ibuilt 18 years ago weighed 25 poundsand would have cost nearly $100 if Ihadn't cannibalized some old radios forthe parts and tubes . .. remember tubes?When I built Thunderbolt a few monthsago it cost five dollars and weighed in atabout eight ounces. What made the dif-ference? Solid-state components, includ-ing a silicon -controlled rectifier, makeit lighter and cheaper-and it worksmuch better and faster.

How It Works. Sound picked up by amicrophone is boosted by an amplifierwhich feeds the signal in the form of arectified pulse (via R3 and D1) to thegate and cathode of the SCR. The SCRis internally like three diodes connected(alternately) in series-positive-negative-positive-so it acts like a conventionalrectifier in the reverse direction. Thus,the SCR's forward conduction is con-trolled by operating the "switch," orgale. Since the sound we are picking up

is a single, sudden sound of short dura-tion, it acts like a pulse, when magni-fied by the amplifier, and it causes theSCR to conduct. An electronic flash unitconnected across its anode and cathode"sees" this conduction as a direct shortso it flashes.

In practice, you will find a wide lati-tude of application techniques possible.You can control the microphone's sensi-

tivity so it will respond only to certainhigher level sounds, if the ambient noiselevel is high. Additionally, you can se-lect the time at which an event is pho-tographed by varying the distance be-tween the event and the mike.

Various Applications. Let's say, forexample, the event to be photographedis a coin dropping into water. By placingthe mike very close to the container of

The inside view of Thunderbolt. Except for the ampli-fier PC board, with its many components, the box islargely uncluttered. You can see R1, R2, and S1 allmounted on the front panel, and the 9-VDC transistorbattery mounted on the rear.


water, and by turning up Thunderbolt'ssensitivity control, you can freeze thecoin as it first touches the water. Onthe next shot, repeat the event, butplace the mike farther away from thepoint of impact. The sound must nowtravel farther to reach the mike and theflash will go off at a later stage in thesplash sequence.

By repeating this process, you canget a series of shots to cover the entiresequence from the coin first touchingthe water, to the final catapulted drop-let falling back into the water. It couldbe a club flattening a golf ball, a dartbursting a balloon, a hammer shatteringa light bulb, or a (patient) athlete div-ing into a swimming pool. Any eventwhich produces a sound, faint or deaf-ening, can be recorded on film at thedecisive moment chosen by you.

The great advantage of Thunderboltis that it is totally electronic, as op-posed to the electromechanical heavy-weights of a few years ago. The olderdevices depended on mechanical relaysand electromagnets to close a switch.This mechanical energy transfer addedmilliseconds to reaction time. Even thatis a significant interval when you areplanning to break up into sequencessuch events as bursting firecrackers andshattering lightbulbs. Once the soundgets to Thunderbolt's mike the reactiontime approaches the speed of light.That's about as fast as you're going toget-in this world.

Putting Thunderbolt together is easy,because the most complicated part-theamplifier-is a module, ready to wireinto a circuit with just a few simpleconnections and a handful of otherparts.

Building It. Begin by selecting an am-plifier. Almost any inexpensive modulewill do as long as it has an outputtransformer. Note that most moderntransistor amps don't have an outputtransformer. Radio Shack and Lafay-ette Electronics sell suitable amp mod-ules for less than six dollars apiece.Any amp capable of delivering a couplehundred milliwatts is sufficient. I scav-enged the amp for my Thunderboltfrom an old, discarded portable tapeplayer. You can find many of these oldreel-to-reel relics in second-hand storesfor a dollar or two. Goodwill and Sal-vation Army Thrift Shops are a goodhunting ground. All you need do withthese old units is carefully trace andidentify the input and output leads andthe battery supply leads. If you get aunit that's fairly intact, it may evenhave volume and tone control potswhich are of the correct value for yourThunderbolt.

The cabinet I show in the parts list

will accommodate almost any transistoramp you select. You could even getambitious and build a simple transistoramp. Most any old tube amp will alsowork fine, though it'll be quite bulky.

Just which mike jack, you use willdepend on the plug on the microphoneyou use. It may be a standard phonejack, or the miniature type-whatever,as long as it matches your mike plug.When you have all the parts in hand,arrange them on the cabinet's frontpanel and mark the panel for themounting holes to be drilled. Partsplacement is not critical, but the leadsto RI and R2 should be kept short. Ifyou locate SI close to the sensitivitycontrol, R2, then you can use point-to-point wiring for the SCR, DI and R3.They are rigid enough to be self-sup-porting if the leads are kept short; other-wise a tie -point terminal can be used.Follow the schematic and wiring illus-trations carefully and you'll have notrouble. You must use shielded (co -axaudio cable) for the input connectionsfrom RI to your amp.

Hookup To Flashgun. After makingall the connections, double check yourwork. Be sure you have connected theSCR's three leads correctly and checkthe polarity of DI. When you are sureeverything is in order, you'll need to

Closeup of the front panel, showing theway SCR1 is mounted directly on S1, andD1 and R3 attached to R2.

make a connector cord for your flashunit. Insert the PC plug of your flashextension cord into the flash unit's synccord. Both ends of some brands of ex-tension cords look almost alike and youdon't want to cut off the wrong end.With one end plugged into your flashunit to make sure, cut off the other endclose to the plug. Strip off the insula-tion and carefully separate the braided

RI

o

JI

N

4,y AMPLIFIER

OUTPUT

GROUND

R2

Ri

MIKEINPUT

DI

mom +J2

TO FLASHER

SI 9vDc

Schematic diagram for Th ander-bolt. As you see, most of thecomponents are encapsulated inthe amplifier, which is describedfully in the text. Virtually anyamplifier will do, as long as itproduces a couple hundred mil-liwatts. The diagram belowshows the connections to SCR1.

CATHODE(c

PARTS LIST FOR THUNDERBOLT

R1-10,000 ohm potentiometerR2-5,000 ohm potentiometerR3-2,200 ohm half -watt resistorDI-PIV 50 volts Rectifier Diode11-To suit your mike. (see text)12-AC chassis -mount receptacleSt-SPST slide switch

GATE(9)

ANODE(a)

(VIEWED FROM BOTTOM:

SCR-Silicon Control Rectifier (General Elec-tric C5G or equivalent in TO -5 type case.)

Misc.-Wire, solder, two control knobs, chas-sis box (see text), a PC type extensioncord for electronic -flash sync cord, andan AC plug. Total cost for all parts shouldnot exceed $12, excluding chassis.

You'll find Thunderbolt to be one of the most useful photographic accessories.It's easy to build, both at the worktable and on the pocketbook, and is a truly funproject. Before you know it, you'll be happily strobing away roll after roll.


THUNDERBOLTshielding from the inner conductor ofthe co -ax cord. There is little or nostandardization in the photo industry.so you can't be sure that the inner con-ductor of any given sync cord is con-nected to a positive voltage whenplugged into a flash unit. Some unitshave a positive ground and some have.a negative ground. In order to makesure your Thunderbolt will work withany flash unit, you need a plug whichcan be reversed for any polarity match.You may have more than one flashunit and they may not be the same.hence the adaptor cord.

Plug one end of your modified cordinto Thunderbolt and the other into theflash unit's sync cord. Set the sensitivitycontrol, R2, at the center of its rotationand input control, RI, fully counter-clockwise. Plug in a microphone andapply power to both the switch unitand the flash unit. The flash may fireonce or twice by itself before it settlesdown. If the flash unit keeps firing asfast as it recycles, reverse the plug inJ2 to get the correct polarity match.

With the polarity established, whistleor hum into the mike as you slowlyturn RI clockwise. The flash should gooff. From this point, it's a matter ofsee -sawing controls RI and R2 backand forth until you get the hang ofyour mike's sensitivity. The best way todiscover what your Thunderbolt ci.-1 dois to use it in a closely controlledtest set-up. This procedure is easier

This is one of the things you can do withThunderbolt. You can use it to captureany sound -producing motion instantane-ously, as long as the object to be photo-graphed is within the range of your elec-tronic flash gun.

Diagram of the partslayout for Thunder-bolt. The componentsare pretty evenly dis-tributed between thefront panel and thebox, and connected bya few hookup wiresand some shielded ca-ble. Make sure that thewires znd the cableare long enough andflexible so that therewont be any trouble asyou close the box afterconstruction.

with an assistant, so recruit a friend.Against a dark background, set up a

clear glass, or bowl, of water. Place themike as near to the bowl as possiblewithout it getting into the picture area.Position the flash on a tripod and aimit at the bowl. The camera, also tripodmounted, should be aimed at the bowlat a 45 degree angle to the flash. Focuson the surface of the water and com-pute your f-stop as you normally wouldfor a flash shot using the flash's guidenumber divided by its distance to thesubject. (For instance, if the manufac-turer's recommended guide number foryour flash is 45 when used with ASA25 film and your flash is placed fivefeet from the subject, divide 45 by five.Since the answer is nine, choose thef-stop closest which is f-8).

Set the camera's speed control on"B" as you would for a time exposure.Attach a locking type shutter releasecable to the camera and position yourassistant close to the bowl, but out ofthe camera's field of view.

Turn off all the lights in the roomand open the lens with the shutter re-lease cable, but do not remove the lenscap yet. With your assistant poised overthe bowl, ready to drop a coin into thewater, turn on the flash unit and theswitch unit. The flash may go off, trig-gered by the sound of its own switch,which is why you've left the lens capon. Wait for the flash to recycle, thensnap your fingers. It should go off again.When it recycles, remove the lens capand give your assistant a visual signal

to drop the coin. As the coin hits thewater, the flash will go off and you canclose the shutter and replace the lengcap.

On the next shot, move the mike afoot or two farther away and repeat theprocess. On successive shots, move themike exactly the same distance fartheraway. You should have a complete se-quence after about six to eight shots.

The film should be a very slow film,that is one with a very low ASA. num-ber, such as Plus -X by Kodak, whichhas an ASA of 125. If you have a set-up which requires you to have moreroom illumination in which to work,use an Othro type film which is insen-sitive to red light. With this film, youcan use a fairly bright red light in theroom without affecting the film imagewhile the lens is open.

Once you've done a series such asthe water bowl and coin, you will knowwhat Thunderbolt can do for you andhow to predetermine its sensitivity to agiven sound. When you have all its pa-rameters for operation understood andset up, you can start thinking of thingsto do with Thunderbolt. Its applicationsare virtually limitless, since the princi-ple of stopping sound -producing motionis an especially fascir ating one. Youcan use it indoors in ordinary ways,such as the coin and bowl technique,or you could even use it for crime de-tection, by fixing it at night on a win-dow or door you expect an intruderto come through. Any sound he makeswill take his picture. Good luck!


0\ r OF THE SHUTTERBUG'S most sat-isfying accomplishments is pro-ducing his own color prints. For

years the time spent on and the cost ofmaking color prints were discouraging,but with modern color chemistry, suchas the Beseler system, you can turn outquality color prints in less time than for

by Herb Friedman

It's easy to make quality, bright color prints at home withmodern color chemistry and this electronic color analyzer!

black and white (about 3 minutes), andthe prints will be far superior to any-thing you're likely to get from a colorlab.

One thing that takes the drudgeryout of color work-besides the chem-istry-is a color analyzer, a device thatgives you the correct filter pack and

MAGENTASUBTRACTIVEPRIMARY

BLUEADDITIVEPRIMARY

REDADDITIVE PRIMARY

CYANSUBTRACTIVE PRIMARY

YELLOWSUBTRACTIVEPRIMARY

GREENADDITIVEPRIMARY

Any one of theprimary colors onthis circle iscomposed of itsimmediatelyadjacent colors inequal amounts.Each primarycoloris also comple-mentary to thecolor directlyacross the centerof the circle.Complementarycolors addedtogether formneutral densities.It is the balancingof additive primarycolors of photo-graphic lightsources and sub-tractive -type colorfilters that providescontrol in colorprint photography.

exposure time at the very first crack.Mo_ often, the very first print madewith the analyzer will be good. At most,it will take perhaps 0.10 or 0.20 changeof filtration for a superb print. This isa lot less expensive and time-consum-ing than making test print after testprint. In fact, it's really the color an-alyzer that puts the fun into makingyour own color prints!

Color Analyzers Are Not Cheap.A decent one costs well over $100, anda good one runs well over $200. But ifyou've got even a half-filled junk boxyou can make your, own color analyzerfor just the junk parts and perhaps $10to $15 worth of new components.

A color analyzer is basically a minia-ture computer. You make a "perfect"print the hard way-by trial and error-and then calibrate the analyzer to yourfilter pack and exposure time. As longas you use the same box of paper andsimilar negatives, all you need to do tomake a good color print is focus thenegative, adjust the filter pack and ex-posure so the analyzer reads "zero," andhit the enlarger's timer switch. Even ifyou switch to a completely differenttype of negative, the analyzer will putyou well inside the ballpark, so yoursecond print is a winner. (And even if


COLOR ANALYZERthe filtration is off, the exposure willprobably be right on the nose.)

Construction. The color analyzershown was specifically designed for thereaders of this magazine-essentially anelectronics hobbyist with an interest inphotography. All components are read-ily available in local parts stores or asjunk box parts. Several protection de-vices have been designed into the cir-cuit so accidental shorts won't produce

a catastrophe. The printed circuitboard template has foils for both incan-descent and neon meter lamps, as wellas extra terminals so you can use eithera socket and plug or hard wiring forthe color comparator and exposure sen-sor. In short, you can make a lot ofchanges to suit your individual needs.

The template for ICI uses a half-minidip, Signetics V -type package leadarrangement. However, you can alsouse an IC with a round (TO -5) con-figuration. If anything is wrong with theIC you can get the TO -5 out easily. The

PARTS LIST FOR

BR1-50-PIV, 0.5 -amp or higher silicon bridgerectifier

C1, C2-500-uF, 10-VDC or better electrolyticcapacitor

01, 02 -6.2 -volt, 1 -watt zener diodeICI-type 741C operational amplifier, see text11 -5 -pin socket, DIN -type (optional, see text)M1 - 0 to 1-mA DC meter, see textP1 -5 -pin plug, DIN -type (optional, see text)PC1, PC2-Clairex CL5M5L photocell, do not

substituteR1 -10,000 -ohm, 1/7 -watt resistorR2, R3-1-megohm potentiometer, see textR4 -500,000 -ohm potentiometer, see textR5--100,000-ohm potentiometer, see textR6 -10,000-ohm trimmer potentiometer (Mallory

MTC-14L4 for exact fit on PC board)R7, R8 -820 -ohm, 1/2 -watt resistorR9 -100,000 -ohm, 1/2 -watt resistorS1 -2 -pole, 4 -position rotary switch (Allied Elec-

tronics 747-2003; adjust stops for 4 positions)S2 -spst switchT1 -117 -volt primary, 24 to 26.6 -volt secondary

transformer, see text for point-to-point wiring

TalTOP VIET.

R6

10K

R7

MI

0-1mA

+ 6 2V

6.2V

COLOR ANALYZER

(Note: you can also use two less expensive12 -volt transformers with secondary windingsconnected in series -aiding, if you have thespace.)

The printed circuit board for the Color Analyzeris available direct from Electronics Hobby Shop,Box 192, Brooklyn, NY 11235 for only $5.50. USorders add $1.50 for postage and handling;Canadian orders add $3.00. No foreign orders,please. Postal money orders will speed delivery;otherwise allow 6-8 weeks for delivery.If you cannot obtain the Clairex Type CL5M5Lphotocell locally, write to Electronics HobbyShop at the above address, enclosing $3.50 foreach photocell. U.S. orders add $1.50 for post-age and handling. Canadian order add $3.00. Noforeign orders, please. New York State residentsadd sales tax. Postal money orders speed de-livery; otherwise allow 6-8 weeks for delivery.

Misc.--cabinet, pilot lamp for meter, 2 -in. or3 -in. size Kodak Wratten filters #70, d98, and#99 (available from photo supply dealers),calibrated knobs, wire, solder, hardware, etc.

half-minidip removal might result in de-struction of the PC boa -d. We'll explainhow to install the TO -5 IC on the PCboard later.

You can either buy or make theprinted circuit board ,see parts list).Either way, the first step is to preparethe printed circuit hoard. If you do ityourself, make it any way you like,using free -hand or template resist. Noth-ing is critical, but he certain there areno copper shorts between the terminalsfor ICI. Use a #56 hit for all holes.Then use a larger bit for transformerTI's mounting screws (#4 or #6screws), a 1/4 -in. bit for resistor R6,and a #30 to 40 bit for the linecordconnections (any bit that will allowthe linecord wires to pass through theboard).

Assemble the power supply and checkit out before any other components areinstalled. Install transformer TI first.Any 24 -volt or 25.2 -volt center -tappedtransformer that will fit on the boardwill be fine. Get something small, like100 milliamperes. A Wescom 81PK-100is a perfect fit.

Bridge rectifier BR1 is the low cost"surplus" found in many distributors.This type has the positive and negativeoutputs at opposite ends of a diamond.The AC connections a7e the remainingopposite ends. Note that BR I is in-stalled in such a manner that its negativeoutput is farthest from transformer T1while the positive output is nearest toTI. Make certain your bridge rectifierhas the same lead configuration; if it isdifferent, modify the printed circuit tem-plate to conform to the rectifier you'reusing. Get it right the first time.

Finally, install Cl and C2, R7 andR8, and zener diodes Dl and D2. Takecare that the capacitors and zenerdiodes are installed with the polaritycorrect. If the capacitors have theirnegative leads marked with an arrow orline, these markings face the oppositeedges of the PC board (negative to theoutside). The zener diodes are installedso that their cathodes (the banded ends)face each other towards the center ofthe board.

Initial PC Checkout. When the powersupply is completed, temporarily con-nect a linecord. Connect the negativelead of a meter rated 10 volts DC orhigher to the foil between TI's mount-ing screws (that's ground). Connect themeter's positive lead to the junction ofR7 and DI, which is in the center ofthe board; the meter should indicate ap-proximately +6.2 volts DC. Then con-nect the positive meter lead to the R8and D2 junction, which is near the edgeof the board. You should get approxi-mately -6.2 volts DC'. If the voltages


141

1P°14.**: .

4it

LIGHTINTEGRATOR

'COLOR'PHOTOCELL

DRILL FOR:(.'" N06 SCREW

- 3/41N

ce,---NO 27 DRILL

BENG

SIDE VIEW

51/4 IN

DRILL /1/2 -INHOLE

The color comparator photocell Z -bracket is installedunder a light integrator. If your enlarger has a filter holder

under the lens, attach the Z -bracket to the holder.

TOP VIEW( BEFORE

BENDING)

BENC

are far apart in value, or if the polarityis wrong, make certain you find themistake before installing ICI.

Disconnect the linecord and completethe PC assembly. If you use a 24 or 28 -volt pilot lamp to illuminate the meteryou connect to the holes adjacent toTi's secondary (24-V) leads. If youplan to use a neon illuminator, install a100,000 -ohm resistor (R9) on the PCboard and connect the lamp to the holesmarked "neon." The lamp must haveas little illumination as possible. Incan-descent 24 or 28 -volt lamps must bethe miniature or "grain of wheat" typerated approximately 30 to 60 mA; thelamps come with attached leads. Donot use pilot lamps of the 100 to 500mA variety. The excessive light willconfuse the analyzer.

To install ICI when it is the metalcan TO5 type, fan out the #1 to 4 leadsand #5 to 8 leads so they form twostraight lines. Note that the lead oppo-site the tab on a TO5 package is #8.Insert the leads into the board leaving -

about 1/4 inch between the IC and theboard. The IC is correctly installed ifthe tab faces away from the transformer

Rear view of author', «ilor anakier .how,vertical mounting of the circuit hoard.

towards the nearest edge of the PCboard. Solder ICI and cut off the excesslead length.

The edge of the PC board nearestICI has four sets of paired foil termi-nals. These are provided as mountingterminals if you connect the photocellcomparator and sensor without the useof a plug and jack. However, we strong-ly suggest the use of the specified DIN-type connectors as they allow for easyrepairs if the connecting wires break.(The connectors aren't that costly).

Potentiometers R2 through R5 canbe linear or audio taper, though audiotaper gives a slightly smoother adjust-ment; use whatever you have in stock.

The analyzer shown is built in a Bud7 -inch AC -1613 Universal SlopingCabinet. This is the least critical itemand you can substitute whatever cabi-net you prefer. Just be certain the cabi-net will accommodate the type of meteryou use.

Meter MI should be 0-1 mA with azero -center scale. But these are expen-sive, so you can substitute any standard1-mA meter you want. You will simplycalibrate the instrument for zero -center.

If you use a neon pilot lamp mount itdirectly above the meter and shield theforward brilliance with a piece of blacktape; the lamp should radiate straightdown onto the meter scale. If you usethe meter in the parts list, remove thefront cover by pulling it forward. Thenremove the meter scale. As shown inthe photographs, place a black dot ap-proximately 3/16 -inch wide at the cen-ter of the scale. If you want, you canalso modify the meter for the incandes-cent lamp. Drill a 1/4 -inch hole in thelower right of the meter from the rear.Position the meter in the cabinet andmark the location of the meter hole onthe panel. Remove the meter and drilla 413 -inch hole in the panel. When themeter is installed you can pass a "grainof wheat" lamp through the panel intothe meter. Reassemble the meter andcomplete assembly.

The Comparator. The photocellsused for the comparator and exposuresensor, P1 and P2, must be Clairex typeCE.,5M5L. Make no substitutions. Froma piece of scrap aluminum 3/4 to 1 inchwide, fashion a Z -bracket to the di-mensions shown. Drill a 1/2 -inch holeclose to the end of the longer Z -leg.Fasten the other end of the Z -leg toyour enlarger's under -lens filter holder.If your enlarger does not have a filter

BR1 C2 R8 n2 !C1 RI

TI Cl R7 DI R6This is the parts location when our PCboard is used. To get a free template ofthe PC board, send a Self -AddressedStamped Envelope to: Davis Publications,Dept. T, 229 Park Ave. South, New York,NY 10003.

3/16 INHOLE -

FORWIRE

PHOTOCELL EPDXY

CUT

,,,,,,,,,c

The exposure sensor photocell is mounted in anything that will keep it in place onthe easel. This example was epoxy -cemented into a large control knob after the outside

dial section was ground off. In typical operation, thesensor is placed under thelens with the light integrator or filters.


COLOR ANALYZERholder, or if it has a permanent swing -away red filter under the lens, mount aPaterson swing -away light integrator(available from local photo shops) un-der the lens. Fasten the short leg of theZ -bracket to the integrator-which haspre -drilled holes-so that the 1/2 -inch

hole is on the optical Center ofthe lens. Then cement photocell P2

the switch and the control "C" for cyan.(We suggest you paint the cyan knobinsert a blue-green. Also paint the otherknobs the appropriate color.) AdvanceSI one position clockwise, find the cor-rect knob and label both "M" for ma-genta. Advance the switch another posi-tion clockwise, find the knob and labelboth "Y" for yellow. The last switchposition and knob is labeled "W" forwhite (white light exposure). Make cer-tain the C, M, and Y controls are read -

TO Sla,bWIPERS

C

M

Y

W

R1

METER

TO 24VPANEL LAMP

1 4IG1

8 5

CT}-R7 -1

-Cx- I2V

lcDI GI

(GROUND)

DRILL OUT

-R8

D2lc G2 +

PRIMARY 117 VAC

S:2

T1

NE2

frT

TISECONDARY (OPTIONAL )

There are few parts on the PC board and nothing is critical. Modify the boardif you wish. Trimmer potentiometer R6 should be a flat mount, so it can

be adjusted through a hole in the cabinet.

in the hole and attach the connectingwires; these can be extra -thin zip cordsuch as used for short -length speakerconnections. (This whole bit reads a lotmore complicated than it is. Use thephotographs as a guide.)

Photocell P1, which measures the ex-posure light, can be mounted in any-thing heavy enough to hold it in placeon the easel. The photographs show thephotocell epoxy -cemented in an over-size control knob.

When the complete analyzer is as-

sembled, attach oversize calibratedknobs such as the Calectro E2-715 toR2 through R5. The knob calibrationsare important so they should run out tothe very edge of the knob skirt. If thecalibrations don't run to the edge youwon't be able to preset the controls withany reasonable degree of adcuracy.Place a fine line or other indicator di-rectly above each knob.

Checkout. Connect the photocells tothe control unit and apply power. Don'tworry if the meter pins at either end ofthe scale. Set switch SI to the extremeclockwise position and adjust R2through R5 until you find the controlthat changes the meter reading. Mark

ing P2, the color comparator mountedunder the enlarger lens.

Set SI to any position, set all othercontrols to their mid -position, and turnon bright room lights. If the meter pinsout or approaches full scale deflection,adjust trimmer control R6 so the meterpointer just pins (don't be afraid topin the meter). Depending on theamount of light the meter pointer willpin right (for bright light) and left (for

Close-up of meter face showing a smallscale -illumination lamp in lower rightcorner. This lamp should not be operatedat full voltage to avoid fogging the film.

dark or very low light). This is normaland there will be no damage to thecircuit or the meter. (Note: If you usea zero -center meter the pointer willbarely pin on both sides.)

Install the Z -bracket under the lens.If your enlarger uses a filter holder un-der the lens insert a diffusion screen orglass, or a Beseler Light Integrator orsimilar ground glass in the filter holder.You are now ready to make colorprints.

The first thing you need to makefine quality color prints is a high speedchemistry, such as the two-step Beselersystem which can produce a finishedprint in two minutes. The second itemyou need is the electronic color analyzerfor which we've already given you theplans.

Color Variables. Color materialssuch as the negative, printing paper, en-larger lamp, and even color correctionfilters vary in their sensitivity to lightcolors from batch to batch, roll to roll,and time to time. Even the enlarger'soptical system can have a color cast.For this reason it is generally impossibleto place a negative in your enlarger,expose the paper, and develop a good-let alone decent-color print.

To avoid upsetti-ig a controlsetting while grcping for theon -off switch in the dark-room, mount switch 52 as faras possible from the controls.


r PAINTINGCOLOR

NEGATIVES

Pros ides a wealth oforthwhile info for

photographers inter-ested in the color printtechniques availablefrom Kodak or yourphoto dealer. Theirpublication No. E-66.

One way we can correct for thesevariables is through an additive ex-posure, exposing the paper throughblue, green. and red filters for differinglengths of time. Since blue, green, andred create all the colors in additiveprinting, any correction can be obtainedby controlling the precise timing of eachexposure. The additive system is a painin the neck for the hobbyist, for theslightest desired change in the colorrendition or saturation (exposure) caninvolve changes in the exposure throughall three filters.

A printing system that's easier to useand more favored by hobbyists is thesubtractive exposure. A single filter packmade up of two of the filters known asYELLOW, MAGENTA, and CYAN makesall the color corrections at the sametime. This filter pack is placed betweenthe enlarger lamp and the negative; vir-tually all modern enlargers have a draw-er in the lamphouse to accommodatea filter pack. A single exposure throughthe filter pack is all that's required tomake a color print. Some of the moreexpensive enlargers have what is termeda "dichroic head" with variable filtersas part of the light system; the exactvalue of filtration is simply dialed bythe user. Again, all the color correctionis provided at one time by the dichroichead so only a single exposure isneeded.

More Info. A full and complete treat-ment of both types of color printing iscontained in the Kodak publicationPrinting Color Negatives; this book isa required reference for anyone whowants to make quality color prints. Thebook also gives .the most convenientoperating procedures for electroniccolor analyzers.

The subtractive printing procedure isparticularly well adapted for use with acolor analyzer, is the easiest method forthe amateur, and is exceptionally fast-handling. so the illustrations to followwill refer to the subtractive system.

An electronic color analyzer basicallyconsists of a photocell (vacuum tubephotomultiplier or photoresistor) posi-tioned under the lens, blue, green, andred filters mechanically positioned overthe photocell (or positioned over thecell by hand) and a meter that indicatesthe amount of light falling on the cell.The meter is connected to the photocellthrough independent potentiometers asshown in the figure. Color analyzerreadings will be accurate for most nega-tives and lighting situations as long asthe same box of printing paper is used.The system needs to be recalibratedonly when the printing paper is changed(so purchase boxes of at least 100sheets to avoid extra work).

The first step is to make a really fineprint from a decent negative. You cando it the hard way, one print at a time,or use a Beseler Subtractive Calculatorwhich puts you inside the ball park onthe first try. When you have made aprint with satisfactory flesh tones andcolor saturation don't disturb the en-larger or timer controls.

To Continue. . . . Place the coloranalyzer's probe on the easel or swingit uncle' the lens (if it is mounted onthe enlarger). Install a light integrator-which is nothing more than a piece ofground glass or its equal-under thelens, between the lens and the analyz-er's probe. The light integrator scram-bles the picture into a diffused "whitelight" which contains all the colorelements of your negatives andthe filter pack. Place a blue filter(Kodak Wratten No. 98) on top of thelight integrator. (Note that most hobby-ist analyzers have a selector .switch thatalso mechanically positions the correctfilter over the photocell.) Turn on theenlarger and adjust the analyzer's yel-low control for a convenient referencemeter reading. (Usually, center -scale Or"null" is used as the reference reading,but any meter reading can be used asa null.)

Remove the blue filter, install a green

FILTERS

,IGHT FROM

KulGRN I

ENLARGERRED!' Pt+OTO -

CELL

YELLOW

MAGENTA

CYAN

WHITE

The basic color analyzer. Once controlsare matched to a "standard" negative,just select filters for a null on themeter for each individual color and white.

filter (Kodak Wratten No. 99), switchthe analyzer to MAGENTA and adjust themagenta control for a null meter read-ing. Remove the green filter, install ared filter (Kodak Wratten No. 70),switch the analyzer to CYAN and adjustthe cyan control for a null meter read-ing (the color controls yellow, magenta,and cyan refer to the color of the sub-tractive filters in the filter pack). Fi-nally, remove all filters from under thelens, switch the analyzer to WHITE andadjust the white control (exposure con-trol) for a null meter reading.

(The color analyzer in this projectuses a separate photocell for the ex-posure. If. you look at the easel you'll

Modern color print chemistry techniquesfrom Beseler include this subtractive colorcalculator to aid filter selection.

see a shadow cast by the Z -bracketholding the color comparator cell. Posi-tion the exposure cell on the easel so itis just off the edge of the shadow. Ifyou prefer, you can place several thick-nesses of opaque paper over the colorcomparator cell and use it for thewhite measurement, though we suggestyou use the separate cell.)

When all the controls are adjustedyou have programmed the color char-acteristics and exposure of your "refer-ence" print into the analyzer, and youshould note the control settings andexposure time for future use.

Down to Business. Now assume youwant to make a print from anothernegative. Put the new negative in theenlarger. Then set the degree of en-largement and focus, leaving the lenswide open. Place the analyzer's probeunder the lens, install the light integra-tor and set the analyzer's switch toCYAN. Install the red filter on top of thelight integrator and adjust the lens aper-ture until the meter indicates null.Switch the analyzer to MAGENTA, installthe green -reading filter and note themeter reading. If it is not at null, addor remove magenta filters (from thefilter pack) until the meter shows anull. Then switch the analyzer to YEL-ow, install the blue -reading filter and


COLOR ANALYZERmodify the yellow filtration in the filterpack until the meter shows a null.Finally, set the analyzer to WHITE, re-move all reading filters and adjust thelens aperture for a null indication.

Through the color analyzer you havenow established a new filter pack andexposure for the new negative. If thenew negative uses similar lighting to thereference negative the print should beperfect. If the lighting was considerablydifferent the print will be good-ac-ceptable to most people, but requiringjust a slight filter pack modification fora great print.

Swinging Filters. In the previousexample the filter pack would wind upwith magenta and yellow filters-whichis what is generally needed. Some Koda-color negatives, however, might requirecyan hers plus magenta or yellow (butnever all three). This information willhave been programMed into the coloranalyzer, so you will have no difficultyif you make a slight modification inprocedure. The first meter reading, theone where you adjust the lens's aper-ture, should be made for the filter youare not using in the filter pack. Forexample, if your basic filter pack hascyan and magenta, switch the analyzerto YELLOW, place the blue -reading filterin position on the light integrator, andclose down the lens for a null indica-tion. Then proceed with the other rad-ings. If your reference negative did notrequire cyan in the filter pack, if it hadyellow, magenta, or both, and you finda new negative just can't be pulled infor null meter readings with yellow andmagenta filters, it indicates the newnegative requires cyan filtration, so startwith the assumption that yellow is not

Kodak color printing filters. Typical filterdesignation CP2OY means color filter witha .20 density; the color is yellow.

required. It you still can't null themeter, it means magenta should not bein the filter pack.

As we mentioned, a more thoroughdiscussion and procedure for using acolor analyzer is found in Kodak'sPrinting Color Negatives.

Most, but not all, commercial coloranalyzers use photomultiplier tubeswhich have no light memory, nor arethey confused by infrared from the en-larger lamp. These units are, as youwould expect, relatively expensive. Lowcost models use photoresistors.

More Data. Photoresistors are infra-red -sensitive and they have a light mem-ory, both of which can confuse themeter. The infrared is easily handled byinstalling a heat or infrared filter glassin your enlarger (it should be there toprotect the negative anyway). The lightmemory is handled by using a consistentmeasurement procedure. The best wayis to turn the enlarger off, install thereading filter and the light integrator,turn off the bright room lights, countto five, and then turn the enlarger on.

Professional equipment used by color labs includes thisKodak Video Color Negative Analyzer. It uses a 5 -in. color

TV screen to assist an operator in selecting the correct filter.

Take the meter reading. or adjust theappropriate color control, slide the newreading filter in place before withdraw-ing the old one, switch the analyzer, andmake the new meter reading. Repeatthis for the third reading filter. You'llnote that this procedure keeps brightwhite light from falling on the photo-cell between meter readings. If youwant to change filters under roomlights, make certain there are about fiveseconds of darkness between turning theroom lights out and turning the enlargeron.

The whole bit might sound somewhatcomplicated, but after you've runthrough the procedure once or twice toget the hang of things it shouldn't takeyou more than a minute or so for a fullcolor analysis of a new negative.

The Kodak Wratten filters needed areavailable from professional camerashops. For the construction project,color analyzer 2 -in. or 3 -in. KodakWratten filters Nos. 98 (blue), 99(green), and 70 (red) are recommend-ed. If you have difficulty obtainingthese specific filters you can make thefollowing substitutions, through theanalyzer's precision will be slightly re-duced: 47B (blue), 61 (green), and92 (red).

The Pro Shop. We could not closewithout some words on commerciallyprocessed color prints such as you mightorder from a drugstore or camera shop.Commercial color labs have as high (ifnot higher) a remake rate than theamateur if quality colcr prints are de-sired. As a general rule, it takes twotries to get a decent color print, so thehobbyist with a color analyzer is wayahead of the game because he can turnout, at worst, two good prints for eachthree first tries. The average is evenhigher than this as the hobbyist getsskilled in the use of a color analyzer.

Commercial labs come close to a:lobbyist's results only when they areequipped with a video analyzer such asthe Kodak Video Color Negative An-alyzer Model 1-K; and Kodak onlyclaims a 75's + first try acceptance ratefor their analyzer. The video analyzeris a 5 -in. x 5 -in. TV display. The opera-tor views the color negative as a posi-tive color TV image, and adjusts theTV's controls for proper color balanceand brightness (saturation). The con-trol settings are translated to the print-ing equipment's filter adjustments sothat the final print is similar to theimage displayed on the TV.

The video analyzer is a fast and easyway to get good color prints on thefirst try, but since video analyzers costin the thousands, the color analyzer isthe best thing going for the hobbyist.


IF YOU NEED AN INEXPENSIVE andhighly portable audio test set, thisFull Range Audio Generator

(FRAG) is for you! Our friendlyFRAG delivers variable and fixed out-puts of sinusoidal waveform from 10Hz to over 15 kHz and up to fivevolts peak -to -peak.

The Circuit. There are several circuitnetworks which can produce a sinus-oidal waveform, including the Phase-

Shift and the Twin -T. It is the latterwhich will be examined here, as itproved in application to be the mostsuitable for the FRAG.

As shown in the Twin -T Oscillatordiagram, we have a Low -Pass networkof RI, R2, and Cl in parallel with aHigh -Pass network formed by C2, C3,and R3. The combined network is con-nected between the inverting input andoutput of a gain device, such as thefamiliar 741 integrated circuit op -amp.Typically, RI = R2, while R3 is one-half to one -tenth of RI, and CI = C2,and C3 = 2C1.

Since the phase shifts for the twonetworks are opposite, there exists, intheory, only one frequency where thetotal phase -shift from input to outputwill reach 180°, at which point sinus-oidal oscillations will occur, providedsufficient gain is available. The approx-imate frequency will be

F =2 w RI Cl

Varying any or all of the networkelements will cause the nominal fre-quency to change, accompanied by adrop in output, until oscillation can nolonger be sustained. Over a certainrange, varying the resistive elementssimultaneously, as by a ganged poten-tiometer, will yield a useful frequencyspan, provided the gain can be raisedappropriately, but without causing over-driven distortion.

Shunting the Twin -T network with a

'PRA%ourfriendig

generator/By Frederick W. Chesson

fixed resistance RF yielded fair results,in experiments conducted to obtain awide operating range consistent withsimplicity. It was then found that ad-dition of a diode back-to-back pair,forming an active feedback element,gave a considerably greater range, asshown. Further experimentation finallyshowed that even greater improvementcould be obtained by connecting thefeedback elements between output andthe offset -null terminal associated withthe inverting -input. Three switch posi-tions give ranges of 10-100 Hz, 100-1000 Hz. and 1 kHz - 10kHz. A fixedoutput of about 5 VPP ard a variableoutput of 0-1.0 VPP were added toprovide a choice of useful signal levels.

Put It All Together. For conven-ience in portability, a utility box havinga five inch length by two and one -quar-ter inch height and width was selected(Either Bud CU -2104A or PremierI2P3886 types are suitable).

A photo shows the parts placementof the prototype, with the range -capaci-tors being strung between the rangeswitch and a perf-board mounting the

integrated circuit and other compo-nents. Check the drawing to see howthese components may be placed on atwo inch square section of perf-boardhaving 0.1 inch spaced holes. A pairof No. Six ground lugs are bent at rightangles to serve as miniature mountingbrackets. There is sufficient room fora 14 -pin DIP IC socket for the 741 op -

amp, should replaceability be desired.Although a mini -dip 8 -pin 741 was usedin this circuit, the standard 14 -pin unitwill do as well, paying attention to thepin connections. The nine -volt transis-tor battery (Eveready type 222, orequivalent) is secured in place by anS-shaped half -inch wide aluminumbracket.

.ie only component difficult to findis a three -gang 250K, 250K, 25K po-tentiometer, used for variable frequen-cy settings. If a ready-made assembly(preferably log -taper) cannot be ob-tained, use a built-up unit, like Cen-tralab Fastach components.

Optional resistors R4, R5, and R6are included so that the variable fre-quency dial may be rotated to maxi-

PERFBOARDRI, R2, R3(SEE TEXT)

9V BATTERY

R 7 IC I

Use the parts layout given for the perfboard and you will have no trouble wiring thecapacitors point-to-point as shown here. Be certain that the long leads do not short outagainst each other by keeping them as straight as possible.


audio generatormum frequency without having the cir-cuit drop out of oscillation, as it wouldshould RI, R2, and R3 fall too low.Temporarily omit the feedback resis-tor(s) RF for later adjustment. If afour pole -three position switch (suchas Calectro E2-168) is available, theneach range may have its own individ-ually selected feedback resistor formaximum efficiency.

Adjustment and Operation. An oscil-loscope is essential for adjustment ofthe friendly FRAG to determine op-timum waveform and amplitude andfor rough frequency determinations. Afreqeuncy-counter is also useful, al-though the FRAG is not intended to bea precision audio generator.

Before applying power, set the inputbias potentiometer R7 for approximatemidrange position and connect a dec-ade resistance box, set at about 33Kohms, in place of RF. Set the RangeSwitch to its middle (X100) positionand the variable frequency control toits mid position. Connect the scope(and frequency counter, if available)to the fixed output terminals.

Switch on the power by turning theOutput control to mid -position. Thescope should display a more or lesssquare wave of about 200 Hz. Adjustthe decade box, or individual fixedresistor, for a sinusoidal waveforw.ofmaximum amplitude, consistent withlow distortion. If the wave is flattenedat top or bottom, try adjusting R7while rechecking RF. Rotate the vari-able frequency control from one endto the other. rechecking RF and R7

R7

CIO

Rf I

Rf2 Rf3OPTIONAL(SEE TEXT)

ICI

NO.6GROUND LUGS

R4

R5

R6

-DI

D2

CII

Use this parts layout for your perfboard.Rf2 and Rf3 are optional, as mentioned inthe text. Also, use a socket for IC1.

OUTPUTCCNTROL

VARIABLEFREQUENCY -N..

On:e built, yoc willfind our fiendly FRAGto be one of the mostuseful accessories. Thefixed and variableoutputs, the variablefrequen:y cont '.l, allcombine to mawFRAG one versatileinstrim.mt.

NE 'WORK

741

3'

DI

-10

-44-1D2

DYNAMIC AMFLITUDE CONTROLWITH DICDES IN FEEDBACK LOOP

Shuntng a Twin -T network with feedbackresistance (F.f) yielded fair results. Theadditiot of a back -t. -back diode pair as anactive feedback element greatly tended toincreas-? the FRAG's operating range.

TWIN-/NETWORK

- 6741

10

FIXED OUTPJT

RANGE

RI R2

CI

2I IC3IR3

GAIN}

I--- OP AMR

VARIABLEOUTPUT

Rf RI R2 R3 -2-10

CI = C2 C3: 2CI

BASIC TWIN -T OS:ILL ATOR

11.

This basic Twin -T circuit uses a Low -Passnetwork (RI, R2 and RI) in parallel witha High -Pass network IC1, C2 and C3). Asthe phase shifts for eadi circuit areopposite, sinusoidal oscillations will occurat only one frequency, given sufficient gain.

OCT

LI D3 D5-04--

4D6- Rf I

-"----".w-.Rf2 . S itt

Rf3

VAR ABLE WAVEFORM GENERATION

TYP CALWAVEFORM

During developrr ent of the RAG, additional diode pairs were Acted to see if theywould further ircrease the variable frequency range. They did --tit at the costofadding some distortion. This, lowever, results in some interesting, tones-music!


should distortion occur. Amplitude willbe less at each end of the dial, and willdrop out entirely at the upper end, un-:ess the optional resistors R4, R5 andR6 have been included. A maximumoutput of 5 VPP should be obtainableat the fixed output terminals and up to1 VPP at the variable output jack. Ifseparate feedback resistors are used

(with a four -pole Range Switch) re-check the other two range positionsand select the correct individual resis-tors and mount them on the perf-board.Otherwise, a single feedback resistor willhave to be a compromise for best op-eration over the entire span of all threeranges.

The variable frequency dial may be

.R4 Fj R2A.

R7

Swi1_CT C2 C3

SWIb 6

+ 9VDC

SW2

d R3

R5

SWIG

Rf

PARTS LIST FOR THE FRIENDLY FRAG

IC1---Type 741CC1-.22uF capacitorC2-.02uF capacitor (Allied 710R1136 or

equiv.)C3-.002uF capacitor (Allied 710R1093 or

equiv.)C4, C7-.1uF capacitorsC5, C8 .01uF capacitorsC6, C9 --.001uF capacitorsC10 --.1uF capacitorC1I -10uF electrolytic capacitorC12-220uF electrolytic capacitorDl, D2 --1N914 silicon diodesR1, R2, R3-- 250,000 -ohm, 250,000 -ohm.

25,000 -ohm, ganged potentiometer (Cen-

tralab "Fastach")R4, R5--10,000-ohm, 1/4 -watt resistorR6 -1,000 -ohm, 1/4 -watt resistorR7 --5.000-ohm trimmer potentiometerR8 -4,700 -ohm, 1/4 -watt resistor

If you ever need a Full -Range AudioGenerator, then call it by its initials, FRAG,and start building a fun and interestingproject. Our FRAG uses a neat and uniquemeans of building which can be easilyduplicated following instructions in thearticle. A main perfboard is positioned inthe middle of a rectangualr metal box andthe many capacitors the circuit calls fo are

18

2 7

3 64 ; 5

ICICI?

5 VPPFIXEDOUTPUT

R9.- 1,000-chm potentiometer (Allied 854-5800 or equiv.)

SW1-3-pos tion, 3 or 4 -pole miniature rotaryswitch (Calectro E2-168 or ecuiv.)

SW2-- potentiometer switch (mount on backof R9)

RI --feedback resistors (see text)11-Pair of five -way binding postsJ2 --RCA type phono jackMisc.--9-V battery, battery clip, perf board

with .I -in. spacing, perf. board terminals,DIP socket, a 5 x 2.25 x 2.25 -inch chassis(such as the Bud CU 2104A), wire, solder,etc.

Allied Electronics' address is:401 East 8th St., Ft. Worth, Texas 76102Calectro Electronics' address is:400 S. Wyman St., Rockford, III. 61101Centralab Electronics' address is:P.O. Box 8E8, Fort Dodge, Iowa 50501

wired point-to-point to the components onthe perfboard. It's quick and easy, andresults in a very small and compact,professional -looking instrument. If youever get tired of having FRAG work for aliving, a simple and reversiblemodification, also explained in the text,will turn HMG into something of asongstress. She is a very friendly FRAG!

calibrated simply on a 1 to 10 basis,which should hold good for the three.ranges. If a linear potentiometer is used(all that was available in the Fastachcomponents at time of construction)the dial will necessarily be non-linear,which is why a log -taper pot is moredesirable. Also, due to mechanical back-lash in the stacked sections, it is best

Looking at FRAG from the front shows thefrequency range selector, as well as theoutput terminals and level controls on top.

to move well past an over -shot fre-quency point before reversing to zeroback in. The 0-1 VPP shielded jack isbest for low-level output applicationsinv,,Iving audio amplifiers and otherhigh -input impedance gear. The 5 VPPfixed -output terminals are useful forgeneral purposes, or where it may bedesired to construct fixed voltage -divid-er networks.

Although the battery drain is quitemodest, make sure to turn off the testset when not in use.

Range Switch Positions

X FREQ. SW1a SIN1b/c10 10-100 CI C4/C7100 100-1000 C2 C5/C81K 1K -10K C3 C6/C9

Other Applications. During develop-ment of the circuitry, additional diodepairs were tried to see how far their"Jynamic feedback" operation couldextend the variable frequency range.Although two pairs gave some increase,this was at the expense of waveformpurity. This distortion, however, can beput to use in the area of electronicmusic. The last diagram shows how achain of diodes, with individually se-lected feedback resistors may be switch-ed in to provide for the generation ofinteresting synthetic tones . . . anotherbenefit of this original FRAG!


oBy Jorma Hyypia

HOW OFTEN HAVE YOU searched fruit-lessly for a special switch? Prob-ably dozens of times-if you're at

all an active builder. The next time thishappens, consider custom -building yourown complex switches using inexpen-sive magnetic reed switches and smallceramic magnets. Such do-it-yourselfswitches offer several advantages. Theyare relatively inexpensive, silent, andlong lasting, as there are no rubbingcontacts and the reed contacts aresealed in glass, away from corrosiveatmospheric gases.

You can purchase two sizes of mag-netic reed switches and the ceramicmagnets from Radio Shack. The largerswitch (Cat. No. 275-034; 13/4" over-all length) comes in a 4 -for -790 blisterpackage. The smaller "Micro Mini"switch (275-035; 11/4" long) comes 10to a package, for $2.99. The magnetscost 10 cents each, regardless of size.The smallest, 1/2" diam. disc ("button")magnet is the most useful, but you mayneed the larger 11/4" disc or 1" x 3/4"rectangular magnets to build reallylarge, complex switches.

The several custom-built switchesshown in this article only hint at thevirtually limitless design combinationsthat are possible. Study the drawings to

CROSSED REEDSWITCHES

Make a single -pole, 2 -position, on -before -off rotary switch with two crossed reedswitches and a rotatable disc magnetpositioned above them. When themagnet's axis is parallel with a switch's 4 REED SWITCHESlong dimension, that switch remains off;the other switch is simultaneously on. Inthe intermediate, 45° position, both A single -pole, 4 -position switch is accom-switches are on. Use this arrangement plished by a vertically -oriented discwhen the second switch must come on magnet passing over four reed switches,

switch turns,gimoisL_ lake arranged in a square.

learn how magnet orientation and direc-tion of travel past the reed switchesaffect switching action.

Carpetak Tape, a cloth tape with ad-hesive on both sides that is used to holddown carpets, is excellent for mount-ing- the reed switches -.o panels. Theswitches adhere firmly, yet can be re-moved without damage. For greaterpermanence, you may wish to useepoxy cement for mounting once youknow exactly where to locate the reedswitches. Generally, it is best to locatethe magnet and reed switches on thesame side of the panel; however, it isalso possible to put the switches on oneside of a non-magnetic panel and orientthe magnet on the other side. The ce-ramic magnets are of extremely hardmaterial, and you may have poor suc-cess if you try to hacksaw them smaller.Try breaking the magnet by clampingin a vise and striking with a chisel; itmay not break cleanly across, but grind-ing on an emery wheel may be prac-tical. When possible, just use the mag-nets as they are. Mount them in alu-minum holders as shown here, or glueto support arms with epoxy adhesive.

The following brief descriptions ofvarious switch types should help clarify

of build:11g switches:

DISC MAGNET INVERTICAL POSTIONON ROTATING ARM

r-1-1

LJ

108 101 ELECTRONIC FROJECTS 1978

A rotary switch with a 1/2" diam. ceramicmagnet mounted vertically turns theswitches on individually. The magnet armis turned by a knob on the other side ofthe panel, or can be turned continuouslywith a small motor drive for constantscanning applications.

Single -throw, multi -pole. These canbe constructed simply by mounting reedswitches in parallel, and passing theedge of a vertically -mounted magnetover them to trip all switches simul-taneously. If you . need a sequentialswitching action, just angle the magnetabout 30 degrees so that the parallelreed switches are tripped in 1, 2, 3, 4order. If the magnet movement con -

SIMULTANEOUS MULTI -POLE

ON- BEFORE -OFF

Magnetic reed switches, available fromRadio Shack, come in two convenientsizes; the overall lengths, including leads,are 1 h/4"' and 13/4". Both are rated at 0.56amperes at 125 volts. The small, 1/2"diam. disc magnet is handiest, but the 1"diam. disc and 1" x 3/4" rectangular mag-nets may be desirable for building com-plex, multi -pole switches.

tinues in the same direction, the switch-es will go off in the same 1, 2, 3, 4sequence, on the other hand, if mag-net movement is reversed ,when allswitches, are on, the switches will gooff in the reverse 4, 3, 2, 1 order.

Multi -position, single -pole. Arrangethe reed switches one after the other,like cars of a train. You can keep theswitch smaller by using two lines of

SEQUENTIAL MULTI -POLE

_

SIMULTANEOUS "ON"

r --SEQUENTIAL SINGLE - POLE , 5 -POSITION

Here are various magnet and reed switch orientations all of which achieve differentswitching actions. Position the magnets and reed switches exactly as shown and asfurther discussed in the text, for best results.AL AL

staggered switches, as shown. As thevertically -oriented disc or rectangularmagnet passes over the switches, each"on" switch goes off before the nextswitch comes on.

A photograph shows a sliding switchof this general type, but one made tofunction as a double -pole, single -pole,double -pole sequencer. A simple lock-ing device consisting of a lock washerunder the knob on the other side of thepanel permits locking the movement atany desired position. Note the "guide"strip near the slot; a square nut thatholds the magnet support arm on theknob shaft bears against this guide tokeep the magnet properly aligned overthe reed switches.

Rotary switches. These are easier tobuild than slide switches, and there aremany ways to achieve special switchingcharacteristics. Note that when the edge(diameter axis) of a disc magnet isaligned with the long axis of a reedswitch there is no switching action.

MAGNET POSITIONS

2 SWITCHES "ON"

I SWITCH "ON"

ALL "OFF"

A complex switching method is achievedby passing a horizontally -oriented magnetover a square of four reed switches. Whenthe magnet is in a "corner" two adjacentswitches are on; in other positions onlyone switch is on.

101 ELECTRONIC PROJECTS 1978 10C

JL

Thus if you mount several reed switch-es next to each other, and rotate themagnet directly over the center of theswitches, you obtain more or less simul-taneous on -off action.

If two switches are crossed a vertical-ly -mounted rotating magnet will turnone switch on and the other off whenthe magnet axis is parallel to the longaxis of one reed switch. In the inter-mediate position, both switches are on;thus you can have on -before -off actionwith a very simple physical arrange-ment. To make a double -pole version,cross four reed switches in pairs.

A 4 -pole, 4 -position rotary switchcan be made by arranging four reedswitches in a "square" and adding avertically -oriented disc magnet so thatit can be swung in a circle over the

MICRO MINIREED SWITCHES

SMOOTH WASHERS

centers of the reed switches. This pro-vides an off -before -on switching action,each "on" switch first going off beforethe next one comes on.

Some strangely useful things beginto happen if you mount the disc magnethorizontally instead of vertically. As themagnet passes over a corner of thesquare of reed switches so that it ispartly over the ends of two adjacentswitches, both switches go on. Rotatethe magnet a little further, so that it isover just one switch and that switchstays on while the other goes off. Curi-ously, when the horizontally mountedmagnet is over the center of a switch,that switch goes off. This is exactly theopposite of the on -action caused by avertically -mounted magnet. ' Conse-quently, this type of rotary switchprovides sequential double -pole andsingle -pole action, with four fully offpositions.

Multi -pole Rotary. Such switchescan be constructed by stacking addi-tional reed switches atop the first fourthat make up a basic square. Mount

[1_

SQUARENUT

GUIDE

SPLIT LOCKWASHER

KNOB

ALL

1/2"

k_ 5/8"

BOLT

OHOLE

The ceramic magnet of this sliding switchpasses over five Ws" size reed switchesto provide double -pole, single -polesequencing. Separate diagram shows asimple mechanism which permits locking themagnet "on" or any "off" position.

the rotatable magnet inside the "box"formed from the stacked reed switches.When the long dimension of the mag-net is perpendicular to stacks on oppo-site sides of the box, all of thoseswitches will go on; other stacks at 90°to these will remain off because themagnet axis is parallel to them. Byusing one of the larger rectangular mag-nets, you can easily stack at least a halfdozen switches on a side, for a total of24 switches; 12 would be on at any onetime, 12 off. When the magnet is in theintermediate, 45° position, all switchesare off.

BEND AROUND MAGNET

I 3/8"

Here is a sliding switch designed to function as a double -pole,single -pole, double -pole sequencer. A locking device of a lockwasher under the knob on the other side of the panel permitslocking the movement at any desired position. The supportarm is positioned to keep the magnet aligned properly.

OFF

ON

ON

By positioning a rotatable magnet in the center of a square of four reed switches you have a double -pole rotary switch. Byslacking magnets on top of the basic four, and using a larger magnet, as many as twelve on -positions are possible at eachactive orientation.


Linear Off -Before -On. Mount parallelswitches far enough apart so that, as avertically positioned magnet approachesthe switches from one side, the firstswitch will go on and off before thenext switch is affected. Here's a handytrick that enables you to pull the paral-lel reed switches much closer togetherto form a more compact switch: Posi-tion a small disc magnet over the cen-ter of the first switch so that its longaxis (diameter) is parallel to the longaxis of the switch. If you have beenpaying attention, you already know thatin this position the magnet has no effecton the switch. Now slowly rotate theswitch away from this pirallel orienta-tion until you hear the switch click on.Mount the magnet in its sliding holderso that it passes over the center of thereed switch in this slightly angled posi-tion. This deliberately weakened mag-netic action permits location of thenext switch much closer to the first-as close as about 3/4"-and still obtainoff -before -on switching.

There's no problem, of course, if youwant on -before -off action because thenyou can mount the reed switches asclose to each other as you like. A mag-net approaching from the side will turnthe first on, then the second, beforeturning the first off. Bear in mind thatif the magnet approaches the pair ofswitches from the end directions,you obtain approximately simultaneousdouble -pole switching.

If you have but one reed switch, andthe vertically -oriented magnet ap-proaches from one side of the reedswitch, it has a longer "reach" andswitching action occurs while it is rela-tively far from the center of the switchThis relative sensitivity, relating to di-rection of magnet travel, could be animportant factor in some switch -designproblems.

Special Designs. As you play aroundwith your reed switches and magnetsyou will undoubtedly discover manyvariations on the ideas given here. Forexample, suppose you wanted a slidingmulti -pole switch that always switchesthe reed switches on in the same se-quence. As the magnet travels over theparallel reeds, the switches come on in1, 2, 3, 4 order. But as you slide themagnet back to its original starting posi-tion, the reeds would go on in reverse4, 3, 2, 1 sequence-which is what youdo not want. So what's the answer?Simply mount the magnet on a holder

OFF - BEFORE - ON(LONG SPACING)

OFF- BEFORE - ON( SHORT SPACING)

CRITICALANGLE

ACTION

Spacing of adjacent reed switches is important if the first switch must go off beforethe next turns on. When the magnet is in its strongest orientation (left), the reedswitches must be far apart. If the magnet is positioned at an angle slightly removedfrom where it does not switch, the two reed switches can be closer together and

in the on -before -off action.

C

B

OFF

---- ON

-. OFF

ON

OFF

Orientation and direction of movement of a disc magnet influence switching action.No switching occurs as a horizontal magnet moves across the reed switch as at upperleft. If the magnet passes along the length of the reed (upper right), switching to "on"occurs when the magnet is near either end of the reed, but not when it is directlyover the contact points in the center of the reed. Switching occurs if the magnet isvertically oriented as at lower left, but over a shorter range if the magnet movesalong the "5" path than along the "1" path. If the magnet is turned 90° (lower right),no swirching occurs when it is moved along either of the indicated paths.

that permits it to be turned 90° at theend of each sweep. This way the mag-net can be in its "active" orientationgoing one way, and in its "dead" orien-tation going the other way. Thus it ispossible to return the magnet to thestarting position, for subsequent normalswitching order, without affecting theswitches on the return sweep.

I have not tested these ideas, butit seems likely that you could construct

such truly off -beat switches as, forexample, a level -indicating switch bysuspending the magnet on a short pen-dulum so that it will swing close toeither of two parallel magnets to elec-trically signal tilting. And it may befeasible to create a vibration -detector inmuch the same manner, but mountingthe magnet on the end of a flat or coilspring so that vibrations will swing itin -and -out of the switching range .


LITERATURELIBRARY

301. Get the '78 Eico Catalog and see their do-it-yourself kits and factory assembled electronicequipment. Specialties are test equipment,burglar/fire alarms, hobbyist and auto electronics.302. International crystal has illustrated folders con-taining product information on radio communica-tions kits for experimenters (PC boards; crystals;transistor RF mixers & amplifiers; etc.).303. Regency has a new low cost high performanceUHF/FM repeater. Also in the low price is their10 -channel monitoradio scanner that offers 5 -bandperformance.304. Dynascan's new B d K catalog features testequipment for industrial labs, schools, and TVservicing.306. Get Antenna Specialists' catalog of latest mo-bile antennas, test equipment, wattmeters, acces-sories.308. Compact is the word for Xcelite's 9 differentsets of midget screwdrivers and nutdrivers with"piggyback" handle to increase length and torque.A handy show case serves as a bench stand also.310. Turner has two catalogs on their CB micro-phones and antennas. They give individual specifi-cations on both lines. Construction details help inyour choice.311. Midland Communications' line of base, mobileand hand-held CB equipment, marine transceivers,scanning monitors, plus a sampling of accessoriesare covered in a colorful 18 -page brochure.312. The EDI (Electronic Distributors, Inc.) catalogis updated 5 times a year. It has an index of manu-facturers literally from A to X (ADC to Xcelite).Whether you want to spend 29 cents for a pilot -light socket or $699.95 for a stereo AM FM receiver.you'll find it here.313. Get all the facts on Progressive Edu-Kits HomeRadio Course. Build 20 radios and electronic cir-cuits; parts, tools, and instructions included.316. Get the Hustler brochure illustrating their com-plete line of CB and monitor radio antennas.

318. GC Electronics offers an "Electronic tremicalHandbook" for engineers and technicians. It is a"problem solver" with detailed descriptions, usesand applications of 160 chemicals compiled forelectronic production and packaging. They are usedfor all typos of electronic equipment.320. Edmund Scientific's new catalog contains over4500 products that embrace many sciences andfields.321. Cornell Electronics' "Imperial Thrift Tag Sale"Catalog features TV and radio tubes. You can alsofind almost anything in electronics.322. Radio Shack's 1978 catalog colorfully illus-trates their complete range of kit and wired prod-ucts for electronics enthusiasts -CB, ham, SWL,hi-fi, experimenter kits, batteries, tools, tubes, wire,cable, etc.323. Get Lafayette Radio's "new look" 1978 catalogwith 260 pages of complete electronics equipment.It has larger pictures and easy -to -read type. Over18,000 items cover hi-fi, CB, ham rigs, accessories,test equipment and tools.327. Avanti's new brochure compares the qualitydifference between an Avanti Racer 27 base loadedmobile antenna and a typical imported base loadedantenna.

328. A new free catalog is available from McGeeRadio. It contains electronic product bargains.329. Semiconductor Supermart is a new 1978 cata-log listing project builders' parts, popular CB gear,and test equipment. It features semiconductors -all from Circuit Specialists.330. There are nearly 400 electronics kits in Heath'snew catalog. Virtually every do-it-yourself interestis included -TV, radios, stereo and 4 -channel,hobby computers, etc.

331. E. F. Johnson offers their CB 2 -way radio cata-log to help you when you make the American vaca-tion scene. A selection guide to the features of thevarious messenger models will aid you as you gothrough the book.

332. If you want courses in assembling your own

TV kits. National Schools has 10 from which tochoose. There is a plan for GIs.333. Get the new free catalog from Howard W.Sams. It describes 100's of books for hobbyistsand technicians -books on projects, basic elec-tronics and related subjects.334. Sprague Products has L.E.D. readouts for thosewho want to build electronic clocks, calculators,etc. Parts lists and helpful schematics are included.335. The latest edition of the TAB BOOKS catalogdescribes over 450 books on CB, electronics, broad-casting, do-it-yourself, hobby, radio, TV, hi-fi, andCB and TV servicing.338. "Break Break," a booklet which came intoexistence at the request of hundreds of CBers, con-tains real life stories of incidents taking place onAmerica's highways and byways. Compiled by theShakespeare Company, it is available on a firstcome, first serve basis.342. Royce Electronics has a new 1978 full lineproduct catalog. The 40 -page, full -color catalogcontains their entire new line of 40 -channel AM andSSB CB transceivers, hand-helds, marine communi-cations equipment, and antennas and accessories.344. For a packetful of material, send for SBE'smaterial on UHF and VHF scanners, CB mobiletransceivers, walkie-talkies, slow -scan TV systems.marine -radios, two-way radios, and accessories.345. For CBers from Hy -Gain Electronics Corp. thereis a 50 -page, 4 -color catalog (base, mobile andmarine transceivers, antennas, and accessories).Colorful literature illustrating two models of moni-tor -scanners is also available.350. Send for the free NRI/ McGraw Hill 100 -pagecolor catalog detailing over 15 electronics courses.Courses cover TV -audio servicing, industrial anddigital computer electronics, CB communicationsservicing, among others G.I. Bill approved, coursesare sold by mail.353. MFJ offers a free catalog of amateur radioequipment-CW and SSB audio filters, electroniccomponents, etc. Other lit. is free.354. A government FCC License can help youqualify for a career in electronics. Send for Infor-mation from Cleveland Institute of Electronics.355. New for CBers from Anixter-Mark is a colorful4 -page brochure detailing their line of base stationand mobile antennas, including 6 models of thefamous Mark Heliwhip.356. Continental Specialties has a new catalogfeaturing breadboard and test equipment for theprofessional and hobbyist. Descriptions, picturesand specifications aid your making a choice.359. Electronics Book Club has literature on how toget up to 3 electronics books (retailing at $58.70)for only 99 cents each ... plus a sample Club Newspackage.

1111

361. "Solving CB Noise Problems" is published byGold Line and tells you how to reduce the noiseand get a clearer signal. In ciscussion and dia-gram you can find out about the kinds of noise,their sources, and the remedies.

362. El&F Enterprises' Truckloed Sale catalog of-fers 10% off all merchandise: (military or indus-trial surplus) speaker kits, TV games, computerterminals, tools, TV components, lensei, and more.

363. Send for computer enterprises' catalog ofmicrocomputer systems for personal, business, edu-cational and industrial users. They claim the great-est bargains in microcomputer equipment, systems.parts and supplies.

364. If you're a component buyer or specifier, you'llwant this catalog of surplus bargains: industrial,military, and commercial electronic parts, all fromAllied Action.

365. Electronic Supermarket hss a new catalog ofalmost everything in the field -transformers, semi-conductors, tv parts, stereos, speakers, P.C. boards,phones, wire and cable, tools, motors.

366. Send for Poly -Packs' new catalog featuringhundreds of bargains: new Barrel Pack kits, hobbycomputer peripheral parts, fiber optics, solar en-ergy chips, digital clocks. and more.

367. Optoelectronics' new ca:alog features theirnew Frequency Counter, a 6 -digit clock calendarkit, mobile LED clock, biorhythm clock, digit con-version kit, and many others.

368. Cherry Electrical Products has a handbookdescribing their new "PRO" keyboard for personalcomputer, hobbyist and OEM users. Included areinstructions on how to customize it on -the -spot,schematics, charts, and diagrams.

369. Motorola Training Institute offers a brochureon two new home -study courses: Four lessonscover semiconductors, designed for all techniciansservicing electronic equipment; the 34 -lesson pro-fessional FM two-way radio course is for thoseplanning to service land -mobile equipment.

370. The 1978 catalog from Computer Warehousehas data on 10 different microcomputers, with usedperipherals, and available for immediate delivery.Over 1,500 products are covered, new and used,from over 170 different vendors

371. Your computer system needn't cost a fortune.Southwest Technical Products offers their 6800computer complete at $395 with features that costyou extra with many other systems. Peripheral bar-gains are included here.

372. See how you can save with Olson's "ErectorKit" Computer System; also their factory wired ver-sion which includes a 2 -volume Bell & Howellinstruction course. Send for information.

101 ELECTRONICS PROJECTSBox 1849, G.P.O.New York, NY 10001Please arrange to have the literature whose numbers I have circled below sent to me assoon as possible. I am enclosing 50c for each group of 5 to cover handling. (No stamps,please.) Allow 4-6 weeks for delivery.

301 302 303 304 306 308 310 311 312 313 316 318

320 321 322 323 327 328 329 330 331 332 333 334

335 338 342 344 345 350 353 354 355 356 359 361

362 363 364 365 366 367 368 369 370 371 372

300 Enter my subscription to Elementary Electronics for 9 issues at $5.97.Check enclosed. Add $1.00 for Canada and all other countries. H8C181

1978 ED.Void After July 30, 1978

NAME (print clearly)

ADDRESS

CITY STATE ZIP1


Checkerboard(Continued from page 78)

less breadboard, or placed in contactwith the bare wire groups You can testas you go by using a slide, toggle orrocker switch at SI, or push -to -test witha momentary switch.

Checking Diodes. A properly oper-ating diode will conduct in one direc-tion only, and will not conduct whenthe leads are reversed. So you cancheck a diode with just two passes onChecker Board. If it lights the LED nomatter which way it's connected, yourdiode has an internal short. If it won'tlight the LED no matter which way it'sconnected, it's opened up. If it lightsthe LED only when connected, thenyou can identify the anode end (thetriangular arrowhead on schematicrepresentations) as being connected tothe red alligator clip (at the junction ofRI, CI and the base of Q1). The cath-ode (bar) end is then connected to theblack alligator clip (ground).

Checking LEDs. You can follow theinstructions for checking diodes tocheck LED's, but that's the hard way.The LED you test will light up, too,assuming it's good, when you test it onChecker Board. Make sure you get thepolarity right. You can also trace 7 -segment and multiple -digit LED dis-plays to see which pin does what.

Checking Electrolytics. The thingthat most often goes wrong with elec-trolytic capacitors is that they short out.And that's the easiest thing to spot withChecker Board. Connect the + lead to

the red alligator clip and the - lead tothe black, or plug the electrolytic rightinto the solderless breadboard. This testwill be mere fun with the momentaryswitch. Push it and watch the LED.You should see a bright flash that de-cays into darkness. The bigger the elec-trolytic, the longer the flash lasts. Ashorted electrolytic won't go out-anopen one won't flash.

Checking Crystals. Connect the twocrystal leads to the alligator clips. Ifthe LED lights brightly, the crystal isgood. If it lights dimly, the crystal isgood but will not work in all kinds ofoscillator circuits. If the LED does notlight at all, it probably means the cry-stal is bad. But it may mean that thecrystal is one of the few, obscure typesthat cannot make Q1 oscillate in theChecker Board circuit. Most crystals, ifgood, will light the LED brightly.

Checking Switches. With CheckerBoard connected to any pair of switchcontacts, the LED will light wheneverthere is continuity between the con-tacts. When there is no continuity, itwill not light. With this information, asheet of paper and a pencil, you canmethodically analyze when continuityoccurs with each change of setting ofan unknown switch. This can tell youwhat kind of a switch it is. And, ofcourse, when you know what kind ofa switch you have, Checker Board cantell you whether or not it's workingproperly.

Checking Continuity. A closed cir-cuit will light the LED, an open circuitwon't. (We're speaking of DC con-tinuity here). With this in mind, you

can check cables, connectors, printedcircuit paths, relays, light bulbs andmany other devices. As long as the test-ing -path resistance doesn't get too high(just how high is too high depends onyour particular LED and what shapeyour battery is in), anything that needsto maintain continuity in order to work(or discontinuity, in case you're lookingfor shorts) can be checked on theChecker Board.

Checking Out Checker Board. Yes,Checker Board even checks itself out.Just clip the two alligator clips together.If everything is working, the LED willlight.

Light up!

Add Tone to Your Phone(Continued from page 81 )

The meter indicates RMS in terms ofthe average voltage of a sine waveformso the reading is slightly off becausethere are two sine waves. The 'scopesees the vector addition of the twotones, and when the tones are in phasethe peak value is greater than the peakvalue of the individual tones. So, toavoid blowing any associated transistorequipment just remember that the max-imum pad output is nominally 3.5 voltspeak to peak regardless of what yourVOM or VTVM indicates.

No Adjustments. Unlike some of theelectronic touch-tone encoders theWe^tern Electric telephone dialer padsrequire no adjustment, nor do theydrift. Just install one and it works.

Ask Hank, He Knows(Continued from page 13)

Time Stands StillI recently picked up some capacitors

in sealed, foil lined envelopes. The enve-lopes are dated August 1, 1955. They arefixed mica capacitors. Are the capacitorsstill good? How long can one keep capaci-tors before they vary from their specifiedvalue? Is there a special way to keep ca-pacitors "fresh" longer?

-R. F., East Hills, NY

You could say that mica capacitors werethe first "solid-state" components. Themica used to separate the capacitor platesare flaky rocks formed millions of yearsago. The phenolic moulded case is dur-able, will last many years. Don't worryabout a mica capacitor going bad afteryears of no use or continuous use. In allmy years of servicing friends' radios.phonos, etc., I came across only one badmica capacitor-that's good performance.

Ring of FireMy power vacuum machine for the shop

is not working properly. I looked at themotor and a ring of fire eminates from the

point where the brushes touch the com-mentator and the fire circles the commen-tator as the motor turns. What's wrong?

-R. W., Ludlow, MA

I assume you have good brushes in themachine, and if new ones were inserted,they were broken in properly. If the "fire"still exists, then phase the brushes. This isdone by loosening a few screws so that theframe holding the brushes can be rotatedabout the commutator a few degrees. Dothis while the motor is running and adjustfor minimum fire or glow. Tighten screws.

Foreign TypesI have several foreign -made receivers

and tape machines that need solid-stateparts. When I go to order them by mail,I have to order from several suppliers. Isthere one place I can go to?

-D. N., Wichita, KNWrite to Fugi-Svea Enterprise, P.O. Box

40325, Cincinnati, Ohio 40325 and tellthem Hank sent you. They have a verygood product line and should be able tohandle 100% of your needs. They requirea minimum order of ten dollars.

Welcome to the HobbyHank I'm a beginner and only received

one issue up to now on my three-year

subscription. I'd like to get into BCB DX-ing and would like to know what kind ofantenna I should use.

-M. A., Norwalk, CAIf you are getting started in BCB DX-

ing, I suggest two things immediately.First, start logging all the stations youcan receive with whatever you have avail-able. Listen in the early evening, late atnight and early morning, especially justbefore, during and after sunrise and sun-set. Gain listening experience. Second,start reading everything you can find thatcovers the subject. As for your antenna,for a start use what you have. If youmust, run a long-wire antenna. Any size isgood (25 feet is super for a beginner).

It's BasicWhat do you mean by GOSUB in com-

puter language?-B. D., Fargo, ND

Typically, a Basic computer programmay read 110 GOSUB 340. This means,at this point in the program, it is addressedto go to a sub -routine beginning at line340. When the sub -routine is completed,the program will return to line 111, orwhatever line number appears immediatelyafter line 110. Since there are so manyrepetitions operations, the GOSUB instruc-tion saves valuable memory.


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In Canada, all other countries,$6.95.

Name(please print,

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H8C033

CB New Products( 'ontinueri from 77

hread. The "Bumper Mate" is also avail-able with 18 ft. of Mil Spec type RG-58A/U coaxial cable and a genuinesoldered PL -259 connector (Model#HWM-19C). Sells for $19.50. For fur-ther information, write to Anixter-Mark,5439 West Fargo, Skokie, IL 60076.

Communications DeskThe Telco communications console,

known as the Comm -Sol Model CS -50,is the answer to the space problem forall communications enthusiasts. It pro-vides the user with an area for all of hiscommunications equipment, and at the

le time, serves as an attractive piece


of furniture that blends with your home'sdecor. Completely conceals all the equip-ment when not in use and prevents un-authorized use. Comm-Sol's modularconcept and construction allows addi-tional units to be arranged attractivelyto provide all the work, storage andfunctional space you desire. Easy to as-semble and install, no specal toolsneeded, and can be assembled with onlya dime. All holes are predrilled and spe-cially reinforced with metal in all areasof stress. Finished in rich walnut veneer.Sells for $139 95 For additional infor-mation, write to Telco Products Corpora-tion, 44 Seacliff Ave., Glen Cove, NY11542.

Burn -Out Proof DC Power SupplyA new DC power supply designed for

CB service application, designated Model244 Mobil/Comm Power Supply, offersfeatures of value to CB service techni-cians. The fully -adjustable voltage rangeof 10.5 to 14.5 VDC is accurately meter-ed on large 21/2 inch meter with thecalibrated standard 13.8 volt settingclearly indicated. Full adjustability and0.5% regulation permits duplication ofactual storage -battery operating condi-tions such as low -voltage and over -voltage operation. Continuous -duty threeampere output is protected against shortcircuits by fold -back current limiting.Even dead shorts will do no damage. Anadditional advantage' of fold -back currentlimiting is that during high current -loadconditions that may exist in malfunc-tioning transceivers, the power supply


will not shut off, but, automatically re-duce the current output to a relativelysafe level. When the meter switch is inthe AMPS position the output current isindicated with 3% accuracy. After theshort circuit is removed the unit returnsto normal operation, no fuse to replace,no circuit breakers to reset. The HickokModel 244 Mobil/Comn Power Supplyis available now at Hickok distributorsfor $125.00. For further informationwrite to Hickok Electrical InstrumentCompany, 10514 Dupont Avenue, Cleve-land, OH 44108.

Fools the CrooksThe Barker & Williamson model AT -200antenna matcher mates 2 -meter amateurmobile transceivers to automobile AM/FM receiver antennas. The Model AT -200is intended to provide the theft -foilingbenefits of disguised and hideaway an-tennas at lower cost and to eliminatethe nuisance of constantly putting upand taking down a second antenna. TheAT -200 consists of a tuneable matchingnetwork, an output indicator, and a se-lector switch in a compact case, withtwo coaxial cables for ccnnections to theentertainment radio and the 2 -meter rig.The front panel contains a tuning knob,a two -position (AM/FM or 2 -meter) se-lector switch, and an output indicator

CIRCLE 66 ON READERSERVICE COUPON

light. The unit is supplied with a mount-ing bracket and installation instructions.Power capacity is 100 watts. To use theModel AT -200 with a 2 -meter transceiver,place the selector switch in the 2 -meterposition, key the transmitter, and adjustthe tuning knob for maximum brightnessof the LED tuning indicator. With mostvehicle antennas, the VSWR can be ad-justed to 1.2:1 or lower. With the selec-tor switch in the AM/FM position, theantenna is fed to the entertainmentradio. The Model AT -200 antenna match-er is available through Barker & William-son distributors and dealers. Introduc-tory price is $22.50. Barker & Williamsonalso manufactures the Model AT -140 an-tenna matcher for the 27 -MHz CitizensBand service. This unit performs thesame functions as the Model AT -200, butin the 11 -meter CB band. For additionalinformation, write to Barker & William-son, Inc., 10 Canal Street, Bristol, PA19007.

1 1 4 101 ELECTRONIC PROJECTS 1978

New Products(Continued from page 12)

magnification to allow for less criticalfocusing. The new Robins "Stylee" Cart-ridge Maintenance Kit, catalog No. 41-039 carries a suggested list of $10.00.For further information, write to RobinsIndustries Corp., 75 Austin Blvd., Com-mack, NY 11725.

Aircraft Clock/TimerIf you're into flying, you may want to

assemble a low-cost, five -function air-craft clock/timer kit by Heath. The01-1154 has two digital LED displaysthat show various timing functions. Theupper display shows GMT/ZULU time.The lower display shows any one of fourtime functions selected by the pilot;local time; 24 -hour timer for total triptime; and a preset alarm time for fuelmanagement or check point notification.The displays dim automatically for nightflying. The 01-1154 mounts in a stand-ard 31/2 -in. instrument panel cutout. It is


FAA/PMA approved and meets all DO -

160 requirements. Mail-order priced at$149.95. For further information, writefor a free copy of the latest Heathkitcatalog: Heath Company, Benton Harbor,MI 49022.

AM/FM Stereo ReceiverSony's new STR2800 receiver features

20 watts per channel, minimum RMS at8 ohms from 20 Hz to 20 kHz with nomore than .5% total harmonic distor-tion. Intermodulation distortion is also.5%. The amplifier is direct coupled forhigh stability, wide frequency response,and low distortion. The tuner affordsclear FM reception: 50 dB of quietingis reached with only 50 uV of input instereo; ultimate signal-to-noise is a veryquiet 68 dB. Selectivity is 50 dB, cap -


ture ratio 1.5 dB, and separation 35 dB(at 1 kHz). Price is $240.00. For moreinformation, write to Sony Corporationof America, 9 West 57th St. New York,NY 10019.101 ELECTRONIC PROJECTS 1978

Triggered Sweep 5 -in OscilloscopeThe EICO Model 480 Oscilloscope offersDC to 10 MHz bandwidth, AC and DCCoupling, 11 position calibrated attenu-ator, 10trV/cm sensitivity, and pushbutton operation. For the service shop,electronics lab or production facility,you'll find more than suffic ent verticaldeflection sensitivity, horizontal sweep

Al

o e

ca Q

IMP


speeds and bandwidth response for test-ing color or black -and -white TV receiversand any other electronic equipment. Allcircuits are on four P/C boards for easein servicing. Controls are human engi-neered and are grouped 4unctionally.They are color -coded for qLick identifi-cation and easy use. The custom -moldedbezel is ideal fur camera mounting. Abuilt-in TV sync separator makes trouble-shooting on solid state TV receivers asnap. Frame of line triggering is selectedautomatically by the scope in conjunc-tion with sweep speed setting. Problemsare quickly located and identified, thanksto the calibrated time base. A fully -regu-lated power supply provides stable volt-ages regardless of line and load fluctua-tions, and a calibration voltage of 0.2volts peak -to -peak square wave is avail-able for probe (the EICO Model LCD.10X), a high -impedance probe that mini-mizes circuit load during test. Suggesteduser net is $425.00. For further informa-tion, write to Mark Ehren, EICO Elec-tronic Instrument Co., Inc., 283 MaltaStreet, Brooklyn, NY 11207.

Crimp It TerminalsQuality Terminals, a national distributorof electro-connective parts, offers a use-ful selection of 240 of the most -used,insulated, color -coded, crimpable, solder -less terminals, together with a combina-tion wire stripper/crimping tool and aheavy-duty, 25 -drawer steel parts cabi-net. All for $24.95 plus $3.00 shipping

CIRCLE 46 ONREADERSERVICECOUPON

and handling. Tool and terminals arefirst quality and American made. Selec-tion of terminals consists o' 9 sizes ofring type, 8 sizes of fork tongue, 3 sizesof butt splices and male and femalequick disconnect in various sizes. Forfurther information, contact QualityTerminals, 368 Hillside Avenue, Need-ham, MA 02192.

Preamp/AmplifierDynaco/Dynakit has introduced a new

moderatelypriced integrated preamp/am-plifier, the SCA-50, which offers a num-ber of features. The unit is availableassembled or in kit form. As a kit, it isextremely easy to assemble, requiringonly simple tools and a few eveningswork. Most circuitry is factory -wired onprinted circuit boards, and pre -tested. It


is rated at 25 watts continuous averagepower output per channel. Both thetone control and preamplifier circuitsuse low voltage regulated power sup-plies so that AC line fluctuations willhave no effect on audio performance.In the amplifier section, the output cir-cuit is full complementary symmetry andthe bias supply thermally tracks the out-pu: transistors. This cuts down on notchdistortion-that type of distortion whichmany believe is the source of transistorsound. The SCA-50 has a price of$249.00 for the factory -assembled unitand $149.00 for the kit. Detailed infor-mation is available from Dynaco/Dynakit Box 88, Cole Road, Blackwood, NJ08012.

Blackjack ProgamRCA lets you play Blackjack with itsStudio II home TV programmer. The pro-grammer is a combination video gamearr.' educational device which can beused with any size black -and -white orcolor TV set. It has five games built intothe console and employs plug-in solidstate cartridges for additional add-on'games. The built-in games are: Freeway,Addition, Bowling, Patterns and Doodles.The new plug-in cartridge offers Black-jack. In Blackjack the action and excite-ment of Las Vegas casinos are pro-grammed onto the home TV screen.

EHEIMIOBET

1031W31163 T 1E16


Players are staked with 200 dollars andcan bet up to 10 dollars per hand. Intrying to beat the computer, who is thedealer, players are offered the chanceto "hit" (request another card), "stick"(slay with the cards they have) or "dou-ble down" (double their bet but get justone more card). Optional retail price ofRCA's Studio II is $149.95. The add-onBlackjack cartridge is optionally priced at$19.95. For further information, write toJoe Searfoss, RCA Distributor and Spe-cial Products Division, Deptford. NJ08096.

115

CLASSIFIED MARKET PLACE 1

101 ELECTRONICS PROJECTS -PUBLISHED ANNUALLY. The rote per word for Classified Ads is $1.00 eachinsertion, minimum ad $15.00 payable in advance. Capitalized words 401g per word additional. To beincluded in next issue, write to: R. S. Wayner, DAVIS PUBLICATIONS, INC., 229 Park Ave. So., N.Y. 10003.

AUTHOR'S SERVICE

PUBLISH YOUR BOOK! Join our successful au-thors. Publicity, advertising, beautiful books. ABsubjects invited. Send for fact -filled booklet and freemanuscript report. Carlton Press, Dept. 5MD. 84 FifthAvenue. New York 10011.

BLUEPRINTS. PATTERNS & PLANS

NEW CRAFT PRINT CATALOG -Choose from over100 great easy -to -build plans. Send $1.50 (completelyrefunded with your first order). BOAT BUILDER,(CP Div.) -229 Park Avenue South, New York, NY10003.

BOOKS & PERIODICALS

FANTASTIC book bargains! Many up to 70% off.Moneymaking. Photographic, Handicrafts. How -To.Educational. Request free catalog! H. G. Enter-prises, P.O. Box 1262, New York, NY 10025.

BUSINESS OPPORTUNITIES

$30.00 HUNDRED Stuffing Our Circulars intoStamped Addressed Envelopes. Immediate Earnings.Beginners Kit 82.00. COLOSSI, 1433-61 Street, DC -3,Brooklyn, NY 11219.

10009e PROFIT Bronzing Baby Shoes. Free Litera-ture. NBC. Box 1904 -DO. Sebring, FL 33870.

$500.00 profit stuffing $1,000 envelopes. Details$1.00 (Refundable). Elamco, Be13337 D5, Waldo,AR 71770.

GUARANTEED $178.00 WEEKLY. Work one hourdaily. Free Brochure. FAS, Box 13703, San Antonio,TX 78213.

$350 weekly mailing letters. Free details. Bronx -',file House, Box 311 D, Bronxville, NY 10708.

HOW TO RECRUIT COMMISSION SALES -PEO-PLE! Free details! Success publications. 35 Inter-lachen Place. Excelsior, MN 55331.

STAY HOME! EARN BIG MONEY addressing en-velopes. Genuine offer 104. Lindco. 3636 -DA. Peter-son, Chicago 60659.

CABLE/FM Broadcast station. Start f....Lr own.Operate from home, church, school. No investment/experience needed. Excellent Income. Free details.CAFM, Box 5516GC. Walnut Creek, CA 94596.

MAKE YOUR CLASSIFIED AD PAY. Get "Howto Write A Classified Ad That Pulls." Includes cer-tificate worth $2.00 towards a classified ad In thispublication. Send $1.50 (includes postage) to R. 8.Wayner, Davis Publications, Inc., Dept CL, 229Park Avenue South, New York. NY 10003.

EXCITING new way to wealth. Proven by profes-sional men and women. Illustrated particulars. Send$2.00 to Texas Funding, Box 210919, Dallas. TX 75211.

$600 Guarantee per 1,000 envelopes mailed per in-struction! Ippersiel RR. 1/c Noelville, Ont. POM2N0.

$60 HUNDRED ADDDESSING envelopes. Guaran-teed earnings! D'Aloisio 30-B Gladys Ave. $7, Mt.View. CA 94043.

MAIL-ORDER BOOK DEALERS WANTED! FreeDetails! Books, P.O. Box 395 B, Excelsior. Minne-sota, 55331.

SELL diet products -Inches Away, E. 12426 -19th,Spokane, WA 99216.

$60 hundred addressing envelopes. Guaranteedearnings. Rasmussen. DP48, 1747 N. 450 E., Ogden,Utah 84404.

$300.00 MONTHLY. Start immediately. Stuff enve-lopes at home. Information, send self-addressedstamped envelope. Village. Box 2285-DFD, Irwindale,CA 91706.

DETECTIVES

NEW! The Big Brother Game ... 230 pages detec-tive technicaues, FBI, CIA, KGB, OSS. wiretapping.tailing, electronic surveillance. surreptlous entry.weapons. countermeasures, much much more ... post-paid $9.95. Quimtronix, Box 548 -DV, Seattle, Wash-ington 98111.

DO IT YOURSELF

30-100W Amplifier Kits under $53.00. Free catalog:Audiovision, Box 955 Stn B, Willowdale, Ont. M2K2T6.

EDUCATION & INSTRUCTION

EARN a BACHELOR, MASTER, DOCTOR degreewithout attending class. Credit for life learningexperience. KENSINGTON UNIVERSITY. 512 EastWilson Ave.. Glendale, Calif. 91209, 213-245-7224.

ELECTRONIC Math Fundamentals. Here's a fastand easy practical guide to electronic mathematicsthat refreshes and teaches powers of 10 computa-tions. symbols, exponents and decimal point relation-ships to enable you to learn and understand Micro.mini, Kilo and Mega calculations. Send $1.50 formanual to: Econal Products Co., Dept. M, P.O. Box2498, Littleton, Colorado 80161.

UNIVERSITY DEGREES BY MAIL! Bachelors,Masters. Ph.D.s.. . . Free revealing details, Coun-seling Box 389 -EP 4, Tustin, CA 92686.

GET INTO BROADCASTING: Become DJ. engi-neer. Start your own station, get free equipment.records. Free details. "Broadcasting." Box 5516-C4E,Walnut Creek, CA 94596.

COLLEGE degree by mail, via resume. Education,2560 South Robertson, Beverly Hills, CA 90211.

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MATCH EXTENDER. No burned fingers lightingfireplaces, candles, pilot lights. $2 to: Al, Box222D, Richfield, Ohio 44286.

HI-FI EQUIPMENT

GO To Bed With Music: Control I Automaticallyswitches your system off. Works with Records, Tapes,Tuners. $49.95. Electromedia, P.O. 265, Livingston.NJ 07039

HYPNOTISM

FREE Fascinating Hypnosis Information! Startling!DLMH, Box 487 Anaheim, CA 92805.

INVENTIONS WANTED

IDEAS, inventions, new products needed by inno-vative manufacturers. Marketing assistance availableto individuals, tinkerers, universities, companies withfeasible concepts. Write for Kit-EHO. 12th Floor.Arrott Building Pittsburgh, PA 15222.

MAIL ORDER OPPORTUNITIES

EARN EXTRA MONEY by mail. Proven Program.Free details. Smiths, 317 Madison, Kenton. Ohio43326.

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$250.00 profit/thousand possible -stuffing -mailing en-velopes. Offer: Rush stamped addressed envelope:Universal-ADVS X16180 Fort Lauderdale, FL 33318.

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$30.00 HUNDRED STUFFING our circulars Intostamped addressed envelopes. Beginner's Klt $2.00.Mustachi, P.O. Box 46D4, Brooklyn, NY 11219.

$500 per thousand stuffing envelopes, free sup-plies, rush stamped envelope: Moseley, 14 Rodney,Seaford. DE 19973.

LOOKING FOR INCOME SECURITY? Unlimitedearnings possible selling books and information bymail. No experience work from home -tested program-free details -stamp appreciated, Austin Security, 50Madison Avenue, 1st Floor, Bridgeport, CT 06604.

$50,000 easily in short time addressing, mailingenvelopes. Free details, Darby & Sons, Box 1213-13,Evanston, IL 60204.

$500/thousand suttfing envelopes. Free details. Rushself stamped envelope. H. Mognet Co., Box 449D,Warren, OH 44482.

$180.00 WEEKLY Mailing Circulars. Start Im-mediately. Z dy, 422F Clermont Ave., Brooklyn.NY 11238.

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MONEYMAKING OPPORTUNITIES-Cont'd

NEW EASY HOMEWORK PLAN. STUFF CIRCU-LARS. BIG Eli Write: Mil, 5343-J, Diamond Ins..San Francisco, CA 94131.

$180 weekly possible addressing envelopes. Jean,Box 72040, Burbank. CA 91510.

SINCERE HOMEWORKER AGENTS WANTEDNOW! Part-time or full. Do not confuse with usualworn-out offers. No experience needed. Full detailssend $1.00 to: Barnett Publications, P.O. Box 378,luka, MS 38852.

$2,000 monthly possible stuffing envelopes! Sendstamped self-addressed envelope. Craft, Box 2230 D,Oceanside, Calif. 92054.

OF INTEREST TO WOMEN

CASH FOR BOXTOP LABELS' Information 15e.Refund Bulletin, Box 503-D, Cape Giradeau. MO63701.

PERSONAL

PUBLIC RELATIONS FIRM DESPERATELYNEEDS $10.00 bills with 3 sevens in serial number.Will reward with FREE Florida Vacation for two,good anytime during year, Write: Quicksilver Enter -place, 274 Woodworth Ave., Yonkers, NY 10701.

DATES GALORE! Meet singles -anywhere. CallDATELINE, toll -free (800) 461-3245.

SINGLE, Widowed, Divorced? Nationwide intro-ductions! Identity, Box 315 -DC, Royal Oak, MI 48068.

JAPANESE introductions! Girls' photographs, de-scriptions. brochure, details, $1.00 INTER -PACIFIC,Box 304 -SC, Birmingham, MI 48012.

RECORD Telephone conversations privately -auto-matically. Leave recorder Unattended. Robert's, Box49SM, Parkridge, IL 80068.

SWEDISH girls! Details -photos $1., Sweden Inter-national, Box 7425 -DC, Chicago 60680 USA.

WIN BIG AT CASINO GAMES! Learn the secrets!Write: Research -404, Box 1189, Burbank, CA 91507.

BEAUTIFUL MEXICAN GIRLS! Correspondence.Photos, details free! "Latins," Box 1716 -DE, ChulaVista, CA 92012.

1,000 Ladles Photos/350 Men in world's largestmatrimonial catalog $5.00. Box 12, Toronto, CanadaM4A 2M8.

JAPANESE Girls Make Wonderful Wives. We havelarge number of listings. Many interested in mar-riage. Only $1.00 brings application, photos, names,descriptions, questionnaire. Etc. Japan International,Box 156 AA, Carnelian Bay, CA 95711,

MAKE your will! 4 forma plus attorney's informa-tion booklet $2.00. Sullen Enterprises, Box 3068 -DI,Rochester, NY 14614.

BEAUTIFUL Mexican -Oriental girls Needing Amer-ican Boy -Friends. Free Details, "actual" photos.World, Box 3876 -DC, San Diego, CA 92103.

PSYCHIC advises on business, love and personaldirection. Donations appreciated. Jamil, P.O. Box10154, Dept. M, Eugene, OR 97401. Phone anytime.(503) 342-2210.

ADULT Pleasure Products -over 600 items! Giantcatalog $1.00. Clifton's, 1068, Saugus, CA 91361.

BEAUTIFUL, girls. Free information Introductions,Box 454, Nestor, CA 92053.

RADIO -TV

TV TUBES 36e each. Send for Free 48 page colorcatalog. Cornell. 4217-W University, San Diego. CA92105.

BUILD Distance Crystal Sets. 10 plans -25e: Hand-book "18 Different" -50e. Catalog 25e, refundable.Laboratories, 1477 -EH, Garden Grove, CA 92642.

LINEAR AMPLIFIERS, 25-100 watt solid state.OMNIPOLARIZED BASE ANTENNAS. Portable/mo-bile/memory 300 wiz FREQUENCY COUNTER, Con-struction plans: $3.00 each, 3/$7.50. Specify fre-quency band! Kits available. Free catalog! PANAXIS.Box 5516-0444E, Walnut Creek, CA 94596.

RUBBER STAMPS

RUBBER stamps made. Three lines $3.75, RubberStamps, B1337 -E4, Waldo AR 71770.

THERE IS NO CHARGE FOR THE ZIP CODE -PLEASE USE IT IN YOUR CLASSIFIED AD

Computer New Products(Continued from page 68)

tively store 32K, 48K and 64K bytes ofdata as the model code numbers imply.In addition to high -density storage, theboards feature flexible organization, bat-tery backup and memory protect capa-bility, transparent refresh and reducedpower requirements. Storage can bededicated to one computer or shared byseveral computers. The memory boardsinterface directly with the bus and con-tain read and write data buffers. Eachboard is organized as blocks of 16Kbytes (16,384 8 -bit words). Block address-ing is jumper -selectable. To facilitatebattery backup, each board contains anauxiliary power bus and memory protectcontrol that prevents read or write ac-cesses during system power -down se-quences. Typical power consumption is15 watts in normal operation, less than7 watts on backup battery power. Maxi-mum access time is 450 nanoseconds.Maximum cycle times: 600 ns, read; 600ns/1140 ns for write cycles; 585 ns forrefresh cycles. Prices: SBC 032, $1,650;SBC 048, $2,300; SBC 064, $2,950. Circle65 on Reader Service Coupon for moreinformation about this project from IntelCorp.

Programmable Communications Interface-Signetics says this first programmablecommunications interface (PCI) featuresa MOS/LSI circuit that combines thefunctions of a Universal Synchronous/

Asynchronous Receiver I Transmitter(USART) with those of a baud rate gen-erator in a single 28 -pin, dual -line pack-age. Model 2651 PCI is claimed to pro-vide extremely cost-effective solutions tomany data communications problems inintelligent terminals, communications con-trollers, data concentrators, front-endprocessors. Capabilities include modem

control, support of IBM's BISYNC proto-col, asynchronous echo mode, and localand remote self -testing. The chip is fullyTTL compatible, operates from a single+5V supply, and does not require a sys-tem clock. It's compatible with most 8 -bitmicroprocessors, including the 2650,8080, Z80 and 6800. The PCI is pro-grammed to handle characters from 5 -to 8 -bits in length. The internal baud rategenerator provides 16 different program -selectable baud rates for the transmit andreceive clocks; these range from 50 to19:2K b is per second. Price: $17.15.Circle 19 on Reader Service Coupon.

Digital/Analog Electronics Course-ADD-book ONE, a single -volume guide to adesigned program of experiments in digi-tal and analog electronics is availablefrom E&L Instruments at a price of $17.The 400 -page workbook is a tutorial andexperiment manual based on E&L's ADD8000, a modular electronics laboratory ina bench -top case. The experiments were

written expressly for persons wanting togain a working knowledge of electronicswithout formal classroom study; suchpersons may be practicing engineers orscientists, technicians, college studentsor serious hobbyists. Ten experimentalunits cover subjects completely relevantto the latest digital and analog instrum-ments and measurement techniques.The ADD 8000 contains all needed signalsources, displays, power supplies andbreadboards. Circle 54 on Reader ServiceCoupon for further information.

YourHoroscope

By Jack Schmidt

LIBRA-Frustrations may occur asplans fail to jell. Don't hesitateto stop for tonight and to startover again the following day.

SCORPIO-Long awaited communicationsmay jail to materialize as planned.

Patience should be your watchword.

GEMINI-Personal activities ofa highly social nature may be

interrupted by mechanical failure.

LEO-Governmental regulations mayinterfere with hobby activities

with subsequent increases in cost.


Herb Laneya tough-minded

optimist.How about you?

Herb takes his future seriously. Without worrying about it.He knows his CIE training is giving him valuable skills in electronics.Skills a lot of people will be glad to pay for. And that's good reason

for all the optimism in the world. How about you?

I.earning new skills isn'tsomethiniz you just hi eczc through.Especially in electronics You'vegot to really want success if you'regoing to build your skills properly.

Herb knew that right from thestart. But he also knew whatrewards he could earn if he tooksome time and did it right. He knewthat. in today's world. people whoreally know electronics find a lotof other people . . . even wholeindusti ies ... looking for their help.

How about you? How much doyou want that thrilling feeling ofsuccess ... of being in demand?Enough to work for it?

Why it pays to buildskills and know-how.

One of the things that got Herbinterested in electronics is thatelectronics seems to be somethingjust about everybody needs. Almosteverywhere you look these days-in a business office ...amanufacturing plant ...adepartment store ... a doctor'soffice ... a college ... even yourown home you'll find all kinds ofelectronic devices.

That spelled "opportunity" toHerb. Plus he liked the idea ofhaving a set of skills that mightlead to jobs in places as differentas a TV station ... a hospital ...anairport ... a petroleum refinery.

But what Herb liked most aboutelectronics is that it's just plaininteresting. Even though it takestime and effort to learn, the subjectis so fascinating it almost doesn'tseem like "studying" at all!

How CIEkeeps you interested.

C I E's unique study methods doa lot to keep you interested. Sinceelectronics starts with ideas ... withprinciples ...CIE's Auto -

Programmed° Lessons help you get

the idea-at your own mostcomfortable pace. They break thesubject into bite -size chunks soyou explore each principle. step bystep, until you understand itthoroughly and completely. Thenyou start to use it.

How CIE helps youturn ideas into reality.

Depending on the program youchoose. CIE helps you apply theprinciples you learn in a number ofdiffeient ways.

If you're a beginner, you'll likelystart w ith CIE's ExperimentalElectronics Laboratory. With thisfascinating workbench lab. youactually perform over 200experiments to help you grasp thebasics! Plus you use a 3 -in -1precision Multimeter to learntesting, checking. and analyzing.

In some programs. you buildyour own 5MHz triggered -sweep.solid-state oscilloscope-and learnhow to "read" waveform patterns... how to "lock them in" for closerstudy ... how to understand andinterpret what they tell you.

To help you develop practical.skill -building knowledge you thenreceive a Zenith 19" diagonal

solid-state color TV featuringremovable modules. You learnhow to trace signal flow ... how todetect and locate malfunctions ...how to restore perfect operatingstandards.

What to do first.(Jet all the facts. Send for CIE's

FREE school catalog and careerinformation package TODAY.Check all the CIE programs - andsee which one's right for you. Doit now.

Why it's importantto get your FCC License.More than half of CIE's courses

prepare you for the FCC Licenseexam. ] it fact, based on continuingsurveys, close to 4 out of 5CIE graduates who take the examget their Licenses!

1 hat's important. For some jobsin electronics, you must have yourFCC License. For others,employers often consider it a markin your favor. It's government -certified proof of specificknowledge and skills!

Free catalog!Mail the card. If it's gone. cut

out and mail the coupon. If youprefer to write, mention the nameof this magazine. We'll send you acopy of C I Es FREE schoolcatalog-plus a complete packageof independent home -studyinformation! For your convenience.we'll try to have a representativecall to help you with courseselection. Mail the card or coupon-OF write: CIE. 1776 East 17thStre st Cleveland. Ohio 44114.

rCleveland Institute of Electronics. Inc.1776 East 17th Street, c.leveland, Ohio 44114

Accredited Member National Home Study Council

YES... I want to succeed in electronics. Send me myFREE CIE school catalog-including details about all electronics courses -

Iplus my FREE package of home -study information! PRINT NAME

A DD ESSI( I I Y

S FATE _ /I P/WE _ _ PHONE (area :ode)

CIE

APT.

Check box for G.I. Bill information: Veteran Active Duty

Mail today! 0E-12

IF YOU'RE WAITING FORSOLDERLESS BREADBOARDS TO BE

FASTER, EASIER, MORE

VERSATILE AND LOWER-PRICED...Incredibly inexpensive. EXPERIMENTORsolderless sockets begin at S5 50*IS4 00' for the 40 tie -point quad bus strip)A spool of solder costs more

Microprocessors and other complexcircuits are easy to develop. EachEXPERIMENTOR quad bus gives youfour bus lines By combining quads.8-, 12- and 16 -line address and databuses can be created, simplifyingcomplex data/address circuits.

Infinitely flexible. Circuits can go inany direction, up to any size All EXPERI -MENTOR sockets feature positive inter-locking connectors that snap togetherHorizontally and/or vertically. And un-snap to change a circuit whenever youwish.

Easy Mounting. Use 4-40 screws fromthe front or 6-32 self -tapping screwsfrom the rear. Insulated backing lets

any surface.

EXPERIMENTOR 350. $5.50'46 five -point terminals plus two 20 -point busstrips 0 3"centers 3,8 x 3' 2 x 2" I"-

EXPERIMENTOR 650. 66.25'46 five -point ; . u point busstrips 0 6" centers. 38 x 3'_2 x 234".

Mix and match. Use large and small chipsin the same circuit without problems.There are two sizes of EXPERIMENTORsockets with 0.3" and 0 6" centers

Full fan -out. A CSC exclusive. The onlysolderless bfeadboard soc Nithfull fan -out capabilities for micro-processors and other larger 0.6") DIP's.

EXPERIMENTOR QUAD BUSSTRIP. $4.00' Fu o 4u pointbus strips. '3'8 a 6 x

Designated tie -points. Sim-plify translation from bread-board to PC -boards or wiringtables.

EXPERIMENTOR 600.$10.95' 94 five -point fermi -

plus two 40 -point busstrips 0.6" centers, 3/8 x 6 x

Accepts all standard components.EXPERIMENTOR sockets conform to an 0.1"grid and are DIP compatible. Also acceptIC's. transistors, diodes,LED's, resistors.capacitors, transformers. pots, etc.

Easy hookup. Components push in and pullout instantly. Use #22-30 solid AWGwire for jumpers.

Rugged, dependable construction.Sockets are constructed from abrasionresistant materials and withstand 100°C.Each one features non -corrosivenickel -silver contacts.

EXPERIMENTOR 300. $9.95'94 five -point terminals plus two 40 -point busstrips. 0.3" centers; 3/8 x 6 x 2".

WHAT ARE YOU WAITING FOR?Discover today how soideriess breadboarding can save time and money on every circuit you build. Get

acquainted with EXPERIMENTORIM sockets' and how they simplify circuit design, assembly and testing.Eliminate the hassles and component damage of soldering. No special hardware or jumper cables

required, either. And the price is so low, it's hard to believe."Order today. Call 203-624-3103 (East Coast) or 415-421-8872 (West Coast): 9 a.m.-5 p.m. local time.

Major credit cards accepted. Or see your CSC dealer. Pi ices slightly higher outside USA."CONTINENTAL SPECIALTIES CORPORATION

t U.S Patent No D235.554

=M=70 Fulton Terrace, Box 1942, New Haven, CT 06509, 203-624-3103 TWX 710-465-1227

WEST COAST. 351 California St.. San Francisco. CA 94104, 415-421-8872 TWX 910-372-7992GREAT BRITAIN: CSC UK LTD., Spur Road, North Feltham Trading Estate.

Feltham, Middlesex. England, 01-890-8782 Intl Telex: 851-881-3669CANADA: Len FinkIer Ltd , Ontario


'Manufacturer srecommended resa'e

c 1977. ContinentalSpec,aams Corporation

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