Todaronics - americanradiohistory.com · 2019-07-17 · switch $139.00! These supplies are ideal for IBM compatibles, they fit beautifully ... clap to your hands and the robot starts

ronicsToda July 1984

52 . 95MM70924

Canada's Magazine for Electronics & Computing Enthusiasts

Sinclair's QLUK computer success

0

057438 709 4 1

ComputerReview

Sony SMC-70

EXCELTRONIX(416) 921-8941 1-800-268-3798Bulletin Bd. (416) 624-5574 Telex 065-24218319 College St., (416) 293-1796 Toronto, Ont. MST 152Catalogue shipping rates are incorrect. Please call us for correct charges. Prices in catalogue arefluctuating. Use as guideline.

TWO NEW EXCELTRONIX LOCATIONS!Ottawa Hamilton

NOW OPEN 217 Bank Street 72 James St. North(613) 230.9000

Store hours 9:30 to 6:00 Monday -Saturday: to 9:00 p.m. Friday.

PRINTERSStar Gemini 10X $359Gemini 15X $599Delta 10 (160 cps) $739Epson MX100 $995Epson RX80 (Replaces MX80) $495Epson FX80 (New) $798Epson FX100 (New) $1069TTX (Daisy Wheel) $649Mictrotek $139

MONITORS

Zenith ZVM122 Amber $139Amdek Green $129Zenith ZVM123 Green $129Amdek Colour 1 $445Roll and DG $419

APPLE CARDS16K card Multiflex $58.00128K card $210.00Proto Board $15.0080 -Column Card $84.00Z80 Card $59.00EPROM Programmer from $69.00(for 2716, 2732, 2732A, 2764, with soft-ware) Parallel Printer Card withcable $69.00Wizard Parallel Card $95.00Serial Card $99.00

New Macintosh with printer $4,295Apple 2C with monitor $1,885

New Macintosh, based on 68000 with 3"Disk Drive (smaller version of LisaTM).Diskette Software now available $3,195

MODEMSEPM 310 Smart Modem $99(300 Baud, IBM Comp) $359Apple a la Modem (300 Baud) $215Micromodem (Apple Comp) $475Signalman (300 & 1200 Baud) $495Smart Modem 1200 Baud $899

FAMOUS MULTIFEX Z80 STARTER KIT'SPECIAL $299.00Ideal Learning Tool,

A&T $299.00see page 16 of catalogue

Memory Chips4164.150n5 (1x64K single +5V)Motorola 59.95T.I. 57.954116-200ns (1x16k) $1.744116-150ns (1x16k) 51.992114L-200 ns (1kx4 static) 52.496116-150 ns (2kx8 static RAM) 58.94(Pin compatible with 2716 uses negligibleamount of power)2016.150 ns (2kx8 static) $8.742102L-200 ns (1kx1 static) $1.945101-CMOS RAM 53.842708-(1kx8 EPROM) $6.742716-(2kx8 EPROM single +5V) 55.502732-(4kx8 EPROM single +5V) 58.952532-(4kx8 EPROM single 5V) 58.742764-(8kx8 EPROM single 5V) $12.95

HUGE STOCK OF LS

Diskettes51/2" Diskettes. Boxes of 10

Maxell MD1 534.00Maxell MD2 $52.95Verbatim $34.00CDC 526.953M 532.95Accutrak $26.952 Ectype Diskettes in a plasticbinder sheet $5.89Flip N File 50 $44.95Diskminder (75) $33.95Dysan $39.00BASF $34.00BASF with case $35.00

1

-1HARG

UNIVERSITY OF TORONTO/MULTI FLEX 6809Board, great for learning about 6809 and com-puting in general with A & T $499.00Economy Terminal A&T $369.00Package Deal A&T $849.00

Smith -CoronaPrinter

L1000Bi-directional

daisyWheelSerial/parallel

port$599

'JoysticksEconomodel $19.95Wico Red Ball $42.95Self -Centering with twoadjustable controlsSuper offer $64.00Kraft Joystick(Apple, PC) 64.95Kraft Paddles $48.95

TG JoystickDeluxe Model $75.00TG Paddles DeluxeModel 64.95Hayes Mach Ill $58.95Model DeluxeTable Top $59.00Hayes Mach II $48.95

Siemens 8" disk drivesS.S.D.D. $79.00Buy 2 for 559.00 eachD.S D D $89.00 singleBuy 2 for $69.00each

Super Computer CaseIdeal for 8088 or 6502 boardsUnmatchable quality, all -Canadian made

\x$87-00!

IBM CompatibleKeyboard $189.00Maxlswltch or cherry

Featuring theMultiflexCompatible Drive

Only$249

rw

PRICE POLICYRemember that at Exceltronix allprices are negotiable for quantitypurchases. If you cannot afford largequantities on your own how aboutstarting a Co-op.

Package Deals:Al Drive & ControllerB2 Drives & ControllerController onlywith softwareVISTA DRIVEQUENTIN DRIVE

1 year warranty

$310$549

$69$119$299$299

Controller$89

With AppletmSoftware

$119

SuperbPower SupplyUncased Dual 12V:(one at 2.8A, one at 2A).-12V at 0.5A, +5V at 5A plus

$69.00!Cased model, with fan, cord andswitch $139.00!These supplies are ideal for IBMcompatibles, they fit beautifullyinto IBM compatible cases.IBM is registered trade mark of IBMCanada Limited.

Check our catalogue for far, far morethan you see here. If you didn't get itin your May copy of ETI or CN!, sendfor your free copy.

MAIL ORDERSSend a certified cheque or money order (do not send cash). Minimumorder is 510 plus 53 minimum for shipping. Ontario residents mustadd 7°° provincial sales tax. Visa. Mastercard and American Ex.press accepted: send card No . signature. expiry date and name ofbank

Head Office: 319 COLLEGE STREET, TORONTO, ONTARIO. CANADA. M5T 1S2 (416) 921-8941Circle No. 27 on Reader Service Card.

SURPLUSTRONICSCanadian Made

AsReviewed

EliMaY 1983:Send for aFREE COPY

we will not be undersold960-1350

OUR FAMOUS6502 BOARDNOW NEW & IMPROVED VIDEO SECTION

This 6502 board is a vast improvement on others available:646 RAM (8.4164 chips)80 a 24 video included on boardFloppy Disk Controller includedFIVE additional slots

Superb quality plastic case Excellent keyboard including numeric

keypad EPROMS (blank) included

$669Our prices are low due to our mass produc-tion assembly, which makes it hard forothers to compete.

W you receive a FREE Z80 PC BOARD ANDFREE 128K RAM DISK PC BOARD when you orderthe complete package (BLANK

Our boards are professionally made, flow soldering &cleaned & use only high quality prime parts.

280 blank PCB included Available preassembled byPowerful power supply (5V 5A, +120 2 special order only.up to 3A peak. -5V 0.5A. -12V 0.5A) Ideal for educationalHydro -approved whereas many others applications.

are not!

N0

You can now get an IBM compatible without wasting yourinvestment in a 6502 system. Talk to us about our generoustrade-in scheme.

BEST PRICE8088 SystemBest Prices in CanadaComplete System with 64K, expan-dable to 256K. Comes with ColourGraphics, Floppy Controller and oneDS, DD 51/4" Disk Drive, Keyboard,Case and Extra Heavy -Duty, FanCooled Power Supply.

System comes with 5 peripheral slots. Op-tional 8087 arithmetic processor available.Floppy controller can handle up to 4 drivesand as an option can a serial port and real-time clock. Completely built and tested andsold with a blank EPROM. Compatible withYou -Know -Who. Systems are now in stock butdue to extraordinary demand at time of goingto press, order now to prevent delays.Please Note: We do not sell any proprietarysoftware.

$1,989

a

I I:

USN

Peripheral Boards for your IBM PCPrototyping CardFloppy Controller CardColour Video Card

$33.00

$289.00

$299.00

Parallel & Game Port Card....$149.00EPROM Programmer. Starts at$149.00

Expansion Cardwith many options $Call

Attractive Case (as shown above)$85.00Keyboard (as shown above). . .$187.00

Super Power Supply, made to fit abovecase, with cooling fan $135.00

8088 Board, with 64K on board (provi-sion for 256K), as described in our 8088System.Assembled and tested $499.00

Form a Buyers Group. Buy in groups of 5 or more and youcan save hundreds of dollars each.

MonitorsZVM-122 Amber $139.00ZVM-123 Green $129.00Roland Colour 1 $395.00Amdek Green $129.00

EPS Keyboard $399.00Apple Compatible. IBM Moduleavailable. Distributor for Ogivar

Apple PeripheralsAssembled and Tested

Serial Card $ 85.00Z80 Card $ 58.0080 x 24 84.0016K RAM $ 58.00Prototyping Board $ 14.50Parallel Printer Card $ 59.00... with cable & connector $ 69.00128K Board (No IC's) $ 49.00...with IC's & 64K RAM $129.00...with IC's & 128K RAM $210.00Crazy Card $ 58.00Eprom Programmer $ 68.00

Disk DrivesApple Compatible $249.00Controller $ 59.00...w/software $119.00

One year warranty

All prices subjectto change

PrintersA. Gemini 10x $359.00B. Special Multiflex parallel card withcable. Shop and compare $ 69.00Package price of A and B $415.00Gemini 15x $598.00

5" Green ScreenMonitors. $59

Huge variety of Surplus stock at low, low Prices. Newshipments arriving. No reasonable offers refused.Prices subject to change without notice!

Surplustronics, 310 College Street, Toronto, Ontario, M5T 1S3

Telex No.065-24218

Mail Orders add $5.00 minimum for shipping &handling. Ontario residents add 7% P.S.T. Visa,Mastercard and American Express cards ac-cepted: send card number, expiry data, name ofbank and signature. Send certified cheque ormoney order, do not send cash.

Circle No. 29 on Reader Service CardMore lines to serve you better

(416) 960-1350

Intelligent Robots You Build Yourself'0 0 0 a new world of educational fun

ElectronicControl

111011/11T1111111011 I II

AVOIDERMV -912 blue)

t Sensor /control PC hoard ready assembled)

An intelligent robot which knows how to avord hittingwall. The robot emits an infra -red beam whichdetects an obstacle in front.

$69.95

Movement : 3 legs on each side by crank motion. Control : Infrared sensor including infra -red

diode/photo diode/IC* Power source (Not included) ; Battery type

I.5V -AA"x49V x I

ElectronicControl

NIT1111\/w I I

MONKEYMV -919 (yellow)(Seosur/ control PC board ready assembled/

Order your MONKEY to "Move" with a bud voice or

clap to your hands and the robot starts rompng alonga rope and stops alter a while by himself

$39.95

...Movement : Two alternatively moving gripperrms driven by crank motion.

Control : Sound sensor. including condensermicrophone/transistor.

Power source (Not includedl : Battery typeI.5V "N"w 2

ElectronicControl

111/01A /IT'V11%01111 II

LINE TRACERMV -913(Sensor/control PC board ready assembled,

Guided by an infra -red light sensor the robot sod au-

tornatcaly lotion any bed, One drawn on white paper.

Movement : 3 wheels driven by 2 DC motors. Control I Infrared sensor includmng infrared

diode/photo diode/ IC* Power source (Not include& : Battery type

1.5V-A.V. 029V x I

How to play : Draw a black line on white paperboard. Line width should be IVmm minimum wide. Narrowestturning radius must be at least15 cm

$64.95

ElectronicControl

111/11111/191"1111%0W I I

PIPER -MOUSE

MV -915 blurSensor/ control PC board ready assembled,

The s a Supersonc-Robot controlled by a Supersoruc

sound sensor and an ebctronic <mud channel).

Use the *Mete attached to the kg and Piper Mouse

sod tolbw your commands immediately turning to the

Ott stop, Wrong to the right, mop. advance and stop.

$69.95

Nlovernent : 3 wheels driven by 2 DC motors.Control : Supersonic sound sensor including

condensor microphone and printedcircuit hoard.

*Power source (Not included} : Battery typeI.5V "AA" x 2

9V x1

ElectronicControl

111111111%1IIT1,10111 II I

SoundSkipper

MV -917 (yellow)I Sensor/control PC board ready assembled)

Order the SOUND SKIPPER to 'Walt' with a budvon. or clap your hands the robot marts waling andstops alter a while by hensell

$39.95

hlovement : Two alternatively moving legs drivenby crank motion.

*Control : Sound sensor including condenser1111C roplume/ istor.

fewer sage (Not included) : Battery typeI.5V x 2

NOW AVAILABLE FROM:

A.J.K. HOBBY ELECTRONICS Joyceville, Ont. (613) 548-8336ASSEF TV & STEREO Windsor, Ont. (519) 948-4171FOCUS SCIENTIFIC Ottawa, Ont. (613) 236-7767GLADSTONE ELECTRONICS Toronto, Ont. (416) 787-1448

(Toll free) (800) 268-3640MASTERMIND EDUCATIONAL TECH. Toronto, Ont. (416) 487-7177MICRO COMPUTER CLINIC Nanaimo, B.C. (604) 753-0983ORION ELECTRONICS Kitchener, Ont. (519) 576-9902SCIENCE TECH Montreal, P.Q. (514) 844-6443THE SOFTWARE SHOP Willowdale, Ont. (416) 223-9611

EDG Electronic Distributors Inc.3950 Chesswood Dr., Downsview, Ont. M3J 2W6

Dealers Inquiries Invited (416) 636.9404

ElmtronicsAudit Bureau

To yof Circulationda

Vol. 8. No. 7 ISSN 07038984July 1984 I NJ -1- l=?N.1 AT I CD NJ A I_

60

Features11Principles Of Metal LocationYou'll be amazed at all the stuff buriedbeneath your feet.

24A Look At The Sinclair QLA British computer success, soon to beavailable here.

26Coping With ComponentsPart Two. How to tell a component froma door knocker.

32Computer ReviewThe Sony SMC-70 is the graphics fan'sdelight.

39Machine Language, Part TwoConversing directly with your CPU.

41Computing TodayJohn Rudzinski provides some computerutilities via 6502 assembler.

45Circuit IdeasReplacing Tech Tips, our new featurelooks at camera control.

55Designer's NotebookExar Super Timer.

60VLFs And The MagnetosphereIf you need a bigger VLF, put it in themagnetosphere, says Roger Allan.

63ArmstrongA pioneer in the development of AM andFM receivers.

18Motor ControllerRun fans and vacuum cleaners atpointlessly slow speeds.

47Stylus TimerMeasures the hours until it self-destructsalong with your records.

Columns, News andInformationFor Your Information 7Order Form 53Binders 54Book of the Month 54Subscriptions 54ETI Bookshelf 50Next Month 53Product Mart 58

Our CoverVisions of treasure dance in Ed's head; seepage 11. Photo by Bill Markwick. TheSony SMC-70 is reviewed on page 32;photo courtesy of Sony.

Electronics Today is Published by:Moorshead PublicationsEditorial and Advertising OfficesSuite 601, 25 Overlea Boulevard,Toronto, Ontario, M4H IBITelephone (416) 423-3262

Editor:Editorial Assistant:Director of Production:Creative Manager:Production:

Circulation Manager:Advertising:

Advertising (Que.):

William MarkwickEdward Zapletal

Erik BlomkwistAnn Rodrigues

Douglas GoddardNeville WilliamsNaznin Sunderji

Lisa SalvatoriOmar Vogt

Rick MayJohn McGowan & Associates

(514) 735-5191

Publisher: H.W. Moorshead; Executive Vice -President: V.K. Mars k ell; General Manager:S. Harrison; Controller: B. Shankman; Accounts:P. Dunphy; Reader Services: C. Wyatt, S.

Halladay, H. Brooks, K. Adams; AdvertisingServices: C. Zyvitski, Dealer Services: A. Nagels.

Newsstand Distribution:Master Media, Oakville, Ontario

Subscriptions$19.95 (one year), $34.95 (two years). For US add $3.00

per year, other countries add $5.00 per year. Pleasespecify if subscription is new or a renewal.

Postal InformationSecond Class Mail Registration No. 3955. Mailing ad-dress for subscription orders, undeliverable copies andchange of address notice is:Electronics Today International, Suite 601, 25 OverleaBlvd., Toronto, Ontario, M4H IBI.

Advertisers' IndexActive Components Sales Corp 68Allan Crawford and Associates 42, 43Audiovision 65BCS Electronics Limited 31, 67, 70Biplex Systems Inc. 61Brunelle Instruments Inc. 64Circuitronics 34Compu-Order 64Computer Mail Order 6Computer Parts Galore Inc 8, 9Daetron 31Electronic Control Systems 64, 66Electronic Distributors Inc. 4

Electronic Packaging Systems Ltd. 61Exceltronix 2, 72Gentec Computers Inc. 34

Electronics 30Kaientai Electronics Merchants Ltd. 31Locust Computer Systems Corporation ....61Mark Gee Enterprises 61McGraw-Hill 29Metermaster 44Orion Electronics Supplies Inc. 71Pacific Rim 69Surplustronics 3

Tradeport Electronics 64, 66

ETI-JULY-1984-5

COAONTARIO/QUEBEC1-800-268-3974

PUM AARcct' CSAADA(L)

TORONTO OTHER PROVINCES828-0866 1-800-268-4559

We Carry a Wide Selection of Software From:Artworx, Broderbund, Commercial Data, Creative Software, Epyx, Atarisoft, Hes, Sirus,

Microspec, Synapse, Thorn, Spinnaker, Timeworks + Many More. Call us for prices!

COMPUTERS

(All equipment under full warranty in Canada.)Price subject to change without notice.

(All orders Shipped within 48 hrs, upon payment.)

MONITORSAPPLE CALL AM DEKCOLUMBIA CALL Video 300 $229.00COMPAQ CALL Video 300 A 239.00EAGLE CALL Video 310A IBM 249.00FRANKLIN CALL Colour 1 + 429.00HEWLETT PACKARD CALL Others CALLIBM CALL BMCSANYO CALL 12" Green 125.00DISK DRIVES 12" Amber 135.00

CDC (for IBM) $339.00 GORILLA12" Green 139.00

INDUS 12" Amber 149.00GT ATARI Drive 549.00 NEC CALL

MSD PANASONIC CALLMSD-1 C64 Drive 519.00 PRINCETON GRAPHICSMSD-2 C64 Drive 855.00 HX-12 819.00

PERCOM CALL QUADRAMRANA Quadcolor RGB 809.00

1000 (Atari) 479.00 SAKATA CALLEliteElite 2 579.00 USI CALLElite 3 799.00 ZENITH

SANTA CLARA CALL Amber 159.00

TALLGRASS CALL GreenColour

149.00699.00

TAN DONTM -100-2 DS/DD 339.00 CARDSTM -50-2 DS/DD 349.00 AST RESEARCH CALL

TRAK QUADRAM CALLATD-2 565.00 HERCULES

MODEMS Graphic cardPLANTRONICS

598.00

ANCHOR Colorplus 699.00Mark I (RS232) 129.00Mark II (Atari) 129.00 ACCESSORIESMark III (TI -99) 179.00 KEYTRONICMark IV (CBM/PET) 199.00 KEYBOARDS CALLMark V (Osborne) 159.00 KOALA PADMark VI (IBM) 279.00 All Computers CALLMark VII (AA/AD)Mark XII (1200 Bd.)

193.00489.00 INTERFACES

HAYESSmartmodem 300Smartmodem 1200

356.00799.00

Batteries IncludedBus Card80 Col. Card

CALLCALL

Smartmodem 1200BMicromodem IIMicromodem II +

749.00432.00489.00

CARDCOPar Printer InterInt/Graphics

75.00119.00

Micromodem II e 439.00 TYMACC64 to EPSON OKI 148.00NOVATION

MPCJ -Cat 163.00 Apple Dumpling GX. CALLSmartcat 103Smartcat 103/212

289.00649.00

PKASOUniversal Card 225.00Autocat 356.00

212 Apple Cat 929.00 Dealer Enquiries InvitedPC -Cat 549.00 Write or telephone for our FREE catalog

Mil=1VISAlei Ontario residents add 7% P.S.T.

Computer Mail Order Canada 2505 Dunwin Drive, Unit 3 Mississauga, Ontario L5L 1T1

PRINTERSBMC

401 Letter Quality $923.00BX-80 Dot Matrix 399.00

C. ITOHGorilla Banana 299.00Prowriter 8510P 550.00Prowriter 1550P 899.00F10-40 1529.00F10-55 1999.00

DAISYWRITER2000 1499.00

COMWRITERCW2..LQ 12CPS 749.00

EPSONRX80 449.00RX8OFT 525.00FX80 749.00FX100 1049.00

JUKI6100 769.00

OKI DATA82 475.0083 899.0084 Par 1499.0084 Ser 1650.0092 695.0093 1159.00

MANNESMANN TALLYSpirit 80 469.00160L 895.00180L 1229.00

SMITH CORONAL1000 589.00

STARGemini 10X CALLGemini 15X CALL

BROTHERHR 15 CALL

TTX CALL

DISKETTESBASF

BA1 D SS/DD W/Case 28.99BA2D DS/DD W/Case 35.99

ELEPHANTEL1 SS/DD 27.99EL2 SS/DD 29.99EL3 DS/DD 39.99

MAXELLMXD1 SS/DD 37.99MXD2 DS/DD 54.99

NASHUAND1D SS/DD W/Case 26.99ND2D DS/DD W/Case 38.99

VERBATIMVE1 SS/DD 31.99VE2 DS/DD 43.99VE1C SS/DD W/Case 34.99VE2C DS/DD W/Case 46.99

To order: Send money order, certified cheque, personal cheques must clearour bank, VISA or MASTERCARD. (Include card # and expiry date

signature) Add 5% for shipping and handling. Minimum $5.00 per order.

Circle No. 24 on Reader Service Card

CopyrightAll material is subject to worldwide copyrightprotection. All PCB patterns are copyrightand no company can sell boards to our designwithout our permission.

LiabilityWhile every effort has been made to ensurethat all constructional projects referred to inthis magazine will operate as indicated effi-ciently and properly and that all necessarycomponents are available, no responsibilitywhatsoever is accepted in respect of the failurefor any reason at all of the project to operateefficiently or at all whether due to any fault inthe design or otherwise and no responsibility isaccepted for the failure to obtain componentparts in respect of any such project. Further noresponsibility is accepted in respect of any in-jury or damage caused by any fault in designof any such project as aforesaid.

Editorial QueriesWritten queries can only be answered when ac-companied by a self-addressed, stampedenvelope. These must relate to recent articlesand not involve the staff in any research. Marksuch letter ETI Query. We cannot answertelephone queries.

BindersBinders made especially for ETI are availablefor $9.25 including postage and handling. On-tario residents please add provincial sales tax.

Back Issues and PhotocopiesPrevious issues of ETI Canada are availabledirect from our office for $4.00 each; pleasespecify by month, not by feature you require.See order card for issue available.

We can supply photocopies of any articlepublished in ETI Canada; the charge is $2.00per article, regardless of length. Please specifyboth issue and article.

Component Notation and UnitsWe normally specify components using an in-ternational standard. Many readers will be un-familiar with this but it's simple, less likely tolead to error and will be widely usedeverywhere sooner or later. ETI has opted forsooner!Firstly decimal points are dropped andsubstituted with the multiplier: thus 4.7uF iswritten 4u7. Capacitors also use the multipliernano (one nanofarad is 1090pF). Thus 0.1 uFis 100nF, 5600pF is 5n6. Other examples are5.6pF = 5p6 and 0.5pF = Op5.Resistors are treated similarly: 1.8Mohms isIM8, 56kohms is the same, 4.7kohms is 4k7,100ohms is 100R and 5.60hms is 5R6.

PCB SuppliersEli magazine does NOT supply PCBs or kitsbut we do issue manufacturing permits forcompanies to manufacture boards and kits toour designs, Contact the following companieswhen ordering boards.

Please note we do not keep track of whatis available from who so please don't contactus for information on PCBs and kits. Similarlydo not ask PCB suppliers for help with pro-jects.

K.S.K. Associates, P.O. Box 266, Milton,Ont. L9T 4N9.B -C -D Electronics, P.O. Box 6326, Stn. F,Hamilton, Ont. L9C 6L9.Wentworth Electronics, R.R. No. I Water -down, Ont. LOR 2H0.Danocinths Inc., P.O. Box 261, Westland MI48185, USA.Arkon Electronics Ltd., 409 Queen Street W.,Toronto, Ont., M5V 2A5.Beyer & Martin Electronic Ltd., 2 Jodi Ave.,Unit C, Downsview, Ontario M3N IH I.Spectrum Electronics, 14 Knightswood Cres-cent, Brantford, Ontario N3R 7E6.

for your igformatioq

10,

Franklin CX SeriesFranklin Computer of New Jerseyhas unveiled their new four -modelCX line of computers. The biggestfeature is compatibility with variousoperating systems - the top -of -the -line 2M, for instance, can run AppleDOS, CP/M, and MSDOS; it alsocan read Kaypro and Osborne for-mats. Other features are one or twoDSDD drives, business software byArtsci, a minimum of 64K RAM,and a seven inch monitor. Availablein Canada shortly, the U.S. modelsstart at $1,395.Circle No.60 on Reader Service Card

Cesco Electronics, 4050 JeanTalon W., Montreal, Que. H4P1W1 (514) 735-5511, has a newcatalogue of components and ac-cessories; it's free by phoning,writing, or visiting. There arebranches in Quebec City, Ottawa,and Toronto.

IBM has announced the success ofan experimental one -megabitmemory chip. It uses IBM'ssilicon -aluminum -metal oxide pro-cess (SAMOS), and operates froma single 5 volt supply. Access timeis 150 nanoseconds. No mentionwas made of availability or price,but the prototypes were made onthe same production line as their64K -bit chips, so it shouldn't taketoo long to hear more about them.

Speaking of IBM, they havefiled a lawsuit against SpiralesComputers of Montreal; they'reseeking an injunction to preventthe importing and marketing of aTaiwanese computer which IBMsays is infringing their copyright.Cloners beware.

Electronic Packaging Systems an-nounced yet another dealer fortheir line of BICC Vero hardware:Montcalm Electroniques Inc., 97Boul. des Laurentides, Ville deLaval, Quebec 1176 2T2.

Circle No.59 on Reader Service Card

SpudShamrock Computer Inc. has an-nounced the introduction of theShamrock professional Utility Drive(SPUD).Shamrock Computer Inc. is a Cana-dian company which has been manu-facturing disk drives for Apple andApple compatible computers forover a year. The Shamrock SPUD3.5" Apple II compatible disk drive,offering 328K storage on 80 tracks,was introduced at both the Ottawa

High Technology and TorontoComputer Fair shows. The SPUD3.5" drive plugs into the existing Ap-ple controller card and is suppliedwith a menu driven 5-1/4" utilitydiskette that allows users to config-ure their Apple 11 system and to copytheir existing 5-1/4" software ontothe more convenient 3.5" plastic -encased diskettes. Contact them at89 Telson Rd., Markham, Ont. L3R1E4 (416) 474-0113.


New Header PinsAptronics Corporation announcesfast delivery on their full line of 295Series Headers. 295 Headers areavailable in both straight and right-angle configurations. They aredirectly interchangeable replace-ments for other industry -standard.295" Headers. 295 Series Headersare available in full or polarizedrows. Standard polarized headershave second circuit voided (postremoved). Headers feature standard.025" square posts, .100" spacingbetween posts, and are available withup to 30 contact posts per row. AtAptronics dealers, or contact Len -brook Electronics, I 1 1 Esna ParkDr., Unit 1, Markham, Ont. L3RIH2 (416) 477-7722.

Orcle No.57 on Reader Service Card

ETI-JULY-1984-7

COMUTERn n riTI- 17 1,1 nriri i ii\ i _s Lil ILUNL INC.

316 College St.Toronto, Ontario M5T 1S3

Toll Free Orders Only1-800-387-1385Order Checking (416)925-8291#

Technical Data (416)925-1105

GREAT1111111111111

DEALTHE GREAT DEALCARRIES ON FOREVER AND GETS BETTER

Our proven 6502 motherboard plus a numeric case plusa black beauty powersupply plus a numeric keyboardplus any 4 bare pcb for $225.00SOLID ABS

NUMERIC i$59.95

"----- ..,%t

,_/

MODEMCASE

At last, an affordable Modem, wehave cloned a board similar to theSSM Modem that features: APPLE II & APPLE Ile

COMPATIBLE 40/80 COLUMN SUPPORTED FULLJHALF DUPLEX AUTO ANSWER/AUTO DIAL TOUCH TONE OR PULSE

DIALING AUDIO MONITOR CHANNEL IN PLACE FIRMWARE HAYES MICRO MODEM II

COMPATIBLE RUNS ASCII EXPRESS AND

MOST OTHER PROGRAMS DIRECT LINE CONNECTION

We have tried it out and it is verygood and very reasonably pricedfor it's quality $229.00Bare PCB only $ 24.95

.-_. SYSTEM

..

. *.-.,.

N....s.,..,'SAVIOURto

2 grounded 3 wire switched sockets, pilot light, surgeprotector and on -off switch to turn off your system andtwo plugged in items $45.00OUR 6502 BOARD

Now only $29.95 still withall the versatility of theoriginal and a full 8 slots.

0eDIGITAL

MULTI -METERAMAZINE QUALITY

r-

_.

.....

mom.e

EXTRA FEATURE Diode test circuit Lo voltagetery indicator Auto -Zeroprotection, all ranges ABSOne hand push buttons.

AT LOW COST

569.96

1.. ., ....

101/01.1Aar FOkiv CIRCUIT

-R

t:

ohms, 0.5v Lo bat - Auto polarity Overload

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BARE PCB

(A) REAL TIME CLOCK PCB $14.95(B) QUAD DRIVE CARD (FIANA( $24.95(C) 9 VOICE MUSIC PCB $14.95(0) BUFFER PRINTER PCB $19.95(E) GRAPPLER PCB $19.95(F) CABLE FORD, E, SPECIFY $24.95(G; 80 COLUMN, SOFTSWITCH $14.95(H) DISC CONTROLLER PCB $12.95(I) Z-80 PCB $12.95(J) SSM MODEM PCB $24.95(K) MOUNTAIN MULTIFUNCTION $24.95(L) 128K (SATURN) PCB $19.95(M) RGB COLOR PCB $24.95(N) EPROM PROGRAMMER PCB $12.9510) PIA PCB $14.95(P) WILD CARD PCB $12.95(Q) SAM TALKING CARD $12.95(R) RS -232 PRINTER PCB $12.95(5) RS -232 MODEM (COMM) PCB $12.95(T) RS -232 ASYNCHRONOUS PCB. $14.95(U) SPRITE GRAPHICS PCB $17.95

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Make your Appletm or 6502PCtm. This attractive metallooks just like you -know -who,to take all the 6502 Motherthat are now sold. Keyboard Case

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$ 69.95$ 1995.

MAIL ORDERSWe accept: Personal Cheques, Postal Money Orders,Certified Cheques, Travelers Cheques, Visa, AmericanExpress, Mastercard, Bank Draft. We ship C.O.D. onlyby CANPAR and Truck. We do not use Canada PostC.O.D. We will send your goods via CANPAR or CanadaPost unless you say otherwise. You will be charged amin. $3.00 for delivery and handling or more if yourgoods are heavier than the $3.00 weight or if you spe-cif y another delivery service that charges more. AllOnt. res + 7% sales tax. We sell wholesale to anyretail store or other reseller with a sales tax exemptionno. as long as a realistic quantity is bought. We shipwithin a week if in stock and we will cancel any back -orders over 4 weeks unless otherwise instructed. 20%Restocking Charge.

6502 STUFF

BB POWER SUPPLY $ 79.95ABS NUMERIC CASE $ 59.95ASCII NUM KEYBOARD $ 99.00SYSTEM SAVIOUR FAN $ 45.00GREAT DEAL $225.00Z-80 WIRED $ 55.0080 COLUMN WIRED $ 75.0016K WIRED $ 59.95WILDCARD WIRED $ 45.00SAM TALKER WIRED $ 45.00128K WIRED, NO IC'S $ 39.95128K WIRED, 64K $119.00128K WIRED, 128K $199.00D)SK(3) FOR 128K $ 20.00

BARE PCB FIRMWARE ETC.

(A) REAL TIME CLOCK DISK $ 8.00(B) 9 VOICE MUSIC, 2 DISKS $16.00(C) GRAPPLER EPROM $ 8.00(D) 80 COLUMN, 3 EPROMS $24.00(E) SSM MODEM EPROM $ 8.00(F) MULTIFUNCTION EPROM . $ 8.00(G) 128K, 3 DISKS $20.00(H) RGB CARD PROM $ 9.00(I) RGB CARD DISK $ 8.00(J) EPROM PROG. EPROM $ 8.00(K) WILD CARD EPROM $ 8.00(L) WILD CARD DISK $ 8.00(M) SAM TALKER DISK $ 8.00IN) SPRITE DISK $ 8.00


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At last, a nice new case for the IBM look -a -likeboards. Not cut for 6502. Fits the power supplytypes listed on this page and has cutouts forPC or XT (specify) card spacing, with card -guides and plastic Drive inserts and all moun-ting hardware, and with the greatest featureever, a hinged lid that allows rapid and easyaccess to the insides. Spring clips hold it on atfront so no screws need to be undone $89.95

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Olivetti PortableThe MIO is based on CMOS techno-logy and uses the 80085 processor.Standard interfaces include a parallelprinter port, an RS232 (up to 19200baud), integrated modem, cassetteand bar code reader interface. The li-quid crystal display (LCD) tilts to athirty degree angle for optimumviewing while leaving the keyboardat a proper angle for typing. TheMIO is even further enhanced by acomplete library of software whichincludes spreadsheets, databases,order entry, word processing, salesmanagement, Forth, assembler etc.For further information, contact:Patricia Smith, Olivetti CanadaLimited, 1390 Don Mills Road, DonMills, Ontario, M3B 2X3 (416)447-3351.


Hi -tech MouseketeerWill Walt Disney Productions re-instate the famous Mickey MouseClub? And will they be using, as thisphoto suggests, a microprocessor -controlled, servo -operated, 256K,MS-DOS compatible mouse hat? Weleave this to the reader's speculation.

Multitech PC/XTFollowing the introduction of theMPF-PC in November 1983, Multi -tech announces its latest addition tothe company's MPF line of IBM PCcompatible computers. The MPF-PC/XT features an integrated 10megabyte fixed disk drive. Backingup the Winchester hard disk drive isa 360 KB capacity floppy disk drive,facilitating new program entry andcopying of data files. The MPF-

TVRO FilterTerrestrial interference Trap4616-60/80 incorporates a 60 MHztrap and 80 MHz trap, both switch -able in and out.The trap may be used as a diagnostictool during installation or as areceiver accessory to optimize recep-tion channel by channel. Impedanceis 75 ohms and connectors are typeF. Notch loss is 20 db minimum and3 db bandwidth is approximately 4MHz. Each notch is frequencytunable ± 5 MHz to compensate fornominal downconversion error. Formore information contact Emily

Who is the Tradeport ElectronicsGroup? Well, they're a newmanufacturer's rep, located at1179 Finch Ave. W., Downsview,Ont., M3J 2G1 (416) 736-0866.They represent all sorts of elec-trical and electronic measuring in-struments, training devices, andR&D equipment, especially hard -to -locate firms from Europe:Black Star, Radford, Ferrograph,ITT France, Grundig, etc.Circle No.51 on Reader Service Card

PC/XT also provides a standard128K bytes of RAM expandable onboard to 256K bytes, dual serialcommunication ports, one parallelport, monochrome/color graphicsadaptor, five IBM compatiblesystem expansion slots, and more.The suggested retail price of theMPF-PC/XT, including the mono-chrome video monitor, is U.S.$3,995. At Multitech dealers.


our idormatiory

Bostick, Microwave Filter Com-pany, Inc., 6743 Kinne St., EastSyracuse, NY 13057.Circle No.55 on Reader Service Card

Comet AntennaMitsubishi Electric Corporationrecently finished assembling ahuge, 64 -meter diameter antennafor observation of Halley's Comet.When completed in late Octoberthis year, it will be Japan's largest,and one of the world's largest,deep space probing antenna. Mit-subishi Electric is building theantenna for the Education Mini-stry's Institute of Space andAstronautical Science, which is incharge of the PLANET -A Projectto observe Halley's Comet ap-proaching the sun in 1986. Thecomet comes close to the sun every76 years.

More on piracy: a ProvincialCourt in Calgary convicted a26 -year old gentleman on 50counts of software piracy. He wasduplicating commercial softwarefrom a flea market booth on awhile -you -wait basis, at five to tendollars a shot. Despite pleas fromthe software industry for a publichanging, the judge delayed senten-cing. The case will no doubt set alegal precedent.

The Ferranti range of CM SeriesCO: waveguide lasers, RF or DCexcited, covers the power ratingfrom 1 watt to 30 watts and is in-tended for applications such asrangefinding, communications,beacons, velocimetry, lasersurgery, in addition to a widerange of industrial applicationssuch as cutting and welding ofplastics, mask fabrication, engrav-ing, etc. For additional informa-tion, please contact: EP Elec-tronics International Inc., 187Denison St., Markham, Ont. L3R1B5, (416)475-8316.Circle No.53 on Reader Service Card

The Ontario Government has anew catalogue - slightly used civilservants. No, but really, they'vecompiled a list of more than 900Canadian producers of computers,word processors, components andsoftware. It's available for $10.00from the Ontario GovernmentBookstore, Publication Services,5th Floor, 880 Bay St., Toronto,Ont. M7A 1N8 (416) 965-6015.Circle No.52 on Reader Service Card

10-JULY-1984-ETI continued on page 66

Principles ofMetal Detection

ETI looks at the history, tech-niques and uses of all kinds ofmetal detecting, from treasure -hunting to bomb disposal.

by Richard Turner

METAL DETECTION is a subjectseldom mentioned in electronics journals,but recently it has attracted much atten-tion in the daily press. Detectorists havebeen featured on many a front page withtheir finds of explosives or buriedtreasure, and perhaps even more whileassisting the police in searches forweapons in some very controversialmurder cases. However, metal detectionhas been around for about ten decadesnow and has been used for a very widerange of applications, and thus should beof interest to electronics enthusiasts.

HistoriesWhile for hundreds of years treasureseekers and prospectors have used devicessuch as divining rods, magnetic needlesand a variety of "doodlebugs" to aid theirsearches, it was not until 1879 that thefirst practical, scientifically proven instru-ment was built. The credit for thisdicovery goes to Professor D.E. Hughes,who demonstrated his 'Induction Bal-ance' to the Royal Society in that year.

The Induction Balance attracted agreat deal of interest among the scientistsof the day, including the Chief Chemist ofthe Royal Mint who acquired one of thefirst units for the assaying of coins. Alex-ander Graham Bell applied the InductionBalance to the location of an assissin'sbullet in the body of American PresidentJames Garfield.

This 'electric' metal detection had agood scientific start and it is worth ex-amining in closer detail some of the manyuses of the technology.

In Hughes' Induction Balance, aLeyden Jar supplied current to amicrophone which was placed in contactwith a ticking clock. Alternating currentwas achieved by a manually activatedresonating spring contact assemblyfeeding two induction coils wound in op-position to each other. The pick up con-sisted of another pair of identical coilswired as a circuit with a further three coilsand a telephone. This arrangement was

adjusted for complete silence in thetelephone. To 'detect' or 'analyse' metal,the sample was placed on the primarycoils, thus disturbing the mutual induc-tion so that sound was heard in thetelephone. Then the indicating coil in thesecondary circuit was moved along a scalemarked in degrees until silence was ob-tained again. Different samples could beidentified against a previously preparedchart. This instrument was sensitive tosuch a degree that coins of the samedenomination, but with varying amountsof wear, could be distinguished from eachother.

Another detection principle devel-oped in Victorian days worked on 'Secon-

dary Induction'. This involved a complexset-up but gave a considerable detectionrange. And indeed, when demonstrated ata Welsh metal mine at the turn of the cen-tury, it was found that metal ores could bedetected up to three hundred yards away.

Briefly, the set-up was as follows: abattery supplied the primary current to amotorized contact breaker which 'chop-ped' it into a high frequency and fed theprimary winding of a transformer, wherethe voltage was stepped up. The secon-dary output was fed to a pair of probesplaced in the earth. A similar pair ofprobes placed some distance away fedanother transformer to which there wasconnected a galvanometer. If there was no

ETI-JULY-1984-11

Principles of Metal Location

metal in between probles, the input signalwould 'scatter' in all directions and thegalvanometer would remain at zero. Thepresence of ores or large metal objectswould attract the voltage fed into theground, producing an indication on themeter.

Electronic PrinciplesWith the advent of electronics, thetransmit -receive technique was quite ac-cidentally developed. During World WarOne, the military developed sound rang-ing and direction finding equipment. Itwas soon found that large masses of metalsuch as bridges, railways and ships at seainterfered with the equipment and muchre -design was necessary for proper opera-tion. However, the 'interference' turnedout to be a benefit as this led to thedevelopment of metal detectors for sens-ing enemy submarines and tanks at a con-siderable distance.

In the post World War One years, thetransmit -receive technique was used forelectrical prospecting and forms the basisof most metal detectors today. Theheterodyne principle found much favourin the late 1930s and was used extensivelyuntil about five years ago. A more recentinnovation in metal detection technologyoperates on the DECCO principle whichwas developed at Oxford ArchaeologicalResearch Laboratory in 1966. Decay ofEddy Currents in Conducting Objects isnow better known as pulse induction. Fewpeople are aware of what an importantfunction metal detectors perform for theirwellbeing and comfort. Most and possiblyall food and pharmaceutical products arepassed through metal detectors to ensurethere are no nuts, bolts, swarf, pins orother alien items in them. Medicines likepills and powders receive the same treat-ment. Shoes are tested for unwanted in-sole tacks and even such products as tex-tiles, carpets and linoleum are passedthrough a metal detector before dispatchto the customer.

In quarrying and mining industriesthe burden is checked for tramp metalsuch as drill rods, dipper teeth, and pickand shovel ends to prevent damage to cut-ters and diamond tipped grinders. Most ofthe world's airports are equipped with'walk through' metal detectors to combatthe carrying of illegal weapons. Accuratelocation of pipes has to be known whenmechanized road or trench digging takesplace. Lumber jacks and tree surgeonsscreen trees to detect bracing tie bars,bolts or nails which may be covered bygrowth and thus prevent a danger topower operated saws. Reclaiming timberis very much a practice with DIY en-thusiasts, but why risk damage to yourelectric plane or sander by nails etc, whena quick scan will save the expense of newplane blades or sanding strips?

Medical ApplicationsAs already mentioned, Bell used the In-duction Balance to detect a bullet in ahuman body, and ever since that timemedical metal detection has flourished. In1885 the Royal Army Medical Corpsdeveloped quite a different metal detectorfor locating bullets and shrapnel inwounded soldiers. During World WarTwo electronic metal detectors weredeveloped in Britain (Barnato JoelLaboratories), Germany (Siemens Elec-tric) and the USA (Waugh Laboratories).The European detectors used theheterodyne principle at VHF, while theAmerican unit was an electronic versionof Induction Balance.

Currently the world's most advancedmedical and veterinary detectors are ofBritish manufacture, the Rope -Halllocator for Opthalmic and Medical ap-plications (Keeler Instruments) andTektamet PI for veterinary use (GoringKerr PLC). These high technology andpatent protected detectors not onlydistinguish ferrous from non-ferrousmetals but also indicate which metal ispredominant. Thus the surgeon or vet hasan instant indication as to what techniqueto use for extraction. If the metal is non-ferrous, a conventional cut and sewmethod would be employed, but a metalwhich has ferrous content can be removedby an electromagnetic extraction techni-que, eliminating surgery.

Treasure SeekingWith the Royal Mint using the InductionBalance for the assaying of coins, itbecame apparent that this instrumentcould be adapted for the location ofprecious metals. Soon 'Buried TreasureFinders' were very much the fad of Vic-torian society, and were seen wanderingabout the countryside with very strange

looking devices. However treasure hun-ting did not reach its peak until the earlyTwenties, when an Englishman by thename of Williams emigrated to Panamawhere he got a concession from thegovernment to seek out the treasure con-cealed before the sacking of Panama Cityby the notorious pirate Captain Morgan.

Devising a transmit -receive metaldetector capable of locating metals up toforty feet beneath the ground, he soonlocated cellars and secret tunnels packedwith precious metals. Williams becamevery rich and his fame spread far andwide. Being a generous man he gave theplans for his metal detector to anybodywho asked for it, and some of thoseungrateful individuals even filed patentsfor it as their own invention. Thus withmetal detectors being produced on a largescale, the rich with time on their handsonce again took up the seeking of buriedtreasures. Most of them headed for theCocos Islands where legend said thatmuch treasure had been concealed bypirates. Franklin D. Roosevelt, a promi-nent lawyer, was one of the first to land,and even after he had become President ofthe USA he returned for another try.Malcolm Campbell, Admiral Nicholsonand Commander Worlsey also led expedi-tions to the Cocos Islands.

Detectorists TodayHowever, pirate and legendary treasuresare very much of a myth and today'sdetectorists take a much more practicalview, seeking lost coins, jewellery and thelike which has accumulated in the groundover the last two thousand years. Manypreviously unknown coins and artifactshave enriched our museums after beingfound in that way. Occasionally largehordes of coins are found.

Even wrecked ships can spreaddanger on the coasts, and an example of

The portable, belt -carried MD 199 can be used with a variety of probes. The one shown is a handprobe.

12-JULY-1984-ETI

principles of Metal Location

this was the wreck of Aeolian Sky whichdischarged its cargo of deadly cyanidecanisters. In a situation like this a promptsearch and recovery operation is requiredwith metal detectors, as shifting sands andseaweed were quickly concealing thecanisters. In this particular instance, theDetector Information Group (DIG) or-ganized a search to assist Coastguards andPolice, whose resources were stretched tothe limit. This operation proved such asuccess that an annual beach clearancenow takes place in May along the SouthCoast of England.

In the second half of this article, weshall take a closer look at the technicalaspects of various detection techniquesand brief specifications of commercialequipment. The block diagrams are insimplified form and show only the basicrequirements for such detectors.

Heterodyne (BFO) PrincipleOf all the possible ways of detectingmetal, the heterodyne principle is perhapsthe best known. After all, most radios useBFO (Beat Frequency Oscillator), so thesystem is easily understood even by alayman. The technique is simple, econom-ical and produces very satisfactory results.The detector can be constructed fromreadily available radio parts; if a searchcoil of small but intense field is required(for instance, for medical applications) aready made ferrite rod aerial can be used!

For larger areas and deeper penetra-tion, the search coil is usually wound inmultilayers on a circular former althoughprinted circuit coils are also known. On adetector with wide range tuning, it ispossible to detect metal against a metallicbackground, for instance, copper pipeembedded in reinforced concrete.

Off ResonanceDiscrimination (ORD)In this technique, the search coil is drivenby a frequency which typically differs byabout 3 dB from the natural resonant fre-quency of the tuned circuit. This arrange-ment automatically gives a very selectivedetection. If for instance a discriminatingdetector is required for non-ferrousmetals, the signal generator is driven at ahigher frequency, but for ferrous metalsat a frequency which is below the naturalresonant frequency of the search coil.Thus in "treasure hunting" applications,excellent rejection of unwanted objects(nails, bottlecaps etc.) is achieved whileretaining good sensitivty to desirable findsof coins, jewellery and the like. The maindrawback of the system is thermal in-stability, for instance, if the detector iskept in the trunk of a car during hotweather, the search coil alters its naturalresonance, and the separation between thedrive and natural frequency of the tuned

REFERENCEOSCILLATOR

SEARCHOSCILLATOR

MIXER FILTER AUDIOAMPLIFIER

Fig. 1. A block diagram for a Heterodyne Principle (BFO) detector, the simplest type for a homeconstructor to design.

SIGNALGENERATOR

Ill

VAR ICAPTUNER

COMPARATOR

SAMPLEAND HOLD

DE-MODULATORAMPLIFIER

DCAMPLIFIER

DIFFERENTIALAMPLIFIER

AF VCO

Fig. 2. The Off Resonance Descrimination System. Very selective, this method is favoured by"treasure hunters".

UZiOV

;7;

RECEIVEAMPLIFIER

SAMPLINGGATE

PULSEGENERATOR

SAMPLEPULSE

GENERATOR

14 INTEGRATOR AMPLIFIER AF VCO -r(

Fig. 3. The block diagram of a pulse induction system. This method uses the ability of metal objectsto absorb and reflect electromagnetic radiation as eddy currents which can be detected.

circuit drifts so far apart that detectionbecomes difficult, if not impossible.

Pulse Induction System (P.I.)This system differs from all the othermethods as no oscillators or tuned circuitsare required. Detection is achieved by thephenomenon of decaying currents inmetal objects (DECCO). Thus a highamplitude short duration pulse is injectedinto the search coil, which emits electro-magnetic radiation within its range. Softobjects such as soil or even aluminum foilallow the energy to penetrate and dispersewhile solid metals, especially magneticmetals, absorb and reflect this energy inthe form of eddy currents which readilyproduce EMF in the search coil,generating a signal in the receiveamplifier.

The main drawback of this principleis that Earth's magnetic field renders thedetector oversensitive to ferro-magneticmetals. Although discriminating -typepulse detectors are now available, these donot provide such a good selection ofdesirable objects as continuous wavediscriminators.

Induction Balance Method (IB)This old and complicated, but most sen-sitive, detection principle requires several(or multitapped) search coils, and so is notexploited very much these days. Howeverits sensitivity to precious metals is unsur-passed. As explained earlier in thisfeature, with a suitable arrangement evenworn coins can be distinguished from newones. This is achieved by phase -anti -phasemagnetic fields which can be generated by

ETI-JULY-1984-13


1,1cIng. ÂF

RELSX110.4OSCILLATOR

T

`."

,TDETECTOR

SENSIANAL IFIER

SITIVITV

DETECTOR

Fig. 4. Induction Balance, the oldest and most sensitive method of detection, is now not much usedbecause of its complexity.

PD.(DETECTOR

PULSEGENERATOR

-1:11111.

UTOSHUTDOWN

REFERENCEAMPLIFIER

OUTPUTDE L,

Fig. 5. The Balanced Coil method, a simplified version of Induction Balance, favoured for "pro-duction line" detectors because it is very sensitive at speed.

OSCILLATORT

DISCRIMINTION

tor Prost

CR ILIA TOR

90' PHASES

CR MU AEON 1J4.11%

NOD I:TOR MAIL !Elf R

F

=TO.

RE vC0

Fig. 6. A block diagram for the Transmit -Receive Radio Technique, popular for its simplicity andability to discriminate between worthless and valuable metals.

complex coil arrangements, but energizedby simple electronic circuitry with a verymodest current consumption.

Balanced Coil Application (BC)This is a simplified adaptation of the In-duction Balance very much favoured bymanufacturers of industrial detectors. Andindeed the block diagram shows in

simplified form an arrangement for a

"feedthrough" conveyer type instrument.The search cons arc usually of rectangularform wound in single layers, offering very

high sensitivity. Typically a one millimetremetal sphere can be detected at a velocityof 40ft per minute through a 12 x 4in aper-ture.

The oscillator also initiates the pulsegenerator which is connected in a feedbackcircuit, thus offering a self checking func-

tion and automatically stopping the detec-tor should a fault occur. If unwanted metalis detected, the reject timer allows the pro-duct to leave the search head and reach therejection point where it is removedautomatically from the conveyor belt.

Transmit -Receive RadioTechnique (T -R)This technique operates on true radio prin-ciples, and it can be seen why metal detec-tors come under the scope of WirelessTelegraphy Act. calk),

already explained) the transmitter was

quite a separate item from the receiverwhich could be placed a considerabledistance away, offering very deep penetra-tion. However in recent times the trend has

been to combine both units into one casefor compactness and portability. A simple

sine wave oscillator drives a tuned circuit ofa suitable frequency. A tuned search coil(or coils) feeds an RF amplifier to boost theincoming signal for the purpose of phasediscrimination, eliminating unwantedsignals from the ground (minerals etc.) andoffering discrimination between unwantedobjects and precious metals. Straight-forward output ciruitry is employed. Thesimplicity of this technique makes it a veryattractive proposition to manufacturers of`hobby' type detectors which usuallyoperate in the VLF spectrum.

Equipment SurveyTo conclude this article, a survey is in-cluded of some commercially manufac-tured equipment manufactured in the UK.Each company has been limited to a max-imum of five entries.

Some explanatory notes are worthyof inclusion as some readers may wonder,for instance, what is the difference bet-ween a hand and portable detector? Ahand detector is a completely self contain-ed one-piece unit whose total length doesnot usually exceed eighteen inches.However, headphones or earpieces maybe supplied as optional extras. Portableunits will have a separate search coil (orcoils) or probes and electronics case, andcan be in a shoulder -slung case or a hipmount design. Usually a range of optionalextras are available, as in the case ofmedical detectors where even a reset footswitch is provided. A bench unit would beusually powered by mains and have arange of search probes for various ap-plications.

Walk Through, as its name suggests,is a weapons type detector and at least onecompany manufactures such a unit in a`portable' version which can be folded upand transported in the trunk of a car!Hobby detectors are usually of one-piececonstruction with the search coil forground searching mounted on an ad-justable shaft which may be mounted onan electronics case. Some models areavailable in hip mount versions. Thisdescription also applies to underwaterdetectors. Conveyer type detectors arelimited to industrial applications, andsuch detectors are available with searchcoils from about 1 inch diameter (forpharmaceutical applications) to 50 feet fortextile industries.

ETI would like to thank Terry Can tin ofThe Midas Touch for his assistance in

metal locators.For further injormauXd

The Midas Touch,

20:0Ain

Toronto,McRae Drive,

(416) 421-4249

9

14-JULY-1984-ETI

A Pulse Induction Metal Detector

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The schematic of a pulse induction type of metal detector.

HOW IT WORKS

Oscillator IC2a generates a positive pulsewhich turns on Q1, with the result that acurrent builds up in search coil LI. At theend of this pulse, QI is turned off and thevoltage waveform shown below appearsacross the coil, and falls to zero in time X.If metal is near the coil, the voltage fallsmore slowly to zero (i.e., time Y). Opera-tional amplifiers ICI and IC4 amplify thecoil voltage 10,000 times. Monostablemultivibrators IC2b and c generate a se-cond pulse, accurately timed after the firstpulse, which is used to turn on an electronicswitch (formed by lC3a,b and c) just as thecoil voltage is reaching zero.

As metal approaches the coil, thevoltage across it decays more slowly.Therefore, the pulses passed by the elec-tronic switch get bigger.

Integrator IC5b amplifies and smoothsthe pulses from the electronic switch anddrives meter ME 1. The output voltage fromthe integrator thus increases as the coil ap-proaches metal, and this is registered on themeter.

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The underside of the search coil head and sections of the head showingcoil wire leadout and routed up into the handle.

Winding The CoilsThe housing is plywood or hardboard. 178 mm x 203 mm (7 x 8 in-ches) with grooved beading on the edges to hold the wire. Pass about 1metre of 28 swg enamelled copper wire through the hole and then wind22 turns of wire around the grooved beading. Pass another metrethrough the hole; the two ends of the wire should be long enough toeasily reach the electronics.

ETI-JULY-1984-15


An Induction Balance Metal Detector

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The schematic of an Induction Balance type of metal detector.

HOW IT WORKS

The heart of the circuit is the search coil, L I

and L2. These two coils, which are essen-tially identical, are arranged in the sameplane with a small overlap in such a waythat there is practically no inducative coup-IMg between the two. There is minimumpickup when the fields generated in LI arecancelled in L2 when in free air. Any metalbrought into the electro-magnetic field of1_1 will distort the field, causing pickup inL2.

QI is a straightforward Colpitt'soscillator working at a nominal 130 kHz.This type of circuit is very stable and the useof polystyrene capacitors also help withstability. The supply to this stage is

separately decoupled by R4 and CI.The pickup coil L2 is tuned by means

of C4 and C5 and amplified by Q2 whichfeeds to the level control RVI. This controlsthe "free air" state of the circuit and is setto the point where the later stages are justoperating. The signal is further amplifiedby Q3 (here it is still an RF signal) and is

detected by DI and D2. When no metal is inthe vicinity of the search coil and with RVI

correctly adjusted, a DC voltage of about500 mV appears across C8. R9 increases theeffective input impedance of Q4 as seen by

the detector stage.Q4 is just held off by the voltage

available but as soon as any metal distortsthe electromagnetic field, L2 produces alarger RF signal, a higher voltage across C8

and a consequent fall (from 8 V) in thevoltage at the collector of Q4. This voltageis also monitored by the meter in parallelwith the load resistor of Q4. The fall involtage is dependent upon the proximityand/or size of the metal near the searchcoil.

It is necessary to ensure that the DCvoltage fed to the next stage is clean andRI2 and C9 act as a filter to remove anyresidual AC even if this is at low frequen-cies.

1C2 (the next but one stage) is a voltagecontrolled oscillator - but to operate thisso that metal is indicated by a rising note,

rather than a falling one, the voltage at the

junction of C9 and RI2 has to be invertedand this is achieved by ICI: in "no -metal

conditions, there is about 2 V at the outputof this op -amp which rises when metal isnear. This stage quickly saturates to giveabout 7 V at pin 6. ICI has unity gain.

IC2 is a voltage controlled oscillator.In "no -metal" conditions it gives about 70Hz which rises to 500 Hz when metal is pre-sent, diode D3 gives a rapid recharge to CJ..and affects the mark/space ratio of the.P-

rsrencies ifput which results in lower battery cogive ation. R20 and C12 can be altedifferent range of audiodesired. con -

The output is taken to a volume

trol and fed to the LM380 audio power

amplifier whichin turn feeds the speaker.

The levers of signal around Q2,3,4 are

all dependent upon transistor gain,

temperature and supply voltage, but this

doesn't matter because the level control

RVI is adjusted until Q4 just begins to con-

duct.Current drain for the complete circuit

is in the order of 50 mA.

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The search coil. This is LI and L2 which are made from two coils originallywound on a 140 mm former and then squeezed into the shapes shown.

16-JULY-1984-ETI

Winding The CoilsThe search head is the key to the whole operation; be prepared to

spend some time experimenting.The housing of the coils is not important; a rectangular shape is

used for ease of construction. The coils LI and L2 should be sand-

wiched between two pieces of hardboard or plywood separated by two

pieces of wood about 6 mm thick.To wind the coils, you'll need a cylinder about 140 mm (51/2 in-

ches) in diameter. Using 32 swg enamelled copperwire, trap one end

Onto the lot ttwr with tane and wind 40 turns as close together as possi-

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Motor ControllerProject

Electric drills, saws, grinders, food blenders etc., all benefit fromhaving some sort of control over their speed. Simple electric motor

speed controllers, while proving speed control, have limited ability tomaintain motor speed constant over widely varying loads. This project

overcomes the limitations of these simple units and, despite itssimplicity and low cost, is remarkably effective.

By Jonathan Scott

JUDGING BY users' remarks on the short-comings of speed controllers on a variety ofelectrically driven appliances, and frommuch personal experience and observation,there is a considerable need for a well -de-signed speed controller for use with electricdrills, grinders, saws, food blenders andother appliances driven by 'universal' elec-tric motors.

The more expensive power drills nowcome with a variable control built into thetrigger. Food blenders come festooned withan array of buttons marked with a ludicrousrange of words with every synonym from`mix' to 'masticate' represented!

These gadgets all have a severe limita-tion, namely, that they really only havevoltage controllers, not speed controllers,for the motor in the unit. They vary thespeed but provide little or no feedback speedcontrol.

In the case of the power drill with aspeed control in the trigger, the operator isin a position to adjust the trigger contin-uously in response to variations in the speedof the shaft, thus effectively becoming partof a feedback loop and serving as the speedregulating element.

The variable speed function of theselatest drills is really not designed to allow the

slow steady pace needed for delicate orlaborious jobs, but to allow the unit to act asan electric screwdriver, when fitted with theappropriate bit, where constant speed is notnecessary.

Blenders, however, are items which youtypically want to turn on and add more andmore ingredients (adding more load) as theprocess progresses. What happens? Theblender slows down as the load increasesand it's real pain to have to keep adjustingit. If you're not careful, or in too much of ahurry, you can stall the motor quite easily.

Older electric drills and most high rpmgrinder never had any sort of variable speedadjustment, electrical or mechanical.Grinders fitted with a special 'pad' wheel areused for building, too. But you have to bequite deft, otherwise it's easy to buff rightthrough the undercoat of a painted objectbecause of the ferocity of the thing.

If you need to drill a particularly toughsubstance with an older drill, then you haveto be prepared to wear out the fine, sharpdrill tip very quickly.

So, there is a distinct requirement forsome device which can be placed betweenthe appliance plug and the power that can beused to not only set the motor speed, but toregulate it as well.

The perils of simplicityThere seems to be fundamentally threedegrees of complexity in the way one candesign these circuits, each with advantagesand disadvantages. All techniques employsome method of sensing the motor back-emfand adjusting the power delivered to keepthe back-emf relatively constant.

For the sake of attaching 'handles' toeach fundamental technique, I shall dubthem - the crude/economical method, therefined/economical method and the com-plex/ultimate method.

For this project I have chosen the mid-dle course for reasons which will become ap-parent shortly.

The crude/economical method is thesimplest and for that reason has an extra-ordinary advantage in that it has a low partscount. This sort of circuit requires a diode ortwo, a pot, a couple of resistors and littleelse apart from the SCR switching element(see Figure 1). Now, it is hard to beat thissort of economy, but such circuits have afew annoying limitations.

Firstly, they will not usually driveanything but the most sensitive SCRs be-cause they deliver very low gate currents.

18-JULY-1984-ETI

Fig. 1. An example of the crude/economical typeof motor speed controller. This is the circuit of theETI Speed Controller.

Secondly some component values can becritical, resulting in touchy or erraticresponse if tolerances are a bit out or theunit is driving an unusual motor. Lastly, thelack of an amplifying element in the feed-back means that the speed regulation, whilebeing above normal for a universal motor, isnowhere near perfect and the speed doesdrop under load.

To separate the two further types ofcontroller requires a reasonable familiaritywith what goes on when controlling auniversal electric motor, so I will discuss thetechnique I have used in this project nowand then go on to the explanation of furtherrefinement.

Fig. 2. Fundamental circuit elements of the con-troller used in this project. Note that Vdc is theback-emf of the motor.

Controller techniqueA universal electric motor appears as aresistance, an inductance and a voltagesource in series. The elements of the phasecontrol system I have used - an SCR and a`flywheel diode' - are connected as shownin Figure 2.

The voltage across the motor terminalsduring operation of this circuit will appearsomething like that shown in Figure 3. (Notethat the vertical axis is not to scale.)

Considering the cycle from the peakonwards, let us examine the reason behindthe appearance of each part of thewaveform.

Say that, at some speed setting, theSCR is fired into conduction at about the100° point of each positive half cycle. Theload voltage jumps to a value very nearlyequal to the mains voltage at that point (less

the small drop across the SCR) and followsthe mains cycle variation until the end ofthat half cycle (i.e. at the 180° point).

Thus, the point between 0° and 180°,of the positive half cycle, where the SCRfires, defines how much voltage is deliveredto the load (the motor). Varying the delaybefore firing provides a means of varyingthe power delivered to the motor. This isknown as phase control, for clearly obviousreasons.

At the point where the mains voltagefalls below the back-emf voltage of themotor you would expect the current throughthe motor to become zero and the SCR toturn off. But, this is not quite the case as theload is not purely resistive. The inductivecomponent of the motor forces its terminalvoltage negative in an attempt to maintainmotor current, and indeed, the load voltagewould follow the mains negative for someway if it were not for the diode connectedacross the motor terminals.

This diode conducts as the motorvoltage goes beyond about 0.7 volts negativeand carries the 'flywheel' current from themotor's inductance, generated by the col-lapsing magnetic field, allowing the SCR toisolate.

The flywheel current persists until theenergy stored in the motor's windings is ex-hausted. This takes typically two to fivemilliseconds.

Were the diode not there, a large nega-tive -going pulse would result. This, in itself,is not a bad thing, but it is easy to block thisand reduce the net dissipation in the SCR,allowing it to control a larger device for thesame ratings and prevents the need to makethe controller circuitry more complex toresist the negative -going voltage.

At any rate, some way into the negativesupply half cycle, the inductance ceases tobe the dominating voltage source within the

motor and the back-emf becomes evident.As you may see from the diagram, the

motor voltage rises to a level defined by theapparent dc source within the motor equiva-lent circuit. (The tack-emf generator').This voltage is a result of residual magnetismin the metal of the armature and field coilsand the relative motion of these twoelements.

The actual back-emf developeddepends on a number of factors, a majorone being speed so it is a good representa-tion of the motor's instantaneous speed.

There is some noise evident on theback-emf voltage, it is not a smooth dc level.This noise is partly due to commutationhash (high frequency spikes) and partly dueto different amounts of residual magnetismin different armature segments etc.However, the noise is not sufficient toobscure the speed signal, or back-emf.

In a typical universal electric motor theback-emf would average around 10 volts atfull rpm. The control circuitry in the con-troller looks at this dc signal and varies thepoint at which the SCR fires, increasing thedelay if the motor attempts to speed upunder decreasing load, or decreasing thedelay if the motor attempts to slow downunder increasing load.

The Perils Of ComplexityIt turns out that, in the case of most motors,a very satisfactory degree of speed regula-tion can be achieved with only a hint of hun-ting detectable at very low speeds. This ismost fortunate as it means that one does notrequire to advance to the next step of com-plexity, namely using the third techniquementioned earlier - the complex/ultimatecircuitry with its own compensating systemincorporated to guarantee the stability of thesystem under all conditions, despite largeloop gain.

Fig. 3 Waveform of the voltage across the motor when using the ETI speed controller. (Vertical axisnot to scale). The dashed line shows the power line input waveform.

ETI-JULY-1984-19

motor Controller

HOW IT WORKSThe speed of an appliance's motor attached tothe project, is controlled by applying themains voltage to it at a set point of the mainspositive half cycles, as seen in Figure 3. This isdone by turning an SCR on at the appropriatepoint in the cycle. Turning on the SCR earlierin the cycle applies more voltage, increasingthe speed, while turning the SCR on later ap-plies less voltage, decreasing the speed.

The SCR (SCR1) is 'fired' by applying apositive pulse to its gate. This is effected byICI, an optically -coupled triac driver contain-ing a LED coupled to pins 1 and 2 and a bi- 'i rectional optically -operated 'switch' coupledto pins 4 and 6. When the LED in ICI is off,the switch is off. When the LED is turned on,the switch conducts. If pin 4 is positive withrespect to pin 6, it will forward -conduct frompin 4 to pin 6, and vice -versa if pin 6 is positivewith respect to pin 4. So that only positive -going pulses are applied to the gate of SCR1,D3 ensures that the switch in ICI can onlyconduct during mains positive half cycles.

Resistor R6 simply limits the currentthrough ICI pins 4 and 6, while RIO preventsfalse triggering of SCRI due to small leakagecurrents.

The control electronics consists of Q1,Q2, PUTI, ICI, RV1 and associated com-ponents. The 'flywheel' diode is D6. Powersupply for the control electronics is derived bya half -wave rectifier from the mains input.This consists of D2, R2 and C1. This supply isregulated by ZD1, a 33 V zener, R2 providingcurrent limiting. Cl is charged up during themains positive half cycles and substantiallyholds its charge during the negative halfcycles.

The SPEED control, RV1 is part of apotential divider - R3/RV1/R4. The wiperof RV I sets a reference level on the emitter ofQl. This can be anywhere between about 4 Vand 15 V (with respect to the neutral line),depending on the setting of RV1.

Now, let us see what happens from thepoint where the mains positive half cyclescrosses through the zero point, going negative,at 180°, assuming SCR1 has been fired duringthe preceding half cycle.

Referring to Figure 3, as the mainscrosses through zero, going negative, D6 (theflywheel diode) will conduct, holding the ac-tive (A) load terminal at about -0.6 V. TheSCR then becomes reverse biased and ceasesconducting.

Capacitor C3 will have been charged to acertain voltage (via R12/R13), but will now bedischarged via D5. Any charge on capacitorC2 will be discharged via D4/DI/R1.

Diode D6 remains conducting until theinductive backlash of the motor (as explained

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in the text) dissipates. The voltage at the loadactive terminal (with respect to the neutralline) then rises to the back-emf level. D5 isnow reverse biased, allowing C3 to chargeagain via R12/R13 until it reaches the level ofthe back-emf + 0.6 V (D5's forward conduc-tion voltage). Small positive -going 'spikes' onthe back-emf level are ignored (momentarilyreverse biasing D5) due to the time constant ofR12/R13 and C3. This prevents erratic controlcircuit operation due to this noise. Neverthe-less, small fluctuations are still present in thenegative peak level held by C3.

Transistor Q2 is forward biased by thevoltage drop across R12. The collector of Q2sources charging current to C2, but this is helddischarged via D4/D1/R1 until the mainsnegative half cycle crosses the zero point andthe next positive half cycle begins. When itdoes, and Dl/D4 are reverse biased, C2 willcommence charging at a rate determined bythe collector current of Q2.

The programmable unij unction trans-istor (PUTI) has its gate held at about 4 V(with respect to the neutral line) by the poten-tial divider of R7 -R8. When C2 charges to 0.6V above this level, the PUT will 'fire', deliver-ing a current pulse to the LED in ICI. Thiswill operate the switch in ICI and SCRI willfire.

The rate at which C2 charges, determinesat what point in the cycle the PUT and thusthe SCR will be fired. There are twomechanisms for determining the rate at whichC2 charges, and thus the point in the cycle atwhich SCR1 is fired.

DE

Firstly, a reference level is set at the emit-ter of Q1 by the setting of RV1, the speed con-trol. The collector -emitter current of Q2 willdepend on the value of the voltage at thispoint and the value of R9, assuming the basevoltage is held constant. Thus, varying RV1varies the charging rate of C2, setting thepoint at which SCRI fires.

Secondly, the base current of Q2 varies(and thus the collector current) depending onthe voltage drop across R12. If the back-emfof the appliance motor falls, such as with anincrease in motor loading, the voltage held onC3 will decrease (pulled down by D5 conduc-ting current through the load) until it reachesthe new value of the back-emf plus 0.6 V (D5forward drop). This will increase the voltagedrop across R12 and thus increase the baseand collector current of Q2. Thus, C2 willcharge more rapidly each mains positive halfcycle, firing the PUT and SCRI earlier in thecycle. This applies more power to the motorso that its speed is maintained.

If the back-emf rises, such as it wouldfrom a decrease in motor loading, the voltageon C3 will rise and the voltage drop acrossR12 will decrease, decreasing the collector cur-rent of Q2. Thus, C2 in this case will chargemore slowly, causing the SCR to fire later inthe cycle. This will reduce power to the motorso that the set speed is maintained.

The function of R11 is simply to limit thecurrents in Q2 during those parts of the cyclewhen Q2 is not responding to the back-emfsignal.

The reason that this type of circuitry isto be avoided, for the applications con-sidered in the introduction to this article, isthat it would require a great deal more elec-tronics (and cost!). This would basically en-tail a mechanism capable of smoothlyholding the back-emf signal so it could befurther processed, which means some kindof sample -and -hold gate plus some syn-chronizing signal. Once isolated, the signal iseasily dealt with, but the process is much

more complex than the simple instantaneousmethod employed in Fig. 1.

One further refinement in a complex/ultimate controller may occur to the astutereader: namely, having the circuit capable ofusing the full 360° (or very nearly) of themains supply cycle. The systems describedso far, all assume that an SCR will be usedto control the current delivered and not atriac. Hence, at most, only 180° of themains cycle is available as the SCR must re-

main in a blocking state during the negativehalf cycle. Although a triac would permituse of the negative cycles, as would full -wave rectifying the mains before applying itto the SCR, these methods have one pro-blem.

The sensing of speed, so that the speedmay be regulated, requires access to theback-emf voltage, blanked immediatelyafter a current zero. Hence, any attempt toemploy near -continuous power application

20-JULY-1984-ETI

Inside. Construction is quite straightforward - but take heed of the safety precautions mentioned in thetext! Note that in use there may be a slight 'dead band' at either end of the speed control rotation wherenothing happens.

would be hampered by the inductive'backlash' concealing the motor's true back-emf value. Any such system would have tobe capable of operating in a mode which leftonly every fourth or sixth half cycleunemployed for the purpose of 'getting at'the back-emf for speed sensing.

While possible, this would not only re-quire considerable circuitry, but would alsotend to impart some roughness to the torquedelivered. Hence, such methods are wellabandoned for the applications for whichthe controller has been designed. It is arealm of circuit complexity which returnsbenefits only with physically large machines.

Back To The ProjectThe controller has been deisnged to be agood compromise between the crude/economical and complex/ultimate con-troller. Speed can be set from full rpm on noload (at 'half power') down to less than one -tenth normal. This is lower than you're everlikely to need. On low speeds and withoutany load there is a tendency for motors to'hunt' about the set speed, power being ap-plied in detectable jerks. But, even when on-ly a light load is applied, this has the effectof damping the control loop, improving thecontrol and smoothing out the variations.

The torque characteristics of the circuitare excellent, until you approach the 180°limit of the cycle - which is, in any case,way beyond what you will need in commonsituations.

A good 'worst case' example is that ofmaking houmous, a particularly thick andpasty (tasty, too!) dip in a blender. Initially,the mixture is oily, but as the blending pro-ceeds it changes to a very glutinous con-sistency and blenders invariably begin tolabour agonizingly at this point. With thecontroller in control - no problems!

ConstructionSafety is a major consideration in a projectsuch as this. Choosing a box in which tohouse the components has to be donecarefully because the project will be used in

a work environment, and is likely to en-counter more than the usual amount ofrough treatment.

I chose a strong, but not brittle, plasticcase which comes in two halves, secured byrecessed self -tapping screws that set intoplastic pillars in the bottom half of the case.

Shape is unimportant, along with size,just so long as all the components can be fit-ted with ease and the box is not overlay.large. If you choose a box with a metalfascia or panel, make sure this is securelygrounded. If you can, get a box which pro-vides internal posts to which the pc boardand SCR mount can be secured with self -tapping screws so that no metal parts attach-ed to these can protrude through the exteriorof the case. If you must use a case thatdoesn't meet this requirement, secure 'theworkings' with nylon nuts and bolts. All thisis for your own protection.

The potentiometer used was of the con-ventional type, having a metal case, bushingand shaft. I grounded the pot. case, asshown in the wiring and overlay diagram. Ifpossible, it would be an even better idea toobtain a pot. with a plastic bushing andshaft.

The mains cable must be firmly securedwith either a clamp -type grommet where itenters the case, or with an ordinary grom-met followed by a cable clamp. I used both aclamp -type grommet and a cable clamp, forgood measure. (That's probably overdoingit, but, please yourself - Ed.)

Best place to start assembling the pro-ject is by drilling the few necessary holes inthe box. If you are making a direct copy ofthe prototype, then positioning of the majorcomponents is clear from the internalphotograph. If you're using a different box,then arrange the major components firstand determine where you have to drill holes.Don't crowd the parts against one another.Use the blank pc board as a template formarking its mounting hold positions.

If you're using an SCR type that is notin a stud -mount package, then you'll haveto arrange a suitable mount for it. I used aC220D type in a stud -mount, screwing it toa small piece of aluminum which also serves

PARTS LIST

Resistors (all 1/2W, 5% unless noted)RI 56kR2R3R4R5R6R7R8R9RIORI 1R12R13RVI

CapacitorsCIC2C3

22k, 1W82k27k33k1k527k3k38k2I k

10k100k15k100k/A linear pot.

22u/35 V RB electrolytic100n10n

SemiconductorsDl -D5D6ICIPUT1Q1,Q2SCR1

1N4004, EM410 etc.1N5404, 1N5606 etc.MOC3021 triac opto-isolator2N6027, DI3TI etc.2N3905any type, 400 PIV/6A orgreater

Miscellaneouspc board; case - 135 x 100 x 38 mm orsimilar size to suit; 3 -pin panel -mount mainssocket; mains cable and plug; small scrap ofaluminum, self -tapping screws; screw terminalblock; etc.

as a heatsink of sorts. SCR dissipation issmall, so this heatsink/mount need only besmall.

Just bolt the SCR to the heatsink with-out any insulator, and use some thermalcompound to improve thermal contact bet-ween the body of the device and the heat -sink. REMEMBER - the heatsink will beat MAINS POTENTIAL, so make surewhen mounting it that no securing bolts pro-trude through the case or use nylon nuts andbolts.

I mounted the SCR separately to the pcboard so that a wide range of SCR types andpackages could be readily accommodated,from the stud -mount C220D I used in theprototype, to small 6 A -rated, flange -mountplastic pack devices.

It is difficult to specify a 'load rating'for the project in terms of the SCR'scharacteristics, because of motor surge cur-rent characteristics and the range of motorratings in appliances. A 6 A -rated SCR willhappily handle an appliance rated to draw anominal 2 A under 'normal' load. TheC220D used in the prototype will reliablyhandle an appliance rated at four to fiveamps, right up to full revs setting underalmost -stalled -rotor conditions.

Before attaching the 3 -pin panel -mountmains outlet socket to the outside of thecase, attach colour -coded wires to its ter-minals and thread these through the holesdrilled for them in the case. Take care that

ETI-JULY-1984-21

Motor Controller

SCR1

brown

brown

OUTPUT TOAPPLIANCE

blue

brown

tCt

rT R5cr

power socketA i viewed from rear

SPEED

band

Diodes

PUT1a9

01,02

CABLECLAMP

yellow greenlongest)

screwterminal

yellow green

MAINSLEAD

ci

11

Overlay and wiring diagram. Follow this to assemble the pc board and wiring up of the external com-ponents.

you get the active (A), neutral (N) andground (G) wires correct. Use wire from ashort length of stripped -down mains flex.

When attaching the power cable, cutback the sheath so as to expose some 150mm of the three wires to provide connec-tions later. Make sure the cable is very firm-ly secured.

Mount the potentiometer using nuts onboth sides of the case panel and lock thebushing tight so that there's no possibility ofthe pot. body coming loose and beingrotated when the knob is turned.

Assemble the pc board next, accordingto the overlay diagram. You'll find it easierto solder the diodes in place first, followedby the resistors, capacitors and the rest ofthe semiconductors. As usual, watch theorientation of all the semiconductors andthe electrolytic capacitor (C1).

Having done that check it. Make anespecially careful examination of the solder-ing as diagnosis of problems will bedangerous and/or difficult later, because theboard operates 'live'. In other words, if youare going to make only one project workfirst time this year, make it this one.

Attach the three wires that go to thepotentiometer. Better colour code or markthese in some way to avoid confusion andwiring errors. Make sure they're longenough. Ordinary hookup wire will do for

these. An ordinary piece of hookup wire canalso be used for the lead to the SCR gate.The leads to the SCR anode and cathodecarry mains potential and load current andshould be wired using mains -rated wire. Getit from some stripped -down mains flex, likebefore.

Now wire up the mains input cable andthe mains outlet socket to the pc board, thencheck it.

Note that the ground wire on the mainsinput cable should be longer than the activeand neutral wires. Should the mains cablecome adrift, the ground wire would then bethe last to break.

The Try OutWhen you're satisfied that the project is cor-rectly together, it's time for a try -out. Justplug in your drill, blender, or whatever intothe outlet socket, set the speed pot. a bit upfrom minimum, plug the controller into themains, and switch on. See that the ap-pliance's motor rotates at some low speed.Advance the speed control and see that themotor speed increases, as expected. Ifnothing's happening at this stage, switchoff, unplug everything, and go over yourwiring (this assumes you know the applianceworks).

If that works, then try applying a loadwith the motor set at some convenient speed

and see that the controller maintains themotor speed. If not, you've got troubles onthe pc board and you'd better unplugeverything and go over it.

If you are using the unit with anunusual motor, where the inertia of the ar-mature may be greatly different to that ex-pected by this circuit, you can vary the gainof the feedback amplifier by simply chang-ing the value of R9. This can be varied bet-ween a minimum of about 150 ohms and amaximum of 22k.

Thus, if the motor hunts excessively(especially at low speed settings), R9 may beincreased from the 8k2 value shown, reduc-ing feedback loop gain and restoring stabili-ty at a small price in speed constancy. If thereverse is the case, you can acquire tighterregulation by reducing R9 - but check thathunting is kept to a minimum.

Finally, several words of caution are inorder. The power bursts which are appliedto the motor by the SCR switching and thecontrol system variations with the motor ar-mature running at low speed, applies a lot ofstress to the motor's brushes and armaturewindings, so the controller should not be us-ed in applications where it's not reallynecessary. Wear from the controller's use isunlikely to significantly shorten the life of anappliance, but it is never good practice tostrain a mechanical device unnecessarily.

In addition, many appliance motors,particularly drills, employ a small coolingfan on the armature. The cooling effect ofthe fan is reduced, and extended periods ofoperation at low speeds should thus beavoided. Ell

22-JULY-1984-ETI

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ETI-JULY-1984-23

A Look atthe Sinclairs QL

A giant step forward . . . or aleap in the dark?

CLIVE SINCLAIR, British designer of theZX-80/81/Spectrum computers, and nowSir Clive, is about to have another go atcapturing the lion's share of the micromarket. Sales of the Spectrum (neverreleased in Canada) were excellent, and SirClive expects to do the same with his newQL (for Quantum Leap).

The QL retails for 399 pounds sterl-ing, between $800 and $900 Canadian.North American release is planned for thefall, but production shortages may meandelays.

As pointed out at its launch, there isno other computer offering anything likethe power of the QL at anything near theprice; the inclusion of four useful and welldesigned programs is a nice touch, and asensible precaution against one of the mostserious threats to a new computer - lackof software support. This is a marketinglesson which Sinclair has learnedthoroughly but which others absorb only atgreat cost.

But then marketing is largely whatSinclair Research Ltd. are all about. Themethod is easily grasped, if not so readilyfollowed by companies with less nerve.Somehow Sinclair manage to make and selltomorrow's computer today, at yesterday'sprice. It is a leap -frogging process thatreverses the normal procedure by whichmarketing -men take surveys to determinewhat the public wants, and then producewhat they think the public needs. It is atechnique (which has worked so far)whereby a new and innovative producecreates its own market: after all, was there

24-JULY-1984-ETI

tion, two custom chips are employed: oneis dedicated to memory management andthe display, while the other looks after thetwo microdrives, the local area networkand RS232C transmission. A real-timeclock is also included, maintained by aback-up battery - a most useful facilitywhich, in the age of digital watches, is inex-plicably missing from most computers.

Internal RAM stacks up at a fairlymassive 128K, of which 9K is free to theuser; an 0.5 Mbyte expansion board is pro-mised, which will take total RAM to 640K!The 32K ROM contains the new QDOSoperating system, which promises to bevery interesting, and an enhanced versionof Sinclair BASIC, dubbed SuperBASIC.

QDOS is described as " . . . a singleuser multi -tasking, time -sliced system. . ."and was developed to take advantage of thepower of the 68008 CPU. Multi -tasking(the ability to handle several jobssimultaneously) allows the QL to runseveral programs at once, each with an in-dependent screen window -a feature nor-mally available only on far more expensivecomputers.

SuperBASIC offers several im-provements over the old Sinclair BASIC.For a start it incorporates the structuredPROCedure format used by BBC BASIC;it is also said to be user -extendable and torun at a constant speed, so that programexecution time does not depend on thelength of the routine. Other features in-clude easy interfacing to machine code,and access to the QDS operating system.

In And OutThe QL's keyboard has a full sizedQWERTY layout with sixty-five keys in-cluding a space bar, five function keys and

really a demand for a small inexpensivehome computer until Sinclair released theZX80? The QL may well follow the samepattern.

The QL is very carefully positioned tobridge the gap (if there is one) betweenhome and business computer users: on theone hand it is cheap enough to competewith the Acorn/BBC, Commodore 64 andthe like, but also powerful enough (at leastpotentially) to compete with Apple, CBMand even the IBM PC. Yet Sinclair candid-ly admit that although they see the QLprimarily as a business machine, they haveno idea what uses the QL will ultimatelyfind in the hands of the target 3.5 millionusers world wide. In other words havingcreated a supply, they earnestly hope thatdemand will follow!

Certainly the QL has features to at-tract interest from all sections of thecomputer -buying public, and promises tobe an interesting machine to explore.

Inside StoryThe specification of the QL is worth con-sidering in detail. The main processor isMotorola's MC68008, the baby of the68000 family but nevertheless a mostpowerful CPU. It has a 32 -bit internalstructure and is fully compatible with68000 code. The 20 -bit wide address buscan directly access 1M byte of memory (ormemory -mapped I/O), but the most attrac-tive feature to Sinclair must have been its8 -bit data bus, which means the 68008 canbe operated with standard byte -widememories and support chips.

As well as the 68008 the QL includesan Intel 8049 8 -bit CPU with 2K ROM and128 bytes of RAM on the chip. Thishandles the keyboard, sound generationand the RS232C receive function. In addi-

four separate cursor controls. It is, ap-parently and a last, a proper keyboard!

Two microdrive units are built in, anda further six can be daisy -chained onto theexpansion socket. However, these must beQL Microdrives; those made for Spectrumcannot be used, though the cassettesthemselves are compatible if formatted forthe QL.

A port at one end of the computer ac-cepts ROM cartridges up to 32K in capaci-ty, but once more ZX ROM cartridges arenot suitable.

The QL offers alternative display out-puts. Best quality is obtained from theMonitor port, which will drive either anRGB or a monochrome monitor. Twographics resolution modes are available:512 x 256 pixels with a choice of four col-ours (red, green, black, white, plus a 'stip-ple' feature) or 256 x 256 with a palette ofeight colours. Normal character format ona monitor display is 25 rows x 85 columns.

The UHF TV output display modesare similar, but the use of the stipplefeature is not recommended and thecharacter format is typically forty sixcharacters, depending on software.

Other features built into the QL in-clude a local area network (QLAN) pro-viding a link -up for up to sixty-four QLs orSpectrums, two RC232C ports and twojoystick ports.

Onwards And OutwardsIn addition to the 0.5 Mbyte memory ex-pansion, an interesting list of peripheralsand extensions is planned for the QL. Themost important of these are the 68000assembler, the analogue/digital interface,Winchester (hard disc) interface, modemand the parallel printer interface.

Finally there is the manual. A previewcopy was released to interested journalistsat the press launch, and while it would beunfair to criticise it at this stage it is plainlyincomplete, with large sections either miss-ing or very skimpy; one hopes that the finalstyle is less opaque than that of the draftversion. Bad documentation is un-

forgivable and a sin which infuriatesreviewers and often leads to unfavourablecomment on the computer itself.

SoftwareThe 'software suite' supplied with the QLwas written and licensed from Psion andconsists of four integrated programs: QLAbacus, a spreadsheet; Archive, a datamanagement/filing system; Easel, agraphics design program; and Quill, awordprocessor.

All four are supplied on Microdrivecassettes and make extensive use of theQDOS operating systems, capability forseparate screen windows. At the top of thescreen is a Control window, which at alltimes displays a list of current optionsavailable, to the user; few lines of thescreen to show information about the workin progress; and the Display window, alarge area across the middle of the screen,shows the work.

The screen format is identical in allfour programs, as is the command struc-ture, so the learning curve for the completesuite is likely to be quite short. In additiondata is transportable from one program toanother so that, for example, businessgraphics can be generated from data im-ported from the spreadsheet.

Many other tasty features are listed inthe documentation, including many foundonly on up-market business computers, sothe indications are that the QL softwaresuit will be a joy and a delight to use -Murphy's Law permitting.

Paper TigersLest readers begin to think that the QL isall things bright and beautiful, a flawlessexample of computing engineering unmat-ched by any other, it has to be said that theQL does have a few shortcomings. Indeedthe sceptics have already compiled a list ofthem.

The most serious criticism is the com-plete lack of a facility found on every com-puter in the QL's price range . . . a cassetteinterface (it's worth mentioning that a flop-py disc interface is missing, too).

The implication of this is that cheapsoftware is unlikely to be available forsome time, because blank Microdrivecassettes currently cost around $15.00 atretail prices, and the medium is not suitablefor high speed duplication either. Taking aslightly longer view, though, it will pro-bably not be too long before add-oncassette and/or floppy interfaces areavailable. Another possibility is that soft-ware houses will go for ROM -based pro-grams, though this development must waiton the release of the 68000 assembler.

The Microdrive system itself is not yetproven to the satisfaction of many buyers.However the QL Microdrives may provemore efficient than those made for the

Spectrum; according to the provisionalmanual, QDS routinely stores as many filesas possible in spare memory, reducing wearand tear on the tape and greatly increasingaccess time. And the 0.5M byte RAM packprovides a very substantial amount of sparememory! Another serious albeit temporaryproblem; is the lack of a parallel printer in-terface.

The remaining criticism of the QL (sofar) have about them a faint aroma of sourgrapes. Complaints have been made aboutthe use of the 68008; its data bus is only8 -bits wide rather than 16, so it will be onlya quarter as fast as the 68000 because it hasto perform four times as many fetches; andwith a clock speed of only 7.5MHz and QLwill be slower than some of the faster 8 -bitcomputers. Well, I wouldn't bet on it.

In fact both the 68000 and the 68008fetch instruction in pairs of bytes (words),so there is not all that much difference bet-ween them, and Motorola data shows thaton a 'quick sort' bench -mark test the 68008clocks in only 10 milliseconds slower (30%)than the 68000 CPU running with amemory management unit. And at first ap-pearances, the 68008 instruction set looksextremely powerful and compact (a pointmade several times by Motorola in compar-ing their 68000 family CPUs with other16 -bit processors), so machine code pro-grams should run very quickly on the QL.

The remaining criticism to date con-cerns the choice - or rather the lack ofchoice - of colours in high resolutiongraphics mode. This criticism is relevantonly to dedicated games -players, and evenso its ultimate strength will depend on theeffectiveness of the stipple feature in pro-ducing shades and tones.

Of course there will undoubtedly beother valid criticisms of the QL (it would betoo much to expect any computer to beperfect) and these will show themselveswhen review models become available.Then experience will tell whether or not theQL lives up to its specification. The QL willnot win kudos for the missing cassette in-terface, but this is not an insoluble pro-blem: where Sinclair leads, others tend tofollow, and if fast performance is anyguide the QL and its add-ons will be everybit as successful as earlier Sinclair com-puters. ETI

ETI-JULY-1984-25

Coping withComponents Part 2

This month we conclude ourseries on component identifica-tion with a look at capacitors.

CapacitorsA CONSIDERABLE variety of capacitortypes are now available to the hobbyist,and most people will have a junkbox withmany capacitors which are of unknowntypes, or carry strange markings in-dicating the values. The tables given hereshould identify most of the values, andthe text and illustrations, the type ofcapacitor. It is important to select the cor-rect type of capacitor for the job, asalthough there is some overlap in manyapplications, each variety has particularattributes which will make it more suitablefor some purposes than others.

All capacitors are, of course, able tostore electrical energy and consist of twoparallel conducting surfaces separated byanother material, which is an insulator,and known as the dielectric. The cheapestsuch dielectric is air, although the hob-byist will normally only meet this invariable capacitors (see later). The com-monest dielectrics in fixed capacitors aremica, ceramics, paper, plastic and lesscommonly, oil, with other materialssometimes being used.

As DC current cannot flow through acapacitor, they are often used to separateDC and AC signals within a circuit. Nordoes AC current actually flow through thecapacitor - the movement of electronsfrom one electrode to the other only givesthis appearance.

The amount of electrical energywhich can be stored depends on the valueof the capacitor, and the dielectricmaterial used in its construction will deter-mine the relative size for a particularvalue. A vacuum is used as a reference forthe 'dielectric constant' with a value of 1- higher vlaues give the amount ofenergy stored per unit/volume as a ratioto this reference. Most plastic dielectricssuch as polyester and polycarbonate haveconstants of around 3, mica around 6,and tantalum about 11. One material,barium titanate has a dielectric constant

up to 15,000 and is used in the dielectric ofmany ceramic types to achieve the veryhigh capacitance/volume ratios in lowvoltages.

Temperature stability is often impor-tant, and especially in RF oscillator cir-cuits, attention must be paid to thischaracteristic. It is usually expressed inparts per million (ppm) per degree Cen-tigrade temperature change, and may bezero, positive, or negative.

The tolerance against the markedvalue of any capacitor will depend on itsconstruction - in the case of electrolytictypes, this may be as much as -20/ + 80%in any unit. However, this is usually not aproblem in electrolytic applications, butshould be kept in mind if the value hasbeen calculated for any applications. Inthe opposite direction, mica types areavailable with tolerances of 1 or 2%, butof much lower capacitance value.

Paper CapacitorsCommon some years ago, these havetended to be less frequently used. They areconstructed by winding alternating stripsof metal foil and paper into a roll withleads attached, or inserted into each end,

Table 2Capacitor Markings

Polyester capacitors have the same codingas resistors with first significant figure ofvalue at the top of the capacitor. An addi-tional band at the end will indicate theworking voltage: brown = 100 V, red =250 V, yellow = 400 V.

Ceramic capacitors are usually marked withtheir value in figures (the old band mark-ings have virtually disappeared) i.e., 22p =22pF or 2p2 = 2pF2.

The "n" system is also frequently metwhere if the "n" precedes the figure, it is amultiplier of i.e., n22 = 220pF; or if itfollows the figures, it is a multiplier of1000: i.e., 10n = 10,000pF, 220n =220,000 pF. Note that:

1500pF = .0015uF = 1n5

Also, another method is two significantfigures plus multipler to the power of 10,i.e.,:

104 = 100,000pF (100n or OuF1)102 = 1,000pF (In or OuF001)

then impregnating with wax or a syntheticmaterial, before environmental protectionby means of an outer encapsulation.

The method above gives a capacitorwith appreciable inductance - this can bereduced by a slight variation in themethod of winding the layers when thefoils are wound, so that they can be crush-ed together at the end and the completeend is then soldered to the wire lead.

These capacitors are best in voltagework, although the fact that paper willeasily absorb moisture can lead to pro-blems - the insulation resistance disap-pears quickly. Audio work was a commonapplication at one time, but plastic basedtypes are now normally used to theirsmaller size and better electricalcharacteristics.

Mica CapacitorsMica is a natural mineral (although syn-thetic mica is now made) normally foundind in granite rock formations, and hasthe advantage of being totally inert, and agood insulator. It is also extremely stable(although it does absorb moisture) mak-ing this material excellent for high stabili-ty work, with a temperature coefficientnot exceeding ± 100 ppm, and it iscapable of passing high RF currents.

Mica capacitors are constructed byassembling alternating sheets of mica andfoil, with the foil overlapping the micasheets at each end. Alternating foils arethen wrapped together and leads attachedto opposite sides, covering the wholeassembly with a dipping of epoxy resin, ora moulding to prevent water contamina-tion. Tolerance specifications vary from± 20 to ± 1%. In the 1% ranges,capacities up to 50pF are often alter-natively specified as ±OpF5, due to thepractical difficulties in obtaining ± 1% atlow values.

A particular variety of mica capaci-tors, normally referred to as 'silver mica'are widely used in RF oscillator circuits,due to their excellent stability. The con-struction is different to the normal mica,as a thin film of silver is formed on eachside of the mica sheet to act as electrodes,before impregnation, lead attachment andepoxy -encapsulation. Temperature coeffi-cients are around + 30-50 ppm.

Where the leads inductance would bea problem, a specially cased version isavailable without leads where the layersare sandwiched between metal clamps.

26-JULY-1984-ETI

131

32

23

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10 4

POLYSTYRENE

8

SILVERED MICA

3.2 5.1 °I

91

2.54

TMONOLITHIC CERAMICSRESIN DIPPED

9

6.51

DISC CERAMICS

I2.5

TSUBMINIATUREPLATE CERAMIC

Polystyrene capacitors offer high insulationresistance with good electrical properties.

Nllca capacitors are used where high stability isrequired.

Ceramic capacitors are available in a numberof different forms, each suited to a particularapplication.

N.B.: All dimensions in millimeters. Allcapacitor sizes vary according to the value;those shown are typical of each type.

These can be soldered directly to a printedcircuit board, and are often used inVHF/UHF RF transmitter applications('UNELCO' type).

Ceramic CapacitorsFor a variety of case sizes, and confusingmarkings, it is difficult to beat the ceramiccapacitor, probably most familiar in itsround disc form. They are widely used indecoupling applications and at RF, asthey have low series inductance, and innearly all low capacity (up to about OuF1)non -critical applications. The dielectricmaterial is normally an inorganic ceramiccompound, with the higher capacitancetypes using one, or a mixture, of thehigher dielectric constant substances suchas barium titanate, mentioned earlier.

Silvered electrodes are formed on eachside of the dielectric to which leads are at-tached, prior to covering with an epoxycoating for protection.

These high volume/capacitance ratiotypes are often referred to as medium orhigh K types (K being the dielectric cons-tant) and have a number of disadvantagesover the lower value type (up to about400pF) which use lower K materials. Theirtemperature coefficients are extrerr-lyhigh (tens of percent in some cases), andthe capacitance is affected by the level and

temperature coefficient groupings. Thevariation is from ± 30 to ± 1000 ppm, ingroups, and as the change is linear, theyhave considerable use for temperaturecompensation in oscillator circuits. Thecase is often rectangular or square (with athin cross-section) and a colour top iden-tifies the grouping - these are often refer-red to as plaquette types. Tolerancegroupings can be as low as 201o.

One of the recent introductions is themonolithic ceramic capacitor; which cangive a very high capacitance for a very

10.5

4

5

ALUMINIUM ELECTROLYTICDOUBLE -ENDED AXIAL)

1.5

SUB -MINIATURE(RADIAL)

Electrolytic Capacitors: Axial electrolytics (top) are available in values up to 47000, and at voltageratings to 450 V. Radial types, either standard of subminiature (shown at bottom), are supplied in morerestricted value and voltage ranges, but take less space on a printed circuit board.

type of voltage (AC/DC) present. Al-though they are both excellent fordecoupling in solid state circuits both forlogic and RF, they have no place in RFfrequency determining applications.Tolerances are often in the 20/ + 80%region.

When selecting a ceramic capacitorfor RF decoupling purposes, use values of.01uF for use up to about 15MHz;.0047uF to about 80MHz; .0022uF up to120MHz; and 100pF (.001uF) to around400MHz.

The smaller values have much morepredictable temperature coefficients andgood stability, and are available in

12.5

12

182 MINIATURED CASEIErjPIEATURE

Polyester Capacitors: The example shownabove is the familiar "C280 Polyester"capacitor. The dimensions are typical forvalues to 47n.

small size, together with a low AC im-pedance, making them ideal for high den-sity solid state coupling and decouplingwork in logic circuits, although they aremore expensive than other ceramics.

Construction is by sandwiching alter-nate layers of ceramic compounds andresins and metal electrodes to form a largemulti -layer unit. After heat processing,the blocks are cut into small units, thearea determining the capacity value,solderable and encapsulations added, andin this form can be used as 'chip'

115

to

8.5

98 MINIATURE LAYER

Polyester Capacitors: The box -like, silver col-oured capacitors are sometimes referred to incatalogues as "Siemens" type, after themanufacturer.

ETI-JULY-1984-27

Coping with Components

POLYESTERENCAPSULATEDAXIAL LEADS

18

Polyester Capacitors: Axial polyester types are especially rugged and useful for high temperature en-vironments; working voltages to 400 V DC (200 V AC).

capacitors (with minimal inductance andsuited to automatic insertion), or haveleads applied plus encapsulation to give anormal style capacitor. Besides the High Ktype, they can also be obtained intemperature compensating styles and ultrastable forms. Tolerance ranges are similarto the other ceramic types.

Tantalum Electrolytic: Preferred for accuracyin i.e., timing, filter circuits. They have verylow leakage currents and good stability, butcannot withstand reverse voltages.

Plastic FilmThe most common type is the polyesterfilm capacitor which find wide applicationin DC circuits. The most familiar type willbe the Mullard C280 type, which is alsometalized and which look like lozenges,encapsulated in a hard lacquer case.Tolerances are around 10 to 20%, with ahigh temperature coefficient of about20%. Construction is similar to that ofpaper types, with the plastic film replacingthe paper.

Polycarbonate types find applicationin AC circuits as they have a very lowpower factor (power factor is the ratio ofimpedance to resistance). The tempera-ture coefficient is very low. If you need todecouple AC mains input lines, this is thetype to use.

Polystyrene is an extremely goodmaterial for capacitors, as it has excellentstability, and a very slight negativetemperature coefficient. The latter pro-perty can be put to good use in compen-sating for the positive temperature coeffi-cient of mica capacitors in oscillator cir-cuits. Care needs to be taken in soldering

these, as it is easy to damage the plasticand short out the metal layers aspolystyrene will melt at 90 degrees Cen-tigrade. Tolerances down to 1% can beobtained.

Metalized variants of some of theabove are common - the plastic film iscovered with a few microns thick layer ofmetal particles, often by vacuum deposi-tion - and produce a higher capacity in asmaller volume. Use for DC applications.

Electrolytic TypesEveryone will be familiar with this type ofcapacitor, although modern technologyhas produced many variants under thisgeneral title. The major difference bet-ween these and the previous types ofcapacitor, is that we are now dealing withan electro-chemical construction, ratherthan a passive one. They have manydisadvantages, but despite this are widelyused in virtually all high (greater than 1

microfarad) capacitance DC applications.There are two main types of elec-

trolytic capacitors - aluminum and tan-talum.

Aluminum ElectrolyticIn these, which are the traditional type,two aluminum foils are separated by in-sulating paper and wound into rolls.These rolls are then impregnated with anelectrolyte, and after electrical stabiliza-tion, sealed into an aluminum (orsometimes plastic) container.

The normal types are 'polarized' i.e.,they have positive and negative terminals.The anode, or positive terminal, is one ofthe aluminum foils, with a layer of oxideformed on this foil as the dielectric - theoxide is actually formed as DC current ispassed through the capacitor. The type offoil used affects the capacitance, with anetched foil providing a greater contacterarea with the electrolyte which forms thecathode, and therefore a much greatercapacitance over plain foil types. The

other foil contacts the electrolyte and con-nects the outer world. In many cases, thecase is also the cathode, and may becovered in a wrap of plastic as insulation.The paper interleaves serve to preventshorts between the two electrodes, andhold everything in close contact.

It is possible to obtain non -polarizedversions, which can be used in AC oraudio applications - you can make yourown by connecting two polarized capaci-tors back-to-back. Never apply ACvoltages to polarized capacitors - yourun the risk of an explosion which can oc-cur if the capacitor is overloaded. Ifpolarized electrolytics are to be used in AFapplications, a DC bias must be appliedwhich is greater than the peak AC voltageto prevent damage.

POLVCARBONATEENCAPSULATEDRADIAL LEADS

Polycarbonate: The material has better elec-trical characteristics than polyester and shouldbe used instead, in ore critical situations. Abrass -encapsulated axial form is available forsuper -critical (i.e., high temperature) applica-tions where price is of no concern!

The electrolyte used depends on theapplication, but it should be able to repairany damage to the oxide film, and also torecombine any gases evolved by DCleakage current. If this does not happen,pressure will built up in the container withobvious results - larger units usuallyhave a pressure relief arrangement toavoid danger.

Electrolytic capacitors have a largeDC leakage current compared with othertypes, and this factor may be important ifthe capacitor charge is critical, as say intiming circuits. After a period on the shelfnot being used, the oxide layer can start todisintegrate and allow a very large leakagecurrent to flow. If full working voltage isapplied in this condition, the capacitorcan be seriously damaged - it should bereformed first over a period of hours bypassing a small current through thecapacitor via a 10-15k resistor, until theleakage current has dropped to a lowstable value.

Values of electrolytic types vary fromOuF1 to one farad, and the sizes from verysmall PCB mount types with wire termina-tions (either axial or radial), to be verylarge computer grade types (high rehab&

28-JULY-1984-ETI

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Using this new technology, the industry is offeringcompact, affordable computers that handle things likepayrolls, billing, inventory, and other jobs for businessof every size... perform household functions includingbudgeting, environmental systems control, indexingrecipes. And thousands of hobbyists are already owners,experimenting and developing their own programs.

Growing Demandfor Computer Technicians

This is only one of the growth factors influencingthe increasing opportunities for qualified computertechnicians. The U.S. Department of Labor projects overa 600% increase in job openings for the decade. Mostof them are new jobs created by the expanding worldof the computer.

Learn At Hometo Service Any Computer

NRI can train you for this exciting, rewardingfield. Train you at home to service not only micro-computers, but word processors and data terminals, too.Rain you at your convenience, with clearly written"bite -size- lessons that you do evenings or weekends,without going to classes or quitting your present job.

Your training is built around the latest model ofthe world's most popular computer. It's the amazingTRS-80111 Model 4, now with disk drive and the capa-bilities and features to perform a host of personal andbusiness functions. No other small computer has somuch software available for it, no other is used andrelied on by so many people. And it's yours to keep forpersonal and business use.

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advanced. You analyzeand troubleshoot usingthe professional 4 -function1,CD digital multimeteryou keep to use later in your work. Then you use thelab and meter to actually access the interior of yourcomputer...build special circuits and write programsto control them. You "see" your computer at work anddemonstrate its power.

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Coping with Components

t y), with screw terminals. Workingvoltages are equally varied from 3 V forhigh capacity miniature PCB types to400/600 V for power supply applications.Tolerance groupings are wide - often-20/ + 80% against nominal markedvalue.

Tantalum ElectrolyticThis material is very popular in the formof tantalum bead capacitors, allowingminiature capacitors which are very stableand have long life - however, most can-not withstand reversed polarity to any ex-tent. The construction of tantalum foiltypes is similar to that of aluminum types,but using tantalum in place of aluminum.In this case, the size will be similar to analuminum one.

In wet -slug and solid electrolytetypes, the anode is a pellet of masses oftiny tantalum beads partly fused togetheror a sintered pellet; covering these with alayer of oxide gives a vast increase incapacitance over aluminum types for agiven size. The DC leakage current isgreatly reduced and there are no shelf lifeproblems; together with the size reduc-tion, these factors make them verypopular in high density solid state work,although their cost is appreciably greater.They are very useful for timing circuits.

DACE is:

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Send for fret catalogue full of other fineproducts.

Send cheque or money order:J.A.C. Electronics P.O. Box 83, Stn. "E"Montreal, Quebec', H2T 3A5 (514) 270-6730Que. res. please add 9% P.S.T.(add 5% Shipping & Handling)

5

Polyester. This is a metalized film capacitor us-ed in computer circuits and for professional ap-plications.

Variable TypesThese are generally known as 'tuning'capacitors, and are normally air spaced,although vacuum types are available forhigh power transmitting applications. Theevolution of the transistor radio has alsobrought with it the plastic dielectricvariable which offers high capacitancevariation in a small, low cost package(sometimes referred to as 'polyvaricons').Finding the larger high capacitance typesis not so easy as it once was, as solid statehas virtually eliminated the need for them,but rallies are useful sources if they areneeded - otherwise they are expensive tobuy new.

The air spaced types are available in awide variety of sizes, capacitance, andvoltage combinations. Multi -section typesganged together are common, and oneparticular type allows one-half of the gangto increase capacitance as the other halfreduces. They are constructed fromparallel sets of intermeshed plates, one setof which can rotate. The rotating platesare known as 'rotors' and the fixed platesas 'stators'. They are usually made ofaluminum, brass, or copper, and may besilver plated in the last two cases for highfrequency applications. The capacitanceavailable is determined by the area of theplates, their number, and the air gap bet-ween them.

Varying the shape of the plates asthey mesh, is sometimes used to give alogarithmic response to the capacity/rota-tion curve as an aid to linear calibrationcurves on analogue tuning dials.

The air gap determines the voltagerating above which arcing will take placebetween the pces - .015" gap will allow600 V DC working, while transmittingtypes may have air gaps as high as 0.25"for 900 V.

Maximum capacitance values varyfrom a few tens of pF to about 400pF -the minimum capacitance for any unitdepends on its construction, and could bearound 3 to 5 pF for a 20-40pF maximum,to 20-40 pF for a 360pF version. Thisminimum unmeshed capacitance has to betaken into account when calculatingoscillator or tuning coverages, and alsothe extra capacitance added by the wiring

to the capacitor, usually referred to as`stray capacitance'.

Trimmer CapacitorsAnother area where styles vary im-mensely. The basic air spaced trimmer is aminiature version of its big brother, withthe vanes sometimes cut for a solid slug,rather than made individually as in thelargest types. Screwdriver adjustment isnormal, rather than via a shaft, and theoverall capacitance value is unlikely to bemore than 50pF. If higher values are re-quired up to several hundred pF, micacompression trimmers may be used. Theseconsist of two flexible metal plates, bet-ween which is a layer of mica. An ad-justing screw is inserted through holes inthe plates, into a ceramic base - tighten-ing the screw compresses the leavestogether, thus varying the capacitance.

Film dielectric trimmers are commonnow, and give miniature components ofhigh stability - available up to about60pF maximum.

Ceramic disc trimmers have the ad-vantage of being extremely stable and areavailable in a wide range of values andsizes - sub -miniature types of only a fewmm in diameter can be seen in somewatches. Construction is basically a rotorwith an area of silver plate on its top sur-

statorplate has a similar plated area, and thetwo halves are held together by suitablespring pressures. The two mating surfacesare ground very flat for stability. As therotor is turned, the area of overlappingplate is varied thus altering the capacit-nace. Maximum values are about 100pF- the temperature coefficient of thesemay be several percent of the markedvalues.

There are, of course, other types ofresistor and capacitor which you maycome across - however, the preceding en-compasses most types, and should helptowards a better understanding of thelimitations inherent in particular construc-tions. Ell


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Sony SMC-70 Review

A new CP/M-based colour computer from the peoplewho brought you go -anywhere -stereo and wristwatch TV.

WHEN SONY first dropped us a line to letus know that they were sending a micro ourway, I thought that my ears were playingtricks on me. Was this the same Sony whohave brought us the latest in audio andvideo gadgetry? You bet your ears it is!

Sony's contribution to the ever-growingmicro market is the SMC-70 microcom-puter, a CP/M based, 8 -bit, colour com-puter.

RAM ChargedAt first glance, it looks much like anyother micro around. A closer examinationreveals a machine which not only runsCP/M, but has some outstanding graph-ics capabilities as well. The heart of the

by Edward Zapletal

SMC-70 is the workhorse Z80 -A MPU.The 64K bytes of RAM may not seem likemuch, but considering that on top of thisthere is an additional 32K bytes of videoRAM, 2K of character RAM, 2K of at-tribute RAM and 2K of ProgrammableCharacter Generator RAM (PCG), thisshould be sufficient for most applications,especially if the disk unit is used. The at-tribute RAM is used for specifying thecolour of characters and symbols, settingthe background colour, and inverting bet-ween characters and background. As forROM, there is an ample supply of this aswell, 32K bytes. This is comprised of 9Kfor the System Monitor, 22K for SonyBASIC, and 1K for character font.

From A To ZThe 72 -key QWERTY keyboard issomewhat awkward, but it contains all thenecessary buttons for graphics andediting. Next to the space bar there is avery prominent red and white key with an"H" branded on it. At first glance itlooks like something one might see on thePresident's desk in the White House; inreality it is a very useful programmableHELP key which can be used to gainassistance in software such asGRAPHICS EDITOR, GRAFTALK,and certain other applications, includingthe word processor. The five program-mable function keys are the heart and soul

32-JULY-1984-ETI

of the '70; all the graphics and word pro-cessing are controlled quite effectivelywith these, and once you are used to thissystem, it's a breeze. There is also fullfour-way cursoring, as well as HOME,CLR, DEL, and INSERT keys, and theentire keyboard has auto -repeat.

Seeing It In ColourThe SMC's video display is reallysomething, although since it's a Sony youwouldn't expect anything less from thepurveyors of BETA and Walkmans. TheCRT has three display modes: Charactermode, Graphic display, and the Borderdisplay, which are superimposed on oneanother. The Character display is com-prised of 8 x 8 dot matrix/character, 80 or40 char. by 25 lines, and the characterscan be programmed in 8 colours. Thebackground colours can be changed andthe characters can be inverse or blinkingas well. The Graphic mode is brokendown into four sub -modes of differingresolution and colour choice: 1) 160x 100dots - 16 colours - 4 screen pages; 2)320 x 200 dots - 16 colours; 3) 640 x 200dots - 4 colours; 4) 640 x 400 dots in themonochrome mode. The Border displaygives a choice of 16 colours. All of this,when displayed through the Sony'sKX-1211 HG component TV-RGB moni-tor, made for a very impressive presenta-tion.

Micro DrivingThe SMC-70 which was left with us wasaccompanied by a dual disk drive unitwhich accepts the new 3.5 inch, high den-sity mini -disks, which are also in use onthe Apple Mac and Lisa computers. Thissystem, developed by Sony, is capable ofstoring a staggering 1 Megabyte of infor-mation on one double -sided, doubleddensity mini -diskette. Sony supplied uswith single -sided single density disks witha capacity of 280K bytes. Also available isa cassette tape storage system, but on amachine such as this, it is highly unlikelythat it would be needed for much morethan simple programming applications.

CP/MA comforting thought, when reviewing anew micro, is in knowing that it runs anoperating system which is pretty well likedby prit' near everyone. Just pop in theCP/M system disk and you're off to theraces. All the normal stuff is there: PIP,STAT, ASM, DUMP, etc. Instead ofFORMAT and COPY, Sony uses a utilitytided BACKUP, which lumps the twoprevious ones together into a menu drivenutility. The SMC version of CP/M hasbeen extended for colour and graphics ap-plications which are superior in quality toanything on the market of late.

SoftwareJust as an automobile won't run withoutsome sort of fuel in its tank, a micro ispretty much useless without sufficientsupporting software. Aimed at the lowerto mid -priced business level, the SMCruns a variety of packages such as: Super-Calc 1 & 2, a complete accountingpackage, Sony disk BASIC, CB -80 (asouped -up business BASIC for graphics,colour and sound). Data Base Manage-ment, Word Processing (WordStar, Let-terwriter) with a spelling checker andmailing list option. The really big sellingpoint for the SMC-70, though, is itsgraphics.

Custom TextThe three packages available are veryentertaining and not extremely difficult tolearn. The Video Titler package lets you

create text in three character sizes, as wellas six different type faces in sixteen col-ours. The text created with the VideoTitler can then be superimposed over avideo image by interfacing the SMC-70with a suitable video display system (eg.,Sony video disc player and KX-1211 HGcomponent TV). This was demonstratedto me at the recent Computer Fair inToronto, and the potential for this type ofdisplay would seem to lie in the educa-tional, industrial, and tourism sectors,just to name a few.

Disney Anyone?Graphics Editor is a totally menu -drivenpackage which allows the creation of fullcolour graphics images from the keyboardor optional graphics tablet. It sports suchfeatures as variable "zoom editing."320 x 200 - 16 colour resolution andsuperimposition with external videoequipment. All graphics are created usingthe five function keys positioned along thetop edge of the keyboard. The commandsfor drawing, storing, saving, loading,overlaying, etc., are always displayed atthe bottom of the screen for easyreference. A data disk supplied by Sonyrevealed some very colourful likenesses ofDisney characters which we could changeand tamper with to our heart's content.Concise and meaningful prompts lead youinto the various levels of the editor. If atany time you become bogged down, youcan always press the panic button (HELPkey), which dumps you out to a screenhelp file and advises you on the correct ac-tion to take. So, at this point you thinkyou've lost your treasured graphic crea-tion? Nope, the SMC-70 returns you towhere you were when you yelled for help.The one obvious thing which seems to belacking, at least on a sophisticatedgraphics machine such as this, is a joystickfor moving the cursor around. TheGraphics Editor is certainly worth thelook if you're thinking of graphic assisteddisplays for any reason.

Bars and PiesGenerating charts and graphs is usually achore when the software being used is justnot quite good enough. Sony's Graftalk

ETI-JULY-1984--33

package makes it quite simple to enter thedata, title the various axes, as well as col-our and label desired portions of yourwork. There is also the capability of usingSuperCalc data with Graftalk, as well asdata created with Letterwriter, eliminatingthe need for re-entry of lengthy data files.

End of FileAfter having explored the SMC-70 for afew days, it would seem that it certainly

has a future in the video graphics market.Its one strong point is that it's a CP/Mbased system which has very good soft-ware potential, and very good graphicscapabilities which are not found on toomany CP/M systems. Its ability to inter-face with video systems makes it attractivefor presentations of all kinds. However,the era of the 8 -bit micro would seem tobe passing, slowly, but still passing. Butgiven the reliability of CP/M and the

Computer Review

number of existing Z80 based systems, aswell as Sony's reputation as a leading elec-tronics manufacturer, the SMC-70 willprobably survive the flooding market.The cost of the SMC-70 can be brokendown as follows: Computer $1895, DualMicro -drive Unit $1495, Printer $1095,Trinitron Component TV KX-1211 HG$1299, RGB and Printer cables $90 each.CP/M and one of either the Word Pro-cessor or Data Base Managementpackages are included. For more informa-tion contact: Daryl Duda, SonyMarketing Headquarters, 411 GordonBaker Rd., Willowdale Ont., M2H 2S6.(416) 499-1414.

Quick ReferenceMfg:Price:

CPU:RAM:Screen:Graphics:Colours:Sound:Video:

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34-JULY-1984-ETI Circle No. 10 on Reader Service Card Circle No. 31 on Reader Service Card.

Canada's Microcomputing Software Magffzine

Up to theMinute Reviews

News ofGames, Business,Home, Professionaland EducationPackages

Exciting NewApplications

Soft for IBM,Apple, CPIMCommodore,Radio Shack,Macintoshand more

II Canadian Sources

From The Editor,Not knowing about software is a multiple edgedsword. Not only don't you know what you need;you don't even know what you're missing. It's ter-ribly easy to leap upon the first package thatcomes within waving distance of your applicationand then bend your application to suit it.

This is not the way it should be.There is software for every use, perfect soft-

ware for any conceivable purpose . . but findingwhat you want can be a drag, if for no otherreason than the constant repitition of the tunefrom Mission: Impossible playing inside yourhead.

The fabulous thing about editing a magazinelike this is that you get to play with every packagein the cosmos. However, this is extremelytiring . . . the fabulous thing about reading amagazine like this is that you get the benefit of be-ing able to play with every package in thecosmos without actually having to do all that typ-ing.

Software Now! will keep you abreast ofwhat exists, tell you what probably shouldn't existand inform you about where to get it so you canmake it all exist for your needs.

We know that Software Now! is going tobecome one of the most essential accessories anycomputer user can own. Subscribe . . . Now! . .

and let us prove it to you.

CJ/me. ifird"

Steve RimmerEditor,Software Now!

S

A New Canadian Publication for the Ultimate MediumThe difference between we humans and the other inhabitants of theplanet is our capacity for making tools. Civilization is oftenmeasured by its grasp of technology . . . it's through his use of toolsthat man has come to be able to manipulate his environment.

The computer is the ultimate tool . . . it is, like man himself,unspecific, and thus adaptable to virtually any task. The same com-puter can be a bookkeeper, a game, an artist's palette, acomposer's amanuensis, a word processor or a programmer'sdevelopment station.

The computer itself is simply a box full of chips. The power of com-puters lies in the software that runs on them.

Software Now! is the new magazine for people harnessing the-power of the microcomputer. In its pages you will find the informa-tion which you will need to choose and apply the software that willdedicate your computer to your tasks. It will help you make senseof the miriad of similar software packages, translate the intricatecomplexities of software claims, understand the watershedbreakthroughs in software development . . . and even have a bit oftime left over to dematerialize a few aliens.

First Issue Oct

Perhaps most exciting, however, is that the pages of SoftwareNow! will contain news about software for applications you'venever even considered running on your computer. Imagine havingan overview of the work of the world's most gifted programdevelopers . . . and you'll have a good idea as to what this newpublication is about.

Software Now! will be dealing with a broad range of systems andapplications, encompassing eight, sixteen and thirty-two bitmachines and software as diverse as video games, drafting systemsand spreadsheets.

We've reached a level of development in microcomputer softwarewherein one needn't be a computer genius to apply a computer. Infact, one can operate a computer with only a bit more expertisethan one needs to successfully make toast. The key that will unlockthe power of your computer is the software you plug into it.

The key to that software is understanding.The key to understanding software is Software Now!

The PedigreeSoftware Now! is published by Moorshead Publications, whichalso brings you Computing Now!, Electronics Today, Computersin Education and the Printout newsletter. It has been producingsuccessful magazines in Canada since 1977.

Moorshead Publications is unique in the way it producesmagazines. The expertise in applying microcomputers has allowedus to make virtually the entire process of publishing electronic. Theeditorial in the publications is created on word processing terminalsand computer type set. All the financial planning is handled bycomputer, as is filing and list management. The company also

maintains an on line telecommunications computer to communicatewith its readers.

The Editor of Software Now! is Steve Rimmer, who also editsComputing Now! In the first year of its existence Computing Now!went from a standing start to having over twenty two thousandsubscribers, making it Canada's largest consumer microcomputerpublication.

Steve has had experience with a wide range of software, fromword processors to sophisticated music and graphics packages. Heuses a number of computers, including several CP/M basedmachines, an IBM, an Apple II +, a Commodore and a MacIntosh.

36-JULY-1984-ETI

Features In The QueueThis is some of the editorial we have lined upfor the first few issues of Software Now! Youcan expect it to change a bit . . . new soft-ware springs up almost daily, and SoftwareNow! will always feature the most importantdevelopments in this dynamic field. Articlesbeing developed during the preparation forthe magazine include:

Computer Aided Drafting On a Micro Techniques in MacPaint How to choose aSpreadsheet Apple Software Crate Get-ting to the Root of UNIX The DigitalResearch Pantry A Thousand and OneWord Processors IBM's Productivity Family Can Mac Write? Professional SoftwareRoundup Power Programs for the 64 Ap-proaching the C Word Processing SupportPrograms dBase II Enhancements Will itRun Multiuser? Concurrent CP/M .

Reviews: 10 Base Mighty Mail WORD -BASE Easy Script Computer Chef Elec-tronic Circuit Analysis Program SuperexRetailer MAI Basic Four The Print Shop TK!Solver Microsoft BASIC for the Macin-tosh Sundog Turbo PASCAL for the IBM AutoCAD MultiMate Lexicheck andWord Juggler Dataflex Symphony Om-niterm 2 DB Master Paint Magic.

In addition to this look for these regularfeatures:The Library (Our monthly survey of

books)By The Boards (Public domain software)Arcade (A blast at the latest games)Short File (A short overview of new

releases)

The Amazing Software Now!Software Disk

Free to Charter SubscribersAt Moorshead Publications, we have always managed to launch new magazines witha flying start; this time we want our previous records to be smashed. We believe wehave come up with "an offer you can't refuse".The Amazing Software Now! Program Disk is, we believe, the best offer evermade to Charter Subscribers to a new magazine. A charter subscriber is one whohelps provide the initial circulation base and we feel they deserve something special- what we are offering is just that.

The disk contains some fairly amazing custom written material:CalcNow: A real spreadsheet program with many as the new features of

programmes costing a small fortune. CalcNow is perfect forthose who want to experiment with a spreadsheet and are dyingto see how they work. It is far from a toy.

DataBom A flexible data base manager and is a version of a program wedeveloped for our own company use.

Poker: Life is not complete without a video game.Phone Jada A telecommunications terminal.

The contents of the disks vary depending on the system and additional programscome for some systems: see overleaf for a more complete description.

The Software Now! Disk is available in a huge number of different formats but wehaven't forgotten you if you haven't got a disk drive or a system that we can ac-comodate: everyone will also receive a hard copy listing of those programs written inBASIC (listed for Microsoft Basic for you to modify yourself).

This disk will be sent to you FREE if we get your subscription order beforeSeptember 30th, 1984. Early orders will get their disks as soon as processing andshipping time allow, later orders will receive them with the first copy of the magazine.

The Software Now! Disk is not available at this time EXCEPT to Software Now!Charter Subscribers. The software is currently in the final stages of developmentbut we must rcocrve the right to modify the content.

Software Now! is available at a charter rate of $19.95 for a one year subscription,$34.95 for two years. This rate is valid until September 30th, 1984. This rate includesyour choice of a free software disk . . . please specify the machine operating systemand format you want the disk to run with: check those available.

Software Now! Subscriptions25 Overlea Boulevard Suite 601

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YOUR GUARANTEEIf, you do decide that Software Now! is not the magazine youexpected or want, or if you decide to cancel your subscriptionfor any reason or no reason, you may do so and receive arefund on the unexpired portion at any time.

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ETI-JULY-1984-37

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Phone JackMost computers have telecommunications hard-ware built into them . . . it's a shame that theydon't all have software available to drive it. Thisprogram does basic telecommunications and,while its features do vary a bit from system tosystem . . . based on what the operating systemsallowed us to impliment . . it does provide forthe basic requirements of calling computerbulletin boards and dial up mainframes.

Utility PackMost revisions of the disk will also have a choiceselection of utility programs. These vary a lotfrom system to system so it's a bit difficult todescribe them all here. However, these are the lit-tle routines that make life so much easier whenyou sit down at the keyboard and switch on.

Ent, deo OW 0 MISSft IL/

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Poker!We wanted to include a game on the disk and,after some deliberation decided that a good dim-ly lit, smokey card game would fill the bill best.This one simulates five card draw poker in theproper cowboy style. It can deal, draw, call,bet . . . do everything but cheat and pull its sixgun on a really bad hand. POKER! features agraphic display of the cards being played.

For CPIM* users: CalcNow, DataBox, Poker!,Utility Pack, Phone JackFor Apple lI +DOS Users: CalcNow, Databox,Poker!, Phone Jack, Utility Pack plus Clef Hanger(An Apple Music Box), Skyhook (a teletype con-verter) and Fruit Crate (a BBS).For IBM Users: CalcNow, Databox, Poker!,Utility Pack, Phone Jack plus Bandit (A slotmachine simulator)For Macintosh Users: CalcNow, Databox,Poker, Phone Jack and Letterhead (a stationarygenerator).For Commodore Users: CalcNow, Databox,Poker, Utility Pack and Phone Jack.For TRS-80 Model III and 4: CalcNow,Databox, Poker

This software is available as a free gift to chartersubscribers to Software Now! magazine. To beeligible to receive this disk your subscriptionorder must be at our offices no later thanSeptember 30th, 1984.

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L

38-JULY-1984-ETI

Machine LanguagePart 2In this second part of this series,Bob Bennett looks for impliedand immediate addresses on thecomputer's memory map.

WHEREABOUTS in RAM your machinecode program will go depends on thememory structure of your computer. Alook at the computer's memory map willshow the areas in RAM reserved by thecomputer for 'housekeeping' duties.These duties consist of keeping tabs oneverything that happens while the com-puter is switched on. Figure 5 shows aportion of a memory map for no com-puter in particular; how it works is fairlysimple, but does require a lengthy ex-planation.

The display file is shown as occupy-ing 704 addresses, each of one byte: these704 bytes store information relating to thepicture on the screen. The working area ofthe screen in our example consists of 32columns by 22 rows, and 32 times 22equals 704. The reason I referred to work-ing area is that there are usually two rowsat the bottom of the screen reserved forthe input data. As a rule the top left handcorner of the screen is position 0,0, andthis is the first address in the display file.Suppose that you printed the letter A inposition 0,0: the code for letter A wouldbe stored in address 16384.

The print buffer is merely a tem-porary storage area for data going out to aprinter, but this area can often be used bythe programmer.

Any good computer handbook has asection devoted to the system variables,which are a series of reserved addressesusually given short names. These ad-dresses contain information, dealing withwhich comprises the major portion of thehousekeeping I mentioned before. Eachsystem variable consists of one, two, orvery rarely, three or more bytes. If there isonly one byte then the address will usuallycontain a number, the value of which maydetermine the action to be taken by thecomputer.

If there are two bytes, then the twoconsecutive addresses of the systemvariable themselves hold an address. This

HEXADDRESS 0

4000

42C0

43C0

ROM 16K

DISPLAY FILE704 BYTES

PRINTER BUFFER256 BYTES

SYSTEM VARIABLES180 BYTES

BASIC PROGRAM

VARIABLES

.../"'-

----

DECIMALADDRESS 0

16384

17088

17344

Fig. 5 Portion of generic memory map.

is usually the starting address of an area inRAM where a particular variable isstored. For example, when you assign let-ters or strings as variables, the informa-tion relating to those variables is held inan area of memory. If you had a systemvariable called VARS, this would consistof two bytes, and would hold the startingaddress of that area.

The area of RAM, from the systemvariables onwards, is the part that is ofprimary interest to machine code pro-grammers. As your list of variables is add-ed to, or subtracted from, then the area itoccupies can fluctuate. This is true of thearea taken up by your BASIC program, asyou add or delete lines. Areas in RAM canbe reserved for machine code programs,and there is usually plenty of informationaround telling you how to do it for yourparticular computer.

How . . .

Once you have found out where to putyour program, the next task is to get itthere! There is really only one way it canget there, but there are several methods ofdoing it (that's a bit like saying 'there isonly one road to Rome, but there aremany means of transportation'). The pro-gram is POKEd into addresses, byte bybyte. Starting with the first address, andthe first byte, the addresses are in-cremented after each POKE.

If you're not familiar with POKE,it's how you get information into RAM.Consider this example of a direct com-mand, POKE 32000,119 decimal: thismeans place the decimal number 119 intoaddress 32000. If your computer allowsyou to use hex direct, then the commandcould be POKE 32000,77 hex. The corn-

ETI-JULY-1984-39

Machine Language

plementary command to POKE is PEEK,so, after entering the above example, theinstruction PEEK 32000 would cause thenumber 119 decimal to be printed to thescreen. Of course, you can only POKE in-formation in RAM, but you can PEEK ateither RAM or ROM.

Probably the most widely usedmethod of entering machine code pro-grams into home micros is with a hexloader. If your micro doesn't support hexdirect, then the hex code has to entered asa string, sliced and then converted todecimal before POKEing into the ad-dresses. Otherwise, the decimal conver-sion can be left out. Another methodmight use the READ/DATA statements ifyour computer has them.

Assemblers and compilers can also beused to get your program into memory.Taking the assembler first, this is a pro-gram that could either be resident in ROMor loaded in via tape, etc. This will takeyour assembler language statements andconvert them into machine code. Beforethe program can run, however, thestatements are checked for validity, andan opportunity is given to edit the pro-gram. A compiler is a program, usuallyloaded into the computer, which convertsa higher level language, such as BASIC,into machine language. If the last twomethods have to be loaded in then they douse up memory, which is usually aprecious commodity. So how the programgets into the computer is a combination ofpersonal preference and what your com-puter will support.

What . . .

The instruction set, mentioned lastmonth, is where you will find all the in-structions you will use in machine codeprograming. Ideally they will be in tabularform, giving both decimal and hex-adecimal notation, and sometimes you

might find the binary form given as well.Also they should include the assemblermnemonics, and the number of bytes perinstruction. Those of you with Sinclairmicros have everything that you need,apart from the byte count, in the hand-book. Because the instruction set for theZ80 is very comprehensive I will be usingthat for the examples I give. Don't worryif your computer doesn't have a Z80CPU, the same principles will apply.

Don't Forget The Post Code!Before very long 16 -bit micros will be ascommon in the home as the eight -bit onesare now, but until then I will be dealingonly with the eight -bit variety. Addressingmodes are simply a way of getting aroundthe fact that addresses require 16 bits, butour data word is only eight bits long. Thefirst addressing mode I'll explain is the im-plied because it is the simplest, and onlyone byte long.

Sometimes known as the registerdirect, the implied mode is so namedbecause the data source and destinationare implied in the instruction. For ex-ample, to load the B register with the con-tents of the C register requires the instruc-tion 41 hex in the Z80 set. Here the sourceis the C register and the destination, the Bregister; this could be shown as C B. In-crementing and decrementing registers,and No OPeration and RETurn instruc-tions use the implied mode.

NOP, or no operation, is self ex-planatory, nothing happens (nothing, thatis, except a fractional waste of time). Thisis a very useful instruction that could beused in a timing loop, or to occupy ad-dresses that you intend to overwrite withdata later on in the program. Or perhapsyou haven't quite decided what to do inone patch of the program. An approx-imate number of NOPs will reserve thespace for you until you have made up

"It was very expensive, but it's an authentic old crystal set. You can tell, becausethe digital frequency readout is in Roman Numerals."

your mind. As for the RETurn, this isperhaps the most important instructionyou will use. Without it, in some com-puters, you could be stuck in an infiniteloop. In its simplest form, it can beregarded as an instruction to return to theplace from where you were sent - morewill be explained later.

All simple register to registertransfers use the implied mode, but as anexercise see how many of these instruc-tions you can find in your set. The goldenrule is that there is one byte in the wholeinstruction.

For Your Immediate AttentionThe immediate mode is the next easiestaddressing mode that you can use. Aswith the implied, the immediate modedoes not involve any addresses, but thereare now two bytes per instruction. The in-struction 3E hex in the Z80 set means loadregister A with the number that follows;in the 6502 set the same instruction wouldbe A9 hex. This might have the mnemonicLd A,n, or M A, or even MV1 A,D8;note that the names are not CPU instruc-tions; they are just humanised memoryaids. That last menmonic sums everythingup nicely because it means, move im-mediate(ly) into A a data byte of eightbits. Other instructions of this type in-clude add n to a particular register or sub-tract n from a particular register. Again asan exercise, pick out all the immediatemode instructions out of your set.

Now that we have reached two byteinstructions, I'd like to clear up a pointthat seems to confuse newcomers tomachine code programming. The ideathat the same byte can represent two dif-ferent things might seem at first glance tobe perplexing, but stop and think. Let metake as an example the instruction above,load A with n. This could be written in aZ80 program as 3E,3E (or for the 6502,A9,A9). What happens is that when thecomputer gets to the first 3E it regards itas an instruction, an instruction to loadthe byte that follows (which also happensto be 3E) into register A. What the secondnumber stands for is up to you, as the pro-grammer, to decide. It may be just anumber you want to manipulate, or itcould be the code of a character you wantto print to the screen. Whatever, the com-puter recognized the first 3E (or A9), asan instruction requiring two bytes. Aftercarrying out that instruction, the com-puter would carry on with the rest of theprogram from the instruction which cameafter the second byte. Every instructionbelongs to a class that requires one, two,or more bytes for proper execution. It isthe programmers responsibility to ensurethat the computer starts off in the rightplace! ETI

40-JULY-1984-ETI

urriptitir.5Mk,

by John Rudzinski

AT around six -thirty in the morning, afterwatching the obligatory morning cartoons,a select breed of professional worker goesto work in Silicon Valley, U.S.A. Grabbinga quick coffee and a wicker basket, thesehard workers trod into the fields to begintheir backbreaking occupation.

Chip picking.In the summer months, the chiptrees

blossom. Branches bend with bough -breaking clusters of TTL, op -amps,encoder -decoders, and microprocessors.When ripe, the chips fall - feet earthward- to the ground where the chip -pickersstoop to collect them.

The oddballs on the chiptrees fall up-side down, feigning death in hope of escap-ing unseen under cover of darkness. This isto be expected of the inverting amplifiers,but seems unusual for the TTL... the so-called logic chips.

The favourite fruit of the chiptree,however, is the 6502 microprocessor. Ad-mittedly, it's nothing fancy... what with aneight -bit accumulator, two eight -bit indexregisters, an eight -bit stack pointer and asixteen -bit program counter, it's fairly ar-chaic as opposed to some of the monstersthat've been skittering out from Intel andMOS Technology these days. Still, it's aremarkably easy chip to both understandand program, which is why it remains afavourite today.

QuickiesThe three short assembly programs thatfollow are written for the Apple ][ + com-puter or similar abomination. There's a

6502 Utilities °-Even though manufacturers have been producingmicroprocessors with thirteen digit names for years now, the 6502is still a programmer's favourite. Three programs are listed belowto give your fingers some practice. You'll also learn why the chipsin your computer try to crawl out of their sockets at night...reason for this... it's the only micro I have.

I used to have a VIC-20, but I'm okaynow.

Program One, Password Protection,isn't actually a program... it's a subroutineto a program that you have to supply. Itmight prove useful in a disk pre -boot situa-tion where you don't want Russian spiesdiddling with your data. When BRUN, itlets potential perpetrators know that yourprogram is protected, and they're to supplya password before anything useful will hap-pen. If, in this case, "BLA-AT", (thesound of an unhappy disk drive) isn't typedin, the program will gleefully erase itselffrom memory.

Naturally, you're free to replace thepassword with any six letter word thatstrikes your fancy. Be careful to BSAVEbefore you BRUN it... backspaces are con-sidered valid characters as well.

If you've spent hours looking aroundfor a chart to find the hexadecimalequivalents of a number of keyboardcharacters, you might get a kick out ofProgram Two. Comprised of 262 bytes, itwill inhale a string or strings of up to 255bytes rattled off the keyboard, ponder themeaning of life for a few moments, thenspew out the hex. Before I obtained a sym-pathetic assembler, I always had to lookeach character up in a table, then jam themindividually into memory to displaywhatever string I wanted to convince toburn CRT phosphor.

Hitting a Control -C will tell the pro-gram you've finished your input unless youtype over the 255 character limit. It getssomewhat violent should this happen andlays the hex on you unrequested. You justcan't convert a novel to hex with a 262 byteprogram.

2

5

5

6

PASSWORD PROTECTION

(C) 1984 - J. RUDEIHSKI

**110111.1**-114.*r***Irkft

10

MG $0800

11 BUF EQU $200012 CLS EQU $FC5015 GET EQU 1803514 PRINT EQU SPUD15 C/R EQU 8808016 BASICI EQU MOO17

0800: 18 18 FIND CLC

0801: 90 28 19 BCC BEGIN0805: C2 CC CI 20 PASS ASC .BLAAAT.0809: D4 CB C9 21 STRI ASC .THIS PROGRAM PROTECTED..0820: 8D 22 DB MD0821: SD 23 DB 0$800822: C5 CO 04 24 STR2 ASC 'INTER PASSWORD: .0852: 20 58 PC 25 BEGIN JSR CLS

0835: A2 FF 26 LOX flIFF

0857: E8 27 XLOOPI IN%

0858: BO 29 28 CPX 01290838s FO 09 29 BEQ PAM!'083C: BD 09 08 30 LOA 10111,8

0838: 20 ED FD 31 ln PRINT0842: 18 32 CLC

0843: 90 F2 33 BCC %L0081

0845: A2 FF 34 PASSGET LOX f$FF

0847: 08 35 %L0082 INX

0848: CO 06 36 CPX f$06

084A: FO 28 37 BEQ RIGHT084C: 20 35 FD 38 JSR GET

0848: 48 39 PHA

0850: A9 D8 40 IDA f$D80852: 20 0 FD 41 JSR PRINT01155: 68 42 PLA

08562 DD 05 08 43 CMP PASS,X0859: DO 58 44 BRE BYE

0858: If 45 AROUND CLC

OM: 90 89 46 BCC XLOOPI085E: 8D 47 STR3 DB 1$800/15F: 09 CF D5 48 ASC .YOUR PROGRAM STARTS MERE087A: 20 BE FD 49 RIGHT !SR C/R

0870: AO 00 50 IDE f$000878: CC 95 08 51 CPT DATA0852: DO If 52 BNB WIPE0584: A2 FE 53 LDX 83880886: 08 54 8L0083 INX

0837: BO IC 55 CPX f$1C0889; PO 09 56 BEQ END

08811: BD 3! 08 57 LOA STA5,X0550: 20 ED FD 38 JSR PRINT0091: 18 59 CLC

0892: 90 F2 60 BCC %L001.3

0894: 60 61 END *TS

0695: 00 62 DATA DB 81000896: 88 95 Of 65 BYE SIX DATA0899: 18 64 CLC

0898: 90 IF 65 BCC AROUND089C: A9 BF 66 WIPE LDA 8$87089E: A2 FF 67 LOX UFFDUO: U ff XLOOP4 INX

011AI: CO 96 69 CPX 0$9601185: 70 06 70 HQ 8801

OAS: 90 00 05 71 STA 7180,X08881 18 72 CLC

08891 90 75 73 BCC %L001,4

OUB, 4C 00 BO 74 ENDI !MP BA5IC1

--- END ASSEMBLY ---

TOTAL ERRORS; 0

ETI-JULY-1984-41

Computing Today

My favourite creation is ProgramThree. Entitled Subliminal Advertising,it's the shortest of the three listings at 1 1 1bytes. It's a bit odd in that it appears tosimply ask a question and then wait foryour input. What it's actually doing is lay-ing in wait for a victim to answer itsquery. No matter what is typed, one ofETI's sister publications shows up on thescreen, one character at a time, inresponse to each keypress.

The public has a right to know.:ASS

2

3 STRING INPUT AND HEX4

5

6

7

8

9 On $080010

11 BUF

12 CLS

Al CET

14 /HEX

15 PRINT16 C/R

0800: 4C 22 08 170803: C5 CE D4 18 STR1

0822: 20 58 FC 19 BEGIN0825: AO FF 20

0827: CO 21 YLOOPI

0820: CO IF 22

0820: FO 09 23

082C: 89 03 08 24082F: 20 ED FD 250832: 18 26

0833: 90 P2 27

0833: 20 88 FD 28 ENTER0838: 20 88 FO 2908511: A2 FF 30

0830: 88 31 XLOOPI083E: 80 FF 32

0840: FO 25 33

0842: 20 35 ID 34 GRAB

0045: A8 35

0846: CO 85 36

0848: FO 10 37

0841: CO 88 38

084C: FO 09 39

084E: 9D 00 20 400851: 20 ED FO 410834: 18 42

0855: 90 86 43

OW: 20 ED FD 44 BXSPACt085A: A9 AO 45

085C: 20 ED FD 46085F: A9 88 47

0861: 20 ED FD 480064: 18 49

0865: 90 DB 50

0867: 81 51 ?STRING0868: 48 52

0869: 20 BE FD 530860: 20 88 FD 34086F: 18 55

0870: 90 10 56

0872: CI CE C4 57 STR2

0082: AO FF 58 NOTE0884: CB 59 YLOOP20885: CO 11 60

0887: FO 09 61

0889: 89 72 08 62088C: 20 ED FD 630881: 16 64

0890: 90 F2 65

0892: 20 88 FD 66 CONVERT0895: 20 88 PD 670898: 18 68

0899: 90 01 69

0898: 00 70 DATA089C: 68 71 SKIP08915: 8D 9B 08 72080.0. A2 FF 73

08,12: E8 74 X1.00P2

0883: EC 98 08 7508A6: FO OE 76

080.8: BD 00 20 7708AB: 20 DA FD 7808AE: A9 AO 79

0880: 20 ED PD 80OM: 18 81

0884: 90 IC 82

0886: 18 83 END0887: 90 OD 84

0889: CD CF D2 85 5TR3

08C6: 20 88 FD 86 CHOICE08C9: 20 88 FD 8708CC: A2 FF 88

08CE: 88 89 SLOOPS08CF: E0 00 90

0801: FO 09 91

0805: BD B9 08 920806: 20 ED FD 950809: 18 94

080A: 90 F2 95

080C: 20 55 FR 96 YESNO08DF: AA 97

08E0: 10 D9 98

0882: DO 15 99

08E4: A9 D9 1000016: 20 ED FD 10108E9: A9 C5 102

0888: 20 ED FD 1030888: A9 775 10408F0: 20 ED FO 105INFO: 20 OE FD 1060836: 4C 22 08 10708E9: A9 CE 108 BTE

08FB: 20 ED FD 10908F8: A9 CI 110

0900: 20 ED FD 1110903: 60 1120904: 00 115

0905: 00 II4


TOTAL ERRORS: 0

262 BYTES GENERATED THIS ASSEMBLY

CONVERSION

********

EQU $2000EQU $FC58EQU $F055EQU IFOOAEQU 8F0817

EQU IFD8E!MP BEGINASC .ENTER STRING. HIT AC WHEN DONE..JSR CLS

LDS I$FFINT

CPR 181F1180 ENTERLDA STRI,Y!SR PRINTCLCBCC YLOOPI

JSR C/R

!SR C/11

LDX #IFFINX

CPS I.FFBCC: ?STRING

JAR GETTAYCP. f$83BEQ ?STRINGCP. f$88BEQ BKSPACESTA BUI,XJSR PRINTCLCBCC SLOOP]JSR PRINTLDA f$A0JSR PRINTCIA /888JSR PRINTCLCBCC GRABTXAPHAJSR C/R

JSR C/R

CLC

BCC NOTEASC NOW, IN HEX:.LDY IIFFCPY

CPT f$11

BEQ CONVERTLOA STR2

!SR PRINTCLCBCC YLOOP2JSR C/R

!SR C/R

CLCBCC SKIPBRA

PTALOX DATALOX 1IFFINX

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BCC XLOOP2CLCBCC CHOICEASC "MORE? (T/N):JSR C/RSIR C/R

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CPS #809BNE BYELDA 1$D9JSR PRINTLDA /RCSJSR PRINTLDA #203JSR PRINT!SR C/R

JMP BEGINLDA

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BRA

BRK

:ASM

2

3

6

5

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8

WrIeN SUBLIMINAL ADVERTISING

* (C) 1984 - J. RUDZINSKI

*It

10

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ORG

EQU

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$0800IFC508E035IFDED$FD8E

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0800: 20 58 EC 16 JSR CLS0805: 10 17 CLC0804: 90 20. 18 BCC QUERY0806: 07 C8 CI 19 STR1 ASC .WHAT IS YOUR FAVORITE COMPUTING.0825: 80 20 DB 1$8150826: CD CI C7 21 ASC "MAGAZINE/ .0830: A2 FF 22 QUERY LOX IIFF0832: 88 23 XLOOPI INS0833: 80 2A 24 CPX 0$20.

0835. FO 21 25 BEQ ANS0837: BD 06 08 26 LDA 1111.8085.4: 20 ED FD 27 JSR PRINT0830: 18 28 CLC083E: 90 F2 29 BCC XLOOP10840: C3 CF CD 30 STR2 ASC .COMPUTING NOVI MAGAZINE..0858: A2 FF 31 ANS LDX f$FF085A. 80 32 XLOOP2 INX08511: 10 18 55 CPX f$180850: FO OC 34 BEQ END0851: 20 35 FD 55 !SR GET0862: BD 40 08 56 LDA ST112,X0865: 20 ED FD 57 JSR PRINT0868: 18 58 CLC0869: 90 EP 39 BCC XLOOP20066: 20 88 FD 40 END JSR C/R086E: 60 41 RTS


TOTAL ERRORS: 0

111 BYTES GENERATED THIS ASSEMBLY

EscapeNight falls with a hushed thud, and thecrickets rub their legs together in anticipa-tion. The pickers have gone home to theirrespective basement apartments and thelights in the deserted factory hum endlesslyto an absentee audience.

Crawling out from under a dandelioncarcass, a 74LS02 stretches its fourteensilvery legs, peers carefully through thegrass, then:

The gunshot report cracks through thestill air, and the newly -ventilated chip doesan inspired airdance before landing at thefeet of the poacher.

"Poor little runt," he muses, dropp-ing the deceased into a sack full of itsbrethern.

He lifts the sack over his shoulder andbegins his walk home. It's been a goodhaul. There'll be chips with the fishtonight.

ETI

Where to BuyFLUKE

Digital /AnalogMultimeters

Fluke 70 Series Digital Analog multimetersare available in Canada through the Jet Stockprogram of Allan Crawford Associates Ltd..or from the following distributors:Vancouver, B.C.

R.A.E. Industrial Electronics Ltd. 291-8866Instrument Service Laboratories Ltd. 278-4511

Victoria, B.C.Queale Electronics Ltd. 388-6111

Nanaimo, B.C.Queale Electronics Ltd. 758-8166

Vernon, B.C.Interior Electronics Ltd. 545-2394

Kelowna, B.C.Interior Electronics Ltd. 860-0585

Kamloops, B.C.Interior Electronics Ltd. 374-5002

Edmonton, Alta.Cardinal Industrial Electronics Ltd. 483-6266Instrument Service Laboratories Ltd. 463-7488

Calgary, Alta.Cardinal Industrial Electronics Ltd. 259-6817

Regina, Sask.Radio Supply & Service Ltd. 352-8642

Winnipeg, Man.Wes Electronics Ltd. 632-1260

London, Ont.C.M. Peterson Co. Ltd. 434-3204

Toronto, Ont.Electro Sonic Inc. 494-1555C.M. Peterson Co. Ltd. 247-5437Armatek Controls Ltd. 251-3111E IL Instruments Canada Ltd. 624-6660

Peterborough, Ont.Weesco-Peterhorough 745-2493

St. Catherines, Ont.C.M. Peterson Co. Ltd. 685-7377

Kitchener, Ont.C.M. Peterson Co. Ltd. 745-0981

Sarnia, Ont.C.M. Peterson Co. Ltd. 344-3382

Windsor, Ont.C.M. Peterson Co. Ltd. 253-1161

Hamilton, Ont.C.M. Peterson Co. Ltd. 528-0151

Thunder Bay, Ont.C&F Electronic Distributors Ltd. 345-6515

Sudbury, Ont.Sonic Northern Ltd. 674-0764

Timmins, Ont.Sonic Northern Ltd. 264-1228

Sault Ste. Marie, Ont.Sonic Northern Ltd. 254-1418

Ottawa, Ont.Electronic Wholesalers Ltd. 746-4413

Montreal, Que.Electronic Wholesalers Co. Ltd. 769-8851Franklin Electric Canada Ltd. 341-6260

Chicoutimi, Que.Franklin Electric Canada Ltd. 545-8313

Noranda, Que.Simtronique Inc. 762-1874

Halifax/Dartmouth, N.S.Weesco-Maritimes 465-3730

St. John's, Nfld.Rideout Tool & Supply Ltd. 745-2240

42-JULY-1984-ETI

Allan Crawford Associates Ltd.Test & Measurement Division

Toronto: (416) 678-1500 Montreal: (514) 731-8564 Ottawa (613) 722-7682Halifax: (902) 463-8640 Vancouver: (604) 294-1326 Calgary: (403) 230-1341


The Digitalvs.Analog

battle is over.

*buys

you the new champion.125 The new Fluke 70 Series.They combine digital and analog displays for

an unbeatable two -punch combination.

Now, digital users get the extra resolution of a

3200 -count LCD display.

While analog users get an analog bar graph for

quick visual checks of continuity, peaking, nulling

and trends.

Plus unparalleled operating ease, instant

autoranging, 2,000+ hour battery life and a

3 -year warranty.

All in one meter.

Choose from three new models. The Fluke

73, the ultimate in simplicity The feature -packed

Fluke 75. Or the deluxe Fluke 77, with its own

multipurpose protective holster and unique

"Touch Hold" function (patent pending) that cap-

tures and holds readings, then beeps to alert you.

Each is Fluke -tough to take a beating.

American -made, to boot. And priced to be, quite

simply, a knockout.

So call for more information.

FROM THE WORLD LEADERIN DIGITAL MULTIMETERS.

1111.4Melt

Fluke 73 Fluke 75 Fluke 77S125° S185°Analog/digital display Analog/digital display Analogidigital displayVolts ohms 10A diode Volts ohms 10A mA. Volts ohms. 10A mAtest diode test diode test

Autorange Audible continuity Audible continuity0.7% basic dc accuracy Autorange/range hold "Touch Hold'. !unction2000 hour battery life 0 5% basic dc accuracy Autorange/range hold3 -year warranty 2000+ hour battery lite 0 3% basic dc accuracy

3 -year warranty 2000 4- hour battery life

3 -year warranty

Multipurpose holster

Suggested Canadian price including duty and federal salestax Provincial taxes extra

FLUKE

OSCILLOSCOPES!The Best Buys Available

Model 65810100 MHz Bench/Portable Scope

;fie Now.

.1 I $2395.00

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Model 65601Dual Trace Bench/Portable Scope

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A HYBRID COMBINING ANALOG ANDLOGIC FUNCTIONS

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or 8 Logic Channels, or 3 Analog and 8 Logic

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DEALER INQUIRIES INVITEDHead Office: 214 Dolomite Drive, Downsview, Ontario M3J 2P8

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where applicable.

OTTAWA (613) 238-7007 El

I

II

111

Camera Remote The System

ControlThe infra -red remote controllergives the freedom to shoot photosfrom a distance, even from theother side of a window.

MANY of the more recent cameras tocome onto the market have provision foran electric remote release, with the cameraeither being triggered directly or via anautowinder/motordrive. This type ofrelease simply consists of a twin cable witha push button switch at one end and aplug at the other to match the camera orwinder. The switch activates either theelectronic shutter or an actuator in thewinder. This method gives excellentreliability, but it still requires a long cableto carry the signal to the camera. This canbe undesirable for some types ofphotography, and the cable also makes anexcellent trip -wire!

For many purposes it is better to usea wire -less method of control, such as aninfra -red or ultrasonic system. The latteroffers slightly greater range, but infra -redsystems have the advantage of operatingquite well through a window, so that thecamera equipment outside the house canbe operated from within. The camera con-trol system described here is of the infra-red type, operates reliably over a range ofat least 6 metres, and is at least equal inthis respect to the air release which it wasdesigned to replace. It has mainly been us-ed with a Pentax LX camera plus auto -winder, but it also worked well when triedwith a Minolta XD7 (which is triggereddirectly), and it should work with anycamera which has an electric release facili-ty. The prototype has been built as asingle channel system, but the equipmentcould easily be modified for multichanneluse with multi -camera set-ups, as will beexplained in greater detail later.

TRANSMITTER

AFOSC

BUFFER -D)I.R. LED

The block diagram of Figure 1 shows thearrangement used in this remote controlsystem, as it is not practical to use a highoutput power from the receiver. A simpleDC system is consequently impractical, asthe signal received from the transmitterwould often be swamped by the ambientinfra -red level. Instead, an AC system isused, with the transmitter providing anamplitude modulated beam. The infra -redsignal is generated using a special type oflight emitting diode, and this is drivenfrom an audio oscillator via a buffer stagewhich provides the fairly high drive cur-rent required. This gives a crude form ofmodulation with the LED simply beingswitched from fully on to fully off, but forthis application nothing more complex isneeded.

NOTES:IC 1 55501 BFY51LED1 = TIL311

ci100u

RV110k

R11k

R22k2

The audio frequency output from thediode is not likely to be very large in prac-tice, and would typically only be a fewtens of microvolts. A high gain amplifieris therefore used to boost this signal to ahigh enough level to operate the followingstage, which is a Phase Locked Loop tonedecoder. This circuit has an electronicswitch at its output, and this is turned onif an input signal at a frequency within itsnarrow locking range is received. Thetransmitter is adjusted so that itsoperating frequency is at the centre of thelocking range, where the PLL decoder ismost sensitive.

There are two reasons for the use of aPLL decoder in the circuit; one is simplythat it gives almost total immunity tospurious triggering by electrical in-terference or noise. A second advantage isthat it enables two remote control systems

IC1555

C2I 22n

Fig. 2. The circus diagram of the transmitter stage.

Another special type of diode is usedat the receiver to produce an electricalsignal from the received infra -red pulses.This is a large photodiode that gives goodsensitivity, and although the diode itself issensitive to a large part of the light spec-trum, an integral infra -red filter removeslight outside the infra -red range. Thisprevents strong light in the visible part ofthe spectrum from saturating the diodeand preventing the system from operatingproperly.

I.R. LED

Fig. 1. A block diagram of the whole remote control system.

HIGHGAINAMP

P.L.L.TONE

DECODER

SW 1ON/OF F

I 6V

1OR

131

to be used side -by -side without one alsoactivating the other - provided the twooperate on slightly different frequenciesthat is.

A monostable multivibrator is usedas the next stage of the receiver, triggeredby the output switch of the PLL tonedecoder; the monostable drives a VMOSswitching transistor which in turn controlsthe camera. The monostable is used to en-sure that the VMOS switch is activated fora long enough time to operate the shutter,

MONOSTABLE

RECEIVER

VMOSCAMERA

SWITCH

ET1-JULY-1984-45

Circuit Ideas

even if only a brief input signal is received.This helps to give more reliable operationif the system is used at virtually its max-imum range.

Transmitter CircuitFigure 2 shows the circuit diagram of thetransmitter, based on a 555 astable oscilla-tor. This gives a roughly squarewavesignal, with RV1 used to trim the outputto the appropriate frequency (around 5kHz). The output stage of the 555 is bare-ly able to provide sufficient output cur-rent to drive infra -red emitter DI at the re-quired current of around 150 milliamps,so Q1 is used as an emitter follower bufferstage to give more reliable and consistentresults. Operating push-button on/offswitch SW1 supplies power to thetransmitter and activates the camera.

Receiver CircuitThe receiver unit is a little more complex,as can be seen from the circuit diagram ofFigure 3. D2 is the infra -red photo diodethis can be used as a photovoltaic cell,producing an output voltage which isroughly proportional to the receivedinfra -red intensity; however, slightly'higher sensitivity is obtained by using it ina potential divider circuit. Here its reverseresistance varies with the received infra-red intensity, giving a varying voltage atthe output of the divider circuit. Thissignal is coupled by C4 to the input of ahigh gain amplifier which uses Q2 and Q3as straighforward common emitteramplifiers. C5 rolls -off the response of thefirst amplifier in the radio frequencyrange to prevent instability. The couplingcapacitors can have quite low values dueto the fairly high operating frequency ofthe transmitter; this helps to filter out 60Hz hum received from AC lighting which

-R7

31100

RSMt7

LED

RII152

RlaNOUSICI NE5117IC.3 - 556Q2.3 BMOCbl VMS7A3

SW/2031/033

.C131011/

CS02 snotsLED2 /IL 201I

.".C3

RSI 2

Rs Iln

1000 CI

.0.,ICI

ISESS7IC3565

- II2GS

CS1:t .'CASIFRA

CS

WO .

DI

4 W

U: 2.1 .5'M

Fig. 3. The circuit diagram of the receiver stage.

could otherwise drive the amplifier intoclipping and desensitize the circuit to thesignal from the transmitter.

An NE567 (IC2) is used in the tonedecoder, R11 and D3 form the collectorload for its output transistor, and LED1lights up when the tone decoder is ac-tivated. This is useful when adjusting thefrequency control of the transmitter, andit also helps when setting -up the equip-ment ready for use.

The negative output signal from thetone decoder is used to trigger IC3, whichis a 555 used in the standard monostablemultivibrator configuration. Q4 is theVMOS output transistor, driven directfrom the output of IC3; note that thecamera or autowinder must be connectedto SKI so that Q4 is fed with signal of theright polarity (centre pin positive).

ConstructionThe connection from the camera orautowinder to the receiver is made usingan electric release for the particularcamera or winder you are using, and thisremote control unit can only be used if asuitable release is available. The push-button switch on the release is removedand a plug to match SK1 is fitted in its

"Special this week only - our Jacketed Wire comes withtwo pairs of pants."

place. With the camera or winder con-nected to SK1 (and switched on where ap-propriate), a multimeter set to a fairlyhigh DC volts range can be used to deter-mine the polarity of the voltage on SK1 sothat this can be correctly wired to theprinted circuit board.

Like the transmitter unit, the receiveris powered from four 1.5 V cells. As it islikely that the unit will be left running forlong periods, NiCad rechargeable cells areprobably the most practical power source,but primary cells can be used if preferred.

AdjustmentRV1 is given the correct setting by trialand error. With the output of thetransmitter aimed at D2 in the receiverfrom a short distance away, it should bepossible to get LED1 to light up by ad-justing RV1. If not, switch off both unitsat once and thoroughly recheck them forerrors. Once LED1 can be made to lightup, it is a matter of gradually moving thetwo units further apart and readjustingRV1, as necessary, to keep LED1 lit. Thisis continued until the maximum range ofabout seven metres is achieved.

Remember that the unit can onlyfunction properly if the infra -red radia-tion from the transmitter has a transpar-ent path to D2 at the receiver. The unit isquite directional, mainly due to the built-in lens of DI, and the output of thetransmitter needs to be aimed reasonablyaccurately at the receiver, especially whenthe system is used at something ap-proaching its maximum range.

If it is necessary to control two orthree cameras, a separate receiver unit foreach one must be used. However, C10 ineach unit must be given a slightly differentvalue (15nF, 22nF, and 33nF are suitable).A separate transmitter circuit can be usedfor each receiver, housed in a single caseand powered from the same battery. C2 ineach transmitter would have the samevalue as C10 in the receiver unit it is to ac-tivate. It would be possible to have asingle transmitter circuit with a switchedoperating frequency, but this would notgive the option of firing two or threecameras simultaneously. Eli

46-JULY-1984-ETI

Stylus TimerProject

Do you play your records with asmoothly -contoured, precision -engineered, highly -polishedstylus - or a worn-out nail?Check your playing hours withthe ETI Stylus Timer. Designand development by PhilWalker.

FOR modern styli and cartridge combina-tions, the life of the stylus may run to manyhundreds or even thousands of hoursbefore replacement is necessary. The trou-ble is that even at five hours each and everyday (which is quite a lot) it will take over sixmonths to accumulate 1,000 hours playingtime. If you are like us, you could easilyforget whether you changed the old naillast week or last year, quite apart fromknowing how long it has been used sincethen.

Don't worry, help is at hand - thisdevice is designed to measure the totalnumber of hours your stylus has been inuse since you last changed it and give someindication of that measurement.

The device has six LEDs which, in thebasic configuration, change every 167hours, totalling 1,000 hours. This could beused to indicate that a check on stylus con-dition would be carried out either at homeor by your local dealer. When the last onecomes on it will stay on until the device isreset (assuming the power is on).

As mentioned above, the basic designallows for 167 hours per step, the last oneoccurring after 1,000 hours. This can bemodified to 330, 400, 830, or even 1,700hours per step giving replacement times ofup to 10,000 hours for the very lightestequipment (or Scrooges), or 83 hours perstep if your equipment is a little heavierthan some or you want to keep your stylusin tip-top condition all the time.

In order to eliminate dependence onmains supplies when the equipment is notin use, the device contains a rechargeablebattery which provides the microamp or soneeded to keep the CMOS devices active.Also, the. LED display is turned off whennot required to conserve battery power. Toprevent accidents, the reset facility isdisabled when the device is on standby.

Designs DiscussedThe circuit uses standard CMOS integratedcircuits for most functions in order to keepthe standby power as small as possible.This enables us to use a 8V4 rechargeableNi-cad battery ensuring that with intermit-tent use the device should operate almostindefinitely. (In fact a normal dry -cell 9Vbattery will give a very long life but maynot like the charging current flowing into itvia R7).

The power for the LED display andthe timing signal for the logic are takenfrom the AC input. This is any 60 Hzvoltage source giving between 12 and 20 Vat about 50 mA. For preference this supplyshould be switched with the turntable orequipment mains supply.

The first method of detecting stylususe we considered involved detecting thepresence of a music signal from the pickup.However, if the signal was tapped off afterthe RIAA preamp, we realized the projectcouldn't be built by readers who lacked theconfidence to muck about inside their ex-pensive commercial hi-fi. On the otherhand, putting the project between the deckand the preamp would lead to the knottydesign problem of not degrading the

pickup performance. Thus we opted for amechanical solution, but adventurousreaders may care to adapt this project fortheir own needs. Note that we CANNOTgive any technical advice if you do try it.

The circuit operates by detecting whenthe tone arm is away from its rest positionand then allowing the rest of the circuit tocount at 60 or 120 Hz. The 60 or 120 Hz isdivided by about 72 million in order todriver the final counter at one pulse every167 hours. The already decoded outputs ofthis device (IC5) are used by the outputdrive (IC6) to power the display.

The final counter (IC5) has ten decod-ed outputs of which only the first six areused. These control IC6 and thus thedisplay. When the sixth output of IC5 goeshigh, it disables the counter chain causingthe sixth LED to remain on indefinitely.

IC6 contains six inverting bufferswhich have three -state outputs. This facili-ty is used to switch off the LEDs and con-serve power.

A transistor (Q2) was used in thestandby battery circuit so .that whenoperating from the AC input, the supplyvoltage to the ICs was a little different tothat when operating from battery alone.

ETI-JULY-1984-47

Stylus Timer

NOTEMI IS 401068M7 15 401038IC3 IS 45188ICI IS 402013ICS 10 40178IC6 IS 4502801 IS 7117802 15 8C1821DI 4 ARE 104148ZDI IS 6V8 400n116 ZENERLED1 IS 111321E02 5 ARE GREEN LEDSLEDS IS YELLOW LED1E07 IS RED LED

-NA/VWR710k

8481 8V47

+ C24700 NICAD

100

R6

C3 100n= P81

4 L1

7

10

IC3.

IC3b

-614

1K 1013

ICI

-..C4-"'an.1-8-114

3 15

2

4 3

7

10 10

18

CS

5 8

1 13 ICR--4--

ALL8430R

R10 14- LED2R11

R12+a,3 LED3

LEDS

11218

LEDS

LED7

Fig. 1. Circuit diagram of the ETI Stylus Timer. The various lettered links are used to select the timing period (see text).

HOW IT WORKSThe 60 Hz power input is rectified by BR1and charges C2 via DI. Q2 and R7 form asimple voltage regulator using the battery B1as a reference. If there is no AC input, thenD6 isolates the rectifier circuitry from Q2and BI supplies the very small bias currentneeded to keep the CMOS devices active viathe base -emitter junction of Q2.

R4, D3 and ZDI form a moderatelystable voltage for the optical sensor and aninput to the power detection circuitry 1C1b.The output from the optical sensor (LED1and Q1) is taken via R5 and R6 to !Cie eitherdirectly or via !Cie. This allows the circuit tooperate with either an open or blocked lightpath as required.

Depending on the position of link A -Bor A -C a 60 or 120 Hz signal will be appliedto ICI f. The voltage of this signal is limitedto RI, R2, D2 and ZDI to prevent damage toICI.

IC2 is connected such that it divides by220 or 219 as determined by the input fromICId. This is accomplished by the deviceloading its internal eight bit counter with thebinary number on its inputs each time itreaches a count of zero. In this case the mostsignificant seven bits are wired to 1101101X= 218,0 while the least signficant bit (X) isswitched between 0 and 1. The output fromthis stage drives IC3, a dual decade divider.The Q4 output from lC3a controls the divi-sion ratio of IC2 as outlined above. As the

Q4 output is only high for two clock periodsout of 10, the effective division ratio of IC2is:

8/10 x 220 + 2/10 x 219 = 219.8

IC3b is used to divide by 2 in the standardcircuit and then drives IC4 which does therest of the division required (a factor of 2"or 16384) to give a one cycle in 167 hourssignal.

IC5 is a decade counter with 10 decodedoutputs. Each output is high for one clockperiod of the 167 hour input signal (or longerif counting is suspended). Only the first sixoutputs are used to drive IC6 and the sixthoutput also inhibits IC3b to prevent furthercounting. IC6 is a hex buffer with three -stateoutputs which have a fairly high impedencestate by a signal on pin 4. This facility is usedto prevent the LED display taking currentwhile the AC supply is off.

The reset switch' PB1 is connected in anunusual place so that it can only pull the in-put to ICIa low when the power sense circuitindicates that the AC supply is present.When operated, the reset circuit applies ahigh logic level to the reset inputs of IC's 3, 4and 5 for about a second. IC2 is not resetand will cause an error of two or fourseconds in the timing, but in a hundred hoursor so, this is not significant.

Also the LED voltage can be stabilized atthe correct value. The configuration allowsthe battery to be trickle -charged from thesame supply.

ConstructionThe construction of the main unit isstraightforward if a little fiddly on accountof its small size. Assemble the componentsonto the PCB including the three links butexcluding LED 2-7. Place the assembledPCB in the bottom of the box and align itover the wider spaced fixing holes with C2next to the space for the battery. Mark thepositions for the LEDs on the front panel

and the jack sockets and PB1 on the backpanel. Also mark a position for the powercable grommet. Drill all these holes in sizesto fit your components.

Wire up the switch and sockets. Thecommon connection from R4 on the boardshould go to the sleeve connections on thejack sockets to prevent accidental short cir-cuits via the panel. The LEDs should nowhave their leads bent so that they will go in-to the board while the LED body protrudesthrough the panel. Finally connect the bat-tery connector and the AC power lead. Thelatter should be a twin lead shielded cableterminated in a three pin DIN plug orsimilar to pick up the supply.

DETECTOR

EMITTER

UNDER SIDE 0E13'

FELT OR NONSLIP MATTING

3.5mmJACK PLUG

FILL WITH EPDXYRESIN AND PAINT

PHOTOTRANStitOR

/ /

2.5mmJACK PLUG

Fig. 2. Constructional details of our sensor. Us-ing different sized jack plugs will prevent incor-rect connection.

48-JULY-I984-ETI

BATTERY

AC SUPPLY112 -15VI

a'6 6 6

NOTE ANODE CATHODE

FLAT

FLAT CATHODE LTD1-7 COLLECTOR 01

Fig. 3. Component overlay.

The SensorThe purpose of the sensor housing is tohold the emitter and receiver in line and ex-clude some of the ambient light. Our sen-sor was constructed from an offcut ofblack Plexiglas about 90 x 55 x 55 mm).A U-shaped slot was cut out of the longerside of the smaller piece; then a hole wasdrilled in the thickness of the material inboth legs of the U to take the opticaldevices and hold them in line. The backedge of the U was slotted to take the shield-ed wire from the phototransistor.

Three holes were drilled along the cen-tre line of the other piece of Plexiglas; twoto take wires and one to take a mountingscrew. The underside of the base piece waschannelled out using a rasp attachment in ahobbyist drill to conceal the wires.

The sensor device is mounted in thetop hole to reduce the amount of ambientlight reaching it. The screened wire fromthe phototransistor is run along the slot inthe plastic and down the hole in the base.The slot can be filled with resin and paintedwhen finished.

If a small three-way connector can beobtained, this could be used in place of thetwo jacks and a single length of shieldedcable would suffice to connect the sensor.

Power SupplyThe AC power supply is very simple andconsists of a small transformer, fuse, neonindicator and three pin DIN socketmounted in a small box. Construction isvery straightforward and, if the specifiedbox is used, most small 6 VA transformerswill fit onto the moulded pillars in the box,obviating the need for external screws.

Use and ModificationsTo use the stylus timer, the sensor shouldbe positioned so that the tone arm inter-rupts the light beam when it is in the restposition. Make sure that it does not foulthe arm at any time if you have any sort ofautomatic control.

If possible, the AC power supply forthe device should be obtained from yoursystem. Anything from 12 to 15 V AC maybe used without modification. Up to 25 Vmay be used, but R4 and R7 should then be1k0 1 W and 27k respectively. If the supplyis greater than 25 V, one side of anyavailable supply is grounded, or if youprefer not to tamper with your system,then use the simple power supply describ-ed.

With the sensor in position and asuitable AC supply connected, press the

reset button on the unit. The first greenLED should light and stay lit for 167 hoursof playing time, followed by the next LEDuntil the red LED lights to indicate replace-ment overdue. If the power supply is swit-ched off at any time, the accumulated timeis stored until the power is restored.

Other time intervals can be used in thedevice by changing the link positions.Changing A -B to A -C doubles the timeperiod. Changing G -J to G -K or G -L in-creases the interval by 21/2 or 5 respectivelywhile changing it to G -H halves it,although it will not stop on the last countas before. In some of these other positionsthe intervals between the lighting of eachLED may not be as regular as before(especially G -K). If it is desired to havecounting enabled when the light path isobstructed, then link D -F shoilld be chang-ed to D -E.

PARTS LIST

Resistors (all VaVV, 5%)RI,2 100kR3 330RR4 470RR5,8 47kR6,9 4M7R7 10kR10-15 680R

CapacitorsCl 10n ceramicC2 100u 40 V axial electrolyticC3,4 100n ceramic

SemiconductorsICI 4010613IC21C3IC4IC5IC6QIQ2D1-4ZD1BR1LEDILED2-5LED6LED7

40103B4518B4020B401713450213TIL78 IR receiverBC182L, 2N3904, etc.1N41486V8 400 mW zener50 V, 1 A bridge rectifierTIL32 IR transmitter2 mm green LED2 mm yellow LED2 mm red LED

MiscellaneousFBI subminiature131 8V4 Ni-cad

PCB battery clips; case 125(Vero 75-2682A); 3.5 and 2.and sockets; three pin DINto connect to power unit);small grommet; 100 x 55sheet.

push-button

x 65 x 30 mm5 mm jack plugsplug (if requiredthin twin cable;x 6 mm acrylic

AC Power Unit (If Required)12 V, 6 VA mains transformer; 100 mA fuseand fuseholder; mains neon; case 125 x 65x 50 mm (Vero ref. 75-2684B); three pinDIN socket; line cord; grommet; solder tags.

Eli

ETI-JULY-1984-49

ajects,,sing RelaysSCR's&Tnacs

ElectronicsSimplified -Crystal SetConstruction

Electronics Today BookshelfBased on sales

from

Moorshead

Publications

Book Service

lectronic Books1 BP73: REMOTE CONTROL PROJECTS $8.10

OWEN BISHOPThis book is aimed primarily at the electronics enthusiastwho wishes to experiment with remote control. Full explana-tions have been given so that the reader can fully understandhow the circuits work and can more easily see how to modifythem for other purposes, depending on personal re-quirements. Not only are radio control systems consideredbut also infra -red. visible light and ultrasonic systems as arethe use of Logic ICs and Pulse position modulation etc

2 BP90: AUDIO PROJECTS $7.60F.G. RATERCovers in detail the construction of a wide range of audit,projects. The text has been divided into preamplifiers andmixers, power amplifiers, tone controls and matching andmiscellaneous projects.

3 The GIANT HANDBOOK OF ELECTRONIC CIRCUITSTAB No.1300 $27.95About as twice as thick as the Webster's dictionary, and hav-ing many more circuit diagrams, this book is ideal for any ex-perimenter who wants to keep amused for several centuriesIf there isn't a circuit for it in here, you should have no dif-ficulty convincing yourself you don't really want to build it

4 ELECTRONIC TROUBLESHOOTING HANDBOOKAB019 $11.95This workbench guide can show you how to pinpoint circuittroubles in minutes, how to test anything electronic, and howto get the most out of low cost test equipment You can usi,any and all of the time -saving shortcuts to rapidly locate antirepair all types of electronic equipment malfunctions.

5 BP74: ELECTRONIC MUSIC PROJECTS $7.20R.A. PENFOLDAlthough one of the more recent branches of amateur elec-tronics, electronic music has now become extremely popularand there are many projects which fall into this category. Thepurpose of this book is to provide the constructor with anumber of practical circuits for the less complex items ofelectronic music equipment, including such things as a FuzzBox, Waa-Waa Pedal, Sustain Unit, RevtJrberation andPhaser-Units, Tremelo Generator etc.

8 BP44: IC 555 PROJECTS $ 7.75E.A. PARR, 11.Sc.,C.Eng., MILE.Every so often a device appears that is so useful that onewonders how life went on before without it. The 555 timer issuch a device. Included in this book are Basic and GeneralCircuits, Motor Car and Model Railway Circuits, Alarms andNoise Makers as well as a section on the 556, 558 and 559timers.

7 BP37: 50 PROJECTS USING RELAYS,SCR's & TRIACS $7/5F.G.RAYER, T.Eng.(CEI),Assoc.JERERelays, silicon controlled rectifiers (SCR's) and bi-directionaltriodes (TRIACs) have a wide range of applications in elec-tronics today. This book gives tried and practical working cir-cuits which should present the minimum of difficulty for theenthusiast to construct. In most of the circuits there is a widelatitude in component values and types. allowing easymodification of circuits or ready adaptation of them to in-dividual needs.

8 BP79: RADIO CONTROL FOR BEGINNERS $6.80F.G. RAYER, T.Eng.(CEI),Assoc.IERE.The aim of this book is to act as an introduction to RadioControl for beginners to the hobby. The book will commenceby dealing with the conditions that are allowable for suchthings as frequency and power of transmission. This is follow-ed by a "block" explanation of how control -device andtransmitter operate and receiver and actuator(s) produce mo-tion in a model.

Details are then given of actual solid state transmittingequipment which the reader can build. Plain and loadedaerials are then discussed and so is the f ield-strength meter tohelp with proper setting up.

The radio receiving equipment is then dealt with whichincludes a simple,receiver and also a crystal controlledsuperhet. The book ends with the electro-mechanical meansof obtaining movement of the controls of the model.

9 99 TEST EQUIPMENT PROJECTS YOU CAN BUILDTAB No.805 $15.95An excellent source book for the hobbyist who wants to buildup his work bench inexpensively. Projects range from a sim-ple signal tracer to a 50MHz frequency counter. There arecircuits to measure just about any electrical quantity.voltage, current, capacitance, impedance and more. Thevariety is endless and includes just about anything you couldwish for!

1 0 BP76: POWER SUPPLY PROJECTS 7.75.PENFOLD

Line power supplies are an essential part of many electronicsprojects. The purpose of this book is to give a number ofpower supply designs, including simple unstabilised types,fixed voltage regulated types, and variable voltage stabiliseddesigns, the latter being primarily intended for use as benchsupplies for the electronics workshop. The designs providedare all low voltage types for semiconductor circuits.

There are other types of power supply and a number ofthese are dealt with in the final chapter, including a cassettepower supply, Ni-Cad battery charger, voltage step up circuitand a simple inverter.

ELECTRONIC THEORYELEMENTS OF ELECTRONICS - AN ON -GOING SERIESF.A. WILSON, C.G.I.A., C.Eng.,8P62: BOOK 1. The Simple Electronic Circuit

and Components $8.45BP63: BOOK 2. Alternating Current

Theory $8.45BP64: BOOK 3. Semiconductor

Technology $8.45BP77: BOOK 4. Microprocessing Systems $11.70And CircuitsBP89: BOOK 5. Communication $11.70The aim of this series of books can be stated quite simply -it is to provide an inexpensive introduction to modern elec-tronics so that the reader will start on the right road bythoroughly understanding the fundamental principles involy-ed.

Although written especially for readers with no morethan ordinary arithmetical skills, the use of mathematics isnot avoided, and all the mathematics required is taught asthe reader progresses.

Each book is a complete treatise of a particular branchof the subject and, therefore, can be used on its own with oneproviso, that the later books do not duplicate material fromtheir predecessors, thus a working knowledge of the subjectscovered by the earlier books is assumed

BOOK 1: This book contains all the fundamental theorynecessary to lead to a full understanding of the simple elec-tronic circuit and its main components

BOOK 2: This book continues with alternating currenttheory without which there can be no comprehension ofspeech. music, radio, television or even the electricityutilities.

BOOK 3. Follows on semiconductor technology,leading up to transistors and integrated circuits.

BOOK 41 A complete description of the internal work-ings of microprocessor.

BOOK 5: A book covering the whole communicationscene.

PH247: DIGITAL TECHNIQUES $19.95Covers logic circuits, Boolean Algebra, flip-flops, registers,combinational logic circuitry, and digital design.

PROJECTS

BM: ELECTRONIC PROJECTS FOR BEGINNERS $ 7.75E.G. RAYER, T.Eng.(CEI), Assoc.IEREAnother book written by the very experienced author - Mr.F.G. Raver - and in it the newcomer to electronics, will finda wide range of easily made projects. Also, there are a con-siderable number of actual component and wiring layouts, toaid the beginner.

Furthermore, a number of projects have been arrangedso that they can be constructed without any need for solder-ing and, thus. avoid the need for a soldering iron.

Also, many of the later projects can be built along thelines as those in the 'No Soldering' section so this may con-siderably increase the scope of projects which the newcomercan build and use

221: 28 TESTED TRANSISTOR PROJECTSR.TORRENS $5.00Mr. Richard Torrens is a well experienced electronicsdevelopment engineer and has designed, developed, builtand tested the many useful and interesting circuits includedin this book. The projects themselves can be split down intosimpler building blocks, which are shown separated by boxesin the circuits for ease of description. and also to enable anyreader who wishes to combine boxes from different projectsto realise ideas of his own

BP71: ELECTRONIC HOUSEHOLD PROJECTS $7.20R. A. PENFOLDSome of the most useful and popular electronic constructionprojects are those that can be used in or around the home.The circuits range from such things as '2 Tone Door Buzzer',Intercom, through Smoke or Gas Detectors to Baby andFreezer Alarms.

See order form in this issue.

50-JULY-1984-ETI

Electronics Today BookshelfBP49: POPULAR ELECTRONIC PROJECTS $ 7.75R.A. PENFOLDIncludes a collection of the most popular types of circuitsand projects which, we feel sure, will provide a number ofdesigns to interest most electronics ...onstructors. The pro-jects selected cover a very wide range and are divided intofour basic types: Radio Projects, Audio Projects, HouseholdProjects and Test Equipment.

BP94: ELECTRONIC PROJECTS FOR CARS AND BOATSR.A. PENFOLD $7.60Projects, fifteen in all, which use a 12V supply are the basisof this book. Included are projects on Windscreen WiperControl, Courtesy Light Delay, Battery Monitor, CassettePower Supply, Lights Timer, Vehicle Immobiliser, Gas andSmoke Alarm, Depth Warning and Shaver Inverter.

BP95: MODEL RAILWAY PROJECTS $7.60Electronic projects for model railways are fairly recent andhave made possible an amazing degree of realism. The pro-jects covered include controllers, signals and sound effects:striboard layouts are provided for each project.

B P93: ELECTRONIC TIMER PROJECTS $7.60E.G. RAVERWindscreen wiper delay, darkroom timer and metronomeprojects are included. Some of the more complex circuits aremade up from simpler sub -circuits which are dealt with in-dividually.

BP113: 30 Solderless Breadboard Projects -Book 2R.A. Penfold $8.85A companion to BP107. Describes a variety of projects thatcan be built on plug-in breadboards using CMOS logic IC's.Each project contains a schematic, parts list and operationalnotes.

BP104: Electronic Science ProjectsOwen Bishop $8.85Contains 12 electronic projects with a strong scientificflavour. Includes Simple Colour Temperature Meter, Infra -Red Laser, Electronic clock regulated by a resonating spring,a 'Scope with a solid state display, pH meter and electro-cardiograph.

B P110: HOW TO GET YOUR ELECTRONIC PROJECTSWORKING $7.60R.A. PENFOLDWe have all built circuits from magazines and books only tofind that they did not work correctly, or at all, when first swit-ched on. The aim of this book is to help the reader overcomejust these problems by indicating how and where to startlooking for many of the common faults that can occur whenbuilding up projects.

B P84: DIGITAL IC PROJECTS $7.60E.G. RAVER, T.Eng.(CEI),Assoc.IEREThis book contains both simple and more advanced projectsand it is hoped that these will be found of help to the readerdeveloping a knowledge of the workings of digital circuits.To help the newcomer to the hobby the author has includeda number of board layouts and wiring diagrams. Also themore ambitious projects can be built and tested section bysection and this should help avoid or correct faults thatcould otherwise be troublesome. An ideal book for bothbeginner and more advanced enthusiast alike.

BP67: COUNTER DRIVER AND NUMERAL DISPLAYPROJECTS $7.05F.G. RAYER, T.Eng.(CEI), Assoc. IERENumeral indicating devices have come very much to theforefront in recent years and will, undoubtedly, find increas-ing applications in all sorts of equipment. With present dayintegrated circuits, it is easy to count, divide and displaynumerically the electrical pulses obtained from a great rangeof driver circuits.

In this book many applications and projects usingvarious types of numeral displays, popular counter anddriver IC's etc are considered.

BP99: MINI -MATRIX BOARD PROJECTS $7.60R.A. PENFOLDTwenty useful projects which can all be built on a 24 x 10hole matrix board with copper strips. Includes Doorbuzzer,Low -voltage Alarm. AM Radio, Signal Generator, ProjectorTimer. Guitar Headphone Amp, Transistor Checker andmore.

B P103: MULTI -CIRCUIT BOARD PROJECTS $ 7.60R.A. PENFOLDThis book allows the reader to build 21 fairly simple elec-tronic projects, all of which may be constructed on the sameprinted circuit board. Wherever possible. the same com-ponents have been used in each design so that with arelatively small number of components and hence low cost,it is possible to make any one of the projects or by re -usingthe components and P C B all of the projects.

BP107: 30 SOLDERLESS BREADBOARD PROJECTS -B OOK 1 $8.85R.A. PENFOLDA "Solderless Breadboard" is simply a special board onwhich electronic circuits can be built and tested. The corn.ponents used are just plugged in and unplugged as desired.The 30 projects featured in this book have been speciallydesigned to be built on a "Verobloc" breadboard. Whereverpossible the components used are common to several pro-jects, hence with only a modest number of reasonably inex-pensive components it is possible to build, in turn, every pro-ject shown.

BP106: MODERN OP -AMP PROJECTS $7.60R.A. PENFOLDFeatures a wide range of constructional projects which makewe of op -amps including low -noise, low distortion, ultra -highinput impedance, high slew -rate and high output currenttypes.

CIRCUITS

How to Design Electronic ProjectsBP127 $8.95Although information on standard circuit blocks is available,there is less information on combing these circuit partstogether. This title does just that. Practical examples are usedand each is analysed to show what each does and how to ap-ply this to other designs.

Audio Amplifier ConstructionBP122 $8.95A wide circuits is given, from low noise microphone and tapehead preamps to a 100W MOSFET type. There is also the cir-cuit for 12V bridge amp giving 18W. Circuit board or strip -board layout are included. Most of the circuits are wellwithin the capabilities for even those with limited ex-perience.

Electronic Circuits for Model RailwaysBP213 $4.50Lots of circuits including three types of controllers includingone with simulated inertia and one with high power. Signal-ling and lighting systems are discussed at length and thesuperession of RF interference. There are also 4 "steam whis-tle" and "chuff er" circuits.

BP80: POPULAR ELECTRONIC CIRCUITS -B OOK 1 $7.75R.A. PENFOLDAnother book by the very popular author. Mr. R.A. Penfold,who has designed and developed a large number of variouscircuits. These are grouped under the following generalheadings; Audio Circuits, Radio Circuits, Test Gear Circuits,Music Project Circuits, Household Project Circuits andMiscellaneous Circuits.

BP98: POPULAR ELECTRONIC CIRCUITS, BOOK 2 $8.85R.A. PENFOLD70 plus circuits based on modern components aimed at thosewith some experience.

B P39: 50 (FET) FIELD EFFECT TRANSISTORPROJECTS $ 6.75,F.G. RAYER, T.Eng.(CEI),Assoc.IEREField effect transistors (FETs), find application in a widevariety of circuits. The projects described here include radiofrequency amplifiers and converters. test equipment andreceiver aids, tuners, receivers, mixers and tone controls, aswell as various miscellaneous devices which are useful in thehome.

This book contains something of particular interest forevery class of enthusiast - short wave listener, radioamateur, experimenter or audio devotee.

B1417: SIMPLE L.E.D. CIRCUITS $5.40R.N. SOARSince it first appeared in 1977, Mr. R.N.Soar's book has prov-ed very popular. The author has developed a further range ofcircuits and these are included in Book 2. Projects include aTransistor Tester, Various Voltage Regulators. Testers and soon.

B P42: 50 SIMPLE L.E.D. CIRCUITS $3.05R.N. SOARThe author of this book, Mr. R N. Soar, has compiled 50 in-teresting and useful circuits and applications. covering manydifferent branches of electronics. using one of the most inex-pensive and freely available components - the Light Emit-ting Diode IL.E.D.1 A useful book for the library of bothbeginner and more advanced enthusiast alike

THE ACTIVE FILTER HANDBOOKTAB No.1133 $13.95Whatever your field - computing, communications, audio,electronic music or whatever - you will find this book theideal reference for active filter design.

The book introduces filters and their uses. The basicmath is discussed so that the reader can tell where all designequations come from. The book also presents many practicalcircuits including a graphic equalizer, computer tape inter-face and more.

MASTER HANDBOOK OF 1001 PRACTICAL CIRCUITSTAB No.800 $19.95MASTER HANDBOOK OF 1001 MORE PRACTICAL CIR-CUITSTAB No.804 $23.95Here are transistor and IC circuits for just about any applica-tion you might have. An ideal source book for the engineer,technician or hobbyist. Circuits are classified according tofunction, and all sections appear in alphabetical order.

B P118: HOW TO USE OP AMPS $8.85E.A. PARRA designer's guide covering several op amps, serving as asource book of circuits and a reference book for designcalculations. The approach has been made as non -mathematical as possible.


BP65: SINGLE IC PROJECTS $6.05R.A.PE NFOLDThere is now a vast range of ICs available to the amateurmarket, the majority of which are not necessarily designedfor use in a single application and can offer unlimitedpossibilities. All the projects contained in this book are sim-ple to construct and are based on a single IC. A few projectsemploy one or two transistors in addition to an IC but in mostcases the IC is the only active device used.

BP117: PRACTICAL ELECTRONIC BUILDING BLOCKSBOOK 1 $7.60Virtually any electronic circuit will be found to consist of anumber of distinct stages when analysed. Some circuits in-evitably have unusual stages using specialised circuitry, butin most cases circuits are built up from building blocks ofstandard types.

This bpok is designed to aid electronics enthusiasts wholike to experiment with circuits and produce their own pro-jects rather than simply follow published project designs.

The circuits for a number of useful building blocks areincluded in this book. Where relevant, details of how tochange the parameters of each circuit are given so that theycan easily be modified to suit individual requirements.

223: 50 PROJECTS USING IC CA3130 $5.00R.A.PEN FOLDIn this book, the author has designed and developed anumber of interesting and useful projects which are dividedinto five general categories. I - Audio Projects II - R FProjects III - Test Equipment IV - Household Projects V- Miscellaneous Projects

224: 50 CMOS IC PROJECTS $3.75R.A. PENFOLDCMOS IC's are probably the most versatile range of digitaldevices for use by the amateur enthusiast They are suitablefor an extraordinary wide range of applications and are alsosome of the most inexpensive and easily available types ofIC.

Mr. R A Penfold has designed and developed a numberof interesting and useful projects which are divided into fourgeneral categories- I - Multivibrators II - Amplifiers andOscillators III - Trigger Devices IV - Special Devices.

THE MASTER IC COOKBOOKTAB No.1199 $17.95If you've ever tried to find specs for a so called 'standard'chip, then you'll appreciate this book. C L Hallmark hascompiled specs and pinout for most types of ICs that you'dever want to use

B P118: PRACTICAL ELECTRONIC BUILDING BLOCKS -Book 2R.A. PENFOLD $7.60This sequel to BP117 is written to help the reader create and experiment with his own circuits by combining standard typecircuit building blocks. Circuits concerned with generatingsignals were covered in Book 1, this one deals with process-ing signals. Amplifiers and filters account for most of thebook but comparators, Schmitt triggers and other circuits arecovered.

BP24: 50 PROJECTS USING IC741 $3.75RUDI & UWE REDMERThis book, originally published in Germany by TOPP, hasachieved phenomenal sales on the Continent and Babanidecided, in view of the fact that the integrated circuit used inthis book is inexpensive to buy, to make this unique bookavailable to the English speaking reader. Translated from theoriginal German with copious notes, data and circuitry, a"must" for everyone whatever their interest in electronics.

VMOS PROJECTS $7.70PENFOLD

Although modern bipolar power transistors give excellentresults in a wide range of applications, they are not withouttheir drawbacks or limitations This book will primarily beconcerned with VMOS power FE Ts although powerMOSFETs will be dealt with in the chapter on audio circuits.A number of varied and interesting projects are coveredunder the main headings of. Audio Circuits. SoundGenerator Circuits, DC Control Circuits and Signal ControlCircuits

B P50: IC LM3900 PROJECTS $5.40H.KYBETT,B.Sc., C.Eng.The purpose of this book is to introduce the LM3900 to theTechnician, Experimenter and the Hobbyist. It provides thegroundwork for both simple and more advanced uses, and ismore than just a collection of simple circuits or projects.

Simple basic working circuits are used to introduce thisIC. The LM3900 can do much more than is shown here, this isjust an introduction. Imagination is the only limitation withthis useful and versatile device. But first the reader mustknow the basics and that is what this book is all about.

ELECTRONIC DESING WITH OFF THE SHELF INTEGRATEDCIRCUITSAB016 $12.95This practical handbook enables you to take advantage ofthe vast range of applications made possible by integratedcircuits. The book tells how, in step by step fashion, to selectcomponents and how to combine them into functional elec-tronic systems. If you want to stop being a "cookbook hob-byist", then this is the book for you.

ETI-JULY-1984-51

Electronics Today BookshelfRADIO AND

COMMUNICATIONSBP96: CB PROJECTS $7.60RA. PENFOLDProtects include speech processor, aerial booster, cordlessmike, aerial and harmonic filters, field strength meter. powersupply, CB receiver and more

222: SOLID STATE SHORT WAVE RECEIVERS FORBEGINNERS $4.70R.A. PENFOLDIn this book, R A Penfold has designed and developedseveral modern solid state short wave receiver circuits thatwill give a fairly high level of performance, despite the factthat they use only relatively few and inexpensive com-ponents

111.91: AN INTRODUCTION TO RADIO DKing $ 7.60This book is divided into two main sections one to amateurband reception, the other to broadcast bands Advice is givento suitable equipment and techniques A number of relatedconstructional projects are described

B P105: AERIAL PROJECTS $7.60R.A. PENFOLDThe subject of aerials is vast but in this book the author hasconsidered practical designs including active, loop and fer-rite aerials, which give good performances and arereasonably simple and inexpensive to build The complextheory and math of aerial design are avoided

BP125: 25 Simple Amateur Band AerialsE.M. Noll $7.60Starting from simple dipoles through beam, triangle and evenmini-rhombics (made from TV masts and 400ft of wire) this ti-tle describes several simple and inexpensive aerials to con-struct yourself. A complete set of dimension table are in-cluded.

BP46: RADIO CIRCUITS USING IC's $ 5.40I.B. DANCE, M.Sc.This book describes integrated circuits and how they can beemployed in receivers for the reception of either amplitudeor frequency modulated signals The chapter on amplitudemodulated (a m) receivers will be of most interest to thosewho wish to receive distant stations at only moderate audioquality, while the chapter on frequency modulation (f mreceivers will appeal to those who desire high fidelity recep-tion

B P92: ELECTRONICS SIMPLIFIED -CRYSTAL SETCONSTRUCTION $6.80F.A. WILSONAimed at those who want to get into construction withoutmuch theoretical study Homewound coils are used and allprojects are very inexpensive to build

BP70, TRANSISTOR RADIO FAULT-FINDING CHART$ 1,00CHAS. E. MILLERAcross the top of the chart will be found four rectangles con-taining brief descriptions of various faults, vis - soundweak but undistorted, set dead. sound low or distorted andbackground noises One then selects the most appropriate ofthese and following the arrows, carries out the suggestedchecks in sequence until the fault is cleared

AUDIO

205: FIRST BOOK OF H141 LOUDSPEAKERENCLOSURES $3.05B.B. BARAN!This book gives data for building most types of loudspeakerenclosure Includes corner reflex, bass reflex, exponentialhorn, folded horn, tuned port, klipschorn labyrinth, tunedcolumn, loaded port and multi speaker panoramic Manyclear diagrams for every construction showing the dimen-sions necessary

110W TO BUILD A SMALL BUDGET RECORDING STUDIOFROM SCRATCH. . .

TAB No.1166 $15.95The author, F Alton Everest, has gotten studios togetherseveral times, and presents twelve complete, tested designsfor a wide variety of applications If all you own is a monocassette recorder, you don't need this book If you don't wantyour new four track to wind up sounding like one, though,you shouldn't be without it.

BP51: ELECTRONIC MUSIC AND CREATIVE TAPERECORDING $7.75M.K. BERRYElectronic music is the new music of the Twentieth CenturyIt plays a large part in "pop" and "rock" music and, in fact,there is scarcely a group without some sort of synthesiser orother effects generator.

This book sets out to show how electronic music can bemade at home with the simplest and most inexpensive ofequipment. It then describes how the sounds are generatedand how these may be recorded to build up the final com-position

BP81: ELECTRONIC SYNTHESISER PROJECTS $6.80M.K. BERRYOne of the most fascinating and rewarding applications ofelectronics is in electronic music and there is hardly a grouptoday without some sort of synthesiser or effects generatorAlthough an electronic synthesiser is quite a complex pieceof electronic equipment, it can be broken down into muchsimpler units which may be built individually and these canthen be used or assembled together to make a complete in-strument

ELECTRONIC MUSIC SYNTHESIZERSTAB No.1167 $10.95If you're fascinated by the potential of electronics in thefield of music, then this is the book for you Included is dataon synthesizers in general as well as particular models. ThereIS also a chapter on the various accessories that areavailable

TEST EQUIPMENT

B P75: ELECTRONIC TEST EQUIPMENTCONSTRUCTION $6.80E.G. BAYER, T.Eng. (CEO, Assoc. !EREThis book covers in detail the construction of a wide range oftest equipment for both the E lectronics Hobbyists and RadioAmateur Included are projects ranging from an EFTAmplified Voltmeter and Resistance Bridge to a FieldStrength Indicator and Heterodyne Frequency Meter. Not on -IV can the home constructor enjoy building the equipmentbut the finished projects can also be usefully utilised in thefurtherance of his hobby.

THE POWER SUPPLY HANDBOOKTAB No.806 $15.95A complete one stop reference for hobbyists and engineer,Contains high and low voltage power supplies of every con-ceivable type as well mobile and portable units

REFERENCE

B11115: INTERNATIONAL TRANSISTOR EQUIVALENTSGUIDE $11.75ADRIAN MICHAELSThis book will help the reader to find possible substitutes fora popular user -orientated selection of modern transistors.Also shown are the material type, polarity, manufacturerselection of modern transistors Also shown are the materialtype, polarity, manufacturer and use. The Equivalents aresub -divided into European, American and Japanese The pro-ducts of over 100 manufacturers are included. An essentialaddition to the library of all those interested in electronics,be they technicians, designers, engineers or hobbyists Fan-tastic value for the amount of information it contains.

B P108: INTERNATIONAL DIODE EQUIVALENTS GUIDEADRIAN MICHAELS $8.95This book is designed to help the user in finding possiblesubstitutes for a large user orientated selection of the manydifferent types of semiconductor diodes that are availabletoday. Besides simple rectifier diodes also included arcZener diodes, LEDs, Diacs Triacs, Thyristors, Photo diodesand Display diodes

B PI: FIRST BOOK OF TRANSISTOR EQUIVALENTS ANDSUBSTITUTES $5.75B.B. BARAN'This guide covers many thousands of transistors showingpossible alternatives and equivalents Covers transistorsmade in Great Britain, USA. Japan, Germany, France, Europe,Hong Kong. and includes types produced by more than 120different manufacturers

BP14: SECOND BOOK OF TRANSISTOR EQUIVALENTSAND SUBSTITUTES $6.75B.B. BARAN!The "First Book of Transistor Equivalents" has had to bereprinted 15 times The "Second Book 'produced in the samestyle as the first book, in no way duplicates any of the datapresented in it The "Second Book" contains only additionalmaterial and the two books complement each other andmake available some of the most complete and extensive in-formation in this field. The interchangeability data coverssemiconductors manufactured in Great Britain, USA, Ger-many, France, Poland, Italy, East Germany, Belgium, Austria,Netherlands and many other countries

TOWER'S INTERNATIONAL OP -AMP LINEAR IC SELECTORTAB No.1216 $12.95This b.,ok contains a wealth of useful data on over 5,000 Op -amps and linear ICs - both pinouts and essentialcharacteristics A comprehensive series of appendices con-tain information on specs. manufacturers, case outlines andso on

CMOS DATABOOKTAB No.9114 $9.45There are several books around with this title, but most arejust collections of manufacturers' data sheets This one, byBill Hunter, explains all the intricacies of this useful family oflogic devices the missing link in getting your owndesigns working properly Highly recommended to anyoneworking with digital circuits.


ROBOTICSTHE COMPLETE HANDBOOK OF ROBOTICSTAB No.1071 $15.95All the information you need to build a walking, talkingmechanical friend appears in this book. Your robot can takemany forms and various options - light, sound, and proximi_ty sensors - are covered in depth

HOW TO BUILD YOUR OWN SELF PROGRAMMINGROBOTTAB No.1241 $13.95A practical guide on how to build a robot capable of learninghow to adapt to a changing enviroment The creaturedeveloped in the book, Rodney, is fully self programming,can develop theories to deal with situations and apply thosetheories in future circumstances.

B UILD YOUR OWN WORKING ROBOTTAB No.841 $10.95Contains complete plans - mechanical, schematics, logicdiagrams and wiring diagrams - for building Buster Busteris a sophisticated experiment in cybernetics you can build instages. There are two phases involved: first Buster is leashled, dependent on his creator for guidance; the second phasemakes Buster more independent and able to get out of toughsituations.

VIDEO

BP100: AN INTRODUCTION TO VIDEOD.K. MATHEWSON $7.60Presents in as non -technical a way as possible how a videorecorder works and how to get the best out of it and its ac-cessories Among the items discussed are the pros and consof the various systems, copying and editing, internationaltape exchange and understanding specifications

Tab1519: ALL ABOUT HOME SATELLITETELEVISION $22.95Covers such aspects as where to buy, problems in setting upyour TVRO station and how to solve them, antenna sitingand equipment selection

Tab1490: VIDEO CASSETTE RECORDERS:B UYING, USING AND MAINTAINING $14.95A complete handbook for the video enthusiast You'll learnabout how the systems work and how to choose as well astake a technical look at the inside workings. There are alsosections on making your own video recordings

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PH255: COMPLETE GUIDE TO READING SCHEMATICDIAGRAMS, 2nd EditionJ. DOUGLAS -YOUNG $9.95Packed with scores of easy -to -understand diagram and in-valuable troubleshooting tips as well as a circuit finder chartand a new section on logic circuits.

B P101: HOW TO IDENTIFY UNMARKED IC'S $2.20K.H. RECORROriginally published as a feature in 'Radio Electronics', thischart shows how to record the particular signature of an un-marked IC using a test meter, this information can then be us-ed with manufacturer's data to establish the application

B ASIC TELEPHONE SWITCHING SYSTEMSTALLEYHB27 $15.50The Revised Second Edition of this book, for trainee andengineer alike, includes updated statistical data ontelephone stations, and new and improved signaling methodsand switching techniques. It also includes E & M signaling in-terf ace for electronic central offices and automatic numberidentification methods used in step-by-step, panel andcrossbar central off ices

PH252: DIGITAL ICs: HOW THEY WORK AND HOWTO USE THEMA. BARBER $10.95The dozens of illustrations included in this essentialreference book will help explain time -saving test procedures,interpreting values, performing voltage measurements. andmuch morel

AUDIO AND VIDEO INTERFERENCE CURESKAHANERHB21 $8.95A practical work about interference causes and cures that affect TV, radio, hi-fi, CB, and other devices Provides all the in-formation needed to stop interference Schematic wiringdiagrams of filters for all types of receivers and transmittersare included Also, it supplies simple filter diagrams toeliminate radio and TV interference caused by noisy homeappliances, neon lights, motors, etc

8P121: How to Design and Make Your Own PCBsRA. Penfold $7.60The emphasis is on practical rather than theoretical techni-ques. Starts by giving simple methods of copying frommagazines, carries on with photographic methods of produc-ing PCBs and continues with layout design

52-JULY-1984-ETI

Go ahead and answer his question, dear. If he's smarter and stronger thanyou, how come you're giving the orders?

It's a new speaker design. It seems to work best with vocal music.

ETINEXTMONTHRobotsRoger Allan looks at thenew robotics: small, af-fordable robots for homeand educational uses.

Model Railway SwitchController ProjectTurn out those turnouts with a capacitive dischargeosrvfem-t thnt ,;etr..-21 Errhtc eAc .van

rrojectsby R.A. PenfoldList Price $7.70

Number BP83

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Available from: Moorshead Publications 25 Overlea Blvd.Suite 601, Toronto, Ontario M4H 1B1 (416) 423-3262

\See order form in this issue. All prices include shipping. No sales tax applies

ETI Car Ramp/Magazine BinderIt's spring again, and time to change the oil and find out what's caus-ing that annoying rattle when the engine's idling. We know what adrag it can be, especially when your head gets stuck between theground and the oil pan, so we're offering our incredible new ETI CARRAMPS!

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Sturdily made from the finest materials, the Car Ramp/MagazineBinder offers you a lifetime of enjoyable use, unless of course you ac-tually try to drive your car up onto them. They're available for $9.25each - don't forget to specify which one you'd like - and Ontarioresidents, sadly, must add 707o Provincial Sales Tax. Order from:

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Timing long periods has alwaysbeen a problem because of thehigh leakage characteristics ofthe timing capacitor. This is nolonger true. The XR-2240 IC isa programmable timer capableof producing ultra -long timedelays without sacrificing ac-

curacy.

THIS IC CAN generate time delays from microseconds up to five days, and with alittle ingenuity can generate a delay of a couple of years! A functional block diagramof the IC is shown in Figure I. "

The circuit consists of an internal timebase generator, a programmable 8 -bitcounter and a control flip-flop. The time delay at the output is set by an external CRnetwork and can be any period from 1.CR to 255.CR. Herein lies the secret. The CRtimebase generator can be set to give a very accurate short period, and binarymultiples of this short period are then programmed and taken from the output. Eachoutput is capable of sinking approximately 5 mA of load current.

The features of the IC are:1. Timing from microseconds to days.2. Programmable delays: I.CR to 255.CR3. Wide supply voltage range: 4 V to 15 V4. TTL compatible inputs and outputs5. High accuracy: 0.5%6. Excellent temperature stability7. Period T=CxR

Circuit OperationThe timing cycle is initiated by a positive -going pulse on pin 11. This trigger pulse per-forms three functions:I. Activates the timebase generator2. Enables the counter3. Sets all counter outputs to the /ow state

The timebase generator produces timing pulses with a period, T, equal to 1.0 R.These clock pulses are counted by the binary counter inside the IC and the timingperiod is complete when a positive -going pulse is applied to pin 10 (i.e., the circuit isreset). In most applications, one or more of the output terminals are connected backto the reset input. The circuit will commence timing when the trigger pulse is applied,and automatically reset on the completion of the timing period.

Remember, the outputs are normally high and are set to low when timing is in-itiated, returning again to the high level on completion of the timing period.

VESWIJEIT 'Sd d

Super Timer --The XR-2240

Designers Notebook

REGULATOROUTPUT

TIME BASEOUTPUT

TIMING RC

MODULATION

TRIGGER

RESET

Fig. 1. Functional block diagram of theXR-2240.

Circuit ConstructionThe binary outputs, pins 1 to 8, are opencollector and can be connected together toa common pull-up resistor. The output ofthe timer will be low as long as any oneoutput is low. In this manner the timedelays associated with each output can beadded by simply connecting them togetherto a common bus. The outputs can be us-ed individually or wired together.

For example, the output at pin 4 is 8x CR = 8T. If pins 4 and 3 are connectedtogether, the output will become 12 x CR= 12T.

Figure 3 shows the actual connectionsfor a practical circuit. When the power isapplied with no trigger or reset inputs, thecircuit sets up to the initial state of all out-puts high. Once triggered, the circuit istotally immune to any additional triggerinputs until the timing period is com-pleted, or a reset pulse is applied.Choice of Timing ComponentsOnce a signal timing period, T, is

1011

11111

tt TOBY

100

C

0.01

ak

BARI 0.01 0.1 I 10 100 1000

IMMO C 50)s) RECOMNIENOGO VALUES

us 10 soIOUs 1 rns 100 me

TIMERASE PERIOD

I NOMOGRAPH OF CR PERIODS

10100

Fig. 4. Graphs to assist in the choice of valuesof C and R.

established, the output can be determinedby 'wiring -in' periods of T following abinary progression. However, the pro-cedure may have to be reversed when acertain accurate output period is required.

For example, if a timing period of 6hours 30 seconds is required, first convertthe time to seconds:

TRIGGER

TIAIEBASEOUTPUT

COUNTEROUTPUTS

... TIME

1111T11111111111111111111

PIN 2

PIN 3

PIN 4

Fig. 2. Output waveforms and timing diagram.

= 6 x 60x 60 + 30= 21630 seconds.

The maximum number of timing periodsavailable with one IC is:(1+2+4+8+16+32+64+128)T = 255T. Therefore the period of T can becalculated:

T = 21630/255= 84.82 seconds

With a low -loss capacitor (such as tan-talum) as one timing component, R can be

T CR - 100 µF x 1 M - 100 secondsPeriod of Output

T 1002T 2004T 4008T 800

16T 160032T 320064T 6400

128T 12800255T 25500

secs = 1.7 minsecs = 3.3 minsecs = 6.7 minsecs = 13.3 minsecs = 26.7 minsecs = 53.3 minsecs = 1.8 hourssecs = 3.6 hourssecs = 7 1 hours

Table 1. Example of accurate time available usingthe XR-2240.

calculated. If C = 100 uF:T = CR

Therefore:R = T/C

= 84.82/(100 x 10-6)= 848.24 kilohms

This can be tailored precisely for very ac-curate timing with a resistive network orpotentiometer, or simply rounded off to850k.

Figure 4 shows two graphs which willassist you in choosing:I. The recommended range of timing

component values.2. The time period, (T), up to 100

seconds, to be expected from combina-tions of C and R values.

An example of output periods to beexpected using a 100 uF capactior (tan-talum) and 1M resistor as the timing com-ponents is shown in Table 1.

The type of circuit operation discuss-ed to this point has been monostable i.e.,

V.

TRIGGER

47k

OUTPUT PULSE = I OFF OR A COMBINATION OF OUTPUT PERIODS

Fig. 3. Connections for a practical circuit.

56-JULY-1984-ETI

Fig. 5. Astable operation under control of external trigger and resetcontrols.

the output goes low on triggering, stayslow for the timing period and returns to ahigh level. It will not time again until it isretriggered. An XR-2240 can also be usedin a free -running or astable mode.

Astable OperationTo operate in this mode, the reset line topin 10 is disconnected from the output.

Figure 5 shows an astable circuitunder the control of the external triggerand reset signals. It will start timing whenan external trigger pulse is applied, andwill not stop until a reset pulse is applied.

Alternatively, the circuit can be madetruly free running. The circuit in Figure 6self-tirggers automatically when the poweris switched on, and continues to operate inits free running mode indefinitely.

When the timer is used in this mode,each counter output can be used in-dividually as synchronized oscillators, orthey can be connected together to providecomplex pulse patterns.

Ultra -long DelaysIn some applications, delays of four daysmay be required. This is particularlyuseful in electronic farming for control-ling the rate of supplementary feeding.The timing components required can becalculated thus:

4 days = 96 hours= 5760 minutes= 345,600 secs.

Maximum number of T combinations =255

Therefore:T = 345600/255

= 1355.3 secs= 22.6 minutes

Incidentally, 20 minutes is about thelongest time recommended for 1.CR asanything beyond this suffers from leakageproblems.

Fig. 6. Free -running circuit.

V.

LvI,A1

F274ll

n nnnnnn16 9

X11-2240UNIT 1

R2475

IA

XR-2240UNIT 2

uuuuuuuu

TRIGGER

OREACT

RI

V.

RS105

OUTPUT

Fig. 7. Cascaded XR-2240s.

T = CRif C = 500 uF (low leakage)

R = T/C= 1355.3/(500 x 10-6)= 2M7

Two XR-2240 ICs can be cascaded togenerate extremely long time delays.When used in this format, the reset andtrigger terminals of the ICs are tiedtogether and the timebase of unit 2 dis-abled as shown in Figure 7.

The output is normally high. When apositive -going trigger pulse is applied, theoutput goes low and stays in the low statefor (256)2 = 65,536 periods of the timbaseoscillator. Therefore, the totaly timingperiod of two cascaded units can be from256.CR to 65,536.CR. The output isavailable in 256 discrete steps by selective-ly connecting one or a combination of theoutputs from unit 2 to the output bus.

With T = 20 minutes an example ofan ultra -long delay can be given.

CR = T = 20 mins.65,536T = 1,310,720 min.

= 21,845 hours= 910 days= 2.5 years!

This article highlights the use of anXR-2240 as a precision timer. Other ap-plication suggestions are:1. Sequential timing2. Binary pattern generation3. Frequency synthesis4. Pulse counting or summing5. A/D conversion6. Digital sample and hold

Further information on the IC can beobtained from Exar Integrated Systems ortheir agents (Active Component Sales).

This article was made possible by thecourtesy of Exar Integrated Systems. Datawas taken from their publication'XR-2240/2340 Programmable TimerCounter.' Ell

ETI-JULY-1984-57

Product Mart Where Buyers Find Sellers

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FREE COMPUTER SOFTWARECATALOGUE. Save $$$$ by Direct Mail onFlight Simulation, Games, Trivia, Educa-tional and Home/Business Software foryour Apple, Atari, Commdore-64, VIC-20,IBM. THE SOFT WAREHOUSE, Dept. 14,P.O. Box 1983, Winnipeg, Man. R3C 3R3.

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..1ETI-JULY-1984-59

1/LIFs and theMagnetosphere

A process of wave interaction inthe magnetosphere can amplifyvery low frequencies.

by Roger Allan

THE PROCESS of dumping electronsfrom the magnetosphere into theionosphere goes on all the time and is amechanism that helps maintain theequilibrium of the radiation belts, par-ticularly the Van Allen belts, which sur-round the earth. The dumping process isdue to natural processes and transmittedwaves from the ground. Very often, high -power transmitters induce over half of thewave energy that exists in the magneto-sphere. This process, known as field/ef-fect/wave interaction results in the deflec-tion of free electrons from themagnetosphere down into the ionospherein a process identical to that caused bysunspot activity. When the freed electronsenter the ionosphere they create aminiature aurora borealis - small lightemissions - that can be detected. In addi-tion, it is felt that X-rays are releasedwhich should be discernable.

For some years, scientists have believ-ed theoretical calculations which indicatedthat such ground based generation ofVery Low Frequency (VLF) radio wavescould result in these waves not only beingtransmitted thousands of kilometers butalso amplified by the dumping process.

Acting under the sponsorship of theU.S. Office of Naval Research, LockheedPalo Alto Research Labortory and Stan-ford University recently released theresults of an experiment, known as SEEP(Stimulated Emission of Energetic Par-ticles), which indicates that such a processin fact takes place, and further, that theamplification produced by the dumpingprocess increases power factors by bet-ween 1,000 and 10,000 times (30-40 db).

The discoveries of this research pro-gxam could lead to the improvement ofradio communication by using magneticfield lines to capture and amplify VLF

Part of the SEEP experiment carried aboard the S 81-1 satellite. Circular objects in the foregroundare thermal radiators, used as part of the cooling system for the electron sensors which must operateat low temperatures for best sensitivities.

radio waves by utilizing that very largevolume of space surrounding the earththat up until now hasn't been fully ex-plored for its communication potential.Further, it provides a basis for improvedminimization of deleterious heavy sunspotactivity throughout the world.

Essentially, the experiment used a1 -Mw U.S. Navy VLF transmitter atCutler, Main, Annapolis, Maryland andJim Creek, Washington (used to com-

municate with submarines), and a 4 kwtransmitter operated by Stanford Univer-sity for the National Science Foundationat Siple, Antarctica, along with detectorsmounted on the S 81-1 satellite - part ofthe USAF Space Test Program. Further,other satellites, specifically the DynamicsExplorer 1 and the International Sun -Earth Explorer flying at a higher altitudethan the S 81-1, also carried VLF receiversto measure the intensity, frequency and

60-JULY-1984-ETI

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VLFs and the Magnetosphere

GEOGRAPHICLATITUDE

90150 120 90 60 30

GEOGRAPHIC LONGITUDE

PARTICLE IMPACT 1E6101

PULSED

VLF WAVES

INTERACTIONREGION

X-RAY IMAGER VIEWING

Location of high -power VLF Transmitters used in the SEEP experiment, along with a schematicrepresentation of the interaction between pulse -coded very low frequency waves and the electronsspiralling around a magnetic field line connecting the Earth's northern and southern hemispheres.The high -power transmitters were turned on when the satellite was traversing regions (shaded areas)through which the displaced electrons moved. The interaction region marked in the diagram is at analtitude of approximately 8,500 km.

2 x 102

1 x 102

NAATRANSMITTER

ON 10

E > 45 keV

E > 3.5 kaV

17 AUGUST 1982

8680 8690 8700 8710 8720 8730 8740

L SHELL 2.08 2.18 2.29 2.40

LAT (NORTH) 33.3° 34.6° 36.0° 37.4°

LONG (EAST) 294.5° 294.2° 293.9° 293.5°

Example of Modulated Electron Beams

modulation timing of the transmittedwaves above the interaction region - withsuch data being recorded at Siple andPalmer Antarctica, and Roberval Quebec,to correlate the data.

The transmitters were modulated inten different on -off patterns, andevidence was sought in the output of cool-ed silicon detectors on board the S 81-1while it was in low orbit of approximately250 kilometers while the satellite was pass-ing under a region exposed to interactionsinitiated by one of the four ground sta-tions. Analysis shows that, for example,using a 3 -sec on, 2 -sec off format resultsin a 32 db increase in power, the amplifi-cation being due to the magnetosphere.

In addition to the particle detectors,the S 81-1 also carried an airglowphotometer and X-ray mapping spec-trometer to record expected side effectsresulting from collisions between thedisplaced electrons and the constituents ofthe atmosphere. No data was generated inthis part of the experiment due to an ap-parent lack of sensistivity on the part ofthe equipment.

While the experiment was deemed asuccess, several questions remain, such aswhy amplification seems to occur only atcertain times, and how the wavespenetrate the ionosphere and enter themagnetosphere. These sorts of questionsmay be answered by two follow up ex-periments. The first, involving what wasoriginally known as the Waves in SpacePlasmas (WISP) instrument, now knownas the RPDP (Particle InteractionsRecoverable Plasma Diagnostic Package),is currently under development by theCentre for Research in ExperimentalSpace Science (CRESS) at York Univer-sity in Toronto. Expected to be launchedon the Shuttle as part of the Spacelab 6mission in 1986 or 87, it will be used tostudy the effect of radio waves in the fre-quency of 0.3 MHz to 30 MHz on theEarth's ionosphere and magnetosphere. Asecond experiment, also under develop-ment by CRESS for the same Spacelab 6mission, known as the Energetic Ion MassSpectrometer (EIMS), may also answersome of these questions. It will allowscientists from the Herzeberg Institute ofAstrophysics in Ottawa to investigate theproperties of charged ions and moleculesin the earth's atmosphere. By taking ad-vantage of the large weight carryingcapacity of the Shuttle, EIMS will have asensitivity and precision far superior tothose of previous space -borne instru-ments. It will be used to measure the com-position and energy distribution of ionspecies occurring naturally in themagnetosphere as well as tracer ions in-jected as a result of other NASA ex-periments. ETI

62-JULY-1984-ETI

ArmstrongFew of us are aware of the enor-mous contribution Edwin Arn-strong made to the developmentof radio. Sadly, like manyfamous inventors, he wasbedeviled by legal wranglingover his patents.

THERE'S A VERY hallowed place inradio history not far outside New York City.After you escape from the confusion ofKennedy Airport, you cross the GeorgeWashington Bridge and take the green andpleasant Palisades Parkway, which pointsyou towards upper NY State. Not far out,yet in wild, forested country, you'll see atransmitting aerial. Ask, and you'll be toldthat it is Edwin Armstrong's radio station.

Edwin Armstrong was born inManhattan, New York, in 1890. His folkswere well-to-do: his father a publisher, hismother a former schoolteacher, and bet-ween them they fostered in their son afascination for the mechanical and electricalgadgets with which he was constantly sur-rounded. The turn of the century in NewYork was the age of the inventor. A steadystream of inventions were being registered atthe US Patent Office, and each was eagerlyseized on to be marketed and advertised. Inmany ways it was an inventor's paradise,but as many were to find out, the paradisehad a few traps in it. Young Edwin caughtthe mood and at the age of 14, decided thathe would be an inventor. The newest thingaround was radio, and it was this field thatEdwin chose, surrounding himself with coilsand crystals, earphones and morse keys.

We know very little of what he did inthose days, because like many inventors, hewas shy and secretive. The next milestone inhis career was his entry to Columbia Univer-sity to study science and engineering - andto chalk his name on the list of radiopioneers long before his studies were com-plete. Radio at the time (about 1910) hadvery limited uses, mainly because of the very:ow sensitivity of receivers. Lee de Foresthad just invented his Audion, a three elec-trode tube of the type we now call a triode,and this permitted some amplification of thefeeble signals from a tuned circuit. Atuniversity, Armstrong, was able to lay hishands on one of the first of these tubes, andto start making use of it. Within a few mon-ths, he had made one of the majordiscoveries in radio, that of positive feedback.

A modern FET superregenerative receiver similar in operation to Armstrong's circuitry. VR1 con-trols the regenerative effect, increasing the gain by using positive feedback.

First Milestone - RegenerationThe idea was simple enough. The primitivetube had a very low gain at radio frequen-cies. Armstrong hit on the idea of feedingthe signal back to be amplified again, and hecalled the idea regeneration. A regenerationreceiver was hundreds of times more sen-sitive than the average receiver of the day, sothat Armstrong's invention was undoubted-ly one of the milestones in radio progress. Itwas immensly successful and every radio,from then on, with any pretensions to sen-sitivity, incorporated regeneration. Arm-strong himself had already found out thatexcessive positive feedback could causeoscillation, and so paved the way for all elec-tronic radio transmitters to replace the crudespark -coil or alternator types which werethen used.

It could have, and should have, beenthe moment of his greatest triumph, but itwas soured in a way that was to haunt himfor the rest of his life. His patents werechallenged by de Forest, and the judges andlawyers, ignorant of the principles involved,ruled that Armstrong's patents were invalid.To its great credit, the scientific community

never accepted the legal judgement, andrecognised Armstrong with every honourthey could bestow. Many inventors fromthat day on, however, have regarded patentrights as a playground for lawyers and havepreferred to get in first with the manufactur-ing of an invention rather than trust to theirability to profit from licensing agreements.

Second Milestone -The SuperheterodyneAt the outbreak of war in 1914, Armstrongwas appointed to the US Army SignalCorps to research into improved radiocommunications. Details of his work arenot easy to obtain even now, because of thesecrecy which surrounded the tack -roomboys', but one invention of this period isoutstanding, and will probably remain soas long as radio is used. Until then, allradio receivers were either crystal sets,using no radio frequency amplification, ortuned radio frequency (TRF) receiverswhich used coils and capacitors to tuneeach amplifying stage to the frequencywhich was being received. TRF receiversare useful up to a point, but they have great

ETI-JULY-1984-63

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Armstrongdisadvantages when large amounts of gainare needed. One disadvantage is that thetuning of each circuit has to be changedwhenever a different frequency is wanted.Another is that even very small amounts ofsignal, if fed back from the output to theinput, can make the receiver oscillate andso radiate interference. All this was solvedby Armstrong's invention of the superhe-terodyne (superhet) receiver.

In a superhet receiver, each incomingfrequency is tuned, amplified and thenconverted to an intermediate frequency(IF) by mixing it with a signal from anoscillator. The same IF is used no matterwhat the input frequency on that particularrange happens to be. Tuning becomeseasier because there are fewer variable tun-ed circuits, feedback is less of a menancebecause the signal which is most likely tofeedback (the IF) is not at the same fre-quency as the input. It's difficult nowdaysto imagine radio without superhetreceivers: from the pocket transistor radioright through to the mighty radar receiver,all use Armstrong's superhet principle.

This work earned Armstrong morethan fame. During the 1914-18 war, he hadmet David Sarnoff, founder of the RadioCorporation of America. (Armstrong had,in fact, married Sarnoff's secretary). Sam -off was utterly convinced of the entertain-ment possibilities of radio, and he boughtmany of Armstrong's patent rights. In the

early twenties, the sudden blossoming ofradio as an entertainment medium meant aboom in radio manufacture, and madeArmstrong a dollar millionaire because ofthe royalties which were paid by radiomanufacturers.

Third Milestone - FrequencyModulationDespite his new wealth Edwin Armstrongremained withdrawn, and continued towork at Columbia University. His themenow was the elimination of radio in-terference, a topic which was to occupyhim to the day he died. His work was fruit-ful: in 1933 he took out patents on the fre-quency modulation system - FM. Theidea of modulating the frequency ratherthan the amplitude of a radio wave makesit possible to design receivers which arecompletely insensitive to the amplitudemodulation caused by interference. At thetime, though, only the Army Signal Corpsreally saw the usefulness of FM. Arm-strong found himself with an uphill strug-gle to convince even his friends that his newsystem was capable of providing broad-casting of a quality totally unknown at thetime. He began the construction of an FMtransmitting station, using his own per-sonal wealth. It swallowed over $300,000and was completed in 1939 - just in timefor the wartime economy drive to make it

out of the question to operate the station,or for manufacturers to switch to makingFM receivers. Frequency modulation wasto prove its value in World War II,however, and once again, Armstrongworked in military research projects.

After the war, FM started to be ac-cepted slowly. The problem was mainlycost, and what boosted sales more thananything else was the new craze for hi-fiwhich suddenly brought in its wake an ap-preciation of better quality radio broad-casting. These could have been the days oftriumph for Armstrong, but the nightmarewhich had haunted him from his earlyyears was to recur. Once again, his patentswere challenged in the courts, and he wasput under the strain of trying to provetechnical points to an audience of peoplewho were technically ignorant and an-tipathetic to the quiet unassuming inven-tor. To add to his worries, his vast expen-diture on FM was not yielding him anyreturn, and in 1954, with his fortune spentand his brilliant invention being tossedabout the courts by lawyers, Edwin Arm-strong committed suicide.

He left behind him a monument asvast as any man can ever hope for. Everyradio receiver and every FM transmitter inthe world is the result of Edwin Arm-strong's patient and little -publicisedachievements. Only his name deserves to bebetter known. ETI

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Circle No. 3 on Reader Service Card ETI-JULY-1984-65

continued from page 10

New PrintersCentronics Canada Inc. has an-nounced the new Horizon series ofhigh -quality dot matrix printersfor small systems and personalcomputer applications. Twomodels are currently available.Model H80 is a 160 cps dot matrixprinter, with paper handling abilitythat includes fully adjustable trac-tors, A4 cut sheet for letters, singlepart roll paper and a truetypewriter -style font plus interfac-

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For your information-The first equation processor everdeveloped for personal computers,TK!Solver® , has been made moreuseful for architects, buildingdesigners and construction engin-eers. Software Arts, creator of theVisiCalc® and TK!Solver pro-grams, is now offering a

TK!SolverPackTM for BuildingDesign and Construction. Forpeople who use equations, for-mulas and modeling for analysis,design and planning, TK!Solver isa tool that saves time and increasesefficiency by solving equationsautomatically. The programfeatures a unique backsolvingcapability, which allows users tosolve for any variable in an equa-tion without reformatting the pro-blem. In addition, TK!Solver per-forms iterative and list solving,produces tables and graphs, con-tains an automatic unit conversionfeature, and has 15 models forsolving design problems in residen-tial construction.

Looking for another source of wireand cable? Amecan Industriesstock audio cable, station wire,communications cables, varioushookup wires, high voltage cables,cords and more. They have anoutlet in Montreal at 4747 BourgSt., St. Laurent, Que. H4T 1H9,and outlets in Mississauga and Ed-monton.Circle No. 49 on Reader Service Card.

The Honourable Donald John-ston, Minister of State for Scienceand Technology and for Economicand Regional Development andMinister responsible for SpacePolicy (his friends call him 'Don')has announced a 38% increase inthe Space Expenditure Plan to$446 million over the next twoyears. Electronics manufacturerswill no doubt profit from thebudget increase.

Zenith has introduced new stereocolour television products designedfor consumers to receive TVbroadcasts with stereo sound andbilingual audio. Features include:25 -inch diagonal console colourTV sets with built-in stereo/ -second -language adaptor; and 19 -and 13 -inch diagonal colour TVsets with built-in second -languagedecoders.

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-For your information

Heath PortableThe IBM-compatible Heath HS -161Portable PC is available in single ordual 5.25 -inch floppy disk drive con-figurations with each drive having astorage capacity of 360 kilobytes.Both versions are available in eitherkit form or fully assembled. All have128 kilobytes of RAM memorythat's expandable to 320 kilobytes onthe main memory board and to 640

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Electrical Testing InstrumentsLtd., announces a solid statedielectric strength tester. TheModel HVA-2.5/100C is housed ina portable aluminum case and isused in production, acceptance,design and repair testing of alltypes of equipment requiring CSA,ASTM, NEMA, UL and IEEEtesting standards. The features ofthis instrument are solid state tran-sient free switching in zero cross-ing, breakdown and leakage in-dication, secondary metering oftest voltage and positive manualreset on breakdown. TheHVA-2.5/100C has been designedfor use as a simple tool for dielec-tric strength, "HIPOT" orbreakdown testing of all electricalor electronic equipment and ap-pliances. Contact them at 3015Kennedy Rd., Unit 12, Scar-borough, Ont., MIV 1E7 (416)292-8181.

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Boy, I wish somebody had coaxialconnectors that would just twist onto shielded cable and eliminatethose tiresome crimping pliers.They do? B&L Coaxial Connec-tions, 50 Silver Star Blvd., Unit209, Scarborough, Ont., MIV 31.3(416) 292-3906, has them all over.Ask for the BNC/TNC line oftwist -on connectors.Circle No. 46 on Reader Service Card.

If any ETI staff member gets upsuddenly from a chair, the staticspark makes eight computers im-mediately erase their disks. DataAccessories Corp. Ltd., of 209Wicksteed Avenue, Toronto, Ont.,M4G 2C1 (416) 423-4070, is offer-ing a Computer Care Centre kit;the cleaning fluid included is saidto leave an anti -static film on thecomputer and its surroundings.We must order several cases.Circle No. 35 on Reader Service Card.

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HM 204 20 MHz Dual Trace -$1120, -Sensitivity 2 mV-20V/div Timebase range 2 s/div-20 ns/div Automatic peak -value triggering to 50 MHz Variable sweepdelay Single sweep mode Y -Output Z -modulation Over -scan indicator.

HM 203 20 MHz Dual Trace - $835, -Western Europe's best selling 20 MHz -Scope! Sensitivity 2 mV -20 V/div Triggerbandwidth 40 MHz Timebase range 0.2s -max. 4Ons/div

HM 103 10 MHz Single Trace - $550, -Small, compact service scope Sensitivity 2 mV -20 V/div Time -base range 0.2 us -0.2 s/div TV -V and TV -H triggering.

»ModularSystem«HM 8000

An expandingrange ofsignal generators,multimeters,counter/timers,etc....

For more detailswrite or call collect:

ELECTRONICSLIMITED

980 Al ness St. Unit 7,Downsvlew, Ontario.

M3J 2S2(416)661.5585

TELEX 065-28169

Circle No. 15 on Reader Service Card ETI-JULY-1984-67

for your information -Screen PhotosSystems for producing presentation -quality instant color photographichard copy have been announced byPolaroid Canada Inc. The hard copysystem features a recorder for per-sonal and small business computers.Called the Palette computer imagerecorder, the new system makesPolaroid 35mm Autoprocess colorslides and 31/4 x 41/4 -inch instant col-or prints of color or black and whitecomputer graphics. Contact: Com-munications Dept., 350 CarlingviewDr., Rexdale, Ontario (416)675-3680.Circle No. 43 on Reader Service Card.

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1984 Mail Order Catalog

The One Stop Shop For AllYour Electronic Needs!

Conveniently located across CanadaMontreal5651 Rue FerrierMontreal, QuebecH4P 1N1(514) 731-7441

Ottawa1023 Merivale RoadOttawa, OntarioK1Z 6A6(613) 728-7900

Toronto14 Carlton StreetToronto, OntarioM5B 1K5(416) 977-7692

Calgary3220 -5th Ave. N.E.Bay 2Calgary, AlbertaT2A 5N1(403) 235-5300

Mail Orders to Montreal Address.Visit your nearest Active store, call, write or circle

the Reader Service Card for your copy Of Active's new catalog.

Downsview86 St. Regis Cr. N.Downsview, OntarioM3J 1Y8(416) 630-0400Vancouver3070 KingswayVancouver, B.C.V5R 5J7(604) 438-3321

Computer RegulatorFor sensitive electronic equipmentrequiring single-phase, 208 V out-put, an expanded line of hardwiredMicro/Minicomputer Regulatorsfeaturing a new 208 V output inaddition to standard 120-240 Voutputs, is now available fromSola Electric, a unit of GeneralSignal. For use primarily with mid-size computer installations, thenew Micro/Mini models are avail-able in 60 Hz designs rated for 500VA to 15000 VA loads. Amongthese, 7.5 kVA, 10 kVA and 15kVA Micro/Mini units will also ac-cept 208 V input. Contact SolaElectric, 377 Evans Ave.,Etobicoke, Ontario (416)255-6465.Circle No. 42 on Reader Service Card.

The new Gladstone ElectronicsSpring/Summer catalogue is ob-tainable free of charge from 1736Avenue Road, Toronto, Ont.M5M 3Y7 (416) 787-1448. It in-cludes CB, a new Sinclair com-puter, robot kits, software, hard-ware, etc.Circle No. 41 on Reader Service Card.

High speed MOSFETSA new family of small signal Mosfetsis now available from Ferranti Semi-conductors. This ZVN33 transistorseries has been designed with ex-tremely compact geometry to permitswitching times under 10 nano-seconds. As a resuh, these devicesare ideally suited to applications suchas telecommunication switching cir-cuits and other designs requiringsuperfast switching. Noted specifica-tions are breakdown voltages -20to 200V, low thresholds (VGSth) -2.4V max, and input capacitances aslow as 35pf. Available in the hi-relE -Line (TO -92) and TO -39packages, the ZVN33 Mosfets arepriced at 30' each in 1K quantities.Leadtime is 4-6 weeks. For addi-tional information, contact FerrantiSemiconductors, 87 ModularAvenue, Commack, NY 11725; (516)543-6200.Circle No. 40 on Reader Service Card.

Looking for a wide range of in-dicator lights, LEDs, and so forth?Len Finkler and Co., 80 AlexdonRd., Downsview, Ont. M3J 2B4offer their comprehensive 44 -pagetechnical guide and catalogue,"The Source for IndicatorLights."Circle No. 39 on Reader Service Card.


MINE NM

IIIMEM

MS MN =II =III MI

InternationalPeripherals for your IBM PC

Colour Video Board $339.00

Floppy Controller Board $299.00

128K Memory Expansion Board $399.00

w/2 Serial & Parallel Port LASER Disk Drive $349.00

(Teac FD55B Mechanism) IBM Compatible Keyboard

*ILL SER HARD DRIVE

10 Mbytes 5-1/4" Winchester Hard Drivewith Controller, Cable and Diskette forIBM PC

for Apple (with Power Supplyand Case)

$1,699

$1,999

$189.00

*LASER SLIM LINETeac FD55B Mechanism for IBM and IBMCompatibles. Access time 6 MSECStorage capacity 40 Tracks 328 Kbytes

$299.00LASER Slimline for Apple and AppleCompatibles

$279.00Storage capacity 40 Tracks 163 KbytesAccess time 6 MSEC Controller $55.00with purchase of Disk Drive

QCAL 8000IBM PC -WORK -ALIKE 8088 Processor 128K RAM Detachable Keyboard One LASER Disk Drive (DSDD)

w/Teac 55B Mechanism Disk Drive Controller Colour Video Board Heavy -Duty Power Supply

w/Built-in Cooling Fan Five Expansion Slots

$2295.00(Does NOT include software ormonitor) This is NOT a kit

*LASER $269.001 I FULL HEIGHT

Shugart SA -390 Mechanism for Apple andApple Compatibles Access time 14 MSECStorage capacity 40 Tracks 163 KbytesController $55.00 with purchase ofDisk Drive

Call us about Disk Drivesfor Commodore

fiOAll QCAL, Laser and Mastone products are distributed exclusively in Canada by

PACIFIC RIM ELECTRONIC IMPORTS INC.P.O. Box 7050, Station M, Edmonton, Alberta T5E 5S9 CANADA

Dealer Inquiries Call (403) 475-0855 or Telex 037-41683 PACIFICRIMWrite or call for QCAL Dealer nearest you

WRITE OR CALL TODAY FOR SUMMER DISCOUNT MAIL ORDER CATALOGUE

Apple, IBM (IBM PC) and LASER are registered trademarks of Apple Computer Inc.,IBM Corp. and Laser Micro -systems Inc. respectively


Series 600 PreamplifiersAccording to Precision FiltersInc., their Series 600 high input im-pedance, differential preamplifiersfeature "excellent" low noise andcommon mode rejection perfor-mance over a frequency responserange of 0.5 Hz to 500 kHz. Thesepreamplifiers are available insingle -ended and differential ver-sions. Standard fixed gains of0,10,20,30 and 40 dB or switchedgains are available; gain deviationwith power supply and tempera-ture changes is typically 0.002 dBper volt or per °C respectively.

The Series 600 provides fulloutput of ± 10 volts peak to 100kHz. Full output response is main-

tained at up to ± 15 mA load cur-rent, with total freedom frompeaking effects with complexloads.

The differential version canoperate from ± 9 V DC to ± 18 VDC power supplies. Single supplyversions, positive and negative, areavailable for supply range of 18 VDC to 36 V DC. Power supplynoise rejection is excellent, greaterthan 80 dB over the entire frequen-cy response range.

For more information, con-tact Precision Filters Inc., Dept.600, 640 Cherry Street, Ithaca, NY14850, (607)277-3350, Telex646846.Circle No. 38 on Reader Service Card.

For your iriformatioryi1.11t:ItAAA.;01011010

Epson MS-DOS

A new plug-in board that allowsthe 8 -bit Epson QX-10 PersonalBusiness Computer to run 16 -bitMS-DOSTm and PC -DOS softwareis now available. Titled the QX-PCTM, this board was developedand manufactured by Titan Tech-nologies of Ann Arbor, Michigan.The QX-PCTm board converts theZ-80 based QX-10 to MS-DOScompatible 16 -bit operation. Userscan conveniently have access toCP/MTM, MS-DOS and Valdocssoftware all on this same machine.The QX-PC operates at 5 MHz,

supporting the graphics, printerand serial port features of theQX-10, making them accessiblefrom MS-DOS. The optionalboard is available with 192K or256K bytes of memory. It can bepopulated to 512K bytes with aseparate option card. The 192Kversion is immediately availablethrough a national network ofauthorized ZX-10 dealers, with asuggested list price of $1129. Con-tact Epson Canada Ltd., 21 Pro-gress Court, Unit 18, Scar-borough, Ont., M1G 3V4 (416)431-5588.Circle No. 37 on Reader Service Card.

This summer, NovAtel Commun-ications of Calgary will begin fieldtrials of Canada's first 800 MHzcellular communications network.A mobile test vehicle will be usedto verify system parameters in theseven -cell Calgary test network.Success of the project will nodoubt mean the possibility of por-table phones in every car beforelong.

ES FOR SALEURCE FOR OSCILLOSCOPE PROBES

M TEST LEAD SETS.

*ow 4444400,4414,

Your ProbeSpecialists

Colin Canadian Sales ft Stocking Source

Low cost High Quality Excellent Performance Slender, Flexible Cable

Wide Range of Choice Switchable X1 and X10

Attenuation Factor 100 MHz Ilandwith

MODEL SP100

$5010

ELECTRONICSLIMITED

980 Alness St. Unit 7,Downsviaw, Ontario,

M3J 2S2(416) 661.5585

TELEX 065.281 09

THE SATELLITEEXPERIMENTER'SHANDBOOK

Satellite BookThe American Radio Relay Leagueannounces their Satellite Ex-perimenter's Handbook, a collectionof information on how to receiveand use broadcasts from satellites;these broadcasts include amateurradio, weather, TV, etc. Chapters in-clude orbits, tracking, antennas, andmore. Contact: ARRL, 225 MainSt., Newington, Connecticut 06111(203) 666-1541.Circle No. 36 on Reader Service Card.

The International Maritime Satel-lite Organization (INMARSAT)has sent letters to the bidders forits new series of satellites, inquir-ing as to the feasibility of the newsatellites carrying 406 MHztransponders, which would be usedfor relaying distress alerts fromsatellite radio beacons. The 406MHz transponder is also being car-ried on the satellites used in theCOSPAS/SARSAT system, asearch and rescue system devel-oped by Canada, the UnitedStates, France and the SovietUnion, all of which are INMAR-SAT member countries. TheCOSPAS/SARSAT satellites havebeen credited as being instrumentalin the saving of more than 180lives, since the first satellite, aSoviet Cosmos satellite, was laun-ched in June 1982.

Circle No. 2 on Reader Service Card70-JULY-1984-ETI

RION ELECTRONICS . . COMPUTER ROOM ORION ELECTRONICS COMPUTER ROOM

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WINNER:Ultra -modern!Super -efficient!Fully AppleCompatible $995.00Please note the distinct featuresWinner offers:'Dual microprocessors 6502 & 2.80A'RS -232 built In'Disk drive Interlace card built In401130 column text display and auto change videooutput port by soft switch

'76K RAM with 4 expansion slots

'16K ROM'DOS 3.2 & DOS 3.3 capability'Apple & CPIM compatible'ASCII keyboard with function keys and a numerickeypad

Uppertlower caseStreamilne case'OS could be changed when desired without affectingother memory RAM

0cecr

IH

0

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CP80 DOT MATRIXPRINTER

7X8 DOT MATRIX80 CPS, 640 dots/line per secondBidirectional80 Column normal142 CompressedFriction & Tractor FeedStandard Centronics ParallelSame as EPSON 80

$495.00

'1TXT. 1014

RELIABLE DAISYWHEEL RO PRINTER

1014 FEATURESII SERIAL AND PARALLEL INTERFACE WORDSTAR COMPATIBLE QUIET OPERATION PROGRAMMABLE PITCH AND LINE

SPACINGII COMPACT AND DURABLE MICRO, MINI, MAINFRAME COMPATI-

BLE INTEGRAL PIN FEED GUIDE (AD-

JUSTABLE) RIBBON CARTRIDGES AND PRINT-

WHEELS READILY AVAILABLE.

SEE OR CALL ABOUT OUR EX-TENSIVE LINE OF PRINTERS.

Mini Modem

APPLE COMPATIBLECOMPUTERS

48K Color Computer with numerickeys & function keys $549.95

64K Color Computer with numericand function keys $598.95

64K Color Computers (Dual -6502 &280A, CP/M), Numeric & functionkeys $649.95

For systems one 12" Green Monitor,1 Disk Drive & Disk Controller card

$500.00

All above Systemswith New IBMTRI

Styling 100.00 extra

Detachable Keyboard Programmable Function Keys Built in Key Words for AppleTM

Soft, DOS Room for two Slim Line Drives

$99.45

00

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3300

00mz-m

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PartsDB-25P ConnectorDB-25S ConnectorCovers for 25'sDB-9P

DB-9SCovers for 9's2716 EPROMS2764 EPROMS4164 RAMS 200 N/S4116 RAMS 200 NIS2016 RAMS

EPROM ERASERS P.E. 14Bata time $129.95

S 4.95$ 5.95S 2.25S 3.95S 4.95S 1.98S 6.95$14.95$ 9.75S 1.75S 9.75

Disk HoldersDisk Bank (50 Disks) $39.95DX 85 (55 Disks) $39.95Data Defender (70 Disks) $39.95Flip "N" File 10 8.95Flip "N" File 15 $13.95Flip "N" File 25 $34.95Flip "N" File 50 544.95Flip "N" File Original 50 $29.95

DiskettesXidex SS/DD $29.95Xidex (Plain Box) SSIDD $24.95Xidex DS/DD 539.953M Diskette SS/DD $29.95Verbatim (Datalife) SS/DD $34.95Maxell MD 1-DS/DD $34.95Maxell MD 2-DD/DD $49.95Dysan SS/SD 104-1 $29.95Dysan SSIDD 104-2 $34.95Dysan DS/DD 204-2 $49.95Disk Cleaning Kit Recoton $34.95

6502 BOARDS & ACCESSORIES

Swivel.MonitorAmber

GM 1211 $165.00

More MonitorsRoland CB 141 Colour $395.95Amdek Colour $395.95GM 1201 Green 12" $149.95GM 1201 Amber 12" $159.95Zenith Green 12" $139.95Zenith Amber 12" $149.95

More Available

Orion ElectronicSupplies Inc.

40 Lancaster Street WestKitchener, Ontario N2H 4S9

(519) 576.9902

ORION ELECTRONICS

ABB-I 645.00APPLE II Compatible.Dual CPU Bare BoardComm Card 109.00Serial interlace RS232CCard for APPLE II ciorCable & ManualMC.1 609.00Integer Card

AEC.I 60900BO Column Card

67900MC-,

MA ICPMI CardAM, 14900Parallel Prrnier Card

&SCA 08900Serial Printer Card

ALGA $65.00InK RAM (Language Card

SPeach Card 67500Wild Card 100.00Modern Crd 5175.00,Networker)

OD Column Switch 19.95Colour RF ModulatorSel 525.00

AM& 2 599.00Keyboard NumericKeypad won FunctionKeys replacement forAPPLE II

AC.2 50.00Beige APPLE II Case IlaaDore Keyboard)Case & KeyboardNurnenc $175.00APS.2 990.00Switcliong Power Supplyfor APPLE II. 5V 5amps 12V al] amps6V a amp 12X a .4amps ow Onof swItch 6connecting wiresAAA,2Ors Drives , APPLE IICompatible. ExcludingController Card 1200.00With Controller 236500ADC, 50.00DISC plive Contr..,Card for two drives. AppleII CompatibleAPPLE II PS a regosteredtrade mark of Apple Cornouter Inc

Master Charge & Visa, COD. Cheque,MoneyCrders accepted. COD's, shipp-

ing & insurance extra. Write for ourFREE FLYER.

Prices subject to change withoutnotice.

Timex Sinclair 1000

VoOM Nis eV C. fla Va.

I ......all

Assembled$39.95

Z1031 Printer$99.00

16K Sinclair Memory $35.00Books Hardware

COMPLETE Zx8) BASIC COURSE Inc 2

tapes 16.05NOT ONLY 30 PROGRAMS. 1K 11105

MACHINE LANGUAGE MADE SIMPLE 1045DOI ROM DISASSEMBLY PART A4 PARTB 24.05UNDERSTANDING 2X81 ROM 11105TrS 1000 PROGRAMS. GAMES andGRAPH!. 1415LEARNING TrA BASIC 2305THE BASIC HANDBOOK 250529 EXPLODING GAMES 1005COMPUTER FOR KITS SINCLAIR EDITION BIMMASTERING MACHINE CODE ON floor 2X61 3415ITS 1003 USERS GUIDE Nor t1 18.115EXPLORERS GUIDE TO THE zeal ICH23,81 POCKET BOOK le.05GETAWAY GUIDEGETTING AOUAINTED WITH YOUR 2X111 1005

Sinclair PrintersTimex Printer64K RAM (Memotech)32K RAM (Memotech)16K RAM (Sinclair)Memotech 16K RAM500MA

99.00125.00149.00

79.0035.0039.95

8.95Memopak Centronics TypeParallel Printer Interface 119.00MemopakLX81 Keyboard 119.00

Additional Hardware & Softwarefor the SINCLAIR &XIII

AVAILABLE ON REQUEST.

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COMPUTER ROOM ORION ELECTRONICS COMPUTER ROOMCircle No. 20 on Reader Service Card ETI-JULY-1984-71

EXCEL TRONIX(4161921 -8941Bulletin Bd. (416) 624-5574 Telex 065-24218 Toll -Free Number:319 College St., (416) 293-1796 Toronto, Ont. MST 152 1-800-268-3798

OR The Loaded "BEST"Everything in our $1995 System plus: Two DS. DO 51/4" Disk Drives On -board 256K of RAM RS232 Port $2595

SOFTWARE FOR YOUR IBM Lotus 1, 2, 3 $439 Wordstar $399 Multiplan $219 dBASE II $479 Flight Simulator $62.95Great Selection of other software for yourIBM available.IBM is a Trade Mark of IBM Canada Limited

Mail Order: Call for shipping costs. Rate will dependon methods chosen and distance.Call our TOLL -FREE number for more information.

1-800 268-3798(Toronto area call 921-8941)

Call in and let us demonstrate the "BEST" to you at319 College Street, Toronto. Store hours 9:30 to 6:00Monday -Saturday: to 9:00 p.m. Friday.

The "BEST"IBM Compatible Microcomputer

See the Reviewin March 1984

Computing Now! $1995Not a kit - a complete system

This prices includes: 64K of RAM with pre -

socketed provisionfor 256K

One disk drive.SA455. Double Sided.Double Density

Colour Video Board Floppy controller

capable of handlingup to four DS. DD5'/4" disk drives andsocketed for op-tional serial portand real time clock Monitor not

Included

Warranty:Full 120 dayWarranty

Prices does NOT includeIBM (Microsoft) BASIC

OR 10 Meg Hard Disk VersionEverything in our $1995 system plus: 10 Meg Hard Disk Drive &

Controller On -board 256K of RAM RS232 Port $3995

PERIPHERALS FOR YOUR IBM Color Video Board

Has provision optional RS232 port and real$299$299 Floppy Controller Board

time clock.$149

Will also drive parallel printer Parallel and Game Port Card

256K Memory Expansion Card and real timeclock. Allows you to add a further 256K to yourIBM's existing 256K capacity for 1/2 Megabyteof total memory.

$289With 128K RAM on boardWith 64K RAM on board

$369With full 256K RAM on board $530

EPROM Programmer $149For 2716, 2732, 2764 and 27128.

Disk Drive - SA455 $299 IBM Compatible Case $ 99110 IBM Compatible Keyboard $189 Super Heavy Duty Power Supply $ 69

See our other ads for monitors, printers etc.,

arcle No. 28 on Reader Service Card.

Documents

Todaronics - americanradiohistory.com · 2019-07-17 · switch $139.00! These supplies are ideal for IBM compatibles, they fit beautifully ... clap to your hands and the robot starts