http://myweb.tiscali.co.uk/norcimradiocontrol/Radio14.htm

MODEL RADIO CONTROL ELECTRONICS

ALL OF THE NORCIM WEBSITE NOTES ARE FREE TO USE IN PART OR FULL ON YOUR WEBSITE OR TO COPY AND USE FOR ANY REASON YOU WISH.

The norcim website is for electronic enthusiasts with an interest in Model Radio Control. This first page contains technical and fault finding information about Micron model control electronic kits. Further pages have been added which cover other electronic circuits for model control.

Get a Voki now! The pages involve content from other model aircraft and boat electronic enthusiasts and if you have an idea worth adding to the site dont hesitate to contact me norcimguy below. The site is completely non-commercial and no money is accepted for any links or products that are covered. It is simply an enthusiasts site!

The norcim website began life as a single page with detail of the Micron Radio Control company which was started here in the UK in 1973 by the founders, Ada and Terry Tippett. These people found a profitable niche in the model control market at that time by producing kits of parts for modellers to actually build their own Radio Control System! Many of the mechanical parts used for the transmitter kits and receiver kits were unique parts designed by Micron. Some parts were patented. The building instructions were very large detailed drawings similar to plans found in model aircraft kits, so modellers felt at home with construction.The Micron company employed around twelve people for almost a decade and sold many thousands of kits to most countries of the world by direct mail order.OK..why a single page? Well the founders were at retiring age and were wanting a buyer for the company! Within six weeks of this single page offer on the web, several buyers had shown interest and the company finally had new owners. (The power of the Web!!)

After the sale of MICRON the single NORCIM page continued and gave helpful fault finding notes for the kits. (note that NORCIM mirrors MICRON!) if you were wondering where that strange title came from! With help from other like minded nuts, the Norcim site has slowly increased in size and is now eleven pages with many links to other similar stuff. (and some not so content related stuff!) Content from the late Dave McQue has given much content to the site. Mike Hawkins shows how retro R/C can be built. R/C Universe also adds some excellent up to date coverage and videos of todays R/C products. Recent input by David Caudrey to the Norcim site has been invaluable in that all of his historical Reverse engineered records which are printed here, would have been lost forever.if it were not for this Guys incredible talent for taking things apart. (see Davids page9, page10, and page11) by linking at the bottom of this page.

Norcim Notes7 page includes some mini reviews of interesting products with links to the supplier.Norcim Notes8 page.Mike Hawkins takes over with some superb retro built R/C gear using VALVES! Hes also given circuits.The feeds from R/C Universe on this page and page7 are always updated and well worth a click or three.Norcim Notes12 is by kind permission of Ron Js circuit website. Simply packed with alarm,timer,LED circuits and tutorials. Theres also component selection advice and FREE electronic software for your PC. A very professional enthusiast site!

PLEASE NOTE:- the information on this site is somewhat fragmented! I apologise for this! Its just the way that the site has slowly increased in size. Simple navigation between pages can be found at the bottom of every page.

Thanks for reading!

THE NOTES KICK OFF WITH FAULT FINDING THE MICRON RECEIVER KITS:-

General If assembled correctly; all four receivers in the micron range should perform correctly at switch-on. There is little or no variation between range (sensitivity) and other characteristics of correctly assembled versions of the same type. (It is even difficult or impossible to pick out a good one to keep for yourself).The FET receiver generally will show slightly more range to complete loss of signal compared to the other versions, (probably owing to increased front end stage gain.)For receivers that dont work on completion of assembly. These often have a built in mistake and rarely suffer from a faulty component. Look for 4k7 and 47K resistors in wrong places as reds and org colours are similar in artificial light. Also people get 4K7 mixed with 270K as they are the same three colours but opposite way round.Coils that have been cut wrong and mounted the wrong way round. IF coils may have had the centre pin cut too short. The winding loops around this pin and if cut too short will cut the winding. (Check primary pins for continuity using low ohms on meter)Sometimes capacitors get mixed up and you may find a 47p and a 47uf in the wrong places or similar.Have a sample PCB to hand or do a pencil rubbing of the boards before construction, as it is possible for customers to join two small copper lands with solder so that it looks correct as one land. (Particularly mini Rx)Look carefully at the 104 caps, either the yellow type or the blue type as after soldering, the leg can become detached from the side of the capacitor, shown by a crack around the outside edge of the cap. This fault only occurs if the capacitors have been mounted very close to the board where the thermal shock of soldering is increased. If in doubt another 104 cap can be touched to the bottom of the PCB, across the suspect cap, during test to see if the problem clears.Look for the obvious, as many times, ICs are put in the wrong boards or the wrong way round. Check that only Futaba, Fleet, Multiplex, JR, or GWS, receiver crystals are being used in the receiver.Check that only the transmitter manufacturers crystal is being used in the transmitter. (use of a different make of Xtal will almost certainly result in an off frequency transmission.

The decoders of the receivers rarely produce problems providing component values are correct. Very, very rarely a significant static shock (type that stings your finger when closing the car door) can knock out the Cmos chip and this is shown by scope input readings to the chip (normally clock @ 4volts & reset ramp of around 3 volts) being clamped at below 1 volt. Indicating that the chip inputs have gone low impedance and the chip needs replacing.Often customers use flux on the boards when soldering which unfortunately has an acid content and therefore adds many unwanted resistors to the circuit. This condition can be detected visually with residue on the boards. The only possible cure is to clean the residue from both boards using a toothbrush soaked in methylated spirits but often the flux has impregnated the board and satisfactory operation cannot be regained and the receiver is not recoverable. Replacement is the only answer.Receivers that work but show low range this mostly points to the antenna input bits. Happily there are few of these parts involved. (The 159 coil, the 27p capacitor, the antenna input cap and the capacitor feeding pin16 input of the 3361 chip. Often the flex antenna can be shorted to ground with a solder whisker on the PCB or a stray wire from the flex antenna remaining on the board surface and touching the metal coil cover. When cleared with a model knife, normal range is restored. Perhaps the wrong capacitor has been inserted across the 159 coil. Is the coil the correct way round? If the 159 coil responds to tuning, then the lack of range could be further on in the circuit.If the front end is checked out and OK then a possible lack of range could be found in the filter section of the receiver. The filter section has its input from pin3 of the 3361 filters the 10KHz spot frequencyfeeding it back into the 3361 pin 5. The filters involved vary with the receiver type. The standard and Comp receiver use a transistor between the filters with associated resistors/capacitor. The filters rarely go wrong but the transistor can be inserted with its legs wrong and associated resistor values need checking. The transistor gives around 10/12dB gain when fitted correctly. If you have an oscilloscope, the following can be checked. With the Tx on the bench, with about 25 cm of aerial, pin 3 or the base of the transistor will show around 0.1 volt of mixer output. If the transistor is working OK then there will be 1/1.5 volts of IF at its collector. (as seen on the scope). It is worth mentioning that the 3361 works well without this extra gain as in the mini receiver.

The amp in the mini Rx is also used to increase white noise of the whole circuit so that with the transmitter switched off, there is a pile of noise activity at pin9, which bombards the 4015 decoder to keep its servo outputs quiet. Note: - the mini receiver works differently and without the IF amp there is a much reduced noise level at its 3361 pin9. This lower noise helps to keep the 4017 decoder servo outputs quiet when the Tx is switched off.Voltage levels around the circuit. I must admit that I do not have any record of voltage levels. I often made sure that the receiver board was getting 4volts supply from the decoder board (or slightly more,) but beyond that always used the scope to prod around during faultfinding.Remember that after trying to get a receiver with a fault working, the coils could be well out of correct setting. This does not matter for the 159-antenna coil, as the receiver will still work at close range at any possible setting of this coil.The setting of the IF coil however is critical to a quarter of a turn to get any response at all from the servos. Resetting visually as compared with a working receiver or a new replacement coil is a useful start.The Transmitter Power Meter kit available from micron is sensitive enough to detect the oscillation of a receiver Xtal stage if its antenna is held very close to the crystal. Also but not so convenient maybe, a spectrum analyser will pick up the receiver crystal stage by simply holding the input probe close to the Xtal.

Mild jittering or servo noise using the Micron FET receiver. Although range and general performance of early dual conversion micron receivers seemed OK, reports from some parts of the UK seemed to point to an odd noise in the servos when a typical range test was carried out with the transmitter antenna collapsed. The noise also appeared to come and go and often, when the receiver was sent back to Micron, The noise could not be provoked and the receiver checked out as OK. This peculiar effect turned out to be talking and music from broadcast transmissions on the 13 MHz band! The receivers image frequency. A simple series LC filter in the antenna circuit was fitted and this completely eliminated the problem. ( 4.7 uH inductor and a 27p capacitor) See circuit later.

MICRON TRANSMITTER GENERAL NOTES:- The very first Micron transmitter circuitry that I assembled was actually fitted into a redundant commercial transmitter case and sticks. The transmitter had developed a fault that was not repairable but the hardware was still excellent including sticks, switches, meter, antenna etc. Some ingenuity was necessary to secure the two Micron printed circuit boards in place but the end result made an excellent transmitter working on the 35MHz band!Transmitter electronics kits are not available from Micron now. The seven-channel circuitry changed in recent years owing to the obsolescence of the dedicated Motorola R/C coder chip. The replacement coder is interchangeable with the earlier type and now uses bog-standard easy to get electronic parts, which are readily available from most hobby electronics shops. There is little point in commenting on the earlier circuitry as inevitably most problems involved the special IC, which is now unobtainable. The only practical remedy for repair of these is replacement with the later version coder board.

The photo to the left is now 37 years old! It shows one of the first Micron PL-7D transmitter designs. All the popular transmitters of the time (Skyleader, Kraft, F and M, Sprengbrook, Orbit etc were all still anodized aluminium boxes! The styling was a little ahead of its time and still looks well alongside many R/C systems of today. The unique triple universal joystick mechanisms were also designed by micron and patented.

Having assembled several of the later coder boards and seen other peoples efforts, the faults found were as follows: -Blown 4017 IC. This is usually caused by incorrect battery wiring giving a reverse input voltage! The other circuitry survives but it is worth replacing the 22uF. Usually a new 4017 solves the problem but the battery wiring must be checked before switching on again.Note that the coder circuit will run without the IC plugged in at around 1 KHz which can be seen at the yellow output wire on a scope, or even heard using a crystal earpiece. This test shows that most of the circuit is functioning except the IC. If there is no life, check component position, in particular the correct positioning of the transistor legs into the board.Working but a channel(s) is missing this fault can often be traced to an incorrect setting of one of the joystick pots. All the stick pots must be pre-set so that their wiper is at mid position, when the sticks and in-flight trims are at a centre position. This can be checked using a multimeter.

It is also possible that one of the crimped connectors of the plug-in flylead from the stick, has not located correctly in the plastic shell and as a result, the crimp has pushed out of the top of the shell. Relocating the crimp, making sure that the small plastic fingers of the shell are pushed in to secure the crimp, is usually a cure.Another possibility is a blown diode (usually caused by accidental shorting of the board to the edge of the metal case, during testing and adjustment). Often this can be confirmed using a multimeter on low Ohms setting across each diode in turn (there are 10 of them!), to find the odd one out, followed by replacement.Coder board quality, I have seen more than one coder Printed board now which was not up to the usual crisp copper etch that is normally seen. On these boards it was necessary to carefully inspect the copper lands and cut through with a model knife, the several bits that not intended to be joined! So look carefully with light behind the board. The Transmit Section is a smaller board that feeds the antenna and like the coder board, if assembled correctly, does function at switch-on. The outputs of this board has been passed by the ERA (Electrical Research Association) for UK 35MHz Type Approval and although the unique circuitry has remained the same, later versions are even cleaner, owing to the better specification of present day semiconductors. Setting up of the three coils for RF output is simplified by using the single LED indicator supplied! Even if done wrong it is impossible for the output to interfere with other users of the band! The latest versions are now supplied with a pre-fitted surface mount output transistor, which reflects changing technology.Not working at all this points to resistors or capacitors in the wrong places. Remember if you find one wrong then there will be another where that one should have been! Look for coils that have had the wrong pins snipped. These will need replacement. Check the transistor legs are going into the correct holes on the board. Check that only Micron or Futaba crystals are being used and Tx is indicated on the crystal tab. Try another crystal in case the one fitted is duff.Reverse Polarity fault. This always shows itself as a burned brown/black 100R resistor in front of the output transistor. Unfortunately both the output transistor and RFC will need replacing. The oscillator coil always survives, as does all of the other circuitry.

THE MICRON DUAL CONVERSION R/C RECEIVER

The fundamental advantage of Microns receiver front end is acknowledged in the RSGB Radio Communications Handbook, 5.16. As a result, the receiver Jfet does handle strong out of band transmissions particularly well.Microns use of the FET is interesting in that some of the known disadvantages of this device have been addressed. JFETs, used in mixer stages, do like, a high oscillator drive to work well. Unfortunately JFETs also have poor isolation of the oscillator frequency and this results in the oscillator frequency being transmitted via the receiver antenna! Although this transmission could still be termed as flea-power; Just imagine thousands of such receivers on a good flying day, all transmitting on a frequency that has nothing to do with radio controlled model aircraft! The interference to other users of the radio spectrum would be at risk and it is important that R/C receiver emission is kept to an absolute minimum.The Micron FET receiver uses dual conversion Crystals. This means that the oscillator frequency is a full 10.7MHz away from the receiver antenna coil tuning; the antenna input-tuning coil grounds much of the bleed-through of oscillator power. A further attenuation of the oscillator power is done via a series tuned LC trap at the JFET input (D McQue input). The resulting bleed through of the oscillator to the antenna is in the order of a couple of nanowatts and considered insignificant.

Another problem with JFETs was the divergence of characteristics from one device to another but technology has advanced and JFET characteristics are now much more controlled, with even selected versions of the same device available.

The Micron FET receiver circuit diagram comes next and surprisingly, its almost as simple as the Mini receiver that they do, except for the two transistors added on at the front! I will try and run through the circuit as best as I can without causing too much pain for the reader!The 35MHz parent transmitter signal is picked up by the 85cm flex antenna. (Length is not critical). This excites L1, producing a 35MHz signal input to the BF244A (gate). The 27p/4.7uH trap grounds the 13.5MHz image frequency and the 24.3MHz oscillator leak through via the 15p cap. Meanwhile the 24.3MHz plug-in crystal oscillator circuit output is injected via the 0.1 cap to the BF244A source terminal and mixing of the two frequencies occurs, producing a 10.7MHz output at the BF244A output. There are several other frequencies produced by mixing but the 10.7MHz crystal filter rejects these.The selected 10.7MHz signal is passed on to pin 16 of the Motorola 3361 chip. Mixing takes place for the second time using the on-board 10.245MHz Xtal oscillator. This produces a 455KHz signal at pin 3. This signal is filtered by the 10KHz filter (CFU455HT) and then amplified in the chip, with the FM content being detected at pin 9.The 4k7 and .022 cap at pin 9 get rid of white noise on the output signal, leaving rounded signal pulses (from the transmitter) of about 0.5v peak to peak. Note L2 needs adjusting to achieve this. Pin 12 is an input to a squaring amp with outputs at pins 13 & 14. These two outputs (4v pp) are used to clock the standard Cmos counter chip, giving up to 8 servo outputs. The 2N3904 provides an extremely servo noise free supply of around 4volts to the whole receiver. The image frequency rejection of this receiver is around 60dB which means that transmitted signals on the 13.6MHz band (image band) would have to be a million times stronger to cause a significant interference problem. This compares with normal single conversion receiver image rejection figures of around 10dB, allowing 34MHz band signals to cause havoc when only 11 times stronger! The 34MHz band is for Ministry of Defence use and has been little (if any) used over recent years. www.rfcandy.biz/shop/

A HOT TIP !

If you use one of the cycle pump type de-soldering tools, try pushing a short length of silicone fuel tubing on to the nozzle end so that just a couple of millimetres protrudes from the tip. The resulting soft end seals around the solder joint better as the tool is used and also reduces the recoil kick back. The silicone tube is also unaffected by the solder iron heat!

MODEL CONTROL TRANSMITTER OUTPUT TESTER CIRCUIT

This next circuit lends itself not only for home checking but also club and quick model shop checks. The circuit checks for correct power output of any 35 or 40 MHz radio control transmitter is shown. These things are called field strength meters and are a standard piece of electronic equipment in the service workshop to check the output power of R/C transmitters. Field Strength Meters (as they are called) are usually based around a reasonable size sensitive 50uA moving coil panel meter. These are now listed (Farnell) between 20 and 30 each (before circuitry!). This circuit is based around the National Semiconductor LM661CN Cmos quad op-amp IC. The circuitry components should cost no more than 4.00! and it has greater sensitivity than the standard meter type. Transmitter output strength is shown by four Superbright red light emitting diodes. A correctly functioning R/C transmitter, will illuminate three to four LEDs at a distance of 10 metres away. Adjusting the length of the short telescopic aerial will allow all LEDs to operate at a shorter distance for indoor checking. With occasional use, a four AA alkaline battery lasts over a year (even occasionally leaving the thing switched on)The OA47 diode seems to work best but more difficult to get. L1 needs to be initially adjusted to illuminate the maximum number of LEDs at a range of 10 metres or so. Once set thats it. The Toko coil used is no longer manufactured but many are still in the pipeline and there are alternatives. Remember, if you set L1 using a 35MHz Tx then the unit will only check other 35MHz transmitters. If 40MHz Txs are to be checked, set L1 using a 40MHz Tx. L1/C1 form a tuned circuit at 35MHz. A 35MHz Tx will excite this coil and cause a resonance of L1. D1 detects this and a little current flows at 35 million times a second! into C2. This increases the voltage across C2 (slightly) in proportion to the power of the transmitter signal. The LMC660CN is a Cmos op-amp and has little effect on the input circuit. The op-amps are arranged as voltage comparators using the potential divider R1-R5. The resistor values are selected to give a 3dB step between op-amps flipping on. (each one showing twice the transmitter power output) So with a weak signal, IC1D output will illuminate LED4. As the received signal gets stronger, the remaining LEDs will illuminate in turn, until all four are illuminated. An excellent practical layout of this circuit using Veroboard and some up to date components can be found at www.pm.keirle.com/

SOME USEFUL LINKS:-

www.micronradiocontrol.co.uk kits for R/C receivers, speed controllers, servos, chargers, etc.www.modelflying.co.uk Radio Control Models & Electronics one of the leading UK R/C model aircraft magazines.www.rcmodelworld.com Radio Control Model World one of the leading UK radio control model aircraft magazines. www.epemag.wimborne.co.uk Everyday Electronics a leading UK hobby electronics magazine.www.flyingsites.co.uk general information regarding radio control model aircraft.The UK Radio Control Council the Radio Control technical advisory council to the Govt OFCOM.www.rc-soar.com Info about radio control soaring models (and independent coverage of micron receiver assembly!)www.nikamelectronics.co.uk RF Electronics Company used by micron for development of UK R/C systems.www.ShortRangeDevices.co.uk companion site to above with possible model to ground modules 433MHz to 5GHz.www.elektor-electronics.co.uk edge of electronics UK/Netherlands magazine. Electronic projects/PCBs.http://home.HiWAAY.net/~mjn EF info plus PIC based speed controller design absolutely free! See Radio2www.customelectronics.co.uk flight simulator system for model aircraft, speed controller & other items.Alans Hobby Web Links A comprehensive A to Z of hobby related web sites.www.glue-it.com Model enthusiast site with many links and info including model railway topics.www.actionkit.co.uk electronic kits for models and GCSE projects, see Radio3 bottom of page.http://www.iroquois.free-online.co.uk Dave Days Home Page.everything to do with model aircraft and more!http://www.rcmodelreviews.com/ simply one of the best R/C electronic sites you are likely to come across. Bang up to date technology explained.http://www.webx.dk/index.htm superb website for R/C electronic projects. Excellent circuit diagrams and assembly photos. By Thomas Scherrer.

http://www.zen22142.zen.co.uk/index.html CIRCUIT EXCHANGE INTERNATIONAL Website by Andy Collinson. Electronic and radio schematics, design and simulation. Welcome to Circuit Exchange International. My site contains electronic and radio schematics in ten categories. In addition, there are sections on circuit simulation, design, analysis and a practical section containing tutorials. This is a free site and mostly my work, however I do welcome contributions. Everyone who has helped in the making of this site is listed on my credits page. This home page has kindly been translated into several languages, and you can use google translator for others. Thank you for visiting my site.

The following links come from Alans Hobby Web Links (above) .these links are just a tiny part of of Alans Dictionary of Model Radio control but this tiny part fits with the content of this website perfectly..many thanks my flying friend.

2.4-GHz Spectrum Analyzer - Low Cosr

Altimeter Project

Altimeter - Winged Shadow Systems - micro

Black Wire Corrosion

Circuit Central

Circuit Diagrams for Model Aircraft

Circuits for RC gadgets - Jo Aichinger ***

Creating Printed Circuit Boards - Easy DIY

Design for RC models - Russia

Do-It-Yourself Radio Control Electronic Projects & Gadgets

Dump "r" DIY discharge RX and TX packs

Electronic projects and tutorials ***

Electronic Circuits for the Hobbyist - Tony Van Roon

Electronic Gadgets (Projects) for RC - Tony Van Roon

Electronics Pages - Circuits etc by Tomi Engdahl's

Electronics Hobby Page

Electronize Model Electronics

High Frequency - Archives ***

kens RC home page

LED Calculator - RC Cam Projects

Lost Model Alarm (LMA ) - Plane Finder with fail safe

Plane finder _ Lost Model Alarm

Merlin PCB Designer

Newark Electronics, Catalog = Electronic Components

OHM'S Calculator

Optic Isolators - S.M.Services (U.K.) Ltd

Philips Semiconductors;

Radio control electronics - DIY fault finding and repair [Norcim] *** Radio Electronics Pages - Build your own TX & RX

Ram Radio Controlled Models Home Page

Receiver & Solenoid wiring for use with SLA (Gell Cell battery)

RC Creative Electronics

RC Frequency Monitor - DIY

RC Groups Discussion - DIY Electronics

RC Systems - DIY build your own & other RC projects.

Schiepatti Switch - for camera operation, glow driver etc

Servo Driver

Stefan's Electric R-C Web Site

Supercircuits Inc. ..Micro video camera etc.

Sirius Electronics-TX Diodes bridging

Suding Associates Inc. - Main Page

Technical Library

Voltage regulator = BEC 5V & 6V for Boats, cars and airplanes

traffic light security for external links.

Did you know that the new Spread Spectrum (2.4 Gig stuff) technology has been around for 70 years? You need to watch this video right through, Dont switch off! thinking its not relevant, then ask your grandparents about Hedy Lemarr! http://www.youtube.com/watch?gl=CA&hl=en&v=xUyhPDVBiaI

Recent visitor map for Norcim website 16 Nov 2011

You can contact me.norcimguy at gmail.com

Thanks for reading!

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NORCIM NOTES1 home page. Micron R/C fault find both Transmitter and ReceiversNORCIM NOTES2 40 MHz conversion of Tx and Rx plus Glow control and PCM thoughtsNORCIM NOTES3 35MHz transmitter circuit. Electric glider design. 459MHz conversion notes.NORCIM NOTES4 Economy electric flight. 15 amp relay switch circuit. Lost model alarm. History R/C.NORCIM NOTES5 Receiver sensitivity test results from Dave McQue including receiver circuit notes.NORCIM NOTES6 History of R/C systems including early PPM encoding and decoding circuitry.NORCIM NOTES7 Miscellaneous model information plus electronic components and some 2.4GHz stuff. NORCIM NOTES8 mainly unique model design for radio control and vintage radio control electronic circuits.NORCIM NOTES9 nostalgic transmitter circuits collected by David Caudrey. Also some original circuit designs.NORCIM NOTES10 further nostalgic original circuit designs for radio control by David Caudrey.NORCIM NOTES11 original R/C circuit designs from David Caudrey and some electric motor testing.NORCIM NOTES12 RON JAYs circuit pages. Simply a multitude of alarm circuits, timer circuits, LED circuits, Tutorials,Choosing parts and components, useful free circuit software, free circuit simulator. Magic Stuff !NORCIM NOTES13 DAVID CAUDREYs world of the Operational Amplifier. A page devoted to the OP AMP with possible applications within radio control systems. Many original design circuits. (content still being added Sept 2011)NORCIM NOTES14 a discussion of tuned circuits used in model radio control from DAVID CAUDREY and TERRY TIPPETT

The newcomers guide of Spread Spectrum radio control simple advantages of the 2.4 Gig radio control band for model control.

A change of subject ?.... The energy saving light bulb Myth. How UK households have been conned into paying a billion pounds for free light bulbs that dont work!

A simple demonstration of how to fly a model helicopter a superb video showing how to get started with model helicopters

This cant be real ! or can it? A full size airplane looses a wing and the pilot lives??

MICROSOFT ANTIVIRUS award winning security program for business and home computers at a seriously competitive cost.

This is a continuation page of the norcim web site notes, covering still more ideas and info.

Possible use of the Micron FET7 receiver on 40 MHz.

This is a Dual Conversion receiver and several enquiries have come in about its possible use on the 40 MHZ band for model boats and cars. Providing you can get hold of 40 MHz receiver crystals (preferably Futaba manufacture) then the changes to the FET 7 receiver are not too drastic! All of the changes are at the front end and involve the change of the 33uH inductor, (fig 2 on microns drawing) to a 22uH value available from Farnell Components* part number 513-477. The 27p capacitor and 4u7 inductor is simply snipped out as not needed on the 40MHz band. The front 159DZ antenna coil will need re-setting for maximum range using a 40MHz transmitter and you will find that this will involve almost exactly one turn of the core further down, clockwise, than the setting for 35MHz. Ideally the 27p capacitor across the coil would be changed for a 22p but as its under the coil, this is not practical. If starting from scratch then fit a 22p! The setting of the L2 coil (several type numbers were used for this coil) should not need any alteration.

If your posh! and have an oscilloscope to use when setting up home built receivers, then it is worth realising that the scope lead and scope, when connected to the receiver, adds to the antenna circuit of the receiver! When removed the antenna coil may not be perfectly set! To counteract this effect, a special scope lead can be made using a scope input DIN connector with two half metre, or so, flex wires terminating with mini crock clips or similar, with a 1K resistor in each lead at the crock clip. The resistors filter the RF antenna effect while still allowing the receiver output signal to show on the oscilloscope. The scope output on all the Micron receivers is from pin 9 of the 3361 IC after the 4k7 resistor.

If your not so posh! and dont have an oscilloscope, then I have found that reliable tuning of R/C receivers can be done with a crystal earpiece costing little more than a Euro (or less than a pound!). They usually come with thin flex wiring, terminating with a jack-plug. If the tip is held on the resistor from pin 9 (micron receivers) with the other metal bit resting against the metal can of the coil (or owt thats negative), then you can plainly hear the transmitter signal as a buzzing sound! The discriminator coil, L2 can then be set for maximum loudness. For setting the antenna coil.put the receiver and battery in a card box and move away from the transmitter until the buzzing diminishes slightly. Now adjust the front antenna coil L1 for maximum loudness or reception of the buzzing sound. (note that a hiss can be clearly heard either side of the Tx signal buzz). Thats it! And it can be very accurate.Its probably worth mentioning that the L2 coil on micron receivers can also be set using a multimeter. With the meter pos lead to the pin 9 resistor, and neg lead to battery negative, simply adjust L2 to achieve a reading of 2 volts, (with the transmitter switched on!).

http://www.howesmodels.co.uk/RadioControl/viewProducts.php?CatID=41 http://www.discovercircuits.com/R/rad-control.htm A Word about Micron transmitters and 40 MHz.

The MICRON 35/40 1996 transmit sections always made use of Fleet Control Systems crystals for use of the 40 MHZ band. These were manufactured by the IQD crystal company in Somerset and suited the Micron transmitter kit perfectly without any circuit change at all! However these crystals have been obsolete for some years now. In an attempt to find an alternative, I have found that the standard Micron transmit section will work with Futaba 40 MHz crystals providing a capacitor value is changed. The capacitor in question is the 56p across the base/emitter of the BF450 transistor. If this is raised to a value of 150p, then Futaba 40 MHz crystals can be used. The transmit section has to be tuned to the new band using the LED tuning device that comes with the Micron transmitter kit. A small reduction in range may result from using these crystals, (as the Tx crystal is one third of the output frequency unlike the Fleet crystals which were half frequency) but this can be corrected if necessary by reducing the 100R output transistor, input resistor to 68R. This is probably unnecessary however, as the range required with model boats, is lower than that required for model aircraft. Remember, Micron transmitters must use the special micron loaded antenna and the 40 MHz version must be usedfor this mod. UPDATE 27/8/02 a possible small but significant improvement in output power on 40 MHz can be achieved by reducing the 27p across L1 to 22p. This allows a better position of L1 core, giving a little more RF transfer to the secondary winding.

Another Word about Micron transmitters on the 35 MHz band. A few constructors of recent Micron transmitter kits have expressed grave doubts about the range or power output of their latest version of Microns offering, as the current consumption of the whole transmitter is less than 80 milliamps! In my opinion this is totally understandable as their latest Micron Tx kit consumes about half the power from the batteries of any other commercial 35 transmitter. Surely this can only mean half the range!? Micron however point out that this is simply not the case and despite the small battery power needed, the range, even with their mini loaded antenna is still comparable with the commercial counterpart and the answer is simply the use of their loaded antenna system. To prove the point, R/C Model World magazine March 2000, in their electronics project series, covered a Transmitter Output Tester that measures the field strength (power) of any Tx at a distance of 10 metres. I have used this smart device now many times and conclude, I wouldnt be without it. Not only does it show that the Micron Tx output is comparable with other transmitters but its occasional use with any transmitter gives great confidence of correct output. All of this becomes more interesting really, when you consider that the Micron transmitter can work for up to twice as long as other transmitters, between charges. Good for a day (or two) on the slope!

http://www.hobbyprojects.com/R/rf_radio_frequency_tansmitters.html http://www.qrp.pops.net/transmit.asp http://www.qsl.net/yo5ofh/links/transmitters.htm

Yet another Word! on Micron transmitters

a couple of recent enquiries, ask if the latest Micron transmit section could be used in earlier Micron transmitters. A quick consultation with Roger Keately at Micron and a search through the mountains of drawings and sketches he had, suggested that this had been thought about and indeed possible. The only thing needed is a special connecting flylead to connect the older (excellent but now obsolete!) NE5044 encoder to the new transmit section. This lead is shown and can be made up using parts available from most electronic stores or Micron. The odd thing about this lead is that it can be fitted any way round! ie there is no specific end which must go to the coder or RF section, the wiring appears to sort itself out, whichever way round the lead is fitted.

TRANSMITTER ANTENNAS (telescopic aerials in old money!)

I know youve read it before but it is a fact that telescopic aerials were never designed for model use! The caster base fuel gets into these things, dries out into a gum, almost making it impossible to collapse the aerial down without bending or breaking it! If this is not bad enough the grunge thats living in the aerial, sadly reduces the range of the Tx. (simply because of poor electrical contact of each telescopic section). Occasionally, unscrew the antenna, extend it and squirt WD40 into the bottom screw hole. A few collapses and extensions, using a kitchen towel to clean the antenna will prolong its active life! (Aahhh!). A word of warning though! If the aerial has been left in the grunge condition for too long, then after the above servicing, you may find that the top section is so slack that it slides back under its own weight! The only consolation is that the only thing keeping it extended before cleaning, was grunge and this prevented the aerial working correctly anyway. Should this happen, the antenna needs replacing.

A LITTLE WHILE AGO

An electronic modeller contacted me with an idea of using a speed controller circuit to keep the glow-plug of a four-stroke motor, hot at low revs and tick-over. Unfortunately the detail of the mail involved, has disappeared and I now cant give credit to the guy who was originally involved. However his idea is shown in the circuit alongside and involves the modification of his Micron speed controller to achieve the above. It is well accepted that 4stroke motors often cut out at low revs or tick-over, particularly when using low nitro fuels. Some 2strokes can also suffer from this when using less expensive straight fuel and could also benefit from this device! The Micron speed controller is very easy to modify, as its a kit! The only mods involved are the changing of the original 0.22 uF capacitors to a value of 0.47uF (see circuit) and the addition of a 5v resistorLED which shows the glow state of the Glow-plug. The finished unit plugs into the throttle output of the receiver (together with the throttle servo, so you will need a two way plug!). The resulting Glow-plug controller, heats the glow-plug, (Using an on board nicad battery) from about quarter throttle, with very little heat, down to full heat at tick-over. The on board nickel cadmium single cell battery needs to be about 2000 mAH or more to last the flying session. Setting up the controller involves adjusting the 22K trim-pot to just give maximum brightness to the LED, when the motor is set at tick-over. You should then notice that as the throttle is slowly increased, the LED looses intensity until around a quarter throttle, when the LED (and therefore plug) is not glowing at all. 2% petrol added to a basic mix of glow fuel often helps with general performance and tick-over. (more than 2% does not work well) The use of a synthetic oil based fuel compared with castor-based type, in itself, helps with both throttling and a reliable tick-over. The petrol mix idea, mixes with both types of fuel.

http://www.sentex.ca/~mec1995/gadgets/glow.htm http://www.freeinfosociety.com/electronics/schematics/sensor-based/modelengineglowplugdriver.pdf

RECEIVER BATTERY MONITOR this is about the simplest circuit you can get using a simple zener voltage diode (BZX79C3V9 Farnell order code 369-378). The circuit is shown alongside and simply plugs into a spare servo output of the receiver. The idea is that, providing the receiver battery is well charged (4v8 plus), then the transistor TR1 remains conducting at all times and the red LED shows no warning. However as the battery begins to sag, the demands of the servos pull the voltage down below TR1 conduction and the LED flashes. It is important that use of this circuit involves stirring two or three servos before and after each flight. If the LED flashes, then its time to go home and charge the battery!

A 12 VOLT GLOW-PLUG DRIVER Please note that this circuit has not been assembled or tested

but it is offered for experiment by those electronic nuts who may wish to assemble it and modify if necessary. Needless to say that if you do dabble and get results (or dont), then do let the web site know! The circuit is based on a standard text book multivibrator and its voltage supply is the starter battery used by modellers. It fires a stream of thin 12 volt pulses to the standard 2 volt motor glow-plug, simulating a 2 volt supply. The 47K pot allows adjustment of the width of the pulses to suit the type of glow-plug used (simply adjust the pot to obtain a rich orange glow with the glow-plug used) A zener diode allows automatic fattening of the pulses when the starter motor load abruptly pulls the battery voltage down. Q1 and Q2 are BC184LC or similar transistors with Q3 being a BUZ11A or similar power mosfet. The LED will illuminate when the plug lead is connected to the glow-plug, providing the plug element is intact. The LED should be a high brightness type. Q1 and Q2 must be high gain type, preferably better than 400 at around 2 mA. Worth a mention is that the glow-plug connector type should be of the box-spanner type. The clip on type can so easily clip on to the motor body and head causing a short circuit which would not be good news for the BUZ11.

SOME EXCITING STUFF has just come in from long lost flying friend, Alan Pratt. We first met when Alan was a student at Sheffield University. While I get the pictures sorted, Im going to let Alan explain things :-

Reviving an interest in R/C modelling after a 16 year break I decided to give my old Micron radio gear a technical facelift. I had used PIC microcontrollers prior to my retirement from industry and being mindful of the attractions of pulse code modulation this seemed a logical approach. The coder and decoder boards are built and tested and work fine. An electronic speed controller is bread-boarded and this also works fine. I have standardised on the PIC 16C84 (16F84) microcontroller because it can be repeatedly re-programmed making it ideal for development work. It also has non volatile eeprom data memory which enables the system user to store operational data eg. failsafe settings.

Photo 1 shows the coder board driving a standard Micron RF board (27 MHz early 80's vintage). The main components are the PIC, a low cost 8 bit serial A/D converter and an HC4051 analogue switch. A maximum of 8 channels is possible with this configuration although I have provided for 6 on this board and am currently only using 4. The two potentiometers set the +ve and -ve reference voltages for the A/D converter and hence the servo pulse width range. The small sockets at the bottom of the board will accept one of the proprietary FM Tx modules (418 or 433 MHz) which are widely available. I have a notion to download data from air to ground and this provides a development route for bench testing. I have written the PIC program to generate either pcm or ppm code.

With my version of pcm the control information for each channel contains an address element and a data element. The data is variable to effect the control but the address is fixed for each channel and can be used to check for valid data. In this way it is easy to detect invalid signals (eg. due to interference or out of range) and invoke failsafe settings.

Photo 2 shows the Rx decoder board with a Micron Rx. Apart from the +ve and -ve supply it needs only one connection to the Micron Rx - the pulse output. The other Rx output used to reset the 4015 chip on the Micron decoder is not required. To aid development and range checks I have included a miniature LED which lights when valid data is being received. I have fitted two DIL switches on the board. Only one is currently used. It selects either control or program mode. In program mode, with the model's controls adjusted to suitable failsafe settings the data can be stored in the PIC's memory. The second switch is connected to a spare PIC input pin for an as yet undefined purpose. (pcm or ppm?). An attraction of microcontrollers is that additional functionality can often be added later simply by re-programming.

I don't claim that this is ground breaking technology nor that it represents the only approach to the subject. The project serves to satisfy a personal interest in hobby electronics and provides a technical challenge. As with most of my projects development/modification is on-going without any planned timetable so its status could be classed as 'fluid'.

Alan Pratt

A GREAT BOOK to have to hand, is the RSGB (Radio Society of Great Britain) RADIO & ELECTRONICS COOKBOOK. (ISBN 0 7506 52144) Edited by Dr George brown. This is an excellent book covering the radio side of electronics from the ground up. Topics starting with What is a resistor? What is a capacitor? and Radio waves explained introduce more than eighty excellent constructional projects and gadgets including, A radio that is powered by three lemons!, A solar powered radio, Christmas tree lights and more. Amateur band receiver and transmitter projects are there too! This is a real easy book to understand and I recon would be an excellent book for school use that could span from mid GCSE level right through to A level and beyond! I cant think of any another book that could do that with the radio side of electronics.

Alans Hobby Web Links A brilliant site listing thousands of Hobby links, in carefully prepared sections, on an A to Z basis! Provides a stepping-stone directly to the topic of interest! Simple to use, and saves the time and frustration of searching. Click Here (use the Back arrow to return to Terrys radio notes!)

The following link is provided by Google and well worth the click!

http://www.google.co.uk/images?rlz=1T4ADFA_enGB385&q=rc+transmitter+circuit&um=1&ie=UTF-8&source=univ&ei=Gh9BTcXzLoep8QPIi_E8&sa=X&oi=image_result_group&ct=title&resnum=7&ved=0CE4QsAQwBg&biw=1003&bih=556

Thanks for reading.

NORCIM NOTES1 home page. Micron R/C fault find both Transmitter and ReceiversNORCIM NOTES2 40 MHz conversion of Tx and Rx plus Glow control and PCM thoughtsNORCIM NOTES3 35MHz transmitter circuit. Electric glider design. 459MHz conversion notes.NORCIM NOTES4 Economy electric flight. 15 amp relay switch circuit. Lost model alarm. History R/C.NORCIM NOTES5 Receiver sensitivity test results from Dave McQue including receiver circuit notes.NORCIM NOTES6 History of R/C systems including early PPM encoding and decoding circuitry.NORCIM NOTES7 Miscellaneous model information plus electronic components and some 2.4GHz stuff.NORCIM NOTES8 mainly unique model design for radio control and vintage radio control electronic circuits.NORCIM NOTES9 nostalgic transmitter circuits collected by David Caudrey. Also some original circuit designs.NORCIM NOTES10 further nostalgic original circuit designs for radio control by David Caudrey.NORCIM NOTES11 original R/C circuit designs from David Caudrey and some electric motor testing.NORCIM NOTES12 RON JAYs circuit pages. Simply a multitude of alarm circuits, timer circuits, LED circuits, Tutorials,Choosing parts and components, useful free circuit software, free circuit simulator. Magic Stuff !NORCIM NOTES13 DAVID CAUDREYs world of the Operational Amplifier. A page devoted to the OP AMP with possibleapplications within radio control systems. Many original design circuits. (content still being added Oct 2011)

The newcomers guide of Spread Spectrum radio control simple advantages of the 2.4 Gig radio control band for model control.

A change of subject ?.... The energy saving light bulb Myth. Do they work and at what cost!

More circuits and chat for the Radio Control enthusiasts out there who have an interest in the electronics side of the hobby.

A 35MHz AND 40MHz TRANSMITTER CIRCUIT

Commercial transmitters for use with model aircraft have a range of around a mile. This is provided by an RF section of usually three or four transistors with the use of plug-in crystals to change the frequency channel. The 35 MHz R/C band is now used for model aircraft in many countries, so the following circuit is shown with component values for the 35 MHz band. The basic transmit circuit is very simple and involves just the middle section of the diagram shown. This consists of a crystal oscillator stage T2 that runs at half the output frequency, followed by a frequency doubling stage T3.All the circuitry to the right of T3 is simply there to filter harmonics and spurious signals. (and it does this particularly well by suppressing all but the 35 Meg signal by more than 56 dB! This is an excellent figure for EMC, electro magnetic compatibility and non-contamination of the radio spectrum).The circuitry to the left of T2 is there to give a small (0.75 KHz) controlled shift the oscillator frequency, with each servo position pulse that comes from the transmitter coder circuitry. The resistor capacitor input to T1, slows the switching of T1, so that the shifting of the transmitter output frequency, with each pulse, is smooth. This keeps the transmitted signal narrow band. The output of this circuit has been independently tested by the ERA (Electrical Research Association) and is perfectly suitable for use on the 35 and 40 MHz bands.It never ceases to amaze me that just two transistors and a few components together with a 9-volt battery can potentially transmit up to a mile radius! The circuit is based around Fuaba spec plug-in crystals (available from most model shops). All resistors are 0.25 Watt 5%. Capacitors are disk ceramic except C12 which is a 16v electrolytic. All coils are Toko 7mm type. A mild modification to the circuit is shown in FIG 1A. the two extra components shown in red, lift the DC input level of T3 to produce an almost on situation for T3. (because of the 0.45 volt drop across the 1N5711 diode). T3 still works in Class C operation but only just. The resulting pulses from the PA transistor T3, are more fatter and more pronounced. More output power can be expected from this modification but T3 becomes hotter and needs an effective heat sink fitted. T3 in this configuration is better as a 2N3866 (TO5 package) transistor as a heat sink can be easily fitted.

A BARRIE ALLEN DESIGN POWERED GLIDER The Sun electric motor was mentioned in circuit notes2. Well the guy who was in on testing this motor actually designed a model to go with it! Its called Whisper(there are still some of these naturally talented people out there! Makes you sick!). The model however, turned out to be one of the most enjoyable electric planes Ive ever flown and I still fly it whenever I can. Its basically a V tail glider with wing area and overall dimensions that were dreamt up to suit the first examples we had of the Sun motor. The fuselage was made wide enough to just take two standard size servos side by side and deep enough (6 cm) below the wing to allow the 7 cell AA battery pack just foreword of the servos. The speed controller and receiver are positioned under a removable hatch just foreword of the wing. The Graupner 9x5 folder prop gives really good performance, producing thermal height two or three times using NH cells. Fuselage is of conventional balsa construction with foam wing. (built up wing could even be better). The motor was arranged to give a full 10 degrees downthrust to prevent too much nose-up on full power. We found that very slow landings were achievable by applying up elevator, without the model dropping a wing. Think its the effect of the V tail cutting into the airflow when the tail is low, but Im sure there are more qualified nuts out there who can explain this finding. Change the battery pack for a standard six cell sub-c pack and fit a Graupner speed 600 electric motor gives further performance. The servos need mounting further back to accommodate the larger battery pack. Note also that a standard six cell sub-c battery pack charges more easily from a portable 12 volt leisure battery supply.

http://www.dmoz.org/Business/Consumer_Goods_and_Services/Recreation/Models/Remote_Control/Gliders/http://www.flyingsites.co.uk/newcomers/intros/gliders.htm

IDEAS FROM NASA!

When a little web site like ours, popped up in the NASA Research Centre, USA, George Beeler kindly made some time to Email us about a simple check for a dead receiver!

Re: Simple first order-check on a dead receiver.

Dear Terry,I happened on this quite by accident, but it is a very useful tool. If you have a relatively sensitive general coverage receiver, you never have to open a receiver to determine if the Local oscillator is non-functional.

Most good quality general coverage receivers (such as most amateurs and short wave listeners have) will be able to detect and pick up the un-modulated local oscillator. So you either set your short-wave radio to the known oscillator frequency or offset the receive frequency by +/- 455 kHz to detect the local oscillator. Since the oscillator is un-modulated, you will need to turn on the BFO (Beat Frequency Oscillator) in the receiver to be able to hear the squeal when you plug in or turn on the receiver.

So why doesn't a good frequency counter pick this up? If it did, you would never get a good frequency indication, as it would be chasing every weak signal for many miles. So the threshold is set to some reasonable level to squelch the micro-Amp level signals.This technique is great when you are checking old equipment, crash checking the receiver, and in handy checking for oscillator drift as the tone will change by the frequency change, which you can see on an oscilloscope.

I think it would be very useful for a group such as yours, who might not have thought about it, to have a good General coverage radio around.

Good to share, George B. Beeler.

Many thanks for that George. I wish the Beeler check had been around some years ago when I was fixing R/C receivers for a living! Take care and do keep us in mind for the future!

http://www.ac6v.com/homebrew.htm

A REASON FOR SOFT UNCOMPRESSED FOAM RUBBER PACKAGING OF THE RECEIVER

Is that when used in a power model, some of the electronic components are microphonic. (probably not a dictionary word but means act like a microphone!). High vibration levels caused by poor packaging, induces an unwanted electronic ripple at the receive circuit output. This in turn can cause semi-erratic servo control on PPM systems and possible complete signal lock-out of PCM systems. The suspect microphonic components in receivers were found to be the electro-mechanical items like coils and filters. Filters tended only to show a problem at certain resonant frequencies. NOW GO AND CAREFULLY PACK YOUR RECEIVER IN NICE SOFT, UNCOMPRESSED, FOAM RUBBER! (And dont give a damn what the model shop people say!) AN EXPERIMENT

to prove the above point, can be done. (Sorry! The following info is aimed only at the real hardened electronic crackpots out there!). A test rig, can be built around a 120mm/150mm 8 OHM full range HI-FI speaker unit. A 2mm Ply disc of maximum diameter is dropped into the speaker cone, with epoxy around its edge. This gives a platform for the test receiver to be strapped to, using hooks and elastic bands. I used a simple square wave 555 astable oscillator with a PNP/NPN power drive to the speaker. The frequency of the drive unit was about 30 to 300 Hz. This reflected tick-over speed, to full power, of a typical Glow-Motor used for model flying. A 6v 0 6v nicad battery supply was used but this could be increased (if you wish the receiver to revert back to kit form within a few minutes!!) Flex wiring is needed for the receiver battery input and the oscilloscope output of the audio test point on the receiver. Warning! The resulting noise produced by the test rig will certainly wake the neighbours if not the dead!

If youre a Crackpot like me then..HAPPY RECEIVER DEMOLITION!

USE THE 459 MHz R/C BAND WITH YOUR YOUR FAVOURITE PPM TRANSMITTER! Well Malcolm Perry has come up with a device that simply plugs into the Buddy-Box socket of your Tx and Hey Bingo! your transmitting on the UHF band! Malcolm has even developed a UHF receiver capable of up to eight channels!

Why not UHF? By Malcolm Perry

The UK has for many years allocated a band in the UHF part of the radio spectrum for model control use. This part of the spectrum commonly known as the 459Mhz band is today hardly, if ever used for model control. Equipment has been manufactured in years gone by, by companies such as Reftec and Cotswold, but today there is, to the best of this writer's knowledge no manufacturer supplying model control equipment on UHF. When you consider that modellers often have to wait to use a frequency at a popular site, this is a great pity.

I have for several years experimented with systems using this band with various degrees of success. I thought that your readers might be interested in a recent attempt to develop a viable receiver using this band. In the past I have built complete systems - from scratch! - a laborious task if you consider all the mechanics as well as electronics that goes into a system!

The system I am going to describe makes use of the licence free (MPT) modules now available in this part of the spectrum. In fact the UHF band is now shared, so modellers do not have exclusive use of all the frequencies, which is a shame. The modules you can buy are in the lower part of the band, but this sharing is not all bad news. A characteristic of UHF is that it does not propagate far and to date I have not experienced any interference on the frequency I have chosen. The modules are designed to a specification, and the one chosen is a dual conversion superhet with a low noise amplifier front end. In fact the modules are complete and will with a little interfacing accept a TTL logic drive and at the receive end reproduce the same.

TRANSMITTER

My idea as you can see from the attached picture is to use the 'buddy box' trainer facility to take the output from a standard transmitter and interface it into the UHF TX module. Simple really and the advantage is that there is no modification to the transmitter that might invalidate its approval standard. The unit can be removed and the transmitter operated normally just by removing the DIN plug. In fact a simple adaptation of the interface means that when the UHF module is plugged in the normal internaltransmitter is disabled - an important additional safety feature.

RECEIVER

Perhaps the most difficult part of the exercise was to develop a practical receiver, given that today's modellers expect small size and lightweight as standard. You can tell from the attached picture that this receiver is reasonably small; its actual dimensions are Length 60mm, width 42mm, and depth 34mm. Weight 70grams. For this you get 8 channels, only 7 used with my transmitter combination and the exclusivity of the UHF band, It would be fair to add that the receiver is slightly more complicated, because I found that the recovered data from the UHF module was prone to noise bursts (glitching in modeller's terms) This was considerably reduced by the use of a Phase Locked Loop discriminator in place of the internal quadrature detector. The decoder board is fed by the receivers second IF frequency at 455kHz.

CONCLUSION

I think the answer to my question "Why not UHF" is pretty simple and it is not necessarily a technological one. The particular '459mhz' band is only available in the UK and the majority of model control manufactures are international companies - hence there is little incentive to manufacture equipment that could only be marketed in the UK. This maybe an over simplification, but at least part of the reason why we cannot buy equipment manufactured for this band. Finally I would add a health warning - developing systems that perform safely requires careful design and analysis or the old adage that your "model might come crashing out of the sky" could become true! Still as I said at the start, it is a shame that more use is not made of this band or, as I noticed, one of your writers has already said we will loose it.

http://uk.excite.eu/search/radio+control?source=googlelt&q=radio+control&cst=fs&csc=3736494329&csk=radio%20control&gclid=CO_cqZTT0aACFRI-lAodBnNczw

JOYSTICKS AND THINGS!

several Emails have arrived recently asking how to wire-in transmitter joysticks, that have a separate potentiometer for in-flight trim. The circuit shows one of the ways to do this and was actually used by Micron in many of their transmitter kits. The circuit used, terminates with a three-pin socket. If the socket is reversed when at the Tx coder, then the servo in the model works in the opposite direction (an added bonus!), giving what is called servo-reverse. Microns older 5044 coder used this set-up without problem but the later 4017 coder can give some problems owing to the restricted current drive capabilities of the standard Cmos 4017 chip. The trouble is, that available joysticks use a 5K main pot with an in-flight trim pot of also 5K. This results in a 2K5R load for the 4017 chip. Unfortunately this is borderline current output for the chip! A solution to this problem could be found by replacing the 5K in-flight trimpot with a pot of higher value, say 22K, which would reduce the load on the 4017 chip. The HEF4017BT was found to give the best drive current some time ago but there may be 4017 devices with better drive capability now, which would alleviate the problem. However try this circuit first!

GOT ONE OF THE THOUSANDS OF PPM RADIO CONTROL SYSTEMS OUT THERE?

Then read on again, because this Multi Servo Failsafe unit from Alan Pratt will transform the safety of your system and add to your flying, sailing, or driving confidence! The picture shows one of the DIY prototypes that I managed to snaffle for testing. With only five components, it can be assembled in around fifteen minutes! (Wow, have things changed since I was a lad!).The commercial possibilities of a Surface Mount version of this unit, in my opinion, are big by modelling standards. It is estimated that 10s of thousands of eligible model radio control systems exist in the UK alone. Production investment, with only five components, would be relatively low and the unit can be customer pre-set to suit almost any make of R/C system and any model aircraft, boat, or land vehicle.The unit simply plugs in-line from the receiver to the servos. Under heavy radio interference or loss of signal, it will automatically drive the servos to a position, pre-set by the pilot! This is magic for the average flyer and a must for quarter scale. Initial bench testing has also revealed other technical benefits of the AntiFerence program that Alan has developed for use in his microcomputer device. I am convinced that this is not the last we are going to hear of this exciting development! Me?well Im off to fly with the snaffled unit installed and just itching to switch the transmitter off at 500 feet!

HAD AN EMAIL

from Mohamed Shiraz Kaleel and well worth a mention! Mohamed pointed me in the direction of a real interesting group web site. These people actually build their own electric flight motors from CDROM drive motors! The site is extremely detailed and professional. A massive amount of technical info is available there showing how to convert CDROM motors into powerful brushless type flight motors capable from slow flight to 2kW! There is even details of the necessary electronic drive unit including, even a kit of parts! Well worth a visit if you are a mechanical and electronic nut, wishing to see the cutting edge of brushless technology. http://www.yahoogroups.com/group/lrk-torquemax/

IN 1950 (WHEN BEER WAS TUPENCE A PINT!)

There was just one transmitting frequency for model control! At the flying field you simply waited for the existing model in the air to fly away then it was your turn to entertain the masses of kids that would materialise from absolutely everywhere! It was probably as far back as this, that the initial seeds were sown, that slowly germinated into what is now called the Radio Control Council of the UK. This is a body of representatives, experts and Gurus from all walks of the radio control model world. They descend upon the Boardroom at Bletchley Park MOD establishment around twice a year and with coffee and sandwiches, discuss the future of model radio control. Liaison with the government Radio Agency is continual and on occasions Radio Agency officials attend these meetings.

One of the staggering achievements of the RCC is that UK modellers now have over 120 frequencies available for model control! Other technical inputs of the RCC include the introduction of FM radio in 1978, Narrow Band 10KHz FM radio 1980, A new 35 MHz band for models 1981, Development of transmitter Type Approval testing procedure, A special surface model (boats/cars) band on 40 MHz, (leaving the 35 MHz band for aircraft only), European Harmonisation of model frequencies and specs, Discussion of receiver Type Approval, R/C System EMC testing..and the list goes on! (Not a lot of people know that!!!)

So! The next time you get back from flying with a smile on you face! Just you point yourself in the direction of Bletchley Park and salute these guys!! World R/C frequency info and other technical info is available on the RCC web site @ www.ukrcc.org

WANT TO KNOW OF AN ELECTRONIC KIT SUPPLIER WITH THINGS LIKE

Speed controllers, servo testers, Micro FM receivers, Micro AM receivers, chargers for nicads and NiMH batteries, chargers for 6v and 12v Gel cell batteries, Big range of electric motors for models, Servo slowdown kit, Servo failsafe, Big range of Sound Simulators for model boats, Battery eliminators, Tx power device, and more! Well simply tune into www.action-electronics.co.uk to find a super range of electronic kits for us model people and GCSE electronic projects. Contact is Dave Milbourn.

Photo shows actionkits DUAL SWITCHER KIT but there are many more!

NORCIM NOTES1 home page. Micron R/C fault find both Transmitter and ReceiversNORCIM NOTES2 40 MHz conversion of Tx and Rx plus Glow control and PCM thoughtsNORCIM NOTES3 35MHz transmitter circuit. Electric glider design. 459MHz conversion notes.NORCIM NOTES4 Economy electric flight. 15 amp relay switch circuit. Lost model alarm. History R/C.NORCIM NOTES5 Receiver sensitivity test results from Dave McQue including receiver circuit notes.NORCIM NOTES6 History of R/C systems including early PPM encoding and decoding circuitry.NORCIM NOTES7 Miscellaneous model information plus electronic components and some 2.4GHz stuff.NORCIM NOTES8 mainly unique model design for radio control and vintage radio control electronic circuits.NORCIM NOTES9 nostalgic transmitter circuits collected by David Caudrey. Also some original circuit designs.NORCIM NOTES10 further nostalgic original circuit designs for radio control by David Caudrey.NORCIM NOTES11 original R/C circuit designs from David Caudrey and some electric motor testing.NORCIM NOTES12 RON JAYs circuit pages. Simply a multitude of alarm circuits, timer circuits, LED circuits, Tutorials,Choosing parts and components, useful free circuit software, free circuit simulator. Magic Stuff !NORCIM NOTES13 DAVID CAUDREYs world of the Operational Amplifier. A page devoted to the OP AMP with possibleapplications within radio control systems. Many original design circuits. (content still being added Sept 2011)

A change of subject ?.... The energy saving light bulb Myth. Do they work and at what cost!

ECONOMY ELECTRIC FLIGHT was outlined in Radio1 and Radio2 pages.

Well the picture shows one of the test models, a Graupner Biene, using the Sun motor, on a typical climb to thermal height, and it will do this twice on seven GP AA nickel hydride cells from CPC electronics.com at just 1.00 per cell. With the motor costing just 2.30 from JPR electronics, this shows just how inexpensive good electric flight can be. The AA cells give around ten minutes of full power in the air using a Perkins Distribution (most model shops) 8x5.5 electric flight prop. Increased climb rate can be had, by using a Graupner 9x5 (most model shops) electric flight prop, but this reduces full power in the air to around 8 minutes. Increased performance can be had with a Groaupner speed 600 motor and a standard 6 cell sub C battery pack. (see page 2)The following circuit shows a simple speed controller. Many of these controllers have now been used with test models using Micron receivers and all have performed well. The few components of the controller allows home construction for less than 3.00! The controller is based around a CD4001N quad 2-input NOR gate IC which can cost as little as 30p from your electronics store! The real expensive bit is the MOSFET output transistor which could lay you back around 2.50. The single MOSFET drives the SUN motor (including standard 380 and 540 motors) using seven cells (8.4volts) with no problem. You can even cut the metal tag off the transistor to make the controller more compact, without overheating of the MOSFET. The input circuitry produces a saw-tooth waveform with each servo pulse. This can be adjusted via trimmer R5 to trigger IC1A gate to produce a 50/50 mark space output thus driving the motor at half speed. Changes in the pulse width cause the saw-tooth waveform level to change giving variable speed from fully ON through variable to fully OFF condition. The circuit without the optional 5v regulator is intended for use with a separate receiver battery. If the LM2940 is fitted then the receiver, servos and controller are supplied by the flight battery.This simple circuit is more suited to receivers with full rail voltage output pulses (usually Cmos decoder chips) and has been tested using Micron, Fleet and RCM+E receivers.Using the three remaining gates of the CD4001BCN in parallel gives adequate drive for up to five MOSFETs in parallel for hot motors. (at the relatively low switching speeds!).D2 and C5 provide good suppression of motor interference for the Sun motor, which has no internal brush suppression capacitors. For Hot genuine electric flight motors just follow the suppression instructions supplied with the motor.

http://norbique.rchomepage.com/esc/ http://trebor69.tripod.com/speedcnt.htmlhttp://www.stefanv.com/rcstuff/esc.htmhttp://www.rc-airplane-advisor.com/electronic-speed-controller.html

ITS SERVO TESTER TIME!

The following circuit offers manual control of almost any make of R/C servo, using just a receiver battery (4.8 nicad) for power. The components should cost you no more than a 1.50 or just over 2 Euros! and it should work with all makes of servo. The circuit is a text-book two transistor multivibrator providing an 18 to 20ms cycle time which suits R/C servos. The circuit is however extremely lob-sided! In that one side produces around 17ms delay before triggering the other side, which only stays on for 1.5ms! Its this side that the servo output is taken from. The 4k7 pot with knob, produces a pulse variation from 1ms to 2ms at the output which can be used to test most known servos. C3 provides sufficient damping of servo noise to let the circuit work correctly. Its worth mentioning that the hfe of the transistor used must be high, better than 250 @ 1ma. So if substituting, then pick a high gain device.

http://www.rc-cam.com/servotst.htm http://forum.allaboutcircuits.com/showthread.php?t=13813 http://www.555-timer-circuits.com/servo-tester.html

THOUGHTS ARE NOW WITH FAST CHARGING NICAD AND NICKEL HYDRIDE BATTERIES

There are several methods of fast charging model car and electric flight batteries but the most popular system, is called the Voltage Peak Detect Method. When NC or NH batteries are charged, their voltage slowly rises to a peak (when fully charged) but this is quickly followed by a small but significant dip in the battery voltage. Peak detect fast chargers, rely on their ability to detect this small voltage drop when the nicad is full and terminate the charge before overcharge damage is done. A simple peak detect method for six or seven cell sub-C batteries is shown. At switch-on, (connection to the 12v supply), the forward volts of D1 holds the inputs of the OP AMP apart, preventing any switching of the output. Initially, the voltage across D1 (which is a Schottky RF diode) can be as high as 0.3v but this quickly reduces within minutes to less than 0.05 volts because of the extremely low current flow through the diode. C1 then, follows the increasing nicad voltage (which can be as close as 0.02 volts when near to full charge). At full charge, the nicad voltage begins to fall..D1 soon becomes reversed, (also IC1A inputs!) causing IC1A output to flip. This terminates the charge current. The result is a fast, half to one hour, automatic cut-off charge! There is no need to discharge the nicad first. Full charge is detected even with a partly charged nicad. It is important that C1 is one of the recent Aluminium Electrolytic low leakage type capacitors. (Rubicon TWL series 47UF16V-16TWL47MO811 Farnell order code 499-067). Its worth mentioning that the 1N6263 has a lower reverse leakage current than general purpose schottky diodes. This helps at the peak detect point.

NEXT THOUGHTS ARE WITH CHECKING TRANSMITTER RANGE

This next circuit lends itself not only for home checking but also club and quick model shop checks. The circuit checks for correct power output of any 35 or 40 MHz radio control transmitter is shown. These things are called field strength meters and are a standard piece of electronic equipment in the service workshop to check the output power of R/C transmitters. Field Strength Meters (as they are called) are usually based around a reasonable size sensitive 50uA moving coil panel meter. These are now listed (Farnell) between 20 and 30 each (before circuitry!). This circuit is based around the National Semiconductor LM661CN Cmos quad op-amp IC. The circuitry components should cost no more than 4.00! and it has greater sensitivity than the standard meter type. Transmitter output strength is shown by four Superbright red light emitting diodes. A correctly functioning R/C transmitter, will illuminate three to four LEDs at a distance of 10 metres away. Adjusting the length of the short telescopic aerial will allow all LEDs to operate at a shorter distance for indoor checking. With occasional use, a four AA alkaline battery lasts over a year (even occasionally leaving the thing switched on)The OA47 diode seems to work best but more difficult to get. L1 needs to be initially adjusted to illuminate the maximum number of LEDs at a range of 10 metres or so. Once set thats it. The Toko coil used is no longer manufactured but many are still in the pipeline and there are alternatives. Remember, if you set L1 using a 35MHz Tx then the unit will only check other 35MHz transmitters. If 40MHz Txs are to be checked, set L1 using a 40MHz Tx. L1/C1 form a tuned circuit at 35MHz. A 35MHz Tx will excite this coil and cause a resonance of L1. D1 detects this and a little current flows at 35 million times a second! into C2. This increases the voltage across C2 (slightly) in proportion to the power of the transmitter signal. The LMC660CN is a Cmos op-amp and has little effect on the input circuit. The op-amps are arranged as voltage comparators using the potential divider R1-R5. The resistor values are selected to give a 3dB step between op-amps flipping on. (each one showing twice the transmitter power output) So with a weak signal, IC1D output will illuminate LED4. As the received signal gets stronger, the remaining LEDs will illuminate in turn, until all four are illuminated.

FURTHER THOUGHTS NOW RE: THE FAST NICAD CHARGER ABOVE

Fig 1 shows a possible output stage for charging a 7v2. nicad. Note that this is not a constant current circuit but should work OK. Note that the 1R resistor will initially let through a charge current of around 3 Amps which will slowly fall to 1 Amp or less at peak detection. The MOSFET in this version would not need to be fastened to a heat sink as it is in a fully on condition when charging and will need to dissipate little heat. The 1R or 2R resistor however will get very hot and would benefit from a heat sink. The 1R resistor value should be used for sub-C nicads. The 2R2 resistor is a better value with less current flow for 7v2 AA nicads. Fig 2 shows another possible output circuit in which the charge current through the MOSFET (Q2) can be set by adjustment of the 22K trimpot. A charge rate of 2 Amps is suggested for 7v2 nicad batteries. Some care will be required with the setting of the 22K pot and best to start with the wiper at the negative end of the pot. The charge rate should be reasonably constant with this circuit, owing to the bias characteristics of MOSFETs. Note that this circuit uses the MOSFET (Q2) to restrict the charge current flow and therefore Q2 will get hot! AND will need to be clamped to a metal heat sink. IT MUST BE POINTED OUT THAT ALTHOUGH THE PEAK VOLTAGE DETECTION CIRCUIT HAS BEEN WELL TRIED USED TO DATE, THE TWO ABOVE CIRCUITS FIG1 & FIG2 ARE POSSIBLE OUTPUT CIRCUITS AND ARE INCLUDED FOR EXPERIMENT.

A POWER SWITCH FOR R/C RECEIVERS

Fig 3 shows a simple circuit that can be plugged into one of the receiver servo outputs to switch on and off an external load of up to 15 Amps. The circuit is shown driving an electric flight motor but for boat people the relay could switch several torch bulbs, or a high power halogen lamp, or winch, or sound circuit. The dotted line shown from the relay back contact to ground provides dynamic braking of the motor when using folding props with electric flight. The input components form a text-book diode pump circuit. The trim-pot is set so that thin pulses from the transmitter pump up C1 voltage to just get the Logic Level MOSFET, conducting. The current flow through the relay however, is very small and well below that necessary to close the relay contacts. But throwing the stick at the transmitter to get fat pulses, increases the voltage across C1, allowing much more current flow through the MOSFET and the relay closes. Both 5 volt and 6 volt relays have been used in this circuit with windings of 55R to 90R. Notice that only the Rx pulse input and the negative input is required from the receiver (The red positive input is simply left unconnected). The current drain of the circuit on the receiver battery is almost undetectable. At higher voltages of the external circuit, the MOSFET (Q1) tends to limit the current flow through the relay to acceptable levels. The MOSFET, RFD4N06L (or similar) is a TO 251 (I-Pak) device and may get warm with a 12 volt external supply. This is normal. Several relays are suitablefinder type SPCO 16A Farnell code 431-308or smaller 12Amp version finder type Low profile 21 series Farnell code 321-0224. Smaller low profile relays are now available and should be suitable.

EVER LOST A MODEL IN A CORN FIELD??? Well this next 555 circuit will detect its position!

PIEZO SOUNDER DEVICES ARE SMALL AND WEIGH JUST 5gms! These small units can be heard up to 100 metres away in quiet countryside conditions, particularly if they are switched on and off! The following circuit uses a 30p 555 timer IC, to drive one of these Piezo sounders. The 555 is configured as a 50/50 astable pulse generator which sounds the piezo thing around once a second. Transistor TR1 keeps shorting C2 with each servo pulse, so that the 555 IC cant get going. The piezo sounder remains quiet during normal flight conditions. Should the model decide to land in a corn or rapeseed field, then switching off the Tx allows TR1 to go open circuit and C2 to begin its charge/discharge cycle enabling the 555 to switch the piezo sounder on and off at around once per second. With careful listening, the model can be located! Suitable piezo sounders are Farnell order code 927-181 or 927-119. The receiver input stage should suit most makes of receiver including those with low voltage servo pulse output.

AND WHERE IT ALL BEGAN!

Did you know that one of the first offerings from the Micron people was a pulse proportional system? Based around a Mighty Midget electric motor? Full kits were available from around 1962! The system used a single electric motor to pulse both rudder and elevator control surfaces. Surprising proportional flight could be achieved with this system, which was termed Galloping Ghost (because of the noise of the flapping control surfaces!). One of the flight demonstrations of the system, involved several passes through soccer goalposts (at a medium throttle setting, as there was no throttle control), which was quite an achievement alongside the standard reed equipment of the day.The receiver (shown bottom left) used a super-regen front end (only allowing one model to fly at a time!) was designed by early R/C pioneer, Doug Bolton. Other R/C equipment of the day used self-centre toggle switches on the front of the transmitter for full throw of the control surfaces Joystick units had not been invented! So joysticks for the Micron people transmitter kits had to be individually made from brass stock with piano wire wound springs! Two external pots provided the in-flight trims. Early transmitter circuitry used a variable rate saw-tooth generator (unijunction) followed by a varying level Schmitt trigger to generate the mark/space and pulse/rate, pulses for the mighty midget actuator. Later circuitry used a curious diode gated two-transistor astable-multivivrator, which gave a logarithmic effect to the rate channel (elevator). This improved the elevator effect to perform outside loops, when using the mighty midget actuator. Unfortunately this effect could not be used with the later more popular American Rand actuator.

Rapidly advancing multi-channel analogue and digital technology saw the demise of this kind of simple pulse proportional control but there is little doubt that these early systems began the trend into true proportional control of model aircraft.

The photos show one of the early Micron People Galloping Ghost proportional systems, which is now forty years old! When last tested with replaced nicad batteries.It still worked!.and without any doubt, it would still fly a model through those soccer goalposts! Unfortunately my grey matter has slowed down somewhat and there is no way now of proving this!

A photo of one of the models that flew with this system is shown and probably dates around 1962 ish. Although looking good, it was found that the pulsing of the radio system was clearly seen whenflying. Other models used at the time were the Gasser and the Charles Rail design called Galloper both were plans from the Aeromodeller magazine. The conclusion was that the greater length of the fuselage from the wing to the tail actually helped to damp out any visual hopping effect of the elevator. The use of a heavy motor, prop and motor mounting plate also helped. This produced a situation of having to add lead to the tail of the model to get the correct CG. This extra weight at the tail end dampened out the pulsing elevator effect. The pulsing rudder never seemed a problem and under all flying conditions could not be noticed when flying. Memories of early galloping ghost models that I flew, showed that they were extremely good at slow flying during the glide after the motor had cut. In fact I remember that with one model, I could often bring round into wind with the intention of landing several yards in front of me, but Full Up elevator at that point produced a slow fully controlled rise into my chest where the model was caught. I never achieved this with later models fitted with proportional gear. One reason could be that GG models were built of balsa and tissue covered (they were light!). On reflection an additional reason for this uncanny control could be the fact that at extremely low speeds, the wing was continually stalling and uninstalling with the hopping effect of the elevator at full UP of the system. (generally the elevator is kicked UP around twice a second with full UP joystick and hopping is noticeable).

Interested?......then here are some links to the historic Galloping Ghost system with even a video !http://ruijsink.nl/mm-hist.htm http://www.rcsoaring.com/rcsd/RCSD-2009-08.pdf http://www.rcgroups.com/forums/showthread.php?t=265447 http://www.youtube.com/watch?v=xBSRmlIGSWQ http://www.singlestickstuff.com/ AN AUTOMATIC CHARGER FOR 2 VOLT GLOW BATTERIES

This simple circuit charges part-charged two-volt glow batteries in an hour or two, with auto slow-down to trickle charge. (The charge rate gradually reduces toward the end of charge, to minimise battery gassing). The power input is taken from the 12-volt field starter battery (or car battery). Both input and output are polarity reverse safe and the green LED will only illuminate with correct input and output connections. The Car Bulb LMP1 indicates charge, taking pl