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Vol.7, No.9; September 1994 FEATURES FEATURES   6 How To Use The TEA1100 Fast Nicad Charger IC by Leo Simpson Versatile chip features switchmode or linear operation 16 Electronic Engine Management, Pt.11 by Julian Edgar Fueltronics’ Turbo Control Centre RID YOUR NICAD batteries of the dreaded memory effect with this automatic discharger. It will discharge the pack to its correct endpoint voltage so that it can then be recharged to full capacity – see page 18. 87 Review: Metex M3850 Digital Multimeter by Marque Crozman All the usual features plus a PC interface PROJECTS TO TO BUILD BUILD PROJECTS 18 Automatic Discharger For Nicad Battery Packs by John Clarke Rids your batteries of the dreaded memory effect 31 Build The MiniVox Voice Operated Relay by Darren Yates Fast-acting unit fits on a small PC board 34 An Image Intensified Night Viewer by Leo Simpson THIS VOICE OPERATED RELAY (or VOX) is built on a compact PC board. It has almost no turn-on delay & a 3-second release time. Details page 31. Lets you see by just the light of the stars 54 An AM Radio For Aircraft Weather Beacons by Darren Yates Picks up airport weather beacons in the longwave band 66 Dual Diversity Tuner For FM Microphones; Pt.2 by John Clarke Construction & alignment details SPECIAL SPECIAL COLUMNS COLUMNS 40 Serviceman’s Log by the TV Serviceman Lightning strikes thrice 63 Amateur Radio by the TV Serviceman HERE’S A NIGHT VIEWER that’s ideal for wildlife observations or any other activity where you need to see in the dark. It uses a 3-stage image intensifier tube so that you don’t need a separate infrared light source. Details page 34. Using 2-line Keplerian elements to track satellites 80 Vintage Radio by John Hill Building a classic crystal set 84 Remote Control by Bob Young Modellers with dedication; Pt.2 DEPARTMENTS DEPARTMENTS   2 4 24 53 73 Publisher’s Letter Mailbag Circuit Notebook Order Form Bookshop 87 90 92 94 96 Product Showcase Back Issues Ask Silicon Chip Market Centre Advertising Index YOU CAN USE THIS simple radio to receive up-to-the-minute reports from airport weather beacons. It uses two ICs & operates in the longwave AM band – turn to page 54. Cover concept: Marque Crozman August 1994  1 Publisher & Editor-in-Chief Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Darren Yates, B.Sc. Reader Services Ann Jenkinson Sharon Macdonald Advertising Enquiries Leo Simpson Phone (02) 979 5644 Regular Contributors Brendan Akhurst Garry Cratt, VK2YBX Marque Crozman, VK2ZLZ John Hill Jim Lawler, MTETIA Bryan Maher, M.E., B.Sc. Philip Watson, MIREE, VK2ZPW Jim Yalden, VK2YGY Bob Young Photography Stuart Bryce SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. A.C.N. 003 205 490. All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Macquarie Print, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $49 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 34, 1-3 Jubilee Avenue, Warrie­ wood, NSW 2102. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 979 5644. Fax (02) 979 6503. PUBLISHER’S LETTER Where to now for satellite TV? Over the last few months, there has been a flurry of devel­opments in the pay TV/ satellite TV saga and many people must be wondering what comes next. When will they be able to actually start subscribing to pay TV services? After all, most, if not all, of the satellite and cable licenses have been snapped up and people could be forgiven for thinking that actual services will start “real soon now”. Well the truth is that some very limited services are about to start and may well have started by the time this issue goes to press but note the word “limited”. Very few people will be able to take advantage of them. For the vast majority of people, pay TV is many years away, as in “turn of the century” or well after that. It is significant that potentially the biggest player in the pay TV arena, the so-called PMT (Packer/Murdoch/Telecom) syndicate, sat on its hands during the recent licence sales. Clearly, they are not interested in satellite TV and if you hark back to my Publisher’s Letter in the August 1993 issue, you can see why. With Telecom’s vast phone network open to it, it has no need for satellites. And while little may appear to be happening on that front, much is happening behind the scenes. Telecom has let some huge contracts for its CATV project for the major residential areas of Brisbane, the Gold Coast, Sydney and Melbourne. As part of that, Telecom Australia has awarded a $160 million plus contract to Philips to provide the technical equipment and know-how to deliver full interactive television to Australian audiences. Telecom has also chosen the Digital Equipment (DEC) Wizard Subscriber Manage­ment System, while Scientific Atlanta has been chosen to supply customer set-top units. Philips will play a major role in the network upgrade which will involve a rollout of more than 10,000 kilometres of cable. And nor is optical fibre the only part of the story. Philips also has been developing the capability of sending cable TV via twist­ed wires, so much of the existing network might also be able to be used eventually. Clearly, Telecom is in the box seat for pay TV and all the other services to come in the future. So things are happening but if you want to watch overseas source programming right now and for quite a few years to come, there is only one way to get it: install your own dish and satel­lite receiver. There is a large variety of programs available, beamed into Australia, and more are coming as time goes on. And this plethora of programming is certain to be available even after pay TV is up and running. So if you have a hankering for satellite TV, get into it now. Otherwise, you could be waiting for many years to come. Leo Simpson ISSN 1030-2662 WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Trade Practices Act 1974 or as subsequently amended and to any governmental regulations which are applicable. 2  Silicon Chip High Purchase Costs Taking a “Bite” Out of Your Budget? NOT AT MACSERVICE. WE HELP YOU STRIKE BACK BY OFFERING THE LOWEST PRICES AND GOOD OLD FASHIONED SERVICE - Just look at these SPECIALS BALL EFRATOM M100 Rubidium Frequency • Factory cal. certs. • Perfect for ISO    accreditation • GPS applications • Ruggedised military    design TEKTRONIX 5440 Oscilloscope • DC to 60MHz • 1mV - 100V/div (x 10) • Dual Trace • Dual Timebase • Large Screen TEKTRONIX 7603 Oscilloscope • Mil spec AN/USM 281-C • Triggers to 100MHz • Dual Trace • Dual Timebase • Large Screen SUPER SALE $850 GREAT VALUE $2950 (new) Video Dist Amp & Cable Equaliser   $100 ADVANCE PP7 30V3A DC Power Supply   $150 AVO MK.IV Avometer With Cal.   $275 BPL CB154/4 Electrolytic Cap Bridge   $450 B&K 1466A 10MHz Oscilloscope   $275 EH 129 Pulse Generator   $90 ELGENCO 603A White Noise Gen 5MHz   $200 ENI 503L RF Power Amp 40dB 510MHz $1025 FLUKE 102 VAW Cal Meter    $75 FLUKE 9010A Logic System Troubleshooter $1000 GR 1608 LCR Meter – Lab Standard $1500 HP 211B 10MHz Square Wave Generator   $275 HP 302A Audio Selective Level Meter   $145 HP 400L True RMS Voltmeter   $170 HP 410B Vacuum Tube Voltmeter   $130 HP 432A 10GHz Power Meter (c/w sensor)   $875 SUPER DEAL $950 HP HP HP HP HP HP HP HP I/S Elect. MARCONI MARCONI MARCONI MARCONI MARCONI MARCONI MARCONI HEWLETT PACKARD HEWLETT PACKARD 200CD Audio Oscillator 410C Multimeter • 5Hz to 600kHz • 100Hz to 700MHz • 5 Ranges • AC/DC Volts • 10V Out • DC Amps • Balanced Output • 10 ohms to 10M ohms • Complete with probes BARGAIN $265 RIDICULOUS $79 467A Power Amp   $175 536A Frequency Meter   $75 721A 30V 0.3A Power Supply    $60 1610B Logic Analyser   $450 1980 100MHz Storage Oscilloscope $1650 3400A True rms voltmeter   $425 6226A Power Supply 40V 1.5A   $200 54111D Ultimate Digital Storage Scope $19000 845 Prog Function Generator   $800 TF893A Power Meter   $150 TF1020A RF Power Meter 75Ω 100W    $75 TF1020A-1 RF Power Meter 50Ω 100W   $150 TF1245/46/47 Q Meter 40KHz-300MHz   $600 TF2167 RF Amplifier 47dB gain   $600 TF2300 FM/AM Mod Meter   $300 TF2300A FM/AM Mod Meter   $495 MARCONI TF2300B MARCONI TF2303 MARCONI TF2700 MARCONI TF2701 MARCONI TF2914 PACIFIC PM1017 RACAL 9500 SHALLTRONIX 10K SIEMENS G2212 SIEMENS P2005 SOLA Series 200 Spectral Dyn. SD112-1 Systron Don. 1037 Telequipment CT71 TRIMAX G1B VARIAC Mod Meter 1200MHz $1100 AM/FM Mod Meter   $550 LCR Bridge   $325 Universal Bridge in circuit   $700 Insertion Signal Analyser   $150 Log Freq-Voltage Converter   $150 100MHz GPIB Counter   $350 Decade Box   $150 1.6/18.6MHz Generator   $250 Controllable Phase Meter   $200 750VA Line Stabiliser   $180 Voltmeter Freq-Log Conv 2ch   $150 500MHz Counter   $350 Curve Tracer   $900 Ionisation Tester 10kV   $260 0/280V <at> 15A   $260 NEW METROLOGY INSTRUMENTS AT FANTASTIC PRICES!!! M36 $55 VCE 150 $120 CM 25 $45 SEPTEMBER SPECIAL TEKTRONIX 465M 100MHz Oscilloscope VCE-150 VCE-200 VCD-150 DI-10 DI-1 TDI-0.8 CM-25 CM-50 150mm/6" Electronic Digital Vernier in box $120 200mm/8" Electronic Digital Vernier in box $180 150mm x 0.02 Dial Vernier Caliper   $75 10 x 0.01mm Dial Indicator   $45 1" x 0.001" Dial Indicator   $45 0-0.8 x 0.01mm Test Dial Indicator   $95 0-25mm x 0.01mm Outside Micrometer   $45 25-50mm x 0.01mm Outside Micrometer   $55 The Name That Means Quality CM-75 50-75mm x 0.01mm Outside Micrometer   $65 CM-01 0-1" x0.001" Outside Micrometer   $45 MB-6 CZ-6C Magnetic Base Stand   $55 VC-150 Dual Scale Vernier Caliper 150 x 0.02mm/6" x 0.001"   $35 VC-200* Dual Scale Vernier Caloper 200 x 0.02mm/8" x 0.001"   $45 VC-600* Dual Scale Vernier Caliper 600 x 0.02mm/24" x 0.001" $250 HI-600 600mm/24" x 0.02mm Height Gauge $550 *WITH FINE ADJUSTMENT Affordable Laboratory Instruments SSI-2360 60MHz Dual Trace Dual Timebase Oscilloscope BRA BRAN D EQUIP NEW MENT ND EQUIP NEW MENT Bandwidth DC to 100MHz; Rise time <=3.5ns; Deflection factor 5mV/div to 5V/ div in 10 steps; DC accuracy ±2%; 2-channel display mode; Horizontal deflection - main & delayed timebases; A - 0.5s/div to 0.05µs/div in 22 steps; B - 50ms/div to 0.05µs/div in 19 steps; Trigger - main/delay sweep; Coupling AC, DC, LF Rejection, HF Rejection TOP VALUE $1150 • • • • • • 60MHz dual trace, dual trigger Vertical sensitivity 1mV/div. Maximum sweep rate 5ns/div. Built-in component tester With delay sweep, single sweep Two high quality probes $1050 + Tax PS303D Dual Output Supply • 0 to 30V and 0 to 3 amps • Four output meters • Independent or Tracking modes • Low ripple output $385 + Tax PS303 Single Output Supply PS305D Dual Output Supply PS305 Single Output Supply • 0 to 30V and 0 to 5 amps $430 + Tax • 0 to 30V and 0 to 3 amps • Two output meters • Constant current/voltage • Low ripple output $225 + Tax • 0 to 30V and 0 to 5 amps $260 + Tax IF IT’S NOT HERE WE CAN GET IT... CALL US FIRST OR CALL US LAST... BUT DON’T FORGET TO CALL US! MACSERVICE Australia’s Largest Remarketer of Test & Measurement Equipment 26 Fulton Street, Oakleigh Sth, Vic., 3167   Tel: (03) 562 9500 Fax: (03) 562 9615 **Illustrations are representative only MAILBAG Colour video fader works well I wrote to you sometime ago regarding an apparent fault I had with a kit for the Colour Video Fader featured in the August 1993 issue of SILICON CHIP. It was fading/wiping to midgrey rather than black. That letter was a trifle premature. In a moment of inspiration, I decided to replace the two ICs that had come with the kit. The fault then disappeared and all is now OK. One of the ICs was obviously faulty. Incidentally, I used to work in the non-technical side of television and radio, both in several Australian cities and overseas in London. In those days, the apparatus to enable a broadcast studio to fade to black took up considerable space in the racks, with its valves, transformers, large power supply and all. And it must have cost a bomb. To think that a handful of small components in a little black box can now do the same thing is mind-boggling. Congratulations to the chap who designed it. Barry Freeman, Morphett Vale, Vic. Thanks for reader response Just a short note to thank you for publishing my letter in the “Ask SILICON CHIP” pages of the June 1994 issue, asking for a diagram for the BWD539D scope. The response has been great and to date I have received about 10 replies. The oscilloscope has been fixed and the fault was a tran­sistor in the trigger circuit that feeds the timebase. Bob Riding, Fingal Bay, NSW. Basic components in short supply I am writing to you with some concern over the fact that some of Australia’s major electronic retail suppliers are going out of some of the most basic components. While I am speaking mainly of basic radio parts such as variable capacitors and ICs such as the ZN414, some are even 4  Silicon Chip SILICON CHIP, PO Box 139, Collaroy, NSW 2097. going out of the humble OA90 series germanium diodes! I have heard all the old arguments about “we only stock what the customer wants ... etc” but I am afraid that this is not good enough. In England and America, you can still buy things like 415pF metallised variable capacitors and pre-wound aerial coils straight from the factories in those countries. In all fairness to the importers and retailers of these products, I can see their point in not stocking their warehouses with useless products that no one wants to buy. But what about the next generation of enthusiasts who have never ever laid eyes on the most basic of electronic components, who have been in the hobby for perhaps several years, and still don’t know one end of a crystal set from the other? I will admit that this all sounds pretty much like a storm in the electronic teacup but I detect a trend in the larger suppliers and a dangerous one wherein we may see the day that they simply go out of the most basic lines altogether. I believe that this situation requires an explanation and perhaps some action on the part of suppliers in general. If I were them, and I had products that weren’t selling well, I think that I would like to know why. So perhaps some kind of customer survey is warranted before we all have to start junking circuits to get parts that we could have if the retailers had the fore­sight to ask their customers some questions, instead of their marketing managers. Austin Hellier, Alice Springs, NT. with reproductions of fabric used in vintage radios. For example, if I were to receive a sample of fabric, I would analyse the types of yarns used and the pattern and then reproduce the fabric accordingly. Ms N. Moore, PO Box 171, Kyogle, NSW 2474. Vintage style fabrics available Valve technology still relevant to some I am a weaver of interesting and different fabrics. Recent­ ly a friend who is a restorer of vintage radios noticed a partic­ular piece of my woven fabric and commented that it quite accu­rately resembled radio cloth of 1950-60 vintage. He suggested that I write to you asking whether I may be able to supply other radio enthusiasts Series wanted on telephone technology Please allow me to offer special congratulations for the excellent series on the “Evolution of Electric Railways” and “The Story of Electric Energy”. I am sure that I am not the only reader who has learnt a great deal from these series. May I suggest that you consider a similar series on the Telecommunications Network. As a Technical Officer with Telecom I can assure you that the vast majority of people, including those involved with or interested in electronics, have no idea how complex the modern system is, or that Australia has a very exten­sive fibre optic cable network. The recent proposal to lower the mains voltage to 230VAC seems to be a recipe for disaster. From my experience it seems that many items of equipment can barely cope with the fluctua­tions in mains voltage currently experienced and surely the lower mains voltage would be either on the lower limit or outside the original design tolerance, thus making this equipment even more unreliable. A. Christie, Boronia, Vic. Comment: a series on telephone technology could be worthwhile. Any volunteers to write it? When I read your Publisher’s Letter concerning valve ampli­ fiers in the July 1994 edition, I was flabbergasted. While most of it was fair and balanced, the last line was, I feel, over the top. Let’s put the valve versus transistor amplifiers debate in perspective, at least from my point of view. Why do valves sound different to transistors? The human ear is more tolerant of even harmonics as compared to odd harmonics. Valves produce predominantly even harmonics as a by-product of the amplification process and transistors produce predominantly odd harmonics. This is why they do sound different. I prefer the sound of a valve amplifier. Now I realise that valves do have some shortcomings. When compared to a transistor amplifier, large power valve amplifiers are expensive to build but let’s face it, I and probably many other people do not re­ quire powerful amplifiers to enjoy listening to music. Most modern speakers are efficient enough to produce plenty of volume with only modest power inputs. My first amplifier produced only 3.5 watts per channel, for example, and I found this to be enough for my needs, so an amplifier of only 20 watts would, I feel, be enough for most music listeners. I realise there are people who feel that they have to have at least 100 watts or more per channel and the biggest possible speakers but I think this is just hype, or a keep up with the Jones next door type attitude. The quality of sound from a rea­sonably well-designed amplifier is good enough for me to enjoy and probably many others as well. With life in general getting busier and busier most people don’t get a lot of time to sit down and do some serious music listening; most people just have some pleasant music running as they go about their busy life. I know I do. So reasonable quality sound is all I require and most valve amplifiers are capable of that task. Valve amplifiers are certainly more expensive to build than transistor amplifiers. Parts for a valve amplifier are not com­monly available here in Australia but they are there if you look for them in the right places. There are a growing number of shops specialising in valves and related components. I have always found Arthur Courtney of Resurrection Radio very helpful and friendly. If you have any problems in finding circuits or parts, try looking in some of the English electronics magazines, as one of them recently released a kit and individual major parts for a 20 watts per side amplifier. The cost of a valve amplifier runs into many hundreds of dollars sometimes, but it can be spread out to make it a bit easier. Besides, the thrill of the chase only makes the final product more satisfying. I must admit that these are my thoughts only, but I am sure many other people probably feel the same way, and I don’t think that valve amplifiers should be just brushed off as having “no place in modern technology”. Keep up the otherwise good work. D. Haddock, Kamerunga, Qld. Comment: as far as the production of harmonics is con­cerned, transistor amplifiers have a big advantage in that they can have far more negative feedback applied to correct the dis­ tortion. The very best valve amplifiers could only have about 20dB of neg­ ative feedback because of the phase limitations brought about by the out­ put transformers. Today’s transistor amplifiers start with pretty linear performance even in open loop and may have 60dB or more of negative feedback. That is one reason why they are so much better. Lowered mains voltage is a lost cause I have read with interest your recent passionate editorials on the subject of the national grid voltage debate. I am rarely moved to print but on this occasion you have you lost the plot! C’mon now, where on earth do you expect to find commonsense – in a politicians’ mind? Now even Blind Freddy knows that to reduce the grid voltage would cost us all very dearly and would have the same meaningless effect as passing a law to raise the height of every doorway in Australia by 10%. However, the thin veil of the average Austral­ian politician’s mind is only known to cover their personal ego, opportunistic political gain and the securing of a firm grip on their superannuated golden egg. No, I think we have a difficult problem here and believe me, commonsense, the favourite, will be the last runner. I noted P. Badham’s Mailbag com- ments (SILICON CHIP, July 1994) and whilst in general agreement, I am disappointed that we are advised to “accept the inevitability” of European conversion. Yes our imported/dumped electronic equipment may well be designed for 230VAC, but for truly 230VAC sensitive equipment, how about we don’t import it in the first place? That would then create a whole new market or a conversion after-market that could be well supported by our own local electronics indus­tries, and heavens knows, we need that sort of employment produc­ ing enterprise here at the moment. No, Mr Badham, please consider the bigger picture. May I also ask you all to consider one last but very im­ portant aspect: the humble GPO (general purpose outlet) plug. Since time immemo­rial or whenever, we have had in Australia one common, standard design for a 240VAC GPO plug and socket arrangement, available from Cairns to Marble Bar, Darwin to Hobart. Whether by good luck or good judgement it has stood the test of time. Next time you visit England, just count up the number of different variations of this wee beastie. My point is this: who is to say that every X number of years or so the British Government, whether an EEC partner or in post partnership disarray, might not change their voltage standards yet again, like the design of their GPO plugs? Surely we can be as independent of our former colonial masters as the Americans? Or shall we wait for a future (and probably some­what short) Australian Fearless Leader to pass a very sensible law to lower the height of every doorway in Australia by 10%. They were too high anyway. C. O’Donnell, Hoppers Crossing, Vic. Comment: our much admired GPO socket will be modified in the nottoo-distant future, as determined by the same people who want to bring about the reduction in mains voltage. Future GPO sockets (ie, mains power points) will have a circular recess which will make most presently used AC & DC plugpacks obsolete and unusable. August 1994  5 How to use the TEA1100 fast nicad charger IC The TEA1100 nicad charger IC, as used in our recent Fast Nicad Charger project, has a number of interesting features which put it out in front. These include digital voltage sampling and filtering as well as switchmode or linear operation. We look at these in detail and go through some design examples. By DARREN YATES & LEO SIMPSON The Philips TEA1100 Battery charger IC is a 16-pin DIP package which contains everything to produce a simple yet highly integrated battery charger for nickel cadmium (NiCd) and the new nickel metal hydride (NiMH) batteries which have a higher capaci­ty than nicads. The TEA1100 has three methods of guarding against over-charging: temperature detection, clock timeout and an advanced form of voltage detection referred to as “dV sensing”. Supply voltage Unfortunately, the chip has a fairly awkward supply voltage range, which is between 5.65V and 11.5VDC. This makes it not quite suitable for car operation without supply regulation cir­cuitry and not low enough to permit operation from a 5VDC regula­tor. However, a 7808 or 7809 regulator will be more than adequate and, in fact, you can even get away with just a standard zener diode/transistor buffer voltage stabiliser such as that used in the Fast Nicad Charger design published in the May 1994 issue of SILICON CHIP. Linear or switchmode As we mentioned in the introduction, the TEA1100 IC can run in linear or switchmode operation. The benefit of the switchmode option is the efficiency which can be gained by charging lower voltage cells from a higher Fig.1: this circuit using the TEA1100 in switchmode was the basis for the Fast Nicad Charger published in the May 1994 issue. The design example in the text will enable you to tailor the circuit to your application. 6  Silicon Chip Fig.2: this linear version of the TEA1100 circuit could be used in RF-sensitive applications. In this case, the output of the chip is taken from pin 2 rather than the PWM output of pin 1. voltage supply rail. This feature was used in our Fast Nicad Charger project. If you’re wanting to charge Nicads in a noise sensitive application then you can easily set the IC up to charge in linear mode, greatly reducing the circuit noise. The linear circuit uses less components than the switchmode circuit but has considerably more heat dissipation, as you would expect. Fig.1 shows a sample switchmode circuit, very similar to that featured in our May 1994 issue. Fig.2 shows a linear charge circuit, powered from the 240VAC mains supply. And finally, to give some idea of the chip complexity, Fig.3 shows the block diagram of the TEA1100. dV sensing Instead of comparing the voltage of the battery being charged to a static voltage reference, the TEA1100 uses a dynamic process called “dV sensing”. The “dV” term comes from calculus and refers to the process of looking for a very small change in battery voltage. The TEA1100 compares the present battery voltage to the previous sampled voltage and checks for a 1% drop. The theory behind this is that when a nicad is being charged, its voltage rises very gradually towards full capacity but once past this point, the battery voltage begins to drop slightly. If a battery charger circuit does not look for this voltage drop, it will never give an optimum charge – it will either under or over-charge. Either way, the battery life will ultimately be reduced. Fig.4 shows the characteristic rise in battery voltage during charge and the slight droop as it reaches full charge. The TEA1100 ends the charge cycle upon sensing a 1% drop in the battery voltage. That amounts to about 16mV for a typical nicad cell. Now you might be wondering how they manage to reli­ably detect 16mV when the circuit lines could be subject to all sorts of noise and switching frequencies, if the chip is being operated in switchmode. The answer lies in the method of sampling the battery voltage. The PWM (pulse width modulation) is disabled for 10 clock cycles, after which the sample and hold amplifier takes a meas­ urement of the battery voltage. This way, the noise generated by a “ringing” or decaying supply rail is removed and a much greater degree of accuracy maintained. The 10-cycle delay gives sufficient time for the inductor to stop ringing but it does mean that the inductance must lie within a particular range – it must be high enough in value so that it will perform its job as an inductor in a switchmode circuit but it must be small enough in value so that the supply rail is quite stable by the time 10 clock periods have passed. We’ll talk about this more a little later. The dV sensing comes under the block entitled “battery full detection” in the diagram of Fig.3. As already noted, the TEA1100 does not compare the battery voltage to a static reference. Because it is a dynamic process, the monitored input voltage need only be between 0.385V and 3.85V. This is fed to pin 7 which is labelled “VAC” for Voltage ACcumu­lator. The way it works is like this: The VAC voltage is sampled at a rate equal to the clock frequency divided by 216. Each VAC voltage sample is digitised and stored in a register with a quoted resolution of 12.5 bits. At the time of the next sample, the stored value is converted back to an analog voltage and compared with the voltage on the VAC pin. If the VAC voltage is higher than the stored value, then this new value is digitised and stored in the register, overwrit­ing the previous value. If not, the previous value remains in the register. The circuit then checks for a 1% drop as we mentioned before and if found, switches the circuit to trickle mode and flashes the LED (connected to pin 15) to indicate that the bat­teries are fully charged. This clever mix of analog and digital circuitry results in a dynamic process which takes the battery’s physical characteris­ tics into consideration. Since no two nicads charge up to exactly the same voltage, this relative method provides accurate “full” detection for all cells, regardless of their final voltage. Incidentally, much the August 1994  7 VP 12 Vref 10 VS 6 NTC 3 Rn 11 IB 5 CP 9 Vr1 SUPPLY GND 16 Vhigh PROTECTION Vr3 MAINS ON RESET V In LSP Iref > t AO 2 A2 Vr2 Vlow PROTECTION Vr4 LS 4 A1 > > OSC DISABLE TIME OUT > R s+h BATTERY FULL DETECTION VAC 7 PWM 1 PWM & R TIME OUT PROTECT > LED 15 R 1/10 OSC TO PWM :1:2:4 PRESCALER COUNTER CONTROL CURRENTLESS SENSING AUX PULSES 13 OSC 8 PR 14 SYNC Fig.3: the block diagram of the TEA1100. This complex chip senses the small drop in voltage which occurs at the end of charge for nicad & NiMH batteries, so that the charger can be automatically switched off. same monitoring method was used in the “Fast Charger for Nicad Batteries” featured in the January and February 1991 issues of SILICON CHIP. The beauty of the dV sensing system is that the VAC input (pin 7) can be anywhere between +0.385V and +3.85V. This means that the VAC resistor divider network can be the same whether you wish to charge two or 10 cells, or any number of cells in between. To satisfy this condition in the circuit of Fig.1, R14 should be 47kΩ while R15 should be 10kΩ. C8, the input filter capacitor, can be 10µF 16VW. Note that to satisfactorily charge 10 cells, you will need an input voltage of at least 22V DC when in switchmode because the maximum pulse duty cycle is 78%. The above is based on an overvoltage level of 1.7V/cell and a nominal battery voltage of 1.2V/cell. The VAC input has four voltage thresholds which determine the chip’s behaviour. Firstly, below 0.3V, the IC assumes a short circuit (crook) battery and switches to trickle charge mode; above 0.385V and below 3.85V, the IC uses the dV voltage detec­tion method 8  Silicon Chip to determine the charge state; and finally, above 4.25V, the IC assumes open circuit or no batteries present and switches off. The impedance of this input is greater than 200MΩ. Note too that for charging just one or two cells, the VAC input (pin 7) can be connected directly to the cell(s). Output voltage This brings us to an important feature of the Fast Nicad Charger published in May 1994 and one which has caused confusion to many constructors of this circuit. Since the circuit relies on dV sensing to end the fast charging mode, it goes without saying that it will not work unless it is actually charging cells. If you attempt to test the circuit without a nicad battery load, it will switch off. Our testing instructions for the above circuit would have added to this confusion by referring to an open circuit output voltage test. The point is that you cannot test the charger’s output voltage unless cells are connected. If you attempt to simulate the presence of cells with a large electrolytic capaci­ tor, the output voltage will rise until pin 7 reaches +4.25V whereupon the circuit will switch off. In fact, the circuit of May 1994 does not even need the switch to select between two and four cells. The switch setting for two cells can be omitted and then circuit will happily charge two, three or four cells in series without further modifications. In admitting this mistake, we can only plead that it only become obvious after close reading of the copious application information which Philips has made available on the TEA1100. 0.5% detection In some cases, such as “fast-charge” nicads and NiMH cells, a dV of 0.5% is more appropriate due to the higher level of input charge current they can tolerate. This IC can provide charge rates up to an incredible five times the battery capacity or “5C”. An example of this would be charging a racing pack in about 15 minutes. This increased sensitivity can be easily achieved by in­serting a zener diode of about half the battery voltage into the sensing resistor string. An example of this can be seen in Fig.5. The zener diode is selected to be about half of the fully charged battery voltage, based on a level of 1.7V/cell. Protection Apart from the active protection features already men­tioned, the TEA1100 features under-voltage shutdown and tempera­ture sensing with a thermistor input circuit. The first of these, the under-voltage shutdown, activates when the supply voltage falls below 5.25V. In this case, the IC goes into a “power down” mode in which it becomes non-active and draws around 35µA (45µA maximum). The second form of protection involves a negative tempera­ture coefficient (NTC) thermistor to monitor the temperature of the battery during charging. This feature wasn’t included in our May 1994 project to keep the construction simple. In practice, where this feature is used, the therm­ istor is incorporated into the battery pack and is automatically connected when the battery is put on charge. The temperature monitoring feature is recommend­ed for batteries which need to be recharged as soon as they have been removed from their load. The classic example of this is 1200mA.h racing packs for electric model aircraft and cars. The drain on these batteries is very high - often tens of amps or more – and so they will be quite hot (or even stinking hot!) when they are removed from the load. The danger is that if you fast-charge a hot nicad battery, you can damage it. The temperature protection provided by the TEA1100 prevents fast charging from occurring while the battery temperature is outside the specified range. The NTC thermistor is featured on the circuit of Fig.1 and is connected to pin 3. If the thermistor is not required, it can be omitted from the cir­cuit, together with R11. Fig.4: the voltage characteristic of a 2-cell nicad battery back during charge. If charging continues beyond the droop in voltage, cell damage can occur. VOLTAGE (V) For example, for a 6 cell pack, the maximum voltage is 6 x 1.7V = 10.2V, so a zener diode of 5.1V would be suitable. The maximum voltage level the VAC input will now see is 5.1V, so the input resistor divider must now be recalculated accordingly. R14 on Fig.1 could then be reduced to 22kΩ. CHARGE TIME (MINS) capacitor connected to pin 13. This timeout period is usually set to about 125% to 150% of the expected fast charge time but in critical high charge rate applications, you can set it to the expected charge time (100%). In practice, the timeout period should only be set by adjusting the capacitor (C at pin 13), as varying the reference resistor will change other circuit parameters. Design example The easiest way to understand how to use this IC is to go through a design example, using the circuit of Fig.1. This way, you’ll get an idea of what has to be done and the order in which you have to do it. Let’s say we wanted to design the timeout circuit to run a charger which will charge up a set of four nicad cells in one hour. If we use the 150% rule, then our timeout period, tTO, will be Timeout counter Finally, there is the backup protection of a timeout coun­ter, which automatically shuts down the charger after a time equal to 226 times the clock period, has expired. The clock period is determined by the reference resistor connected to pin 10 and the timing Fig.5: a zener diode equal to half the fully charged battery voltage can be added to the circuit to enhance the dV sensing capability so that it will detect a drop of 0.5%. 1.5 x 60 mins = 90 mins. The timeout period is determined by the following formula: tTO = 226 x Tosc x p where Tosc is the clock period and p is a prescaling factor which you can program to be either 1, 2 or 4, depending on how you connect pin 8. By leaving pin 8 open, you set the prescaling factor to 2. Connecting it to pin 6 sets it to 1 and pulling pin 8 to ground sets it at 4. The beauty of this system is that it allows you to have three different charge periods without having to change the timing components. For our example, let’s connect pin 8 to pin 6 to set the prescaling factor (p) to 1. The oscillator frequency (1/ Tosc) now needs to be 12.4kHz (ie, Tosc = (90 x 60)seconds/226). As mentioned be­ fore, this frequency is set by the time constant formed by the reference resistor Rref (R13) and the oscillator capacitor Cosc (C7) based on the following equation: Tosc = 0.93(Rref x Cosc) Now Rref is chosen to be within the range of 12.5kΩ and 125kΩ based on the necessary charge current. In our example, let’s assume that the resistor is 27kΩ. Plugging this value into the above equation gives a value for Cosc of .0032µF which we can quite happily round to .0033µF. Charge current settings OK. Let’s say that we wish to charge our batteries at a fast rate of 700mA. R4 and R8 are used to set the current. R4 should be a 5W type. You have some leeway in picking the value of this resistor, so long as its value August 1994  9 Using the TEA1100 fast nicad charger IC results in a voltage drop of between 50mV and 200mV when the circuit is in fast charge mode. You can work out a suitable value for R4 from the following equation: Vcs = Ifast x Rcs where Ifast is the fast charge current and Rcs is R4. In our design example, 0.1Ω will give us 70mV which is within the de­sired range. R8 is referred to as the fast charge current set resistor Rfc and it can be calculated from the following equa­tion: Rfc = (Ifc x Rref x Rcs)/1.25 where Ifc is the fast charge current rate, Rref is the 27kΩ reference resistor R13, and Rcs is the 0.1Ω current sensing resistor R4. By using this equation, we get a value for Rfc of 1.512kΩ, so a 1.5kΩ 1% resistor will be perfect for R8. determined by the worst case ripple current at the trickle current setting and follows this equation: Lmin = Vo’max(1-delta)Tosc/2Iav where Vo’max is the maximum battery voltage plus the forward diode voltage drop. For four cells, this works out to be 6.8V + 0.7V = 7.6V. This is based on the fact, that the maximum voltage per cell will be 1.7V; “delta” refers to a charge current duty cycle of 50%. So, using the above equation, we get a minimum inductance value of: Lmin = 7.6 x (1-0.5) x 80 x 10-6/2 x 0.35 = 434µH. Hence the inductor can be anywhere between 5mH and 434µH. Why not go for the perfect compromise and settle upon 2mH? What inductor? Winding an inductor presents many constructors with a problem since they don’t have access to the necessary information involving readily available toroids. Indeed, a comprehensive article on this subject alone could take many pages. However, to keep it simple, we’ll just deal with the three readily available iron powder toroids made by Neosid and available from Altronic Distributors and Jaycar Electronics. The general formula for inductance using these toroids is: n = 1000 √(L/AL) where n is the number of turns, L is the inductance in millihen­ries (mH) and AL is the inductance factor of the particular core. For the smallest core, Neosid 17-732-22, 14.8mm OD, AL is 44; for the medium core, Neosid 17742-22, 33mm OD, AL is 59; and for the largest core, Neosid 17-745-22, 44mm OD, AL is 116. Having calculated the number of turns to obtain the re­quired inductance on the core of your choice, you then must check whether it is likely to be saturated at your proposed operating current. To do this, we calculate the core energy with the fol­lowing formula: E = LI2 where E is measured in joules, L is the inductance in henries and I is the current in amps. For the three cores Earlier on, we mentioned that with switchmode operation, you have to be careful in selecting the value of the inductor – too low a value will result in the circuit not working efficient­ly and too high a value will result in the dV sensing circuitry picking up remnants of the switching voltage due to the “ringing” effect of the inductor. For this dV sensing to work, the induc­ tance current should have decayed to zero within nine clock cycles. So the maximum inductance is set by the following equa­tion: Lmax = 9 x Tosc x (Vo + Vf)/Io where Tosc is the period of the clock frequency, Vo = the flat battery voltage (around 1V per cell) plus the voltage drop across the fast recovery diode D2 (usually taken as 0.8V) plus the voltage across the current sensing resistor. Io is the average current through the inductor which is a fast charge current. In the example we’ve been working through, this would give us a maximum inductance of: Lmax = (9 x 80µs x 4.8V)/700mA = 5mH. This assumes four cells with a flat voltage of 1V each, plus the 0.8V drop for the fast recovery diode, D2. The 80µs figure is the clock period at 12.4kHz. The minimum inductance value is 10  Silicon Chip Winding an inductor under discussion, the maximum stored energy levels are 0.71mJ for the 14.8mm OD core; 5.1mJ for the 33mm OD core; and 16mJ for the 44mm OD core (OD stands for outside diameter). If the core you have chosen will saturate at the required current and inductance, then you will have to use a bigger core. One final point must be covered here before we leave the subject of induct­ors and that is that the actual current flowing in the induc­tor referred to in the formulas above is the pulse current; it is not the charging current. Typically, the pulse current will be twice the average charging current. Trickle charge When in trickle charge mode, the TEA1100 continues to pulse the battery with the fast charge current but at a much lower duty cycle. As it seems with just about everything else on this IC, you have a choice of one of two ways to set the trickle current, depending on how you connect pin 11, designated the “Rn” input. The first method is to leave pin 11 unconnected. In this case, the repetition and duration of the trickle current pulses is determined by the chip itself. The repetition rate is set as 2-14 x tTO = 330ms in our example. The duration time is set to 0.75 x 29 x Tosc, where Tosc is the clock period. In our example, this works out to be 31ms. This also gives us a duty cycle for the trickle current of 9.4%. The average trickle charge current based on this duty cycle is set by the following equation: Itrickle = Ifc/2 x duty cycle = 30mA. The second method is to set the average trickle current yourself by connecting a resistor Rn to pin 11. The rule for this resistor is that it must be within the range of 25kΩ to 250kΩ and must be greater than the reference resistor Rref. The new trickle current equation looks like this: Itrickle = Ifc x (Rref/Rn) x duty cycle With Rn equal to Rref (27kΩ), the trickle current is 60mA and 7mA with Rn equal to 250kΩ. Linear design example Let’s say that we want to charge three “AA” cells in one hour, using the circuit of Fig.2. The required TABLE 1 Number of cells to be charged Transformer secondary voltage (V RMS, full load) Capacitor value (µF/A) Capacitor voltage rating (VDC) 2 7 4000 16 3 9 3000 25 4 11 2400 25 5 13 2000 35 6 15 1700 35 7 17 1500 40 8 19 1300 40 9 21 1200 50 10 23 1100 50 current is based on the following equation: Iout = (A.h x 60 x 1.4)/charge time (mins) So for a 600mA.h battery, the current would need to be: Iout = (600mA.h x 60 x 1.4)/60 = 840mA In case you’re wondering why it just isn’t 600mA, the reason is that there are substantial losses in the battery when charging takes place, so you need to increase the charge current by 40% to make up for these losses (ie, heat etc.) At this current, the main pass diode D5 can still be a 1N4004 but the transistor will have to be something like a TIP32C, a device which can handle the current and the power dissipation. And it will need a heatsink. Power dissipation Table 1 gives the required transformer secondary voltage and the suggested capacitance per amp of required current and voltage rating of the filter capacitor. Now for our design exam­ple, to charge up three cells, we need a transformer secondary vol­tage of 9.1V. The power dissipation can be found from the follow­ing equation: Pdiss = 1.3 x Iout x (Vsec - 2.0) = 1.3 x 0.84A x (9.1 - 2.0) = 7.8W Basing this on a maximum temperature rise of 55°C above ambient, the required heatsink will have to be better than 55°C/7.8W or 7°C/W. Now obviously, this is quite a bit of power being wasted so you will have to decide whether the need for a linear charger outweighs the benefits of the switchmode alternative. OK, so we’ve determined the cur- rent we require and now we have to tell the TEA1100 what we want. To do this, we again start with a reference resistor of 27kΩ, just as for the switchmode version. Next, we have to choose the main current sensing resis­tor (R1) and again, for our charge current of 840mA, a 0.1Ω 5W resistor will give us 84mV which is good enough. Remember that this resistor doesn’t set the current on its own. This is done by resistor R3 on the circuit. This resistor is determined by the following equation: Rfc = (Rref x Rcs x Ifc)/1.25 and in our design example, R3 becomes: R3 = (27kΩ x 0.1Ω x 0.84A)/1.25 = 1.814kΩ A value of 1.8kΩ will be close enough. Trickle charge As with the switchmode version, the trickle charge current can be set to just about anything you want. By connecting the prescaling pin (pin 8) to pin 6 and leaving resistor R7 open circuit, the TEA1100 will automatically set the trickle charge current to 1/20th of the fast charge rate. In our example, this would work out to be 42mA. Now this may be too high, in which case, you can change the trickle current by connecting resistor R7 from pin 11 to ground. The relationship between this resistor and the trickle charge current is set by the following equation: R7 = (1.25 x Rfc x 0.094)/(Itrickle x Rcs x p) Let’s say we wanted the trickle current to be 15mA instead of 42mA. By working through the above equation, resistor R7 would need to be: R7 = (1.25 x 1.8kΩ x 0.094)/(15mA x 0.1Ω x 4) = 35.2kΩ. A 36kΩ 1% resistor will get you fairly close to the mark. You should note a couple of things here. Firstly, we’ve had to change the prescaling factor to four. Now the reason for this is that the prescaling factor not only works on the timing circuitry but also on the charge current ratio; that is, the ratio of the fast charge current to the trickle charge current. With a prescaling factor of one (pin 8 to pin 6), the maximum ratio is 20:1. For a prescaling factor of two (pin 8 open circuit), it is 40:1 and for four (pin 8 to ground), it’s 80:1. Now for our design we want a ratio of 840mA/15mA = 56:1. Setting the prescale to either one or two won’t get us this value so we have to go to a prescale factor of four. The reason for the change is that if resistor R7 is greater than twice the reference resistor R6, then the IC automatically selects half of the fast charge reference current. This gives us our maximum 20:1 with a prescale of one, 40:1 with p set to two and 80:1 with p set to four. In most situations, resistor R7 should not be less than the reference resistor. If by working through the equations, you find that R7 is less than R6, either change the prescaling factor or remove the resistor from the circuit altogether. Timeout counter settings The last thing to do is to set the timeout period and since we have already set the reference resistor R6 to 27kΩ, the only component value which affects the time is capacitor C4 and this can be determined by the following equation: C4 = (60 x timeout)/0.93 x Rref x p x 226 Getting back to our design example, let’s say that we’re happy with a trickle current of 42mA and we want the timeout period to be 60 minutes. Capacitor C4 then works out to be: C4 = (60 x 60)/(0.93 x 27kΩ x 1 x 226) = .00213µF (.0022µF will be close enough). Note too that this capacitor value will change if you change the pre­ scaling factor as in the above example where we looked at a trickle current SC of 15mA. August 1994  11 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au Electronic Engine Management Pt.12: Fueltronics’ Turbo Control Centre by Julian Edgar Australian company Fueltronics has recently released an automotive turbo­ c harger boost control unit. Called the “Turbo Control Centre”, the device under­cuts its competitors in price while also providing more features. It uses a Signetics 80C575 micro­con­troller and sophisticated software to control the turbo boost in modified cars. The unit consists of two solenoid-operated valves, an elec­ tronic control unit (ECU) housed in a diecast aluminium box, and a dashboard mount­ed liquid crystal display with control knobs. Conventional control Conventional turbocharger boost pressure control is by a wastegate – a valve which diverts exhaust gas around the tur­ bocharger’s exhaust turbine when the appropriate manifold super­charging pressure has been reached. The wastegate is operated by a rod connected to a diaphragm, one The Turbo Control Centre uses a microcontroller & sophisticated software to modulate turbocharger boost pressure. Note that the board in this photo is not totally populated, with the output transistors & some ICs still to be added. 16  Silicon Chip side of which sees manifold pressure. As boost pressure rises, the diaphragm deflects and the connecting rod opens the exhaust turbine wastegate valve. Electronic control The Turbo Control Centre makes use of this conventional mechanical control but changes the pressure seen by the wastegate actuator by bleeding air from the pressure line connecting the diaphragm to the manifold. A pulsed solenoid valve is used to do this and the greater the pulse-width used, the higher the boost pressure experienced. In order to allow relatively small valves and plumbing to be used, a restricting orifice is placed upstream of the bleed valve T-piece. There are several advantages in using electronic control of the wastegate. First, “wastegate creep” – where the rate of boost increase starts to taper off before the required level is reached –is avoided. With electronic control, the boost level can rapid­ly rise to the specified level before wastegate opening occurs. This means that quicker acceleration is enjoyed. Second, electronic management allows greater driver control over boost levels. The Turbo Control Centre uses two preset levels of boost, which are initially set with internal potentiom­ eters. These preset levels are selected using a pushbutton switch. Alternatively, the user can select the manual Turbocharger control is achieved using two solenoid-operated valves. The smaller valve on the left is used as a pulsed bleed valve & reduces the pressure seen by the wastegate actuator. The larger valve at right is used as a throttleclosed pressure-relief valve & is designed to give better driving response. Electronics engineer Jiri Bruderhans was responsible for the hardware development of the boost controller. The unit has been designed so that it can be interfaced with engine management software. boost setting, which allows control over the supercharging level via a dash-mounted 10-turn potentiometer. The other valve used by the Turbo Control Centre works as a throttle-closed blow-off valve. Conventionally, when the throttle is quickly closed following acceleration (eg, during gear chang­es), the rapid pressure build-up upstream of the turbo’s compres­sor slows the turbo. A slight lag in boost build-up then occurs when the throttle is opened again. The Turbo Control Centre blow- off system senses air pres­ sure both upstream and downstream of the throttle valve using electronic pressure sensors. When the pressure being experienced before the throttle blade is greater than after the butterfly, the large (25mm plumbing) valve is opened and this air is bled back to the turbo air intake. This allows the turbo to keep spinning at a high speed so that the boost quickly rises when the throttle is next opened. The difference required in the pressures either side of the throttle butterfly before the blow- off valve opens is adjustable with an internal pot. Shown on the dash-mounted LCD screen is the boost level in either numerical or bargraph form, and the selected boost control (Preset 1, 2 or Manual). In addition, the word “Blow!” is indi­cated when the blowoff valve is open. The display is also used during the setting-up procedure. The two signal inputs come from the pressure sensors, both of which are mounted within the ECU and are fed by small bore rubber hoses. The microprocessor and output drive circuitry is also within this box, with just the display electronics and input switches located in the dash-mounted unit. Hardware & software Running at a clock speed of 12MHz, the Signetics 8051-family 80C575 microcontroller has a tough job to do, especially in preventing boost oscillation around the selected boost level. The 8.5Kb program – which is written in 805X assembler language with ‘C’ 805X cross-compiler language used –required the great­ est design effort in allowing boost to rapidly rise without over-shooting the preset value. Inadvertent excessive boost can cause engine-destroying detonation. The program uses a differential equation for convergence, which allows the rising boost level to approach the preset level in a manner which allows system damping. The boost control valve remains closed until the boost level reaches a “window” set at 75% of the preset value. When this occurs, the control valve starts closing, with the software setting its pulse width on the basis of the rate of approach or the distance to the preset value. When the boost level reaches 95% of the preset value, the valve operation changes again, with a different feed­back loop being employed. Engine management Finally, since Fueltronics also rewrite software chips for factory engine management systems, the Turbo Control Centre has been designed to interface with new engine management software. This means, for example, that when the high boost preset is selected, an engine management program with the appropriate fuel and ignition maps can be automatically SC brought on-line. August 1994  17 If you own equipment which uses nicad batteries, then this discharger is for you. Used correctly, it will maintain the full capacity of your battery pack & extend its useful life. It can even rejuvenate an old battery pack that’s suffering from the memory effect. Automatic discharger for nicad battery packs By JOHN CLARKE While nicad batteries are designed to provide reliable power over many charge/discharge cycles, most people find that their new battery pack starts to give trouble after only a few such cycles. This problem is particularly prevalent in mobile tele­phone battery packs. The pack provides a reasonable “talk-time” when new but this quickly diminishes after a few weeks of use. When this happens, many people assume that the battery pack is crook and buy a new one. But that’s normally a complete waste of money. As a general rule, the battery will still be quite OK and just needs to be revived. 18  Silicon Chip The problem can usually be attributed to the so-called “memory effect”. This is a characteristic of the nicad cell whereby it ceases providing current when it has discharged to the level from which it was last charged. Thus, if a nicad battery pack is repeatedly recharged with half its capacity still remaining, it will eventually stop delivering power at half capacity. This means that, for the example given above, the battery’s capacity is effectively halved. Of course, if the battery is continually recharged from its 75% level, the problem is exacer­ bated. It will now only provide 25% of its capacity. With that in mind, it’s not hard to understand why mobile telephone batteries “run out of steam” so quickly from new. The only solution to this problem is to ensure that the nicad pack is fully discharged before recharging commences. This will ensure that the pack can deliver its full capacity every time. That’s where this Nicad Discharger comes in. It discharges the nicad pack until it reaches its full discharge voltage of 1.1V per cell, at which point it automatically switches off. The pack can then be removed and recharged to its full capacity on a charger. By adopting this technique, the dreaded mem­ory effect is avoided. 2x1N4004 D2 D3 Q1 BC327 C E 33k 3.6V 1.5k 910  560  430  330  430  1.8k A D1 1N4004 B 3 S1 NOMINAL BATTERY VOLTAGE 2 8 IC1a LM358 1 9.6V 10k Q2 BC338 B  K 680 C K LED2 REVERSE POLARITY  A 680 CELLS UNDER DISCHARGE D4 1N4004 S2 START E 4 7.2V 8.4V LED1 DISCHARGING 33k 4.7k 4.8V 6V 27 5W 2.7k REF1 LM3362.5 VR1 ADJ 100k 5 6 7 IC1b 470  Q3 BD679 B E 12V ADJUST VR1 FOR 0.49V 1.8k C 2. 7  B PLASTIC SIDE E E C B C VIEWED FROM BELOW ADJ K A 3-10 CELL NICAD DISCHARGER Fig.1: the circuit is powered by the battery under discharge. When the START switch (S2) is pressed, Q1 turns on & the battery voltage is fed to a resistive divider. The voltage selected by S1 is then compared with a reference voltage using IC1a, which turns on Q2 to maintain power when S2 is released. IC1b & Q3 form a constant current source which discharges the battery to an end point of 1.1V per cell. When this point is reached, Q2 turns off & the discharge cycle ceases. Note, however, that several full discharge/charge cycles may be necessary to fully rejuvenate a battery pack that is already suffering from the memory effect. This technique is called “deep cycling”. Provided that the pack is OK in other respects, this treatment is usually completely effective and leads to a dramatic increase in battery life and performance. And, of course, you will save money – nicad batteries are expen­sive. Discharge rate Our Nicad Discharger discharges batteries at a nominal 200mA rate until the end point voltage of 1.1V per cell is reached. During this time, a LED on the front panel glows to indicate that the pack is discharging. When the end point of 1.1V per cell is reached, the discharger switches itself off and the LED goes out to indicate the end of the discharge cycle. Thus, for a 7.2V battery pack, the end point voltage is 6.6V. That’s because there are six cells in a 7.2V pack (ie, each cell is at 1.2V when fully charged). Similarly, the end point voltage for a 12V pack is 11V. Note that nicad cells maintain a virtually constant 1.2V output until they are almost fully dis­charged. The unit is very easy to operate – all you have to do is connect the positive and negative leads to the battery pack, set the range switch to the rated battery voltage, and press the START button. The rest all happens automatically and you simply wait until the DISCHARGE LED goes out before removing the pack for recharging. A second LED on the front panel lights to warn you if the pack is accidentally connected with reverse polar- ity. No damage to the Nicad Discharger (or to the pack) will occur if you do this – just reverse the connections to correct the problem. In fact, this design is based substantially on the Nicad Discharger published in July 1992. This was a popular unit but, following publication, we received many requests for two extra voltage ranges below 6V. This new circuit adds these ranges and can now handle nicad packs ranging from 3.6V to 12V over seven ranges. In addition, the new design includes the aforementioned automatic switchoff feature and the reverse polarity indicator – items that were missing from the previous design. Circuit details Fig.1 shows the circuit details of the Nicad Discharger. It’s based mainly on Main Features • Seven ranges; suitable for 3.6V, 4.8V, 6.0V, 7.2V, 8.4V, 9.6V & 12V nicad battery packs • • Discharges battery down to 1.1V per cell • • • Discharge indicator LED Automatic switch-off with negligible current drawn after end point voltage is reached Reverse current protection & LED indicator Self-powered from discharging cells August 1994  19 430  1.8k 430  330  REF1 D3 33k LED1 10k VR1 A K Q2 560  33k B C E 1.5k Q3 Q1 2. 7  D2 680  S2 D1 2.7k 470  910  680  1.8k 4.7k 1 IC1 LM358 S1 K D4 27W 5W TO CELLS A LED2 Fig.2: install the parts on the PC board as shown in this wiring diagram. Make sure that all polarised parts are correctly oriented & mount the 27Ω 5W resistor slightly proud of the board to allow the air to circulate beneath it for cooling. Fig.3: check your PC board against this full size etching pattern before installing any of the parts. dual op amp IC1, transistors Q1-Q3, and voltage reference REF1. The op amp is an LM358 which can operate from a supply rail as low as 3V. This allows the circuit to operate correctly while discharging a 3.6V battery pack to an end point of 3.3V. Initially, when a battery pack is connected, no current flows in the circuit since all transistors are off. The circuit is turned on simply by pressing momentary pushbutton switch S2. When this happens, base current for Q1 flows via its 4.7kΩ base resistor, the base emitter junction itself and the 27Ω emitter resistor. Q1 thus turns on and applies power to pin 8 of IC1, to voltage reference REF1 via a 1.8kΩ resistor, and to a resistive divider string (33kΩ - 1.8kΩ). REF1 is an LM336-2.5 voltage reference and this device provides a constant 2.5V output over a wide current range from 400µA to 10mA. This voltage is fed to trimpot VR1 which is adjusted to provide a 0.49V Fig.4 (above): here are the mounting details for Darlington transistor Q3. It must be isolated from the front panel using an insulating washer & its leads bent at right angles to mate with the pins on the PC board – see photo at left. 20  Silicon Chip reference for the inverting input (pin 2) of comparator stage IC1a. IC1a compares the voltage at the wiper of switch S1 with the 0.49V reference on pin 2. If the voltage on pin 3 is greater than 0.49V (ie, the battery is not fully discharged), pin 1 of IC1a switches high and turns on transistor Q2 via a 10kΩ base resistor. This in turn ensures that Q1 remains on and that the circuit remains powered up when S2 is released. At the same time, LED 1 (the DISCHARGE indicator) turns on, since there is a path to ground via the 680Ω resistor and Q2. IC1b and Darlington transistor Q3 form a constant current source which discharges the battery at a nominal 180mA. The non-inverting input of IC1b (pin 5) is set at 0.49V (the reference voltage from VR1), while the inverting input (pin 6) monitors Q3’s emitter voltage. IC1b’s output appears at pin 7 and drives Q3 via a 470Ω resistor. As a result, a voltage of 0.49V is maintained across Q3’s 2.7Ω emitter resistor and this sets the current through Q3 to about 180mA. This current flows via diode D4 to discharge the cells. In addition, some discharge current also flows through LED 1 and IC1, so that the total discharge current adds up to a nominal 200mA. The resistive divider network sets the cutoff voltages for the various battery packs. This network is tapped off using switch S1 and the sampled battery voltage then fed to pin 3 of IC1a which operates as described previously. In practice, the resistor values were selected so that, for each range, the voltage on S1’s wiper is at 0.49V when the pack has discharged to 1.1V per cell. These resistor values take into account the fact that the voltage across the 27Ω 5W resistor increases by about 30mV for every volt applied to the circuit. When the voltage at S1’s wiper subsequently drops just below 0.49V (ie, when the battery pack drops just below its end point voltage), pin 1 of comparator IC1a switches low and removes the drive to Q2. Q2 thus turns off and so Q1 also turns off and interrupts the power to the circuit. This also turns off the DISCHARGE LED and transistor Q3 (since there is no longer any drive from IC1b), and so the bat­tery ceases discharging. PARTS LIST 1 PC board, code 14306941, 101 x 49mm 1 plastic case with aluminium lid, 115 x 65 x 40mm 1 front panel label, 64 x 126mm 2 alligator clips (1 red, 1 black) 1 150mm-length of red hook-up wire 1 150mm-length of black hookup wire 1 small cordgrip grommet 1 knob to suit 1 single-pole 7-position rotary switch 1 momentary pushbutton switch 1 TO-126 mica or silicone insulating washer 1 3mm screw & nut to mount Q3 1 100kΩ vertical trimpot (VR1) 5 PC stakes This view shows how the fully-assembled PC board appears after the front panel has been removed. Note that Darlington transistor Q3 should be mounted on the front panel before soldering its leads to the stakes on the board. Reverse polarity protection for the circuit is provided using diodes D1-D4 and the 27Ω resistor. If the battery is con­nected with reverse polarity, D1 clamps the voltage across IC1a to just 0.6V, D2 and D3 conduct to prevent destructive reverse breakdown of Q1, and D4 prevents reverse current flow through Q3. The 27Ω resistor provides current limiting under reverse polarity conditions. This device dissipates about 3.4W when a 12V battery is incorrectly connected, hence its 5W rating. Finally, LED 2 is forward biased under reverse polarity conditions and so lights to provide a visual warning. Board assembly The Nicad Discharger circuit is built on a PC board coded 14306941. Fig.2 shows the wiring details. Begin the construction by installing PC stakes at the external (plus & minus) lead positions and at the BCE positions for Q3. This done, install the resistors, taking care to ensure that you have the correct value in each position. Table 1 shows the resistor colour code but it’s also a good idea to confirm each value using a digital multimeter, as some of the colours can be difficult to decipher. The 27Ω 5W resistor should be mounted about 2mm above the PC board so that the air can circulate beneath it for cooling. Now install the IC, the diodes and transistors Q1 & Q2. Make sure that these components are all correctly oriented – pin 1 of the IC is adjacent to a small notch in one end of its plastic body. Note that Q1 is a PNP transistor Semiconductors 1 LM358 dual op amp (IC1) 1 LM336-2.5 reference (REF1) 1 BC327 PNP transistor (Q1) 1 BC338 NPN transistor (Q2) 1 BD679 NPN Darlington transistor (Q3) 4 1N4004 1A diodes, (D1-D4) 2 3mm red LEDs (LED 1,LED 2) Resistors (0.25W, 1%) 2 33kΩ 2 680Ω 1 10kΩ 1 560Ω 1 4.7kΩ 1 470Ω 1 2.7kΩ 2 430Ω 2 1.8kΩ 1 330Ω 1 1.5kΩ 1 27Ω 5W 1 910Ω 1 2.7Ω TABLE 1: RESISTOR COLOUR CODES ❏ No. ❏  2 ❏  1 ❏  1 ❏  1 ❏  2 ❏  1 ❏  1 ❏  2 ❏  1 ❏  1 ❏  2 ❏  1 ❏  1 Value 33kΩ 10kΩ 4.7kΩ 2.7kΩ 1.8kΩ 1.5kΩ 910Ω 680Ω 560Ω 470Ω 430Ω 330Ω 2.7Ω 4-Band Code (1%) orange orange orange brown brown black orange brown yellow violet red brown red violet red brown brown grey red brown brown green red brown white brown brown brown blue grey brown brown green blue brown brown yellow violet brown brown yellow orange brown brown orange orange brown brown red violet gold brown 5-Band Code (1%) orange orange black red brown brown black black red brown yellow violet black brown brown red violet black brown brown brown grey black brown brown brown green black brown brown white brown black black brown blue grey black black brown green blue black black brown yellow violet black black brown yellow orange black black brown orange orange black black brown red violet black silver brown August 1994  21 This view shows how the front panel is attached to the PC board & secured via the switch bushes. Note the mounting details for transistor Q3. Discharge Current 12V 11V 210mA 8.8V 200mA 8.4V 7.7V 7.2V 6.6V 6.0V 5.5V 4.8V 4.4V 3.6V 3.3V 190mA 180mA Turn-off accuracy: within 10mV per cell. Leakage current after discharge: <2µA at 11V; <0.25µA below 6V. Reverse battery polarity current: 370mA <at> -12V; 140mA <at> -6V; 70mA <at> -3.6V. BATTERY VOLTAGE 3.6V . + . 8.4V . 9.6V . 12V + own label from the published artwork – see Fig.5. Because it handles most of the current, Q5 requires a modest amount of heatsinking and this is achieved by mounting it on the lid of the case – more on this later. PRESS TO START + End Point Voltage 9.6V + + REVERSE DISCHARGE POLARITY NICAD DISCHARGER The unit is housed in a plastic utility case which has an aluminium lid. This is fitted with an adhesive label measuring 64 x 126mm or you can make your Range (Batt. Voltage) 7.2V . Final assembly Specifications 6.0V . 4.8V . while Q2 is an NPN type, so don’t get these two transistors mixed up. Trimpot VR1 and REF1 can be installed next (watch the orientation of REF1) but leave Q3 off for now since it must be mounted on the metal lid of the case. Switches S1 and S2 are soldered directly to the PC board – see Fig.2 and the photos. The two LEDs can now be installed in the respective loca­tions but don’t solder their leads yet. That step comes later, after they have been pushed through their mounting holes on the front panel of the case. Be sure to orient the LEDs correctly – the anode lead of each LED is the longer of the two (see pinout diagram on Fig.1). Fig.5: this full-size artwork can be used as a drilling template for the front panel. 22  Silicon Chip Begin the case assembly by attaching the label to the lid, then drill holes to accept the two 3mm LEDs, switches S1 and S2, and a 3mm mounting screw for Q3. Note that it’s best to drill small pilot holes for the two switches and then slowly enlarge them to the correct size using a tapered reamer. Deburr all holes after drilling and pay particular atten­ tion to the area around the transistor mounting hole –it must be perfectly smooth and free of metal swarf to avoid punch through of the insulating washer used later to isolate the transistor from the lid. A hole should also be drilled in one end of the case to accept a cordgrip grommet for the battery leads. As supplied, the rotary switch will have 12 positions, so you will have to adjust the selector ring to change it to a 7-position type. To do this, simply remove the nut and lockwasher from the threaded bush, then lift the selector ring and rotate it so that the locating pin goes in slot seven. Check that the switch does indeed now have seven positions, then trim the length of the shaft to suit the knob. Fig.4 shows the mounting details for tran­ s istor Q3. It must be electrically isolated from the front panel using a mica washer. Make sure that the mounting area is perfectly smooth and smear both sides of the mica washer with heatsink compound (not necessary if a silicone washer is used) before bolting the assembly together. The leads of the transistor are then bent at right angles so that Test & adjustment To test the unit, you will need to drill a small access hole through the front panel immediately above VR1. Alternative­ly, you will have to temporarily remove the front panel. Next, connect a 6V battery pack (or variable supply) to the circuit and wind VR1 fully anticlockwise to ensure that the discharge transistor (Q3) remains off. This done, set S1 to the 4.8V range and press S2 to start the discharger. Check that there is now 6V between pins 8 & 4 of IC1 and 2.49V across REF1 when S2 is released. The DISCHARGE LED (LED 1) should also be alight. If everything checks out so far, connect your multimeter across the 2.7Ω resistor (next to Q3) and adjust VR1 for a read­ing of 0.49V. This adjustment sets the reference voltage applied to IC1a and ensures correct operation of the constant current source (IC1b & Q3). Switch off immediately after making this adjustment and re-attach the front panel (if necessary). If you have a variable power supply, check that the discharger switches off at the correct voltage for each range selected (see specifications). The reverse polarity indica­tor circuit can be tested by reverse connecting the power and checking that LED 2 lights. Finally, always be sure to set S1 (the range selector switch) to the nominal voltage of your battery pack before press­ing the START switch to begin the discharge cycle. For example, if your nicad pack has a nominal output of 7.2V when fully charged, then set SC S1 to the 7.2V range. SILICON CHIP SOFTWARE Now available: the complete index to all SILICON CHIP articles since the first issue in November 1987. The Floppy Index comes with a handy file viewer that lets you look at the index line by line or page by page for quick browsing, or you can use the search function. All commands are listed on the screen, so you’ll always know what to do next. Notes & Errata also now available: this file lets you quickly check out the Notes & Errata (if any) for all articles published in SILICON CHIP. Not an index but a complete copy of all Notes & Errata text (diagrams not included). The file viewer is included in the price, so that you can quickly locate the item of interest. The Floppy Index and Notes & Errata files are supplied in ASCII format on a 3.5-inch or 5.25-inch floppy disc to suit PC-compatible computers. Note: the File Viewer requires MSDOS 3.3 or above. ORDER FORM PRICE ❏ Floppy Index (incl. file viewer): $A7 ❏ Notes & Errata (incl. file viewer): $A7 ❏ Alphanumeric LCD Demo Board Software (May 1993): $A7 ❏ Stepper Motor Controller Software (January 1994): $A7 ❏ Gamesbvm.bas /obj /exe (Nicad Battery Monitor, June 1994): $A7 ❏ Diskinfo.exe (Identifies IDE Hard Disc Parameters, August 1995): $A7 ❏ Computer Controlled Power Supply Software (Jan/Feb. 1997): $A7 ❏ Spacewri.exe & Spacewri.bas (for Spacewriter, May 1997): $A7 ❏ I/O Card (July 1997) + Stepper Motor Software (1997 series): $A7 POSTAGE & PACKING: Aust. & NZ add $A3 per order; elsewhere $A5 Disc size required:    ❏ 3.5-inch disc   ❏ 5.25-inch disc TOTAL $A Enclosed is my cheque/money order for $­A__________ or please debit my ❏ Bankcard   ❏ Visa Card   ❏ MasterCard Card No. Signature­­­­­­­­­­­­_______________________________ Card expiry date______/______ Name ___________________________________________________________ PLEASE PRINT Street ___________________________________________________________ Suburb/town ________________________________ Postcode______________ Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number (Bankcard, Visa Card or MasterCard). ✂ they mate with the BCE PC stakes on the board. The front panel can now be attached to the PC board by fitting the matching holes over the switch bushes and doing up the locking nuts. Note that S1 is fitted with a large star washer, while S2 has a flat washer fitted to its bush (these washers all go behind the front panel). This done, the two LEDs can be pushed into their front panel holes and their leads sol­dered. The assembly can now be completed by attaching the battery leads to the PC board (red for positive, black for negative). These leads pass through the cordgrip grommet in one end of the case and are terminated with alligator clips or with some other suitable connector for your battery pack. August 1994  23 CIRCUIT NOTEBOOK Interesting circuit ideas which we have checked but not built and tested. Contributions from readers are welcome and will be paid for at standard rates. VCC LDR1  IC2d 4093 12 1M 47k 14 13 100k 3 100 270k 47k 0.1 11 6 7 7 IC1 2 LM741 4 4001 6 100k D2 1N914 D1 1N914 5 2 0.1 10 1 10M 14 IC3b +12V 4 IC3a 4.7k 3 1 IC2a 8 IC3c VCC 16 47k Q1 BC548 7 9 VR1 100k RLA D3 1N4001 16 IC4 10 CLK4040O12 1 3 14 CLK 2 10 8 11 D11 1N914 1 IC5 D5 4017 D6 5 D7 6 2 3 10 47k 1 13 12 S1 IC3d 4 5 11 330k 6 8 ENA RST 13 15 22k +12V VCC 10M D10 1N4004 5.6k 1 EXTERNAL INPUTS D3 7 D4 10 D8 1N914 1 10k 10M D9 1N914 VR2 1M 5 47k IC2b 6 Q2 BC548 6 7 2 4 4 8 IC7 555 4.7k 3 Q3 BC548 5 1 220 RLB .01 D4-D7 4x1N4004 +12V IC6 7808 IN AC INPUT 1000 GND OUT 10 Timer for security lights This timer can be used to turn on security lights from dusk until dawn or for a preset period ranging from 3-7 hours. It also has provision for connection of a PIR sensor. LDR1 is connected to the non-inverting input of op amp IC1 which 24  Silicon Chip VCC 0.1 S1 : 1 : DUSK TO DAWN 2 : 3 HOURS 3 : 4 HOURS 4 : 5 HOURS 5 : 6 HOURS 6 : 7 HOURS functions as a Schmitt trigger. When darkness falls, the output of IC1 switches low. During daylight, IC1’s output is high and this is fed via NOR gates IC3c & IC3d to hold counters IC4 and IC5 reset. When IC1 goes low, the reset is removed from IC4 and IC5. IC2d’s output now goes high which sets the flipflop consisting of IC3a and IC3b. Pin 3 of IC3a now goes high and turns on Q1 and relay RLA. This turns on the lamps. IC4 is clocked by Schmitt trigger oscillator IC2a and provides a division of 2048. Pin 1 of IC4 clocks decade counter IC5. Trimpot VR1 is adjusted so that one pulse per hour is fed to IC5. As IC5 clocks, each of its outputs goes high in turn. When the output that is selected by S1 goes high, flipflop IC3a/b will be reset which means that pin 3 will go low. This will turn off the relay. Nothing more happens now until night falls again. When it does, the process will repeat itself. The 555 timer, IC7, provides for PIR sensor or light beam relay sensor control. When a positive going pulse is applied to either external input, pin 4 of IC2b will go low. This triggers the 555 monostable. Its pin 3 goes high to turn on transistor Q3 and relay RLB, for a time period determined by the components at pin 6 of IC7. Q2 makes the 555 retriggerable so that further pulses to the external inputs will reset the circuit for another period. A kit comprising all components, relays and rotary switch but not including the mains transformer or the boxes is available for $49.95 plus $5 for postage & packing. Contact CTOAN Electronics, PO Box 211, Jimboomba, Qld 4280. Phone (07) 297 5421. Tester for radio control servos This circuit can be used VR1 50k to check servos for their maximum throw, direc18k tion of travel, current consumption, jitters or glitch­ es, as well as being used 6 for linkage adjustments in 5 models without the need to use a transmitter. In a radio control system the receiver sends down to each servo a train of pulses corre­sponding to the stick positions on the transmitter, where the width of each pulse determines the position of a particular servo. The pulse width usually varies from 1-3ms with a repeti­tion rate of about 40Hz. The pulses are positive in radios such as JR, Sanwa, Futaba and Multiplex. These pulse width commands can be simulated by a variable-duty cycle oscillator built around two gates of a Automotive voltage regulator This automotive voltage regulator is based on a circuit sent in by Bevan Paynter of Williams, SA. The original version was used to replace the electromechanical reg­ulator in his car, although this revised version has not been built and tested. An automotive voltage regulator works by controlling the current in the field of the alternator, which in turn controls the stator output. In this circuit, ZD1 conducts when the alter­nator output reaches 14.2V, turning on Q3. This turns off Dar­ lington pair Q1 & Q2, which were completing the field circuit.As the voltage drops below 14.2V, ZD1 ceases conducting, Q3 turns off, and Q1 & Q2 turn back on again. 500mA FS 100  10 0.1 D1 1N4001 SIG .047 4 0.22 5.4V 6V 150k IC1b S1 D2 1N4001 OFF 4.8V 4011 2 1 IC1a 3 12 13 14 IC1d 7 11 8 9 SERVO 6V IC1c 10 0.8-3ms ~25ms 4011 quad 2-input NAND gate IC. The 0.22µF capacitor and 150kΩ resistor at pin 2 set the ON-period of the oscillator to about 25ms (ie, 40Hz rate), while the .047µF capacitor at pin 3 together with the associated 18kΩ resistor and 50kΩ potentiometer (VR1) allow the pulse width to be varied from 0.8-3ms. The resulting negative pulse train from pin 3 of IC1a is buffered and inverted by IC1d, with pin 11 connected to the positive signal input of the servo being driven. IC1c further inverts the signal train to provide a negative pulse train. A cheap VU-meter shunted by two 1Ω resistors provides current monitoring with a full scale sensitivity of 500mA. Diodes D1 & D2 and switch S1 make the circuit able to provide pulse trains to suit various receiver voltages. Manfed Schmidt, Edgewater, SA. ($20) TO CATHODE-ANODE This switches the field JUNCTIONS OF STATOR ALTERNATOR DIODES current back on again LIGHT and so the output volt+12V age settles at 14.2V. D2 D3 D4 D1 protects Q1 from 3x1N5404 spikes and transients generated by the field D1 FIELD coil switching action. 1.5k COIL 1N4002 1k It is absolutely critQ2 BD139 ical to obtain a 12.8V ZD1 Q3 zener diode for ZD1, to 12.8V BC337 obtain a 14.2V charg­ Q1 ing voltage. All zener 2N3055 1k 1k diodes vary from their nominal rating, so CHASSIS you will have to test a Finally, for a 9-diode alternator, number of 13V zeners discard diodes D2-D4 (since these to obtain the correct value. Note: diodes will already be present in for zero temp­era­ture coefficient of the alternator). Note that transisthe zener voltage, use two 400mW tor Q3 should be mounted on a zener diodes (6.2V and 6.8V nomheatsink. inal) in series. This will give much SILICON CHIP. improved temperature stability. August 1994  25 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd This tiny board is a voice-operated switch designed to fit into the tightest space. It uses a single IC & includes a SPDT 12VDC relay. It has almost no turn-on delay & a 3-second release time. By DARREN YATES S O WHAT IS A VOX? Well, VOX stands for voice-operated relay or switch. They’re most often used in “hands-free” communication such as amateur transceivers, mobile radios and some public address applications. The idea behind a VOX is that instead of the user pressing a button on the microphone to speak (ie, the press-to-talk switch), the sound of the voice is used to activate it instead. This leaves the user with an extra hand free to sit back with scones and a nice cup of tea. Our circuit uses one IC and a tiny SPDT (single-pole dou­ b le-throw) relay which can be used to switch on or off just about anything you like (but not 240V equipment). The relay we’ve used comes from Altronics (Cat.S-4140) and measures only 16 x 11 x 10mm – pretty tiny for a mechanical relay with a contact rating of 2A. In keeping with this, we’ve made the rest of the circuitry as small as possible so that you could install the VOX almost anywhere. It runs from a 12VDC supply and current drain is low, about 5 to 7mA quiescent and around 35mA when the relay is actu­ated. Circuit description The circuit for the MiniVOX is shown in Fig.1. As you can see, it is a “bare-bones” design involving an LM358 dual op amp (IC1), one transistor, the relay and a few other components. Voice signals are picked up by the electret microphone and fed to op amp IC1a. This is connected as a non-inverting amplifier with a gain of 151 or +43.6dB. The 100pF capacitor across the 150kΩ feedback resistor rolls off the high frequency response above 10kHz so that there is no chance of the circuit responding to spurious RF signals. The output of op amp IC1a at pin 1 feeds two diodes, D1 and D2, which Build the MiniVOX voice operated relay All the parts except for the electret microphone are mounted on a small PC board. Keep the microphone well away from the board, otherwise the relay noise will repeatedly trigger the VOX circuit. The circuit is suitable for switching low voltage equipment only (up to about 30V). function as a half-wave voltage doubler. These rectify the audio signal to produce a DC voltage across the 2.2µF capaci­tor which is directly proportional to the loudness of the sound fed to the microphone. This DC voltage is fed to the remaining op amp in the pack­age (IC1b) and this is connected as a comparator. The DC voltage from the rectifier is fed to pin 5 while a resistive voltage divider applies about +2V to pin 6. Once the DC voltage across the 2.2µF capacitor rises above the voltage at pin 6, pin 7 of IC1b pulls high, which turns on transistor Q1, a BC548 NPN type. This turns on the relay and lights up LED 1. Q1 remains on and the relay is actuated while ever the DC voltage at pin 5 is above the voltage at pin 6. Because of the high gain of op amp August 1994  31 D4 1N4004 10 10k 10k 3 8 IC1a 2 LM358 MIC 1 0.1 D3 1N4004 1k 2x1N914 D2 D1 100pF 6 1M K LED1 5 2.2 63VW  A 7 IC1b 12V PLUGPACK RLY1 10k B C Q1 BC548 E 4 2.2k 150k B 1k 2.2 25VW E C E B VIEWED FROM BELOW C A K MINIVOX VOICE OPERATED RELAY Fig.1: the circuit is based on dual op amp IC1. IC1a functions as a microphone preamplifier & this drives a diode charge pump based on D1 & D2. When the voltage across the 2.2µF capacitor on D2’s cathode exceeds a preset level, pin 7 of Schmitt trigger stage IC1b switches high & turns on Q1 & the relay. PARTS LIST 1 PC board, code 06109941, code 47 x 44mm 1 electret microphone insert 1 2A SPDT relay (Altronics Cat S-4140) Semiconductors 1 TL072, LM358 dual op amp (IC1) 1 BC548 NPN transistor (Q1) 2 1N914, 1N4148 small signal diodes (D1,D2) 2 1N4004 rectifier diodes (D3, D4) 1 red light emitting diode (LED1) Capacitors 1 10µF 25VW PC electrolytic 2 2.2µF 16VW PC electrolytic 1 100pF ceramic Resistors (1%, 0.25W) 1 1MΩ 1 2.2kΩ 1 150kΩ 2 1kΩ 3 10kΩ IC1a, together with the addi­ tional gain in the half-wave voltage doubler, the circuit has a very fast response to audio signals. On the other hand, the “release” time (the time taken for the relay to drop out) takes about three seconds, as determined by the time constant compris­ing the 2.2µF capacitor shunted by the 1MΩ resistor and the threshold voltage of IC1b, as set at pin 6. Diode D3 is connected across the coil of the relay to pro­tect the transistor when it switches off. If the diode was not there, the inductive kickback from the relay coil when the cur­rent is switched off could destroy the transistor. Power for the circuit can come from any 12VDC source; eg, car battery, DC plugpack, SLA battery – whatever you like. Diode D4 prevents reverse polarity connections from damaging the cir­cuit. Construction All of the components, including the LED and the relay are installed on a small PC board coded 06109941 and measuring 47 x 44mm. Before you begin any soldering, check the board thoroughly for any shorts or breaks in the copper tracks. These should be repaired with a small artwork knife or a touch of the soldering iron where appropriate. When you’re happy that everything appears to be OK, you can start construction by installing the wire link, followed by the resistors, diodes, capacitors, IC, the transistor, the LED and finally the relay. Note that to make the board as small as possi­ble, all of the resistors and diodes are mounted on their ends. Each component has a spacing of 0.2-inch or 5mm between its pins. Use the overlay wiring diagram to ensure that each compon­ent goes into the correct position. You will find that the circuit works best with the micro­phone connected to the circuit via a pair of flying leads about 50mm long. Don’t make them too long otherwise the leads may pick up hum. Because the relay switching itself makes noise, it’s quite easy for the circuit to “chatter” because of the relay sound being picked up by the mike. So keep the microphone away from the relay. RESISTOR COLOUR CODES ❏ No. ❏  1 ❏  1 ❏  3 ❏  1 ❏  2 32  Silicon Chip Value 1MΩ 150kΩ 10kΩ 2.2kΩ 1kΩ 4-Band Code (1%) brown black green brown brown green yellow brown brown black orange brown red red red brown brown black red brown 5-Band Code (1%) brown black black yellow brown brown green black orange brown brown black black red brown red red black brown brown brown black black brown brown Another place for experimentation is in the threshold resistors. By adjusting the A N/C RELAY 10kΩ and 2.2kΩ resistors, you Q1 D3 can adjust the threshold or N/O A 1k more importantly, the on and 10k 10k 10uF off delay times. Having a higher 2.2k D2 threshold voltage will mean K IC1 that the circuit takes longer to 10k A LM358 D4 2.2uF 1 MIC switch on for some sounds and K 150k 12V will switch off sooner wherePLUGPACK D1 as a lower threshold voltage 100pF 2.2uF (achieved by reduc­ i ng the Fig.2 (left): some of the parts on the PC board are mounted “end-on” to save space, as 2.2kΩ resistor) would result shown on this wiring diagram. Fig.3 at right shows the full-size PC etching pattern. in a very quick on time and a longer release time. Don’t forget to include the PC stakes immediately and check your circuit You could also use this circuit as a as well. These will make it much easier against the overlay diagram for pos- very simple front door light whereby for you to solder the connecting leads sible errors. a sound triggers the relay to switch to the board. on a 12VDC light globe for say 30 secExperimentation onds. You could adapt the circuit to Installation This circuit provides plenty of do this by simply replacing the 2.2µF You can easily install the board possibilities for experimentation. By capacitor with a 10µF capacitor and in existing equipment wherever you using a 150kΩ feedback resistor with increasing the 1MΩ resistor to around can find enough room and a suitable IC1a, we have fixed the sensitivity of 3.3MΩ. The light globe connects to the 12VDC supply. the circuit to one which should suit relay outputs. Again, you can adjust the sen­sitivity When the unit is powered up, the most people. Alternatively, you could quiescent current should be around replace this feedback resistor with so that the circuit picks up sounds 5-7mA, increasing to around 35mA a 200kΩ logarithmic pot which will close to your front door and ignores with the relay in action. If it is sub- allow you to vary the sensitivity over cars passing in the street. Why not SC give it a try? stantially more than this, switch off a wide range. COM 0.1 1k 1M LED1 K August 1994  33 Night viewers are not new but those presented in maga­zines in the past have really needed an infrared source to enable them to see well in the dark. With the design presented here, it is possible to see just by the light of stars. In fact, you can even use the tubes featured here for astronomy. By LEO SIMPSON Lift the veil of darkness with an Image Intensified Night Viewer This project employs a 25mm or 40mm 3-stage fibre optically coupled image intensifier tube. The resultant cascaded tube has a typical luminous gain of over 50,000. If all that seems a mouth­ful it is because it embraces some pretty fancy technology which is still not available to some countries. Image intensifier and image converter tubes operate on the same principle. An image is focused by an 34  Silicon Chip external lens onto the photocathode target of the tube and this cathode emits electrons in response to the incident photons. The electrons are then accelerated by a cone-shaped electrode to strike a luminescent screen. Because each photon landing on the photocathode target ultimately gives rise to many photons from the luminescent screen, the result is a gain in luminous intensity. In the tubes being discussed for this project, the photo­ cathode responds to the infrared region of the spectrum while the luminescent screen has TOP OF PAGE: at night, vegetation which is in complete darkness can be seen in intricate detail on the green screen of the Night Viewer. This simulated shot does not show the distortion at the edges of the screen which is really only apparent as you pan the Night Viewer across the scene. This is a 25mm version of the Night Viewer, with all components sprayed black. Note that the Night Viewer must only be used in the dark. green phosphor (much like the screen of an oscilloscope) and so the image is green. Hence, this sort of tube is also referred to as an “image converter”. The photocathode is actually spherical in section, deposit­ed on the inside face of the window. Ideally, the luminescent screen should have the same radius of curvature as the photo­cathode but in practice, a flat screen is used. This results in image distortion (stretching) at the edges of the screen. The cone shaped electrode is held at the same high voltage as the screen and the voltage between the photocathode and the screen is typically 12kV to 15kV. Typical single stage image converters give a luminous gain of about 75 and in practice, if they are to be used for effective night time viewing, they need an infrared light source to illu­minate the scene. For an image converter to be really effective, it needs two or three stages, as depicted in Fig.1. Here, the screen of the first converter is used as the image input to the photocathode of the second converter and so on. The coupling between stages is in the form of plano-concave fibre optic lens­es. The tubes supplied for this project are used and may have some small but negligible blemishes. Due to the complexity of the cascaded tube construction, small blemishes were acceptable even in new tubes. Several different tubes are available for this project, 25mm and 40mm in screen diameter. Whichever one is used, an input lens fits at the front of the case, arranged so it focuses the scene onto the cathode of the imaging tube. Therefore, the lens serves the same purpose as in a camera and the type of lens is chosen for the application, just as it would be for a camera. You can have a wide-angle lens for close-up work, a tele­photo lens for distance viewing or even a zoom lens. In order to maximise the light being transferred from the scene to the tube, fast (large aperture) lenses should be used. The prototype unit pictured in this article employs a 100mm f2 lens. The prototype unit also employs a low cost dual lens magnifier. If the eyepiece is removed, the screen of the imaging tube can be photographed or videotaped. These tubes don’t need much light to operate. 100 millilux (one tenth of a lux) is the maximum recommended exposure. The life of a tube is reduced with prolonged exposure to this light level. The tube can produce a useful output down to 500 microlux (0.0005 lux). Starlight is about 0.001 lux. In comparison, modern colour TV cameras need about 2 lux and most sensitive monochrome TV cameras need at least 0.1 lux. SCREENS PHOTOCATHODE CONE-SHAPED ELECTRODE FIBRE-OPTIC WINDOWS Fig.1: a 3-stage image converter tube has each section linked together by fibre optic couplings to markedly increase the luminous gain. August 1994  35 C3-C14 220pF-.001 5kV D3-D14 BY509 D2 1N4007 C14 T1 R1 150  D14 NE1 R2 22k S1 Q1 2N2219 C1 100 B1 9V B C2 .047 350V NE2 C SCR1 C106D A R3 22k E C13 G D12 C11 D11 D10 C10 D9 C9 +13.5kV T2 C3 C4 D3 K R4 22k D1 1N4148 D13 C12 D4 C5 D5 C6 D6 C7 D7 D8 C8 -13.5kV PCB GND B E C VIEWED FROM BELOW PASSIVE NIGHT VIEWER POWER SUPPLY KAG Fig.2: the EHT supply for the Night Viewer has three sections: a ringing choke inverter involving transformer T1, a capacitor discharge converter involving SCR1 & transformer T2, & the voltage triplers. Just to give some idea of how sensitive these tubes are, we used the prototype to look at the night time sky and found that it really accentuated the detail in the Milky Way! 65mm plastic tubing is used to house the 25mm image con­ verter tubes, while 90mm stormwater plastic tubing is used for the 40mm units. These plastic tubes, their matching joiners and end caps, are readily available from plumbing suppliers. The resultant dimensions of the fully constructed night viewers are approximately 70mm outer diameter and 180mm long for the 25mm version, and 90mm diameter and 280mm long for the 40mm version. Required circuitry As already noted, an image converter requires a high vol­tage supply of about 12-15kV but the current needed is low, less than 10 microamps. The circuit for the supply produces an EHT voltage of around ±13.5kV when powered from a 9V battery. Current drain is about 14mA, giving a useful life of around 20 hours from a standard battery or about 60 hours from an alkaline battery. The circuit of Fig.2 has three sections: the inverter, the converter and the voltage triplers. The inverter section is a ringing choke oscillator consisting of transformer T1, R1, D1 and transistor Q1. Resistor R1 provides bias current to make the oscillator start, and also supplies feedback to maintain oscilla­tion. Diode D1 protects the base-emitter junction of Q1 when the base voltage swings negative. The oscillator operates at around 120Hz, set mainly by the transformer. C14 C13 C12 D13 C11 D11 C10 D9 +13.5kV C9 D2 T1 100uF NE1 T2 22k NE2 D1 Q2 22k C3 .047 22k 150  B1 D10 D12 D14 S1 The resulting AC voltage at the primary of T1 is stepped up by the secondary and is rectified by diode D2. This diode charges capacitor C2 via the primary winding of transformer T2. When the voltage across C2 exceeds the breakdown voltage of the two series-connected neon lamps, NE1 and NE2, (around 150V) the neons turn on. This triggers the C106D SCR, and C2 is quickly discharged through the SCR via the primary winding of T2. Once the capacitor is discharged, the neons go out, the SCR turns off and the charge cycle starts again. During the discharge cycle of C2, a high-voltage pulse with a peak-to-peak voltage of 4.5kV is produced at the secondary of trigger transformer T2. This pulse is applied to two separate 3-stage Cockroft-Walton voltage tripler circuits. The tripler made up by diodes D4-D9 and capacitors C4-C9 produces -13.5kV. Another tripler made up by diodes D10-D15 and capaci­ tors G A K SCR1 D3 C4 D5 D4 C6 C5 D7 D6 C7 D8 -13.5kV C8 GND 36  Silicon Chip Fig.3: everything except the voltage triplers is mounted on a small PC board measuring 50 x 28mm. The triplers are hardwired & then potted in neutral-cure silicone sealant although this step does not take place until after the circuit is tested & connected to the image converter tube. This photo of the Night Viewer shows the wiring inside the plastic case before the triplers are potted. C10-C15 produces +13.5kV. Voltage regulation is achieved by the neons, as the voltage applied to the primary of T2 is constant at 150V peak. The circuit will produce a relatively constant output for a DC input voltage from 7-12V. Circuit construction Everything except the voltage triplers is mounted on a small PC board measuring 50 x 28mm. The wiring diagram is shown in Fig.3. This board is mounted, together with the triplers, in a standard plastic utility box measuring 130 x 68 x 43mm. The triplers are hard-wired and then potted in neutral-cure silicone sealant although this step does not take place until after the circuit is tested and connected to the image converter tube. Several points must be watched during assembly of the PC board: (1) Make sure the metal side of the SCR faces towards the centre of the board; (2) Make sure that the polarity of diodes D1 and D2 and capacitor C1 is correct; and (3) Resistor R1 is in­stalled “end-on”. The two triplers are hard-wired as shown in Fig.3. Their wiring should be kept as compact as possi­ble. A lead length of 5mm for all components is OK. Note that the polarity of the diodes is different in the two triplers. With the circuitry complete you can proceed to a test, before any connec- tions are made to the image converter tube. The test can be done before the tripler sections are potted but note that only one tripler section can actually be connected at a time in this no-load condition. Having a supply produce ±13.5kV is possible in free air but a total of 30kV is not. When you switch on the power with either of the triplers connected, it is most likely that there will be some corona discharge around the tripler diodes. This won’t damage anything but keep a safe distance from this part of the circuit. The current drawn from the battery should be about 14mA. If a wire connected to the circuit earth is placed close to the relevant EHT output lead, you should be able to obtain sparks up to about 5mm long. After the battery is disconnected, you should connect the earth wire directly to the EHT output in order to discharge all the capacitors. Note that when the circuit is working, you will not see the neons light. This is because of the short duty cycle – you will only see the neons glow when you look at them in the dark. If the circuit does not work try measuring the AC voltage at the base of Q1; it should be around 0.45V RMS measured with a digital multimeter. The AC voltage measured at the cathode of D2 is about 45V RMS measured with a digital multimeter. Don’t try measuring the EHT voltages unless you have a suitable EHT probe, otherwise you will damage your meter. If all is well with the preliminary tests, you can proceed to finish the project. As supplied, the image converter comes prewired. You will need to mount the image converter in the The 3-stage image tube is supplied pre-wired. Note that all of the tube metalwork is connected to the EHT supply and therefore must be fully isolated so that no user contact is possible in the finished Night Viewer. August 1994  37 PARTS LIST This little jig, made of two pieces of scrap PC board, simpli­fies the hard-wiring of the two triplers. The hot melt glue is used to pot the triplers after they are wired into circuit. 1 prewired 3-stage image intensifier tube 1 objective lens (see text) 1 eyepiece lens (see text) 1 PC board coded OATLEY JM 2 neon lamps (NE1, NE2) 1 inverter transformer (T1) 1 trigger transformer (T2) 1 9V battery and snap connector 1 miniature SPDT toggle switch 3 22kΩ 0.25W 5% resistors 1 150Ω 0.25W 5% resistor Semiconductors 1 2N2219 NPN transistor (Q1) 1 C106D SCR (SCR1) 1 1N4148 signal diode (D1) 1 1N4007 1A diode (D2) 12 BY509 or equivalent 8kV 3mA diodes (D3-D14) Capacitors 1 100µF 25V electrolytic 1 0.47µF 350V polyester 12 220pF to .001µF 5kV ceramic Miscellaneous Silicone sealant, epoxy adhesive, hot melt glue, hookup wire, solder, plastic tubing & fittings, galvanised steel tubing. A close-up view of the completed EHT supply, showing how the triplers are potted with hot melt glue in a compartment at the end of the plastic box. plastic tube, as shown in Fig.4. This shows the image converter tube suspended in the plastic tube which is fitted with a sleeve of galvanised steel, held in place with the plastic fittings. These fittings will ultimately be glued into place using plumbers’ PVC glue (as used for gluing plastic sewer and stormwater fittings). At the ends of the plastic tube, the image converter tube should be sealed into place using hot melt glue or silicone sealant. This will do two things: support the tube mechanically Where to buy a kit This project is available in kit form from Oatley Elec­tronics, PO Box 89, Oatley, NSW 2223. Phone (02) 579 4985; Fax (02) 570 7910 A kit comprising a 25mm prewired 3-stage image converter tube, plastic pipe and fittings for the tube case, metal X-ray shield sleeve and the EHT power supply kit is available for $290 plus $10 for postage and packing. The same kit for a 40mm image con­verter is $390 plus $10 for postage and packing. Also available is a suitable eyepiece lens for $18 and an objective lens for $75. The plastic box for the power supply is $4. Payment may be made by cheque, postal money order or credit card. Oatley Electronics also have cheaper kits with single stage image intensifier tubes. For further details, contact Oatley Electron­ics. Note: copyright of the PC board for this project is owned by Oatley Electronics. 38  Silicon Chip and prevent any user contact with exposed metal which is connect­ed to the outputs of the triplers. However, before you do any work with glues or sealants, you must drill holes in the plastic tubing, the metal sleeve and the plastic case, to allow the three wires to pass through and con­nect to the outputs of the triplers. Naturally, these holes must line up precisely. After the holes have been drilled, the plastic box is glued to the plastic ring at the objective lens end of the tube hous­ing. You can use plumbers’ PVC glue for this job but the box will need to be held in place temporarily with strong adhesive tape. After the PVC glue has set, some hot melt glue can be used to fill the join between the plastic box and the metal sleeve. That done, connect the triplers and mount them at one end of the plastic box and partition it off with a piece of plastic as shown in one of the photos. Then fill the tripler compartment with hot melt glue. -13.5kV GND +13.5kV 2mm FOR PROTOTYPE 40mm FOR PROTOTYPE TUBE 1 TUBE 2 PROTOTYPE EYEPIECE "PEAK" 10x PLALUPE No.2032-10 OBJECTIVE LENS EPOXY TUBE 3 65mm STORM WATER PIPE POLYURETHANE FOAM BLOCKS 65mm STORM WATER PIPE END CAP SHORT TUBE CUT FROM A 66mm STORM WATER PIE JOINER EPOXY 65mm STORM WATER PIPE END CAP METAL X-RAY SHIELD Fig.4: the image converter tube is suspended in a plastic tube which is fitted with a sleeve of galvanised steel which functions as an X-ray shield. -13.5kV +13.5kV GND TUBE 2 TUBE 3 SCREEN END OF TUBE ANODE END OBJECTIVE LENS END OF TUBE CATHODE END TUBE 1 Fig.5: this diagram shows how the tube sections are wired to the EHT supply. Mount the PC board and the battery in the plastic box – they can each be secured simply by pressing them into a small blob of Bostik Blu-Tack adhesive. Remember to connect the switch in series with the 150Ω resistor and the battery snap before mounting these two components. Finally, you will need to glue your objective lens and eyepiece lens to the PVC end caps and these can be secured to the completed tube assembly with small self-tapping screws. You are now ready to use your completed Night Viewer. Remember to avoid the temptation to test or use the Night Viewer during the day time. Using it under daylight or in brightly lit rooms will damage the tube. Keep a lens cap on the objective lens when not in use as this will also protect the lens from damage. The prototype was sprayed with black paint to finish it SC off. WARNINGS HIGH VOLTAGE: The EHT power supply used in the Night Viewer is not capable of delivering any significant current continuously but it can provide a nasty electric shock. Make sure that the capacitors are discharged before working on the circuit. LIGHT EXPOSURE: An imaging tube can be damaged if it is exposed to bright light. Do not store or use the tube in daylight. The tube will not be damaged if it is exposed to normal room light during construction, but with no power applied. For longest life a completed viewer should be stored in the dark and used in the dark. Normal night time street lighting levels and street lights are not a problem. Using it in daylight can damage it. X-RAYS: Low level X-ray radiation is emitted by most imaging tubes. This radiation is mainly emitted around the sides of the tubes and not from the screen or the cathode of the tube. The radiation level is reduced to very low levels by housing the whole tube assembly in an outer tube made of galvanised steel – see Fig.4. EXPORTING: exporting these tubes to some countries may be pro­hibited, or may require special export permits. Do not export these tubes to any other country prior to consulting the appro­priate authorities. August 1994  39 SERVICEMAN’S LOG Lightning strikes thrice A popular superstition when I was a youngster was that various calamities – natural or manmade – always happened in threes. Well, that was according to the adults who knew all about these things. I never did believe it but a recent experience does have me wondering a little. The story is really about video recorders; and I use the plural term deliberately because it involves no less that four machines, all of the same brand – but different models – which turned up on the bench in quick succession. And three of them had suffered lightning strikes. See what I mean! The first one was a Panasonic NVJ1A, a run-of-the-mill model now about four years old and no longer in production. It is owned by one of my regular customers who, incidentally, is someth­ing of a computer buff, a point of some interest as it tran­spired. He came into the workshop one morning, pushed the machine across the counter with the cover removed and said, “Will you put a fuse in it. It’s stopped and the fuse is blown”, pointing to the offending component. Well, he wasn’t wrong; one glance at the blackened glass was enough to confirm that. But it was obvious from the way he spoke that he firmly believed that the fuse was the only thing wrong. And when I gently suggested that this was an effect, rather than a cause, he was quite reluctant to accept the idea. There is only one answer in such cases. I fished out an appropriate replacement, fitted it and applied power. Splat! – one fuse destroyed. After that, he didn’t argue. But it was only then that he told me about the storm and the fact that his power main had apparently been struck. And so he agreed to leave the machine with me. But I warned him that, if he was lucky, the damage would be confined to the power supply. If he wasn’t, it could be a lot more serious. I didn’t attack it immediately. There were other jobs ahead of it, the owner had indicated that he was not in a hurry, and I was not at all familiar with this power supply. I had a manual but had not had occasion to service this section before. All I knew was that it appeared to be fairly conventional switchmode supply. Strike two In any case, before I could get it on the bench, what should turn up but another Panasonic recorder; an NVFS90A. This is a very much up-market Super VHS model, with all the bells and whistles one can imagine – and a price tag to match. But for all that, its power supply is almost identical with the NV-J1A. And it had also suffered a lightning strike; not from the same storm but 40  Silicon Chip Fig.1: the power supply circuit for the Panasonic NV-FS90A video recorder. The components to be checked out included the mains fuse (F1101), the bridge rectifier (D1102), the starter circuit across the output of the bridge rectifier, the auto vol­tage selector IC (IC1101), and safety resistor R1125. from one a couple of days later. In this case, however, there were no obvious symptoms and the fuse was still intact. Its owner was anxious to get it fixed as quickly as possible. In all these circumstances, I decided to let the FS90A jump the queue. After all, I had to familiarise myself with the power supply on one machine or the other, so it might as well be on the more urgent one. The power supply is a self-contained unit which is housed in a metal box. It sits in the rear lefthand corner and is easily removed by undoing a few screws. The box itself measures about 150 x 50 x 65mm and the bottom cover can be sprung off quite easily, although the top can present problems. Not all models have the same top. Some, including these two models, cover all the box and are quite easy to remove. In other models, they are only about 50mm long and are quite tricky to remove. To make matters worse, there is nothing in the manual covering this procedure. The secret lies under a small plastic label, marked “AC IN”. This can be peeled off and it is then possible to see how the cover and body are slotted together. In all models, the construction is quite compact and this makes them a little diffi­cult to work on but not seriously so. As I have already noted, the mains fuse (F1101) was intact and there were no other visible signs of damage. Well, it didn’t take long to establish that bridge rectifier D1102 was open circuit; a rather strange fault in the circumstances – I would have expected a short circuit. Anyway, that’s how it was. And, since I didn’t carry this item in stock, it would have to be ordered. But what else could have been damaged? The next major component after the bridge rectifier is a small IC (IC1101), which is described as an auto voltage selector – more about this later. There was no conclusive way to test this IC without a new rectifier but I made a few resistance measurements across the appropriate pins and, judging by the transistor configurations shown within the IC, I suspected that it may be faulty also. So that was added to the order list. So what about the NV-J1A machine? Like the NV-FS90A, it would almost certainly need some replacement parts. Closer exami­ nation revealed one important difference between the FS90A and the J1A; the J1A was fitted with a protective thermistor (D1101) across the mains, a refinement the FS90A lacked, in spite of its up-market price tag. I hoped that this might have prevented further damage. And yes, this had broken down and taken out the fuse. So maybe that was all that was needed. I had a replacement on hand, fitted it, and tried again. No joy; another fuse for the garbage bin. I moved on to the bridge rectifier and confirmed that this was the real culprit – it had broken down. So another bridge was added to the order. Next to consider was the auto voltage selec­tor IC, which was a different type from that in the FS90A. Be­cause the J1A had apparently suffered a heavier wallop than the FS90A, I also ordered a replacement for this IC, just in case. So the order was duly despatched and a couple of days later I had the spares on the bench. Naturally, I went straight to the FS90A and fitted the new rectifier. I made a quick check but no joy. Well, I’d suspected the auto voltage IC anyway and it was easy to fit the new one, so that was the next step. In fact, when I pulled the old one out and compared measurements with the new one, my suspicions were confirmed. Unfortunately, when the new one was fitted there was still no response, so it was back to basics. Measuring August 1994  41 So that was something I had learned – the hard way – and is well worth jotting down for future reference. It could save an embarrassing bounce. Back to the J1A across the bridge rectifier showed 300V plus, which seemed logical, and so I moved on to pins 3 and 4 of the auto voltage selector IC, which should have had essentially the same voltage between them. In fact, it was zero. From there it was no great effort to find the culprit. R1125, a 2.2Ω safety resistor in the negative line from the rectifier, was open circuit. Well, that was no great problem; 2.2Ω safety resistors are a readily available component and I always have stock on hand. A new one was fitted and the machine came to life. A thor­ ough workout confirmed that all functions were performing cor­rectly and I gave the machine the usual clean and lube routine before ringing the owner with the good news. A nasty bounce He came in the following morning, which was a Saturday, and collected it. And I naturally assumed that that was end of that story. Not so – he was on the phone first thing Monday morning with the bad news. The thing was dead at first switch-on. It wasn’t a good way to start the week. All I could do was ask him to bring it back in and assure him that I would sort it out. Back on the bench, it didn’t take long to find the reason; the 2.2Ω safety resistor I had fitted had failed. I could find no obvious reason for this, so I fitted another one, switched on, and the machine came good. I put it through several on/off cycles – the previous failure had obviously occurred at switch-on – and it came good every time. 42  Silicon Chip I left it for a while to attend to other jobs, then tried again. Bingo! It was completely dead. And yes, it was the 2.2Ω resistor. But why? With no obvious clues I realised I needed help. I could spend a week trying to puzzle this out and more than likely be no further advanced at the end of that time. I rang one of my con­tacts at Panasonic and put the problem to him. His reaction was immediate. “What kind of safety resistor are you using?” I replied that it was a standard 2.2Ω 1W type such as one buys at the (electronic) lolly shop; the kind of thing everyone uses. “But not from Panasonic?” “No – does that matter?” “You fit a Panasonic type and you wont have any more trou­ble.” Sensing a certain amount of incredulity on my part, he went on to spell out the difference (more on that in a moment). In any case, I had little option; I ordered the type he nominated – several, in fact – and when they came to hand fitted one to the FS90A. And that really was the end of it; the machine has given no further trouble. The crucial difference So what is so magical about the Panasonic component? It is a wire wound type, as distinct from the more usual metallised types. And, although it is rated at only 1W, as are the other types, it is capable of withstanding a much heavier switch-on surge. And this particular power supply does have a heavy switch-on surge. This, in turn, is a byproduct of the auto voltage selector system. In the meantime, I had gone back to the J1A. I had already replaced the thermistor, established that the bridge rectifier had failed, and suspected that the auto voltage selector IC might be faulty. In fact, this latter suspicion proved to be correct. So the rectifier and IC were replaced and, on a hunch, I checked the 2.2Ω safety resistor. I wasn’t really surprised to find it had failed and was grateful that I had the correct replacement type on hand. And with all that attended to, the machine came to life. More importantly, it operated in all modes – an important point, because lightning strikes don’t always stop at the power supply. They can pick on odd components anywhere in the system and create faults which can be very difficult to track down. So the owners of both the FS90A and the J1A were lucky; the damage in either case could have been much more serious. Strike three Machine number three was an NVFS65A. It had also suffered a lightning strike and, as it transpired, had suffered more damage that the other two. And, of course, with the first two under my belt, I was feeling pretty cocky about this one, the power supply being essentially the same. But pride goes before a fall. I went through the same rou­tine: the fuse, the rectifier, the safety resistor and the IC, all of which needed replacement. But it still wouldn’t deliver voltage and I began digging deeper into the circuit. I didn’t have much luck initially. Panasonic suggested some likely components to be either tested or replaced, as did a colleague who was also familiar with these units. But none of the suggestions helped. So I was at a temporary dead end. I say temporary, because I was quite confident that I could track down the trouble, given time. But the owner had other ideas. He called in to see how things were going and I told him quite frankly that the job had proved far more difficult than thermistor across the mains and the surge protector at the power point. Yet it was still damaged. On the other hand, nothing else in the house was damaged, nor was there any indication that any of the surge protectors had been activated. And by “activated” I mean destroyed because, as far as I know, all these surge protectors are sacrificial devic­ es; once activated they have to be replaced. Fig.2: the power supply for the Panasonic NV-J1A video recorder is basically similar to that in the FS90A but also features a surge protection thermistor (D1101). I had originally anticipated. “Well,” he said. “What about fitting a new power supply?” This was the last thing I would have suggested. I told him that yes, I could do that, but it would prove pretty expensive. He shrugged his shoulders. “Hang the expense. If that will solve the problem, go ahead and fit it”. So that’s what was done. In fact, Panasonic didn’t supply a complete replacement; just a new board to fit in the metal case. And that put the machine back in operation. But while having the machine fixed was gratifying in one sense, it was somewhat frustrating in another. I was still keen to know what the problem really was and anticipated that I could probably retain the old board and solve the puzzle at my leisure. But that was not to be either. Before I could even raise the matter the owner indicated that he wanted to take it and, since it was his property, there was nothing I could do about it. So that one must remain a mystery. Surge protectors Still on the subject of lightning strikes, I mentioned earlier that the owner of the J1A was a keen computer buff. The significance of this is that he had become more than usually aware of the risk of power line surges, of whatever origin, to his precious computer equipment. As a result, he had fitted surge protectors to most of his power outlets, including the one normally used for the video recorder. So the recorder had two levels of protection; its own Machine number 4 Machine number four was a model NV-L20 and it came in shortly after the first three. It was completely dead also but there was no suggestion of a lightning strike. On the other hand, the failure did look as though it might be linked to a mains shut-down, at least indirectly. As the owner explained, the machine had been operating normally immediately prior to a planned maintenance shut-down by the supply authorities. All householders had been warned and there was no great hassle involved. However, when power was restored a couple of hours later, the machine was dead. I didn’t attach much importance to this initially, writing it off as mere coincidence. And it might have been too but what I found made me think. With the previous jobs still fresh in my mind I went through the power supply in short order; the fuse, safety resis­tor, and rectifier were all intact, with the usual 300V plus out of the rectifier. Nor could I find anything obviously wrong with the voltage selector IC. With all those items cleared, suspicion fell on the starter network. This consists of four resistors (R1102, R1103, R1123, and R1124) across the rectifier output and a 1µF 400V electroly­tic capacitor from the junction of R1103 and R1123. The arrange­ ment is broadly similar to many starter circuits used in TV sets. And a common fault is an open circuit or high value resistor. In this case, however, all the resistors checked out OK, leaving the capacitor as the prime suspect. And so it proved to be. When I pulled it out and checked it, I could get no reading at all on the capacitance meter. So that was an easy one; a new capacitor and the machine came good. SATELLITE SUPPLIES Aussat systems from under $850 SATELLITE RECEIVERS FROM .$280 LNB’s Ku FROM ..............................$229 LNB’s C FROM .................................$330 FEEDHORNS Ku BAND FROM ......$45 FEEDHORNS C.BAND FROM .........$95 DISHES 60m to 3.7m FROM ...........$130 LOTS OF OTHER ITEMS FROM COAXIAL CABLE, DECODERS, ANGLE METERS, IN-LINE COAX AMPS, PAY-TV DECODER FOR JAPANESE, NTSC TO PAL TRANSCODERS, E-PAL DECODERS, PLUS MANY MORE For a free catalogue, fill in & mail or fax this coupon. ✍     Please send me a free catalog on your satellite systems. Name:____________________________ Street:____________________________ Suburb:_________________________ P/code________Phone_____________ L&M Satellite Supplies 33-35 Wickham Rd, Moorabin 3189 Ph (03) 553 1763; Fax (03) 532 2957 August 1994  43 SERVICEMAN’S LOG – CTD I gave it a routine clean and lube and returned it to the customer. But where did the mains shut-down come into this? I have no doubt that the capacitor was on its last legs anyway and it is important to appreciate that power is applied to this part of the circuit at all times, whether the machine is being used or not. Only when power is turned of at the mains is the voltage across the capacitor removed. My theory is that this voltage contributed to a certain amount of “forming” of the capacitor – enough to maintain a small amount of capacitance which was sufficient to allow the system to start. Removing this voltage for a couple of hours was the last straw that sank the camel’s hump. But, of course, it’s only a theory. Auto voltage selector Finally, this might be as good a time as any to expand on the auto voltage selector system. It is designed to allow the machine to work on a very wide range of voltages, although there is no mention of this in the manual. The specifications simply say “230-240V, AC, 50-60Hz.” However, a practical test confirmed that it can be plugged into 110V (which I have available in the workshop) and still operate quite normally, without any adjustments. There is nothing especially new about this concept; it has been around in many TV sets for several years now, although the particular circuit configuration was new to me. Also, it is not something we think much about in this country, being blessed with a 240V 50Hz standard which is used virtually everywhere through­out the continent. But from a manufacturing and marketing point of view, the advantages are obvious. Not only does the one power supply suit all countries but it is even useful within some countries. This would be particularly so in countries like Japan, which has a variety of power supply systems in different areas. While the 110V 60Hz system is On Sale Now At Selected Newsagents Or buy direct from SILICON CHIP Price: $7.95 (plus $3 for postage if ordering from Silicon Chip). Order today by phoning (02) 979 5644 & quoting your credit card number; or fax the details to (02) 979 6503; or send cheque, money order or credit card details to PO Box 139, Collaroy, NSW 2097. 44  Silicon Chip the one most commonly used, many areas use 220V 50Hz. I also understand that there are some 220V 60Hz and 110V 50Hz systems. It all adds up to a real nightmare, not only for manufacturers and distributors but also for consumers who wish to move from one area to another. And to further complicate matters, the same type of power outlets are often used for both voltage systems. It doesn’t take much imagination to visualise SC the problems this can cause. SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au ORDER FORM BACK ISSUES MONTH YEAR MONTH YEAR PR ICE EACH (includes p&p) TOTAL Australi a $A7.00; NZ $A8.00 (airmail ); Elsewhere $A10 (airmail ). Buy 10 or more and get a 10% discount. Note: Nov 87-Aug 88; Oct 88-Mar 89; June 89; Aug 89; Dec 89; May 90; Aug 91; Feb 92; July 92; Sept 92; NovDec 92; & March 98 are sol d out. All other issues are currently i n stock. $A B INDERS Pl ease send me _______ SILICON CHIP bi nder(s) at $A12.95 + $5.00 p&p each (Australi a only). N ot avail abl e elsewhere. Buy five and get them postage free. $A SUBSCRIPTIONS ❏ New subscription – month to start­­___________________________ ❏ Renewal – Sub. No._______________   ❏ Gift subscription ☞ RATES (please tick one) Australia Australia with binder(s)* NZ & PNG (airmail) Overseas surface mail 2 years (24 issues) 1 year (12 issues) ❏ $A90 ❏ $A49 ❏ $A114 ❏ $A61 ❏ $A135 ❏ $A72 ❏ $A135 ❏ $A72 ❏ $A240 Overseas airmail ❏ $A120 *1 binder with 1-year subscription; 2 binders with 2-year subscription GIFT SUBSCRIPTION DETAILS Month to start__________________ Message_____________________ _____________________________ _____________________________ Gift for: Name_________________________ (PLEASE PRINT) YOUR DETAILS Your Name_________________________________________________ (PLEASE PRINT) Address___________________________________________________ Address______________________ _____________________________ State__________Postcode_______ ______________________________________Postcode___________ Daytime Phone No.____________________Total Price $A __________ ❏ Cheque/Money Order ❏ Bankcard ❏ Visa Card ❏ Master Card 9am-5pm Mon-Fri. Please have your credit card details ready ______________________________ Card expiry date________/________ Card No. Phone (02) 9979 5644 Signature OR Fax (02) 9979 6503 Fax the coupon with your credit card details 24 hours 7 days a week Mail coupon to: OR Reply Paid 25 Silicon Chip Publications PO Box 139, Collaroy 2097 No postage stamp required in Australia August 1994  53 A long-wave AM receiver for aircraft weather information This simple receiver uses two ICs & will pick up airport weather beacons in the LW band. Use it to receive up-to-the-minute weather reports. It runs off a 9V battery & is easy to build. By DARREN YATES If you’re interested in aircraft or flying then you’ll no doubt already have a receiver that taps into the airport frequen­cies around the country. You can always pick up interesting information, particularly during aircraft emergencies and bush­fires. Information on the strength and direction of 54  Silicon Chip the recent NSW fires was broadcast by pilots back to ground bases and to nearby airports on this band. However, there is another band which gives up-to-the-minute weather and visibility information and these stations can be found on the LW (long-wave) band and are known as Weather Beacons. They often contain Morse code information along with a recorded message about the current temperature, visibility and cloud levels and current usage of a particular airport. The weather beacon at Sydney International Airport even has a computerised voice broadcasting this information. This band is located below the AM broadcast band and ex­ t ends from around 190kHz up to 450kHz. This low-cost long-wave receiver is designed to pick up this band and the bottom of the AM broadcast band, enabling it to pick up Sydney’s ABC Radio National station at 576kHz. Its frequency coverage extends from below 200kHz up to 580kHz. It uses D1 1N4004 Q1 BC548 E C 10 16VW 100 16VW 1.5k B S1 9V A LED1 RED 470  IC1 ZN414,YS414 IN COM L1 220pF 1 VOLUME VR2 10k RF GAIN VR1 10k .033 100k 0.1 100k K 1 63VW OUT  3 8 IC2a LM358 100k Q2 BC337 B 5 1 2 6 IC2b E B Q3 BC327 1k L1 = 200T, 0.2mm DIA ENCU WIRE WOUND ON A 10mm DIA FERRITE ROD 85mm LONG 1 WEATHER RADIO YS414 IN OUT ZN414 IN COM COM 100 16VW E 7 4 100k C 10  C 8 0.1 B OUT E C A K VIEWED FROM BELOW Fig.1: the circuit is essentially a TRF (Tuned Radio Frequency) design based on a ZN414 radio IC. This tunes over the long-wave band & feeds the recovered audio to VR2. The audio stages comprise IC2a & IC2b which drives a pair of complementary emitter followers (Q2 & Q3). just two low-cost ICs and three transistors. Sensitivity of the receiver is very good – Sydney’s beacon could be picked up without an external antenna from the author’s home in Penrith and Richmond Air Base was no problem at all. Circuit description Let’s take a look at the circuit of the Weather Radio, as shown in Fig.1. As you can see, it’s quite straightforward, using a ZN414 TRF receiver in the front end and an audio amplifier to drive the loudspeaker (TRF stands for Tuned Radio Frequency). Looking at the circuit, the ferrite rod antenna L1 and variable capacitor gang VC1 form a parallel resonant circuit which tunes the frequency of interest. The tuned frequency is fed to IC1, the ZN414 . This IC contains more than a dozen transis­tors which amplify and detect the RF and then amplify the recov­ered audio. The output appears across, and is filtered by, a .033µF capacitor. The 10kΩ pot VR1 applies DC via a 100kΩ resistor to the tuned circuit which enables the IC to vary the RF gain. IC1 only requires about 1.3V at very low current to work, so the 470Ω resistor provides the load for the circuit as well as supplying the power to it. Q1 and LED 1 form a simple voltage regulator which provides a constant 1.3V output across the 10µF capacitor to power IC1 (via the OUT pin). From the 470Ω resistor, the output signal is AC-coupled to the 10kΩ volume potentiometer, VR2, and then to the audio ampli­fier. This consists of an LM358 (or TL072) dual op amp and two complementary transistors. The first op amp (IC2a) is connected as an non-inverting amplifier with a gain of 101, as set by the 100kΩ feedback resistor from pin 1 to pin 2. Pin 1 of IC2a then drives IC2b. This op amp drives complementary transistors Q2 and Q3 directly and they operate in class B mode, without any quies­cent current to minimise crossover distortion. However, the resulting harmonic distortion is low since the transistors are included in the feedback network PARTS LIST 1 PC board, code 06107941, 102 x 44mm 1 57mm 8Ω loudspeaker 2 10kΩ log potentiometers (VR1,VR2) 1 60-160pF tuning gang (VC1) 1 85mm length of ferrite rod 6 metres of 0.2mm enamelled copper wire 3 knobs 4 100mm plastic cable ties 1 plastic utility case, 158 x 99 x 53mm 1 front panel artwork 1 miniature SPDT switch (S1) 1 9V battery snap connector 1 9V alkaline battery Semiconductors 1 ZN414 TRF radio (IC1) 1 LM358, TL072 op amp (IC2) 1 BC548 NPN transistor (Q1) 1 BC337 NPN transistor (Q2) 1 BC327 PNP transistor (Q3) 1 5mm red light emitting diode (LED1) 1 1N4004 rectifier diode (D1) Capacitors 2 100µF 16VW electrolytic 1 10µF 16VW electrolytic 3 1µF 63VW electrolytic 2 0.1µF 63VW MKT polyester 1 .033µF 63VW MKT polyester Resistors (1%, 0.25W) 4 100kΩ 1 470Ω 1 1.5kΩ 1 10Ω 1 1kΩ Miscellaneous Screws, nuts, washers, solder. August 1994  55 10uF .033 IC1 100uF Q2 1uF VC1 4 5 6 7 8 9 1uF 1 100k 7 D1 IC2 LM358 8 100uF VOLUME VR2 9 3 Q3 100k 1k 0.1 4 10  1.5k 100k 1 2 100k 470  Q1 RF LEVEL VR1 5 0.1 6 1uF 1 2 3 BATTERY NEGATIVE LED1 SPEAKER BATTERY POSITIVE L1 Fig.2: install the parts on the PC board as shown here & take care with IC1 as it looks identical to a TO-92 transistor. VC1 has its two sections connected in parallel to give a range of 0-220pF, while the leads to the ferrite rod antenna must be kept well away from the loudspeaker & the rest of the circuit. of the op amp and since the overall gain of this stage is a minimum; ie, 100% negative feed­back and therefore, unity gain. To maintain high frequency stability in the complementary emitter follower output stage (comprising transistors Q2 & Q3), a Zobel network con­ sisting of a 10Ω resistor and a 0.1µF capacitor is connected across the loudspeaker. Power is supplied from a 9V battery with diode D1 providing reverse polarity protection. Note that since IC1 requires only a low voltage and because the supply voltage to the audio amplifier is not critical, you could easily run the circuit from a 6V supply. However, to do this you would need more space to fit the batteries into the case. Construction Most of the components for the Weather Radio are installed on a PC board coded 06107941 and measuring 102 x 44mm. This is then mounted inside a standard plastic case measuring 158 x 99 x 53mm. The PC board is mounted on one side of the case (behind the front panel), as shown in the photographs. Before you begin any soldering, check the board thoroughly for any shorts or breaks in the copper tracks. These should be repaired with a small artwork knife or a touch of the soldering iron where appropriate. When you’re happy that everything appears OK, you can solder in the resistors and diodes, followed by the capacitors. This done, install the transistors and IC1 and IC2. Note that IC1 has three leads and looks identical to the transistors, so check this component carefully when installing it on the board. Tuning gang Fig.3: this is the full-size etching pattern for the PC board. 56  Silicon Chip The tuning gang is a plastic dielectric type with two sections of 0-60pF and 0-160pF. These two sections are connected in parallel on the PC board to produce a variable capacitor of 0-220pF, as shown on the circuit of Fig.1. The capacitor is secured to the PC board with two 2.5mm screws and then its three tags are soldered to short lengths of tinned copper wire The ferrite rod antenna is attached to the rear of the case using plastic cable ties. Additional cable ties should be used to lace the wiring to the pots, switch, loudspeaker & LED to maintain a tidy appearance & to prevent tuning drift. which are passed through the associated holes in the board and soldered in place. Drilling the case Before you go much further, you will need to do some work on the plastic case. The board is mounted on one side of the case, as mentioned above, along with the RF Gain and Volume control potentiometers (VR1 & VR2). The loudspeaker is mounted in the bottom of the case and when the lid is attached, the whole assembly is turned upside down so that the loudspeaker faces up. You will need to drill holes for the loudspeaker grille, the PC mounting pillars, the knob shafts, power switch and the LED. The latter two items are mounted on one end. Perhaps the easiest approach to drilling the case is to use the front panel artwork (included with this article) as a template. You will need to drill a circular pattern of holes for the loudspeaker and four holes to mount the ferrite rod antenna which we will now discuss. The tuning coil L1 is wound as a single layer of 200 turns of 0.2mm enamelled copper wire on an 85mm length of ferrite rod 10mm in diameter. If you need to cut the rod to this length, the way to do it is as follows. File a nick around the rod at the point you wish to cut it and then snap it off. If you try cutting it in any other way it is sure to shatter. Start off by winding one turn around the rod about 13mm from one end and anchor it with some sticky tape. This done, continue by winding on the 200 turns. It doesn’t need to be exactly 200 turns so if you’re out by a few turns either way, it won’t matter too much. RESISTOR COLOUR CODES ❏ No. ❏  4 ❏  1 ❏  1 ❏  1 ❏  1 58  Silicon Chip Value 100kΩ 1.5kΩ 1kΩ 470Ω 10Ω 4-Band Code (1%) brown black yellow brown brown green red brown brown black red brown yellow violet brown brown brown black black brown 5-Band Code (1%) brown black black orange brown brown green black brown brown brown black black brown brown yellow violet black black brown brown black black gold brown This close-up view shows the PC board after all the parts have been installed & the wiring completed. Note that shielded audio cable must be used for all connections between the pots (VR1 & VR2) & the PC board. The loudspeaker can be secured inside the case using super-glue. Make sure that the turns are tight and close to each other. Once you’ve wound the turns, anchor the other end with some more sticky tape and then carefully cover the whole winding with tape. This done, strip the enamel from both ends of the coil and tin them with solder. The rod is attached to the side of the case opposite the PC board, as shown in the photos, and is secured using two plastic cable ties. Before the PC board can be mounted in the case, you will need to fit a suitable shaft to the tuning gang, to enable a knob to be fitted. We did this using a fairly crude but effective method – super-glue. First, we roughened the end of the tuning gang shaft with a file and did the same to a 15mm long tapped metal spacer. A dab of super-glue was then applied to the tuning shaft and the two Fig.4: this fullsize front-panel artwork can be used as a drilling template for the various controls & the indicator LED. were butted together and then put to one side to allow the glue to dry. This method works sur­prisingly well. Mount the PC board using metal pillars, screws, nuts and lockwashers. Finally, wire in the two pots and the speaker and then fit knobs to the shafts of the pots and the tuning gang. The LED and speaker can be mounted (permanently) with super-glue, while the battery can be held in place using double-sided sticky tape. Alternatively, you can make up a metal bracket to hold the battery in position. Testing Before testing the receiver, check your work thoroughly for any possible errors. Once everything is correct, connect your multimeter across the On/ Off switch. This places the multimeter in series with the supply to allow you to measure the current drain. Select a low current range (200mA) on the multimeter, then connect the battery and check the current reading. Depending on where the tuning gang is sitting, and with the volume control well down, you should hear some low-level static coming through the speaker. The current consumption should be about 10mA. Any more than 20mA and you should switch off imme­ diately and check for errors. Now advance the volume control to about half way and then advance the RF gain control as well. The static should rise markedly and the loudspeaker may even squeal, depending on the setting of the tuning gang. If everything is OK, you should be able to tune across the long-wave band and pick up one or two low frequency AM broadcast stations as well. The weather beacons will be below these. Adjust the RF gain control to increase the signal level until the circuit starts to oscillate (squeal) and then wind it back a little. Next increase the volume until it is at a comfortable level. SC RF gain 190 580 Weather Radio Volume Tuning Frequency (kHz) August 1994  59 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au AMATEUR RADIO BY GARRY CRATT, VK2YBX Using 2-line Keplerian elements to track amateur satel­lites Several low-cost computer programs are now available to accurately keep track of satellites. This article explains the origin of this data & shows how easy it is to put it to use. Considering the increasing interest in satellite reception by amateurs, it is not surprising that the demand for 2-line orbital elements to predict the location of a satellite at any particular time is also increasing. In addition, the prolifera­ tion of personal computers makes the calculation and display of satellite data in real time a relatively simple matter. Fortunately, Keplerian data is freely available to ama­ teurs, primarily through computer bulletin boards. However, in order to properly understand Keplerian elements, some history is in order. Orbital mechanics, as applied to artificial earth satellites, is based largely on celestial mechanics, initially founded on the work of James Kepler and Issac Newton and expanded on by mathematicians during the 18th and 19th centuries. Eventu­ally, the theory became so accurate that when astronomers ob­served discrepancies between their observations and the theoreti­cal results, they were able to determine that the errors were caused by variations in their astronomical timescales. In 1956, astronomers changed the time scale from one based on the rotation of the Earth (universal time) to a new scale based on the orbital motion of the Earth around the Sun (ephemeras time). With the advent of atomic timekeeping, astronomical timescales Fig.1: this “screen-grab” shows the menu page for the STSORBIT PLUS satellite tracking program. were eliminated completely and the ability to predict orbital locations became supremely accurate. Computer programs One of the spin-off products of the US space effort was the creation of the computer program known as “STSORBIT PLUS”, de­signed and used by NASA to track satellites, including the Space Shuttle. There is now a public domain version of this program available on many computer bulletin board services. In addition, AMSAT offer their own program, “INSTANT TRACK”. By “plugging in” the latest data sets or Keplerian ele­ments, it is possible to very accurately predict the location of a satellite at any particular time. This is very useful for tracking amateur satellites in polar orbits and satellites used for rebroadcasting television programs that are not located in geostationary orbit. In theory, the centrifugal force resulting from the speed of a satellite is balanced against the gravitational pull of the Earth and this keeps a satellite orbit constant. In practice, however, gravitational forces from the Sun and the Moon, plus atmospheric drag (applicable to satellites at an altitude of 1000km or less), have the effect of degrading the orbit. For this reason, it is important to use current elements. Moreover, some satellites are deliberately launched into low Earth or polar orbits, in order to provide coverage over all major land masses. These satellites might orbit the Earth once every 90 minutes or so, so a computer “prediction” for future passes is of paramount importance to amateur operators. Table 1 shows the primary orbital August 1994  63 Table 1: Keplerian Elements Data for each satellite consists of 3 lines in the following format: Name 1 NNNNNU NNNNNAAA NNNNN.NNNNNNNN + .NNNNNNNN +NNNNN-N N NNNNN 2 NNNNN NNN.NNNN NNN.NNNN NNNNNNN NNN.NNNN NNN.NNNN NN.NNNNNNNNNNNNNN COLUMN DESCRIPTION LINE 1 1 Line number of element data 2 Blank 3-7 Satellite number 8 Not used 9 Blank 10-11 International designator (last 2 digits of launch year) 12-14 International designator (launch number of the year) 15-17 International designator (piece of launch) 18 Blank 19-20 Epoch year (last 2 digits of year) 21-32 Epoch day (Julian day & fractional portion of the day) 33 Blank 34-43 1st time derivative of mean motion (0.1 revs per day) 44 Blank 45-52 2nd time derivative of mean motion (0.01 x revs per day) 53 Blank 54-61 Radiation pressure co-efficient 62 Blank 63 Ephemeras type (specified ephemeras theory used) 64 Blank 65-68 Element number 69 Checksum LINE 2 1 Line number of element data (ie 2 for line 2) 2 Blank 3-7 Satellite number 8 Blank 9-16 Inclination in degrees 17 Blank 18-25 Right ascensions of the ascending node in degrees 26 Blank 27-33 Eccentricity in tenths of units 34 Blank 35-42 Argument of perigee in degrees 43 Blank 44-51 Mean anomaly in degrees 52 Blank 53-63 Mean motion in revolutions per day 54-68 Revolution number at epoch 69 Checksum 64  Silicon Chip parameters used in satel­lite data elements, while Table 2 shows actual 2-line data elements for a few popular satellites. In order to make use of these Keplerian element sets, which can be downloaded from their international source on a weekly basis, it is first advisable to obtain a copy of a suitable tracking program such as “ TRAKSAT ”, “ INSTANT TRACK ”, “STSORBIT PLUS” or “PC-TRACK”. As elements are distributed, they are allo­cated a incremental number such as TLE428 (the last three numbers signify the set). Of course, downloading Keplerian elements from computer bulletin boards does require some level of computer literacy; ie the ability to create directories, download data, etc. Running STSORBIT PLUS STSORBIT PLUS has the ability to track multiple satellites in real time. Fig.1 shows the menu page for STSORBIT PLUS. At initial installation, create a directory called “STS”. After installation, the program will issue a prompt for local UTC time offset (eg, Sydney has +10 hours difference). After complet­ing this, the main menu of STSORBIT PLUS will present a variety of options. The first and most important step is to set the Earth sta­tion location. F10 from the main menu gives a sub-menu where F2 allows the user to set new local co-ordinates. The user can then insert a capital city location, which gives the program a base for position calculations. To do this, the program searches its internal database of over 1500 locations for a match. F6 selects the map type used to view the world and satel­lite orbits. Toggling the F6 key allows selection of either World, Ortho, Quad or Zoom. For slow PCs, the World map is the best selection as the program draws a very impressive and complex map of the world, complete with city names and rivers. After this initial setup, current Keplerian elements must be down­ loaded from an accurate source. These should be downloaded into the same directory as STSORBIT PLUS. To import the 2-line elements in order to track a satellite, select F2 from the main menu, then enter the 2-line element filename and the satellite name. The program will then display relevant data on the selected satellite. By now simply keying ENTER, the program will draw a map of the world and display the orbital position of the selected satellite in real time; eg, the track taken by polar orbiting satellites can easily be seen. By selecting F3 from the main menu, a “pass prediction” will be displayed for the selected location. Where to buy software Other features of this and similar programs are beyond the scope of this article. For those interested in obtaining regis­tered copies of the software mentioned in this article, the following will be of interest: • TRAKSAT is available from the author: Paul E. Traufler, 111 Emerald Drive, Harvest, AL 35749, USA. A non-registered version costs $US10, while a laser-printed operations man­ ual will cost an additional $US15. A registered version costs $US25 (add $US5.00 for shipping and handling to Australia). Commercial licenses are also available from $US50. • PC TRACK version 3.0 can be obtained from: Thomas C. John­son, 9920 S Palmer Road, New Carlisle, Ohio 45344, USA. It costs $US45 + US15 for shipping and handling. • STSORBIT PLUS is available from the Satcom BBS (phone 02 905 0849) or from the author: David H. Ransom Jr, 7130 Avenida Altisima, Rancho Palos Verde, CA 90274, USA (check costs with author before ordering). An additional map database is also available from the author for $US10. SC Allow 3-6 weeks for delivery. Table 2: Sample 2-Line Elements Optus B1 1 22087U 92054A 94191.61718487 -.00000112 00000-0 10000-3 0 4146 2 22087 0.0916 108.4637 0002995 329.9719 232.0275 1.00270935 18457 Intelsat 5 F-8 1 14786U 84023A 94190.52379876 .00000053 00000-0 00000+0 0 6425 2 14786 2.7646 69.4432 0046903 321.8887 264.9499 1.00275209 1695 Oscar 10 1 14129U 83058B 94176.41110075 -.00000306 00000-0 10000-3 0 2893 2 14129 27.0856 321.0039 6024383 189.2195 150.8337 2.05882336 54986 UoSat 2 1 14781U 84021B 94190.56754595 .00000133 00000-0 30431-4 0 7063 2 14781 97.7855 204.2441 0011153 193.8486 166.2415 14.69228336553597 Noaa 10 1 16969U 86073A 94193.01550214 .00000098 00000-0 60319-4 0 7694 2 16969 98.5052 201.2581 0012183 257.8226 102.1588 14.24897002406033 RS-10/11 1 18129U 87054A 94191.83829016 .00000023 00000-0 90572-5 0 9258 2 18129 82.9253 311.3579 0011286 326.8723 33.1722 13.72339043353150 Satellite b p y v Apogee a F2 ra ea F1 Perigee x rp Fig.2: this diagram shows the major orbital parameters of a satellite: a = semimajor axis; b = semiminor axis; ra = apogee radius; rp = perigee radius; F1 = focal point 1; F2 = focal point 2. Fig.3: STSORBIT PLUS can display data in several map formats, including World map as shown at left & Ortho map as shown at right. Note that the displays are in colour & are not shown to best advantage here. August 1994  65 Dual diversity tuner for FM microphones; Pt.2 Construction & alignment of the Dual Diversity Tuner does not require any special equipment or tools apart from an alignment tool & a tuning wand which can be easily made. There is little wiring involved since most of the parts are assembled onto PC boards. By JOHN CLARKE The prototype for the SILICON CHIP Dual Diversity Tuner was built into a 1-unit high black anodised rack case with screen printed front and rear panels. Two PC boards are used to accom­modate the components: (1) a main board coded 06307941 and meas­ uring 207 x 161mm; and (2) a satellite board coded 06307942 and measuring 28 x 49mm. The latter carries the RF preamplifier components and is shielded by a boxed section made from 15mm-high single-sided PC board. A further strip of single-sided PC board divides this box into two sections, to provide additional shielding for the RF preamplifier components. Following assembly, the shielded RF preamplifier module is mounted 66  Silicon Chip directly on the main PC board. Begin construction by comparing your PC boards against the published patterns to verify that all tracks are intact and that there are no shorts between tracks. Some holes may need to be enlarged to accept the relevant components; eg, the mounting holes for L10, T1, T2, VC2 and for the PC stakes. The hole used to secure the tab of REG1 to the PC board may also need to be enlarged to accept the mounting screw. Note that there are only four holes in the RF preamplifier board. These allow short lengths of tinned copper wire to pass through from the track (top) side of the board and through the main board for both mounting and earthing purposes. Unlike the main PC board, all components in the RF preamplifier are mounted on the track side of the board. Main board assembly Fig.7 shows the overlay diagram for the main PC board. Begin construction by inserting PC stakes at all external wiring points and at test points TP1 & TP GND. This done, install all the low profile components such as the links, resistors and ICs. Table 2 shows the resistor colour code but it’s also a good idea to check them on your multimeter as some of the colours can be difficult to decipher. Take care to ensure that the ICs are all oriented correctly and that each is mounted in the correct location. The 5W resistor is mounted about 1mm proud of the PC board to allow the air to circulate beneath it for cooling. Mount the diodes next but again be sure to use the correct type at each location. Diodes D1-D4 are marked with the BA482 type number and are smaller than the 1N4148 diodes used for D6-D8. D5, the BB119 varicap, looks very similar to a 1N4148, so be sure to check its type number carefully 6 1 5 4 2 BASE DIAGRAM TOP VIEW L1-L4 6T, 0.5mm DIA ENCU WIRE ON PHILIPS 4313 020 40031 BALUN COR 3 5 before installing it on the board. Take care with the orientation of each diode and note particularly that D2 and D3 face in opposite directions. The capacitors can now be installed. There are several different types used on the PC board, so make sure that you always use the correct type at each location. Ceramic capacitors are mostly used in the FM tuner section of the board, while MKT and electrolytic capacitors are used throughout the remainder of the circuit. Table 1 lists the relevant capacitor codes and their corresponding values. Make sure that the electrolytics are cor­rectly oriented. Note particularly that the 10µF electrolytic and 0.1µF MKT capacitors near IC3 are installed with their bodies flat against the PC board. You will need to bend their leads through 90° to do this, however. The capacitors are mounted in this way so that the leads to LEDs 1-3 in the bargraph display can pass over the top of them – see photo. Similarly, the 4700µF capacitor near REG1 is also installed lying down –see Fig.6. Its body should be secured to the PC board using silicone rubber compound to prevent possible lead damage due to vibration. The 3-terminal regulator (REG1) is mounted on a small heat­sink. Smear the mating surfaces with heatsink compound before bolting the assembly to PC board. Coils Fig.6 shows the coil winding details. L1-L4 are wound onto a balun former 4 2 3 6 1 2 3 L10 F1, S1 WINDING: PINS 6 AND 1, S2 10.5T, 0.5mm DIA ENCU WIRE T2 WINDINGS: PINS 1, 2 AND 3, 3T, BIFILAR 0.25mm DIA ENCU WIRE PINS 5 AND 4, 4T, 0.5mm DIA ENCU WIRE COILS T1, T2 AND L10 WOUND ON NEOSID TYPE 'A' COIL ASSEMBLY 99-007-96 (BASE, FORMER, CAN AND F29 SLUG) 4 5 6 T1 WINDINGS: PINS 4 AND 6, 3.5T, 0.5mm DIA ENCU WIRE PINS 3 AND 2, 2T, 0.5mm ENCU WIRE NOTE: WIND COILS IN SAME SENSE AS ABOVE L5 1.5T L6 6.5T 1 F2 L7 8.5T L5-L9 WOUND ON 4mm DIA MANDREL USING 0.6mm DIA ENCU WIRE L8 1.5T L9 6.5T Fig.6: this diagram shows the winding details for all the coils in the Diversity Tuner. Be sure to use the wire diameter specified for each coil & make sure that each winding is wound in the direction shown. A complete description on winding each coil also appears in the text & this should be closely followed. (six turns of 0.5mm-dia. ECW), while L5-L9 are air cored and are made by winding the appropriate number of turns of 0.6mm ECW onto a 4mm (5/32-inch) mandril. You can use a drill bit for this. Note that L5, L6 and L7 are wound in a clockwise direction, while L8 and L9 are wound anticlockwise. Wind each turn close to the previous turn as shown in the diagram. T1, T2 and L10 are wound on the Neosid coil formers. Begin by inserting the coil formers into the bases, then wind T1 using 0.5mm ECW exactly as shown. Note that the two windings are wound in opposite directions and should be immediately adjacent to each other. Make sure that you get the winding phases (directions) correct, otherwise the local oscillator won’t work. Note that the enamelled copper wire is easily terminated on the base pins by August 1994  67 S2 .01 D7 10k .01 1 .01 47  0.1 0.1 0.1 .033 K 1.5k 220k IC3 LM3914 GND 10uF 1 A 10k 10k 220k 10k LED1 LED2 LED3 LED4 LED5 LED6 LED7 LED8 LED9 LED10 0.1 2.7k 1.2M 10k 10k TP GND VR3 1 0.1 3.9K 10uF 2.7k 1 330k IC5 LM393 0.1 VR2 82 5W 10k 2.7k TP1 VR1 1uF IC4 LM358 10  300  4.7k 56k 4.7k 1.5k 0.1 47k 220k .001 0.33 27k 1 1 IC2 TDA1576 750  10k D8 0.1 0.1 0.1 33pF .0068 100k 33k 22k IC6 LF353 100k 560pF 39k IC11 4017 X1 X2 33pF L10 100k SHIELD 47k 10  47uF 1 T2 T1 D5 REG1 7812 0.1 3.3k 33pF 10  0.1 .01 15pF 10  390pF 1 .01 390pF 1.8pF 33pF 6.8pF L9 IC1 TDA1574 220k .01 10 .01 220k VC2 6.8pF L8 47uF IC8 74C14 .001 33pF 10uF .01 10  3.9pF .01 1 .01 .001 SHIELD L6 10  SHIELD VC1 IC12 7555 L5 27pF .001 4700 0.1 Q1 .001 1 .01 220k 390 L7 2.2k 22k .01 IC7 4066 .001 SHIELD D9-D12 .018 IC9 7555 .01 2.2k 12.6VAC 0.1 D4 .01 D6 L4 D1 SHIELD 10k ANT B L3 .01 L1 D3 10k .01 L2 2.2k .01 .01 IC10 4013 D2 .01 2.2k ANT A 10  GND 10  GND O/P 10uF 1 47pF VR4 A K A K LED11 RED LED12 GREEN 1 Fig.7: install the parts on the main PC board as shown in this wiring diagram. The RF preamplifier board (top, left) is also mounted on the main board & is enclosed in a shield made from single-sided blank PCB material (see Fig.9). Note that the parts in the RF preamplifier are installed on the copper side of the board, with connections to the main board made via feedthrough capacitors & wire links. 68  Silicon Chip Keep all component leads as short as possible when assembling the PC board, particularly around the FM tuner stages at the top of the PC board. The 4700µF electrolytic capacitor at bottom right should be secured to the board using silicone rubber compound to prevent its leads from breaking. heating the wire with your soldering iron until the enamel melts and then applying solder. T2 must be wound with extreme care. To wind this coil, first take the 250mm-length of 0.25mm ECW, cut it in half and twist the two wires together using a hand drill and a vyce until there is about one twist per millimetre. This done, solder one wire end (S1) to pin 3 of the base and the adjacent end (S2) to pin 2. Wind on three turns as shown, then use your multimeter to identify the other end of the wire connected to pin 3. Solder this end (F1) to pin 2 and connect the remaining end (F2) to pin 1. The other winding between pins 4 & 5 uses four turns of 0.5mm ECW. It must be wound in the opposite direction to the bifilar winding. Note that Fig.6 shows a gap between each turn for the bi­filar winding but this has only been done for the sake of clari­ty. In practice, the turns should all be close-wound (ie, imme­diately adjacent to each other), while the top winding should be immediately adjacent to the bifilar winding. Coil L10 (the quadrature coil) consists of just a single winding. Wind it in the direction shown and terminate the top and bottom leads to pins 1 & 6 respectively. Once wound, the coils can all be installed on the PC board. Mount L8 & L9 so that they sit about 1mm above the board surface. T1, T2 and L10 can only be installed one way on the PC board since their middle pins are offset, but make sure that you don’t get them mixed up. A metal can is then fitted over each coil and is secured by soldering its lugs to the earth pattern of the board. Finally, the ferrite slugs can be screwed into the formers using a plastic alignment tool (available from TABLE 1: CAPACITOR CODES Value 0.33µF 0.1µF .033µF .018µF .01µF .0068µF .001µF 560pF 390pF 47pF 33pF 27pF 15pF 6.8pF 3.9pF 1.8pF IEC 330n 100n 33n 18n 10n 6n8 1n0 560p (n56) 390p (n39) 47p 33p 27p 15p 6p8 3p9 1p8 EIA 334 104 333 183 103 682 102 561 391 47 33 27 15 6.8 3.9 1.8 your electronic parts retailer). Do not use a screwdriver for this job since this will crack the ferrite. August 1994  69 S1 NEUTRAL (BLUE) CORD GRIP GROMMET FRONT PANEL SECONDARY LED12 K ANTENNA 'A' PAL SOCKET LEDS1-10 50  COAX A ANTENNA 'B' PAL SOCKET LED11 AUDIO OUTPUT RCA SOCKET 12.6VAC C NO S2 NC REAR PANEL VR4 COVER WIRING OF S1 AND F1 WITH INSULATING SLEEVING BROWN BLUE POWER TRANSFORMER EARTH LUG EARTH (GREEN/ YELLOW) ACTIVE (BROWN) ACTIVE (BROWN) 250mA FUSE PRIMARY Fig.8: use 240VAC-rated cable for all mains wiring & insulate all exposed terminals on the fuseholder & switch S1 using heatshrink tubing (see text) to prevent any possibility of accidental shock. The mains cord earth lead (green/yellow) must be soldered to an earth lug which is securely bolted to chassis. 70  Silicon Chip The LED bargraph display and LEDs 11-12 can be installed now. The 3mm LEDs used for LED 11 and LED 12 are installed with their leads untrimmed, so that the LEDs can later be bent over and pushed through matching holes in the front panel. Watch the polarity of the LEDs – the anode lead is the longer of the two. The bargraph (LEDs 1-10) must be mounted so that the front of the display is 14mm from the edge of board. This is done to ensure that it will later sit flush with the front panel – see Fig.8. To achieve this, it will be necessary to extend each lead using a short length (about 25mm) of tinned copper wire. Bend the leads at right angles about 6mm above the board before soldering the bargraph in position. As before, take care with the polarity of this device. As with individual LEDs, the anode lead of each LED in the bargraph is the longer of the two and it is a good idea to mark the anode end of the device before extending the lead lengths. RF preamplifier The RF preamplifier board can be assembled now – see Fig.7. Before This photo shows the method used to mount the bargraph LEDs (LEDs1-10). The lead lengths must all be extended using short lengths of tinned copper wire & the leads must all be bent through 90° after soldering so that the bargraph mates with its front panel cutout. mounting any of the parts, it must be mounted copper side up on the main PC board and secured by passing short wire links through the four mounting points (indicated by solid dots on Fig.6). Solder these links at each end to the surrounding copper pattern to secure the two boards together. This done, the parts can be mounted onto the preamplifier board by soldering their leads directly to the undrilled copper lands (ie, the parts are mounted on the copper side of the board). Keep all leads as short as possible and take TABLE 2: RESISTOR COLOUR CODES ❏ No. ❏   1 ❏   1 ❏   6 ❏   3 ❏   1 ❏   2 ❏   1 ❏   1 ❏   1 ❏   2 ❏ 10 ❏   2 ❏   1 ❏   1 ❏   3 ❏   4 ❏   2 ❏   1 ❏   1 ❏   1 ❏   1 ❏   9 Value 1.2MΩ 330kΩ 220kΩ 100kΩ 56kΩ 47kΩ 39kΩ 33kΩ 27kΩ 22kΩ 10kΩ 4.7kΩ 3.9kΩ 3.3kΩ 2.7kΩ 2.2kΩ 1.5kΩ 750Ω 390Ω 300Ω 47Ω 10Ω 4-Band Code (1%) brown red green brown orange orange yellow brown red red yellow brown brown black yellow brown green blue orange brown yellow violet orange brown orange white orange brown orange orange orange brown red violet orange brown red red orange brown brown black orange brown yellow violet red brown orange white red brown orange orange red brown red violet red brown red red red brown brown green red brown violet green brown brown orange white brown brown orange black brown brown yellow violet black brown brown black black brown 5-Band Code (1%) brown red black yellow brown orange orange black orange brown red red black orange brown brown black black orange brown green blue black red brown yellow violet black red brown orange white black red brown orange orange black red brown red violet black red brown red red black red brown brown black black red brown yellow violet black brown brown orange white black brown brown orange orange black brown brown red violet black brown brown red red black brown brown brown green black brown brown violet green black black brown orange white black black brown orange black black black brown yellow violet black gold brown brown black black gold brown August 1994  71 iron for this job and run generous fillets of solder along the joints to hold the shield pieces in position. It is not necessary to solder along the complete perimeter; just solder the boards together where you can. The internal 38 x 12mm board should be installed with its copper side facing L5 and L6. Note that the bottom edge of this board sits about 2mm above the preamplifier board, to provide clearance for one of the transistor leads. With the shield assembly completed, the leads of the ceram­ ic feedthrough capacitors can be connected to the main board and to the RF preamplifier board using short lengths of tinned copper wire. The exception here is the .001µF feed­ through capacitor that’s connected to Q1’s source; it only has one end connected to the RF preamplifier board. The lead at the end of the capacitor on the outside of the shield is simply snipped off. The two link connections are made using 0.6mm ECW. Solder the shield pieces to the RF preamplifier board as shown in this photo & note that the internal shield piece is installed with its copper side facing L5 & L6 (to the right). The ceramic feedthrough capacitors are connected to the main board & to the RF preamplifier board using short lengths of tinned copper wire. 72  Silicon Chip 8 15 A 12 25 15 A 8 care with the orientation of Q1 – its label should face upwards and the longest lead should be adjacent to L7. Do not install the .001µF ceramic feedthrough capacitors yet, since these mount into the shield pieces. Instead, install vertical tinned copper wire links at each capacitor position so that these can later be soldered to the capacitor leads. The two longest shield pieces can now be drilled to accept the four feedthrough capacitors and the two feedthrough links. Fig.9 shows the drilling details. Clean away the copper from around the two link holes using an oversize drill to prevent any possibility of the links shorting to the copper. The copper surrounding the capacitor feedthrough holes should be left intact and tinned with solder. You are now ready to install the feedthrough capacitors. These should be pushed through so that their flanges are on the copper side of the shield pieces – see photos. This done, the metal bodies of the capacitors should be soldered to the sur­rounding copper. 9 22 27 41 53 COPPER SIDE AT REAR OF PANELS ALL HOLES 3mm DIA. REMOVE COPPER AROUND HOLES 'A' DIMENSIONS IN MILLIMETRES Fig.9: here are the drilling details for the two long shield pieces used in the RF preamplifier. Once all the feedthrough capacitors are in, the shield pieces can be soldered to the perimeter of the preamplifier board to form a complete enclosure. Use a fine-tipped soldering Final assembly The completed board assembly is now ready for installation in the case. To simplify the description, we will assume that you are building the unit from a kit which has pre-punched holes and screen-printed front and rear panels. If you are building the unit from a short-form kit, you will have to drill the holes yourself using the PC board and wiring diagram as a guide. Assuming that the holes have all been drilled, assemble the case and attach the four rubber feet to the base. This done, install the various items of hardware on the front and rear panels, then mount the PC board onto the baseplate using 5mm standoffs and 3mm screws and nuts. Check that the LED bargraph display fits neatly into the slot provided in the front panel and insert the two 3mm LEDs into their respective holes. The transformer can be mounted next; it is secured using 4mm screws and nuts. The earth lug is secured using a 4mm screw, nut and star washer. Tighten this assembly firmly, so that there is no possibility of the earth lug coming adrift. Important: scrape away the paint or anodising from around the earth lug mounting hole before installing the earth lug SILICON CHIP BOOK SHOP Newnes Guide to Satellite TV 336 pages, in paperback at $49.95. Installation, Recept­ion & Repair. By Derek J. Stephen­son. First published 1991, reprinted 1994 (3rd edition). This is a practical guide on the installation and servicing of satellite television equipment. The coverage of the subject is extensive, without excessive theory or mathematics. 371 pages, in hard cover at $55.95. Servicing Personal Computers By Michael Tooley. First pub­ lished 1985. 4th edition 1994. Computers are prone to failure from a number of common causes & some that are not so common. This book sets out the principles & practice of computer servicing (including disc drives, printers & monitors), describes some of the latest software diagnostic routines & includes program listings. 387 pages in hard cover at $59.95. The Art of Linear Electronics By John Linsley Hood. Pub­lished 1993. This is a practical handbook from one of the world’s most prolific audio designers, with many of his designs having been published in English technical magazines over the years. A great many practical circuits are featured – a must for anyone inter­ested in audio design. Optoelectronics: An Introduction By J. C. A. Chaimowicz. First published 1989, reprinted 1992. This particular field is about to explode and it is most important for engineers and technicians to bring themselves up to date. The subject is comprehensively covered, starting with optics and then moving into all aspects of fibre optic communications. 361 pages, in paperback at $55.95. Digital Audio & Compact Disc Technology Produced by the Sony Service Centre (Europe). 3rd edition, published 1995. Prepared by Sony’s technical staff, this is the best book on compact disc technology that we have ever come across. It covers digital audio in depth, including PCM adapters, the Video8 PCM format and R-DAT. If you want to understand digital audio, you need this reference book. 305 pages, in paperback at $55.95. Power Electronics Handbook Components, Circuits & Applica­ tions, by F. F. Mazda. Published 1990. Previously a neglected field, power electronics has come into its own, particularly in the areas of traction and electric vehicles. F. F. Mazda is an acknowledged authority on the subject and he writes mainly on the many uses of thyristors & Triacs in single and three phase circuits. 417 pages, in soft cover at $59.95. Surface Mount Technology By Rudolph Strauss. First pub­ lish-ed 1994. This book will provide informative reading for anyone considering the assembly of PC boards with surface mounted devices. Includes chapters on wave soldering, reflow­ soldering, component placement, cleaning & quality control. 361 pages, in hard cover at $99.00. Electronics Engineer’s Reference Book Edited by F. F. Mazda. First pub­ lished 1989. 6th edition 1994. This just has to be the best reference book available for electronics engineers. Provides expert coverage of all aspects of electronics in five parts: techniques, physical phenomena, material & components, electronic design, and applications. The sixth edition has been expanded to include chapters on surface mount technology, hardware & software design, Your Name__________________________________________________ PLEASE PRINT Address____________________________________________________ _____________________________________Postcode_____________ Daytime Phone No.______________________Total Price $A _________ ❏ Cheque/Money Order ❏ Bankcard ❏ Visa Card ❏ MasterCard Card No. Signature_________________________ Card expiry date_____/______ Return to: Silicon Chip Publications, PO Box 139, Collaroy NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details; or fax to (02) 9979 6503. semicustom electronics & data communications. 63 chapters, in paperback at $140.00. Radio Frequency Transistors Principles & Practical Appli­ cations. By Norm Dye & Helge Granberg. Published 1993. This timely book strips away the mysteries of RF circuit design. Written by two Motorola engineers, it looks at RF transistor fundamentals before moving on to specific design examples; eg, amplifiers, oscillators and pulsed power systems. Also included are chapters on filtering techniques, impedance matching & CAD. 235 pages, in hard cover at $85.00. Newnes Guide to TV & Video Technology By Eugene Trundle. First pub­ lish-ed 1988, reprinted 1990, 1992. Eugene Trundle has written for many years in Television magazine and his latest book is right up date on TV and video technology. 432 pages, in paperback, at $39.95.  Title Price  Newnes Guide to Satellite TV  Servicing Personal Computers  The Art Of Linear Electronics  Optoelectronics: An Introduction  Digital Audio & Compact Disc Technology  Power Electronics Handbook  Surface Mount Technology  Electronic Engineer’s Reference Book  Radio Frequency Transistors  Newnes Guide to TV & Video Technology $55.95 $59.95 $49.95 $55.95 $55.95 $59.95 $99.00 $140.00 $85.00 $39.95 Postage: add $5.00 per book. Orders over $100 are post free within Australia. NZ & PNG add $10.00 per book, elsewhere add $15 per book. TOTAL $A August 1994  73 This view clearly shows the three feedthrough capacitors & the feedthrough link on one side of the shield box. Note that the feedthrough capacitor on the other side of the shield box is not directly connected to the main PC board. assembly to ensure a good earth contact. Fig.8 shows the final wiring details for the tuner. Exer­cise extreme care with the mains wiring. Begin by stripping back the outer mains cord sheath so that the leads are free to reach from the back panel to the mains switch (S1) on the front panel. This done, push the mains cord through the entry hole until about 40mm of the outer sheath is inside the case and clamp it securely using a cordgrip grommet. The Neutral (blue) mains lead goes directly to power switch S1, while the Active (brown) lead goes to S1 via the fuse. The transformer primary connections go to the remaining switch contacts, while the secondary leads are twisted together and connected to the 12.6V AC input on the PC board. Note that the lead from the centre tap of the transformer is not used and can be cut off. Use heatshrink tubing to insulate the bare fuse and switch contacts to prevent accidental shock. This is done by sliding some heatshrink tubing over the leads before soldering them. After the connections have been made, the tubing is pushed over the switch and 74  Silicon Chip fuse bodies and shrunk into place using a hot air gun. The green/yellow lead from the mains cord is soldered di­rectly to the earth lug. Leave a loop in this lead so that it will be the last lead to come adrift if the mains cord is wrenched out of the grommet. Be sure to use shielded audio cable for the wiring to the pot and to the output RCA socket – see Fig.8. This shielded audio cable should be kept well away from the power transformer to prevent hum injection into the audio signal. The antenna test switch (S2) can be wired using 3-way rain­ bow cable. Note that some switches do not have the same Common, Normally Open, Normally Closed (C NO NC) pin arrangement as shown in Fig.8, so check your switch before making the connections. The PAL sockets are wired with 50Ω RF cable. Finally, use cable ties to secure the wiring as shown in the photographs. Note that the mains leads should be laced togeth­er so that if one lead comes adrift, it cannot come into contact with the case. Before applying power, it is a good idea to check your work carefully for wiring and component placement errors. In particu­ lar, check that the mains wiring is correct, that all parts are correctly oriented, and that there are no vacant holes on the PC board. Note that there are two test points on the PC board: TP1 and TP GND. You can connect the negative lead of your multimeter to TP GND for all subsequent measurements. Voltage checks Apply power and check that +12V appears at the output of REG1. If it is below this, switch off immediately and check the regulator circuit and for shorts on the +12V rail. If the voltage is correct, check that +12V is present on the supply pin of each IC (ie, pin 15 of IC1; pin 1 of IC2; pins 3 & 9 of IC3; pin 8 of IC4, IC5, IC6, IC9 & IC12; pin 14 of IC7, IC8 & IC10; and pin 16 of IC11). The source of Q1 should be at about 4V, which sets the quiescent current through the device at about 10mA. You should also be able to measure 4V at G1 of Q1 (and on the other side of the 220kΩ gate resistor). G2 of Q1 should be at about +12V unless the tuner happens to be tuned to a very strong signal. This is very unlikely at this stage since the tuner has not been aligned and no antenna is attached. Fig.10 (above) shows the full-size etching pattern for the main PC board, while Fig.11 at left shows the etching pattern for the RF preamplifier board. Check your boards carefully for etching defects by comparing them with these patterns before mounting any of the parts. August 1994  75 Lace the internal wiring together using cable ties & note that the mains leads should be laced togeth­er so that if one lead comes adrift, it cannot come into contact with the case. The shielded audio cable should be kept well away from the power transformer to prevent hum injection into the audio signal. The drain of Q1 should be close to +12V. At this stage, one of the active antenna LEDs should be lit or they may be alternately flashing at about a 1-second rate. In addition, check that the Neon lamp in the on/off switch is glow­ing but do not expect the signal level LEDs to light at this stage. Assuming that all is well so far, you can now move on to the alignment procedure. Alignment Alignment of the tuner requires only a few simple tools. You will need a screwdriver-type alignment tool, a tuning wand, a multimeter and an FM wireless microphone. An alignment tool has a plastic handle and a small tip made of either brass of tough plastic. It must be used because an ordinary screwdriver would detune the coil being adjusted and, as previously mentioned, could easily crack the ferrite cores. The tuning wand (see photo) is used for aligning the RF preamplifier stage. It consists of a short length of plastic tubing with a ferrite core at one end and a brass screw at the other. This tool can easily be made as shown in the accompanying photograph. It decreases the inductance when the brass end is introduced into an air-cored 76  Silicon Chip coil and increases the inductance when the ferrite core is introduced into the coil. During alignment, the multimeter is used to monitor the signal level at TP1, while the wireless microphone is used as the signal source. The step-by-step alignment procedure is as fol­lows: (1). Connect a simple antenna to the antenna A input. A 300mm length of copper wire plugged into the antenna socket will do the job. (2). Adjust VR1 so that the first LED in the bargraph is just extinguished or is very dim (FM microphone off). This will set the meter signal output range. Adjust VR2 and VR3 so that the wiper of VR2 is at 0.8V and the wiper of VR3 is at 0.3V. (3). Connect the multimeter between TP1 and TP GND and set it so that it will read a 0-3V range. (4). Switch on the FM microphone and place it close to the antenna. Now press and hold the antenna test switch to select antenna A and adjust the slug in T1 using the alignment tool until a voltage appears on the multi­meter. Depending on the initial state of tune, the signal strength meter will either show full scale or only a few LEDs will be lit. Adjust T1 for a maximum voltage reading. Note: this maximum voltage must be less than 2.5V, other­wise the meter circuit may overrange and a false maximum may be obtained. To overcome this problem, simply move the FM microphone further away from the receiving antenna. (5). Adjust T2 for a maximum reading, then adjust L10. This done, adjust T1 again (this is necessary since adjustments to L10 retune the local oscillator due to the AFC). (6). Repeat step 4 to obtain the maximum signal. Note that it is difficult to tune L10 if the slug is adjusted too quickly – tune the slug slowly to avoid missing the signal peak. Note also that all three coils may have a small range over which the signal remains at maximum. In each case, find the centre of this adjust­ment range and set the slug to this position. (7). L6 and L9 can now be adjusted for maximum signal. Begin by spreading L6 and L9 so that there is about 0.5mm between each winding turn and adjust VC1 and VC2 for maximum signal. (8). Insert the brass end of the tuning wand into L6. If the signal level decreases, try the ferrite end of the wand. If the signal decreases again, then the coil is correctly tuned. More than likely, the coil will not be tuned and will need to be stretched or closed slightly so that both ends of the tuning wand produce a drop in signal strength. If the signal goes down with the brass end of the wand and increases with the ferrite end, close the coil slightly by squeezing it gently with your fingers. Repeat the above test to see if the coil is now tuned. Conversely, if the signal goes up with the brass end and down with the ferrite end, then the coil will need to be stretched slightly. Retest the coil with both ends of the wand after each adjustment until the tuning is correct (ie, both ends of the wand cause the signal level to decrease). (9). Repeat step 7 for coil L9, then repeat the entire alignment procedure again to make sure that everything is spot on. (10). Switch off the FM microphone and set VR2 (the mute threshold trimpot) fully clockwise. Now adjust VR2 anticlockwise until pin 7 of IC5a just goes low. Antenna installation The antenna requirements for the SILICON CHIP Dual Diversi­ ty Tuner are not particularly difficult. You can use commercial FM dipole antennas, TV “rabbit ears” or 1/4-wave whip antennas. It is not necessary to use antennas with gain such as multi-element Yagis. Dipole and rabbit ear antennas usually have a characteris­tic impedance of 300Ω, so you will need to use a balun transform­er (for TV sets) to match these antennas to the 75Ω input sockets on the rear panel of the tuner. TV balun transformers are avail­able for a few dollars from your local parts retailer. A 1/4-wave whip is simply a 300400mm length of wire which plugs into the rear of the tuner. You can make one up by connect­ing a suitable length of stout enamelled copper wire to the centre pin of a PAL plug. The second antenna must be separated from the first by at least three metres and this is best done using a PAL plug to PAL socket extension lead. When installing the tuner, the antennas should be mounted above the stage or the audience to minimise signal attenuation due to people and room objects. Adjust the audio level pot so that the signal output level matches the mixer or amplifier requirements. After each setup, always test the unit by having somebody move around with the FM wireless microphone. The signal strength meter on the tuner will give you a good indication of the signal strength from each antenna. Use the test switch to select the second antenna to verify its performance and check that the Diversity Tuner au­tomatically switches between the two antennas as the microphone is moved around. SC This home-made tuning wand is used for aligning the RF preamplifier stage & consists of a short length of plastic tubing with a ferrite core at one end & a brass screw at the other. It decreases the inductance when the brass end is introduced into an air-cored coil & increases the inductance when the ferrite core is introduced into the coil. August 1994  77 SPECIALS BY FAX If your fax has a polling function, dial (02) 579 3955 and press your POLLING button to get our latest specials, plus our item and kit listing. Updated at the start of each month. HF ELECTRONIC BALLASTS Brand new “slim line” cased electronic ballasts. They provide instant flicker free starting, extend tube life, reduce power consumption, eliminate flicker during operation (high frequency operation), and are “noise free” in operation. The design of these appears to be similar to the one published in the Oct. 94 SILICON CHIP magazine. One of the models even includes a DIMMING OPTION!! Needs external 100K potentiometer or a 0-10V DC source. We have a good but limited stock of these and are offering them at fraction of the cost of the parts used in them! Type A: Designed to power two 32W - 4’ tubes, will power two 40W - 4’ tubes with no noticeable change in light output, has provision for dimming: $26 Type B: Designed to power two 16W - 18" tubes, will power two 18W - 18" tubes with no noticeable change in light output: $18 MISCELLANEOUS FLAT NOSE PLIERS: $4 per pair. BATTERY CHARGER: S2 accessory set for Telecom Walkabout “Phones”. Includes cigarette lighter cable, fast rate charger, and desktop stand. Actually charges 6 series connected AA Nicad batteries: $27. BATTERY PACKS: Contain 6 AA Nicad batteries wired in series, can easily be pulled apart, used units, satisfaction guaranteed: $2 per pack. LITHIUM BATTERIES: Button shaped with pins, 20mm diameter, 3mm thick. A red led connected across one of these will produce light output for over 72 hours (3 days): 4 for $2. CIGARETTE LIGHTER LEADS: Cigarette lighter plug with 3 metres of heavy duty fig. 8 flex connected. Should suit load currents up to 20A: 5 for $5. SUPERCAPS: 0.047F/5.5V capacitors: 5 for $2. HOUR METER: Non resettable, mains powered (50HZ), WARBURTON FRANKI, 100,000 Hours maximum, 0.01Hr resolution: $15. PCB MOUNTED SWITCHES 90 deg. 3A-250V, SPDT: 4 for $2. AC POWER SUPPLY: Mains in, two separate 8.5V/3A outputs, in plastic case with mains power lead/plug and output leads/plugs: $15 Ea. MONITOR PCB’s: Complete PCB and yoke assembly for high resolution monochrome TV monitors (no tube). Operate from 12V DC, circuit and information provided: $15. MODEMS: Complete mains powered non standard 1200 baud Telecom approved modems. We should have brief information available. Limited stock at below the price of the high quality case that these are housed in: $30 for 2 modems. MEDICAL LASER One only water cooled medical laser with selectable outputs: Argon (7W multiline) or Dye laser (1W red). Large water cooled unit with a separate control box and accessories (350kg): $15,000 LEVEL RECORDER One only, Bruel & Kjaer level recorder type 2305, in good condition: $300 78  Silicon Chip DIE CAST BOXES These large (187 x 120 x 56mm) aluminium die cast boxes have several holes drilled in them and have a C&K toggle switch and a 6.25mm phono socket fitted. New units from an unfinished production project: $4 Ea. WELLER SOLDERING IRON TIPS New soldering iron for low voltage Weller soldering stations and mains operated Weller irons. Mixed popular sizes and temperatures. Specify mains or soldering station type: 5 for $10. NICAD BATTERY PACKS Brand new Toshiba 7.2V-2.2AHr Nicad Battery packs in a plastic assembly: $20 Ea. If you purchase three packs we will supply a matching fast charger (90min.) that can charge up to three of these batteries (one at a time). Modern unit that employs “delta V” voltage detection to terminate charge, needs an external 12V-2.2A unregulated supply: $60 for three battery packs and a three way charger. PLUGS/SOCKETS 3 pin chassis mounting socket and a matching covered three pin plug. Good quality components that will handle a few amperes at low voltage: $5 for 4 pairs. DYNAMIC MICROPHONES Low impedance dynamic microphones with separate switch wiring, 3.5mm mic. plug, 2.5mm switch plug, as used on most cassette recorders: $4 Ea. 40mW IR LASER DIODES New famous brand 40mW-830nM IR laser diodes, suit medical and other applications: $90 Ea. Constant current driver kit to suit: $10. HIGH POWER LED IR ILLUMINATOR This kit includes two PCBs, all on-board components plus casing: Switched mode power supply plus 60 high intensity 880nm IR (invisible) LEDs. Variable output power, 6-20VDC input, suitable for illuminating IR responsive CCD cameras, IR night viewers etc. Professional performance at a fraction of the price of the commercial product. COMPLETE KIT PRICE: $60 LOW COST 1-2 CHANNEL UHF REMOTE CONTROL Late in October we will have available a single channel 304MHz UHF remote control with over 1/2 million code combinations which also makes provision for a second channel expansion. The low cost design includes a complete compact keyring transmitter kit, which includes a case and battery, and a PCB and components kit for the receiver that has 2A relay contact output! Tx kit $10, Rx kit $20. Additional components to convert the receiver to 2 channel operation (extra decoder IC and relay) $6. INCREDIBLE PRICES: COMPLETE 1 CHANNEL TX-RX KIT: $30 COMPLETE 2 CHANNEL TX-RX KIT: $36 ADDITIONAL TRANSMITTERS: $10 FIBRE OPTIC TUBES These US made tubes are from used equipment but in excellent condition. Have 25/40 mm diameter, fibre-optically coupled input and output windows. The 25mm tube has an overall diameter of 57mm and is 60mm long, the 40mm tube has an overall diameter of 80mm and is 92mm long. The gain of these is such that they would produce a good image in approximately 1/2 moon illumination, when used with suitable “fast” lens, but they can also be IR assisted to see in total darkness. Our HIGH POWER LED IR ILLUMINATOR kit, and the IR filter are both suitable for use with these tubes. The superior resolution of these tubes would make them suitable for low light video preamplifiers, wild life observation, and astronomical use. Each of the tubes is supplied with an 9V-EHT power supply kit. INCREDIBLE PRICES: $120 for the 25mm intensifier tube and supply kit. $180 for the 40mm intensifier tube and supply kit. We also have a good supply of the same tubes that may have a small blemish which is not in the central viewing area!: $65 for a blemished 25mm intensifier tube and supply kit. $95 for the blemished 40mm intensifier tube and supply kit. SIEMENS VARISTORS 420VAC 20 joule varistors that are suitable for spike protection in Australian 3 phase systems: 10 for $5. TAA611C ICs TAA611C Audio power amplifier ICs, no more information: 5 for $5. INTENSIFIED NIGHT VIEWER KIT SC Sept. 94. See in the dark! Make your own night scope that will produce good vision in sub-starlight illumination! Has superior gain and resolution to all Russian viewers priced at under $1500. We supply a three stage fibre-optically coupled image intensifier tube, EHT power supply kit, and sufficient plastics to make a monocular scope. The three tubes are supplied already wired and bonded together. $290 for the 25mm version $390 for the 40mm version We can also supply the lens (100mm f2: $75) and the eyepiece ($18) which would be everything that is necessary to make an incredible viewer! MAINS POWERED GAS LASER Includes a professional potted mains power supply and a new 3mW red tube to suit. One catch, this supply requires a 4-6V (TTL) enable input which is optically isolated, to make the unit switch ON. Very low consumption from a 4.5V battery. $100 for a new 3mW tube plus a TTL mains power supply to suit. SUPER DIODE POINTERS - HEADS These pointers probably represent the best value when you compare them on a “brightness per dollar” basis. They are about 5 times brighter than 5mW/670nm pointers! They have an output of 2.5mW at 650nm, which is about equal in brightness to a 0.8mW HE-NE tube!! SPECIAL INTRODUCTORY PRICE: $150 We will also have available some of the 3V diode modules used in these pointers at approximately $125, and also some 2.5mW/635nm laser diode modules with special optics at approximately $280. VIDEO TRANSMITTERS Low power PAL standard UHF TV transmitters. Have audio and video inputs with adjustable levels, a power switch, and a power input socket: 10-14V DC/10mA operation. Enclosed in a small metal box with an attached telescopic antenna. Range is up to 10m with the telescopic antenna supplied, but can be increased to approximately 30m by the use of a small directional UHF antenna. INCREDIBLE PRICING: $25 TDA ICs/TRANSFORMERS We have a limited stock of some 20 Watt TDA1520 HI-FI quality monolithic power amplifier ICs, less than 0.01% THD and TIM distortion, at 10W RMS output! With the transformer we supply we guarantee an output of greater than 20W RMS per channel into an 8ohm load, with both channels driven. We supply a far overrated 240V-28V/80W transformer, two TDA1520 ICs, and two suitable PCBs which also include an optional preamplifier section (only one additional IC), and a circuit and layout diagram. The combination can be used as a high quality HI-FI Stereo/Guitar/P.A., amplifier. Only a handful of additional components are required to complete this excellent stereo/twin amplifier! Incredible pricing: $25 for one 240V-28V (80W!) transformer, two TDA1520 monolithic HI-FI amplifier ICs, two PCBs to suit, circuit diagram/layout. Some additional components and a heatsink are required. LIGHT MOTION DETECTORS Small PCB assembly based on a ULN2232 IC. This device has a built in light detector, filters, timer, narrow angle lens, and even a siren driver circuit that can drive an external speaker. Will detect humans crossing a narrow corridor at distances up to 3 metres. Much higher ranges are possible if the detector is illuminated by a remote visible or IR light source. Can be used at very low light levels, and even in total darkness: with IR LED. Full information provided. The IC only, is worth $16! OUR SPECIAL PRICE FOR THE ASSEMBLY IS: $5 Ea. or 5 for $20 GAS LASER SPECIAL We have a good supply of some He-Ne laser heads that were removed from new or near new equipment, and have a power output of 2.5-5mW: very bright! With each head we will supply a 12V universal laser power supply kit for a ridiculous TOTAL PRICE of: $89 AA NICADS Brand new AA size Saft brand (made in France) 500mA Hr. batteries, also have solder connections (can be removed): $2 Ea. or 10 for $ 16. TWO STEPPER MOTORS PLUS A DRIVER KIT This kit will drive two stepper motors: 4, 5, 6 or 8 eight wire stepper motors from an IBM computer parallel port. Motors require separate power supply. A detailed manual on the COMPUTER CONTROL OF MOTORS plus circuit diagrams/descriptions are provided. We also provide the necessary software on a 5.25" disc. Great “low cost” educational kit. We provide the kit, manual, disc, plus TWO 5V/6 WIRE/7.5 Deg. STEPPER MOTORS FOR A SPECIAL PRICE OF: $42 CAMERA FLASH UNITS Electronic flash units out of disposable cameras. Include PCB/components and Xenon tube/reflector assembly. Requires a 1.5V battery. $2.50 IR LASER DIODE KIT auto iris lens. It can work with illumination of as little as 0.1Lux and it is IR responsive. Can be used in total darkness with Infra Red illumination. Overall dimensions of camera are 24 x 46 x 70mm and it weighs less than 40 grams! Can be connected to any standard monitor, or the video input on a Video cassette recorder. NEW LOW PRICE: $199 IR “TANK SET” A set of components that can be used to make a very responsive Infra Red night viewer. The matching lens tube and eyepiece sets were removed from working military quality tank viewers. We also supply a very small EHT power supply kit that enables the tube to be operated from a small 9V battery. The tube employed is probably the most sensitive IR responsive tube we ever supplied. The resultant viewer requires low level IR illumination. Basic instructions provided. $140 BRAND NEW 780nm LASER DIODES (barely visible), mounted in a professional adjustable collimator-heatsink assembly. Each of these assemblies is supplied with a CONSTANT CURRENT DRIVER kit and a suitable PIN DIODE that can serve as a detector, plus some INSTRUCTIONS. Suitable for medical use, perimeter protection, data transmission, IR illumination, etc. For the tube, lens, eyepiece and the power supply kit. 5mW VISIBLE LASER DIODE KIT We include a basic diagram-circuit showing how to make a small refrigerator-heater. The major additional items required will be an insulated container such as an old “Esky”, two heatsinks, and a small block of aluminium. $40 Includes a Hitachi 6711G 5mW-670nm visible laser diode, an APC driver kit, a collimating lens - heatsink assembly, a case and battery holder. That’s a complete 3mW collimated laser diode kit for a TOTAL PRICE OF: $75 BIGGER LASER We have a good, but LIMITED QUANTITY of some “as new” red 6mW+ laser heads that were removed from new equipment. Head dimensions: 45mm diameter by 380mm long. With each of the heads we will include our 12V Universal Laser power supply. BARGAIN AT: $170 6mW+ head/supply. ITEM No. 0225B We can also supply a 240V-12V/4A-5V/4A switched mode power supply to suit for $30. 12V-2.5 WATT SOLAR PANEL SPECIAL These US made amorphous glass solar panels only need terminating and weather proofing. We provide terminating clips and a slightly larger sheet of glass. The terminated panel is glued to the backing glass, around the edges only. To make the final weatherproof panel look very attractive some inexpensive plastic “L” angle could also be glued to the edges with some silicone. Very easy to make. Dimensions: 305 x 228mm, Vo-c: 18-20V, Is-c: 250mA. SPECIAL REDUCED PRICE until the end of 94!: $20 Ea. or 4 for $60 Each panel is provided with a sheet of backing glass, terminating clips, an isolating diode, and the instructions. A very efficient switching regulator kit is available: Suits 12-24V batteries, 0.1-16A panels, $27. Also available is a simple and efficient shunt regulator kit, $5. CCD CAMERA Monochrome CCD camera which is totally assembled on a small PCB and includes an SOLID STATE “PELTIER EFFECT” COOLER-HEATER These are the major parts needed to make a solid state thermoelectric cooler-heater. We can provide a large 12V-4.5A Peltier effect semiconductor, two thermal cutout switches, and a 12V DC fan for a total price of: $45. ITEM No. 0231 RUSSIAN NIGHT VIEWER We have a limited quantity of some passive monocular Russian made night viewers that employ a 1st generation image intensifier tube, and are prefocussed to infinity. CLEARANCE: $180 INFRA RED FILTER A very high quality IR filter and a RUBBER lens cover that would fit over most torches including MAGLITEs, and convert them to a good source of IR. The filter material withstands high temperatures and produces an output which would not be visible from a few metres away and in total darkness. Suitable for use with passive and active viewers. The filter and a rubber lens cover is priced at: $11 DOME TWEETERS Small (70mm diam., 15mm deep) dynamic 8ohm tweeters, as used in very compact high quality speaker systems: $5 Ea. We also have some 4" woofers: $5 Ea. VIDEO ZOOM LENSES Wire antenna - attached, Microphone: Electret condenser, Battery: One 1.5V silver oxide LR44/G13, Battery life: 60 hours, Weight: 15g, Dimensions: 1.3" x 0.9" x 0.4". $25 REEL TO REEL TAPES New studio quality 13cm-5" “Agfa” (German) 1/4" reel to reel tapes in original box, 180m-600ft: $8 Ea. MORE KITS-ITEMS Single Channel UHF Remote Control, SC Dec. 92 1 x Tx plus 1 x Rx $45, extra Tx $15. 4 Channel UHF Remote Control Kit: two transmitters and one receiver, $96. Garage/Door/Gate Remote Control Kit: Tx $18, Rx $79. 1.5-9V Converter Kit: $6 Ea. or 3 for $15. Laser Beam Communicator Kit: Tx, Rx, plus IR Laser, $60. Magnetic Card Reader: professional assembled and cased unit that will read information from plastic cards, needs low current 12VDC supply-plugpack, $70. Switched Mode Power Supplies: mains in (240V), new assembled units with 12V-4A and 5V-4ADC outputs, $32. Electric Fence Kit: PCB and components, includes prewound transformer, $28 High Power IR LEDs: 880nm/30mW/12deg. <at> 100mA, 10 for $9 Plasma Ball Kit: PCB and components kit, needs any bulb, $25. Masthead Amplifier Kit: two PCBs plus all on board components: low noise (uses MAR-6 IC), covers VHF-UHF, $18. Inductive Proximity Switches: detect ferrous and non-ferrous metals at close proximity, AC or DC powered types, three wire connection for connecting into circuitry: two for the supply, and one for switching the load. These also make excellent sensors for rotating shafts etc. $22 Ea. or 6 for $100. Brake Light Indicator Kit: 60 LEDs, two PCBs and ten Rs, makes for a very bright 600mm long high intensity Red display, $30. IEC Leads: heavy duty 3 core (10A) 3M LEADS with IEC plug on one end and an European plug at the other, $1.50 Ea. or 10 for $10. IEC Extension Leads: 2M long, IEC plug at one end, IEC socket at other end, $5. Motor Special: these motors can also double up as generators. Type M9: 12V, I No load = 0.52A-15,800 RPM at 12V, 36mm Diam.-67mm long, $5. Type M14: made for slot cars, 4-8V, I No load = 0.84A at 6V, at max efficiency I = 5.7A-7500 RPM, 30mm Diam-57mm long, $5. EPROMS: 27C512, 512K (64K x 8), 150ns access CMOS EPROMS. Removed from new equipment, need to be erased, guaranteed, $4. Green Laser Tubes: Back in stock! The luminous output of these 1-1.5mW GREEN laser diode heads compares with a 5mW red tube!: $490 for a 1-1.5mW green head and a 12V operated universal laser inverter kit. 40 x 2 LCD Display: brand new 40 character by 2 line LCD displays with built in driver circuitry that uses Hitachi ICs, easy to drive “standard” displays, brief information provided, $30 Ea. or 4 for $100. RS232 Interface PCB: brand new PCB assembly, amongst many parts contains two INTERSIL ICL232 ICs: RS232 Tx - Rx ICs, $8. Modular Telephone Cables: 4-way modular curled cable with plugs fitted at each end, also a 4m long 8-way modular flat cable with plugs fitted at each end, one of each for $2. 12V Fans: brand new 80mm 12V-1.6W DC fans. These are IC controlled and have four different approval stamps, $10 Ea. or 5 for $40. Lenses: a pair of lens assemblies that were removed from brand new laser printers. They contain a total of 4 lenses which by different combinations - placement in a laser beam can diverge, collimate, make a small line, make an ellipse etc., $ 8. Polygon Scanners: precision motor with 8 sided mirror, plus a matching PCB driver assembly. Will deflect a laser beam and generate a line. Needs a clock pulse and DC supply to operate, information supplied, $25. PCB With AD7581LN IC: PCB assembly that amongst many other components contains a MAXIM AD7581LN IC: 8 bit, 8 channel memory buffered data acquisition system designed to interface with microprocessors, $29. EHT Power Supply: out of new laser printers, deliver -600V, -7.5KV and +7kV when powered from a 24V-800mA DC supply, enclosed in a plastic case, $16. Mains Contactor Relay: has a 24V-250ohm relay coil, and four separate SPST switch outputs, 2 x 10A and 2 x 20A, new Omron brand, mounting bracket and spade connectors provided, $8. FM Transmitter Kit - Mk.II: high quality high stability, suit radio microphones and instruments, 9V operation, the kit includes a PCB and all the on-board components, an electret microphone, and a 9V battery clip, $11. FM Transmitter Kit - Mk.I: this complete transmitter kit (miniature microphone included) is the size of a “AA” battery, and it is powered by a single “AA” battery. We use a two “AA” battery holder (provided) for the case, and a battery clip (shorted) for the switch. Estimated battery life is over 500 hours!!: $11. High Power Argons: the real thing! Draw pictures on clouds, big buildings etc., with a multiline water-cooled Argon laser with a few watts of output. “Ring” for more details. Argon-Ion Heads: used Argon-Ion heads with 30-100mW output in the blue-green spectrum, will be back in stock soon, priced at around $400 for the “head” only, power supply circuit and information supplied. Two only 10:1 video zoom lenses, f=15150mm, 1:1.8, have provision for remote focus aperture and zoom control: three motors, one has a “C” mount adaptor, 150mm diam. by 180mm long: OATLEY ELECTRONICS MINIATURE FM TRANSMITTER Phone (02) 579 4985. Fax (02) 570 7910 $390 Ea. Not a kit, but a very small ready made self contained FM transmitter enclosed in a small black metal case. It is powered by a single small 1.5V silver oxide battery, and has an inbuilt electret microphone. SPECIFICATIONS: Tuning range: 88-108MHz, Antenna: PO Box 89, Oatley, NSW 2223 Bankcard, Master Card, Visa Card & Amex accepted with phone & fax orders. P & P for most mixed orders: Aust. $6; NZ (airmail) $10. August 1994  79 VINTAGE RADIO By JOHN HILL Building a classic crystal set Building a classic crystal set can be a lot of fun. This unit is based on an old navy design & offers excellent perfor­mance considering the circuit simplicity. I recently joined a radio collectors’ club – The Vintage Radio Club of North East Victoria Inc. This group meets at vari­ous locations around the Sheppar­ ton, Benalla and Wangaratta region and has a membership of about 40. The North East Club is a fairly active group. Not only do they meet on a regular monthly basis but they also put out a monthly newsletter which is a remarkable effort in itself and a credit to those concerned. And every year, the club presents to one of its members a special achievement award called the “Helli­er Award”. Les Hellier was a radio pioneer in the Wangaratta district in the early 1920s. His family were happy to have his name used by the club for their annual award and have supplied a shield for use as a perpetual trophy. Last year, everyone who wished to participate in the award activity built a Little General receiver. This year’s effort centres around the building of a crystal set. Personally, I think the crystal set project is a great idea as it allows members with little practical experience to participate in the event. There are two award categories this year – vintage and open – so the award will have joint winners. Classic crystal set Anyway, this preamble is simply a lead up to explain why I have just finished building a crystal set. I am pleased to say that my home-made receiver has turned out to be an outstanding performer and it has been well worth the effort. What’s more, I found building this simple little radio to be an interesting and rewarding project. The heart of any crystal set is the crystal detector. This particular detector uses a genuine Neutron crystal & bronze catswhisker. The Neutron crystal is manmade & is not a natural lead sulphide galena crystal. 80  Silicon Chip To be perfectly honest, I cannot take much credit for my crystal set because it has been built to a well-proven design. It is a home-made version of the Technicraft-cum-Orpheus “Super Crystal Set”, without the spiderweb coils, plus a few minor modifications of my own. I also decided on a name change to distinguish my version and it is now the “Classic Crystal Set”. The receiver is of elaborate design (for a crystal set), having three coils, a 10-position stud switch, two variable capacitors and four controls on the front panel. As the set is to be entered in the vintage category, it has been built to look like a 1920s production, complete with a catswhisker type crystal detector, black bakelite panels and vintage style control knobs. The cabinet also follows this pattern; it has a lift up lid and is made of solid blackwood timber. Design origins The previously mentioned Super Crystal Set was originally designed by David Whitby and is based on early navy circuits. The Super Crystal Set, as well as several other vintage radio kits, were quite popular about 10 years ago. In fact, it was these Technicraft kits that started me in vintage radio. If they had not come along at the right time, I would most likely be doing something else for a hobby today. David eventually sold his vintage radio department to Richard Wilson who then sold the kits through the Orpheus Radio Museum in Ballarat. When Richard eventually decided to get out of the vintage radio business, the production of Technicraft kits suddenly came to an end. No doubt this range of receivers will become quite collectable. Retailing at $89, the Super Crystal Set kit was not cheap and many would- These ancient aerial and earth terminals are just the thing when building a 1920s style crystal set. The parts used in vintage construction should be from the right era, or at least look as though they are. The Classic Crystal Set’s coils were wound on old (& very rare) 2-inch diameter black bakelite tubing. A thin piece of wood has been used to isolate the coil taps. This photo shows the two old style variable capacitors used in the crystal set. The one on the left has a range of about 0-100pF & the larger one a range of about 0-500pF. Both are plain, single bearing types & both re­quired cleaning & adjustment before they could be used. be builders were discouraged by the price. If you now want to build this remarkable crystal receiver, simply do as I have done; build it using conventional coils and utilise what odd bits and pieces you may have available. Whether or not the receiver is made to look like a vintage set or not is entirely up to each individual constructor and the components available. Be­cause my 80T TAPPED 20,10,10 10,10,20 AERIAL 80T 0 receiver has been built as a vintage replica, the rename to Classic Crystal Set seemed appropriate. Design points I like to think of this particular receiver as being a TRF (tuned radio frequency) crystal set. While some would argue that the RF section is nothing other than a loading coil, there really CRYSTAL DETECTOR 18T 500pF 10 STUD SWITCH 100200pF EARTH .001 HIGH IMPEDANCE 'PHONES Fig.1: the circuit for the Classic Crystal set uses a tapped loading coil which is accurately tuned with a trimmer capacitor. is a bit more to it than that. Sure it is a tapped loading coil but my design improvement incorporates a variable capacitor so that the resonance peak can be accurately obtained. Without this trimmer capacitor, the eight turns between the taps is much too coarse if the resonance point of a particular station is midway between taps. As far as I’m aware, a loading coil is nothing but a tapped coil in series with the aerial. It is often mounted on a separate board and operates independently of and outside the crystal set. On the other hand, the accurately tuned RF coil in the Classic Crystal Set is inductively coupled to the detector stage by a variable coupling coil arrangement. That seems like a tuned non-amplified RF stage to me. Anyway, whether you agree with me or not, you would have to admit that a TRF Crystal Set sounds intriguing and gives the receiver a bit of class. If anything ever needed its image lifted in this day and age, it would have to be the humble crystal set. So a TRF it is! Collecting the parts It is surprising just how long it takes to bring a simple crystal set project to completion. Just finding all the necessary bits and pieces was a major operation and quite a few hours were spent locating the required parts. Knowing that you have someth­ing and knowing where to find it are two different August 1994  81 A pair of Browns type F high-impedance headphones was used with the Classic crystal Set. Also shown is an adapter which allows phones with standard lead tips to be used with a quarter-inch phone jack. described in crystal set terms as being mediocre (20 metres long and 6 metres high), this remarkable little receiver can even pull in interstate stations. Adelaide and Sydney stations (5CL, 5AN and 2BL) sometimes come in at surprisingly good volume levels. Of course, they often fade to nothing for lengthy periods too. I must also stress that these interstate stations are in the 50kW class and this fact allows them to be received at great distances – even on a crystal set. However, the most incredible reception feat that the Clas­sic has managed so far is 4QD in Emerald, Queensland – 1500km as the crow files. Once again, this is a powerful 50kW station. The original Technicraft Super Crystal Set will also receive 4QD. It would appear that I’m in a good reception area for these particular transmissions. I might also add that listening to these distant stations is not damaging my hearing to any extent and nor are the headphones being greatly overstressed. They are loud enough to identify and that’s about all. Detector stage The variable coupling coil setup was installed in one end of the detector coil. It is mounted on a hardwood shaft & the coil connections run through the shaft to the outside. Note that the coil is bound with thread to keep it together. things. Clean­ing and repairing these parts took up a considerable amount of time too. Mention should also be made of the convenience of having a lathe in one’s workshop. The variable coupling coil control, in particular, would have been difficult to incorporate without the lathe. The big advantage of a crystal set of this design type is that it is so selective, yet it seems to produce this selectivity without loss of volume which is contrary to what one would expect. Selectivity is something that is really important in my locality because of a local 5kW station, 3CV (Central 82  Silicon Chip Victoria) on 1071kHz. Not only is 3CV a mere 6km away from my location but it also occupies a central position on the dial. Most single coil crystal sets cannot handle such a situation and provide only single station reception – the strong local. However, the Classic Crystal Set with its two tuned cir­cuits, variable coupling coil and tapped detector coil enables the operator to tune out the local station to a remarkable de­gree. 3CV can be suppressed sufficiently to receive about eight other stations on those special nights when reception is particu­larly good. Using an aerial that can only be Looking at the circuit (Fig.1), one can say that the detec­tor stage of the receiver is just about as standard as a crystal set can be. There are no special techniques involved and attach­ing the antenna to the top of the detector coil would produce a fairly basic crystal set. The secret of the set’s brilliant performance must there­fore be in the RF section ahead of the detector stage. The tuned RF coil and its accompanying variable coupling coil is where the performance comes from. This particular circuitry produces good selectivity without any significant loss in volume. Tuning the receiver is a two-handed job and it takes a while to pick out those elusive stations. When a station is located, it needs to be logged on a chart so that it can be found again. This is where it helps if the controls have numbered dials. In the case of the Classic, the tuning dial is numbered, the RF coil trimmer is numbered, the stud switch is numbered and the coupling coil control knob arrow operates best at around the 12 o’clock position. It is therefore easy to return to a station once these control positions have been accurately logged. RESURRECTION RADIO Valve Equipment Specialists Repairs – Restoration – Sales The finished receiver successfully captures the vintage look of the 1920s. The crystal detector was mounted high on the back of the front panel where it is out of harm’s way. Another stud switch for the detector coil taps would have been a good idea but there really wasn’t room to accommodate it on the front panel. Instead, an internal wander lead and alliga­tor clip is used. Once set for best results, it seldom needs moving. The crystal used in the detector is not the usual lead sulphide natural galena type but a genuine “Neutron” crystal. These special man-made crystals have a surface which contains hundreds of small sparkling facets and good spots abound. The Neutron crystal was actually broken in half with a pair of side cutters so that the catswhisker operates on a freshly exposed surface of the crystal. When set on a good spot, the Neutron crystal performs equally as well as a germanium signal diode, although an ohm meter indicates otherwise. Alternate switching from crystal to diode produced no difference in reception quality or sensitivity. However, the signal diode is a bit more convenient to use. If you have an interest in simple radio receivers, then this particular The parts visible in this photo include the tapped RF coil, the rear of the stud switch & the trimming capacitor. The alligator clip at the left is used for selecting the detector coil taps & once set rarely needs shifting. VALVES – 1200 types in stock    EL34/BCA7 matched $30 ea.    6L6GC matched $28 ea. Parts are available for the enthusiast, including over 900 valve types, high voltage cap­a citors, transformers, dial glasses, knobs, grille cloth etc. Circuit diagrams for most Australian makes and models. Send SAE for our catalog. WANTED: Valves, Radios, etc. Purchased for CASH Call in to our NEW showroom at: 242 Chapel Street (PO Box 2029), Prahran, Vic 3181. Phone: (03) 510 4486; Fax (03) 529 5639 circuit will not only test your construction skills but will also reward you with a top performing crystal receiver. Whether it is operated in the city or in some remote country area, it will give a surprisingly good account of itself. So it’s off to the Hellier Award meeting at the weekend. I’ll tell you how it SC all went next month. This view shows the variable coupling coil setup & the drive shaft to the front panel. Note the brass “clock spring” connec­tors on the shaft. Rotation of the coupling coil is restricted to half a turn. August 1994  83 REMOTE CONTROL BY BOB YOUNG Modellers with dedication; Pt.2 This month, we will look at the work of one of the most dedicated, versatile & highly skilled modellers I have ever had the pleasure to make the acquaintance of, in a lifetime of active modelling. For personal reasons he has asked me to withhold his name so I will henceforth refer to him only as John. I first met him when I was operating out of my father’s newsagency at Tempe back in the mid 1960s. At that time, he pur­chased a 10-channel reed system from me for a model yacht. Over the years our business relationship grew into one of those friendships that thrives for a time only to diverge for a period and then comes back to life, and always with the feeling that no real time has elapsed since our last meeting. During those years I have watched his interest in modelling grow and mature, with his work now at what I consider to be the level of a master craftsman. The staggering thing about John is the diversity of his interests and This model racing semi-trailer tractor, built to a scale of 1:12, has an incredible range of radio-controlled func­tions, including windscreen wipers, all lights & the horns. 84  Silicon Chip the intensity with which he pursues them. When he decides upon a course of action it is carried out to the most unbelievable levels of achievement and excellence. The photo­ g raphs accompanying this article attempt to show how diverse are his interests but they don’t do full justice to the excellence of his workmanship and that is a great pity for the final products are a joy to behold. Model railroads Possibly his most abiding interest is in model railroads. His home is a stunning testimony to a lifetime of non-stop mod­ elling work. His HO (1:87) scale layout, on which he has been working for over 25 years (in between other projects), occupies a large building dedicated to this layout alone. It is the only model railroad layout I have seen which features an electrical storm complete with a sequence of lightning, thunder and (get this) torrential rain, over a section of the track. My close involvement with John came about as a result of our mutual interest in model and full size aviation. Again, he never did things by halves and John’s Airforce, as we jokingly referred to it, featured over thirty very elaborate R/C aircraft, mostly true to scale and all built to a level of excellence that would put most R/C modellers to shame. Our midweek flying ses­sions live on in my memory as some of the most interesting and enthusiastic periods in my modelling career. The energy of the man was infectious and all of us in the group at that time worked like demons, constantly competing to turn out better and better models. However, by the early 1980s business life was becoming very tough and family and business commitments pulled us apart once more. During this time the airforce was retired and sold off and John’s son developed into a world class R/C car driver and thus lured John into the international world of competitive high performance R/C cars. Again, nothing was done by halves and during this time John set up an engineering section home workshop that is enough to dumbfound even the most blase modeller. Actually, I have seen professional engineering shops that were nowhere near as well equipped as John’s playpen. They certainly are not as neat, as well lit or as well laid out. The work that comes out of this workshop is first class. Possibly my favourite is his model of a semi-trailer, complete with working everything! Constructed totally from scratch from aluminium stock and sheet, this model really is a work of art. It is powered by an O.S. 40 4-stroke engine and really has to be seen to be believed. Essentially, it is a model of a racing car transporter, the trailer being fitted with working model racing cars and a workbench complete with a working model vice, a 44 gallon oil drum with working pump and a contingent of mechanics, drivers and various tyre-kickers. A close-up view of the 16-channel radio control transmitter built by Silvertone for control of a racing model semi-trailer. It looks as though it might be easier to drive the full size machine! Racing truck cab In his spare time as a lark, John built a racing truck cab but the concept of model truck racing has never really caught on. Shown in one of the accompanying photos is the custom 16-channel Silvertone transmitter which I built especially for the Semi Trailer project. The channel logos give some idea of the complex­ity of the finished model: steering, forward and reverse gear shift, throttle, brakes, blinkers, horn, fog lights, high and low beam headlights, parking lights, hazard lights, windscreen wip­ ers, engine sound and one spare auxiliary control. I had to design and build a relay switching unit which worked directly from the receiver servo outputs for the lighting circuits, the receiver being a custom built Silvertone 16-channel AM unit. This racing truck was demonstrated several times at model gatherings but now holds pride of place in a static collec­tion of models that range from HO scale tableaus, through to R/C models of yachts, This view of the racing model semi-trailer shows the cab tilted forward to reveal some of the radio control gear. The engine assembly of the model semi-trailer has a radia­tor & a belt-driven fan. Note the servos at the rear for forward/reverse selection of the gear box. August 1994  85 battleships, tanks, cars, trucks and aircraft. However, the piece de resistance in his home modelling complex is his garden layout. Here is a backyard designed to give the maximum pleasure to John and his modelling friends. The centrepiece of the layout is an R/C car racing circuit with 1:22 scale cars around which runs an LGB railroad layout. Battery power Radio controlled models coupled together with sound effects have a heightened sense of realism. The R/C racing circuit has crowd sounds coming from the pavilion & merry-go-round sounds from the fairground behind. This general view of the layout shows the car racing track in the centre surrounded by the LGB (1:32) scale railway layout. The locomotives are battery powered & radio controlled. LGB rolling stock is built to Scale 1 (1:32) and has a track gauge of 44.5mm. The locomotives are battery powered (essential for outdoor operation) and operated by radio control, as are the sound systems. The latter are housed in enclosed wagons along with a fair sized speaker to give good bass repro­ duction. The sound system responds to the locomotive speed and throttle settings, and horns and whistles are included. The overall effect of the entire layout is breathtaking when fully powered up. I have never fully appreciated sound effects in models, particularly model trains, but used skilfully they add a new dimension to modelling and to my mind they are now a must in any good modelling installation. John uses sound ef­fects in a way that I have never encountered before. They include the sound of a helicopter warming up on the helipad, the roar of the crowd in the stands, music from the merry-go-round in the fairground, the chuff of the steamer climbing an incline and the burble of a diesel loco waiting at the level crossing. All of these effects add a sense of life and drama to a model complex that is busy in the extreme. Future plans A view inside on of the goods wagons coupled to a diesel locomo­tive. The wagon contains the battery packs & radio controlled sound system. 86  Silicon Chip John’s one complaint with his layout is that the points are manually operated at the moment, so true to form he has commis­sioned Silvertone to design and build a 20-channel R/C points control system. I hope to present the details of this system in a future column. However, enough of my account. The photographs presented tell the story more effectively than any amount of prose. Next month I will present the story of John and his son and their successes in the field of national and SC international R/C car racing. PRODUCT SHOWCASE Metex M-3850 digital multimeter has PC interface As well as all the common features you would normally expect to find on a current auto-ranging digital multimeter, this Metex M-3850 has frequency, capacitance & temperature measurement, transistor testing, dual display & the ability to store data for later analysis. The M-3850 has a large back-lit dual liquid crystal display. The main display is a 4000 count array with 15mm high digits and it is supplemented with a smaller 4000 count display in the top right-hand corner. Small icons show the current operating mode while a bargraph provides analog in­dication of the measurement. Press­ ing the function button scrolls through the various modes. The secondary display can be used as a data hold facility, to keep account of a measured maximum, minimum or a value relative to a preset value, while the main display shows the cur­rent reading. In dual mode, it allows two measurements to be displayed at once. For instance, the primary dis­play can show a DC supply voltage while the other displays the frequency of the ripple on the supply, or the temperature can be displayed in Cel­sius on the main display and Fahren­heit on the secondary display. As with most DMMs, there are separate terminals for the current ranges which are used in conjunction with the large rotary selector switch, the milliamp terminal is used for current measurements on the 40mA and 400mA ranges while the Amp terminal is used for measurements up to 20A (one range only). The meter can be set to measure AC or DC using the DCW/ AC button. For voltage measurements, the CALLING ALL HOBBYISTS We provide the challenge and money for you to design and build as many simple, useful, economical and original kit sets as possible. We will only consider kits using lots of ICs and transistors. If you need assistance in getting samples and technical specifications while building your kits, let us know. YUGA ENTERPRISE 705 SIMS DRIVE #03-09 SHUN LI INDUSTRIAL COMPLEX SINGAPORE 1438 TEL: 65 741 0300    Fax: 65 749 1048 August 1994  87 Hakko 926 soldering station The Hakko 926 is a deluxe sol­dering station builffor production work or for use by service techni­ cians and enthusiasts. It has a 50 watt ceramic element and a hold­ing temperature accuracy of ±0.5C. Tip temperature can be varied from 200-480°C. The iron is well balanced and has a rubberised grip, while the cord is burn-proof silicone and has strain relief at both ends. The 5-pin connector has a locking ring to prevent accidental disconnection. The station has a heavy base and is fully electronically controlled via the temperature knob on the front panel. A LED indicates that the iron is heating. The stainless steel sponge tray is removable and has an excess solder tray that overhangs for easy solder collection. The unit comes with a 3-pin plug and the tip is grounded for ESD protection. A 1.6mm conical tip is K ALEX The UV People ETCH TANKS ● Bubble Etch ● Circulating LIGHT BOXES ● Portuvee 4 ● Portuvee 6 ● Dual Level TRIMMER ● Ideal PCB DRILL ● Toyo HiSpeed MATERIALS ● PC Board: Riston, Dynachem ● 3M Label/Panel Stock ● Dynamark: Metal, Plastic ✸ AUSTRALIA’S NO.1 STOCKIST ✸ K ALEX 40 Wallis Ave, East Ivanhoe 3079. Phone (03) 9497 3422, Fax (03) 9499 2381 88  Silicon Chip supplied but many other styles are available. The manual is comprehensive and states the specifica­tion and calibration adjustments for all possible tips. A “CAL” trim­pot on the base of the unit is used for this purpose. The holster has been designed to be placed on either side of the station for ease of use and is an­gled by loosening off the adjust­ment screw. The Hakko 926 soldering sta­tion sells for $259 and is available from all Dick Smith Electronics stores and resellers. ranges run in the following sequence: 400mV, 4V, 40V, 400V and a maxi­mum of 1000V DC or 750VAC. The meter is fully autoranging but has the facility to lock onto a single range when needed. This is done by selecting the R-H (Range Hold) mode and then stepping through the ranges using the Up or Down button. When it comes to measuring frequency, the Metex M-3850 really shines. Most DMMs that measure frequency are hard put to measure up to 1MHz but this unit can go to 40MHz. Input sensitivity is quoted as better than 100mV RMS for frequencies up to 30MHz to over 300mV for frequen­cies above 30MHz. It has good capaci­tance ranges too: 4nF, 40nF, 400nF, 4µF, 40µF and 400µF (1nF = .001µF). The resistance ranges run as follows: 400W, 4kW, 40kW, 400kW, 4MW and 40MW. The meter provides an audible continuity alarm for resistances below 30W and the diode test range will light most LEDs. Maximum open circuit voltage for the diode test is 2.5V. Another good feature of the Metex is the auto-off switch. It turns the me­ter off if none of the pushbuttons or the selector switch has been touched for 10 minutes. Without this feature, most DMMs become battery eaters and that becomes frustrating when the bat­tery dies just as you are about to take a crucial measurement. For transistor hFE measurements, the maximum reading is 4000 which will allow the Metex to measure many Darlington transistors. However, the instruction manual warns that some Darlingtons have internal resistors (be­tween base and emitter) and these can give rise to misleading results. An interesting mode is the ‘Comparison’ function. The icon ‘CMP’ ap­pears on the display and the meter uses two memo·ries as high.and low to test the current reading against and displays ‘Hi’, ‘Low’ or ‘Pass’ depending on the value. All told, the Metex has 10 memories for storing data and these can be stepped through using the Function button. Datalogging Where the Metex is outstanding is in its ability to be transformed into a datalogger. It can be connected to a PC or compatible with an optional serial interface which is accompanied with software. This enables measurements to be stored away with time stamping. Values can be graphed either in real time or replayed later. The software is mouse driven and has pull-down menus. Two serial ports are therefore needed to get the software running, one for the mouse and another for the meter. Collected data can be viewed in three modes: a line graph that autoranges its Y axis (as the meter does); a time-stamped history of collected values; and a large mim­icked display of the meter itself. Col­lected values are stored in ASCII files that can be replayed by the software or loaded into other software for fur­ther analysis. All told, the Metex M-3850 digital multimeter is an attractive package with lots of features. It is supplied in a vinyl case with separate sections to store the meter and test leads. Recommended retail price is $229.50 while the computer interface and software is a further $18.95. Other options in­ clude a rubber holster and an external temperature probe. For more information on the Metex M-3850, contact your local Jaycar Elec­ tronics store or reseller. Phone (02) 743 5222. Celestion SRA series power amplifiers Celestion’s new SRA series power amplifiers feature the com­ pany’s dual rail soft-switch output stage, employing linear, output­derived class G amplification. The soft-switch design means that the switch to the upper rail is inaudi­ble. It provides the advantages of dual rail operation, with a big in­crease in efficiency and a corre­ sponding reduction in the genera­ tion of heat, without the distortion generated by fast-attack rail switch­ing. Built to survive the rigours of touring, all SRA series amplifiers feature a heavy-gauge steel chassis coupled to a transverse heatsink to add rigidity. A continuously vari­able cooling fan temperature con­ trolled from the heatsink is an­other feature. Heavy duty output relays are employed to protect the loudspeaker load and a logic-con- trolled power-up sequence enables the outputs only when the amplifier has settled. Outputs are continu­ously monitored and are disabled in the event of operation outside specified tolerances. Output pro­tection status is provided on the front panel. All operational controls, the fan, filter and tamper-proof bridging and ground lift switches are acces­sible from the front panel, without the need to remove the amplifier from its rack. The rear panel has provision for a variety of New range of low-cost snap-fitting cases This new line of poly­s tyrol cases all have moulded pillars for mounting PC boards The larger cases all have ventilation slots and separate plastic front and rear panels Sizes available are 207 x 68 x 179mm, 151 x 58 x 139mm and 94 x 47 x 134mm (W x H x D). The smaller cases in the range do not have separate front and rear panels but have moulded slots, as well as pillars for PC board mounting. There are two different sized case halves and these may be mixed and matched to build cases of three different heights. The half case sizes are 71 x 24 x 123mm and 71 x 15 x 123mm (W x H x D). A baby case is also available but is not snap-fitting and is sized 70 x 47 x 40mm. All cases are available in black and a grey-white. For more information on these cases, contact Anton’s Trains, Cnr Prince & Mary St, North Parramatta, NSW 2151. Phone (02) 683 3858. mating connectors, including parallel latching XLRs for daisy-chaining, heavy duty binding posts and Neutrik Speakon connectors. Presently, two SRA models are available: (1) the SRA1000 with 510 watts into 4-ohms or 1020 watts bridged into 8-ohms; and (2) the SRA1600 with 815 watts into 4-ohms or 1620 watts bridged into 8-ohms. For further information contact Amber Technology Pty Ltd, Unit B, 5 Skyline Place, Frenchs Forest, NSW 2086. Phone (02) 975 1211 or fax (02) 975 1368. PC COMPUTERS (08) 364 0902 (08) 332 6513 36 Regent St, Kensington, South Australia High Power 2.5 Watt Transmitter Kit FMTX1 $69 This kit uses a single transistor to provide up to 2.5 watts into a 50-ohm load. It can be set on the FM band from 88-108MHz. Audio is 500mV P-P with Australian pre-emphasis. Power supply from 12-24 volts DC. Range up to 100 miles. Leaky coax distribution can be used with any of our transmitters, terminate up to 2km of coax with a 50-ohm resistor and no radiation occurs. Use a 150-ohm WW pot and you can set the level of radiation up to 300 metres from the coax. You can use this method to comply with DOTC schedule 3. XTAL Locked 30mW Transmitter (The best quality kit transmitter in Australia) FMTX2B $49 This transmitter is XTAL-locked on 100MHz (XTAL supplied) and is the most stable kit transmitter on the market. It features a 3-stage design with only two tuned circuits and a clean output. This design can be used as the basis of a station exciter. Digital Stereo Coder (All Digital Design With Australian Pre-emphasis) FMTX2A $49 This is a universal stereo coder able to be used with all of our transmitter designs and many others. Its performance is superior to domestic encoder single chip designs. Dozens have been sold to FM stations as a standby stereo coder or with the FMTX2B as an exciter. Both FMTX2A and FMTX2B on 1 PCB as a complete stereo transmit­ter FMTX5 $99 MAX I/O Board for PCs (Talk To The Outside World) $169 This kit features 7 relays, ADC, DAC, stepper motor driver with sample software in Basic and connects to a PC’s parallel port. Now also available I/O bits software for MS Windows so you can program functions without being a programmer. Call relays by a name like stop relay, assign its own icon - uses a simple VISUAL interface to make your own PLC. Full developer’s version has DOS runtime so you do not require Windows and optional sup­port for LCD displays. Data logging ADC and DAC boards and more. MAX version $169. FM Band Linear Amplifier Kits (All Imported Kits) New 30mW to 1 watt linear coming in September 1994 (advance orders taken) 500mW to 5 or 10 watts $199 250mW to 25 watts 15 watts to 110 watts $599 40 watts to 300 watts Power supplies and heatsinks not included in short form kit price. $99 $249 $999 Other kits available. Call for a list or see Silicon Chip April-June 1994 or the Silicon Chip Model Railway Book. August 1994  89 Silicon Chip Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC. April 1990: Dual Tracking ±50V Power Supply; VOX With Delayed Audio; Relative Field Strength Meter; 16-Channel Mixing Desk, Pt.3; Active CW Filter For Weak Signal Reception; How To Find Vintage Radio Receivers From The 1920s. BACK ISSUES September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Build The Vader Voice; Motorola MC34018 Speakerphone IC Data; What Is Negative Feedback, Pt.4. November 1988: 120W PA Amplifier Module (Uses Mosfets); Poor Man’s Plasma Display; Automotive Night Safety Light; Adding A Headset To The Speakerphone. April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors; 32-Band Graphic Equaliser, Pt.2; LED Message Board, Pt.2. May 1989: Build A Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; LED Message Board, Pt.3; All About Electrolytic Cap­ acitors. Encoder; Studio Series 20-Band Stereo Equaliser, Pt.2; Auto-Zero Module for Audio Amplifiers (Uses LMC669). October 1989: FM Radio Intercom For Motorbikes Pt.1; GaAsFet Preamplifier For Amateur TV; 1Mb Printer Buffer; 2-Chip Portable AM Stereo Radio, Pt.2; Installing A Hard Disc In The PC. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY & Morse); FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways. December 1989: Digital Voice Board (Records Up To Four Separate Messages); UHF Remote Switch; Balanced Input & Output Stages; Data For The LM831 Low Voltage Amplifier IC; Installing A Clock Card In Your Computer; Index to Volume 2. June 1989: Touch-Lamp Dimmer (uses Siemens SLB0586); Passive Loop Antenna For AM Rad­ios; Universal Temperature Controller; Understanding CRO Probes; LED Message Board, Pt.4. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Speed­ing Up Your PC; Phone Patch For Radio Amateurs; Active Antenna Kit; Speed Controller For Ceiling Fans; Designing UHF Transmitter Stages. July 1989: Exhaust Gas Monitor (Uses TGS812 Gas Sensor); Extension For The Touch-Lamp Dimmer; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm. February 1990: 16-Channel Mixing Desk; High Quality Audio Oscillator, Pt.2; The Incredible Hot Canaries; Random Wire Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs, Pt.2. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; High Or Low Fluid Level Detector; Simple DTMF March 1990: 6/12V Charger For Sealed Lead-Acid Batteries; Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel June 1990: Multi-Sector Home Burglar Alarm; Low-Noise Universal Stereo Preamplifier; Load Protection Switch For Power Supplies; A Speed Alarm For Your Car; Design Factors For Model Aircraft; Fitting A Fax Card To A Computer. July 1990: Digital Sine/Square Generator, Pt.1 (Covers 0-500kHz); Burglar Alarm Keypad & Combination Lock; Simple Electronic Die; Low-Cost Dual Power Supply; Inside A Coal Burning Power Station; Weather Fax Frequencies. August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Mains Appliances (9 Minutes); Horace The Electronic Cricket; Digital Sine/Square Wave Generator, Pt.2. September 1990: Music On Hold For Your Tele­ phone; Remote Control Extender For VCRs; Power Supply For Burglar Alarms; Low-Cost 3-Digit Counter Module; Simple Shortwave Converter For The 2-Metre Band. October 1990: Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs; The Dangers of Polychlorinated Biphenyls; Using The NE602 In Home-Brew Converter Circuits. November 1990: How To Connect Two TV Sets To One VCR; A Really Snazzy Egg Timer; Low-Cost Model Train Controller; Battery Powered Laser Pointer; 1.5V To 9V DC Converter; Introduction To Digital Electronics; Simple 6-Metre Amateur Transmitter. December 1990: DC-DC Converter For Car Amplifiers; The Big Escape – A Game Of Skill; Wiper Pulser For Rear Windows; Versatile 4-Digit Combination Lock; 5W Power Amplifier For The ORDER FORM Please send me a back issue for: ❏ September 1988 ❏ November 1988 ❏ April 1989 ❏ May 1989 ❏ June 1989 ❏ July 1989 ❏ September 1989 ❏ October 1989 ❏ November 1989 ❏ December 1989 ❏ January 1990 ❏ February 1990 ❏ March 1990 ❏ April 1990 ❏ June 1990 ❏ July 1990 ❏ August 1990 ❏ September 1990 ❏ October 1990 ❏ November 1990 ❏ December 1990 ❏ January 1991 ❏ February 1991 ❏ March 1991 ❏ April 1991 ❏ May 1991 ❏ June 1991 ❏ July 1991 ❏ August 1991 ❏ September 1991 ❏ October 1991 ❏ November 1991 ❏ December 1991 ❏ January 1992 ❏ February 1992 ❏ March 1992 ❏ April 1992 ❏ May 1992 ❏ June 1992 ❏ July 1992 ❏ August 1992 ❏ September 1992 ❏ October 1992 ❏ January 1993 ❏ February 1993 ❏ March 1993 ❏ April 1993 ❏ May 1993 ❏ June 1993 ❏ July 1993 ❏ August 1993 ❏ September 1993 ❏ October 1993 ❏ November 1993 ❏ December 1993 ❏ January 1994 ❏ February 1994 ❏ March 1994 ❏ April 1994 ❏ May 1994 ❏ June 1994 ❏ July 1994 ❏ August 1994 ❏ September 1994 ❏ October 1994 Enclosed is my cheque/money order for $­______or please debit my: ❏ Bankcard ❏ Visa Card ❏ Master Card Card No. Signature ____________________________ Card expiry date_____ /______ Name _______________________________ Phone No (___) ____________ PLEASE PRINT Street ________________________________________________________ Suburb/town ________________________________ Postcode ___________ 90  Silicon Chip Note: all prices include post & packing Australia (by return mail) ............................. $A7 NZ & PNG (airmail) ...................................... $A7 Overseas (airmail) ...................................... $A10 Detach and mail to: Silicon Chip Publications, PO Box 139, Collaroy, NSW, Australia 2097. Or call (02) 979 5644 & quote your credit card details or fax the details to (02) 979 6503. ✂ v 6-Metre Amateur Transmitter; Index To Volume 3. January 1991: Fast Charger For Nicad Batteries, Pt.1; Have Fun With The Fruit Machine; Two-Tone Alarm Module; LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers When Servicing Microwave Ovens. February 1991: Synthesised Stereo AM Tuner, Pt.1; Three Inverters For Fluorescent Lights; LowCost Sinewave Oscillator; Fast Charger For Nicad Batteries, Pt.2; How To Design Amplifier Output Stages; Tasmania's Hydroelectric Power System. March 1991: Remote Controller For Garage Doors, Pt.1; Transistor Beta Tester Mk.2; Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose I/O Board For PCCompatibles; Universal Wideband RF Preamplifier For Amateurs & TV. April 1991: Steam Sound Simulator For Model Railroads; Remote Controller For Garage Doors, Pt.2; Simple 12/24V Light Chaser; Synthesised AM Stereo Tuner, Pt.3; A Practical Approach To Amplifier Design, Pt.2. May 1991: 13.5V 25A Power Supply For Transceivers; Stereo Audio Expander; Fluorescent Light Simulator For Model Railways; How To Install Multiple TV Outlets, Pt.1. June 1991: A Corner Reflector Antenna For UHF TV; 4-Channel Lighting Desk, Pt.1; 13.5V 25A Power Supply For Transceivers; Active Filter For CW Reception; Tuning In To Satellite TV, Pt.1. July 1991: Battery Discharge Pacer For Electric Vehicles; Loudspeaker Protector For Stereo Amplifiers; 4-Channel Lighting Desk, Pt.2; How To Install Multiple TV Outlets, Pt.2; Tuning In To Satellite TV, Pt.2. August 1991: Build A Digital Tachometer; Masthead Amplifier For TV & FM; PC Voice Recorder; Tuning In To Satellite TV, Pt.3; Step-ByStep Vintage Radio Repairs. September 1991: Studio 3-55L 3-Way Loudspeaker System; Digital Altimeter For Gliders & Ultralights, Pt.1; Build A Fax/Modem For Your Computer; The Basics Of A/D & D/A Conversion; Windows 3 Swapfiles, Program Groups & Icons. October 1991: Build A Talking Voltmeter For Your PC, Pt.1; SteamSound Simulator Mk.II; Magnetic Field Strength Meter; Digital Altimeter For Gliders & Ultralights, Pt.2. November 1991: Colour TV Pattern Generator, Pt.1; Battery Charger For Solar Panels; Flashing Alarm Light For Cars; Digital Altimeter For Gliders & Ultralights, Pt.3; Build A Talking Voltmeter For Your PC, Pt.2; Modifying The Windows INI Files. December 1991: TV Transmitter For VCRs With UHF Modulators; Infrared Light Beam Relay; SolidState Laser Pointer; Colour TV Pattern Generator, Pt.2; Index To Volume 4. January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V 8A Power Supply, Pt.1; Baby Room Monitor/ FM Transmitter; Automatic Controller For Car Headlights; Experiments For Your Games Card; Restoring An AWA Radiolette Receiver. February 1992: Compact Digital Voice Recorder; 50-Watt/Channel Stereo Power Amplifier ; 12VDC/240VAC 40-Watt Inverter; Adjustable 0-45V 8A Power Supply, Pt.2; Designing A Speed Controller For Electric Models. March 1992: TV Transmitter For VHF VCRs; Studio Twin Fifty Stereo Amplifier, Pt.1; Thermostatic Switch For Car Radiator Fans; Telephone Call Timer; Coping With Damaged Computer Direct­ ories; Valve Substitution In Vintage Radios. April 1992: Infrared Remote Control For Model Railroads; Differential Input Buffer For CROs; Studio Twin Fifty Stereo Amplifier, Pt.2; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. May 1992: Build A Telephone Intercom; LowCost Electronic Doorbell; Battery Eliminator For Personal Players; Infrared Remote Control For Model Railroads, Pt.2; Aligning Vintage Radio Receivers, Pt.2. June 1992: Multi-Station Headset Intercom, Pt.1; Video Switcher For Camcorders & VCRs; Infrared Remote Control For Model Railroads, Pt.3; 15-Watt 12-240V Inverter; A Look At Hard Disc Drives. July 1992: Build A Nicad Battery Discharger; 8-Station Automatic Sprinkler Timer; Portable 12V SLA Battery Charger; Multi-Station Headset Intercom, Pt.2; Electronics Workbench For Home Or Laboratory. August 1992: Build An Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; Dummy Load Box For Large Audio Amplifiers; Internal Combustion Engines For Model Aircraft; Troubleshooting Vintage Radio Receivers. September 1992: Multi-Sector Home Burglar Alarm; Heavy-Duty 5A Drill speed Controller (see errata Nov. 1992); General-Purpose 3½-Digit LCD Panel Meter; Track Tester For Model Railroads; Build A Relative Field Strength Meter. October 1992: 2kW 24VDC To 240VAC Sine­wave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal Stereos; Electronically Regulated Lead-Acid Battery Charger. January 1993: Peerless PSK60/2 2-Way Hifi Loudspeakers; Flea-Power AM Radio Transmitter; High Intensity LED Flasher For Bicycles; 2kW 24VDC To 240VAC Sine­wave Inverter, Pt.4; Speed Controller For Electric Models, Pt.3. February 1993: Three Simple Projects For Model Railroads; A Low Fuel Indicator For Cars; Audio Level/VU Meter With LED Readout; Build An Electronic Cockroach; MAL-4 Microcontroller Board, Pt.3; 2kW 24VDC To 240VAC Sine­ wave Inverter, Pt.5; Making File Backups With LHA & PKZIP. September 1993: Automatic Nicad Battery Charger/Discharger; Stereo Preamplifier With IR Remote Control, Pt.1; In-Circuit Transistor Tester; A +5V to ±15V DC Converter; Remote-Controlled Cockroach Servicing An R/C Transmitter, Pt.1. October 1993: Courtesy Light Switch-Off Timer For Cars; Wireless Microphone For Musicians; Stereo Preamplifier With IR Remote Control, Pt.2; Electronic Engine Management, Pt.1; Programming The Motorola 68HC705C8 Micro­controller – Lesson 2; Servicing An R/C Transmitter, Pt.2. November 1993: Jumbo Digital Clock; High Efficiency Inverter For Fluorescent Tubes; Stereo Preamplifier With IR Remote Control, Pt.3; Siren Sound Generator; Electronic Engine Management, Pt.2; More Experiments For Your Games Card. December 1993: Remote Controller For Garage Doors; Low-Voltage LED Stroboscope; LowCost 25W Amplifier Module; Peripherals For The Southern Cross Computer; Build A 1-Chip Melody Generator; Electronic Engine Management, Pt.3; Index To Volume 6. January 1994: 3A 40V Adjustable Power Supply; Switching Regulator For Solar Panels; Printer Status Indicator; Mini Drill Speed Controller; Stepper Motor Controller; Active Filter Design For Beginners; Electronic Engine Management, Pt.4. February 1994: 90-Second Message Recorder; Compact & Efficient 12-240VAC 200W Inverter; Single Chip 0.5W Audio Amplifier; 3A 40V Adjustable Power Supply; Electronic Engine Management, Pt.5; Airbags: More Than Just Bags Of Wind; Building A Simple 1-Valve Radio Receiver. March 1994: Intelligent IR Remote Controller; Build A 50W Audio Amplifier Module; Level Crossing Detector For Model Railways; Voice Activated Switch For FM Microphones; Simple LED Chaser; Electronic Engine Management, Pt.6; Switching Regulators Made Simple (Software Offer). April 1994: Remote Control Extender For VCRs; Sound & Lights For Model Railway Level Crossings; Discrete Dual Supply Voltage Regulator; Low-Noise Universal Stereo Preamplifier; Build A Digital Water Tank Gauge; Electronic Engine Management, Pt.7. March 1993: Build A Solar Charger For 12V Batteries; An Alarm-Triggered Security Camera; Low-Cost Audio Mixer for Camcorders; Test Yourself On The Reaction Trainer; A 24-Hour Sidereal Clock For Astronomers. May 1994: Fast Charger For Nicad Batteries; Induction Balance Metal Locator; Multi-Channel Infrared Remote Control; Dual Electronic Dice; Two Simple Servo Driver Circuits; Electronic Engine Management, Pt.8; Passive Rebroadcasting For TV Signals. April 1993: Solar-Powered Electric Fence; Build An Audio Power Meter; Three-Function Home Weather Station; 12VDC To 70VDC Step-Up Voltage Converter; Digital Clock With Battery Back-Up; A Look At The Digital Compact Cassette. June 1994: 200W/350W Mosfet Amplifier Module; A Coolant Level Alarm For Your Car; An 80-Metre AM/ CW Transmitter For Amateurs; Converting Phono Inputs To Line Inputs; A PC-Based Nicad Battery Monitor; Electronic Engine Management, Pt.9 May 1993: Nicad Cell Discharger; Build The Woofer Stopper; Remote Volume Control For Hifi Systems, Pt.1; Alphanumeric LCD Demonstration Board; Low-Cost Mini Gas Laser; The Micro­soft Windows Sound System. July 1994: SmallTalk – a Tiny Voice Digitiser For The PC; Build A 4-Bay Bow-Tie UHF Antenna; PreChamp 2-Transistor Preamplifier; Steam Train Whistle & Diesel Horn Simulator; Portable 6V SLA Battery Charger; Electronic Engine Management, Pt.10. June 1993: Windows-Based Digital Logic Analyser, Pt.1; Build An AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; A Digital Voltmeter For Your Car; Remote Volume Control For Hifi Systems, Pt.2 July 1993: Build a Single Chip Message Recorder; Light Beam Relay Extender; AM Radio Trainer, Pt.2; Windows Based Digital Logic Analyser; Pt.2; Quiz Game Adjudicator; Programming The Motorola 68HC705C8 Micro­controller – Lesson 1; Antenna Tuners – Why They Are Useful. August 1993: Low-Cost Colour Video Fader; 60LED Brake Light Array; A Microprocessor-Based Sidereal Clock; The Southern Cross Z80-based Computer; A Look At Satellites & Their Orbits. Au g u s t 1 9 9 4 : H i g h - Powe r D i m m e r Fo r Incandescent Lights; Dual Diversity Tuner For FM Microphones, Pt.1; Build a Nicad Zapper; Simple Crystal Checker; Electronic Engine Management, Pt.11; Philips’ Widescreen TV Set Reviewed. PLEASE NOTE: all issues from November 1987 to August 1988, plus October 1988, December 1988, January, February, March & August 1989, May 1990, and November and December 1992 are now sold out. All other issues are presently in stock. For readers wanting articles from sold-out issues, we can supply photostat copies (or tear­sheets) at $7.00 per article (incl. p&p). When supplying photostat articles or back copies, we automatically supply any relevant notes & errata at no extra charge. August 1994  91 ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. Multiple coil version of transistor ignition I would like to suggest a redesign of your Transistor Assisted Ignition as described in the May and June 1988 issues of the magazine. It has occurred to me that it would be possible to fit multiple ignition coils, connected directly to each spark plug, thereby effectively bypassing the distributor, with its inherent losses through carbon tracking, moisture, rotor to plug lead contact, etc. Fully electronic systems such as on the Commo­dore utilise a sensor to detect crankshaft angle and deter­ mine the firing point for each cylinder. My proposal is to use the existing distributor for this purpose, which would no longer be a “distributor” as such, but more of a rotary switch. Using four opto or Hall-Effect sensors (for a 4-cylinder vehicle) within the distributor, these would ultimately trigger, in correct order, the appropriate coil for each spark plug. I accept there may be difficulties in fitting sensors for 6 or 8-cylinder vehicles but I am aware that some opto sensors are quite small and some 8-cylinder distributors quite large, so I believe it would be possible. Also, the cost of multiple coils at around $35 each 1.5V to 9V converter needs shielding I recently built one of your 1.5V to 9V converters, as described in the August 1992 issue of SILICON CHIP. It works pretty well, giving about 8.7V at no load and holding up quite well up to a load current of 36mA, at which point the voltage is 8V. With fingers firmly crossed, I tried it out on a small radio (Tandy Realistic 12-719). Much to my surprise, it worked well on FM, with no interference that I could hear. 92  Silicon Chip may be a problem but still comparable or even cheaper in some cases than a fully electronic system, without the need to also fit a crankshaft sensor, with whatever mechanical difficulties that may present with some vehicles. I hope you can envisage the advantages of retrofitting a fully electronic “distributor-less” system to an older vehicle, and at first glance it would seen simple and ideal if the exist­ ing distributor can be used as the “crankshaft position” sensor, thereby avoiding the losses involved in routing the high tension current by this means, also allowing full coil current to reach the plugs by close positioning and short leads with regard to the ignition coils. Vacuum and centrifugal advance of the ignition could still be preserved as with present electronic trigger modifications to points type distributors. Additionally, each coil would be operating at only a fraction of normal require­ments, extending its operating life due to cooler running, with the added advantage of a much greater period between firings, allowing each coil a much longer period to build up current before it is required. One other question if I may. I have a fuel flow sensor, impeller type, specification 22Hz <at> 10 litres/hr. I also have AM, however, was a completely different kettle of fish, with a lot of whistling background noise. This doesn’t worry me too much, since I usually listen to FM anyway, but it would be handy to be able to hear AM occasional­ly without being tortured. Could you suggest a simple RC filter that would do the trick? (J. K., Kenmore, Qld). • It is possible to minimise hash by installing the device in an earthed metal box and also keeping the ferrite rod of the radio as far away as possible from the converter. a LED display module which counts up by 1, with a negative pulse to the input. I intend testing it to find the number of pulses per litre flowed, then to use a counter/divider to convert to one pulse per litre to trigger the LED counter to count up by 1. Have you published a suitable counter/divider interface which I could use for this purpose? (P. C., Dundas, NSW). • You are proposing a very expensive conversion. You would need a complete transistor assisted ignition circuit, including the MC3334P chip, to drive each ignition coil. Actually, with a “dwell-extended” design such as our tran­sistor assisted ignition, the coil is conducting for virtually all of the time so that its dissipation is more or less constant, regardless of the spark rate. Thus, the coils would not run cooler. This brings us to a real problem with your proposed multi-coil system and that is the total current drain. Typically, the current drain in a “dwell extended” system is much higher than in a Kettering system with the dwell set by the points. For a single coil, the current can be expected to be around four or five amps and so for a 6-coil system the current would be around 30 amps. This is too much for the typical car alternator to handle when the headlights are on – the current drain would simply be too much. Lastly, while the distributor may seem like a clumsy me­chanical device, it is actually a very efficient high voltage switch and the losses are of little importance in a transistor assisted ignition system. That is why the vast majority of cars, one exception being the Holden Commodore, use a distributor. In fact, it is a paradox that the Holden Commodore has gone to the refinement of a multi-coil ignition system when its V6 engine is such a harsh running beast – a legacy of its 90° angle between the cylinder banks. We published a 3-digit counter in the September 1990 issue. This may be suitable for your fuel flow sensor. Using Polyswitches for loudspeaker protection I wanted to build the 50W audio amplifier published on the March 1994 issue and I figured the 2-way bookshelf speakers published in January 1993 issue would be an excellent match. I would like to protect the speakers using Polyswitch protectors but the thing is, how would I connect the Polyswitches on the crossovers and what sort of Polyswitches do I need? I also want to know what kind of Polyswitches would suit a “Nippon America” 10-inch 100W RMS sub­ woofer with an impedance of 4Ω? I would like to run it with the 50W amplifier. One last question: can Polyswitches be connected in parallel to double their maximum current rating? (M. C., Yarraville, Vic). • We featured Polyswitches in the 50W and 100W amplifier designs published in the December 1988 issue of SILICON CHIP. Suitable devices are stocked by Jaycar Electronics. You can insert them individually in series with the tweeter and woofer or just have one to protect each system. For the latter approach, we would suggest the Cat. RN-3415 from Jaycar. These could also be used to protect your 10inch speakers. You cannot connect Polyswitches in parallel as they will not share the current equally. Another vote for a signal strength meter In reference to the letter from B. P., of Port Macquarie, in the April 1994 issue, I too would be blessed if you would design a signal strength meter and present it as a project. As he states, commercial units are expensive and no doubt this is due to their flexibility and accuracy; a design based around a tuner/front end from a VCR should be just as good. I have included with my letter the circuit of a tuner/front end which is made by Sanyo and are easy to come by secondhand – most of their Beta machines are fitted with them. The beauty of this unit is that it only requires +12V for the supply and 0-12V to tune across the entire band. Band­ switching is achieved by taking one of three lines high as required. This makes it an ideal choice for a portable unit as it can then be Notes & Errata Microprocessor-Controlled Nicad Battery Charger, September 1993: a number of errors have come to light in the circuit on page 17. Pin 6 of IC2 should be labelled pin 1 in Fig.1 and the 330Ω resistor associated with Q3 should be in series with the emitter resistor. VRI and the 30kΩ resistor are reversed com­pared with the PC board layout on page 20. The lower of the two series resistors to earth from pin 9 of IC1 should be 2.2kΩ. Finally, the 100µF capacitor at the output of the 5V regulator is shown with incorrect polarity on the wiring diagram on page 20 and the 12V relay has been omitted from the parts list. 4-Bay Bow Tie UHF Antenna, July 1994: readers in eastern states who are having difficulty purchasing 4.74mm dia, 0.91mm wall thickness aluminium tube for this project should note that it can be purchased from the Alcan Aluminium Centre, Lidcombe, NSW (Phone 02 647 9900) or ordered from them through their local Alcan Centre. Readers in other states may also do this but they will have to pay freight from Sydney to their location. The reflectors and dipoles may be made from thicker tubing or rod; eg, 6.35mm diameter with suitable adjustment being made to the dipole mounting clip dimensions. The reflector, dipoles and the connector harness pieces could also be made powered by eight 1.5V cells or a 12V sealed lead acid bat­tery. In designing the meter, the following should be taken into account: (1) It needs to be able to detect and display signal strength from 1µV up to 2-3V (via a switched attenuator); (2) It should have a large, easy to read display, either a moving-coil meter or a digital readout (if not both); (3) It should be easy to calibrate without the use of expensive test equipment and have optional outputs at the rear for IF (to use the meter as a substitute tuner) and Video/Audio to feed to a monitor for picture quality evaluation. Judging by the comments I have had from others, a project like this would be extremely popular, as most from 4.74mm dia aluminium rod. For the harness pieces this material will need heating and hammering on an anvil in the areas where holes have to be drilled. The connector pieces could also be made from 3.2mm aluminium rod which is readily available from CIG welding cen­tres. Discrete Dual Supply Voltage Regulator; April 1994: the PC board pattern and the overlay pattern featured on page 31 has an error in that pin 3 of IC1b is not grounded. The board can be corrected by connecting a short link across to the adjacent GND track. Fast Charger for Nicad Batteries, May 1994: this circuit has caused confusion to many constructors because of its method of dV sensing to end the fast charging mode; it will not work unless it is actually charging cells. If you attempt to test the circuit without a nicad battery load, the output voltage will rise until pin 7 reaches +4.25V whereupon the circuit will switch off. For further background on this circuit, refer to the arti­cle on using the TEA1100 IC on page 6 of this issue. Dual Diversity FM Tuner, August 1994: the varicap diode D5 is shown on the circuit the wrong way around. It is shown correctly on the wiring diagram of this month’s issue, on page 68. commercial units start around $1500. There have been other designs presented before but in general they were uncalibrated or involved lengthy construction. (S. W., Hamilton, NZ). • The problem with designing such an instrument is not so much the tuner front end but that of calibration. Without calibration, such instruments are fairly useless. Tuners do not respond equal­ly over their band and therefore it is necessary to produce a calibration curve for each individual instrument if the results are to be accurate. This really does make it difficult for us to produce a useful product unless we can come up with a simple calibration procedure. At the moment, we don’t SC have a solution. August 1994  93 MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. CLASSIFIED ADVERTISING RATES VINTAGE RADIO Advertising rates for this page: Classified ads: $10.00 for up to 12 words plus 50 cents for each additional word. Display ads (casual rate): $25 per column centimetre (Max. 10cm). Closing date: five weeks prior to month of sale. To run your classified ad, print it clearly in the space below or on a separate sheet of paper, fill out the form & send it with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details to (02) 979 6503. VINTAGE RADIO SWAP meet/fair. Inc. military, amateur radio and antique sound. Sunday 23rd October, 1994 10am to 5pm. Glenroy Technical School Hall, Melbourne. Bookings: R. Howarth, PO Box 9, Junortoun 3551. Phone (054) 49 3207. _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ FOR SALE REAL TIME ICE!!! The only way to go. MOTOROLA 6805 EMULATOR and programmers. Prices and data from Graham Blowes, Mantis Micro Products, 38 Garnet Street, Niddrie 3042. Phone (03) 337 1917 (a/h), (03) 575 3349 (b/h). Fax (03) 575 3369. WEATHER FAX programs for IBM XT/ ATs *** “RADFAX2” $35 is a high resolution, shortwave weather fax, Morse & Rtty receiving program. Suitable for CGA, EGA, VGA and Hercules cards. Needs SSB HF radio & Radfax decoder. *** “SATFAX” $45 is a NOAA, Meteor & GMS weather satellite picture receiving program. Needs EGA or VGA plus “WEATHER FAX” PC card. *** “MAXISAT” $75 is similar to SATFAX but needs 2Mb expanded memory (EMS 3.6 or 4.0) and 1024 x 768 SVGA card. All programs are on 5.25-inch or 3.5-inch disks (state which) & include documentation. Add $3 postage. Only from M. Delahunty, 42 Villiers St, New Farm, Qld 4005. Phone (07) 358 2785. Enclosed is my cheque/money order for $­__________ or please debit my RCS RADIO PTY LTD Card No. ✂ ❏ Bankcard   ❏ Visa Card   ❏ Master Card Signature­­­­­­­­­­­­__________________________ Card expiry date______/______ Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ 94  Silicon Chip RCS Radio Pty Ltd is the only company that manufactures and sells every PC board and front panel published in SILICON CHIP, ETI and EA. RCS Radio Pty Ltd, 651 Forest Rd, Bexley 2207. Phone (02) 587 3491    Zelcon Technic Pty Ltd • • • • PCB Supplier Photoplotting Services SMT/Through-Hole Assembly CAD facilitites PO Box 149, Glenorchy, Tas 7010 Ph: (002) 71 8120, Fax: (002) 71 8182 BBS: (002) 73 0799 TRANSFORMER REWINDS 350 Watt Power MOSFET Amplifier Module • • • • As published in the June 1994 issue of Silicon Chip. Kit price $159.00. Postage and handling $8.00. Payment by M/C, B/C, Visa, Cheque or Money Order. 3kg O/N Air Bag $10.00 Computer & Electronic Services Pty Ltd 27 Osborne Avenue, Trevallyn Launceston, Tasmania 7250 Phone 003-34 4218; Fax 003-31 4328 MEMORY & DRIVES PRICES AT AUGUST 1ST, 1994 SIMM (all 70ns) Parity/No Parity 1Mb 30-pin $60/54 4Mb 30-pin $208/195 2Mb 72-pin $135 4Mb 72-pin $235/212 8Mb 72-pin $470/415 16Mb 72-pin $900/765 32Mb 72-pin $1690/1590 MAC 6Mb P’BOOK CO-PROCESSORS 387S/DX to 40 $350 $90 LASER PRINTER HP with 2Mb $198 ALL TYPES OF TRANSFORMER REWINDS COMPAQ PROLINEA TRANSFORMER REWINDS 8Mb $476 EPROM & SRAM EMULATOR: 2K x 8 (or 16) to 64K x 8 (or 16). Down­load and verify via standard PC printer port. Supports Binary, Intel and Motorola hex formats. Including Binary Editor. For more information, contact Northern Eastern Digital, PO Box 1252, Collingwood, Vic 3066. Fax (03) 484 5133/432 1063; Phone (03) 432 1699. MICASOFT Electronics and Computing tutor program, written in UK, ideal for TAFE, schools, or individual use. Now available in Australia. Send $1.80 in stamps for demo disk (tell us what size). $7 $8 IBM PS.2 55 x 65 SXVP 4Mb L40/N33 4Mb 90/95 PS1 4Mb $298 $280 $250 TOSHIBA 2000SX 44/6400 $460 $280 8Mb 4Mb SUN SPARC 10/20 16Mb SPARC 10/20 64Mb $975 $4080 DRIVES – SEAGATE 261Mb 16ms 2yr w 528Mb 12ms 2yr w 1052Mb 9ms 5yr w $315 $480 $1170 1st Floor, 100 Yarrara Rd, PO Box 382, Pennant Hills, 2120. Tel: (02) 980 6988 Fax: (02) 980 6991 SUBSTITUTE FOR A HANDFUL OF ICs: Parallax “BASIC STAMP”. A gen­er­al purpose small circuit module, it is really a 25 x 50mm board with a computer chip (4MHz PIC 16C56), EEPROM, 8 I/O pins, board space includes prototyping area. Program it on a PC (only 33 instructions) with development kit which includes one “BASIC STAMP” ($249 plus S/T & post), extra modules ($66 plus S/T & post). Send 45c stamp for more information. Parallax distributor and techni­cal support in Australia: MicroZed Computers, PO Box 634, Armi­dale, NSW 2350. Facsimile (067) 72 8987. 70ns 70ns Sales tax 21%. Overnight delivery. Credit cards welcome. 5-Year warranty. Ring for latest prices. Reply Paid No.7, PO Box 1058, St Marys, NSW 2760. Ph: (02) 833 1146. Fax: (02) 623 5559. SATELLITE TV DX SUPER RX receiver. Threshold 2.5dB. Also digital picture, sound, synchron, resolution processors. Mobile DX re­ceivers, pay TV decoders. TV, radio, picture, sound mod­ulators. Digital, analog signal meters. Send $5 for info and catalog/refundable to John Papp, PO Box 472, Sanderson, NT 0812. Fax/Ph:(089) 27 4985. DRAM DIP 1Mb x 1 256 x 4 PELHAM MicroZed Computers, PO Box 634, Armidale 2350. FLUORESCENT INVERTER KIT (SC, Feb 91) (Soft Technology No. 46): 12V, 24V or 48V/16W version. Secondary wind, board plus compon­ents $30 plus $4 p&p. SOLAR BATTERY CHARGING REGULATOR: short form kit 12V or 24V (SC, Jan 94) 10A $54 plus $4 p&p. Additional Mosfet $8 and Schottky diode $5 to make 20A regulator. With every kit ordered FREE used LEAD SEALED BATTERY 12V/4Ah or 6Ah while stocks last. Good condition but no warranty. Only p&p is charged for battery. Ring for postage cost. Cheques and postal money orders accepted with mail orders. Send orders to: Otakar Priboj, PO Box 362, Villawood, NSW 2163, Australia. Phone (02) 724 3801. INTELLIGENT INFRARED RECEIVER (ref SILICON CHIP, March 94). Now with 8 outputs. Use your TV or VCR infrared remote control trans­mitter to control your TV or hifi appliances with an intelligent infrared receiver kit. Also available infrared transmitters, preprogrammed and learning models. For details call BENETRON P/L (018) 20 0108. MANIPULATE MODELS, Machines, Men or Mice from the serial port (9600, N, 8, 1) of your PC using my PICEX Controller. It’s a tiny computer with its own Operating System controlling 16 I/O lines. Very simple programming language. You can even drive it from any VDU or terminal. Has 3 LEDs, 26pin MAD bus and 34-pin RELAY8 bus. Up to 256 boards can be driven from 1 serial port. Short form kit includes programmed PIC16C57-XT chip, board, 4MHz Xtal, and MAX-232 $70, A&T $130. Promo disk $2. Don McKenzie, 29 Elles­mere Crescent, Tullamarine 3043. Phone (03) 338 6286.    SILICON CHIP BINDERS These beautifully-made binders will protect your copies of SILICON CHIP. They feature heavy-board covers, are made from a dis­tinctive 2-tone green vinyl & have the SILICON CHIP logo printed in gold-coloured lettering on the spine & cover. To order, just fill in & mail the order form on page 79, or phone or fax your order to: Silicon Chip Publications, PO Box 139, Collaroy Beach, 2097. Phone (02) 979 5644. Fax: (02) 979 6503. August 1994  95 Microprocessor For Stereo Preamplifier Now back in stock: the 68HC705-C8P pre-programmed micro­pro­cessor for the Infrared Remote Controlled Stereo Preamplifier (SILICON CHIP, Sept.Oct. 1993). Also suits the Remote Volume Control (May & June, 1993). Price: $45 + $6 p+p Payment by cheque, money order or credit card to: Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. Phone (02) 9795644; Fax (02) 979 6503. THE HOMEBUILT DYNAMO: (plans) brushless, 1000 DC watt at 740 revs. $A85 postpaid airmail from Al Forbes, PO Box 3919 - SC, Auckland, NZ. Phone Auckland (09) 818 8967 any time. Rotor magnets (3700 gauss) kit now available. VALVE AMPLIFIERS: Australian made. Mono, stereo, guitar using 2A3, 211, 6L6 or 807 valves. Williamson reproductions. Parts available for DIY constructors. Circuit diagrams and construction details for many types of valve amplifiers. Valve equipment repairs. Lancroft Pty Ltd, PO Box 439, Bexley 2207. Phone (02) 567 5390. THE 8051 MICRO-COMTROLLER book includes a simulator disk ($40). ROMLoader EPROM Emulator (EA Jan/Feb 92, EA June 94) (PCB $30). 8051 Proto-Boards (EA Feb 93) (PCB $30). Tantau Australia, PO Box 1232, Lane Cove, NSW 2066. Phone AH (02) 878 4715. SmallTALK for PCs: voice digitiser for 286’s and up Play speech on your PC’s speaker with no sound card! 3 minute version $34.95 HDD version $39.95 Optional QLB/LIB libraries $14.00 All orders add $3.05 p+p. Send your cheque/order to: RAT Electronics AUSTRALIA PO Box 641, Penrith, NSW 2750 Ph: (047) 77 4745 Fax: (047) 77 4745 Altronics ................................ 60-62 Aust. Audio Consultants...............95 Av-Comm................................57,77 Computer & Elect. Services.........95 David Reid Electronics ..............33 Dick Smith Electronics........... 12-15 E. R. Audio...................................96 Harbuch Electronics....................33 ELECTROSTATIC LOUDSPEAKERS 3-PANEL FULL RANGE DESIGN, AVAILABLE IN KIT FORM OR FULLY ASSEMBLED. LOCALLY DESIGNED & MANUFACTURED. FOR INFORMATION BROCHURE, PHONE/FAX (09) 397 6212 OR WRITE TO: E. R. AUDIO, 119 BROOKTON HWY, ROLEYSTONE, WESTERN AUSTRALIA 6111. Instant PCBs................................95 Jaycar ................................... 45-52 Kalex............................................88 L & M Video.................................43 Macservice....................................3 Oatley Electronics.................. 78-79 PC Computers.............................89 Pelham........................................95 Rat Electronics............................96 RCS Radio ..................................94 UNUSUAL BOOKS: Electronic Devices, Fireworks, Locksmithing, Radar Invisibility, Surveillance, Self-Protection, Unusual Chem­ istry and more. For a complete catalog, send 95 cents in stamps to Vector Press, Dept S, PO Box 434, Brighton, SA 5048. Rod Irving Electronics .......... 26-30 PRINTED CIRCUIT BOARDS for the hobbyist. For service & enquiries contact: T. A. Mowles (08) 326 5590. Silicon Chip Software..................23 2.2kVA VARIAC unenclosed $200. 110V 1kVA transformer enclosed $100. Phone (047) 87 8968. SILICON CHIP FLOPPY INDEX WITH FILE VIEWER Now available: the complete index to all SILICON CHIP articles since the first issue in November 1987. Now you can search through all the articles ever published for the one you want. The index comes as an ASCII file on a 3.5-inch or 5.25-inch floppy disc to suit PC-compatible computers and you can use any word processor or our special file viewer to search for keywords. Simply enter in the keyword(s) and the index will quickly find all the relevant entries. All commands are listed on the screen, so you’ll always know what to do next. Price $7.00 + $3 p&p. Send your order to: Silicon Chip Publications, PO Box 139, Collaroy 2097; or phone (02) 979 5644 & quote your credit card number; or fax the details to (02) 979 6503. Please specify 3.5-inch or 5.25-inch disc. 96  Silicon Chip Advertising Index Silicon Chip Back Issues....... 90-91 Silicon Chip Binders....................95 Silicon Chip Bookshop.................73 Silicon Chip Projects Book........IBC Tektronix....................................IFC Transformer Rewinds...................95 Yokogawa................................OBC Yuga Enterprise...........................87 Zelcon Technic.............................95 _________________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 587 3491. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone (09) 828 5730. • H. T. Electronics, 35 Valley View Crescent, Hackham West, SA 5163. Phone (08) 326 5590. Especially For Model Railway Enthusiasts Order Direct From SILICON CHIP Order today by phoning (02) 9979 5644 & quoting your credit card number; or fill in the form below & fax it to (02) 9979 6503; or mail the form to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. This book has 14 model railway projects for you to build, including pulse power throttle controllers, a level crossing detector with matching lights & sound effects, & diesel sound & steam sound simulators. If you are a model railway enthusiast, then this collection of projects from SILICON CHIP is a must. Price: $7.95 plus $3 p&p Yes! Please send me _______ copies of 14 Model Railway Projects Enclosed is my cheque/money order for $­_________ or please debit my  Bankcard    Visa Card    Master Card Card No. Signature­­­­­­­­­­­­_________________________ Card expiry date_____/_____ Name _________________________Phone No (____)_____________ PLEASE PRINT Street ___________________________________________________ Suburb/town __________________________ Postcode____________