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Electronics for the enthusiast ~ {;;;;;!£-~§· c::::;;, ----· ' =-"" __ ~ ~ ~~ SERVICING - HIFI - - ~l..!!:~':ii,,,~ = ~,cs ~~ ~ c1RO __;;:= ~ 3 ·1.W·Si#•);l;t-Mt• iM•!iiMii--:W STEREO CONTROL PREAMPLIFIER - new benchmark performer The original & best TV serviceman ..... ~ Projects to build: z ~ Mega-fast nicad charger ~ lor R/C enthusiasts :c ~ Automatic light controller ~.; with infrared sensor ! Convert your car to .! breakerless ignition CIJ 0 OPTIMUS 304: TANDY'S SURPRISE LOUDSPEAKER PACKAGE ::, c. ::, <( Q) a: Appliance repair: has Mr Fixit had his day? Fluke. First Family of DMMs. When accuracy, performance and value are important, professionals the world over look to Fluke - the first family of DMMs. Reliable Fluke-quality 3½- or 4½-digit DMMs fit every need - from design engineering to industrial troubleshooting. There's the low-cost 70 Series - the most DMM you can get for the money. The tough 20 Series - totally sealed and built to survive the dirtiest, grimiest, roughest jobs. The reliable 8020B Series - made to withstand the rigors of the field service environment. The precise 8060A Series the most powerful and complete test and measurement system available in~ handheld package. And, of course, the versatile Bench/Portables that carry on the Fluke tradition for precision and durability in lab-quality bench instruments. Fluke comes in first again with the world's largest selection of quality accessories to help extend the capabilities of your DMM even further. There's no need to look anywhere else. Uncompromising Fluke design and leading edge technology are the reasons why attempts at imitation will never fool the millions of professionals that accept nothing less than a Fluke. FROM THE WORLD LEADER IN DIGITAL MULTIMETERS. IFLUKEI ® ELMEASCO Instruments Pt,,. Ltd. Dealer enquiries welcome faik to your local Elmeasco distributor about Fluke • A.k.L._ John Pope Electrical (062) 80 6576 • J Blackwood & Sons (062) 80 5235 • George Brown (062) 80 4355 • ~ Ames Agency 699 4524 • J Blackwood & Sons• George Brown 519 5855 Newcastle 69 6399 • Auto-Catt Industries 526 2222 • D.G.E. Systems (049) 69 1625 • W.F.Dixon (049) 69 5177 • Ebson 707 2111 • Macelec (042) 29 1455 • Novacastrian Electronic Supply (049) 62 1358 • Obiat Ply Ltd 698 4776 • Petro-Ject 569 9655 • David Reid 267 1385 • Selectroparts 708 3244 • Geoff Wood 427 1676 • N.TERRITORY J Blackwood & Son (089) 84 4255, 52 1788 • Thew & McCann (089) 84 4999 • O~EN¥£ Auslec (07) 8541661 • G.Brown Group (07) 252 3876 • Petro-Ject (075) 91 4199 • St Lucia Electronics 52 7466 • Cliff t:le rorncs 55 • Nortek (Townsville) (077)79 8600 • L.E.Boughen 369 1277 • Fred Hoe & Sons 277 4311 • The Electronics Shop (075) 32 3632 • Thompson IQstruments (Cairns) (070)51 2404 • S AUSTRALIA Protronics 212 3111 • Trio Electrix 212 6235 • Industrial Pyrometers 352 3688 • J Blackwood & Sons 46 0391 • Petro -Ject 363 1353 • TASMAWA George Harvey (003) 31 6533 (002) 34 2233 • VICTORIA Radio Parts 329 7888 • George Brown Electronics Group 878 8111 • G.B. Telespares 328 4301 • A.W.M. Electrical Wholesalers • Petro-Ject 419 9377 • J Blackwood & Sons 542 4321 • Factory Controls (052) 78 8222 • Mektronics Co 690 4593 • Truscott Electronics 723 3094 • WAUSTRALIA Atkins Carlyle 481 1233 • Debbie Instruments 276 8888 • Protronics 362 1044 JUNE 1988 FEATURES LOOKING FOR A NEW stereo control unit to .go with your power amplifier? This unit has excellent performance, plenty of control features, and is easy to build. See page 28. ~ ~u ~ -~ ~ 10 What is Negative Feedback? by Bryan Maher Pt.2 - Why we need negative feedback 15 Realistic Optimus 3-Way Loudspeakers by Bob Flynn Three-way system is good value for money 80 The Evolution of Electric Railways by Bryan Maher Pt.8 - The first 3-phase AC electric railway 86 Digital Fundamentals, Pt.8 by Louis Frenzel Introduction to microcomputers PROJECTS TO BUILD I rn ., _ ~ SERVICEMAN'S LOG this month tells the story of a ringin picture tube. There's also the usual collection of zany cartoons. Turn to page 38 28 Studio 200 Stereo Control Unit by Leo Simpson New benchmark performer is easy to build 44 Convert Your Car to Breakerless Ignition by John Clarke Get rid of those old-fashioned points 56 Automatic Light Controller by Branco Justic Uses an infrared sensor to detect movement 62 Mega-Fast Nicad Battery Charger by Greg Swain Charges a 7.2V racing pack in just 20 minutes SPECIAL COLUMNS 6 The Way I See It by Neville Williams For all practical purposes, Mr Fixit has had his day! 16 Vintage Radio by John Hill Cleaning up a vintage radio receiver 38 Serviceman's Log by the original TV serviceman Ring out the new, ring in the old 72 Amateur Radio by Garry Cratt Build an RF sniffer probe & preamplifier THIS MEGA-FAST NICAD CHARGER will recharge a 7.2V nicad racing pack in just 20 minutes. It then switches off to prevent overcharging. Details page 64 DEPARTMENTS 2 Publisher's Letter 3 Mailbag 4 News & Views 19 Back Issues 51 Book Reviews 69 Circuit Notebook 75 Subscriptions 77 Product Showcase 94 Ask Silicon Chip 95 Notes & Errata 96 Market Centre LAST MONTH, we showed you how to install a highenergy ignition system in your car. This month, we show you how to replace the points with a Hall Effect pickup for maximum performance and even less maintenance. See page 44. JUNE 1988 1 SILICON CHIP Publisher & Editor-in-Chief Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn PUBUSHER'S u:·1-1'ER Advertising Manager Paul Buchtmann Regular Contributors Neville Williams, FIREE, VK2XV Bryan Maher, M.E. B.Sc. Jim Yalden, VK2YGY Garry Cratt, VK2YBX Jim Lawler, MTETIA David Whitby Photography Bob Donaldson Editorial Advisory Panel Philip Watson, MIREE, VK2ZPW Norman Marks Steve Payor, B.Sc., B.E SILICON CHIP is published 1 2 times a year by Silicon Chip Publications Pty Ltd. All material copyright (c) . No part of the contents of this publication · may be reproduced without prior written consent of the publisher. Kitset suppliers may not photostat articles without written permission of the publisher. Typesetting/makeup: Magazine Printers Pty Ltd , Waterloo, NSW 2017. Printing: Macquarie Publications Pty Ltd, Dubbo, NSW 2830. Distribution: Network Distribution Company. Subscription rates are currently $42 per year (12 issues). Out, side Australia the cost is $62 per year surface mail or $1 20 per y~ar air mail. Liability: 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. Address all mail to: Silicon Chip Publications Pty Ltd , PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 982 3935. ISSN 1030-2662 • Recommended and maximum Australian price only. 2 SILICON CHIP Decision trees and preamplifiers It is quite surprising how, when a particular project has been designed for the magazine, a whole host of related applications then suggest themselves. Sometimes we can act immediately on these ideas; at other times they remain to be followed up later. The most recent example of this was when we designed the 50/lO0W module published in December 1987. No sooner had we published it than the idea of a higher-rated stereo power amplifier was mooted. The result was the Studio 200 power amplifier described in February 1988. And as soon as that hit the streets, we had readers clamouring for a matching stereo control preamplifier and other related projects. Luckily, we had foreseen the demand for a stereo control unit and started development work on it as soon as possible. The result appears in this issue, as part one of a two-part article. We're very proud of the Studio 200 Control Unit. Whether it will be hailed by the dyed-in-the-wool hifi enthusiast we don't know but it does bring together a number of highly desirable features. First of all, it uses a new low-noise dual op amp, the LM833, from National Semiconductor. This op amp not only has very low noise, but is also very cheap. Second, by using these LM833 op amps, we have been able to keep the circuit complexity to a pleasingly low level; just four dual op amps, four transistors and four diodes, plus the power supply components. As a result, the overall price of the control unit should be something of a benchmark for economy; a little over $200. Third, the overall performance is as good as or better then virtually any stereo preamp/power amp combination costing up to $3000 or more. By contrast, the overall cost of the Studio 200 preamp/power amp combo is going to be around $630. Just to focus on one aspect of performance, the unweighted signal to noise ratio for the high level inputs is 103dB or better. Very few amplifiers, regardless of price, offer this level of performance. That may seem surprising, but it's the kind of performance needed if the amplifier chain is not to degrade the signal quality from compact discs. Finally, the new control unit has an excellent headphone output with exactly the same level of performance. This is unusual for two reasons. Most stereo control units do not have headphone outputs at all and most integrated amplifiers give mediocre performance from their headphone sockets. This is the third in a series spawned by the original project published back in December 1987. We have quite a few to go before the series will be exhausted. When you consider all the projects we have published so far and all the possible project ideas that will flow from each of these, that's a lot of decision trees. How many projects will it mean over the next few years? Leo Simpson MAILBAG Computers are OK Congratulations on your great magazine. Finally, there is some competition in the electronic magazine market. Now down to business. In your May editorial, Leo Simpson said that there will be computer projects. Now this is fine as long as there are not too many of them. I have worked with computers for almost six years now (on business and games machines) and find them interesting. But for the beginner, they can be very over-bearing. The solution, I think, is to start a series dealing with computers at a very basic level, and then work up, perhaps with a few low-cost projects included with the articles. Perhaps a few other readers might like to comment on this. A few other suggestions for your magazine: how about a series on electronics? This could benefit readers both young and old. It would (a) help people to learn the basics and (b) help more experienced people brush up on a few key points. Louis Frenzel's articles on Digital Fundaments were excellent. I am presently studying this subject at certificate level and found the series to be a great help to me. Finally, I wish you the best of luck for your magazine and hope that you keep up the high standard you have held for your last seven issues. Steven Schulz Bayswater, Vic Project suggestions In response to a request in your March issue, I would most definitely like to see a project for a public address amplifier. During the last 12 months, I have had two organisations ask me if I could find a suitable PA amplifier for them, but commercial units were either too large and/or too costly. All that is required is a unit with two microphone inputs and perhaps a line input for tape, etc. At the same time, do not forget to publish an article on suitable loudspeakers, etc. Some readers may also appreciate an article on installing such a system. Another project I would like to see SILICON CHIP, PO Box 139, Collaroy Beach 2097. is a musicolour project. The current musicolour kit has a few limitations although it is basically a good design. The beat triggering filter needs to be adjustable for the chase mode, each channel needs a sensitivity control, and it needs adjustable bandpass filters so that the centre frequencies can be shifted. I would like to congratulate you on a fine magazine which is to the quality of some years back. For a couple of years, the quality of Australian electronics magazines fell. Your new magazine has good general reading and thought provoking articles, such as "Serviceman's Log" (which I always read first) and "The Way I See It". A. T. Morgan Paradise, SA Thank you for your project suggestions. We've already developed a circuit very similar in principle to a musicolour but offering considerable operating refinement. This will be published as the "Discolight" in our July issue. We also have a new highpower PA amplifier under development. you may not be aware of their triggering characteristics. We have run some tests and found, when using sine waves, that the polyswitch trips extremely rapidly at a current that is 2.5 to 3 times the nominal or stated rating. This means that a 1.15 polyswitch might trip at 3.45 amps and into 8 ohms this means 95 watts. Similarly, the 2.45 might trip at 7 amps and into 8 ohms this means 432 watts. Perhaps you may care to review the value in light of the above comments. R. Grant Chapel Hill, Qld Thank you for your Jetter. That "f]aming great bolt" on the Studio 200 is not nearly as apparent on the unit as it looks in the photo [we used a black anodised type). However, there's nothing to stop you from mounting the transformer on a suitable bracket bolted to the bottom of the chassis, just inside the front panel. We did a lot of practical testing in selecting the PTC thermistors and are confident that the values we have selected are correct. Flamin' great bolt The MEN system I note with some interest your new venture and wish you well. The new format looks good and the lean/mean approach to staff numbers should prove profitable. I was very interested in the article describing the 100W p·ower amplifier. Its performance is good and it looks easy to put together with, at last, a reasonable size bracket to thermally connect the output transistors to the heatsink. The bad news is that you were not the first to use a polyswitch as a protection device. The IREE Brisbane Audio Group preceded you by several months. The 200-Watt Stereo Power Amplifier is a beauty but why oh why did you spoil the front panel with that flaming great bolt? Could not the toroid have been mounted horizontally on say a 3mm sub-panel for strength or did you not have the room? On the matter of the polyswitch, you have specified a high value and I refer to the article entitled "Your House Wiring Could Kill You" written by Leo Simpson in the November 1987 edition of SILICON CHIP. There are a number of points concerning requirements for wiring arrangements that I would like to comment on in terms of the SAA Wiring Rules, AS 3000-1986. • AS 3000 is called up by all Electrical Regulatory Authorities throughout Australia and as such all consumer installations would need to comply with the requirements of that standard. The multiple earthed neutral (MEN) system is one of three systems recognised by AS 3000. • Fig.1 of your article and related text imply a common main earth and main neutral bar or link. This has been precluded by AS 3000 since 1982. A separate earth link and neutral link must be provided. • Various references are made to the consumer's water pipe as the connection point for the main earthing continued on page 90 JUNE 1988 3 NEWS&VIEWS ,, / More FM broadcast services Pursuant to a landmark decision made by the Whitlam Federal Government in 1974, commercial FM radio broadcast services are gradually being extended nationwide. The rate of expansion depends partly on the reallocation of TV stations from the FM band to UHF, but, as well, on the ability of the various areas to sustain an additional radio broadcaster. According to the Minister for Transport and Communications, Senator Gareth Evans, the present government's overall plan is to tend commercial FM services to more then 4.2 million Australian listeners outside mainland state capitals by 1992. Lismore, NSW (population 104,000) and Townsville, Qld (population 150,000) have both been provisionally judged capable of sustaining an additional independent commercial station and licence applications have been invited to that end for final determination by the ABT (Australian Broadcasting Tribunal). The new services could reasonably be expected to be on air by early 1990. ex- The new Philips CD 201 half-height internal CD-ROM fits into any standard 5-1/4 inch floppy disc slot. It is shown here with the 'caddy' and interface card. Storage capacity is up to 500 gigabytes per disc New CD-ROMs to store masses of information - up to 500 gigabytes Having successfully developed and launched the compact disc as a fine music source, and with video applications awaiting only commercial exploitation, Philips are now claiming clear leadership in another quite different field: CDROM or the use of compact discs to store huge amounts of information for subsequent access by computers. As pointed out in the January 1988 issue (p.85), compact discs can store at least 500 gigabytes per disc, equivalent to 150,000 A4 pages of ordinary printed text, or the contents (minus pictures) of Grolier's American Academic Encyclopaedia. They are a natural repository for large data bases and have already been applied for that purpose. At a presentation in Sydney during April, Guy Norman, Philips' national marketing manager for CDROM and Laser Interactive Products, introduced what he described as the company's new "Total CD-ROM Solution". The object is to cater for the many organisations 4 SILICON CHIP that will inevitably want to develop and publish their own CD-ROMs, To this end, Philips have structured what is claimed to be the most comprehensive range of hardware, software and support services in this part of the world. More than that, it has already taken orders for the preparation of Australian CDROMs with a wide potential market appeal. Pictured above is just one item of hardware, the CD half-height internal CD-ROM drive, with the appropiate interface card and a disc caddy which, like a floppy disc pack, allows the unit to operate with the slot either horizontal or vertical. If the disc drive looks familiar, it probably is. It has been designed to fit, if desired, into virtually any 5-1/4 inch floppy disc aperture in an existing PC. The new Philips drive systems boast an average data access time of 500 milliseconds - the fastest drives on the market. For more information, contact George Sprague on (02) 925 333 or Guy Norman on (02) 888 8222. Radio pirates saved from the yard-arm! During April, the Department of Transport and Communications declared an amnesty for operators of unlicensed radio transmitters in and around Dubbo, in mid-western NSW. A temporary licensing centre, set up in the local CES office, attracted an average of 200 inquiries (confessions?) per day. About 85% of the inquiries came from private owners of unlicensed CB (citizens band) equipment but a variety of commercial and other radio coi:nmunications equipment needed to be inspected for licensing, including aircraft and marine transceivers, land mobile units and base stations. Concern about the caretaker's daughter Blame George Sprague of Philips for the reminder about the old music hall song: ''Who takes care of the caretaker's daughter when the caretaker's busy taking care?" What he's really on about is: who is in a position to check precision test equipment used in standards laboratories operated by organisations like Qantas or the Australian Army? His preferred answer, it seems, is the new Philips Calibration Laboratory at Moorebank, NSW. Part of the Philips Defence Electronics Facility, the laboratory was established to support the complex digital and analog equipment required for testing the RAAF F/A-18 Hornet's radar. Back in 1983, a joint study by the Australian Government, Hughes Aircraft and McDonnell Douglas had shown that there was no facility in Australia with the necessary credentials, accuracies, capabilities and capacity for the task. Now, after a 3-year setting-up program, the laboratory is able to offer calibration, testing and maintenance for a wide range of scientific, industrial and medical instruments George Greaves, Philips defence and projects manager at Moorebank, says that the Cal Lab facility is unique in that its own standards are traceable both to the US National Bureau of Standards and to the Australian National Measurement Laboratory. The 450 square metres laboratory includes four separate rooms covering general electronic instruments, AC/DC and resistance, RF microwave, and mechanical properties. The rooms are constantly environmentally controlled, constantly monitored by recorders, and autonomous for power at 240V and 115V, 50 and 60Hz, plus a separate ground earth system. HP1000 computers are used for system management and calibration procedures. For further information: George Sprague (02) 925 3333. Home recording on CDs! New system could sink DAT According to a Tandy spokesman, the company has developed a new compact disc system which makes it possible to record music, video or computer data on disc and to erase it at will, hundreds of times. What has startled the Japanese hifi industry is not so much the fact that Tandy has the necessary technology but that they are talking about a compact disc player/recorder that will sell for the equivalent of around $A500. Present Japanese optical disc player/recorders, developed mainly for storing computer Altronics wholesale office for Sydney Altronic Distributors Pty Ltd has opened an office at the Sydney Executive Centre, 119 Willoughby Rd, Crows Nest, NSW 2065. The telephone number is (02) 436 0422 aiid, by the time you read this, fax facilities should also be operational. In a recent press release. Altronics Sales Manager Fred Bloffwitch emphasised the importance of the NSW market and the Audio tapes aren't always true to label Despite the old saying that "fifty million Frenchmen can't be wrong", TDK maintain that around that number of "phony" audio tapes have been dumped on the world market by racketeers, in packaging that is meant to be mistaken for the genuine TDK product. To date, the counterfeiters have .concentrated on audio tapes, because they are relatively easy to imitate and their reduced price looks like a tempting bargain. TDK view the problem so seriously that they have appointed an "overseas project data, sell for at least sixteen times that figure. If Tandy can come up with an economical re-recordable disc system, it could drastically affect the world market for DAT (digital audio tape) player/recorders, in which Japanese manufacturers have an enormous investment, as yet unrecovered. In Japan, DAT equipment presently costs around · $A1000. Their planning has been based on an assumption that an economical and competitive disc record/replay system would be 10 to 20 years away. need to streamline customer relations in this area, particularly in respect to his company's wholesale trading activities. Mr Colin Fobister has been appointed as sales coordinator for NSW. Contacted by SILICON CHIP, Mr Fobister emphasised that the new Willoughby facility is purely a business office and does not carry stock. It is concerned primarily with the wholesale side of the business. Retail mail order customers should -continue, as normal, to deal direct with Altronics in Perth. coordinator" to track down offenders. Tape counterfeiters have been particularly active, they say, in south-east Asia, notablY. Taiwan and Hong Kong but, recently, a Singapore Company, Sound Enterprises Pty Ltd, was raided and 6,200 pieces of fake TDK audio tape, 1,000 wrappers, 108,000 index cards and 165,000 outer cassette casings were confiscated by police and destroyed. The managing director was fined $2,000 and a civil action for compensation instituted. As yet, no counterfeit TDK tapes have come to light in Australia, but buyers should still beware of bargain offers. ]UNE 1988 5 THE WAY I SEE IT By NEVILLE WILLIAMS For all practical purposes Mr. Fixit has had his day! For generations, a major raison d'etre for a father, husband or son has been their ability, at short notice, to repair household gadgets. But according to a reader from Berala, NSW, that traditional role is now at risk. Who needs a handyman around the modern home when the best he can do with a faulty electrical appliance is to discard and replace it? To be sure, I have met a few men in my day who never have lived up to the traditional stereotype; who have even boasted of their inadequacy when faced with anything mechanical or technical. But, more commonly, I have been pleasantly surprised at the number of men who have relished the opportunity, at evenings or weekends, to put aside the business suit, the briefcase and the telephone and to get stuck into the mechanical or technical tasks that needed to be tackled around the family home or family car. The reader referred to above is concerned about one specific area but, if I've taken the broad brush approach to his letter, it's because he has struck a sympathetic cord in one who feels frustrated by any gadget which either has to be discarded prematurely or is subject to a daunting minimum service charge and delay for some fault that, not so long ago, would have been readily fixable at home. I quote: Dear Mr. Williams, I wonder whether you, like me, object to appliances which have been assembled with tamper-proof screws? More and more manufac6 SILICON CHIP turers, these days, are putting these screws into their products. What they are saying, in effect, is: "you are prohibited from servicing this device". The situation is now such that I think twice about buying any product fitted with tamper-proof screws. I like to be able to fix anything I buy or at least inspect the inside, if the necessity should arise. After all, what guarantee is there, if the product does finally break down, that the company that made or imported it will still be around to fix it? Consider the simplest of all servicing jobs - the renewing of a power "Who needs a handyman around the home when the best he can do with a faulty appliance is to discard and replace it?" cord. It is annoying enough that most appliance cords now come with moulded plugs, which means that the plug has to be thrown out as well as the cord. Another simple repair job often made difficult is the unclogging of electric hair dryers. When people with long hair use dryers, it is inevitable that hairs occasionally get pulled into the air inlet. Eventually, enough gets wrapped around the motor shaft to stall it. Pulling these dryers apart to clear them is a tricky job. I wonder how many hair dryers have been consigned to the tip for want of this otherwise simple repair. The problem goes even further. I feel sure that some appliance cords are designed to perish prematurely. I am thinking particularly of the removeable cords fitted to electric frypans and the like. They generally have a neoprene or similar synthetic rubber sheath which tends to perish on exposure to the grease and oil which is inevitably present. Why are the newer plastic materials not used here? And just try replacing the cord on a frypan controller. It's impossible! Yet the cost to replace such a controller is around $30 or more. Is that reasonable? I think not. I'd appreciate your views on this subject. S.L. [Berala, NSW). While, as I said, I have a considerable empathy with the sentiments expressed by S.L., in actually commenting on them, I run the risk of sounding like an apologist for the manufacturers of a whole range of household appliances hair dryers, irons, Phil Watson turns the clock back Dear Neville, I was most interested to read your comments in the February issue of SILICON CHIP and your reference to my recollections of the pilfering techniques employed at the HMV factory many years ago. It certainly stirred up a lot of memories. It wasn't only transformers which were dropped on- to the railway embankment; the transformers were often accompanied by the chassis to which they were attached. And, when I say chassis, I don't simply mean a piece of folded metal; they were completely wired and tested receiver chassis, minus only the valves and dial glasses. These would be smuggled out later by a variety of ruses. The drop was usually made from the factory root - second floor level - to which employees had ready access, with very little supervision. The trick was to hold the chassis by the corner diagonally opposite the transformer, so that it landed on the transformer corner. The embankment was manmade, consisting mainly of soft earth bonded by grass roots. Even so, it says something for the ruggedness of these chassis that they were able to withstand .such an unofficial drop test. It's a pity that the company wasn't in a position to boast about it in their advertising! As for the "Trojan Horse" in reverse, it was part of a much more serious offence, involving pilfering on what might be termed theft on a "commercial" scale. A team of characters was involved. Only recently employed, they must have regarded the company's goodwill as a gift from the gods. Many components were involved but mainly valves. It was wartime and valves were in short supply. For domestic receivers, they could only be bought with government approval and on a strictly limited basis. It often happened that a batch of several hundred receivers would be completed before all the valve types required came to hand. The receivers would be given a final test and rough alignment, using test valves in place of the missing types, then stored on racks on the factory floor until the missing types came to hand. There could quite happy to invite the comtoasters, can-openers, electric jugs, kettles, portable cookers and so on. plainants to "have a go" themLike it or not, we have to face the selves in the marketplace and see fact that, by and large, manufachow they get on. turers produce items of the kind S.L. nominates the use of tamperthat purchasers vote for, with proof screws as his pet hate, along with the implication that buyers plastic cards, at the sales counter. As buyers, we tend to favour pro- neither have nor need right of acducts which have instant supercess into their own property. ficial appeal: non-cumbersome, Maybe the real implication is that slick and streamlined in apthere is no need for anybody to gain pearance, backed by a known com- access: owner, vendor, service pany and competitively priced. mechanic or manufacturer; that the That description implies mass proproduct can reasonably be exduction using plastic mouldings and pected to outlast the warranty. If it associated economy measures, doesn't, rather then fix it, it's automated assembly with a . easier and cheaper to replace it minimum labour content, and the with a new one, for free or pro rata. smallest possible allowance for After warranty, well ... A classic example, it would seem, spare parts and service. I would imagine that, if pressed is that of household steam irons, · to revert to the old way of doing . mentioned to me recently by a things, with bins full of components, handyman relative. Time was, he tediously hand-assembled with nuts complained, when you could and bolts, manufacturers would be dismantle irons and gain access to well be a hundred or more chassis lying around with one, two,· three or even four valves in them, of which there was no simple record. So valves discretely swiped from here and there would not be immediately noticed. In fact, the operation had an unhappy ending for the main culprits. The scale of theft was such that the police were called in and, "acting on information received", eventually raided these characters' premises. And what a haul they scored. As well as items . that the HMV factory had not even missed, there were swags ·of others swiped from several other factories where the culprits had previously been employed. The sour note was that the rest of us could no longer borrow a signal generator for the weekend for a spot of unofficial servicing. So we all paid the price for a small number of rogues. Here's hoping that this may add a further small insight into the notso-official history of the Australian electronics industry. Keep up the good work. Philip Watson, Jannali, NSW. the faceplate and element for cleaning and repair. But no longer. The latest models use plastic studs which are heat formed. To gain access, you would have to butcher them. Unlike hair dryers, which S.L. classifies as "difficult", my aforesaid relative has given up on certain brands of iron, which he classifies as "impossible" - even though they still exhibit the failings of their breed. Yes, S.L., I too have a collection of power cords with moulded plugs, salvaged with the fond idea that they might come in handy some day. But they never seem to do so, even as 3-metre extension cords. The price of one-off cord-grip sockets, these days, is generally such that it's easier and cheaper to buy a complete, imported pre-packaged lead and leave the salvaged cords in the junk box! And that reminds me. I also have JUNE 1988 7 THEWAYI SEE IT - CTD a growing collection of freestanding electric can openers that still work - except for one small detail: they no longer reliably open cans! One would judge that a slight re-positioning of the support and cutting wheels would make all the difference but there appears to be no provision either to do it or to have it done. Says the retailer: "All you can do is buy a new one sir. It so happens that we currently have this line on special ... ! Go ahead. Tell me I'm lousy but, even more than discarding cords and plugs, I hate tossing into the garbage perfectly serviceable 240V drive motors. As for frypan controllers, I seem to have been fortunate so far; maybe it's just as well. I'll leave open for comment the correspondent's suggestion that some power cords are designed to perish prematurely. I really have nothing to go on but I would prefer to think that the problem has more to do with ignorance or first cost, than with calculated exploitation. Those plastic pillars! If I seem to be treating S.L's protest in a rather fatalistic manner, it's probably because there 's another aspect of modern massproduced plastic technology that annoys me even more than the matters he has raised: it's the way that the cabinets of electronic devices are held together by self-tapping screws driven into integral plastic pillars. The method is used alike in little cheapie devices and units costing hundreds of dollars. Brackets, brass pillars or brass insets are presumably much too fiddling and expensive, when you can get away with integral moulded pillars and simple holes to accommodate self-tapping screws. The idea works - provided the screws are driven home, first up, by an accurately set tension driver and subsequently handled only by people with a suitably sensitive touch. But they aren't and, when faced with anything but new moulded cabinets of this type, it comes almost as a pleasant surprise to find even a majority of the assembly screws still functional. To misuse an in-phrase, the remainder just manage "to hang in there". For example, the top shell of a computer printer that I sometimes use is held in place by four (or is it five?) self-tapping screws, inserted from beneath into moulded pillars, hanging like stalactites from the underside of the top shell. In this model, the top has to be lifted off to gain access to the mode switches and, naturally, I've always been pretty careful in so doing, when a switch needs to be reset to suit another computer. There came the day, however, when the printer had to be returned for major service and it subsequently became apparent that, in addition to fixing the fault, somebody had over-tightened and stripped all but one of the self-tapping assembly pillars. When I complained to the service manager about this apparent carelessness, he was singularly unrepentant. "It happens all the time", he said. "We just stick a plug of wet paper in the hole and retighten the screw as normal! '' Whether he realised it or not, his company had just lost my further custom. Plugging the hole may sometimes suffice in non-critical situations and, in others, it may just be possible to substitute a heavier gauge screw - but you can't count on either measure. What a boon if someone could come up with a way of re-lining the hole or, better still, inserting a sleeve to receive a stan- dard small metal-thread screw. He/she would deserve a (plastic?) medal! The safety aspect But, getting back to S.L's original theme, I have the uncomfortable feeling that the progressive denial of access to domestic appliances is not only contributing to a throwmentality, but is also likely to influence the perception about who needs, or has, the right to repair anything plugged into the power mains. While this may already be spelled out by existing rules and regulations, they are not readily enforceable at a handyman or professional odd-jobber level, where physical access has traditionally been easy and repair has required little more than a modicum of familiarity, common sense and the odd spare part. But close off this existing "grey" area for any reason and, almost by definition, we will begin to expose the borderline as to who has the legal right to repair what, in relation to anything plugged into the power mains. Should this right be reserved for licenced electricians only, or can anybody carry out repairs, provided they do not compromise the specifications on which the device was granted type approval in the first place? Looking ahead, it opens up quite an area for speculation, extending to that very nasty one, in this age of increasing litigation, where individuals can find themselves financially accountable for any harm caused by activities which are arguably negligent or illegal. Pursue that one and you could finish up questioning the role of husbands, handymen, odd-jobbers - indeed, anyone without an electrician's licence! This is nonsense In the meantime, a reader from Nelly Bay, Qld, has something more Go ahead. Tell me I'm lousy but, even more than discarding cords and plugs, I hate tossing into the garbage perfectly serviceable 240V drive motors. 8 SILICON CHIP Advertising slogans a nonsense I noted with interest your remarks on the reluctance of some dealers to provide service on the electronic goods they sell. They advertise extensively, using such slogans as "we stand behind the products we sell". This is nonsense. Most electronic retailers are in the business purely to sell merchandise. They will bend over backwards to make a sale but, as soon as the item becomes unserviceable, they no longer want to know you. There are a few decent retailers, maybe one in each city. We must get to know them and maintain contact. I have learnt through bitter experience that it is best to give to say on the matter of routine backup service. His comments appear in the panel at the top of this page. When I wrote that first article, it was with the full expectation that some readers, at least, would be anxious to defend themselves as retailers or to insist that the picture, as pairited, was altogther too gloomy. But this latest letter merely adds to by far the majority opinion that back-up service facilities for electronic equipment are · in deep crisis. I commend the reader's advice, learned the hard way: seek out a supplier in your area who has a good reputation in this regard and stick with them. You may have to walk away from a few "bargains" in the process but clearance items may not be all that attractively priced if, in a few weeks or months time, you find yourself lamenting the day you bought them! Radio factories in the '30s My comments on conditions in Australian radio factories during the '30s have brought to light a couple of letters, one of them in the accompanying panel from a former confrere, Phil Watson. The other is from a Victorian reader who, I would judge, will not mind me using his name in full. Of particular interest is the fact that he worked in the Melbourne Eclipse factory, about which we junior Sydneyites one dealer all your business. He will get to know you and give you satisfaction, should you ever require service. In another area, project kits are fllso traps for the unwary. The parts are often wrongly selected, certain parts are missing, or the illustrated instructions are so badly printed that it is impossible to read the diagram. What you wrote was no doubt distasteful to you but it had to be said eventually. Maybe a few dealers will be motivated to "pull up their socks". (Signed but initials withheld by request). in the '30s knew very little. We simply assumed that it was much like all the rest. Here's his letter: Dear Mr. Williams, Your article in February's SILICON CHIP certainly reawakened some memories for me. I had just left school in 1936 at the tender age of 15 and spied an advertisement in the daily paper reading: "Boys wanted to learn the radio trade, apply Eclipse Radio." [There were obviously no equal opportunity laws in those days) . Since I had mode a few crystal sets and was fascinated by radio, I prevailed upon my father to allow me to apply. The pay was fourteen shillings ($1.40) for a five and a halfday week (44 hours) and I had to travel 50km from home to work. Conditions were poor and the factory was old and depressing. I worked in the loudspeaker department where Saxon loudspeakers were made. My particular task was to twist together the four loudspeaker leads so that someone else could solder a plug on the ends. I would then carry the finished loudspeakers to the test booth wh e re an "engineer" would apply test tones. Any rejects would have to be carried back to the assemblers. We would clock in and out morning and evening and, from time to time, there would be a search for stolen parts. When word was passed back along the waiting queue that a search was in progress, the boys would empty their pockets and a variety of parts would litter the ground. I stayed about two months and what I learned about radio was harmless. Fortunately, my experiences did not totally quench my enthusiasm, although it was another 25 years before I trained as a technician. Ten years later, I was teaching electronics to other young hopefuls though few of them could be said to be enthusiasts. Thanks for your writings over the years. They have been appreciated. Noel Jackson, VK3CNJ, (Kilsyth, Vic). Many thanks, Noel, for your letter and for the glimpse inside the Eclipse factory. My only real contact with Eclipse products was when I first joined Reliance Radio in 1933. Prior to commencing manufacture on their own account, they had been selling Eclipse receivers in Sydney and a few of them came back through the factory for service or as trade-fns. While I would scarcely have been qualified to pass judgment on them, we juniors certainly didn't hold them in any kind of esteem. Gold spray notwithstanding, they seemed tizzy and tinny in the American manner, as distinct from the stolid, solid, battleship grey, British/Australian approach. Saxon loudspeakers were no great prize either and the trade-in chassis were full of leaky capacitors and clumsy glass-tube resistors that could never be taken at face value. But my most vivid memory was the wiring, done with white, rubber-covered hook-up. Depending on the age and environment, it would variously have hardened and fractured into a sequence of tubular beads, and/or have gone all gooey and so permeated the wire strands as to render them completely impossible to re-solder. Maybe they weren't as bad as all that but, at the time, they seemed to be! Thanks Noel and thanks again, Phil, for your very worthwhile contributions to the " living history" of the Australian radio industry. ~ JU N E 1988 9 Pt.2: Why We Need Negative Feedback WHAT IS NEGXI'IVE In our second article on Negative Feedback, we see that open loop amplifiers, with their errors, distortions, uncertain gain, and erratic DC output level are just not good enough. Negative feedback is the answer. Open loop amplifier By BRYAN MAHER The story goes that in one quite "with-it" family a sister and brother, Krystie and Tyson, both avid SILICON CHIP readers, were interested in somewhat different applications of electronics in their spare time. Krystie wanted to build a small amplifier to drive some earphones, to be driven by her small cassette player. Two batteries would have to serve as the power supply for this project. Tyson, on the other hand, was more interested in using electronics to measure things, like some of the small voltages and currents he met in his experiments and working models. He already had a small cheap voltmeter, but yearned for a good DVM (digital voltmeter). In this direction he had a bright idea. He would buy one of those 4-digit panel-mount voltmeters (they're not too expensive) and then would build a little amplifier to go in front of it to raise the sensitivity. He thought that would be just as good as those expensive lowreading DVMs he had seen advertised. Not being endowed with much cash, both Krystie and Tyson needed the best results-per-dollar available. Krystie contemplated building a simple one-transistor amplifier with a gain of 30. That should be 10 SILICON CHIP sufficient for her needs. Wanting to keep it simple she thought she would do without this negative feedback idea she had been reading about - she just couldn't see why she needed it. Consulting a book on circuits, she drew up a simple single transistor stage powered by two 9-volt bat- + T 9V: ...L. C1 Vin teries, with one cheap transistor, three resistors and a couple of capacitors, as in Fig.l(a). She had learned that the symbol for such an open loop amplifier (ie, one without any feedback) is the simple triangle shown here as Fig.l(b) where G represents the amplifier open loop gain. Doing a few pages of calculations she figured G would be somewhere about 30. --1.--..,_----l'--I J T 9V : C2 ...I.. Fig.l(a): Krystie's little headphone amplifier. Rt, R2 provide the bias, while R4 helps to stabilise the DC levels and bias conditions. But the results are not good - the text tells why. ··- v- I N P U T ~ OUTPUT Vin ·· ·· Vout OPEN LOOP AMPLIFIER Fig.l(b): we use the triangle as the general symbol of any open loop amplifier. G represents the value of the open loop gain. We could callously term any open loop amplifier a " super optimist" amplifier where some applied input voltage produces an output which "we hope and pray" is a faithfully magnified image of the input. Unfortunately, Krystie found this simple amplifier was hopeless. Gain was not a critical factor in her application, as long as it was near enough, but distortion was rampant. Also the frequency range was disappointing; both very high and very low notes seemed pretty weak. Why? Let's see: Any electronic system, transistor or linear electronic amplifier without any feedback at all is called an open loop system. Its gain from input to output is called the open loop gain, and for this we use the symbol "G". G = open loop gain = output voltage 7 input voltage before any feedback is used. For an amplifier with an open loop gain which is not too large, we can measure G under any one set of conditions by measuring input and output voltage, keeping the input voltage small (to avoid false readings by overdriving). An example will illustrate this concept: Example 1: Open loop amplifier If input voltage Vin = 50 millivolts results in output voltage Vout = 1.5V [without any feedback), then input and output voltage. This is known as amplitude distortion, and is caused partly by the transistor's current gain, hFE, being a function of the collector current. Fig.2(a) shows the relation between hFE and collector cµrrent for one particular transistor, the 2N2891. Graphs for many transistors have this familar "hump" shape. FEEDBACK? Open Loop Gain G = Vout + Vin = 1.5V + 50mV = 30 We use the triangle symbol in Fig. l(b) as the universal symbol for all open loop amplifiers, large or small, single stage or multi-stage, and write "G" within to remind us that G stands for the value of the open loop gain. This leads to distortion. The output is not an image of the input. Changes in hFE The other component of amplitude distortion is caused by the value of hFE also being a function of transistor voltage Vce, the voltage from collector to emitter. As Fig.2(b) shows, Vee plus the voltage across the load V1 always add up to the constant supply voltage Vcc· At peaks of output, the current through (and voltage across) the collector load swings to its greatest value, leaving a minimum number of volts across the transistor, resulting in less gain due to decrease in hFE· This "collector non-linearity" is typical of all transistors. As well, if the circuit was designed so that at no signal the transistor operated at the peak of the hFE curve, then for both upward and downward signals we would be operating at higher and lower collector current, resulting in lower hFE as Fig.2(a) shows. Waveform comparison The output and input waveforms should be exactly the same shape, one an exact but magnified image of the other. By applying both input and output voltages to individual inputs of a dual trace CRO (cathode ray oscilloscope), and carefully adjusting the CRO gain controls of each channel, we can attempt to superimpose the output waveform upon the input waveform. If the output is an image of the input, the two can be made to exactly cover each other, no matter what the shape of the input waveform. If they cannot be made to coincide, then the output contains distortion. What's wrong with open loop? What was wrong with Krystie's single transistor amplifier? Why was the distortion so terrible? And the frequency range so poor? The trouble with all open loop systems is that inadequacies in the electronic system produce an output different from that desired. We find that: (1.) The value of G changes as temperature changes. (2.) G has different values at different frequencies. (3.) G has different values at different input signal voltages. Amplitude distortion One of the most serious faults in an open loop amplifier is the way the gain G varies depending on the 100 90 +vcc 2N2891 80 ( ;i; ~v- I'\ 70 ~,/' 60 C "'ffi ., 50 ... 40 30 I\ ... 0: \ \ / 0: ~ / ... ~ = 0: 1/ ...=~ \ 20 10 0 1mA 10mA 100mA 1A 10A COLLECTOR CURRENT (iC) Fig.2(a): nearly all transistors have a "bumpy" relationship between current gain hFE and collector current ilc, This is the graph for pulsed DC values of hFE for the 2N2891, when the collector-emitter voltage Vce is held constant at 5.0 volts. Fig.2{b): at the highest power output, most of the available voltage is expended across the load, leaving only a small voltage across the transistor. Such low values of Vce cause reduction in transistor current gain hFE at maximum collector current. w ~ = w ., "' "' Fig.2(c): the result of reduced gain with increasing collector current. The transistor fails to achieve maximum output swing, producing a distorted output waveform. ]UNE 1988 11 +12V 147.7uA t t 4.8746V 'I' 12V: ' Yin R1 ~ 03 .,. R3 -12V Fig.3(a): in this DC-coupled amplifier, Ql's collector voltage is a delicate balance. If a small drop in transistor temperature reduces collector current from 147.7,uA to 141.7,uA, the quiescent voltage would rise from 7.1254 volts to 7.3234 volts. This upwards DC drift in quiescent voltage would be amplified by all following stages. r----------------v+ Cc Cc Vin-lt-+---+-t .,. Fig.3(b): in an AC-coupled amplifier capacitors Cc and transformer T isolate any DC drift in one stage, preventing amplification of DC drift by following stages. Soft overload Fig.2(c) shows the output current waveform resulting when we try to swing the output transistor until it is practically "full on". The top of the current waveform looks compressed and finishes up with a different shape compared to the bottom. The rounded top of the waveform is sometimes referred to as a "soft overload characteristic". This lack of symmetry causes distortion rich in even harmonics. Music waveforms so mistreated have a kind of "squashed" or muffled distorted sound, lacking in any "brilliance". Odd harmonics No doubt you have heard the familiar saying "all transistors are non-linear". This results from the non-linear base voltage/base current diode characteristic in every 12 SILICON CHIP junction transistor. This causes considerable odd (particularly third) harmonic distortion. With open loop systems that's just too bad! Whether a simple onetransistor stage or the largest of open loop amplifiers, the results will always be distorted music. Quite disgusted by the distortion of her little open loop amplifier spoiling her favourite music, Krystie put it aside and wandered off to see her brother's progress with his voltmeter project. She found Tyson in deep dejection, staring unbelievingly at a small printed board sporting two transistors and a handful of resistors. Clearly everything was not right. Uncertain gain and DC level The story she heard, different from hers, was nevertheless just as sad. He had built up this tiny open loop amplifier which we show here as Fig.3(a), and while it worked and drove the DVM (digital voltmeter) he had purchased, the whole affair was useless because of errors. He couldn't quite understand it, as he had previously built another amplifier, shown as in Fig.3(b), which was more-or-less successful. His new circuit had three things wrong with it: (1.) The amplifier was supposed to have a gain of 100, but for his 4-digit DVM reading to be meaningful in all digits, that gain needed to be 100 ± 0.1 %. Though his gain was about 100, accurate it wasn't! (2.) The gain of the open loop amplifier was too hard to calculate. Even though Q3 of Fig.3(a) is an emitter follower, it does not have gain equal to one; actually its more like 0.95. As for the other stages, Ql and Q2, it was an awful lot of work calculating the two-stage gain, and even then his calculation didn't come out equal to the measured figure. (3.) Worst of all, his new DVM did not read zero when the amplifier input voltage was zero. Adding potentiometer VR1 as a DC level adjustment seemed like a good idea. But when he adjusted VR1 for a zero reading on the DVM (with the amplifier input zero and grounded), it did not stay at zero. If it couldn't do that no other reading of input voltage would have any real meaning. Instead of maintaining a steady reading of four zero digits (with zero input), the DVM reading varied all over the place, "like something crazy", as he put it! Consolation he deserved, but he needed to know how to fix it. Forgetting her own distortion problem for a moment, Krystie realized that Tyson's amplifier badly needed: (a) Gain that could be calculated and achieved with ease and accuracy; and (b) A DC output level that would stay put; ie, remain reading zero all day if necessary, as long as the input was zero volts. If he could achieve those two goals, his DVM would be an inexpensive, accurate and useful piece of equipment. Gain calculations The gain of a multi-stage open loop amplifier is quite difficult to calculate accurately. To do such a calculation all the component values, all the transistor parameters and many interconnected factors have to be known and taken into account. The output impedance is often higher than we would like, and the DC level is not sufficiently constant for some applications. Indeed, in some DC-coupled high gain open loop amplifiers it is quite usual for the DC output level to be positively erratic, drifting wildly. DC level in open loop Generally, in all open loop amplifiers, the actual DC output level depends for a start on whether the various stages are DCcoupled to each following stage. If they are all AC-coupled (ie, via a capacitor or transformer) as in the example of Fig.3(b), there isn't much of a problem. The coupling capacitors block all DC voltages while AC signals are passed to the next stage. In Fig.3(b) we have shown the use of coupling capacitors and also a transformer, either of which isolates DC levels. Though popular once upon a time, transformercoupling is little used these days because of the cost and the distortion introduced by the transformer itself. But a few applications still need transformers. Thermal DC drift If, on the other hand, the stages are all DC-coupled, as in Fig.3(a), then any drift in DC output level in the first stage becomes part of the signal seen by the second stage. Hence DC drifts of early stages are amplified by the following stages to become dangerously large at the final output. Tiny DC drifts in the first stage can be due to seemingly minor events. Typically, the breezes that blow through a room may cool the transistor slightly, reducing its hpE (and hence the collector current) just a tiny bit. This raises the collector voltage and hence the output voltage of that stage. But that small DC rise may be many times the size of the wanted signal at that point. Let's look at a second DC-coupled example: Example 2: if in Fig.3(a): Ql gain = 10 Q2 gain = 10.53 Q3 gain = 0.95 Load resistor R6 = 33kfl, then Ql collector current = 147.7µ,A, Ql collector voltage = + 7.1254 volts Wanted signal = 4.3 millivolts at Ql collector Now if a small drop in transistor temperature reduces hFE causing Ql 's collector current to fall by 6µ,A, then: Ql collector current = 141. 7µ,A, Ql collector voltage = 7.3234 volts. Thus, the DC drift in the collector voltage is Vdrift = 7.3234 - 7.1254 volts = 198 millivolts. Notice that the change in the collector voltage caused by the temperature drop is about 46 times bigger than the wanted signal at that point. Amplified DC drift As all stages are DC-coupled, this DC shift caused by the change in Ql's temperature will be amplified (along with the wanted signal) by later stages. In all stages, and in the output, the erroneous DC drift remains 46 times bigger than the wanted signal! To Krystie and Tyson it was obvious that the output of the last stage will be mostly the erroneous amplified DC drift of the first stage. They will have the ridiculous situation of an output signal with about 4600 o/o error. But help is at hand in the form of negative feedback. The application of that great friend, negative feedback, in the correct quantities can turn poor ugly duckling amplifiers into star performers! But wait, enthusiastic reader, first let's look into a few more details of open loop amplifiers. Amplifiers can have two types of input terminals. We call an input t e rminal "non inverting" or "positive" or "+" if the input signal to that terminal causes an output of the same polarity. But we call an input terminal "inverting" or "negative" or " - " if the input signal to that terminal produces an output of inverted (ie, opposite) polarity. Amplifiers with both types of terminals are said to have "differential inputs" and the absolute value of gain from either terminal to the output is the same. The symbol for such an open loop linear amplifier with differentiRl inputs is shown in Fig.4. Vin(1)=t>G I Yin (2) Vout - Fig.4: the symbol for a differential open loop amplifier. The two inputs are explained in the text. Gain with two inputs The output is proportional to the input signal applied to the noninverting terminal; and also proportional to 'the negative of the input signal' applied to the inverting terminal. That is (still with no feedback applied): Gain from non-inverting input terminal to output = G; and Gain from inverting input terminal to output = - G. In Fig.4 where we have named two inputs: if Vin(l) is the signal applied to the non-inverting input; Vin(2) the signal applied to the inverting input; and Vout is the output resulting from both inputs together, then Vout = G(Vin(l)) + ( -G)(Vin(2)) Vout = G(Vin(l) - Vin(2)) Differential polarities Two examples will illustrate a vital point. Example 3: if Vin(l) = 56.0mV Vin(2) = 51.0mV and G = 387; then V0 ut = 387(56 - 51)mV = 387(5)mV = 1935mV Vout = 1.9V JUNE 1988 13 Problems? ... and you don't have our 112 page catalogue ... Example 4: If Vin(l) = 47.0mV Vin(2) = 51.0mV and G = 387; then Vout = 387(47 - 51)mV -= 387(-4)mV = -1548mV Vout = -1.5V Polarities Notice that where both inputs are positive: if Vin(l)> Vin(2), the output is also positive but if Vin(l) <Vin(2), the output is negative. Keep that fact in mind. We will use it again soon. Notice another point in those two examples. We have expressed the answer to only two significant figures (and even feel tempted to use only one figure), because we know that the value of the open loop gain G is so unreliable. you've got real problems! ARISTA ... your one-stop problem solver. Audio leads ... Batteries ... Chargers ... Battery holders ... Cables ... Car accessories ... CD accessories ... Converters ... "Cutec" ... Earphones .. . Fuses ... Headphones .. . Intercoms ... Knobs .. . Microphones and accessories ... Mixers ... Multi meters ... Plugs/Sockets, etc ... Plug adaptors ... Power packs and leads ... PA ... Disc and Tape care ... Security equipment ... Signal modifiers ... Solderless terminals .. . Storage boxes ... Switches ... Telephone and TV accessories ... Tools and Technical aids .. . Video accessories ... Wiring accessories ... You name it and we're bound to have it ...Try us ... NOW! Get your catalogue... it'II solve a whole lot of your problems! Just send $2 + 50c p&h and your return address to: ARIST~ ELECTRONICS PTY LTD PO BOX 191, LIDCOMBE, NSW 2141 14 SILICON CHIP Variable open loop gain The value of open loop gain quoted in the above examples, 387, could be the value for some amplifier at one set of conditions. The pertinent conditions are the temperature of the transistor junctions, the values of Vin(l) and Vin(2) and the signal frequency . The change in hFE with temperature in all transistors, the temperature coefficient of the resistors used, and the circuit configuration all influence the sensitivity of the circuit gain G to thermal change. A wide ambient temperature rise could even slowly double the value of G! But the change in G could be quite fast by self-heating at the semiconductor junction if a large signal is applied to the tiny base of a very small transistor. Changes in any of those pertinent conditions will lead to distortion and errors in the output. So distortion and errors are inevitable with open loop amplifiers. The problem is that all open loop amplifiers, knowing nothing of the errors in the output, are content to go on merrily leaving us to put up with their distortions and other errors. As we saw last month, we can improve on this state of affairs if the first stage of the system could be "informed" of the output errors so that the system can compensate for its own "mistakes". Basic block diagram The general idea of how such "information about errors" can be conveyed back to the front end of the amplifier is illustrated in the basic block diagram of Fig.5. Of course the amplifier has to be so arranged that it will " act on" this information about errors in the output and do something to correct the situation. Vin FEEDBACK PATH Fig.5: the basic idea of all feedback amplifiers is that information about the state of the output is fed back to the amplifier input, to allow the amplifier to take action to compensate for its own faults. The operation of all negative feedback systems is simply that a sample of the output is "fed back" to the front end of the system to be compared with the input signal. The result of this comparison controls corrective action automatically taken by the system. Negative feedback action (1.) The input signal gives an idea of what the output should be. (2 .) The sample of the output fed back to the front end gives an indication of what the output actually is. (3.) The first is what you want, the second is what you've got. (4.) The two should be the same. (5 .) If they are not, we must arrange for the amplifier to take corrective action . (6.) This comparison is done by subtracting the fed-back output sample from the input, to give tp.e difference (Input - Feedback). (7.) This "difference" is the vital quantity which the self-correcting amplifier will use to compensate for all its errors and distortions. Then life will be beautiful. Exactly how this is done we must leave until next month. Bye for now. ~ HIFIREVIEW Realistic Optimus 304 3-way loudspeakers Recently we reviewed the Realistic Nova-15 loudspeakers from Tandy (see Dec. 1987). This time we decided to look at the Realistic Optimus 304 system which, though more expensive, can still be considered a budget priced loudspeaker. The Optimus 304 is a bass reflex 3-way system with a rated power handling capacity of 100 watts. The woofer is a nominal 30cm in diameter with a paper cone and a foam rubber roll surround, and is built on a pressed steel chassis with a large ferrite magnet for the motor. The mid-range unit is a 13cm diameter unit, again with a paper cone and a fabric roll surround. Despite its unusual appearance, the tweeter is also a paper cone The Optimus 304 is a bass reflex 3-way system with a rated power handling capacity of 100 watts. Note the plastic moulding fitted to the tweeter. unit with a nominal diameter of 5cm. Cross-over from the woofer to the mid-range occurs at lkHz and from the mid-range to the tweeter at 4kHz. Both the mid-range and tweeter have voice coils which are ferrofluid cooled. Ferrofluid is a gel like mixture with ferric oxide held in suspension and retained in the voice coil gap by the magnetic field. The ferrofluid provides mechanical damping of the voice coil as well as improving the heat dissipation. This improves the power handling capability of the speaker. The enclosure is made from 12mm particle board covered with black vinyl simulated timber veneer on the top, bottom and sides. The baffle board is 12mm particle board with a dark grey vinyl finish. Large plastic dress rings are used to conceal the mounting flanges of the woofer and mid-range drivers and give the completed enclosure an impressive appearance when the baffle is removed. A feature of the baffle is the black plastic moulding fitted to the front of the tweeter. Tandy call this an "acoustic lens" . This presumably has been provided to give even dispersion of the high frequencies. A black speaker cloth on a removable plastic grille frame completes the enclosure. Overall dimensions of the enclosure are: height 82.5cm, width 37.8cm and depth 29.2cm. A check of the loudspeaker's impedance showed that, for frequencies from 20Hz to 3kHz, this was close to or above the nominal impedance of 8 ohms. From 4kHz to continued on page 96 JUNE 1988 15 VINTAGE RADIO By JOHN HILL • Cleaning up a vintage receiver A thorough clean-up is usually the first step in restoring a vintage radio receiver. But beware all sorts of dangers can be hidden under the chassis. Also, you should resist the temptation to simply plug 'er and try 'er out. There is no reason why those with little or no knowledge of valve radio receivers can't work on them, but they should be aware of the dangers that lurk underneath the chassis. Unlike transistorised equipment, valves operate at very high voltages and, in many instances, some of the older sets have DC voltages well in excess of 300 volts which is backed up with large capacity electrolytics. So be careful. Don't get involved unless you have some knowledge of the workings of valve receivers or without reading up on valve technology. That said, let's now get on with the restoration work. The vintage radio enthusiast is frequently faced with the seemingly impossible task or restoring a derelict receiver. There !ire many ways of going about the job but it should be approached in a methodical manner. Perhaps the first impulse when restoring an old radio is to plug the set into a power point to determine whether or not it is working. This impulse should be resisted as some of these old sets may have been collecting dust in someone's garage for anything up to 20 years. Cleaning is important if the restoration is to be neat and attractive. It also make the chassis much easier to work on. 16 SILICON CHIP What's more, the reason it was banished to the garage was probably because it had stopped working or was acting up in one way or another. When this is the case, it's asking a bit much to expect the set to work. If the radio does have problems, then damage to certain parts could occur if it's switched on for any length of time. A few of the more serious problems are listed below. First, if a high-voltage capacitor has short-circuited, the full maximum high-tension current will flow through the HT choke [or the speaker field coil as the case may be) and may damage these components if the set is left on. A glowing red-hot anode in the rectifier valve will indicate this sort of problem. Second, a burnt out speaker transformer has a similar effect on the output valve, except that in this instance the screen of the valve will glow red hot. As many output valves are blackened inside, a redhot screen could easily go unnoticed. If you do decide to ignore the above advice, the set should only be turned on for a brief period of time to test it. But check the mains wiring first and remember to watch the two previously mentioned valves while listening for sounds or arcing and harsh, horrible noises from the speaker. Also, watch for smoke from some raidly overheating component. Still want to switch it on? If you are lucky, sound will burst forth after about a 15-second period and you will be pleased that your latest acquisition actually works. Looking at it realistically, there's more likelihood of the set not going The knobs on this old Astor seemed to be welded on and at least four attempts were made to remove them before they finally yielded. and, instead, you're faced with a full-scale investigation to locate the cause(s) of the trouble. This, as far as I'm concerned, is the best part of the restoration work, for nothing gives me more satisfaction than to bring an old valve set back from the dead. Now fixing an ancient radio is a different process to restoring it. If just fixing it, the fault would be found and that would be it. But when restoring a set, the complete unit should undergo extensive renovation in order to make the radio look and perform as though it was new, or as near new as is humanly possible to attain. Hence, my procedure may differ considerably to that of a serviceman doing a routine repair. Removing the chassis The first step in the restoration is to remove the chassis from the cabinet. While this should only require the removal of the knobs and a few screws from underneath, the job is not always that easy. Often the knobs are rusted onto the potentiometer shafts in a rather tenacious manner. Not all pot shafts are made of brass and many are plated steel. This is where 20 years in the garage can take its toll, for if water has found its way into the works, then many components are likely to Knobs for vintage radio receivers are scarce so care should be taken not to damage them. Sets that are not worth restoring should be stripped for parts. be rusted .or corroded. As vintage knobs have steel screws and often fit steel shafts, the result can be a permanently attached knob. There is only one thing to do in such a case and that is to apply a squirt of WD40 or some similar .fluid to the offending screws and shafts, then allow sufficient time for it to penetrate and take affect before attacking the screws. Even the WD40 treatment doesn't always work that well and a screwdriver with a correctly fitting blade will be needed to slacken those rusty screws. A block of wood wedged under the knob for support allows extra pressure to be applied to the screw without bending the pot shaft. Well, the knobs are off, all the screws are out and the chassis is out of the cabinet. Once again, it sounds simple, but this elementary operation could put you in hospital. Watch out for Red Backs I have seen so many Red Back spiders in old radios it isn't funny. They seem to like hiding underneath the chassis in a similar manner to the way they hide under sheets of corrugated iron. Fortunately, I discovered a Red Back during my first restoration and it was a good lesson to learn. I now always look for spiders and frequently find them. With the creepy crawlies evicted, the restoration work can Compressed air is a handy aid when cleaning old radio chassis. This homemade outfit was put together for just a few dollars. JUNE 1988 17 them. Others have had small bones, chewed up pumkin seeds and peanut shells, presumably brought there by resident rodents. Other miscellaneous bits and pieces include a door key, a penny and a rubber suction cap off a toy pistol. Cleaning up A good selection of brushes helps greatly at clean-up time. begin and there is no better way to start than with a thorough clean up of all the chassis components. A variety of brushes can be used to scrub off the dirt and grime and a blast of compressed air often helps a lot. The chassis clean-up is made easier if the valves are removed first, but be careful to note their positions beforehand. The amount of cleaning up to be done will depend on where the set has spent its life. If a radio has been in a lounge room or a bedroom, then it will be full of easily removed fluff. On the other hand, if the radio has been in a kitchen, then the chassis and most of the components will be smothered in a smeary film of cooking grime that has accumulated over a period of many years. Some kitchen radios are truly revolting inside and the grime is so thick it can be scraped off with a knife. Then again, if a set has spent time in an outdoor shed, there is a good possibility that the cabinet will be well-stocked with the droppings of many generations of mice. These same little critters can also get under the chassis and nibble into many vital components. The work of a vintage radio enthusiast is not always pleasant! It is quite amazing what one finds inside old radios, apart from the odd Red Back that is. Several of mine have had large wasp nests in All manner of strange things can be found inside old radios, including wasp nests. You should also watch out for Red Back spiders. 18 SILICON CHIP Considerable time is needed to clean up a dirty, rusty chassis and one often has to resort to coarse wire brushes and even emery cloth to smooth over some of the rough areas. A kerosene-soaked rag is handy when it comes to shifting kitchen grime, and a few small brushes, such as a suede shoe brush or a hard-bristle toothbrush, can also be of use. As most chassis require repainting, the better the clean-up, the better the finished job will look. More work is needed to clean up the valves which are usually just as grimy as the rest of the set. A number of precautions should be observed here and the first one to consider is the valve's identification number. You can either scratch the number into the base with a scriber point or attach a sticker. Either way, be sure to record the number before it gets wiped off with the cleaning rag. Valves can also be damaged by cleaning them apart from the obvious damage caused by dropping them. Octal and pre-octal valves frequently have a top cap connection that is loose. These caps can easily A spray with WD40 or similar penetrating fluid often helps loosen stubborn control knobs. The knobs can then be cleaned with a stiff brush and detergent. be broken off with overenthusiastic cleaning. The valve bases can also be loose and too much waggling back and forth while cleaning could disturb some of the base pin connections. The base pins themselves are often very grotty, or even corroded a nice shade of green. They should also receive close attention regarding cleanliness. The average 5-valve set can have about 30 valve base connections, none of which are soldered. They are all dry connections just waiting to give trouble and are suspect when it comes to making proper contact with the valve socket pins. Naturally, the valve sockets should also be thoroughly cleaned. The use of a pipe cleaner and compressed air helps greatly. The pipe cleaner can also be dipped in a suitable cleaning fluid (metho or WD40) if the sockets are particularly dirty. Tuning capacitor Another component that requires fastidious cleaning is the tuning capacitor which is often completely fouled with fluff, dirt and grime. A 25mm-wide paint brush does a reasonable job of reaching between the closely spaced plates and, again, a blast of compressed air is of great assistance. One must be fairly careful when cleaning underneath the chassis as there may be some quite delicate wiring (the short wave coils for example) that could easily be broken. It's not the place to go poking around with a hard-bristle brush. Clean carefully on the underside of the chassis. In all seriousness, this preliminary clean up before the restoration work commences is really quite important. It makes all the difference when working on the set for it is much more pleasant if everything is clean and tidy. The simple act of cleaning the valve pins and sockets alone has brought many a valve radio back to life again. Failure to clean these dry connections can give rise to many difficult to locate faults, so it pays to do the job well. Next month, we'll look at checking out the valves. lt; Did you miss these issues? ",.. I Issue Highlights November 1987: Car Stereo in Your Home; 1GHz Frequency Meter; Capacitance Adapter for DMMs. December 1987: 1 00W Power Amplifier Module; Passive lnfrared Sensor for Burglar Alarms; Universal Speed Control and Lamp Dimmer; 24V to 12V DC Converter January 1988: Bowtie UHF Anten , acking Power S 9 tom Phone Ainge , ~ ier Adapter for FM Tuntirte:". February 1988: 200 Watt Stereo Power Amplifier ; Deluxe Car Burglar Alarm ; End of File Indicator for Modems; Simple Door Minder; Low Ohms Adapter for Multimeters. March 1988: Remote Switch for Car Alarms; Telephone Line Grabber; Low Cost Function Generator; Endless-Loop Tape Player. April 1988: Walkaround Throttle for Model Railroads; pH Meter for Swimming Pools; Slave Flash Trigger; Mobile Antennas for the VHF and UHF Bands. May 1988: Optical Tachometer for Aeromodellers; High Energy Ignition for Cars; Ultrasonic Car Burglar Alarm ; Restoring Vintage Radio Receivers . Price: $5.00 each (incl. p&p). Fill out the coupon below (or a photostat copy or letter) and send it to : SILICON CHIP, PO Box 139, Collaroy Beach, NSW 2097. Please send me a back issue for □ November 1987 □ December 1987 □ February 1 988 □ March 1 988 D dttl"lt:10F~1 □ April 1988 Hrns (Sold Out) □ May 1988 Enclosed is my cheque or money order for $ ..... ... or please debit my □ Bankcard □ Visa Name .... ... ......... ............... ........ .......... ............... .......... .. .. ... ..... ... .. . Address .. ..... .. ...... .......... .... ......... ...... .. .. .... ...... ...... .. ..... .. ....... ..... .. . Suburb/town ....... .. .... ...... .......... .. ... .. ................ Postcode .... .. ... .. .... . Card No ........ ... ...... .. ..... .... ... ... ......... .... .. .. ... .. ..... .. ...... ........ ...... .... . Signature ....... .... ....................... ...... .Card expiry date .. .... ./ ... ... ./ ...... . ~----------------- ______ J ]UNE 1988 19_ /N EW FROM JA YCAR - AUSTRALIAN - ' ~! ~~o~ t~L~olu~~ 12 VOLT PLUG PACK BARGAIN ~ w~ ;e' : :stralian made storage cases, one of which will actually replace an imported parts drawer~ , ,' , : .. 1_ Interlocking Parts Drawers ~ -- 1 A two drawer case, wrth 3 removable plastic 1 insen boxes in the lower drawer. These are ideal to remove from drawer to find that nut or resistor, without taking out the complete drawer, Side and top/bottom keying system allows you to use just a few, or build a whole wall of drawers as your parts expansion dictates. Flange on the rear of the case has two screw holes for easy mounting. Slide handles also takes Identity cards, which are supplied. Size 137(D) x 97(H) x 85(H)mm. Beige colour. Cat. HB-6305 .,,/J, 11· Famous Arlec brand 240 volt to 12 volt DC plug pack at 1 amp. an',;/JrjrW•' ~ It has a twin lead about 2 metres long on the 12V side, plugs directly into 240V outlet. These normally sell for abcut $40. We have purchased a quantity from an OEM and can ~ pass them on to you for about 1/2 price. (// Cat.MP-3022 ONLY $19.50 · · · •.. ·.,. • .,. · .:' A. , · • : r(ll(!A SA VE 50% •· - · · · ~,_, ~" r CLOCK MOVEMENT WITH BUILT-IN PENDULUM DRIVER $5.95 10 up $5.50 ea This module measures 87mm long x 55 wide x 35mm deep and uses 1 x AA battery. Clock movement is supplied with 3 sets of hands, and pendulum is a suspended arm within the module which swings back and forth. A surtable pendulum can be attached to the bottom of the arm. Fit your own custom clock face . Great for novel applications. Available sometime in June. Cat. XC-0103 Component Drawer Large see through drawer which has fall forward opening action, rather than usual drawer action. Interlocking both vertical and horizontal, can be fastened to wall, beige in colour. Unlimited uses. Removable compartments for easy cleaning . Size 11 (H) x 103(W) x 83(D)mm. Cat. HB-6308 $5.95 $22.95 Utility Box Ideal system for the serviceman, or mobile workshop, or just to keep all those resistors and capacrtors tidy. Also ideal for fishing tackle bcxes and many other uses . Six of these utility boxes will frt snugly into the carry case pictured. Size of utility box 188 x 115 x 36mm. Colour opaque whrte. Cat. HB-6310 1$2.29 • Very corrpact • Powered by 1.5V AA battery that lasts for one year • ± 15 second/month accuracy 110 up $2.10 ea IUtility Carry Case ISpecifically designed to hold 6 utilrty boxes I portable snugly to give a 30 compartment totally pans storage system. ICat. Size 365 x 210 x 80mm. Colour white. HB-6312 I$17.95 ISPECIAL INTRODUCTORY OFFER 16 · UTILITY BOXES AND A CARRY CASE FOR ONLY '-!28.9~ SAVE $2.74._ _ _ _ _ _ _ _ _ _ _ • NEW MODEL • Bonus metal hook to hold clock on wall • Bonus on/off swrtch Fit your own custom clock face. Great for novel applications such as fitting to pictures, boxes, photographs etc. SUPPLIED WITH 3 SETS OF HANDS !~~-::~ ..J PASSIVE INFRARED DETECTOR PRICE BREAKTHROUGH PULSE COUNT PIR FOR UNDER $100 It had to happen, and Jaycar is the first to offer you a quality PIA wnh pulse count for under $100. Jaycar was the first to offer pulse count PIRs way back in February 1987. Since then we've sold thousands I Pulse count virtually eliminates false alarms. Here's how it works. The circurt first senses an alarm (pulse 1) and then goes into alarm standby mode for 30 seconds duration. If during the 30 seconds standby mode a second alarm event occurs (pulse 2), the detector goes immediately into alarm, and the standby period will be extended for another 30 seconds . tt there is no second alarm pusle during the 30 seconds standby mode the detector returns to normal condition. Features: • Coverage 12 metre x 12 metre • Detection angle 110° • Detection beamss • 38 • Adjustable angle • Tamper proof protected • N/C and N/0 output Cat. LA-5017 ONLY $99.95 NEW MODEL EXTRA FEATURES SAME PRICE Quartz Crystal Clock Movement NEW SHIPMENT DUE IN JUNE ~ g • TERMINATOR PIR WITH PULSE COUNT Jaycar are proud to announce a new PIA to our range. The Terminator has features found in those really expensive PIRs FEATURES • Pulse count which vinually eliminates fals e alarms • 48 detectio n beams in 3 ran ges 1~~~~1i.~A::::~,fUp ; f ; ; y: ; n??at. LA-5020 • . 8" TWINCONE SPEAKER BARGAIN We have made another speaker scoop purchase. This time from New Zealand of all places. These are made in NZ and are very high qualrty. There is one small catch although, they are 4 ohm. 10 WATT $8.95 10 up $8 20 WATT $13.95 10 up $12.95 Cat. CE-2322 Cat. CE-2323 NEW RE-DESIGNED VIFA SPEAKER KITS FOR 1988 SA-100 Upgraded AEM6102 speaker kit. Uses new Call into any one of our showrooms for an audition (not Concord) SA-50 design crossover, and they do sound better. Complete kit with cabinets: Unbelievable sound from such small speakers. Measures only 26(H) x 17(W) x 195(D)cm. Incorporates a 5" woofer and D19 dome tweeter. See AEM magazine for a full review, May edition. Complete kit with cabinets only: $799 $399 SA-130 Upgraded AEM6103 speaker kit. New design SA-70 Upgraded EAS0/60 speaker kit incorporating 8'' woofer and D19 tweeter. Corrplete kit with calbinets only: "::: $4=9=9:::::::::::::::::::;;:::= = • · CASTORS crossovers, new slimmer cabinets, upgraded dome tweeter. Corrplete kit and new designed crossovers are excellent value at: ◄ ~- $1199 See our catalogue for full details. \ .., .: .. : ·,,.) Another scoop surplus stock buy. Set of 4 castors to suit speaker boxes, TV's or anything for that matter. Castors are mounted on a 37mm square metal bracket which is simply screwed to the speaker bo, etc. by 4 self tappers. (Screws not supplied) .i Originally used on colour TVs. / Cat. HP-0838 SET OF FOUR $5.00 C"•. ~ ~~-l Who needs a noisy car alarm, after you have installed one of these in your vehicle. It's operated from a hidden switch. Simply turn it on when you leave your car, and nyour car is stolen, it won't go very far without any petrol. Supplied with instructions, pre-wired switched, hardware and even two alarm stickers. Quality M&D Alarm brand. Add to this our deluxe red light f"1sher kit - KJ-7000 $19.95, and who needs an alarm? Cat. XC-2050 -~ ·- -- $69.95 DUMMY CAMERA BARGAIN We all know that shoplifting and vanalism cost a small fonune very year. It has been demonstrated that television surveillance cameras in the right environment can discourage this activity. This is where you come in. We have made a grea1 purchase of realistic-looking Dummy TV Cameras. They are Australian made, are supplied with adjustable swivel mounting bracket, fixing screws, flashing LED circuit board and 2 flashing LEDs. One red LED is mounted in a bezel on the front of the camera to add reality and the other - would you believe - is mounted BEHIND the dummy cameras lens I It looks really corny when it flashes and you COULD·disconnect that LED but tt a thief was ignorant of the cameras operation it may make the camera look more realistic to him. Also supplied is the 2 x D cell nylon battery holder to power the flasher circuit. A fake cable wallplate is also supplied as well as a very conspicuous 21 O(W) x 160(H) sett adhesive sign which says "THESE PREMISES ARE PROTECTED BY TIME-LAPSE ANTI-THEFT CAMERAS" The text of the sign is in orange-red fluorescent ink against a black background. BUT HURRY I We have around 300 of the cameras at this below normal manufacturers price. We do not ever expect to be offered similiar stock again. Cat. LC-5310 1 - 4 pieces 10 - 19 pieces 20+ pieces MIDRANGE Quality 5" sealed back midrange with large magnet. Made in NZ. Power Handling System 100 watts rms Freq. Response 350- 7.5kHz Resonant Freq. 400Hz Sensitivity 90dB/1 W - 1 metre lrrpedance Bohm Cat.CM-2078 High quality NZ made s Power Handling 20 Freq. Response 80 Resonant Freq. 80 Sensivity 90 Cat. CW-2104 $18.95 $19.95 UEL CUTOUT / . .. SOLENOID .~ ~ -.. 5 - 9 pieces MORE NEW SPEAKERS $49.95 $42.95 $39.95 $37.95 each MIDRANGE Same as CM-2078 speaker except that it has a metal surround . Cat. CM-2079 $24.50 DRY TRANSFER LETTERING Quality lettering sets, available in 4 different styles. Can be used on most smooth surfaces including metal , glass. plastic, wood, cardboard and paper. Ideal for lettering on rack cabinets, control panels, etc. Simply posItIon the letter and rub with the cap of a ball point pen or soft pencil. Made in Holland. STYLE 1 Black lettering 4mm high. Capital letters, lower case letters, numbers. Sample MNuv 123 - Cat. NL-4100 STYLE 2 Black lettering 6.5mm high. Capitals, lower case, numbers . Sample DEZ stI 982 Cat. NL-4102 STYLE 3 Silver letters with black shadow 7mm high . Capital letters and numbers. Si mr'i8 !G n us 367 Cat. NL-4104 STYLE 4 Flourescent yellow on black background. Capitals and numbers. Sample A J P 1 4 Cat. NL-4106 ALL ONE PRICE $2.99 per sheet BASIC CIRCUITS NEW BOOKS FOR '88 Featuring more than 300 worked examples and 900 practice problems. Electric Circuits is written for electricaVelectronics students in colleges and technical institutes. The text covers electricity and the structure of matter, basic and corrplex circuits and vectors, DC and AC measurements, complex networks, and much more. Practice problems include schematic diagrams and emphasising alternate solutions . Topics covered include : · :-c:· • Electricity and the Structure of Maner • Ohm's Law and Electrical units • Resistance and Conductance • Energy and Power • Simple Series Circuits • Simple Parallel Circuits • Complex Networks and Kirchoff's Laws • DC Network Theorems • Capacitance and Capacitors • Magnetism and Electromagnetism • Inductance and Inductors • Sources of Electronnotive Force • DC Electrical Measurements • Sine-Wave Forms • Complex Algebra and Electric Vectors • Basic AC Circuits • AC Network Theorems and Bridge Circuits • Power in AC Circuits • Resonance . . • • • Simple Linear Circuits and Nons1nuso1da'I' Voltages • Polyphase Circuits . ·• • Transformers . • • AC Electrical · , · _. Measurements n • Appendices i clude: Values of Exponential nd Functions, Units, a Mathematics. 260 Hard cover • size mm x 180mm · 888 pages · Cat. BH-0904 NEW'88 $69.95 Active Filter Design This comprehensive text provides both students and engineers with a clear understanding of the hows and whys of active filter design. Commonly used filtering terms are given, and a broad array of filter circuits are examined. Aids for determining which filtering circuit to use in a given application are supplied. The discussion then progresses through to the final theoretical chapters which deal with mathematical approximations in a clear, concise manner. Also included are illustrations and descriptions of basic filters, the advantages and disadvantages of filter types, general transfer functions, and normalisation and Soft scaling. cover. Size 225 ~!~. ~a~~sgoo x 150mm. - ..._ _- NEW'88 $22.95 IBM PC & PC XT USE RS REFER ENCE MANUAL second $45.00 Edition Expanded to include the features of the more powerful PC XT, this revised edition contains the most up-todate information available on the IBM PC. From system setup through using DOS and programming techniques, this book provides users with clear, step.., , . by-slap explanations of IBM PC hardware and · ~ · J software. complete with numerous illustrations and examples. It covers the IBM PC and PC XT collectively and also highlights the dirterences between these systems. Includes:• comparisons between the PC and XT • using DOS 3.1 • upgrading your PC to an XT • information on the customised hardware configurations of the PC and XT • explanations on how to load programs on a fixed disk and how to organise directories. Soft cover- size 235mm x 180mm • 479 pages Cat. BH-0902 TELEPHONE DIVERTER New Model available in June This professional quality product will automatically transfer incoming· calls to another telephone number, anywhere. Your business will not lose any important calls if you move, as incoming calls can be diverted to your new office address. Two telephone line are required while the YT-6510 is not Telecom approved nis a very well made product. A 7.5V AC adaptor is provided. Cat. YT-6510 $199 DIAL DRUM/CORD PACK BARGAIN This will probably be your first and last chance to ever buy assorted dial drums. As used in the old day tuners, they are ideal for the hobbyist who likes experimenting. This pack contains $37.75 worth of dial drums and dial cord and you can have one for only $5. You will not see dial drums again - especially al this clearout. once in a lffetime price. Your junkbox needs some dial drums for the future. WHAT YOU GET Value $5.50 $15.00 $3.00 $12.50 $1.75 $37.75 108mm dial drums x 2 54mm dial drums x 10 57mm dial drums x 2 40mm dial drums x 1O 2.5 metres dial cord NEW LITHIUM BATTERY No. CRD2320 As used in IBM and other corrputer clocks. 3 volt. Cat. SB-2530 $7.95 . . ·_: · LOWER PRICES ON HITACHI MOSFETS FOR 60000 AMP 2SJ56 2SK134 WAS 22.95 19.50 NOW 14.95 13.95 CAT ZT-2450 ZT-2455 ALL FOR ONLY $5.00 Cat. HM -3.130 DON'T MISS OUT LAST CHANCE - EVER DISCOUNTED KITS AT CLEAROUT PRICES SAVE $$$$$$$$$$ MUL TIMODEM II SALE WAS $349 JUNE SPECIAL ONLY $249 SAVE $100 AVTEK MULTICOM SAVE$50 ONLY $99.50 Cat. XC-4840 Cat. XC-4822 Cat Description KA-1687 Electronic Rain Guage KA-1688 Electronic Stroboscope KA-1689 Experimenters Power Supply KA-1678 Electric Fence - Hi Power KE-4728 Phone Ring Tone Customiser KE-471516 Intelligent Modem Kk Mag EA March 87 EAAug87 EASepl87 EA Oct86 ETI June 87 ETI 8516 WA'"s • $49.95 $13.95 $26.95 $229.00 $29.95 $428.00 with Power Supply Philips 8" Woofer AD80652/W8 Ideal for smaH sealed enclosures. Maximum enclosure volume is 25 litres. Great bass. Recommended crossover frequency 2,500Hz. Freq. Response 50 - 4kHz Resonant Freq. 39Hz POwer Handling 50 watts rms Flux Densny 1.2i: Total Moving Mass 17.5g Compliance - Spkr. Unmounted 1.02mm/N Voice Coil Height 10mm Cone Diameter 25mm Magnet Mass 450 grams Mass of Speaker 1.15kg 74HC SERIES FROM JAYCAR 74HCOO $0.75 Cat. ZC-4800 74HC02 $0.75 Cat. ZC-4802 74HC04 $0.75 Cat. ZC-4804 74HC11 $Q.75 Cat. ZC-4820 74HC139 $1.25 Cat. ZC-4850 74HC368 $2.95 Cat. ZC-4870 74HC373 $2.95 Cat. ZC-4874 74HC393 $2.95 Cat. ZC-4880 74HC4075 $0.95 Cat. ZC-4896 We have available a small range of HC series LS for a limited period. J~ TURN YOUR SURPLUS STOCK INTO CASH!! ·Jaycar will purchase your surplus stocks of components and equipment. We are continually on the lookout for sources of prime quality merchandise. CALL GARY JOHNSTON OR BRUCE ROUTLEY NOW ON (02) 747 2022 ,_ ~·· .,. ,....,...~"' •I: ,.';· ·.--·. Cat.CW-2115 >: NORMALLY $49.50 ~ JUNE SPECIAL --: · · ONLY $39.50 · i:c -• • • WIJ?,P:'-!'}JJ!="!=J, ~, OFFER No2 GENUINE FM DIVERSITY WIRELESS MIC/ GUITAR LINK SELLOUT SAVE AROUND $300 Genuine NADY 201 HT microphone wireless system corrprising of YD-04 microphone (virtually identical performance to Shure SM-58), integral antenna (no dangling wires) low battery light and professionally rugged. Measures 222(L) x 36(Dia)mm weighs 238 grams. Use 9V cell. Included of course is the 201 "True Diversity" receiver matched to the same frequency. System perlormance and range similar to 201 GT above You would DIE if you knew where we bought this shipment of brand-new (You see this system used by TV entertainers in the US all the limel) genuine US-made NADY wireless PA gear froml Suffice to say that they lost a (If more than one ordered or 1 x 201GT and 1 x 201 HT ordered they will be supplied on different frequenfortune to liquidate this current model merchandise. ONCE AGAN their cies) . staggering loss is YOUR GAIN. Cat. DT-5030 OFFER No1 SAVE AROUND $200 Genuine NADY MODE L 201 GT Gunar wireless microphone link which includes FM "True Diversity" receiver, bodypack transmitter wnh high impedance input (sunable for guitar pickups. bass, sax. etc). The body pack accepts a standard 6.5mm plug and the audio lead acts as the antenna, neat I The body pack measures 96 x 60 x 203mm and weighs only 70 grams. It requires a 9V alkaline battery. Both transmitter and receiver are crystal locked and offer 20-20.000Hz ±3dB frequency response and 120dB (max SPL A-weighted) dynamic range. Output is line level 600 ohms. Minimum adverse operating range 200 feet, lineof-sight 1500 feet. Elsewhere you will pay $800+ for this system in Australia. But, while they last you will be able to get this product from us for only $5991 That's right, you WILL SAVE around $200 over the normal price in Australia! (Australian rec. retail $799). (If more than one is ordered, they will be scpplied as separate frequencies). Cat. DT-5020 $599 INC tax $699 INCtax DON'T JUST SIT TH~.-~ BUILD SOMETHING!!! TRANSISTOR IGNITION 240 VOLT LINE FILTER Refer SIiicon Chip May '88 A high energy ignition system which uses the cars existing Ignition coil and points, with extended dwell and compatible with our Hall Effect and Opto Ignitions. Complete kit with PCB, diecast box and all components. Cat. KC-5030 Refer EA June '88 Kit Includes box, 240V socket and plug, PCB and all components and hardware. Cat. KA- t703 _ _$_3_9_.9_5___ _ . ._ $49.95 FM RECEIVER ACTIVE CROSSOVER ~ - Refer EA June '88 Kit includes PCB, box, front panel, planetary reduction drive, TDA7000 chip and all components . Cat. KA-1704 Refer ETI June '88 Short form kit includes PC board and all on board components. Transformer is extra Vat. M P-1012 $ 19.95 Cat. KE-4733 $55.00 $39.95 • ••••••••••••••••••••••••••••••••••••••••• •• • • •••••••••••••••• BABYMINDER CD HEADPHONE AMPLIFIER Ref: ETI April 1988 Monitor your baby s room for crying. Will trigger a light or buzzer in another room. Kit includes box, PCB, and all components except 12V AC plugpack and dynamic mic. Cat. KE-4732 Ref : EA May 1988 Kit will measure current gain and Vbe of all popular power transistors - even Darlingtons I All project specified parts in the kit. pH METER Ref: Silicon Chip April 1988 Kit includes PCB, plastic case, meter and scale, front panel and all components. Probe is extra. $39.95 Cat. KA-1700 $22.95 RF DETECTOR PROBE Cat. KC-5027 Ref: EA May 1988 This simple but very effective RF probe enables you to troubleshoot RF circuits by enabling you to 'hear' the RF signal I You can 'trace' RF just like audio I Kit includes all specltied parts except the felt tip pen case. The project must be used in conjunction with the KA-1699 Bench Amp ($39.95) described in April 1988 EA. Cat. KA-1701 $49.95 Ref : Silicon Chip April 1988 Includes all the features of The Railmaster plus walkaround thronle. All components supplied less box and relay. $49.95 SIMPLE TESTER FOR POWER TRANSISTORS $24.95 TRAIN CONTROLLER pH probe and solutions to suit Cat. QP-2230 $79. 95 $13.50 $89 .00 LOW COST 50MHz 4 DIGIT DIGITAL FREQUENCY METER NiCad CHARGER Ref: AEM April 1988 Will fully charge then trickle charge - or trickle charge only. Will charge up to 10 cells at once. Incorporates own plug pack box. Cat. KM-3067 Cat. KC-5031 Cat. KC-5029 Ref: EA April 1988 Amplltier offers power output of 5 watts, signal tracer has high input impedance and a wide range of input sensitivities. Complete kit including box, speaker, PCB and all components. Plug pack not supplied. Cat. KC-5028 Ref: Silicon Chip May 1988 Check the rotational speed cl objects remotely with this project. Ideal for cars, model planes, fans, rotating shafts etc. The Jaycar kit comes with all specltied parts case, etc. Ref: Silicon Chip April 1988 Kit includes PCB, box, all components and hardware. Requires 12V AC plug pack Cat. MP-3020 $13.95 $34.95 BENCH AMP/ SIGNAL TRACER Cat. KA-1699 RECENT KIT RELEASES OPTICAL TACHOMETER Ref: EA May 1988 A low cost but high sensitivity, high input imped ance unit measuring to well over 50MHz. All parts mount on one PCB. The Jaycar kit includes case, front panel and all specified parts. Cat. KA-1702 $24.95 $35 BOOKS FOR $2!!!!!!!!! Some worth up to $35. Limited quantity. Available through mail order dept. only. Atari: Games & Recreations x 12 How to Micro Computerise your Business x 8 The New Technology x 3 ..... · ··· •··........ . VisiCalc applications book x 5 __ . .-: . .. · •·" "'··· . 1 Son of Cheap Video x 4 ·., -:-."· Gneesis 2 x 1 '-: · • -: C Prag Techniques for Mac x 1 .·. •-:-." .• ·.• ··.··., ..." .... ...Tl99/4A Basic Program (book and program cassene) x 9 $99 CYCLIC (Endless Loop) TAPE PLAYER BARGAIN COMPONENT This is not a kit. Simply record a message onto the unit (microphone not supplied) and you can have a message from 15-30 seconds long repeated continuously or when necessary. Built-in amplltier - only needs a speaker. Dimensions 70(W) x 56(D) x 45(H)mm. Weight 86 grams. Cat. YT-2720 As featured in Silicon Chip project March 1988. $10 Cat. RE-6280 150 Mixed Capacitors $1 O Cat. RE-6~0 35 pots, trimpots, sliders $1 O Cat. RP-3902 20 Slider pots $10 Cat. RP-3903 100 mixed BC type transistors $11.95 Cat. ZT-2170 100 3mm & 5mm LEDs $19.50 Cat. ZD-1694 100 mixed IC sockets $24.95 Cat. Pl-6490 50 assorted Resistor Networks $1ClCat. RR-3380 20 precision 1% & 2% Capacitors $12.50 Cat. RG-5198 ~ !~o~~ ~ $29.95 THIS IS YOUR LAST CHANCE!!!!!!! :_ w.t Pf ! ~ ft../1..I~_ HEAD OFFICE 1 ~ MAIL ORDERS 0 0 137 3 POST & PACKING 9 7 0 _f_:i_i_1_r_i_~_l..;.,:_:..:.;~d;_:_}_:_;_:_:______~_t_R:_:~_:~-~-{-~-~-~1_;_:_:_o~_:_~:_:_a__f_i~_rn_s_10_o_l_li_l_i_j_l_l~_o- - --, MAIL ORDER VIA YOUR "fr ROAD FREIGHT ANYWHERE IN AUSTRALIA $13.50 L-~- - - -- - -- - - - - - - - - - - -- ----------------' VISA ■ ~ro SYDNEY · CITY 117YorkSt 102) 2671614 Mon-fr, 8 30 - 5 30 Thurs 8 30 pm • Sat 9 12 GORE HILL 188 Pac1f1c Hwy cnr Bellevue Ave (02 1439 4799 Mon-Fr, 9 • 5.30 Sat 9 - 4pm CARLINGFORD Cnr Carl1ngford & Pennant Hills Rd (02) 872 4444 · Mon-Fr, 9 - 5 30 Thurs 8.30 pm - Sat 9 2pm BURANDA OLD 144 Logan Rd (07) 393 0777 Mon-Fr, 9 - 5 30 Thurs 8 30 Sat 9 t2 CONCORD 115 Parramatt a Rd J02) 745 3077 • Mon-Fri 8.30 • 5 30 - Sat 8.30 - 12 MELBOURNE-CITY Shop 2. 45 A'Beckett St City (03) 663 2030 Mon-Fr, 9 • 5 30 fr, 8 30 - Sat 9 • 12 HURSTV ILLE 121 Forest Rd (02) 570 7000 • Mon-Fr, 9 • 5.30 Thurs 8.30 pm· Sal 9 · 12 SPRINGVALE VIC 887-889 Spring"le Road Mulgrave (03) 5~7 1022 Nr Cnr Dandenong Road Mon-Fr, 9 - 5 30 fr, 8 30 Sat 9 · 12 .AVTEK MEGAMODEMS ' • Automatic dial, answer and disconneel • Fully Hayes AT Smartmodem compatible • Automatic speed conversion (Model 123,only) • Austpac compatible • Audio and visual feedback SPECIFICATIONS CCITTVV21, Bell 1003, CCITTV22, Bell 212, Data Standards (CCITTV V23 • model 123 only) 300/300, 1200/1200 Data Rate& (1200n5 & 7511200 model 123 only) Interface CCITTV V24 (RS232C) Power Requirements240V AC power consumption less than 1 wan Dimensions 27(H) x 120(W) x 165(D)mm Weight Approx. 250 grams Command set Hayes AT compatible Warranty Extended 12 months r.iWHAT - - -A-FLOP! ------, Fibre Optic Evaluation Kit We thought more eleC1ronic enthusiasts would be into libre optics, but it seems we were wrong. The EDU-LINK kit is a fibre optic evaluation system consisting of TTL corrpatible transrritter board, IR LED, one metre of fibre optic cable, photodiode and TTL compatible receiver board. The fibre optic connectors are also included. Complete step-by-step instruelions are included as well as theory of operation and tutorial notes. An ideal learning aid lor engineers, students and electronic hobbyists alike. Cat. KJ-6520 WAS$49.95 NOW $34.95 _- ~°-U-LINK ' SAVE $15.00 'r \.. •__________ ,. Model 12 Model 123 Cat. XC-4850 Cat. XC-4852 $375 $449 UNIDIRECTIONAL WIRELESS TIE CLASP MIC QUALITY TIE CLASP MICROPHONE Low impedance, omni-directional electret condenser. A very small microphone which clips on to your tie. Supplied wnh 3 metres of cable to a 3.5mm plug. 1k ohm impedance. Frequency response 40 - 16kHz. Cat. AM-4067 $29.95 $36.50 500mW <at> 6V Audio Amplifier A six transistor 1/2 wan amp for the cost of two harmurgersl It has two transistor tape preamp which is NAB equalised and a four transistor power amp. It has facilities to take line level inputs. The (irregularly shaped) board measures roughly t lO(L) x 48(W)mm. Each arrp comes complete with schematicand connection diagram. (2 required for stereo). ,..) IBM PC/XT COMPATIBLE CARDS - SELLOUT Your last chance to grab one of these at a sellout price. Stock is only in our York Street store. For mail order customers, please phone (02) 267 1614 to check stock availability and to place your order. Strielly limited quantities, some nems there are only a cot.pie left. Cat Descript10n WAS NEW XC-5010 10MHz Turbo motherboard $499 $349 XC-5016 1/0 Plus 2 card $139 $99 XC-0018 Colour graphic video card $139 $99 XC-5020 Multi 1/0 board $199 $149 XC-5022 Colour graphics/printer card $159 $119 XC-5026 Parallel printer card $59 $39 XC-5030 Floppy disc controller $69 $49 XC-5031 Universal 640k RAM card $249 $179 XC-5050 150Wpowersupply $189 $149 XC-5070 Keyboard $179 $129 "'"™ 10 up $3.50 uch Another Jaycar surplus stock purchase. Famous Big Mouth car alarm system. Install in 5 minutes. Features easy installation, automatic on/off, loud alarm signals, auto reset. We have seen these advertised for $39.95 and even $49.95. . We have a limned quantny available at only t~t~., risk losing your car! -; - Cat. XT-6020 $3.95 ea r1ave you got your copy yet? It has 132 pages and over 4000 producis for the electronics enthusiast and professional. Two easy ways to get yours: (1) Call into any Jaycar store. Only $1 (2) Send $2 to PO Box 185 Concord 2137 and we will send you one. GORE HILL OPEN SATURDAYS UNTIL 4pm BE A YOUNG ENGINEER! QUARTZ DIGIAL WATCH What a great idea for the kids. An LCD quartz digital watch in a kn. You get the band , the lens, watch case, watch module, strap pins, bat1ery and a screwdriver. The watch has five functions - hours , rrinutes, month date, seconds and a back light. Ideal for parts also. Cat. KJ-7100 $5.95 ;. , "SYNTOM " A Jaycar Special Project The Syntom is a very effective drum synthesiser that can produce a variety of fixed and falling pnch effeels , triggered either by tapping the unn itself, or by striking an existing drum to which the device is attached. Four potentiometers give control over different characteristics of the sound . The decay pot governs the time taken for the sound to die away after each strike, from less than 1/10 sec. to several seconds, giving a wide range of envelopes. The frequency of the note is variable over the entire audio range by means of the pier control, and the sweep control introduces a voltage causing the pnch to fall as the amplitude decreases. These controls, when used in combination with each other enable the most popular drum synthesiser effects heard on commercial recordings to be obtained. Power requirements 9V 216 banery. Kn includes PCB, all components, case and Scotchcal front panel. Cat. KJ-6502 $42.50 Another jaycar exclusive purchase. Allows you to connect twO phones to the one socket. These normally sell for $7,50 .,#'~ 1988 JAYCAR ENGINEERING CATALOGUE ONLY $3.95 BIG MOUTH CAR ALARM BARGAIN TELEPHONE DOUBLE ADAPTOR SENSATION SAVE 47% This incredibly small microphone just clips on your tie or collar and transmns on FM. No more messy wires to trip overl • Tunable 88MHz · 108MHz FM • Frequency Response tOOHz • 10kHz • Electret condenser type Cat. AM-4068 JAYCAR KITS Electronic Australia Kits KA-1010 KA-1109 KA-1115 KA-1116 KA-1117 KA-1119 KA-1220 KA-1225 KA-1230 KA-1390 KA-1392 KA-1428 KA-1430 KA-1505 KA-1506 KA-1508 KA-1522 KA-1535 KA-1550 KA-1555 KA-1556 KA-1500 KA-1559 KA-1561 KA-1562 KA-1563 KA-1574 KA-1582 KA-1595 KA-1598 KA-1610 KA-1626 KA-1630 KA-1635 KA-1636 KA-1650 KA-1652 KA-1660 KA-1670 KA-1674 KA-1675 KA-1677 KA-1679 KA-1681 KA-1682 KA-1683 KA-1684 KA-1685 KA-1686 KA-1687 KA-1688 KA-1689 KA-1690 KA-1691 KA-1692 KA-1693 KA-1694 KA-1695 KA-1696 KA-1697 KA-1698 KA-1699 KA-1700 KA-1701 KA-1702 Musicolor4 Electric Fence 300W amp module 300W power supply 300W speaker protector $125.00 $23.50 $119.95 $105.00 $23.50 Transistor tester $21.50 Signal tracer $27.95 Transistor & PUT tester $26.50 Zener diode tester $16.95 Freq counter 50MHz $169.50 Prescaler 500MHz $46.50 Function generator $129.50 Vocal canceller $24.95 TAI Hall effect $44.95 Transistor assisted ign $42.50 $29.95 Touch light dimmer $115.00 Guitar effects BBD Ignition killer $23.50 Deluxe car alarm $89.50 COUAM stereo decoder $26.50 Ultra sonic movement det. $34.95 Railmaster controller $109.95 Railmaster walkaround $13.95 Railmaster diesel sound $22.50 Railmaster steam sound $22.50 Railmaster light control $21 .95 30V 1A power supply $89.50 House alarm $169.00 Digltal capacitance meter $85.00 $99.95 40W inverter 121230V 300W inverter 121230V $249.00 Video fader $24.95 12V lamp flasher $12.95 AM/FM stereo tuner $599.00 $99.50 AM/FM remote control Playmaster 60/60 $329.00 Blueprint 60/60 $369.00 Electric fence $59.50 Light saver $15.99 Digltal photo timer $89.95 Screecher car alarm $34.95 Audio oscillator (metered) $165.00 Turbo timer $29.95 3 band short wave radio $79.50 Dual track power supply $129.95 Ba«ery monitor $14.95 8 channel 1/R transmitter $45.00 IR receiver (std) $127.95 I R receiver (add-on) $55.00 Elec1ronic rain gauge $49.95 Elec1ronic stroboscope $13.95 Exp. power supply $26.95 DI box $39.95 TV col bar/pattern gen $149.00 Voice operated relay $24.95 Metronome $19.95 Volt/continuity test $29.95 AC/DC Millivoltmeter $46.50 Econ. Temp probe DMM $19.95 Utility timer $21.95 Trans, FET, Zener test $55.00 Bench amp, signal trace $39.95 Power transistor tester $22.95 RF detector probe $13.50 50MHz Dig Freq meter $99.00 Australian Electronics Monthly Kits KM-3010 KM-3012 KM-3015 KM-3016 KM-3030 KM-3040 KM-3042 KM-3050 KM-3054 KM-3056 KM-3058 KM-3060 KM-3061 KM-3062 KM-3063 KM-3064 KM-3065 KM-3066 KM-3067 KM-3068 BOW Mosfet arnp 120W Mosfet amp Listening pos1 RTTY encoder Ultrafidellty prearrp Dual speed modem Speech synthesiser Workhorse amp Audio clipping meter 100W module less MFets 64 packet radio Balanced line driver Microphone prearrp RS true 232 interlace Uo satellite decoder Octave EO mod RS true 232 interlace VHF rec for wea1her sa1 NiCad charger FM minder bug $59.50 $79.50 $39.95 $32.50 $359.00 $169.00 $43.50 $35.00 $14.50 $79.50 $59.96 $99.50 $36.95 $24.95 $55.00 $59.95 $27.95 $99.00 $24.95 $11.95 KE-4033 Temperature probe $32.95 KE-4050 ETl480 SOW amp module $27.50 KE-4052 KE-4048 KE-4200 KE-4204 KE-4220 KE-4405 KE-4666 KE-4578 KE-4690 KE-4698 KE-4706 KE-4711 KE-4720 KE-4722 KE-4724 KE-4725 KE-4728 KE-4729 KE-4730 KE-4731 KE-4732 ETl480 1DOW amp rrod $34.50 ETl480 power supply $29.50 5000 power amp $499.00 5000 1/3 octave equaliser $219.00 ETl499 150W Mosfet amp$109.50 ETl581±/-15V power/s $27.50 RS232 Centronics inVf $32.50 ETl340 car alarm $79.50 ETl342CDI $79.50 4 sector house alarm $29.95 DI box $42.50 Mini FM transmitter $9.95 Digital sampler $119.00 RS232 Commodore $16.95 Parametric equaliser $23.50 Solder iron temp control $39.50 Ring tone customiser $29.95 Guitar preamp $45.00 Solar gen p/supply $12.95 Telephone intercom $59.95 Baby minder $34.95 Capaci1ance me1er Off-hook indicator Car radio power supply 1GHz Digi Freq meter Subcarrier adaptor Telephone ringer Speed controVdimmer 24 to 12V converter SOW amp mdule 100W amp module Door minder Protector car alarm Dual track power supply Low ohms adapt DMM Mode end file ind Line grabber - phone Remote car alarm Ph meter Train controller CD H/phone arrp Optical tacho Syntom drum synth 8 channel mixer Console Psupply above 2601 1/3 octave Eq: 2010 10 band stereo Eq. Red light flasher Electronic~ Today International Kit Microwave leak detector Mixer preamp Signal Spkr protector NiCad battery charger $17.95 $39.50 $22.50 $14.95 ·= ~\I ~ ~:s: HEATSHRINK TUBING II SHRINKS WITH A MATCH ~ 10up $3.25 er U • 2 colours • remains flexible after shrinking • all supplied in 1 metre lengths Size Red Black Price 1.3mm WH-5540 WH-5530 $1.75 2.5mm WH-5541 WH-5531 $1.75 3.5mm WH-5542 WH-5532 $1.85 5mm WH-5543 WH-5533 $1.95 7mm WH-5544 WH-5534 $2.10 10mm WH-5545 WH-5535 $2.50 16mm WH-5547 WH-5537 $3.25 Shrinks to 1/2 the size listed $42.50 $595.00 $119.00 $239.00 $169.00 $19.95 This incredibly little piezo screamer measures 57(L) x 33(H)mm emits a 116dB wail. It's deafening! As used in the screecher car alarm kit. Cat. LA-5255 $17.95 "SCREECHER" CAR ALARM Scare the pants off would be thiev with this great kitl • Fits under dash • Alarm goes off inside car • Unbearable sound Cat. KA-1675 UHF TV TUNER Sanyo Model T1087RA Yet another fabulous scoop purchase. A corrpact high quality tuner that operates from 526·814MHz (corresponding to channels 28 thru 63). This tuner is designed for Australian standard reception (AS1053 1973), and is offered at a very klw price. You can grab one now for the silly price of $29.951 This price includes circuit diagrams and connection drawing. You can have a photocopy of the complete manual for $4 but a lot of the info is in Japanese! This is a very cheap way to convert a VHF only TV to UHFI (Some skill may be required). Spees: Power +12V DC nominal <at>14mA. Case neg. Bandwidth 526-814MHz (28-63 eh). AFT +6.5V. Dimensions 150 x 65 x 28mm. Tuning multi rotation of 1/4 "shaft. Knob not supplied~ Cat. DM-1000 DIGITAL MULTIMETER WITH FREQUENCY COUNTER $29.95 t) • CAPACITANCE TESTER • TARNSISTOR TESTER • 20 AMP CURRENT • HIGH IMPACT CASE Cat. QM-1555 $159 Q9.99] ' lffl ~··v, ~-~ .. ... J ~~. - DC• KE-4013 KE-4014 KE-4023 KE-4029 $27.95 $12.95 $28.95 $299.00 $22.95 $19.95 $18.95 $59.00 $32.95 $38.95 $37.50 $79.50 $99.95 $29.95 $9.95 $19.95 $33.95 $49.95 $89.00 $24.95 $49.95 Jaycar Kits KJ-6502 KJ-6504 KJ-6505 KJ-6531 KJ-6535 KJ-7000 SPECIAL 3 95 ea TWEETY PIE Silicon Chip Kits KC-501 0 KC-5011 KC-5012 KC-5013 KC-5014 KC-5015 KC-5016 KC-5017 KC-5018 KC-5019 KC-5020 KC-5021 KC-5022 KC-5023 KC-5024 KC-5025 KC-5026 KC-5027 KC-5028 KC-5029 KC-5031 M ILLUMINATED ROCKER SWITCH •GREATFoRAMPs • SPDT, BA, 240V • • ILLUMINATED ACTUATOR • AS USED IN THE P/MASTER 6 0 / 6 0 ~ •SIZE21X15mm • PANEL CUTOUT 13 X 19.5mm ~ Cat. SK-0965 ~ • Cat price $7.50 ea ~~ I~ occ• •• .-.::~. _. / '"''<,;' ~ j - -:- COIII Y/0 5.25" DISC SENSATION Another unbelievable scoop purchase by Jaycar . .· . , . We have available a quantity of US brand "Discimate • 5.25 • SSDD discs. They are supplied in a handy plastic box of 10 which opens to alklw easy access to discs. , The box has one of the best opening actions we've seen. We can offer a 5 year warranty. These discs are so cheap we can only sell them in boxes of 10. Cat. XC-4751 , ..... · ·•:, ...... £; I' I,; GIVEAWAY ,: •. '. :· "'·; PRICE ~... .,_, __ ,,,. $9.95 BOX 10 .. JAVCAR QUALITY KITS PERFECT FOR SCHOOLS, HOBBYISTS and ENGINEERS 1GHz FREQUENCY COUNTER Ref: Silicon Chip Nov/Dec 1987 Cat. KC-5013 $299.00 . TV COLOUR BAR PATTERN GENERATOR Ref: EA October 1987 Cat. KA-1691 ~ $149 PLAYMASTER 60/60 BLUEPRINT AMP KIT Ref: EA May/June/July 1986 Cat. KA-1652 $369.00 G~·ltf.:n.··AW◊k-. ! -. ·,· ~ j: , . "' :• . l " i ,,..., I •-, •••• ·- ,~,m ••• •.. ·,:'- ' , -•-• .. • HIGH IMPEDANCE AC/DC MILLIVOLTMETER Ref: EA December 1987 Cat. KA-1695 $46.50 FUNCTION GENERATOR Ref: EA April 1982 Cat. KA-1428 $129.50 50MHz FREQUENCY COUNTER Ref: EA Dec/Feb 1982 Cat. KA-1390 $169.50 500MHz Preecaler Cat KA-1392 $46.50 DIGITAL CAPACITANCE METER Ref: EA August 1985 Cat. KA-1695 $85.00 CAPACITANCE ADAPTOR FOR DMM Ref: Silicon Chip Nov 1987 Cat. KC-5010 $27.95 TRANSISTOR, FET & ZENER TESTER Ref: EA February 1988 Cat. KA-1698 $55.00 PLA YMASTER AM/FM TUNER KIT Ref: EA Dec/Feb 1986 Cat. KA-1635 $599.00 8 CHANNEL AUDIO MIXER Ref: EA April/May 1983 Cat. KJ-6504 $595.00 Pictured with optional desk console ETl480 SERIES AMP MODULES 50WATT Cat. KE-4050 $27.50 100 WATT Cat. KE-4052 $34.50 POWER SUPPLY Cat. KE-4048 $29.50 r. -----------, Bug Box Quality Video/Audio RF Modulator This is essentially a flat tray measuring 123(L) x 83(W) x 15(D)mm moulded in anti-static plastic with a clear locking plastic sliding cover. The cover has numbers marked on it that correspond to the compartments inside. It also has a unique patented feature which enables you to reveal one compartment per row wrthout revealing the others and endangering their contents. The Bug Box will hold 60 x 8 pin IC's or 30 x 14, 16, 18 or 20 pin IC's in rts 30 separate compartments (each compartment measures 25.4(L) x 9.5(W) x 12.7(D)mm. The Bug Box tray is blue in colour and slides .into the Bug Cage described elsewhere on this page. Cat. HB-6350 $5.95 each Our best ever unrt. This modulator has been specially built to our stringent specifications. It is a VHF unrt swrtchable to Aust. Ch 3 or 4. The audio is placed at the correct subcarrier frequency and output frequency is stable wrth good strong signal. Full specs (we mean FULL) are suppliedwrth each unit. ~ Cat. LM-3848 · $19.95 ..- ~-.....: - .,----- ·-- NEw•ss 10 or more $5.45 each $7.95 each 10 or more $7.45 each Bug Cage The heavy duty moulded cabinet accommodates up to 6 Bug Boxes. Once inserted each tray is spring loaded to stand proud of the front of the cabinet to allow easy removal between thumb and index finger. The cabinet also has tongue and groove dovetails to allow adjacent Bug Cages to interlock together to .make a modular storage system. Size: 128(H) x 100(W) x 131 (D)mm Cat. HB-6366 $9.95 each 10 or more $9.25 each Bug Cage Cover A snap in clear acrylic door that can clip on the HB-6366 Bug Cage. Holds all trays securely in place and enables the user to identify various trays without the need to open the cabinet. As the trays are spring mounted in the cage, the cover keeps them securely in place. The trays w ill not rattle when a Cage Cover is frtted and is therefore a definite requirement for mobile use. Cat. HB-6370 \:ee - . ))'1 \: '. --- ~ ·"::_ :: Easy to install, size 70 x 50mm, sticky tape already supplied on back. Includes alarm stickers. Requires 2 x AAA batteries (not supplied), Cat. SB-2375 $1.95 for 2. Cat. LA-5090 ---- ----~ \!r•' "' Cat. XE-4950 LSI BUG BOX PICTURED $14.95 SAVE $5 .. -'. ___ , _, ... ' otor/Gearbox Kits Each of the kits shown below contains a motor wnh press-frt brass cog, gearbox housing, 3mm x 110mm steel drives haft, 2 intermediate shafts, 7 gearwheels and 6 nylon bushes. The motors will run from a source of 1.5 - 4.5 volts DC and depending on load consume between 200 - SO0mA A typical gearbox arrangement is shown in the exploded drawing. Two sizes are available, YG-2710 with a (small 20mm dia.) motor and the YG-2712 with 25mm motor with higher torque and oilite bearings. All components (apart from the motor) are UK or Franch made. SMALL MOTOR LARGE MOTOR Cat. YG-2710 Cat. YG-2712 $14.95 $18.95 See 1988 catalogue for reduction tables Cat. XE-4951 $19.95 EL CHEAPO $2.50 DESOLDERING BRAID Our usual desolderwick is sold in a plastic spool and contains 5 feet for $2.50. That's approximately $1.50 per metre. El cheapo braid is 2mm wide and will take solder off a PCB reasonably well although the braid gets a brt hot because there is no plastic spool to hold. You could easily put some in your old spool. Supplied in a 5 metre length for $2.50. That's 50- metre - or 113rd the price of normal desolderwick. Cat. NS-3025 5 metre pack Please note: braid is not loaded wrth flux and will not work qurte as well as normal desolder braid. THE JAYCAR 1988 -132 PAGE ENGINEERING CATALOGUE NOW AVAILABLE- ONLY $1 .00 I .J MAIL ORDERS ~~~~~1~~)a$4c;~~o~~ .................·..•.....la,;...... ' Replacement tube HEAD OFFICE ~~~~· " . . $99.50 • ~,~: f -~~--- ■ ~ro etc. "' the full range illustrated in the 1988 catalogue _ VISA _ This is the proverbial answer to a maidens prayer I It's all very good being able to program EPROMs easily but how do you ERASE them quickly and safely. You can put them out in the sun for an undertermined time or use a special high power UV tube in an unprotected 20W fluoro batten . You could also end up with a wh ite walking stick! If you need to regu larly erase the contents of EPROMs (even NEW EPROMs could be corrupted wrth random data) then this is your most cost-effective solution. It will erase up to 9 x 24 pin devices in complete safety to your eyes and your chips, in around 40 minutes for 9 chips (less for less chips). This US-designed product has a special safety conductive-foam chip drawer and has a double insulated design for you r safety. We are very excited about this product and we are sure you will be too. FEATURES • Erase up to 9 chips at a time • Chip drawer has conductive foam pad • Mains powered • High UV intensity at chip surlace ensures thorough erase • Engineered to prevent UV exposure • Long UV tube ine SPECI FlCA TIONS Operating Voltage 240V 50Hz Power Consumption 8watts Capacrty 9 to 24 pins UV Source Wavelength 253.7nm UV Intensity 6.4mW/cm2 Tube Life 3000 hours Dimension 21.7 x 8 x 6.8cm Weight 670 grams Similar in principal to the HB-6350 except that it is meant to store larger IC's or resistors, caps, etc. Also anti-static. Same external dimensions but with 3 compartments 107(L) x 25.4(W) x 12.7(D)mm which run the length of the tray . Six vertical and six horizontal clear plastic dividers are included to further subdivide the compartments in whatever configurat ion the user requires . Colour blue with clear cover. Cat. HB-6358 10 or more $6.45 each - Ultraviolet EPROM Eraser LSI Bug Box $6.95 each Car Theft Deterrent Save your car for less than $20 It's a black box wrth 12 digits on the top (like a calculator) and a flashing LED. It looks very similar to the controller on a very expensive car alarm (the one that guarantees your car won't be· stolen). So with this sitting on your dash, would be thieves will th ink you have a high qualrty alarm, and move on. Can be used on rts own, or to complement any existing alarm system. Use on cars, around the home, on boats, ~o~{~~~:~~1~~o;~l~r POST & PACKING fi~ IUI! Irn 2137 1 10 ~F_A_C_S_IM_I_L_E_(~0_2~)_74_4_0_7_6_7_____T_O_L_L_F_R_E_E~(0_08~)_0_22_s_s_s_ _0_vE_R_s _00_ _ _s__o_o_ _~ MAIL ORDER VIA YOUR "a' ROAD FREIGHT ANYWHERE IN AUSTRALIA $13.50 -='-"-'=-'"-=~ ==~-- - - - - - - -- - - - - - - - - - - - - -----.....1 SYDNEY - CITY 11lYorkSI (02) 2671614 Mon.fr, 8 30 - 5 30 Th urs 8 30 pm Sat 9 - 12 GORE HILL 188 Pacil,c Hwy cnr Belle vue Ave (02) 439 4799 Mon-fn .9 - 5 30 Sat 9 - 4pm CARLINGFORD Cnr Carl1ngford & Pennant Hills Rd 102) 872 4444 Mon- f r, 9 - 5 30 Thurs 8 JO pm - Sat 9 2pm BURANDA OLD 144 Logan Rd (07) 393 0777 Mon- f r, 9 - 5 3D Thurs 8 30 - Sat 9 - 12 CONCORD t 15 Parramatta Rd (02) 745 3077 Mon.fr, 8.30 - 5 30 • Sat 8 30 • 12 MELBOURNE-CITY Shop 2. 45 A'Bec kett St City (0 3) 663 2030 Mon.fn 9 • 530f n 830 Sat9 12 HURSTVILLE 121 fores t Rd (02) 570 7000Mon.fr, 9 • 5 30 Thurs 8 30 pm - Sat 9 - 12 SPRINGVALE VIC 887-889 Spnng'3le Road Mulgrave 10315,7102 2 Nr Cnr Dandenong Road Mon -F n 9 - 5 30 Fn 8 30 - Sat 9 12 Studio 200 Stereo Control Unit Ever since we published the Studio 200 stereo power amplifier in our February 1988 issue, there has been a constant stream of requests from readers for a matching stereo control unit. Well here is it is: low profile, reasonable cost, excellent performance, plenty of control features and easy to build. By LEO SIMPSON & BOB FLYNN Designers have all sorts of different philosophies when they sit down to produce a stereo control unit. Some take the purist approach: no tone controls, a minimum of switching, very few control facilities and so on. Then they charge a mint for it on the assumption that nobody would buy such a spartan unit unless it had extraordinary performance (and it must have exotic performance otherwise price would not be so high, eh?). At SILICON CHIP we have to take the constructors and the high fidelity enthusiasts into account. They all want high performance but they don't want a unit which is too complicated or expensive to build. And we think that most people want a 28 SILICON CHIP good range of controls. Most people want tone controls and a balance control, for example, although they may seldom use them. They also want plenty of inputs and outputs and tape monitoring facilities. Most people also prefer to see a stereo/mono switch on the control panel, even though, again, it may seldom be used. And finally, a headphone socket is required, although this facility is often omitted on many separate control unit/power amp combinations. Of course, we were not developing this control unit just to suit the Studio 200 power amplifier. It had to match any commercial stereo power amplifier with an input sensitivity (for full power) of 1V RMS. So these were some of the considerations we had in mind as we set about developing this control unit. Actually, it has been under development almost since the ink was dry on our February issue but our readers were not to know that. Features The new Studio 200 control unit is housed in a one unit high standard rack-mounting case. It does not need to be mounted in a rack though; it can situated above or below its accompanying power amplifier or it can be positioned up to three metres away from the power amplifier. Overall dimensions of the chassis are 483mm wide x 44mm high x 290mm deep, including knobs and rear projections. As already intimated, the Studio 200 stereo control unit has the usual line-up of controls: bass, treble, balance, input selector, tape monitor switch, stereo/mono switch and volume control. It also has a tone defeat switch and a headphone socket. The internal circuitry has been greatly simplified by the use of a new low cost, low noise dual op * Main Features Very low noise on phono and line level inputs - better than many CD players. Very low harmonic and intArmodulation distortion. Up to seven stereo program sources can be connected. Tape monitor loop. Separate headphone amplifier giving very high quality. * * * * amp, the LM833 made by National Semiconductor, Inc of the USA. In fact, the total semiconductor count is quite small. Apart from the power supply which is quite standard with two 3-terminal regulators, the entire active circuitry of the control unit uses just four LM833 dual op amps, four transistors and four diodes. Years ago, op amps were just not good enough to be used in high performance low noise circuitry by themselves. They had to be preceded by low noise discrete transistors in order to get the best performance. But this new dual op amp from National Semiconductor is just one of a new breed which has been released in the last year or so. And it really does perform, as the spec panel accompanying this article shows. So good is the performance that it is as good as or better than the majority of commercial stereo control units, even those which retail for thousands of dollars. In fact, when * Headphone socket disables output signal to power amp. Stereo/mono switch Tone and balance controls with centre detent. * * * Tone defeat switch. * Easy-to-build contruction using three separate PCB assemblies. * Estimated cost: $230.00 you think about it, the designers of many of today's so-called state-ofthe-art control units must be pretty slack. We think that any commercial stereo control unit, integrated amplifier or receiver which offers a phono signal-to-noise ratio of worse than B0dB and a high level SIN ratio worse than 95dB unweighted is poor. Most manufacturers tend to quote A-weighted figures too, which show their equipment in a better light. Some readers may think that calling for such high signal-to-noise ratios is unnecessary but it isn't, if the signal from CD players is not to be degraded. The Studio 200 is phenomenally quiet: on the phono input, with a typical magnetic cartridge fitted, the signal-to-noise ratio is - 86dB with respect to an input signal of 10mV at lkHz, with a noise bandwidth from 20Hz to 20kHz (ie, an unweighted figure]. On the high level inputs, the signal-to-noise ratio is 104dB or better, with the same noise bandwidth. A-weighting improves these results by about 2 or 3dB. Interestingly, the total dynamic range available via the phono inputs of the Studio 200 is in excess of 109dB. This is the ratio of the phono input overload capability (150mV at lkHz] to its equivalent input noise voltage (0.5 microvolts]. So as far as dynamic range is concerned, the phono input is also better than that available from compact discs. Unfortunately, neither vinyl discs or phono cartridges have this capability. Inputs and outputs The Studio 200 caters for no less than six pairs of inputs and it also has a tape monitor for connection of inputs and outputs from a cassette recorder. This means you can connect up to seven stereo program sources. The Selector switch is labelled as follows: Phono, CD, Tuner, VCR, Aux 1 and Aux 2. The rear panel has an array of 18 RCA sockets to provide for all the inputs and outputs. Push-on push-off switches are used for the tape monitor, tone defeat and stereo/mono switches. These are accompanied by symbols on the front panel which indicate their settings. The balance, treble and bass controls each have a detent to indicate their centre settings. The volume control has multiple detents. The headphone socket has an inbuilt switch to disconnect the control unit's output signal to the JUNE 1988 29 RIAA/lEC PREAMPLIAER SOURCE__. TAPE .------,TONE-OEFEAT TUNER eJ S1a INPUT SELECTOR AUX. 2 lj'" TAPE OUT OTHER CHANNEL VCR AUX. 1 BASS AND VOLUME 50k LOG. MONO TREBLE CONTROLS S4a .,. BALANCE~~-<r 10k M/N S5a .,. ::::::;v.,. HEADPHONE AMPLIFIER TAPE IN .,. Q POWER ":r' AMPLIFIER T I ~ HEADPHONES OTHER CHANNEL Fig.1: all the features of the new stereo preamplifier are illustrated in this block diagram. To keep things simple, only one channel is shown. The second channel uses exactly the same circuitry. power amplifier when headphones are in use. This stops you from unwittingly blasting your loudspeakers when you are using headphones. It also allows you to turn off the power amplifier when you are using headphones. This last point is important because when a power amplifier is off, the control unit's output signal is loaded by the unenergised input transistors (in the power amplifier). This could cause serious distortion. The headphone amplifier has the potential to deliver more than adequate drive so that even insensitive headphones can be driven to painful levels (not that you should da this if you value your ears). With 32-ohm phones, the drive can exceed 100 milliwatts while for 8-ohm phones the drive capability is more than 40 milliwatts. This means that if you are the audio equivalent of a "petrol head" you will be able to listen at headsplitting sound levels without disturbing your neighbours in the slightest. Curiously, listening via a set of closed headphones is the only way that most hifi enthusiasts will ever be able to experience the full dynamic range of compact discs. Most listening rooms have quite a lot of background noise and this tends to mask the really quiet signals on compact discs. Signal to Noise Ratio Readers will notice that we have quoted two separate figures for the various signal-to-noise ratios of the Studio 200 : (1) Flat, with a noise bandwidth (-3dB points) of 20Hz to 20kHz; and (2) A· weighted , according to the CCIR characteristic. To our knowledge, there is no self-contained commercial test equipment which will perform such measurements. To enable us to measure the signal-to-noise ratios of today's extremely quiet high fidelity equipment, we have designed a state30 SILICON CHIP of-the-art AC millivoltmeter using the best available low noise op amps. This instrument enables noise measurements to be made down to better than - 60dB with respect to one millivolt RMS (that's less than one microvolt) . This means that it • can make noise measurements in excess of 1 20dB A-weighted or flat (with respect to 1V RMS) which is far better than the best CD players. The new AC millivoltmeter will be described in a coming issue of SILICON CHIP. Unfortunately though, the headphone outputs on some commercial amplifiers and receivers are not as quiet as the main amplifier outputs (some have quite high hum levels via the headphone outputs). So not only are the amplifier outputs not as quiet as they should be, as we noted above, but the headphone outputs are even worse. By contrast, with the Studio 200 control unit and power amplifier combination you really do get phenomenally low background noise, on both the headphone and the main amplifier outputs. Omissions To keep the unit reasonably simple and inexpensive, we have omitted a couple of features that are found on some amplifiers and control units. First, there is no speaker switching, which is quite unwieldy when you have a separate control unit. Second, we have not provided for moving coil cartridges; there are relatively few in use and the trend is away from turntables anyway. Third, we have not provided for dubbing and monitoring between two cassette decks. Dubbing is possible though, if the outputs of one deck are fed into a pair of the auxiliary inputs. Inside the chassis, the circuitry is accommodated on three printed cir- cuit board assemblies. We did consider designing one large printed board to accommodate all the circuitry but that would have caused problems. First, we wanted to have the control knob centres below the centreline of the front panel (so the control legends could be above the knobs). This meant that the board for the tone controls has to be upside down in the chassis. Second, we wanted to keep the power supply components and the phono preamplifier as far away from each other as possible and we wanted the phono preamp right at the relevant input sockets. When these and other conflicting requirements were taken into account, we could not justify having one large printed board - it would have had a lot of wasted space and it probably would have made the overall assembly harder to work on. Ergo, there are three board assemblies; one for the power supply, near the transformer, one for the phono preamp and input selector and one for the four dual op amps comprising the volume, bass, treble and balance controls and the headphone amplifiers. Circuitry Now let's have look at the circuit features which are illustrated in the block diagram of Fig.1. This shows one channel only, to keep matters simple. Remember that all circuit functions are duplicated in the second channel. The same goes for the main circuit diagram of Fig.2. S1 is the 6-position selector switch. It selects the input signal and its wiper feeds the tape output as well as the following Tape Monitor switch S2. This selects the signal from S1 or from the cassette deck connected to the Tape In inputs. The signal then goes to S3, the stereo/mono switch, which shorts the two channel signals together to obtain the mono function. When the mono function is switched in by S3, the left and right · channels of the selected program source will load each other (as far as the difference signals are concerned). To avoid any degradation in signal quality due to this effect, Specifications Frequency Response Phono inputs: RIAA/IEC ±0.3dB from 20Hz to 20kHz High level inputs: within ± 1dB from 1 OHz to 1 OOkHz Total Harmonic Distortion Less than .005%, 20Hz to 20kHz, at rated output level for any input or output. Signal-to-Noise Ratio Phono (moving magnet): 86dB unweighted (20Hz to 20kHz) with respect to 1 OmV input signal at 1 kHz and rated output with 1 kO resistive input termination; 90dB A-weighted with respect to 1 OmV input signal at 1 kHz and rated output, with 1 kn resistive input terminal. High level inputs (CD, Tuner, etc): 104dB unweighted (20Hz to 20kHz) or better, with respect to rated output (with volume at maximum) with Tone Defeat switch in or out; 107dB A-weighted, with respect to rated output (with volume at maximum) with Tone Defeat switch in or out. Separation Between Channels -62dB at 1 OkHz; -81 dB at 1 kHz; and -93dB at 1 OOHz with respect to rated output and with undriven channel input loaded with a 1 kn resistor. Input Sensitivity Phono inputs at 1 kHz 4.3mV High level inputs 240mV Input impedance (phono) 50k0 shunted by 1 OOpF Input impedance (CD, etc) 50k0 Overload capacity (phono) 1 50mV at 1 kHz Output Level Rated output, 1.25V; maximum output, 8.4V RMS; output impedance, 4700; headphone output, 40 milliwatts into 80 phones, 1 00 milliwatts into 320 phones. Tone Controls Bass, ± 1 OdB at 1 OOHz; treble, ± 12dB at 1 OkHz Phase With tone controls defeated, non-inverting (ie, zero phase shift) from phono to main output; non-inverting from high level inputs to main outputs. Non-inverting from all inputs to Tape Out. With tone controls in circuit, inverting from phono and high level inputs to main outputs (ie, 180° phase shift). there are tkn resistors between S1 and S2 and in the Tape In signal path to S2. After S3 the signal is fed to the volume control and then to a noninverting op amp stage with a gain of 5.7. From there, the signal goes to the unity gain feedback tone control stage, which can be taken out of the circuit by the Tone Defeat switch, S4. After S4, the signal goes to the balance control and then to S5 which is integral with the headphone socket. It normally feeds the control unit's signal to output sockets and thence to the following stereo power amplifier. When a headphone jack plug is inserted into the socket, S5 switches the signal to the headphone amplifier. This has a gain of two. Circuit description The complete circuit diagram (for one channel) is shown in Fig.2. The four op amps are depicted as ICla, IC2a, IC3a and IC4a. The pin numbers for op amps IC2a, 2b, 2c and 2d in the second channel are shown in brackets on the circuit. ICla is the phono preamplifier JUNE 1988 31 The circuitry for the new control unit is accommodated on three PCB assemblies: one for the tone controls, one for the phono preamplifier PCB, and one for the power supply. The tone control board is mounted upside down in the chassis. and equalisation stage. It takes the low level signal from a moving magnet cartridge (typically a signal of a few millivolts) and applies a gain of 56, at the median frequency of lkHz. Higher frequencies . get less gain while lower frequencies get considerably more, as shown in the accompanying equalisation curve of Fig.3. To be specific, a 100Hz signal has a boost of 13.lldB while a 10kHz signal has a cut of 13.75dB. The phono signal is fed directly from the input socket via a small inductor, a 1500 resistor and a 47µF bipolar capacitor to the noninverting input, pin 3 of ICla. The inductor, series resistor and shunt lOOpF capacitor form a filter circuit to remove RF interference signals which might be picked up by the phono leads. The lOOpF capacitor is also important in capacitive loading of the magnetic cartridge. Most moving magnet (MM) cartridges operate best with about 200 to 400pF of shunt capacitance. The lOOpF capacitance in the control unit plus the usual 200pF or so of cable capacitance for the pickup leads will therefore provide an optimum shunt capacitance. For its part, the 47 µF bipolar capacitor is far larger than it needs 32 SILICON CHIP to be, as far as bass signal coupling is concerned. But having a large capacitor means that the op amp "sees" a very low impedance source at low frequencies and this helps keep low frequency noisEl, ganerated by the input loading resistors, to a minimum. RIAA/IEC equalisation The RIAA equalisation is provided by the feedback components between pins 1 and 2. These equalisation components provide the standard time constants of 3180µs (50Hz), 318µs (500Hz) and 75µs (2122Hz). The phono preamplifier also adds in the IEC recommendation for a rolloff below 20Hz (7950µs}. This is provided by the 0.33µF output coupling capacitor in conjunction with the load represented by the 50k0 volume control, together with other low frequency rolloffs in the circuit. One of these rolloffs (at around 4Hz) is caused by the l00µF capacitor in series with the 3900 resistor. The 3900 resistor sets the maximum AC gain at very low frequencies while the l00µF capacitor ensures the gain for DC is unity. This means that any input offset voltages are not amplified (by more than one) which would inevitably cause trouble with unsymmetrical clipping and premature overload in the preamplifier. As noted above, the signal from the phono preamplifier is coupled via S1 and S2 to the volume control. From there the signal goes via a lµF capacitor to non-inverting op amp IC2a. The feedback around this stage is set by the 4.7k0 and tkO resistors to give a gain of 5.7. The .formula for this calculation is given by: Av = (4.7k0 + lkO) + lkO = 5.7. The input (pin 3) of IC2a has a series tkO resistor acting as an "RF stopper" to prevent the possibility of strong RF signals (from local radio or TV transmitters) being detected inside the op amp. The 180pF capacitor across the 4. 7k0 resistor also provides a high frequency rolloff (above 180kHz) to ensure low sensitivity to RF signals and ensure stability of the stage. Tone controls Besides providing gain, IC2a acts as a low impedance source to dri~e Fig.2 (right): the circuit is based on ► the new low-noise LM833 dual op amp. Note that one channel only is shown; the figures in brackets refer to IC connections in the second channel. The circuit is powered from regulated ± 15V rails. r:r: L1 PHONO +15V 47 * .,. 100pF OOk .,.. 1 +15V .,. - 15V * 16k * 200k VOLUME VR1a 50k LOG. * 390() *1 % METAL FILM -15V 4.7k 1001 BP MONO ·plm• co 180pF 1k STEREO TUNER VCR 22 BP .,. OTHER CHANNEL AUX 1 AUX 2 TAPE OUT TAPE IN .,. .01 BASS VR2a 22k +15V 22k +15V 8211 HEADPHONES 10k j +:/ OTHER / CHANNEL / HEADPHONES S5a - 15V I 10k .,. AEER I I I I [ I AMPLIFIER I .01 250VAC I 10k (6 ') S6 I .,. __'T- __ __ ____ _ ___ _ __ D3-D6 4x1N4002 I / I __} m ECB "o..,u.,_ T_._ _....._ _ _~ - - - - - - - - - - - - - , 1 1 - - - + 1 s v 240VAC .ffi_., N-'---------' GND E • .,. 1000 25VW STUDIO 200 STEREO CONTROL UNIT SC01 -1-688 ]UNE 1988 33 PARTS LIST Hardware 1 rack-mounting case (Altronics Cat. No. H-0411) 1 30V 150mA centre-tapped transformer (Altronics Cat. 3 1-metre lengths of hook-up wire 3 plastic cable ties 1 60mm length of heatshrink tubing No. M-2855) 1 push on/push off SPST mains switch with black button {Altronics Cat. No. S-1090) 1 2-pole 6-position rotary switch (input selector) 3 2-pole push on/push off PCB mount switches (Lorlin or similar) with black knobs 5 22mm-dia. black anodised aluminium knobs (with index mark) 1 cord-grip grommet 1 3-way insulated terminal block 1 black binding post terminal 18 insulated panel-mounting RCA sockets 1 PCB-mount 6. 5mm headphone socket with integral switch (Jaycar Cat No PS-0180) 1 1 /4-inch solid shaft coupler 1 72mm long 1/4-inch shaft 1 1 /4-inch ID x 3/8-inch OD bush for switch shaft 1 mounting bracket (for selector switch) 4 rubber feet 2 solder lugs 2. FX111 5 ferrite beads Printed circuit boards 1 phono preamplifier board, code 01106881, 180 x 125mm 1 switch mounting board, code 01106882, 54 x 32mm 1 tone control board, code 01106883, 300 x 94mm 1 power supply board, code 04106881, 71 x 52mm 40 1 mm-dia. PC pins 4 6mm spacers Cable 1 3-core mains cord and moulded 3-pin plug 1 metre of figure-a shielded audio cable the tone control stage IC3a. This has the tone controls connected in the negative feedback network. When the bass and treble controls are centred (ie, in their "flat" settings), the gain of the stage is one, over the frequency range up to at least lOOkHz. Winding the bass or treble control towards the input side of IC3a [ie, setting the controls for boost) increases the gain for frequencies above ZkHz for the treble control and below 300Hz for the bass control. The reverse happens when the tone controls are rotated in the opposite direction. This has the effect of increasing the negative feedback 34 SILICON CHIP Semiconductors 4 LM833 low noise op amps 2 BD1 39 NPN transistors 2 80140 PNP transistors 8 1 N4002 rectifier diodes 1 7815 3-terminal regulator (NB: 78L 15 not suitable) 1 7915 3-terminal regulator (NB: 79L 15 not suitable) 1 5mm red LED and bezel Capacitors 2 1 OOOµF 25VW PC electrolytics 4 100µF 16VW PC electrolytics 2 1 OOµF bipolar electrolytics 2 4 7 µF bipolar electrolytics 2 22µF bipolar electrolytics 2 6.8µF bipolar electrolytics 2 1µF bipolar electrolytics or miniature metallised polyester (Wima MKS 2) at treble and/or bass frequencies and the effect is treble or bass "cut". The amount of treble boost and cut provided by IC3a is limited by the 3.9k0 resistors on either side of the 25k0 treble pot. Similarly, the amount of bass boost and cut is limited by the 22k0 resistors on either side of the lOOkO bass control pot. (Yes, we can immediately see those bass hungry readers will want to fiddle the circuit to obtain more bass boost. Don't do it. Too much boost can lead to instability, increased tendency to overload, and general loss of moral fibre in 2 0.33µF metallised polyester (greencap or miniature) 4 0. 1µF metallised polyester (greencap, monolithic or miniature) 2 .015µF metallised polyester (5% tolerance preferred RIAA preamp) 2 .01 µF metallised polyester 4 .004 7 µF metallised polyester (tone controls) 2 .004 7 µF metallised polyester (5 % tolerance preferred RIAA preamp) 2 180pF ceramic 2 1OOpF ceramic 2 1OpF ceramic Potentiometers 1 dual gang 1 OOkO linear potentiometer, PCB-mounting (bass) 1 dual gang 50k0 log potentiometer, PCB-mounting (volume: must not have loudness taps; it won't fit) 1 dual gang 25k0 linear potentiometer, PCB-mounting (treble) 1 dual gang 1 OkO M/N potentiometer (balance) Resistors (0.25W, 5%) 2 x 1 MO, 2 x 1 OOkO, 6 x 22k0, 6 x 1 OkO, 4 x 5.6k0, 2 x 4. 7k0, 4 X 3.9k0, 1 X 1.5k0, 8 x 1 kO, 2 x 4 700, 2 X 1000, 2 X 820 Resistors (0.25W, 1 %) 2 x 200k0. 4 x 1 OOkO, 2 x 16k0, 2 X 3900, 2 X 1500 today's youth.) Note how S4a, the Tone Defeat switch, bypasses the circuitry associated with IC3a. Its output feeds the balance control via a 4700 resistor and 6.BµF capacitor. The 4700 resistor is there to provide short-circuit protection to IC3a, in the event of the output being short-circuited. It also lets IC3a drive long cables [well, not too long) without cable capacitance causing stability problems. The 6.BµF capacitor is there to block any DC offset voltage at the output of IC3a from being fed to the input of the stereo power amplifier. It also stops DC from appearing To make construction really easy, the control pots, pushbutton switches and headphone socket are soldered directly to the tone control board. Full wiring diagrams of all the PC assemblies will be published next month. across the balance control pot, which could otherwise become noisy. + 1,- 20 20Hz (7950µs)---;" / ~ 50Hz (3180µs) '- I;/ I'--, Headphone amplifier I +10 I/ '' -~ I/ PROPOSED IEC ~ Following the balance control is / S5, the power amp mute switch 2.120kHz (75•s) / which is inside the headphone r-, ' I / socket. This diverts the output ............ ) signal of IC3a to the headphone 500Hz (31B•s) ;-.,_, amplifier which consists of IC4a combined with transistors Ql and Q2. The two transistors are there to _10 ~ boost the output current capability of the LM833 op amp. They are '\. slightly forward-biased (to keep "\. cross-over distortion to a minimum) I "\ I I I by the two diodes connected bet- -20 2 10 100 HERTZ 1k 10k 20k ween the bases. Fig.3: this is the RIAA compensation curve of the new preamplifier showing This is a version of the '' current the IEC modification to roll off the response below 20Hz. This has the effect mirror" circuit employed in many of removing low frequency noise as well as the :rumble on all records. op amps. It works by balancing the voltage drop across each of the The output current of the head- transformer feeding a bridge recdiodes with the base-emitter phone amplifier is limited by the tifier and two 1000µF capacitors. voltage of the associated transistor. 820 resistor. This provides short- This produces unregulated supplies Provided the diodes are similar in circuit protection and protects the of. about ± 22 volts which are then characteristics to the base-emitter headphones against damage in the fed to 3-terminal regulators to projunctions of the transistors it works unlikely event of the amplifier being duce balanced supply rails of ± 15 well as a low-power class-B damaged (which would otherwise volts. amplifier circuit without the need cause ± 15 volts to be applied That's all we have space for this to manually adjust the quiescent across the headphones). month. Next month we'll present current (ie, the current drawn with Power for the circuit is provided the construction and troubleno signal present). by a 30 volt centre-tapped mains shooting details. ~ '" ', ,, ~- ' JUNE 1988 35 PROFESSIONAL UALITY AT ICK SMITH ELECTRONICS 6.5MHz CRO Every hobbyist knows how valuable a good oscilloscope is: probably the most useful piece of test gear you can own. Hear's what it offers: •Retrace blanking for a much clearer display •10mV per division vertical sensitivity $ •250mV/division external horizontal sensitivity •10Hz to 100kHz, plus external timebase •Internal or external sync •Useable response to beyond 6.5MHz Ideal for the shack, the work bench, in service work, in the classroom and also in assembly applications. Solid state electronics (apart from the tube!) means fast warmup and extremely low drift. Cat Q-1280 399 Dual Trace CRO - 20MHz With Inbuilt Component Checker illiL,,,,~ Kl Specifications: Vertical bandwidth: DC to 6.5MHz (-3dB) Attenuator: 1/1, 1/10, 1/100 and ground Horizontal sensitivity: 250mV/div or more Timebase: 1OHz to 1OOkHz Sync: External or internal Input Impedance: 1 Meg//35pF You could buy one of those big-name oscilloscopes (the ones with the big-name price tags) and you probably wouldn't get all the features of the DSE CRO. It's a fully professional quality dual trace model offering outstanding performance for the price! Features: • 20MHz bandwidth (- 3dB) • Use in single or dual trace mode • Dual trace in chopped or alt mode • Complete with 2 probe sets • Inbuilt component checker - for capacitors, inductors, transistors, diodes, zeners, etc. • And much, much more! Cat Q-1260 Complete with 2 sets of probes! s999 .; . m • "IMITH ~ Specifications: DC-20MHz (- 3dB), with less than 17.5ms rise lime and 3% overshoot Deflection: 5mV/div to 5V/div in 10 calibrated steps (1-2-5 sequence) Accuracy: ±3% . Timebase: 0.1us/2V/div to 2/div in 20 calibrated steps (1-2-5 sequence) Uncalibrated control to at least 5/div Triggering modes: peak or normal from either/both channels or external Trigger Sensitivity: 0.5V/div Sweep delay: 0.fus to 10ms in 6 steps. NSW • Albury 21 8399 • Bankstown Square 707 4888 • Blacktown 671 7722 • Bondi Junction 3871444 • Brookvale (Warringah Mall) 93 0441 • Campbelltown (046)27 2199 · ' • Chatswood Chase 4111955 • Chullora 642 8922 • Gore Hill 439 5311 • Gosford 25 0235 "" • Hornsby 4 77 6633 • Liverpool 600 9888 • Maitland 33 7866 • Miranda 525 2722 • Newcastle 61 1896 • North Ryde 88 3855 • Parramatta 689 2188 • Penrith (047)32 3400 • Railway ~ · Square2113777• SydneyCity2679111 • Tamworth661711 • Wollongong283800• ACT • Fyshwick 80 4944 •VIC• Ballarat 31 5433 • Bendigo 43 0388 • Box Hill 890 0699 • Coburg 383 4455 • Dandenong 794 9377 • East Brighton 592 2366• Essendon 379 7444 • Footscray6892055• Frankston 783 9144 • Geelong 43 8804 • Melbourne City670 9834 • Richmond4281614 • Ringwood 879 5338 • Springvale 547 0522 •OLD• Brisbane City 229 9377 • Buranda 391 6233 • Cairns 311 515 • Chermside 359 6255 • Redbank 288 5599 • Rockhampton 27 9644 • Southport 32 9863 • Toowoomba 38 4300 • Townsville 72 5722 • Underwood 341 0844 • SA • Adelaide City 232 1200 • Beverley 347 1900 • Darlington 298 8977 • Elizabeth 255 6099 • Enfield 260 6088 •WA• Cannington 451 8666 • Fremantle 335 9733 • North P.erth 328 6944 • Perth City 481 3261 • TAS • Hobart 31 0800 • NT• Stuart Park 81 1977 .• DIC ?J . , ~ £~j (ij; YOU WON'T BEAT THE QUALITY OF SCOPE Irons~ ~~~!ig~~!!~!s / / Famous rnM =l ,J a-, :13 ,11·1r1 Hand Tools u 0:!I:J size for precisi_on models, turntable cartndges, etc. At our low prices you can afford to buy a couple m case you lose one! Flat Blade: cat T-6010 Philips· cat T-6015 s·1 3011 ~\mm H ; x mm 5 7 0 MADE IN ITALY Around the world, Piergiacomi tools are known for their outstanding quality and reliability. They're the choice of professionals - and now DSE has available this superb range. Expensive? Yes, they do cost more than our hobbyist range: but once you feel the quality. feel the precision, you'll realise they're worth every cent! Theresa Piergiacomi for every purpose ... all tools feature heavily insulated handles with sprung action blades and locking bush. . Miniscope J 95c EACH L $ Cutting Nipper with back-angled cut Designed especially for pcb soldering work. The ~ Stubby Drivers cutting edge is on the opposite side to normal allowing o a 1mm pigtail to remain ready for soldering - or allowing clearance of the soldered joint if you trim the $ pigtails after soldering. Clever - and it works! Blade opening 7mm, handles up to 1.3mm copper wire. 3261 catT- (D Cutting Nipper with standard cut Ultra-precision cutter with standard anQled blades ~ allowing completely flush cutting. Special safety o • feature: sping in blade prevents flying pigtails. Blade opening 4mm, cutting capacity 1mm copper wire. 62 catT-32 Standard $1695 Inclined Frontal Cut Nippers ~ _ Medium Duty/) Big enou9h to get a good strong gnp and plenty of th i:~r~gt~/r~~J~ii~~ e you've got the right tool for just about any job. . Flat.Blade: cat T-6050 P•ll1ps: Cat T-6055 Size: L 1501Rm D511m H6.511m S Handle: 95 x 25mm bends·it away from pcbpcb so assembly the component won't out. Fantastic! Makes a breeze - fall and solve_s one of the biggest bUQbears of hobbyists! Blade openmg 6mm, cuttmg capacity 1mm copper wire. 3264 Cat T- · s 1995 Shears For larger cutting jobs - like mini scissors but with extra strength needed to get through metal, plastics, etc. 18mm length blades means they'll handle coax cable, etc. Blade opening 10mm, cutting capacity 1.6mm copper wire. Cat T-3265 Needle Nose Pliers Tweezer-like ends for reaching into almost inaccessible places - and flat blades so delicate components won't be damaged. 40mm long blades with 15mm opening at end. Cat T-3266 Aat Nose Serrated Pliers ~ · ·"·4 '. · s2295 195 1795 $ ?:-,~ ~ 1695 '--------------_,. Scoze Cordless Sol er Gun Already own a multimeter? This set has everything else .and then some! Auto electric checker (6-12-24V), heavy duty pliers, crimp terminal set... with 60 assorted crimp lugs, insulation tape, even connecting wire! A must for the hobbyist, technician - or even the motorist. Cat T-4834 TheIdProfessional S . S I 'Pocket' 0 er1ng ys em The totally portable professional soldering system from Portasol. The equivalent of 10-60 watts of power with temperature adjustment up to 400 ° Celsius. Just the thing tor hobbyists, technicians, repairers .. anyone who needs EACH to make repairs, alterations, etc. on the spot! cat T-1374 Everyone needs a b i g ~ gun sometimes! Strong enough for the toughest work - ideal for the tradesman. Flat Blade: Cat T-6060 Philips: Cat T-6065 Size: L 200mm D7mm H 100 x 25mm EACH $395 ~~t~ef:J~~:~rat,re adjast1llle ln,n MITH I s7 995 • 4 Tips incl1dlng hot klllfe and blow ton:111 • Tip cleaning sponge • Heavy dlly plastic case witb clip-01 iron sland • llltane powered - refills in seconds . -------------- • Avenge 90 minutes contlnuou use Spare tip to satt Cat T-1375 $12.95 Arlec Mini Vice I Everything for quick and easy wiring repairs - with no soldering! Ideal tor automotive and hobby use. Here's what you get: • Multimeter • Crimp Tool • Pliers • 2 Screwdrivers• Neo Tester (rated tp 500V) • Selection of crimp lugs. All in a handy, heavy duty carrying case. Perfect for throwing in the car - just in time! Cat T-4832 • -,..------------------a=-- ..~ -~. . . s129 38 Piece Deluxe Repair Kit with Multimeter 68 Piece Multipurpose Repair Kit -- For soldering where you want it. Powerful enough to handle the same jobs as 60W mains irons, but inbuilt Ni Cads give you up to 100 solder joints f · t d · d EACH away rom power pom s an extension cor s. · Includes plugpack tor overnight chargin9; heats in just six seconds and takes standard Mimscope spares. Supplied with charger, two spare elements and two spare bits. Cat T-1600 •----------------------• ]:D~ _ _ Heavy Duty Fine (2.5mm) ends with serrations along blade mean extra grip when you really need it. 12.5mm opening $ with 40mm long blades. Cat T-3267 :DIC I/$195 ~ Two birds with one stone! Not only cuts the pigtail, but ,, ("'\Q ~ · 95 59 ~ The world-famous Australian! Scope irons are i d ' '"' e~•'I tor the hobbyist, the work bench, the lab everywhere. Because they're made tou9h to take it, they can! Huge 150 watt capacity and 1t itelivers heat from cold in just six seconds. You dictate the temperature you want. Stainless steel noncorrosive barrel. With spare tip and element. cat T-1605 Needs 3.3V<at> 30A. Scope Transformer cat T-1692 $59.95 EACH 'I w s1995 ~-~ ~ , s5295 . Ideal for general purpo~e electronic work. Spot-on for 1/, Whitworth! Rat Blade: Cat T-6000 PhTps c tT 6035 11 : a Size: L 75mm 0 3.2m111 H 57 x l 5mm Very easy to handle, allowing leads to be cut 1.5mm ~ irom plane - perfect for soldering or to clear soldered joint. The blade tip is angled at 30° to allow access to tight spots. Blade opening 9mm, cutting capacity 1mm copper wire. cat T-3263 Inclined Cutter and Bander Superscope Great for confined space - or that tough screw which needs extra muscle. You can really get a grip on these! Rat Blade: CatT-6020 Philips: cat T-602s Size: l 38mm D6mm H45 x 30mm 1695 , Li9htweight and a delight to handle and use, t~t '¾_ Mmiscope is perfect for general service work, kit building, etc. Finger tip control gives precise temperature - the equivalent of irons in the 10 to 70 watt range. Use Scope transformer for correct operation. With spare tip and element. CatT-1660 Needs 3.3V<at> 30A. Scqpe Transformer cat T-1692 $59.95 Need a third hand? Here's one that won't let go! The · mini vice from Arlec attaches to any table, desk, bench, etc. (up to about 40mm thick). 50mm wide jaws hold tight - opens up to around 60mm for those big jobs. More than strong enough tor cutting, filing and other testing applications. cat T-4748 ·LL s1595 MAJOR DICK SMITH ELECTRDNICS AUTHORISED STOCKISTS: •NSW• ~ : Sound Components, 244 Beardy St, 72 4981 • - : Ballina Electronics, 102a River St, 867022 •llwnl: F.R.H. Electrical, 28StationSt, 611861 •-Ill: Hobbies&Electronics, 310xideSt,884096•-:Newtronlcs, 131 PacificHwy,439600•Cdls-:CoffsHarbour Electronics, Shop 3, Coffs Harbour Mall, Park Ave, 52 5684 • - . . , Deni Electronics, 220 Cressy St, 81 3672 • _ , Chris's HI-Fi, 11100 Talbraoar Street, 82 8711 • _ , Forater Village Electronics, Shop 36, Forster Shopping Village, Breese Pde, 54 5006 John Sommerlad Electronics, Shops 5 &6 Mackenzie Mall, 32 3661 • - : Miatronics, 166-170 Banna Ave, 624534•-: Lt\:WillingEleelronics, 32LawrenceSt, 221821 Orummond -•Entertainment 36ForthStreet 626265 ,i.-., Leeton RecordC8ntre, 121 Pine Ave, 532081 1 . -_c-=-i:..::..i..::.a~.>.·.:..:::•Lll..L:'-=-<L.:.. ~h!lSt~~3895 • ..:;..'1:":w;,2E~~:. 21~~=.-r:::nit~~:3J!t~~~·.;i1aW!t .,..., Hall of Electronics, The Horton Centre, 124Horton St, 837440•0..., Fyfe Electronics. 296SUmmerSt, 626491 •s,rt,p,N: W.llington'sElectricalOiscounts, 132M~, 514888 • T_, Brad's Electronics, Shop 6, Civic Cinema Centre, PulteneySt 526603 • _ , TumutElectronics, 62 Russell St, 471631 • _ , PaulsElectronlc &Hobby Toys, Shop 1, 10 IYasa1 St, 55 2454 • WIiia: Phillips Bectrooics, 60Fo!Syth St, 216558• : Wellinglon Electrical Service, 110LeeSt, 452325•"-: Keith DollgesElectronics, 1868oorowaSt, 821279•0:•telllc, ColacElectronics, 215MurrarySt, 312847•-,: FindersPtv. Ltd., 90BroadwaySt,681333•-: MorwellElectromcs, 35HolmesRd,34 133 • a.,,,rt,o: Phillips Electronics ~Ltd., 137 High St, 21 9497 ......, Ro~aine Ply. Ltd, 16 Sml1h St. 23 4255 • _ , Mart1ronics, Shop 12, Nortolk Plaza, 743 Raglan Pde, 62 9870 • QUJ • . . . , ., Bob Elkin Electronics, 81 Boortlon!I St, 72 1785 • _ , Electro-Mart, 9Tay Ave, 918533 • : DvsartV~eotrooixs, Shop 1,JacarandaCrtShoP!lingCentre, lk!een Elizabeth Drive, 582107 • _ , Splitec, Shop 5, cartwriQhtCentre, Nicklin Way, 94 7349•-.W: Stevens Electrooics, 42VictoriaSt, 51 f723,....._.,, Ketler Electronics, 218AdelaideSt, 2145 9• ■ btt: Otrtback Electronics, Shop 71, Bar1dyHwy, 43 3475•-: Nambour Electronics, Stlop4, Lowan House.Ann St, 41 16 0 4 • - -: SUnshinePltoneSVstems. Shop 6, SUnsllineBazaar, SUnshineBeach Ril,47 #l<l•IA •■-, HutchessonsCommunicationsCentre, 5 Elizabeth St, 250400•...., ~ Bridge Communications, 246Adelaide Rd, 32 6476 •WA •May: Micro Electronics, 133 Lockyer Ave, 41 20TT •llonlM: Batavia L~hting& Electrical, 98a Chapman Rd, 231842 2; 165 854836•1'1Ntllllal: tvan Tomek ~ics, 30AndersonS1reet, 732531 •TM• _: • •la_, e=.'Ts~~stt~:r.=~~~J ~.:.:~~j~1~~~l:e':.~rir33 •= :.~=cser.::ce~. ~:n5Mr~~;4~~ ~v:==~~~~-~Elde~t= ~~~ ~~~ •=: Ring out the ne-w, ring in the-old If that heading sounds like a new year greeting suffering from alcoholic inversion then let me assure you that it is not; it is quite deliberate and was inspired by one of the most blatant and disgraceful rip-offs that I have ever encountered. The story started with a telephone call from a potential customer who had just moved into the area and who had been given my name by a regular customer. The caller explained that he had a Philips 56cm K9 colour set which had failed completely and wanted to know how best to go about getting it serviced. Could I call and collect it, could I service it in the house, or would he have to bring it to the shop? I'm trying to avoid house calls as much as possible these days, unless there are special circumstances. They are time consuming - and therefore expensive - and with the ever increasing complexity of modern devices it is becoming more and more difficult to do a proper job away from one's own bench. One exception is very large sets, and particularly where it would be unreasonable to expect the person concerned to manhandle it. Another is where the symptoms suggest that the fault might involve the location: antenna problems, local interference, and so on. In this case I advised the caller that I would call if this was essential, but that it would save time and reduce costs if he could manage to bring the set in. He accepted the situation happily enough, and added that he could probably manage to bring the set in without too much bother. In the event, having the set on my own bench was a very wise decision. And so it was that he duly turned up with the set in the back of a station wagon, and I helped him bring it into the shop. I then took the opportunity to quiz him about the set's history; previous problems, service work &c. He turned out to be quite well clued up in this regard; much better than most. Previous jobs ~~--AND AOt>l::D 11-IA'T H~ C.OU\...P :BR,NG 71-\e: Se:.T \ N WrTHOUT 000 ,oo 38 SILTCON CHIP MUCH :BOT\-\E'R.oo The set had had two major service jobs performed on it quite recently; one by an independent serviceman and one by a large wellknown service organisation. In the first case, the picture tube had been replaced and in the second case a new tripler had been fitted. (Not many customers would even be able to remember the name of a tripler!) For his part he was anxious to get some idea of how long the job was going to take and what it was likely to cost. Naturally, I wasn't prepared to commit myself on either question, but suggested he might like to wait while I turned the set on and made a preliminary check. So I turned it on and confirmed the behaviour as he had described it on the phone; no picture, no sound, no raster. I pulled the back off the set and that was my first shock! The previous serviceman had obviouly been a European gentleman by the name of Rufus Gertz - and boy, was he ruf. The two screws which secure the two swing-out boards were missing, and the strip cover over the power supply was missing, as were the screws which hold it. I kept the observation to myself and reached for the multimeter to measure the 155V supply rail on the horizontal scan board. I fully expected to find a low voltage here, as is typical of a shorted horizontal output transistor for example, and which produces just such symptoms. Instead the voltage was high, up around 180V. The most likely explanation was that, instead of a short circuit on the horizontal scan board, there was an open circuit. Another vague possibility was a fault on the power sup- .ply board. Although unlikely, it was easy to check because I carry a spare power supply board on hand, and it takes only a few moments to make the swap. In fact, my board behaved exactly the same, putting suspicion back on the horizontal scan board. At this point the customer was still waiting patiently, hoping that I could give him some idea of the likely seriousness of the problem, so I swung the two boards out for a visual examination, in case there were any obvious clues or damage which I needed to know about. In fact there didn't appear to be anything obvious on the boards, but there was something else that caused me to reel back - metophorically speaking that is. Remembering the customer's comment about a new picture tube I fully expected to find a typical re-built tube from one of the local companies which do such a good job in this field. Instead, the set was fitted with an original Philips tube. It wasn't the tube which had been fitted to the set when new - which was fair enough, seeing that it was supposed to have had a new tube fitted - but neither was it a new tube. A ring in This model set was originally fitted with a type A56-120X, whereas the tube now in the set was a later type, the A56-410X, which is almost identical with the 120X except that f L· r"./z ,. ·- ...... "-' ~ a'nt it is fitted with a fast acting heater to bring the picture up more rapidly at switch-on. Well, there was nothing sinister about that either; the real giveaway was a little Philips sticker on the tube. Traditionally, every new Philips set carries at least two of these stickers; one on - typically - the horizontal scan board and one on the picture tube, and both carry the serial number of the set. But in this case the serial number on the picture tube sticker was not the serial number of the set. So the tube was obviously not a rebuilt tube, from which any such stickers or labels would have been removed. Nor could it be a new tube from Philips, fitted by someone else, because it would not have carried a sticker either. In fact, it was obviously a tube salvaged from a junked set which had been rung in on an unsuspecting customer. Once again I kept my own council. I needed time to think about this one. Getting back to the immediate technical problem, it was now obvious that I could not give the customer any meaningful answer as to the time or cost involved. All I could do was suggest he come back later in the day when I might have a better idea of the problem. So that was how we left it. Back at the bench I stoked up the CRO and prepared to do battle. All the indications were that the horizontal output stage was not working so I started by checking the base of the horizontal drive transistor, TS430, a BD232 which is fed with horizontal pulses from module U330, at about 1.5V p-p. In fact, this came up spot on, so all was well so far . But it was a different story at the collector of TS430. There is supposed to be 400V p-p signal at this point, but there was nothing. And for a very good reason; there was no DC voltage on the collector. This situation, in turn, was due to the sad demise of R440, a 1200 resistor in the collector supply line from the 155V rail. It was cooked to a cinder and had obviously suffered a very severe overload. But the reason for this was not immediately obvious. I first suspected that TS430 had broken down, but an in-situ check seemed to rule this out, at the same time ruling out the breakdown of any other components in the collector circuit. One possibility was that something was breaking down at the operating voltages, which were a lot higher than I could apply with the ohmmeter. So the easiest way to find out JUNE 1988 39 several more times, but only for about a second on each occasion. Pondering over all the symptoms I decided that the horizontal drive transistor, TS430, was the most likely suspect. I pulled it out and checked it as thoroughly as possible, but it gave no sign of any fault. Nevertheless, having gone this far, it was just as easy to fit a new one and remove one possible culprit. And that seemed to be it. I ran the set for several hours more, until the customer came back in the late afternoon, and it behaved perfectly during that time. There seems to be little doubt that TS430 was suffering from intermittent breakdown and, sooner or later, would have destroyed R440 once again. Follow up checks have confirmed that there has been no sign of any shutdowns, no matter how brief. SERVICEMAN'S LOG What about the tube? our ~~ W\1'\-1 11-(E: NEW.,.., IN W\TI-\ 11--\e:. OL-V seemed to be to replace R440 and see what happened. Which I did, and nothing happened - nothing untoward, that is. The set came good immediately and produced a very good picture, the only qualification being that the brightness control was obviously set a good deal higher than the average position for this set. As far as I was concerned this served only to confirm what I-had already discovered; the tube was well past its prime. It probably had a couple more years life in it, but that was pretty poor value for the price of a new tube. But my more immediate concern was to find an explanation for the failed R440. Resistors can fail spontaneously, but they don't cook themselves in this manner. Something else had failed, and would probably fail again. It was simply lying doggo for the moment. So I left the set running and busied myself tidying things up inside it. I fished out some screws to secure the swing-out boards, and salvaged a power supply cover 40 STLICON CHIP strip from a junked chassis. Then I tackled the leads associated with the tripler. Whoever had replaced the tripler had at least been a disciple of our friend Rufus; no attention had been paid to the original dress of these leads, something which can be quite important where the very high voltages are concerned. There were even a couple of bare connections which can develop corona discharge in unfavourable conditions. I re-dressed the leads and covered the bare connections with a coating of Silastic, cleaned away some dust and grime and, in general, made the set look more like a new one. With everything thus tidied up I turned the set on again and let it run on the bench while I went on with other jobs. I was still puzzling over the failure of R440. Happily, my tenacity was rewarded. The set suddenly shut down, but only for a second or so, then came good. I left it running and it shut down again - and again. In fact it did it So that was that, at least in the technical sense. But what about that bodgie picture tube? Should I tell the customer what I had found? It was a diplomatically dicy situation. Not surprisingly, many people don't like being told they have been ripped off; in their minds it implies that they have been less astute than they should have been. There is also the risk that a serviceman delivering such news may be suspected of simply trying to discredit the previous serviceman and enhance his own image. This risk is particularly high where the critisism is purely subjective or speculative, rather than based on hard fact. I was still pondering these points when the customer returned in the late afternoon. He was accompanied by his wife this time, which gave me further food for thought. Would I precipitate a domestic argument along the lines of, "I told you not to take the set to that bloke"? I bided my time, initially simply describing the fault I had found, and emphasising that they should contact me again in the event of any trouble. Both appeared to grasp the situation, and the points I was making, quite well. All of this was more or less routine, of course, but it did give me a chance sum up both parties. And having done so I finally took the bull · by the horns. I broached the subject by asking them to confirm that a new picture tube had been fitted recently and, when they did so, asked if they would mind telling me what this had cost. They were quite happy to discuss this and recalled that the replaceregular correspondent, J.L. of ment had cost them about $300; Tasmania. It is particularly inwhich is about the going price for teresting in that it relates to my supplying and fitting a re-built picstory in the February notes concerture tube - if it is the genuine artining a National TC-2004. In fact , it cle. At this point I broke the bad appears that this story provided the news and quickly followed up the clue which enabled J.L. to solve a statement by demonstrating how I completely different fault. This is knew this to be so. And I even went how he tells it. so far as to offer to back them if The story that follows relates to they felt inclined to take the matter the same chassis, but in a different to the Trade Practices Commission. model, and provides another sympI was quite genuine about this. I'm not in the habit of dabbing in tom to add to the villainies of that colleagues for what I might regard · particular capacitor. This set was a TC-1802 and came to me with the as doubtful business ethics, or complaint that there was no pictechnical incompetence, at a ture, only a line across the centre of relatively minor level, if only the screen. The owner was convincbecause it is virtually impossible to make such accusations stick. And, ed that the picture tube was shot in any case, such tactics usually (the pessimistic type froni the February notes!), and refused to reap their own reward. But something as blatant as this believe me when I tried to convince is another matter. It is hard enough him otherwise. I fired up the set and, sure for the service industry to maintain enough, there was the line across an honest image in the public eye often due to genuine misunderstan- the centre of the screen. But it dings - without characters like wasn't quite the classic frame colthis perpetrating genuine frauds of lapse symptom; the line was hiccupping slowly. At about two second inthis magnitude. The customers' response was tervals the picture would expand to the top of the screen and then colrather surprising. I am quite sure that they accepted my statement completely but, no, they didn't want ( to become involved in any such claims. More to the point, they didn't seem to be particularly shocked at my revelation and I gained the very strong impression that they had already arrived at a similar suspicion. So that was it. I didn't press the point and they seemed happy enough with the job I had done, didn't quibble over the bill, and gave every indication that they would be back next time they wanted service. Which is about as much as one can wish for. A vital clue At a more technical level, here is another contribution from my lapse again. I had never seen a fault like this, and was at a loss to know where to start looking. I suppose you have to get lucky eventually; Murphy has to take a holiday sometimes. I decided to start looking from the vertical output end, and to check the voltages first. This proved to be the right way to go and I had the answer in two minutes flat. This chassis uses a push-pull vertical output stage, TR407 and TR408, fed from ± 25V rails. I found the + 25V at the TR407 collector, but there was no - 25V at the TR408 collector. I checked back along the - 25V rail to find diode D406 (UF-2) shorted and R445 open. · R445 is a rn fusible resistor, apparently intended to protect the diode. Replacing both put the set back into working order - for a while. In fact, I had no sooner replaced the cabinet back when I noticed that the original pulsating line fault had returned. A minute later I had confirmed that the diode and resistor were shorted and open, respectively. This was quite a blow, because everything had worked normally for an hour or so before I replaced the cabinet back. All voltages had been correct, and waveforms almost exactly according to the manual. So what kind of fault could kill a 400V, 1A diode running at 25V and something less that lA? I spent the next hour minutely ex- :'(il"i. . oo.,I SPE:N\ n-\E:. NE:XT HOIJ'R. L.-OOKING FO'R. AN'-f-r\-\\NG TH~T IV\\Gt-\T K I L--l- 1'-\ C: 'Dl 01) E: ooo JUNE 1988 41 SERVICEMAN'S LOG ammmg the set, looking for anything that might kill the diode. In particular, I was looking for something that might generate high voltage spikes in the line output transformer. I found nothing. So it seemed that all I could do was get the set going again and hope that further observation might provide a clue. Unfortunately, I had used up my last UF-2 diode and had to cast around for a suitable substitute. I chose an OA636/600 on the grounds that it was a fast recovery 1A diode, with a 200V margin over the UF-2 . With the new diode and another 10 resistor in place the set came good and ran steadily for several days. I called the owner and suggested he pick it up. He couldn't make it straight away and it was more than a week before the set went home. And during all that time it ran perfectly. But it wasn't home for long. The owner was on the phone the same evening with the revolting news that it had failed again, in exactly the same way. I was back inside the chassis the next day searching vainly for something- anything- that could have killed those diodes. And one of the puzzling aspects was why it was only the negative rail that was giving trouble. Both rails used identical components and were supplied from opposite ends of the same ·transformer. I considered the possibility of a temporary short in the PNP output transistor, TR408. But if so, and if it had drawn enough current to take out R445, it should have at least distressed its rn emitter resistor, R434. But this latter was in pristine condition, with not the slightest bubble on its paintwork to suggest that it had ever been more than warm. While I was contemplating the problem the February edition of SILICON CHIP arrived and, as usual, I turned straight to the Serviceman's Log, where I found the story about the baulky TC-2004. There was little similarity between 42 SILICON CHIP +160V + C564I T +24V Simplified circuit of the National 2004 chassis power supply, showing how the 160V, + 25V and - 25V rails are derived from windings on the horizontal output transformer, T552. that story and mine, except that they both involved a form of vertical trouble. Common factor But there was one common factor; one part of the vertical oscillator stage is powered from the 160V rail, the one that caused all the trouble in the TC-2004. So, with renewed hope, I set TETIA CORNER Ran k Arena C2205 Picture varies with volume control setting. Picture becomes weak or disappears, fine tuning changes, chroma weak but noisy, and sound clicks and pops - all as the volume control is moved. Finally, set blows rude raspberry when switched off. Cure: C351 (1 0OµF 16V electroly t ic) open circuit. This capacitor is an emitter bypass on the sound output transistor. The symptoms occur because the wrong feedback information from the output emitter upsets the 1 9V rail via TR301 , the audio driver transistor. Symptom: about checking this rail. Series resistor R559 , inductor L556, and diode D553 were all perfect, but when I came to the l0µF electro, C564, I reckoned I had struck oil. The negative terminal exhibited a perfect dry joint; I could move the capacitor and see the pigtail wobbling about in a hollow in the solder What this could do to the 160V rail, particularly in regard to generating spikes, doesn't bear thinking about. And, of course, such spikes could appear in the vertical oscillator and drive stages and damage components in the output stage. I set about resoldering the pigtail, but it didn't want to be fixed. There seemed to be some corrosion on it. So I removed the capacitor and got another surprise. There was a fair bit of its inside outside, with the rubber plug pushed almost out of its seating. It also had a heavy encrustation of dried electrolyte and had only about half of its original capacitance. I fitted a new one. I had re-stocked with UF-2 diodes so a new one was fitted at D406, plus a new C424 lO00pF capacitor across it, and a new 10 resistor at. R445 . At switch-on the set came good immediately, although the height was a little excessive and the vertical centering slightly out. Both responded to the appropriate controls and the set ran for several days before being returned to its owner. And - fingers crossed - it has given no trouble since. And that's J.L.'s story, which makes a very useful addition to the February notes. That 160V rail certainly has a lot to answer for . J.L. goes on to comment about the loss of sound in the February story, which I was unable to follow up. He points out that the 12V rail, which supplies the sound IF and the brightness and contrast controls, is derived from the opposite end of the winding which provides the 160V rail, and that they share a common chassis connection via a plug and socket. And he suggests that a spurious resistance in this connection could allow faults in the 160V rail to appear on the 12V rail. Well, it's a thought J.L., and worth keeping in mind. ~ wpoD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS .. . WOOD FOR CHIPS ... WOOD FOR C CABLE SPECIALS SMC Terminated Coax Adiwtable from 10--60W Limited quantity only of high quality coax cables terminated at one end with a high quality SMC connector. Available in RG178 - 1.25m long $14.95 RG174 - 1.2m long $13.95 RG174 - 0.7m long $8.00 BulN•lnFllnl l lghN r Rainbow Cable 9 way multistrand 23x0.2 $2.00130cm or $5.50/metre ~ G Hook Up Wire Im 10c 15c 14c 23c 14c 23c 30c 30c /100m $8.00 $13.00 $12.00 $19.00 $12.00 $19.00 $27.00 $27.00 C) 1x0.5 7x0.079 7x0.1 19x0.1 ~ 30c 65c 30c 40c $28.00 $59.00 $28.00 $38.00 Wire Wrap Kynar 30AWG 20c $19.50 Cl: C) lJ.. § ~ ~ G Cl: C) lJ.. Cl PVC 1x0.5 (low voltage) 7x0.2 (low voltage) 16x0.2 (low voltage) 24x0.2 (low voltage) 16x0.2 (250V) 24x0.2 (250V) 30x0.25 (250V) 32x0.2 (250V) Teflo11 See E.A. April -"an eX1remely attractive approach .. ." It's a gas soldering iron ... it's a blow torch ... it's a hot knife ... it's a hot blow. And it comes in a neat carry kit complete with a bit wipe r. No cords or batteries yet it gives the equivalent of a 1Oto 60W iron . You can get up to 90 minutes average continuous use from a single fill. J\nd you refill it in seconds using a standard butane gas lighter refill. Tip temperatures as high as 400°C can be set. The kit includes one soldering t ip, a hot knife, blow torch and hot blow. The cap contains a flint lighter. The complete kit comes in a handy case (with stand for the iron) wh ich just about fits in your pocket. Porta-Sol Professional Is $81.00. Fluke Multi meters LH0091 CD True RMS to DC Converter ~ ~ Cl: C) ·IJ.. Cl C) ~ ~ G Cl: C) lJ.. Cl C) ~ ~ G Cl: C) lJ.. Cl C) ~ ~ ··:t: ll Cl: C) lJ.. Cl C) ~ A great investment for professional users. Geoff has the 20 series and 70 series. Check the prices!! This IC provides true rms conversion with 0.5% accuracy untrimmed. With external trim a reading accuracy of 0.05% is possible. Normally $68.50. Limited quantity at $39.95. HM50256 256k DRAM 150nS $9.10 each 64k DRAM .- NS Ceramic $5.50 LM337H TO-5 Adjustable Negative Regulator Output voltage adjustable from 1.2 to 4 7V. Handles up to 1.5A. Two resistors set the voltage. One capacitor needed for frequency compensation. Line regulation 0.01%N typical, Load 0.3% $4.00 each 0 F Y O Geoff has sold hundreds of 'em to servicemen and technicians. Complete and ready to use like the Professional but you only get the iron and b it $39.95. PORTASOL TIPS Expand the capability of your Portasol Iron with spare tips -available for . standard iron in 1mm, 2.4mm, 3.2mm , 4 .8mm and hot knife tip. Professional tips come in same sizes plus hot blow and blow torch . Tips are not interchangeable between irons, so specify Standard or Professional w hen ordering . Tips arc- "'.!I $12.95 each. SSkHz I ansforr miniature $1.50 3 HCHO s ~ ~ Not a very popular item at the normal price of $1 .50 each but if you have a use for them we'll let you have em for only 50cents each ii you 'll buy a packet of 25 for just $12.50. , ·'--";':~~;~'."azin9 .. ) .. OWIK -, - WIR ~ · STRIPP R" LH0094CD Multi-Function Converter This is a high accuracy multi-function converter for precision dividers , multipliers, squarers, square roots, companders, linearization and other mathematical functions. The multiplier power is set by the ratio oi two resistors. Accuracy is 0.05%. Limited quantity available at under half price. Only $70 each PORTASOL STANDARD SOLDERING IRON i ·-~ C IMPE Model $192 Model $205 Model $339 Model $365 Model $545 Model $625 73 75 77 23 25 27 Fluke 70 Serles • 3200 count display • 75 adds beeper · e 77 adds Touch Hold Fluke 23 • 10A range • Rugged, High energy safe e Touch Hold Fluke 25 & 27 e Touch Hold • 0.1 % accuracy • Min-Max on 27 • Relative mode on 27 UGN3020T Hall Effect Device in T0-92 can $1.90 each ELEC RONICS P Geoff has been looking around for a really good crimp tool for stripping cables and crimp ing those con nector lugs on. He's found it - the US made PARTEX Cwik Stripper I Strips, Crimps & Cuts. Rugged steel jaw automatically adjusts for wires from 26 to 10AWG. Easy snap action with no nicking, scraping or breaking of conductors! Handles most th in jacketed multi-conductor wire too one squeeze for the jacket, another for thll conductors Crimps solderless terminals from 10 to 22AWG and IT'S COLOUR-CODED (Red (1 .5mm) Blue (2.5mm) and Yellow (6.0mm)) so you get the right pocket for each termination . Preci sion machined, hardened steel cutters. Comfortable insulated handles. This one is for the professional who is doing a lot of crimping and well worth $34.95. LTD ~ a 0 .,., 229 Burns Bay Road , (Corner Beatrice St.) ING IN Nsw Lane Cove West, N .S.W. P.O . Box 671 , Lane Cove N .S.W. 2066 a Telephone: (02) 4271676, Fax: (02) 428 5198. () 8.30am to 5.00pm Monday to Friday, 8.30am to 12 noon Saturday . Mail Orders add $5.00 to cover postal charges . · Next day delivery in Sydney add $5.00. All prices INCLUDE sales tax. Tax exemption certificates accepted if line value exceeds $10.00. BANKCARD, MASTERCARD, VISA, CHEQUES OR CASH CHEERFULLY ACCEPTED )J l: ~ Get rid of those old-fashioned points Convert your car to breakerless ignition Fitting electronic ignition to your car is one thing but that is only doing it half right. Why not get the full benefit of electronic ignition by whipping out the points and fitting a Hall Effect pickup in your distributor? By LEO SIMPSON & JOHN CLARKE Let's be frank; the electronic ignition presented in last month's issue is good but it could be better. It is a vast improvement over the outdated Kettering system fitted to tens of thousands of cars but it does not give the full benefit. After all, no new cars fitted with electronic ignition as original equipment still have points, do they? No, the designers have gone all the way and designed the ignition system from the ground up to work without points. Even when mated to an electronic ignition as presented last month, points still hold the system back. As we noted in that article, you still need to adjust the points and re-do the timing every 20,000km or so, to compensate for wear on the rubbing block. If you don't do this, one day you'll attempt to start the car and then find that it won't, because the points are operating with virtually no gap at all. We know, we've seen it happen. Even without the wear problem on the rubbing block, points are far from perfect. Not only do they bounce on every closure but as the distributor shaft wears (due to the loading from the points rubbing By combining the Bosch rotor and vane assembly (left) with the Siemens Hall effect pickup (right), you can eliminate the points in your car. Such a breakerless system never requires adjustment or maintenance. 44 SILICON CHIP block), the distributor cam tends to wobble. Both these effects lead to less precise timing and so the engine does not run as smoothly as it otherwise would if the ignition timing was perfectly consistent. By contrast, with a Hall Effect switch in place of the distributor's points, the engine timing only has to be adjusted once and then it will stay correct, for the life of the vehicle. The engine will run noticeably smoother, particularly at idle. One thing to remember though is that even an all-electronic ignition requires some maintenance. You still have to check and replace spark plugs at regular intervals, to obtain best performance and fuel economy. Many owners ignore this fact and let their cars run for years without replacing the spark plugs, or even so much as cleaning and regapping. That says a great deal for the reliability of modern ignition systems but it is a foolish omission. With these points in mind (pun fully intended), we designed the printed board of our new electronic system so it could also be used with Hall Effect triggers. These are used in the electronic ignition systems of many new cars, chiefly those from Europe. Two types of Hall Effect trigger device are described here, one from Siemens and one from Sparkrite of the UK. With one or other of these devices, virtually all vehicles available in Australia can be fitted with breakerless ignition. A separate panel in this article gives a brief description of the Hall · Effect. We suggest you read it now. Hall Effect Devices In many ways, the Hall Effect device is the ideal replacement for I REGULATED_ SUPPLY +VSO--W>lr-_ .,....._ _ _ _ _ _ ___ OUTPUT .,. X HALL GENERATOR....._____, GND . .,. HALL EFFECT HALL EFFECT SWITCH Fig.1: although discovered in 1879 the Hall Effect did not become useful until it was produced in semiconductor form. Fig.2: this is the schematic of a typical digital Hall Effect device as used in the Siemens HKZ-101 trigger. What is the Hall Effect? Most people know that when a conductor is moved through a magentic field, a voltage is generated at its ends. This principle is used in alternators and generators to produce electricity. And when a conductor carrying a current is placed in a magnetic field, a force is applied to the conductor. This principle is used in all electric motors. But there is another possible interaction with magnetic fields and electric currents and this is known as the Hall Effect. It was discovered in 1879 by E.E. Hall at the Johns Hopkins Unviersity, in the USA. It happens in all electric conductors but is about ten million times more pronounced in semiconductors. Fig.1 demonstrates the principle of the Hall Effect. A thin plate of semiconductor material carries an electric current and is placed in a magnetic field which passes at right angles through the surface of the plate. A DC voltage then appears between the two edges of the semiconductor plate. Note that the semiconductor does not have to move. The voltage is produced with no moving parts. The voltage produced is called the points. It has no contacts, is unaffected by dirt or light (as optoelectronic sensors are), and its output is independent of the operating frequency (ie, engine revs). As well, it has a wide operating temperature range and high electrical noise immunity. The Sparkrite Hall Effect unit is the Hall voltage and is given by the equation: Vo = RH X I X B/t where B is the magnetic field strength, I is the current th_rough the semiconductor and t is its thickness. RH is the Hall constant of the semiconductor material. Thus, the Hall voltage is directly proportional to the strength of the magnetic field and to the current through the semiconductor. It is also inversely proportional to the thickness of the semiconductor so the thinner the material, the higher the Hall voltage generated. Note that the polarity of the Hall voltage is dependent on the direction of the magnetic field. Hall Effect devices are made from semiconductors such as indium arsenide and indium arsenide phosphide. These semiconductors are selected because of their high Hall constant, relatively . low temperature coefficient · (for the Hall effect), and a number of other parameters which go towards producing a good Hall Effect device. Typical Hall Effect devices are integrated into a three lead package which is depicted in Fig.2. This includes an internal constant Cl!rrent source, (le), an used in conjunction with a ring magnet assembly which fits over the distributor cam. The ring magnet has four or six poles, depending on the motor it is to be used with. Each time a pole comes close to the device, a voltage is generated which causes the electronic ignition circuit to produce a spark. amplifier for the voltage produced by the Hall generator, a Schmitt trigger (which is an amplifier designed to overload and clip the signal voltage), and an output transistor with open collector. Such Hall Effect devicf3s as depicted in Fig.2 have a "digital" output which is high or low: They . are typically specified for operation with the south pole of a magnet (hence the above reference to magnetic field direction). Not all Hall Effect devices have digital outputs though. Some are linear. They have an internal buffer amplifier but no Schmitt trigger. They produce an output voltage which is positive or negative with respect to a reference voltage, depending on whether they are in the vicinity of a north or south magnet pole. For further reading: (1 ). Sprague Integrated Circuits data manual. Available from VSI Electronics (Australia) Pty Ltd. Phone (02) 439 8622. (2). Discrete Electronic Components, by F. F. Mazda. Published 1981 by Cambridge University Press. ISBN 0 521 23470 0. The Sparkrite system is suitable for cars with the following distributors: Motocraft and Autolite 4 and 6 cylinders, Bosch 4 cylinder, Lucas 4 and 6 cylinders, AC Delco D202 and D204 4 cylinder, Nippondenso 4 cylinder and Hitachi Datsun 4 cylinder. It does not suit the majority of JUNE 1988 45 ,--------t-------11--------+---------------+12VVIA IGNITION SWITCH 3300 •---HTTO DISTRIBUTOR 100n 5W 2.2k 100n 8200 0.5W + RED .01 OPTIONAL CUT-OUT SWITCH H~m1 l:!ISl!!l.G·-~ SENSOR GRN GNO BLK 470k 02 BC337 22k 5 t-·lt·-__,,,Wlr-......::i IN ----<1-.--1 7 IC1 OUTl'MC3334P REF 3 0--+--\AM....-tl---"f--f GND 2 1 4x1N4761 (75V 1W) 8 0.1 56k . __ _ _ _ _ _ _ _....,__ ___._ __ _ _ _ _....,__ __.._ _ _ _ _..,__ _ _....__ _ CHASSIS .,. C B CASE eOc HIGH ENERGY IGNITION SYSTEM 0 1 0 B VIEWED FROM BELOW SIEMENS HALL SENSOR INPUT SC05·1·688 Fig.3: this is the complete circuit of our high energy system with the Siemens HKZ-101 Hall Effect sensor. It is only slightly different from the circuit published last month. Note the optional cut-out switch which can be an effective deterrent against thieves. Australian-made 4, 6 and 8cylinder vehicles but most of these are taken care of by the Siemens device. The Siemens HKZ-101 Hall Effect sensor incorporates a magnet and is used with a rotating soft iron vane which triggers it on and off. This vane assembly incorporates the distributor rotor button and is made by Bosch. It is is available for most Chrysler, Holden and Ford cars plus some other makes which have distributors made by Bosch, Delco, Lucas, Disilea and Nippondenso. The vane assembly is available on order from your local Repco auto electrical store. Operating temperature of the Siemens HKZ-101 is from - 30° to + 130° Celius. Before deciding to use the Siemens Hall Effect sensor, make sure that the rotating vane assembly for your particular vehicle is available. In fact, make sure you have it in your hot little hand before you start work on the rest of the system. If you don't, there might be tears of frustration later. Both the Sparkrite and Siemens sensors are available from Jaycar stores. If you use the Siemens sensor you will have to make a suitable 46 SILICON CHIP mounting bracket to mount it on the baseplate inside the distributor. The Sparkrite sensor is supplied with all the necessary mounting hardware required for installation, including a selection of ring magnets. Circuitry Different versions of our electronic ignition circuit are required, depending on whether the Siemens or Sparkrite Hall Effect devices are used. Fig.3 shows the circuit using the Siemens HKZ-101 device. The only difference between this circuit and that produced last month for the points version is in the omission OUTPUT vs 150!) HALL SWITCH . GNDI ...r1GNO SPARKRITE SENSOR The Sparkrite Hall sensor is a two-terminal device which is used in conjunction with a ring magnet fitted over the distributor cam lobes of D5 and C2 , and the substitution of an 8200 0.5W resistor for the 470 5W wirewound resistor. There is also an additional 1000 resistor to provide the positive supply to the sensor. The 8200 resistor provides a "pull up" for the open-collector output of the Hall Effect sensor. We have made provision for a cut-out switch in series with the sensor output. This could be hidden under the dash of the vehicle and would provide good anti-theft protection. If you don't want the switch, it can be left out and a link wired in its place. The output of the HKZ-101 sensor connects via a 1OkO resistor to the base of Q2. Q2 is switched on when the Hall Effect output is high (when the iron vane enters the gap of the sensor) and off when it is low (when the iron vane is not in the gap). From there on, the circuit is identical with that published last month. Whenever Q2 turns off, Qt also turns off and the ignition coil delivers a high voltage pulse to the spark plug. Sparkrite Hall sensor Whereas the Siemens device is a 3-terminal package, the Sparkrite device has only two terminals. Fig.4 shows how it is internally connected. The supply input to the Hall sensor and output are tied together with a 1500 resistor and the output is taken from the positive supply terminal. The Hall Effect unit inside the Sparkrite device is actually a Sprague UGS-3020T. It is rated for operation over a temperature range of - 40° to + 125° Celsius. When one of the poles of the ring magnet is close to the Sparkrite device, its output is low; ie, less than 5 volts. When the pole moves away, the output is high; ie, above 6 volts. The problem with the Sparkrite sensor is that its output does not go fully high (say, to 12V) and nor does it go fully low, to OV. This is because the current though the Sparkrite sensor varies from between about 5 and 10mA with the output high. When the output goes low, the Hall Effect device sinks additional current, up to 25 milliamps. This means that the Sparkrite sensor is trickier to connect and needs additional external circuitry to make it work. Fig.5 shows the circuit modifications needed to connect the Sparkrite sensor to the electronic ignition system. The mods consist of a constant current source to feed the sensor and a zener diode to detect the change in output voltage. The modified circuit works as follows. The constant current source involves transistor Q3, diodes D6 and D7, and the 180 and 1k0 resistors. The current through diodes D6 and D7 sets the voltage at the base of Q3 at 1.2V below the incoming 12V supply. Since Q3 is effectively a PNP emitter follower, this sets the voltage across the 180 resistor to 0.6 volts. The resulting current through the 180 resistor, and thus through Q3, is approximately 33 milliamps (0.6V 7 180). This current of 33 milliamps can feed to the OV rail via two paths. First, when one of the ring magnet's poles is near the Sparkrite sensor, it will be conducting and most of the current will be passing via the internal 1500 resistor. This will mean that the output voltage at the Vs ter- +12V B 1.2V EOC VIEWED FROM BELOW 08 6.8V 1W TO BASE OF 02 1k OPTIONAL CUT-OUT SWITCH 1k _ _ _ _ _ _ _ _ _ _,___.GNO SPARKRITE HALL SENSOR INPUT Fig.5. these are the modifications to the circuit when the Sparkrite Hall sensor is used instead of the Siemens device. Q3 is a constant current source while zener D8 is a voltage detector for the sensor. minal will be about 4 to 5 volts or thereabouts. When the output of the Sparkrite device goes high, it only draws some 5 to 10mA and the rest of the current from the collector of Q3 goes via zener diode DB and the series 3300 resistor. This current then goes into the base of Q2 and causes it to conduct. From there on, the circuit operation is identical with that described last month. Assembly Instructions for the assembly of the ignition circuit were fully described last month. Fig.6 shows the component overlay diagram and wiring layout if you are using the Siemens HKZ-101 device. If you intend to use the Sparkrite unit, follow Fig.7. Sparkrite sensor installation The kit for the Sparkrite Hall Effect sensor is supplied with all the necessary fittings required for installation plus detailed instructions on fitting. Fig.8 shows the general installation in exploded form. Firstly the points, damping rubbing block, flexible earth lead, the COIL - EARTH ® 01 B{!; Fig.6: follow this wiring diagram if you are using the Siemens HKZ-101 Hall sensor. If you don't want the cut-out switch, replace it with a wire link. Note that the + 12V line comes from the ignition switch. JUNE 1988 47 precision. Simply allow a small gap so there is no scraping. Reconnect the flexible earth lead between the distributor baseplate and distributor body. Static timing Fig.7: follow this diagram if your using the Sparkrite Hall sensor. Again, the cut-out switch can be replaced with a wire link. The cut-out switch could be installed at a later date, if you wish. capacitor and connecting screw for the points lead should all be removed from the distributor. Select the correct magnetic cam adaptor and adaptor plate for the trigger head, as listed in the instructions. Install the adaptor plate and trigger head on the baseplate of the distributor. The lead passes through the side entry hole of the distributor using one of the supplied grommets. Now the cam adaptor can be installed. For clockwise rotating distributors the dot on the cam adaptor should be upwards. For counter clockwise rotating distributors, the dot should face downward. This is an important part of installation since accuracy of timing is set by the magnets in the cam adaptor. These have been optimised for one direction of rotation. Check that the trigger head is centred with respect to the cam adaptor. Some of the spacers provided may be required to achieve this. The specified gap between the cam adaptor and trigger head is 0.4mm, however due to irregularities of the adaptor this adjustment cannot be made with any A static timing adjustment is necessary before connecting the trigger head lead to the electronic ignition. To do this connect a 4700 resistor between the sensor output lead and the + 12V terminal of the battery. Measure the voltage between ground and the output of the sensor using your multimeter. Now rotate the engine by hand (it might sound silly but you know what we mean) until the ignition timing marks are correctly aligned. The distributor should now be rotated until the voltage jumps from about 4.5V to 10.5V. This is the firing point for the sensor. ~ROWRARM A ee MAGNETIC ROTOR CAM ADAPTOR TRIGGER HEAD SPACER~ ~ ~ AOAPWR PCA" ADAPTOR PLATE BASEPLA,T~_.E~~~ When you purchase the Sparkrite sensor you will be supplied with an array of metal brackets and a selection of ring magnets to suit your car's distributor. The ring magent fits over the distributor cam. 48 SILICON CHIP Fig.8: this diagram from Sparkrite literature shows how the sensor is installed in a typical distributor. The original rotor button is retained. PARTS LIST 8-11.Smm l--0.1-1.Bmm HALL OUTPUT VOLTA3E t _ •ff _.__...., I TRIGGERING POINT FOR SIEMENS HALL SENSOR Fig.9: this diagram shows the critical dimensions for setting up the Siemens HKZ-101 sensor in a distributor (see text). Recheck the timing again by rotating the engine two full turns (to get cylinder No.1 back to the firing point) and readjust the distributor if necessary. The Hall sensor lead can now be connected to the electronic ignition. The ignition timing should now be set to the manufacturer's specifications using a timing light. Version No.1 (Siemens) 1 0.01 µF metallised polyester 1 PCB, code SC-5-1-588, 102 x 59mm 1 diecast box, 11 0 x 30 x 63mm 1 Bosch rotating vane assembly (see text) 4 6mm standoffs 3 solder lugs 1 grommet 1 T0-3 mica washer and insulating bushes 1 T0-3 transistor cover Resistors (0.25W, 5%) Semiconductors 1 Siemens HKZ-101 Hall Effect sensor 1 MJ10012 NPN power Darlington (Motorola) 1 BC337 NPN transistor 4 1N4761 75V 1 W zener diodes 1 MC3334P ignition IC (Motorola) Capacitors 2 O. 1µF 1OOV metallised polyester 1 x 4 70kD, 1 x 56kD , 1 x 22kD, 1 x 1 OkD, 1 x 2.2kD , 1 x 8200 0 .5W, 1 x 3300, 1 x 1 oon, 1 x 1000 5W Miscellaneous Automotive wire, screws, nuts, shakeproof washers, solder, heatsink compound, etc. Version No 2 (Sparkrite) Delete 1 1 1 1 56kD 1 OkD 8200 1 oon resistor resistor 0.5W resistor resistor Add 1 Sparkrite contactless trigger pack 2 1N4004 1 A diodes 1 6 .8V 1W zener diode 1 BC557 PNP transistor 2 1 kn 0.25W resistors 1 3300 0.25W resistor 1 180 0 .25W resistor Siemens Hall Effect sensor installation Fig.9 shows how the Siemens Hall sensor should be installed to provide reliable triggering. The vane needs to penetrate the sensor by between 8 and 11.5mm. The triggering point is between 0.1 and 1.8mm from the centre line of the unit. To install the sensor, remove the distributor from the vehicle. To do this, rotate the engine until cylinder number one is at the firing point (ie, align the rotor button with the timing mark on the distributor). With the distributor out of the vehicle, find the position where the points just open for the number one cylinder using a multimeter set to read "Ohms". Mark the position on the distributor body where the centre of the rotor is now positioned. This is the point where the Hall effect sensor's output should go high. The Sparkrite sensor is instaJled close to the ring magnet, in the same position as the points. After initial timing, no further adjustments are required. Now remove the rotor, points and capacitor plus ancillary components such as a rubbing block if fitted. The Hall sensor should be mounted near where the points were located so that there is sufficient lead to exit from the distributor. The exact location for the Hall sensor is determined as follows: Fit the vane assembly to the JUNE 1988 49 The Siemens Hall sensor is rivetted to an adapter plate inside the distributor. Note that the original rubbing block has been retained to minimise camshaft wobble. distributor and align the rotor with the firing point previously marked. The Hall Effect sensor should now be positioned so that the leading edge of one of the metal vanes is about half way through the slot (ie, you will have to determine the direction of distributor rotation). Mark out the position of the sensor, taking care to ensure that the vane will pass through the gap without fouling. A suitable mounting plate can now be made to fit the Hall sensor to the distributor advance plate. The mounting plate must also posi- This is the same distributor but with the Bosch rotor and vane assembly installed. Clean and simple isn't it? Oil, dirt and heat are no problem with this system. tion the sensor at the correct height, so that the vane penetrates the Hall sensor by between 8 and 11.5mm. Note that Fig.9 shows the arrangement for a counter-clockwise rotating distributor. Clockwiserotating distributors are timed as the vane enters the Hall sensor from the other side. The Hall Effect sensor is rivetted to the adaptor plate through 3.5mm holes which are countersunk under the plate. The adaptor plate can then be secured to the distributor advance plate using machine This is the ignition module as wired for the Siemens sensor. Sharp eyed readers will note that a short wire link is missing. We fixed it after the photo was taken. Note the loop in one lead of each diode, included as stress relief. 50 SILICON CHIP screws, nuts and washers. Try to take advantage of any existing holes. The leads from the Hall Effect sensor should be passed through the existing points lead grommet. Check that the vanes pass through the gap in the sensor without fouling and that the leads are dressed to allow full movement of the distributor vacuum advance plate. Note that some distributors use a separate rubbing block, in addition to the points. This should be left in place so that any mechanical slack in the shaft bearings will be taken up. Reinstall the distributor in the engine, taking care to ensure that the rotor points towards the distributor timing mark. Check that the timing marks on the engine are correctly aligned, then check that the leading edge of one of the vanes is near the centre line of the sensor. Rotate the distributor slightly if necessary to get the correct static timing position. Connect the leads from the Hall Effect sensor to the electronic ignition via a suitable automotive electrical connector. A 3-pin connector will be required and these are available from kit suppliers and automotive accessory shops. Finally, the engine should be started and the timing adjusted to specification using a timing light.~ BOOKSHELF Hardcover ARRL Handbook The ARRL Handbook for the Radio Amateur. 65th edition published October 1987 by the American Radio Relay League, Newington, Connecticut. Hard covers, 284 x 216mm, 1192 pages. ISBN O 87259 065 8. Price $49.95 (from DSE stores). Many readers will be familiar with the ARRL handbook which has become a standard reference for amateurs and electronics enthusiasts alike. Each year it is updated gradually with material which has previously been published in the ARRL journal QST. This edition is very similar in format to previous years but this is the first year it has been offered as a hardcover book. Many people will welcome this change as such a large publication tends to fall apart with constant use, in the soft cover 1'HE 1988 form. In the hardcover form, it is an even more impressive publication. There are no less than 40 chapters which are grouped under the headings Introduction, Radio Principles, Modulation Methods, Transmission, Construction and Maintenance, and On the Air. If you are looking for a standard reference text on basic electronics, with a particular leaning to radio communications, it is hard to go past this book. It has a good content of build-it-yourself projects for the radio amateur, including test equipment and antennas for the amateur bands. For those familiar with the previous edition, new construction projects are the emphasis of this new edition. For those interested in CW mode (ie, Morse code) there is a deluxe memory keyer which runs from batteries. There are also two receiver projects and a computer controlled receiving converter. Other new projects include a linear QSK transverter for 160 metres, a low-powered balanced Transmatch and a DTMF decoder. If you don't have a recent edition, you should certainly have a look at the latest ARRL Handbook. Our review copy came from Dick Smith Electronics. It is available from all DSE stores. Integrated Circuit Substitution Handbook Towers' International Op Amp Linear IC Selector by T. D. Towers and N. S. Towers. Published 1982 by Manish Jain for B. P. B. Publications, 376 Old Lajpat Rai Market, Delhi. India. Soft covers, 192 pages, 183 x 247mm. Over 4000 op amps and similar devices are listed in this comprehensive selector guide. It not only lists op amps but devices such as comparators, transconductance amplifiers, differential output amplifiers and current amplifiers. The devices covered are from manufacturers in the USA, UK, Europe and Japan. The book is not a substitution guide with type numbers from one manufacturer compared with another, but a detailed listing of specifications and pin-outs for each device. The manufacturer is listed as well as European and USA equivalents. The book begins with an in- troduction to the op amp, and discusses symbols, specifications and pin-out assignments. continued on page 85 JUNE 1988 51 ~:: ■!!!■•1 : 1111::=111.1~:: : 1,111,1:111:\.\;. \. \..:•:..:; .';.::•.:;.·:.•·:.:.•:. :.]:!;:111:\:::■~.:;.:·!: .·: .: .'~:.~' :. : : :i: ; ····· · ···············=•:❖.•:•.•.•. mazing Offer - Top Selling nal Semiconductor Data B ½ Price NormallJ This Month $17 .50 13.50 High Speed CMOS 12.95 National Logic 39.50 MOS Memory 12.95 Hybrid Product 12.95 Interface Date Data Aquisition B 1020 B 1025 B 1045 meter $8.75 6.75 6.50 19.75 6.50 6.50 ::::::;:::::::::::::::::;::::::::::::::•:::;:•:;: Famous lnphone Brand Cordless Phones $125 Shop soiled and Demo Stock Cordless Telephones an Incredible $125 - All guaranteed in perfect working order - and even better any marks or scratches are quite minor (barely noticeable in most cases). Save $74 On This Great Portable Phone Mini Alarm 15V 100mA AC/AC Adaptor Fantastic for Door, Window or Cupboard - this great little alarm simply fixes to one surface ( usually fixed surface) with the reed switch magnet screwed to the moving door window sash etc. Arm Iha system by simply .switching on - battery drain is minisule! Operates from 9V Battery (not supplied) 1/ 2 Price Normally Normally Now H H H H H H H 0365 0367 0370 0372 0375 0377 0380 Rack Frame 6 unit (3 70MM) Panel Set for H 0365 Rack Frame 18 unit (907MM) Panel Set for H 0370 Rack Frame 30 unit (1450MM) Panel Set for H 0375 Rack Frame 38 unit (1804~M) - -~ $ 99 .50 s 85 .00 49.00 129.50 89.00 169.95 129.00 199.95 39.00 99.00 79.00 149.00 99.00 175.0C 1-1 H H H H H H 0382 0385 0386 0390 0391 0395 0396 Now Panel Set for H 0380 $149.00 $119 .00 Rack screw M6 PK1 2 Natural 2.95 2 .00 Rack screw M6 PK100 Natural 19.95 17.00 Rack screw M6 PK12 Black 2.95 2.00 Rack screw M6 PK100 Black 19.95 17.00 Rack captive nuts M6 PK12 3.95 3.00 Rack captive nut M6 PK100 28.50 25.00 . . . . .i.i.• :::: ;; ::: .•.•..·.-_._._.: :'.:'.:=:'.:=:=:;?L - . -- ·---·· · ·--·- ······ ··· ·· ....... ...... .... . .-.·.•.·······•:::::::•::::::::::i: IIICIIIBBI IIJ.11:;:::8'--I\ :n11m11.:1:1.a:::::::1111:::111::::a1:::I~::::::::;~· ~i:::i:Vi:i~i f~ $:;ji':: This Month p Quali D Series Connectors! Only $119 Fantastic Value D Serles Computer Connectors. Gold Plate Profe11ional Serles Micron Electronic Tem erature Controlled Temperature lectable olderlng Statlo ·s•"• . Exhilarating Sound Performance Brllllant Dlgltal Headphones lncredlbly Comfortable • Utilizes newly developed flat disk vibrator copper clad aluminium wire voice coil and somarium cobalt Magnet. The resultant reproduction is outstanding• lmpedance45Ohms • Maximum input 400 mW• Frequency Response 20Hz to 20KHz. Ji The MICRON T 2440 soldering station offers the ultimate in contro11ea / temperature hand soldering 320 deg.C 350 deg. C 380 deg.C, 410 deg. C. (608 deg. F. 662 deg.F, 716 deg.F, 770 deg. Fand824 deg.F) Fixed temperatures are selectable by rotating the detained rotary switch freely without changing heater or tip. C 9010 - ~~~r,;r;f;~~;g{fE-Wftgf:~\r;:~::~ Temperature Readout via lead bargraph instantly visable. Patented HHllng Element. Heat Capacity. Full 48 watts of het energy available for heavy duty work. Zero Voltage Switching The ,~j~~~1;~~~~~~;$1f~ll~£~~ $ 19.50 High Quality UHF 14 Element YAGI Le11 Than 1/2 Price! These high grade Yagi Antennas are from DX Antenna Co of Japan and originally sold for over $70! We bought up an entire import shipment at distress stock rates & hence the fantastic savings to you . D825 P 3200 P 3210 P 3220 P 3230 P 3240 P 3250 P 3290 Features: • Non-Microphone Measurement System • LCD Readout • Blood Pressure Monito • Pulse Rate Monitor · 110 Bi Male 25 Pin Fmale 25 Pin Male PCB RVL Fmale PCB RVL Male PCB mnt. Fmale PCB mnt. Backshell cover ___ 2.47• f 2.74• . 3.50 3.90 3.00 3.95 1.10• Carry Case Ne"' s12.so tAode\ \! 4.95 5.50 4.95 6.90 4.95 6.25 2.20 .. DON'T PAY : Mon,1oring the card,ovascuiar system of every me!?2~~ fa! ! , ~n•~~ \ ~~,~~~;:~::,0."ncJ~~~Ym~~1r:~~~:e~~;; ~•~~~•,:,:~~~I ~~~~!~eg~a~~~~:e ~h~~~:j'° \Jjt: f:i{fj 1 · · · · · - · · -·-:__ ·_11 _ _. :.:.:.:.:.:.:Xr'.2'.........................;.:,:•:•=•~ ::::::::.....•.'.:\f~]\: =•=•~ ••:·:·:·::::s:=:•••:••m•:: ••••::::·: •· · · ·•·❖•❖••··············...·· _,_N .. ,_____ _ _: _i_i__1_·_::_·1_1_;_~ _ -- - . . 1• _:_ 1 _: : :_: : - A (A Dollar Or So Morel) There are some quite valid reasons of course. Such as fully punched chassis and hardware. Beautifully screened faceplates and panels. Prototypes built, tested and proven in our lab. Easy ~~~:l~~~:s~ig~1~n!v!~dn~!J rielpfull advice is just :;II I I Simple single PC board construction. }}K2S1os99.oo High. input impedance. 4 different input sensitivities suits virtually all requirements and delivers 5 watts of power. Complete with own in built speaker. (EA May'88) Checks R.F. Circuits Brilliant Performance Stereo Pre Amp 1 2565 I s12 .oo (SIiicon Chip June/July'88) Out-Performs Commercial Units Costing $600 Plus Po er Tran ea l ne ::,1uaI0 ,uu ::itereo l;ontrol Unit is companion to the studio 200 stereo power amplifier (or other power amps) . It features slim 1u rackmount profile, treble, bass, balance. input selector, tape monitor switch, stereo/ mono switch and volume control. Inputs include phono, tuner, CD, VCR and tape loop. tor (EA May'88) Gain Matched, Power Transistors for Ampllfler Output Stages K5015 s229 s Super simple circuit, enables evaluation of current gain and Vbe of power transistors & Darlingtons. K 2532 s24 .95 ~~a~g So y arch'88) This incredible "Voice" generator will store 127 messages or statements each an amazing 128 bytes long. (A sentence such as "You've left the lights on" uses only 31 bytes) Simply programmed with an eprom programmer and PC or you can purchase the pre programmed 56 message Eprom Cat.No. K 9502 for just $20.00. Refer to ETI March '88 Th;, ~;:d%c.:;;A;;l:;:;~fa:,;;' Yo, ;399 f1:;;;:;;;,;;;;;;;;.1, 7 (ETI Dec'8 ) Charge Your Batteries Free From The Sun Features: • In-Built speaker protection• Toroidal Transformer (low hum)• Black Satin Finish• Low leakage power supply capacitors 2 ~~~t~~\~etr~:sc:oa~~=d~fo ~ :'o::~~ell ;;~~f;::11:n::u;9;it~u~s~~:e;~~~s;.into 8 Ohms Freq. Res.(al 1W) Per Channel Power Ampllfler "·; :~:";i3~~;"' ~!tif~t!l~it~=!:f1~i~J~~ii:¥fi~f:t::: ·- ::=:::::=::::::::::::.:-:.·-:-:•·•:•.· ·.· •• · · · • · · •· • · . ... . - ...• ~. . . . .•f!'t.'<s.ll•'?" . ·.• .• ·• ·•,·• ·• ·• ·.....• ·• ·•·:i •P.t:lW'!.•.•·•·•.•·•···••.•·•.·.··• · •.•.• .• ·l• : ■1:1l.•. . .'.•.•.•.lflR . .• .·• ><-'.IBB lmFIS, .... ~ )Ui;i# .... 1 ~:en:~:tic for installing at home, behind your car dash or for interfacing with alarm systems, J• ;95~;1 ~~r~;~~lsi;~rg~ e:~p~l~q~rts ;oc,,,.. ,,,,. ···•······· )(: )(: ::::::::::::::::;:::::-:-:-·•··-···· •11a: . :III IDI ::): . 1\JfJJ1rtf mrt1?t=::=: ••••··••••····••···•·•···••••· :1::::: : .·.·-:.·-·❖:•:•:•:•:• (See ETI Aprll'84) Uses Vibration Sensors To Guard Against Tampering Ii Vandall1m FEATURES: Auto Arming with Exit and Entry delays • Dash Mount status indicator• Remote Protection of bolt-on accessories • Inc . circuitry to monitor any failure of dash warning lights • Protects youf expensive stereo from unauthorized removal. K 4341 s22.50 K4342 s7.5o nc (See ETI Aprll'B0) One of the most useful pieces of equipment in an Electronic work-shop is a simple Amplifier Module to test circuits. • 250 Mi Iii watts output into4 Ohms• Runs off single 9V supply• Can give 0.5 watts when run on 12V plus heatsink. K 2105 i:l \\llllli! li JI\:'] =Qt)\ l l i I\ :'/ ]It=?/,' 2V D f )ii(' •.,!, - ''Ul ., .1', ~ ·2 =:·•··•• .: ·;',.1, . ~ , ...... /i f 0 K437o s129.oo Suits any G.D. player - suitable for for all headphones - low or high impedance, very low noise and distortion, does not hinder the CD performance. Simple plug in connection. Requires external 12V AC plug pack. !~~!~:~ ; ~~;:~:t~i~o~~~t~~0e6~tput is 13.6V at 5 amps. . Feature,: • Internal & External Sirens • Dash lamp flasher • Battery back up • Delayed & Non delayed inputs• Ignition killer• Easy to build and install. (See ETI Jan'81) Studio Specifications Here is general purpose power Amplifier module suitable for Hi Fi, guitar and PA applications employing sturdy reliable MOSFET's in the output. Power Output 150W RMS into 4 Ohms 100W RMS into 8 Ohms (At onset of clipping) Frequency Re1ponH 20Hz to 20KHz +0-0.5db 10Hz to 60KHz +0-3db Measured<at> 1W & 100W levels Input Sen1ltlvlty 1 Volt RMS for full output NolH 114db below full output (Slllcon Chip Aprll'88) Adds Headphone Faclllty To Your C.D. Player 2 :a?fa~f~i.e;~~se etc. to 3255 Ii: \ll \ \1 :---K-- - - - (Slllcon Chip Feb'88) Save Over $100 On An Equivalent Commercial System Moafet Power p Module 150 Watt s22.70 (Slllcon Chip Dec'87) ::::<M;?'='=' ='=' Po ecto r Alarm V s59 .50 K 4340 A R lnc.Mic Cable & Connectors 59 00 5 ----·--------------- K 5350 s25 .50 Manufacturers, Contractors and Bulk Users ~~2:.~.~C) ~l~l~W.::~::;:~~~:: : ~: .~~:: ~: Perth Metro & After Hours (09) 328 1599 ALL MAl°L ORDERS P.O. Box 8350 Perth Mail Exchange W.A.6000 Allow approx 7 days from day you post order to when you receive goods $7.00 OVERNIGHT JETSERVICE - We process your order the day received and despatch via . Overnight Jelffrvlce Courter for delivery next day Country areas please allow additional 24-48 hours. Weight limit 3Kgs (3Kgs covers 95% of Orders). Chances are there is an Altron~c~T:e::~~igR!~~~~YE::_ check this list or phone us for a~1~!vl d~~~r~~~eliv:~~.orders of 10Kgs or more must travel Express INSURANCE - As with virtually every other Australian supplier, we send goods at consignees risk . Should you require comprehensive insurance cover against loss or damage please add 1% to order value (minimum charge $1). When phone ordering please request " Insurance". details of the nearest dealer. PI•••• Note: Resellers have to pay the cost of freight and insurance and therefore the prices charged by individual Dealers may vary slightly from this Catalogue - in many cases, however, Dealer prices will still represent a ~~~~-~~~: I :;:~;~~~f~~;;: ; '.;i; ~~~;:;·~:.~!~;; ::;;~~-~~~.~~;~;:;~~;:~~~:~~:~;~;~~~ 1.•,•.•,•.•.1.•,•.n ., .•.•.•.•,•.•,•.•,•.•,•.•,•.•,1.• - ···?'jf:/''=' )z j\{: II /{{ I 5;~JuR:i~ ~:~a;~~o;A 35~!~~.t~~~~K::~~IE:lec~ro~c/80:~::• !:;;~!onics 5483:ICE 8PRINGi :1l scC1T-ilec:i~n~~=c;:0~:3 c:~~:~~n!le:i:;~:: CHELTENHAM Talking Electronics 5842386 CROYDEN Truscott Electronics ■ 7233860 PRESTON Preston Electronics 4840191 COUNTRY BENDIGO KC Johnson ■ 411411 MORWELL Morwell Electronics 346133 NS AND CITY Delsound P/ L 8396155 SUBURBAN FORTITUDE VALLEY Economic Electronics 2523762 WOODRIDGE David Hall Electronics 8082777 COUNTRY CAIRN S Electronic World ■ 518555 BUNDABERG Bob Elkins Electronics 721785 GLADSTONE Supertronics 724321 MACKAY Philtronics ■ 578855 ROCKHAMPTONAccesa Electronics (East St.) 221058 Electron World 278988 TOOWOOMBA Hunts Electronics ■ 329677 TOWNSVtLLE Solex ■ 722015 SA CITY Electronic Comp & Equip. 2125999 Force Electronic ■ 2125505 SUBURBAN BRIGHTON Force Electronics ■ 2963531 CHRISTIE& BEACH Force Electronics ■ 3823366 ENFIELD Force Electronics ■ 3496340 FINDON Force Electronics ■ 3471188 COUNTRY MT.GAMBIER South East Electronics 250034 WHYALLA Eyre Electronics ■ 454764 HOBART George Harvey ■ 342233 LAUNCESTON George Harvey ■ 316533 Nichols Radio TV 316171 CITY David Reid Electronics ■ 2671385 CARINGHAH Hicom Unitronics 5247878 LEWISHAM PrePak Electronics 5699770 SMITHFIELD Chantronics 6097218 COUNTRY COFFS HARBOUR Coifs Habour Electronics 525684 GOSFORD Tomorrows Electronics ■ 247246 NELSON BAY Nelson Bay Electronics 813685 NEWCASTLE Novocastrian Elect.Supplies ■ 62135S NOWRA Ewing Electronics■ 218412 RAYMOND TERRACE Alback Electronics 873419 WOLLONGONG Newtek Electronics ■ 271620 Blue Ribbon DHlers are highlighted with a ■. These Dealers generally carry a comprehensive range of Altronic products and kits or will order any required item for you. 1 1 !1 1111 t•I Low-cost circuit controls outside lights AUTOMATIC LIGHT Wont to switch on outside lights automatically when someone approaches your house at night? This automatic light controller will do the job. By BRANCO JUSTIC Many householders are now installing automatic light controllers to monitor driveways, pathways and other approaches to their homes. These units typically employ a passive infrared movement detector to detect the presence of body heat and then automatically switch on outside lights, usually for a preset time. Such systems enhance the safety and security of your home as well as adding convenience. You can forget about fumbling for keys in the dark or leaving outside lights on for guests. Leaving lights on is often a dead giveaway that a house is unoccupied. With this type of system, there is no need to leave lights on; they will turn on automatically when you or anyone else approaches. And the reaction of any intruder when lights suddenly switch on outside a home that appeared to be empty is obvious. The automatic light controller described here can be built for around half the cost of commercial units. It marries the Passive Infrared Movement Detector described in the December 1987 issue of SILICON CHIP with a simple control circuit. For the prototype, both circuits were housed in a sturdy electrical junction box fitted with a couple of floodlights, but this could be varied to suit your particular application. In fact, many readers will probably elect to delete the floodlights and simply use the controller to switch existing outside lights. An optional override switch allows the lights to be switched on manually if required. Commercial sensors Another option is to use the control board with a commercial PIR detector or, depending on circumstances, with other types of movement detectors. For example, you could combine the control board with the ultrasonic movement detector described last month to automatically switch on hallway lights or to light a stairway. For outdoor use, the infrared sensor is the one to go for. This is because it triggers only when it detects body heat and cannot be false triggered by other moving objects (eg, swaying tree branches). Other types of movement detectors would be virtually useless for outdoor use. Naturally, the range of the unit will depend on the type of detector used. The passive infrared sensor used here will give a useful range of about 12 metres when fitted with the wide-angle lens. To make it as versatile as possible, the control board has two inputs, one for normally-open relay contacts and the other for normallyclosed contacts. This means that it should work with most types of sensors. A light dependent resistor (LDR) on the control board monitors the ambient light level and disables the circuit during daylight hours. Perimeter monitoring The Automatic Light Controller uses a passive infrared sensor and is built into a sturdy plastic case fitted out with a couple of floodlights. The lights switch on for 40 seconds whenever the infrared sensor detects body heat. 56 SILICON CHIP Provision has been made on the control board for connecting several units together in parallel, for perimeter monitoring. When this is done, all the controllers will be activated if there is movement in any one of the covered areas. The lights then switch off only after the CONTROLLER +1 4V PASSIVE INFRARED MOVEMENT DETECTOR MODULE t ,-- 0 11 47k 47k ® _fL INPUT 1 u 240V LAMP(S) D1 0 1N4148 INPUT 2 0.1 MANUAL OVERRIDE Sl 0. 1 LINK 0.1 250 VAC 47k 1M GND .,. X GND D6 TO OTHER CONTRDLLER/S 08 B FROM OTHER CDNTRDLLER/S t DELETE IF N/C CONTACTS NOT USED AT INPUT 1 AUTOMATIC LIGHT CONTROLLER SCD3·1-0688 .,. Fig.I: the control circuit can accept either high or low logic inputs from an external movement detector. When movement is detected, pins 3 and 4 of IC2 switch high, the MOC3021 triggers, and Triac Qt turns on and lights the lamps. timer in the last activated control board has expired. The units are interconnected using inexpensive low-current alarm cable but note that each unit requires its own mains power connection. Of course, running two or mor e units in parallel is entirely optional and can be ignored if you require only a single automatic light controller. How it works Refer now to Fig.1 which shows the circuit diagram of the control board. It's built around a 4093 quad Schmitt NAND gate, a MOC3021 optically coupled Triac driver, and an SC151 Triac to switch the lamp(s). PARTS LIST 1 PIR movement detector (as described in the December 1987 issue) 1 Clipsal No.265/4 Series H.D. IP56 plastic case 1 printed circuit board, code OE12 1 1 mains transformer with 11 VAC secondary 1 MPY 76C569 LOR 1 or more floodlights (see text) Semiconductors 1 SC151 D Triac 1 MOC3021 Triac driver 1 40 93 quad NANO Schmitt trigger 4 1 N4004 silicon rectifier diodes 6 1 N41 48 silicon signal diodes Capacitors 1 4 70µ.F 25VW electrolytic 3 0 . 1µ.F monolithic 1 0 .1µ.F 250VAC metallised polycarbonate Resistors (0 .25W, 5%) 1 x 1 MO , 1 x 1 OOkO, 3 x 4 7k0, 2 x 2 .2k0, 2 x 4700, 1 x 1 OOkO miniature trimpot Miscellaneous Screws, nuts , solder, hookup wire, cable clamps, silicone sealant. JUNE 1988 57 In this version, the passive infrared movement detector was mounted on the lid of the case (right) while the control board is mounted on the base. Note the insulating material covering the mains transformer terminals. Keep mains wiring neat and tidy. Power for the circuit is derived from a mains step-down transformer. Its 10V AC output feeds a bridge rectifier and 470µF 25VW electrolytic capacitor to produce a smoothed DC voltage of about 14V. This DC voltage powers the control board and the external movement detector feither PIR or ultrasonic). The control logic has two inputs, designated Input 1 and Input 2 on the circuit diagram. Input 1 is used with external sensors employing normally-closed relay (NC) contacts, while Input 2 is used with sensors employing normally-open (NO) contacts. Let's consider Input 1 first. Normally, this input is held low by the NC relay contacts and thus pin 12 of IC2c will also be low. This means that pin 11 of IC2c will be high, pins 3 and 4 of IC2a and IC2b will be low and the MOC3021 (ICl) will be off. So Ql and the external lamp(s) will also be off. When the relay contacts open (ie, when movement is detected), Input 1 is pulled high via a 47k0 resistor and the resultant pulse applied via D9 and a 100kn resistor to pin 12 of IC2c. Assume for the moment that pin 13 of IC2c is also high. Pin 11 of Where to buy the parts Parts for this project are available from Oatley Electronics, 5 Lansdowne Pde (PO Box 89), Oatley, NSW 2223. Telephone (02) 579 4985. Prices are as follows (mail orders add $3.50 p&p): PCB plus on-board parts for PIR Movement Detector as per December 1987 SILICON CHIP (lenses supplied) ................ $54.95 PCB plus on-board parts for Control Board (includes transformer, terminal strip and the LOR) .... ... ...... ........... .... .. ... $24 .95 Note: copyright for the PCB artwork associated with this project is retained by Oatley Electronics. 58 SILICON CHIP IC2c will now go low and the outputs of paralleled inverter stages IC2a and IC2b will switch high. These drive the LED inside the MOC3021 which in turn triggers the internal diac. This then turns on Triac Ql via a lkO resistor to light the lamp( s ). Input 2 works in similiar fashion except that it is normally held high and is pulled low when the external sensor is triggered (ie, a set of relay contacts close, or a transistor turns on). This low signal is then inverted · by IC2a and the resulting high applied to pin 12 of IC2 via DlO and R7. After that, the sequence of events is exactly as set out above for Input 1. Note that D9 and DlO together form a simple diode OR gate (ie, input 1 or input 2 can deliver a. high signal to pin 12 of IC2c). The 10okn resistor and associated O. lµF capacitor on pin 12 of IC2c form a low pass filter. This stops false triggering due to noise and RF pickup when long interconnecting cables are used between the sensor and the control board. Daylight inhibit Now let's look more closely at the function of IC2c. Pin 13 of IC2c is connected to a voltage divider consisting of VR1, a 2.2k0 resistor, a 4700 resistor, and the light dependent resistor LDR1. LDR1 is there to stop the circuit from working during daylight hours. This happens in the following way. For IC2c to pass signals through from its pin 12 input to its output, pin 13 must be high (ie, close to Vee). For this to happen, the combined resistance of the 4700 resistor and LDR1 must be much greater than the combined resistance of VR1 and the 2.2kQ resistor. This means that LDR1 must be in darkness (so that its resistance will be very high). During daylight, when light illuminates LDR1, its resistance will be low and so pin 13 will be low and no signals will pass through IC2c. Trimpot VR1 sets the light level at which the circuit will trigger. When the lights turn on, the LDR circuit is disabled by the O. lµF capacitor connected to pin 13 of IC2c. This works as follows. When the outputs of IC2a and IC2b go high to turn the lights on (via IC1 and Triac Qt), the 0.1µF capacitor is charged via the 4700 resistor and diode D5. This effectively latches the circuit up until the timer in the sensor module turns the lights off. Inputs A, B and C and output X allow up to four controllers to be connected together in daisy-chain fashion. In this configuration, the output (X) _of each controller is connected to an input (A, B or C) of all the other controllers. Diodes D6, D7 and DB form an OR gate so that the controller can be activated by applying a high to any of the inputs (ie, input A or input B or input C). When an external controller is triggered, this high is applied via that controller's X output. Thus, when one controller is triggered, it automatically triggers all the other controllers and lights all the lamps. Construction Most of the parts for the controller are installed on a printed circuit board (PCB) coded OE121. j_ ---I......... SWITCHED 240V AC TD LAMPS • • • r:i ........... __._. ~ ~1-D:-,m~ 470uF + ~O.l 05 X <at> e . . , ; "'~ c'-!:' c::.. B(/) «::::)e ..cJ>,e 0.1\J ~ 8~-bJ§ 1 GNO 0 :c:Jj j ~\\ 1 r-. {illg)e QzDe 0.1 0~ • !;;: : • VR1 LDRl D7 D~6 ~ e[TI[)e {ill[]e ~t Dl~::;: tDELETE IF NORMALLY CLOSED CONTACTS NOT USED AT INPUT 1 PASSIVE INFRARED MOVEMENT DETECTOR FRESNEL LENS NOTE: CHANGE R15 TO 8.2M TO INCREASE OH TIME TO 40 SECONDS 1J Fig.2: mount the parts on the control board as shown here. Take care with the mains wiring and note that some of the tracks on the board operate at mains potential. Fig.2 shows the parts layout. Begin construction by installing all the resistors and diodes, then install the larger components. Note that the 47kQ pull-up resistor on Input 1 must be deleted if you don't in- tend using this input. (Diode D9 could also be deleted in this case). The resistor to be deleted is marked with an asterisk. The power transformer is mounted directly on the PCB and is JUNE 1988 59 CONTROLLER 3 Fig.3: here's how to wire two or three controller boards together for perimeter lighting. When one controller switches on, it automatically triggers the others. secured using screws and nuts. Four insulated wire links are then run between the transformer terminals and points on the PCB. An insulated terminal block terminates the A, B, C, X and ground connections from other controllers, while PC stakes are used for other external wiring connections. Once completed, the control board can be tested separately. Connect mains wiring to the board and connect the output to a 240V incandescent lamp. The LDR should be left disconnected at this stage. The board is now ready for testing but, before plugging in, check all wiring carefully. You should also note that some of the tracks on the PCB operate at mains potential, so exercise extreme caution. In fact, we strongly recommend that you position the whole assembly in the specified plastic case before plugging it into the mains. Now switch on. If the 47k!l resistor has been installed on Input 1, the lamp should light. The lamp should then extinguish if Input 1 is shorted to ground. If the 47k!l resistor has been left out, the lamp should initially be off but should light when Input 2 is shorted to ground. If eveything works OK, disconnect the unit from the mains and connect the LDR to its respective terminals on the printed board. Check that the unit now operates in darkness but not in a well lit room. VRl can be adjusted to set the ambient light level at which the lamp will no longer turn on. Finally, check that the DC output voltage is around 14V. The Passive Infrared Movement Detector should be constructed and tested as described in the December 1987 issue of SILICON CHIP. There's just one change to make - the value of R15 should be increased to 8.2M!l to increase the on°time to approximately 40 seconds. In you want the lights to remain on for longer than this, increase the value of C12 (use a lowleakage electrolytic of tantalum type). Final assembly The two PCB assemblies are housed in a sturdy plastic electrical junction box made by Clipsal (type No.265/4 Series H.D. IP56}. This type of box is readily available from electrical wholesalers and hardware stores (eg, BBC). continued on page 68 Take care with component orientation when wiring up the control board. Note that the 47k!J resistor on Input 1 must be deleted if you don't intend using this input. 60 SILICON CHIP , . ; ( .,r,6,l,_.,\V .... 1-9 10 t Normally $7 .95 10 1 25 1 Cal . S 12500 . 1-9 $4.95ea $4.25ea $3.95ea QUALITY 3mm LEDS Cat. No. Col. 1-9 210140 Red $0.15 210141 G m $0.20 210143 Ylw $0.20 2 10145 o,a S0.20 10 1 100 1 $0.12 $0.15 $0.15 $0.15 $0.10 $0.12 $0.12 $0.12 QUALITY 5mm LEDS Cat. No. Col. 1-9 210150 Red $0.10 210151 Gm $0.15 210152Ylw $0.15 10 TURN WIRE WOUND POTENTIOMETER Spectrol Model 534 ¼" shaft. Equiv (Bourns 3540S, Beckman 7256) Dials to suit 16-1-11, 18-1- 11 , 2 1-1 - 11. R14050 SOR R141 00 SK R14055 100A A1411 0 10K R14060 200R R14120 20K R14070 S00R R14130 SOK R 14080 1K A14140 100K R 14090 2K 1-9 10+ $9.95 $9.50 "'"' I I KEY SWITCHES 10 + 100+ $0.09 $0.08 $0.12 $0.10 $0.12 $0.10 ~:~i{:i~:M~,:~c~~nts of heat for Designed by Rod Irving. H10525 105 x 75mm .. .. .. H 10529 105 x 100mm H10534 105x 140mm H10535 105 x 150mm H10542 105 x 195mm H10543 105x200mm ---c::::r------ $ 3.50 $ 4.95 . .. $ 5.50 ... . $ 7.90 ... $ 8.90 .. . $ 9.95 .. . $10.95 .. . $10.95 .. . $11 .95 ... $12.95 ... $26.95 H10520 105x30mm ...... H10546 105x225mm H10549 105x300mm H10560 105 x 600mm I ' ~I I WIRE WRAP IC SOCKETS Black anodised wlth a thick base plate. this radial fin heatsink can H10538 105 x 170mm ~ I HIGH EFFICIENCY RADIAL FIN HEATSINK "' i These quality 3·Ievef wire wrap _sockets are tin-plated phosphor bronze. Cat.No. P10579 P10580 P10585 P10587 P10590 P1 0592 P10594 P10596 P10598 8 14 16 18 20 22 24 28 40 Description 1-9 10+ pin $1.50 $1 .40 pin $1 .85 $1.70 pm $1.95 $1.80 pin $1.95 $1.80 pin $2.95 $2.70 pin $2.95 $2.70 pin $3.95 $3.50 pin $3.95 $3.50 pin $4.95 $4.50 We have millions of diodes In stock! + 100+ 1000+ IN4148 Small signal Cat. 210135 341 2½41 241 IN4004 400V 1A Cat.2 10107 441 3½41 341 HIGH INTENSITY RED LED BAR GRAPH Dimensions: Overall: 63mm across, 5mm high . LEDs: 10x5mm x 1mm Cat.No 1-9 10+ 210180 $2.95 $2.75 NICADS! Save• fortune on expen1lve throw away batteries wtth these qualfty Nlc■ds and Rechargersl Size ELECTRET MIC INSERTS With pin s for easy board insertion . Cat. C10170 1-9 10+ 100+ $1.20 $1.00 $0.90 Desc. 1-9 10+ 100+ AA 450 mA.H. $2.95 $2.75 $2.50 C D WELLER WTCPN SOLDERING STATION DIODE SPECIALS 1-99 RCA GOLD PLATED PLUGS AND SOCKETS For those who need the ultimate in connection. Essential for laser disc players to get that fantastic sound quality. Plug Cat. P10151 $2.95 Socket Cat. P10150 $2.25 The WTCPN Features: • Power Unit 240 V AC • Temperature controlled iron. 24VAC • Flexible silicon lead for ease of use • Can be left on without fear of damaged tips ! The best is always worth having . Cat. T1 2500 .. .. .... ... .. R.R.P. $149 SPECIAL, ONLY $129 THIS MONTH ONLY! 1.2 A.H. 1.2 A.H. $9.95 $9.50 $8.95 $9.95 $9.50 $8.95 SUPER DELUXE B ATTERY CHARGER • Charges from 1 to 10D,C,M,AAA, N, and up to 3 x 9V batteries at the same time. • Dual colour LED in first three compartments to designate 1·5V or9V. • 240V AC/50Hz. • Approval No. N10637 Cal.M23525 .. .. .. .............. $59.95 ROD IRVING ELECTRONICS IS AUSTRALIA'S COMPLETE ELECTRONICS STORE. ---=--==- TRIGGER TRANSFORMERS $1.45 Cat. M10104 • MET, SAVE$30 D ftill --- - ./ - -- DB25 CONNECTOR SPECIAL S! We have just imported 50,000. So you get to save a small fortune! DB25 MALE (P109001 1-9 10+ $1 .00 160+ $0.90 $0.80 DB25 FEMALE (P10901) 1-9 10 + 100+ $1 .00 $0.90 ~ CAN NON TYPE CONNECTORS This instrument is a compact. 1-9 P10960 3 PIN LINE MALE. 10 + $3.90 ...................... $3.50 P 10962 3 PIN CHASIS MALE $3.00 ...................... $2.50 CORDLESS RECHARGEABLE SOLDERING IRON • Built in solder point illumination • Easy replacement of solder tip • Protective stand which also functions as charging unit • Sponge pad attach to stand • Plug pack power adaptor • Includes Nicad battery • lnstructtion manual • 12 months warranty Cat. T1 2480 .. ... Normally $79.95 P10964 3 PIN LINE FEMALE $4.50 ...... ............... . $3.90 P10966 3 PIN CHASIS FEMALE $4.95 ...................... $3.95 a SPECIAL, $69.95 Packs of 10. DIS DID without boxes. or brand name . Just their white paper Jacket. and index labels. (5 114·· disks includes write protects). 51 5 ' ·•·· " NO BRAN D.. DIS KS • "' DISK STORAGE (DD100-L) Efficient ana practical. Protect your disks from being damaged or lost! Features ... • 100 x 51/4 " disk capacity • Smoked plastic hinged lid 1 0 :• Contemporary ~~~1Z ~a~ ~eJS ~~:~ g~se. design c 1so20 .............. . only $17.95 DOUBLE SIDED/DOUBLE DENSITY 10 ; DISKS 100 + DISKS 1.000 -- 0lSKS $8·95.. $8·50" $7·8088 (ALL PR ICES PER 10 DISKS) 3 1 , · .. NO BRAND" DI SKS DOUBLE SIDED/DOUBLE DENSITY 10 •DISKS I OO• DISKS I .OOO ·DISKS $27 $26 NORTHCOTE: 425 High St. Phone (03) 489 8866 CLAYTON: 56 Renver Rd . Phone (03) 543 7877 SOUTH AUSTRALIA , Electronic Discounters PIL , 305 Morphett St, ADEL AIDE 2 ~s1~~i~ls !~/!a!i,n1ersta1e due 10 lre1gh1costsl MAIL ORDER: Local Orders: (03) 543 7877 Interstate Orders: (008) 33 5757 All Inquiries: (03) 543 7877 CORRESPONDENCE, P.O. Box 620, CLAYTON 3168 Telex : AA 151938 Fax : (03) 543 2648 - MAIL ORDER HOTLINE 008 335757 1031543 7877 Now'you can buy absolute top quality disks that are also the cheapest in Australia! They even come with a lifetir:ne warranty! So why pay 2·3 times the pnce for the same quality? without short circuit except 200 ohm Range which shows "000 or 00 1" • ~ ~~~~;iev~oltage protection Rod Irving Electronics MELBOURNE: 48 A 'Beckett St. Phone (03) 663 6151 ITOLLFREEI (STRICTLY ORDERS ONLY) LOCAL ORDERS &INQUIRIES " NO BRAND '' DISKS! 1 •f~t~a~;~ .!~~Ff()C?_t~~:1r~~es SPECIAL$79 -- $1.20 MULTIMETER • Diede testing with 1 mA fixed current. • Audible Continuity Test. • Transistor hFE Test. SPECIFICATIONS Maximum Display: 1999 counts 3 ½ digit type with automatic polarity indication Indication Method: LCD display. Measuring Method: Dual-slope in A-D converter system OveMange Indication : "1"' Figure only in the display. Tem perature Ranges: Operating Q,C to + 40,C Power Supply: one 9 volt ballery (006P or FC- 1 type of equivalent) Cal. 091530 Normally $109 ""'-.- DIECAST BOXES Diecast boxes are excellent for RF shielding, and strength. Screws are provided with each box. H11451100x50x25mm S 5.95 Ht 1452 110 x 60 x 30mm . S 6.50 H11453120x65x40mm $ 6.95 H 11461120x94x53mm . $11.50 H 11462 188x 120x78mm . $13.50 H11464188x 188x 64mm .. . $29.50 3800 ;upJe~g~a~rJm~:raf~~;!~~~~~~d DC and AC voltage. DC and AC current. Resistance and Diode. for testing Audible continuity and transistor hFE . The Dual-slope A· D Converter uses C·MOS technology for auto-zeroing, polarity selection and oveMange indication. Full overload is provided . It Is an ideal instrument for use in the field , laboratory. workshop, hobby and home applications. Features ... • Push-button ON/OFF power switch. • Single 30 position easy to use rotary switch for FUNCTI ON and RANGE selection. • 112" high contrast LCD . • Automatic over-range indication with the "1" displayed. • Automatic polarity indication on DC ranges . ,Ii/I- ---- $24 (ALL PRICES PER 10 DISKS) POSTAGE RATES, $1 $9.99 $10 $24.99 $25 $49.99 $50 $99.99 S100 S199 $200 $499 $500 plus $2.00 $3.00 $4.00 $5.00 $7.50 $10.00 $12.50 The above postage rates are for basic postage only. Road Freight, ~~~~t::tf~~~~~~~~r;ia~~i.11 be All sales tax exempt orders and wholesale inquiries to : RITRONICS WHOLESALE. 56 Renver Rd, Clayton. Ph . (03) 543 2166 (3 lines) Errors and omissions excepted Prices and specifrcations sub1ect lo change . :~~ia~~s ~i;;,~;r~aii~en~rn~~~:~s Machines 'Apple 1s a registered 1rad11mark ·oenotes registered tradmarks 01 the11 respecllve owners MEGA BATTE A large finned heatsink is necessary to keep the main power transistor cool. A LED on the front panel lights when the batteries have charged. This Mego-Fast Nicad Charger will safely charge o 1300mAh nicod racing pock in 20 minutes. It's easy to build and can be powered from a 12V car battery or from a 12V battery charger. By JOHN CLARKE & GREG SWAIN Radio-controlled (R/C) model cars are a lot of fun, but the hobby comes with one in-built frustration - under normal use, the batteries go flat within about 30 minutes. It's even worse under race conditions, when heavy loads are placed on the battery pack. In these conditions, the batteries can go flat in less than 15 minutes. What's needed is a way of quickly recharging the battery pack so that it can be put back into service as soon as possible. According to the manufacturers, for correct charging of nicad batteries, each cell should be first discharged to its end point (usually around 1. 1V) and then recharged at the 10 hour rate for 14 hours. This 62 SILICON CHIP means that if the battery pack is rated at 1300mAh, it should ideally be recharged for 14 hours at a 130mA rate. But what R/C car enthusiast wants to wait for 14 hours while the battery pack is recharged? To overcome this problem, many enthusiasts resort to fast charging. In its crudest form, this simply involves connecting the 7. 2V nicad pack to a car battery via a pair of resistive leads. The resistive leads limit the current into the nicads to a safe value but with one proviso you must remember to disconnect the leads after a preset time to prevent overcharging, otherwise you'll damage the cells. Damaging a racing pack is expen- 1.8 1.7 - ~ / / I I 1.4 1.3 0 10 15 20 CHARGE TIME (MINUTES) Fig.1: charging curve for a single cell in a 7.2V 1300mAh racing pack. Note how the voltage falls at the end of the charging cycle. sive, since they cost around $60 to $70. Clearly, there has to be a better way. Automatic switch-off The Maga-Fast Nicad Charger charges at a high rate but stops overcharging by automatically switching itself off when the cells are fully charged. How does it do this? Well, when a nicad cell is fully charged, further charging leads to a slight drop in its output voltage. The charger has inbuilt circuitry to FAST NICAD RYCHARGER +12V BA NOMO-C:r--.r.~--------------------------------------------, 7.2V 1300mAH NICAD PACK1000 25VW 100 25VW + - - 02 1N414B 10M 2200 25VW 2200 25VW + 2200 -25VW - + _ 01 BYX9B A 10A VR2 20k 470k .01 0 / 04 1N414B CURRENT SOURCE 0 8 VIEWED FROM BELOW MEGA-FAST NICAD CHARGER SC14-1·05BB Fig.2: the circuit diagram. ICla, IClb, Qt and Q2 form the constant current source, IClc is the level detector, and ICld is the timer circuit. The circuit is reset at the end of the charging cycle by disconnecting the supply. detect this voltage drop and then turn itself off. Fig.1 shows the charging curve we plotted for a single cell in an Arista NCRP72 7.2V 1300mAh super racing pack. Note that the voltage across the cell rises steeply towards the end of the charging cycle and then levels off and begins to fall. The charger cuts off when the cell voltage just begins to fall. To ensure fast charging, the charger pumps a constant current of six amps into the battery pack until the end point voltage is deteded. As a further safety measure, an inbuilt timer is included in the circuit. If the end point voltage is not reached, the timer will automatically shut the charger down after a preset time. If you like, you can regard the timer as a "belts and braces" feature to ensure that the charger shuts down within a specified time. Without the timer, the circuit might not shut down if connected to faulty cells. The front panel of the charger features two LED indicators, one red and one green. The red LED lights when power is applied to the charger, while the green LED lights when the battery pack has charged. How it works Fig.2 shows the circuit diagram. IC1a, IC1b, Ql and Q2 form the 6A current source, IC1c is the level detector, and IC1d forms the timer circuit. Let's see how the circuit works. LED 1 is used for the power indicator and as a voltage reference. Trimpot VR1 feeds a portion of the LED voltage to pin 12 of IC1 b which, together with ICla, drives Darlington pair Ql and Q2. The current through Q2 develops a voltage across its 0. rn emitter resistor and this voltage is applied to pin 13 of IC1b via the 27kn resistor. So IC1 b compares the voltage developed across the 0. Hl resistor with the voltage setting from VR1. Thus IC1 b sets and controls the current through Q2. Now what is IC1a doing there, tacked on to the output of IC1 b? The problem is that IC la is not up to the task of driving Ql by itself. So IC1a is connected up as a "current follower". It monitors the voltage produced by IC1b between pin 14 and the base of Ql and it acts to produce the same voltage across its own 1000 output resistor. So for every milliamp delivered by IC1b, IC1a does the same. Voltage monitoring As mentioned above, the circuit automatically shuts off when the battery pack is fully charged. This condition is detected by IC1c. JUNE 1988 63 comparator IClc will normally be low, D4 will be reverse biased, and the charging cycle will continue. When the nicad battery pack nears the end of the charging cycle, the voltage across it will suddenly start to reduce instead of increasing as before. This will mean that the voltage at pin 5 will rise above that on pin 6 and so the output of IClc will go high. D4 will conduct, pin 13 of ICl b will be pulled high, and so Ql and Q2 will be turned off. At the same time, D2 conducts and latches up IClc so that the circuit remains off. LED 2 is also now forward biased and so it lights to indicate that the battery pack is fully charged. Timer circuit The printed circuit board is mounted in the case on 6mm standoffs and secured by machine screws and nuts. Use 4mm (or thicker) auto cable for all wiring connections and pass all external leads through grommetted holes. Both inputs of IClc monitor the voltage across the battery pack via separate time constant circuits. Pin 5 has a relatively short time constant (22k0 and lOOµF) while pin 6 has a long time constant (22k0 and 1000µF). So IClc is set up to detect the point . at which the voltage across the battery starts to reduce. During most of the charging cycle, the battery voltage will be increasing at a very slow rate. This means that the voltage at pins 5 and 6 will be steadily decreasing (with respect to the negative supply rail). Further, because of the short and long time constants, the voltage at pin 5 will always be slightly lower than at pin 6. Hence the output of r; Above is a full size reproduction of the printed circuit artwork. 64 SILICON CHIP Comparator stage ICld and its associated components form the timer circuit. A reference voltage derived from trimpot VR2 is applied to the pin 3 input, while pin 2 is connected across an RC timing circuit consisting of a 2200µF capacitor and a 470k0 resistor. When power is first applied to the circuit, the 2200µF capacitor is discharged. This means that pin 2 will be high, pin 1 low and D3 reverse biased. Thus the timer initially has no affect on the rest of the charger circuit. Now consider what happens as the capacitor charges towards the negative rail via the 470k0 resistor. Eventually, the voltage applied to pin 2 of ICld will drop below the pin 3 reference voltage. When this happens, pin 1 of ICld will switch high and pull pin 5 of IClc high via D3. Thus, pin 7 of IClc switches high and shuts down the charging circuit via D4 as described previously. Essentially, the timing circuit is included as cheap insurance against the circuit not shutting down via the level detection circuit. In most cases, by the time the timer operates, the output of IClc will have already switched high and the circuit will have shut down. Trimpot VR2 allows the timer to be set so that it operates shortly after the nominal charging period. It should be set to cut out at around 20 minutes Power for the circuit is derived from a nominal + 12V supply [eg, a Fig.3: here are the wiring details for your Mega-Fast Nicad Charger. Note that transistors Q1 and Q2 must be insulated from the metal case (see text and Fig.4 below). car battery or a battery charger). The two 2200µF 25VW electrolytics provide supply line filtering, while diode Dl and the BA fuse form a simple but effective "crowbar" protection circuit to guard against reversed battery connections. If the connections are reversed, Dl conducts and blows the fuse. The large power diode is installed directly on the PCB and secured from the copper side using a nut and star washer. When the nut is tightened, the star washer bites into the copper pattern and thus ensures good contact with the cathode (K) of the power diode. A short piece of tinned copper wire is used Construction Construction is straightforward with most of the parts mounted on a printed circuit board (PCB) coded SC14-1-588 and measuring 112 x 69mm. This is housed in an aluminium case measuring 133 x 76 x 54mm. A large finned heatsink mounted on the top of the case provides heat dissipation for the 2N3055 power transistor. Fig.3 shows how the parts are mounted on the PCB. You can start assembly by soldering in the small signal diodes, 0.25W resistors and the ICs. When these have been installed, you can mount the electrolytic capacitors, the trimpot and O. rn 5W power resistor. The latter should be mounted 1-2mm proud of the PCB to allow air circulation. -TRANSISTOR 0 HEATSINK 0 ~---CASELID ~ j_ <:$ ® © ~-INSULATING BUSH ~ - SOLDER <at>.....-- LUG WASHER <at>....---SPRING WASHER <at>----NUT Fig.4: mounting details for transistor Q2. Smear all mating surfaces with heatsink compound and check the final assembly with a multimeter. for the anode connection. Once the diode is in place, the two LEDs and the BD139 transistor can be installed. Before mounting the two LEDs, be sure to correctly identify their anode (A) and cathode (K) leads (see circuit diagram). The leads are then bent at right angles about 2mm from the LED body and the LEDs installed so that their centres sit about 4mm proud of the PCB. If you've followed the above procedure correctly, you will find that the LEDs overhang the front of the PCB by about 3mm. This is important, since the LEDs later have to protrude through the front panel of the case. The BD139 transistor should be mounted using a 12mm lead length. Note that the metal side of the transistor body faces away from the PCB. With the PCB assembly completed, attention can be turned to drilling the metal case. First, mark out and drill mounting holes for the PCB in the bottom of the case, then temporarily mount the PCB on 6mm standoffs (bend the LEDs back) and JUNE 1988 65 Close-up view of the printed circuit board assembly. The o.rn resistor is mounted 1-2mm proud of the PCB to allow air circulation for cooling. mark the mounting hole for the BO139 transistor (Ql). The PCB can now be removed and holes drilled to accept Ql 's mounting bolt and an adjacent rubber grommet (see Fig.3). This done, carefully affix the front panel artwork to the case and drill clearance holes for the two LEDs. Note that the front panel artwork is not centred top and bottom on the case. Instead, it must be positioned so that the bottom edge is 4mm from the bottom of the case (see photo). Additional holes can now be drilled in the lid to accept the fuseholder, power lead grommet, and heatsink mounting screws (see photo). Be sure to position the fuse so that it will clear the capacitors mounted at the end of the PCB when everything is later assembled in' the case. The 2N3055 power transistor is mounted using a mica washer .and insulating bushes to electrically isolate it from the heatsink and case. The method of assembly is shown in Fig.4. You can mark the holes for mounting the transistor using the TO-3 mica washer as a template. After drilling, remove any burrs using a larger diameter drill. Check that the contact area is free of metal swarf and grit, then smear a thin layer of heatsink compound on the transistor mounting base and on both sides of the mica washer before screwing the assembly together. After the transistor has been screwed down, use your multimeter (switched to a high "Ohms" range) to check that it is completely isolated from the case. If the reading shows a short, remove the transistor and check the mating MEGA-FAST NICAD CHARGER 7 UJ CJ) => u. L 0 POWER 0 CHARGED <( _J Here is an actual-size reproduction of the front panel artwork. 66 SILICON CHIP surfaces carefully for small pieces of metal. The PCB and off-board components should be wired using 4mm auto cable (don't use thinner wire). This won't fit into normal PCB holes so we suggest that you use PC stakes at all external wiring points on the PCB. Use 1-metre or longer lengths of wire for the power leads and terminate them in alligator clips to allow rapid connection to the car battery. The charging leads for the nicad pack should be 100mm or longer. They can be terminated in a suitable socket, to accept the plug from the battery pack. To avoid confusion, use red cable for the positive leads and black for the negative leads. Once the wiring has been completed, the PCB can be mounted in the case and secured on 6mm standoffs using machine screws and nuts. Push the LEDs through the front panel holes and secure the BD139 transistor to the side of the case using a screw and nut. Note that the metal face of the BD139 must be isolated from the case using a TO-220 mica washer. An insulating bush is not required since the hole in the transistor body is already insulated. As before, smear the mating surfaces with heatsink compound before bolting the transistor to the case. Finally, use your multimeter to check that the metal tab is correctly isolated. You can do this by connecting the multimeter between the collector lead of the transistor and the case. If everything is correct, the meter will indicate an open circuit condition. Setting up At this stage, it's a good idea to go back over your work and check carefully for wiring errors. If everything checks out, set both VR1 and VR2 fully anticlockwise, connect a discharged nicad battery pack to the charger output, and connect your multimeter across the o.rn 5W power resistor. Set the multimeter to a low voltage range. Now connect the supply leads to a 12V car battery and slowly adjust VR1 for a reading of 0.6V on the meter. This corresponds to a current of 6A through the nicad bat- z DAVID REID ELECTRONICS Aust. Pty. Ltd . PORTASOL SCIENTIFIC CALCULATOR "AA" Nicads "PROFESSIONAL" BUTANE GAS IRON KIT EL-506H 10 DIGIT L.C.D. DISPLAY Four arithmetic calculations, constant calculation, memory calculation, degree/minute second ,_. decimal degrees conversion , trigonometric function, inverse trigonometric function , logarithmic function , exponential, square and power, Xth root of Y (\/y) , square root, reciprocal , factorial , co-ordinates con version, statistical calculation , hyperbolic and inverse hyperbolic functions , percent change , etc . A MUST FOR EVERY STUDENT, TECHNICIAN. COMPLETE w1TH WALLET AND INSTRUCTION MANUAL. 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Box 010 3 Sydney 2000 $1 - $25: $3. 00 P&P $26 & over: $6.00 P&P CAR ALARM KIT (See SC Feb '88) This refined car burglar alarm has about every feature you could possibly want to keep would be thieves away. FEATURES: • Internal & External Sirens • Dash lamp flasher • Battery back up • Delayed & Non delayed inputs • Ignition killer • Easy to build and install. $ 129 TRANSISTOR, FET, ZENER TESTER KIT (See EA Feb/Mar '88) New updated circuit incorporates facilities for testing transistors, FETs and Zeners Features: • Gain • Leakage • Breakdown Voltages • Zener Voltage • Polarity - NPN/PNP etc. $49.95 AC/DC MILLIVOLT METER KIT EACH Precision measure critical circuits Designed to cause minimal circuit loading whilst reading very low level voltages. Features: AC/DC range • 7M Ohm input impedance • Reverse polarity indicator • Operates off 1 9V battery (not included) • 10mV to 30V ranges in 8 steps • Zero position • Battery Test position. $ _ 55 00 VISA ]UNE 1988 -- EA. (See EA Dec '87) D89 D825 ADAPTORS 9 PIN PLUG to 25 PIN SOCKET . ...... CAS 23 9 PIN SOCKET to 25 PIN PLUG . _CAS 24 $10.95 ~"' "PROTECTOR" * MINI " DIN " CONNECTORS 12AX7 $8.45 12AT7 $8.45 . $13.25 6AU4 ..... $11 _50 6CA7. $13.50 6L6 1 X2 $7 .95 PLUS MA NY MORE IN STOCK. Ring for availability and price. ,, REfflTEH H EAT-SHRINKABLE PRODUCTS PTY L TO HEATSHRINK TUBING * EA. TELEPHONE DOUBLE ADAPTOR NS D LINEAR DATABOOKS Vol 1. $2.95 67 PARTS LIST 1 PCB, .code SC14-1-588, 11-2 x 69mm 1 Scotchcal label, 1 1 0 x 40mm 1 folded aluminium case, 133 x 76 x 54mm 1 finned heatsink, 7 5 x 11 0 x 33mm 1 panel mount 3AG fuse holder 1 SA fuse 2 6mm grommets 4 6mm standoffs 2 metres red automotive cable (4mm dia). 2 metres black automotive cable (4mm dia.) 4 3mm dia. x 1 5mm screws 4 3mm nuts 3 2.5mm dia. x 10mm screws 3 2.5mm nuts 1 solder lug 1 T0126 mica washer 1 T0-3 mica washer plus insulating bushes 1 socket to suit plug on 7. 2V Nicad battery pack 2 automotive battery clips 4 rubber feet tery pack. Since the timer is also going to be adjusted during this procedure, you should also note the precise time when the 12V source is connected. Assuming that the battery pack Semiconductors 1 2N3055 NPN power transistor 1 BD139 NPN transistor 1 BYX98-300(R) 1 OA 300V diode 2 5mm LEDs (1 red , 1 green) 3 1 N4148, 1 N914 diodes 1 LM324 quad op amp Capacitors 3 2200,uF 25VW PC electrolytic 1 1000,uF 25VW PC electrolytic 1 100,uF 25VW PC electrolytic 1 0.0 1,uF metallised polyester Resistors (0 .25W, 5%) 1 x 1 OMO, 1 x 470k0, 1 x 27k0, 2 X 22kQ, 1 X 2.2k0, 1 X 6800, 3 X 1000, 1 X Q. 10 5W, 2 X 20k0 miniature vertical trimpots Miscellaneous Solder, heatsink compound, tinned copper wire, etc. was flat to begin with, it should take about 20 minutes for the pack to recharge. During this period, you should carefully monitor the temperature of the battery pack. If the battery becomes hot, disconnect Automatic light controller The accompanying photographs show the general layout inside the case. As can be seen, the PIR movement detector is mounted on the lid of the case, supported on 18mmlong pillars. Before mounting the detector, you will have to make a cutout in the lid to clear the lens assembly. A 7mm hole will also have to be drilled in the lid to accept the LDR. The control board is mounted on the bottom of the case and secured using machine screws and nuts. Drill holes to accept the mounting screws plus an extra hole ih the bottom left corner (looking from inside the case) for the mains cord entry. You will also have to drill a hole in the adjacent end for the mains cord clamp, plus additional holes in 68 SILICON CHIP continued from page 60 the sides of the case to accept the lamp holders (or to pass wiring to external lamps, depending on requirements). It's best to complete the wiring to the control board before mounting it in the case. Light duty hookup wire can be used for connections between the two PCBs and to the LDR but note that the wiring between the control PCBs and the lamps must be run using 240V AC cable. Lace up the cables or use cable ties to keep the wiring tidy. The control PCB can now be mounted in the case and the mains cord secured using a suitable clamp. The prototype used a clamp fashioned from scrap aluminium and secured with a screw and nut. This same screw and nut also it from the charger immediately. Under normal circumstances, the battery pack should become warm and the "charged" LED should light at the end of the charging period (ie, after about 20 minutes). As soon as the "charged" LED comes on, disconnect the battery pack but leave the charger connected to the 12V source. Now quickly connect your multimeter (set to volts) between pin 1 of ICld and ground and adjust VR2 so that pin 1 switches high. This effectively sets the timer so that it disables the charger shortly after the end of the normal charging cycle. To check the timer action, disconnect the charger from the 12V source, leave it for a minute or so to discharge the circuit's capacitors and then reconnect it, without a nicad battery pack in place. Then check that LED 2 comes on after 20 minutes. When you are using the charger and want to charge several battery packs in succession, remember to disconnect the charger from the 12V source after each pack is charged. This resets the timer and the voltage monitoring circuit. Footnote: the Mega-Fast Nicad Battery Charger can also be used to charge lower voltage packs (eg, 5.6V nicad packs) without any changes to the circuit. lb secures a piece of insulating material to cover the mains terminations on the transformer. (In the kit supplied by Oatley Electronics, this material will be Presspahn or Elephantide ). We suggest that the cut-outs for the PIR lens assembly and the LDR be weather-sealed using a silicone sealant. If possible, try mounting the unit under the eaves of the house, out of the weather. A licensed electrician should be employed to connect the unit to existing house wiring. Note: on boards presently being supplied by Oatley Electronics, it is necessary to modify the pattern asssociated with the relay coil on the PIR movement detector. Instructions on how to do this are being supplied with the board (see Notes and Errata on page 95). lb 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. Dual power circuit has backup battery indication This power supply circuit delivers close to 9V DC under mains power and indicates whether it has switched over to battery power. Under mains power, the 7805 is set up to deliver + 9.5V DC. DZ is forward biased while D3 is reverse biased. Diode D1 is also forward biased, which holds pin Zand pin 6 of the 555 timer high. This forces the pin 3 output of the 555 low. Hence the light emitting diode LED 1 stays alight while ever the mains power is present. If the mains supply fails, DZ is reverse biased and D3 is forward biased and the output is ----+---+12v Brighter flashing lamp for burglar alarms Some commercial burglar alarms use a flashing LED to indicate that the alarm is active and as a warning to would-be tea-leaves. The problem with LEDs is that they can't be seen in daylight, particularly when the sun is shining brightly. This circuit substitutes an incandescent lamp for the LED and produces a highly visible fla shing indicator. To avoid problems of connection, the existing connections to the LED are used to drive the input side of an optocoupler (which has an inter- nal LED). The output side of the LED is then used to turn on a BC337 transistor (Qi) which drives the dashboard flasher lamp (Jaycar SL-2694). The optocoupler can be the readily available 4NZ8. Flashing pilot lamp This simple circuit can often be fitted inside the plastic housing of a panel-mounting lamp assembly. It is a very low current circuit but the flashing indicator catches the eye. It is a relaxation oscillator based on the fact that the neon lamp is open circuit until the voltage across supplied by the 9V battery. Vee is now around + 8.4V DC. Diode D1 is now reverse biased and the 555 timer can operate in astable mode (ie, it can oscillate). The LED and the piezo indicators will now pulse alternately on and off to indicate that battery power is being used. $20 to Ian Davies, Cheltenham, Vic. it rises to its breakdown voltage, after which it becomes a low resistance. The circuit works as follows. First the 0.1µF capacitor is charged from the mains voltage via the diode and 10MO limiting resistor. When the voltage across the capacitor reaches the neon breakdown voltage, normall y around 60 to 90 volts, the capacitor is discharged via the lamp. The heavy current is sustained down to a fairly low voltage, at which point the neon becomes an open. circuit again. When the neon switches off, the voltage across the capacitor begins to rise again for another cycle. $12 to Steve Payor, Kogarah Bay, NSW. 240VAC 0.1 200V NEON• JUNE 1988 69 Did you miss out? Dick Smith Electronics' brand new 1988 Hobbyist and Enthusiast catalogue is now available in al l store s! Call in for your FREE COPY now . . . or phone (02) 888 2105 or write to DSXpress, PO Box 321 , North Ryde 2113 and ask for one to be posted! Spray Freezer Instantly freezes components to -50° Celsius. Ideal for coolin~ and servicing electronic/electrical components, shrinking shafts, bushes; etc. 350g spray can with nozzle. Cat N-1056 Matte Silver Spray Paint Heat Transfer Compound Anti-glare silver paint for a smooth, elegant finish to that special project. Quick drying paint is ideal for front panels, cases, etc. 150g spray can. Cat N-1076 From Electrolube, specialists in chemical service aids to the electronics industry. Heat transfer compound comes in 10ml syringe for easy applicatian. Cat N-1200 Non silicon Non metallic Permagard Moisture Displacement Di splaces water and moi sture, penetrates, lubricates and provides protection against corrosion. In 250g spray can . If you've already got some in the workshop - put some in the car 1 Cat N-1065 s7so $595 Contact Cleaner Lubricant Improves electrical contact, reduces wear, suppresses arcing, loosens sulphide and tarnish film , inhibits corrosion an maintains stable low contact resistance. In handy 300g can with spray tube. Cat N-1042 :":r' :-~,~ -~~ i l!W'.{~ ' !ff:_-;~ 13.8V <at> 1.5A Regulated Just right for CB's, car radio/stereos, small amateur transceivers (hand-helds especially), etc. 13.8 volts DC regulated with terminals for easy connection . Makes a great service supply, too. Cat M-9545 See-Through 3 Pin Plug Up to 8 batteries at once ... The DSE NiCad Charging Cabinet The universal charger that'll do a big bunch of NiCad batteries at one time! Charges AAA, AA, C, D and 9 Volts in virtually any combination. That's right up to 8 ce lls and/or 3 x 9 volts at one time. Cat M-9505 Same as 3 pin plug, but see t h r o u ~ h so you can see faulty or broken wiring, etc. Cat P-5401 90 1 See-Through Line Socket $ ·~s3995 cord~$43o As for P-5401, but extension end. See through: for safety's sake. C~;~lock ~ r Sto~s plugs and sockets pulling apart - it's dangerous and inconvenient. Added safety for your extension cords. Cat P-5412 13.8V/4A Peak For the 2m or small HF amateur transceiver, a supply for 'auto' equipment, even a bench supply for service work! With a 3 amp continuous (or 4A continuous at 75% du!}' cycle!) and a huge 8 amp in stantaneous peak rating, its ideal for those higher current and higher peak demand applications. Cat M-9547 • Heavily lleatHnk for maxim1m output Suppressor Plug<at>• Standard 3 P.in AC plug, with capacitors fitted to reduce unwanted pops and crackles from audio equipment. Cat P-5425 ·f ) $ International Traveller Adaptors Having trouble with power points overseas? Here's the answer! A neat little adaptor that converts our 3 pin plug to virtually anything used in the world. One piece (so you won't lose bits). Use active/neutral pins only: daes not connect earth. pit P-5652 N.B. Dees not adapt voltage!!! 95 8 Take Out Those Spikes and Spru!les From Your Computer. Deluxe mai ns filter eliminates all the garbage from your computer for a clean line of supply. So if you're having 'crashing' problems this could be the answer! Rated at 240V, 2 amps. Cal M-9850 Energy authority approved. • Colour coded output lenaina.ls • LED lndlcalor also shows overload or short circuit 5 BATTERY HOLDER AND SNAP 149 Battery Snap 25tre)b~ • NSW • Albury 21 8399 • Bankstown Square 707 4888 • Blacktown 671 7722 • Bondi Junction 387 1444 • Brook'fale (Warringah MaH) 93 0441 • Campbelttown (046)27 2199 • Chatlwood Chase4111955• Chutlora 642 8922 • Gore Hill 439 5311 • Gosford 25 0235 • Hornsby 477 6633 • Liverpool 600 9888 • Mattfand 33 7866 • Miranda 525 2722 • Newcastle 61 1896 • North Ryde 88 3855 • Parramatta 689 2188 • Penrith (047)323400• RaitwaySquare2113777• SydneyCity2679111 • Tamworth661711 • Woffongong28380b • ACT• Fyshwick 804944 • VIC• Ballarat31 5433 • Bendlgo43 0388 • Box HiH 8900599• Coburg 383 4455 • Dandenong 794 9377 • East Brighton 592 2366 • Eas&ndon 379 7444 • Footscray 689 2055 • Frankston 783 9144 • Geelong 43 8804 • Melbourne City 670 9834 • Richmond 428 1614 • Ringwood 879 5338 • Springvale 547 0522 •OLD• Brisbane City 2299377• Buranda391 6233 • Caims311 515 • Chermside 3596255• Redbank2885599• Rockhamplon279644 • Southport329863• Toowoomb.1384300• Townsville 72 5722. • Underwood 341 0844 •SA• Adelaide City 232 1200 • Beverley 347 1900• Darlington298 8977 • Elizabeth 255 6099 • Enfield 260 6088 • WA •'Cannington 451 8666 • Fremantle 335 9733 • North Perth 328 6944 • Perth City 481 3261 • TAS • Hobart 31 0B0Q •NT• Stuart Parle 811977 Order by phone Toll Free (008) 22 8610 lor DSXpress 24 hour Despatch. &-Channel IR Remote Controller Just think about the possibilities - remote control for your TV, CD, VCR, model railway or even mains powered appliances such as lamps, alarms, heaters, the coffee perculator ... almost anything! This unit can control up to 8 functions plus mute and up/ down! What's more, it allows you to custom build the kit to suit your own specific application - construct with all functions or just those required. Receiver Cat K-3434 s 127 IR Transmitter IR Remote Control Preamp Foll command over your hi-Ii system without moving from your chair! The IR Remote Preamp comprises a complete preamp in which all functions can be selected by infrared remote control. And it's loaded with features! Plug it into your existing system via the tape monitor loop or use it with a power amp in a new system. ~An incredible array of LEDs give a constant status report on ,. ~~'-~ the entire system. The bargraph volume display automatically indicates bass, treble, balance (up/down) while these functions are being set. Cat K-4003 259 5 Car Alarm UHF Remote Switch The do-it-yourself way to car alarm convenience. A remote switch for your existing car alarm. Cumbersome keys are now a thing of the past with this easy to build kit idea. The kit consist of a 304MHz receiver, decoder IC and output relay on a single PCB which is installed in a compact aluminium case. ~ The receiver in the DSE kit is small enough to fit on your keyring yet (unlike some other kits available) large enough to accomodate all the components easily. After installation you can remotely switch your existing car alarm from distances up to 40 metres. Kit options include momentary II.asher indicator and piezo alarm or siren capability for alarm set. Cat K-3256 For use in conjunction with the IR Receiver (K-3434). Housed in sturdy plastic case with pre-punched and screened panel and 12 function buttons. Cat K-3433 s3995 Wireless Stereo Headphone Link Enjoy high quality sound reproduction on your headphones without messy cables - with the DSE Stereo lnfrared Headphone link. It saves having your ears ripped off when someone trips over the cable, allows you to listen to your favourite program while the rest of the family listens to theirs and it's ideal for anyone who's hard of hearing! Both the Transmitter and Receiver are packaged in a compact case, which can be held in one hand, so they're not going to clutter up the table, television and benchtop. Use it on your stereo, TV... anything! Ftltlm • Volume control on both transmitter and receiver • Compact case - 68 x 136 x 26mm (both) • Screened aluminium front panel • Great range • Suits-32-100 ohm headphones or high efficiency speakers • Transmitter power - 12V plug pack • Receiver power - 9V battery • FM stereo transmission. T1111111llllr Cat K-4005 lllcliHr Cat K-4006 $ TV Colour Bar & Pattern Generator The serviceperson's right hand man/ If you're in the trade, this has to be a cinch to build! Portable, the pattern generator is powered by a 12 volt AC plug pack and provides 8 patterns - colour bars, red/white/black screen, crosshatch, vertical/horizontal lines and dot pattern. , Sure better value than ready made models! Cat K-3473 $ ae ~ 95 each Safety Yellow 3.5 Digit with Tr, Diode & Continuity plus Battery Checking This one has all the usual ranges, including current to 10A and resistance to 200 megs, but it also has a continuity checker with a fast 100ms response time, a diode and transistor checker, plus a battery checker it tests under actual load conditions. It takes a single 9V battery (and tells you if it's low!) and comes complete with a flip-down handle that doubles as a stand. Cat 0-1445 Safety Yellow 3.5 Digit with CaP., Tr, Diode & Continuity Very similar to our 0-1445 multimeter, with slightly different ranges. This one features a capacitance checker (2nF to 20uF) in place of the battery check ranges, and goes to 20 megohms as its top resistance range. Features very high overload protection (at least 500 volts DC, up to 1200V DC on most ranges), and the meter is fuse protected. Resolution is very respectable 100uV/100nA, with a very fast 300ms cycle time. Cat 0-1465 s9950 E-Z Cable Checker The name says it all! Every roadie, every band in the world needs one of these. Even the amateur sound recordist, club or church PA operator - anyone involved in aurio cables will find the E-Z Check invaluable. Simply plug your cct-le in - Cannon, 6.5mm mono or stereo, RCA or BNC - and a series of LEDs tell you if it's okay. Imagine the time saving when searching for that elusive cable fault. Cat Q-1532 LAST YEAR'S PRICE $79 NOW ONLY S 1995 AMATEUR RADIO By GARRY CHATT, VK2YBX A low cost RF sniffer probe and preamplifier This low cost RF Sniffer will avoid loading problems when measuring critical low-level oscillator circuits in amateur gear. It has a gain of 30dB from 1-500MHz and plugs directly into your CRO or DFM. One of the most commonly encountered problems when working on RF equipment is how to measure the frequency oflow-level oscillator or mixer circuits. Most frequency counters have a typical input sensitivity of 5-10 millivolts and require direct connection to the circuit being measured. But direct connection to critical oscillator circuits can create problems, due to loading effects of the probe. Even a xto CRO probe with an input capacitance of several pF can "pull" the operating frequency of an oscillator so much as to ma:ke 100 any reading meaningless. Another problem with direct connection is that you must locate the correct point on the circuit to connect the probe. This can be time consuming if a circuit is available and just about impossible if the circuit is not available. A far easier method of confirming the operating frequency of an oscillator mixer or amplifier is to use a "sniffer probe". This typically consists of a miniature antenna followed by a broadband amplifier of modest gain. The antenna is simply placed close to the circuit to 100 FX1 115 FERRITE BEAD r---e-- HW.......,..--...--.--w-H- -1---.---;.---.::::::::~--+12v 4700 .01 .01 1200 4.10 (8.201/8.20) RF SNIFFER SC04-1-0688 1200 +· E Fig.1: the circuit consists of three virtually identical stages based on RF transistors Qt, Q2 and Q3. Each transistor is connected as a common emitter amplifier to give around 30dB of gain from 1-500MHz. 72 SILICON CHIP The circuit is housed in a plastic jiffy case and plugs directly into your CRO or DFM. pick up the signal. The amplified signal can then be fed to a frequency counter or oscilloscope. Circuit details Fig.1 shows the circuit of a simple amplifier that will do the job. It consists of three virtually identical AC-coupled stages, with RF transistors Qt, Q2 and Q3 . Qt, Q2 and Q3 are all 2SC3358 (or equivalent) RF transistors which have a gain bandwidth product (fT) of 7GHz (4.5GHz for 2SC2369} and a typical hFE of 120. Each transistor is connected as a common emitter amplifier and each emitter load is 4.10. The total gain over the three stages is 30dB (with a 12V supply) from 1MHz to 500MHz, and the output stage (Q3} is capable of driving a 50-ohm load. The circuit can be powered from Fig.2: the circuit is built RF-fashion on the copper side of a small piece of unetched PCB material. Follow this coded photograph carefully during construction and be sure to keep lead lengths as short as possible. r f 30mm - - - - - ~ - - - - - - - 9 D m m STftlP BACK OUTER SHEATH AND BRAID co" HEATSHRINK TUBING --------.-! \ RG58 CABLE PARTS LIST ~ BNC PLUG Fig.3: the sniffer probe is made from RG58 cable, heatshrink tubing and a BNC plug. The dimensions shown are provided as a guide and are not critical. Above: close up view of the sniffer probe. The heatshrink tubing isolates the end of the braid from components above ground potential. a 9V battery, although this will give lower gain than the 12V supply depicted on the circuit. The unit is best constructed on a piece of unetched circuit board material measuring 77 x 15mm. This provides a good ground plane on which to mount the components. 1 blank (unetched) piece of PCB material, 77 x 15mm 1 ferrite bead (eg, FX1115, DSE Cat. L-1 430) 1 small rubber grommet 1 plastic jiffy case, 83 x 54 x 28mm 2 BNC panel-mount sockets 1 BNC plug (for sniffer probe) 1 120mm-length RG58 coaxial cable 2 banana plugs (1 red, 1 black) 3 2SC3358, 2SC2369 or BFR90/91 RF tansistors (available from Dick Smith Electronics\ 7 .01 µF ceramic capacitors Resistors (0.25W, 5%) 2 X 1 kO, 3 X 4 700, 1 X 3300, 3 X 1200, 2 X 100, 6 X 8.20 Miscellaneous Heatshrink tubing, 1-metre twincore cable (for supply leads), 1-metre RG58 coaxial cable terminated with BNC plugs (for connection between RF Sniffer and DFM) JUNE 1988 73 Above: the completed RF Sniffer in action. The unit avoids loading problems when you are checking out low-level oscillator circuits in all sorts of RF gear. Power for the circuit is derived from an external + 12V bench supply. The input and output coupling capacitors are soldered directly to BNC sockets. The earth lugs on the sockets a,;e soldered to the groundplane on the PCB. Because the unit will be operating up to UHF, it is important that lead lengths be kept to a minimum. By mounting components on the copper side of the PCB blank as shown in the coded photograph (Fig.2), lead lengths can be kept to practically zero. A useful aid to construction is a pair of tweezers, which can be used to hold components in place as they are soldered. Do not be afraid to apply sufficient heat to component leads to ensure a good soldered joint. Most semiconductors are rated at 300°C within 2mm of the 74 SILICON CHIP semiconductor junction for 15 seconds or so, which is ample time to ensure a good connection. A simple probe can be made by terminating a 120mm-length of RG58 cable in a BNC connector (Fig.3). At the other (sniffer) end of the cable, strip back 30mm of the outer sheath and braid from the inner conductor. A short length of heatshrink tubing can then be shrunk over the end of the sheath and braid. This will prevent the earthed braid from coming into contact with components that are above ground potential. The unit should ideally be built into a metal case but you could also use a plastic zippy case coated internally with conductive nickel spray, to provide shielding. However, we did not find shielding necessary and simply mounted the unit in a standard plastic jiffy case (see parts list). You will have to drill holes in either end of the case to accept the input and output BNC sockets. Once these have been mounted, the PCB assembly can be dropped into position and secured by soldering the earth lugs on the BNC sockets to the groundplane. The free ends of the input and output coupling capacitors are then soldered to the centre terminals of the sockets. The prototype was powered from an external 9-1 ZV source via a twin-core cable fitted with banana plugs (for connection to a bench power supply). The other end of the cable passes through a grommetted hole in the side of the case. Terminate the leads as shown in Fig.2 and don't forget the ferrite bead over the positive lead. Alternatively, you can fit a 3.5mm DC socket so that the unit can be powered from a DC plugpack supply. Another option is to power the unit from a 9V battery housed inside the case. If this option is chosen, an on/off switch should be fitted as the quiescent current is around 40mA. ~ THE ELECTRONICS MAGAZINE FOR THE ENTHUSIAST WE INVITE BECOME You To A SUPPORTER We believe that electronics is a fascinating pursuit, and the most useful hobby that anyone can have, particularly for a young person in school. Anyone with a good grounding in electronics is better prepared to meet the challenge of today's and tomorrow's technology. Because we believed that many more people should 'come to know about and enjoy electronics, we decided to start a new magazine expressly for electronics enthusiasts, whether they be nervous beginners or seasoned veterans. We called it SILICON CHIP, a name which focuses on the very basis of today's electronics technology. We started SILICON CHIP as an independent magazine completely free from the influence of any existing publishing company, because we wanted to establish the highest possible standards for accuracy and attention to detail. Our team is very small: founders Leo Simpson and Greg Swain, plus full time staff members John Clarke and Bob Flynn. SILICON CHIP has now been on sale for seven months and has been very well received. Even at this early stage, you, the readers, have clearly indicated that SILICON CHIP is the most entertaining and best produced electronics magazine in Australia. Considering the hard work in getting started, it has been a very gratifying response. But we want to make SILICON CHIP even better. To do this, we need the resources to employ more people; we need the services of technical illustrators, writers, designers and other creative people. This is the only way that we can be sure of attaining the highest possible editorial standard. We know this is what you want. Your letters tell us. But we can only do this with your enthusiastic support. Already, many hundreds of readers have taken out subscriptions to give SILICON CHIP a solid start but we we would like to have thousands more. If you haven't already done so, please give us your vote by becoming a subscriber. By doing so, you will be ensuring the future of an entertaining, informative and independent SILICON CHIP magazine. Regular Features Projects For * Constructional The Enthusiast Review * HiFi Digital Electronics Course * Circuit Notebook * Vintage Radio * Junie Mail The Serviceman's Log * Amateur Radio, by Garry * Cratt, VK2YBX The Way I See It, by Neville * Willams * Book Reviews Most magazines sell their subscriber list to mail order companies, to earn extra income. We will not do this. We will lose some money by adopting this policy but we believe that your privacy ·is paramount. BECOME A SUPPORTER BY FILLING OUT THE POSTAGE FREE SUBSCRIPTION COUPON OVERLEAF ► JUNE 1988 75 FREEPOST SUBSCRIPTION COUPON BACK ISSUES To: Freepost 25, Silicon Chip Publications, PO Box 139, Collaroy Beach, NSW 2097, Australia. NO POST AGE STAMP REQUIRED IN AUSTRALIA NAME (Mr/Mrs/Ms) .................. ... ......... ...... ..... .... ...................................... . STREET ...................................................................................................... . SUBURB/TOWN .......................................................... POSTCODE ........... .. 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Subscription cost: 1 year (12 issues) 2 years (24 issues) Within Australia □ $42 □ $84 Overseas surface mail □ $62 0 $124 Overseas air mail □ $120 □ $240 Enclosed is my cheque or money order for$ ........... or please debit my D Bankcard D Visa Card No ...................................................................................................... . Signature .................................................. Card expiry date ...... ./ ...... ./ ....... Subscription to commence in ..................................................................... . I I ! I I I I I I I I I I ----------------------, GIFT 2 to: NAME (Mr/Mrs/Ms)......................................................................... ... ........ STREET. .. .......................................... ...... ................................. .... ............... SUBURB/TOWN .......................................................... POSTCODE............. Subscription cost: 1 year (12 issues) 2 years (24 issues) Within Australia D $42 D $84 Overseas surface mail □ $62 □ $124 Overseas air mail □ $120 □ $240 Enclosed is my cheque or money order for$ ........... or please debit my D Bankcard D Visa Card No............................ ............... ...................................... ...................... Signature ......... ...................... ........... ........ Card expiry date ...... ./.. .... ./....... Subscription to commence in ........................................ ·............................. I I I I I I I I I I I I I 76 SILICON CHIP February 1988: 200 Watt Stereo Power Amplifier; Deluxe Car Burglar Alarm; End of File Indicator for Modems; Simple Door Minder; Low Ohms Adapter for Multimeters. March 1988: Remote Switch for Car Alarms; Telephone Line Grabber; Low Cost Function Generator; Endless-Loop Tape Player. April 1988: Walkaround Throttle for Model Railroads; pH Meter for Swimming Pools; Slave Flash Trigger; Mobile Antennas for the VHF and UHF Bands. May 1988: Optical Tachometer for Aeromodellers; High Energy Ignition for Cars; Ultrasonic Car Burglar Alarm; Restoring Vintage Radio Receivers . Price: $5.00 each (incl. p&p). Fill out the coupon on page 1 9 (or a photostat copy or letter) and send it to: Silicon Chip Publications, PO Box 139, Collaroy Beach, NSW 2097 . LIMITED NUMBERS OF BACK ISSUES ARE AVAILABLE SO DON'T x._ ____ ------------------------' Note: photocopy this coupon if you don't wish to cut the magazine, or include the relevant details in a letter. Issue Highlights n_E_L_A_Y_..;___ __, 2GHz digitising oscilloscope The new Philips PM 3340 advanced digitising oscilloscope offers a 2GHz signal acquisition and nieasuring capability, combined with an ease of use comparable with that of conventional lower frequency instruments. Based on the sequential sampling principle, the FM 3340 measures, analyses and stores recurrent input signals from 1mV upwards. High accuracy measurements are assured by a 10-bit resolution, coupled with 510 measuring points along the time axis. As a result, the instrument is ideal for high-speed electronics technologies such as EGL and advanced CMOS. A high dynamic range allows signals of over 1V to be investigated on a scale of 1mV/div, while the in- Precision oiler for electronic equipment Here's a useful little item if ever there was one. A precision oiler about the size of a fountain pen, it has a long tip for poking into inaccessible p_oints in a chassis. It is very handy for putting just the right amount of oil into motor bearings and so on. It is also ideal for lubricating tools, model locos, loys and electric appliances. The oil itself is claimed to be specially processed to perm an en tl y disperse microminiature particles of Teflon and Fluon. It also contains detergents to give it a penetrating action to free nuts, bolts and bearings. Available from all Tandy i I stores, the precision oiler is just $3.19. strument's "running average" mode eliminates noise at this level of gain and yields a clean, sharp display. Along the time axis, pre and post-triggering facilities allow signals before and after the trigger moment to be displayed. Various dedicated processing modes are provided for including a useful save/stop difference function, which allows an input signal differing from a stored reference to be detected and stored in memory for later examination. A full range of mathematical functions is also available, while built-in IEEE-488 and RS-232C interfaces render the PM 3340 highly compatible for computer control and data downloading. There is much more but, for further details, contact George Sprague on (02} 925 3333 or Graham Blanchett on (02} 888 8222. Low current LED displays Siemens has released two new 7-segment LED displays which typically only require 2mA per segment, making them eminently suitable for portable or batterypowered equipment. With a forward voltage of 1.9V, the displays can be directly driven by a CMOS micropocessor, CMOS gates and LSTTL (low power Schottky TTL}, and are available in common anode or common cathode versions, in red or green. Light output is 600 microcandelas per segment. Relevant type numbers are HDN-1105, 1107, 1131 and 1133. For further information. contact the Electronic Components Dept, Siemens Ltd, 544 Church Street, Richmond, Vic. 3121. Phone (03) 420 7315. Wire wrapping tools from Geoff Wood Geoff Wood Electronics are offering two different tools to facilitate wire-wrap connections. The " Just Wrap", for 0.63mm JUNE 1988 77 Micronta digital fever thermometer About the size of a traditional fountain pen and powered by a small internal battery, the Micronta digital thermometer displays body temperature directly in degrees centigrade. ·when slipped out of its case, and switched on by depressing the power button once, it normally displays "Lo". The sensing tip . is then placed under the tongue or armpit and the readout shows a flashing "C" as the temperature gradually rises. After about one minute under the . tongue or three minutes under the armpit, the flashing should cease and pressing the power should display the normal body temperature of 34.5 degrees. If the body temperature is higher than 3 7 degrees, a red warning is displayed. Depressing than plastic, it is described as a wire "wrapping/stripping unwrapping tool" and is also for use with 0.63mm square posts. Again, instructions for use appear on the rear of the pack. It is priced at $29.90 and despite its name, would appear to be intended as much for casual professional use as for hobbyists. Geoff Wood Electronics Pty Ltd is at 229 Burns Bay Rd, Lane Cove West, NSW (PO Box 671, Lane Cove 2066). Phone (02) 427 1676. Stereo headphones in a handy pack square posts, is manufactured by the OK Machine & Tool Corp, USA, and is priced here at $11.95. Moulded from blue plastic, it comes complete with a spool of insulated wrapping wire, as pictured. Instructions on the flip side of the blister pack explain the routines for both point to point and daisy chain wiring and indicate that refill spools are available with blue, red, yellow and white insulated wire. The "Hobbywrap" wire wrap tool is made in Japan for OK Industries Inc of New York. Quite small and made of metal rather 78 SILICON CHIP If headphones pose one common problem, it could well be where to store them when not actually in use. Left in the open they are untidy and collect dust; in a drawer they often take up more room than can be spared. The Arista EPS-200 "Digital Stereo Insidephone" offers a way around this problem in that they can be tucked into a softpack the switch once more switches the unit off. Automatic switch-off occurs anyway after 30 minutes. The Micronta thermometer is available from Tandy stores at $29.95, battery included. small enough to be hidden out of sight on a shelf or in a drawer. The description "Insidephone" relates to the fact that they are inserted directly into the respective ears, without need for a headband. Arista point out, however, that they are genuine dynamic types, with a tiny moving coil system and diaphragm in a chamber behind the earplug. The nominal impedance is 32 ohms, making them eminently suitable for use with most current hifi equipment, with either analog or digital source signals. The quality of reproduction is very good, particularly in view of the modest price - $39.95. The EPS-200 phones (those pictured are wrongly branded as ESP-200) are fitted with a rightangle 3.5mm stereo phone plug. After use, the phones can be stored as shown and the cord wound neatly on the spool by turning a small handle on the rear of the case. They are available from Arista outlets but for more information contact Arista Electronics Pty Ltd, 5 7 Vore St, Silverwater, NSW 2141. Phone (02) 648 3488. TDK releases five new video tapes TDK (Australia) Pty Ltd have announced the release of a new super quality 8mm video tape, available in 30 - , 60 - and 90 - minute cassettes and retailing respectively for $18.95, $22.95 and $27.95. The new MP-8mm tape uses an iron formulation of the "highest purity and density" known as "Super Finavox", and said to offer the highest BET value of any tape in consumer use in the world. (BET is a unit of measurement indicating the size of the formulation particles. The higher the BET value, the smaller the particles and the better the tape). IDK produced the first ever 8mm video tape in 1984 but, for this new product, they claim: • Smoother tape surface, resulting in lower modulation noise; • Higher RF output for improved video performance; • Five layer construction for reliability in all 8mm equipment; • Wider dynamic range and sonic purity. The last of these claims refers to FM soundtrack recording, where the high packing density and surface smoothness ensures very low modulation over the FM band, as recorded. The tape is also eminently suitable for PCM digital sound recording. TDK also forsees a bright future for the VHS-C format and draws attention to their new E-HG and HDXPRO tapes, available with a 30-minute playing time, at normal speed, and retailing respectively for $18.95 and $29.95. The E-HG is an excellent general purpose fomulation, suitable for both indoor and outdoor filming, able to withstand heavy usage and capable of delivering excellent pictures in the LP mode. With a BET figure of 50m2/g, the HD-XPRO tape is claimed to be the highest quality of any tape in the VHS-C format, ideally suited for original mastering or as a master tape suitable for editing. Elegant storage for integrated circuits Do you have large numbers of different integrated circuits. This elegant storage system from Jaycar consists of interlocking plastic cabinets holding six drawers each. Each drawer can be divided up into 30 small compartments, big enough to hold just one IC. The drawer comes with a lid which can be slid off to expose the compartments progressively so the risk of dropping all the ICs on the floor is minimised. Sound like a good idea? Check it out at your closest Jaycar Electronics store. JUNE 1988 79 PT.8: THE FIRST THREE-PHASE AC ELECTRIC RAILWAY THE EVOLUTION OF ELECTRIC RAILWAYS Since so many of the world's electric railways ore powered by high voltage AC, it is surprising that more countries did not try using induction motors. One country that did recognise the advantages was Italy. By BRYAN MAHER Up to the year 1900, railways were almost entirely steam powered and little heed was given to the few electrified lines then existing. These were all short DCpowered systems, working at voltages in the range 250 to 750 volts. Many were quite small, from the famous Volkes Electric Railway (world's oldest and smallest work- ing electric line) at Brighton, England, to the growing suburban underground or elevated systems of big cities such as London, New York and Chicago. The Union Passenger Railway built at Richmond, Virginia, in 1887 was the first electric line in the USA, and a world-first venture into longer electric systems. Elsewhere LAMINATED STEEL POLES AND MOTOR YOKE vmu SERIES AELD AC SUPPLY 200V-1kV 16.6Hz ~ ARMATURE REVERSING SWITCH Fig.2: the series traction motor is so named because its fields are in series with the armature. To reverse the motor, the connections to the armature (or to the field coils but not both) are swapped by means of the reversing switch. 80 SILICON CHIP Fig.1: AC series motors use a core made of laminated steel sheets, each insulated from the next by an iron oxide scale. This breaks up eddy current paths and reduces power losses. on the world scene, a small difficult section of (otherwise steam) main line might be electrified, such as a world-first at Baltimore, USA where the tunnel district was electrified in 1895. But, for the most part, the railway magnates of the world ignored such ventures into electric traction. Instead, they concentrated on more serious matters, like steam locomotive traction. High voltage AC As we saw last month, the BernLotschberg-Simplon Railway (the famous BLS) of Switzerland came to the notice of the railway world in 1906-1913 when they built the first full-size electric standard gauge heavy-haul main line through extremely difficult mountainous terrain. Their choice of single-phase high voltage alternating current (15kV, 16.6Hz) was innovative, showing that properly designed series motors worked very well on a low frequency AC supply. Furthermore, by carrying a large transformer on Fig.3(a): sectional view of an industrial 3-phase AC squirrel cage induction motor. The 3-phase stator winding produces a rotating magnetic field which is followed by the rotor because of the current induced into the rotor's copper bars. (Photo courtesy General Electric). the locomotive, they could use voltages as high as 15kV (and consequently lower currents) on the overhead contact wire. The onboard transformer then stepped down the high voltages to any convenient lower voltage, between 500 and 1000 volts, for the controllers and motors. of iron-oxide, which breaks the eddy current path and greatly reduces the eddy current problem. Provided the series AC motor is run on low frequency alternating current, the interpoles [described last month) work satisfactorily and the motor's brushes run without commutator-to-brush arcing. Series motors on AC Note that the single-phase AC series traction motor is a straightforward development of the series DC motor. The only real difference between the two types is that in the AC series motor all the iron in the magnetic path is laminated steel, to avoid eddycurrent heating and power loss in the iron. Eddy currents are caused by stray voltages being induced in the iron itself by the presence of alternating current fields in the motor. Because the iron has a very low resistance, very large stray currents flow in "eddies" in the iron, causing heating of the iron and resultant power loss. So, instead of solid iron being used for the cores of the field coils and the magnetic pathways of the frame, a laminated assembly of many sheets of steel is used. Each steel sheet is insulated from the next by the natural scale Fig.3(b): end view of the 3-phase stator coils of a squirrel cage AC induction motor, with rotor removed. (Photo coutesy General Electric). Perhaps you might wonder how the AC series motor runs correctly even though the supply is reversing in polarity (ie, current direction reversing) every 60 milliseconds? Why doesn't the motor rotate backwards-and-forwards on each cycle. The answer is that the motor's direction is determined by the relative direction of currents in both the armature and field coils. During each AC half-cycle the currents in both reverse at the same time, so there is no change in the direction of rotation. When the train driver wishes to reverse the train, his reversing switch swaps the connections to either the armature or fields (but not both). However, in common with its DC counterpart, the AC series motor still has a commutator and brushes, which do become dirty and oily with use, and wear out. Maintenance is a necessity. The DC motor, based on the inventions of Michael Faraday of England in 1831, was further developed by Frank Sprague of the USA in 1884. This gave Thomas Edison encouragement to push for DC to be chosen for electric railways, street lighting, and domestic and industrial power. AC induction motor In that same year, 1884, a Hungarian electrical engineer, Nikola Tesla (1856-1943) had migrated to the USA. Four years later he took out a US patent on an electric motor which had no need of a commutator or brushes, because of his clever application of the laws of alternating currents. By using a 3-phase AC supply (rather than single-phase), Nikola Tesla invented a method whereby the AC currents flowing in three sets of coils in the stator (stationary part) produce a rotating magnetic field. A rotor (rotating part) carrying closed-circuit coils will have currents induced in these coils. Such rotor currents interact with the stator magnetic fields , causing the rotor to follow the rotating magnetic field of the stator. Thus the rotor rotates, even though there is no direct electrical connection to the rotor coils. Because it works by induced JUNE 1988 81 TWIN OVERHEAD CATENARY WIRES BONDED \ TOP CATENARY WIRES " +3kVDC OVERHEAD WIRING DROPPERS - - - PHASE A " ' - / OVERHEAD CONTACT WIRES \.: / PHASE A PANTOGRAPH PltASE B - PHASE B PANTOGRAPH BOTH CONTACT WIRES ._,/ +3kVDC ""' ----------◄- - 3-PHASE ELECTRIC LOCOMOTIVE CABIN 3kVDC ELECTRIC LOCOMOTIVE CONTROL NEGATIVE RETURN j FORCED AIR FAN \ INSULATORS CONTROL 3-PHASE CABLES TO TRACTION MOTOR BEARING ONE EXTRA-WIDE PANTOGRAPH TO CONTACT BOTH OVERHEAD WIRES DC 3kV TRACTION MOTORS 3-PHASE AC TRACTION MOTORS SLEEPER BOTH RAILS BONDED MAKE NEGATIVE OF 3kVDC SUPPLY RAILS BONDED TOGETHER FORM PHASE C Fig.4: end view sectional diagram of a 3-phase AC electric locomotive. Two overhead contacts provide phases A and B while the bonded rails supply phase C. The motor is very simple but speed control is difficult. rotor currents, this type of motor is called an AC induction motor. Nikola Tesla sold the rights of his motor patent to George Westinghouse (!846-1914), an American inventor (whose name we have heard before as the inventor of the Westinghouse rail air brake). It seems that Westinghouse and his company advocated AC power reticulation to homes and factories, in competition with Edison's DC systems. Tesla's AC induction motor gave the Westinghouse company a big advantage. Together with the development of the transformer, this led to the success of the Westinghouse Company in the highly competitive electricity business. 82 SILICON CHIP Fig.5: conversion of the old 3-phase AC system to a 3kV DC railway was accomplished by bonding both overhead wires together and connecting them to a 3kV DC supply. The bonded rails form the negative return. High voltage 11kV 3-phase 60Hz AC power lines could run long distances to American suburbs, there to be transformed down to 110 volts for homes and factories. Unfortunately, both DC and AC systems were installed in competition in many cities around the globe. Where AC was installed, various frequency systems were adopted in different cities and countries. Most of the USA uses a 60Hz supply, most of Europe, Australia and many other countries are on ·50Hz, and some like Japan have both 50Hz and 60Hz systems. The shrinking world still suffers from the resulting incompatibilities. But DC system advoc;ates did not give up easily. Hundreds of towns in the USA and elsewhere were wired for DC, before the advantages of AC power systems for general use became widely recognised. (Some readers may even remember shops in York Street, Sydney having DC mains and appliances as late as the 1950s). In some countries a few very forward-thinking people tried experimenting with alternating current quite early. As early as 1899, some railway engineers in Italy wanted to test AC induction motors for traction purposes. The Italian steam locomotives of the day, innovative though they were, needed imported coal supplies, while northern Italy, with its high mountains, lakes and fast snow-fed rivers had the potential for great hydroelectric power systems. Such power stations must be built in the mountains, but the proposed railway electrification was required hundreds of kilometres away, down in the cities. Three phase AC traction motors Therefore the engineers chose 3-phase high voltage AC as their system, with transformers at appropriate locations to step down the voltage to usable levels. That took care of distribution but then there was the problem of using the new 3-phase induction motors for traction. They installed a complex system of overhead wiring above some of their existing rail tracks to supply three phases to a specially built electric locomotive. Two separate overhead wires supplied two of the phases, while the running rails were bonded together to supply the third phase. The roof-top pantograph was in two insulated sections, each separately in contact with one overhead wire, but kept clear of the other. The gyrations of the pantographs in keeping contact with only the correct wire (and not shortcircuiting both overhead wires at crossovers and points) was an example of ingenious Italian engineering. BEARING/ THREE COILS/ ON ROTOR I ____ STATOR THREE COPPER SLIP RINGS ON INSULATED CENTRES __, Fig.6: a 3-phase wound rotor induction motor has three coils wound on the rotor which are connected via sliprings to three stationary speed control resistances. When all resistances are in circuit, the motor runs at low speed and develops greatest torque. Constant speed motors The induction motor does have one big problem though - its "synchronous speed' '. Synchronous speed is the constant speed of rotation of the motor's magnetic field, and is fixed by the frequency and the number of motor poles. For instance, a 2-pole motor on a frequency of 50Hz has a synchronous speed of 3000 RPM (ie, 50 revolutions per second). Some possible supply frequencies and corresponding motor speeds are shown in Table 2. When on full load the rotor always wants to rotate at about 96% of the synchronous speed. The fact that an induction motor rotor tends to rotate at the one fixed speed is excellent for driving factory machines such as lathes, grinders, planers, air compressors Fig.7: a DC industrial motor with the top half lifted to show the brushes, two main poles and one interpole. The armature and remaining two poles are in the lower half. (Photo courstesy General Electric). etc. But this one-speed property is not much good for trains. Also the starting torque of a simple induction motor is not very high, maximum torque being attained after accelerating to about half the synchronous speed. Nevertheless, the attraction of simple low-maintenance traction motors and cheap trackside substaJUNE 1988 83 Table 1: Notable Electric Railway Dates Date State/ Country Railway System 1842 Scotland E&G DC 120V (battery) Robert Davidson built the first electrically powered railway vehicle 1879 Germany Siemens DC First electric railway to carry paying passengers (demonstration only) 1880 England Volkes DC World's oldest and smallest permanent electric railway 1890 England London DC 750V third rail London tube, underground and Southern, suburban electric railway system 1900-28 Italy FS AC 3-phase Largest ever 3-phase railway 1906-13 Switzerland BLS AC 16.6Hz 15kV World's first full size electric main line railway 1912 Great Northern AC 25Hz 5000 HP loco, 214km of electrified track in Rockies USA Details 1914-20 USA Milwaukee DC 3kV First US railroad to electrify 400km main line 1915-22 Sweden Lappland AC 15kV 15 & 16Hz 9500 HP rod drive locos pulling 5000 tonne iron ore trains 1918-25 Switzerland SBB AC 15kV 16.6Hz Swiss Federal Railway all main lines electrified 1'919-23 Norway Lappland AC 15kV Norwegian end of Lappland line electrified 1919 VA DC 1.5kY First electric train in Australia 1920-34 France Midi DC 1.5kV Electrified all the south-west of France 1920-22 Germany DB & DR AC 15kV 16.6Hz First German main line to be electrified 1922-70 Norway NSB AC 15kV 16.6Hz All Norwegian lines except Bodo line electrified 1923 Victoria VA DC 1.5kV First electric locomotive in Australia (coal lines) 1926 NSW SRA DC 1.5kV Sydney suburban electric railway and underground 1929 USSR USSR Railway DC 3kV & AC 25kV Russian railways commence electrification (mixed AC and DC) 1980 Switzerland to Austria AC 15kV 16.6Hz International system still in use 1930 USA Virginia AC 11kV 25Hz Virginia Railway electrified mountain coal lines, strongest ever locomotives 1930 USA Penn AC 11kV 25ttz Pennsylvania Railroad commenced electrification :1932-81 USA Penn AC 11kV 25Hz General Electric "GG-1 ", the first and most longlived high speed electric express locomotive ,1934 USSR USSR Railway DC 850V Moscow metro underground electric railway commenced 1934 France Midi DC 1.5kV Completed electrification all Midi lines, SW France 1950 France SNCF AC 25kV Construction commenced for North and East of France 1979 Old QR AC 25kV 50Hz Brisbane suburban electric railway (first high voltage AC railway in Australia) 1986 Old OR AC 25kV 50Hz Delivery of first 25kV AC locomotive in Australia (July 1986) 1986 Old Seaworld AC 415V 50Hz First monorail in Australia '1986 Old OR AC 25kV 50Hz Opening of Gladstone-Rockhampton-Blackwater electrification (6th September 1986); first long distance AC high-voltage electric railway in Australia Victoria ' 84 SILICON CHIP tions (consisting of simply a 3-phase transformer and protection) was considerable. Thus, the Italian 3-phase electric railway began in a small way in the year 1900. Wound rotor induction motors An alternative construction for a 3-phase induction motor is to install three windings on the rotor, connected to three shaft-mounted sliprings, which have stationary carbon brushes. These brushes carry the rotor currents out from the motor to three external variable resistances. Shorting out these three resistances results in the motor running at 95 % of synchronous speed, but with some resistance in circuit the motor runs at a slower speed. More resistance still results in still lower motor speed and more shaft torque. When a value of external resistance is selected such that all the resistance in the rotor circuit (rotor winding plus external resistance) is numerically equal to the inductive reactance of the rotor winding at line frequency, then the induction motor develops its maximum starting torque. For electric locomotive applications, this condition results in maximum starting drawbar-pull; ie, highest locomotive pulling force. This, of course, is the best choice for starting a heavy train. So effective did the Italian 3-phase AC railway become that the system was continually extended. It replaced steam locomotives on many lines and became the world's largest and most successful 3-phase electric railway system, lasting until 1971. However, the difficulty of building the double overhead contact wire installation, especially over the complex trackwork at the approaches to large city terminal stations, produced much engineering opposition, and for good reason. Also all induction motors always have a fixed top speed, as shown in Table 2, which restricted the running speed of trains. Italy adopts 3kV DC Because of these objections, all new Italian railway electrification Table 2: Induction Motor Synchronous Speeds Frequency Number of Poles 50Hz 50Hz 50Hz 50Hz 50Hz 25Hz 25Hz 25Hz 25Hz 25Hz 16.6Hz 16.6Hz 16.6Hz 16.6Hz 16.6Hz 2 4 6 8 12 2 Synchronous Speed 3000 1500 1000 750 500 1500 750 500 375 250 1000 500 333.3 250 166.7 4 6 8 12 2 4 6 8 12 undertaken after 1928 used the 3kV DC system, despite the extra maintenance necessitated by the DC series motors with their commutators and brush gear. The 3kV DC system gradually took over lines previously constructed as 3-phase AC systems, beginning at the city of Genoa in 1928, until all AC lines were converted to 3kV DC by 1971. The conversion from 3-phase AC to 3kV DC was done initially by removing the 3-phase AC supply, and bridging the two previouslyseparate overhead wires together (without physically moving them) to become a common positive 3kV overhead conductor. Then each DC electric locomotive was equipped with a rooftop pantograph wide enough to run in contact with both overhead wires, as shown in Fig. 4. The DC return current flows (as usual) via the running wheels and rails. Of course all new installa- . , ~ ~ 0 RPM RPM RPM RPM RPM RPM RPM RPM RPM RPM RPM RPM RPM RPM RPM tions used a single overhead contact wire for the positive 3kV DC conductor. In the early part of this century the electric railways of the world were poised to proliferate, but as Table 1 shows, many and varied were the voltages and frequencies adopted by different countries and systems. AC and DC systems will continue to have their devotees throughout this century, and maybe well into next. Next month, we will again consider high-voltage AC single-phase low frequency railway systems. Acknowledgements Thanks to ASEA/Brown Boveri, SBB (Swiss Federal Railway), BLS (Bern-Lots c h be r g-Simpl on Railway), SJ (Swedish Railways), FS (Italian State Railway), and GE (General Electric Company, USA and Aust.) for data, photos and permission to publish. ~ J)~ ·-✓• g ·$ g ~~ ....~&.nn11fl.■111~lli111 RCS Radio Pty Ltd is the only company which manufa.ctures and sells every PCB & front panel published in SILICON CHIP, ETI and EA. 651 Forest Road, Bexley, NSW 2207 Phone (02) 587 3491 for instant prices 4-HOUR TURNAROUND SERVICE Bookshelf continued from page 51 Specifications listed include supply and temperature maximums, gain, offset voltage, input current, slew rate, input impedance, CMRR (common mode rejection ratio) and PSRR (power supply rejection ratio). Finally, there are several appendices which include a glossary of op amp terms, abbreviation codes, manufacturers' lettering designations and case outline and pin-out diagrams. In summary, a very useful book for checking out unknown or obscure devices, or when a device is unavailable and an equivalent is wanted. Our review copy came from Dick Smith Electronics. Copies are available from Dick Smith stores. Digital IC selector handbook Towers' International Digital IC Selector, by T.D. Towers. Published 1987 by Manish Jain for B. P. B. Publications, 376 Old Lajpat Rai Market, Delhi, India. Soft Covers 246 pages, 175 x 243mm. This selector for digital ICs provides information on 10,000 separate digital devices. It covers devices from the USA, UK, East and West Europe, and Japan. The ICs are listed in alphabetical order with descriptions of IC operation and control specifications. Information is given for the type of IC (CMOS, TTL, ECL, etc), its use and description, the type of casing, supply voltage, temperature, speed, pin-out, manufacturer and substitute device. Diagrams are shown for pin-outs of each device in the appendices . The usefulness of this reference can be limited, particularly when information is required for design purposes. However as a source of information on IC function and operation, the book is excellent. For more detailed information on particular devices, the reader should refer to manufacturers' data. Our review copy came from Dick Smith Electronics. Copies are available from Dick Smith stores.~ JUNE 1988 85 DIGITAL FUNDAMENTALS We get into the heart of the microcomputer to discover what makes it tick. LESSON 8: INTRODUCTION TO MICROCOMPUTERS By Louis E. Frenzel AS YOU HAVE SEEN in previous lessons, digital circuits are a collection of gates and flipflops wired together to accept binary inputs from some source, process them, and generate one or more new outputs that will perform some useful function. There is nearly an infinite variety of ways that the various logic elements can be interconnected to process the inputs. The process itself may be nothing more than simple decoding or multiplexing performed by a combinational circuit. Or the circuit may be the more complex sequential type that performs various timing and sequencing operations. In either case, as shown in Fig.1, we can represent the circuit with a "black box." The inputs can come from a variety of sources: from a keyboard, switches of one type or another, transducers that sense various physical values, or binary information from some other piece of equipment that may be under test, evaluation or analysis. The outputs may operate displays such as LEDs, LCDs or CRTs; or drive actuators such as relays, solenoids or motors. Or they may simply be binary words that will be transferred to another piece of equipment for storage or further manipulation. So far, we have assumed that the digital circuits would be made up of individual integrated circuits: gates, flipflops, functional MSI (medium scale integration) circuits, PLAs (programmable logic arrays), or other LSI or VLSI circuits. The circuit may be combinational, sequential, or a mix of the two. However, there is an option to using conventional logic circuits, and that option is called a microcomputer. In this lesson, we are going to discuss microcomputers and show how they can be used to replace large collections of more conventional digital !Cs connected to form a custom circuit for some dedicated ap86 SILICON CHIP plication. In subsequent lessons, we will cover microcomputer input/output techniques and programming. What is a Microcomputer? A microcomputer is a miniature digital computer made with an LSI (large scale integration) circuit, which contains most of the circuitry ordinarily associated with a digital computer. This special LSI circuit is known as a microprocessor. We will speak more about microprocessors in just a minute, but first let's talk about digital computers in general. A digital computer is an electronic device that processes data. Data, of course, refers to binary words or numbers to be used in calculations, or information that must be stored or retrieved, such as ASCII text. Or the data may be simply random collections of binary signals that represent input information that must be processed in some way. Processing refers to the way data is manipulated. In its simplest form, processing may simply refer to the storage and retrieval of the data. Other kinds of processing might be mathematical operations, like addition or subtraction, or logical operations such as AND, OR, XOR and inversion. Processing may also mean Fig.1: when we are interested primarily in input and output signals, we can use a "black box" to represent some kind of digital circuit, combinational or sequential, that processes the inputs to generate new outputs. operations such as searching, sorting, editing or pattern matching. Digital circuits, as we have defined them in this series, meet this definition because they process data, and they may be designed to perform any of the abovementioned functions. Although a digital computer can perform the same functions, it does so in a different way. The key element in the definition of a digital computer is that the processing or manipulation takes place automatically. The digital computer is set up by programming, which specifies the way in which the data is going to be processed. We can accomplish our processing objective by replacing the black box in Fig.1 with a digital computer. The processing is automatic and preprogrammed. Classifying Digital Computers There are three basic types of digital computers: mainframes, minicomputers and microcomputers. Mainframes are the large computers used in business and government for large data processing tasks: they are used for financial and accounting systems, storage, retrieval and manipulation of customer credit files, airline reservations, and the like. Mainframes are super fast in their processing and store enormous amounts of data. Minicomputers are smaller than mainframes but are still very large and powerful. Because of their very high speed, they are generally associated with problem-solving in scientific and engineering applications. However, they are also used for business data processing and other functions. Microcomputers are the smallest classification of digital computers. They are low in cost and small in size. The most visible type is the personal computer which is used for a wide variety of data processing operations. The type of microcomputer we are most interested in, for the purpose of this series, is a special version usually ref erred to as a dedicated controller. This type of microcomputer is designed to perform a specific function. Unlike a personal computer, it is not general purpose in nature and cannot be used with a variety of software packages. Instead, this kind of microcomputer is built into the piece of equipment and is difficult to distinguish from the hardware itself. It is simply the control circuitry for the equipment that happens to be implemented by the microcomputer. In other words, the microcomputer replaces conventional logic circuitry that otherwise would have been implemented with individual gates, flipflops and MSI circuits. Dedicated microcomputer controllers are found in all kinds of equipment, such as TV sets, stereo hifi systems, auto dashboards and emission control systems, photocopiers, and so on. In any case, the key distinguishing characteristic of a microcomputer is that it is implemented with a special LSI device known as a microprocessor. Digital Computer Organisation As shown in Fig.2, a digital computer is made up of four basic sections: the memory, the control section, r CENTRAL PROCESSING UNIT (CPU~ I _ _ _ _ _..;.,__ MEMORY II CONTROL I.......,,._..,...... I I ________ ! _ .._ I I I I I INPUT/OUTPUT (l/0) I ARITHMETIC/LOGIC SECTION l... - - - - - - _.ll-----t'\. "-r------,1' I I _J DATA SIGNALS TO EXTERNAL DEVICES TO BE CONTROLLED OR MONITORED Fig.2: regardless of its type, a computer is made up of four sections - the memory, a control section, an arithmetic/logic unit, and an input/output unit. The control section can be a central processing unit (CPU), or a microprocessor. the arithmetic logic unit, and the input/output unit. Let's take a brief look at each of these sections. Memory The memory in a microcomputer is usually a combination of both RAM and ROM (see Lesson 7 in this series). This memory is used to store two types of information: data and instructions. Data represents those binary numbers or words that are to be processed. They may be numerical values, ASCII codes for the text of a written document, or simply random collections of binary signals that represent inputs or outputs that are collected and organised as binary words. In any case, it is the data words stored in the memory that will be manipulated by the computer. Instructions, which are stored in either RAM or ROM, are unique to computers. They are special binary codes that tell the computer how to manipulate the data. For example, an instruction may be an 8-bit binary number. With eight bits, 256 different instructions could be represented, which might specify arithmetic operations such as addition and subtraction, a logical operation such as AND or XOR, or data movement operations that cause binary words to be moved into or out of memory or cause transfers between registers. All computers have a special repertoire of these special codes known as an instruction set. They define the architecture of the computer and provide a wide range of ways in which the data can be manipulated. To process data, a number of instructions are written sequentially and stored in memory. Such a sequential list of instructions is called a program. A program defines a specific sequence of operations that process the data in some way. The purpose of the computer is to sequentially interpret and execute these instructions stored in memory and this, in turn, accomplishes the processing. JUNE 1988 87 This approach to digital processing is generally known as the stored program concept. It was invented by mathematician John Von Neumann and is the basis of operation for all digital computers. Control The control section of the digital computer fetches the instructions stored in memory one at time, interprets them, and executes them in sequence. The control unit gets one instruction from memory, decodes it and determines which function is to be performed next. It then issues control signals to the other sections of the computer so that the specified operations are carried out. Arithmetic-Logic The arithmetic/logic section is the section of the digital computer that generally carries out most processing operations. It is usually made up of a set of registers where the data to be manipulated is temporarily stored. In turn, these registers drive an arithmetic/logic unit (ALU), which is a collection of logical circuits which perform mathematical and logical operations. Serial shift and rotate operations can also be performed. It is usually the ALU that receives signals from the control unit to perform the operation specified by the instruction. As shown in Fig.2, the control section and ALU are closely related and interconnected. For the most part, they can be treated as a single block or section. The combination is usually called a central processing unit, or CPU. A microprocessor is simply a single-chip LSI CPU, which is sometimes referred to as a microprocessing unit, or CPU. How a Microprocessor Works Fig.3 shows a block diagram of a microprocessor. This has has been divided into two primary sections: the arithmetic/logic section and the control section. The control section of the CPU contains the instruction register and the program counter. The program counter holds the address of the memory location where an instruction is stored. To execute a program, the program counter is set to the address of the first instruction in the program. The content of the program counter (ie, the instruction address) is then transferred to an address register in memory. The address location is decoded (usually on the RAM or ROM chips) and that location in memory is enabled. The instruction stored there is transferred over the data bus into the instruction register. The instruction decoder looks at the instruction word and identifies the function to be performed. The timing and control circuits in the control section then generate the apDATA/INSTRUCTIONS TO/FROM MEMORY r----------- ---7 I I PROGRAM COUNTER I I I CONTROL SECTION A Typical Microcomputer The typical microcomputer consists of a single chip microprocessor, a set of RAM chips, and one or more ROMs that contain a dedicated control program. The input/output section is usually made with integrated circuits which have been specifically designed to interface the microcomputer to the external circuits or equipment involved in the application. For small, dedicated applications, single-chip microcomputers can be used. These devices contain the CPU, the ROM where the dedicated control program is stored, a small amount of RAM where data can be stored temporarily, and a variety of input/output circuits, which connect to the equipment being controlled. A good example of an application is the microcomputer used in most printers. SILICON CHIP I I TIMING AND CONTROL CIRCUITS The input/output (1/0) section of a digital computer is used to communicate with external circuits and equipment. Inputs to be processed are fed to the 1/0 section and either stored in memory or processed directly by the CPU. Binary words that are to be transferred to some external circuit or device are transferred from the memory or the CPU to the external equipment via the 1/0 section. As you might expect, special input/output instructions to the CPU are used to control the 1/0 section. I I 1/0 88 ADDRESS TO MEMORY I I I CONTROL SIGNALS TO ALL OTHER SECTIONS I r--------------1 I I - - -..✓ I ---II ...'"'ft"-~- I I ALU II I ____ I II II ---ARITHMETIC-LOGIC SECTION JI L....--------------- Fig.3: a CPU generally provides two independent functions - a control section and an arithmetic/logic unit which are interconnected through an external data bus. propriate control pulses that cause the desired action to be carried out. Once the instruction has been executed, the program counter is incremented so that the next instruction in sequence is fetched and executed. This process continues until the program is fully executed. The arithmetic/logic section of the computer consists of a main working register called the ac- 16-BIT REGISTERS 8-BIT REGISTERS 16-BIT REGISTERS 8-BIT REGISTERS PROGRAM COUNTER ACCUMULATOR A REGISTER PROGRAM COUNTER ACCUMULATOR REGISTER INDEX REGISTER ACCUMULATOR B REGISTER INDEX REGISTER X INSTRUCTION REGISTER STACK POINTER INSTRUCTION REGISTER INDEX REGISTER Y STATUS REGISTER CONDITION CODE REGISTER STACK POINTER REGISTER 6502 6800 (b) (a) Fig. 4: although there are differences in the internal architecture of the 6800 and 6502, both use the program counter to point to the next instruction in sequence. cumulator and the arithmetic/logic unit (ALU). The arithmetic/logic section carries out most of the operations designated by the computer's instruction set. All data transfers and arithmetic/logic operations take place in the accumulator. Most arithmetic and logic operations involve two operands. (Operand is just the name of a number to be involved in an arithmetic or logic computation). For example, an add operation involves the two numbers to be summed. One of the operands is stored in the accumulator while the other is stored in memory. The lwo operands are then used in the desired operation. The result of the operation, in this case the sum, is stored back in the accumulator. The operand previously stored in the accumulator is lost. The ALU in most microprocessors is capable of carrying out addition and subtraction as well as the basic logic operations AND, OR, XOR, and complement. Other instructions are used to manipulate data in the accumulator. For example, the accumulator can be cleared (set to zero), incremented, or decremented. Data can also be transferred from a desired memory location to the accumulator or taken from the accumulator and stored in a desired memory location. The arithmetic/logic section also permits data in the accumulator to be shifted or rotated to the right or to the left of a given number of bit positions. Typical Microprocessors Now let's look at a real microprocessor: in fact , we will examine two units which are similar in architecture and design. The first is the 6800 which, although introduced in the mid-1970s, is still in use today. The 16800 was used in some of the earliest personal computers, among them the MITS Altair 680, Southwest Technical Products SWTP 6800, and the Wavemate, but it has now virtually disappeared in this application. However, the 6800 is still widely used as a dedicated controller. The other microprocessor we will look at is the 6502. This CPU was designed by the same group that created the 6800. They left Motorola and developed the 6502 for MOS Technology. The 6502 is an improved or optimised version of the 6800. It too was widely used in personal computers and is still used in personal computers such as the Apple Ile/c and Commodore 64/128. Both the 6800 and 6502 have an architecture and operation that is simple and straightforward. In fact, they are essentially the same as the generic microprocessor described earlier. The 6800 and 6502 are 8-bit microprocessors (all microprocessors are rated or ranked by the basic number of bits they process simultaneously). That is, data transfers and arithmetic or logic operations are made on parallel 8-bit binary numbers or words. The 6800 and 6502 have 8-bit internal registers, an 8-bit ALU and an 8-bit data bus through which all data transfers between CPU, memory and I/O take place. A general block diagram of each of these microprocessors is shown in Fig.4. Note that only the main registers are shown. These will be explained next. CPU Registers The most predominant circuit in a micro (short for microprocessor) is the register, which is capable of storing one binary word. As the data and instruction words are moved from one place to another they are typically passed through or temporarily stored in the various registers. As data is processed, words are transferred into and out of these registers from external sources such as the memory and I/O devices. In addition, inter-register transfers in the micro also occur during processing. All micros have three basic registers: the program counter (PC); the instruction register (IR) and the accumulator (ACC). Fig.4 shows the register structure for the 6800 and 6502. Let's look at each. Program Counter The program counter (PC) contains the address of the next instruction to be fetched. As each instruction in a program is fetched and executed, the program counter is incremented so that it points to the next instruction in the sequence. The program counter also specifies how many bytes of RAM and ROM a CPU can address. The PC's output is sent to the memory where it selects a desired word. In the 6800 and 6502. the PC holds a 16-bit word, therefore, 216 or 65,536 (64K) words of RAM and/or ROM can be addressed. Instruction Register When the CPU fetches an instruction word from memory to be executed, that word is stored in the inJU NE 1988 89 struction register (IR). The word is then decoded to determine which operation is to be performed. In the 6800/6502, the instruction register holds an 8-bit instruction word or an op code as it is called. Accumulator The accumulator is the basic processing register of the micro. Words to be used in arithmetic or logic operations are stored here. Data transfers to or from memory and input/output devices are also passed through the accumulator. Not surprisingly, the accumulator size in the 6800 and 6502 is 8-bits. While all micros contain at least one accumulator register, some have more than one. By using more than one accumulator significant increases in speed can be achieved. Also, programs written for multiple accumulator machines typically involve fewer instructions and less programming effort, which significantly improves use of the available memory space. The 6800 has two accumulators, the 6502 has one. Some CPUs have sets of 8 or 16 accumulators usually called general-purpose registers. All micros feature these basic registers but they also feature additional registers, which further improve operations. Some of these are as follows. Index Register An index register stores a binary word that is used in address-modification operations. Typically, the content of the index register is added or subtracted from the address associated with an instruction. The index register content can be loaded from memory, stored in memory, incremented, or decremented with special index register instructions. This process of using an index register for address operations is called indexing. By using an index register, the number of instructions used in some programs can be significantly reduced. This is particularly true where sequential operations on a list or table of Mailbag continued from page 3 conductor. This arrangement has been prohibited by AS 3000 for some 12 years. The standard now requires that the main earthing conductor be run directly to an earth electrode. Where the water piping is metallically continuous from inside a building to the point of contact with the ground, such piping must be connected by an equipotential bonding conductor to the main earthing conductor. With the increasing use of non-metallic water piping, this bonding may not be necessary. • You refer to the fact that some current flowing to earth will do so via the earth electrode and water pipe as a "previously unconsidered fact". This is simply not true. The advantages and disadvantages of the MEN 90 SILICON CHIP data are to be performed. The 6800 has one 16-bit index register, the 6502 has two. Status Register The status or condition-code register is a group of flipflops that are either set or reset - depending upon the outcome of processing operations in the ALU. As arithmetic, logic or shift operations are performed, the various status flipflops are set or reset to indicate a specific machine state. The status word may be monitored and stored so that the condition of the computer at a given time can be determined. The various flipflops in the status word can also be tested under program control so that the program being executed can be modified. Jump or branch conditions that change the program sequence are usually determined by the information stored in the status register. Some of the conditions monitored by the conditioncode register are arithmetic operations, such as: accumulator equals zero, carry out of the most significant bit of the accumulator, accumulator overflow, and accumulator negative. In the 6800 and 6502, the status or condition code register contains eight bits. Stack Pointer The stack pointer is a 16-bit address register that is used to reference some particular part of the. micra's random-access memory. The stack itself is a specific portion of memory set aside to temporarily store data in a particular sequence. The stack pointer is used to address this data when it is being stored or retrieved. The stack is set aside especially for stack operations and is not used to store ordinary sequences of instructions or data. Nor does it have a fixed size. The number of memory locations used by the stack depends upon how it is used. The stack is a last-in, first-out (LIFO) memory. The data words to be stored in the stack are written and system are well understood by both SAA Committee EL/1, who are responsible for AS 3000, and the Electricity Supply Association of Australia. Every method of earthing has such advantages and disadvantages and is a point which would be conceded by supply authorities throughout the world. • Connections between an earth bonding clamp and an earth electrode may be subject to corrosion as you suggest. However, such connections, where exposed to weather, are required to be suitably protected. Also, the standards for household appliances that are likely to produce DC current, such as TV sets, hair dryers, and the like, have requirements which limit the amount of current that can be injected into the household wiring. Based on feedback from the elec- trical contracting industry and supply authorities, it is suggested that corrosion of an extent likely to degrade electrical safety is not a common occurrence. • While a warning is included in the article to point out that unlicenced persons should not tamper with any wiring, I would like further warning against the practice you describe and picture concerning the 3-core extension cord. Removal of the sheathing of a flexible cord to expose single insulated cable and then to further tamper with such wiring is not a practice which could be recommended. I hope these points have clarified some aspects of modern wiring arrangements. J. C. Tinslay Executive Officer Standards Association of Australia OP CODE OP CODE HALF OF ADDRESS OP CODE ADDRESS OR DATA HALF OF ADDRESS (a) SINGLE WORD (b) TWO WORO (c) THREE WORD Fig.5: the number of 8-bit (byte) instruction words depends on the particular computer. A one-byte word provides only the op code. A two-byte word provides the op code and an address or operand to be processed. A three-byte word provides both the op code and a 16-bit address. retrieved sequentially so that the last item stored is the first item to be retrieved; the first data item stored will be the last retrieved. The stack pointer register is used to determine the limits of the stack and to identify specific word locations in the stack. In the 6800 and 6502, the stack pointer register is 16-bits, and it can point to any one of 65,536 different memory locations. This means that the stack can be located anywhere within the maximum addressing range of the microprocessor. To set up the boundaries of the stack, the stack pointer register is usually loaded under program control with special instructions used for this purpose. Once the stack pointer has been initialised, it is then incremented or decremented to access sequential memory locations. Stack, store and retrieve operations are called push and pull (or pop) respectively. The Instruction Set The instruction set is the complete list of instructions that a micro is capable of executing. The programmer uses the instruction set to develop complete programs that perform a desired process, calculation, or control function. It is the instruction set that really defines the architecture of a micro. It specifies the number and types of registers and the logic circuits and how they are all interconnected. The instruction set for each micro is fixed and is unique to that device. Types of Instructions Two types of instructions are used in microprocessors: memory-reference and non-memory reference. A memory-reference instruction identifies some particular memory location where the operand to be used by that instruction is stored. The instruction usually contains an address that designates the location of the operand. For example, an ADD instruction contains an address that points to one of the operands to be added. The other operand is usually in the accumulator. A non-memory reference instruction does not have an address associated with it. This type of instruction simply defines a type of operation to be performed somewhere in the computer. The location of any data to be used, if any, is usually in a CPU register. Instructions are further classified by the types of operations they perform. Some specific types are listed below. Data Movement Instructions - specify data transfers from one location to another. The transfers can take place between internal registers or between the internal registers and the computer's memory. Arithmetic/Logic Instructions - identify unique arithmetic and logic operations such as add, subtract, logical AND, compare, or other operations. Data shift and rotate operations are usually included in this class of instructions. Decision-Making Instructions - test for certain conditions in the machine and cause the sequence of the program to be modified. If the test condition is met, the operation specified by the instruction is performed or otherwise the next instruction in sequence is executed. Usually, the operation is a jump or branch operation that causes the micro to begin executing a sequence of instructions different from the normal sequence specified by the program. Such instructions allow the micro to make decisions based on conditions that exist in the CPU or external circuits. Input/Output Instructions - cause data transfers to take place between the CPU and the I/O interface. Instructions for handling interrupts are usually included in this instruction class. Not all microprocessors have I/O instructions. For example, the 6800 and 6502 do not have I/O instructions as such; they simply use the data movement instructions to enable data transfers to external devices and circuits. Instruction-Word Formats - all microcomputers have a basic fixed word length. The 6800 and 6502 both feature an 8-bit word. The memory is organised as many sequential storage locations for 8-bit words. These words (bytes) may be data or instructions. Usually, data words are eight bits or less in length. However, this limits the number size to a maximum of 255; additional memory locations may be allocated if greater number sizes are required. For example, two sequential memory locations can be used to store a 16-bit word, thereby increasing the number size up to 32,767. (One-half of the word would be stored in each of the two adjacent memory locations). However, keep in mind that the micro will only process eight bits of data at a time. Instruction words are similar. Some instructions can be defined by a single 8-bit word. Others require two or three sequential 8-bit words. Fig.5 shows the three most commonly used instruction word formats. In Fig.5a, a single 8-bit word defines an instruction. This byte usually contains the op code - a specific bit pattern that causes some unique operation to take place. Such single word instructions are usually nonmemory reference instructions since they do not contain an address. Fig.5b shows a two-byte instruction. The first eight bits define the op code. The second 8-bit word in an adjacent memory location usually contains an address of the operand to be processed. When the instruction is executed, the operand stored in the second word location is used. If the second word is an address, it references some location in memory where the operand is stored. Fig.5c shows a three-byte instruction. As usual, the JUNE 1988 91 first 8-bit word contains the op code while the next two 8-bit words contain a 16-bit address which identifies the memory location where the operand is stored. MICROPROCESSOR (CPU) Addressing Modes Another important part of the architecture of a micro is the way that it addresses data or instruction words. The more different ways that memory words can be referenced, the more powerful and flexible the micro is. Many of the addressing modes greatly speed up and simplify the processing operations. The following addressing modes are used in most micros, including the 6800 and the 6502. Implied No specific address is used with implied addressing; instead, the location of the operand to be used in the processing is implied by the instruction itself. Implied addressing is used with non-memory reference locations. With these instructions, the operand is usually stored in a register that is the subject of the given instruction. For example, accumulator increment, decrement, or shift instructions imply that the operation is to take place on the operand stored in the accumulator. Immediate Immediate addressing assumes that the operand is contained within the instruction itself, usually as the second byte of a two-byte instruction word. With this arrangement, the operand is available immediately for processing, thereby eliminating the need to address memory and to perform a read operation prior to executing the instruction. Immediate instructions are used to speed up computation. Direct When the direct addressing mode is used, the address bits are a part of the instruction word. The adADDRESS 14 (DATA) ADD INSTRUCTION 63 (DATA) STA INSTRUCTION HALF OF ADDRESS HIIIII} = HALF OF ADDRESS H111111 16-BITS 1111111111111111 65535 ""' ~ 1 - - - - - ~ Fig.6: the microprocessor communicates with the memory and input/output functions through a data bus, an address bus and a control bus. The control bus provides the functions other than data transfers and memory addressing. 92 SILICON CHIP dress may be simply the second 8-bit byte of a 2-byte instruction, or it may be defined as the second and third bytes of a 3-byte instruction. Direct addressing is the simplest and most intuitive of all the address modes, and is the one most often used. Remember, the total number of address bits determines the maximum number of memory locations that can be referenced. In the 6800 and 6502, the address word size is 16 bits, thereby permitting a total of 65,536 words (64K bytes) to be addressed. Direct addressing is sometimes referred to as absolute addressing. Register In register addressing, the op code specifies a register where the operand is stored. Register Indirect In this address mode, the instruction op code specifies a register that contains the address of the operand. This register must be loaded with the proper memory address prior to executing the instruction. Relative RAM LOA INSTRUCTION 4 TO EXTERNAL Fig.7: program instructions for the computer are stored in memory in sequential order. An individual address might contain an op code, a data value, or another address where the program stores or retrieves data. In the relative addressing mode, the effective address of the operand to be used by the instruction is obtained by adding the direct address in the instruction word itself to the contents of the program counter. The address in the instruction word is used to specify a displacement from the address of the instruction currently being executed. (This address is contained in the program counter). This method of addressing permits the program and the associated data to be relocated anywhere in memory without changing the direct addresses in the program. The relocation of the program is simply a matter of adjusting the value of the program counter. Indexing Indexing or indexed addressing was discussed earlier in connection with the index register. As you may recall, the effective address designating the storage location of the operand is formed by adding the address in the instruction word to the contents of The microprocessor, or MPU, is just a CPU. To form a complete computer, memory, I/O and other circuits must be added. The MPU is usually indicated as a single box, as shown in Fig.6. The MPU communicates with the other circuits by way of many input and output lines. These lines are typically organised as buses. For example, all 8-bit data transfers into and out of the MPU take place over the data bus. [The data bus is eight lines over which data can travel in either direction). Another group of 16 lines on the MPU forms the address bus. An address from the program counter or other source in the MPU is put on the bus and sent to RAM, ROM, or an I/O device. The address identifies and enables a memory location or I/O circuit which will accept data from or send data to the MPU. The remaining lines of the MPU are collectively known as the control bus. These input and output signals are used to control MPU operation. value (14) to be transferred to the accumulator. This instruction uses immediate addressing. Locations 2 and 3 hold an add [ADD) instruction. Byte 2 is the op code, while byte 3 is the data word (63) to be added to the value in the accumulator. Locations 4, 5 and 6 hold a store [ST A) instruction. Byte 4 is the op code, while bytes 5 and 6 form a 16-bit address that tells where in RAM the contents of the accumulator will be stored. To start the program, the program counter - the PC - is loaded with O so that it will access the first instruction in the program. Byte O is loaded into the instruction register and decoded. The PC is incremented and the data in byte 1 is loaded into the accumulator. The PC is now incremented again and the ADD instruction is fetched from byte 2 and put into the instruction register. After decoding, the PC is incremented and the data in byte 3 is accessed, then added by the ALU to the data word in the accumulator. The sum 77 then appears in the accumulator. The PC is then incremented again to fetch the STA instruction in byte 4. The op code is loaded into the instruction register. Next, the PC is incremented twice to bring in bytes 5 and 6. Together they form a 16-bit address [65 ,535) that is sent to the RAM instead of the PC content. This enables the selected RAM location. The sum in the accumulator is sent via the data bus to this location. The program ends at this point. Executing a Program The Next Lesson the index register. Index registers can be loaded, stored, incremented, or decremented by using special index-register instructions. In addition, the contents of the index register may also be tested by decisionmaking instructions. Making a Microcomputer with a Microprocessor To complete our discussion of microprocessor operation, let's take a look at how a 6800 or 6502 would execute a simple program. Refer to Fig.7. This shows several bytes of RAM where the program is stored. In memory locations O and 1, a load accumulator [LDA) instruction is stored. The first byte contains the op code, the second contains the data In the next lesson we will cover I/O operations. Then, in the final lesson, we will examine other 6800 and 6502 instructions and show you the processes used to create programs that perform a variety of functions. ~ Reproduced from HANDS-ON ELECTRONICS by arrangement. Copyright (c) Gernsback Publications, USA. SHORT QUIZ ON DIGITAL FUNDAMENTALS 1. A microprocessor is an LSI _ _ _ _ _ _ __ 2. The four major parts of a digital computer are: a. b. c. d. LESSON 8 8. An area of RAM used to temporarily store data is called the _ _ _ . The register that contains the address of this area is called the _ _ _ _ __ 9. The address of the operand to be used in a computation is usually contained within the _ __ 3. A CPU is made up of the _ _ _ _ _ section and the _ _ _ _ _ _ section. 10. A microcomputer that replaces conventional logic circuits in performing a specific function is often called a ______________ 4. The two kinds of information stored in a computer memory are ___ and _ _ _ words. 11 . Communication with the world external to a microcomputer takes place via the _ _ _ section. 5. A program is a sequential list of ______ that performs a specific function. 6. The main processing register in a CPU is the 7. The register that points to the next instruction to be fetched and also deterrnJnes maximum memory size is called the __________ ANSWERS 0 /1 . ~ ~ Je110Jiuo:> pere:>1pap ·o ~ uo1pnJisu1 ·6 J8lU!0d >PBlS ')1:>BlS ·g Jaiuno:> weJ5oJd · L JOre1nwn:>:>e ·9 suo1pnJisu1 ·g SU0!PnJlSU! 'BlBP ·17 :>!50f/:>!I8Wl.fl!JB 'I0JlU0:> '8 0/1 ·p :>!50i/:>!l8Wl.fl!JB ·:> !0JlU0:> ·q A.Jowaw ·e l!Un 6u1sse:>0Jd IBJlU8:) · ~ ·z JUNE 1988 93 ASK SIUCON CHIP Got a technical problem? Can't understand a piece of jargon or some electronic principle? Drop us a line and we'll answer your question. Write to: Ask Silic..,n Chip, PO Box 139, Collaroy Beach, NSW 2097. Amplifier power and varistors I intend to build one of the amplifiers described in the December '87 and February '88 issues. I see no problem with the construction but am a bit confused about the power output ratings, such as 50 watts into 80 and 100 watts into 40. Does this mean that the 50 watt version should only be fed into a speaker with 8-ohm voice coil and the 100 watt version fed into a 4-ohm speaker? If this is so, what happens when the 50W version feeds a speaker with, say, three 8-ohm speakers in parallel, giving a much lower load resistance? My second question is, what is a Varistor? One is listed on page 40 of the Dick Smith catalog with a 250V rating. I had been under the impression that this was a device for varying the AC voltage and current in a circuit, something like a variable choke. However, when I went to purchase one it looks like a large ceramic capacitor. The sales people seemed to have no idea what Query on 78L05 regulators Over the years I have seen many power supply circuits using 7805 3-terminal regulators but very seldom have I seen the low power version, the 78L05, used. The same goes for the 79L05. Why is it that these devices are so seldom used, particularly in circuits published in electronics magazines? (R.U. , Castlecrag, NSW). • No doubt the main reason why the 78L05 has been less frequently used is that the 7805 has been more readily available, at a price that was usually cheaper than the lower-powered device. 94 SILICON CHIP it was for. Can you enlighten me? (M.B., Toukley, NSW). • You are not alone in your confusion over amplifier power ratings so it is appropriate that we explain the subject. At one time there was little confusion, when valve amplifiers were used. Then, the output transformer was designed to match the valve output stage to a particular loudspeaker impedance and if you used another speaker impedance you obtained less power. Now, things are a little more complicated. Our 50W design presented in the December 1988 issue is intended only for loads of 80 nominal impedance. That means that you can't use 40 speakers or several 80 speakers in parallel. If you do, two things might happen. First, the amplifier will attempt to drive the speakers but on loud signals the protective thermistor will limit the output current to a safe value and therefore less power will be delivered than if the correct load was used. Second, the output transistors might be damaged by attempting to drive a reactive load of too low an At present though, a survey of parts prices shows that the 78L05 is priced on a par with the 7805 so perhaps there is now more reason to use it. The 78L05 is not just a lowpower drop-in replacement for the 7805 though. Its internal circuit is quite different. Not only doesit have a much lower output current capability (less than lOOmA versus more than one amp for the 7805 ), it also has an inferior output impedance and a much lower " ripple rejection" than the 7805. The only parameter in which the 78L05 can be regarded as superior to the 7805 is in its quiescent current. This is the current drawn by the regulator when no output impedance; ie , their second breakdown ratings could be exceeded. By contrast, the 100 watt design can be used with 80 or 40 loads. If you use a 40 load the maximum power output will be 100 watts or very close to it. If you use an 80 load, you will get a maximum power output of 50 watts; ie, half the power. So there is no advantage in building the 100 watt version if you intend to use it with a single 80 loudspeaker system. On the other hand, if you want to use a pair of 80 speakers in parallel, giving a load of 40 (nominal), you need the 100 watt version. Your confusion about Varistors is also understandable since the name does suggest the concept of a variable resistor. In fact though, a Varistor is an over-voltage protection device. They are of the same family as voltage dependent resistors (VDRs) although in recent years the term Varistor seems to have become more commonly used. VDRs and Varistors are semiconductors which are based on sintered metal oxides, such as zinc current is being delivered. To be specific, the maximum quiescent current of the 7805 is 8mA while the maximum figure for the 78105 is 5mA. If you compared the typical quiescent current figures, the 78L05 is 3mA, about half that of the 7805. That is to be expected too, since the 78L05 is intended for battery powered applications where current drain is critical. To sum up, the 7805 can be used in just about every application where the 78105 has been specified, except where current drain is critical, but the reverse does not necessarily apply. These remarks also apply to other regulator comparisons, such as the 7905 and 79L05. and bismuth oxide. In fact, Varistors have also been referred to as "metal oxide varistors", or MOVs for short. VDRs and Varistors are very widely used as over-voltage protection devices in telecommunications networks (there are several in every telephone), television sets, computers and any equipment which is sensitive to voltage transients. In a typical application the MOV is placed across a supply or signal line and it does nothing (ie, it is open circuit) until a voltage transient comes along which exceeds its breakover ratings. It then breaks down and conducts very heavily. When the voltage transient has passed, the MOV reverts to its open circuit condition. In recent years, another device has been developed to provide a similar protection action to Varistors. Called "Tranzorbs" they are effectively high power zener diodes but with very high current ratings. They are available in unidirectional and bidirectional (two zeners back-to-back) versions and have surge ratings up to 1500 watts. Wants transistor equivalent I would like to make an acoustic probe project from an English magazine and have discovered that I can buy all the parts except one. This is a BC214L silicon PNP transistor. None of the well-known electronic shop catalogs list it and I find that in my cross-reference guide (ie, the back pages of the DSE catalog) no substitute is shown. Could you suggest where I could buy this tranistor in Australia or which transistor I could use instead? (J. McC, Burpengary, Qld). • The BC214L is a low noise, high gain PNP transistor which is the complement of the NPN BC184L. The commonly listed equivalent of the BC184L is the BC549. The most readily available equivalent to the BC214L is the BC559 although you could use an older type such as a BC159. We don't know of any retailer who stocks the BC214L. 100k Walkaround throttle for model railroads I read with much interest your article on the Walkaround Throttle for Model Railroads in the April issue of SILICON CHIP. My particular query is whether the pulse frequency of 200Hz can be increased to between 400 and 500Hz. The reason I ask this is because the model locomotives which I build use careless motors which need either smoothed DC or a pulse rate of between 400 and 600Hz. If this frequency is not supplied, the armature will stop between pulses, causing jerky and noisy operation which shortens the life of the precious metal brushes. If I decrease the .0lµF capacitor on pin 6 of ICld would I achieve the required pulse rate? If so, what value would you suggest? Also, if I incorporated a changeover switch, could I switch between high speed pulses for careless motors and the original 200Hz pulses for conventional motors. (G.N., Wattle Grove, WA). Notes & Errata Remote Switch for Car Alarms, March 1988: a small inductor should be inserted between the base of QZ and the negative side of the 2.2µF capacitor in the receiver circuit. This is to prevent RF energy from reaching ICla and thus desensitising the circuit. The inductor can be made by winding eight turns of 0.63mm enamelled copper wire on a 3. 2mm former (ie, a 1/Bth-inch drill bit). It can then be installed directly on the PCB in place of an existing wire link. Note that the 2 .2µF capacitor is shown with reversed polarity on the overlay diagram and should be installed the other way round. Finally, the l00kO resistor connected to the base of QZ should be reduced to 47k0 to increase the damping across LZ. Passive Infrared Movement Detector, December 1987: the PCB layout 500Hz ~ .0047! .0047J Fig.1: this circuit allows the walkaround throttle to be switched between 200Hz and 400Hz pulse frequencies • You've got the general idea G.N. To double the pulse frequency, all you have to do is halve the value of the .0lµF capacitor on pin 6 of ICld. The nearest pref erred value is .0047µF . This will give a nominal pulse frequency of just over 400Hz. Fig.1 shows how the circuit can be wired so that you can switch between 200Hz and 400Hz pulse frequencies. Note that in the 200Hz position, the two .0047 µF capacitors are connected in parallel. The 400Hz pulse frequency is then obtained by switching out one of the .0047 µF capacitors. connects the relay, D3 and R18 to + 5V instead of to + 12V (as shown on the circuit diagram). To fix this problem, isolate these components from the + 5V rail by cutting the copper track at two locations. The isolated section should then be connected to the + 12V rail using an insulated wire link. Finally, the isolated section should be bypassed by connecting an insulated wire link between the + 5V output of IC6 and the track to pin 7 of IC5. Readers should also note that capacitor C6 (22µF) is shown connected with reverse polarity on the overlay diagram (the circuit is correct). In addition, the polarity of C14 (lO0µF) is not marked on the overlay. Be sure to connect the positive side of the capacitor to + 12V. Full details of the above modifications are supplied with the PIR Movement Detector kit sold by Oatley Electronics. JUNE 1988 95 CEN'I' Cash in your surplus gear. Advertise it here in Silicon Chip. Advertising rates for this page: Classified ads - $7 .00 for up to 15 words plus 40 cents for each additional word; Display ads (casual rate) - $20 per column centimetre (max. 10cm). Closing date: five weeks prior to month of sale. If you use a PO Box number, you must include your permanent address and phone number for our files. We cannot accept ads submitted without this information. To run your own classified ad, put one word on each of the lines below and send this form with your payment to: Silicon Chip Classifieds, PO Box 139, Collaroy Beach, NSW 2097 FOR SALE NEARLY 1500 PRINTER buffer kits now sold. Prices start at $39 for a 256K short form kit . All items advertis· ed are in stock. Dealer enquiries welcome. Bulk discounts. Schools, Govt. Depts. orders accepted . Oh yes!! IBM compatible. Australian designed and manufactured. Ideal project for user groups and students. For a free catalog send a 37c stamp to: Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043. PLEASE PRINT EACH WORD SEPARATELY, IN BLOCK LETTERS 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ($7.00) 300W INVERTER, EA 9/85, $200. Calculator HP32E $40. 1 00W sub· woofer amplifier and loudspeaker, EA 78/82 , $200. Phone (03) 534 4624 a.h. Name ....... .. ...... ....... ..... ..... ..... ..... ....... ... ..... ..... ...... ... ....... .... . Address ............ ........ .... ..... ..... ...... ... ... ... ....... ..... .. ....... ... . Suburb/Town Postcode ... Enclosed is my cheque or money order for$ ..... Bankcard □ Visa □ .. ..... or please debit my KIT FIX SERVICE - Having trouble getting your EA/ETI/SC kit to work? Phone (03) 7 49 3480 for estimate or send kit to K. Hunter, 5 Yatama Crescent, Werribee 3030. Card No ......................... ... .. ... .. ... .... .... .. .. ..... .. ... .... .... ........ .. .. ... ........ .. .. .. ... ... .. ... .. Signature . . . . . . . . . . . . . . . . . . . . . . . . .............................. . Optimus 304 loudspeaker continued from page 15 15kHz the impedance was below 8 ohms, dipping to a minimum of 4. 7 ohms at lOkHz. Thus the 304s should not present a loading problem to the vast majority of solid state amplifiers. The highest measured impedance was 24.8 ohms at 65Hz. This peak and one that was evident below 14Hz are typical of the double hump response curve that occurs naturally in a reflex or tuned port speaker enclosure. An impedance peak of 17.3 ohms was also apparent at lkHz, this being at the woofer to mid-range cross-over point. Listening tests with signal from a sine wave generator indicated a fairly smooth frequency response across the audio range, the exception being some peakiness in the 2kHz to 3kHz area and some enclosure panel resonance at around 65Hz. Below this, the response tapered off smoothly to about 40Hz. (Note: enclosure panel resonances are virtually impossible to build out of a simple enclosure 96 SILICON CHIP constructed from timber and so this speaker is not alone in this respect}. With music the Optimus 304s have a clean, forwarc. sound and on classical music they made for very pleasant listening, with no indication of being tiring in long lis ~ening sessions. Auditioned against two other pairs of much higher priced speakers they held their own very well indeed and displayed no obvious vices. Because of their higher than average sensitivity [claimed 91dB SPL for 1 watt at 1 metre}, these speakers may be used with amplifiers and receivers with power outputs of modest levels, say from about 10 watts per channel, and still produce good sound levels. The Optimus 304s come with a 5-year warranty and are priced at $229.95 each. At this price we consider them to be surprisingly good value for money. They are well worth consideration by anybody wanting to purchase a larger 3-way system without breaking the bank. (B. F.} le Advertisers Index Our advertisers are vital to the success of SILICON CHIP. Please give them your support. Altronics . . . 52·55 Arista Electronics .. 1 4 Avtek . . . IBC David Reid . 67 Dick Smith Electronics . 36,37 70,71 Elmeasco . IFC Geoff Wood Electronics .. 43 Jaycar Electronics . 20-27 Kenwood Australia . . OBC RCS Radio .. 85 Rod Irving Electronics . 61 Scan Audio . 79 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. • Jemal Products, 5 Forge St, Welshpool, 6106. WA 6161. Phone (09) 350 5555. MODEMS Don>t buy imported unsupported The Avtek advantage • Australian designed Australian manufactured Australian supported MEGAMODEMS 12/123 The Avtek Megamodems provide Australia's best value communications products, with a range of fully automatic, autodialling modems, Megamodems are suitable for data transfer from personal computers, terminals, mainframes and mini host computers and for all videotex services such as Viatel. The use of the latest technology has enabled us to make the Megamodem more compact and reliable than any other modem, Price is very competitive and reflects efficiencies incorporated in the design. The Megamodems are locally designed and built. Service, support and specialist R&D for the Megamodem range is all based in Australia. Available either as a standalone RS232 model or as a plug in 1/2 card for IBM PCs and compatibles, The Megamodem range of modems are Telecom authorised. Specifications Data Standards Data Rates MAIL ORDER WELCOME VIS4 Automatic Dial, Answer, and Disconnect: The Megamodems will automatically answer an incoming call and connect the computer to the line.When originating a call it will then dial out the required number and auto-connect to the computer at the other end It will then "hang-up" at the end of a communications session. Both pulse and tone dialling are supported, The modem Is compatible with new Telecom exchanges and modern PABXs and can handle high speed tone dialling, Fully Hayes AT Smartmodem Compatible: The Megamodems are industry standard ''HAYESSMARTMODEM "compatible which means they can take advantage of all the communications facilities of packages such as Crosstalk, Open Access, Symphony and Multicom. All communications parameters such as baud rate, parity and number of stop bits are set up automatically by the software and the Megamodem, Using appropriate software data can be sent and received while the Megamodem is unattended. CCITTV21, Bell 103, CCITT V22 Bell 212, (123 model only CCITT V23) 300/300, 1200/1200 (123 model only 1200/75, 75/ 1200) l■ -c~ BUY DIRECT FROM THE MANUFACTURER Model 12 & PC12 $375~ax Model 123 & PC123 $449~ax r~--=-~vTrl( L(;·~-~~ , I ~J CJ PO Box 651 Lane Cove 2066 Telephone (02) 888 5533 Facsimile (02) 887 2839