Fullscreen HTML5Med Res (??MB)HTML4

Leo Simpson and Greg Swain present ... Hi-Fi review: Marantz's clever new PM-35 stereo amplifier cvc)es counted 1000 gating time, sec 10 10 128 l~O 10 1 1 12 8 ,1 .1 .01 DIGITAL FREnueruc1.v2a . ,01 .12a METER Publisher & Editor-in-Chief Leo Simpson, B.Bus. "'=' ~ ~ ~ t:: __, -=--1----q;___,a;::= __, __. __, __, ..... _._. __, _. __, .......... __, ------ NOVEMBER 1987 ,.....II - ~ _.i __, ~ ~ -...J-A,-,J--1 ~ ~ __. __, ::::: _t:::;__ __, ~ I -- FEATURES 6 The Evolution of Electric Railways by Bryan Maher Part 1 - The birth of steam and electric locomotives 11 Silicon Chip Hifi Review by Leo Simpson Marantz PM-35 Integrated Amplifier 76 Your House Wiring Could Kill You by Leo Simpson Your house wiring can develop a dangerous fault 83 Digital Fundamentals, Pt.1 by Louis Frenzel Teach yourself digital electronics 88 Guide to Discrete Components, Pt.1 by Leo Simpson Find out about the basic electronic building blocks PROJECTS TO BUILD 20 Capacitance Adaptor for Your DMM by John Clarke Checks values from 0-2.2 microfarads 32 1 GHz Digital Frequency Meter by Steve Payor Superb performance yet easy to build 54 Car Stereo for Your Home by Greg Swain A surplus car radio makes a cheap hifi system 66 Off Hook Indicator for Telephones by John Clarke Tells you when an extension phone is off the hook !Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec .) Robert Flynn Regular Contributors Neville Williams, FIREE, VK2XV Bryan Maher, M.E. B.Sc.(Elect. Eng.) Garry Cratt, VK2YBX Jim Lawler Photography Bob Donaldson Editorial Advisory Panel Philip Watson , VK2ZPW Norman Marks Steve Payor, B.Sc., M.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: Masterprint Pty Ltd , Dubbo, NSW 2830. Distribution: Network Distribution Company. 72 A Portable Electronics Workbench by Leo Simpson Build it before you build your next project SPECIAL COLUMNS 14 The Way I See It by Neville Williams They'll sell you anything but don't ask them to fix it 46 Serviceman's Log by the original TV serviceman With friend 's like that 90 Amateur Radio by Garry Cratt Introducing amateur radio DEPARTMENTS 2 Publisher's Letter 70 Product Showcase 5 News & Views 94 Ask Silicon Chip 51 Bookshelf 62 Circuit Notebook 96 Market Centre Subscription rates are currently $42 per year (12 issues). Outside Australia the cost is $62 per year surface mail or $1 20 per year 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. Introducing Silicon Chip: the new electronics magazine for everyone Welcome to Silicon Chip, Australia's newest and most entertaining electronics magazine. We're not going to get bogged down with the boring side of electronics technology. Too much of electronics technology is not exactly exciting or accessible to the average person in the street. But there is a great deal which is directly usable and enjoyable in electronics. We know you want to read about it. Whether you are interested in building your own amplifiers, constructing loudspeakers, becoming involved in amateur radio, model aircraft and so on, or just interested in the latest developments in the wonderful world of electronics, Silicon Chip is the magazine for you. Why call it Silicon Chip? What better name is there? If you think about it, every electrical or electronic piece of equipment these days relies on silicon chips either directly or indirectly. Taking that idea further, virtually every aspect of modern life is involved in some way with what we know as the silicon chip. Hence, the name is apt. Silicon Chip is based on the idea that you don't have to be an engineer or technician to understand electronics. If you are interested in modern technology, Silicon Chip is for you. By definition, everyone is vitally interested in modern technology because it impinges on every aspect of our lives. Therefore, yQu'll want to read about it, in Silicon Chip. In this magazine, we are presenting electronics for everyone. We know you will like it. We aim to encourage the person new to electronics, as much as possible. If there are things about electronics that interest you or you can't understand and would like help with, don't hesitate to write to us. Two features, beginning in our first issue, are included with the beginner particularly in mind. They are Digital Fundamentals, which is the basis of so much of today's electronics, and Ask Silicon Chip where we give answers to your questions. We'll also have a succession of small electronics projects which are useful, cheap to make and enjoyable. On the othe-r hand, if you are already a keen electronics enthusiast, Silicon Chip is also for you, most definitely. We aim to bring you the very best constructional projects designed with performance in mind, without going over the top in cost. And have a look at News & Views, Product Showcase, and Designers Notebook. We think you will agree that they are right on target. Let us talk about a particular aspect of our advertising policy, because we have some very definite ideas on this too. We will not be accepting adve,:tising for cigarettes or alcohol. Adverts for these products are directed to specialist magazines from time to time and in the past they have invariably been accepted by the big companies concerned. Not in this magazine they won't. We don't dispute anyone's right to smoke or to drin1< alcohol, provided no-one suffers as a result, but we will not do anything to help promote these products. We are independent of any publishing company and so we can be up-front in expressing this policy. And because we are completely independent, we don't have huge financial backing. Nor do we have high-power advertising salespeople to sell space or provide promotion. We are doing it all ourselves. The people concerned directly, those who have gone way out on a limb to produce Silicon Chip, are Leo Simpson, Greg Swain, John Clarke and Bob Flynn. That's all. We are supported by a number of very experienced contributors and a small but very helpful group of advertisers. We are very thankful for their support. Will you support us too? With your enthusiastic support we will quickly grow to become Australia's biggest and most vil•27.;:__ 2 SILICON CHIP THE ELECTRONICS MAGAZINE FOR THE ENTHUSIAST WE INvITE You To BECOME A SUPPORTER We believe that electronics is the most useful hobby that any person 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 strongly believe that many more people should come to know about and enjoy electronics, we decided to form a new magazine devoted to electronics enthusiasts. We have called it Silicon Chip, a name which encapsulates the driving force behind all of today's electronics technology. Silicon Chip is starting off as an independent magazine, founded by Leo Simpson and Greg Swain. We have a very small team of devoted staff including our full-time electronics engineer, John Clarke and our very experienced draughtsman, Bob Flynn. We have started as a completely indepenconsuming approach if we were not completedent magazine, free from the influence of any ly independent. existing publishing company, because we You can help us establish a high standard wanted to establish the highest possible stanfor our publication by becoming a supporter. dards for accuracy and attention to detail. We The more subscribers we get, the more also wanted complete editorial freedom. Every resources we can devote to improving the article you see in this magazine has been quality of our magazine and to the promotion carefully selected and prepared by us to of the understanding of electronics. establish this high standard right from the The only way that we can survive and grow outset. is with your support. Please give us your vote Similarly, our circuit and wiring diagrams by becoming a subscriber. Not only will you be have been very carefully laid out by our ensuring the survival of a completely draughtsman Bob Flynn to make them as independent publication, you will be showing logical and as easy to understand as possible. your support for a strong and healthy We could not take this careful and timeAustralian electronics industry in the future. I I I I I 1 I I I I I I I Regular Features Junie mail Inside each issue of Silicon Chip you will find carefully prepared features such as: Amateur Radio, by The Evolution Garry Cratt, VK2YBX of Electric Railways Guide to Discrete The Way I See It, Electronic Devices by Neville Williams Constructional Projects Digital Electronics Course For The Enthusiast The Serviceman's Log * * * * * * * Most magazines sell their subscriber lists 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 NOVEMBER 1987 3 WE NEED YOUR SUPPORT Please support our new magazine by becoming a subscriber. You can also give a year's subscription to Silicon Chip as a Christmas gift. Just fill out the postage-free coupon below, place in an envelope, and mail to the adress shown at the bottom of the page. ---------------------------7 FREEPOST SUBSCRIPTION COUPON Yes please, I would like: D one subscription for myself D for a gift(s) D one for myself plus gift(s) MY NAME IS ................................ ................................................................ . Mr/Mrs/Ms/other ADDRESS ...................................................................................................... . SUBURB/TOWN ............................................................... POSTCODE .......... . GIFT 1 to: NAME .. .... ... ............. ......... ......... ... ...... ............................. .... ... ....... ....... ......... . Mr/Mrs/Ms/other ADDRESS ........................................... .................. .... ..................................... . SUBURB/TOWN ............ ................... .................... ... ... ......POSTCODE .... .... .. . GIFT 2 to: NAME ........................................... .......... ............. ...... ............... ..... ........... ..... . Mr/Mrs/Ms/other ADDRESS ......................................... .... .. .... .. ............. ..... ........ ........ ..... ...... .... . SUBURB/TOWN .... ........ ......... ............. .............................POSTCODE ... .. .. ... . Subscription cost: 1 year (12 issues) Within Australia D $42 Overseas surface mail □ $62 Overseas air mail □ $120 2 years (24 issues) □ $84 □ 124 □ 240 Enclqsed is my cheque or money order for $ .......... or please debit my □ Bankcard □ Visa Card No ................................................... .............................................. ........ . Signature ........................ ...............................Card expiry date ... .. ./ ..... ./ ...... Place your coupon in an envelope (no stamp required) and mail to: Freepost 25, Silicon Chip, PO Box 139, Collaroy Beach 2097. 4 SILICON CHIP PLEASE NOTE: Subscriptions will commence with the December 1987 issue for coupons received by Monday 16th November and with the January 1988 issue for coupons received between 17th November and 20th December. I I t I I I NEWS&VIEWS Shielding for business offices stops eavesdropping. Oh yeah? Stories still do the rounds about how it is possible to pick up the signals radiated by computers and thereby tap into sensitive data. Supposedly the eavesdroppers need nothing more than a TV set, an antenna and a cheap processor to see what is displayed on computer monitors. Now, according to a recent issue of "New Scientist", the British company Pilkington Glass has come up with the solution in the form of a laminated glass with an embedded layer of indium tin oxide. Companies will now be able to house sensitive computers and monitors in completely shielded cages without having to resort to windowless rooms. Which is all very well. But consider just how much spurious signal is radiated by the average computer. First, there is the hash radiated by its switchmode power supply. Then there is the hash related to its timebase, its processors and the associated parallel 16 or 32-bit data and address lines. Then there is the radiation from any serial or parallel data lines to peripherals and video monitors. Finally, there is radiation from the sweep circuitry of the video monitor and from all the peripheral devices such as printers. In the average business office there might be dozens of individual computers and all their associated gear radiating a plethora of low-level signals. If anybody can eavesdrop on that lot with just a TV set, an antenna and a "cheap processor" (where do you get it?) they must be clever little Vegemites. What do you reckon? AWA throws telephone accessory market into a tizz In a move which could severely disrupt the supply of telephones and telephone accesories, AWA has moved to enforce the patent rights which it owns on the design of the Telecom-approved 6-pin plug and socket. Suppliers and distributors of telephones and accesories to the booming retail market report that legal moves have been made against them to stop selling all telephone equipment which uses the Telecom plug and socket. At least one major distributor reacted by placing an order for 10,000 plugs only to find that they were a great deal more expensive than the equivalent Asian-sourced plug, that Telecom had to approve the order, and that delivery times extended for many months. Opinion around the traps is that if A WA and Telecom persist with the move then it will merely accelerate the trend to the use of the Americandesigned Modular System plugs and sockets. These are also Telecom approved and are already used on a range of existing Telecom approved equipment such as the Commander range of phones. Sounds like a case of cutting off your plug to spite your phone. In any case, should Telecom, a monopoly itself, grant a monopoly on supply of a crucial part to another company? Ten year warranty on Philips products In a radical move, Philips is now offering a tenyear parts warranty on major products such as TV, video and audio systems. From October of this year, purchasers of these major Philips products can obtain the extended parts warranty by paying the optional fee of $49.95 within thirty days. Philips have offered the service to reassure customers who are concerned about parts backup in the distant future. The extended warranty covers the replacement of any defective functional component, provided the repair is carried out by Philips Service or a Philips authorised service centre. Batteries and cartridge styli are specifically excluded. Full information on the warranty is given in a brochure available from Philips service centres. Good onyer Philips! CD portables to become less common If a number of industry comments about CD portables are anything to go by, CD portables might become a lot less common. The problem with these highly refined and miniaturised products is that the buying public cannot see value in such expensive miniature gear. Therefore the local branches of some Japanese audio companies are figuring that bringing in CD portables is just too much of a risk, so there will probably be fewer CD portables sold. The same attitude affects the sales of so-called midi-sized rack stereo systems although to a lesser extent, and audio companies have had difficulties pushing this gear. Apparently, the average consumer figures that if he (or she) is laying out hundreds or thousands of dollars for audio gear then it should not be tiddler-sized. Fair enough too. Who wants to peer at microscopic knobs and labels to be able to use the gear? NOVEMBER 1987 5 By BRYAN MAHER PART 1 - THE BIRTH OF STEAM AND ELECTRIC LOCOMOTIVES The early 1800s to the 1920s saw the greatest expansion of transportation and industrialisation the world has ever seen, and it was all based on the steam locomotive. But within another 40 years the steam locomotive would be largely obsolete because of the diesel electric loco and the electric loco. The world changed - for better or for worse - one Lenten Sunday morning in 1803. The place was a 6 SILICON CHIP small Welsh village, the parish church in particular . Young Richard Trevithick had chosen this day to try out his dream. Trethivick was a Cornishman by birth, a South Wales coalmine captain by profession, and an inventor by choice. He had long observed the large stationary steam engines used to pump water from the mines. Trevithick reasoned that if the boiler and the engine were wheel- mounted, might not the pistons and cranks actually turn the vehicle wheels themselves , producing motion? The model To test the idea, Richard Trevithick built a model: four wheels, a boiler with a small fire under it, and two steam cylinders with pistons connected to cranks on the wheels. The next thing needed -,--· In this first article, we examine how the steam loco developed from a curiosity to massive engines weighing 550 tonnes, while in the some period electric locomotion was only just beginning. Richard Trevithick quickly gathered his invention in his arms and ran off. Though none realised it, the world changed then and there: ·no longer would the human race depend on animals for transport. The railway era had begun. Stories spread quickly in Wales and very soon young Richard was offered a wager by workmates. •'Bet you cannot build a full-size machine that can haul our mine coal trucks". For years the mines had used four wheeled trucks, hauled by pit ponies plodding between parallel flanged rails or plateways. The tracks were placed a suitable distance apart so the wheels, two shafts and pulling chains were just clear of a horse's buttocks. In England the Clydesdale horses, being the largest, set the required spacing between rails at about 56.5 inches. Thus, even today, the world "Standard Railway Gauge", the distance between inside edges of the rails, is just that: four feet, eight and one half inches (or 1435mm). with steel rails carried on slabs of timber, steel or concrete "sleeping" in the ground. was a suitable place for a trial run. Roads were wet and muddy but the dry stone paved area in the village church yard was inviting. He lit the fire, raised steam and off it ran in the direction of the church front doors. Success! The first dream of his life achieved! At that moment the church doors were flung open from within, and fresh from a sermon on the evils of the world came the village parishioners. With one look at Richard's steaming, hissing running machine they turned and stampeded back into the church screaming "The Devil himself is after us". The very first loco Within 12 months young Trevithick had built his first steam locomotive at Winfield's Foundry in Gateshead and ran it on the Pen-ydarran mine railway tracks, so winning the bet in 1805. The era of mass travel had begun. 20 years later, on 27th September 1825, another pioneer, George Stephenson, had also realised a lifelong dream, having convinced sufficient moneyed people to share in his new company, the Stockton And Darlington Railway. The world's first Public Railway, was opened with suitable fanfare, ceremony, and (let's say this bit very quietly) some derailments. Many world firsts can be claimed for that year: at Stockton in Durham County the very first railway ticket was sold, the first iron railway bridge was built, the first architect-designed sculptured stonework railway viaduct was constructed and, for the benefit of you and I, the world's first photograph of a working train was taken. This was also the first railway to be established across public land, roads and streets, by authority of an Act of Parliament. Such was the genius of George Stephenson that from his fertile mind came the basic design of the first real steam railway locomotive capable of operating a public railway, running for hours on end hauling freight and passengers, in short - the first working railway system. True, there were other locomotive designers in the field before Stephenson. But Richard Trevithick's 1805 model at Gateshead, the Blenkinsop model of 1812 and William Hedley's 1813 Puffing Billy all used principles that failed on the hard road of experience. Some used a single cylinder, all used gear drive and one used a huge flywheel. George Stephenson's success was based on hard experience gained with his Killingsworth locomotives, which were designed for hauling coal out of mines. Improving on these, he designed his 1825 model christened "Locomotion". Opposite page: the Pennsylvania GGl class made by General Electric were America's first and most long-lived high speed mainline electric locos. These 214 tonne monsters did daily service on the Pennsylvania Railroad for nearly 50 years up until 1981. (Amtrak photo). NOVEMBER 1987 7 / / ' ,.,.~,- ./~:/~ / // ~ NSW loco No 4601 undergoing trials in 1956. One of twenty electric locos built for the Blue Mountains section, these 2.8MW 114 tonne units have given 30 years of excellent service. (NSW SRA photo). Of vital importance were the two double-acting cylinders; ie, power was produced on every piston upstroke and on every down stroke. Rod-coupled to four driving wheels, with cranks on opposite driving wheels set 90 degrees apart, these formed a combination which always produced starting tractive effort (drawbar pull) no matter in what attitude the loco had previously stopped. Contrast this with the typical stationary one-cylinder single-acting steam engines of the day, producing power during less than one half of each revolution, during the piston down-stroke, and requiring a large J=.=~~~~===-.=~~~~~-•f . . /~e.-½ ~,< .-.~- . . l- -r :+~:-J -~t~-' ~ };,,~L"":::li'lo~l:r~l~~ ~~ ~ ?, ·~i.... 0 tt · i.~-:_ -: . u., ~(~ --~::::-- ~~~t~ ~:?~-'-~-~---~~~t~:-~;--.~v~·:~ :·.~:/-~/I;-.-·~·:-:~~~~ 0 1 The world's first electric "Locomotive" designed and built by Robert Davidson in 1842. It weighed 6 tonnes, carried its own batteries and ran at 7km/h. (Original drawing reproduced by courtesy of the British Science Musiem and the Institute of Electrical Engineers London). 8 SILICON CHIP flywheel to drive the load during the remainder of each circle. Furthermore, starting required the flywheel to be pulled by hand to a suitable attitude with the piston halfway down the cylinder. George Stephenson's Locomotion used two extra eccentric cranks on a driving axle to drive two slide type steam valves, called "D" valves, mounted between the wheels. These admitted steam from the boiler to the power cylinders at appropriate timing. The timing could be varied to save steam after the train was accelerated by admitting short bursts which were then allowed to expand within the cylinder. Further timing variation reversed the direction of running. Also at the end of each piston stroke the valves opened a path from the cylinder to exhaust spent steam up the funnel to improve the draft for the fire. These design principles seemed obvious to George Stevenson at the time but not even he could forsee their extensive future. His simple genius was such that these basic ideas would prove essential and perforce become the design foundation of every steam locomotive ever built. Improvements With his ideas now known worldwide, improvements quickly came as other designers entered the field. Within nine years, steam cylinders would be changed to horizontal position to facilitate springing of driving wheels. And, in America, that fabulous loco designer Samuel Baldwin introduced leading bogies to allow higher running speeds on curves. Eventually the number of driving wheels on some locomotives would reach as high as twenty and engine weights would grow from Locomotion's tiny 6 tonnes to as much as 550 tonnes. But only the introduction of superheating and higher boiler pressures caused any real increase in efficiency over Stephensons's original design. It is an amazing fact that George Stephenson's essential design was never changed in all the entire dynamic 130 year saga of the steam loco. Diagram of the motors of Robert Davidson's first Electric Locomotive. A, B, and C are iron bars attracted in turn by switched electromagnets Ml and M2. (Drawing by Anthony F. Anderson reproduced by permission). pulley grooved plate 1upport bars andl• llcl Enter electric traction In the midst of the frenzied advances in steam railways, there were other developments of significance. In Scotland, we find Robert Davidson, a manufacturing chemist of Aberdeen. Born in the year of Richard Trevithick's steam locomotive success, he attended Marischal College at the University to study the Arts, but spent so much time delving into chemistry, electrochemistry and the brand new science of electromagnetics that he never did graduate. Apprenticed to his father in the grocery trade he left this for a freelance career manufacturing yeast, dyes and other chemicals from which he made sufficent money to support experiments with fundamental variable-reluctance type electric motors. The Edinburgh And Glasgow Railway, opened on Feburary 21 , 1842, ran a regular timetable of four steam trains in each direction daily. In the third quarter of that year Robert Davidson persuaded the Railway management to allow The battery design used by Robert Davidson. Two or four of these batteries powered his first loco. The zinc and iron plates were pulled out of the electrolyte to control the speed of the loco. (Drawing by Anthony F. Anderson reproduced by permission). The field magnets of Robert Davidson's traction motors used iron plates as laminations. (Drawing by Anthony F. Anderson reproduced by permission). NOVEMBER 1987 9 This 109 tonne 2.9MW electric loco is the first of a fleet of electric locos to be used in Queensland for hauling coal. It has been designed with triple bogies, to traverse very tight curves, and is powered from a 25kV AC overhead line. him to use their tracks for an experiment of his, in between train schedules of course. He had constructed a full-size rail truck 4.9 metres long, 2.13 metres wide, with wooden cylinders surrounding both axles. On each cylinder he had mounted three long iron bars and a threesegment commutator. Attracting the iron bars were eight electromagnets whose coils were switched by the commutators, direct current being supplied by two banks of oells. There were 80 cells originally, with more added later. These zinc-iron batteries consisted of a wooden trough divided into cells, each containing one zinc plate in between a pair of iron plates, all plates being supported by a wooden lid. Each plate was 300mm x 380mm and the electrolyte for his battery was 1:7 sulphuric acid and water. It appears that he used a pulley system to raise and lower the plates in the electrolyte, and this con10 SILICON CHIP stituted the motor speed controller. With all this massive electrical gear it is not surprising that the complete truck weighed about 6 tonnes. The electromagnetic theory known at the time was not sufficiently complete for Robert Davidson to appreciate the severe eddy current losses incurred by his use of solid iron in rapidly switched magnets, for it was probably this loss more than any other factor that limited the speed achieved by his "Locomotive" to about 7km per hour. Thus the world's first electric railway vehicle capable of carrying people ran at Edinburgh on 22nd September, 1842 over a distance of 2.4 kilometres. Unfortunately, Davidson did not publish his results, nor did he patent his inventions. But his achievements were observed and documented by other scientists and engineers to whom we are indebted for these details of the world's first electric locomotive of any size. Following Michael Faraday's primeval direct current motor and generator principles of 1821 and his homopolar generator of 1831, Negri built the first electromagnetic motor (actually a vibrator) and Pixii constructed the first commutator in 1832. It was mentioned in Michael Faraday's correspondence that Robert Davidson was producing useful electromagnetic motors in 1837 and railway applications were then predicted, although his activities in the earlier part of that decade are unknown. In other countries Thomas Davenport had a model electric railway running at Brandon, Vermont in 1837 and Jacobi in Russia had electric propulsion of a ship working in 1838. One Captain Taylor patented an electric motor in 1840 which appears to be a copy of Davidson's earlier electric railway "Locomotive" and other work exhibited to the public at Aberdeen in 1840. A strange regressive design electric locomotive was built in the USA by one Mr Page in 1851 and run on the Washington & Baltimore Railroad. It copied steam reciprocating mechanics although it was electromagnetically operated. Apparently it was unconvincing. Not surprisingly, the railway owners of the world took little or no notice of these electrical developments for more than · 40 years. They just continued to outdo each other with bigger and faster steam locos. No challenger to those hissing, puffing monsters could be seen coming from any direction, even by the most farsighted prophet. Yet such forecasters would all be wrong, for just out of sight over the temporal horizon two happenings would eventually change the railway scene completely. But that will be our story next month. Grateful thanks to Prof. A.F. Anderson; Prof. C. Davidson; Queensland Railways; NSW SRA; Amtrak, Clyde/ASEA-Walkers; and IEE (Eng) for material and permission to reproduce. ~ HIFIREVIEW Marantz PM-35 Integrated Amplifier This high-quality 35 watt per channel amplifier from Marantz breaks new ground in design and manufacture. Reviewed by LEO SIMPSON Marantz is a hifi company that has been around for a long time although it has had a number of changes of circumstances over the years. To celebrate its 35 years of operation, Marantz has just released its 35-series digital monitoring series. This consists of the PM-35 amplifier, the ST-35 synthesized tuner and the SD-35 cassette deck. For the very first Silicon Chip hifi equipment review, we decided to make it timely indeed, and evaluate the PM-35 amplifier, a unit which we think will establish a performance benchmark for low priced hifi amplifiers. The PM-35 designation not only has some significance in the celebration of Marantz's 35 year history, it also indicates the nominal power rating of the amplifier - 35 watts per channel. Surprise, surprise. In appearance, the PM-35 is unmistakably Marantz and owes much to the award-winning PM-94 model. But whereas the $3300 PM-94 is intended for those with very big wallets, the PM-35 is very much the amplifier for everyman. It sports a good range of control facilities and manages to do so without looking too "technical" and, for that matter, without being too unobtrusive. I am one of those people who likes an amplifier to look the part; I am not keen on really spartan styling. The four main controls, volume, selector and bass and treble, are all good-sized knobs which are well labelled. The selector has an adjacent columnar display in which very tiny LEDs indicate the selected program source. The input source designations are CD (compact disc), phono (MC), phono (MM), tuner, and TV/aux. The seldom used Balance control is a small knob under the Selector. All the other controls are pushbutton switches: power, speaker selector, tone defeat, tape/DAT monitor, loudness and CD/phono direct. We'll talk more about the last switch later. On the rear panel, the PM-35 has two pairs of gold plated RCA sockets for the CD and phono inputs, plus another four pairs of sockets for the other inputs. There are four pairs of shrouded binding post terminals to enable the connection of two pairs of loudspeakers and there is also a voltage selector NOVEMBER 1987 11 The Marantz PM-35 has generous heatsinks and plenty of ventilation to keep the traI).sistors cool. switch (220/240V AC). The two core mains cord is removeable. Design philosophy Inside the chassis, the Marantz PM-35 may not look very different to another in its price range, at least on a casual glance. But close examination reveals that this Marantz represents quite a different design approach to that of most Japanese amplifiers up till now. Perhaps we should qualify that statement. Most Marantz equipment is made in Japan but is designed in Eindhoven. Paradoxically, the chief designer is the notable Ken Ishiwata who is undeniably Japanese. The Marantz PM-35 is different is at least two main aspects. First, it does not use hybrid modules for the power amplifiers. Hybrid modules have the virtue (for the manufacturer) of being small, self-contained and (probably) cheap. But they usually do not offer the same level 12 SILICON CHIP of performance or overall power output as a carefully designed amplifier of equivalent nominal power output, using discrete transistors. Second, the Marantz PM-35 does not use lots and lots of transistors. It uses relatively few. In the past, Japanese amplifiers did, and still do, seem to use transistors for the sake of having lots of them. The total semiconductor count was in fact a selling feature. By this approach a power amplifier containing over 100 transistors would have to be much better than one containing only thirty, wouldn't it? Not necessarily so. This is not a good engineering approach from the point of view of reliability or ultimate sound quality. Marantz has been clever in reducing the number of transistors and integrated circuits to the minimum needed to get good performance. In the phono preamplifier, there are only four transistors coupled with the dual operational amplifier stages. These provide all the gain required for moving coil and moving magnet cartridge operation plus RIAA/IEC equalisation. The power amplifiers account for the rest of the semiconductors. There are no active stages for the tone controls as these are incorporated in the negative feedback loop of the power amplifiers. The Marantz PM-35 is not the first amplifier to use such an approach but it is still relatively uncommon. Not only is the power amplifier circuitry simple and straightforward, so is the power supply. It consists of a fair-sized transformer and bridge rectifier feeding a pair of 6800µ,F 42VW electrolytic capacitors. The latter are Elna "hifi""capacitors which we assume have been included because of lower than normal internal impedance. Apart from the general simplicity of the circuitry another interesting aspect of the PM-35's circuitry is the CD/phono direct switch. The concept of the CD/phono direct switch is simple and is a good one. It has been used on other Marantz amplifiers, beginning with the PM-94. The idea is that you bypass a lot of circuitry and therefore do not have any distortion contribution from that circuitry. Usually, the omitted circuitry is mainly that for the tone controls. As we have already pointed out though, the Marantz has no tone control stages as such, so no active circuitry is actually bypassed by the CD/phono direct switch. This is shown on the block diagram in the owner's manual. The switch controls a couple of small relays to bypass the selector and tape monitor switches, and the balance control, to connect the signal directly to the volume control. Ostensibly then, there is no real point to having the CD/phono direct switch but a little further thought shows that there is. Consider that if a tape deck is connected to the tape monitor loop and other program sources are connected to the amplifier then both the tape monitor and selector switches could contribute to signal degradation in terms of loading, crosstalk and extraneous signal injection. Therefore, it is worth having. Another interesting aspect of the Marantz PM-35 is the beautifully finished front panel. At first sight this looks like another example of the normal high standard of finish which the Japanese consistently achieve with black anodised aluminium extrusions. It is no mean feat to anodise aluminium to a consistent colour (black is a colour, by the way, being a particular combination of aniline dyes used in the anodising process). But the PM-35 front panel is not an aluminium extrusion, it is plastic. It is by far the best finished plastic moulding we have seen and we would have been fooled completely had we not looked at the interior of the case. Well, what is the advantage to the user of having a plastic front panel, even if it is well finished. Sooner or later amplifier panels become scratched. On black anodised aluminium scratches The PM-35 is one of a series of Marantz hifi components. Here is teamed with the ST-35 digital tuner and SD-35 cassette deck. become very obvious with the result that the appearance is severely degraded - it looks tatty. If you have the misfortune to scratch the PM-35's front panel (and it doesn't scratch easily) it won't be nearly as obvious because the colour goes all the way through rather than being skin deep. Performance Having taken in all the interesting design features of the PM-35, we were keen to give it the once-over for performance tests. Marantz rate the PM-35 is terms of IHF, DIN and FTC specifications. IHF (music) power is quoted as 80 watts per channel into 4 ohm loads and 50 watts per channel into 8 ohm loads. For the FTC ratings, meaning continuous power for rated harmonic distortion of .025% between 20Hz and 20kHz, the PM-35 is rated at 30 watts per channel into 8 ohms and 35 watts per channel into 4 ohms. Signal to noise ratio for the moving magnet phono input is quoted at 86dB (IEC A-weighted) while the equivalent figure of the CD input is 96dB (IEC A-weighted). Without going into all the whys and the wherefores we can say that the Marantz PM-35 passed all the performance tests with flying colours - no problems at all. Well, you'd expect it, anyhow. Sound quality is very good, clean and unfussed. It must be rated highly, particularly among amplifiers in this price range. And the best part is the price. At $549, it is something of a bargain. To sum up, we are very attracted by the design of this amplifier. Its engineering is clever so that the overall product is electronically uncomplicated. It should give many years of faithful service and if it ever does need repairs, it will be an easy amplifier to service. We rate it highly. For further information and a demo, contact your hifi dealer. Marantz equipment is distributed by Marantz (Australia) Pty Ltd, Figtree Drive, Homebush, NSW 2140. Our thanks to Audiosound Laboratories, of 148 Pitt Road, North Curl Curl, NSW 2099, for the use of their facilities in the preparation of this review. 41:: NOVEMBER1987 13 THE WAY I SEE IT By NEVILLE WILLIAMS They'll sell you anything but don't ask them to fix it! Pause long enough to inspect the electrical or electronic wares in u store and you'll find someone at your elbow eager to assist and advise. But call again to report that what you bought has failed and the response is likely to be strictly formal: "Sorry, but we can't help you directly. You'll have to take the matter up with (somebody else)"! In making the above observation, I'm not reacting to something that I just happen to have heard about or read about. On the contrary, a series of frustrating situations, which I encountered at first hand, proved to be the tip of a large and growing problem in the area of equipment servicing. Perhaps I should explain that, when I was younger and more involved in the practical side of the industry, I did most of my own repairs. These days, with dedicated components and technology becoming the rule rather than the exception, I prefer to rely on people who specialise in this work. So I'm a technically informed but otherwise typical consumer. My practice, in magazine articles, has traditionally been to advise other typical consumers to refer their problems, where possible, to the manufacturer concerned or to a local organisation that the manufacturer has accredited for the area. Such advice is based on an assumption that the manufacturer and/or accredited representative should be familiar with the symptoms and problems of their own product range and have ready access to replacement parts. Where direct representation is 14 SILICON CHIP not accessible, I've normally suggested contacting an. established specialist service organisation or, failing that, an individual on-thespot repairman that other consumers are prepared to recommend on the basis of experience. In the light of recent observations, however, I'm less confident in offering that sort of advice. Overall, the reliability of consumer electrical and electronic equipment may have improved but, if it should fail, the provisions for service and repair appear, for a variety of reasons, to be less predictable than they once were. YA WANNA WA\'T' l=OR \"t".. ~ •. " I list below a number of situations which, as mentioned above, were encountered quite spontaneously at a personal level. Heaven alone knows what might come to light if one really went looking for problems! CASE 1 Cassette Tape Data Recorder: owned by a close relative, it was part of an inexpensive but useful computer-cum-word processing setup. It began to mangle tapes and inspection showed that a small neoprene-tyred idler wheel, driving the take-up spool, had failed. I rang the distributor who advised that replacement parts were not available; if submitted for service, they might be lucky enough to score a replacement from a reject unit but they warned that, being no longer under warranty, the minimum service charge would be $40.00. Faced with an indefinite delay and an uncertain result, the owner had little choice but to discard the otherwise serviceable recorder and buy a new one costing around $ 70 - this for the sake of an item worth a few cents! CASE 2 Video Cassette Recorder: it was operating normally when the tuner and clock suddenly went dead, suggesting a possible failure in the supply line to that portion of the assembly. The unit was ticketed to indicate the fault and delivered to the manufacturer's service department. Their response to a subsequent enquiry about its fate seemed to in- dicate that it had been despatched elsewhere for service. It would be repaired as quickly as possible, they said, but six weeks elapsed before I finally got it back. CASE 3 - Microwave Oven: cooking times had become tediously long and, since the unit was about five years old, it seemed likely that it required a new magnetron. It was delivered direct to the service counter of the manufacturer's Sydney complex. An inquiry about three weeks later produced a very vague response and the best part of another month elapsed before it was ready to pick up. While I was waiting for it at the counter, I overheard another customer complaining bitterly that he'd been waiting over eight weeks for a room heater to be fixed - this in the middle of winter! CASE 4 - Computer Printer: when it failed recently, I returned it to the local distributor and emphasised that, as a freelance writer, I was in a bind without it. A week later, I was told that although the printer was ostensibly a standard model, one of the PC boards differed from that shown in the service manual. A replacement for an IC on the unfamiliar board would have to be ordered from overseas. As I write, that was eight weeks ago and the printer is still sitting forlornly in the service department. CASE 5 - Computer Printer Ribbon: I would have been in all sorts of strife for lack of a printer had not a friend loaned me one of another brand which he wasn't using at the time. I managed to couple it successfully to my computer but found that the ribbon was badly in need of replacement. It was from an office system and, without too much apprehension, I rang the supplier. "Unfortunately, sir", I was told, "that system was superseded around 1981 and we no longer supply consumables like ribbons or discs". They suggested that a certain small company in Melbourne might just be able to help. As for other-brand ribbons that could possibly be compatible, they "really didn't know". CASE 6 - Computer Monitor: when I recountered the above to a schoolteacher friend, he was much more interested in sharing his own problem. His personal computer is very much a current model but the monitor had just failed. When he rang the service department of the Australian agent, they quoted an estimated six weeks to repair it, even if he delivered it next morning direct to the service counter - six weeks to repair their own near-new video monitor that would contain far fewer "works" than a small colour TV set! As I remarked earlier, if these situations are what one consumer can nominate off the cuff, at a purely personal level, what would emerge if one went around deliberately turning over stones? When I mentioned the above to an executive in a suburban servicing organisation, he was quite unmoved. His verdict: I'd say they were about par for the course". WHY 'S£'{'1'l..E FOR A l',lE.W ~~1" ~"'EN :~oWN~~?. \ .-1,! ~ Expect about six weeks! So there you have it, customers: nowadays, if you return for repair your cassette radio, TV set, VCR, computer, microwave cooker, room heater, or what have you, be prepared to wait six weeks before you become really impatient or start getting your knickers into a knot! And that's irrespective of whether or not the device is under warranty. I also shared my thoughts with Jim Yalden, VKZYGY, in the course of a casual "rag-chew" on the 2-metre amateur band. Jim has his own company in Milton, NSW, servicing both consumer and professional equipment in the general area. Jim stressed that it was in his own interest to get jobs in and out of the service shop as quickly as possible but it was becoming more and more difficult to do so, mainly because of delays in obtaining critical replacement parts. Some suppliers weren't too bad, he said; others were "hopeless" and, in such cases, neither he nor any other serviceman could avoid long delays. He went on to nominate typical situations that had recently been or still were - a source of acute embarrassment to him, including: • A late model major brand VCR that has been sitting on his shelves for six weeks awaiting a replacement reel motor. Present indications are that it will still be another four to six weeks before he can start the job. • A cassette radio, still under warranty, which he finally returned to the distributor rather than carry the odium for not being able to obtain a replacement for a major component. The buyer has been without it for over six months! • A microwave oven for which he cannot obtain the appropriate magnetron from the supplier. It's been held up in his workshop for seven months and, just before talking to me, he'd heard that the owner had given up and bought another one. • A trawler depth-sounder which he could not repair for want of a critical component. The Australian agent quoted a minimum of seven weeks to import a replacement. Through a Japanese contact, the trawler owner was able to telex an order to that country and the replacement arrived just 10 days later. To someone who can look back to the early days, delays like the above are unthinkable. I learned the ropes at Reliance Radio in Sydney, at that time a small manufacturing-cum-retailing firm which relied heavily for its success on word of mouth recommendations. If a receiver failed, especially during the warranty period, management would do their level best to have the problem sorted out during the next couple of days, NOVEMBER 1987 15 come hail, rain or shine - a phrase that meant something when a serviceman rode around on a motorcycle/sidebox combination. A failed set and a dissatisfied customer were seen as a potentially bad advertisement. When I later transferred to the Amalgamated Wireless Valve Company, part of my new job was to keep track of valves from all sources and devise brochures aimed at helping servicemen effect substitutes for types for which there might currently be no direct replacement. It was a free service intended to generate "goodwill" (remember the word?) for the AWV/Radiotron brand. we now seem to have gone to the other extreme. Just before writing this, I was involved in helping a relative select a new 34cm colour TV set. In the course of so doing, I enquired about warranty and service arrangements for the respective brands on display. Most, it appeared, carried a 12-month warranty covering parts and service. No, 34cm TV sets were not normally serviced in the home but the sales assistant seemed quite uncertain as to whether all or some of the brands had to be returned to the store or direct to the service department of the particular distributor. Either way, the buyer would have to deliver the set and collect it again when it was ready. What about the turnaround time for service under warranty? The answer: an off-handed "Maybe three or four weeks" - as if time didn't really matter. I was left with the firm impression that the assistant's job was to sell the goods, take the money and process the invoice. After-sale ser- 16 SILICON CHIP vice was an incidental that they'd prefer I hadn't pursued. A warranty card was included in the paperwork. It was the W€.LL,t customer's responsibility to fill it t t;OULt> ~ l'I\IU<. out, send it to wherever it had to go, and resolve any problems that might arise with whoever it nominated. Transport is up to you Commenting on this, Jim Yalden, an accredited service representative for a number of different brands, confirmed that most TV sets now carried a 12-month warranty, which required that the smaller models be brought in for repair. He said that he has had to reorganise his own business to restrict in-home service of all kinds. Even with a door-knock fee acceptable to his clients, time spent "piloting" the service van, the inefficiencies of in-situ repairs and the frequent need for a return visit all add up, these days, to a formula for "going broke" He now insists that all transportable items be delivered and picked up by the client, and that includes electrical equipment, radio sets, cassette players, VCRs and TV sets smaller than 56cm. He points out that manhandling 63cm and even some 56cm TV cabinets ("coffins" Jim calls them) is not an easy task for a lone serviceman, further complicated by the attendant risk of scratching or otherwise damaging the cabinet. A serviceman in a nearby town, he said, is now insisting that clients who live outside the town boundaries arrange for a professional carrier to pick up and deliver large TV sets, if they can't handle them in their own vehicle. Another country serviceman, whom I've heard about since, is flatly refusing to make any home calls at all, even though he's accredited for warranty service on most brands. Instead, he's come up with a novel arrangement whereby the local milkman will pick up and deliver items for service, for a separate fee! While country serviceman in particular may regret having to impose such conditions, many may well have little choice in the matter, in the face of escalating costs. The one-time door-knock fee of around $25 is claimed to nowhere near cover travel time, equipment and vehicle costs for a professionally competent technician. If metropolitan servicemen can justify $50, the call charge in the country should allegedly be above that again. However, according to Jim Yalden, sales staff have a moral obligation to acquaint customers with service conditions, particularly with physically large and complex equipment in country areas, and especially if customers live out of town. Spare parts problem As for the shortage of replacement parts and the long turnaround times he, like others I talked to, tended to blame it in part on longterm fallout from the reduced value of the Australian dollar. When the exchange rate was in our favour, the major Japanese companies enjoyed a thriving market and it was no hassle for them to set up their own generously equipped service departments, with access to ample stocks of replacement parts. But now, with the exchange rate down from 300-400 yen to the $A to just over 100, the market for new equipment has shrunk in both volume and profitability, while the dollar commitment for spare parts sufficient for all those models already in the field has gone through the roof. With a restricted inventory, the flow of spare parts is more vulnerable to shipping and handling delays, and to industrial disputes - one of which is tying up deliveries even as I write. Nor is the position being helped, someone suggested, by the different attitude overseas to equipment servicing. In Australia, if a unit fails, normal customer reaction is to get it fixed. In Japan, consumers are encouraged to cut their losses and replace it with a later model. On this basis, it wouldn't be too surprising if the word from Japanese boardrooms is to keep a close watch on the service dollar Down Under! Whether or not this is so, there is certainly ample evidence of the manufacturers' service involvement being rationalised in respect to both spare parts and staffing levels, with the diversion of an increasing proportion of own-brand repair work to outside contractors. Up-to-date information Another major problem area for service technicians was brought to my notice by John Ridley, manager of the Villawood (Sydney) division of Hills Telefix, a company that has kept my own TV sets walking and talking for a number of years - in exchange for the usual insurance fee. In his opinion, technology is running ahead, not only of the real needs of consumers, but the ability of the manufacturers to communicate "how it works" and "how to fix it" information in their own literature, and ultimately to the technicians who have to service the equipment. Even worse, some of the difficulties which have arisen in the field seem not to have been foreseen or allowed for in the development labs, requiring tedious backtracking across national and language boundaries to sort out the problem and the probable need for circuit modifications and/or updated literature. There is a practical limit, says John Ridley, to the amount of experience and information which any one technician can bring to bear on the equipment which, these days, he is likely to encounter in the home. There is also a limit to the amount of literature that he can carry or access or absorb, even given the back-up which a company like Telefix can provide. Jim Yalden agrees, pointing out that a self-employed service technician Illpy now have to pay anything up to $50 for the manual on a new IJlOdel TV receiver or VCR. Yet, without access to many such manuals and to suitably high-tech test equipment, it is simply not possible to service new equipment efficiently or even - in the longer term - to stay in business. That is why, says Jim, TV technicians are "leaving the industry in droves"; and why the number of well-equipped repairmen in country centres is down to around half of what it once was. Caveat emptor! In my view, we as consumers are getting uncomfortably close to the point where that frustrating phrase has to be invoked: "caveat emptor" - let the buyer beware [since he buys without recourse). When next you front up to the sales counter in search of a new TV set, VCR, or other item of electronic gadgetry, heed John Ridley's remarks and don't be too easily talked into investing in the biggest and the best, with the most features and the latest technology. There's not much point in buying facilities that you'll rarely use, and/or gee-whiz technology that may needlessly complicate and add to the cost of future service procedures. If you live, or plan to live in the country, keep in mind Jim Yalden's warning about the currently diminishing numbers of rural What is your view? This story paints a rather uncomplimentary picture of the service available on consumer appliances but there must be another side to it. We are sure that many companies must be doing their very best to provide good service and. are succeeding. We'd like to hear from these companies and from readers. Tell us about your good and your bad experiences . Write to Silicon Chip, PO Box 139, Collaroy Beach , NSW 2097. repairmen, who are prepared, competent and adequately equipped to take on cumbersome, timeconsuming high-tech repairs. Finally, my own two-cent's worth: don't assume that your friendly emporium will take over your service worries, because they've been so nice to you in other ways. Check out the warranty, read the fine print and discover exactly what's involved. What is the warranty period and what does it cover? Does it cover all parts and labour for the full period? Is the work done in the home or does the unit have to be returned for service to the store or to the distributor's service department? If the latter, where is it situated, and during what hours is it open? What is the turnaround time for a typical repair? You may not require service, of course, but if you do, it's well to discover beforehand that the model you are considering has to be delivered to, and picked up from, the front end of a queue at an awkward address (for you) between awkward hours on week days only. Believe me, those are not idle observations. The relative mentioned earlier settled for a 34cm receiver partly because, living alone, it would be small enough for her to transport for service, without assistance. The brand she chose offered the further advantage that during and after warranty, it could be returned conveniently either to the manufacturer or to a nearby service insurance centre. That's the way I see it. ~ NOVEMBER 1987 17 Vibration Sensor! Bargain Coble Clamps! Electric Motor NiCads - Extra Value Packs Cat J -1041 Save with NiCad battery packs! Long life, high power batteries for all your portable power needs. Qty 4 x AA 2xC 2xD 4 X AA 2xC 2xD Type 500mAh 1.2Ah 1.2Ah 600mAh 2.0Ah 4.0Ah Cat No. S-3150 S-3152 S-3154 S-3160 S-3162 S-3164 $18.95 $15.95 $18.50 $19.95 $24.95 $27.95 Non-spill lead -acid batteries . High capacity, ideal for backup {alarm, etc). Or for power in their own right. Can be used in any position! Cat No. Type Price S-3315 S-3316 S-3320 S-3322 1.2Ah 1.9Ah $29.95 $34.95 $35.00 $55.00 .. :;;;:'"·~-- . .. 6.5Ah WAS $2.50 The Button: Cheap Insurance! It simply plugs into any power point - and protects everything on that circuit (le on other power points) from damage caused by _power line spikes. Computers, videos, hi•fis, TV's industrial and domestic machines ... all can be ~ For use with most alarms! Senses vibration in windows, ceilings, doors, etc. Huge savings!! $125 Cat L-525i"O,_."f="='"':';l..l,..:a-..::_ .j Save an incredible $5 OFF the economy Wire Wrapper / Stripper. Get that professional finish! Cat T-3650 $795 Dyna Bolt Eye Pack! ~ WAS $11.95 Save $5!! Keep your Compact Disks clean for the best sound. Look after your valuable investmen,s! :s~~=er$ ~;;~:r;~ a~ . 8~t I ~-- ' . $850 The Biometal Wire Starting Kit lets you make mechanical actuators that can be triggered by heat or electricity. Comes complete with comprehensive instruction manual! $4995 . ·. . CB Antenna Spanner! e~IP" A· . ,__ Heavy duty metal construction for coax cable connections! Cat L-4508 NOW $1 Great savings on 9V NiCads (the [ ) ones most used 1 in transistor radios). 100mAH rated! Cat S-3308 5c . a t Less than 1/2 price! For PCB mounting with 4 positive location positions. Ideal for input selection I Cat 5-2060 MetalUne Plug Made specially for 'D' size NiCads! Takes two or four batteries. Rated at 2 x 3V. Miniature Sllde Switch! 45t _ e Saveon9V NICGds ONLY$995 SAVE50e _ .19) ONLY NICad Charger Reduced! :;9~ M-94f.Si Cat C-7085 WAS $14.95 $1,s Ideal tor Robotics! Cat K-7000 CD Cleaning Kit! For tying support cables for antenna masts to concrete, masonry, etc. 8 x 45mm . 2 per pack! 240 volt primary with secondary tappings 40V <at> 10mA, 19V<at> 200mA and 11.2V <at> 450mA. CatO-1532_ '· Wrap and Save!! s1t o~;, Designed for audio use. Checks cab les in seconds. Ideal for roadies, bands, audio techn icians, etc! $125 NOW $150 Price Gell Cells ( 12V) 2.6Ah Save 40%! Electric Motor with switch . Great for hundreds of projects! Heavy duty cable clamps in pack of five. Keep things neat and secure! Cat H-1972 Pack Of 5 Time Saving Coble Checker Keep one in the glovebox! Two open end and two full ci rcle spanners in one unit to fit all those antenna nuts! Cat 0-4018 99t r"ij $1995 . UHF/VHF Dlplexer! So you can run both UHF and VHF antennas to your video or TV. Designed for indoor u s _,,,, e 0 . Cat L-4470 ,,- $695(- -· -·. Cat M-1200 Coax Relay Save $10!! For PCB mounting it's ideal for all HF, VHF and UHF switching! Rated at 12 volts, 80mA. Cat S-7402 Savel $24)85 MetalUne Socket! Great saving! Heavy duty metal line socket for coax! Cat L-4509 Over 60% Off! 2 Tone Plezol Quality Adaptor "F" Male tc RCA Female! Save $2.45 OFF our normal price! Ideal as a local audio alarm! Emits high pitched warbling sound. 9-16V operation! Save $2!! Cat L-7027 Value! Cat P-2100 $550 WAS $1 .20 • Protects ali"three lines (active/neutral, active/earth and neutral/earth). • Better than 1 Ons response lime. • 150 Joule rating (consumes no power except when a surge/spike Is present). • If you value your equipment, you'll value The Button even more - especially at our great value price! PTY LTD TRIP the light fa~tastic ,.:Jt~:-. ,,~ ~- °'. PAR 38 Coloured Bulbs • ~ 240 volt, highest quality pressed glass with internal reflector. Ideal for semi-rough handling (they are glass, after all) - eg disco and lightshow use. All • rated at 100 watts, ES (Edison screw) fitting . Yellow: Cat S-3850 Blue: Cat S-3854 Red: Cat S-3852 Green: Cat S-3856 $995 Halogen Torch Bulbs At last the voltage bulbs: whiter, stronger light. Less infra-red output so they're more effecient. In fact, the manufacturers say up to 300% brighter than conventional bulbs. 2.8 volt - use with 2 x 'D' batteries Cat S-3950 4.0 volt - use with 3 x 'D' batteries Cat S-3955 5.5 volt - use with 6 volt lantern or 4 x 'D' batteries QualifY. Screwdrivers Cat S-3960 With this great range of screwdrivers you can screw it up without ruining it! Cat No. Type 1 T-6010 Mini - Flat Head 2 T-6015 Mini - Philips Head 3 T-6020 Stub by - Flat Head 4 T-6025 Stubby - Philips Head 5 T-6030 Standard - Flat Head 6 T-6035 Standard - Ph ilips Head 7 T-6040 Popular - Flat Head 8 T-6045 Popular - Philips Head 9 T-6050 Long - Flat Head 10 T_-6055 Long - Philips Head 11 T-6060 Heavy - Flat Head 12 T-6065 Heavy - Philips Head Pay Only $1.50 $1 .50 $2.45 $2.45 $1.95 $1.95 $2.45 $2.45 $2.45 $2.45 $4.45 $4.45 Remember when Y~d'!J!'!!~c~n ~ ele~ ! ~t! .. Relive those wondrous days of yore with our great little electric moto rs! Famou s Mabuchi brand (yes, the ones li ke when you were a kid!), nom inal 3 volts $275 Cat M-9961 ~ All • $765 -1, ··~Jil '' - ~ ~;;;;::;:::zr.if", - Musicolour IV The Musicolour Mk IV in four chase patterns plus auto chase and reverse chase AN D fou r channel colou r organ with built-in micro phone means you're ready to stage a lightsh ow! Comes with sturdy steel case and exclu sive DSE front panel with LED display. Detailed instructions supplied, too! Cat K-3143 " Beat Triggered Stobe What's beter than a strobe for parties? A beat triggered strobe! Really makes your music come alive by flashing in time with the music - hence the name. of course you can also use it in conventional stro be mode - with a variable flash rate up to about 30 flashes per second . Kit includes spun alum inium photo reflector with safety perspex guard, plus super long life discharge capacitors . Cat K-3153 s5995 r 3 Core Flat Ught Cable RSO Daylamps Ideal for display, party or other decorative or warning purposes. Available in four colours; 240V operated . ES base. Yellow: Cat S-3851 Red: Cat S-3853 Blue: Cat S-3855 Green: Cat S-3857 . ., ·. . , , .. BUILDERS ... SPARKS... ·, Need an extra light in the bathroom, lau ndry, work space, etc? 3 core flat 1/113 light cable with insulated earth and rated at 10 amps (1.13mm) at super low prices. Cat W-2060 $595 95~ per metre $70 (100m roll) Your local reselle r is: • NSW • Ballina: A. Cum mings & Co. 86 2284 • Bowral: F.R.H. Electrical 61 1861 • Broken Hill: Hobbies & Electrof'l ics 88 4098 • Charlestown: Newtronics 43 9600 • Coffs Harbour: Coffs Har bour Electronics 52 5684 • Deniliquin: Deni Elect ronics 81 3672 • Forster: Forster Photo Sound 54 5006 • lnverell: Lyn Willing Electronics 22 1821 • Leeton: Leeton Record Centre 53 2081 • Lightning Ridge: Lightning Ridge Newsagency 29 0579 • Lllmore: Deere 21 4137 • Moree: Moree Electrical Services 52 3667 • Newcastte: Newtronics 43 9600 • Port Macquarie: Hall of Electronics 63 7440 • Orange: Fyfe Electronics 62 6491 • Springwood: Wellington's Electrical Di scounts 51 4888 • Taree: Brad's Electronics 52 6603 • TumutTumut Electronics 47 1631 • Ulladulla: Pauls Electronics 55 3989 • Wagga: Phillips Electron ics 21 6558 • Wellington: Wellington Electrical Service 45 2325 • Windsor: M & E Electronics 206 George St, 77 5935 • Young: Keith Donges Electronics 82 1279 •VIC • Boronia: Ray Cross Electronics 762 2422 • Colac: Colac Electron ics 31 2847 • Dunolly: Ken Roberts (Finders) 68 1333 • Echuca: Webster Elect ronics 82 2956 • Mildura: McWilliams Electronics 23 6410 • Morwell: Morwell Electron ics 34 6133 • Rosebud: Pentronics 86 7688 • Shepparton: GV Electronics Centre 21 8866 • Sunbury: Calco Electrical 744 1564 • Warmambool: Marrtronics 62 9870 • Werribee: Gables Photog raphic & Video 741 7089 •OLD• Bundaberg: Bob Elkin Electronics 72 1785 • Ca lm s: Electronic World 51 8555 • Caloundra: Hume·s Electro-Mart 91 4270• Dysart: Dysart Videotronixs58 2107 • Gladstone: Supertronics 72 4321 •M ackay: Stevens Electronics 51 1723 • Mooloolaba: Mat's ~lectronics 44 6588 •Maryborough: Kalla r Elactronics 21 4559 •Mt lu : Outback Electronics 43 3331 • Nambour: Nambour Electron ics 41 1604 • Noosa Heads: Sunshine Phone Systems 47 4444 • Townsvllle: Tropical T.V. 79 1421 • SA • M t Gambief: Hutchessons Communications Centre 25 0400 • Whyalla: Eyre Electronics 45 4764 • WA • Albany: Micro Electronics .41 3.432 • Karratha: Dave·s Oscitronics 85 4836 • TAS • Devonport: A.I. Electronics & Hobbies 24 8322 • Launceston: Wills Electronics 31 5688 • NT • Alice Springs: Farmer Electron ics 52 2967 \ ',,, 3 Core Power Cable"~ Save even more! 3 core fl at 1/178 power cable with insulated earth at this fantastic low price. Usually referred to as builder's cable, rated at 25 am ps (2.5mm) you can have power wherever you need it! Cat W-2062 50 $1 per metre $110 (100m roll) Capacitance adaptor for your D This clever adaptor circuit plugs into your digital multimeter and can measure capacitance up to 2.2 microfarads. by JOHN CLARKE & GREG SWAIN The capacitance adaptor is plugged directly into the DMM terminals. Below is a view inside the PCB version. 20 SILICON CHIP When was the last time you had trouble deciphering a capacitor label? The fact is, it's all too easy to misinterpret capacitor markings. And that's something you can't afford when building projects. A capacitance meter neatly solves this problem. You simply plug the unknown capacitor into the test terminals and read the value in picofarads (pF) or microfarads (µF} directly from the digital display. You can also use a capacitance meter to check suspect or unmarked capacitors and to select critical capacitor values. If you have a digital multimeter (DMM), you may already have a capacitance meter. Many DMMs now include capacitance ranges as standard, and these can typically check values up to about 20µF. If your digital multimeter doesn't have a capacitance facility, this simple adaptor circuit is for you. It plugs directly into the DMM's terminals and can measure values up to 2.2µF in two ranges: 0-2200pF (.0022µF) and 0-2.2µF. Don't be worried by the 2.2µF upper limit - capacitors with values greater than 2.2µF are usually clearly marked and seldom require testing. Note that this adaptor is only +SV 1 T 16VW_I:- 9V : .,. ...L. HIGH LDWO S2a "} VR3 47k NULL ADJUST ON/OFF..,. 3 (b) Cl 390pF+ 2.2 16VW + + - 03 .04 7 t VRl 100k LOW ADJUST TO METER VR2 470(! HIGH ADJUS 1M + ex DMM CAPACITANCE METER 041-1287 LOW : 0pF-.0022uF HIGH : 0·2.2uF LID OF CASE 1- The circuit is based on a single 74HC132 quad NAND Schmitt trigger. It produces a voltage which is directly proportional to the test capacitance Cx. suitable for use with digital multimeters. It cannot be used with analog meters because of their much lower input impedance. Note: digital multimeters usually have a fixed input impedance of 10 megohms. The circuit The circuit is basically a capacitance to voltage converter. You plug a capacitor in, the circuit produces voltage which is directly proportional to the capacitance, and the value is indicated by the digital multimeter. On the lower range, the circuit produces an output of one millivolt per picofarad of capcitance; on the upper range, it produces one volt per microfarad. Just two active devices are used by the circuit: a 74HC132 quad NAND Schmitt trigger (ICl} and a 5V regulator. ICla forms a free-running oscillator with VRl providing frequency adjustment. The square wave output of this oscillator is fed to two inverters, ICl b and IClc. The test capacitor Cx is connected to one of the inputs of IClc. Cx charges via Dl during positive half-cycles of the oscillator waveform and discharges on negative half-cycles via one of two resistance values. On the LOW range, Cx discharges via the lMO resistor, which is connected permanently in circuit. On the HIGH range, Cx discharges via VR2 and its series 6800 resistor (and also via the lM0 resistor which is now in parallel). Now look at ICl b. On the HIGH range, the output of ICla is connected directly to the pin 1 input of ICl b. So the output of ICl bis simply a mirror of the output of ICla. And with no capacitor across the Cx terminals, the output of IClc is virtually identical to that of IClb. If we were to measure the absolute voltage difference between these two outputs, the result would be zero. Now consider what happens when a capacitor is connected across the Cx terminals. Cx charges quickly via Dl and discharges slowly via VR2 and the 6800 resistor. This means that the input to IClc stays high for longer than l.t stays low, depending on the size of the capacitor. So the output waveform from Cx is a series of pulses at the same frequency as ICla but with pulse length inversely proportional to the size of Cx. This is illustrated in Fig.1 . If Cx is PARTS LIST 1 PCB, code SC041-1287, 44 x 62mm (or Veroboard 44 x 62mm) 1 plastic case, 83 x 54 x 28mm 1 Scotchcal label, 50 x 80mm 4 banana plugs (2 red, 2 black) 2 banana panel sockets (1 red, 1 black) 2 alligator clips (1 red, 1 black) 1 DPDT toggle switch 1 SPDT toggle switch 1 9V battery 1 battery clip Semiconductors 1 7 4HC132 quad Schmitt NAND gate (don't substitute) 1 78L05 3-terminal regulator 3 1N914, 1N4148 diodes Capacitors 1 1 OµF 1 6VW electrolytic 1 2 .2µF 16VW electrolytic 1 1µF 16VW electrolytic 1 0.22µF metallised polyester 1 .04 7 µF metallised polyester 1 390pF polystyrene Resistors (0.25W, 5%) 1 x 4 . ?MO, 1 x 1 MO, 2 x 120k0, 1 x 1 OkO, 1 x 6800, 1 x 1 OOkO miniature vertical trimpot, 1 x 4 7k0 miniature vertical trimpot, 1 x 4 700 miniature vertical trimpot. Miscellaneous Rainbow cable, solder, calibration capacitors. relatively large, the positive pulses on pin 8 of IClc will be very short. This is shown as pulse waveform (c).Now, if we measure the averaged difference between waveforms (b) and (c ), we get a voltage which is proportional to the capacitance of Cx. These pulses are filtered by a dual RC filter (10k0 and 2.2µF, and 120k0 and 0.22µF} to give a smooth DC voltage. This voltage is then measured by the DMM which gives a direct readout of the capacitor value. Sadly, things become more complicated when we switch to the LOW range. The bugbear is stray capacitance across the Cx terminals. Without some correction for stray capacitance, measurements of low value capacitors will NOVEMBER 1987 21 (a) (a) (b) (b) (c) Jl___n_n_n__r (11-c) (c) (11-c) STRAY CAPACITANCE ONLY Rg. 1 Fig.I - this waveform timing diagram applies to the HIGH range. Fig.2 - waveform timing diagrams for the LOW range. The positive pulses at (b) and (c) are shorter than at (a) due to capacitor Cl and the stray capacitance at the Cx input. (c) (b·C) n n n ____. ..______. ..______. _ InL Fig. 2 WITH CAPACITANCE ex CAPACITANCE METER Parts layout and wiring diagram for the PC version. Make sure that the IC, diodes and 3-terminal regulator are correctly oriented. have serious errors. Here is where the null circuit comes into play. When S2a selects the LOW range, the output of IC1a is fed to pin 1 of ICl b via diode D2 to charge the 390pF capacitor, Cl. Cl charges quickly via D2 and discharges more slowly via VR3. So the input to pin 1 stays high for a short period, each time pin 6 of ICla switches low. The result is that the positive pulses from the output of IC1 b are slightly shorter than they otherwise would be. This is shown in (b) of Fig.2. (Look closely, it is not apparent at first glance.) Waveform (c) shows the output of IClc with only stray capacitance at the Cx input (ie, no test capacitor connected). The stray capacitance is charged via Dl and discharges via the lM0 resistor. Hence, the positive pulses from the output of IClc are also slightly shorter than they otherwise would be (if there was no stray capacitance). VR3 is the null adjustment. It is set so that the positive-going edge of 22 SILICON CHIP waveform (b) coincides with the positive-going edge of (c) (ie, the delay times are made equal). Thus, if we measure the voltage between (b) and (c ), we will get a zero reading since both waveforms are identical. This is shown in Fig.2 as waveform (b-c). Thus, the effect of stray capacitance is cancelled out. We're not out of the woods yet. Offset voltage When the LOW range is selected, D3 and its series 4. 7M0 resistor are also switched into circuit. D3 feeds the square wave output of IC1c to a voltage divider consisting of the 4. 7M0 resistor and the lOk0 resistor on pin 8 of IC1c. Actually, D3 is forward biased only when the output of ICl b exceeds 3.1 V, and is reverse biased when the output drops below 3.1V. As a result, a fixed + 5mV offset appears on the negative output terminal (ie, the negative terminal is jacked up by 5mV). To null the circuit, the voltage on the positive ter- 0 ON OpF0.0022uF LOW 0 0 0-2.2uF HIGH 0 This actual size artwork can be used as a drilling template for the front panel. minal must also be increased by 5mV. This is achieved by adjusting VR3 so that ICl b actually triggers high before IC1c triggers. Why has this been done? The reason is that the offset voltage overcomes a tendency for ICl b and IClc to lock together when their respective trigger points are close. By adding the 5mV offset, the circuit is nulled with ICl b set to trigger well before IClc. This eliminates the locking problem. On the HIGH range, the stray capacitance is insignificant corn- pared to the Cx value and the nulling circuit is disabled by shorting VR3 with S2a. Similarly, the offset voltage circuit is no longer required and D3 is disconnected by S2b. OK, we're now out of the woods. Power for the circuit is derived from a 9V battery. A 78105 3-terminal regulator provides a regulated + 5V rail so that the oscillator and nulling circuits remain in calibration over the life of the battery. Note that a high speed CMOS NAND gate IC (type 74HC132) should be used in this circuit since this type of IC has shorter propagation times than standard CMOS. This is particularly important when measuring low capacitor values on each range. This is the view inside the Veroboard version. Take great care if you elect to use Veroboard as it is very easy to make a mistake. Construction We built two versions of the DMM Capacitance Meter - one on Veroboard and the other on a small PC board. Both versions fit into a small plastic case measuring 83 x 54 x 28mm. They are plugged into the DMM test terminals by means of banana plugs which protrude through the rear of the case. The lid of the case carries two banana panel sockets and the range and power switches. The test capacitor is connected by alligator clip leads attached to banana plugs which plug into the panel sockets. Although two versions of this project are shown, we strongly recommend that readers build the PCB version. Use Veroboard only if you want to save money and you are an experienced constructor (it's very easy to make a mistake with Veroboard). Cuts in the Veroboard tracks can be made using an over- Above: actual-size PC artwork. 0 0 t~~a:;:,='-"'ii--l 0 0 0 0 The wiring diagram for the Veroboard version. Cuts in the board tracks can be made using an oversize drill bit. size drill bit. Install the resistors, capacitors and trimpots on the board first, followed by the IC and the 3-terminal regulator. Make sure that all polarised parts are correctly oriented. These include the IC, diodes, 3-terminal regulator and electrolytic capacitors. The banana plugs are soldered to the underside of the board as shown in the photographs and further secured using the screw-on insulated mouldings. It will be necessary to cut the mouldings to a length of 6mm so that the battery will fit in the case. We used a self-adhesive label for the front panel and this item will probably be supplied in most kits. Trim the label to size using a pair of (Continued on page 96) The battery is sandwiched between the front panel and the circuit board. Use insulation tape to prevent shorts. NOVEMBER 1987 23 ~M T~Mn~M TVMM JM TVMM~M TVM MJMTVAMJATVAHJATVA H JAT VAH JAYVAH JAYVAHJAYVAHJAYVAHJAYVAHJAYVA HJ AYVAH JAYVAHJAY~AHJAYGAH JAYCARJAYCAR JAYCARJAYCAR JAYCARJ AYCARJAYCAR JAYCARJAYCARJAYCARJ AYCARJ AYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJ AYCARJAYCAR JAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR JAYCAR JAYCARJAYCA RJAYCA RJAYCARJAYCARJ AYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR JAYCARJAYCAR JAYCARJAYCAR JAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR 'JAYCAR JAYCAR JAYCAR JAYCA::l JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR JAYCAR JAYCAR JAYCAR JAYCAR 12-230VOLT JAYCAR INVERTERS JAYCAR JAYCAR 40WAIT JAYCAR Ref: EA Aug 1985 JAYCAR JAYCAR Cat. KA-1598 JAYCAR JAYCAR Ref: EAJanuary 1983 Ref: EA December 1983 Ref: EA September 1984 JAYCAR Cat. KA-1506 Cat. KA-1505 Cat. KA-1560 JAYCAR 300WATI Cat. KA-1559 JAYCAR Ref: EA Sept 1985 JAYCAR JAYCAR • I JAYCAR JAYCAR • • I I JAYCAR JAYCAR JAYCAR JAYCAR ETI480 50 WATI JAYCAR JAYCAR Cat. KE-4050 JAYCAR ~iv.an..::, .1. ~a JAYCAR JAYCAR Ref: EA December 1984 Ref: EA February 1987 JAYCAR Ref: EA Nov 1984 Cat. KA- I 562 ETl480 100 WATI JAYCAR Cat. KA-1563 Cat. KA-1561 JAYCAR Cat. KE-4052 JAYCAR JAYCAR JAYCAR JAYCAR POWER SUPPLY less Transfom,c JAYCAR Cat. Kf>~O~R !l:29.~0 JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR Ref: ETI June 1987 Ref: ETI July 1986 225W4Q JAYCAR Cat. KE-4728 Cat. KE-4 724 JAYCAR Cat. KE-1622 Cat. KE-4722 JAYCAR Ref: ETI October 1986 JAYCAR Cat. KE-4 725 JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR REF: ETI JUNE 1986 JAYCAR Ref: ETI July 1983 JAYCAR CAT. KE-4720 JAYCAR Cat. KE-4033 JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR Ref: ETI Feb/March JAYCAR Ref: AEM July 1985 1985 JAYCAR Ref: ETI December 1985 Ref: ETI July 1979 Cat. KM-3012 Ref: ETI October 1980 JAYCAR Cat. KE-4690 Cat. KI<:-471 I JAYCAR Cat. KE-4013 Cat. KE-4023 JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR Ref: AEM December JAYCAR JAYCAR 1985 Ref: ETI March 1982 JAYCAR Cat. KM-3040 JAYCAR Cat. KE-4220 JAYCAR JAYCAR JAYCAR JAYCAR IAYCAR IAYCAR IAYCAR IAYCAR IAYCAR IAYCAR IAYCAR IAYCAR IAYCAR Ref: AEM February IAYCAR IAYCAR 1986 Ref: EA August 1987 Ref: AEM July 1986 IAYCAR Cat. KM-3042 Cat. KA-1688 IAYCAR Cat. KM-3044 IAYCAR :,::::: IAYCAR :;:{ IAYCAR } } IAYCAR :;:,:.:, TRANSISTOR ASSISTED IGNITION T.A.I. BREAKERLESS VERSION RAILMASTER T-~~·~· CONTROLLER $99.95 $42.50 $21.95 $44.95 No1 FOR KITS $109.95 $13.95 DIESEL SOUND RAILMASTER $22.50 $22.50 SOLDERING ·RING TONE PARAMETRIC IRON CUSTOMISER TEMPERATURE EQUALISER CONTROL $39.95 $35.00 WALK AROUND CONTROLLER RAILMASTER RS232 TO COMMODORE ETI1601 AMP MODULES $26.50 $31.50 lllGH POWER MOSFETAMP $23.50 $16.95 $99.50 TEMPERATURE PROBE FORDVM DIGITAL SAMPLER $119.00 $27.95 MICROWAVE OVEN LEAK DETECTOR SIGNAL SPEAKER PROTECTOR $17.95 $22.50 $79.50 $9.95 DUAL SPEED MODEM 150WATT MOSFET MODULE $169.00 $109.50 CDI KIT 120WMOSFET FM MINI AMP TRANSMITTER $79.50 SPEECH SYNTHESISER ELECTRONIC STROBOSCOPE 6000AMP MOSFET MODULE $43.50 $13.95 $119.00 iIAYCAR !~2!~ •:-:-:-:J ' - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - IAYCARJAYCARJ AYCAR JAYCAR JAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR IAYCARJAYCAR JAYCARJAYCAR JAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR JAYCARJAYCAR IAYCAR JAYCARJAYCA8JAYCA8J~ CA8 J~YCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCAR JAYCAR JAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYQAB. JAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCAR JAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCAR JAYCAR JAYCARJAYCARJAYCARJAYCARJAYCAR JAYCAR JAYCAR JAYCAR JAYCARJAYCARJAYCARJAYCAR JAYCAR JAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCAR JAYCARJAYCAR JAYCA RJAYCAR JAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCAR JAYCAR JAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCAR JAYCARJAYCAR JAYCAR JAYCAR JAYCA R JAYCAR 50MHz JAYCAR JAYCAR FREQUENCY TRANSISTOR JAYCAR JAYCAR COUNTER JAYCAR TESTER JAYCAR Ref: EA December 1981 Ref: EA August 1983 JAYCAR JAYCAR Cat. KA-1390 Cat. KA-1119 JAYCAR JAYCA R JAYCAR JAYCA R JAYCAR JAYCAR JAYCA R JAYCAR JAYCAR JAYCAR GUITAR 50WATTRMS/ JAYCAR DELUXE CAR JAYCAR EFFECTS CHANNEL CAR JAYCAR ALARM JAYCAR Bucket Brigade Delay JAYCAR STEREO AMP Ref: EA May 1984 JAYCAR Ref: EA June 1983 JAYCAR Cat. KA1550 Ref: EA August 1985 Cat. KA-1522 JAYCAR Cat. KA-1600 JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR HIGH POWER ELECTRIC DIGITAL ELECTRIC JAYCAR HOUSE JAYCAR ELECTRIC FENCE CAPACITANCE JAYCAR FENCE ALARM JAYCAR JAYCAR Ref: 1-:A September FENCE CONTROLLER METER Ref: EAJanuary 1985 JAYCAR 1982 Ref: EA October 1986 JAYCAA Ref: EA December 1985 Ref: EA August 1985 Cat. KA-1582 JAYCAR Cat. KA-1109 Cat. KA-1678 Cat. KA-1660 Cat. KA-1595 JAYCAR JAYCAR JAYCAR JAYCA FJAYCAF JAYCAF JAYCAF JAYCAF 300WATT JAYCAF PEST OFF JAYCAF VIDEO AMPLIFIER SPEAKER JAYCAF TURBO TIMER JAYCAF REPELLER MODULE FADER JAYCAF Ref: EA September PROTECTOR Ref: EAJune 1980 JAYCAF Ref: EA November Ref: EA January 1986 1986 JAYCAF Ref: EA July 1980 Cat. KA-1115 1985 JAYCAF Cat. KA-1626 Cat. KA-1679 Cat. KA-1117 JAYCAF Cat. KA-1620 JAYCAF JAYCAF JAYCA F . ,; .' JAYCAF JAYCAF JAYCAF ·.•• JAYCAF JAYCAF JAYCAF DUAL JAYCAF JAYCAF CARALARM JAYCAF TRACKING JAYCAF SCREAMER JAYCAF POWER SUPPLY JAYCA F Ref: EA August 1986 JAYCAF Ref: EA February 1987 Cat. KA-1675 JAYCAF JAYCA F Cat. KA-1682 JAYCA F JAYCAF JAYCAF JAYCAF JAYCAF JAYCAF JAYCAF JAYCAF CAR JAYCAF CD JAYCA F ELECTRONIC JAYCAF BATTERY JAYCAF ADAPTOR RAIN GAUGE JAYCA F MONITOR JAYCAF Ref: EA April 1986 Ref: EA March 1987 JAYCAF Ref: EA May 1987 Cat. KA-1645 JAYCAF Cat. KA-1687 JAYCAF Cat. KA-1683 JAYCAF JAYCAF JAYCAF JAYCAF JAYCAF JAYCAF JAYCAF JAYCA F JAYCAF DIBOX JAYCAF 64KPACKET JAYCA F Ref: ETl September JAYCAF JAYCAF RADIO 1985 JAYCAF Cat. KM-3058 JAYCAF Cat. KE-4 708 JAYCAF JAYCAF JAYCAF JAYCAF JAYCAF JAYCAF JAYCAF JAYCA F JAYCA F JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAAJAYCAR JAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR JAYCAR JAYCARJAYCA RJAYCAR JAYCAR JAYCAR JAYCAF .I AYCAA IAVCAA .IA.YCARJAYCARJA't'CARJAYCA~JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCARJAYCAR JAYCARJA:,:~~~~~~~~~~~~ ~t~~ $21.50 $169.50 $115.00 $189.50 $85.00 $169.00 $23.50 $59.50 $229.00 $29.95 $24.95 $48.50 $23.50 $119.95 .... .. . . $34.95 $49.95 $129.95 $14.95 $59.95 $42.50 .•. ~ . . . , • . . , -· . .. ... . , , ... ... , - · , , ...,, .. , ... , , , ...,, " , .., ,., , ...,,...., , vM , ...., ,...., , VI"\ , vn 1, .JM. 1 VM.n VM.TVI-\M .JI-\TVI-\N JATVAH JATVAH JAYL,AH JAYVAH JAYl_;AH JAYGAH JAYGAR JAYCAR 'CAR JAYCA RJAYCARJAYCARJAYCA RJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR 'CA RJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR 'CARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR 'CARJAYCAR JAYCARJAYCAR JAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJ AYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR ~AR . 'CAR 'CAR 'CAR 'CAR 'CAR 'CAR 'CAR 'CAR 'CAR ECONOMY POCKET 'CAR 'CAR At !as~ a good value AUSTRAf.,JAN MADE ampltfler module that ts rugged, has the 'CAR heatstnk butlt In and ts cheap! 'CAR The 'JAYBRIK' as they are called are basically rugged Mosfet power ampltflers 'CAR manufactured to high standards on fibreglass board With a special DIECASf 'CAR 'CA R heatstnk. All board components are enclosed In a special conformed coating that 'CAR ensures that the amp Will operate 1n extreme environmental condtttons. If In the 'CAR unltkely event of a repair betng necessary the coating can be picked away and the 'CAR • 10,0000/volt offending component replaced. The Jaybrtk Will drtve either 4, 8 ohms or lOOV ltne 'CAR • 19 ranges step-up transformers and has unconditional stablltty. They are virtually bullet proof. 'CAR Cat. QM-1015 They are Ideal for professionals who need slave P.A In a hurry or any Ht Ft or sound 'CAR 'CAR reinforcement appltcation. You simply connect filtered DC and a stgnal to them and 'CAR they are guaranteed to go! 'CAR 'CAR •WITH CAR CAR CONTINUITY CAR CAR BUZZER CAR CAR • 20,0000/volt CAR • 10A DC range CAR Cat. QM-1022 SPECS: CAR J-100 lO0W RMS mln Into 80, With 45-0-45 3A transformer and 1 x 8000µF/75 CAR filter cap each rail and 6A brtdge rect. 45-0-45 ls MAS permttted power supply CAR CAR voltage. (This wtll produce 30V across 80 which ts 112.SW). Max offload volts! 125. • ELECTRONIC CAR Distortion: <0.1% max any frequency typ 0.06%. 0.018<at> !kHz. CAR Frequency Response: 20 • 20kH2 ±OdB (-3dB<at> 200kHz) FETVOM CAR Sensitivity: 850mV p.p. for rated output CAR • Transistor tester Impedance: 47k!l CAR • Centre zero adjust S/Nolse: Over 100 dBW.RT. 850mV CAR • Peak to peak & rms readtng CAR Stab!ltty: Unconditional Cat. QM-1050 CAR Cat. AA-0382 CAR CAR J-50 SOW RMS mln tnto 80. With 25-0-25 2A transformer, 1 x 4700µF /S0V filter cap CAR each side and 3A bridge rect. CAA • l0AMP All other specs the same or better than above. CAR (Ftltcr capacitor values must be doubled for use on 40 loads) CAR DIGITAL Cat.AA-0380 CAR No ttme for Ptc. See next months ads • Transistor tester '.:AR '.:AR • Vinyl case '.:AR Cat. QM-1530 240V 3 PIN PLUG/ENCLOSURE '.:AR Tots enclosure which measures 78(!.l x SO{W) x 40{usable depth)mm • '.:AR has a moulded 240V 3 pin plug lnsert which can be rotated thru 180" '.:AR '.:AR lo allow the adaptor lo mount tn any of 3 positions (see fig# 1). • l0AMPWITH '.:AR There 1s a generous space lnslde the box to ftt relays, electronics, etc '.:AR for whatever reason you ltke. CAPACITANCE '.:AR We expect that many malns powered magazine projects Will require '.:AR METER this unique Jaycar product! '.:AR Cat HB-5950 '.:AR • Dtgttal '.:AR • Transistor tester '.:AR • Vinyl case 0 (1 )AR Cat. QM-1540 '.:A R '.:AR '.:AR '.:AR '.:AR • 4 1 / 2 DIGIT )AR :::AR l0AMP :::AR • Transistor tester :::AR :::AR • Diode tester :::AR • Data hold :::AR Cat. QM-1550 :::AR :::AR :::AR :::AR :::AR • DIGITAL WITH : : AR :::AR FREQUENCY : : AR '.:AR COUNTER :::AR • Capacitance tester :::AR • Transistor tester :::AR • 20 amp current :::AR : : AR • High Impact case :::AR Cat. QM-1555 :::AR : : AR :::AR SAVE $10 : : AR 8" Woofer cat CW-2114 : : AR :AR "SPY IN THE SKY" SENSOR :AR :AR The Pyroelectrtc Infra-red sensor element ts the 'eye' of a passive Infra red detector. :,AARR It measures 10mm high, 9mm Wide and only 6.2mm deep. The IRA.F00I-Pcomes :AR complete With full technical data tncludtng performance graphs, Information on the 10" Woofer cat CW-2117 :AR operating prtnctple and two typical appllcatlon circuits! :AR 'fyptcal Appltcatlons: :AR • Burglar alarms 8,,57.50 :AR • Proximity detectors WHY NOT GIVE A MULTIMETE THIS CHRISTMAS I• $23.50 SAVE $6 NOT A KIT - INSTANT POWER! ~w~:·iAYiiiii'K• $39.95 $79.95 $89.95 $14.95 ~.....,_:~ I□ $129.00 $179.00 '-$.!,f!?,:_O,!? ,.9.95 ;f,4i(IJ (~~ ;AR __ . • Automatic door/shutter switch • Toys, robotics :AR ::::::.: • Accident prevention/machine guard ~11: ~~~~~!.;~ N·,4if1 12" Woofer cat. cw-2130 $64.50 SAVE $15 See our Cat for full specifications :AR :-:':::: · 'AR .·:·:· :ARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAVCARJAYC JAYCARJAYCAR :AR JAYCARJAYCARJAYCARJAYCAR JAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR ~ 2ABJAYCARJAYCARJAYCARJAYCAR JAYCAR JAYCARJAYCARJAY~ARJAYCARJAYCARJAYCARJAYCAR.IAYCAR JAYCAR IAYCAR IAYCAR IAYCAR /AYCAR /AYCAB IAYr.AB JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJ AYCARJAYCARJAYCARJAYCARJAYCARJ AYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJ AYC ARJAYCARJ AYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJ AYCARJ AYCARJAYCARJAYCARJAYC ARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR MASSIVE SCOOP PURCHASE iiDi::n11wP:mrtP:ilf..l:e.~Di1tan;=t:Ir:::::::i:i1i1t 1 Yes, we've made another scoop purchase. These Ionisers are 240 volt operated, draw about 1/2 watt, deliver about 250 btlllon Ions per second, and cover about 25 square metres. It's even supplied with a Tester PC board and spare needles. If you've ever wondered about negative Ion generators, this MUsr be the time to buy one. These were selling for about $80. Jaycar has a limited quantity available for: Cal YX·2905 $29 •95 ,;t,t;:-_..., ,_~..... . .. TV ANTENNA BARGAIN NORMALLY $57.50 SAVE $17.55 g~ o"NL~ $39• ' ' SAVE $50 WORLD CLASS ADCOLA SOLDERING/ DESOLDERING SYSTEM BARGAIN SQUEAKY CLEAN MAINS FILTERS TWO BRAND NEW MODELS, BOTH FULLY APPROVED BY THE ELECTRICITY AUTHORITY 4 OUTLET The MS-4020 will supply up to 4 appl!ances. Each 240V socket ts independently filtered from the other, I.e. Interference from disk drives ts de-coupled from the CP power supply, etc. The filter will suppress Interference from RF sources, spikes, transients and ltght!ng, and supply up to 4 outlets with a total load of 10 Cat. MS-4020 , .c' ' •$169 $269.00 ..-J~: 2 OUTLET The two outlet will handle up to 7.5 amps and wtll suppress Interference from RF sources, spikes, transients and lighting. The two sockets are not Independently flltered although. Cat. MS-4025 •$224 $59. 95 SAVE HEAPS $99.00 BEWARE! There are many mains fllters on the market One sample we evaluated had only one capacitor In ttl PORTABUGAssow~mGmoN--,1 $3 9 5 I 9 I ,. 1• No cords, batteries or gas bottles Heavy duty, tip temperature up to 400°C I •• Adjustable temperature, equivalent to 10·60 watts I •Hard working. up to 60 minutes continuous use Refllls seconds, uses standard Butane gas lighter fuel I ••• Made No leakage current to sensitive circuits lreland • • In In IWAS SELLING FOR $59.95 Jaycar Introduces the product at a very realistic $39.95 I Cat. TS-1420 JAYCARJAYC JAYCARJAYC JAYCARJAYC JAYCARJ AYC JAY( JAYC JAYC JAY( JAY( JAYC We have Just purchased a quantity of VHF TV JAY( antennas from a wholesaler who ts no longer 1n the JAYC AYC TV antenna business. The antennas are a 7 element AYC type suitable for metropolttan areas. They have AYC excellent gain and dtrectMty for areas with AYC moderate st;.rnal strength! For coax use use outdoor AYC balun Cat LT-3026 $3.75. Australtan made. These AYC JAYC Will never b e thts cheap again. JAYC Cat.LT-3166 0 JAYC JAYC JAYC JAYC JAYC JAYC JAY( JAYC JAYC JAYC We have purch ased a quantity of these quality soldering stations and accessories, JAYC and can offer them at never to be repeated prices. Adcola have put their prices up JAYC recently, so these special prices represent a saving of about 4(1)6 on what you can JAYC expect to pay In the near future. See our catalogue for full specs on thts fabulous JAYC JAYC soldering system. JAYC DEAL 1. JAYC JAYC You get • Base station Cat TS· 1470 JAYC • CT7 Iron Cat. TS-1480 JAYC JAYC JAYC JAY< Current price (before price Increase) $192 JAY I JAY< DEAL 2. JAY< You get • Base station Cat TS· 1470 AY< • CT7 Iron Cat TS-1480 • Desolder tool Cat. TS· 1476 JAYI JAYI JAYI Current price (before price Increase) $261.95 JAYI JAYI JAY t JAY I Desolder tool on tts own (tfyou already own the station) JAYt JAYt SAVE $10 JAY1 JAY• Cat TS-1476 JAY1 JAYt JAY• NEW BOOK SHIPMENT JUST ARRIVED JAY• JAY• (See our catalogue for full details) JAY• BS-0402 Video cameras, theory and servicing $29.95 JAY• BS-0404 Introduction to automotive solid state $19.95 JAY• BS-0406 Soul of CP/M $39.95 JAY• BS-0408 Interfacing the IBM computer $32.95 JAY• JAY• BS-0412 Printer connections btble $29.95 JAY• BS-0416 Macintosh programming techniques $44.50 JAY• BS-0422 Computer connections solved $37.95 JAY, BS-0455 Understanding data communications $27.95 JAY1 BS-0456 Understanding microprocessors $27.95 JAY1 BS-0458 Understanding dtgttal electronics $27.95 JAY1 JAY, BS-0518 CMOS cookbook $23.95 JAY1 BS-0522 555 Timer sourcebook $12.95 JAY1 BS-0534 Design of PLL's $18.95 JAY1 BS·0550 Handbook of electronic tables & formulas $34.95 JAY• BS-0580 Programming and Interfacing the 6502 with experiments $28.95 JAYt BS·0582 How to program and Interface the 6800 $25.95 JAYt JAY1 BS-0594 Z80 microprocessor handbook $21.95 JAY1 BS-0596 ZSO microprocessor design projects $25. 95 JAYt BS-0614 Electronic telephone projects $17.95 JAY• BS-0729 How to build speaker enclosures $14.95 JAYI BS-0733 Data communications, network and systems $75.00 JAYI BS-0736 MS-DOS bible $39.95 JAY• JAYI BS-0739 Best book of Lotus l ·2·3 (2nd ed) $26.50 JAYI TAKE 20% OFF THE FOLLOWING BOOKS JAY I JAYI JAYI BS-0420 C programming techniques for Macintosh JAYI BS-0703 Howard Sams crash course digital technology JAYI BS-0720 ~·tbre optics experiments & projects JAYI JAYI BS-0732 Complete guide car audio JAYI JAYI JAYI JAYI JAYI JAYI JAYI JAYI i====a:1-1 JAY1 I 1 ,~; -,,•,1.-.Jr- .-1 ._ _ _. _ ,. . ., , n'.51~ · ., ~f ~'-<ti;, ·,,'U -• .ri!..:_ t'' ~m~ 11 t::h$('1'll sl)l,lc,M>gk;,, ---~ -- -- I I I " ~ " " " '~. hot>byish, ;;::-'--!,,-'-'-'''-; "''"~··="' I I I - GREY JIFFY BOXES If you want some colour In your projects, try a grey J!tTy box. Available In 3 sizes, all with ABS plastic ltds. Cat. HB-6021 UBI (150x90x50) $4.25 Cat HB-6023 UB3 (130x68x41) $3.25 Cat HB-6025 UB5 (83x54x28) $2.45 .li•"' JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJ JAYCARJAYCARJAYCARJAYCARJAYCA JAYCARJAYCARJAYCARJAYCARJAYCA , , ,,c , o ,,, ,c,o ia_vr-_AC 11\ V~ _c I_A _ j~~: JAY1 JAYI JAY t JAY1 JAY1 JAY1 JAY1 JAY1 JAY, JAY• JAY JAY JAY JAY JAY JAY JAYI JAYI JAYI = = = = - JAYI TELEPHONE CALL DIVERTER ROBOTS This unit enables you to divert an Incoming phone caJJ to another location. The dtverter wiJJ divert either ltne (2 llnes required) or wiJI dtvert only one Incoming ltne. There are many other features which you wiJJ find tn the 1987 Jaycar catalogue. NOW Cat. YT-6510 ONLY$199 ECONOMY "FRIENDLY LITTLE ROBOT" Programmable via 8 key keypad on Its "chest". Actions Include music sound, flash 'eye' (ltght on head) tum In both direction, circle, etc. Will accept up to 18 consecutive entties. Also' features a tacttle bumper switch and moveable arms which can grtp small objects. Measures 150mm diameter and 210 high. Battertes extra $4. 75 - 4 x AA & 1 x 9V. CatXR-1020 AVAILABLE $49.95 COMPUROBOT Very sophl~Ucated, microprocessor controJled via 25 key keypad on robots 'head'. Up to 48 separate routines can be entered. Multi speed gearbox, travels in 4 separate directions .. as well as angles and cut"Ves. It has Jtghts and can make sounds. Hundreds sold to prtmary schools. Battertes extra $4. 75 · 4xMand lx9V CaLXR-1024 CORDLESS PHONE The fabu lous Portable Telephone that you can take anywhere around the house, garden or swimming pool. Microprocessor controlled with a range ofup to 250 metres and absolute clatity. Features: • Simple to use and easy to tnstaJI - just plug fn • Operating range up to 250 metres (800 ft) • Secutity code system with 16,348 combinations • Call function at base unit to alert handset • Pulse dialling with audible tone feedback at the touch of a key Cat. Yf-7065 $69.95 This htghly sophisticated robot has ft aJJ. Programmable vta a wireless Infra red hand held controJler with a 25 ·key keypad. 30 page Instruction manual provided. Up to 64 program steps can be entered Into Its memory. Wtll go In any direction, as weJI as make different noises and flash Jtghts. It has two mototised mechanical arms to carry a payload. The robot w!Jl draw with a crayon. lt w1JJ carry the JR controller when not In use. Auto tum-off to save battertes. Size 230(I-I) x 210(W) x 1751D)mm. Rugged case, Japanese motors. Battertes extra $6.33 - 4 x AA & 4 x C Cat XR-1028 $129.95 '• We must be asked so many Umcs per day for U1ts device and now we have finally found tt. Top quality Insulation Displacement type with positive locking cover which insulates termtnat:1on area and acts as --~ .. ., ' . . '••. a strain relief. Cal PP-0920 $6.50 10 up $6.00 each $16.95 QUARTZ CLOCK ONLY COMPASS $5. 95 This great small product has many applications. It's a quartz digital clock and a compass fn one small, handy size. Cat. XW-0250 - - -- • Through Jaycar's surplus stock buying scheme, we have purchased a substantial quantity of an electro that would normally be out of reach of the hobbyists pockel This electro ls made tn Germany by ROEDERSfEINI SAVE $70 WAS $26 NOW 0NLY$19 AT LAST!! 4 PIN DISK DRIVE PLUG STOPWATCH Attractive all weather stop watch as well as a 5 function watch. (Day, date, etc) Complete with a / generous length of knitted lanyard.; Very easy to use. i Quartz con troJled for greater accuracy. CatXW-0380 BARGAIN COMPONENT PACKS 6 ,S00uF 6 3V LONG LIFE ONLY $7.50!! That's tight ROEDERSTEIN brand long life, high tipple current etched electrodes, screw terminals all class! And at a prtce below "Taiwanese". These are absolutely fantastic for power supplies for high power amps, etc. Cat RN-6712 Electtical to DIN 41332 Tolerance -10 +50% Dimensions 50(0) x 80(I-I) Terminal M5 screw $7.50 QUANTITY DISCOUNTS 1-5 6 · 10 11 · 24 25 · 99 100+ $7.50 $7.00 $6.50 $6.00 $5.75 TWEETYPIE '111fs Incredibly litlle pfezo screamer measures 57(1...) x 33(H)mm emits a l 16dB wall. It's deafening! As used In the screamer car a1arm ktt. Cat LA-5255 ONLY $17.95 " " ' vn n .,,,.,1 vn ,, "' " ' v n ,, " " ' v n n "'" I vnn ,J M! vn n 1,/M l VMn tJ M 1 vnn " " 1 V M n "' " I v nn ..,,... ,vMn WM TVM n \IMT V M n .JM I VMn ,JMJ Vf'\n tJMT VMn ,J MT VMn ,J MT VMn ,JM T V Mn J MT V Mn ,J M T VM n ,J M T VMn JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR JAYCAR JAYCAF JAYCAF JAYCAF .. .CAF 30 + 30 WATT STEREO AMP '~ INNER EAR MINI STEREO PHONES .'t'CAF /~ Unique type headphones, so small they INCLUDING PRE-AMPUFIER ~YCAF can be stored In a MATCHBOX. Very high .AYCAF Fully built and tested with separate bass, treble, sound quality and comfortable to use. JAYCAF balance and volume controls. This superb amp ~ JAYCAF Supplied with adaptor plug to 6 .5mm and has Jess than 0 . 1% distortion. There are Inputs ~ JAYCAF spare replacement ear pads. $ for microphone, phono and auxiliary (line) and .J:I JAYCAR Cat. AA-2014 0 JAYCAR all power supply components are on board. Just ~ JAYCAF connect transformer, speakers and a signal • JAYCAR and away you gol ·• JAYCAR INFRA RED PHOTO ELECTRIC RELAY Cat AA-0300 JAYCA R This Is the device JAYCAR which makes all the JAYCAR Test/Alignment LED JAYCAR noise when you walk Transformer to suit JAYCAR Into a shop. Mounts Cat MM-2010 JAYCAR on one side of the JAYCAR Transmitter $22.50 door, and the JAYCAR Lens reflector (which Is 6 WATT 'MICRO' AMPLIFIER CHANNEL JAYCAR supplted) on the JAYCAR JAYCAA other. It wtll sound AMPLIFY YOUR WALKMANI JAYCAR when someone breaks This ltttle amplifier will provide up to 6 watts Into Receiver Lens JAYCAR the beam, or can be JAYCAR 4 ohms from a 15V power supply. Onboard volume switched so It sounds JAYCAR control and high or low Impedance Inputs . for 5 seconds and JAYCAR Walkman' type 'low' and 'high' for standard ltne then resets. 240 volt JAYCAR level signal sources such as tuners, VCR's, etc. JAYCAR operating. (regard as AUX). Output Is short circuit protected . JAYCA R W!ll operate up to A copper heatslnk fin must be soldered to the top JAYCA R 15 metres. Built-In JAYCA R of the IC to achieve thts. buzzer (extension JAYCA R buzzer can be added) SPECIFICATIONS - ·· .. . JAYCAR Power Out 6W (max) Into 4 ohms . . . . · JAYCAR Size 90 X 143 X Input Sensitivity lOOmV . -· JAYCAR 190mm , T.H.D. 0.3% ~ . " ·· JAYCAR Cat. IA-5120 Gain at 6V 38dB · JAYCAR REFLECTOR JAYCAR Power supply 4 · 16V<at> 1·2A JAYCAR CatM-0340 JAYCAR ('rwo required for stereo) JAYCAR See our catalogue for other prebutlt modules ln this range • preamps, power amp, JAYCAR sound switch, ltght switch, IR remote control, speaker protector, LED level meter. JAYCAR JAYCAR JAYCAR Handy everyday calculator In unique carry easel • Compact, JAYCAR economical eight dlgtt, six function calculator with large keys LITTLE PROFESSOR JAYCAR • Full function • Automatic percent key, automatic constant, JAYCAR A marvellous way to teach young children their square root key • Automatic power down JAYCAR maths tables plus addition, subtraction, JAYCAR Cat. QC-7172 $ multtpltcatton and division! JAYCAR • Tables mode gtves practice In math tables JAYCAR Tl30 SLR JAYCAR • Comes with Uttle Professor Activity Book JAYCAR Solar powered sl!de rule calculator. If you can see It • Your child gets two chances to solve the problem JAYCAR has enough ltght to work. • Contains the advanced before Uttle Professor gtves the answer • Contains JAYCAR algebraic and tr1gonometI1c functions • Most needed over 50,000 pre-programmed problems • Makes JAYCAR sltde rule functions roots, reciprocals, logs • Angular learning what It should be • FUN! JAYCAF conversion for degrees, radtans and grads Cat. QC-7160 JAYCA F Complete with vinyl wallet JAYCAF JAYCAF Cat. QC-7164 JAYCAF JAYCA F JAYCAF Tl56 PROGRAMMABLE JAYCAF Ideal for Tech Students, at a bargain price · JAYCAF factortals, impetial to metric conversions JAYCAF JAYCAF (or visa versa), engtneertng and scientific notation, JAYCA F Performs 89 scientific functions, magnificent Integration, stattlstlcs, polar/rectangular conversions, JAYCAF helpful guide book tncludedl stores a constant (even when offl, algebraic operating JAYCAF • Designed for high school and college students · system. Operates In proper mathematical order. JAYCAF scientific functions include logs, reciprocals. 8 dlgtts and 2 exponents. Degrees, radians and grads. JAYCAF powers, roots, factorials, combinations, Cat. QC-7174 JAYCAF permutations, hyperboltcs, complex numbers, JAYCAF JAYCAF polar/rectangular conversions and trtg calcu· JAYCAF latlons Including inverse In degrees, radians or JAYCAF grads • Statistical functions Include mean and JAYCAF standard deviation, normal dtstrtbutlon • Enter JAYCA F numbers and perform calculations In blnaJY, JAYCAF octal, decimal or hexadecimal number bases. JAYCA F Yet another unbelievable deal. JA YCAF Convert numbers. Perform mixed calculations. Once again Jaycar has made a scoop purchase of· this time · Vtatel ADAPTORS JAYCA F • Floating decimal, scientific notation or for'your own TV seU JAYCAF engineering notation. • l O dlgtt/2 exponent That's right, you connect them to your own TV via the antenna and to a telephone JAYCAF dtsplay • Low light solar cells • Guidebook, vinyl line as well. A nifty ltttle Infra-red wireless remote control Is supplted so that you JAYCA F wallet and quick reference gutde. JAYCAF can operate Vtatel from the comfort of your lounge chair! JAYCAF 7 We must emphasise U1at the goods offered arc NOT BRAND NEW and are JAYCAF 'ex-rental', They are In very good condition and fully operational when supplied. _ _ _ _ _ _$....;;;4;..;;;;;9...;_·:9;;;;...;5"'---_ _ _ _ , JAYCAF The adaptor will drive an RGB monitor as well as a telly. It also has parts for a JAYCAF tape recorder and printer and a socket for full QWERlY keyboard. JAYCAF PHOTO INTERRUPTER If you want to Integrate VlATEL Into your home entertainment system then this Is JAYCAF This device enables you to turn a circuit on and off optically. definitely for you. Because of the compact size , thts offer Is available to Mall Order JAYCAF JAYCAF It consists of a moulded plastic housing with an IR LED facing a phototranslstor customers as well as our personal customers · but be quick! ._ •. JAYCAF across a gap. Any object tn the gap will Interrupt the IR beam and consequently Ns<""''• do~mmra<~ • <ocl•""· • . JAYCAF switch the photo transistor on and off. The device Is very fast and !deal for Cat. XV-2210 Inc remote control pad ,.·' I ,.:·, JAYCAF JAYCA F '1 6 JAYCAF , U.6-1 ·:~:"~·. ,,.:·. ·•. : .. - .. JAYCA F • PCB or chassis mounting a r-I I I JAYCAF JAYCAF 0 : ~~~':f~ne piece IC 1 2 JAYCAF cons tructton o3 2 ~ g 'WCAF I • Very fast ~ I CAF APPLICATION: lj_ : I : ~ill CAF CAF • Counter sensor ~ ~ CAF CAF 11.6 I CAF • Edge sensor 25 -{ 1 2.54 CAR • Tape end sensor $ S u1'YCAR . JAYCAR Full specs supplted with each unit. Cat. ZD· I 90 I 1 O+ $7, 95 JAYCAR - -JAYCAR - - -JAYCAR - - -JAYCAR - - -JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCARJAYCAR JAYCAR JAYCAR JAYCARJAYCAR JAYCAR JAYCAFI ,-.,AH JAYCAR JAYCAR JAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCA RJAYCARJAYCARJAYCAR JAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR '" >< n - □ ,-,e n • □ ' "'°' □ ""a• □ ,-,,c, An •• ~ O _!.A Vf'A O...lA>lCACU A""1\CLIAVC IIO 1/\YCAO IAYCAO l"'lCMLJAYCAfLJ A-\ICAB..JAY£AEiJAYCAR JA'lCARJAY _GAR JAYCABJAYCAB ~>°".;.---,---.. ,,. ? 8 95 4:' ONLY$59.95 l • 15. 95 $34.95 • $49.95 MORE VIATEL MADNESS!! ;;:::';',,,i,~'.""'OrnM.. r 4ff1 $! :, ~~ I 1r ONLY $199 <: ..... ·. , . . > --n ~ 1 olLJ :~~~~~;:~in c:: ·~ -::;__~ 1/-- i_____ =--------:IJ, 8 •9 oM IYCAR JAYCAH JAYCAH JAYCAH JAYCAH JAYCAH JAYCAH JAYCAft JAYCA!i JAYCAH JAYCAH JAYCAH JAYCAH JAYCAH JAYCAH JAYCAH JAYGAH JAYGAH JAYGAH JAYGAH JAYCAH JAYGAH IYCARJAYCARJAYCA RJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR IVCARJAYCARJAYCARJAYCARJAYCARJAVCARJAVCARJAVCARJAVCARJAVCARJAVCARJAVCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR \VCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAVCARJAVCARJAYCARJAVCARJAVCARJAYCARJAVCARJAYCARJAVCARJAVCARJAYCARJAYCARJAVCAR JAVCARJAYCAR IYCAR IYCAR IYCAR IYCAR IYCAR IYCAR IYCAR The same wholesaler who sold us the antennas (see elsewhere these ads) Is also IYCAR no longer In the alarm business. We purchased a quantity of these and can offer IYCAR them for less than 1/2 prtce. IYCAR The alarm Is basically suitable for flats, units, one room, garages, etc., but tt can IYCAR also form the basis of a "butld-up" aystem. 1VCAR \YCAR IDEAS FOR USING ALARM IYCAR SIMPLE ALARM IYCAR IYCAR The most simplest way to use 1s to simply sit the unit on a shelf. It can be IYCAR switched on/ off from the un1t• and can be plugged directly Into 240 volts through IYCAR an adaptor MP-3012 $18.95. IYCAR • It has a delay function, so It won't alarm before you switch tt off. IYCAR This small module measurtng 130(1..j x 60(W) x 35(D)mm uses 1 x AA cell. It If you wish, you can mount an external horn speaker, and It has factlttles for IYCAR causes a suspended arm within the module to swing back and forth. A suitable IYCAR batte,:y back-up (5 x C size). pendulum can be attached to the bottom of the arm. (Note: pendulum drtvcr Is IYCAR MORE INVOLVED SYSTEM IYCAR NOT a clock). Batte,:y (alkaline) Will last over a year. Cal XC-0110 $14.95 The alarm can be the basis of a comprehensive aystem. IYCAR IYCAR The unit can be screwed Into a shelf, and hard wired from behind. A keyswitch QUARTZ MOVEMENT WITH SWITCH \YCAR can be used and mounted on a plate either Just Inside the front door, or even IYCAR outside. CONTACTS \YCAR There Is an output for NC and NO circuits. \YCAR Thts Is virtually Identical to our XC-0100 standard movement except that It has a NC can be used for Window and door reed switches and passtvve Infra red IYCAR set of switch contacts that close every hour. These contacts can be used to trtgger detectors. NO can be used for panic buttons, smoke detectors and PIRS. IYCAR the "melody modules" (see elsewhere these ads). IYCAR The unit can be switched for Instant alarm, so If an Intruder walks In the room IYCAR Supplied with hands. Cal XC-0105 $16.95 the alarm sounds Instantly. IYCAR Rechargeable battertes can be used In case of power fatlures and are autoIYCAR MD-01 MELODY MODULE - 12 SONGS matically charged by the unit. There Is a butlt-tn output relay which allows you to IYCAR use any device which operates on 240V e.g. floodllghts, diallers, etc. This module consists of 2" speaker with electronics mounted on the speaker IYCAR IYCAR We beletvc thts alarm at $49. 95 ts a bargain, That other btg electronics retailer frame. A single AA batte,:y holder Is attached. When the switch wires are shorted IYCAR has the exact unit (with power supply) In their catalogue for $139.00. the module plays one tune from tts repertoire of 12. It cycles through the 12 unttl IYCAR If you can't afford a full system with panel and PIRS eve,:ywhere then this Is the tt comes back to the first. (Typical tunes are nurse,:y rhymes). Cat. XC-0115 IYCAR unit for you. \YCAR $12.95 Power supply to suit Cat. MP-3012 $18.95 IYCAR Cat. LA-5140 IYCAR IYCAR IYCAR IYCAR IYCAR IYCAR IYCAR IYCAR IYCAR \YCAR IYCA R IYCAR IYCAR IYCAR IYCAR \YCAR Thts tiny module measurtng 45(1..j x 30(W) x 4mm (thtnl} Is the module that you IYCAR find In those crazy musical Xmas cards. When tiny sprtng switch contacvts are IYCAR closed tt plays ''Twtnkle, Twinkle Utile Star''. Absolutely useless and eventually IYCAR IYCAR annoying. Great fun to butld Into anything ghastly! Cat. XC-1030 $3.95. IYCAR IYCAR IYCAR 1 \YCAR 2 MELBOURNE LOCATIONS IYCAR (,.,. 45 A'BECKETT STREET CITY \VCAR IYCAR 887 SPRINGVALE ROAD MULGRAVE IYCAR IYCAR ECONOMYPIR IYCAR IYCAR • Coverage 12m x 12m SCOOP PURCHASE!! IYCAR • 14 twin beam deleclors IVCAR • NO or NC contacts IYCAR • Tamper protected ·and walk test IYCAR Cal. IA-5017 IYCAR IYCAR IYCAR You guessed it, another Jaycar buy far, =r,;; below manufacturers cost :b;-;= ·;~~::: :::: :•: 1VCAR IYCAR buy at a normally stlly price because other people have lost heavily. IYCAR This time 11s a VERY HIGH QUAUIY cassette deck mechanism that cost over $35 1YCAR US In 1000 lots! This JAPANESE MADE mechanism Is deck only - t.e. a door ts not IYCAR WITH PULSE COUNT fltted nor are there buttons. The deck Is not operated by mechanical buttons and 1YCAR all control ts by electrtc signals, therefore the deck could easily be software IYCAR A new addition to our range. After the tremendous controlled, 1YCAR acceptance of our lA-5019 Pulse count, we have 1YCAR The deck also features an air damper cyltnder for soft eject, massive capstan found a lower cost unit with Pulse Count. IVCAR flywheel, lit Ft head and excellent specs. (see below). • 30 beams 2 (dual sensor elements) 1YCAR This deck Is ideal as either a fast htgh capacity PC memo,:y storage or as a retrofit 1YCAR • Wide angle multi layer coverage . to an existing cassette deck to tmprove performance. • • 12 metre coverage IYCAR 1YCAR • Tamper protected and walk test wo,ili oo, •- o.c,1YCAR • Pulse count trtggertng I 1 • . ··: : I 1YCAR Cat. LA-5018 ' ·.: :.: IYCAR 1YCAR ;;it;,•1590 \9!\' .·.· ...,. ,,., ) IVCAR ,YCAR • 4 track, 2 channel Phillps compact cassette deck• Tape speed 4.75cm/sec • Wow ,YCAR LA5019 PULSE COUNT and flutter <0.12% RMS • Wtndtng time 110 sec FF & REW C-60 • Working volts 9 ,YCAR 15V • Supplted with I 2 page comprehensive manual tncludtng circuit diagram, The absolute latest technology Is used In thts PIR. ,YCAR FEATURES, truth table, etc. ,YCAR • Dual element pyroclectric sensor 1YCAR ,YCAR • Pulse count trtggertng ctrcullty ,YCAR • Fresnel lens array large coverage 1YCAR • 24 dual element detection zones ,YCAR for long, mtd and short range protection ,YCAR • Surface or comer mounting without 1YCAR extra accessories ,YCAR Cat. LA-5019 1YCAR ·CC·C· 1YCAR \.:... 1YCAR -::/· 1YCAR :/. ULTRASONIC BURGLAR ALARM ONLY$49.95 SAVE$89 JAYCAR No1 FOR PASSIVE INFRA RED DETECTORS ■i;a=,~;!~ SAVE $10.00 $99.00 'C~·-.;,r11 ' : i ;1 $119 ••,,~,$SO.""" $24.95 ,. .. $139 :~g~~ : IYCAR <?: IYCAR :,\· _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __. IYCAR . ·..1\."",·•-•_•_•_•_•_•_•_•_•_•_•_•_•_•_•_•_•-•_•_•_•_•_•_•_•_•_•_•_•_•_•_•_•_•_•_•_•-•-•-•-•-•-•_•_•_•_•_•_•_•_•_: IYCARJAYCARJAYCARJAYCARJAVCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAVCARJAYCARJAVCARJAYCARJAVCARJAYCARJAYCAR JAYCARJAYCAR 1YCARJAVCARJAVCARJAYCARJAVCARJAVCARJAVCARJAYCARJAYCARJAVCARJAYCARJAYCARJAVCARJAVCARJAVCARJAYCARJAYCARJAVCARJAVCARJAVCAR JAYCARJAVCAR IYCAR JAYCARJAVCA RJAVCARJAYCARJAYCARJAVCARJAVCARJAYCARJAVCARJAYCARJAYCARJAYCARJAVCARJAVCARJAYCARJAYCARJAYCARJAVCARJAVCAR JAVCARJAVCAR 0 \YCA9 IAYCAR iAYCAR IAYCAR IAYCAA IAYCAR IAYCAR IAYCAR IAYCAR IAYCAR lAYCAR IAYCAR IAYCOR 10.YCOR IAYCAA IAYCJ\P IOYCOP IAYCOP JOVCOA IOYCAP I A Y C A ~ Dear Customers, Sometimes we have trouble gettlng new kits tnto stock the month they are described and advertised. We advertise these products In good faith, but we arc occasionally let down by numerous things. The major problems encountered which hold up new kits arc: • PCB artwork from the magazine Is the biggest problem. It Is very often late, and occasionally Incorrect • Specialist components Is a big problem. We order such parts the moment we receive parts lists, and arc often quoted 12-14 weeks delivery. • General poor avatlablllly of components, as most arc Imported. We arc not Just maldng excuses, we would dearly love to have all new kits on the shelf when the magazine article appears, but sometimes it Is not possible. We suggest you fD.ve us a ring first and check avatlablltly on new kits before you visit. TV COLOUR BAR & PATTERN GENERATOR Ref: EA October 1987 Cat KA-1691 $139.00 BEGINNERS POWER SUPPLY Ref: EA Sept 1 ~ 7 Cat KA-1689 ::;;26.95 D.I. (DIRECT INJECT) BOX Ref: EA Oct 198 1. Cat KA-1690 ::;;39 •95 LOW COST FLASH STROBOSCOPE Ref: EA August).987 Cat KA-1688 ::;;13.95 • BALANCED LINE DRIVER Ref: EAMAugu5_1987 Cat KM-3060 ::;;99.50 ,------------------------, I I NOVEMBER IS A BIG MONTH FOR KITS WITH 8 NEW ONES!! VOICE OPERATED RELAY Ref: EA Nov 1987 Elevtates the need to push the button when using a microphone. Shortforrn kit, no hardware. Cat. KA-1692 $24.95 HIGH QUALITY GUITAR PREAMP 1GHz Digital Frequency Meter! Ref: Silicon Chip (New Magazine) Nov '87 'Silicon Chip' Magazine, a new magazine to commence this month have produced as their first project an absolute rtpper design. It Is a full 0-lGHz (1000MHz) DFMI Make sure that you get a copy of the magazine to read all about It Jaycar will be doing the full kit but It won't be available until at least the end of November. Cat KC-5013 ONLY $299.00 1,r--i:i2n 11.JC..:iu•• Ref: ETI Nov 1987 Features of the ETI 1424 Include a top boost and normal Input, two pre-eq ltne Inputs, bass & treble controls, effects send and return, sweep eq, 4 post eq & line inputs and master volume. PCB pots. supplied when available. 6.5mm sockets, transformer and knobs are not supplied. Cat. KE-4729 $45.00 R FOR PHONE Ref: Silicon Chip Nov 1987 If you have two or more telephones on the one ltne, • VOLTAGE & CONTINUITY -TESTER with this project a LED will flash on the phones not used to Indicate the ltne Is In use. One kit ls needed for each telephone. PC board and components supplied. (Unit mounts In telephone). Cat. KC-50ll $19.95 CAR RADIO POWER SUPPLY 1 gating time, sec 10 12B ,01 PER 1Mn/10 1 .1 . .m 12,8 1.28 ,128 DIGITAL FREQUENCY METER Build this superb ~ November, 1987 1GHz Digital Frequency Meter By STEVE PAYOR This superb 1GHz Digital Frequency Meter will outperform any other instrument in its price range. It uses the highest performance ICs, provides both frequency and period measurements, and features an 8-digit LED readout. 32 SILICON CHIP There is only one way to describe the performance of our new 1GHz Digital Frequency Meter - it's superlative! The design brief for this instrument was simple: it had to be the best DFM for its price available in Australia. It also had to include both frequency and period measurement modes, a frequency cycles counted 1000 i,ating time, sec 10 · ·· ' . :.: 10 . ·· ••····· .,.. · 1Z11,, · 12.8 l28 128 o,o,rAL FREtlUENtv MEren·• These two views show the new counter in period mode (left) and frequency mode [right). The unit is housed in an attractive plastic instrument case, with the LED displays hidden behind a red acrylic panel. Note kHz and µsec indicators. response to 1GHz, switchable gating times, and an 8-digit readout with switchable decimal points and overflow indication. And, as if that wasn't enough, the all-up kit price had to be kept to less than $300! It took a lot of doing, but we've managed to come up with a very refined design that beats the socks off anything else going. This design not only outperforms existing kit DFMs but also commercial units costing many times more. To meet our design objectives, we selected three key parts for the circuit: Intersil's ICM7216A LSI frequency counter, Motorola's MC10116 triple differential line driver, and Philips' SAB6456 1GHz divide-by-64 prescaler/amplifier. The ICM7216A counter IC was chosen because it contains all the circuitry necessary to count, generate gating signals, latch data, and drive an 8-digit multiplexed LED display. It also includes a highfrequency oscillator and control inputs for decimal point placement and gating time. The 10116 and SAB6456 ICs are used at the inputs of the 0-lO0MHz and 1GHz ranges respectively. Both are high-speed EGL devices and feature excellent sensitivity across their respective bandwidths around 20mV in the case of the 10116 and 10mV (max.) for the SAB6456. The 10116 has been around for a number of years and has been used as a 0-lO0MHz preamplifier in many commercial DFMs. The SAB6456 is a more recent device, originally designed as a switchable prescaler for use with UHF/VHF television tuners It has a guaranteed range of operation from 70-l000MHz. Three other EGL devices have also been used in the circuit: two 10131 dual-D flipflops which have been configured as divide-by-five and divide-by-two counters, and a 10100 three input NOR gate. Finally, a few inexpensive CMOS chips round out the IC count in our new DFM. These devices are used for frequency division and logic switching. Main features Let's take a look at some of the features of the unit. As seen from the front of the instrument, there are two groups of four pushbuttons: the RANGE buttons, which move the position of the decimal point, and the FUNCTION buttons which select the various period and frequency modes. Throughout the following circuit description, these buttons will be referred to as Rl, R2, R3, R4 and Fl, F2, F3 and F4 respectively. The RANGE buttons select the gating time when in frequency mode, and the number of cycles counted when in period mode. The FUNCTION buttons select the various operating modes: either period or three frequency ranges (0-l0MHz, 0-l00MHz or 10MHz-1GHz). Immediately below these pushbuttons are two BNC input sockets. One of these has an input impedance of 1MO shunted by 10pF and is used for period and frequency measurements up to 100MHz. ThesecondinputhasaninputimNOVEMBER 1987 33 10Hz-10DMHz(; INPUT . _ • 100MHz PREAMP AND SCHl,ITT TRIGGER 16Hz{;;::; INPUT':(' ,-, COUNTER ICM7216A LI DISPLAY TIMEBASE RATIO IC1 +64 FRED/PERIOD SWITCHING T Fig.1: this diagram shows the main circuit blocks of the counter. Signals applied to the 10Hz-100MHz input are amplified, and divided by 10 or fed direct to the base of a TIL level translator (Q2). Similarly, signals applied to the 1GHz input are divided by 128 before reaching Q2. Q2, in turn, clocks an Intersil ICM7216A counter IC which drives the LED display. pedance of 500 and is used for frequency measurements up to one gigahertz (1GHz). An interesting feature of the unit is the provision of four switchable gating times: .01, 0.1, 1 and 10 seconds for the 10Hz to 100MHz input, and 0.128, 1.28, 12.8 and 128 seconds for the 1GHz input. The gating time is simply the time over which measurements are made before the display is updated. A long gating time means a higher count and greater resolution, but the drawback is slow update times. Selectable gating times thus make for a more versatile unit. You can opt for high resolution or fast update time, or a compromise between the two, as the situation demands. In the period mode, the gating switches select the number of cycles counted before the reading is displayed - either 1, 10, 100 or 1000. This mode allows very accurate measurement of low frequency signals (ie, those below about lOkHz). As before, you can opt for high resolution, fast update time, or a compromise between the two. All readings are displayed direct1y in kilohertz (kHz) or microseconds (µsec) , depending on the mode selected. As you can see from the photographs, the display features both kHz and µsec indicators, together with LED indication of the mode selected. Another LED, situated in the top left-hand corner of the display, provides overflow indication. 34 SILICON CHIP Easy to build We've put a lot of work into making this unit easy to build so that the specs of your assembled kit will match those of the prototype. All parts, with the exception of the power supply components, are mounted on two printed circuit boards which are soldered together at rightangles by means of matching solder pads. A red acrylic panel fitted with a Scotchcal label is attached to the display PCB by means of the BNC input sockets. The whole assembly then slides into matching grooves in a compact plastic instrument box. A third PCB accommodates the power supply components and is mounted together with the transformer, on the rear panel. We did this so that heat-generating components, such as the power transformer and a voltage regulator IC, were as far away from the sensitive counter circuitry as possible. Circuit description Before getting down to details, it is interesting to note that only two logic families are used in this frequency meter: the aforementioned ECL (Emitter Coupled Logic) for the high-speed "front end" circuitry, and CMOS for the remainder. All the ICs are common types except for the 1GHz ECL prescaler (Philips SAB6456) and the main CMOS counter/display driver (Intersil ICM7216A). Another interesting feature is the complete elimination of front-panel wiring. This was made possible by using PCB-mounted pushbutton switches and by electronically switching signal paths. Normally, one would expect to see a bank of mechanically latched and interlocked pushbuttons, but here the mechanics have been replaced by CMOS logic circuitry. Viewed as a whole, the circuit is quite a jigsaw puzzle, so we will examine it one section at a time, starting with the inputs. The 0-lOOMHz input This input is used for period measurements to 0.4µs (2.5MHz) when function button Fl is pressed, and frequency measurements up to 100MHz. The input impedance is nominally lMO with protection against all but the worst overloads. Firstly, .any DC component of the signal is removed by the 0.047µF input coupling capacitor. The signal is then clipped by a pair of BAW62 high-speed silicon diodes in conjunction with a series 180k0 current-limiting resistor. Note: do not substitute other types here as these diodes have exceptionally low capacitance (lpF typ.) and a high current rating. To maintain a flat frequency response, the 180k0 resistor is shunted by an 18pF capacitor (Cl) which compensates for the stray capacitance to ground across the 820k0 resistor of about 4-5pF (due to the diodes and JFET Ql). A JFET source-follower (Ql) is us- a little daunting, but this is achieved with a standard EGL differential line receiver (10116) and careful circuit layout. Note: readers unfamilar with the internal circuitry of EGL should refer to the accompanying panel. The 10116 contains three differential amplifiers, each with complementary outputs. Also provided is a DC bias voltage, VBB (pin 11 ), which we have used to bias the inputs of the first stage (IC2b). The signal is capacitively coupled from the JFET buffer stage and, by keeping as much symmetry in the layout as possible, most of the noise picked up at this point is effectively cancelled by the balanced differential input. This is important because the proximity of the 8-digit multiplexed LED display makes for a very noisy environment. The DC balance of the first stage is adjusted by VRl. Since each in- ed to buffer the input signal, and the voltage gain of this stage is about 0.7. Not shown on the circuit diagram, but connected to the source of the JFET, is a small "guard" track which surrounds the input circuitry on the PCB. This helps to minimise the stray capacitance around the input components, and the net result is an effective circuit input capacitance of only 6pF. In practice, by the time we add an input socket and plug, it is closer to lOpF. 100MHz preamp This part of the circuit amplifies the incoming signal and converts it to a "clean" square wave suitable for the logic and counting circuitry. At first glance, the requirements of high gain and a frequency response flat to 100MHz may seem put draws approximately 13µA of bias current, this lkO multi-turn trimpot can shift the DC input voltage by ± 13mV. The voltage gain of the first stage is about seven. The second stage (IC2c) has some negative feedback to reduce its gain. This feedback is applied from one output to its corresponding inverting input by two 1000 resistors. If IC2c was an operational amplifier, it would have a gain of - 1 via the inverting input and + 2 via the non-inverting input, giving a total differential gain of three. But since the open loop gain is only seven (instead of practically infinity in the case of an op amp), the actual stage gain is closer to two. There are reasons for reducing the gain here. First, using all the available gain would make the circuit too sensitive. To give a good stable reading, a DFM must be able All About Emitter Coupled Logic +SV vcc vcc - - - - - - - - - - - - +sv --,---·- OUTPUT I OUTPUT l -7-...-- INPUT PULL-DOWN RESISTORS INPUT ov VEE ..._......._no~ffuT HIGH +4.3V f t + -=- =t:L CIRCUIT SYMBOL OR LOW OUTPUT +3.4V 50k 4mA - - - - - - - - - - - - - VEE OV i:3:r::R CIRCUIT SYMBOL Fig. 3 BASIC ECL LOGIC GATE Fig. 2 BASIC ECL DIFFERENTIAL AMPLIAER Emitter Coupled Logic (ECL) was one of the first forms of bipolar logic to be produced as monolithic integrated circuits, back in the early 1960s. Today, it is still the fastest form of logic available, with propagation delays of less than one nanosecond per gate quite common. The ECL 10,000 series ICs used in this project are slowed internally to make them less critical to use with normal circuit wiring. The propagation delay is 2ns and the rise and fall times have been slowed to 3.5ns. ECL ICs are normally designed to run from a -5.2V supply (VEE), t but they also work quite well from a +5V supply; ie, Vee= +5V and VEE= 0V. Fig.2 shows the basic structure of an ECL differential amplifier. Depending upon which input is at the higher voltage, either the left or the righthand transistor in the differential pair will be turned on and the voltage across its collector load will be about 0.9V while the collector of the other transistor will be at Vee. Each collector output is buffered by an emitter follower , which gives an output voltage swing between +3.4V (logic low) and +4.3V (logic high). An external pull-down resistor is required on each used output. Fig .3 shows how this basic structure is modified to form a logic gate. A number of transistors (one for each input) are connected in parallel on one side of the differential circuit, while the transistor on the other side is connected to an internally generated bias voltage (VBB) which is half-way between the high and low logic levels; ie, about +3.8V. When one or more of the inputs is taken above +3.8V, the current shifts from the right to the left hand side of the emitter-coupled circuit and the NOR output goes low, while the OR output goes high. NOVEMBER 1987 35 Altronics Will Deliver Any Of These Quality Products To Your Door Faster Than Any Other Australian Supplier Or Your Money Back (Within 24 Hours To Every Capital City and Suburbs - Allow Additonal 24 - 48 Hours For Country Areas) 11111111111111111 IllIIll II UIIIH II Hiil IIIIOII II IIIIIIIIIUlll llllllll lllllmmn Qlllllll III U1111111111111111Ill In Ill II Ill II Ill Ill Ill Ill Ill I1111111111111111 HI 1111111111111 . ,., Toroidal Power Transformers 31.! SA VE $ $ $ SA VE $ $ $ Great Little PA Amplifier Why a Torlod? • Smaller size and weight to meet modern -- slimline .. requirements • Low electrically induced noise demanded by compact equipment • High efficiency enabling conservative rating whilst maintaining size advantages. • Lower operating temperature • Simple, qu ick single bolt mounting. Thi• natty llttla amp/It/er lncludH aome ,.,,,,,rlcabl• fNlutN wll/c/1, unt/1 now ,,..,. only bHn avallabl• on "fY ..pena/re commercial /lama •-O- Balanced Mlc Input- 160 Watt Model1 This enables you to run very long microphone leads without troublesome interference or hum pickup. Bel1nced llne output - This enables you to run the speaker lines right alongside the microphone line without instability. Con1t1nt voltage design allows you to switch on one speaker circuit or all circuits together without any noticeable variance in output sound level. Rugged Ultra Quiet- Now With Metal Diecast Frame Output Power la a genuine 30 watts Into either 100V llne or 4 Ohms. Durable Die Cast Aluminium Venturi PBT Plastic impeller of 94V-O material. Shaded pole motor. A 2000 ........... cat.No. 240V High Specification Computer Fans 80mm x 80mm x 32mm $259 Air Flow 45 C.F.M. Input Power 16W Speed 2300 RPM Noise Level 31 dba. Cat. F 1020 $24.50ea $22.50 4 or More 120mm x 120 x 38mm Air Flow 80C.F.M. Input Power 25W Speed 2600 RPM Noise Level 43 dbA. Cat. F 1030 $24.50ea Super Compact Transformer Delivers 12, 15, 24, 27, 30V At Up to 10 Amps Just The Shot for 12 & 24 V, Supplies & Charging; Circuits Multlpurpose 120VA Transformer 0 ~~~~~f;s ~~~tti "'IfPti~r:i~~~0 ~n expensive grain oriented steel. Look at the size! Just 110mm Wide by 65mm High by 65mm Wide. Weight 1.25Kgs. M 2175 Primary 240V secondary 1 0--12V <at>5A,15V <at>4A secondary 2 0--12V <at>5A,15V <at>4A $22.50 4 or More Fan Finger Guards $1.50 (for 110mmFan) $1.50 M 3050 M 3055 M 3060 M 3065 M 3070 M 3075 M 3080 SEC.V 12 18 25 30 35 40 45 + 12 + 18 Electronics Australia Projects + 25 + 30 + 35 + These are the Genuine English TOROIDS as Specified in various 40 + 45 $59.esea 5 Up $55.ooea 300 Watt Model1 Cat.No. M 3085 M 3086 M 3088 M 3090 M 3092 M 3100 M 3105 12 18 25 30 35 40 45 + + + + + + + 12 18 25 30 35 40 45 Dimensions $69.esea 5 Up $65.ooea & Weight 160 VA Model1110 Diam. 45"m m H. 1.8Kgs. Leads 200mm 300 VA Model• 125 Diam. 45mm H. 2.5Kgs. Leads 200mm F 1022 (for 80mm Fan) F 1032 Engineers Multimeter $10 Off This Month Includes Continuity Buzzer 10 Watt Twin Cone Speaker 8" (200mm) Great for PA, Background Music and Hifi extension use. Over 90 ,000 sold in Australia . Cat. C 2000 20,000 Ohms/Volt DC• 8,000 Ohms/Volts AC. Mirror backs ed scale • Overload protected . 10 amp DC current range. Unique carry handle doubles as a bench stand . RANGES DC Voltage 2.5, 10, 50, 250, 1000V AC Voltaae 10, 50, 250, 1000V Declbell -8db to +62db DC Current 5 , 50, SOOmA Ohm meter 0-6 meg. Ohms in 3 r'anges,50 Ohms centre sc_a le. Size 135 x 91 x 39 mm 1 $12.95 10 Up $11.00ea 1-9 lncludel Battery THter Q 1018 Normally $39.95 Now $29.95 Why Rltk Unnecessary Heart Attack? 20MHz Logic Probe 200g RHI Input Z 1M Ohm . TTL Logic Hi LED greater than 2-3V. Logic O Lo LED Less than 30% Vee. Min Detectable pulse width 30 nSec . Cat. Q 1272 $7ea 10 or More . $6 $29.95 Horn Relay 12-16V coil 20 Amp Contacts . S 4130 1/2 Price $3.75 Heart disease strikes down many people in the ir early 40's (or even 30's). The tragedy remains that had such victims been alerted, remedial medical. physical and dietary action could have been prescribed to avoid ~~a~f~. a;i~i;iany cases restore full bodily · Blood Pressure and Heart Rate Monitor Feature,: • • • • Non-Microphone Measurement System LCD Readout Blood Pressure Monitor Pulse Rate Monitor Why Pay $150? X 3055 Only $11 Q Used with your multi· meter - Reads exact zener voltage up to 60V. K 2620 cts To Build $12.50 Fantastic New Kit From EA Super Large LED Display Module (Display 150 x 60) Need to produce an LEO display that can be seen from a long way off? This sin11Ie digit 153mm high seven segment LED display module is just what you need. It can be used as·a replacement for both common anode and common cathode LED displays, can be either multiplexed or DC driven, and can be provided with a decimal point on either the right or left. Save A Bundle On Those Dangerous Pesticides Mosfet Power Amp Module 150 Watt Here is a high power. general purpose power Amplifier module suitable for HiFi, guitar and PA applications !!mploying sturdy, reliable MOSFET'a in the output sta e. Build EA's Great Ultrasonic Pest Repeller EA' s "Pest Off" generates frequencies between 23KHz and 64KHz claimed to be the best for t~~~t?e~ffKm ~vermin and. 1 External DC Supply Requlred20 -24V at 150mA K 1225 $49.95 SPECIFICATIONS: Power Output 150W RMS into 4 Ohms 100W RMS into 8 Ohms (At onset of clipping) Frequency RHponM 20Hz to 20KHz +0 -0.5db 10Hz to 60KHz +0 -3db (Measured at 1 Wand 100W Levels) Input Senllllvlly 1 Volt RMS for full output This Natty Single Button Security Lock Is Just The Shot For Your Garage, Workshop, Wine Cellar Or Front Door 4-Dlglt Combination Lock Blowing Fuses Blowing Your Cool? You Need This electronic combination lock has a four digit security code which is entered using a single pushbutton switch. For added security, each number of the code must be entered within certain time restraints. Once the correct code has been entered, the circuit triggers a solenoid operated door catch to unlock the door. Altronlc Kit Hou■ad In ■turdy Jiffy Box. K 1925 ..... $35.oo Excludes Solenoid Door Catch (Available from your local Security Store) TRANSISTOR ASSISTED IGNITION WITH DWELL EXTENSION K 2535 Noln 114db below full output Total Harmonic Dlelortlon 0.006%<at> 1KHz 12W 0.03%<at> 10KHz 12W Stablllty Exceptional (tested to full output driving 3.3uF into short circuit at w 10KHz) . $32.solrr iuse Dead easy to build. and (even better) there are only 3 electrical connections required to the car wiring system. K 4010 ......... The Electronic Fuse Hum 98db below full output $39.50 _The Power House Arrives Massive 600 Watt Inverter Oper■tH lrom 12 or 24 Volt •Y•t• m• via lntemal wiring connection• Big brother to our 300W Model this brilliant design can be internally connected for either 12 or 24V operation. Full 600 watt output - and that will power a fantastic array of appliances e.g. Lighting, Electric Motors, Electric drills, Hi Fi, TV Sets, Computer. An absolute muat for· HouH Power or for the Truck, Tractor etc. Complete Kit Fully Built & Tested $399-.oo $499.oo All you do is clip the unit across ttie DC holder (fuse removed), dial up the required current (max. 10A) and if the circuit draws more than this then the circuit "trips" or opens . Thus power is removed from the device. FHturea: Fast blow - slow blow setting • Manual reset button • LED fuse tripped indicator • Operates off 1 single 9V battery (not supplied)• Two current ranges0-1A & 0-l0A • Any current setting available up to 10A • Current Settings easily adjustable via. a pot and cal ibrated scale. • Housed in a rugged Jiffy Box. A Must for prototyping and service work. No Electronic workshop should be without one. Video Enhancer This classy digital timer allows prescision timing for photographic processing from 1 second up to 9 minutes 59 seconds in 1 second increments. Featurea: Large easy to read LED displays. Hold switch which interrupts timing and focu s switch which bypasses the timer settings. K 1850 Sharpen• up your picture whan Copying Video to Video Here's a almpl• but effective video enhancer that is super •HY to build at a fraction of the cost of . commercial models. Unit sharpens picture detail, and can actually improve the quality of a copy by amplyfying the top end of the video signal K 5825 $42.so I \ With Soldering Stations Costing $150 and More, This Represents Excellent Value Temperature Controlled Soldering Station , (liAl:lept.'lltl) Controls the-temperature of your -r:i~~~~t:i~~~":i~8JJ_'.:~5~~t;~~~~~~d soldering iron plugs straight in , no ..._ need for modification. . ' The Altronics Kit comes complete Pre-punched and silk screened.K 6400 { '.r - $35.oo · Screecher Car Burglar Alarm This alarm drives off wouldbe thieves with an ear splitting modulated tone. Once activated it is near impossible to stay within the confines of the car. FHtur••= Entry Delay • Exit Delay • Alarm Timer • Lamp Flasher• Three second soft alarm reminder. Piezo siren produces modulated tone of 110dbat 1 metre. Simple to build and install. Two S.naor Input• Ultrasonic Movement Detector This Ultrasonic Movement Detector proviaes an open window etc. Connects directly to an any movement up to 3 metres within an an I ~ ;:; ::t: (") :z: n 0 t=: Cl) = I .,. µsec PERIOD .,. kHz FREQUENCY TO 100MHz FREQUENCY TO 1GHz 1 0 0 0 0 0 D 1 . Fl +128 +10 +1 +1 .011- FUNCTION LEDS 270{) 100MHz PREAMP AND SCHMITT TRIGGER 100{) . F2 . F3 .,. .,. F4 (CMOS) FROM PUSHBUTTDN LOGIC J 1N914 D9 1N914 .Jit ECL-CMOS TRANSLATOR ... 2N5485 B VIEWED FROM BELOW 2N4258 ~- +5V FRONT PANEL BOARD 4,t,.UB,, -- - - - - - - - - - - - 12~4 HLMP-2300 NOTCH--"'W 8C549 B F4 (ECL) GOD cOE E ·LJc s F3 14 +---+-'ll------t--➔----tl.....,_+5V .,. 470{! 1GHz FREQUENCY METER F1 .0R.F2 ,------t----.------t----------J-----------t-----,-+sv 04 1N914 10 10VW 10 .----+----,10VW+ Fig.4: the front panel circuitry. Signals from the 100MHz preamp (IC2) and 1GHz prescaler circuits (ICt) are fed to NOR gate IC3. The signals are then divided by counter stages IC4 and IC5, or fed direct to the base of level translator Q2. kHz kHz FREQUENCY TO 10MHz 0 0 D 1 0 0 0 1 .,. .01.I UNITS OVERALL PRE-SCALING DISPLAY DIVISION RATkl +64 1GHz PRESCALER MODE .,. .01I. IC1 SAB6456 SYNCHRONOUS +5 COUNTER .,. .01+ ,--------------------4....--4.________________________.,....__ r----t--t-----+SV FUNCTION INPUTS F1 F2 F3 F4 t' 10MHz-1GHz Cl 18pF 10131 .011 ..---------------+------------+5V Most of the counter circuitry is mounted on two PCBs which are soldered together at rightangles. This view shows the parts on the main counter PCB. The Intersil ICM7216A is at the right. to ignore the noise which is always present on the signal. The sensitivity we have chosen is about optimum for most audio and RF measurements without the need for an input attenuator. The second reason for using negative feedback has to do with maintaining the high-frequency performance, which will be discussed a little later. The third stage, IC2a, may appear similar to the second stage, but in this case the feedback is positive rather than negative. This means that IC2a functions as a Schmitt trigger rather than as a linear amplifier. The positive feedback around IC2a causes it to latch in either the 1 or O state when no signal is present. To toggle the output, the signal amplitude must exceed the hysteresis voltage which is about 450mV. By working backwards from the here, we can calculate the theoretical sensitivity of the instrument; ie. 450mV divided by 2 (second stage gain) divided by 7 (first stage gain) divided by 0.7 (JFET buffer) divided by 0.82 (input protection) = 56mV p-p, or 20mV RMS. Any noise signal with an amplitude of less than 56mV peak-to- peak will thus be ignored. At frequencies above 50MHz, the sensitivity of the Schmitt trigger is degraded somewhat by the phase shift (propagation delay) within the ECL amplifier. Thus, the positive feedback becomes less positive. At the same time, the negative feedback around the previous stage becomes equally less negative; ie. the gain of the second stage actually increases slightly. The serendipitous result is a relatively constant sensitivity up to around 100MHz, without the need for small "peaking" capacitors across the feedback resistors. Fig.6 shows the measured performance of one of the prototypes. The sensitivity was better than 20mV RMS over most of the frequency range, rising to around 90mV at 140MHz. The small "bumps" at 50Hz and 500Hz were caused by internal noise - from mains hum and the multiplexed digital display respectively. This noise slightly degrades the theoretical noise immunity, reducing the maximum amount of "ignorable" noise at the input socket from 56mV p-p to about 30mV p-p. A test point is provided at the output of IC2a for setting up and testing the above circuitry. The state of the Schmitt trigger can be monitored by plugging a 1.7V red LED into a pair of Molex pins on the PCB. The number of turns of trimpot VRl required to turn the LED on or off provides a convenient check of circuit operation. Following IC2a, the now digital signal is routed to the base of TTL level translator Q2 via one of two paths: either directly via ECL OR gate IC3d when Fl or F2 is selected, or via IC3b and a high-speed divideby-10 counter when function F3 is selected. The 1GHz input This input is used for frequency measurements from 10MHz to above 1GHz, and is selected by pressing function button F4. Surprisingly, this is one of the simplest parts of the circuit, thanks to the use of a Philips SAB6456 UHF prescaler (ICl). As mentioned above, this IC is normally intended for use in TV tuners where its function is to divide down the frequency of the local oscillator, as part of a frequency synthesiser circuit. Because it is designed to be driven by small-amplitude sinusoidal signals over a wide frequency range, it is ideal for our application. NOVEMBER 1987 39 ~ ~=- _ l z n :J:: ' -,!,- ~ 3 ,._J 1 µJ, 2 13 r:::-1, CONTROL I F4 ,i=,, ~ 0lfil.!£1!L_ 14 12 INPUT +5V T 9 s ~ 5 I 12 0 . in 11 7.8125Hz REFERENCE E C - , ◄• - - , I 1 I 7 ':' "!" .J.! r 1 ,!.It I~ If FUNCTION PUSHBUTTONS RATNJ ~ I a,!'!!! ~ .,. 10VWL 10 .,. ,I_ 1 ~F- . I ~ 2 3 _ 11' CE ,..._., -l R3,, I C b 11 g ! 8 I l d 1 4 1 __ J - J. I -' j I 7 I L:lr-1 a - - 4r::::-13 slo OUT ~ IN ____!ill_ 4r::::::::-,3 5 · j E N 240VAC '--<> Sl 13 c ~ ~ C f DP --1k§L .,!£l9!!.. 12 11 F4 12 11 POWER SUPPLY BOARD 1 , 01; 16VW 200 ·-r- - E DV t5V .,. -!!- ~ - s DP 018 8C549 Bfr C B 0.11;:i UT ~ t E .,. GND 7805 1"" IN • 1k 470D a\.!: 33D -- +5V p_ DP ~~c s _ DP :+ o.i _ y-IC11d ~11 D12 1 F3 101 - - - 111 ~ F2 1 F1 12 1or::::::-l11 4x1N4001 014 i.:.;_;;a.., _ __. 'lov :;: jo ~~ ~F" 2155A 7216A DECIMAL POINT SELECTION 5 ~ - Al IC1lb ~ 13 ~ d - p DP 8xHDSP-5501 ON FRONT~N~BOARD_ _ - 1-=jr - _ _._ _ _ _ _ _ _ ___, 1s L.:+:,J IC11c r-::::, 9 8 16 • L.:::,=-l B Jl...-.0 IC9c -~ IC10c I 8-DIGIT MULTIPLEXED DISPLAY ____icn_ - d L:l:J ~ 1s 15 ,--~--4--777---721 SE~mroN &A I - - ef_ fc ,-, I g b a .---4---+-J&--7777--_, ~ I •--3-----R4f: f 3 12 14 7 I. ~I. (: 1 0 1 RANGE PUSHBUTTONS R21,· 1 I ,1 • r l& 47k -~-■---■- 14 15 CK RESET ICl 2 4017 ON FRONT PANEL BOARD ____ - - · 1 R11 ·,' •..:PUSHBUTTON LATCHING 1M .022: 010{ 1N914 """ .,. 10VW ...J 1GHz FREQUENCY METER F2 F3 F4 FREQUENCY FREQUENCY FREQUENCY ,.. ---I---~-- - - - I' 16 15 RESE 47k IC13 4017 CE 13 1 2 3 7 4 O CK14 "":l:- I+ 10 .!!!! ------<1---,,-, - +5V ..---t----.---r--7--,.---, 500Hz t5V 1 4 +64 IC7 ,.J4 IN 4024 RESET 12 1& r-i: I a _ _ _ _ _ _ _ __. ....Jl!3i!,8--f3~,8~-J:3Wi.1L~-~3!,B'T"..J~3£BT_,a;:3:;::,B"i_,.;3:.B,_.._3,.,8, ._..;.._ _ _ _ _ _ _- - , I I I I 1 I 1 OVERFLOW ~---====1:.~======~1 I I 1 1 I LEDS (:,_ r HLMP-1301 '\ • :>,. - -- --- - - Fig.5: diagram showing the counter, display and power supply circuitry. Also shown is the latching circuitry for the function and range pushbuttons (IC8-12}. This section will be described next month. L I II C 500Hz • CLOCK _ T .01.I!'!!! ◄;Jo-______-..-:t~_-________ __ j PERIOD ' F1 , ..... - Bf r' E I ~ 016 BC549 4.7k ., ,. . ,._ 2.2k 1k '-.:::: L--' -______________ , 10k 15 . - - - - . - - - , - - 8 ;~ B r- dlj C-'L:c=====--------------t-nttrt=::il b 1 a 7 1 -:500Hz FILTERING ANO SHAPING • · I 0022 • lOk -:- I 100pF.I!'!!! • l DP 4 1 I I ==================--------11~•~~t=========---1 8 D7 ,1-6 15 D8 ::1;17 ll~ 19 I I ~------------------------==:t============================~--7 :::::::::::::::::::::::::::::::::::::::::::::~~~~~~l~~~~::::::::::::::::::::::::::::::::::::::::~::::: ;---7 3 1802i • 22 21 01~ltg 03 D4 20 I - ,..---l.---4---------~ L.:;;J F3•-...----+-, 4 . rJ F2 40111!..!n!!L 1r::-,2 1 .- 11P . F1 4016 IC9a - W 40 IC 11 +5V .,. lOOpFI. 10k IC& ~u 124 I ICM7216A INPUT A SC OUT .-!!HOLD 28 26 RESET ~◄►~-~-~~ :~ RANGE 0-1DMHz FROM FRONT PANEL BOARD 4-40pf 13 ovw.I,- 25 DSC IN pF 10MHz"T" 10M ::a - •• .l 39 "" - 100D~ 1 n 0 r=: Cf.J = lO0mV 70 w - c.:, ~ I I I I I r C1=15pF I 50 I 0 ...if> 30 :!:a ~ 20 r:c ------ 10mV 10Hz ...- l.---" V~ r--.. .__ V V 100Hz !kHz 10kHz I I/ lO0kHz 1MHz 10MHz 100MHz 200 FREQUENCY Fig.6: the measured sensitivity of the prototype was better than 20mV RMS over most of the range, rising to about 90mV at 140MHz. 1v.---------r----.------....-------r-----. SAB6456 - +---+-- - - - - - +- -+-- t - ---t w c.:, ~ 10mV 0 ...> ;;::, 11. :!:a en == r:c 100µV 1 - - - -- --+----+--- 50 - - - + ----+-+--- 100MHz 500 1GHz --1 2 FREQUENCY Fig.7: the SAB6456 has a guaranteed range of operation from 70-lO00MHz with a sensitivity of lOmV. Actual devices have a cutoff frequency of typically 1.7GHz. Pins 2 and 3 are differential ECL inputs, which are biased internally, so that the only external parts needed are two input coupling capacitors. These capacitors should ideally be leadless ceramic "chip" types, since the inductance of the leads on ordinary ceramic capacitors can be a problem at 1GHz. However, we have found that Philips miniature ceramic plate capacitors (2222-629 series) are useable, provided they are seated right down on the PCB, with an absolute minimum of lead length. Note: this applies to all the O.OlµF ceramic capacitors used throughout the circuit for highfrequency coupling and bypassing. No overload protection is provided on the 1GHz input since the usual pair of back-to-back diodes would provide too much of a capacitive load at 1GHz. In any case, most applications will not require a solid connection to this input. The sensitivity is very high, and according to the manufacturer's specifications, is guaranteed to be better than 10mV RMS from 70MHz to 1GHz (Fig.7). The typical input sensitivity at 1.2GHz is, in fact, a mere 50µV RMS, and the input will usually oscillate at this frequency when no signal is applied. In practice, this is of no consequence since the prescaler will stop oscillating when a valid signal is present. In fact, this self-oscillation provides us with a convenient way of checking the DFM operation on the 1GHz range - pressing the F4 button, with no input connected, should give a reading of around 1.2GHz. Note that the maximum input voltage for reliable counting is 300mV RMS. The input impedance is 5600 is parallel with 5pF at low frequencies, and 300 in parallel with 1.5pF at 1GHz. Inside the SAB6456 (ICl) is a binary counter which can be set to divide by 64 or 256, depending upon the mode control pin (pin 5). With pin 5 open circuit the division ratio is 64. What we would really like is a divide-by-10 or divide-by-100 prescaler, but such devices are quite expensive. Instead, we have managed to make do with the divide-by-64 option, followed by an additional divide-by-2 stage implemented with normal ECL circuitry. The fact that our 1GHz signal is divided by 128 instead of 100 does not cause any real problems, as will be shown next month. As shown in Fig. 7, the actual cutoff frequency for the SAB6456 is typically 1.7GHz. After dividing by 128, this leaves a signal of 13MHz for the ICM7216A counter chip. Since typical 7216 devices can count to 15MHz, our DFM can comfortably exceed its nominal 1GHz specification. The differential outputs of the SAB6456 are at pins 6 and 7 and the output voltage swing is typically from + 4V to + 5V. The addition of emitter follower stage Q3 to pin 7 gives us normal ECL signals and NOVEMBER 1987 41 PARTS LIST FOR 1GHz DFM 1 plastic instrument case, 200 x 160 x 70mm (W x D x H) 1 display PCB, code sc04 1-11 8 7 -1 , 1 94 x 61 mm 1 main counter PCB, code sc041-1187-2, 190 x 55mm 1 power supply PCB, code sc041-1187-3, 54 x 44mm 1 translucent red acrylic panel, 195 x 64 x 1 .5mm 1 Scotchcal label, 195 x 27mm 1 10MHz parallel AT-cut crystal 2 BNC panel sockets 8 momentary contact pushbutton switches 1 21 55 power transformer 1 push on/push off SPOT mains switch 1 mains cord and plug 1 cord clamp grommet 1 two-way mains terminal block 3 solder lugs 2 PC pin connectors 2 5mm metal standoffs 3 25mm 6BA screws and nuts 1 7mm dia. plastic plug (as used with mains sockets) 4 rubber feet Semiconductors 1 SAB6456 prescaler IC (Philips) 1 10116 ECL line driver 1 10100 ECL 3-input quad NOR gate 2 10131 ECL dual D flipflops 1 ICM7216A 10MHz universal counter 1 4024 7 -stage binary counter 4 4016 quad bilateral switches 2 401 7 decade counters 16 BC549 NPN transistors 1 2N4258 PNP transistor these are applied to pin 10 of IC3c which forms part of the signal path control logic. Control logic IC3 is a quad NOR gate, type 10100, which selects the appropriate signal routing. Pin 9 of this IC is a common enable input which is grounded, so that IC3a, b, c and d function as 2-input NOR gates. When button Fl (period) or F2 (frequency to 10MHz) is pressed, pin 13 of IC3d and pin 5 of IC3a go low. IC3a is used as an inverter, so 42 SILICON CHIP 1 2N5485 N-channel FET 3 BAW62 high-speed silicon diodes 4 1 N4001 silicon diodes 7 1 N914 silicon diodes 1 7805 5V 3-terminal regulator 8 common anode LED displays, Hewlett-Packard HDSP-5501 or equivalent 2 red light bar modules, Hewlett-Packard HLMP-2300 5 miniature red LEDs 1 red LED (for testing) Capacitors 1 2200µF 16VW axial electrolytic 1 1 OOOµF 1 6VW PC electrolytic 5 1 OµF tantalum 2 0.1 µF ceramic 15 0 .01 µF Philips miniature ceramic plate, type 2222-629 (0.2-inch lead spacing) 1 0 .047µF ceramic 1 0.022µF ceramic 1 0 .0022µF ceramic 1 1 OOpF ceramic 1 39pF NPO ceramic 1 1 8pF ceramic 1 4-40pF trimmer capacitor Resistors (0.25W, 5%) 2 x 1 OMO, 1 x 1 MO, 1 x 820k0, 1 x 180k0, 2 x 47k0, 3 x 10k0, 11 x 4 .7k0, 3 x 2.2k0 1%, 4 x 1k0, 15 X 4700, 2 X 2700, 1 X 1200, 4 X 1 000, 1 X 330, 1 X 1 kO multi-turn trimpot Miscellaneous Mains rated cable (32cm), hookup wire (50cm), heatshrink tubing. its output goes high and resets flipflop IC4b. At the same time, IC3d gates the signal from IC2a through to the EGL-CMOS level translator (Q2). Note that when two ECL gates share a common output pull-down resistor, either or both gates can take the output high, and so an OR function is obtained without using any extra gates. Thus, the EGLCMOS translator (Q2) can be driven by IC3d when the output of IC4b is low, and by IC4b when IC3d is low. When button F3 is pressed (fre- quency to 100MHz), we need to insert a divide-by-10 circuit. This is done in two stages: a divide-by-5 stage consisting of IC5a, IC5b and IC4a, and a divide-by-2 stage consisting of IC4b. Before we discuss how the divide-by-5 and divide-by-two counters work, note that IC4 and IC5 are dual D flipflops, with two clock inputs per flipflop which are ORed together. Pin 9 is a common clock input for both flipflops, while pins 6 and 11 are separate clock inputs. Either input can be used to clock the flipflop, provided the other is taken to a logic 0, or grounded. The D flipflops operate as follows: when the clock input goes to a logic 1, the data present at the D input is latched by the flipflop and appears at the Q output. The divide-by-5 counter This is a synchronous counter. All three flipflops (IC5b, IC5a and IC4a) are clocked simultaneously from the 100MHz Schmitt trigger output via IC3b. When the counter is not needed, it is stopped by applying a logic 1 to the Reset input (pin 4) of IC4a. However, if F3 is pressed, pin 4 of IC4a goes low and the counter functions again. The three flipflops are connected to operate as a shift register; ie, each input is connected to the output of the previous flipflop. The input to the first flipflop, however, is connected to the OR of the Q-bar outputs of the last two stages. This gives a count sequence which divides the clock signal by 5. The divide by two counter (IC4b) is wired with the Q-bar output connected to the D input. This means that each cycle of the clock signal causes the flipflop to toggle and so provide a divide-by-two function. As before, the counter is stopped by applying a logic 1 to its Reset input (pin 13). Now let us look at the function button logic which involves ten transistors from Q4 to Q14. This part of the circuit controls the signal switching to the EGL-CMOS translator (Q2). Normally, Q4 to Q6 are on while Q7-Q14 are off. Let's say that function button Fl is pressed [ie, period mode is Electronic switching means that internal wiring has been kept to an absolute minimum. Matching slots at the front of the case accept the main PCB and front panel assembly, while power supply components are mounted on the rear panel. selected). When this happens, the Fl line is latched high by IC13 (4017) and so transistors Q7 and Q8 are turned on. This then turns on LED 4 and LED 2 which are the period mode and µsec display indicators respectively. QB also controls Q4 via diode D9. Normally, Q4 is turned on by its 4.7k0 base resistor and pin 13 of IC3d and pin 5 of IC3a are both held high. When Flis pressed, however, QB turns on and pulls Q4's base low via D9. Q4 thus turns off and pin 13 of IC3d and pin 5 of IC3a are pulled low by Q4's 4.7k0 emitter resistor. IC3d is now enabled and gates the signal from the 100MHz preamp through to the base of the ECLCMOS level translator (Q2), as discussed previously. Note that, during this time, IC4b is held reset by the high on the out- put [pin 2) of IC3a, while IC4a is held reset by Q5 which is on. Thus, the divide-by-5 and divide-by-2 counters are disabled. Q6 is also on and disables IC3c which controls the signal routing for the 1GHz input. If F2 (10MHz) is now pressed, Q7 and QB turn off and Q9 and QlO turn on. This turns on LED 5 and LED 3 [via D5) which are the mode and kHz indicators respectively. Q4 is again turned off, this time via DB, and so IC3d again gates through the signal from IC2a to the base of QZ. If F3 (100MHz) is pressed, Ql 1 and Q12 are turned on and light LED 6 and LED 3 (via D6). Q12 also turns off Q5 which releases the reset on IC4a and thus enables the divide-by-5 counter. At the same time, pin 2 of IC3a goes low and enables IC4b. As a result, signals from the 100MHz preamp are now gated via IC3b and pass through the divide-by-5 and divide-by-2 stages before being fed to the ECL-CMOS translator. Finally, when F4 (1GHz) is pressed, LED 7 and LED 3 light and Q6 is turned off by Q14. Q5 is on and so IC4a will now be disabled. The divide-by-2 counter [IC4b) , however, will still be enabled by the low on pin 2 of IC3a. Thus, when F4 is selected, signals from the 1GHz divide-by-64 prescaler are gated by IC3c and fed to the divide-by-2 counter [IC4b). That's all we have space for this month. When we resume next month, we'll describe the counter circuitry and the latching circuitry for the pushbutton switches. In addition, we'll give you all the construction details. N OVEMBER 1987 43 ~,, " 'AT' COMPUTER! At lastl-The perfect opportunity for the hobbyist to build the perfect computer••• Perfect because it has in it what YOU want! Ali the features of the "AT" - blinding speed, high expandability, and so on - but you put it together yourself - and $ave! There's more: each board or module comes with a full 12 month warranty PLUS individual, professionally prepared manuals - no Jinglish to decipher! And-best of all, you don't have to buy it in one hit: add what you want, when you want it (and when the pocket allows itl) Look at the features: SUPERB QUALITY HINGED CASE "Baby AT' case in heavy gauge steel, heavily covered in damage-resistant bone crinkle finish. The lid is hinged and locks up for instant Internal access - no more undoing screws! - - - - - ~ • Large enough for expansion - but features a footprint of just 430mm square! cat x - 1oos •- - - - ONLY $175 200W POWER SUPPLY Completely pre-assembled - even to the on/off switch and input sockets! Simply slots into place in cutouts provided in case. Heavily plated steel case for minimum RFI with integral whisper-quiet fan. 200W capacity is ready for . . . anything! cat x-1010 ONLY $275 "BABY AT' MOTHERBOARD Again, completely pre-assembled . No risk of dry joints you just connect appropriate cables (as described in detailed manual included), On-board capacity for 1Mb RAM and 8 slots for expansion in true"AT" format. Offers 6, 8, 10 & 12MHz speed (switch & software selectable) giving outstanding software compatability PLUS blinding speed when you need it, and time & date memory with battery back-up. cat x-1000 JUST $995 PLUG-IN CARDS Cards for the various graphic standards, printer ports, serial port etc etc. Choose the one that suits your requirements and remember, you can always upgrade later! CGA plus Parallel Printer Card Cat X-2010 $129 MGA plus Parallel Printer Card Cat X-8141 $149 EGA Card with Hercules compatability Cat X-2013 $399 Serial/Parallel/Game Card Cat X-2012 $139 DISK CONTROLLERS Your choice of hard/floppy or floppy disk controller card: choose the one that suits your needs best. Both plug in to motherboard. Floppy Controller (2 disk drives 1.2Mb or 360Kb) Cat X-2014 $129 Hard/Floppy Controller (2 of each) Cat X-2008 $399 DISK DRIVES Also include appropriate cables. 1.2Mb Floppy Disk Drive Cat X-2200 $269 20Mb Hard Disk Drive Cat X-2203 $795 (Other higher capacity Hard Disks available if required) KEYBOARDS Two types available: 84 Keys with top quality "Alps" keyswitches Cat X-3820 $129.00 101 Keys - with numeric keypad Cat X-3821 $149.00 WHERE ELSE BUT DICK~SMITH ELECTRONICS PTY LTD OSEB450/RT1087 Build (or give!) a Kit this Kitmas ... Kits make great gifts: beats a pair of sox anytime! Dick Smith's own Fun Way_ Into Electronics Here's great value: the Fun Way One gift box. All the components needed to build any of the projects in Fun Way One . .. and the book Is Included loo! All 7 "" '°' '"'" Pmi~" $25! "'" ,_,.,, . ,o b,lld 1,d,do, ~ Dog & Cat Communicator /. ' --. ,. ., Beer Powered Radio • · •· Morse Code.Practice Set Crystal Sets Mini Amplifiers And much, much more And the really big one ... Get the Jumbo Gift Box! Over thirty great projects to build from all three Fun Way books. And the books are included! Over $120 worth of goodies crammed into this value-packed box. Any kid from 6 to 60 would think It was Christmas. (Now that sounds like a good Idea!). Cat K-2690 Or the Deluxe Job The ultimate in protection! One of the best alarms around - better than most commercial units. Includes Its own siren output ( doesn't rely on car horn), has provision for back-up battery ... and it's about the best investment you could make for your car. Cat K-3252 $9995 $2450 How do you test a Add an Ignition Zener? Killer for 100% Fun Way One Protection Project Packs Two project packs to allow you to build any of the kits. Project Pack One allows you to build any of the first ten kits in Fun Way One. Project Pack Two gives you the additional components required to build any of the 20 kits (needs Pack one too!) Note Fun Way One book is NOT included with these kits. Fun Way One: Project Pack One Cat K-2600 $895 Let's see. Out with the power supply. Work out the series resistor. Get the voltmeter and put it across the zener. Turn on the supply. Woops! Wrong resistor. One cooked Zener . .. Or you can build the Zener Diode Tester. Very simply and accurately checks Zeners __..__without danger. Expeciaily handy in the service lab when the markings are worn off! Cat K-3051 Nothlng's worse than a car that misbehaves. Especially if you're trying to knock it off. Imagine. It starts, but very soon splutters and stops. Bill Sykes thinks the car's crook and goes off searching for another! You return to your car, reset the ignition killer - and drive away! Cat K-325.,:5---~::=::--~~ s2295 <at>) ~lii[l"iJ (MJJ·~ Fun Way One: Project Pack Two Cat K-2610 Fun Way TWO Ready for something more advanced? Fun Way Two has another twenty projects to build - all on modern printed circuit boards. And we even teach you how to solder! Fun Way Two Bonus Pack indudes the Fun Way Two book, a quality soldering Iron, a pack of solder, a nine volt battery, AND the most popular kit In Fun Way Two: the Wireless Microphone. 5 Cat K-2620 Look Mum. No Bike! Bikes (the vroom vroom variety) are, unfortunately, very vulnerable. Don't become the victim of a very vulnerable vroom vroom . Flt a bike alarm to your bike and It'll scream its head off if some light fingered larrlkln tries to lift it. Easy to build, easy to flt - suits most bikes. Cat K-3249 $3995 $269 And one for the Car, Too! ~~~pr!~ !t~!!!ay Three kits and you'll be ready to tackle most projects. The Fun Wa't/ Three Bonus Pack Includes . ~-~-=-.,~ ~=-. the Fun Way Three book and not ~ ,- - ---. one, but TWO popular Fun Way •"~, · Three kits: the Cricket and the ;,: _ Mini Amplifier. Great value! ~ ~ s2995 Hi It One, Two and Three Gift Box ~ Police statistics are staggering: and.your car could be next. Build this simple alarm and the odds are back on your side. It's very easy to make, operates on "voltage drop" principle so no holes are needed for key switches, etc. It worksl Cat K-3250 $1695 Wanta GREAT AMPLIFIER? Build yourself a MOSFET AMP. It's great! And our value-packed kit makes It even greater! 42 watts per channel into 8 ohms - with professional specs and features. Comprehensive step-by-step manual included to make it easy on you . Compare it to commercial amplifiers at three and four times the -~;;;;;;;;;;;;i;;;;;r~?priice! Cat K-3515 70cm YAGI KIT Build your own Yagi for UHF. This 13 element design is simple to construct (all the hard work is done for you!) Strictly while stocks last. Cat K-6305 Cat K-2670 If they're really into electronics, they'll LOVE the gift box. It has kits to build from all three Fun Way books: nearly one hundred dollars value for only $59.95! Build a flashing brooch, a wireless microphone, cricket, mini amplifier and more. Cat K-2680 s5995 DICKeSMITH ELECTRONICS PTY LTD ORDER BY PHONE: TOLL FREE DSXpress ON (008) 22 6610 For 24 hour despatch 70cm Phasing Harness q Want to stack a couple of Yagis for more gain? Use this ready-made Phasing Harness. At UHF every uB (microBel - as distinct from dB) is a help - so help yourself! Cat K-6299 $1 095 ~ While stocks last! With friends like that "With friends like that, who needs enemies?" So goes the popular saying, implying that someone one trusted as a friend has not come up to scratch in a crisis or, worse, has deliberately betrayed that friendship, usually for his own personal gain. Cynical though the expression may be, there seems to be a lot of it going around. These thoughts were prompted by a recent experience involving a customer and a video recorder. He was one of my regular customers and the recorder was a model AV14 manufactured by Mitsubishi and marketed by AWA. This is a relatively recent model which first appeared about three years ago, and one with which I am reasonably familiar. So when the customer opened the conversation with the innocent remark, "Will you have a look at this recorder for me?", I expected some fairly routine electrical or mechanical fault. "Sure", I replied, "What seems to be the problem?" Then he dropped the bombshell: "It's been dropped". That rocked me somewhat. Of all the things one should not do to a video recorder, dropping it would be at the top of the list. Of course there is dropping and dropping how far had it fallen, on what had it landed, and at what angle? These were questions I wanted to ask, if only to help me assess the likely damage and chances of repair. But the sheepish look on the customer's face when he made the announcement suggested that such questions might not be diplomatic, at least at this stage. Picking up the machine, I turned it over and gave it a casual inspection for obvious signs of damage. At first I found nothing, then a closer look revealed a slight flattening of the metal top cover in the rear left hand corner, amounting to only a few millimetres. Well, at least I 46 SILICON CHIP could visualise the angle at which it had landed. And with only that much damage externally, maybe the situation wasn't so bad. But when I looked through the front loading opening it was a different story. The cassette carrier was at a nasty angle relative to the opening, with the left hand side several millimetres higher than it should have been. That set my imagination racing; I could visualise the main frame being twisted or, more likely, fractured, in which case the machine would be a writeoff. I passed these thoughts on to the customer, and suggested that he leave it with me until I had time to open it up and take a more detailed look. And if the damage wasn't as drastic as I feared, I could probably give him some idea of what it would cost to fix. And so we left it at that. A closer look A few days later, when things were a bit slack, I pulled the top cover off the machine and took a closer look. The mechanical deck is well covered by the main printed Special Notice These notes are being contributed by the author who, from 1950 until July of this year, wrote "The Serviceman" in another magazine. We feel sure that regular readers of that series will welcome the opportunity to continue following his electronic adventures in Silicon Chip. circuit board, which would have to be lifted before I could examine the main frame. However, I was agreeably surprised to find that the board itself did not appear to have suffered in any way. I later confirmed that there were no cracks of any kind. Moving the board clear is a somewhat fiddly job in this model. As well as removing the screws holding the board itself it is necessary to remove the front panel and undo a number of screws which hold the operating controls. These are attached to the main board by flexible leads and some care is needed to ensure that these are not damaged as the board is folded back. In fact, this part of the exercise was completed without incident, and I was then able to get a good look at the main frame. Strangely enough, the real problem was not immediately obvious. As far as I could see, the frame was neither bent nor cracked and, possibly due to some kind of optical illusion, it took me a few seconds to work out how it was that the cassette carrier was crooked, even though neither it nor the main frame seemed to be damaged. A frame-up But suddenly all became clear. The main frame was sitting at an angle, relative to the case, and this was why the cassette carrier did not line up with the front opening. And closer examination revealed just why the frame was at this odd angle. The frame is of cast aluminium and is supported in the case by four round pins, or spigots, about 5mm in diameter, which are part of the casting. They are fitted with rubber bushes which, in turn, fit into recesses moulded into the plastic case. And this was where the (Z) UPPER & LOWER DRUM <at> S.GUIDE ROLLER T.U. GUIDE ROLLER<at> AJC HEAD<at> T.U. GUIDE POLE<at> PINCH ROLLER <at> ©TENSION POLE <at>CAPSTAN SHAFT This schematic diagram of a VCR deck layout should help readers envisage the components affected by the unfortunate sequence of events involving the customer's "mate". damage had occurred. The spigot near the front left hand corner of the frame had broken off, together with a small piece of the frame, about half the size of a little finger joint. But that was not all; it had wedged itself under the frame in such a way as to lift the left hand corner of the deck, thus creating the odd angle. Such are the weird things that happen when the irresistable force meets the immovable object. It wasn't much of a job to retrieve the piece of broken casting, whereupon the frame moved back into place and, in spite of the missing support, sat reasonably firm. So normal did everything appear, in fact, that I decided to try loading a cassette. And if it loaded, perhaps it would even play. So I applied power and, when there was no smoke or other signs of distress, pushed a cassette into the carrier. The carrier accepted it and deposited it on deck in the usual way. Well, so far so good and, thus encouraged, I pressed the play button. For a moment I thought this function was going to work also, but I was disappointed. The two guide rollers - (5) and (9) in the accom- panying diagram - which normally pick up the tape and wrap it around the drum, moved only a short distance, then jammed. Finding this fault took a little Ihore time and proved even stranger than what had happened so far. I withdrew the cassette and examined the deck in greater detail. To understand what I found it will be necessary to refer to ·the accompanying diagram and in particular to the tension pole (1) on the extreme left hand side. This pole, as its name implies, is used to tension the tape on the supply side of the drum after the two guide rollers have wrapped it around the drum. It is mounted on a small plate, pivotted on a pin and held in place with a circlip, and which has a short rod extending downwards through the deck. This rod is engaged by a lever which exerts the required tension on the tape via the tension pole. This mechanism sits in close proximity to the curved cut-out in the deck through which the guide rollers, and particularly the supply side guide roller (5) moves during the tape wrapping process. And, by some queer quirk of the forces generated by the fall, the short downward projecting pin on the plate had been forced out of its own opening and into the guide roller slot, effectively jamming the guide roller. And while the fact that this had happened at all was puzzling, the real surprise was yet to come. I couldn't believe that this displacement had taken place without some degree of distortion to some of the parts involved, particularly the tension pole plate. I removed the circlip, pulled the plate out, and examined it carefully. It did not appear to be bent or to have suffered any other form of damage. I replaced it in its correct position, refitted the circlip, then tried the cassette again. And this time it worked; the carrier accepted the cassette, deposited it on the deck and, when I pressed the play button, the two guide rollers picked up the tape, wrapped it around the drum, and set it in motion. I had connected the machine to a TV set and was gratified to see a picture come up on the screen. Granted, there was evidence of tracking error - not surprising NOVEMRER 1987 47 considering what it had been through - but I felt confident that this would respond to routine adjustment. So much for complacency All of which was very encouraging and I felt that I could now regard the machine as repairable and even make a fair estimate as to what it would cost. So much for my complacency. The setup had been running for only a few minutes when the picture suddenly went very snowy, and I had visions of all kinds of nasty faults involving hairline cracks in the main board and the time that might be necessary to track them down. Fortunately, I made a few simple tests first. I stopped the tape, switched the TV set to an off-air channel, and was rewarded with a snowy picture in that mode also. Further investigation showed that the condition could be created or cured by simply wriggling the plug in the "RF OUT" socket on the recorder. Well, that meant a repair job in that section, but I didn't anticipate that it would be all that difficult. So it was time to contact the owner, explain the situation, indicate the likely cost of repair, and see what he wanted to do about it. I rang his home number and the phone was answered by his wife. When I explained who I was and that I was calling about the video recorder the reply was a rather flat and slightly aggressive "Oh that". It didn't need Sherlock Holmes to deduce that there was some lack of domestic agreement in the matter of the video recorder. Naturally, I wasn't keen to become the meat in any sandwich but, on the other hand, I needed someone to make a decision. But before I could say any more, the lady launched into the story about the recorder. "People seem to take my husband for a soft touch. He bought this recorder in a pub for a hundred dollars, from one of his mates". She went on to explain that this mate had been involved in a marital breakup and was short of ready cash. So he had offered my customer "this beaut video recorder for a hundred dollars". Of course, he had conveniently forgotten to mention anything about the recorder's unfortunate encounter with a hard floor, and so the deal was struck, my customer believing that he had acquired a real bargain. It was only when he brought the machine home and tried to use it that he found it wouldn't even accept a cassette. Exactly how he eventually learned what had happened to the machine was not revealed. Perhaps he tackled his mate; perhaps he heard it from somebody else. But one thing is certain: with friends like that, who needs enemies? So much for history So much then for the history. What about the present? I explained to the lady that her husband may not have done so badly after all. I felt sure that the recorder could be repaired, with a possible outlay between $150 and $200, with the latter figure as a firm upper limit. This meant that they would get a recorder for between $250 and $300 a bargain by any standards. As a bonus, there was the fact n{E. \I\DE.O \-\At> 'e.£.E.N INVOLVEO IN ~ W\A~\TA\.. StlE~\<. U~...... . 48 SILICON CHIP that the machine was a current model and, based on my examination of it, one that had had very little use. In that sense it was almost brand new. Apparently I was a better salesman than I realised because, by the time I finished, the lady gave me the go-ahead to fix the machine, without waiting to discuss it with her husband. (Curse my fatal charm). But now I had to deliver the goods. The most important job was to somehow refit the spigot to ensure that the deck would remain stable. Fortunately, the nature of the break made this easier than it might otherwise have been. First, there was the fact that the spigot had not broken off cleanly but had taken a piece of the main frame with it. And second, the angle of the break was such that such stress as it would normally encounter would, if anything, tend to press the two pieces of metal together, rather than the reverse. There was also the fact that, dropping aside, there is not a great --- deal of stress on these spigots; they merely support the weight of the deck. Taking all these factors into account, the repair I envisaged was somewhat unorthodox but, I felt, quite practical. It was based on an epoxy mixture called •'PlastiBond"; a product which, if mixed correctly, cures to a rock hard finish. So I mixed up a batch, coated the two mating surfaces to provide an adhesive function, pressed them together, then built up a thick coating around the joint, taking advantage of as many irregular contours of the frame as possible to provide the best possible grip. The result was a substantial block of epoxy around the joint which should withstand any reasonable stress it is likely to encounter. The next thing to be tackled was the fault involving the "RF OUT" socket. This socket is mounted on a metal box which contains the splitter amplifier and getting at this is quite a job. It is closely linked to the tuner as well as the main board and a lot of leads have to be undone, many needing the solder sucker, before the box can be withdrawn far enough to work on it Then the soldering iron is needed to open the box because the lid is soldered on. I eventually gained access to the inside of the box and the rear of the socket. The pin from the socket protrudes through a hole in a printed circuit board and is soldered to a narrow copper pattern surrounding the hole. The hole is rather larger than the pin, the solder forming a bridge across the gap. This arrangement doesn't impress me very much because even normal plugging and unplugging likely to be encountered in typical use must tend to move the pin slightly, putting a stress on the soldered joint and copper pattern. In this case there had been an abnormal stress on it because the body of the socket was bent several degrees relative to its mounting lugs, and the copper pattern had been pulled away from the board and broken, although making intermittent contact. I removed the socket, straightened it, then refitted it. I ran some solder around the pin in an effort to forming beautifully and had been given "a bit of a flogging". I also gained the impression that any initial reservations on the part of his good lady, concerning his "bargain", had long since been dispelled. So I not only saved a recorder; I might have saved a marriage as well! A fallen General .. suppos~D TO RUN AT l'SV, ~u-r WACS, IN FAC.-f, C LO~E:.~ iO 100V-,,, - ,., fill up the hole in the board and provide mechanical rigidity, then replaced the missing copper pattern with a short length of fine wire. I reasoned that if there was any movement by the pin, the wire should be flexible enough to cope with it. Looking at the damage to the socket etc, I evolved a theory as to how it had come about. I suspect that the lead from the "RF OUT" socket to the TV set was rather short and, when the recorder fell, this lead took most of the weight, even if it wasn't short enough to prevent one corner of the machine hitting the floor. We'll never know for sure, of course, but something had certainly put a lot of stress on that socket. And it had also contributed a lot to the cost of the repair, due to the difficulty of getting at the fault. Only the tracking now remained to be adjusted and this was a fairly routine job. When it was finished, the recorder turned in a first class performance and I had no qualms about have advised the owner to let me go ahead with it. The final bill came out about midway between the figure I had quoted and the owner paid up quite happily. All that was several weeks ago, but the owner was in the shop a few days ago on another matter and confirmed that the recorder is per- My next story is on a quite different theme although some aspects of it are just as puzzling. It concerns a General GC-181 48cm colour TV set, one of several belonging to a local motel and used in the guests' apartments. And the initial description from the owner was simple enough; no picture and no sound. This description was confirmed when I finally switched the set on in the workshop; there was no sound - and neither was there any picture for the very good reason that we had a classic case of frame collapse. Initially, I couldn't decide whether this was likely to be two separate faults, or whether there was a common factor, such as a supply rail, which could be responsible for both. But before trying to track the faµlts on a logical basis I decided to give the set a routine check, dictated by long experience. This set consists of a chassis and main board mounted horizontally in the bottom of the cabinet, plus several auxiliary boards mounted vertically on the main boards by means of plugs and sockets. Among these are the IF Board, Vertical/Power Board, Audio/Horizontal Board etc, plus a Neck Board on the tube. Most of the plugs and sockets are 6-pin types, some boards using two or more such devices to provide the necessary connections. The setup is a very convenient one for servicing, but has not been without problems of its own. The plugs, or male connectors, are mounted on the main board and the sockets on the auxiliary boards, and connections between these are prone to failure. It is the plugs on the main board which are the main offenders. The pins pass through the board and are soldered to the copper pattern on the underside, and it is here that NOVEMBER 1987 49 faulty joints are frequently encountered. As a result, I have long since made it a practice to tackle these joints as a matter of routine whenever I encounter one of these sets, regardless of the fault. And it is surprising how often nothing more is needed to fix the fault. This procedure is further encouraged by the fact that the underside of the main board is fairly easy to get at. Undoing three screws will release the main chassis and allow it to be pulled back far enough in the cabinet to reveal most of the main board underside. And, being a relatively small set, it is easy to tip the cabinet on its side to make it easy to work on. Having done this, and prompted by the frame collapse, I naturally looked first to the two plugs which feed the vertical board. And there it was; around one of the pins (pin 12 of P403) was a tiny patch of what looked like green corrosion. The green lacquer on these boards made it difficult for me to be certain until I checked with a jeweller's loupe, but then there was no doubt. But there was something strange about the condition. For one thing, it appeared to be quite small and confined to this one spot. And even stranger, the corrosion was quite wet. Now I have encountered dry joints, fractured joints, and many kinds of faulty joints, but this is the first time that I have found a wet joint. But there it was, and I can offer no logical explanation for it. I checked carefully for evidence of spillage of any kind around the cabinet or anywhere inside the set, but there was not the slightest sign. So I set to repair the damage. Having cleared away the corrosion I soldered a short length of tinned copper wire to the pin and then soldered this to the copper pattern some little distance away, where it should bypass any long term corrosive effects on the copper track. Then I switched on the set and tried again. Still no sound It came good, at least in that I had a picture. But there was still no sound. So it appeared that there were two separate faults. I pulled 50 SILICON CHIP ., I.I NOW, l HA\IE- ~coo~ t> l)~'( JOl~S I F~C.'t'VREt> jO\~S, ~N~ N\"N'< ~\~\>S Of' l=AU'-'1"< '3'01NTS, &UT nus \S 1\-\E. F\RST ilN\E THAT I H~VE t=OUNO A WET 'J'O\NT,o~)C>)<:;, out the audio/horizontal board, which, as its name implies, carries the audio output stage and horizontal oscillator stage, and reconnected it via extension leads, of which I have several for this set. Then I reached for the voltmeter for a routine check. I didn't get far. The supply rail for the audio stages is supposed to run at 15V but was, in fact, closer to lO0V. Just where this was coming from I had no idea initially, but I didn't like the chances that the three transistors involved - the two output transistors and the driver had survived the situation. It was the physical location of the audio board that gave me the clue. It sits alongside the vertical board which had suffered the faulty plug connection. More importantly, this plug is directly alongside the plug for the audio board, and pin 12 of the latter which carries the 15V supply is alongside pin 12 for the vertical board, which sits at around 106V. What's more, the two copper tracks run side by side for some distance. And that's where the trouble was. What ever the moisture was that had corroded the joint had also apparently penetrated the board and created a path between the two tracks. It is not the first time I have encountered such leakage problems and I have developed a treatment which has proved very effective in the past. The idea is to dig a trough between the two tracks. I use a very small drill, driven by a variable speed power drill, and used as a simple router. It requires a little skill but is not all that difficult if one takes one's time. I took about 15 minutes to do this job but, at the end of that time, all signs of the spurious voltage had vanished. I finished it off with a spray of CRC Clear Urethane Seal Coat, 02049, which is available in an aerosol pack. Then I turned my attention to the audio board and the transistors. As it turned out, only the two output transistors, TR952 and 953, had been damaged and, interestingly enough, one of them had gone open circuit. This was fortunate because, otherwise, the spurious voltage would not have been so immediately apparent. Y'gotta win sometimes! Anyway, that was it. Two new transistors put the sound section back into action and, after a routine check-up, the set was returned to its owner. But I'm still puzzled about the corrosion and what caused it. And why was it so isolated? We'll never know We'll never know I suppose, but here is one other interesting point. My regular readers will recall that several years ago - September 1983 to be exact - I told a story about a set from a motel, a Precedent GC-181 (no relative of the General GC-181), in which severe corrosion was the major problem. In that case, the corrosion was almost certainly caused by the previous proprietor attempting to repair some soldered joints using spirits of salts as a flux. Well, this latest case came from the same motel. Was this another legacy from our heavy-handed plumber-cum-serviceman, but one which had lain dormant for all these years? I agree that the time factor is against this theory, unless the degree of pollution was extremely slight, and it took all these years and perhaps some excessive humidity to provide the final straw. So what do you think? ic BOOKSHELF Be the boss of DOS MS-DOS BIBLE, by Steven Simrin. Published 1985 by Howard W. Sams, Inc Indianapolis, Indiana. Soft covers, 190 x 248mm, 385 pages. ISBN O 672 22408 9. Price $39.95. Anyone who buys an IBM PC or PC-compatible immediately comes up against the mysteries of DOS which stands for Disc Operating System. IBM PCs use PC-DOS while compatibles use MS-DOS but both are virtually identical since they were created by the same company, Microsoft. Some DOS manuals are positively labyrinthine in their approach while others are quite good. Ultimately, the hard road of experience is the only way to become proficient at using DOS commands but you can be helped along considerably by a well-written book on the subject. And even if you are quite proficient at using DOS and may be using it for quite advanced programming, a reference book on DOS can still be very useful. Such a book is the MS-DOS Bible, written by Steven Simrin. The MS-DOS Bible assumes no prior knowledge on the part of the reader. The only assumption it makes is that you have just purchased or have otherwise gained access to a PC and want to know how to turn it on. Most people buying a PC will also have a specific purpose for which they have purchased software and therefore their initial involvement with DOS will be as minimal as possible. As time goes on though, you need DOS more and more if you are to fully utilise the power of your computer. At Silicon Chip we found ourselves in just this situation when we began setting up our computers to cope with the task of preparing and editing copy, and transmitting it via modem to the typesetters. We found MS-DOS Bible quite helpful as we created batch files, disc directories, installed hard disc drives and otherwise readied the systems for work. There are twelve chapters in all, plus a number of appendices. Some of the chapter headings are as follows: MS-DOS Files, Directories, Paths and Trees, Installing a Fixed Disc, MS-DOS Batch Files, Redirection, Filters and Pipes, EDLIN, the MS-DOS Text Editor and Structure of MS-DOS. As with MS-DOS itself, you only need to use as much of the book as is required for the task of the moment. It makes a very good reference. Highly recommended. Our sample copy came from Jaycar Electronics. Now we have just come across an ideal book to teach yourself about logic circuits. Entitled "Understanding Digital Logic Circuits" by Robert G. Middleton, it is written specifically for service technicians. They are now having to repair some of the more exotic equipment such as radio scanners, two-way radios, pushbutton TV tuners, VCRs and so on, all of which contain more and more logic circuitry. While the book is written with technicians specifically in mind, anyone who has a smattering of electronics will find it easy to follow. It starts off with two chapters on gates which are really worthwhile. If you fully absorb all that is in those two chapters, including the material on negated (or reverse) logic, you will be well up on the subject. We won't bother to give a full description of the 19 chapters but Logic made clear Understanding Digital Logic Circuits, by Robert G. Middleton. Published 1982 by Howard W. Sams Inc, Indianapolis, Indiana. Soft covers, 136 x 215mm, 392 pages, copiously illustrated with diagrams. ISBN O 672 21867 4. Price $34.95. For people who have grown up with the analog side of electronic circuitry, the transition to digital logic can be difficult. There is such a large range of new devices to learn about and the different logic families are not compatible. There is one consolation that we can offer to anyone who is presently making that transition: when you finally do become familiar with logic circuitry, there is less to it than meets the eye. Certainly, it is not as complex as the great range of analog circuitry. suffice to say that the subject of logic circuitry is very well covered with a practical approach throughout. There are chapters on Adders, Flipflops, Registers, Counters, Encoders and Decoders, Parity Generators and Checkers, Multiplexers and Demultiplexers, Memories, Digital Voltmeters and Transmission Lines. We can highly recommend this text. It is one of the best we have come across and is available from Jaycar Electronics. 4b NOVEMBER 1987 51 Great Test Gear At Bargain Prices I Integrated Amplifier Kit Featum: A frequency counter is invaluable for the accurate alignment and testing of many modern electronic circuits. • 10Hz - 30 MHz • 10MHz - 150MHz • Power" requirement 'Sixty-Sixty' (EA May,June,July 'II) 150MHz Frequency Counter SPECIFICATIONS:Frequency Range Gate Tim• Accuracy Max. Input Sen•HIYlty:- EA's Greatest Amp Project In 10 Years 10Hz - 150MHz 1 .sec, 6 sec. +/- 1 count 20V P-P 25mV- 100mV 100mV - 300mV 9V DC at 100mA • 60 watt, per channel Into Bohm loads• Very low nolee on all lnputa - better than CD performance • Very low distortion • Excellent headroom • Tape monitor loop• Tone controls with centre detent and defaat switch• Monolatereo switch• Toroidal power tran,former • Eaay-to-bulld construction • Very little wiring. Performance Specification Power Output-a ohm182W Dlatortlon-Leeathan .0'11,at 1kHz. , , . . _ , ........... Phono lnputa - RIM/IEC equallatlon within + - 0.5db from 40Hz to 20kHz Line i.-11nputa - -0.5db at 20Hz and -1db at 20kHz Phono 1kHz ◄.3mV • Line Level - 'nOmV. HUIII 6 Nolee- Phono - 18db • High i.-flnput1-103db. T - Control - . . . - + -12db at 50Hz Trellle- +-12db at 10kHz. Denllllnl laclof • At 1kHz and 30Hz - greater than BO ltallllllJ - Unconditional. . . Input......,,_ Q 1520 ........... $199.oo Use Our 9V Plug Pack M 9004 Audio Frequency Generator Often in testin9 audio circuitry it is necessary to have an accurate and adjustable audio signal source available . This little generator even allows you to test 455KHz IF.stages! .SPECIFICATIONS:Frequency Range Accuracy Output. Waveform, Output Level Output Attenuator 10Hz - 1MHz +/- 3% + 2Hz Sine/Square Sine : 8V RMS Square: 10V P-P 0,-20 db,-40 db and fine adjust. a 1540 ...... . .... $249.oo RF Signal Generator An RF signal generator is an absolute must when it comes.to radio servicing. With provision for both internal and external modulation this .generator is a winner. - -· . , . '•l ., ,~ __...., SPECIFICATIONS:Frequency Range 100KHz - 150MHz . ~ ·a - ED ~ ·• ! - RF Output L•••I Accuracy In 6 Ranges 100mV RMS +/-3% Modulation:' • Internal (30% Depth) 1KHz • External 50Hz - 20KHz • Crystal Locked Oscillator I • a 1550 .... . ...... K5060 performence commerclel unit,. "Thi• New Ampllffer offen a 1frindard of perlormence far aheed of anything we har,e p,.r,loualy pub/11/led and ahffd of moat commerc/al lnteg,.ted Stereo Amp/If/en". "It 11 half to on• third of t1- coat of an Imported Amplifier with equlnlent power output and performance". Says Leo Simpson Managing Editor Electronics Australia Magazine. The reproduct ive purity of these speake·rs simply amazed us. The secret. of course is the DANISH VIF'I .Drivers. VIFA drivers are used in many top selling imported systems such as Bang & Jlufsen. Rogers. Mission , Jamo, DCM Timewindow etc. Build These Fantastic New Playmaster HiFi Loudspeakers See Etectronica Auotralle Sept 'H $199.oo h .._., Function for Relative Me•uremenll a 101s Only $99.95 Free Select either a carry Case or Holster this Month with your a 1075 at no charge Specifications DC Voltage: Rangn 5(200mV, 2V, 20V, 200V, 1000V) DCV Accurancy 0.5%+ 1 DGT AC Voltaa•: Rangn 4 (2V, 20V, 200V ,. 750V) AC'/ Accuracy 0.75% + 5 DGTS Input Impedance 10M Ohm Min. DC Current: Accuracy 20mA-0.75% + 1 DGT 10A-1 .50% + 5DGTS 01077 $9.so Carry Case Keep v.our ubtach DMM looking like new for yearal $9.so $449 full kit K 5090 If your budget won't run to the $600 to $800 needed for a fully Imported pelr of equlvelent epeakers, these are the onea to go for. t Auto Ranging Dlgltal Multlmeter What's this? For want of a better name we've named this thick rubber "cliparound" protector a "Holster" Great protector for field use, dropping on concrete floors etc. $299 Beginner Constructors Can Build this Amplifier Kit - It looks terrific and will .last you a lifetime. Seve $200 or More on comparable Exhilarating Sound Performance Brilliant Dlgltal Headphones Incredibly Comfortable • Utilizes newly developed flat disk vibrator copper clad aluminium wire voice coil and Somarlum cobalt Magnet. The resultant reporduction is outstanding. • Impedance 45 Ohms. • Maximum input 400 mW • Frequency Response 20Hz to 20KHz. .. . $39.so Own An lnphone And Your Neighbours Will Be Green With Envy Here's Why f J No . Installation Costs SimplJ Plugs Into Your Phone Socket • lnphone Is Great Around The Factory or Building Site Its Completely Mobile The Go Anywhere Cordless In phone is not tied to the wall with wires - you simply take it where you want. Never again need you spend half the night crouched around the kitchen bench or draughty hallway with those long winded calls. • Use It By The Fireside rn Your Favourite Chair • Super Handy When Sunbaklng By The Pool IN PHONE is quite simply the finest cordless phone available . No other cordless phone has the quality, security and the features at any where near an · affordable price of INPHONE. AT HOME you can keep in touch around the swimming pool. (Please note the equipment is not waterproof) . In the ·garden . Under the car. While watching T.V. In the bathroom. In Bed . Or next door when you're playing cards or having a Barbecue with your Microphone neighbours. - IN BUSINESS a busy executive can take the INPHONE around the factory, warehouse, showroom, sales yard or construction site or into the car park, and not miss a deal! Also INPHONE is ideal for use in restau rants. IN SPORT on the field or track, the gym, around the swimming pool , Lifesavers on the beach etc. Comprehenalve 6 month• Warranty Brilliant Performer -" PHOO l~RO.nl FANTASTIC CHRISTMAS PRESENT Normally Great Value At $269 Exclusive Offer To Readers Of Silicon Chip Magazine This Month $199 - But You Must Mention This Advert When Ordering We Regret This Special Offer May Not Be Available From Altronics.Dealers 199 5 CAR STEREO IN YOUR HOME Here's how to adapt a surplus car radio-cassette player for use in your home. By GREG SWAIN "Those old valve sets sure had a pretty good sound - much better than you get from transistor radios". When was the last time you heard that sort of statement? But don't dismiss it as mere nostalgia. Those old valve sets really did have the edge over the familiar "tranny", at least in terms of sound quality. The reasons are not hard to find. Compared to modern transistor radios, those old valve sets boasted greater power output, better bandwidth (ie, they reproduced a wider range of audio Jrequencies), better AGC, and lower overall noise levels. They also usually had a decent loudspeaker to reproduce the sound. Take a look in the back of one of those old valve radios and you'll in54 SILICON CHIP variably notice a big loudspeaker, cften 15 or 20cm in diameter (6 or 8-inches in the old terminology). What's more, because the chassis was quite large, the cabinet was also quite substantial and could provide a fair amount of baffling for the speaker. The signal-handling capabilities of valve sets was better, too. They could comfortably handle very high input signals without overload or cross-modulation and had much better automatic gain control (AGC) circuits to cope with the wide range of signal strength variations. These days , bandwidths are much narrower, the baffling is woeful, and the miniature speakers used sound dreadful. Add to that the overload and distortion problems inherent in lower-power audio output stages and it's not hard to see why modern table radios don't measure up to the valve sets of yesteryear. The fact is, you can no longer buy a decent table-type radio. All you can get is ghetto-blaster style radio/cassette players which can be quite expensive, or cheaper clock/radios which can sound really crook. But there is an alternative: adapt a car radio to run off the 240V mains for in-home use. Car radio conversion This is such a ripper of an idea, you'll wonder why it hasn't been done before. As we'll show you in this article, converting a car radio to the mains is quick and easy to do. What's more, you can spend as much or as little as you like. What are the advantages of car radio conversion? First, car radios Choosing your radio D7 MEMORY POWER +l 240VAC 4700 e----.. + 13 4V ~_J ~ - - - - - - - - - ~ - 1 - 6 V _ W_ _ _ - - - - - E A R T H TO CASE OF RECEIVER CAR RADIO/CASSETTE POWER SUPPLY 011·1287 Fig. 1 .;~ I GND Fig.1 - the power supply circuit. The output of the transformer is rectified by diodes D1-D4 and fed to a 7812 3-terminal regulator IC. D5 and D6 jack up the GND terminal by 1.4V so that the supply delivers 13.4V to the radio. offer much better station-pulling power and sound quality than virtually any currently available domestic AM/FM radios, regardless of price. Because they are designed for mobile use, car radios have much better sensitivity and selectivity, and they generally have better bandwidth as well. Second, car radios have desirable extra features not usually found on domestic radios. Many have pushbutton station selection, which is a great convenience feature, while upmarket models feature synthesised tuning, digital frequency display and memory storage of favourite stations. They often also have an inbuilt cassette player, bass and treble controls, and a power output of several watts per channel or more. Finally, car radios are very rugged and are well shielded which reduces interference. A car radio can thus form the basis for a very good sound system. All you have to do is add a mains power supply, two loudspeakers and a suitable cabinet. The old adage that "you get what you pay for" holds true here. You can either take the low-cost way out with a no-frills $25 radio, or you can buy something with a cassette player and a few other fancy features. As a matter of interest, we took a quick flick through the Altronics and Dick Smith Electronics catalogs. Both offer a complete AM/FM-stereo radio-cassette player for $79.95, but you can also buy fully synthesised models with electronic tuning and AM stereo starting at around the $350 mark. Tandy Electronics also carries a wide range of models, with features and prices to suit every budget. Of particular interest is a new synthesised model that sells for just $250. They also have a $400 model with a "logic-controlled" cassette deck, Dolby B-C noise reduction and 15 watts per channel output. Of course, you don't have to buy. You may already have a surplus car radio stashed away in the garage or under the workbench. If so, then the price is right and it's the ideal candidate for conversion to mains power. If you don't already have a radio but want to save money, try a local auto wrecker. They often have car radios available for a few dollars but make sure that the model you choose is still in working order. A radio that's been pulled from a wreck may have been damaged in some way. We decided to go the whole hog and convert a Pioneer KE433AM AM/FM radio-cassette player with synthesised tuning, 18-sta tion memory, AM stereo, and 4 watts per channel power output. This is an excellent radio, although unfortunately no longer part of the Pioneer range. The power supply This view shows the assembled power supply PCB, prior to installation in the radio. Note that the four 1N5404 diodes used in the bridge rectifier are larger than the 1N4002 types (don't confuse these). The leads of the 3-terminal regulator are bent so that the device can be bolted to a heatsink which lies flat on the PCB. Take a look now at Fig.1. This shows the circuit of the power supply. As you can see, the circuitry is very simple. A transformer with a 15V secondary feeds a conventional bridge rectifier consisting of diodes D1-D4. The output of the bridge is then filtered by a 4700µF NOVEMBER1987 55 PARTS LIST 1 car radio (see text) 1 timber cabinet, see text 1 Altronics 21 56 1 5V 2A mains transformer 2 car radio speakers, Jaycar Cat.AS3014 or equivalent 1 printed circuit board, code sc011-1287, 109 x 54mm 1 3-pin mains plug and 3-core flex 1 2-way mains terminal block 1 solder lug 1 clamp for mains cord 1 3 .5mm banana plug 1 U-shaped aluminium heatsink, 27 x 25 x 34mm-high, Jaycar Cat.HH-8508 or equivalent Semiconductors 1 7812 12V 3-terminal regulator 4 1 N5404 3A diodes 3 1 N4002 1 A diodes Capacitors 1 4 700µF 25VW PC-mounting electrolytic 1 4 700µF 16VW PC-mounting electrolytic Miscellaneous Insulated hook-up wire, selftapping screws, wood screws, rubber feet for cabinet, grill coth for baffle. electrolytic capacitor to give a smoothed DC voltage of about 20V. Voltage regulation is provided by a 3-terminal 12V regulator (7812). In this case, however, the GND connection of the regulator is jacked up by about 1.4V by series connected diodes D5 and D6. As a result, the supply delivers a 13.4V output to the radio. The inclusion of D5 and D6 may be seen as " gilding the lily" somewhat. After all, the radio will work quite happily at 12V, so why bother? Our reasons are that the diodes are cheap (about 10c each) and the extra 1.4V improves the available power output from the inbuilt audio amplifiers of the car radio and also improves its RF (radio frequency) sensitivity. D5 and D6 also reduce the power dissipation in the 7812 by lowering the voltage between the IN and OUT terminals. A second 4700µF electrolytic capacitor filters the output from the 7812 and provides high short-term current capability when required. Diode D7 is included as a safety measure and protects the output of the 7812 against connection to external voltages (eg, charged capacitors). Strictly speaking, D7 is not required here as the supply will be permanently connected to the radio. We've included it for those readers who want to build the supply as a free-standing unit for use in other applications. It is necessary to fit a small heatsink to the 7812 regulator to obtain the required current rating. This is because the 7812 includes internal thermal overload protection. Our supply delivers about lA on a continuous basis and 1.5A on a shortterm basis, which should be enough for just about any car radio, even high-powered units. PCB assembly All the parts, except for the power transformer, are mounted on a small printed circuit board coded sc0l 1-1287 (110 x 55mm). Fig.2 shows the parts layout diagram. The parts can be mounted in any order but be sure to install the diodes the right way round. Note that 1N5404 diodes (rated at three amps) are specified in the bridge rectifier (D1-D4) because a high surge current rating is required (by virtue of the 4700µF 25VW capacitor). The two 4700µF capacitors must be oriented correctly. Note that the capacitor adjacent to the bridge rectifier diodes must be rated at 25VW. The other capacitor on the regulator output can have a minimum voltage rating of 16VW. Don't use a 16VW capacitor at the output of the bridge rectifier - its voltage rating will be inadequate. Finally, install the 3-terminal regulator by bending its leads at right angles so that they fit the 13.4 V TO RECBVER MAINS CORO POWER TRANSFORMER MAINS CORO CLAMP Fig. 2 ~ E A R T H TO RECEIVER CASE Fig.2 - here is the complete wiring diagram for the power supply. The active (brown) and neutral (blue) leads from the mains cord are connected to a 2-way terminal block, while the earth wire (green/yellow) is connected to a solder lug secured by one of the transformer mounting screws. A second solder lug is used to earth the case of the receiver. 56 SILICON CHIP There's plenty of room in the cabinet for the radio, two loudspeakers, and the power supply components. We used standard oval car speakers (available from Jaycar at $10.95 each, Cat. No. AS-3014). Note the long-wire antenna and the rightangle bracket at the rear of the radio. Take care with the mains wiring. p~~%~R !l SPEAKER EAR14 II QJ I LEFT SPEAKER POWER AMP R RIGHT sm~~-Ri-- - - - - i . . . J I \ I SPEAKER . RADIO 0 ~ - r - - - - O T O POWER POWER \ ANTENNA POWER9"_ _ _ _ +V • POWERO.__ ___,_ l INPUT MEMORY 0---------.0-M~QRY .--------v -!- (a) :oA~IEOROi---r----OTO POWER \ ANTENNA Rg. 3 • 1tii>~T MEMORYo------ME!~RY , - - - - - - - • -V -!- (b) Fig.3 - the output connections for typical car radios. In (a), the speaker outputs are single-ended. Bridging outputs, like those shown in (b), are often found on high-power radios. holes in the PCB. The regulator can then be bolted to the PCB with its heatsink, as shown in the photographs. The cabinet One of the best things about this project is that you can build your own cabinet. We made our cabinet from dressed radiata pine which is relatively cheap and much easier to work than particleboard. Rather than go for tricky mitre joints, we elected to use butt joints as these are much easier to make. Fig.5 shows the dimensions of our cabinet. Cut the timber to the dimensions shown, then bevel the edges using a plane or sanding block. The panels can then be sand- ed to a smooth finish, ready for assembly. The baffle (front panel) board is secured using cleats. These must be inset from the front edge according to the thickness of the baffle and are either glued or screwed in position. Once the cleats have been installed, the cabinet is ready for final assembly. It's up to you how you secure the various panels. We simply glued them in position using "Aquadhere" woodworking glue. Four large G-clamps were used to hold the cabinet together while the glue was drying. After that, the cabinet was given a coat of walnut stain (British Paints Walnut Stain) and three coats of "Feast Watson" satin silk timber finish. Incidentally, if you are using radiata pine for the cabinet, be very careful in handling the timber. Because it is soft, it is easily marked and grubby finger marks can be a problem too. Be careful also not to get excess glue on what will be the visible surfaces of the cabinet. If all traces of glue are not thoroughly removed they will show up as white spots when the stain is applied. It doesn't particularly matter what you use for the rear panel. We used a piece of perforated Masonite we had on hand. The baffle board can be made from scrap NOVEMBER 1987 57 ANTENNA 100cm Of WIRE FADER ANTENNA PLUG .__---;ANTENNA IN LEFT SPEAKER SPEAKERlt--....---t...J\I EARTH RIGHT SPEAKER +Vt-------, CASE CLOCK/MEMORY -v S1 POWER -v POWER SUPPLY N 240VAC A MEMORY +v +vi----__, Fig. 4 Fig.4 - the final wiring hookup for radios with single-ended outputs and front/back fader controls. If your radio uses bridging outputs, connect the speakers as shown in Fig.lb. timber since it will later be covered by speaker grill cloth. It should be at least 12mm thick to provide the necessary degree of rigidity. Before mounting the baffle board, it will be necessary to make cutouts to suit your loudspeakers and radio. The baffle can then be covered with a suitable fabric. We recommend the use of either an acrylic scrim material (looks like hessian) or a stretch fabric. The fabric should be pulled tight over the baffle and stapled in place. The radio and speakers can now be mounted and the baffle fastened to the cleats using screws installed from inside the ea binet. We suggest the use of standard oval car radio speakers which can be either 150 x 100mm (6" x 4") or 175 x 125mm (7" x 5"). These have good sensitivity and will work quite well without any fancy baffling in the form of sealed or bass reflex cabinetry. Don't use high quality speakers. They are usually far less sensitive and require proper sealed or bass reflex cabinets if they are to sound any good. Hooking up the radio Connecting the radio to the loudspeakers, the power supply SC 0 0 011-1287 IT: 0 0 Fig.6 58 here is a full size reproduction of the printed circuit board. SILICON CHIP and an antenna is a fairly easy task. Usually, it will be possible to identify the various leads from the manual, or from a chart pasted to the top or bottom of the radio. If you don't know what the leads are, you'll have to do some detective work (see panel). Fig.4 shows the hookup for radios with inbuilt front/back fader controls which are normally used with four loudspeakers. Connect the front and back outputs together as shown. If your radio is a higher powered unit with bridging outputs, connect the speakers as shown in Fig.3b. On radios without fader controls, the power amplifier outputs are connected direct to the loudspeakers. Note that power switch S1 can be regarded as optional. If your car radio has an inbuilt digital clock or station memory, the switch should be omitted and the radio turned on and off using its own power switch. The power transformer should be mounted in the cabinet with the mains terminals innermost. Before doing this, solder two short lengths of mains-rated cable to the 240VAC terminals, and sleeve the terminals with plastic tubing . The transformer can then be screwed to the side of the cabinet using selftapping screws. Install an earth solder lug under one of the mounting screws. This should be secured with a lockwasher, to ensure a positive connection. The primary leads from the transformer are connected to a two-way mains terminal block. This should be screwed to one of the front-panel cleats. Make sure that the mains cord is securely clamped and terminate the active (brown) and neutral (blue) leads as shown in Fig.2. The earth wire (green/yellow) is soldered to the solder lug secured by one of the transformer mounting screws. The idea to keep in mind when doing the mains wiring is to make sure that it is not possible for anyone to come into contact with exposed active wiring, even if their hands are probing where they shouldn't be. Note that the metal case of the radio must be connected to mains How to identify the connections Let's say that you've acquired a radio with the leads chopped off a few centimetres from the chassis and don't know which is which. Here's how to sort them out using a multimeter. Fig.3 shows the connection details for typical car radios. First, use your multimeter to identify the ground connection - this will usually be a black wire. The main + 1 2V lead will usually be red. To check this, connect your multimeter between this lead and ground and turn the power switch on and off. If the resistance drops each time the switch is turned on, \ .. ~ 375 ALL DIMENSIONS IN MILLIMETRES A = CUT-OUT AND ORILL HOLES TO SUIT RECEIVER USED 8 = CUT-OUT FOR you've found the power connection. When you find the power lead, leave the power switch on and leave the probe connected to it. Now touch the other probe to the remaining leads in turn. The one that gives a zero reading is the hookup for a power antenna. On electronically tuned radios, there will be an extra power lead that supplies the preset station memories and, perhaps, a clock, even when the radio is turned off. To find this lead connect one of the meter probes to ground and touch the other to the remaining ' ~ 150x100mm SPEAKERS FRONT HELO BY SCREWS THROUGH CLEATS FROM INSIDE MATERIAL:- TOP, BOTTOM AND SIDES 20x190mm DAR RADIATA PINE. FRONT 568x142x12mm THICK RAOIATA PINE. Fig.5 - the cabinet dimensions. We mounted the loudspeakers inside the cabinet but you may prefer to build a smaller cabinet and use separate speaker boxes. earth. This means that you must have a wire running from the radio case to the transformer mounting foot, as shown in the wiring diagram. If this wire is omitted, the radio will be completely unuseable on the AM band, due to a very loud rectifier buzz. Note also that the mains wiring and power supply should be mounted as far away as possible from the antenna socket of the radio. This is to minimise mains interference. The next step is to assemble and install a simple antenna . Cut a 1-metre length of stranded hookup wire and solder it to a standard 3.5mm banana plug. The antenna can then be plugged into the radio. unidentified leads. The memory power lead is the one that starts at a low resistance value and rises to a high value. Disregard any connection that continuously gives a low value, or that starts at a low value and rises to infinity. The remaining leads will be the speaker connections. If your radio has a fader control, use your multimeter to find which pairs give a reading of about 40 ohms. Usually, the lead for the other output in a bridging configuration will be coded the same colour, but will have a stripe added. On the prototype, the antenna was stapled to the inside of the cabinet . In most situations, however, it will be better to simply drape the cable out the back but away from the mains cord. Now for the big moment. Disconnect all the in-line fuses to the radio, so that no power can be applied to it. Apply mains power and check that the DC voltage from the power supply is close to 13.4 volts. A voltage within 0.5V of 13.4V can be consider ed OK. If this checks out, switch off, reconnect the in-line fuses and reapply power. Now turn the radio on with its own on/off switch. There · should be a soft thump from the speakers and you should be able to tune stations in the normal way. If your radio is manually tuned, it will be necessary to peak the antenna trimmer for best AM reception. This adjustment will normally be found next to the antenna jack, although it can also be situated on the front of the case behind the dress panel. To make the adjustment, tune in a weak station near 1400kHz, then peak the trimmer for maximum volume. The final step is to fit the rear panel. That's it - your new table radio is now ready for use. Enjoy the sound. Our first version was so successful that one of our staff members decided he had to have one of his own. It NOVEMBER1987 59 Laboratory Power Supply 3-5 Volta at up to 5 Amps Designed by Electronics Australia, this supply has been one of our most popular kits. Our version Incorporates refinements and Is now housed In an attractive, tough " ABS" instrument case. This all new compact version has been made possible by the use of a highefficiency Toroid Power Transformer. So you win four ways - less heat, less weight - Greatly enhanced appearance and easier to build Remember the Altronlca Kit la fully drtlled and punched. Stunning Dealgn Mak•• Your Tape Machine Sound Like A CD Player Dynamic Noise Reduction Syatem Cut that annoying type hiss and dramatically increase dynamic range of your cassette recordings with this Dynamic Noise Reduction System It This fantastic system Improves signal to noise of your tape deck by up to an incredible 18d8 without treble attenuation. ~,::ry~~:r~~=ddiec8o~~~n~~Pr~•~~~:i~~ct 0 disc players. K 5575 ......... $99.00 EA Dual Tracking Power Supply (S.. ETI Dec.'H) The Ideal Power Supply For The Audiophile Experimenting with Linear Op Amp Designs . Beat Triggered Strobe Add Some Life To Your Next Party Designed by Australian Electronics Monthly. Flashes in time to your music. Will also work as normal strobe. Exclusively customised by Altronics into our H 0480 Instrument Case, making construction a breeze and improving stability and overall appearance. Includes silk screened panel. K 5790 ..... . ........... $59.95 Two Tube Option For Increased Power K 5795 . .. .. ... . ........ . $9.95 FANTASTIC HI TECH - HI SPEC • Floating Ground• Meter , Swltchable V to A • -Volt- I age adjustable to within 10mV • Output + or - 1.3V to+ or -22V at 2 Amps +5V <at> 1 .0 Amps K 3320 Audio Oscillator and Function Generator ,This Ultra low distortion o~cillator is comparable with the very best laboratory standard stmbe _lwtave oscillators. As well as having very low distortion It has excellent envelope S a 11 y, square wave output and output metering 2 Model1 to choo1e from (metered and unmetered) • Frequency range 10Hz - 100KHz in 4 ranges• Output level 3V RMS max adjustable $129.95 ~ Att~nuator Odb , - 10db, -20db, -30db, -40db, -S0db plus fine adjustment • Output 1mpe ance - 600 ohms unbalanced • Output waveforms - sine and square. Check App/lancea And Electrical Wiring All components mount on one •Ingle PCB .making It a brHze to Construct Save $200 and More by Building thl• Fine Kit Project Build This 1000V Megohm Meter (1985 Successor to the " Megger") It uses a transistor inverter to produce a regulated 1000V DC supply which is applied to the insulation_,under test. Insulation resistances between 2M Ohm and more than 2000 Ohm can be measured. K 2550 (See EA July'BS) JUSt $55 VCR Sound Processor Connect your VHS or Beta Video to your home Stereo System via. lhl• superb Stereo Slmulator , Now a quite phenomenal enhancement to your VCR audio quality and impact rea!ism can be achieved br, feeding the Video sound 0 / P through your home Hi Fi system via. EA'•• mply brllllant VCR Sound Procesor. Not only does it give simulated stereo but the inbuilt 5 stage graphic equaliser provides tonal depth for added realism and listening enjoyment. K 5820 ....................... . .......... $59.95 The inverter is ideally suited to powering 12/240V Inverter low wattage mains appliances from the ea, battery while camping .- This considerably for Small Appliances Low Power Dealgn alao Work• H • Battery Charger improves the comfort level of the civilised camper. Similarly, it has uses in boating . Typically, ii can be· used to power an electric shaver, electric blanket , electric can opener or a 40W light bulb . · Alternatively, back In the home (or still on· the camp site). Frequency sensitive items such as belt or idler driven turntables can be powered at a very precise crystal controlled frequency for accurate sound i reproduction. If speed varlatiQn over a small range is required, then a switch is provided to change from the crystal basec 50Hz signal to a variable oscillator.K 07~ *** K 2540 Complete Kit with Front Panel Metering K 2545 Complete Kit Without Metering 300 Watt Inverter With Auto Start Oper11IH From 12V Car Battery Just think how handy it would be to have 240 Volt AC Mains Power when camping or for your boat or Caravan. Auto Start draws power from your battery only when appliance is plugged in and " turned on". i.e. battery can be left permanently connected if desired. Thermal Over Load. Curntnl Regulated. Current Overload K 6752 K 6754 Complete Kit Fully Built & Tested $229.oo $329.oo Bench Top Power Supply 3-30V to 1 amp Max.with variable current llmlt Low-Coat n Checks Values from 1pf -100uf Upgraded Digital Capacitance Meter FEATURES: The readout consists of a bright 4-digit LED display and the full scale readings for each range are 9999.9nF and 99.99uF. No adjustments are FEATURES: necessary when taking a reading. You simply connect the capacitor to the • Tests both NPN and PNP transistors in test terminals and select the appropriate range. The circuit can accurately circuit at the touch of a switch • Tests measure capacitance down to one picofarad (1 pF) . This is made possible Diodes and SCRS as well • No need to by the internal nulling circuit which cancels any stray capacitance switch between NPN and PNP-its automatic. Two LED indicators are used to between the test terminals or test leads. So when you measure a 5pF show condition of device being tested. capacitor, the unit will display 5pF. ~~~;if!~'.•c·.?:i~~iJly box and K 2522 ................................. . * Output 3 to 30V at 1 A • Short circuit protected• Load switching• Current limit- ing. Dual scale meter • Housed in our Deluxe " ABS" instrument case . SPECIFICATIONS: * Output Voltage - 3 to 30V * Output Current - Oto 1 amp (fully variable)* Load Regulation - Better than 0.2% from Oto full load * OutRut Ripple-Less than 2mV RMS. Cat. K 3210 ~!~~:~"ci's $79.oo $6.00 OVERNIGHT JETSERVICE · We process your order the day received and despatch via . Overnight Jetservlce Courter for delivery next 174 ROE STREET,PERJH . day Country areas please allow FOR INSTANT SERVICE additional 24-48 hours. Weight limit 3Kos. PHONE ORDER $6 .00 HEAVY SERVICE - For TOLL FREE deliveries exceeding 3kgs and less than 10kgs-allow 7 days for delivery 008 999 007 $10 .00 HEAVY HEAVY SERVICE - All PERTH METRO orders of 10Kgs. or more must travel AND A/HRS Express Road • Please allow 7 days for delivery. (09) 328 1599 INSURANCE As with virtually ALL MAIL ORDERS every other Australian supplier, we send goods at consignees risk. P.O.Box 8350,Perth Mail Exchange Should you require comprehensive Western Australia 6000 insurance cover against loss or damage please add 1% to order value PACKING & DELIVERY CHARGE · (minimum charge $1).When phone $3.00 DELIVERY AUSTRALIA WIDE ordering please request" lnsu•<1nce". • We process your order the day TOLL l'REE PHONE ORDER received and despatch via. Australia Bankcard Holders can phone order Post. Allow approx.? days from day toll free up to 6pm Eastern Standard you post order to when you receive Time. Remember with our Overnight goods. Weight limited 1Kgs. JetHrvlce we deliver next day. Altronics Resellers Chances are there is an Altronics Reseller right near you - check this list or phone us for details of the nearest dealer. Blue Ribbon Dealers are highlighted with a ■ .These Dealers, generally carry a comprehensive range of Altronic products and kits or will order any required item for you. Don't forget our Expreaa Mall and Phone Order Service - for the cost of a local call, Bankcard, Visa or Maatercard holders can phone order for same day despatch. Please 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 significant cost saving from prices charged by Altronics Competitors. MORE AL TRON/CS DEALERS WANTED If you have a Retail Shop, you could increase your income significantly by becoming an Altronics Dealer. Phone Colin Fobister (09) 328 2199 for Details. VICTORIA CITY Electronic Comp & Equip. 2125999 . .412681 Esperance Communications 713344 GERALDTON Force Electroni c ■ ... 2122672 SUBURBAN SUBURBAN BRIGHTON Brighton ASPENDALE Giltronics . . .... 5809839 CHELTENHAM Talking Electronics ... . 5502386 Electronics ■ .. 2963531 CHR ISTIES BEACH Force Electronics ■ .. 3823366 ENFIELD Force Electronics ■ . . 3496340 PROSPECT Jensen Electrqnics ■ .. 2694744 Lance Rock Retravision . . .. . . 351246 NEWMAN Watronics .. . . . ... 751734 COUNTRY WYALKATCHEM MT.GAMBIER D & J Pease ...... 811132 , South East Electronics . ..... 250034 ..... 521713 .. 522967 CITY Active Wholesale ■ ... 6023499 All Electronic Components .. 6623506 0 ~r~sc!t~EN ■ Electronics .. 7233860 PRESTON Preston Electronics .. .. 4840191 COUNTRY CITY David Reid Electronics ■ .. 2671385 SUBURBAN BLACKTOWN Wavefront Electronics .... 8311908 CARINGHAH Hicom Unitronics . . . . 5247878 LEWISHAM PrePak Electronics .... 5699770 COUNTRY !~~b';'sRY Electronics ■ .... 254066 COFFS HARBOUR Coifs Habour Electronics .. . . .. 525684 GOSFORD BENDIGO KCJohnson ■ . . . 41141 1 Tomorrows Electronics ■ . .. . 24 7246 MORWELL NEWCASTLE Morwell Electronics .. . ... 346133 Novacastrian Elect.Supplies ■ . 621358 SWAN HILL WHYALLA NOWRA Eyre Cornish Radio Electronics ■ ... .454764 Services ......... 321427 Ewing Electronics• .... . 218412 TASMANIA ORANGE HOBART Fyfe George Harvey ■ . 342233 Electronics . . ... . 626491 LAUNCESTON RAYMOND TERRACE Advanced Alback Electronics ...... 315688 Electronics .... . . 87341 ;; George Harvey ■ . 316533 TENTERFIELD · Nichols Nathan Ross Radio TV ...... . 316171 Electronics . .... . 362204 . WINDSOR M & E Electronics ■ Communications . 775935 WOLLONGONG Newtek Electronics ■ . . .. 271620 Vimcom Electronics .... . . 284400 (•11)33~(.1fj~j1] - - ----- --··-· • CITY Delsound P/L .. 8396155 :~:T~:u8D~NVALLEY Fred Hoe & Sons 2774311 E~~~:~~~cs · · · · Electronics . .. . . . 523762 PADDINGTON Jacques Electronics ... . 3698594 SLACKS CREEK David Hall Electronics . . . . 2088808 T OOWONG Techniparts .... 3710879 MACKAY Philtronics■ .... .. 578855 NAMBOUR Nambour Electronics . .. . . . 411604 PALM BEACH The Electronit Centre .. . . .. .... 341248 ROCKHAMPTON Electron World .. . . .. ..... 278988 Access Electronics (East St.) . ....... . 21058 Purely Electronics (Shopping Fair) . 280100 Xanthos Electronics .. . . . . 278952 TOOWOOMBA Hunts Electronics • ; . . . 329677 TOWNSVILLE Solex ■ ..... ... .. 722015 COUNTRY CAIRNS Electronic World . . . .. . ..... 518555 BUNDABERG Bob Elkins Electronics ... ... 721785 GLADSTONE Supertronics . . . . . 724321 Better and Faster Service Than Any Other Au1trallan Suppller or Your Money Back Jack O 'Donnell Mi Director 1 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 . .-------------------+3-15V MIN .047+ C1 MAX..._1-N--+--' MOTOR VOLTAGE 1JUUL n-r 02 1N914 DC speed control for model motors This circuit provides a pulsed supply with a variable duty cycle to give speed control of a small DC motor. This provides consistent control, particularly at low motor speeds. IC1a is used as a simple Schmitt trigger oscillator with a variable HIGH SPEED duty cycle control. VR1, when set to the mid-way position, allows capacitor Cl to charge up via D2 and half of VR1 and discharge via D1 and the other half of VR1. This provides an equal duty cycle square wave output at pin 3. When VR1 is set to the minimum position, Cl charges slowly through D2 and the total VR1 1MO resistance. When the voltage Ra Measuring the tracking of dual potentiometers The tracks of dual ganged potentiometers are often not well matched over their range of rotation. In some applications, such as volume controls in audio amplifiers, tracking performance is important for good stereo balance over the gain range. This circuit measures the difference in resistance between tracks of a dual pot at various settings and indicates the difference 2.2k .... on a meter. The circuit consists of an op amp connected as an inverting stage, with one gang of the pot, Ra, forming the feedback resistance and the Moola, moola, moola! Moola, brass, bread, dough, call it what you will. If you have a good circuit cooking away in the ol' brain cells, jot it down on paper and send it to us. If we publish it, we'll pay you for it. Yep, up to $50 for a really good circuit. So get cracking. Send it to Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. 62 SILICON CHIP across Cl reaches the positive threshold of IC1a the output goes low and discharges Cl to the negative threshold of the IC la input via Dl; the output then again goes high. Consequently, the output of IC1a is high for most of the time. Conversely, when VR1 is set to the maximum position, Cl charges rapidly via D2 and discharges slowly via Dl and the 1MO VR1 resistor. Therefore, the output is low for most of the time. The output of IC1a is buffered and inverted with the paralleled Schmitt triggers IC1b, IC1c, and IC1d. These drive transistor Ql via the 3300 resistor. Ql then drives the motor. The diode across the motor is used as a flywheel diode to conduct the back-EMF of the motor when the transistor is switched off. Ql is capable of driving motors up to BOOmA, but can be replaced with a Darlington BD681 for driving motors which draw up to about 2A. second gang, Rb, as the input resistor. If the tracks of the pot are perfectly matched, the gain of the amplifier will be constant (at unity), regardless of the pot setting. To use the circuit an audio signal source is required. This could be a sine wave generator set to a suitable level, say 1V rms. The output of the op amp is read on an AC meter which could be a millivoltmeter calibrated in decibels or a digital voltmeter. If the latter is used, the signal frequency should be lkHz or lower as some meters have very poor AC response. 2.2k0 resistors are connected in series with both the tracks of the potentiometer under test, to avoid undue loading on the op amp. These resistors will effect the accuracy of the circuit at one extreme of rotation but it still gives a good basis of comparison. Obtain - 5V from a + 5V supply . - - - - - - - - - -......- - +5V 100 + 16VWI .,. When op amps are used in conjunction with 5V logic circuitry, it is usually necessary to provide a - 5V supply as well. Using the Texas Instruments TL497 A switch mode IC, this circuit can provide a - 5V supply at up to 100mA from a + 5V supply. The TL497 A performs the voltage inversion using a minimum of ancillary components: a 200µH choke, three capacitors, three resistors and a diode. Operation of the circuit can be understood by referring to Fig.1. Switch S 1 represents a transistor which is switched on and off at a rapid rate. When S1 is closed, current flows in inductor L. When S1 opens, the current in L now flows via diode D1 and capacitor CF. Thus, a negative DC voltage is developed across capacitor CF. The same principle is used by the TL497 A. Here the internal tran- 22Dpfr S1 01 + 0-<) VI comparison of the output with an internal reference in the IC, via the voltage divider connected to pin 1. The IC then adjusts the duty cycle (on to off times) of the switching transistor to give the correct output voltage. Current sensing is provided by the rn resistor Rcl. This limits the peak current to 500mA. Peak-topeak ripple on the output is held to to less than 50mV by the 68µF capacitor. - I LOAD VO v----------u+ f",g . 1 sistor across pins 10 and 8 of the IC is switched at about 50kHz, as determined by the 220pF capacitor at pin 3. Voltage regulation is provided by + s v - - - - - - - - - 4 - - - - - - - - + - - - - + - - + - - - - 4_ __.__.__._ _ _ _...,. 16 16 15 120!1 14 LED1 --,<-N-.-• ivoi.:-7 IC4 74LS193 2.2k 3 2 IC5 74LS155 OAll-----=161 01 1N4148 0B 2 LED 2 IY1F-6_..._.._,. 13 A LED3 .,. 5 _..._..__,. IY2:F- 6 OCt-----tB LED4 f2 INPUT 4--,~-t-IY3t- <>-1---.01 .,.. -5V 100k Frequency comparator with visual display The traditional ways of testing for the difference between two signal frequencies have been to listen for audible 'beats' or use a Lissajous display on an oscilloscope. This digital method uses a rotating display of four light .,. .,.. emitting diodes. It is useful for setting two frequencies to exactly the same value or it can be used as an accurate indicator of frequency drift. When one frequency is higher than the second, the display rotates in one direction and vice versa. When both frequencies are the same, the display remains stationary. The circuit has inputs for the two signal frequencies. The signals are each fed to an op amp (!Cl, IC2) connected as a Schmitt trigger with a hysteresis of about 100mV. These have an input impedance of close lOMO to minimise loading of each frequency source. The output of each op amp is a square wave which is clamped with Continued next page NOVEMBER 1987 63 'Problem? 1 You want someone to listen • to your portable CD player or • Walkman without being hooked up to headphones or wires .. ? You want to listen to your CD • player (portable or home) • through your amp but only have one auxiliary input... and you have to keep adjusting the volume anyway .. ? 2 (CDA1) ARISTA STEREO WIRELESS TRANSMITTER ... a unit specially developed to allow portable CD headphone output signal to be transmitted directly in to your stereo, car or portable FM radio, its talents extend to the transmitting of any mono/stereo signal from any headphone output to any FM receiver. a diode to protect the following exclusive-OR (XOR) gates. IC3a and IC3c invert the outputs from the Schmitt triggers while IC3b and IC3d provide an exclusive-OR function (the output is high when the inputs are different) between the output of the Schmitt triggers and the inverted outputs of IC3a and IC3c. Note that the outputs of inverters IC3a and IC3c are delayed by an RC network consisting of a 220pF capacitor and 2200 resistor. At every level transition (low to high or high to low) from the Schmitt triggers there is a negative-going pulse from the respective XOR gate, IC3b or IC3d, for the time duration set by the RC delay. These XOR gate outputs are connected to the up and down count inputs of a binary counter, IC4. If the two input frequencies are exactly equal, IC4 does not manage to count at all; each up count is cancelled by a down count. If F, is higher than F2 2 (CDA3) CD PLAYER ADAPTOR • ... conveniently hooks up . • your CD player to your amplifier with a variable signal input. The CD matcher also gives you an extra auxiliary input as well. 2 For further information on the ARISTA solutions and the name of your nearest retailer, please contact: ARISTI\. ELECTRONICS PTY LTD Telephone (02) 648 3488 SILICON CHIP then IC4 counts up while if F2 is higher than F 1 , then IC4 counts down. The binary outputs of IC4 - QA, QB and QC - are connected to one half of a dual 1-of-4 decoder, IC5. As IC4 counts up, the LEDs from 1YO to 1Y3 light up in sequence and when IC4 counts down, the LEDs light up in opposite order. The QA output of IC4 is connected to the Gl input of IC5 so that every time QA goes high the LEDs are blanked. This provides blanking between each LED being lit. Thus, when arranged in a circle, the LEDs appear to rotate one way or the other, depending on which input frequency is higher. The circuit is suitable for comparing frequencies up to about lO0kHz when using the Schmitt triggers. However, if suitable signals are applied directly to XOR gates IC3a and IC3c, the circuit will operate up to about 12MHz. Handy hints and tips Hint #1: When drilling a masonry wall in order to feed through antenna cable, angle the drill upwards at, say 30 degrees, this will make it easier to feed the cable through without damage, especially if it is thick coax. 1 64 Circuit Notebook Hint #2: Do not discard your electric blanket when the heating element becomes opencircuit. Remove the electrical plugs and fittings, which may come in handy at some later date, and strip out the heating wire. This can be done by carefully parting the threads of the fabric so that the end of each heating loop can be cut. The job is a tedious one and takes about half an hour. The blanket can then be washed in the same way as a normal woollen blanket and put to use as a rug or cot blanket. The heating cable itself should be thrown out as it is of no use in conventional electric or electronic circuits. Incidentally, electric blankets should be very carefully inspected each year before they are put on the bed for the winter. Look on both sides of the blanket for any signs of fraying which may expose the heating cable. Once fraying becomes noticeable the blanket should be replaced. Hint #3: If you are having trouble stripping the insulation from fragile wire which tends to break easily, use a hot soldering iron to melt the insulation at the selected point, and then pull the insulation off. This avoids any possibility of nicking the wire with strippers or sidecutters. Be sure to thoroughly clean your soldering iron after this to avoid contamination. -- ------------== --= -----= ------- ----- --- --- - -- = = = = = == = = == = = = = = = = = = = = == = = = = = ==-:. === = = - = Finally, an LCD Multimeter which accurately shows analog- type readings! All those essential dynamics that are often lost on a DMM ... often it's not so much a reading you're after as the change in readings! But there's more: the information is displayed in "bar graph" format for instant recognition and ease of reading. And if you need to expand the scale, it's a simple one-button operation to go to a 1Ox magnification! Plus a data hold function (last reading retained), a maximum hold function (highest reading retained & marked, but readings continue), diode check & continuity, etc, etc: it's one of the best general purpose multi meters available today simply because it does everything better! ~ ~ ~" ~ .,. ,,., ,,o •• •••• < . 1 0 • •• ,;:· '· _ \ a. • 105 step LCD bargraph display giving 1% resolution on any scale (eg 10 volts on 1000V range with mag pressed). • Fast 10/second sampling rate for virtually instantaneous display (much faster than most digitals). • Automatic positive or negative indication • DATA Hold key freezes reading immediately previous to pressing. This can then be magnified (by up to 10: 1) for a more accurate and precise reading. 6 DC ranges ( down to 100mV with virtual 1mV sensitivity), 4 AC ranges, 5 resistance, 3 DC plus diode check and continuity ranges. • Single input terminals mean no swapping of leads when you change to different scales. Fully shrouded test leads supplied, with full instructions. 2.?10._J~~~•',~~~--:::!.:.~ • --- $14 Cat Q-1777 Specifications: Diode: Test current approx 0.5mA, reads Vf on display DCV: 100mV, 2.5V, 10V, 50V, 250V, 1000V, 5Mohm impedance Measuring Method: dual integration mode ACV: 10V, 50V, 250V, 750V (minimum 5k/V, 25k/V on 10V) Sampling: 10 times per second Power:1 .5V (AA) x 2 DC: 2.5mA, 25mA, 250mA Battery Life: Approx 800 hours or more. Res: 250 ohms, 2.5k, 25k, 250k, 2.5M Size: 145 x 86 x 34mm (w x h x d) Cont: 250 ohms max, continuity beeper approx <100 ohms Weight: Approx 250g (inc batteries). Available exclusively from Dick Smith Electronics ORDER BY PHONE: TOLL FREE DSXpress ON (008) 22 6610 For 24 hour despatch DICKeSMITH ELECTRONICS PTY LTD Off hook indicator for telephones You can build this low-cost indicator into your phone to tell when on extension phone is "off the hook". Design by JOHN CLARKE How many times have you been on the phone when someone else in your household has picked up another extension and begun dialling? How many times have you done the same thing to them? It's annoying isn't it? This circuit avoids that hassle. You can build one into each phone so that a LED (light emitting diode) will then flash, on every extension, to indicate whenever the line is in use. Another common problem in a multi-phone household is that possibly you've answered an incoming call on one phone, then moved to another phone to carry on the conversation, leaving the first phone off the hook. Hours later, you discover that the phone is still off the hook and you wonder how many calls you've missed. Again, this circuit will avoid that problem. The circuit uses only one low-cost IC and a handful of other bits which means that the overall component cost, minus the circuit board, is only about six dollars. You could equip three phones for under $20. The unit is very easy to install and it should be possible to fit it into even the most compact pushbutton phone. You simply connect it across the incoming phone lines to the handset (we'll explain that in more detail later). No batteries or power circuits are required since the low It should be possible to fit the circuit into even the most compact pushbutton telephone. The LED must be a high-brightness type. 66 SILICON CHIP current for the circuit comes directly from the phone lines. Free power, eh? Bewdy, mate. Essentially, the circuit is an LM3909 LED flasher IC with some other circuitry around it to monitor whether the phone is on or off the hook. What happens is that when the phone is on the hook the voltage across the incoming phone lines is close to 50 volts DC. When a phone is taken off the hook to answer or make a call, the voltage drops to around 6 volts, depending on the particular phone. In some cases, the voltage may drop below 3 volts, with more than one phone off the hook. Our circuit monitors the voltage across the phone lines and when the voltage drops below about 12 volts, it enables the LM3909 to flash the LED. Now let's discuss the star of the show, the LM3909. This device can operate down to 1.5V and yet can drive a LED which requires 1. 7V or more to turn on. The LM3909 does this by charging a large capacitor and then connecting the capacitor in series with the DC supply to discharge via the LED. Fig.1 shows how this is accomplished. Fig.1 shows the relevant components inside the LM3909 and with a 47µF capacitor connected between pins 2 and 8. Now forget the LED for a moment and consider that Q3 is not conducting. This allows the 47µF capacitor to charge via the 8000, 6k0 and 3k0 internal resistors. PARTS LIST A(2) 6 PHONE LINE + IC1 LM3909 8(6) 8 EOc VIEWED FROM BELOW PHONE OFF-HOOK INDICATOR 121-1187 Fig.2 - the complete circuit diagram. When the line voltage drops below 12V, Qt turns off and Q2 turns on to activate the LM3909 flasher IC. ZD3 protects Q2 against spike voltages. 1 PCB, codeSC-121-1187, 52 x 30mm (or Veroboard) 1 LM3909 LED flasher/oscillator 1 high brightness red LED 1 LED mounting clip to match (optional) 1 BC549 NPN transistor 1 BC550 NPN transistor 1 56V zener diode 1 1 2V zener diode 1 3 .3V zener diode 4 1 N4004 silicon diodes 1 220µF 16VW PC electrolytic capacitor 1 4 7 µF 16VW PC electrolytic capacitor 2 470k0 0.25W resistors 1 120k0 0 .25W resistor 1 1OkO 0 .25W resistor Miscellaneous Solder, hookup wire etc. This photograph shows the PC board version at left and the Veroboard version at right. The capacitor is charged almost to the full extent of the 1.5V battery supply whereupon Q3 is turned on. This pulls the positive electrode of the capacitor down to OV, so that in effect, 3V is applied across the LED, causing it to flash briefly. Then the cyc\e begins again. In giving this summary of the LM3909's operation we are conveniently neglecting the functions of the other internal components but that will suffice for the purpose of this article. . The particular benefit of the LM3909 is that not only will it flash a LED from a low supply voltage, it will do it with very low current drain, at substantially less than one milliamp in the case of the illustrated circuit. That would be almost ideal for our purpose since we want to keep the current drain from the phone lines to an absolute minimum. However, we had to modify the circuit to render the effect of the flasher on the phone lines inaudi- ble. This had the additional benefit of making the current drain substantially lower. Now have a look at the complete circuit. LEDs do it again The complete circuit uses four diodes, three zener diodes, two transistors, two capacitors and a few resistors in addition to the components of Fig.1. Four 1N4004 diodes are con- LEO + 1.5V ,I Fig. 1 I 6 03 3k . . . . _ - - - - - - ,4_____ Fig.1 - relevant components inside the LM3909 plus the external LED and 47µF timing capacitor. nected in a bridge rectifier so that the complete circuit will operate regardless of the voltage polarity of the phone lines. While 1N4004 diodes have a peak inverse voltage rating of 400V which is much higher than the nominal phone voltage would warrant, we are playing safe so that any transient voltages on the line do not blow the circuit. To detect the voltage across the phone lines, the base of transistor Q1 is driven via a 12V zener diode and series 470k0 resistor. When the line voltage is high (ie, when the phones are all "on hook"), the 12V zener conducts and turns Q1 on. This holds the base of Q2 low and prevents it from turning on and so the LM3909 cannot operate. When the line voltage drops below about 12V, the 12V zener ceases conduction and Ql turns off. Q2 can now turn on due to the current through the 4 70k0 resistor feeding its base. With Q2 on, ICl can operate. It is powered from the positive rail via the lOkO resistor and clamped at 3.3V using the zener. A 220µF capacitor provides a low source impedance for the resulting DC supply. ICl is connected to flash the LED at about a one-second rate, as set by the 47 µF capacitor across pins 8 NO V EMBER 1987 67 A tight squeeze, but we made it! This view shows how the circuit was mounted in the lid of a pushbutton telephone. and 2. Current through the LED is limited by the 5600 resistor to reduce the audible effect of the flasher circuit to a negligible level. This meant that we had to specify a high efficiency LED to ensure adequate brightness. It also has the side-effect, in combination with the relatively low value of the 4 7µ.F discharge capacitor, of reducing the "offhook" current drain of the circuit. Incidentally, note that Q2 is specified as a BC550. This type has been specified to give high current gain together with a high collectoremitter voltage rating. Substitutes should not be used. The 56V zener connected across Q2 protects it against transient spike voltages which may be generated by diall- Fig.3 - parts layout for the PC version. Be careful not to confuse the zener diodes. 68 SILICON CHIP ing, the incoming ring voltage or disconnection at the exchange. How many should you build? Not more than 500, at a guess. Seriously though, we suggest that you build no more than three in a single household. While many households may have more than three extensions, we are aware that for the telephone exchange equipment to work reliably, the leakage resistance across the subscriber's lines should not be less than about 50k0. To conservatively meet that requirement then, don't build any more than three. In setting the above limit, we are allowing for the fact that any push button phone in your household (ie, electronic) will have Fig.4 - wiring diagram for the Veroboard version. its own current requirements when "on-hook" and so this must be taken into account. So build any more than three indicator circuits and there is the possibility that Telecom might come a-knocking on your door. Current drain of each indicator circuit is around 200 microamps when all phones are "on hook" (ie, with phone line voltage at 50V). With any phone "off hook" the current drain of each indicator circuit ranges from around 700 microamps at 9V to around 200 microamps at 2.5V. Assembly We have designed a small printed circuit board to pack the components into as small a volume Fig.5 - here is an actual size pattern for the PC board. as is practical. The board measures 54 x 30mm. Alternatively, for those who don't wish to bother with a printed circuit board, we have provided a layout drawing to show how to build the circuit on Veroboard. Mount all the components on the board as shown in the relevant layout diagram (PC board or Veroboard). Mount all the links, resistors, diodes and zeners first. Make sure that the diodes and zeners are mounted with correct polarity. These components can be soldered after the pigtails are cut to length. The two capacitors are next, followed by the trimpot and LM3909 integrated circuit. The LED may be soldered directly to the printed board or connected via a pair of flying leads, depending on how you need to mount the unit in the particular phone. Note that the circuit positions of the LED and 5600 resistor on the Veroboard layout are different from those shown on the circuit and PC board layout (which are the same). However, since the resistor and LED are in series, their physical order does not matter. Q2 should be close to 19V, allowing for voltage drop across the bridge diodes, Dl to D4. Flasher in phone Before you mount the indicator permanently in the phone, it should be connected across the phone lines to check its operation under normal conditions. It can be connected across the phone socket while the phone is still connected. The two connections are to pins 2 and 6 of the plug. If the socket has been wired correctly, pin 2 will have a white wire and pin 6 will be blue. Measure the DC voltage across the phone line with all the phones on hook and note that it is around 50 volts. When you have connected the indicator board, measure the voltage again to ensure that it has dropped only slightly, by less than 0.5V. Now take any of your phones off the hook and check that the LED flashes. It does? Good. Now you have to work out how to mount the indicator in the phone. Don't rush into this job because if you make a mess of it you will have butchered a perfectly good phone. In most cases it will be simply a matter of drilling one hole in the case to mount the LED. You can either use a two piece LED mounting clip or drill the hole so that the LED is a push-fit. The photos will give an idea of how to mount the board itself. ~ Installing a car burglar alarm? You need a crimp connector kit Making it flash With the board complete you can check out the circuit before installing it in the phone. You will need a power supply which can be adjusted to deliver between 3V and up to 20V DC or more. Failing that, the circuit can be checked out with batteries. First set your power supply to between 6 and 9V and check that the LED flashes at about once a second. The flash rate will vary to some extent, depending on the supply voltage. Now increase the supply voltage. By the time you reach about 15V the LED should stop flashing. Ql should be turned on and Q2 should be off. You can confirm this by measuring the voltage between col1e c tor and emitter of both transistors. At 20 volts or thereabouts, Ql should have a collector-emitter voltage of 0.1 V or less. In other words, it should be saturated (ie, fully turned on). Q2's collectoremitter voltage should be close to the supply voltage. If the supply voltage is 20V, the voltage across Sooner or later everyone who has a car will want to modify, repair or otherwise break into the wiring. If you are installing a car burglar alarm or other accessory item you almost always have to modify the wiring. To do a -proper job you need connectors which are secure. That means the use of correct size crimp connectors to suit the wiring being modified. For that purpose, this repair kit from Dick Smith Electronics is ideal. It contains a good combination crimping and wire strip·ping tool, a sturdy pair of long nose pliers , two small screwdrivers with one being a Philips fiead, a roll of PVC insulation tape, 90cm of hook-up wire, a 6/12/24V lamp tester and 60 assorted crimp connectors. The whole lot is housed in a compartmented case with a clear lid. Price is $21.95 from all Dick Smith Electronics stores. NOVEMBER1987 69 Weatherproof loudspeakers and sound columns Centronics printer switch solves connection hassles If you have two printers you want to use with one computer or two computers which need to share one printer, you have a problem. Disconnecting and connecting the Centronics plugs is not a good idea and extra Centronics boards to enable one computer to handle two printers are expensive. Enter the Arista CAS16 Printer Switcher, a small box with three 36-way Centronics sockets on the back and a Heated solder sucker for desoldering The Skandia desoldering tool combines a solder sucker and heating element all in the one housing; This makes desoldering of components on a printed circuit board a simple one-handed operation. Just put the heated tip on the joint to be desoldered, wait till the solder is melted and then press the button to suck off the solder. The desoldering tool is particularly handy on small boards or those fixed in awkward positions where you need three or four hands to hold and manipulate tools, boards and the components to be removed. At $65 from Geoff Wood Electronics, it is a bargain. Why didn't someone think of it before? 70 SILICON CHIP 2-position rotary switch on the front. You simply connect the computer( s) and printer(s) as needed and use the switch to select the combination required. The unit is powered from the computer bus so no batteries or external power is necessary. Nor is there any need to resort to DOS commands to select your printer. The CAS16 is available from all Arista outlets. Altronics in Perth has released a new range of weather-proof loudspeakers and sound columns under the Redford brand. There are five models to choose from, rated from 10 to 40 watts. For home stereo extension speakers, the smaller models would be ideal. The higher powered models are fitted with multitap line transformers and are intended for professional sound and public address applications. For short term use, Altronics claim that the drivers will safely handle 150% of their rated power. All models use a patented cone moisture repellant process, while foam plastic and cloth is sandwiched between the baffle and grille to prevent ingress of water. The rugged enclosures are constructed from aluminium extrusions finished in durable powder enamel, while the end caps are moulded Luran S for UV resistance. For further information, contact Altronics Distributors, 17 4 Roe St, Perth WA 6000. Phone (09) 328 2199. Keyboard extender cable When is an audio cable not an audio cable? Answer: when it is a computer cable. Many people who have IBM PCs or PC-compatibles find that their keyboard cable is not long enough. They want to move the keyboard further away from the monitor and processor. The solution is to buy a 5-pin DIN plug to DIN line socket cable. The Arista cable pictured is 1.8 metres long and is flat so it easily run under equipment. It is available from Arista stockists everywhere. Video line selector for oscilloscopes Universal battery tester and charger If you are going on a holiday, work assignment or photo excursion, there is nothing more irritating than finding that crucial batteries have failed. In those circumstances there is usually no chance of getting a replacement and so opportunities go begging. On the other hand, nobody wants to buy batteries unnecessarily because if you don't use them within a certain time they are a complete waste. This is where this universal battery tester from Dick Smith Electronics really comes in handy. It can test the batteries for your torch, tape recorder, camera, amateur gear and so on. There is a test cavity for virtually every battery on the market. As well, the unit can double as a charger for any 1.2V nickelcadmium cell when a mains DC plugpack is connected. The tester will also check the continuity of torch bulbs and other low resistance components. All that capability comes for $17.95. Examining video waveforms with an oscilloscope can be a real pain at the best of times but if you want to have a look at a particular video line, field or frame you're up the proverbial creek without a paddle. Philips can solve that problem with their PM 8917 Video Line Selector. Feed in a composite video input signal with amplitude from 500 millivolts to 3 volts and the PM 8917 generates sync signals for the display of frames fields or lines. You just dial up the particular video line you want with the three pushbutton decade switches, set the CRO timebase and trigger switches accordingly, and there is the desired signal. The PM 8917 can work automatically with 525 or 625 lines and can also be used with the Philips PM 3360 Waveform Analyser. For further information, contact Philips Scientific and Industrial, 25-27 Paul St North, North Ryde, 2113 . Phone (02) 888 8222. Give static the zap In dry weather static can be a real problem on records and slides. The very act of removing a vinyl record from its platic sleeve can place a substantial static charge on its surface which will then have a strong attraction to airborne dust. Here is a neat solution to that problem: the electronic anti-static gun . Squeezing the handle generates a substantial electric field which can then neutralise any static charge on the record surface. The gun contains a piezoelectric element which is stressed by squeezing the trigger. The resulting charge is dispersed from the nozzle of the gun by two needle electrodes. The voltage across these is limited to about 15,000 volts by an internal spark gap. The method of use is to hold the gun about 20cm above the record surface and slowly squeeze the trigger while moving the nozzle over the disc surface. It works like a charm. The gun is an Arista product and is available from hifi electronic stores throughout Australia. NOVEMBER1987 71 A portable electronics workbench Do you build your electronic projects on the kitchen table? Do you hnte the hassle of clearing it all away and then getting it all out again the next time? Here's the answer. By LEO SIMPSON Let's face it. Most of us don't have a special room or workbench where we can pursue our hobby of electronics. Most of us make do with the kitchen table for our electronics assembly and design work but then you have the problem of clearing it all away for distractions like meals. Having had to put up with this problem for many years, I decided to have a think about solving it. What was needed was some sort of portable workbench arrangement which could accommodate all the electronics paraphernalia of the moment but be packed away at a moment's notice, underneath the bed, on top of the wardrobe or even behind a door. Even if you have a workshop or a workbench in your garage, there are times when you want to work in the kitchen or family room. Maybe you want to be with your family while you work on your hobby or maybe there's a TV show you don't want to miss while you work. In other words there are many good reasons for having a portable workbench that can be set up quickly and with a minimum of fuss. 72 SILICON CHIP I evolved the design of the workbench over a period of several weeks but I am sure that readers will be able to come up with their own refinements. I wanted plenty of space to spread parts around, a power supply, soldering iron, reels of hookup wire and so on. It also had to have a set of parts drawers and provision for tool storage. The idea is that when you finish working on a project for the moment, you can push all the paraphernalia towards the back of the workbench and then put the whole box and dice away. If necessary, you might want to upend it so that it can sit behind a door. It could also be hung up on a wall, out of the way. The end product is a flat work surface 820mm wide by 650mm deep with sloping sides, a closed back and a narrow shelf along the back. Naturally the dimensions can be varied to suit the material you have on hand but it shouldn't be made much smaller otherwise the work area will be too cramped. By the same token, it should not be made much larger either, otherwise it will be too heavy and unwieldy to carry. To make my own workbench, I used white melamine surfaced particleboard which gives a durable and easily cleaned work surface. The sheet I used was 16mm thick but with hindsight 12mm material would be quite strong enough and much lighter to carry. Don't use bare particleboard. It might be cheap but it's unpleasant to work upon and the surface is easily abraded, absorbs any spilt liquids and swells up like a sponge. Even if you try to seal it with Estapol or some other finish it is rarely satisfactory. In short, forget it. Of course, such a workbench (dare we call it a "work centre" or even a "work-station" ) need not be confined to electronic activities. It could be used equally well for other hobby work such as model aircraft, model cars and model trains and could also be used by students for school projects. Don't let your la ck of carpentry skills frighten you away from building the workbench. As long as Ready for work. Doesn't it look impressive? The soldering station is from Dick Smith Electronics ($129) as are the fancy Piergiacomi side-cutters and pliers. The nifty little vyce is an Arista product, also available from Tandy. The reels of hookup wire are from Jaycar, as is the super-large prototyping board ($69.95). you have a circular saw and an electric drill, you can build this project. The assembly process consists of cutting the melamine-surfaced particle board to size, drilling the holes for the screws and then simply screwing it together. No glueing is required, or is possible for that matter, since the melamine surfaces prevent it. You need to start with a sheet 12mm thick which will probably have a minimum size of 1200 x 900mm, depending on where you buy it. Some timber yards and hardware outlets will cut the material to size for you for an extra charge although you will have to check whether this service is available. Failing that, you will have to use a circular saw to cut the material. We would advise against using a handsaw for this job. Saw blades LIST OF MA TERI ALS 16 DIA., 260 LONG DOWELS TO HOLD HOOK-UP WIRE .Jo BASE B20 x652 ALL DIMENSIONS IN MILLIMETRES MATERIAL: 13mm PARTICLE BOARD, MELAMINE COATED BOTH SIDES ALL EXPOSED EDGES COVERED WITH IRON ON EDGE STRIP ASSEMBLE BENCH WITH 50-60mm COUNTERSUNK PARTICLE BOARD SCREWS ANO COVER WITH CRESS CAPS ,k ( , PORTABLE WORK BENCH Fig.1 - this diagram shows the dimensions of the workbench. You can vary the dimensions somewhat, but don't make the work area much smaller than that shown. 1 sheet of 1 2mm melamine surfaced particle board 1 four-way power board (Kambrook, Goldair, etc) 1 8 50mm x 8 gauge countersunk wood screws or Chipboard screws, or 1 8 Furnco Directors (decorative head particle board screws) 1 8 Furnco white Snap Caps size 8/8 (to suit screws, not necessary if Furnco Directors used) 8 25 metre reels of hookup wire (Jaycar Cat No WH-3009) 2 260mm 1 2mm dowels (for reels of hookup wire) 4 large rubber feet Miscellaneous Aquadhere PVA adhesive (to glue dowels in place), iron-on melamine edging tape (Armaflex G-L), double-sided tape. NOVEMBER 1987 73 Now which component was I supposed to remove? Leo Simpson ponders the question as he gives the workbench its first tryout. are quickly dulled by cutting particle boards unless they have silicon carbide teeth. To ensure that you achieve straight cuts, use a straight edge as a guide for the power saw. The idea is to clamp a thin straight-edged length of timber to the particleboard and use it as a guide for the saw. Smooth off the sawn surfaces with a rasp or sanding block before proceeding to the next step, which is to make the various rightangle butt joints to assemble the work bench. The various sections are then screwed together. You can either use long woodscrews or, better still, special particleboard screws such as Furnco "Directors". The latter have better holding power in particleboard than woodscrews although they are more expensive. Alternatively, you can use Chipboard screws which have coarse threads for easy penetration and good holding power. I used 50mm x 8 gauge bright zinc plated countersunk woodscrews together with white Snap Caps (decorative caps made This photograph shows the various pieces of the workbench before it was screwed together. We suggest the use of Furnco Directors to secure the panels (see text). 74 SILICON CHIP by Furnco ). If you use Furnco Directors you will find that they are supplied with decorative caps. Which ever screws you are using, there is no need to countersink the screw heads. In fact, countersinking screwheads in particleboard is not good practice. Snaps caps are supplied with a countersunk washer cum clip while the roundhead of Directors means that no countersinking is required. Assuming the use of 8-gauge screws, each screw position wilf need to have a 1/8-inch hole drilled for the threaded portion and then drilled out to 3/16-inch to take the shank of the screw. Don't drill too deep with the latter size otherwise the screw will have no holding power. I used 18 screws to assemble our workbench and this should be ample. To finish off the exposed edges of the particleboard, use an iron-on melamine edging tape (Armaflex G-L) and then trim to fit using a utility knife. I also mounted some short lengths of 16mm dowel to accommodate eight small reels of hookup wire. Available from Jaycar at $19.95 for a selection of eight colours, each reel has 25 metres of hookup wire (13 strands 0.12mm). Very handy. Finally, fit four decent-sized rubber feet to the underside of the workbench so that it does not scratch or move around on the table. I also fitted a four-way powerboard to one side of the workbench (as made by Kambrook, Goldair, etc) to provide power for a soldering iron, power supply and so on. A set of parts storage drawers can also be set in place next to the reels of wire using screws or double sided tape. You'll also want a set of spring clips (Terry Multifix Tool Clips are the ones) to hold your most oft-used hand tools, such as screwdrivers, pliers and side-cutters. As you can see, the final workbench is a little beauty. You can set it up on a table at a moment's notice and get stuck right into the current job. I wonder why I didn't make it years ago. ~ The poor old hobbyist or engineer wanting one-off pcb's: prototype boards from the manufacturers have been horrendously expensive, making your own always lacked that professional quality! Until now! Dick Smith Electronics is proud to introduce you to the "Datak" range of US-made pcb materials. Top quality, easy to use, make a professional product ... yet extremely good value. What more could you want? D/i.I'AK Individual Com~onents to Build Up or Replenish your Packs. Photofilm Sheet Yellow Filter Makes film positives from magazine art, 1 :1 patterns on film, etc. Two sizes available: 125 x 150mm (6 sheets) Cat N-5705 $1885 200 x 275mm (2 sheets) Cat N-5709 s1aas Film Processing Chemical Pac i< Processes either of above photofilm sheets. Cat N-5909 Complete Photo Tech PCB Kit It's so simple! This kit contains everything the hobbyist or workshop could want to make pro-quality PCB's: 125 x 150mm stell print ing frame, pos-neg film , film processing pack, yellow f ilter, 100g negat ive acti ng etch resist, resist developer. blank pcb's, dry concentrated etchant, 1 :1 resist patterns and tapes and, best of all, COMPLETE INSTRUCTIONS. Cat N-5700 s1049s $11 Avoid ox1dat1on & contamination of patterns: tin them without mess or elecricity. Soluble powder puts bright tin plate over copper of pcb, ready for soldering . Cat N-5730 s12ss Circuit Fix-It Damaged PCB? Fix it easily and simply with this one. Pure copper pads, sheets on self-adhesive carrier to allow virtuall y any repair. Cat N-5900 Photoresist Made Easy Pro quality f rame maKes negs or pos up to 225 x 300mm, from film pattern or even direct f rom printed magazine pages. Contains spring loaded steel exposing frame w ith glass, backboard , yellow f ilter & instructions. Cat N-57 10 Spray pump of negative photo resist (118ml) ready for coating blank pcb's. Easy to use, no tight tolerances required for heating, etc. Cat N-5907 s1a95 $6295 ---;-.r~'f!ll1•i\Zlll..-i • NSW • Albury 21 8399 • Bankstown Square 707 4888 • Blacktown 671 7722 • B!akehursl 546 7744 • Bondi Junction 3871444• Brookva le (Warringah Mall) 93 0441 • Campbc lltown (046)27 2199 • Chatswood Chase 411 1955 • Chullora642 8922 • Gore Hill 439 5311 • Goslord 25 0235 • Hornsby 477 6633 • Liverpool 600 9888 • Maitland 33 7866 • Miranda 525 2722 • Newcastle 61 1896 • North Ryde 88 3855 • Parramana 689 2188 • Penrith (04 7)32 3400 • Railway Square 21 1 3777 • Sydney City 267 9111 • Tamwonh 66 1711 • Wollongong 28 3800 • ACT • Fyshwick 80 4944 • VIC • Ballarat 31 5433 • Bendigo 43 0388 • Box Hill 890 0699 • East Brighton 592 2366 • Cobur~f383 4455 • Essendon 3 79 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 • Buranda 397 6233• Ca irns 311515• Chermside 3596255• Redbank2885599• Rockhampton279644• Southport329863• Toowoomba 38 4300 • Townsville 72 5722 • Underwood 341 0844 • SA • Adelaide City 232 1200 • Beverley 3471900 • Darlington 298 8977 • Elizabeth 255 6099 ;!,:J:'/1',/™·---~-,-·--···-~=•m- ~"'"""""··•--.•·• .. ·•~---.. -- .. -·~ Order by phone: 24 hour despatch through DSXpress. CALL TOLL FREE (008) 22 6610 (Sydney Area, call 888 2105) ~ · EL , - ~ PTY LTD 1TH ICS Your house Virtually every household in Australia uses M.E.N. and it is assumed to be a very safe system. But it is not foolproof. Unless checked out from time to time, it can develop a very dangerous fault. By LEO SIMPSON M.E.N. stands for "multiple earth neutral" and is the system used for wiring the majority of domestic electrical installations in Australia. As specified in the SAA Wiring Rules (AS 3000-1986), the mains neutral wire is connected to earth at the user's switchboard. In most houses this means that the 240V AC mains supply is connected from the power pole in the street via via two cables, active and neutral, with the neutral wire connected to earth via the consumer's water pipe. The earth connection point on the water pipe is usually just at the point where the pipe enters your house. This is important because you need to examine it occasionally to make sure that the connection is sound. As we will show, that connection is vital to the safety of everyone in your household. Typically, the active and neutral 25A SWITCH WATT-HOUR METER oiriN~RE~r FUSE l--,U.-'0---TO OFF PEAK HOT WATER SYSTEM 6OA SWITCH NEUTRAL LINK SWITCH BOARD Fig. 1 76 SILICON CHIP EARTH TO CONSUMER 'S -:WATER PIPE • • g wires from the power pole to your house have a capacity of 70 or 100 amps. This means that the maximum electricity consumption (volts multiplied by amps) for the household is nominally 18.9 kilowatts in the case of 70 amp mains and 24 kilowatts in the case of 100 amp mains. Happily, most homes normally use only a small fraction of their installed wiring capacity although there would be times during winter evenings when it could be easily approached in large households when several radiators, a stove and perhaps one or two other cooking appliances are in use. Why M.E.N? "Multiple earth neutral" is a system which offers improved safety and lower losses in energy transmission. Let's see why. In a normal single-phase 240V AC wiring system (which is what most households have), the nominal voltage of the neutral wire coming into your switchboard is the same as earth, ie, zero volts. But in practice, the voltage is higher because all the current from your house and your neighbours' homes inevitably causes a voltage drop in the neutral ea ble between your power pole and the nearest substation or pole transformer. This is because the resistance of the neutral cable is not zero and so the large currents inevitably mean that there is some voltage present on the neutral. This voltage is a loss in the energy transmission system and is part of the reason why, when At left is a diagram depicting the electrical switchboard of a typical household using the "multiple earth neutral" system. could kill you! The mass of connections to a typical power pole. The neutral return to the substation is the cable to which all consumers are connected (ie, top of photo). Other earthing systems There are two other systems for earthing of consumer electrical installations in Australia. One is known as Direct Earthing while the other ·is referred to as ELCB or Earth Leakage Circuit Breaker. In the Direct Earthing system, the earth wires of the installation are connected to earth via a water pipe or electrode but do not connect to the neutral conductor at the switchboard. In the ELCB system, there are two connections to earth with a sensistive relay coil connected between the two . If a fault current flows to earth, the energy demands are heavy, the mains voltage available at your switchboard is lower than it should be, or would be if it were not for the multiple earth neutral system. Because the neutral wire is connected to earth (ie, the consumer's water pipe), there are actually two return paths for the current pass- potential difference between the two earths will trip the circuit breaker and disconnect the mains supply. Again, in the ELCB system there is no connection between the consumer's earth and the neutral conductor at the switchboard . Throughout most of Australia the ELCB system has been superseded by the MEN system described in the article. The ELCB system was prone to false tripping and improved safety can now be provided by using the MEN system combined with core balance relays. ing through the appliances in your home. Some of the current passes back along the neutral, back out to the power pole and thence via the power lines back to your local substation, pole transformer or whatever. The rest of the current passes back via the earth wire to the water pipe and then via good old Terra Firma itself to the substation. (Editor's note: we have simplified matters here by ignoring the inherent current balance of threephase power energy distribution systems. For a brief explanation, see the panel headed, "Current flow, three-phase and all that".) If you are not familiar with the mains distribution system this may all sound like heresy but it is true. Have a look at Fig.1 which depicts the mains wiring of a typical household installation. This diagram shows the active and neutral connections to the switchboard. The active wire is connected via two watt-hour meters one feeding the off-peak hot water service and the other feeding the rest of the power circuits in the household. Following each watt-hour meter is a large rotary or toggle switch which is typically rated at around 60 amps and is connected via a short length of cable to the Active link. This is a heavy brass bar with quite a few screw connections to take the wires feeding the fuses or individual circuit breakers. The whole Active Link assembly is housed under a plastic cover to avoid accidental contact by anyone who has access to the switchboard. A typical modern houshold may have one 25-amp circuit to feed the stove and oven, three 15-amp circuits to feed all the power points and two or three 8-amp circuits for all the lights. By the way, in the wiring standards, power points are referred to as GPOs which stands for General Purpose Outlet. All the neutral return wires from the household power and lighting circuits are connected together at the Neutral link which is a similar assembly to the Active Link. The difference is that the Neutral link NOVEMBER 1987 77 What's available in clamp-on current meters The Escort ECT-620 has two DC and two AC voltage ranges, two resistance ranges and three current ranges up to 1000 amps AC. It is priced at $155 (tax incl) from Emona Instruments. Phone (02) 519 3933. The Emtek DCT-300 has three DC and two AC voltage ranges, four resistance ranges and three current ranges up to 400 amps AC. It is priced at $141.92 (tax incl) from Geoff Wood Electronics. Phone (02) 427-1676. What's in a clamp-on meter The typical clamp on current meter is a current transformer with a turns ratio of 1 : 1000 with the laminated steel clamp providing the magnetic core of the transformer. With the clamp placed around a cable carrying 1 0 amps AC, the secondary will generate 1 0 milliamps. In analog clamp meters the secondary current is rectified and read on a moving coil meter. In digital clamp meters the secondary current is applied to a shunt resistor and the resulting voltage is read by the digital metering circuitry. Some clamp-on adaptors for digital multimeters will measure DC as well as AC by using Hall effect sensors. 78 SILICON CHIP The Escort ECT-620 has one AC voltage range, one resistance range and two current ranges to 300 amps AC. Priced at $118 (tax incl) from Emona Instruments. Phone (02) 519-3933. also carries all the earth wires from the power and lighting circuits as well as the main earth wire which connects to the water pipe. It also connects to the neutral wire which comes directly from the power pole. So there is a straightforward circuit and it would be natural to assume that all the current which comes in via the active feed wire goes out via the neutral wire. In other words, the current in the active wire is equal to the current in neutral wire. Well, it ain't necessarily so. It is possible that half or more of the return current goes via the Earth wire and the remainder goes via the neutral back to the power pole. To take a particular example, if you were using a 2400 watt radiator which draws 10 amps from the active line, 8 amps might go via the earth wire to the water pipe and the remainder, 2 amps, would go via the neutral return. The simple explanation for this is that the resistance of the neutral cable back to the substation or pole transformer is slightly higher than the very low resistance via the earth path to the same point. Ergo, some current goes via Earth and some goes via neutral. It can't all go via neutral. Having come to terms with this previously unconsidered fact, what does it mean? It means that the supply authorities are able to obtain lower supply losses in the return path than they otherwise would if the MEN system was not used. They also experience less voltage flashovers from neutral to Earth during thunderstorms in appliances which are permanently connected. A common example of this used to occur in stove heating elements. Even though the stove or oven might have been turned off, a lightning strike on a power line would cause many stove elements to break down to chassis. With the MEN system this is not a problem. Where lie the problems? Corrosion is the first problem. Since many small appliances these days use thyristor power controls there is inevitably a DC current imposed on the mains supply. Some of This shot shows Tandy's Micronta clamp-on meter measuring the current in an earth wire to a water pipe. The present model has two AC voltage ranges from 6 to 300 amps AC, and is available from all Tandy stores for $64.95 (Left hand by courtesy of Greg Swain - the rest of him has been edited out.) this direct current will flow via the connection between the earth wire and the water pipe. And the very presence of DC will accelerate corrosion which naturally occurs when dissimilar metals are used, as they normally are. Ultimately, corrosion of the connection between the Earth wire and the water pipe will mean that the connection will be broken. Or if it does not physically break, its resistance will be so high as to be useless. OK, so that means that if you have lost the Earth connection and an appliance such as your washing machine breaks down from active to chassis, the chassis could be lethal. That is bad enough but consider another possibility which is even more likely and which has occurred a number of times quite recently in Sydney. If corrosion has occurred in the connection between your main Earth wire and the water pipe, is it not just as likely that corrosion has progressed in the neutral connections between your house and the power pole? Of course it has. What that means is that the neutral return could now have an appreciable resistance and could easily be around 20 ohms or more. If that is the case, all of the return current will go via the Earth and water pipe. But what if the earth connection has broken? What that means is that if you now have an appliance drawing 5 amps, the voltage impressed across the neutral return path from the switchboard to the power pole will be 100 volts AC. Hmm. So the Neutral link will be floating at 100 volts AC above earth. And all the earths from the various points in the house are connected to the Neutral link. So every appliance plugged in will have have its chassis floating at 100 volts AC above earth - a lethal situation! So your fridge, washing machine, toaster and microwave oven could all be sitting there silently with their metal cabinets at a substantial voltage above earth. Touch one of those and a properly earthed metal object, such as your kitchen sink, at the same time, and it could be curtains! It does happen Don't think that the this scenario is a remote possibility. It happened very recently to a close acquaintance of yours truly. We'll call him Jacko, to protect the innocent. He discovered just such a fault condition had occurred in his home but the reason why no-one had been electrocuted was that his washing machine was separately earthed via a water-pipe just outside his laundry. If he hadn't been the naturally super-cautious person he is, and had not earthed his washing machine separately, years ago, someone could be dead today. But there is more to the story. Having become aware of the dangerous situation with the Earth NOVEMBER 1987 79 parently thinks that current flows into an appliance but not out of it. Eventually, Jacko was able to explain the situation in words of less than two syllables and persuaded said inspector to measure the current in Active, Neutral and Earth, using his tong tester (we'll explain that in a moment). Result: 10 amps in Active, 10 amps in Earth, zero amps in Neutral; inspector perplexed but agrees that something is wrong with the Neutral. Enter council linesman. He renews neutral connection at eaves of house, pronounces situation fixed, leaves. Enter another inspector, tests for current in neutral return, finds none. Problem at power pole. Several days later another pair of linesmen return to renew the active and neutral connections at both the house and power pole. The saga goes on. At the time of writing, an inspector is due to return and pronounce the installation safe . So far, six people from the supply authority have been involved. If all houses in Sydney had to be checked and rectified, it could take a hundred years at this rate. What you should do These two photos show a quick and dirty approach to making a clamp-on meter. The top shows an old relay with the active lead inserted, while below is a transformer doing the same job. and neutral return, our friend Jacko contacted the local electricity supply authority to have the situation rectified. Their reaction does not inspire confidence. On being told that the neutral return was high resistance, the first inspector tested the line with a test-lamp which tests for the presence of voltage only. On detecting the presence of voltage across the active and neutral, he pronounced the situation normal. No problem. On being told that all the current from a 10-amp load was going via the Earth instead of neutral he apparently had difficulty comprehending the situation. (It should be noted here that a test lamp is a very crude test instrument which is essentially a neon 80 SILICON CHIP lamp. It tells the user if there is more than about 90 volts peak present. It does not give any indication of just how much voltage is present. Inspectors seem to place undue reliance on such crude instruments. Enter another inspector, more senior than the first. On having the problem explained to him, and on being asked to measure the currents in active and neutral his response was, "I can measure the current in the Active but I can't measure current in the Neutral because it is all used in the appliance"! Hmm. Here we have a big problem. Here is a senior electrical installation inspector who apparently does not know how current flows! Heap- Do you know where your main earth point is? Take a walk around your house. Where does the water pipe enter the house? That is probably the point where you will find the earth wire connected via a screw clamp. If you can't find it, have a look at your switchboard. There should be a note (in white paint) saying where the earth is. For example, in the author's switchboard, the note says, "Main earth under hall" and lo and behold, if you went under the house (it is partly two-storey) there you would find the earth wire clamped to the water pipe. In some areas where the water service is run in plastic pipe, the authorities specify that the earth connection is made to a long copper-clad steel spike or rod driven at least 1.2 metres into the ground. Alternatively, the earth connection may be made to a strip electrode at least three metres in length and buried at least 45cm underground. When you find the connection, inspect it carefully to see that it is sound and not corroded. If the connection is badly corroded you should have it attended to by a licensed electrician. Alternatively, the earth wire should be cleaned up and reconnected. But before Current flow, 3-phase and all that touching it you should switch off the power with the main switch on your switchboard. If you have another switch, such as for an offpeak hot water service, switch that off too. The reason for switching everything off is to avoid the possibility of having any current flowing in the earth path when you disconnect it. If current was flowing, and the neutral path was poor, you would produce exactly the hazardous situation we have described above. Alright, having determined that your earth connection is satisfactory, how do you check the neutral The second simplification involves the concept of neutral current flowing back to the substation, pole transformer or whatever. This ignores the fact that domestic mains power distribution from the power pole has three phases, each of 24OVAC (with 120 degrees phase difference between each) . In an ideal system, the currents should be balanced so that there is no current flowing in the neutral line. Domestic systems are never ideal though, so appreciable current does flow in the neutral. We have made a number of simplifications in the writing of this article. The first is that we have said that current flows from active to neutral or from active to Earth, as the case may be. In fact, since we are talking about 5OHz alternating current, the current changes its direction 1 00 times a second. It is convenient to think of current flowing from the active line though, because in the words of an electrician we know, "It's the activ_e line that gets ya. It's the one with the juice!" regard themselves as familiar with mains wiring. But there is a way of checking it. There is only one safe and legal way and that is to use a clip-on meter (also known as a tong tester.) return path? At this point we must warn that you must not even think of tampering with the wiring of your switchboard. Not only is it illegal but it could be extremely dangerous, even to those who Special "First Issue" Offer to 'Silicon Chip' readers only! 150Amp Clamp-On Current Probe for just $97.75?1}:S': To coincide with the first issue of 'Silicon Chip' and this special feature on electrical safety, Elmeasco have obtained a limited quantity of clamp on current probes. The Model 4000P is a current transformer capable of measuring ac current up to 150A without breaking the circuit under test. You simply clip the probe to the conductor - just like a clothes peg! The probe connects to any multimeter (lead and plugs supplied) capable of measuring 200mA. In fact the reading on the multimeter will directly correspond. Thus a SA current in the conductor will give a meter reading · of 5mA. You can use the probe with conductors up tq 11 mm in diameter. If you've read the article, you'll know what a great safety accessory this probe can be. Contact your local Elmeasco Office. Model 4000P Specification Current range : 1A to 150A Accuracy : ± 2.5% + 0.15A Division Ratio : 1000:1 Working Voltage : 300V ac rms max Maximum Conductor Size : 11 .1mm (7/16in) ELMEASCO Instruments Pt,,. Ltd. Cheques & Bankcard Welcome NEW SOUTH WALES VICTORIA QUEENSLAND SOUTH AUSTRALIA WESTERN AUSTRALIA 15 McDonald Street, MORTLAKE P.O.Box 30, CONCORD NSW2137 Tel : (02) 736 2888 Telex : AA25887 Fax : (02) 73 3663 12 Marooncah Highway, RINGWOOD P.O.Box 623, RINGWOOD VIC 3134 Tel: (03) 879 2322 Telex : AA30418 Fax : (03) 879 8688 192 Evans Road, SALISBURY P.O.Box 274 SALISBURY OLD4107 Tel : (07) 875 1444 Telex : AA44062 Fax: (07) 277 375:i 241 Churchill Road, PROSPECT P.O.Box 154 PROSPECT SA5082 TEL : (08) 344 9000 TELEX : AA87519 FAX : (08) 269 6411 Scott House, 46-48 Kings Park Road, WEST PERTH P.O.Box 901, WEST PERTH WA0005 Tel : (09) 481 1500 Telex: AA94765 Fax : (09) 321 3026 NO VE MBER 1987 81 The Fluke 80i-410 clamp-on current probe is intended for use with digital multimeters and will measure up to 400 amps AC and DC. It can measure alternating current through a cable without having to break the connection. Now many readers probably have not heard of a clip-on meter let alone have access to one but we'll address that problem a little later. In fact there is no need to measure the current in the neutral return. What needs to be done, and which is a lot easier, is to measure the current in the earth wire to the water pipe. As illustrated in one of the accompanying photos, a clip-on meter does not have meter prods but has a pair of clamp jaws which close around a cable to measure that current. The clamp jaws actually constitute the core of a current transformer. The ea ble to be measured forms the primary winding of the transformer while the meter monitors the secondary winding in the instrument. One of the cheapest available clip-on meters is the Tandy model (Cat No 22-161) which currently sells for $64.95. Checking the earth current Measuring the earth current is simply a matter of fitting the clip-on meter over the earth wire to the water pipe, or over the water pipe itself (between the earth wire connection and the point where the pipe enters the ground), if that is possible. But before you do that you must be sure that your load current is known. The way to do that is switch off all appliances and light fittings in your house, plus the hot water system. Then connect a large heating appliance of known rating. 82 SILICON CHIP If possible, use a 2400W radiator, on its highest setting. This will draw a current of close to 10 amps, depending on the value of the mains voltage and the tolerance on the heating element. So with the 2400W radiator switched on, you know you have a current from the Active of 10 amps. The question is, what is the neutral current? Measure the current in the earth wire, subtract it from 10 amps, and you have the answer. If the earth current is more than say, 5 amps, you have cause for concern. In that case, you should contact your local electricity authority and have them check out your neutral connection. Don't do this test during or just after wet weather. When the ground is saturated, more current will tend to flow via earth than via the neutral path. Most readers will not have access to a clip-on meter but as we have found, it is possible to cobble up a meter circuit to do the job. For one example, we used the core and winding of an old relay and for another, we used a small transformer with part of its windings removed. The object of the exercise is to modify (or butcher) the relay or transformer so that you can fit an earth wire within the magnetic circuit of the core. In the case of the relay, we loosened the screw holding the coil to the armature so that a wire could be slipped into place and then retightened the screw. The voltage developed by the relay coil is then measured across the coil terminals. Similarly, for the transformer, the clamp(s) holding the laminations in place is first removed, then the coil can have turns removed to allow space for the abovementioned wire to be slipped into place. The transformer is then reassembled to allow the measurement to be performed. The only problem with this method, crude and simple as it is, is that you need to calibrate it. Well, this is fairly straightforward and can use the same 2400W radiator, or whatever, as a reference load. You will need a short three-core extension cord fitted with plug and socket. The idea is to separate out the active cable from the power cord and insert it into your cobbled up version of the clip-on meter. Then plug in the radiator and take a note of the reading generated by the coil. This can then be used as a rough guide to the current being measured in the earth wire. Note that it is a rough guide only as such a measuring set-up is unlikely to be linear. Warning Many people will not be qualified or feel confident to make any measurements as described in this article. If they suspect that their electrical wiring is unsafe, they should contact a licensed electrician or the electricity supply authorities. A number of serious questions remain to be answered. Do the electricity supply authorities have any program for periodic checking of customers' Active, Neutral and Earth connections? Or does the first indication come from the customer, complaining that they "got a tingle from that appliance"? And are plumbers and employees of the various Water Boards instructed to take any special electric al safety measures when disconnecting a customer's water supply? In the light of this article there is a previously unsuspected hazard to plumbers and Water Board authorities as well as to the public in general. If readers have any further information on this subject which should be published, please write to us at Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. ') DIGITAL FUNDAMEN'I'ALS. • . I This is the first in a series of short courses that will quickly teach you the basics of digital electronics. We 'II begin by considering binary and· hexadecimal numbers. .. j • .JI I LESSON 1: BINARY DATA By Louis E. Frenzel, Jr. .1 r , ... .... I Digital logic circuits use on-off, pulse-type signals to process and communicate information. Such circuits are now found in virtually all types of electronic equipment. This series of self-instructional lessons introduces the subject of digital electronics. It will show you how digital circuits operate. What you can expect to learn in this article is this: the difference between analog and digital methods; why digital methods are used; binary data representation; converting between binary and decimal numbers; understanding hexadecimal, BCD and ASCII data; how to represent binary information with electronic signals and components; and exactly what is serial and parallel data. analog and digital. The terms analog and digital r efer to the types of signals and circuits used in electronic processes. An analog signal is one that varies smoothly and continuously. Fig.1 shows several kinds of analog signals. A constant positive DC voltage level of 6 volts is illustrated in Fig.lA. An alternating current (AC) signal known as a sinewave in shown in Fig.lB. It has CONSTANT OC VOLTAGE +6V----'/"--r---- VOLTAGE VALUE Electronic applications The three basic applications for electronics are communications, computation and control. In communications, we transmit information from one place to another by wires or radio techniques. In computation, we process data. Numerical, text and o,ther types of information are manipulated with mathematical or logic techniques to create new information. Computers, of course, are our data processors. Control refers to automating industrial and other processes. That means using electronics methods to operate equipment remotely and/or automatically. All three areas of electronics are well known and you can probably name numerous examples of each. Analog and digital There are two basic methods used in implementing electronic communications , computation, and control processes. And there are two basic methods of representing information. Those two methods are O V ' - - - - - ' - -- ----TIME (b) (a) RANDOM ANALOG SIGNAL (c) Fig. 1 - Three sample analog voltages: A, constant DC voltage typical of that produced by a voltage regulator circuit; B, sinewave signal typical of an unmodulated AM broadcast station or signal generator; and C, random analog signal that may be the plot of temperature, light intensity during a cloudy day, or just about any type of non-periodic event. NOVEMBER1987 83 tional weights as units, tens, hundreds, thousands, etc. a peak value ± 3 volts and a peak-to-peak value of 6 Each position is a successively larger power of 10: 10 volts. A randomly varying analog signal is shown in to the O power = 10° = 1; 10 to the 1st power = 10 1 Fig.lC. Although the latter may appear to be random, = 10; 10 to the 2nd power = 10 2 = 100; 10 to the 3rd power = 10' = 1000; etc. The simple illustration it could be a track of temperature during a 24-hour below shows how any decimal number is structured period, a section of a voice signal, or the rise and fall and evaluated. of a local tide. The other type of electronics signal is a digital one. Instead of a smooth, continuous Thousand Hundreds Tens Units variation, a digital signal is made up of clearly 1 9 8 5 1 X 1000 = 1000 9 X 100 = 900 8 X 10 = 80 5 X 1 = 5 defined discrete voltage or current levels with abrupt changes between them. The most 1,000 900 80 5 = 1985 + + + common type of digital signal is the two-level or binary-pulse type signal shown in Fig.2. In In digital circuits, we use binary numbers rather Fig.ZA, the signal switches between the O and + 5V levels. In Fig.2B, the two switched states are - 12 and than decimal numbers. In the binary number system + 12 volts. only two digits, 0 and 1, are used. For example, the While digital signals can have more than two binary number 1010011 represents the decimal discrete levels, typically they do not. The term digital number 83. The digits O and 1 are called binary digits is virtually synonymous with the term binary which or bits. Like the decimal number system, the binary implies two levels. system uses a positional or weighted method. Instead of weights of some power of 10, the position weights in Representing information the binary number as some power of 2. Thus we have Digital and analog signals typically represent infor2 to the O power = 2° = 1; 2 to the 1st power = 21 = mation to be communicated or processed. For exam2; 2 to the 2nd power = Z2 = 4; 2 to the 3rd power = ple, the analog voice signal generated by a microphone Z3 = 8; etc. Note that each successively higher weight might be modulated and transmitted by radio. Or the is twice that of the preceding weight. binary input from a keyboard may be processed by a The structure of a typical binary number is shown digital computer to enter your savings deposit. Those below. signals, representing information (data), are then processed to accomplish some useful end result. Analog Weight 64 16 4 2 1 32 8 1 Number 1 1 0 1 signals are processed by analog (linear) circuits. 0 0 LSB MSB Binary data is processed by digital logic circuits. At one time, virtually all electronic signals and pro64 + 0 + 16 + 0 + 0 + 2 + 1 = 83 cesses were analog. However, with the development of the digital computer, digital methods became more Notice that the binary number is usually made up of popular and widely used. Then, semiconductor a number of bits; in this case, eight. Each bit may be technology gave us digital integrated circuits and the binary O or binary 1. The weight of each position is inmicroprocessor, both of which have revoltionised elecdicated. Note particularly the least significant bit tronics technology. Today, digital methods are prefer(LSB) with the lowest position weight and the most red because of their ease of implementation, low cost, significant bit (MSB) with the highest position weight. reliability and overall effectiveness. While digital The question is: how do you determine what decimal techniques will never replace analog techniques comquantity is represented by a given binary number? pletely, the use of digital techniques has grown continuously over the years and today virtually dominates Converting a binary number to in most electronics applications. Decimal verses binary numbers The information or data to be communicated, processed, or used for control purposes is usually numerical in nature. For that reason, the main language of digital techniques involves Weight 32 16 numbers that can also Number 1 1 represent letters of the 1 X 32 = 32 X 16 = 16 alpha bet and even 32 t16 + special control features. You are familiar with the decimal number system where we use the digits O through 9 in various combinations to represent any quantity. The decimal number system is based upon a method of giving numerical weights to each position or digit in the number. Recall that we usually refer to those posi84 SILICON CHIP its decimal value Evaluating a binary number means determining its decimal value. The process is similar to that used in evaluating any other decimal number. The illustration below shows what we mean. 8 1 X 8 = 8 0 8 + X 4 2 1 0 4 =0 1 2 =2 0 1=0 0 X +· 2 0 + X 0 -- 58 To determine the decimal value of a given binary number, all you do is multiply each bit by its position weight, then sum all those values. Looking closely at the process above, you can see that those bit positions with a zero in them actually have no effect on the outcome. For that reason, they can be ignored. You can OV OFF ON OFF -12V -- W 00 0000 0001 0010 0011 4 5 0100 0101 0110 0111 6 7 Fig.2 - Two commonly used digital signals used in electronic circuits. The left one (A) is from a singleended output such as from a 4000 chip series; and B, the output from a balanced op amp that uses ± 12V DC rails. quickly evaluate the binary number by simply adding up the weights of those positions that contain a binary 1 bit. The secret is in remembering the weight of each position, and that's easy. Converting a decimal number to its binary equivalent Another procedure that you will find handy is that for converting a decimal number into its binary equivalent. The process is essentially that of dividing the original number by two, then dividing the resulting quotient by two continuously until a quotient of zero is obtained. The remainders resulting from each of those divisions form the binary number. Division Remainder 84 .,_ 42-'21 -'10 _,_ 0 LSB 0 1 0 1 0 5 .,_ 2 = 2 2 _,_ 2 = 1 1 .,_ 2 = 0 Binary 0 1 2 3 Therefore, 84 = 1010100 1 MSB Maximum decimal value A binary number, or binary word as it is sometimes called, usually consists of a fixed number of bits when used within one confined system. With that number of bits you can represent a certain maximum value. The same is true of decimal numbers. With a given number of digits, some maximum value can be represented. For example, with four digits, the maximum decimal value is 9999. With a 4-bit binary number. the maximum value is 1111. The question is: what's the maximum decimal value for a given number of binary bits? This value can be computed using the simple formula shown below: Hexadecimal Binary 0 1 2 0000 0001 0010 0011 0100 0101 0110 0111 6 7 1 1100 1101 1110 1111 To represent larger and larger decimal values, binary numbers with more bits must be used. And, as the binary numbers get larger, they become increasingly difficult to work with. For example, it takes 20 bits to respresent one million (1,0448,576 to be exact). It's tough enough to remember a long decimal number, but just imagine the problem of remembering a very long binary number. That task is made easier by the use of a special shorthand known as hexadecimal notation which uses hexadecimal numbers. Hex means six and, of course, decimal means ten; therefore hexadecimal means sixteen. Hexadecimal refers to a special notation as well as a number system using a total of 16 digits. Those digits are the decimal numbers 1 through 9, and the letters A through F. Each digit corresponds to its equivalent 4-bit binary code as shown in Fig.4. The idea is to use the hex digit corresponding to each 4-bit where M is the maximum decimal value and n is the number of bits. To illustrate the use of the formula, let's determine the maximum decimal value you can represent with 4 bits. This is done as shown below: - 12 13 14 15 Hexadecimal notation 4 5 24 10 11 1000 1001 1010 1011 word with their decimal equivalents. There are sixteen values, 0 through to a maximum of 15. Remember that 0 (zero) is a number and it is one of 16 values that can be represented by a 4-bit binary number. Eight bits is a very common binary word size. With 8 bits, you can represent decimal values up to 28 - 1 = 255 . 8-bit words or numbers are so widely used that they have been given a special name. An 8-bit number or word is called a byte. You will also hear the term nibble to refer to 4-bit words. 3 = Binary Fig.3 - The decimal/binary equivalents are listed here for the first 16 numbers. Keep in mind that 0 (zero) is a number. M = 2" - 1 M Decimal 8 9 ON ~TIME 2 = 42 2 = 21 2 = 10 2 = 5 Decimal = (2x2x2x2) - 1 = 16 - 1 = 15 Fig.3 shows all possible combinations of a 4-bit Hexadecimal. 8 9 A B C D E F Binary 1000 1001 1010 1011 1100 1101 1110 1111 Fig.4 - The hexadecimal/binary equivalents are listed here for the first 16 numbers. Compare this illustration to that of Fig.3. When you use the hexadecimal number system for a short while, you will begin to appreciate the convenience of the system. NOVEMBER 1987 85 segment of a long binary number. The result is a shorter hexadecimal number that is far easier to remember and apply. To convert a binary number into a hexadecimal number, all you do is divide the long binary number into 4-bit segments starting with the LSB on the far right. Then, you replace each of those 4-bit segments with the corresponding hex digit from Fig.4. The result is illustrated below. B 1 ~ 0 ~ 0 MSB B t1 1 UP (1) DOWN (D) 1 LSB +5V MSB 0 (DV) 0 (DY) 1 (+5V) LSB 1011 /0001 /0111 /0010/1101 B 1 7 2 D Changing a hexadecimal number back into its binary equivalent is also easy. You simply reverse the above process; ie, you replace each hexadecimal digit with its binary equivalent and string all of the resulting bits together as shown below. 6 F 9 0 5 0110/1111 /1001 /0000/0101 Binary coded decimal (BCD) Besides the standard binary notation for representing a decimal number, some special variations are also widely used. The most common is binary coded decimal (BCD). The BCD system is essentially a hybrid of both the binary and decimal systems. It uses binary digits, but a separate 4-bit group is used to represent each decimal digit individually. The BCD code is the same as the first ten digits (0 to 9) of the hexadecimal code in Fig.4. To represent a given binary coded decimal value, you simply use the 4-bit group representing each digit. An example is given below using the decimal number 4891: 4 8 9 1 0100 1000 1001 0001 A space is left between each 4-bit group to denote separate digits. BCD is a widely used method as it greatly simplifies the conversion process between binary and decimal. It is also an aid in improving communications between man and machine. Where a human operator must interface with a piece of communications equipment, BCD is normally employed. Keyboards generally produce BCD outputs. BCD information from a piece of electronic equipment is normally used to drive the 7-segment decimal displays that are so popular. ASCII A special form of BCD is widely used in computers. Known as the American Standard Code of Information Interchange (ASCII, pronounced ass-key), it normally uses 7-bits to represent not only the decimal digits Oto 9, but also letters of the alphabet (both upper and lower case), punctuation marks, and special symbols. Some examples of ASCII designations are shown below. 8 L J ? Bell 86 011 100 110 011 000 1000 (Last 4-bits same as BCD) 1100 1010 1111 0 111 (This code rings a bell or sounds a tone.) SILICON CHIP 1 (+5V) • 1 (+5V) • .,. Fig.5 - A simple manual switching circuit can be constructed and used to demonstrate binary data for decimal numbers O to 31. The ASCII code is widely used in computers. It is the main code used in communicating information between computers and peripheral devices. For example, virtually all printers produce hard copy output from ASCII input supplied by the computer. ASCII coded data is also what is normally transmitted and received by a modem in digital communications. Representing binary numbers with hardware The reason for using the binary number system in digital equipment is that it is easier to implement binary electronic circuits than it is decimal circuits. Decimal circuits would have to represent at least 10 states. With binary, only two states are required. As a result, any electronic component that can assume two states can be used for binary representation. The result is smaller, simpler, cheaper and faster circuits. The most obvious component to represent a bit is a switch. A switch can be off or on and, therefore, can represent O and 1. Fig.5 shows how a group of slide switches is used to produce binary data. The number being displayed on those switches is 10011 , whose decimal equivalent is 19. The illustration also shows what the schematic diagram may look like. When the slide switch is down, it is closed. The voltage at the output, therefore, is 0 volts or ground potential. That typically represents a binary O (sometimes referred to as a logic low). When the switch is up, it is open. As a result, the output is + 5 volts as seen through the resistor. This represents a binary 1 (or a logic high). Another obvious choice for a component to repre' I , ON: 1 - Q - , OFF:O '' 0 -a- o -a- o -a.·:- o I I 0 = 42 Fig.6 - A six-unit light emitting diode (LED) display can be used to display binary data for decimal numbers from O to 63. The most significant bit is at the display left side. FOUR BITS OF PARALLEL DATA 0 '""' SOURCE OF DATA I I I I I I 0 DESTINATION OF DATA ov- 1 ...., 1. +sv- 1 Fig. 7 - 4-bits of parallel data from a circuit like that in Fig.5 can be transmitted over four lines at the same time. The destination could be another chip on the same circuit board, a remote printer, or some other devices. sent binary data is a simple light. Both incandescent lamps and light emitting diodes (LEDs) are used to display binary information. An off (unlit) display represents a binary 0, while an on (lit) display respresents a binary 1. Fig.6 shows how a typical binary LED display might look. The key component in any electronic circuit is the transistor which is used in digital circuits as a switch. A transistor can be on (conducting), or off (nonconducting). Those are natural conditions representing binary 0 and binary 1 states. Parallel and serial data Binary data in digital circuits is generated, processed, displayed, or communicated. There are two ways in which those things are done: parallel and serial. Parallel binary data is where all bits of a word are generated, processed, transmitted or displayed simultaneously. The data generated by the switches in Fig.5 and that displayed in Fig.6 are both examples of parallel binary data. All bits of the word occur at the same time and can be transmitted from one place to another as shown in Fig. 7. t - START BIT If.-ONE PERIOD ---l-TIME STOP Fig. 8 - An 8-bit serial binary word displayed against time. The other form of binary data is serial. Serial binary data is transmitted or processed one bit at a time. The bits occur sequentially and, therefore, each is handled separately in order. A serial data word is shown in Fig.8. The binary 0's and 1's are represented by voltage levels. Note that each bit occurs for a fixed length of time. If each bit lasts one millisecond, then it will take a total of 8 milliseconds to transmit and process one byte. As you can see, the main disadvantage of serial data is the long time required to transmit or process it. On the other hand, serial data is far less expensive to deal with. Only one set of processing circuits is required to transmit it from one place to another. Despite its low-speed disadvantage, serial data is widely used. It is perfectly suitable for many digital applications. In Lesson 2 next month, we'll take a look at the five basic digital logic elements and learn how to use their truth tables. Reproduced from Hands-On Electronics by arrangement. Gernsback Publications, USA. © SHORT QUIZ ON DIGIT AL FUNDAMENTALS 1 . The three primary eletronics applications are _ _ _ _ _ ,and _ __ __ 2 . a. Smooth , continuous signals are called 5 . An eight-bit number is called a _ _ _ _ _ __ 6 . Write the BCD equivalent of 2805 . - - - - - - - - -- the number ---- b. Digital signals usually have _ _ (how many?) levels. 7 . The special code used to transmit letters as well as numbers is called _ _ _ __ _ _ _ _ __ 3 . Refer to the LED binary display above . What decimal number is represented? _ _ __ _ __ 8 . The maximum decimal value you can represent with 12 bits is _ _ _ _ _ _ _ _ _ _ _ __ 0 MSB -QLSB 4. a. If binary O = O volt and binary 1 = +6 volt, write the binary output voltage levels equivalent to the decimal number 207 . MSB ____ ,____ , _ __ ,___ ,___ ,_ _ _ ,_ _ _ ,_ __ ,LSB. b. The above decimal number expressed as a hexadecimal number is _ _ _ _ _ _ _ _ __ 9. Which method of processing and transmission of binary data is slower? _ __ ____ parallel _ _ _ __ __serial. repas 960t = •- ·e 960t = • - .. c: :geot ·e .o .o 0000 000 ~ 11:::>S'v' . L 0 ~00 ·g a1Aq ·g ::I:) ·q :••• wo •• = 8S7 ' 9+ '9+ '9+ '9+ ·o ·o •9+ •9+ ssv-i ·e (I-ewpap) 69 • = (AJBU!Q) .oo .o •O • ·v ·s ·c: OMI ·q :BoIBUB ·e iOJjUO::l 'UO!IBlndwo::i 'SUO!JB::l!Unwwo::i . • NOVEMBER 1987 87 Silicon Chip's Guide to Discrete Electronic Devices With this first issue of "Silicon Chip" magazine, we begin a series of articles on discrete electronic components. These embrace virtually all electronic components except for integrated circuits. And if you want to understand how integrated circuits work, it is essential to have a prior understanding of discrete components. Electronic circuit components can be divided into two broad categories: discrete and integrated. Discrete components are those which usually only have two or three terminals and provide only 88 SILICON CHIP one circuit function within their package. Integrated components are these days mostly integrated circuits. These usually contain thousands or even millions of internal circuit components which together may provide many functions. Discrete components can be regarded as the basic building blocks for all electronic circuits. They are individually soldered or otherwise connected into circuit and they are made in an almost countless variety of types and values. Passive & Active Devices Within the broad range of discrete devices there is a further division into Passive and Active devices. These terms need defining although as we will ultimately see, the dividing line between active and passive devices is a blurred one. According to The New Penguin Dictionary of Electronics an active device is one which "introduces gain or has a directional function". More generally, an active device Left: all the components in this photograph are discrete devices except for the integrated circuit. Most discrete devices have only two or three connections, but some (such as valves) have many more. Our series will look at the majority of devices. can be one which amplifies, detects or otherwise changes the shape of a signal waveform. Within that definition we can include transistors, diodes and a whole host of semiconductor devices. Similarly, passive devices are those which do not amplify or change the shape of a signal waveform. They include resistors, capacitors, inductors and variations and combinations of these devices. Active & Non-linear Where the distinction between active and passive devices becomes blurred is with the terms linear and non-linear. Most passive components are said to be linear which means that their output is more or less similar, or in direct proportion, to their input. Under that definition most active components can be said to be non-linear. The tricky part comes when considering components such as thermistors which are a special type of resistor. Thermistors are certainly not linear but they are not active either. Fuses, another type of resistor, are passive but also highly non-linear. Incandescent lamps (the familiar light globes), which are resistive components, are again highly non-linear, because their light output and resistance is not at all proportional to the amount of current fed through them. The more you look into electronic components the more you will find that none of them can be simply defined as active or passive, linear or non-linear. Bear with us though, because even though the distinctions are blurred, the scene will become a lot less confusing as you read on. For the moment then, let us blithely assume that everything is black and white and carry on with the thought that there really are these two broad divisions of discrete electronic devices. In fact, TABLE 1: ACTIVE AND PASSIVE DEVICES Active Diodes Transistors Silicon controlled rectifiers Triacs Light emitters Light detectors Trigger devices Hall effect devices Thermionic devices Gas discharge devices Cathode ray tubes X-ray tubes Camera tubes Magnetrons Travelling wave tubes let us list a whole gamut of components under those two broad headings, as shown in Table 1. We could go on but we have probably already started arguments among the academics as to whether some of those devices listed above are legitimate or whether they are merely variants of others. For example, relays and solenoids might be regarded as special types of inductors, while light dependant resistors, thermistors and strain gauges might all be regarded as variants of the broad category of resistors. Well so be it. We have started a few arguments. But we have also left out many devices which are crucial to electronics such as the many different types of transducers, motors, power sources, and peripheral components such as switches, connectors and heatsinks. While we are in the process of making definitions, let us comment on the word discrete. Some people take this to mean small and low power, especially when applied to semiconductor components such as diodes and transistors, which tend to be very small. It is true that most discrete electronic components are very small and there is a continuing trend to make them much smaller. But in using the word discrete to describe the whole gamut of electronic devices, we are embracing some very large and high power components indeed. These can be the very large transformers, Passive Resistors Capacitors Inductors Transformers Relays Solenoids Light dependant resistors Strain gauges Piezoelectric devices Quartz crystals Thermistors Ferroelectric components Incandescent lamps Fuses Antennas capacitors, reactors, rectifiers and circuit breakers used in electrical power distribution. And let us not forget the very large valves used in radio and television transmitters and the even larger antennas used to broadcast the signal. In fact, we could point to specific examples of all the classes of components listed above which are very large and rated for very high power, as well as examples at the other extreme which are highly miniaturised and operate at very low powers. The smallest of these are called surface mount components and these are quite difficult to handle, simply because they are so small. They are specifically designed to be handled and assembled into electronic equipment by machine. Finally, we made the comment above that most discrete components have only two or three connecting terminals and this is indeed true. But it is possible to point to devices which have many terminals, even though they truly come under the heading of discrete devices. Some examples of these are · valves, transformers and cathode ray tubes, all of which can have six or many more terminals. This is just another case where the general rule can be shown not to apply universally. Here then is the end of the beginning. In the next chapter we shall look at the most simple and perhaps the most commonplace discrete component, the resistor. ~ NOVEMBER1987 89 AMATEUR RADIO By GARRY CHATT, VK2YBX Introducing amateur radio With the ready availability of low-priced equipment, there's never been a better time to get started in amateur radio. Here's a quick rundown on what it's all about. Amateur Radio is an exciting hobby enjoyed by over 15,000 enthusiasts in Australia. It is a process of constant learning and acquisition of new skills through experimentation and discussion with enthusiasts with similar interests worldwide. Amateur radio allows access to the latest radio communications techniques and serves as an informal technology transfer on an international basis, often circumventing the red tape of commercial enterprise. The amateur station may be either mobile (ie, fitted to a vehicle) or installed at home in the "shack", allowing the enthusiast to talk to like-minded individuals over distances of hundred of kilometres, and even in other countries. Amateurs have long been recognised as leaders in the development of the more experimental and unconventional modes of transmission and communication techniques. Slow scan television, packet radio, satellite communications - all are now accepted methods for communication on a commercial basis and were pioneered by amateur radio operators. In fact, you could say that Marconi was a radio amateur of sorts! World exploration often relies on amateur radio. Thor Heyderdahl used amateur radio on his Kon Tiki and Ra expeditions, as did Dr David Lewis during his 1978 Antarctic ex- The Yaesu FT726R is a fully synthesised 10W transceiver capable of operating on the 6-metre, 2-metre and 70-centimetre bands. (Photo courtesy Dick Smith Electronics). 90 SILICON CHIP Yaesu's handheld FT73 covers the 430-440MHz UHF band and features digital tuning with 2W output. (Dick Smith Electronics). pedition, the British Trans Arctic expedition of 1968, and recently Dick Smith on his solo world helicopter flight. All used amateur radio as a safety net, knowing that in the event of an emergency they had access to amateur radio operators around the world. Often, amateur radio provides the only communication in and out of disaster areas. Amateurs played a vital part in the 1986 Mexico City earthquakes, Cyclone Tracy in 1974 and, more recently, the earthquakes in New Zealand. Amateur radio provided many vital communications links in the aftermath of each disaster. Amateur radio has also played a large part in the development of space communications hardware and techniques. Since the launch of the first amateur satellite, OSCAR 1, in December 1961, over 18 amateur Satellites have been launched into space. Some are still operating five years after launch. These successive orbiting packages show the enormous possibilities of space communications. The latest addition, JAS-1 (OSCAR 12), allows worldwide automatic message delivery via packet radio! Becoming an amateur To join the ranks of the amateur fraternity only a basic knowledge of electronics is required. You simply require enough knowledge to allow you to continue to build expertise through the enjoyment of your hobby. Basically, there are three entry points to the amateur radio license. Users select the level most suitable to their needs and are required to pass a written [multiple choice) examination to qualify to hold a licence to operate equipment on the amateur bands (see Table 1): (1). The AOCP (Amateur Operators Certificate of Proficiency), otherwise known as " the full call" , allows access to all bands and modes of operation authorised for amateur use. This means access to all HF, VHF and UHF amateur bands. (2). The LAOCP (Limited AOCP) restricts the available bands to VHF and UHF and does not allow CW operation. Many amateurs find that this level is sufficient for their social and technical needs. Consequently, in Australia, the majority of amateur activity occurs on the VHF and UHF bands. (3). The NAOCP or " Novice" license allows HF operation only at reduced power on selected bands. CW operation is permitted to 5 WPM. In addition to the above, the amateur operator may take out a combined "Novice" and " Limited" license (LAOCP/NAOCP). Full and Limited license applicants must obtain passes in examinations for theory and regulations. Full call applicants must also pass a Morse code examination at 10 words per minute (WPM). Novice licence applicants must pa ss a more elementary theory examination, regulations and Morse code at 5 WPM. Additional inform a tion on licences and exams can be obtained Table 1: Bands, Power and Modes of Operation Band Frequencies 160 metres 1.8-1.825MHz 1.825-1.875MHz Power (AV/PEP) Mode Licence 120/400W ALL* AOCP AOCP NAOCP 80 metres 3 .5-3 .8MHz 3 .525-3.625MHz 30W ALL AM/CW/SSB 40 metres 7 .00-7 .3MHz 120/400W ALL AOCP 30 metres 10.1-10.15MHz 120/400W ALL AOCP 20 metres 14.00-14.35MHz 120/400W ALL AOCP 17 metres 18.068-18.168MHz 120/400W ALL AOCP 15 metres 21.00-21.45MHz 21.125-21 .200MHz 120/400W ALL 30W AM /CW/SSB AOCP NAOCP 12 metres 24.89-24 .99MHz 120/400W ALL AOCP 10 metres 28.00-29.7MHz 28 .1-28.6MHz 120/400W ALL 30W AM /CW/SSB AOCP NAOCP 6 metres 50 .0-54.0MHz 120/400W ALL L/AOCP 2 metres 144-148MHz 120/400W ALL L/AOCP 70cm 420-450MHz 120/400W ALL L/AOCP 50cm 576-585MHz 120/400W ALL L/AOCP 23cm 1240-1300MHz 120/400W ALL L/AOCP 13cm 2300-2450MHz 120/400W ALL L/AOCP 3cm 10000-10500MHz 120/400W ALL L/AOCP 1.25cm 24000-24250MHz 120/400W ALL L/AOCP * Emissions authorised for the Amateur Service This do-it-yourself HF transceiver from Dick Smith Electronics can be built to cover any 500kHz segment between 2 and 30MHz. It features LSB, USB and CW modes and a power output of°30W PEP or 15W CW. Table 2: Recommended Texts for AOCP/LAOCP/NAOCP (1 ). (2) . (3) . (4) . (5) . (6) . (7) . (8). " VHF/UHF Manual" ; G. R. Jessop, 500 pages. " 1987 ARRL Handbook" . " Amateur Radio and Electronics Study Guide" ; Ian Ridpath, 21 O pages . " 1000 Questions for Novice Candidates"; Ken Hargreaves, Dave Wilson Rex Black; 11 6 pages. " 500 Questions for AOCP Candidates"; Bill Dunn , Fred Santos, Keith Hargreaves, Dave Wilson ; 94 pages . " Manual of Q & A for the Novice Licence "; Keith Howard ; 100 pages. " The Ham Exam Cram Book"; Keith Howard ; 72 pages. " The Amateur Operator's Handbook" ; Australia Government Publishing Service. from the Wireless Institute of Australia, PO Box 300, Caulfield South, Vic. 3162. To obtain an adequ a te knowledge of the principles of amateur radio, the enthusiast can NOVEMBE R1987 91 choose between correspondence courses, instruction classes at a local radio club, or self study of the recommended texts, available at bookshops, electronic retailers and some radio clubs (see Table 2). Most countries in the free Western World and some in the Eastern Bloc allow amateur operations. The international body which regulates international radio operations is called the International Telecommunications Union (ITU). Member countries subscribing to the ITU enforce regulations via their own government. In Australia, ITU recommendations are acted on by the Department of Transport and Communications (the new Federal government department which combines the old departments of Transport and Communications). The DOTC liases closely with the Wireless Institute of Australia (WIA) which represents amateurs in this country. Through the cooperation of the DOTC and the WIA, a number of other countries accept an Australian amateur radio licence as qualification to operate amateur radio equipment on a temporary basis (during vacation etc). This co-operation between regulatory bodies is called reciprocal licensing. Countries with reciprocal licensing are listed in Table 3. The works - this is the view inside Kenwood's TS-711A all-mode 2-metre transceiver. Note the use of LSI chips in the digital control unit (vertical board). The various sub-assemblies hinge out to enable access. (Reproduced by courtesy of Kenwood Australia). Callsigns All countries have been allocated radio callsign prefixes (Australia's prefix range VHA-VNZ) by the ITU. For the amateur service, Australia's prefix is VK. An amateur callsign is comprised of the national prefix (VK), a state prefix (a single numeral), and a Table 3: Countries with Reciprocal Licence Agreements USA UK NZ Canada West Germany Tonga India Eire Israel Belgium Denmark Vanuatu Fiji Morocco PNG Luxembourg Netherlands Japan Nigeria Norway Portugal Swaziland Sweden Brazil Table 4: Amateur Licences in Australia VK2 VK3 VK4 VK5 VK6 VK7 VK8 3061 2473 1517 1032 902 352 73 LAOCP 959 1037 389 276 221 104 25 NAOCP 946 772 619 332 212 99 49 LAOCP/NAOCP TOTAL: 16,661 362 303 266 122 97 41 20 AOCP 92 SILICON CHIP maximum of three identifiable letters; eg. VK2ABC. A survey of the numbers of amateur licenses on a state-by-state basis is shown in Table 4. Equipment The range of "off the shelf" equipment available to the radio amateur is enormous, and varied enough to suit all applications. The major source of equipment is Japan which is hardly surprising considering that the Japanese have an amateur population of 600,000. Major equipment brand names are Icom, Kenwood, Yaesu, Ten-Tee, KDK and FDK. There are many reputable firms selling radio equipment in Australia and, with such a relatively small market, pricing is always competitive. It's also worth noting that most amateur equipment attracts only 2 % import duty. The option of building your own equipment is also quite viable and virtually everything the amateur could need - power supplies, SWR bridges, preamplifiers, power amplifiers, receivers, transceivers and antennas etc - is available in kit form. We'll be describing projects like these in future issues. Transmission modes There are many modes of transmission authorised for amateur use, including AM, FM, CW, SSB, RTTY, FSK, SSTV and FAX. Some modes make efficient use of the RF spectrum, whilst others are somewhat wasteful; eg. SSB is more efficient than AM as far as distance versus power output is concerned because of the narrow bandwidth utilised. FM offers improved clarity over AM, while RTTY offers a high speed advantage over CW. These modes of transmission are given separate classifications, each having a distinct alphanumeric expression. The first four characters express the necessary bandwidth, (eg, 200H means a signal having 200 Hertz bandwidth). The next group of three characters indicate the type of modulation and the nature of the modulating signal (eg. A3E, where A = double sideband, 3 = a single channel containing analog information, and E = telephony). The last two characters are used to further describe the nature of the modulating signal and are rarely used in amateur radio. Table 5 gives a summary of these classes of these classes of emission. The three most common modes or emissions are: 100HA1A (100 Hertz CW), 2K70J3E (2.7kHz SSB), and 5K00F3E (5kHz NBFM). Table 5: Explanation of Class of Emission Designators First four characters: Bandwidth Fifth character: Amplitude Modulation A = Double sideband B = Single sideband, full carrier. R = Single sideband, adjustable carrier level. J = Single sideband, suppressed carrier. C = Vestigial sideband. Angle Modulation F Frequency modulation. G = Phase modulation . = Phase Modulation K = Amplitude modulation. L = Modulated in width/duration. M = Modulated in position/phase. Sixth character: Nature of the signals modulating the main carrier 1 = A single channel of quantised or digital information without a modulating subcarrier. 2 = A single channel of quantised or digital information using a modulating subcarrier. 3 = A single channel containing analog information. Seventh character: Type of information A = Telegraphy for aural reception (CW) B = Telegraphy for automatic reception (RTTY) C = Facsimile D = Data, telemetery, telecommand E = Telephony F = Television Eighth character: Details of signal K = Narrow band voice information. M = Monochrome television. N = Colour television. Ninth character: Multiplexing details N = None. Repeaters As previously mentioned, the most popular bands in Australia are the VHF and UHF bands. As a result, a huge network of repeaters has emerged, giving mobile to mobile coverage of up to 150km. As the predominant mode for repeater operation is NBFM (narrow band FM), the VHF/UHF repeater service serves to foster intense amateur activity in capital cities and regional centres. Most scanning receivers, by the way, cover the FM segment of the For the really serious amateur - Yaesu's FT767GX is a fully synthesised transceiver that covers all amateur bands from HF through to UHF (1.B-440MHz). Price is around $4995. (Dick Smith Electronics). 2-metre amateur band utilised for repeater operation. So, if you're interested in amateur radio, you can use your scanner to listen to the repeaters. Next issue, we'll look at the VHF /UHF bands in detail and show you how to listen to these bands. NOVEMBER 1987 93 ASK SIUCON CHIP These pages are intended to answer readers' questions on a whole range of topics related to electronics. For the first month or so, we will be answering oft-asked questions but we hope that you, the individual reader, will deluge us with your own questions which we will answer to the best of our ability. Write to Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. Digital and analog: what's it all about? I hear a lot of talk a bout analog and digital audio and analog and digital technology in general. Quite frankly, when anybody starts talking about analog and digital, my eyes start to glaze over because it's so far above my head. In spite of that, I would still like to know about it. Can you explain these terms in language I can understand? • In general terms, the word analog is used to describe the electronic audio equipment that we have lived with for a several generations. It applies particluarly to the way audio signals are recorded and played back on vinyl records and tapes. In both of these storage media, the signal is stored as an "analog" or representation of the original acoustic signal. In other words, the wiggles in the record groove will be directly proportional to the variations in air pressure originally picked up by the recording microphone. Similarly; on tape, the signal is stored as variations in magnetisation which are directly proportional to the original signal. Then when the record or tape is played, the stored signals are converted to electrical signals, amplified and then fed to a loudspeaker which converts the electrical signals into sound. The beauty of the analog process is that it is easy to understand and relate to. It all developed from the original acoustic gramophone in which the stylus playing the record actually vibrated a diaphragm connected to a large horn. Another aspect of analog signals is that they are continuously varying which is in direct contrast to digital signals. In a digital system, the signal switches rapidly between two values which may be regarded as high and low, or zero and one, or on and off. The beauty of such a simple signal is that it is very easy to store in computer memories and is not subject to degradation by the recording medium. The drawback is that if audio signals are to be stored digitally, they must first be encoded and that is quite a complex process. Similarly, to be played back, the digital signal must be decoded. To sum up the encoding process, it involves sampling, quantisation and coding. If your eyes are already glazing over, don't worry, we won't go any further. That should be enough to distinguish the terms analog and digital for the time being. Most people think of compact disc players when they think of digital audio but the new DAT (digital audio tape) recorders use the same technology. 94 SILICON CHIP What is FM multipath? I have read a number of articles on FM reception and have seen the term 'FM multipath' bandied about but I have not been able to gain a clear understanding of the subject. Why does it happen with FM and apparently not with AM reception? • The great problem with radio waves is that they don't pass through solid objects to any great extent. They are reflected instead, by hills, buildings, ships, planes or any solid object. It is reflected signals that cause problems with FM reception and the phenomenon is known as 'multipath' reception. Multipath means literally what it says - signals arriving at the receiving antenna via multiple paths. In the ideal situation, the antenna of an FM tuner would only receive a strong signal, coming via a direct path from the transmitter. In real life though, there are mutliple paths for the transmitter signal to get to the receiving antenna. There will be large buildings and hills which act as a strong reflector. Now as long the direct signal is much stronger than the reflected signals, there is no problem and the reception will be clean and distortion-free. Where things become messy is when the direct signal and the reflected signals are of roughly the same strength. This can easily happen if the receiving antenna is in the lee of a hill or large building. In this latter situation, direct and reflecting signals interfere with one another because, inevitably the signals are never in phase with each other. So the signals reinforce and cancel each other continuously so that the resultant carrier signal being received by the tuner is always fluctuating in signal Some ,FM"tuners h;ndle multipath 'i-eceptf~; ·better than others. These t~ o tuners from Kenwood are among the better performers with a capture ratio of ldB and AM suppression of B0dB for the KT-1100SD and 70dB for the KT990SD. strength. Such a badly fluctuating signal is effectively strongly amplitude modulated with garbage. And that means that a lot of noise and distortion will be produced by the tuner. So what is the solution. Apart from living in a place which has a clear line of sight to the transmitter, matters can be helped a lot by having an antenna which is reasonably directional. This means that the wanted direct signal can be strong, while the reflected signals coming in at an angle will be much weaker and so will not cause so much of a problem. In practice, this means that you should have an antenna designed specifically for FM reception rather than relying on the more or less accidental pickup of antennas designed for TV reception. Top quality FM tuners usually have much less of a problem with multipath reception because of two factors. First, they have very good AM rejection. This means that their circuitry does not respond to amplitude modulation. Second, they have a much better 'capture ratio'. This term refers to the ability of a tuner to differentiate between two FM signals with the same carrier frequency. Really good tuners have a capture ratio as small as ldB. This means that if there are two identical signals which differ in strength by only 11 % , the unwanted signal will be suppressed by 30dB (down to 3%). That can make a dramatic difference .to signal quality in conditions where multipath is bad. Multipath is not a problem for AM broadcasts because of the much longer signal wavelengths. "!ii Why is ignition noise audible on radio? Why is it that when some cars and motorbikes are close to my car with their engines running, I hear loud ticking noises from the speakers of my car radio? Note that it only happens with some cars and bikes. Is the noise coming from the spark plugs of these vehicles? • The ignition system of any car or motorbike is an many quite an efficient transmitter. There is a resonant circuit in which a substantial amount of electrical energy is stored, to wit, the ignition coil and its associated capacitor across the points. There is also a primitive antenna system which radiates some of that energy, to wit, the spark plug leads and the lead from the coil to the distributor. Each time the spark plug fires, the spark plug leads radiate a very strong impulse of electromagnetic energy into the atmosphere. It is then picked up by your car radio and reproduced as a ticking noise. It can be audible on both the AM and FM bands. Ignition interference can also be visible on television receivers and looks like short random horizontal streaks on the screen. In most cars, the current through the spark plugs is reduced by fitting carbon-cored spark plug leads and this reduces the amount of interference radiated. Another factor to be considered is that the bonnet and bodywork of the car constitutes a shield for the spark plug leads and depen- ding on how efficient this shield is, more or less energy will be radiated by the leads. Of ten too, the amount of energy radiated will be dependent on the state of the ignition system itself and cars in which the points are worn and the points capacitor partly open circuit can be quite bad. To sum up, cars and bikes which do cause severe radio and television interference are often in need of ignition system maintenance. The drivers of these vehicles are therefore not only polluting the atmosphere with electrical noise, they are probably also causing more than their share of gaseous pollution too. N OVEM RER 1987 95 CEN'l 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 th is 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 . PLEASE PRINT EACH WORD SEPARATELY, IN BLOCK LETTERS 6 2 3 4 5 7 8 9 10 Our advertisers are vital to the success of Silicon Chip . Please give them your support. Altronics . . . 36,37 ,52 , 53,60 ,61 Arista Electronics ..... .. 64 Australian Geographic . IBC Dick Smith Electronics . .. 18, 19,44,45,65, 75 11 12 13 14 15 ($7 .00) 16 ($7.40) 17 ($7.80) 18 ($8.20) 19 ($860) 20 ($9.00) Elmeasco Instruments . . .. 81 Jaycar Electronics .... 24-32 Marantz Australia . . ... . . IFC Scan Audio Pty Ltd . OBC 21 ($9.40) 22 ($9.80) 23 ($10.20) 24 ($10.60) 25 ($11 .00) PC Boards 26 ($11.40) 27 ($11 .80) 28 ($12 .20) 29 ($12.60) 30 ($13.00) Name ....... .... ... ........ .... ... .... .... ......... ...... ...... ..... .. Printed circuit boards for Silicon Chip projects are made by: R.C .S. Radio Pty Ltd, Suburb/Town .. ........ ....... .. .... ..... .. ..... ........ ... ........... ... ..... .. .. Postcode ............... . . 651 Forest Road , Bexley, NSW 2207 . Phone (02) 587 3491. Enclosed is my cheque or money order for $ ..... .. .... ..... .. ...... .... . ....... or pl ease debit my Bankcard □ Visa □ Jemal Products , 5 Forge Street, Kewdale , WA Card No .... ...... .... ........ ....... .......... ...... .... ... ..... .... ... .... .. .... ..... ....... ..... .... ... ... ... . 6105. Signature ......... ... .... .. ... .. ... .. .... ........ ...... ... ..... ..... ... ..... ... .. ...... ... ... ... .. ... ... .... . Phone (09) 451 8726/2275 . ······ ··· ··· ······ ····· ··················· ··· ····· Address ........ ... ....... ........... ..... ..... ............. ..... ...... .. .... ............... .. ......... .. .... ... ..... .. . Capacitance adaptor for DMMs scissors, then carefully affix it to the front panel. The front panel can now be drilled to take the switches and test terminals. Alternatively, you can use the artwork reproduced with this article as a drilling template. The switches and terminals can then be labelled using Letraset rub-on lettering. Spray the finished panel with Estapol clear lacquer to stop the lettering from rubbing off. Next, mount the switches and test terminals and complete the wiring as shown in the diagrams. The case can now be drilled to accept the board assembly. Two 8mm holes are drilled in the rear panel to provide clearance for the banana plugs, while another three holes are 96 Advertisers Index SILICON CHIP ctd from page 23 drilled in the sides of the case to allow screwdriver access to the trimpots. The assembly goes together with the battery sandwiched between the board and the case lid (see photo). Strips of insulation tape can be used to prevent shorts between the battery case and the trimpot wipers. Calibration Calibration involves first setting the null adjustment (VR3), then adjusting VR 1 and VR2 so that the DMM displays the correct reading for capacitors of known value on the LOW and HIGH ranges respectively. To set the null control, set the DMM to the millivolt range, set S2 to LOW, and adjust VR3 for a reading of 0mV. In practice, it will be difficult to set VR3 so that the meter reads exactly zero, and a reading that is slightly negative will be satisfactory. Now connect a capacitor of known value between 1000 and 2200pF to the test terminals. Adjust VRl so that the meter displays lmV per picofarad (eg, if the capacitor value is l000pF, adjust the meter to read 1V). Finally, select the HIGH range and connect a 0.1-1/.tF capacitor to the test terminals. Adjust VR2 so that the meter displays 1V per microfarad (eg, 0.1V for a 0.1/.tF capacitor, 1V for a 1/.tF capacitor). ~~~ ~; ··::,,? i:-..'7' MEMBERSHIP CERTIFICATE To: Australian Geographic Subscriptions Freepost 3, P.O. Box 321, Turrey Hills, NSW 2084, Australia NO POSTAGE STAMP REQUIRED WITHIN AUSTRALIA Please enter an AUSTRALIAN GEOGRAPHIC subscription in my name for (tick box): □ 1 year □ 18 months □ 2 years NAME _ _ _ __ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ _ ADDRESS _ _ _ _ _ _ _ _ _ __ _ __ _ _ _ _ _ _ _ _ __ _ _ _ _ SUBURB/TOWN _ __ _ __ _ _ _ _ _ _ _ POSTCODE _ _ _ _ _ _ _ COUNTRY _ _ _ _ _ _ _ _ _ __ __ _ _ _ __ _ __ _ _ _ _ _ _ _ Enclosed is my cheque or money order for $_ _ _ _ _ _ _ __ or please debit tltis amount w my □ B=kcanl □ v;sa C«d D MasmC«d ~ Card Number s NOP SIGNATURE Subscription costs for: Within Australia Overseas Surface Mail O verseas Air Mail R 1 year 14 issues ) tJ $A28 D $A40 D $A62 18 months (6 issues) □ $A42 D $A60 D $A93 2 years (8 issues) D $A56 D $A80 D $Al24 Ut