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Audio Test Tones from your PC SILICON CHIP ISSN 1030-2662 MARCH 2002 6 $ 60* INC GST 03 NZ $ 7 50 INC GST PRINT POST APPROVED - PP255003/01272 9 771030 266001 siliconchip.com.au PROJECTS TO BUILD - SERVICING - COMPUTERS - VINTAGE RADIO - AUTO ELECTRONICS GRID CONNECTED SOLAR POWER: Is it worth it? INTELLIGENT SOLAR PANEL CHARGER TO BUILD BONUS: 272p 20 ALTRONI 02 CATALO CS G PLUS: (Aust only) 12V, 70W 6-Channel Infrared Mighty Midget Remote Volume Control www.siliconchip.com.au Power Amplifier for Surround Sound RIAA Turntable Preamp for Modern Amps Itsy-Bitsy USB-powered March 2002  1 LED Lamp SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au/ Contents www.siliconchip.com.au Vol.15, No.3; March 2002 FEATURES 8 Solar Power For All: Does It Add Up? Is solar power a good investment for the average householder? We take a look at some of the figures and the current incentives – by Ross Tester 30 Terra: Mission To Planet Earth A look at the technology behind NASA’s new Earth observation satellites – by Sammy Isreb PROJECTS TO BUILD 16 The “Mighty Midget” Audio Amplifier Module It’s based on a Philips class-H audio amplifier IC and can deliver 36W RMS or 70W music power, all from a 13.8V supply – by Rick Walters 37 The Itsy-Bitsy USB Lamp “Mighty Midget” 70W Audio Amplifier Module – Page 16. It plugs into the USB port and is just the shot for checking motherboard switch and jumper settings – by Stan Swan & Ross Tester 56 6-Channel IR Remote Volume Control; Pt.1 It’s ideal for use with Dolby 5.1 digital decoders and lets you adjust the volume of all six channels simultaneously – by John Clarke 68 An RIAA Preamplifier For Magnetic Cartridges Many modern amplifiers lack phono inputs. This preamplifier solves that problem – by Leo Simpson & Ross Tester 82 A 12/24V Intelligent Solar Power Battery Charger Don’t cook your batteries by connecting them directly to a solar panel. This charger turns off the power when the battery is charged – by Ross Tester 6-Channel IR Remote Volume Control For DVD Players – Page 56. COMPUTERS 23 Generate Audio Tones Using Your PC’s Soundcard Looking for a low-cost audio generator? If you have a PC with a soundcard, this one is for free! – by Greg Swain RIAA Preamplifier For Magnetic Cartridges – Page 68. SPECIAL COLUMNS 40 Serviceman’s Log Do some sets really self-destruct? – by the TV Serviceman 76 Vintage Radio The AWA 719C 7-band console; Pt.1 – by Rodney Champness DEPARTMENTS 2 3 53 54 Publisher’s Letter Mailbag Subscriptions Form Circuit Notebook www.siliconchip.com.au 67 87 94 96 Product Showcase Ask Silicon Chip Market Centre Advertising Index 12/24V Intelligent Solar Battery Charger – Page 82. March 2002  1 PUBLISHER’S LETTER www.siliconchip.com.au Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Production Manager Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Ross Tester Jim Rowe, B.A., B.Sc, VK2ZLO Rick Walters Reader Services Ann Jenkinson Advertising Enquiries David Polkinghorne Phone (02) 9979 5644 Fax (02) 9979 6503 Regular Contributors Brendan Akhurst Rodney Champness, VK3UG Julian Edgar, Dip.T.(Sec.), B.Ed Mike Sheriff, B.Sc, VK2YFK Philip Watson, MIREE, VK2ZPW Bob Young SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 003 205 490. ABN 49 003 205 490 All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Hannanprint, Noble Park, Victoria. Distribution: Network Distribution Company. Subscription rates: $69.50 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 8, 101 Darley St, Mona Vale, NSW 2103. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. E-mail: silchip<at>siliconchip.com.au ISSN 1030-2662 * Recommended and maximum price only. 2  Silicon Chip Wind power is increasing in Australia This month, we have been rather critical of the various campaigns to get domestic electricity users to install solar panels on the roofs of their homes. While the idea of promoting solar power is good, there is little justification for it if it does not have a reasonable payback period. In fact, unless you spend a lot of money on a solar system, say $15,000 or more, you are unlikely to cater for your own energy consumption let alone become a “net seller” to your local grid. We also regard systems without battery storage as being a bit of a joke. One of the attractions of installing solar panels and the other necessary equipment is that you become independent of the local electricity supply. During blackouts, you continue to function normally. If you can’t achieve that, then what is the point? However, the renewable energy story in Australia is looking much better than it was just a few years ago. But the real ad­vances are not being made in solar energy but in wind power. In the last two years or so, some big wind farms have been started and there are more to come. For example, there is the 150 mega­watt wind farm in Portland, Victoria and the recently announced 130MW Woolnorth development in Tasmania to be run by, believe it or not, Hydro Tasmania. In fact, they have mapped out plans for 1000 megawatts of wind power. Stage one of the Woolnorth project will comprise six 1.75MW Vestas wind turbines for an initial installation of 10 megawatts. These wind turbines are much bigger than the 600kW units in­stalled in Australia’s first grid-connected wind farm at Crook­well, in NSW. (We featured in the Crookwell wind farm in the January 1999 issue of SILICON CHIP.) Greenpeace and AusWEA (Australian Wind Energy Association) have jointly launched an official target for Australia to install 5000MW of wind power by 2010. Given the progress so far, that certainly looks achievable. Apart from the initial installation, wind farms cost essen­tially nothing to run and have minimal impact on the environment, so they must be regarded as a very good alternative to any ther­mal power station. Still, while 5000MW sounds like a lot of power, it is really only a small percentage of Australia’s gener­ating capacity. And while wind power is good, what about solar power? Aus­tralia’s solar power potential is far greater than wind power but virtually nothing is happening. The main reason that wind farms are being built is that they are simple turn-key projects: just pay your money and Vestas or one of the other wind turbine makers will install your wind farm quick smart. Considering the relatively small amount of money spent or committed on wind farms so far, Australia has little to boast about. We should be committing funds to make real progress in the development of major solar power stations. Government has to get involved in a big way. Consider this: a typical coal-fired power station these days costs at least one billion dollars. What would happen if the Federal government or one of the states decided to devote one billion dollars to research and development over the next five years with the aim of building a major solar power station? We would make real progress. One billion dollars over five years is a trifling amount, considering our Gross Domestic Product. I am sure such a project would be successful and would put Australia well on the way to eventually generating a major por­tion of its power from the sun. Let’s do it. Leo Simpson www.siliconchip.com.au For FAST access to an external Hard Drive! Infrared Link This infrared link is ideal for use with mobile phones, Cat. 8973 handhelds etc. Also suitable for computers without a built-in IR port. The adapter easily connects to any USB port. Cat 8973-7 Infrared link USB $159 Video editing made easy! The Microgram Keyboard Kolumn Cat. 2621 Provides a Firewire interface from your digital camera to your PC. Bundled Ulead software lets you edit your own movies. Cat 2621-7 $199 Memory Card Reader/Writer Choose from our extensive range of quality keyboards! Cat. 6656 These memory card reader/writers will read and write up to 5 memory card types including Compact Flash, Smart Media, Multimedia ,Secure Digital & Memory Stick via a USB connection. 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Cat 11658-7 2 computers $219 Cat 11659-7 4 computers $449 Also available in PS/2 Cat 11654-7 2 computers ideal for small office/home $199 Cat 11655-7 Cat. 11654 4 computers $399 Cat 11656-7 8 computers $949 Cat. 11655 Cat 11657-7 16 computers $1299 Cat. 11657 Australia wide express courier $ 15 (3kg max) Dealer Enquiries Welcome! Vamtest Pty Ltd trading as MicroGram Computers ABN 60 003 062 100, Phone: (02) 4389 8444 FreeFax: 1 800 625 777 Unit 1, 14 Bon Mace Close, Berkeley Vale NSW 2261 sales<at>mgram.com.au All prices subject to change without notice. Pictures are illustrative only. info<at>mgram.com.au SHOREAD/MGRM0302 Clarification of DVD resolution Some recent letters to the editor have suggested that DVD pictures are considerably better than VCR pictures because of the poor resolution of the latter. In particular, they have spoken of the little more than 200 lines of resolution provided by a VCR, with one letter contrasting this with DVD’s 576 lines. This requires clarification. DVDs and VCRs produce the same vertical resolution. Nominally 625 lines, some of these lines are used during the vertical blanking intervals (during which the electron beam returns from the bottom of the screen to the top). For PAL, the number of displayed lines was traditionally 585. For DVD, 576 lines was settled upon. The difference is insignificant (most displays lose several lines through overscan at both the top and the bottom). This 580-ish horizontal lines spread over the vertical dimension is the same whether the picture is from VCR, broadcast or DVD (assuming a full screen DVD picture). The resolution sometimes specified for VCRs is often stated as ‘200 lines’ or maybe a little more. This is not the vertical resolution but the horizontal resolution. Rather than the pixels that have been talked about most commonly with the advent of computers, the resolution of TV pictures was traditionally speci­fied in terms of the number of vertical lines that could be discerned across the width of the display. This is where the ‘200’ comes from. 4  Silicon Chip By contrast, DVD players are typically capable of between 500 and 540. Note that the picture on a PAL DVD is actually encoded as a 720 pixel wide by 576 pixel high image, so hardware DVD players lose around 17% of the horizontal resolution during the conversion from a digital picture to an analog PAL signal. Stephen Dawson, Gilmore, ACT. Right of reply on DVD widescreen I’m glad to see my letter in the September 2001 issue generated so much interest and comment. What disappointed me, was I feel, most of you missed my point. My gripe was never against DVD and I never once said that DVD doesn’t give a better picture than VHS. It’s the film indus­try that manipulates the film and has the final say on how they will do it. I have already mentioned “What Women Want” and “Titanic”. Now I include “True Lies” and “Airforce One”. How many other movies are being done this way? “Airforce One” was a blatant example. I acquired a Zone 1 NTSC copy of the DVD and the beauty of this one was it is double-sided, one side Widescreen 2.35:1 while the other is Full Screen 4:3. The widescreen, as you guessed, was the 4:3 picture black-barred top and bottom; ie, 44% of the original picture removed. What really annoyed me, the blurb on the cover of this, as it does on most VHS movies, said “Film reformatted to suit 4:3”. What a joke this is, when in these cases, it actually happened the other way around. If the film makers are filming in 4:3, why are they bother­ing with the pseudo widescreen? As I stated in September 2001, I thought widescreen was more picture on the sides, not less top & bottom. So why would anyone in their right mind spend upwards of $4000 on a 76cm widescreen TV when you get the same result with a $2000 to $3000 80cm 4:3 set? My point is I guess, how are movies today initially filmed and then eventually presented. Next time you go to the cinema, take a note of the trailers to up and coming movies. Most are presented in 16:9, however when they become the feature they’re suddenly 2.35:1. All you “couch potato experts” have put your two bob’s worth in but I wish the real experts from the film industry would comment. Also maybe the excellent team at SILICON CHIP could explain the workings of the compression technique used on DVD and what trickery is done to get 500 lines resolution out of a 4:3 and supposedly the same from 2.35:1. Simon Kareh, via email. More on transformer ratings Congratulations on securing the copyright of EA/ETI as noted in the Publisher’s Letter in the January 2002 issue. On a different note, in reference to Ben Lowe’s letter (Mailbag, January) relating to transformer ratings, I am www.siliconchip.com.au afraid that I must side with Mr Lowe. Perhaps I can elaborate a bit on what he wrote. The power rating of a transformer depends on how hot the transformer is allowed to get during use. That in turn depends on two main sources of heat: iron (eddy current) losses in the core and copper (I2R) losses in the windings. Here, “I” represents the RMS current through any winding of the transformer and “R” is its resistance. At 50Hz we can safely assume that eddy current losses are small compared to I2R so it is the loss due to the resistanc­es of the primary and secondary windings that is the more import­ant. In any practicable transformer design there is only a limited space available in which to put the windings. If you want more power you need thicker wire (to reduce I2R losses). This means that you need more space and hence a bigger transformer. In general, the optimal space available for the secondary winding(s) is practically the same whether you have one secondary winding or two. If you design for a centre-tap configuration you would need twice as many turns on the secondary winding(s) as you would for a bridge configuration. This means that thinner wire must be used and the effective winding resistance would be doubled. Imagine a transformer with two identical secondary wind­ ings. You can connect the windings in parallel for a bridge configuration or in series for a centre-tapped configuration. The parallel connection has half the resistance of the centre-tapped configuration for the same no-load output voltage. Therefore the I2R loss under load is halved, which translates into 1.4 times as much total power for the same I2R loss. Although for reduced duty cycles the power loss is in­creased compared with the output power, the duty cycle makes no difference to the advantage offered by the bridge configuration www.siliconchip.com.au over the centre-tapped configuration. This is because for any given duty cycle the RMS current is the same. Hence the I2R loss for the centre-tapped configuration is always double that for the bridge configuration. Incidentally, if you include the I2R loss in the primary winding, which is independent of the output configuration, the advantage of the bridge configuration over the centre-tapped one is somewhat less than otherwise but the principles remain the same. Herman Nacinovich, Gulgong, NSW. Officious letters not necessary I have been away from home for some time and started to catch up on some reading, SILICON CHIP included! I was amazed at some of the correspondence and indeed the tone of some of it. I wish particularly to take issue with Mr Ian Stanley-Eyles’ letter published in your November issue. I gather by the tone of the letter that Mr Stanley-Eyles is either a civil servant or a solicitor, in whichever case there was no need for the very thinly veiled threat embodied in the correspondence, essentially demanding a legal disclaimer and suggesting that a magazine such as yours was in any way acting outside the law deliberately! I do not believe a letter of that tone is needed in the columns of a magazine like this! I wish also to make comment regarding the ongoing debate regarding electrical installations and who may carry out electri­cal work. It seems to me, as it has to others, that the arguments coming from the electrical safety authorities are nothing other than the oft-repeated views of a bunch of electricians turned civil servants trying to keep the “old boys club” going by ex­cluding not only competent laymen, but also highly qualified technicians and engineers, from doing what they are more than capable of doing and doing, in many cases, better than a so-called qualified electrician. The civil servants charged with the duty of public safety in matters electrical should move aside and let people do their own wiring. Steve Newson, via email. Don’t change electronics content Firstly, it’s great to see that SILICON CHIP has not strayed from its original philosophy with regards to content. I have been collecting (much to the anguish of my wife) all the Australian local electronics magazines since 1980 when I was studying electrical engineering at the UNSW and have been a subscriber to SILICON CHIP for a number of years now. I was horrified when the “other” locally produced electron­ ics magazine made a severe change of content direction. Its recent withdrawal from publication probably reflected the same opinion from other readers. I guess what I’m trying to say is that you people at SILICON CHIP are doing a tremendous job and should keep doing what you do best. Con Andrews, via email. Virtues of negative feedback I need to comment a little on your response to the reader “G. W.” who asked questions about the Ultra-LD Amplifier in the February 2002 issue, page 91. I notice that you advertise audio books by Self and Hood in the same issue, pp 86, 87. G. W. and the friends who advise him, would do well to read both of these books. Self and Hood don’t always agree but their books are clear, informative, useful and fun to read. G. W. mentions “a few people I know ... anyone can achieve low THD with lots of feedback”. Many people who know a little of electronics find March 2002  5 feedback difficult and seem to want to regard it with suspicion and as an unnatural “black art”. I am willing to admit that in my student days, I built quite a few amplifiers that oscillated - and oscillators that didn’t. But difficulty doesn’t justify suspicion. Let me try to dispel the biggest part of the feedback myth first. Feedback is not at all unnatural; nature uses it by the truckload. Feedback is what enables us as humans to walk about on two legs. Anything tall and skinny with bendy bits in all sorts of peculiar places is unstable and this becomes conspicuous when we are drunk, asleep or dead - we fall over. In our legs, we don’t just have muscles and bones, we have umpteen nerves dedicated to monitoring what bit is pointing where. Behind our ears, we have special balance canals filled with special fluid and zillions of tiny hairs, so we can know which way is up; we also use our eyes. When doctors ask us to stand on one leg and shut our eyes, they are checking for a certain social disease. It damages nerves and people with that disease don’t get enough feedback and fall over. Moving away from nature a little, feedback is what enables us to drive a car. Most drivers pay attention to where the car is on the road. If too far to the left, they steer to the right; if too far to the right, they steer to the left. Back to bodies: feedback is what keeps us alive. Many, probably most, of the chemicals sploshing about in our bodies are regulated by feedback systems. Too little oxygen, our heart beats faster; too much carbon dioxide, we breathe faster. Many illnesses happen when some feedback mechanism breaks down. No feedback: no us! Let me move on to the “less feedback is better” myth. It isn’t. The authoritative explanation is: P. J. Baxandall, “Wire­less World”, December 1978, pp 53-56. In layman’s terms, a little bit of feedback can do only the easy bit: suppressing the low-order distortion 6  Silicon Chip components. However, it can’t do the difficult bit: suppressing the high order distortion components. Indeed, the way it suppresses the low-order ones is by turning them into high-order ones. A little bit of feedback makes things worse, not better. It is really dumb to do gross, brutal things like using Class A to reduce feedback. The implication that “anyone can use lots of feedback” is a myth too. That is the big problem with feedback. It is necessary but difficult to use lots of it. That is why I made amplifiers that oscillated while I was a student. Feedback is much more like porridge than like sex. Like porridge, feedback needs to be “just right”; bad feedback is bad and definitely not, “better than nothing”. But getting it “just right” isn’t easy. It is necessary to understand it well, to do a few moderately difficult calcula­tions, and to do even more testing to double and triple check that it is “just right”. But once it is right, then it is RIGHT, and it deserves no more suspicion than a person who can stand on one leg with their eyes shut. Keith Anderson, Kingston Tas. Australian 3-pin plug and socket I am able to provide some background to the questions posed by Dick Smith (Mailbag, Jan 2002) regarding the origin of the Australian 3-pin mains plug. The design was adopted, around 1930, as a result of a “Gentlemen’s agreement” (there was no Standards Australia then) between Fred Cook of Ring-Grip, Geoffrey Gerard of Gerard Industries, and Brian Harper Miller of the SECV. They based the design very closely on an existing American plug, and although that American design has apparently now faded into obscurity, I believe that same American design is the reason that Argentina and Chile and probably also China, also use essen­tially the same design. New Zealand copied the Australian design as Australian electrical appliances and equipment were ex­ported across the Tasman. One of the reasons behind the adoption of that particular design by the three Australian gentlemen was that it was cheap to make; the flat pins could be easily stamped out of sheet brass, in contrast to round pins or thicker rectangular ones used in other countries. This was also a consideration when the Chinese authorities officially adopted the design in relatively recent times, despite the considerable inroads the British plug had made due to its use in Hong Kong. The Chinese made one change, however; the earth pin is at the top. This is considered to offer some protection should a conductive object fall between the plug and the socket. An inter­esting piece of trivia is that this is referred to in Hong Kong as the “emu foot” or “emu track” plug, as the socket when viewed with the earth slot uppermost does resemble the track of an emu. I thank Dennis Perry and Norm Zerner (presently and former­ly of Gerard Industries) and Max Steen, a former colleague of mine in the Approvals Branch at ETSA, for their help with this information. David Inkster, Meadows, SA. TV for collector/restorer I have just been given a Healing B/W valve TV set, not working due to blown input fuse. The set is in great condition and may be suitable for a collector. It is a Healing 17, with the circuit diagram in the rear indicating a Chassis 5M150-5M075-4M150-958 RUN 3. I would hate to throw it away and would be happy to pass it on to anyone who could do something with it. Ashley Hosking, PO Box 73, Basket Range, SA, 5138. Phone (08) 8390 3442. www.siliconchip.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: info<at>amn.org.au Australia is going solar – or at least that’s what we’re told by Government agencies, environmentalists and corporate spin doctors. But if you take a really good look look at what’s on offer, arereally you getting at what’s on offer, are you getting a good deal? a good deal? Solar Power for All: Does it Add Up? By Ross Tester 8  S 8  Silicon iliconCChip hip www.siliconchip.com.au www.siliconchip.com.au A ten-panel “plug&power” rooftop system from Pacific Solar. This would be capable of generating 1.5kW and cost between $10,000 and $15,000. Photo courtesy Pacific Solar. W ith much fanfare and breastbeating, several initiatives have been announced to convince Australians to generate their own electricity, simply by placing photo-voltaic (or solar power) panels on their otherwise-wasted roof space. Of course, there is nothing particularly new about generating electricity from the sun. Photo-voltaics have been known about – and used – for many decades. There are two main reasons that it has taken a recent boost in profile: (1) “Green” is fashionable. Concern about the environment has escalated dramatically in the last decade to the point where some people are prepared to pay extra for “green” power. (2) Perhaps even more importantly, vast improvements have been made in the efficiency of photo-voltaic cells in recent years. And with the amount of money being poured into R&D, it is expected this will continue. Coupled with this is a very significant reduction in cost – as volumes rise, costs should continue to fall. “Greenhouse” gases If you say something often enough www.siliconchip.com.au and loud enough, most people start believing it. Could this be the case with the so-called “greenhouse effect”? The theory, albeit very abridged, goes something like this: we humans produce too much carbon dioxide. The two main culprits of CO2 production are (of course) that evil monster, the car, along with fossil-fuel (mainly coal) burning power stations. Problem is, no-one wants to give up their car or turn off the air conditioner! This large amount of CO2 acts like a one-way valve for sunlight (and therefore heat) entering our atmosphere and striking the earth. The earth heats up, which will eventually cause polar ice caps to melt which in turn will cause oceans to rise, flooding low-lying areas. Another consequence is a major change in climatic conditions. Cut the CO2 emissions and we’ll cut the greenhouse effect. It’s that simple. The point is, it is still JUST a theory. Most people are firmly convinced it is fact, simply because there are so many people telling them it is fact. We even have Government departments and agencies set up to deal with the “problem”. However, there are many experts around the world who don’t believe the greenhouse effect is the one true gospel. Many refer to it as the “greenhoax” effect. In 1995, skeptical scientists signed the Leipzig Declaration on Global Climate Change, stating that they “cannot subscribe to the so-called ‘scientific consensus’ that envisages climate catastrophes and advocates hasty actions.” But their voices are generally not heard amongst the incredibly sophisticated PR machine of the environmental lobby. The greenhouse effect is taught in schools as fact. The alternative point of view – that climate change is a natural phenomenon – barely rates a mention. Yes, there is some evidence of global climatic change. That proves the theory, of course – except that there is also evidence that the Antarctic continent is colder now than it has been since records were started! Whoops – better ignore that one! And in the overall scheme of things, we’re still only talking the blink of an eye in not just human history, but the March 2002  9 Wind and water: two of the most prolific and abundant forms of renewable energy. At right is Australia’s largest wind farm near Albany in Western Australia. Below is the turbine hall of a hydro-electric power station. No wonder they call it “clean” power! into the decaying material underground. While not truly renewable energy (it must run out in time!) it is relatively non-polluting (in fact, it uses and therefore removes a potentially polluting gas).    Another form of bio-energy burns the waste material from a production process (eg, the bagasse left over from sugar-cane crushing) in a similar manner. In many instances, this also produces steam and other energy for use in the plant – socalled “cogeneration.” Courtesy Western Power. history of our planet. Who is right? Only time will tell. In the meantime, it does make sense to try to limit the amount of CO2 and other pollutants entering out atmosphere from power stations – if only to make us feel better about the air we breathe! And that’s where “clean, green” renewable-energy electricity comes in. Green power Photovoltaic cells are not the only way to produce non-polluting electricity. There are four main ways to do it: (a) Wind-generated power – this has started to make an impact in Australia recently with several “wind farms” established in relatively-constantly-windy areas. The advantage is that the wind is free, if not constant. One disadvantage, apart from fairly low output per generator, is reportedly the swishing noise of the blades for people living within a few kilometers!    To show just how far wind farms 10  Silicon Chip have come, in January this year it was announced that the world’s largest wind farm, a 520MW, 200 turbine installation, would be built off the coast of Ireland at a cost of more than $1 billion. Proponents claim that wind farms will be able to produce more than two thirds of Europe’s electricity by 2020.    Incidentally, the first grid-connected wind farm in Australia was opened at Crookwell, NSW in 1998. At 4.8MW it doubled the previous wind generation capacity in the country! For more information on the Crookwell wind farm, see the January 1999 SILICON CHIP.    The largest wind farm in Australia is currently the 21.6MW plant at Albany, WA, with twelve 1800kW turbines on 65m towers.    (b) Bio-energy – burns the methane gas created during the natural decomposition of organic material to drive a turbine. Several bio-mass power stations have been established on the sites of old rubbish tips, tapping (c) Water-generated power – immediately, most people think of hydro-electric and for the most part (at least in Australia) they’d be right. However, the “green power” people will not allow their power to be sourced from any new dam or river diversion so this option is now, for all intents and purposes, at its peak (upgrades to existing hydro-electric facilities are allowed). Turbo installations range from backyard, hobby types (perhaps on a stream flowing through a rural property) producing perhaps a couple of hundred watts, to giant dams with huge flows of water, producing many megawatts. There is another source of water power, as yet relatively unknown in Australia, and that is tidal. In many places in the world (including the north-west of Western Australia) tide heights are measured in tens of metres and this inflow and outflow can be used to generate electricity via a turbine. The disadvantage is that the flow stops, builds, reaches a peak, stops, builds in the opposite direction, reaches a peak and stops again, twice every day. Due to lack of flow around high and low tide, electricity of any significant magnitude can only be generated for perhaps half to two-thirds of each six-hour cycle. An ocean wave converter generator is reported to be currently under construction (or at least in planning) off the coast of Portland, Victoria. (d) And, of course, solar power, where in most cases the electrical energy is created through sunlight striking a photo-voltaic cell. Until quite recently, the amount of power generated this way was either very www.siliconchip.com.au small or very expensive – but this is changing. It is solar power we are looking at in this feature. Before we leave this introduction there are two other forms of solar power generation which bear mentioning. The first is where a large “field” (perhaps several hectares) of sun-tracking mirrors (called a “heliostat”) focus the sun’s rays on a steam-producing boiler (usually high on a tower). This in turn drives a turbine, generating electricity. Such systems are in use overseas. The temperature at the focal point of the mirrors can be extremely high – many thousands of degrees! The second form of solar generation, still somewhat in the “theoretical” stage but likely to appear this decade, is a huge solar-powered “chimney”, incredibly tall (a kilometre or more) and 5km wide at the base. The sun heats air at the base which rushes up the chimney, driving turbines on the way. Such a project, which will have a peak output of 200MW, has recently been announced for Ned’s Corner in far north-western Victoria. But this is not quite the solar installation for a suburban house! Solar for all There is no doubt about it – the “push” for solar power is gaining momentum (even if the installation is not quite keeping pace). It received quite a “kick along” prior to the 2000 Olympic Games when 629 buildings in the Olympic Village (now the suburb of Newington) as well as the 19 lighting towers on Olympic Boulevarde were fitted with solar power modules from BP Solar. You may have seen recent television adverts supporting the “solar for schools” project – in fact, there are now more than 25 schools listed as “generators” of electricity via their solar panels. Few, if any, would be significant net producers of power; they would use all the power they generate themselves (thereby reducing their energy bills). They are somewhat fortunate in that most, if not all, of their power demand occurs during daylight hours. When you have large expanses of roof space (and often, in the case of schools, elevated roof space at that, away from shading of trees and other buildings) there is room to fit large numbers of solar panels. The rule is simple: the more panels, the more power. On the downside, naturally, the more panels, the higher the initial cost. But even with a large installed solar capacity, can a school – or even a house – generate enough electricity to make it an economic proposition? You be the judge. One product/company which caught our attention (after much media fanfare!) is “Plug&Power” from Pacific Solar. This company, by the way, is a spin-off from the University of NSW which provided the intellectual property. The company’s vision is “to have developed solar cells seen across the rooftops of the world”. While this is a laudable objective, their claim that “the majority of households have enough sunshine and roof area to produce their entire energy needs” bears closer examination. Its solar panels measure 1.68m x 0.84m (1.41 square metres). Each ELAN Audio The Leading Australian Manufacturer of Professional Broadcast Audio Equipment Featured Product of the Month PC-BAL PCI Format Balancing Board Interface PC Sound Cards to Professional Systems Not only do we make the best range of Specialised Broadcast "On-Air" Mixers in Australia. . . We also make a range of General Audio Products for use by Radio Broadcasters, Recording Studios, Institutions etc. And we sell AKG and Denon Professional Audio Products For Technical Details and Professional Pricing Contact Elan Audio 2 Steel Crt South Guildford WA 6055 Phone 08 9277 3500 08 9478 2266 Fax email sales<at>elan.com.au WWW elan.com.au One of the first modules produced on Pacific Solar’s pilot-line. These 30cm x 40cm modules were sufficiently large for researchers to address most of the issues involved in scaling up technology to commercial size of up to 1m2. Photo courtesy Pacific Solar. www.siliconchip.com.au March 2002  11 its payback period beats me!) Note that none of the grid-connected systems (as far as we are aware) have any form of storage – ie, no batteries. This means you cannot get any power from your system at night, nor anything significant when it’s raining (or even heavy cloud). When it does produce power, you either use it – or sell it. Selling your electricity The owner of this house in Sydney’s inner west “is interested in a sustainable future”. He chose Plug&Power because of the “low maintenance, design and modular construction”. Pic courtesy Pacific Solar. comes complete with its own inverter and is capable of generating 150W in direct sunlight mounted at the right angle on a north/north-east-facing roof. Pacific Solar maintain that the average house in Sydney has enough roof area to allow 21 modules (29 square metres). These are capable of producing around 3.2kW (maximum). Their examples, to give them credit, are based on a probably-more-realistic 15-module, 2.25kW system. According to accepted figures, there is 1500kWh/kW of solar energy available in Sydney per annum. With a 95% efficient panel mounting (28° angle, north-east facing) that reduces the figure to 1425kWh/kW. Their figures assume an annual electricity usage of about 6800kWh in a year. The 15-module system is capable of producing nearly half the annual usage (1425 x 2.25 = 3206kWh). But is that realistic? And what happened to the earlier claim of “to produce their entire energy needs?” I know that in my own case, the 6800kWh is very much understated. My last four electricity bills shows it’s closer to 10000kWh. And that’s for a two-person household (albeit all-electric, with a pool). On the face of it, to produce 10000kWh “to provide all my energy needs” I would need to have not 21 12  Silicon Chip modules but 46. That’s some 66 square metres of roof area which have to face the right direction – north! Admittedly, about 30% of this energy is for hot water and you wouldn't use solar electricity to heat water (you’d simply use a solar heater). But that would take away some of my roof space . . . What cost? So far, we haven’t looked at costs – let’s do so now. To install a solar power system, you’re up for anywhere between $5000 and $30,000, depending on size (of system) and the supplier. Large systems may go even higher (we’ve seen quotes for $50,000). Now before you fall of your chair, it’s not quite that bad because the Australia Government has a rebate program to encourage more people to install solar power. There are various rebates depending on the size of your installation. A small installation is worth $5.00 per watt of installed solar capacity while a larger one is worth $7500 plus (in NSW) $2.40 per watt over 1500W. The program, which is available to all owner-occupiers, runs out in 2004. There are some conditions, one of which is an agreement to keep the system running for at least five years. (Why on earth you would spend all that money and pull it out way inside If you install a system which generates more power than you can use, in many cases you can sell the excess back to your power company. Some energy suppliers apparently do not yet have a firm policy on this but of those that do, the majority will pay you (or give you a credit on your bill) at the same rate as you currently pay for electricity. In at least one case, it’s much more generous than that: the Northern Territory’s Power and Water Authority sell power to you at 12.9c per kilowatt-hour but will buy power back from you at 16.9c per kilowatt hour! Hey, let’s move to Darwin! In some cases the power companies will charge you extra to install either a special bi-directional electricity meter (normal meters cannot run backwards) or install an “outgoing” meter which is read in conjunction with your normal “incoming” meter. The first is subtracted from the second to achieve your power usage. Payback period Putting in a solar system is not going to make you rich in power savings. In fact, it’s probably not even going to break even. Let’s look at the sums: Say the system you put in costs $20,000. Take off the full Government rebate and you’re still paying more than $11,000. If your current electricity bill is, say, an average of $200 per quarter, $11000 is equivalent to 55 quarters – almost 14 years – before you recover your investment. Take into account interest lost or paid and it’s probably more like 20 years. Even discounting a tad for the pittance you’ll receive in energy credits, you’re still well over 18 years before it starts paying for itself. Given that the average Australian family will move house at least once (and probably twice or more) in that www.siliconchip.com.au Better ways to save “greenhouse” gases So installing a solar system on your roof may not be the way to go. But you still want to do something about reducing greenhouse gases. What can you do? There are plenty of things you can do and they will also give you a big payback in terms of reduced energy bills. Here are some of them: (1) Buy a new car. No, we are serious. If your car is more than ten years old, you should buy a new one, to help the environment. Can’t afford a new car? Well, then you certainly can’t afford “plug&power” or any other of these schemes either. (2) Get rid of your lumbering full-size 4WD. We cannot understand how anybody who is concerned about greenhouse gases can justify driving these monstrosities. Typically, they use 80% more fuel than a big car such as a Commodore, Falcon, Mitsubishi Magna or Toyota Avalon. And full size 4WD vehicles use at least twice the amount of fuel compared to medium-size cars such as Ford Lasers, Toyota Corollas, Mitsubishi Lancers etc. safer than 4WD vehicles. OK, so you want a 4WD for your bush holidays. Fine. Buy a small car and hire a 4WD during your holidays – you will still save heaps. (3) Buy a new fridge. If you don’t have air-conditioning or a swimming pool, your refrigerator’s electricity use is a major part of your electricity bill. New refrigerators are much more efficient than your old unit, especially if it is more than ten years old. By the way, put your old fridge on the next council cleanup for recycling. Don’t use it as a beer fridge or give it away for the same use – you do want to see electricity saved, don’t you? (4) Get rid of your freezer. Most households simply don’t need a separate freezer. You’re better off using fresh meat anyway. Instead, buy the largest refrigerator which will fit into your kitchen and use the freezer compartment in that. (5) Replace your old dish-washer. New machines use less water and consume less power. They’re much quieter, too. with a gas system. It may not be cheaper to buy or to run, but it will produce less greenhouse gases. (7) Use gas heating or a reverse-cycle air-conditioner for your home heating in winter. Gas heaters are far more expensive to buy than electric radiators but they produce less greenhouse gas to give the same (or more) heat. The same comment goes for a reverse-cycle air-conditioner. They cool in summer, as well. (8) Install a solar hot water system. This list is not comprehensive but if you really want to spend some money to reduce your greenhouse gas emissions, these are the intelligent decisions you can make. OR you can invest your money in “green” companies. If you have lazy $5000 or more laying about, why not invest it in companies which are committed to a “green” outlook. Apart from being much cheaper to drive (and therefore more greenhouse-friendly), new cars are much (6) Use gas hot water. When your electric hot water system fails, replace it There are quite a few such companies listed on the Australian Stock Exchange or you can invest in an “ethical” managed fund. That way, you benefit the environment and hopefully, make a profit as well. 18 years, you will probably never get out of the red! Can’t afford a big system? Here’s one being marketed at the moment: Pacific Solar’s "Member’s Pack”. It comprises a three-module system along with a Sunlogger (keeps track of energy generated), a Sundown program for your PC and a regular newsletter. It costs just under $6000 (and that’s after the government rebate) but the one thing you can be sure of is that you won’t ever generate much power to sell! They claim this system “on average will supply enough electricity over a year to run the lights, television, video, microwave and toaster of the average house. . .” Oh yeah? Let’s see: the three-module system at best generates 450 watts. But that doesn’t happen from dawn to dusk. Nor does it happen when it’s cloudy or rainy. We mentioned the accepted figure of available solar energy in Sydney is 1425kWh/kw per annum. With the 450W system, you’re going to produce 641kWh per year (.450 x 1425) OK, so you have this 641kWh per year to play with. Now let’s see. In order – lights in an average home, say 10 rooms with an average 75W globe; 750W. Television: oh, about 250W. Video: a modern one, say 50W. Microwave: about 1000W. Toaster (even a measly little one): 800W. All that comes to a smigeon under 3000W. Naturally, not everything is going to be on all the time. The average Aussie TV set is on for 5 hours a day. 5 hours x 365 days x 250 watts = 456kWh per annum. Most people leave their videos on constantly – 440kWh. The toaster may only get a workout for 10 minutes a day (if that) – 48kWh and the microwave perhaps half an hour a day – 182kWh. Lights, of course, vary all over the place and are usually only on for 5-6 hours a night. Let’s then assume that one third of the lights will be on at any one time – say 22kWh (probably a bit conservative because most light usage will be in the kitchen/ living/lounge room areas). That’s 456 + 440 + 48 + 182 + 22 . . . 1200kWh (1.2MWh) per annum, in round figures. Now when I was at school (it was a couple of years ago and things might have changed . . .) 1200kWh into 640kWh doesn’t go (even if I did fail maths!). So who is kidding whom? www.siliconchip.com.au March 2002  13 Solar panel installations do not have to be roof-mounted. This one is on a frame in the back yard and has the added advantage of being able to turn to track the sun, keeping the angle at the optimum for virtually the whole day. Incidentally, buying that 1200kWh from your electricity supplier at 10c per kWh will cost you the princely sum of $120. Makes the $6000 installation cost of the solar system looks pretty sick, doesn’t it? 640kWh would of course cost about $64 so you’re looking at a payback period of, oh, about 100 years give or take. Of course, all this assumes that energy costs will stay around where they are now. While most fuels have risen dramatically in recent years, electricity is one which has shown admirable restraint. Again, I remember from school in the (late!) sixties, we used a figure of 5c per kilowatt hour in maths problems. Today my power bill says I pay 9.38c per kilowatt hour – not bad for forty years of often double-digit inflation! But that’s not to say our electricity costs will not increase in the future: they probably will. Then there may be some better cost justification for domestic solar power. Costs of the solar panels themselves will almost certainly continue to fall. Not only due to costs of production but also due to the huge amount of R&D investment, solar panels will not only get cheaper in the future, they will get more efficient at converting the sun’s energy into electrical energy. And Pacific Solar, among others, are getting pretty excited about thin film solar panels which are expected to start appearing about the middle of this decade. This second generation PV technology is expected to more than halve the cost of manufacture. 14  Silicon Chip While we're talking of the future, let me throw this one in: all the reading I’ve done on this subject tells me that heat is one of the biggest problems with solar panels. So why not produce a solar panel which is water cooled – presto, a solar water heater built into the photovoltaic panel? Sounds feasible, don’t you think? Another random thought (I have plenty of those): it seems to me that cladding a roof (with tiles, iron, etc) then placing the solar panels above that is a waste of roof cladding. Why not make a solar panel which IS the roof cladding? But I digress . . . The environment Most of the “case studies” I have read involve a significant environmental commitment on the part of the homeowner installing solar power. They wanted to “do their bit” for the environment and were willing to pay to do it. Australians today are generally much more environmentally conscious than their parents or grandparents. In those days there was scant information about the environment; there was even less effort to improve it. Today, that’s all changed. We recycle our garbage as much as possible. We try not to pollute our waterways. We’re conscious about dirty car exhausts. And so on. People today get a “warm and fuzzy” feeling about doing the environment good. Even if they are sometimes misinformed or even misguided, that doesn’t hurt anyone and may leave the planet a better place for our children! If you believe in the greenhouse effect and want to minimize CO2, fair enough. Each Plug&Power module installed (or similar product from other suppliers) prevents almost 250kg of CO2 from being generated in a coalfired power station each year. Wow! (Yes, I am being facetious . . .) A 10-module installation (1.5kW) will save over 60 tonnes of CO2 over the system’s 25-year life. Again, in the overall scheme of things this isn’t going to achieve much at all. There are much better ways to reduce energy use and therefore “save the environment” (see separate panel). Despite the intense efforts of the Government and industry to promote solar energy for homes, the Australian Bureau of Statistics has indicated recently that the use of renewable energy, especially solar power for domestic purposes, has actually declined. Perhaps consumers are thinking more with their wallets than their SC hearts? References: (These are just some of the websites where you’ll find information on solar power for the home. Google "solar power" and you’ll get thousands more!) Pacific Solar ("Plug&Power" is their trademark): www.pacificsolar.com.au BP Solar: www.bp.com/bpsolar Western Power (WA): www.westernpower.com.au Citipower (Melbourne): www.citipower.com.au Energy Australia (Sydney): www.energyaustralia.com.au An excellent educational site for school projects, general information, etc: www.env.qld.gov.au/sustainable-energy/publicat/ Links to hundreds of solar power sites: www.pv.unsw.edu.au/solpages.html The "Greenhoax" effect: www.geocities.com/Yosemite/7915/Greenhoax.html (or Google "Greenhoax effect") www.siliconchip.com.au S O F T W A R E : VIDEO SYNC. STABILISER KIT: BACK IN STOCK Various forms of copy protection are used on Video tapes & DVD's, the problem is that this changes the normal signal and may cause playback problems such as jitters. This device removes the copy protection by stripping and reinserting the sync. pulse and thus cleaning the picture. This items comes as a Ready built PCB. The Case shown in the picture & 9V battery are not Supplied. The 9V battery Connector will need to be Soldered to the PCB. KIT PRICE: (K176) $29 30 LED IR ILLUMINATOR KIT: Illuminates Night Viewers or CCD Cameras using 30 of our 880nm / 40° IR leds which have 35mW output. These leds have a forward good stocks and an ongoing source of this hard to (NEW) SOUND BLASTER LIVE! 5.1 SE Voltage drop of 1.65V & a water clear get chip at just ....$8 ea. AND BOSTON ACOUSTICS lens. Operates from 12V DC at NEW!!!! TRIPLE ELEMENT CERAMIC HEATER Approx.300mA. The leds are ASSEMBLY: As used in small household style DIGITAL ENTERTAINMENT heaters, around 2kW total at 240V but not linear, the This special edition is supplied with the PCI card, Software on CD arranged into 6 strings of 5 leds in resistance of each element is around 600ohms and leads to connect the card to a CD-ROM. Visit the creative series. PCB Measures 78 x when cold, could be used at website for further information. These are brand new in their retail 49mm (Replaces The lid of our lower voltages for incupackaging. A manual is not supplied but can be downloaded The Hb1 small Plastic box available Separately). bators or dummy loads card has a digital output KIT PRICE: (K102) $20 etc. etc, 240V/120mm suitable for driving the (USED) 33.6K HAYES ACCURA MODEM: fan, plus a triple mains Boston Acoustics sound Why get a 56K Modem when most telephone lines only rated switch will be system: (SBDE51) $100 allow up to 33.6K? These 33.6K Hayes ACCURA 336 supplied with each unit, These cards can only be External Modems are in good condition. We supply the whole assembly for purchased with a Boston these modems with a 9V <at> 1A plugpack. The less than the price of Acoustics sound system. plugpack has a different connector and will require the fan!: $15 Previous purchasers of changing (correct plug not supplied). We are selling the Boston Acoustics these modems for a small amount of their retail price: sound system may also BARGAIN BUSINESS SPEAKER(ZB0302) $22 each (limited quantity) Purchase these cards. PHONE: BACK AGAIN! (NEW) HOTDOG JUNIOR ITS BACK!!! GIANT SERVO REDESIGNED With a new servo controller chip (M5660L to replace This Web Page Creation the obsolete ZN409), as used by a large number of Software is Brand New in hobby servo manufactures. This kit is Ideal for original packaging. Inc. two robotics projects and will work just like a normal CDs, one Hotdog Junior CD servo with our servo controller kit or with regular for Web Page creation & the other CD has 50,000 Clipart Radio Control equipment. Use your Objects. This software helps own motor and gearbox or you create & publish your first we may have some Web Page in four basic steps. To suit , Check It is designed for children 6 our web site. years & up but it can also be $28 used by adults (beginners). Coming soon We are selling this software NEW FWD/REV & for a fraction of it’s retail price. FWD/BRAKE R/C speed controllers Check out http://www. SERVO CONTROLLER CHIP M5660L sausagetools.com/products/ for more info(ZB0320) $11 ea. Replacement for the obsolete Zn409. We have 5 1 $ 9 6 1 $ AS REVIEWED IN THIS MAGAZINE $5 5 PANASONIC KX-TS85ALW telephones were used during the 2000 Olympics. Lots of features inc. speed dialler, Hands Free Volume Control, Call Waiting, Ringer Indicator, Call Forward, Dial lock, Redial, Recall. You will find these as a newly introDELUXE BINOCULARS: duced product in a Major These 3 x 22 Binoculars are Brand New in original Australian Electronics dealers' packaging. These are adjustable and are very clear catalogue for $161. Manual is with a resolution of 3x. It not supplied but can be downcan also be fully dismantled loaded from our web-site(KXTS85) for experimental purposes. (Used) The Citizen iDP3530 Printer: These Binoculars are These Printers are in excellent condition and are excellent for watching made in Japan. They come with basic software, a cricket, tennis and any Brand New Paper roll and a Ribbon. The Citizen printer is a rugged Point of Sale Printer with a serial RADIO CONTROL CAR / TRUCK REAR AXLE (DIFERENTIAL) other sports. ZB0334 ASSEMBLEY Complete drive assembly from a model car $2 (pack of three) interface. It is capable of being used including wheels, gearbox and a 380 motor. The wheel diameter on A wide variety of hardware (NEW) PROVIEW FRESNEL LENS: is 9.5 cm and the distance Type supplied platforms, not confined to a std These Fresnel Lens are Brand New and and can be Between the outside wheels may differ PC. This opens up a range of used as a rear window lens for backing & driving Is approximately 24 cm. from the other uses such as Capturing safety. The lens enables you As used in some Tandy one shown. call details on a PABX, Logging to actually see many things Electric cars. We have a data from a Weather Station or you cannot see through your good quantity in stock for a recording the Performance inside rear mirror or side Small fraction of of a Solar Water Heater. Any mirror - greatly increases Their retail price. equipment with a standard RS232 port the angle of vision. Also a (MRC1) $13 each is capable of utilising this printer. $99 great experimental item. Dimensions are 7" x 10": (ZB0303) $3 each We have more used test CAMBRIDGE SOUNDWORKS COMPUTER SPEAKERS equipment coming all the time and We have a limited quantity of these Cambridge SoundWorks GCS300 we need to clear stock to make way Computer Speakers. These are Brand New in original packaging that for the next lot. The only way to includes two speakers with power supply, cables, and manual. 395nM UV LED's... make sure you don’t miss out is to Response: 90 - 20kHz... 200mCD $4.70 subscribe to our bargain corner & Amplifier Gain: 12dB <at> Blue LED's receive advanced notice by E-Mail 1KHz volume max... Just send us a blank E-Mail to.... Output Power: 92 dB SPL at . 3.5CD $3.50 5m listening position... b a r g a i n c o r n e r - s u b s c r i b e Power (each satellite): White LED's <at> o a t l e y e l e c t r o n i c s . c o m 2 Watt... 6CD $2.50 Input Impedance: 10CD $4 10K ohms... Controls: On/off/master 15CD $6 Volume on right speaker... 650nM LASER MODULES Weight: 1.5Kg per speaker set including adapter... Dimension:153X101X114mm..(GCS300): $22 - limited quantity. 3mW $18 COMING SOON !!! 6mW $36 LOW PRICE COLOUR CMOS CAMERS WITH FREE VHF MODULATOR ROBOT BUILDERS BARGAIN!!! $99 ULTRA-VIOLET LEDS!!! MORE NEW STOCK LEDS AND LASERS 10mW CK O ST !!! W W NE N NO I $90 Just watch this space or check our web site for more details www.oatleyelectronics.com Orders: Ph ( 02 ) 9584 3563, Fax 9584 3561, sales<at>oatleyelectronics.com, PO Box 89 Oatley NSW 2223 major cards with ph. & fax orders, Post & Pack typically $7 Prices subject to change without notice ACN 068 740 081 ABN18068 740 081 SC_MAR_02 A COMPACT 70W CLASS-H AUDIO AMPLIFIER MODULE Based on a Philips TDA1562Q IC, this compact audio amplifier module can deliver up 70W into a 4-ohm load when pow­ered from a 12V car battery. It’s just the shot for use in a portable PA, a tiny sub-woofer amplifier, a busking amplifier or a car audio amplifier. By RICK WALTERS O UR NEW MIGHTY MIDGET Amplifier can really pack a punch – around 36W RMS continuous into a 4-ohm load when using a 13.8V supply. However, it’s the 70W of output power that it can deliver during dynamic (music) signal conditions that really make you sit up and take notice. As can be seen from the photos and the circuit diagram, the Mighty Midget uses just a handful of parts. It’s built on a PC board that measures just 104mm x 39mm but while its size may be modest, these’s nothing at all modest about its power output. And the noise and distortion figures are pretty good too. At the heart of the circuit is the TDA1562Q IC, de­scribed by Philips as a “monolithic integrated BridgeTied Load (BTL) class-H high-efficiency power amplifier”. It comes in a 17-pin “DIL-bent-SIL” plastic package and is not only designed for use in car audio and portable PA work but for mains applications as well; 16  Silicon Chip eg, mini/midi audio components and TV sound. Specifications The specifications panel and the accompanying graphs show the performance of our prototype, as measured on our Audio Precision test gear. Note that the total harmonic distortion is typically less than 0.2% at 1kHz for output powers up to about 16W PERFORMANCE Output power: 36W RMS into 4Ω Music power: 70W into 4Ω Frequency response: -1dB down at 28Hz and 55kHz Input sensitivity: 130mV RMS (for 36W into 4Ω) Harmonic distortion: typically 0.2% (see graphs) Signal-to-noise ratio: >95dB unweighted (22Hz to 22kHz) RMS, while the signal-to-noise ratio is better than 95dB unweighted (22Hz to 22kHz). The frequency response is virtually ruler flat from 28Hz to 55kHz. Pumping it out So how does it achieve such high output powers when powered from a 13.8V rail? Well, it employs a few clever tricks. Let’s take a closer look. First, the TDA1562Q chip actually incorporates two power amplifiers in its package and these are operated in bridge mode to boost the available output power. Fig.1 – the block diagram of the TDA1562Q IC – shows the general idea. Normally, if we have just one amplifier stage operating from a 13.8V supply, the maximum power that can be delivered into a 4Ω load is about 6W. The reason for this is that the maximum voltage “swing” possible from a 13.8V supply is 6.9V in the positive direction and 6.9V in the negative direction. This is equivalent to about www.siliconchip.com.au C1+ 5 C13 status I/O mode select 16 4 CLASS-B CLASS-H FAST MUTE VP2 10 LOAD DUMP PROTECTION TEMPERATURE SENSOR disable STANDBY MUTE ON VP1 9 LIFT-SUPPLY CURRENT PROTECTION VP* IN+ 1 PREAMP 7 POWERSTAGE 75 kΩ FEEDBACK CIRCUIT TDA1562Q PREAMP POWERSTAGE LOAD DETECTOR 75 kΩ IN- Vref 2 DYNAMIC DISTORTION DETECTOR 8 11 diagnostic OUT- VP* 14 15 kΩ signal 17 GND OUT+ DIAGNOSTIC INTERFACE disable LIFT-SUPPLY TEMPERATURE PROTECTION reference voltage MGL264 15 C2- 13 C2+ 6 PGND1 12 PGND2 Fig.1: block diagram of the TDA1562Q class-H audio amplifier IC. The “Lift Suppy” stages drive external capacitors (C1 & C2) to boost the supply rails when needed. 4.88V RMS (ie, 6.9/1.4142). From there, the mathematics is simple enough – the power output is equal to the square of the RMS voltage divided by the load resistance; ie, P = V2/R. This means that we get 4.88 x 4.88/4, or about 5.95W RMS. However, this is a theoretical maximum and is never re­alised in practice. The actual output power is likely to be closer to 4.5W RMS due to losses in the output devices of the amplifier. One way of obtaining more power is to wire two identical power amplifiers in “bridge” mode, with each amplifier essential­ly a “mirror” of the other. One amplifier drives one side of the loudspeaker in a positive voltage direction, while the other drives the other side of the loudspeaker in a negative voltage direction. As a result, the voltage across the loudspeaker is effectively doubled compared to the voltage delivered by a single power amplifier. This doesn’t just double the power output, though. Instead, as shown Fig.2: the circuit uses a phase splitter based on IC1a & IC1b to drive the inputs of IC2 in anti-phase. www.siliconchip.com.au March 2002  17 Fig.3: total harmonic distortion (THD) vs. frequency at 12W (measurement bandwidth 10Hz-80kHz). The dip at 100Hz is due to cancellation with supply ripple. Fig.4: total harmonic distortion vs. frequency at 36W (measurement bandwidth 10Hz-80kHz). It’s less than 0.5% for frequencies from 30Hz to 10kHz. Fig.5: total harmonic distortion vs. power output at 1kHz (measurement bandwidth 22Hz-22kHz). Fig.6: the frequency response at 1W. It’s just 1dB down at 28Hz and 55kHz. by the above formula, doubling the voltage swing effec­tively quadruples the output power! So if we use two amplifiers which on their own can deliver only about 4.5W into 4Ω, we can expect to obtain about 18W RMS into the same load when they are connected in bridge mode. And 18W RMS is a “helluva” lot better than 4.5W RMS. Jacking up the supply That’s by no means the end of the story, though. As pre­viously stated, the TDA1562Q is capable of delivering 36W RMS and up to 70W of music power. How does it do this? Well, according to Philips, at low output powers, up to 18W, the device operates as a normal BTL amplifier. However, when a larger output voltage swing is re­quired, the 18  Silicon Chip internal supply voltage to the power amplifiers is “jacked up” by using the “Lift-Supply” stages to switch in two external electrolytic capacitors – see Fig.1. There are no details in the specifications as to how the “Lift-Supply” stages work but we assume it’s a type of boot-strapping circuit whereby each of the two power amplifiers in the bridge circuit actually “jacks up” an external 4700µF capacitor to increase the effective supply voltage. Normally, the external electrolytic capacitors are switched across the 13.8V supply and charge to about 12.8V (ie, about 1V less than the supply rail). When extra power is required, these ca­pacitors are boosted up by the respective power amplifiers so that ultimately, the supply voltage is almost doubled. As a result, the amplifier module can briefly deliver much greater output power – up to 70W of music power or up to 36W RMS (ie, continuous power) as previously mentioned. Of course, it cannot maintain 70W of output power for long. The two external capacitors immediately begin to discharge when the amplifier is delivering this sort of power and so the supply rails quickly falls again. On practical music signals, however, this isn’t normally a problem, as the electrolytic capacitors are quickly switched out and charged again between the signal peaks. Class-H or Class-G? Philips refer to this scheme for operating the power ampli­fiers as class-H operation. In class-H operation, the input signal is monitored and the www.siliconchip.com.au supply rail is constantly adjusted to provide just enough voltage for optimum operation of the output devices. By contrast, class-G operation involves monitoring the input signal and switching the output stage between two different supply rails, as required. In this scheme, the (class-AB) output stage is normally connected to the lowest rail and automatically switches to the higher rail for large signal peaks. So which of the two schemes is it? Philips label the TDA1562Q as a class-H amplifier and we are inclined to agree with this although we still don’t know the exact mechanism of the “Lift Supply” circuitry. No matter – which ever label is used, it’s very effective at boosting the output power. Another advantage of class-H (or class-G) operation is that it reduces dissipation in the output stages by about 50%. That’s because the output stages operate at low voltage for most of the time when the amplifier is driven by music signals. This means that the heatsink size can be greatly reduced. By the way, all switching from class-AB to class-H opera­ tion (and vice versa) takes place at zero crossing points of the input signal. This is done to eliminate switching artefacts, which could otherwise cause distortion in the output signal. It’s a very effective technique – we could find no traces of switching noise whatsoever. A rugged device Another good thing about the TDA1562Q is that it is virtu­ally indestructible (within limits). It’s output stage is short-circuit proof (either to ground, the supply rail or across the load) and it features thermal overload protection, good supply ripple rejection and static discharge protection. There are also no switch-on or switch-off plops and the output is automatically muted if the supply voltage drops below the minimum operating level. The thermal overload protection works by automatically switching the device from class-H to class-AB operation if its case temperature exceeds 120°C. This basically disables the high-voltage supply and thus limits the output power to less than 20W. Circuit description Refer now to Fig.2 for the complete circuit details of the Mighty Midget Amplifier. Apart from the TDA1562Q itself (IC2), there is a dual op amp IC (IC1), two air-cored inductors and a few resistors and capacitors. Op amps IC1a and IC1b together function as a phase split­ ter. These stages are necessary to provide a differential input to the amplifiers in IC2, both of which have their inputs at pins 1 & 2. As shown, the input signal is fed to pin 3 of IC1a. This functions as a non-inverting amplifier with a gain of 2.4, as set by the 47kΩ and 33kΩ feedback resistors (ie, Gain = 1 + 47/33). Its output is AC-coupled to pin 2 of IC2 via a 0.1µF capacitor and drives IC1b which is wired as an inverting unity gain ampli­fier. IC1b in turn drives pin 1 of IC2 via a 0.1µF capacitor. As a result, the signal on pin 1 is inverted (180° out of phase) compared to the signal on pin 2 and so we get true differ­ ential drive to IC2, with a gain of 2.4 for each input. The input impedance for each pin is 75kΩ (with respect to Vref) and so the low-frequency rolloff with 0.1µF input capacitors is about 20Hz. Bias for IC1a & IC1b is provided by a voltage divider con­sisting of two 10kΩ Parts List 1 PC board, code 01203021, 104 x 39mm 1 1-metre length of 1mm-dia. enamelled copper wire 1 heatsink (eg, Jaycar HH-8566 & HH-8572; DSE H-3460; Altronics H-0560 & H-0522) 2 2-way PC-mount screw terminal block (5.08mm pitch) 4 PC stakes 2 15mm x 6BA machine screws 2 6BA nuts 4 6BA washers Heatsink compound Semiconductors 1 TL072 dual FET op amp (IC1) 1 TDA1562Q BTL power amplifier (IC2) Capacitors 2 4700µF 16VW PC-mount electrolytic 1 2200µF 25VW PC-mount electrolytic 2 100µF 25VW PC-mount electrolytic 1 0.33µF MKT polyester 2 0.22µF MKT polyester 4 0.1µF monolithic ceramic Resistors (0.25W 1%) 2 47kΩ 4 10kΩ 1 33kΩ 2 2.2Ω 1W resistors. The resulting half-supply voltage (Vcc/2) is then filtered using a 100µF capacitor and is directly connected to pin 5 of IC1b. It also biases pin 3 of IC1a via a 47kΩ resistor and this ensures that pin 1 swings symmetrically about Vcc/2. IC2 operates with a nominal fixed gain of 20 or 26dB. Its two internal There are far more reasons to visit our new website... w w w. f a r n e ll. c o m Secure online ordering Over 90,000 products Easier navigation Over 15,000 data sheets Online stock checking Powerful search engine You get far more from Call 1300 361 005 www.siliconchip.com.au A Premier Farnell Company March 2002  19 Table 2: Capacitor Codes     Value IEC Code EIA Code 0.33µF   330n   334 0.22µF   220n   224 0.1µF   100n   104 (pin 16) is tied high to ensure that the amplifier operates in class-H mode. PC board assembly Fig.7: follow this layout diagram when installing the parts on the PC board. Make sure that all polarised parts are correctly oriented. All the parts for the Mighty Midget Amplifier are accommo­ dated on a PC board measuring 104mm x 39mm and coded 01203021. Fig.7 shows the assembly details. Before mounting any parts, first check your PC board for etching defects or undrilled holes by comparing it with the published pattern (Fig.8). This done, you can start the assembly by fitting the wire links, the resistors and the MKT capacitors. The two 100µF capacitors can then go in, taking care with their polarity. Table 1 shows the resistor colour codes but it’s a good idea to also check them using a multimeter. That’s because some of the colours can be difficult to decipher. The next step is to wind the two inductors that are used in the Zobel networks. These are made by winding 20 turns of 1mm enamelled copper wire onto a 5mm former (eg, a 5mm or 3/16-inch drill). Note that you will have to wind the last five or six turns back over the winding, so that the inductor leads line up with the board mounting holes. Because of space restrictions, the inductors are mounted proud of the PC board, so that they sit clear of the 2.2Ω resis­tors. Clean and tin the ends of the leads before soldering them in position. That done, fit the screw terminal block for the supply connections, followed by PC stakes for the signal input and loudspeaker terminals. Fig.8: this full-size etching pattern for the PC board (code 01203021). amplifiers amplify the signals on pins 1 & 2 and in turn provide out-of-phase (mirror image) signals to drive the bridge tied load (BTL). This BTL consists of a loudspeaker which is fed via two Zobel networks, each consisting of a 2.2Ω resistor and a parallel 880nH inductor. The Zobel networks present a resistive load to the amplifi­er at high frequencies and ensure stability. They also help reduce transient and RF interference, which can be picked up by the loudspeaker leads, from being fed back into the early stages of the amplifiers via the feedback paths. The two external capacitors for the “Lift Supply” blocks each have a value of 4700µF. This value determines the low-frequency power roll-off. Pins 4 and 16 of IC2 have been tied high in this circuit. Pin 4 (Mode) must be tied high for normal operation – tying it low places IC2 into “standby” mode (effectively switch­ ing it off), while leaving it open circuit mutes the output by suppressing the input signal. Pins 8 (Diag) and 16 (Status) are normally used in conjunc­ tion with a microcontroller to monitor various parameters. For example, the “Dynamic Distortion Detector” inside the TDA1562Q can detect the onset of clipping and this information is fed to the diagnostic output. It could then be processed to drive a DC-volume control to attenuate the input signal accordingly and so limit the distortion. Similarly, the diagnostic output can indicate various short-circuit and temperature conditions. It can either be left open-circuit or tied to the +12V rail via a 10kΩ resistor. The Status pin Table 1: Resistor Colour Codes  No.   2   1   4   2 20  Silicon Chip Value 47kΩ 33kΩ 10kΩ 2.2Ω 4-Band Code (1%) yellow violet orange brown orange orange orange brown brown black orange brown red red gold brown 5-Band Code (1%) yellow violet black red brown orange orange black red brown brown black black red brown red red black silver brown www.siliconchip.com.au The Tiger comes to Australia The BASIC, Tiny and Economy Tigers are sold in Australia by JED, with W98/NT software and local single board systems. This close-up view shows the prototype PC board. The final version (Fig.7) has been amended to include a screw-terminal block for the supply connections and also features improved component spacing (especially near the inductors). Tigers are modules running true compiled multitasking BASIC in a 16/32 bit core, with typically 512K bytes of FLASH (program and data) memory and 32/128/512 K bytes of RAM. The Tiny Tiger has four, 10 bit analog ins, lots of 2 digital I/O, two UARTs, SPI, I C, 1-wire, RTC and has low cost W98/NT compile, debug and download software. JED makes four Australian boards with up to 64 screw-terminal I/O, more UARTs & LCD/keyboard support. See JED's www site for data. TIG505 Single Board Computer The TIG505 is an Australian SBC using the TCN1/4 or TCN4/4 Tiger processor with 512K FLASH and 128/512K RAM. It has 50 I/O lines, 2 RS232/485 ports, SPI, RTC, LCD, 4 ADC, 4 (opt.) DAC, and DataFLASH memory expansion. Various Xilinx FPGAs can add 3x 32bit quad shaft encoder, X10 or counter/timer functions. See www site for data. $330 PC-PROM Programmer The TDA1562Q is secured to the heatsink using two 15mm x 6BA machine screws, nuts & washers. This also provides sufficient support for the PC board. IC1 & IC2 can now be installed and the PC board fitted to the heatsink. Make sure that IC1 is installed the right way around, with pin 1 adjacent to the 47kΩ resistor. IC2 can only go in one way, so there’s no chance of confusion here. The next job is to drill two holes in the heatsink to match the mounting holes at either end of the TDA1562Q. That done, deburr the heatsink mounting holes using an oversize drill and smear the mating surface of the TDA1562Q with heatsink compound. www.siliconchip.com.au The assembly can then be bolted together using two 15mm x 6BA machine screws, nuts and washers. You can now complete the assembly by fitting the three large electrolytic capacitors but watch their polarity – electro­ lytic capacitors have a nasty habit of exploding if installed the wrong way around. These capacitors are all left until last to avoid accidental damage and, in the case of the centre 4700µF unit, to ensure access to the lefthand mounting screw for the TDA1562Q. This programmer plugs into a PC printer port and reads, writes and edits any 28 or 32-pin PROM. Comes with plug-pack, cable and software. Also available is a multi-PROM UV eraser with timer, and a 32/32 PLCC converter. JED Microprocessors Pty Ltd 173 Boronia Rd, Boronia, Victoria, 3155 Ph. 03 9762 3588, Fax 03 9762 5499 www.jedmicro.com.au March 2002  21 Fig.9 (above left): the top trace shows the continuous output from the amplifier terminals at 36W into 4Ω. The lower two traces show the individual amplifier outputs which add to give the final BTL output. Fig.10 (above right) shows the same test conditions as for Fig.9 but with a music-power signal at 70W into 4Ω. Note that pin 4 (Mode Select), pin 8 (Diag) and pin 16 (Status I/O) have been brought out to vacant pads. These are not used in this circuit. Testing To test the amplifier module, you will need a regulated power supply with an output of 12-15V DC (eg, a car battery or a 12V SLA battery). Be sure to connect it to the terminal block with the correct polarity. Note: a car battery charger can NOT be used as a DC supply for this amplifier module. That’s because battery chargers deliv­er significantly more than 12V (they have to in order to charge) and also because they don’t include any filtering. Initially, you should connect your multimeter – set to a DC current range – in series with one of the supply leads. This done, switch on and check that the current consumption is some­ where in the range of 110-150mA. If you don’t get this, switch off immedi- ately and check for wiring mistakes. After that, it’s simply a matter of connecting the loud­speaker and feeding in an audio signal to confirm that it works. Note that if you are using a mains power supply to drive the module, it may lack sufficient output current capability for the amplifier to deliver full power during transients. In fact, a low-current supply could even activate the muting circuit in the TDA­ 1562Q, due to the supply rail falling below about 8V. Insufficiently thick supply wire can cause the same problem - use 4mm (copper) diameter automotive cable at a minimum. In practice, to drive the amplifier to full power, the power supply will need to be able to deliver at least 6A. Note too that car electrical systems normally don’t run at 12V. Instead, most run at 13.8-14.4V when the motor is running. The Mighty Midget Amplifier is designed to handle this but don’t push the supply voltage beyond about 16V – you’ll exceed the ratings of the 4700µF electrolytic capacitors if you do. Speaker requirements You can use a huge variety of speakers with this module – even low-power speakers can be used as long as long you don’t wind the wick up to far! The main thing to note is that the TDA1562Q is designed for use with 4Ω speakers and will deliver maximum power into 4Ω. Most car audio speakers are 4Ω for this very rea­son. Of course, the amplifier will also quite happily drive an 8Ω loudspeaker. The drawback is that you will only get half the power output compared to a 4Ω speaker. Finally, there is a common misconception that large speak­ ers require more power to drive than small speakers. This is not usually the case – large speakers are usually more efficient than small speakers of similar rating and will therefore sound louder when SC driven by the same amplifier. UM66 SERIES TO-92 SOUND GENERATOR. THESE LOW COST IC’S ARE USED IN MANY TOYS, DOORBELLS AND NOVELTY APPLICATIONS 1-9 $1.10 10-24 $0.99 25+ $0.88 EACH INC GST 22  Silicon Chip www.siliconchip.com.au Fig.1 (left): the NCH Tone Generator is easy to drive and can generate a range of waveforms from 1Hz to about 20kHz. Fig.2: below: the selected tone can be saved to disk as a .wav file with selectable duration. This make it easy to create a test CD ROM with various tones. Looking for a simple yet versatile tone generator that won’t break the bank. If you already have a PC with a sound card, this one’s for free! By GREG SWAIN Audio tone generators are very useful gadgets when it comes to setting audio levels and for testing audio circuits and loud­speakers. However, provided your requirements are fairly modest, you don’t need dedicated hardware. Instead you can use your PC’s sound card to generate a range of audio tones. After all, why pay out big bucks when you can make a PC do the work for you? All that’s required is a suitable program to make the sound card do its stuff. One such program is “NCH Tone Generator” – a freeware utility from NCH Swift Sound. It works with all flavours of Windows, including Windows 3.1 (remember that?), Win95/98/ Me, Windows NT and Windows 2000. You can obtain a copy from their website at www.nch.com.au/action/ index.html and down­loading tnsetup. exe (208KB). Double-clicking this archive file automatically creates a folder called NCHTONE on your C: drive and extracts and installs three files: nchtoner. exe (the executable), nchtone.hlp (the help file) and uninst.exe (so that you can later uninstall the soft­ware). In addition, a shortcut to the program is placed in the Start menu. Firing up Fig.3: tones that have been saved to disk as .wav files can be played back using media players such as Winamp or the Windows Media Player (WMA). www.siliconchip.com.au Running the software brings up the dialog box shown in Fig.1. You select the output waveform you want by clicking the “radio” button next to it, while the required frequency is en­tered either by directly typing it in or by clicking the “+” and “-” buttons. The tone output is started or stopped by clicking the Start and Stop buttons. If you have more than one sound card in your PC, you can select which March 2002  23 Fig.4: 100Hz sinewave (1.8V pk-pk). Fig.5: 1kHz sinewave (1.8V pk-pk). Fig.6: 10kHz sinewave (1.8V pk-pk). Fig.7: 20kHz sinewave (1.62V pk-pk). Note the jitter in the waveform. Fig.8: 100Hz square wave (2.66V pkpk). Fig.9: 1kHz square wave (2.69V pkpk). Fig.10: 5kHz square wave. The rise and fall times are quite poor. Fig.11: at 10kHz, the waveform is no longer square. Fig.12: 100Hz triangle wave (1.78V pk-pk). Fig.13: 1kHz triangle wave (1.78V pk-pk). Fig.14: 5kHz triangle wave (1.6V pkpk). Fig.15: at 10kHz, the waveform is not triangular and varies in amplitude. one is used to play the sound from a drop-down list. As shown in Fig.1, the available waveforms are: sinewave, square wave, triangle, sawtooth, impulse and white noise. The valid frequency range is from 1Hz to 20kHz (1-20000) but note that the frequency setting is irrelevant if white noise is se­lected. Once you’ve selected the waveform, you can use the Line Out from your sound card to drive external audio equipment in the normal manner. The output level can be adjusted using the mixer settings for the sound card – just double-click the speaker icon on the Taskbar to do this. Note that the program remembers 24  Silicon Chip www.siliconchip.com.au Fig.16: 100Hz sawtooth (2.22V pkpk). Fig.17: 1kHz sawtooth (2.17V pkpk). Fig.18: at 5kHz, the waveform is not much like a sawtooth. Fig.18: the 100Hz impulse waveform. The scope measured it at 200Hz. Fig.19: the same waveform as Fig.18 but expanded in timebase. Fig.20: the 1kHz impulse waveform. The scope measured it at 1.8kHz. Table 1: Keyboard Controls Fig.21: this is the output from the soundcard in white noise mode. Fig.22: this scope shot shows the sinewave and its distortion products. the current settings when it’s shut down, so that they are automatically loaded next time. How does it do this? – simple, it writes the shut-down values to an “ini” file (tone.ini) which it stores in the Windows folder and then looks these values up the next time the program loads. steps but it all happens too quickly to be of any real use for the one octave steps. Keyboard control In addition to using the mouse, you can also drive the program using your keyboard. The keyboard shortcuts are as shown in Table 1. Unlike using the mouse, you can quickly “pan” from one end of the frequency range to the other by holding the keyboard keys down. This can be useful if you want to “slide” up and down the frequency range in semitone www.siliconchip.com.au Performance We were interested to check out quality of the tones, so we hooked our Audio Precision test gear up and took a few measure­ments. The sinewave distortion was pretty good, at just .01% THD at both 1kHz and 5kHz, measured with a bandwidth of 22Hz to 22kHz. Figs.4-22 show some of the waveforms, as captured on a Tektronix TDS 3014 colour oscilloscope. Saving files There’s just one more feature that we haven’t mentioned and that’s the ability to save the selected waveform Key Function Enter Start Esc Stop + Increase Frequency One Semitone - Decrease Frequency One Semitone Ctrl+ Increase Frequency One Octave Ctrl- Decrease Frequency One Octave on the hard disk as a “.wav” file. This allows you to record a range of preset tones which can later be played back by utilities such as Winamp or the Windows Media Player. Fig.2 shows the dialog that appears when you click the “Save As” button in the NCH Tone Generator utility. It automati­cally assigns a filename that reflects the type of waveform selected and its frequency and allows you to set the duration. By default, the file is placed in the NCHTONE folder but if a new folder is specified, it subsequently saves all files to this new location until SC it’s changed again. March 2002  25 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au Terra: Mission to Planet Earth Terra was launched at 1:57 pm EST on December 18, 1999 from Vandenberg Air Force Base, California. After reaching orbit, the satellite successfully deployed its solar array and its high gain antenna to enable communication with other satellites. 30  Silicon Chip www.siliconchip.com.au By SAMMY ISREB The recent NSW bushfire crisis has been one of the worst such events in Australia’s history. The intense media coverage included astounding NASA satellite photos showing the enormity of the situation. Space it seemed, gave the ultimate testimony of the ravages of the fires. So how exactly does the amazing tech­nology behind these images work and what benefits does it pro­vide? S INCE ITS BEGINNINGS in 1958, NASA has focused not just on space exploration but also on the furthering of scientific knowl­ edge regarding planet Earth. With so much unknown about the factors effecting the climate on Earth, NASA embraced Earth System Science, a field encompassing meteorology, oceanography, biology and atmospheric sciences. In the early 1990s, NASA commenced what is known as the Earth Science Enterprise, a detailed study into the Earth as an environmental system. The Earth Science Enterprise is composed of three main components: a series of satellites, an advanced data storage and processing system and various teams of scientists working to analyse the data. On the 18th of December 1999, the first of the Earth Observ­ing System (EOS) series of satellites was launched. The Terra satellite, formally known as the EOS AM-1, was built at a cost of over US$1.3 billion by Lockheed Martin Missiles and Space. The 5190kg Terra circles the Earth at an altitude of around 705 kilometres, with a polar orbit of inclination of 98°. This orbit is specifically designed to descend southwards over the equator at 10:30am (local time), at which time cloud cover is usually at its daily low. Terra orbits the Earth once every 99 minutes. During the 6-year initial duration of Terra, its orbit will be periodically adjusted to maintain its integrity (once per orbit). Five state-of-the-art instruments make up the scientific payload of Terra. These are used to generate an integrated snapshot of the Earth which is far superior to anything available from previous orbital remote sensing techniques. Dr Grassem Asrarm, NASA’s Associate Earth Science Director, commented that Terra “has nearly unlimited potential to improve scientific understanding of global climate change”. www.siliconchip.com.au This map shows the abundance of airborne particulates, or aerosols, over Southern Africa during the period August 14 - September 29, 2000. Low particle concentrations are shown in shades of blue, high concentrations in shades of red. These results were generated from MISR imagery acquired over this time period and processed using MISR’s automated software system. The approach for deriving aerosol amount makes use of the variation of scene brightness and contrast as a function of observation angle. Black areas over the land area correspond to places where a result was not obtained; eg, due to the presence of clouds. Extensive burning of grass and shrubland for land management and agriculture comprises a principal source of these aerosols. Vegetation availability increases northward, hence the greater abundance of haze and smoke in Angola and southern Zaire. The lower aerosol abundance around Lesotho and southeastern South Africa is consistent with the higher terrain elevations near the Drakensberg Mountains. Let’s now have a look at the five different measurement systems on Terra. CERES – measuring radiation balance The two “Clouds and the Earth’s Radiant Energy System” (CERES) instruments aboard Terra provide the most accurate global radiation measuring system ever, allowing in-depth insight into the Earth’s radiation balance. Everything, from plants, animals and even the Earth as a whole, emits energy, some of which leaves the Earth. This provides a balance against the incoming energy from the Sun, maintaining a consistent climate. Know­ledge of this radiation balance and the factors which affect it, is essential for understanding and modelling the Earth’s climate, both now and into the future. The CERES units are essentially scanning radiometers oper­ating at three discrete channels. The first of these is a short­ wave channel for measuring reflected sunlight, ranging from 300nm - 5µm in wavelength. The second, longwave, channel, is designed to measure Earth-emitted thermal radiation in the 8-12µm region. The third channel provides a total radiation measurement between waveMarch 2002  31 SYDNEY Smoking! – this MODIS image shows the December 2001-January 2002 bushfires to the north, south and west of Sydney. lengths of 0.3 - 200µm. Data from the CERES units is ideally suited to some of the following applications: • Determining the effects of solar radiation as an input to global atmospheric models. • Extended range weather predictions. • Increasing our understanding of long-term climatic change. MISR – nine cameras, four wavelengths With the majority of remote-sensing satellite instruments either aimed directly towards the Earth or towards a fixed point in the atmosphere, much information regarding the effects of energy scattering within the atmosphere has been overlooked. The Multi-Angle Image Spectroradiometer (MISR) instrument was de­signed to address this need through the use of nine cameras. One is aimed straight down and there are fore and aft pairs angled at 26.1°, 45.6°, 60.0° and 70.5° from the Earth’s surface. As Terra orbits, the Earth’s surface is progressively mapped by each of the nine cameras in four wavelengths: blue (446nm), green (558nm), red (672nm) and infrared (866nm). MISR is able to acquire a global picture around once every nine days. Operating only during the day due to its visible light requirements, the 149kg instrument draws an average of 72W power and produces an output stream 32  Silicon Chip averaging 3.3 megabits/second. Built by Jet Propulsion Laboratories for NASA, the MISR has already provided a good insight into monthly, seasonal and long term trends of the following: • The amount and composition of atmospheric aerosol particles, both man-made and natural. • The amount, type and heights of cloud cover around the world. • The composition of land surface cover, including vegetation density, health and structure. MODIS – measures infrared The Moderate-Resolution Imaging Spectroradiometer, built by Raytheon (previously Hughes), Santa Barbara, is designed to provide a broad range of observations of the Earth’s atmosphere, land and oceans, in both the visible and infrared regions, with the ability to construct a global snapshot over a two-day period. MODIS features a viewing width of 2330km over 36 separate spectral bands, ranging from 0.4 to 14.4µm wavelength, with spatial resolution ranging from 250 10000 metres. Operating 24 hours a day, MODIS collects data from all spectral bands during daylight hours. In darkness, scanning is solely done in the thermal infrared bands, reducing the output data stream from 10.8Mbps (day) to 2.5Mbps (night). The 274kg MODIS draws an average of 162W of power. Typical applications of MODIS include: www.siliconchip.com.au • • Surface temperature monitoring of both land and sea. Global detection of fires (including fires in underground coal seams). • Ocean colour, to aid detection of contaminants (sediment, photo-plankton, etc). • Cloud characteristics. MOPITT – measures pollution The rather lengthily named “Measurement of Pollution in the Troposphere” (MOPPIT) instrument is designed to increase under­standing of the Earth’s lower atmosphere and its interaction with the land and seas. In order to achieve this, MOPPIT focuses on the distribution, transport, sources and sinks of carbon monoxide and methane in the Earth’s lower atmosphere. MOPPIT consists of a scanning radiometer using gas spec­troscopy to measure reflected radiance in the three absorption bands of carbon monoxide and methane. By measuring the power levels of reflected spectra at 2.3µm (methane) and 2.4 and 4.7µm (carbon monoxide), MOPPIT will be able to determine the concen­trations of these gases within the troposphere. The 184kg MOPPIT was supplied to the Terra team by the Canadian Space Agency. To date, the unit has been generating global maps of carbon monoxide and methane distribution. ASTER – for high resolution images A joint venture between NASA and Japan’s Ministry of Inter­national Trade and Industry, the Advanced Spaceborne Thermal Emission and Reflection Radio­ meter (ASTER) has provided high resolution images of the Earth during its operation. Operating three distinct telescope systems, ASTER includes the following spectral subsystems: visible near infrared (VNIR), shortwave-infrared (SWIR) and thermal infrared (TIR). Each of these subsys­tems employs its own instrumentation and was NASA’s Terra spacecraft is now providing daily views of fires around the world. With the high resolution and sensitivity of the Moderate-Resolution Imaging Spectroradiometer (MODIS) and the instrument’s regular global coverage, Terra is providing an improved fire-detection capability over previous space-based sensors. MODIS is also capable of much higher-resolution imaging of fires, as seen in this image of fires in northern Australia taken on October 2, 2000. www.siliconchip.com.au This globe shows data collected from multiple sensors and integrated into one image. Notice the three-dimensional cloud measurements; these are collected by ASTER and MISR aboard NASA’s Terra spacecraft, while MODIS measures total cloud cover on a daily basis. The El Nino temperature anomaly is visible as red in the Pacific Ocean while the red dots on land show the locations of forest fires. Terra’s ASTER, MISR, MODIS, and MOPITT instruments are all uniquely-designed to observe fires and help measure the smoke and gases they release. Together with CERES, Terra’s instruments help scientist’s understand the Earth as a whole, integrated system. constructed by a different corporation. The ASTER as a whole provides spectral separation to its three units via bandpass and dichroic filters. The VNIR subsystem was constructed by NEC and consists of two telescopes, one pointing downwards and one pointing behind (along the orbit path) to produce stereo images with a very high (15 metres) resolution. These images can later be used to generate 3-dimensional perspectives of the land being analysed. The wave­lengths captured by this instrument are especially useful in monitoring the health of crops and vegetation. The SWIR subsystem, produced by Mitsubishi Electric, oper­ates in six shortwave infrared channels with a 30-metre resolu­ tion. Employing a pointing mirror, the SWIR system can focus on nearby areas of interest, allowing it to study the same area with each orbital pass for several passes. The SWIR system is espe­cially useful for identifying the geological structure of the land being studied. The TIR subsystem, supplied by Fujitsu Ltd, scans five thermal infrared channels with a resolution of 90 metres. As with the SWIR system, a mirror setup is used to allow areas of inter­est to receive higher coverage. Once again, this apparatus is especially useful for geological sensing of ground structure. ASTER weighs in at 450kg and is the largest of the Terra’s five instruments. Together, the three subsystems combine to give the ASTER the following capabilities: • Surface temperatures and emissivities. March 2002  33 This computer-generated image shows the EOSAM1 Spacecraft, with the MISR instrument on board, orbiting Earth. Direction of flight is toward the lower left. The actual locations imaged by the nine cameras, each with four colour bands, along the Earth’s surface are illustrated here with translucent surfaces. • Digital elevation (topological) maps from stereo images con­taining geological information. • Surface composition and vegetation maps. • Mapping of polar ice movements and formations. • Mapping of volcanic activity, both geological and thermal. Power and telemetry systems Terra, like many satellites, is powered by an array of solar cells. Together with a nickel-hydrogen battery bank, the power system provides an average of 2530 watts of power to the craft. All data recorded by Terra is transmitted back to Earth via the Ku-band (15.25 17.25GHz) at a rate of 150 Megabits/second. Command and configuration information is upload­ed to Terra via the S-band (1.7 - 2.3GHz). For each Earth orbit, two 12-minute periods of radio contact are used for these data transfers. Terra global studies As already mentioned, each of the instruments aboard Terra produces separate data sets. It is the combining of the results of several of these instruments by teams of scientists from varied disciplines that is the exciting part of this story. Currently, there are many studies being undertaken using data generated from Terra, with the fire 34  Silicon Chip fighting tools demonstrated during the NSW bushfires being just one of these. Volcanoes, fire and flood Volcanoes and fires around the world not only pose a huge threat to the safety of people and property but also generate a large amount of atmospheric aerosols. Using the MODIS instrument, Terra can scan globally and instantly produce alarms from fires or volcanic eruptions from anywhere in the world. One of the EOS teams currently produces constant lists of fires and lava flows globally, which are quite useful for risk management and evacua­tions. Floods are also a major danger to communities around the world. Based on data sourced from Terra, scientists now have quite accurate models to help predict an area’s susceptibility to flooding. When severe flooding occurs, researchers are able to measure the land area affected, contributing basin area, peak discharge, suspended sediment concentration and meteorological factors, so that the risk can be minimised in the future. Vegetation Terra is able to provide valuable data on the health and distribution of ground vegetation around the world. www.siliconchip.com.au With immense areas of forests being constantly turned into farmland, the Earth’s climate is definitely affected. Scientists are able to use data from the ASTER, MODIS and MISR instruments in studying the impacts of climate change of global vegetation, in addition to providing large scale analysis of agricultural methods. Researchers from The University of California, use the MODIS to monitor the burning of forest land in the Amazon and Africa. These burning activities release carbon dioxide, carbon monoxide and methane, along with other aerosols into the atmosphere. The MODIS can be used to measure the exact quantities and compo­sitions of these gases, as well as vegetation regrowth and change later on down the track. Cities have great impact on the local environment. Dense city planning results in higher summer temperatures, increased health risks, energy consumption and pollution levels. The in­struments onboard Terra are able to assist urban planners in minimising these effects. In fact, since Terra’s launch, studies have shown that vegetation cover and surface albedo (reflectivi­ty) of urban areas have major affects on air temperatures and ozone pollution levels. This is an artist’s rendition of the MISR instrument in cutaway view. The back ends of the nine MISR cameras appear as yellow cylinders. In this orientation, MISR would look down toward Earth. General climatology studies Over the last century there has been an immense impact from human development on the Earth’s landscape. Despite carbon diox­ide levels having increased by almost one third since recording began, global temperatures have only increased by around 0.5°C over the last century – rather less than predicted by traditional climate models. This has revealed limitations in the ways traditional models took in the effects of atmospheric aerosols, changes in cloud cover and the Earth’s oceans in af­fecting climate. Aerosols are tiny particles suspended in the atmosphere. While some occur naturally, human activities have increased atmospheric aerosols by around 10%. Naturally occurring aerosols include material from volcanoes, dust storms, forest fires, biological materials and sea spray. Common human aerosols include materials from the burning of fossil fuels, factories and motor vehicles. While there is still much to be learnt, it is known that aerosols have both direct and indirect effects on the Earth’s climate. The direct effect is the cooling of the Earth by re­ flecting incident sunlight back into space, with the magnitude of this dependent on the type and size of the particles in question. It is known that aerosol cooling from human-generated particles offsets some of the effects of carbon dioxide produced global warming. The indirect effect of these particles is to change the properties of clouds, themselves formed by water droplets adher­ing to aerosol particles. In regions of low particle densities, clouds tend to be composed of large droplets, with regions of high aerosol concentrations having clouds composed of very small droplets. Large droplets do not scatter light well and allow more light to pass through, while clouds of small droplets (caused by lots of aerosols) scatter light and restrict light passed towards the Earth. Also, these brighter, more reflective clouds composed of smaller droplets are less likely to generate rain than www.siliconchip.com.au This is the “business” end of the MISR instrument, which includes the cameras and calibration equipment. The photograph was taken in October 1996, as MISR was being assembled. Subsequently, the parts that supply power, communications and temperature control were added. The entire package was then encased in a protective housing, which was covered with highly reflecting thermal blankets. larger droplet types. Using the MISR instrument, scientists have been able to improve their understanding of the concentrations of aerosols in the atmosphere and their effects on cloud formation, sunlight reflectivity, ground and ocean temperatures and rainfall. With oceans comprising around 70% of the Earth’s surface, this mass of water stores large amounts of heat energy. While originally thought to be a large inert “heatsink”, later studies have revealed the ocean to be a major March 2002  35 The Red Sea golf resort in Sharm El Sheik, Egypt, where President Clinton met with Israeli Prime Minister Ehud Barak and Palestinian Authority President Yasser Arafat, stands out against the desert landscape in this image acquired by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on August 25, 2000. This image of the southern tip of the Sinai Peninsula shows an area about 30 x 40km in the visible and near infrared wavelength region. The vegetation appears in red while the blue areas in the water at the top and bottom of the image are coral reefs. The airport is visible just to the north of the golf resort. ASTER is the only high resolution imaging sensor on Terra and its primary goal is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With a “revisit time” of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth’s surface. The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping and monitoring temporal change. Example applications are: monitoring glacial advances and retreats, monitoring potentially active volcanoes, identifying crop stress, determining cloud morphology and physical properties, wetlands evaluation, thermal pollution monitoring, coral reef degradation, surface temperature mapping of soils and geology, and measuring surface heat balance. contributor to climatic phenomenon. With heat escaping the ocean and creating atmospheric temperature gradients in the surrounding air, winds are generated, creating horizontal currents. Water temperature measurements With temperatures and salt levels affecting vertical cur­ rents, complex water circulations around the world arise. This results in warm surface waters moving poleward where heat escapes more readily to outer space, while cold, deep currents are estab­lished in the ocean depths. Through this system of ocean circula­tion, the oceans and atmosphere work together to distribute heat and regulate climate. This circulation transports enormous amounts of heat, resulting in more moderate climates on land areas that are near the ocean. Using Terra’s instruments, scientists have been able to measure ocean surface temperatures to within 0.5°C. This information, coupled with wind measurements made on Earth, have been invaluable in understanding the effects of the world’s oceans on global climate. With better understanding of most of the variables which affect climate, researchers have been improving a set of tools for the prediction and assessment of the effects of large scale seasonal climate fluctuations, including the El Nino Southern Oscillation index. The Future An artist’s impression of Terra on its way to orbit, follow­ ing its launch from Vandenberg Air Force Base, California, on December 18, 1999. 36  Silicon Chip Since its launch in December 1999, Terra has provided in­valuable data concerning the Earth’s natural processes. If all future missions are as successful as Terra, a lot will SC be learnt about our won­derful planet. www.siliconchip.com.au BE ID PR GIN EA OJ NE L EC R’ T! S The Itsy-Bitsy USB Lamp Have you ever been in the delves of a computer and wished you had some extra light? Here’s a great little USB-powered lamp which you can build in next-to-no-time. Words by Ross Tester From an original design by Stan Swan M any readers will remember a commercial product of a few years ago, the “Itty Bitty Book Light”. It was designed to clip over the top of a book to give just a tiny light on the page when, for example, you were reading in bed and didn’t wish to disturb your partner. Times have changed. Now we’re all working with computers. Many’s the time I’ve been trying to look deep inside a computer and wished it was a bit brighter so I could read type numbers, see plug and socket orientations, check board seating, and so on. Sometimes, even a torch won’t work because it’s too big to get really deep down. You can't get that light where you really need it. Well, here’s the answer. We’ve called it the Itsy Bitsy USB Lamp. It is such a delightfully simple idea we’re wondering why no-one ever thought of it before. www.siliconchip.com.au It started life (and continues) as a student project at Massey University in Wellington, New Zealand – and in fact was submitted to us by the lecturer, Stan Swan. When we say simple, we mean it: just a USB plug on a suitable length of cable, a superbright white LED and a series resistor to limit LED current. The LED and resistor are housed in an inline fuseholder (without its innards!) which makes a superb little “wand” and also protects the electronics, such as they are. Here’s what the Itsy Bitsy USB Lamp looks like: one end has an ultrabright LED wired to a cable attached to a USB plug. It is as simple to build as it looks! March 2002  37 You’ll be surprised by the amount of light you get from the LED, especially if you spend a little bit more and buy one of the really superbright (8000mCd) models (eg, DSE Z-3982). A cheaper, though lower light output (2000mCd) is the Z-3980. The difference in price is significant, though: $8.95 vs $3.95. Of course, you don’t have to use a superbright white LED. In fact, you don’t HAVE to use a white LED at all. This circuit will operate quite happily with any colour and any brightness LED – but you will probably be very disappointed with the light output of most LEDs. For best results, we really do recommend the superbright white types. Yes, they’re more expensive but you get what you pay for! The USB Port In all modern computers, you will find at least one, usually two and often four USB ports. USB stands for Universal Serial Bus, and is one of the latest incarnations of methods to get information in and out of your computer. pick one up for just a few dollars. A local computer shop has a 1m USB extension cable for $6 but you could well do better than this at computer fairs, swap meets, etc. Here’s a tip: get together with a mate and buy a male-to-male USB cable. Cut the cable in half and you can both build an Itty Bitty USB Lamp for half the cost! Strip back about 5cm of the outer insulation and shield from the “bare” end of the USB cable. Normal USB cables have four wires: red, white, black and green (as well as the shield). The green and white carry the data – we don’t need them so they can be trimmed right back (make sure the wires inside their insulation are not exposed at all). A tiny length of heatshrink tubing over the ends of the green and white wires will ensure that there cannot be shorts, either to themselves, to the shield wire or to the red or black wires. Carefully bare about 2mm of the insulation on the red and black wires. Before we go too much further, open up the in-line 3AG fuse holder and remove the wires and spring inside. All we want are the two plastic bits. Slide the longer of the two pieces over the end of the wire, smallest end first. (You may need to drill or ream out the hole a little to accommodate the wire but don’t go overboard! Similarly, this An ECU (that’s technical talk for extra close-up) of a USB plug. It’s a male plug which fits into the female USB socket on the computer. (For more details on the USB port, refer to the article in the November 1999 SILICON CHIP). We’re not particularly interested in information transfer as such. But we are interested in the fact that the USB port offers power to external devices +5V is available on pin 1 (0V on pin 4). Up to 100mA is available from the USB port – far more than we need for this little application. That’s the reason for the series resistor. A 47Ω resistor will limit the current to about 25mA – just about ideal. Construction The first thing you will need is a USB cable with at least one male plug on it. These are becoming fairly common and you should be able to 38  Silicon Chip Here’s the business end of the lamp, fully assembled. The LED just pokes its head through the cable hole in the fuseholder. might be necessary on the other bit of fuseholder to accommodate the LED when we come to it shortly.) The photograph shows this well. Slide the fuseholder down far enough so it is out of the way. Cut the anode lead (the longer lead) of the bright white LED to about 3mm long. Similarly, cut both leads of a 47Ω 1/4W (or even 1/8W) resistor to about 3mm long and carefully solder one lead of the resistor to the anode It’s not exactly rocket science. . . but it’s often the simplest of ideas that are the best. of the LED. The 47Ω resistor will have a colour code of yellow, purple, black, gold (or yellow, purple, black, gold, gold if it’s a 5-bander). It can be soldered either way around. Cut a length of spaghetti insulation (or some tiny plastic tubing) long enough to cover the resistor and its leads, then slide this over the resistor so the connection to the anode is completely insulated. Heatshrink tubing may also be used for this purpose, but is not essential. Cut another two short lengths of insulation (say 5mm) and slide them over the red and black wires of the USB cable. Solder the red wire to the resistor end and the black wire to the LED cathode. By the way, spaghetti insulation is not pasta . . . Now slide the 5mm lengths of insulation over the solder joints – it is important that the bits cannot short out to each other when scrunched up Parts List – USB Lamp 1 USB male plug moulded to suitable length 4-way screened cable 1 Ultrabright White LED (preferably at least 2000mCd) (eg, DSE Z-3980, 3981, 3982, etc) 1 3AG in-line 2-part plastic fuseholder (eg, DSE P-7912, Jaycar SZ-2015, etc). 1 47Ω 1/4W or 1/8W resistor Lengths of thin diameter heatshrink (preferably) or spaghetti insulation www.siliconchip.com.au inside their fuseholder “home”. Strictly speaking, this assembly should be fused in case of a short but even it there is a short the USB port will limit the current available. So no fuse! (But it’s better not to have a short anyway!). Testing Before going any further, check and everything is OK, the white LED should glow brightly. If not, check for shorts or open circuits. Final assembly Slide the fuseholder back up the USB cable, pushing everything inside it until only the LED and abut 3mm of its leads are emerging. Slide the other end of the fuseholder (the shorter end) onto the longer piece so that the LED just pokes the top of its head out the hole (flush with the hole is fine). Twist the fuseholder end onto its body to lock it in place. And that’s it. Now when you need a bright light anywhere around your computer – all you have to do is plug it in to the USB port! The labels You might have noticed two labels on the cable (hey, that rhymes!) in the main photograph. They simply says what it is and not to look directly into the LED. We they were unnecessary and therefore we haven’t shown them SC on the diagram above. check again that everything is as it should be. Most of all, make sure that there is no possibility of any shorts from one lead of the USB cable to another – particularly the green and white (data) wires. (Failure to do this could damage your computer). With your computer on, plug the USB plug into the USB socket. If www.siliconchip.com.au The final assembly of the lamp: it’s a pretty tight fit inside the fuseholder but it does all go in. Just be careful that any exposed leads are insulated with heatshrink or spaghetti before sliding it in. March 2002  39 SERVICEMAN'S LOG Do some sets really “self-destruct?” A TV set, described as “self-destructing”, presented itself this month and was a mystery in its own right. But it also posed another question – how long should one persist in chasing a problem, long after there is any hope of financial reward? So what is this so-called “self-destructing” TV set? I had heard about this phenomenon from several different sources but I had never actually come across one until now. As it turned out, the term “self-destructing” is a gross exaggeration and is much too dramatic – “intermittent failure of a number of power supply components” is a much more accurate description of the fault. Anyway, this particular problem applies mostly to the NEC FS-6831S series employing PWC-3517 chassis. These are generally very reliable TV sets but several rental companies have com­plained of a few sets arriving in the workshop dead, with the power supply “destroyed”, along with IC601 (STR41090) and up to about 10 surrounding components. All the parts are replaced and the set works again for another month or so before it fails again – mostly on start-up with the front panel power switch. Or, at least, that’s the story. Mr Spicer owned one of these sets and it had been fixed several times, by different technicians, until he became fed up and gave it away to another technician who happened to be a colleague. Well, he was determined to fix it and, over the next six months or so, changed just about every part in the power supply. I obtained a scrapped chassis for him so that he could even replace the chopper and feedback transformers (T601 and T602) without cost. Wherever possible, he used genuine new NEC spares but 40  Silicon Chip in the end he lost patience with its repeated failures and offered it to me for spare parts. Though a few technicians have complained about this particular symptom, NEC Technical Support were really unaware of the problem. This chassis has been in production for over 10 years and as previously stated, has been very reliable. Bath time I decided I would give it a go and treat it with great respect. Firstly, I noticed it was a pretty grubby chassis with lots of dust and grime on it, so I decided to give it a bath! No kidding! The secret to washing a chassis is being quick and allowing it a very long time to dry. Note, however, that mains transformers and the like should be removed first as, invariably, they will break down later if allowed to get wet. I squirted the chassis with a commercial household cleaner and brush­ ed the particularly dirty areas before using a high pressure fresh water spray and then very hot water. Pure water is in fact an insulator, not a conductor Items Covered This Month • • • • • • Akai CT-2868AT NEC FS-6831S Sharp CX-51E3 NEC Cromavision FS-6807S Mitsubishi DNA CT 29AX1(A) Philips 25GR6771 G111S chassis – but how often does one encounter pure water in real life? I let it dry for a week, even though it looked dry enough within 24 hours, and it indeed looked very clean – like new. Any remaining grubby spots were then cleaned with more con­ventional PC board cleaning aerosols. Now that it was clean, I could see that some of the elec­trolytic capacitors had been leaking and had bad­ly corroded the sur­ rounding board areas, especially around C406, C411, C501, C611 and C625. These were all replaced after giving the area a very thorough scrubbing and finally applying a fine spray of CRC 2-26. I then soldered every faulty joint I could find on the chassis, paying special attention to areas around the power diodes before replacing all the blown components. I noticed when checking the component values against the circuit diagram that some were not quite the same. I dug up my file on the set and discovered that, over the life of this chassis, two distinct power supplies were made available – one for the 63cm set and one for the 68cm version. This set used a 63cm picture tube and I replaced seven components that a previous technician had incorrectly substituted from the 68cm version (Q601, R417A, R602, R603, R606, R608 and R610). I also applied some of the modifications that have been recommended over the years, especially changing C603 and C604 across the bridge rectifier from 220pF to 4700pF. I also fitted a new insulating wafer for IC601. I didn’t attribute any significance to a failure when using the front panel switch, as this controls the CPU (IC1001) and the 19V/15V supply transistors (Q652), both of which were totally isolated from the power supply. The remote control also operates the CPU IC. When all was ready, I reassembled the chassis and fitted it into the www.siliconchip.com.au Kits without compromise cabinet. I gingerly switched on and everything worked properly. I checked the main power rails, noting that the HT was slightly low at 113.7V at TP91. However, the picture size and blooming were steady with variations of beam current and every­thing was working properly. It is now a month down the track and the set is still switching on and off OK and running fine. If I am right, I would attribute the problem to previous technicians not replacing all the leaky capacitors and failing to clean away the leaked electrolyte. In addition, a previous technician had used incorrect components in this particular set and there were also possible faulty solder joints. Persistence doesn’t pay As I hinted earlier, this story poses the question as to why we sometimes persist with a problem, long after it has become commercially non-viable. In this case, my colleague hung on to the set for about six months and I lost count of how much time I spent on it. Granted, this was spare time (short periods between other jobs, etc) which www.siliconchip.com.au would otherwise be wasted but how does one justify it anyway? The simple answer is “plain stubbornness”. But there is more to it than that. The solution to the problem has a real value and is not just a cause of satisfaction. Every solution becomes another item in one’s stock-in-trade; something to call upon the next time a similar fault is encountered. Every time something is learned, it makes it just that much easier to earn real money the next time around. Not so easy after all! I imagined that Mr Klein’s Akai CT-2868AT TV set was going to be easy when he described the fault as no colour – that is, until he told me he had tried to get it fixed elsewhere and they had given up on it. Usually, most colour faults are fairly easy to fix if one is familiar with the CCIR B/G PAL D system. Howev­er, this is gradually becoming more difficult as digital tech­niques are being added. Anyway, I still felt confident that I could make short work of it. However, when I switched it on and connected “Sound quality to die for” Rolling Stone Magazine “..A new benchmark in every criteria” Best Buys Home Theatre Speaker Kits without compromise from $312 pr to $8,863 pr FreeCall 1800 818882 www.vaf.com.au vaf<at>vaf.com.au March 2002  41 Serviceman’s Log – continued a colour bar generator to the AV input, I was amazed at the appearance of the fault which, I have to confess, is hard to describe. It was as though the chrominance reference oscillator hadn’t locked but instead of different colours, the picture showed alternating bands of monochrome and colour. And at the same time, there was a large shading band (like a shadow) moving slowly from left to right – most bizarre! I also found that the previous technician had changed the jungle section, including chroma decoder IC302, an AN5601K (the same as is used in Panasonic TV sets). He had also replaced about 10 electrolytic capacitors on the motherboard, mainly in the chroma circuits. This was a bit of a worry, as it told me two things. One was that the previous technician was no slouch and two, he had alrea­dy done most of the things I had planned to do. It didn’t leave me much room to manoeuvre. Voltage checks I started by checking the voltage rails and all the voltag­es on IC302. They were all spot on, so I checked the reference oscillator and that was also spot on. I also checked all the work done by the previous technician but everything was totally cor­rect. Yet, to produce such a dramatic effect, something had to be off – really off. I connected a monitor to the video output socket and saw that the picture was perfect up to there. Using the CRO, I then followed the luminance and chrominance signals through Q103 (for TV reception) to IC204 LA7016 42  Silicon Chip (AV/TV switch), and then on through the Teletext module CN501, pins 2 and 7 (note: the Teletext module can be removed provided a link is inserted between these pins). From there, I went to the luminance delay line where the chrominance and luminance are separated – the former goes to pin 5 of IC302, while the latter goes through Q306 to pins 15 & 16. I thought I could detect a slight imperfection of the chroma input on pin 5 and spent a long time investigating this, especially as it seemed to come from the base of the luminance transistor Q306. I tried replacing C312 but in the end I had no explanation and assumed it was a red herring. What I did find was distortion on pin 2 (reference oscillator) and on the chrominance output to the delay line (pin 7) and onwards to the CRT. By now I had almost exhausted all my ideas. The fault seemed to involve two different areas: the alternate couple of lines going black (horizontal frequency) and then the slow moving shadow across the screen (vertical frequency). These could be due to some distortion in the horizontal and vertical pulses but these all where correct on the oscilloscope. The 12V and 5V rails (pins 29 and 10 respectively) had no ripple on them. In the end, I decided I needed to scope every pin of IC302 and see if anything significant would show up. Fortunately, I only reached pin 3, which is the chrominance level control from pin 37 of the microprocessor, before finding a real clue – this pin should have only a pure DC voltage present but there were all sorts of other signals present as well A check with the multimeter showed that a DC voltage was present but that it varied with the colour control. It was now obvious that de­ coupling capacitor C317 (2.2µF) was leaky and replacing it fixed everything. I left it on test for a week before Mr Klein picked it up. However, just as I was demonstrating it, I suddenly noticed a minor new fault symptom on the screen. It was giving an effect like flagwaving at the very top. Even though I noticed it, Mr Klein didn’t, and it was just too late to do anything about it – so out it went. I am now waiting by the phone, biting my nails, waiting for the recall! Dead Sharp Mr Tanundra’s Sharp CX-51E3 TV set (H Chassis) was dead and I was immensely pleased that he had brought it into the workshop instead of trying to get me to fix it in his house. I don’t have a service manual for this model but I do have one for the CX51B2 which is a 14B chassis and not all that different – or so I thought. Although the set was reported as “dead”, it wasn’t really totally dead – just no sound or picture. For starters, there was 115V on TP702 and to the line output transistor Q602 which was good. There was also voltage on the collector of the horizontal driver transistor (Q601) but it was a bit high at about 60V. The oscilloscope showed that the line drive was present from pin 37 of the jungle IC (801, TDA8362) all the way to the horizontal output transformer (T602). However, its frequency was far too high. Consequently, the EHT was down to about 15kV. When I turned up the screen control, there was just a horizontal line, indicating no vertical timebase either. I checked the voltage to IC801 pin 10 and found it was low but it was the horizontal and vertical oscillators I was most concerned about. There was only a small amount of signal on the 8MHz crystal (X802) on pin 35 and the voltage on it was almost non-existent, especially on pin 36. I followed this back, expecting 9V to appear via D633 and R672 but there was none. I thought D623, an 8.2V zener, might be faulty but it was fine. The 9V rail was missing completely. www.siliconchip.com.au On the circuit I was using (14B), the 9V is delivered via Q604 and D733. However, in the H chassis, there is no Q604 but instead there is IC602, a 7809 3-terminal regulator. And there was voltage going in to this device but none coming out. Fitting a new regulator fixed the problem completely, though I am surprised at how hot it ran. I have soak tested the set for a week and Mr Tanundra is happy. A crook NEC Mrs Richardson had arranged for her husband to deliver their 1999 NEC Cromavision FS-6807S TV set to the workshop with the complaint that there was no picture. Because it is such a recent model, I didn’t have a circuit for it and I told him that I would have to order it. His response was that he was under some pressure to get it fixed as quickly as possible although he didn’t say who from. Well, I duly put the order in straight away but in the meantime, I thought that I would take a quick squiz at it. The fault turned out to be a black raster, no screen display and no sound. The chassis was a Thai built PWC2477 which I removed to check for faulty joints. Well, as luck would have it, there were a couple of enormous cracks in the solder around the connections to IC501 and IC502, both 9V 3-terminal regulators. This is just the sort of break a technician needs, being so much easier than the complex microprocessor and/ or signal prob­lems I had been was envisaging. Indeed, it was exactly what the doctor ordered and repairing the cracks fixed the problem Mrs Richardson was delighted to have her set fixed so quickly. A couple of house calls It was a fairly quiet Thursday in what had been a quiet week and so when I received two requests for house calls just outside my service area, I reluctantly agreed – mostly because they were close to each other. The first was Mrs Mason’s 1996 (1994) Mitsubishi DIVA TV set, CT 29AX1(A) (A1 chassis), which she complained had a “green picture”. This sounded relatively easy to fix and was probably a faulty joint on the CRT socket. However, when I arrived, I found the 68cm set to be in a tight, dark entertainment centre connected to all sorts of acces­sories. What’s more, the fault was actually a small dark green raster and there was no sound. To cap it all off, there were two totally un­disciplined, yapping dogs running around the room, determined to trip me. It was going to be one of those days! I stupidly thought there might be something simple I could do and, anyway, I had to look as though I had done something – even though I suspected that this was going to be an expensive workshop job. I hadn’t worked on one of these sets before and it was one with all the bells and whistles, including a wretched motorised swivel base to turn the set with the remote control. I couldn’t help feeling that the user would only ever be likely to use this control once but now it was giving me a real headache. After I had managed to pull the set out far enough to unplug a bunch of AV leads, turn the set around and undo umpteen screws, in the dark, I was beginning to lose it. Trouble was the back was jammed at the bottom by the swivel base and the whole set was pre­cariously balancing on the edge of the pull-out swivel platform of the entertainment centre. Finally, when I lifted it off, I was presented with a large flat chassis with no access under the PC board. Also, I couldn’t work out how to remove it from the case. The plastic frame looked as though it had some sort of catch system on either side near the tube but nothing I could do would free the front control panels which were wedged under the tube. So I tried to regain some self-composure by doing some meter measurements from on top of the chassis. I was trying to identify the main HT rail from the compon­ent side of a complex set I had never seen before. And in any case, I had absolutely no idea of the voltage to expect on this rail, even if I did identify it. I looked for large high voltage rating electros and any diodes nearby which might indicate a chopper transformer but even when I thought I could identify it, there was absolutely no access. Similarly with the horizontal output transistor, which I nearly blew up. Mrs Mason had been watching my activities closely and every so often had been making useful comments – such as, “there’s not much in them these days” and also “I would have thought it would have lasted a lot longer considering how much it cost” (about $2000 four years ago). I kept thinking, “why didn’t you buy a sewing machine in­stead” but bit my lip and stuck to bland mutterings along the lines of “isn’t the weather good?” and “the cricket is fantastic”. In the end, I gave an Oscar-winning performance of measur­ing the resist- MINI SUPER DRILL KIT IN HANDY CARRY CASE. SUPPLIED WITH DRILLBITS AND GRINDING ACCESSORIES $61.60 GST INC. www.siliconchip.com.au March 2002  43 Serviceman’s Log – continued ance of one piece of screening metal to another to convince Mrs Mason that I knew something, before pronouncing that the power supply was faulty and that the set definitely had to go to the workshop – where it should have gone an hour beforehand! She wanted a cast iron quote and an ETA for the return of the set. I was past caring at this point and plucked a figure of $300 and three weeks out of the air. Darkly she said “just wait a minute while I phone my husband”. Surprisingly, five minutes later, she reappeared, smiled, and said that would be OK. Oh well, “them’s the breaks”, I sup­pose. The next drama I had was getting it downstairs and past the dogs and into the car – without letting the dogs out. The car was now full and I still had the other TV set to fix. I prayed I could do something with this in the home, because I couldn’t take two back to the shop. This set was a 1990 Philips 25GR­ 6771, G111S chassis, that was dead. It had had a line across the screen before it died. I arrived to find the set was situat44  Silicon Chip ed on the second floor of Mr Paton’s home which had a small rickety spiral staircase. I knew that this set wasn’t going to leave the house that day and started the conversation with “...and how old is this set?” “Eleven years old, eh? Well, you have had a good run out of it . . . but it is probably past its ‘use-by’ date. Have you thought about getting a new one?” In the event, the “power” problem turned out to be a faulty on/off switch which I didn’t have with me, so I shorted one side of the switch and told them to use the remote control or the wall socket switch to turn it on and off. The white line across the screen was due to a faulty joint around the pins of the vertical deflection socket, which connects to the vertical deflection yoke. I pointed out that this was a temporary repair that would do until they bought a new set. Mr Paton was quite happy about this and I drove off back to the workshop. Back at the ranch I ordered a service manual for the Mitsubishi before exam­ining it more carefully in more congenial surround- ings. The reason the chassis wouldn’t come out was because of two screws in the front panel holding it in. I removed it completely and used an air compressor to blow the dust out. I then removed the PC boards from the plastic frame to get a good look at them. When I removed the power deflection board, I could see that the whole thing had faulty joints everywhere. I spent several hours resoldering everything on all boards before reassembling them. Eventually, I managed to get it all back together and switched the set back on. Amazingly, it all worked perfectly, so I set about retuning the stations and setting up the various menus. And the picture was truly excellent. I found and checked the main power rail at test point TP91A. It checked out at 130V, so I replaced the back and put the set aside to soak test for a week. In the meantime, a few days later, I received a call from Mr Paton that I didn’t really need. He said that the set was dead again and it was making a burning smell just like when I was there. What smell? There had been no burning smell, save possibly the soldering iron. Reluctantly, I said I would call back but that I couldn’t until I could deliver the other TV set, as they were both in the same district. A few days later, I manoeuvred the Mitsubishi past the Mason’s dogs and back into the entertainment centre. Apart from retuning the VCR, DVD and Foxtel, it was plain sailing. And Mrs Mason was happy that it cost less than I had quoted. Mr Paton’s set, on the other hand, I had to treat very care­fully in case I had a fire on my hands. Gingerly, I removed the back and put it into a position where I could see what was going on when I reconnected the power. However, it was all an anticlimax; the set came on perfectly without any bother. I checked for bad connections and any sign of smouldering but just couldn’t fault it. I put it back together again and it still switched on and off perfectly via the wall switch! Mr Paton’s credibility had suddenly taken a huge dive – so much for it being dead and burn­ing! If it breaks down again, he can (1) buy a new set (2), take it elsewhere, or (3) bring it SC into the workshop himself. www.siliconchip.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. 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SUBSCRIBERS QUALIFY FOR 10% DISCOUNT ON ALL SILICON CHIP PRODUCTS AND SERVICES# #except subscriptions/renewals and Internet access Item Price Qty Item Description P&P if extra Total Price Total $A TO PLACE YOUR ORDER Phone (02) 9979 5644 9am-5pm Mon-Fri Please have your credit card details ready OR Fax this form to (02) 9979 6503 with your credit card details 24 hours 7 days a week OR Mail this form, with your cheque/money order, to: Silicon Chip Publications Pty Ltd, PO Box 139, Collaroy, NSW, Australia 2097 * Special offer applies while stocks last. 03-01 CIRCUIT NOTEBOOK Interesting circuit ideas which we have checked but not built and tested. Contributions from readers are welcome and will be paid for at standard rates. Pump controller for solar hot water system This circuit optimises the operation of a solar hot water system. When the water in the solar collector is hotter than the storage tank, the pump runs. The circuit comprises two LM335Z temperature sensors, a comparator and Mosfet. Sensor 1 connects to the solar collector panel while Sensor 2 connects to the hot water panel. Each sensor includes a trimpot to allow adjustment of the output level. In practice, VR1 and VR2 are adjusted so that both Sensor 1 and Sensor 2 have the same output voltage when they are at the same temperature. The Sensor outputs are monitored using comparator IC1. When Sensor 1 produces a higher voltage than Sensor 2, which means that sensor 1 is at a higher temperature, pin 1 of IC1 goes high and drives the gate of Mosfet Q1. This in turn drives the pump motor. IC1 includes hysteresis so that the output does not os­cillate when both Battery equality monitor Almost all 24V power systems in trucks, 4WDs, RVs, boats, etc, employ two series-connected 12V lead-acid batteries. The charging system can only maintain the sum of the individual battery voltages. If one battery is failing, this circuit will light a LED. Hence impending battery problems can be forecast. The circuit works by detecting a voltage difference between the two series connected 12V batteries. Idle current is low enough to allow the unit to be 54  Silicon Chip permanently left across the bat­teries. G. La Rooy, Christchurch, New Zealand. ($30) sensors are producing a similar voltage. Hys­teresis comprises the 1MΩ feedback resistor between output pin 1 and non-inverting input pin 3 and the input 1kΩ resistor. This provides a nominal 12mV hysteresis so that voltage at Sensor 1 or Sensor 2 must differ by 12mV for changes in the comparator output to occur. Since the outputs of Sensor 1 and Sensor 2 change by about 10mV/°C, we could say that there is a degree of hysteresis in the comparator. Note that IC1 is a dual comparator with the second unit unused. Its inputs are tied to ground and pin 2 of IC1 respec­tively. This sets the pin 7 output high. Since the output is an open collector, it will be at a high impedance. Mosfet Q1 is rated at 60A and 60V and is suitable for driv­ing inductive loads due to its avalanche suppression capability. This clamps any inductively induced voltages exceeding the vol­tage rating of the Mosfet. The sensors are adjusted initially with both measuring the same temperature. This can be done at room temperature; adjust the trimpots so that the voltage between ground and the positive terminal reads the same for both sensors. If you wish, the sen­ sors can be set to 10mV/°C change with the output referred to the Kelvin scale www.siliconchip.com.au which is 273K at 0°C. So at 25°C, the sensor output should be set to (273 + 25 = 298) x 10mV or 2.98V. Note that the sensors will produce incorrect outputs if their leads are exposed to moisture and they should be protected with some neutral cure silicone sealant. The sensors can be mount­ed by clamping them directly to the outside surface of the solar collector and on an uninsulated section of the storage tank. The thermostat housing is usually a good position on the storage tank. John Clarke, SILICON CHIP. Component & voltage tester audio and mains) and resistance loads (only visual checks via the LED). The pulses produced can sound too loud for some delicate circuits such as dynamic microphones and headphones, but the pulse is so short that it is virtually impossible to do any damage; the average current flow is only a few milliamps. The circuit needs no power switch as the oscillator only operates when the negative side of the battery is connected through the load being tested. The LED flashes at each pulse as a visual indication that the load is lower than about 1000Ω. The circuit works from a 3V battery pack. To use a 9V battery change the 15Ω resistor to 47Ω, the 1.8Ω resistor to 5.6Ω and the .033µF capacitor to .01µF. LED2, diode D1, zener diode ZD1 and the series 220Ω resis­tor form a voltage indicator which is used to detect and indicate any voltage greater than about 10V. LED2 only illuminates if the voltage rises above the threshold set by ZD1 and D1, which is more than the battery voltage (3V or 9V). These components can be omitted if the device is not going to be used for working on cars. However, it’s quite handy having a device that can check power wires, shorts to chassis and speakers in a car. Philip Chugg, Launceston, Tas. ($30) This simple circuit tests speakers, microphones, transform­ers and voltage. It’s basically a very low frequency oscillator that produces extremely short ‘fruity’ pulses. The type of sound produced is very easy to hear and to determine the precise direction it is coming from, thus making it ideal for checking the phasing in multiple speaker installations. It is also very useful for car stereo installations as well as public address systems where it can drive dozens of speakers directly on a 100V or 70V line system. The signal is also easy to hear on a public address system so that you can drive around a large installation with the window down and easily hear each speaker as you drive past. It is easy to check that a speaker is in phase with its neighbours, by listening for the artificial centre created between two identical sound sources. Q1 and Q2 os­cillate when connected to loads between zero and about 1000Ω. The frequency increases as the resistance of the load increases – 8Ω loads produce about 8Hz output while 100Ω loads will produce about 100Hz output, although it is only approximate. The unit is also useful for checking dynamic microphones (not condenser types), headphones, transformers (both www.siliconchip.com.au March 2002  55 Ideal for use with Dolby 5.1-channel digital decoders, this 6-channel volume control will allow you to adjust the volume of all channels simultaneously. It also includes infrared remote control so that you can adjust the volume from your armchair. Pt.1: By JOHN CLARKE O K, SO YOU’VE JUST bought yourself a fancy new DVD player with inbuilt Dolby 5.1-channel decoding. A matching multi-channel amplifier would also be nice but what if your budget won’t stret­ch that far? For many people, the answer is quite simple – use existing hifi stereo amplifiers that they either already own or can scrounge for next to nothing. Most of us have progressively upgraded our hifi systems over the years and typically have old – but still working – stereo 56  Silicon Chip amplifiers stashed in a cupboard or in the garage. For example, you can use your main hifi stereo amplifier for the two front (left and right) channels, plus a second stereo amplifier for the two rear channels. A third stereo amplifier is then used to amplify the centre and subwoofer outputs from the DVD player – see Fig.1. By the way, you don’t need integrated stereo amplifiers with preamplifier and tone control stages in this application. If you have one or more stereo power amplifiers, they will do the job just fine. Adjusting the volume Using existing stereo amplifiers might be economical but there is one big disadvantage – you have to adjust three separate volume controls (more if an amplifier has separate volume con­trols for each channel). And that’s fiddly. Wouldn’t it be nice if you could adjust the volume of all six channels simultaneously using just one control? That’s just what this project does and as a bonus, it throws in infrared (IR) remote control as well. A low-cost commercial IR remote provides the necessary control signals. Basically, the SILICON CHIP 6-Channel Remote Volume Control ac­cepts all six channels from the DVD player and provides outputs that can be uniformally varied in level with excellent tracking accuracy. These outputs are then fed into the stereo amplifiers, which have their volume controls set to fixed positions. www.siliconchip.com.au As shown in the photos, the unit is housed in a 1U-high rack-size metal case. It’s easy to drive, with just a few controls on the front panel: an on/ off switch plus three pushbuttons for volume up, volume down and mute. A LED bargraph display lets you check the current volume setting. Another feature of the unit is its excellent performance, so that it doesn’t degrade the high-quality sound from your DVD player. It has extremely low noise and distortion and also provides accurate tracking between each channel. This means that the sound balance between the various chan­ n els is maintained regardless of the volume setting. In addition, there is virtually no coupling between channels so that the signal in one channel is not heard in another. Specifications The accompanying specifications panel lists the performance of the unit. In particular, the volume can be adjusted over a 76dB range, with 1dB steps from 0dB (maximum volume) through to -48dB. After that, the volume is adjusted in 2dB steps down to the -76dB attenuation level. The volume can also be Muted at any volume setting to provide an attenuation of at least -96dB. As stated earlier, the volume can be adjusted using either the front-panel pushbutton switches or by the matching buttons on an IR remote control. These controls allow adjustment from full volume to minimum volume in about seven seconds. Alternatively, you can use the Channel Up/Down buttons on the remote control for even Fig.1: this diagram shows how the 6-Channel Remote Volume Control fits into a surround sound system. It accepts the Dolby decoded outputs from a DVD player and in turn drives three stereo amplifiers. faster volume changes. The LED bargraph display consists of 20 LEDs, each representing a 4dB volume step. “In-between” settings are indicated by lighting two adjacent LEDs, which means that the display is actually capable of 2dB resolution – ie, it can in­dicate 38 different volume settings from 0dB to -76dB. Note that the LED bargraph does not indicate the 1dB volume steps that are available down to the -48dB attenuation level. These smaller 1dB changes are provided to give a fine volume adjustment, so that the exact level can be selected for this important range of the volume control. Below the -48dB level, the volume is quite “soft” and so the 2dB level steps are more than adequate. Muting is indicated by flashing the current volume level LED (or LEDs) on the display. It is released by pressing the Mute switch again or by pressing the Up Volume switch. However, the muting remains on if the Down Volume switch is pressed. This allows the volume to be reduced to a more comfortable level while the muting is still in effect. SPECIFICATIONS Total Harmonic Distortion (THD) ������������ 0.002% at 1kHz and 1V RMS (see graph) Frequency Response ����������������������������� -0.1dB at 20Hz and 20kHz Signal-to-Noise Ratio �������������������������������110dB with respect to 1V RMS with 20Hz to 20kHz filter (112dB A weighted) Separation Between Channels ��������������� 80dB at 20kHz, 94dB at 1kHz and 96dB at 100Hz worst case with 1kΩ loading resistor on measured channel and 1V RMS input on other channel Attenuation Steps ����������������������������������� 1db from 1-48dB attenuation, 2dB from 48-76dB attenuation Volume Tracking ������������������������������������� Typically better than ±0.7dB to -60dB, ±1.5dB >60dB attenuation Mute Attenuation ������������������������������������ 96dB minimum Signal Handling �������������������������������������� 4V RMS Display Resolution ���������������������������������� 2dB steps www.siliconchip.com.au March 2002  57 Parts List For 6-Channel Remote Volume Control 1 1U rack case (Altronics H-5035 or equiv.) 1 Universal remote control with Mute, Channel and Volume Up/Down buttons (Altronics A-1007, Jaycar AR-1703, DSE G-1223, etc) 1 2 x 12V 15-30VA mains transformer (Altronics M-4912 or equiv.) (T1) 1 SPST mains power switch (S4) 1 M205 mains panel-mount safety fuseholder (F1) 1 0.5A slow blow M205 fuse 1 7.5A mains lead with moulded plug including earth pin 1 mains cord grip grommet 2 M3 crimp lug eyelets 2 insulated spade connectors (female) 1 .001µF 250VAC X2 MKT polyester capacitor 1 10A 3-way mains terminal block (chassis mount) 1 piece of Elephantide insulation, 35 x 35mm 1 30mm length of 10mm-dia. heatshrink tubing 4 stick-on rubber feet 10 100mm long cable ties 4 8-way 0.1-inch pin header plugs 1 270mm length of 8-way rainbow cable 4 M3 tapped x 12mm spacers 4 M3 tapped x 10mm spacers 2 6mm untapped spacers 17 M3 x 6mm screws 3 M3 x 12mm screws 1 M3 x 10mm screw 5 M3 nuts 2 M3 star washers 6 6g x 10mm self tapping screws for RCA sockets 1 PC stake 6 PC-mount RCA sockets (Altronics P 0210) 1 600mm length of 0.7mm tinned copper wire AUDIO ATTENUATOR BOARD Semiconductors 1 PIC16F84 microcontroller programmed with REMVOL.HEX code (IC1) 1 PC board, code 01103021, 121 x 85mm 2 8-way 0.1-inch pin headers Another feature of the unit is that it remembers the cur­rent volume level when the power is switched off. It then au­tomatically reverts to this volume level when power is next applied. The muting is always initially off when the unit is switched on, even if the unit 58  Silicon Chip Semiconductors 2 LM1973N 3-channel audio attenuator (IC4,IC7) 4 TL072 dual JFET op amps (SGS Thomson or Motorola brands) (IC2,IC3,IC5,IC6) Capacitors 2 1000µF 16VW PC electrolytic 6 10µF bipolar (non-polarised) electrolytic 4 1µF 25VW PC electrolytic 6 1µF bipolar electrolytic or MKT polyester 4 0.1µF MKT polyester Resistors (0.25W, 1%) 6 10kΩ 6 150Ω 2 2.2kΩ 1 1.2kΩ DISPLAY BOARD 1 PC board, code 01103022, 231 x 56mm 1 8-way 0.1-inch pin header 1 TO-220 heatsink, 19 x 19 x 10mm 3 SPDT momentary subminiature pushbutton switches (S1-S3) (Al­tronics S 1498) 3 7.5mm diameter caps for switches 1 M3 x 6mm screw 1 M3 nut 1 18-pin DIL IC socket 1 4MHz crystal (X1) 1 250mm length of 0.7mm tinned copper wire was muted at switch-off. Commercial transmitter As mentioned earlier, this unit can be operated using a commercial IR remote control, which can also be used to control other equipment (eg, a TV, 1 infrared remote control demodulator IC (IRD1) 1 7805 5V 3-terminal regulator (REG1) 6 BC328 PNP transistors (Q1-Q6) 6 1N4148, 1N914 diodes (D6-D11) 4 5-segment green LED bargraph displays (Altronics Z 0972) (LEDs1-20) 1 3mm green LED (LED22) Capacitors 1 1000µF 16VW PC electrolytic 3 10µF 25VW PC electrolytic 1 0.1µF MKT polyester 2 18pF ceramic Resistors (0.25W, 1%) 1 100kΩ 1 470Ω 2 10kΩ 1 220Ω 4 1kΩ 5 120Ω 4 680Ω 1 100Ω 5W POWER SUPPLY BOARD 1 PC board, code 01103023, 71 x 45mm 1 8-way 0.1-inch pin header 4 PC stakes 1 25mm length of 0.7mm tinned copper wire Semiconductors 1 7812 regulator (REG1) 1 7912 regulator (REG2) 1 7806 regulator (REG3) 1 7906 regulator (REG4) 5 1N4004 diodes (D1-D5) Capacitors 2 1000µF 25VW PC electrolytic 2 470µF 16VW PC electrolytic 4 10µF 25VW PC electrolytic Resistors 2 39Ω 0.25W 1% 1 33Ω 5W VCR or satellite receiver). In fact, quite a few IR remote transmitters will work with the 6-Channel Remote Volume Control and some of these are in the parts list. At one end of the scale, you can use a TV-only remote con­trol unit with just www.siliconchip.com.au Fig.2: the block diagram for the 6-Channel IR Remote Volume Control. A microcontroller (IC1) decodes the signals from the switches and the IR receiver and provides a control signal for the audio attenuators (IC4 & IC7). It also drives the LED bargraph display. Volume Up/Down, Channel Up/Down, Mute and Operate controls. Alternatively, you can use a more elaborate unit which can also used to operate some of your other equipment. The main proviso with the IR remote control is that it is able to output Philips RC5 codes. There are three possible RC5 code sets that you can use, so if you already have a Philips TV set and/or VCR, you can select an unused code to avoid control­ling both devices at once. In that case, you will need to purchase a preprogrammed IR remote control that can be set to control satellite receivers (as well as TVs and VCRs). OK, enough of the preamble. Let’s find out how it works. fed to an audio attenuator block. This then atten­uates all six channels, according to the control signals applied via a 3-wire interface from the Infrared Decoder/Controller block (IC1). IC1 is actually a microcontroller. Its job is to decode signal inputs from the Down, Up & Mute switches and from Block diagram Take a look now at Fig.2 which is the block diagram of the 6-Channel Remote Volume Control. It’s really quite simple in concept, with just a few main circuit blocks (you didn’t really want anything too complicated and expensive, did you?). Here’s how it works. First, the six audio signals from the DVD player are www.siliconchip.com.au Fig.3: total harmonic distortion (THD) vs. frequency. As can be seen, the performance is excellent, with THD less than .02% up to around 10kHz. March 2002  59 Fig.4: the audio attenuator section is based on two LM1973 3-channel attenuator ICs. The attenuation level is adjusted according to a 3-wire digital control signal on pins 9-11 and op amps IC2b, IC3a & IC3b buffer the attenuated outputs. the infrared receiver (IRD1) which picks up signals from the remote control. It then generates the 3-wire control signals (Data, Clock & Load) which are applied to the Audio Attenuator. In addition, the microcontroller also drives the 20-LED bargraph display. Finally, the signals from the Audio Attenuator are buffered by op amps IC2, IC3, IC5 & IC6 and fed to the output sockets. These outputs in turn are fed to the audio amplifiers. Circuit details Figs.4-6 show the complete circuit details of the 6-Channel Remote Volume Control. We’ll look at each of 60  Silicon Chip these sections in turn. Fig.4 is the audio attenuator section. For the sake of clarity, only channels 4-6 are shown – channels 1-3 are identical except for the IC numbering which is shown in brackets. IC4 (and IC7) are “3-Channel 76dB Audio Attenuators with Mute” (from National Semiconductor). Each channel includes a resistive array with various tappings to select the requisite amount of signal attenuation. The input impedance is a nominal 40kΩ, while the output impedance varies from 25kΩ to 35kΩ, de­pending on the attenuation level. As indicated previously, the atten- uation level is adjusted using a 3-wire serial digital control signal. The audio signals from the DVD player are fed to IC4 via 1µF bipolar capacitors. These serve two purposes: they roll off the low-frequency response below 4Hz (in company with the input impedance); and they prevents any DC current flow in the resis­tors that make up the attenuators. The outputs from the attenuators appear at pins 6, 20 & 16 (OUT1, OUT2 & OUT3) and are fed to JFET op amp stages IC2b, IC3a & IC3b. These op amps are wired as unity-gain buffer stages and have several functions: (1) they provide low-impedance output signals which are suitable for driving power amplifier stages; (2) their high input impedance prevents loading of www.siliconchip.com.au Fig.5: the control display section is based on microcontroller IC1. This processes the inputs from the switches and IR receiver and provides the 3-wire control signal for the attenuator ICs. It also drives the LED displays. the attenua­tors, thus maintaining the accuracy of the volume setting; and (3) the negligible bias currents flowing in the op amp inputs prevent unwanted clicks in the audio signals as the output im­pedance of the attenuators changes with volume Note that the output of each op amp buffer is isolated from its output terminal using a 150Ω resistor, to prevent instabili­ ty. In addition, the outputs are AC-coupled via 10µF bipolar capacitors to prevent any DC offsets from being fed through to the power amplifiers. The 10kΩ resistors tying the op amp outputs to ground are included to ensure that the outputs discharge to ground when power is removed from the circuit. This prevents switch on clicks when power is reapplied. Note that IC2 and IC5 are actually TL072 dual op amps even though we are using only one op amp in each package. They are specified because the dual-package versions produce a lower switch-on click than TL071 single op amps. For the same reason, it is necessary to use either Motorola or SGS Thomson (ST) TL072s in preference to those from other manufacturers, as these produce the lowest output transients at switch on. Each op amp package is powered from ±12V supply rails. These rails are decoupled at each op amp’s supply pins using a 1µF capacitor, while two 1000µF 16VW capacitors provide overall decoupling of the supply. These relatively large capacitors ensure that the op amp supply rails decay away at a slow rate when power is removed from the circuit, to prevent switch-off thump. The two audio attenuator ICs (IC4 & IC7) are powered from ±6V rails which are decoupled using 0.1µF capacitors. Their Clock, Load and Data inputs are at pins 9, 10 & 11 and these are controlled by microcontroller IC1 (see Fig.5) to set the attenua­tion values. Note that each of the three channels in each IC is individually addressable and could theoretically be loaded with any attenuation value. www.siliconchip.com.au March 2002  61 REG3 7806 +17V FUSE F1 0.5A SLOW POWER S4 T1 M 4912 30VA A 12V IN D1-4: 1N4004 D1 D4 D5 1N4004 IN 12V D2 D3 1000F 25VW +6V 470F 16VW REG1 7812 .001F 250VAC OR 275VAC N OUT GND 39 OUT GND +12V 10F 25VW 10F 25VW 0V 1000F 25VW E 10F 25VW 330 5W (CASE) IN GND OUT 39 REG2 7912 REG1, REG3 GND IN OUT REG2, REG4 GND IN 10F 25VW OUT -12V 470F 16VW IN GND OUT -6V REG4 7906 SC 2002 6-CHANNEL REMOTE VOLUME CONTROL Fig.6: the power supply circuit uses four 3-terminal regulators to deliver ±6V and ±12V rails for the audio circuitry. The +17V rail feeds a 5V 3-terminal regulator in the display section. In this case, however, both IC4 and IC7 have these three control lines connected in parallel. As a result, the attenuation value set for channel 6 is also set in channel 3. Similarly, channels 5 and 2 have the same attenuation value, as do channels 4 and 1. In addition, the software programmed into the microcon­troller sets all channels to the same value. Control & display circuit This circuit section is based mainly on a PIC16F84 micro­controller (IC1) – see Fig.5. It primary function is to decode the signals from switches S1-S3 and from the infrared receiver (IRD1) and provide the 3-wire control signals to IC4 (and IC7). It also drives the 20-LED bargraph display in multiplex fashion. This enables the LEDs to be driven via five common lines at the RB0-RB4 outputs of IC1. The RB5-RB7 outputs and transistors Q1-Q5 select which bank of five LEDs will be driven at any one time. For example, when RB7 is low, Q5 turns on and the anodes of LEDs 16-20 are all high. As a result, any low lines at RB0-RB4 drive the correspond­ing LEDs in this group via series 120Ω 62  Silicon Chip resistors (eg, if RB0 goes low, LED16 will light). When RB7 subsequently goes high, RB6 goes low and selects LEDs 11-15 via Q4. RB6 then goes high and RB5 goes low to select LEDs 6-10 via Q3. When ever one of the RB5-RB7 lines is low, transistor Q1’s base is pulled low via a 10kΩ resistor and an OR gate made up of diodes D6-D8. This turns Q1 on which means that Q2 is off (as are LEDs1-5). However, when RB5-RB7 all go high, Q1 turns off and Q2 turns on (due to its 680Ω base resistor) and pulls the anodes of LEDs1-5 high. These LEDs can now be driven by the RB0-RB4 outputs of IC1, as before. So this simple gating technique allows us to drive four banks of LEDs using only three outputs (RB5-RB7) from IC1. When ever one of the RB5-RB7 lines is low, the RA0 input is monitored to check whether a switch has been pressed. A closed switch causes the normally high RA0 input to be pulled low via either D9, D10 or D11 when an RB5-RB7 line goes low. For example, if S1 (Volume Down) is pressed, RA0 is pulled low via D11 when RB5 goes low. Similarly, if S2 POWER SUPPLY (Volume Up) is pressed, RA0 is pulled low via D10 and RB6. And if S3 (Mute) is pressed, RA0 is pulled low via D9 when RB7 goes low. By this means, the software in IC1 detects which switch has been pressed and generates the appropriate control signals at the RA2-RA4 outputs which are then fed to IC4 & IC7 Note that the 3-wire control outputs are fed to IC4 & IC7 via 1kΩ resistors. These slow down the control signal rise times so that they don’t cause noise in the audio signal. Note also that RA4 of IC1 is an open drain output and requires a pullup resis­tor. This output is high at power up and this ensures that the attenuators are initially set to minimum volume, after which the software quickly takes over and sets the volume to the required level. IR control The infrared receiver circuitry is simplicity itself and is based on infrared receiver module IRD1. This 3-lead device ampli­fies, filters and demodulates the coded signals picked up from the IR transmitter and feeds the demodulated signal to the RA1 input of IC1. It also drives Q6 which flashes the Acknowledge LED (LED21) each time pin 1 of IRD1 goes low. As a result, the Acknowledge LED www.siliconchip.com.au flashes (to indicate that infrared signals are being picked up) each time you press a button on the transmitter. IC1 decodes the signals applied to its RA1 input and, pro­vided the coding is correct, changes its outputs accordingly. The default code is for the TV1 address but this can easily be changed so that you can use either the SATellite 1 (SAT1) or SATellite 2 (SAT2) code (eg, if you are already using TV1 to control your TV set). A 4MHz crystal connected between pins 15 & 16 provides the timing for IC1. The two 18pF capacitors ensure that the crystal is correctly loaded, so that it starts reliably. Power for the microcontroller is supplied via 5V regula­tor REG5. This is isolated from the incoming +17V supply using a 100Ω 5W resistor and decoupled at its input and output using 10µF electrolytic capacitors. In case you’re wondering, the 100Ω resistor causes the 5V supply to rise relatively slowly at power up, to ensure a “soft” start. It also dissipates power which would otherwise have to be dissipated by REG5 (which, in turn, would require a bigger heat­sink). In addition, a 1000µF capacitor is used to decouple the +5V supply line at IRD1. This prevents any switching noise on the +5V supply from being amplified within the infrared receiver. The 220Ω resistor connected across the 5V supply ensures that the voltage falls to zero at switch off. This is neces- Fig.7: install the parts on the audio attenuator (signal) board as shown here, taking care to ensure that the ICs and electrolytic capacitors are correctly oriented. The bipolar capacitors can go in either way around. sary to ensure that IC1 resets correctly when power is reapplied. Power supply circuit Fig.6 shows the power supply circuit. It uses a 24V centre- tapped mains transformer, the output of which is rectified using diodes D1-D4 and filtered by two 1000µF capacitors to produce nominal ±17V rails. These rails are then fed to regulators REG1-REG4 to derive ±12V and ±6V supply rails. Note that REG1 and REG3 are isolated from the +17V supply using diode D5. This ensures that the regulated positive supply rails fall at the same rate as the negative rails when power is switched off. In addition, the outputs of REG3 & REG4 are decoupled using 470µF capacitors rather than 10µF capacitors, as used at the outputs of REG1 & REG2. This ensures that the ±6V supply rails fall slower than the ±12V supply rails at switch off. And that in turn ensures that the inputs to the op amps are tied to ground via the attenuator output resistances while ever power is applied to the op amps. The +17V rail pro- Left: this is the completed audio attenuator board. Note the orientation of the two pin header sockets. www.siliconchip.com.au March 2002  63 Left: another view of the completed audio attenuator board. Make sure that the RCA sockets are seated correctly before soldering their leads. Fig.8 (below): be sure to place the 3-terminal regulators (REG1REG4) correctly when building the Power Supply Board. vides power to the display circuit and this load is balanced by including a 33Ω load resistor across the -17V supply. This is done to produce similar decay times for the ±17V rails at switch off. REG1 39 10F D2 1000F D4 330 5W Note that the +12V and -12V outputs from REG1 & REG2 are decoupled with 39Ω resistors before being applied to the signal circuitry. These resistors slow down the risetime for the op amp supply rails at power up. 470F 10F 10F 470F REG4 0V 32030110 0V 12V 1000F D1 REG2 D3 12V REG3 39 D5 +12V q12V +6V q6V +17V GND GND GND 10F This is the completed Power Supply Board. Mount the 5W resistor slightly proud of the board to aid cooling. FROM POWER TRANSFORMER 6-CHANNEL VOLUME POWER Basically, the power supply has been designed to deliver its various supply rails without causing excessive voltage excur­sions in the op amp outputs during power up and power down. As a result, switch-on thumps Table 1: Resistor Colour Codes  No.   1   8   2   1   4   4   1   1   6   5   2 64  Silicon Chip Value 100kΩ 10kΩ 2.2kΩ 1.2kΩ 1kΩ 680Ω 470Ω 220Ω 150Ω 120Ω 39Ω 4-Band Code (1%) brown black yellow brown brown black orange brown red red red brown brown red red brown brown black red brown blue grey brown brown yellow violet brown brown red red brown brown brown green brown brown brown red brown brown orange white black brown 5-Band Code (1%) brown black black orange brown brown black black red brown red red black brown brown brown red black brown brown brown black black brown brown blue grey black black brown yellow violet black black brown red red black black brown brown green black black brown brown red black black brown orange white black gold brown www.siliconchip.com.au and switch-off instability problems are avoided. Power on/off switching is provided by mains switch S4, with a 0.5A fuse protecting the transformer primary. The .001µF ca­ p acitor across S4’s contacts prevents arcing at switch off, again to avoid sudden transient voltage excursions at the op amp out­puts. Construction The unit is easy to build, with separate PC boards for each of the circuits shown in Figs.2-4. These boards are as follows: (1) an audio attenuator board coded 01103021; (2) a display board coded 01103022; and (3) a power supply board coded 01103023. Figs.7-9 show the assembly details for the PC boards. As shown in the photo, the PC boards are interconnected using 8-way flat cables that plug into pin headers. Signal board assembly Begin the assembly by building the audio attenuator board – see Fig.7. Install the wire links first, then the resistors, ICs and capacitors. Make sure that the ICs and the electrolytic capaci­tors are all oriented correctly. The bipolar (BP) capacitors are non-polarised and can be installed either way around. Table 1 shows the resistor colour codes but we suggest that you also check each value using a digital multimeter as some of the colours can be difficult to decipher. The audio attenuator board can now be completed by installing the two 8-way pin headers and the RCA sockets. Note that it will be necessary to cut off the plastic locating clips at the base of each RCA socket pair before installing it. You can do this using a pair of sidecutters. Push the RCA sockets all the way down onto the board and make sure they are properly seated before soldering their leads. Display board assembly Fig.9 shows the parts layout on the Control & Display board. Again, Table 2: Capacitor Codes      Value IEC Code EIA Code 1µF   105   1u 0.1µF   104   100n 0.001µF 102   1n 18pF   18  18p www.siliconchip.com.au begin by installing the wire links, then install the resistors, diodes and capacitors. Note that the 100Ω 5W resistor should be mounted about 3mm proud of the PC board, to allow the air to circulate underneath it for cooling. The six transistors (all BC338 or BC337) can go in next, followed by the 4MHz crystal (X1). That done, you can install the three pushbutton switches (S1-S3). Next, install an 18-pin DIL socket for IC1 but don’t in­stall IC1 (the PIC microcontroller) at this stage. That step comes later. The 7805 regulator (REG5) can go in now. This device is mounted horizontally which means that you have to bend its leads down by 90° before mounting it on the PC board. This is best done by slipping an M3 screw through the device tab, positioning it on the board and then gripping one of the leads with a pair of needle-nose pliers just before it reach­ es its mounting hole. The device can then be lifted clear of the board and the lead bent down at right angles, after which the procedure can be repeated for the two remaining leads. REG5 can now be fitted to a small mini-U heatsink and the assembly bolted to the PC board using a 6mm M3 screw, nut and star washer. Don’t forget to solder its leads after bolting it down. The 5-segment LED bargraph displays have a plastic moulding that has a raised section at one end and a recessed section at the other. This allows them to be locked together to form one continuous bargraph. Before mounting the displays, first orient each segment so that the anode leads (the longer of the two for each LED) are towards the right. This done, bend the leads down at right angles about 5mm from the plastic body, so that the front faces of the LEDs will sit about 4mm from the edge of the PC board. Now mount the LED segments so that they sit about 2.5mm proud of the board surface. A 2.5mm-thick “standoff” (made from a strips of cardboard, for example) will make this job easy – just sand­wich the standoff between the LED segment and the PC board, solder the two outer leads, then remove the standoff and solder the remaining leads. LED21 is mounted similarly by bending its leads at right angles and Fig.9: the parts layout for the control and display section. Refer to the text when installing the LED displays. March 2002  65 This view shows the assembled Control and Display Board, ready for installation in the case. The four 5-way LED bargraph segments lock together to form a continuous display. installing it so that it lines up with the bargraph LEDs. Similarly, the infrared receiver (IRD1) is mounted by first bending its leads down at right angles close to its body, and then down at right angles again before soldering it to the PC board. The front of this device should be about 1mm out from the front edge of the PC board when it is installed. The Display Board can now be completed by installing IC1 in its socket. Make sure that it is correctly oriented. Power supply board The LED bargraph segments must each be mounted about 2.5mm proud of the PC board and this can easily be done using some folded cardboard to act as a spacer. This board is assembled as shown in Fig.8. The main thing to watch out for here is that you use the correct 3-terminal regulator at each location and that the regulators are correctly oriented – their metal tabs all go towards the 1000µF electrolytic capaci­tors. Note too that diode D5 faces in the opposite direction to diodes D1-D4. The 33Ω 5W resistor should be mounted about 3mm proud of the PC board to aid cooling. That’s all for now. We’ll complete the construction and SC give the test procedure in next month’s issue. The completed modules are installed in a 1U rack chassis and interconnected using two cables fitted with pin headers (details next month). 66  Silicon Chip www.siliconchip.com.au PRODUCT SHOWCASE eLabtronics launches icon-based micro assembly language at WCIT2002 Traditionally, microcontrollers have been programmed using a complex, error-prone assembly language. However, a South Australian based microcontroller company plans to change this with its “bitset” icon-based assembly language. eLabtronics will officially launch bitset worldwide at the World Congress on IT (WCIT2002) to be held in Adelaide from 25 February to 1 March. eLabtronics Technical Manager Miro­ slav Kostecki will present bitset at the WCIT2002 Business Forum. The program itself consists of 10 icons which can be used in any combination to form the total microcontroller instruction set. It makes microcontroller programming simpler, faster and less prone to error, without compromising the controller’s speed or the program efficiency. bitset is set to be used at all levels of education, giving students the opportunity to learn the basics of microcontroller programming at a much earlier age. In fact, bitset is so simple to use that an eight-year-old child was able to use it to program his own burglar alarm. bitset will narrow the “great digital divide” by providing greater accessibility to microcontroller programming. eLabtronics CEO Peng Choo said: “The bitset program has huge implications for Australia and will help establish its reputation as a major ICT innovator”. The company’s display at WCIT­ 2002 will feature a robotic arm which has been entirely programmed by stu- dents using the bitset program. Contact: eLabtronics 12-20 Gilles St, Adelaide, SA 5000 Ph: 08 8231 5966 Website: www.labtron.com.au True RMS Clamp-On Hi-Tester Nilsen Technologies has introduced a true RMS clamp-on meter, the Hioki 3280-20 Clamp-on HiTester. Its compact design makes it possible to securely clamp in even complicated circuitry due to its core thickness of only 9.5mm. There is a need for accurate yet simple measurement of distorted currents, including harmonic components, as well as a need to measure the unbalanced currents that flow through neutral wires in single-phase three-line circuits. The thin 3280-20 allows the technician to easily clamp complicated circuitry, which other instruments cannot do, and it can accurately measure true RMS for even distorted currents. It also provides portability, safety and ease of use, including a drop-proof construction. Contact: Nilsen Technologies Pty Ltd, 43 Sheehan Rd, Heidelberg West, Vic 3081 Freecall 1-800-623-350 Freefax 1-800-067-263 STEPDOWN TRANSFORMERS 60VA to 3KVA encased toroids Tandy have one too . . . Elsewhere in this issue is a D-I-Y RIAA preamp project, intended to fit into existing turntables. Not to be outdone, Tandy Electronics have just put on “special” (until 10th March) a turntable with a built-in preamp (presumably RIAA). The whole deal – “Optimus” turntable AND preamp – is selling for $99.00 (save $30). It is available through any Tandy Electronics store. (Call 1300 728 SC 075 for locations). www.siliconchip.com.au Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 9476-5854 Fx (02) 9476-3231 March 2002  67 R ecording I ndustry A ssociation of A merica PREAMPLI FOR TURNT Did you want to build the Ultra-LD Amplifier described recently in SILICON CHIP? Are you put off because it does not have a preamplifier for a magnetic cartridge? Then don’t be because this self-contained preamplifier has been designed to install under your turntable and give better performance than the RIAA preamp in most stereo amplifiers and receivers. By LEO SIMPSON & ROSS TESTER S eemingly, no sooner than the print was dry on the December 2001 issue which featured the second article on the Ultra-LD Amplifier, than we had several requests for a magnetic cartridge preamp to go with it. What to do? This had not been part of the game plan: there is really not enough space inside the amplifier for a preamplifier. We were also concerned about being able to obtain a sufficiently good signal-to noise-`ratio, if it was somehow packed into the rear compartment of the amplifier. Of course, one neat solution would be to build the LP Doctor featured in the January & February 2001 issues of SILICON CHIP. This not only features a good preamp but it also electronically 68  Silicon Chip removes the clicks and pops on vinyl records. Kits are still available from Dick Smith Electronics. However, as good and effective as the LP Doctor is, many people want just a simple preamp – and that is what we are presenting here. It comes on a single PC board together with its own power supply, including an encapsulated 20VA toroidal power transformer. It is intended to be mounted inside a standard turntable plinth, either on the underside of the turntable chassis or the Masonite (hardboard) cover underneath the plinth. The beauty of having the preamp directly underneath the turntable is that the input signal leads are kept to an absolute minimum and that should mean minimum hum and noise. On the other hand, care has to be taken to ensure that any hum and noise from the turntable motor and mains wiring is minimised. Circuit description Fig.1 shows the circuit. It uses a LM833 dual low-noise op amp, with one op amp being used in each channel. The circuit is practically identical to the preamp stage used in the above-mentioned LP Doctor except that it has higher supply rails and higher overall gain. The higher gain is necessary to raise the nominal 5mV to 10mV signal of a magnetic phono cartridge to the nominal input sensitivity of 500mV rewww.siliconchip.com.au The RIAA Preamplifier and ±15V power supply can be built as one board, as shown here, or divided in two for a separate power supply and preamplifer. The reasons for the “split” are explained in the text. IFIER TABLES quired for full power from the Ultra-LD power amplifier or, indeed, from the “aux” input of most amplifiers. At the same time, the preamplifier needs higher supply rails in order to provide good overload capability for high level signals from the magnetic cartridge. For those who have not seen the previous articles on this preamplifier, we will now describe how the circuit works. Both channels are identical so we will just refer to the left channel. Accordingly, the left channel phono cartridge signal is fed from the input socket via inductor L1, a 150Ω resistor and a 47µF bipolar capacitor to the non-inverting input of IC1a, which is one half of an LM833 dual low-noise op amp. The inductor L1, 150Ω series resistor and the shunt 100pF form a lowpass filter to remove RF interference signals which might be picked up by the phono leads. There is also a 270pF capacitor connected directly across the input terminals and this, added to the 100pF filter network capacitor, provides a capacitive load across each channel of the cartridge. This is done because most magnetic phone cartridges operate best with about 200-400pF of shunt capacitance. Normally, most of the capacitance www.siliconchip.com.au will be present in the pickup leads from the turntable to the preamplifier input but since this preamplifier is intended to be built into the turntable itself the long connecting leads will not be present. In fact, if you know the cartridge manufacturer’s recommended shunt capacitance you can connect the appropriate capacitor on the board instead of the 270pF we have shown on the circuit. Just subtract 100pF from the recommended capacitance and use that instead of the 270pF capacitors. While we’re still at the input circuit, the 47µF bipolar capacitor looks to be far larger than it needs to be in terms of bass signal coupling from the cartridge and so it is. In fact, as far as bass signal coupling is concerned, the capacitor only needs to be about 0.47µF. The reason we have specified such a large input capacitor is so that the op amp “sees” the very low source impedance of the cartridge, especially at low frequencies, and this helps to minimise any low frequency noise generated by the input loading resistors. RIAA equalisation Due to the way in which vinyl discs are recorded and the characteristics of Underneath the old Apan beltdrive turntable which had sat, unused and unloved, under the house since CDs came into vogue. The mains terminal strip can clearly be seen centre of pic; the output cables and wires from the cartridge terminate on a tagstrip hidden under the metal shield immed-iately to the right. March 2002  69 LEFT INPUT L1 (L2) 270pF 150 100k 100k LEFT CHANNEL ONLY SHOWN FOR CLARITY RIGHT CHANNEL IS IDENTICAL (IC PIN NOS IN BRACKETS ARE RIGHT CHANNEL) L1, L2: LINK THROUGH 4330-030-3218 BEAD SC  2002 +15V 47F BP RIAA PREAMP 3 (5) 8 1 (7) LM833 100pF 2 (6) LEFT OUTPUT IC1a (IC1b) 0.33F 4 100 1M -15V 390 F BP 16k 200k .0047F .015F 8 4 1 Fig 1: one channel of the RIAA preamp. Gain is set at 56, making it ideal for use with most amplifier “aux” inputs. typical magnetic cartridges, the input signal to the preamplifier will be very strong at the treble end and becomes progressively less as the frequency drops. To compensate for this, all magnetic cartridge preamplifiers need to substantially boost the bass and cut the treble (ie, equalisation) according to the well-known RIAA characteristic curve. In our circuit, the RIAA equalisation is provided by the RC feedback components between pins 1 & 2 of IC1a (and between pins 6 & 7 of IC1b, the right channel). In fact, there are three capacitors and three resistors which vary the feedback to provide the correct equalisation. For example, the .0047µF and .015µF capacitors provide the required treble rolloff, in conjunction with the 16kΩ and 200kΩ resistors which help determine the gain. This feedback network provides the standard equalisation time constants of 3180µs (50Hz), 318µs (500Hz) and 75µs (2122Hz). The circuit also includes the IEC recommendation for rolloff below 20Hz. This is provided by the 390Ω resistor in series with the 33µF capacitor and the 0.33µF output coupling capacitor. The overall gain of the circuit is set by the 390Ω resistor in series with the 33µF capacitor. This is a compromise between overall gain (set at 56 at 1kHz) and input overload margin. The latter is important because while the nominal signal level from a typical magnetic cartridge may only be about 5mV or 10mV, the level can rise to well over 70mV (or much higher for high- output cartridges). The frequency response is shown in the graph of Fig.3. Signal-to-noise ratio is about as good as you can get with a typical magnetic cartridge, around -83dB with respect to an input signal of 10mV at 1kHz. The actual signal-to70  Silicon Chip noise ratio you achieve depends more on your turntable, its rumble performance, shielding from hum fields and so on. Power supply To make the circuit self-contained, we have included the power supply. It employs a potted 10VA toroidal transformer with two 15V secondary windings feeding a bridge rectifier, two 470µF capacitors and two 3-terminal regulators to produce balanced supply rails of ±15V. Both the power supply and the stereo preamplifier have been combined onto one PC board measuring 210 x 65mm and coded 01103021. This has can be used in one piece or split, to separate the power supply and the preamplifier. This has been done to ensure maximum flexibility. While we intended it to be installed underneath a standard turntable, this may not be practical in some cases where space is ALTRONICS M4330 120V A POWER 15V very limited. In that case, you would need to house the whole PC board in its own earthed metal case. If you do install the preamplifier underneath your turntable, you will need to take great care in order to get hum-free performance. Generally, that means installing the power supply section of the board as far away as possible from the tone arm and its “arc” across the turntable platter. Typically, this means installing it near the motor or in the opposite corner to the tonearm pivot. The preamplifier section of the board should then been installed as close as possible to the tonearm shielded cable terminations, typically near the back of the turntable base. Use very short shielded input leads to the preamp and then terminate the turntable’s existing shielded output leads to the preamp-lifier outputs. Construction Before starting construction, you will need to make that decision about whether to use the PC board intact, or to split it. While you can saw the board apart after assembly (we did!), it is easier to do before it is populated. And before you do anything, inspect the board for any manufacturing defects. We’ll assume you are going to use it intact but if you aren’t, the sequence of construction is much the same. Because the heavier components are mounted at the power supply end, we’ll start with the preamp. Start with the resistors – and as you D1 - D4 4 x 1N4004 F1 1A 240VAC IN 0V 120V 15V 0V N REG1 7815 0V T1 20VA 0V IN OUT +15V GND 470F 25V 100F 16V 0V E EARTH LINK (SEE TEXT) A E N TURNTABLE 7815 IN GND GND IN GND IN OUT -15V REG2 7915 7915 OUT 100F 16V 470F 25V OUT SC 2002 RIAA PREAMP POWER SUPPLY Fig.2: there’s nothing particularly unusual about the ±15V power supply . . . except perhaps that “earth link” which is explained in the text. www.siliconchip.com.au Here’s what the intact board looks like, fully assembled (except for the PC stakes not yet fitted to the preamp inputs and outputs.) The board can be divided where indicated by the dotted line and joined together by 3 wires (+15V, 0V and -15V). Note that there are some minor changes to component values since this photo was taken: the overlay is the latest version. solder them in and crop their leads, use some of those leads for the four links on the board. The accompanying table shows the colour code for the resistors – some are perhaps unusual, being 1% values (the 200kΩ and 16kΩ, for example). If in any doubt, use a digital multimeter to check them before soldering them in. Resistor pigtails can also be used for the “inductors”, which are simply one pass of wire through the ferrite beads. Now move on to the non-electrolytic capacitors, which of course are not polarised (note our earlier comments regarding the 270pF input shunt capacitor). Most of the electrolytic capacitors in the preamp (all bar one, in fact) are “bipolar” types which once again means you won’t be caught out with polarity problems. The one exception is the 10µF right across the supply rails which must be installed as shown on the overlay diagram. There are eight PC stakes to solder in at the inputs and outputs. Originally we had planned to use RCA sockets to make the board as flexible as possible but in the end settled for plain old stakes. Of course, there is nothing to stop you soldering suitable RCA sockets to the stakes, if you wish. The final component at this end of the board is the LM833 op amp which must mount the way indicated. Solder the pins carefully – it’s very easy to get a solder bridge between IC pins. At best, the preamp won’t work. At worst, this could destroy the op amp. Power supply Just about everything in the power supply is polarised. Start with the four rectifier diodes – they mount in pairs with the two in each pair facing the same direction but the other pair mount in the opposite direction. The direction AUDIO PRECISION SCTHD-HZ AMPL(dBr) vs FREQ(Hz) 11 FEB 102 08:40:04 of these diodes 20.000 determines which track 15.000 becomes the 10.000 positive rail and which be5.0000 comes the negative rail. 0.0 Next, solder in the four -5.000 elec-trolytics -10.00 with the orientation shown. -15.00 The larger (input) capacitors -20.00 face in oppo20 100 1k 10k 20k site directions; Fig.3: the preamp equalisation matches the RIAA specificathe two smalltion very closely. www.siliconchip.com.au er (output) capacitors face the same direction. The two voltage regulators are different – one is a positive regulator (7815) while the other is a negative regulator (7915). Don’t mix them up! These are mounted flat on the board with the ends of their leads bent down 90° to pass through their respective PC board holes. To get the bend in the right position, loosely mount the regulators to the PC board with M3 screws and grip the legs with fine (needle nose) pliers where the bends should go. Still holding the legs in the pliers, remove the screw and bend the leads down 90°. The regulators are photographed and drawn with small U-shaped heatsinks fitted. In fact, on the board there is room for much larger heatsinks. Due to the minimal current drain of this circuit, heatsinks are not really necessary – but we have in mind another task for this power supply and preamp later on which will need heatsinks. So we’ve fitted them. No insulation is necessary between regulator and heatsink. What is that task? That would be telling! (Incidentally, if you need a general purpose ±15V supply for other projects, this part of the board is perfect. Is that a clue?) You will note that there is an earth link shown on the circuit and provision made for it on the PC board. In the vast majority of cases, the turntable itself will be earthed to the amplifier (in turn, earthing the preamp via the input leads), so this link will not be necessary. In fact, it may increase hum levels due to the earth loop formed. March 2002  71 Parts List – RIAA Preamp 1 PC board, 215 x 67mm, code 01303021 1 4-way, PC-mounting mains terminal block, (Altronics P2103 or similar) 2 U-shaped heatsinks 8 PC stakes (14 if separated boards) 2 Ferrite beads, Philips 4330-030-3218 or similar 2 25mm lengths 0.25mm enamelled copper wire 1 240V to 30VCT PC-mounting transformer, Altronics M4330 or similar 1 SPST mains rated switch to suit – neon indicator optional 1 M203 or 3AG safety fuseholder, with 1A fuse. 4 (or 7 for split boards) mounting screws – type to suit use (see text) Optional: 1 metal case, minimum 75 x 75 x 25mm inside (see text) Semiconductors 4 IN4004 or similar 1A rectifier diodes (D1-D4) 1 7815 15V 1A positive regulator (REG1) 1 7915 15V 1A negative regulator (REG2) 1 LM833N twin low-noise op amp (IC1) Capacitors 2 470µF, 25VW PC electrolytics 2 100µF, 16VW PC electrolytics 2 47µF, 16VW PC bipolar electrolytics 2 33µF, 16VW PC bipolar electrolytics 1 10µF, 35VW PC electrolytic 2 0.33µF MKT polyester 1 0.1µF MKT polyester 2 .015µF MKT polyester 2 .0047µF MKT polyester 2 470pF MKT polyester 2 100pF MKT polyester Resistors (0.25W, 1%) 2 1MΩ 2 200kΩ 4 100kΩ Hum and noise minimisation 2 16kΩ 2 390Ω We used two resistor pigtails soldered “end on” into the link holes. To prove whether we needed the link, it was simply a matter of shorting them together. Hum levels increased significantly, so we left them open circuit. They won’t do any harm sitting there like that. If your hum level drops when you check the preamp out later, you need the link soldered. The final two “components” to be mounted are the mains input terminal block and the transformer. First the mains terminal block: it is a special noise) into the preamplifier. Second, it is designed to be mounted directly onto the PC board. The only problem with this transformer is that the pins for input and output appear identical so you could solder it in back to front. Again, if you get this wrong, the result will be briefly spectacular (and expensive). Read the label on the transformer and check it twice before soldering it in! The transformer in fact has two primaries and two secondaries, each of which the PC board connects in series. The two 120V primaries therefore become a 240V primary; the junction of the two 15V secondaries is connected to 0V. While the four pins will hold the transformer in place, a self-tapping screw should be used from under the board to hold it secure, relieving the strain on the soldered joints. Check your component placement, polarity (particularly that transformer!) and soldering before moving on to the next phase of the project. 2 150Ω 2 100Ω type designed for mains use with barriers between each screw terminal. Don’t substitute a block without this insulation. One strand of wire astray and bang . . . It’s also important which wire of the three in the mains lead goes to which terminal, but we’ll cover this shortly. The power transformer The transformer for this project was specially chosen for two reasons. First, it is a toroidal type which should mean minimum radiation (and therefore We’re going to put the cart before the horse, so to speak, and briefly mention the physical layout before looking at the wiring. Earlier, we talked about the physical location of the preamp and power supply. To reiterate, you need to get the power supply (transformer, especially) as far away from the pickup as possible (including the complete arc of the tone arm). Initially, we left the PC board in one piece and mounted it so that the transformer was very close to the motor. While performance was good we thought it could be better. So we separated the two parts of the board and mounted the preamp right up close to where the wires emerge from the tone arm. And that dramatically improved the signal-to- Resistor Colour Codes        No. Value 2 1MΩ 2 200kΩ 4 100kΩ 2 16kΩ 2 390Ω 2 150Ω 2 100Ω 72  Silicon Chip 4-Band Code (1%) brown black green brown red black yellow brown brown black yellow brown brown blue orange brown orange white brown brown brown green brown brown brown black brown brown 5-Band Code (1%) brown black black yellow brown red black black orange brown brown black black orange brown brown blue black red brown orange white black black brown brown green black black brown brown black black black brown Capacitor Codes         Value    IEC code    EIA code 0.33uF 330n 334 0.1uF 100n 104 .015uF 15n 153 .0047uF 4n7 472 470pF 470 471 100pF 100 101 www.siliconchip.com.au IN RIGHT www.siliconchip.com.au L NI 100pF 1 100k .0047 16k 150 100k 390 0.1 16k .0047 200k L OUT .015 0.33 10F 12030110 100 2002 )C( 100 L R OUT R 1M 0.33 E E 100pF 100k 200k .015 33F BP 47F IC1 LM833 47F 100k 150 L2 L1 270pF 270pF 390 33F BP 1M E Wiring it up –15V E +15V DIVIDE BOARDS DOWN THIS LINE (IF REQUIRED) –15V E +15V 120OPTIONAL 3 0110 HEATSINK OPTIONAL HEATSINK 2002 )C( REG2 7915 REG1 7815 5197 5187 470F 470F 15V 1N4004 100F 1N4004 1N4004 1N4004 100F OPTIONAL EARTH LINK (SEE TEXT) OK, back to the wiring. Fairly obviously, we needed to unscrew the plywood, masonite or other sheet which covers the bottom of the turntable plinth. Most turntables will have similar plinths. Ours happened to be an Apan belt-drive turntable which had sat unused and unloved under the house since CDs came into vogue. But its belt was still perfect (they made ’em good in those days!), while the cartridge and more importantly the stylus were in great shape. (You should check out the stylus under a powerful magnifying glass or loupe to make sure its point isn’t chipped or worn). In some turntables, the very thin wiring emerging from the tone arm under the turntable will be terminated directly to RCA or similar output sockets. But the majority will terminate to a tagstrip or block, with flying leads going out through the back of the plinth. You have to connect the tone arm wiring to the inputs of the preamp. This might be by resoldering them direct, or perhaps using a short length of stereo shielded lead. Every turntable will be different; you have to make the decision according to yours. In our case, it was easiest to unsolder the flying leads from a tagstrip, solder those directly to the output pins on our preamplifier and use short lengths of shielded cable to connect from the tagstrip to the input pins. On the mains side, first check and double check that the plug is removed from the wall socket! (Don’t laugh, it happens. . .). Now identify where the wiring comes in and how it connects to the motor. Almost invariably, there is some form of switch (often a microswitch) mechanically linked to the tone arm to turn the motor on and off. You need to cut in before that switch – you don’t want the preamp turning on and off with the motor. There are very few turntables with either a power switch or a fuse, yet we wanted to add both of these so the preamp wasn’t permanently left on. So we traced the mains wiring from the power lead and IN LEFT E E R NI E noise ratio. While we used our Audio Precision test gear to confirm the fact, you could actually hear the improvement. Even more improvement was achieved mounting the preamplifier in a metal box – we used a small folded aluminium type which itself was earthed to the 0V rail. We didn’t mount the power supply in a metal box (though theoretically this could be the ultimate!) for two reasons. First, we tried various methods of shielding the power supply and couldn’t measure any improvement but second, and most importantly, parts of the underside of the PC board are at mains potential and we would have had to take extra precautions in the mounting. As it was, we were able screw the power supply board directly to one of the plywood surfaces underneath the turntable, completely covering and insulating the “bitey” bits. Note that the mounting screws are all well away from PC board tracks, which also assists in this regard. Please, be careful when selecting the location for the power supply. If necessary, use some insulated pillars or stand-offs to mount the board. 15V T1 20VA TRANSFORMER SELF-TAPPING SCREW UNDER BOARD TO SECURE TRANSFORMER 120V 120V MAINS RATED TERM BLOCK E N E A Use this diagram in conjunction with the photographs to construct your RIAA Preamplifier. March 2002  73 IN R IN L E R 01103021 01303021 (C) 2002 L E 01303021 01103021 (C) 2002 7915 7815 A E unsoldered the active (brown or perhaps red wire) and took this directly to a single pole mains switch. From there, we connected another length of cable to a fuseholder and yet another length back to original “active” termination on the tagstrip. We used a neon-indicator mains switch which necessitated connecting a length of blue mains-rated cable from the neutral terminal on the tagstrip to the neon terminal on the switch. So far, all we’ve effectively done is include a mains switch and fuse into the existing turntable wiring. To connect the preamplifier, we soldered a length of three-core mains lead to the (now switched and fused) active terminal on the tagstrip, the neutral terminal and the earth terminal. This we ran around the inside perimeter of the plinth, secured with cable clamps, until we got to the power supply board. The outer insulation was removed to a length of about 30mm and the three wires were bared back about 5mm or so. Each was connected to its appropriate terminal on the PC board. You will note that we have used a four-terminal block for the three wires (Active, Neutral and Earth). This is just a bit of added safety: the Neutral and Earth wires (blue and green/yellow) sit side-by-side – these are nominally at the same potential anyway because they are linked back at your switchboard. The Active wire (brown) is separated from the others by an empty terminal. Connecting the split boards Because we (eventually!) decided to separate our two boards, we had to connect them together again. Provision is made for this on the boards. Solder another six PC stakes into the –15V, 0V and +15V positions on both boards and use a suitable length of cable, secured around the inside perimeter of the plinth, to connect them. Colours of the cables are not particularly important as long as the same colour connects the same points on each board! And there you have it. All of those black vinyl things (which many children today don’t even recognise!) which have been sitting in your cupboards can now be enjoyed once again. Oh, by the way – the outputs of the preamp simply plug in to one of your unused “aux” or similar inputs on your stereo amplifier. Sometimes they are labelled “line in”. And if at some time you want to use your turntable with an amplifier that does have “phono” inputs, don’t be tempted to use them with this preamp in circuit. Apart from probable massive overload, you’ll end up with double RIAA equalisation. Not a good sound at all. . . SC Enjoy! N Above is the full-size pattern for the PC board. At right, this is what your RIAA preamplifier should look like if separated from the power supply. At this stage, we hadn’t soldered in any PC stakes. 74  Silicon Chip www.siliconchip.com.au SILICON CHIP WebLINK How many times have you wanted to access a company’s website but cannot remember their site name? Here's an exciting new concept from SILICON CHIP: you can access any of these organisations instantly by going to the SILICON CHIP website (www.siliconchip.com.au), clicking on WebLINK and then on the website graphic of the company you’re looking for. It’s that simple. No longer do you have to wade through search engines or look through pages of indexes – just point’n’click and the site you want will open! Your company or business can be a part of SILICON CHIP’s WebLINK. 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For over 25 years, Wiltronics has supplied the needs of the Electronics Industry, and look forward to continuing this service. WebLINK: www.avcomm.com.au WebLINK: www.silvertone.com.au ALLTAC INTERNATIONAL P/L Tel : (02) 9411 3088 Fax : (02) 9412 1855 WebLINK: www.alltac.com.au WebLINK: www.wiltronics.com.au VGS2 Graphics Splitter NEW! HC-5 hi-res Vid eo Distribution Amplifier DVS5 Video & Audio Distribution Amplifier Five identical Video and Stereo outputs plus h/phone & monitor out. S-Video & Composite versions available. Professional quality. Wiltronics Pty Ltd Tel: (03) 9762 3588 Fax: (03) 9762 5499 For broadcast, audiovisual and film industries. Wide bandwidth, high output and unconditional stability with hum-cancelling circuitry, front-panel video gain and cable eq adjustments. 240V AC, 120V AC or 24V DC. High resolution 1in/2out VGA splitter. Comes with 1.5m HQ cable and 12V supply. Custom-length HQ VGA cables also available. Check our NEW website for latest prices and MONTHLY SPECIALS www.questronix.com.au Email: questav<at>questronix.com.au Video Processors, Colour Correctors, Stabilisers, TBC’s, Converters, etc. www.siliconchip.com.au www.siliconchip.com.au QUESTRONIX All mail: PO Box 348, Woy Woy NSW 2256 Ph (02) 4343 1970 Fax (02) 4341 2795 Visitors by appointment only March 2002  75 VINTAGE RADIO By RODNEY CHAMPNESS, VK3UG The AWA 719C Console; Pt.1 During the 1940s, AWA produced some very impressive sets and some of the best were the 7-band radio receivers. The first models were produced in the early 40s but arguably the best were produced after World War II. An overview of the various 7-band models was given in the May 2001 issue. In this article, we’ll take a close look at one of the magnificent console models, the 719C, and the work involved in re­storing it to its former glory. This particular set had had a rough life. It’s obviously had rodents as house guests at some stage and there had also been considerable cabinet damage due to moisture and exposure to the elements. With care and patience, it has now been fully restored as shown in the accompanying photographs. Now I have to admit that I didn’t do all the work – although I am quite happy when it comes to restoring the electronic circuitry, I am no expert at quality cabinet restoration. So, once I’d removed the chassis and loud­ speaker and dial, the cabinet was passed on to a friend, Laurie Tilley, whose woodworking ability far surpasses mine. Removing the parts Removing the chassis from the cabinet is a tricky job as the dial-scale/band indicator is attached to the cabinet itself and not to the chassis as in most sets. This little design quirk leads to other problems, as will be explained next month in Pt.2 of this article. It is first necessary to unclamp the dial pointer from the dial-cord and remove the band-change indicator cable. If this isn’t done, it’s possible to damage the dial-drive system. Next, the extension shafts that go through the right side of the cabi­net and attach to the band-change and tuning control shafts are removed. The dial-lamp cable and the speaker cable are then un­ plugged, after which the three knobs on the front panel are removed, followed by the four bolts securing the chassis. Because I wasn’t restoring the cabinet myself, I also re­ moved the loudspeaker and baffle-board from the lower section of the cabinet. The baffle-board is held in place with six wood screws, together with large felt washers and sleeves. These help prevent cabinet vibrations which could affect the stability of the local oscillator in the front end of the receiver. The dial-scale assembly was removed by undoing the four screws situated at the corners of the assembly. It was then carefully placed to one side, so that it would not get broken. The whole procedure sounds complicated but it isn’t – just time consuming. The big clean up The dial-scale cleaned up like new although there is some damage to some of the markings for the shortwave bands. 76  Silicon Chip The next task was to thoroughly clean the chassis. As men­tioned earlier, rodents had made their presence felt but fortu­nately, the damage was only cosmetic on the outside of the chas­sis and there was no damage to the components. Although the exterior is now clean, areas of rust and other corrosion are evident and do detract from the appearance. As can be appreciated, completely dismantling a set of this complexity to fully restore the chassis is not something to undertake lightly. Nor were the owners keen to spend the extra money needed to return the chassis www.siliconchip.com.au to pristine condition. The 50 years of felt-like dust that had accumulated at the front of the speaker was removed. It is amazing how much dust can accumulate in a spot that is largely “covered” and is due to the loose weave used in speaker cloth. At this stage, I lubricated all the moving surfaces with light sewing-machine oil. These parts included the control shafts, dial pulleys, switches and the dial pointer slide. Many of them had become difficult to operate due to gumming up and the ingress of dust. All now operate quite smoothly. Next, the dial-scale was carefully washed and the dial-pointer repainted white. Before washing the dial-scale though, I tried washing a small section of the print in an inconspicuous spot, to make sure it wouldn’t come off. In this case, the print remained in place – unlike some I’ve tested where the dial mark­ings are starting to fall off without even touching them. My advice is to be very careful when cleaning dial-scales on the side where the print is. If just dusting cleans a dial-scale sufficiently, don’t do any more as dial-scales are hard to replace. Unfortunately, the dial-scale on this set does have some damage on the shortwave bands, as is evident from the photograph. This damage was present before any work was done on the dial and is not due to cleaning. Apart from this, the dial-scale came up like new. The same goes for the valves, which were also removed and cleaned with soapy water. When cleaning octal valves like this, the trick is to keep the them upside down – that way, the glass envelope can be cleaned without water getting into the base. Make sure that the type numbers don’t get rubbed off during this process – clean the valves gently. Clean valves really do look nice when reinstalled in the chassis. First looks Before really starting a circuit restoration, I like to have a good look at the set to see what needs attention. It is best to determine early whether there are likely to be any faults that are expensive to correct, such as a burntout power transformer or any other obviously distressed components. In this set, some work had been done in the past to replace the original www.siliconchip.com.au The AWA 7-banders are extremely good performers and have an impressive cabinet. In this case, the cabinet came up looking like new. electroly­tic capacitors (the old ones had been left in-situ but discon­nected from the circuit). I find that a headset magnifier is quite an asset when checking into the works of a set as complex as a 7-band AWA receiver. They sell for around $30, while an illuminated magnifi­er is also available at over $100. I prefer the headset magnifier. as it is easy to move around the chassis, and use a lead light of some sort to illuminate the area of interest. Getting back to the set, most of the black “moulded mud” paper capacitors appeared to be in remarkably good condition. Conversely, some of the wiring looked a bit the worse for wear, having perished over the last 50 years, and this included the high-tension wiring and AC input wires to the power transformer. In fact, the transformer would definitely need attention before any power was applied to the set. Both the mains cord and plug had been replaced at some time but neither was in good order. What’s more, the PVC twin flex cord used was not in keeping with the vintage of the receiver. Overhauling the circuitry The first item to receive attention was the power trans­former. I began by using my 1000V insulation tester to check the integrity of the insulation between the mains input and earth and to the other windings. The secondary HT winding was also checked by removing its centre-tap from earth and then testing to earth. The resistance in each half of the winding was also checked using an ohmmeter and they were both the same. Having done those tests to prove that the transformer itself was in good order, it was time to replace the perished wiring. First, the terminal location of each wire emerging from the front (or chassis) side of the transformer was noted on a piece of paper, along with the colour of each wire. This done, I removed the two mounting bolts from the front of the transformer and the two bolts which March 2002  77 78  Silicon Chip www.siliconchip.com.au Fig.2: the set employs a 6-valve superheterodyne circuit with a multi-pole rotary switch for the band switching. Alignment is a complicated procedure but is necessary for top performance. There’s plenty of room in the back of the cabinet for the chassis. The loudspeaker fits in the cabinet immediately beneath the chassis shelf and is just visible at the bottom of the picture. clamp the transformer together, without removing the transformer from the chassis. The front covering plate was then removed so that the high-voltage wiring was exposed. Each wire was then individually removed from its termination and replaced so that no wiring errors could occur. The transformer was then reassembled. The next step was to replace the leaky paper capacitors. As mentioned earlier, most of the black “moulded mud” paper capaci­ tors were quite OK when tested with the high-voltage tester. However, some had previously been replaced with Ducon capacitors which had now gone leaky and these were all changed. The resistors were all within tolerance and none required replacement. Mains cord As mentioned earlier, the mains cord fitted was not in keeping with sets of this vintage. As a result, I decided to fit a new 3-core brown fabric-covered mains lead, which would be similar to the style of lead originally fitted. The mains plug was in poor condition and so this too was replaced. I used a modern plastic plug and although it doesn’t have a vintage ap­pearance, it is safe. The chassis-entry grommet for the mains lead had perished, so this too was replaced. In addition, the lead was securely clamped to the chassis – it’s no longer permissible to tie a knot in the power lead after it enters the chassis, as was common some 50 years ago. As a further safety measure, the earth lead of the power cord was soldered to a lug which was securely bolted to the chassis. As originally manufactured, this set didn’t have an www.siliconchip.com.au earth wire in the mains lead and the chassis wasn’t earthed. The dial cord was also the worse for wear, so a new cord was fitted. Fig.1 shows how this is done. The original 1mm-diameter (approx.) dial cord required two turns around the dial driveshaft to ensure an effective grip. However, I generally use 0.7mm cord so I put three turns on the dial driveshaft just to make sure. This works well and the dial mechanism is much freer than on many sets I’ve come across. It even has a flywheel on the drive shaft so that the set can be rapidly tuned from one end of the dial to the other. A number of the insulated wires within the set had per­ished, so these were replaced one at a time. Finally, a check was made with an ohmmeter to verify that there were no short cir­ cuits, particularly on the HT line. This all checked out, so it was time to start the testing procedure. This was done several times to “form” the electrolytic capacitors and they remained cool during this procedure. The time taken to discharge increased with each on/off cycle, indicating that the capacitors had “form­ ed”. Being relatively modern capaci­tors, they appeared to be quite OK right from the word go. By the way, it’s always a good idea to go through this routine as the electrolytic capacitors may be badly in need of “forming”. If the HT is simply applied and left on, the capaci­ tors may overheat and explode. They may also cause the rectifier to be severely overloaded. However, short term overloads rarely cause a problem and the capacitors will usually quickly “reform”. At this stage, all the valves were replaced in their sock­ets and the set again turned on. A quick check with the multimet­er revealed that all voltages were nominally correct. However, after some time, the HT decreased due to the fact that the 5Y3GT rectifier had come to the end of its useful life. A replacement valve soon fixed that problem. Next, an aerial and earth were con- Looking for an old valve? or a new valve? Firing the set up Power was initially applied to the set with all the valves removed. The AC voltages out of the secondary of the transformer were then checked and found to be a little high. This was to be expected because, with the rectifier valve removed, there is no load on the transformer. I let the set run like this for about 30 minutes and the transformer stayed cool, indicating that it was in good order. The set was then turned off, the rectifier and speaker plugged in, and the mains switched on again. The HT rose to nearly 500V, which is normal with no load in these receivers. The set was then switched off after a few seconds and the electrolyt­ics allowed to discharge. BUYING - SELLING - TRADING Australasia's biggest selection Also valve audio & guitar amp. books SSAE DL size for CATALOGUE ELECTRONIC VALVE & TUBE COMPANY PO Box 487 Drysdale, Victoria 3222. Tel: (03) 5257 2297; Fax: (03) 5257 1773 Mob: 0417 143 167; email: evatco<at>mira.net Premises at: 76 Bluff Road, St Leonards, Vic 3223 March 2002  79 Photo Gallery: Tasma Model 22 and it really is well worthwhile going through the alignment procedure, to get the best out of them. I’ll walk you through the alignment steps in detail next month. Assembling the receiver The Tasma Model 22, manufactured by Thom & Smith, Sydney, in 1931 is a 3-valve TRF receiver. It used the following valves: 224 detector, 247 output and 280 rectifier. (Photo and information courtesy of Historical Radio Society of Australia). nected to the receiver, as it was time to tune around and see whether the set was in working order. I switched to the broadcast band and found a number of stations. 3GG on 531 kHz is a good test where I live, being a 5kW station with a directional antenna some 200km away. If the signal is loud and clear from this station, I know that the set being tested is in good order. Crook grommets There was one problem – the tuning gang mounting grommets had perished and so the gang wobbled around. Unfortunately, unless the coil sub-assembly is dismantled (a major job), it isn’t possible to directly replace the grommets. To get around this problem, I began by cleaning all the hardened rubber out from around the two mounts near the dial drum. I then slit a gang-mounting 80  Silicon Chip grommet through its slot, so that I ended up with two rubber washers. These were then cut so that they could be opened out and slipped around the metal gang mounting posts near the dial drum A small screwdriver to was used push each half-grommet under each flat near the metal mounting posts. They were then secured in place by applying some glue to their outside edges and the chassis. Each half-grommet now provides some support for the gang and there is some give on the mount. Alignment Alignment is quite a task with the AWA “seven-banders” and the 719C is no exception. In fact, I gather that most owners of these sets tend to shy away from aligning them and I can’t say I blame them. That said, they are excellent sets While I’d been solving the circuit problems, Laurie Tilley had been restoring the cabinet as near as practical to its origi­nal condition. It looks good, as the photograph shows, and the owners are happy with the their family heirloom. Once the cabinet had been returned, the speaker and baffle were replaced and the six 50mm mounting screws (along with the felt washers and sleeves) were installed to hold the baffle in place. It really is quite an elaborate system to ensure that baffle vibrations are not transferred to the oscillator tuning components and thus cause instability. The dial-scale and then the chassis were also refitted to the cabinet. The dial-scale has four small screws and the chassis has four larger metal thread bolts holding it to the cabinet shelf. The dial-scale clamp was then re­ attached to the dial cord and the bandchange bowden cable was reattached to the band-change drum. The position of the bowden cable within its clamp allows for some adjustment of the band indicator behind the dial glass. Finally, the extension shafts for the band-change and tuning controls were installed, the knobs fitted and the loudspeaker reconnected. I timed myself doing this job and it takes almost 30 minutes. This included adjusting the dial pointer position and the band-change indicator. As a matter of interest, I later tested myself on a much simpler Precedent mantel set and it took me just 60 seconds to do what had taken half an hour on the AWA set! Disaster strikes Once the assembly had been completed, the set was given a final performance check to make sure everything was OK. The clamp on the dial-cord was then adjusted so that the stations appeared in their correct positions on the dial. By this stage, the set was going nicely and I was admiring the cabinet and its performance when it suddenly stopped working. So what had gone wrong? www.siliconchip.com.au The grid of the first audio stage (6G8G) comes out to a top cap and so, using a time-honoured technique, I touched it with my finger – all I heard was a thin squeak rather than the expected healthy “blurt”. I tried another 6V6GT audio output valve but it made no difference. And that meant that the set had to be disman­tled again, so that I could find out where the fault was. Once I had it dismantled, I tested around the audio section and found no problems. Then a small sliver of wire fell out of the wiring – a leftover from a snipped component lead. Perhaps it was this that was causing the problem but, despite shorting various sections, I couldn’t reproduce the symptoms originally observed. In the end, I concluded that this had to be the answer so the set was reassembled. It worked well for a while – then stopped again. I advanced the volume control and the set suddenly burst into life. This is usually a sign of a bad connection somewhere, either a dry joint or a corroded or poor joint inside a component. At least I was starting to narrow down the source of the problem. It was time to get serious about finding the problem. Often, with intermittent faults, the best approach is to connect the appropriate test equipment and then just wait for the fault to show. In this case, I connected my DMM (set to the 400V range) to the plate of the 6G8G, to measure the plate volts under normal and fault conditions. I also connected an audio signal tracer to the grid of the 6V6GT to see if audio was getting this far with­ out trouble. Note: for safety reasons, it is necessary to switch the set off when changing the test instrument test points. Next, I adjusted the volume controls (at low level) on both the set and the signal tracer for the same volume. After a while the set went quiet but the test instruments showed no change. I then connected the DMM to the plate of the 6V6GT and connected the signal tracer to the same spot. When the fault reappeared, the plate circuit of the 6V6GT was still operating correctly, with both the voltage and the audio the same as before the fault. I then moved the speaker and the fault came and went (this had had no effect previously). Careful inspection using the head­set magnifier revealed a www.siliconchip.com.au Photo Gallery: Airzone Model 300 Manufactured by Airzone, Sydney, in 1934, the Model 300 is a typical Australian “cathedral” style set. It is a 4-valve superheterodyne set with the following valve types: 57 autodyne mixer, 50 amplifier, 59 anode bend detector/output and 80 rectifier. (Photo and information courtesy of Historical Radio Society of Australia). dry joint on the hum bucking coil on the speaker. The joint was resoldered and the radio now operates reliably for the first time in 50 or so years. Summary As mentioned, aligning this receiver can be quite a chore. The “7-banders” are all slightly different in their align­ ment details and dial glasses, which means that the precise details for a particular model are needed if accurate alignment is to be achieved. Unfortunately, very little alignment data is available, except in Volume 6 of the AORSM manuals. However, I have been thor­oughly frustrated by the published alignment instructions and the errors that have crept in. In the end, I developed a method that is relatively easy and is as accurate as possible for all models. The AWA 7-banders are expensive receivers to service, espe­cially if you want to achieve the best performance possible. The performance is (as expected) extremely good and the cabinet is impressive and really looks the part in the lounge room. The tuning range covers 530kHz to 22.3MHz in seven bands. It has band­ spread on the higher frequency bands and has a tuning mechanism that is very free, which makes tuning a dream compared to a normal dual-wave set covering nearly the same tuning range. In summary, the AWA 719C console is a highly sought-after radio, with impressive performance, ease of tuning and a high price tag. If you have the room to display one of these radios, SC go for it. March 2002  81 Higher Intelligence: Solar Power Battery Charger By Ross Tester Elsewhere in this issue there is a feature which doesn’t portray grid-connected solar power in a particularly good light. To show that we’re not against solar power per se, here’s an intelligent battery charger specifically intended for storage-type solar power systems. 82  Silicon Chip www.siliconchip.com.au T here are many people across Australia, nay, around the world, who rely on “free” power from the sun, courtesy of the solar cells mounted on their roofs. For many of those, solar power is their only source of power: typically, these are people who live too far away from the electricity grid to make connection economic. For them, the somewhat questionable economic returns of solar power don’t come into the equation: if you want power, you have to make it yourself. As we mentioned in that feature, the basic choices are hydro, wind, bio-mass or solar. And while there are plenty of micro-hydro systems, wind generators and even some small-scale bio-mass systems, by far the largest percentage of people opt for solar power. However, there are many others, city and country who, for many reasons –environmental, experimental, (or perhaps just plain mental!) have decided that they too would like some of this “free” power. The main difference between solar power in the suburbs or towns and remote solar power is the way the power is used when it is generated. Where increasing numbers of city dwellers with solar power these days probably have “grid-linked” systems, invariably, remote solar power generators must use some pretty muscly batteries to store the power when the sun is out, ready for use when it is (a) needed, or (b) dark/cloudy/rainy/etc. Typically, banks of storage batteries are used. In the past, a lot of people have used (expensive!) traction-type batteries (eg, fork-lift, etc) because these are designed to be deep cycled. Such treatment destines your typical car or truck battery to a very short life. In recent years, batteries have come onto the market which are specifically intended for power storage (eg, solar power) applications. Most systems use series and parallel connected batteries to give both high current and high voltage (well, higher than six or twelve volts!) systems. The reason for this is mainly in the higher efficiency of DC/AC inversion from a higher voltage and lower I2R losses in the system. 24V is common, as is 48V. Above this, though, you Q2 MTP2955 (SEE TEXT) could start to get into difficulties with running from 12V solar cells. That’s not to say a 12V battery system is not perfectly practical; in fact, you can use a commercially-available 12V/240V (or more usually 230V) inverter and save a lot of hassles. Some of these are very efficient, these days. And we aren’t saying that anyone in the middle of suburbia shouldn’t put in a solar power system, if that is your want. Whether you want to save the planet or not (or perhaps you’ve come across some cheap solar panels!) you have every right to put in your own system. Where the situation does become a bit muddied is when you want to connect your solar system to your home wiring, using existing power outlets and so on. The power authorities have some pretty strict rules about how this is done, especially in the way your system is isolated from theirs. We suggest if you do want to put in a solar power system, keep it completely separate from the domestic mains supply. Besides, unless you’re a licenced electrician, you’re not allowed to do D1 A K 0.33 E Q1 BC557 2.2M B C 22k MBR1645 D2 D A 1k 100F 35VW 100 1W S G ZD1 15V D3 1N4004 S D MBR1645 G Q3 MTP2955 100F 35VW 6.8k LINK FOR 12V ONLY 120k 22k 1 7 120k CHARGING 0.033F LED2 22k IC1b 5 13 6 IC1d 4 12 1 7 1k 11 14 FAN CHARGED 9 IC1c 3 S0 +5V IN IC2 L4949 S 2 VR1 2k GND 5 100F 16VW 12k C D5 1N4148 Q4 2N5551 B 120k OUTPUT TO BATTERIES (CON2) 2.2M 1k 10 8 IC1a 8  LED1  22k D4 1N4004 100F 35VW INPUT FROM SOLAR PANELS (CON1) 120k K 0.033F + 1k E 2 – MBR1645 SC  2002 INTELLIGENT SOLAR CHARGER K A MTP2955 D S G D The intelligent charger is built around a specialised IC, an L4949 made by On Semiconductor. It can suit 12V and 24V systems. www.siliconchip.com.au March 2002  83 anything with your home wiring. But that’s another story in itself! Charging the batteries Having invested sometimes thousands of dollars in batteries, it is important to “treat them right” to maximise not only their life but also the power you can store in them and get from them. “Treating them right” means not only the way they are stored (eg, batteries don’t normally like being placed directly on concrete floors), maintained (eg, distilled water level where appropriate) but also in the way they are charged and discharged. It has been fairly common practice to simply connect the solar cells in series with the battery, usually via a series diode to prevent the battery discharging through the cells when they’re not producing power. As the solar cells are essentially a constant current device, this is not a real problem when the batteries are either fully or partially discharged. However, it is not good for the batteries when they are charged. The solar cells don’t know this and they keep on pumping out power while ever the sun shines. Result: overcharged batteries. This will certainly lower the battery life – and that’s why you need a regulator. It senses the state of charge: while the batteries are less than fully charged, it allows the solar cells to pump in as much power as good ol’ Sol will allow. But when they are nearly charged, it starts throttling back the electrons so the battery won’t overcharge. Circuit operation This circuit is designed for either 12V and 24V systems with the chang- Larger-than-life view shows the input and output connectors at the front of the PC board along with the (optional) fan. This fan should not be needed for solar panel systems (a small heatsink will suffice). ing of just one link. At the heart of the circuit is IC2, an L4949 monolithic integrated 5.0V voltage regulator with a very low dropout voltage and additional functions such as power-on reset and input voltage sense. In this circuit we use the 5V regulator because of its extremely low quiescent current. When there is no power source (ie, solar cells) connected, the total current drawn from the battery is around 300uA. We also employ the voltage sensing comparator section of this IC as the main switching device with hysteresis. The power-on reset circuit is not used. Incidentally, a specification sheet for this IC can be found at the manufacturer’s (ON SEMICONDUCTOR) web site: www.onsemi.com/pub/prod 0,1824, p ro d u c t s m _ P ro d u c t S u m m a r y _ BasePart Number%253DL4949,00.html Instead of typing all that, it is probably easier to search for L4949 at google. com as it will be the first item to come up, in less than a second! For the following explanation, assume that there is a supply voltage present at the source (Solar Panel etc), therefore the voltage at pins 9 and 13 of IC1 would be at logic 1. Pin 2 is the input pin for the battery sensor section of the IC. When the voltage at this pin falls to 1.24V the open collector output pin 8 is pulled internally to ground. This pin would normally be connected in series with a resistor and a Battery Low indicator LED to a positive supply. In this circuit pin 8 pulls the input of IC1b to logic 0 level via a 120kΩ resistor so the output from this inverting gate would be at logic 1. Since both the inputs of IC1d are now logic 1 the output would be at logic 0 and LED2 K&W HEATSINK EXTRUSION. SEE OUR WEBSITE FOR THE COMPLETE OFF THE SHELF RANGE. 84  Silicon Chip www.siliconchip.com.au D1 MBR1645 B 15V 22k 22k .033F 100 1W + FAN � C Q1 BC557 K A CON1 INPUT D2 MBR1645 K CON2 OUTPUT 1k 6.8k 22k 120k 120k 100F + � 1 LINK 2 A 100F LINK 1: IN FOR SOLAR PANELS OUT FOR POWER SUPPLIES 1k 120k IC1 4093 D5 120k 4148 G + 1k ZD1 D + E S K 100F + G K 1 LED1 GREEN IC2 L4949 D D3 D4 S A 4148 4148 2.2M LINK 1 0.33 5W Q3 MTP2955 2.2M Q2 MTP2955 2N5551 Q2 & Q3 MOUNTED METAL SIDE UP B E C D1 & D2 MOUNTED METAL SIDE UP Q4 22k A 1k LED2 RED GREY OUTLINE IS AREA OF HEATSINK/FAN (IF USED) .033F 12k VR1 2k 100F + (Red) would light to indicate that the battery was charging. Because of the inverting action of IC1a, the level at the output of IC1c would remain at logic 1 and LED1 would not light. Q4 is turned on via the 120kΩ resistor and the gates of P-channel Mosfets Q2 and Q3 are pulled low via the 22kΩ resistor. Q2 and Q3 conduct, allowing the battery to charge. A small amount of current is fed by the forward biased diode (D5) and the 2.2MΩ resistor to the voltage divider network, thus effectively slightly increasing the voltage at the sensing pin, (pin 2). The addition of this resistor effectively reduces the hysteresis voltage of this part of the circuit. When the voltage at pin 2 rises to 1.34V, the internal transistor at the output is turned off and the voltage at the input of IC1b is pulled high (to +5V), again via the 120kΩ resistor. LED2 is turned off and LED1 (Green) is turned on, indicating that the battery is fully charged. Transistor Q4 and the Mosfets are turned off so the charging ceases. For a 12V battery (LINK2 in) and with the values selected in the resistor divider network and a centred potentiometer, the voltage of the battery being charged will need to reach approximately 14.2V before the charging is stopped. Charging will will resume when the battery voltage drops to 13.7V. For a 24V battery (LINK2 out), the voltage of the battery being charged will need to reach approximately 28.4V before the charging is stopped. Charging will resume when the battery voltage drops to 27.4V. + � LINK 2: IN FOR 12V BATTERIES OUT FOR 24V BATTERIES Same-size views of the component overlay and matching straight-on photograph. The 3.3W resistor in the pic below is actually in the “Link 1” position – but it doesn’t matter ’cos they’re in parallel. Charging from a supply While the circuit is designed for use with solar panels, it can (with a minor modification) be used with other sources of power. Solar panels have a limited current output so it does not matter if they are connected directly across the battery: the current will be similar in value when the battery is “full” or “flat”. When this charger is used as a regulator for solar panels, the 0.33Ω, 5W resistor should be shorted with a link for most efficient operation. In this case the only loss is due to the “on” resistance of the Mosfets and the low forward drop of the Shottky diode/s. www.siliconchip.com.au However if the charger is used in conjunction with power sources that do not have current limiting (for example a bench power supply or an automotive battery charger) the circuit can be made to current limit by removing the link across the 0.33Ω resistor. When the voltage across the current limiting resistor exceeds 0.6V transistor Q1 is turned on, thus reducing the gate voltage applied to the Mosfets. This serves as a simple constant current source, the value of which equals 0.6/0.33A. To increase the current, reduce the value of the resistor. To minimise battery drain when the solar panel is not supplying power, the voltage at pins 9 and 13 of IC1 are logic low and both the LED’s are at turned off no matter what the state of the battery is. Two series diodes, D3 and D4, were added to reduce the supply voltage to IC2 by approximately 1.2V. This is necessary for a 24V battery as although the IC has a transient supply voltage of 40V, its maximum continuous supply voltage is 28V. In each kit are one 10A Shottky diode and two power Mosfets. The total dissipation in the two Mosfets would be approx. 0.15W at 1A, rising to 2.4W at 4A. Doubling the number of March 2002  85 Parts List – Intelligent Solar Charger 1 PC board, 98 x 70mm, code K009B (Oatley Electronics) 1 U-shaped heatsink (or fan/ heatsink – see text) Semiconductors 1 4093 quad NAND Schmitt gate package (IC1) 1 L4949 voltage regulator (IC2) 1 BC557 PNP transistor (Q1) 1 MTP2955 P-channel mosfets (Q2) (Can use two – see text) 1 2N5551 NPN transistor (Q4) 1 MBR1645 Schottky diodes (D1) (Can use two – see text) 3 1N4148 small signal diodes (D3-D5) 1 15V 0.5V zener diode 1 Green LED (LED1) 1 Red LED (LED2) Capacitors 3 100µF 35VW electrolytic 1 100µF 16VW electrolytic 2 .033µF MKT polyester (code 33n or 333) Resistors (0.25W, 1%) 2 2.2MΩ 4 120kΩ 4 22kΩ 1 6.8kΩ 1 12kΩ 4 1kΩ 1 100Ω 1W (for optional fan) 1 0.33Ω 5W (only required if power supply is used instead of solar panel) Optional: 1 12V fan/heatsink mosfets would reduce this total power dissipation by 1/2. Increasing the number of Mosfets results in better efficiency but is hardly needed. Other types of Mosfet with a lower “on” resistance could be used (an MTP2955 has an on resistance of 0.3Ω). As an example a 60W solar panel is rated to deliver approxiamtely 4.3A into a floating lead acid battery (14V). With this panel the mosfets would dissipate a total of about 2.8W. A small heatsink would be necessary but a fan is not. The fan shown in our photographs is an option, for use when the link is removed and the circuit is used as a constant current source. Here the total dissipation in the Mosfets becomes the supply voltage minus the battery voltage times the current. A 1Ω/1W 86  Silicon Chip resistor is supplied in the kit. With this the current is limited to 0.6A, so the dissipation in the two mosfets would be a total of 1.5W for a 2.5V voltage difference (this figure applies when the optional Kenwood plugpack is used). Construction With the exception of the (optional) fan, all components mount on a single PC board, coded K009B. As usual, inspect the board before assembly for any defects – shorts between tracks or broken tracks – and if necessary, repair them. Most of the construction is pretty much standard: start with the lowest profile components first (resistors, small capacitors) and move from their to the larger capacitors (watch the polarity on the electrolytics) and then the semiconductors. Naturally, all semiconductors are polarised so ensure they go in the right way. Leave the two Mosfets and one or two Schottky diodes for a moment. Whether you use sockets or not for the ICs is up to you but if you do, be careful to align the sockets the same way as shown on the PC board overlay, and be even more careful to get all the pins in straight when inserting the ICs. Now’s the time to decide what format you’re going to build the regulator in – ie, for a 12V or 24V system, and whether it is for solar panels or for use with a power supply. For 12V, a small link shorts out the 120kΩ and 22kΩ resistors near the lower right corner of the board (leave the link out for a 24V system). Of course these two resistors are redundant and could be left out but for the sake of ten cents, they might as well be included. The second choice (solar cells or power supply) determines whether the 0.33Ω resistor is in circuit or not. For solar cells, it can be shorted out via a link (left side of PC board) but if you are going to use it on any device without current limiting (or want to make it dual purpose), keep the resistor in circuit (ie, don’t solder the link in). The Mosfet(s) and diode(s) are the last components to solder in. They may look quite similar so don’t mix them up! The one or two Mosfets (depending on your requirements) mount at the top of the board with their metal side(s) up – that is, opposite to the way you would normally solder them into a circuit. This is to allow contact with the heatsink. The one (or two) Schottky diode(s) mount at the bottom of the board (closest to the connectors) and solder in the “normal” way – metal side down. Finally, solder in the two PC board mounting screw connectors, CON1 and CON2 and the board is finished. Setting up To set the charge, you will need to have the 12V or 24V battery connected and the solar panel(s) or power supply connected. You can set it with a power supply and use the same setting for a solar panel but make sure the 0.33Ω resistor is in circuit if you do! Turn VR1 fully clockwise. Monitor the battery voltage (with a multimeter) and when the battery reaches its correct charge voltage (14.2V or 28.4V for 12V and 24V systems respectively), slowly turn VR1 anti-clockwise until the green LED lights. Optional fan If you decide you want to fit the fan (as shown in the prototype) this simply clips over the PC board along with its integral heatsink. However, as we mentioned, for use with solar panels this fan should not be necessary – a small heatsink will suffice. The 100Ω resistor on the PC board allows the nominally 12V fan to run from the higher voltage produced from the solar panels (up to 18-20V). Wheredyageddit? This design is copyright Oatley Electronics (PO Box 89, Oatley, NSW 2223). Phone 02 9584 3563; Fax 02 9584 3561. website: www.oatleyelectronics.com; email sales<at>oatlelectronics.com SC Kit/Component Prices BASIC KIT: PCB and all components but with one Shottky diode: $21.00 Optional clip-on fan/heatsink: $4.50 Extra Mosfets: $3.00 Extra Shottky diodes: $3.00 16.5V/650mA Kenwood plugpack with non-standard mains connector: $4.00 Postage for any qty/mixture: $7.00 www.siliconchip.com.au ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097; or send an email to silchip<at>siliconchip.com.au Battery charger killed a transistor D2 may be OK but it would be wise to check that it is not also a short circuit. I would be grateful for your assistance with the Multipur­pose Fast Battery Charger Mk2 which was featured in the June & July 2001 issues. I have built this project from a Jaycar kit and on switch-on I unfortunately had a short-circuit caused by a tiny piece of metal swarf trapped behind Q2. I have rectified this and all the tests mentioned in the article measure OK. However the voltage across the output terminals remains at full (about 18V), irrespective of the position of switch S5. I have replaced IC1 but this has not improved matters. (D. M., via email). • Almost certainly transistor Q1 has gone short circuit be­cause it would have driven the short-circuited Q2. Questions on harmonic distortion Video sharpening optimisation I’ve recently bought the Doctor Video kit featured in the April 2001 issue of SILICON CHIP and I have tried it out a bit. Although the picture was pretty good, it was not quite as good as I would have liked it to be. In the kit instructions, it says that by varying the 330Ω resistor up or down you can change the amount Can you answer these questions for me with relation to manufacturers’ THD figures for audio power amplifiers? If the test is run at, say, 1kHz <at> 0dBm into 8-ohm loads and the figure they quote is .01%, is this just prior to the onset of clipping? At what harmonic frequency do they measure the distortion – 1st, 2nd or 3rd? Is the test performed the same way or does it vary, depending on what figure they are after (ie, looks best)? (G. G., via email). • Generally, the distortion quoted should be associated with the rated power or maximum power (ie, just of high frequency video boosting given by the sharpen switch. What would be the absolute maximum I should vary it or what is the next best resistor value to use? I also have the same ques­tions about the 82pF capacitor. (P. B., via email). • The limit to video sharpening comes about when you observe more noise and graininess in the picture. So vary the resistor and capacitor with this fact in mind. before onset of clip­ping). Harmonic distortion or THD (total harmonic distortion) refers to all the harmonics and noise contained in the signal. Programmable ignition for a Falcon I realize this may be a bit of a longshot but I was won­dering if there is any known information on fitting the “Program­ mable Electronic Ignition System For Cars” (from March 1996) to an 1998 EL Falcon. Perhaps you may be able to refer me to some information source on how this may be wired to the existing ECU in the car. (J. P., via email). • We strongly recommend against trying to use the Programmable Ignition in any late-model car with an existing engine management system. The OEM system monitors quite an array of sensors in order to control the fuel injection, ignition timing and the automatic transmission whereas the programmable ignition only monitors manifold vacuum. Brighter indicators for rev limiter I have just purchased the Rev Limit­ er project described in April 1999 from Jaycar electronics. I want to know if it is possible to replace the indicator lamps with relays to operate a much bigger indicator light, say a 21W bulb, PARALLAX BS2-IC BASIC STAMP $112.00 INC GST WE STOCK THE COMPLETE DEVELOPMENT SYSTEM www.siliconchip.com.au March 2002  87 Upgrading the 100W DC-DC converter I am currently considering building a couple of your 100W DC-DC converters for car amplifiers, as described in your December 1990 issue. I have a few questions regarding design and component availability. My first question is where do you get the Siemens EC-41N27 ferrite transformer core, bobbin and case? Secondly, I would like to know if there is any immediate problem with pulling 50 more watts out of the converter. If I use slightly thicker winding wire in the transformer and inductors (in proportion with the original sizes, of course) and upgrade the diodes, Mosfets and capacitors in the high current areas, I cannot not see a problem. Your as I run a race-car and want an indicator that I will notice. (T. M., via email). • You can replace each lamp with a 12V relay and a diode, with anode to the transistor collector and cathode to 0V; ie, each diode is reverse biased. Stereo FM Minimitter blows the zener diode I have purchased a Minimitter kit from Jaycar. I have assembled it and I am having a little problem that you may have a solution for. I have tuned the transmitter to 100MHz, without a sound source. As soon as I connect a sound source, the 3.3V zener diode goes up in smoke! I would like to use this transmitter on my computer to transmit MP3 signals to another radio in the house. The circuit is powered with 6VDC comments would be appreciated. Finally, I would like to use one Mosfet per side of the push-pull network. Can I substitute one BUK45660A Mosfet for the two MTP3055s, or will this Mosfet not handle the switching speeds required? (T. B., via email). • The EC41 is difficult to obtain now but the ETD44 should do the job. It will not quite fit into the PC holes but can be made to fit. Also it has a larger area than the EC41 to allow a 55% increase in power. This part is available from Farnell Electronic Components. Phone 1300 361 005 and ask for the cores 305-6405 (two required), the bobbin 305-6326 (one required) and clips 105-775 (two required). You can use higher-rated Mosfets instead of two MTP3055 types. BUK456s should be fine. from the external socket. I am getting the power from the PC using a Low Voltage Adapter Kit (Dick Smith Kit K-3594), as published by EA in August 1997. It basically has 12VDC input shared by a fan, put through the regu­lator to provide the 6VDC output. I can’t find anything wrong there. It provides a very accurate 6.03VDC. The sound source is from the sound card through a 3.5mm headphone jack to an RCA connector. I have checked and re-checked all components and their orientation. As I mentioned above, the circuit seems to work fine without a sound source. Perhaps the output voltage from the sound card is excessive? However, I have powered the transmitter on batter­ies with sound and didn’t have a problem! (A. P., via email). • Not knowing the circuit for the DC power supply you are using, it is hard for us to solve the problem specifically. However, you can be fairly certain that the grounding of the power supply (-Ve terminal) is not at 0V as would be the signal ground for the sound source. You could try disconnecting the ground connection of the signal inputs leads and coupling with a large capacitor (electrolytic 10µF or larger, but ensure correct polarity by measuring with a multimeter). This should prevent the drastic DC current flow between the supply ground and the signal ground. Using the speed control for light dimming I am interested in purchasing the DC motor controller kit (K-3070) from Dick Smith Electronics to use as a DC light dimmer. Is it possible to modify this kit to handle higher currents, say 12A. Possibly using a higher current Mosfet and/or heatsink and wiring? (S. B., via email). • It is not really practical to modify the January 1994 design to get much higher current. Instead, we would recommend the 12/24V 20A speed control published in the June 1997 issue. This is available in kit form from Jaycar. We can supply the June 1997 issue for $7.70 including postage. Universal power adaptor wanted I do a lot of work internationally and have a multitude of chargers/power supplies to power laptops, printers, cameras, phone, etc. Everywhere I go I have a different adaptor/lead for each unit which is annoying and takes up valuable baggage space. Is there a universal power adaptor which I could buy to solve the prob- WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Trade Practices Act 1974 or as subsequently amended and to any governmental regulations which are applicable. 88  Silicon Chip www.siliconchip.com.au Modified PIC tachometer I am trying to modify the PIC tachometer described in the April 2000 issue. I want to replace the LED bargraph with high brightness LEDs on flying leads. It worked fine with the original bargraph on flying leads, with a common earth for LEDs 1-7, another common earth from LEDs 8-10, common signal for LEDs 8-10 and individual feeds for LEDs 1-7. When the high brightness LEDs were hooked up the thing overheated. I am unsure of the reason for the overheating but suspect that the seven 150Ω resistors need to be substituted with another value. lem? I bought some useful units from Dick Smith Electronics but these provide only standard voltages. Some manu­facturers (eg, Canon, Sony) use special voltages; eg, 5.7V and 13V. Would I cause damage if I used a 6V instead of 5.7V and 12/15V instead of 15V? (B. G., via email). • The most practical approach is to buy a switchable regulated plugpack such as the Cat MP-3030 from Jaycar or one of the switchable switchmode regulated plugpacks Cat MP3420 or MP3031, also from Jaycar. They should also be close enough to provide the 5.7V or 13V you refer to. Problem with the 6-LED torch I’ve just built the DSE kit of the 6-LED torch project from the May 2001 issue. It doesn’t work. Actually, it’s the second one I’ve built – the first one works fine so I’ve been able to com­pare the two. I’d just like your opinion. I’m pretty sure the MAX1676 is dead but before I order one from DSE I thought I might check with you first. I’ve checked my soldering, checked for shorts around the 1676 and for continuity from the 1676 to the rest of the circuit, but haven’t resorted to pulling out and replacing resistors and capacitors yet. I’ve also done some static resistance checks versus the good circuit and they seem to be OK. I have measured the voltages on the 1676 pins (to nearest www.siliconchip.com.au I know the PIC is blown because the first two digits don’t function. They do function when the display board is plugged into a functioning processor board but only one high brightness LED lights up. The others may have suffered in the overload. Any help would be appreciated. (S. N., via email). • You should be able to drive LEDs off the PC board without problems. We think you have damaged transistor Q3 so that its emitter and collector are shorted. Alternatively, the commoned anodes of LEDs 9-10 may be shorted to the commoned anodes of LEDs 1-7 on your wiring modifi­cation. Note that these anodes need to be separated. .05V). What caught my attention was pin 5 (Vref) which measures 0.25V. Would this indicate a faulty chip? Overall, the faulty circuit is drawing <1mA, so there are no obvious short circuits. (A. F., via email). • It does appear that the Max chip is not doing its job. You could remove the chip (including carrier PC board) from the good torch and place this in the bad torch to check whether the cir­cuit then works. Before doing this, check the orientation of the IC. We have heard of some constructors not getting the torch to work because the IC is in the wrong way. Luckily, the chip is not damaged if this happens. Request for circuit symbol information If possible, please advise the meaning of the down arrow from the 12V node near C2 to the +12V indicator, as shown in the 12V soldering iron controller circuit on page 78 of the November 2001 issue. My best guess is that this a general indicator mean­ing that this node should be at the specified value; ie, +12V with respect to the common ground. (D. W., via email). • The down arrow means that it connects to other parts of the circuit which also require +12V; ie, pin 8 of IC2. This can be thought of as a drafting “shorthand” which avoids the need to show all supply lines joined together on the circuit. SC SMART FASTCHARGERS® 2 NEW MODELS WITH OPTIONS TO SUIT YOUR NEEDS & BUDGET Now with 240V AC + 12V DC operation PLUS fully automatic voltage detection Use these REFLEX® chargers for all your Nicads and NIMH batteries: Power tools  Torches  Radio equip.  Mobile phones  Video cameras  Field test instruments  RC models incl. indoor flight  Laptops  Photographic equip.  Toys  Others  Rugged, compact and very portable. Designed for maximum battery capacity and longest battery life. AVOIDS THE WELL KNOWN MEMORY EFFECT. SAVES MONEY & TIME: Restore most Nicads with memory effect to capacity. Recover batteries with very low remaining voltage. CHARGES VERY FAST plus ELIMINATES THE NEED TO DISCHARGE: charge standard batteries in minimum 3 min., max. 1 to 4 hrs, depending on mA/h rating. Partially empty batteries are just topped up. Batteries always remain cool; this increases the total battery life and also the battery’s reliability. DESIGNED AND MADE IN AUSTRALIA For a FREE, detailed technical description please Ph (03) 6492 1368; Fax (03) 6492 1329; or email smartfastchargers<at>bigpond.com 2567 Wilmot Rd., Devonport, TAS 7310 P.C.B. Makers ! • • • If you need: P.C.B. High Speed Drill 3M Scotchmark Laser Labels P.C.B. Material – Negative or Positive acting • Light Box – Single or Double Sided – Large or Small • • Etch Tank – Bubble • • Prompt and Economical Delivery Electronic Components and Equipment for TAFEs, Colleges and Schools FREE ADVICE ON ANY OF OUR PRODUCTS FROM DEDICATED PEOPLE WITH HANDS-ON EXPERIENCE We now stock Hawera Carbide Tool Bits KALEX 40 Wallis Ave E. Ivanhoe 3079 Ph (03) 9497 3422 FAX (03) 9499 2381 ALL MAJOR CREDIT CARDS ACCEPTED March 2002  89 REFERENCE GREAT BOOKS FOR ALL PRICES INCLUDE GST AND ARE AUDIO POWER AMP DESIGN HANDBOOK PIC Your Personal Introductory Course From one of the world’s most respected audio authorities. The new 2nd edition is even more comprehensive, includes sections on load-invariant power amps, distortion residuals and diagnosis of amplifier problems. 368 pages in paperback. Concise and practical guide to getting up and running with the PIC Microcontroller. Assumes no prior knowledge of microcontrollers, introduces the PIC’s capabilities through simple projects. Ideal introduction for students, teachers, technicians and electronics enthusiasts – perfect for use in schools and colleges. 270 pages in soft cover. By Douglas Self. 2nd Edition Published 2000 by John Morton – 2nd edition 2001 89 $ $ VIDEO SCRAMBLING AND DESCRAMBLING FOR SATELLITE AND CABLE TV by Graf & Sheets 2nd Edition 1998 AUDIO ELECTRONICS By John Linsley Hood. First published 1995. Second edition 1999. If you've ever wondered how they scramble video on cable and satellite TV, this book tells you! Encoding/decoding systems (analog and digital systems), encryption, even schematics and details of several encoder and decoder circuits for experimentation. Intended for both the hobbyist and the professional. 290 pages in paperback. $ 79 $ UNDERSTANDING TELEPHONE ELECTRONICS By Stephen J. Bigelow. Fourth edition published 2001 4th EDITION Based mainly on the American telephone system, this book covers conventional telephone fundamentals, including analog and digital communication techniques. Provides basic information on the functions of each telephone component, how dial tones are generated and how digital transmission techniques work. 402 pages, soft cover. 65 GUIDE TO TV & VIDEO TECHNOLOGY 3rd EDITION By Eugene Trundle. 3rd Edition 2001 Eugene Trundle has written for many years in Television magazine and his latest book is right up to date on TV and video technology. The book includes both theory and practical servicing information and is ideal for both students and technicians. 382 pages, in paperback. This book is for anyone involved in designing, adapting and using analog and digital audio equipment. It covers tape recording, tuners and radio receivers, preamplifiers, voltage amplifiers, audio power amplifiers, compact disc technology and digital audio, test and measurement, loudspeaker crossover systems, power supplies and noise reduction systems. 375 pages in soft cover. 3rd EDITION $ By Tim Williams. First pub­­lished 1992. 3rd edition 2001. By Ian Hickman. 2nd edition1999. 63 $ Based mainly on British practice and first published in 1997, this book has much that is relevant to Australian systems as a guide to home and small business installations. A practical guide to installation of telephone wiring, ranging from single extension sockets to PABX, with the necessary tools, test equipment and materials needed by installers... 178 pages in soft cover. 90  Silicon Chip EMC FOR PRODUCT DESIGNERS ANALOG ELECTRONICS Essential reading for electronics designers and students alike. It will answer nagging questions about core analog theory and design principles as well as offering practical design ideas. With concise design implementations, with many of the circuits taken from Ian Hickman’s magazine articles. 294 pages in soft cover. VIDEO & CAMCORDER SERVICING AND TECHNOLOGY by Steve Roberts. 2nd edition 2001. 67 85 $ Widely regarded as the standard text on EMC, provides all the key information needed to meet the requirements of the EMC Directive. Most importantly, it shows how to incorporate EMC principles into the product design process, avoiding cost and performance penalties, meeting the needs of specific standards and resulting in a better overall product. 360 pages in paperback. 99 TELEPHONE INSTALLATION HANDBOOK $ 43 85 $ by Steve Beeching (Published 2001) Provides fully up-to-date coverage of the whole range of current home video equipment, analog and digital. Information for repair and troubleshooting, with explanations of the technology of video equipment. 318 pages in soft cover. 67 $$ www.siliconchip.com.au BOOKSHOP ENQUIRING MINDS! LOWER THAN RECOMMENDED RETAIL PRICE WANT TO SAVE 10%? 10% OFF! SILICON CHIP SUBSCRIBERS AUTOMATICALLY QUALIFY FOR A 10% DISCOUNT ON ALL BOOK PURCHASES! AUSTRALIA PUBLICATIONS LAST E! ELECTRONICS We have STRICTLY LIMITED STOCK of these C Electronics Australia publications. Once these are gone, they will not be available from any source – CHAN so get your copy now for your reference library . . . OP AMPS EXPLAINED by Bryan Maher 8 $ 50 pp p& in inc p& 50 $$ 14 (NZ:Z: 14 (N First published in 1988 and reprinted due to its popularity, Op Amps Explained is still regarded as one of the easiest-to-understand reference works on operational amplifiers. Starts with first concepts – negative feedback – and goes right through to power amplifiers, oscillators and filters, supplies, etc. 120 pages, soft cover BASIC ELECTRONICS by Peter Phillips An easy introduction to electronics for students and hobbyists, from basic electronics through to digital. If you want to start at the very start, this is the book you want. Also includes some simple projects to build. 120 pages, soft cover 8 $ 50 in inc p&pp 50 50 (N (NZ:Z: $$14 14 inc incp& p&p)p) ) p&p)p incp& inc SILICON CHIP'S SILICON ILICON CHIP'S HIP'S COMPUTER OMNIBUS First published 1999 ELECTRONICS ELECTRONICS TEST TEST BENCH BENCH First First published published 2000 2000 Hints, tips, Upgrades and Fixes for your computer from articles published in SILICON CHIP in recent years. Covers DOS, Windows 3.1, 95, 98 and NT. A must for the computer user. $12.50 (Aust); $A15.95 NZ (prices include P&P) AA collection collection of of the the “most “most asked asked for” for” Test Test Equipment Equipment projects projects and and features features from from the the pages pages of of Australia’s Australia’s “most “most asked asked for” for” electronics electronics magazine. magazine. Exceptional Exceptional value value at at $13.20 $13.20 (Aust); (Aust); $A15.95 $A15.95 NZ NZ (prices (prices include include p&p). p&p). Want one of these two books FREE? Subscribe to SILICON CHIP and we’ll give you one! See page 53 for subscription order form. O R D E R H E R E ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ANALOG ELECTRONICS..................................................$85.00 AUDIO POWER AMPLIFIER DESIGN...............................$89.00 AUDIO ELECTRONICS.....................................................$85.00 EMC FOR PRODUCT DESIGNERS...................................$99.00 GUIDE TO TV & VIDEO TECHNOLOGY............................$63.00 PIC - YOUR PERSONAL INTRODUCTORY COURSE........$43.00 TELEPHONE INSTALLATION HANDBOOK.......................$67.00 UNDERSTANDING TELEPHONE ELECTRONICS.................$65.00 VIDEO & CAMCORDER SERVICING/TECHNOLOGY........$67.00 VIDEO SCRAMBLING/DESCRAMBLING..........................$79.00 POWER SUPPLY COOKBOOK..........................................$93.00 M'CONTROLLER PROJECTS IN C FOR 8051..................$69.00 ANALOG CIRCUIT TECHNIQUES WITH DIGITAL INT......$69.00 ANTENNA TOOLKIT.........................................................$83.00 INTERFACING WITH C.....................................................$63.00 ELECTRIC MOTORS AND DRIVES..................................$59.00               ORDER TOTAL: $...................... 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ALL PRICES INCLUDE GST Silicon Chip Back Issues 200W Inverter; 0.5W Audio Amplifier; 3A 40V Adjustable Power Supply; Engine Management, Pt.5; Airbags In Cars – How They Work. March 1994: Intelligent IR Remote Controller; 50W (LM3876) Audio Amplifier Module; Level Crossing Detector For Model Railways; Voice Activated Switch For FM Microphones; Engine Management, Pt.6. April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors; 32-Band Graphic Equaliser, Pt.2. Ultrasonic Switch For Mains Appliances; The Basics Of A/D & D/A Conversion; Plotting The Course Of Thunderstorms. May 1989: Build A Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference. October 1991: Build A Talking Voltmeter For Your PC, Pt.1; SteamSound Simulator For Model Railways Mk.II; Magnetic Field Strength Meter; Digital Altimeter For Gliders, Pt.2; Military Applications Of R/C Aircraft. July 1989: Exhaust Gas Monitor; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; The NSW 86 Class Electrics. September 1989: 2-Chip Portable AM Stereo Radio Pt.1; High Or Low Fluid Level Detector; Studio Series 20-Band Stereo Equaliser, Pt.2. November 1991: Colour TV Pattern Generator, Pt.1; A Junkbox 2-Valve Receiver; Flashing Alarm Light For Cars; Digital Altimeter For Gliders, Pt.3; Build A Talking Voltmeter For Your PC, Pt.2. April 1994: Sound & Lights For Model Railway Level Crossings; Discrete Dual Supply Voltage Regulator; Universal Stereo Preamplifier; Digital Water Tank Gauge; Engine Management, Pt.7. May 1994: Fast Charger For Nicad Batteries; Induction Balance Metal Locator; Multi-Channel Infrared Remote Control; Dual Electronic Dice; Simple Servo Driver Circuits; Engine Management, Pt.8. June 1994: 200W/350W Mosfet Amplifier Module; A Coolant Level Alarm For Your Car; 80-Metre AM/CW Transmitter For Amateurs; Converting Phono Inputs To Line Inputs; PC-Based Nicad Battery Monitor; Engine Management, Pt.9. October 1989: FM Radio Intercom For Motorbikes Pt.1; GaAsFet Preamplifier For Amateur TV; 2-Chip Portable AM Stereo Radio, Pt.2. December 1991: TV Transmitter For VCRs With UHF Modulators; Infrared Light Beam Relay; Colour TV Pattern Generator, Pt.2; Index To Volume 4. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY & Morse); FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disk Drive Formats & Options. March 1992: TV Transmitter For VHF VCRs; Thermostatic Switch For Car Radiator Fans; Coping With Damaged Computer Directories; Valve Substitution In Vintage Radios. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Phone Patch For Radio Amateurs; Active Antenna Kit; Designing UHF Transmitter Stages. April 1992: IR Remote Control For Model Railroads; Differential Input Buffer For CROs; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. February 1990: A 16-Channel Mixing Desk; Build A High Quality Audio Oscillator, Pt.2; The Incredible Hot Canaries; Random Wire Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs, Pt.2. June 1992: Multi-Station Headset Intercom, Pt.1; Video Switcher For Camcorders & VCRs; IR Remote Control For Model Railroads, Pt.3; 15-Watt 12-240V Inverter; A Look At Hard Disk Drives. March 1990: Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC. October 1992: 2kW 24VDC - 240VAC Sinewave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal Stereos; A Regulated Lead-Acid Battery Charger. April 1990: Dual Tracking ±50V Power Supply; Voice-Operated Switch With Delayed Audio; 16-Channel Mixing Desk, Pt.3; Active CW Filter. February 1993: Three Projects For Model Railroads; Low Fuel Indicator For Cars; Audio Level/VU Meter (LED Readout); An Electronic Cockroach; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.5. November 1994: Dry Cell Battery Rejuvenator; Novel Alphanumeric Clock; 80-Metre DSB Amateur Transmitter; Twin-Cell Nicad Discharger (See May 1993); How To Plot Patterns Direct to PC Boards. June 1990: Multi-Sector Home Burglar Alarm; Build A Low-Noise Universal Stereo Preamplifier; Load Protector For Power Supplies. March 1993: Solar Charger For 12V Batteries; Alarm-Triggered Security Camera; Reaction Trainer; Audio Mixer for Camcorders; A 24-Hour Sidereal Clock For Astronomers. December 1994: Easy-To-Build Car Burglar Alarm; Three-Spot Low Distortion Sinewave Oscillator; Clifford – A Pesky Electronic Cricket; Remote Control System for Models, Pt.1; Index to Vol.7. April 1993: Solar-Powered Electric Fence; Audio Power Meter; Three-Function Home Weather Station; 12VDC To 70VDC Converter; Digital Clock With Battery Back-Up. January 1995: Sun Tracker For Solar Panels; Battery Saver For Torches; Dolby Pro-Logic Surround Sound Decoder, Pt.2; Dual Channel UHF Remote Control; Stereo Microphone Pre­amp­lifier. June 1993: AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; Digital Voltmeter For Cars; Windows-Based Logic Analyser. February 1995: 2 x 50W Stereo Amplifier Module; Digital Effects Unit For Musicians; 6-Channel Thermometer With LCD Readout; Wide Range Electrostatic Loudspeakers, Pt.1; Oil Change Timer For Cars; Remote Control System For Models, Pt.2. July 1990: Digital Sine/Square Generator, Pt.1 (covers 0-500kHz); Burglar Alarm Keypad & Combination Lock; Build A Simple Electronic Die; A Low-Cost Dual Power Supply. August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Mains Appliances (9 Minutes); Horace The Electronic Cricket; Digital Sine/Square Generator, Pt.2. September 1990: A Low-Cost 3-Digit Counter Module; Build A Simple Shortwave Converter For The 2-Metre Band; The Care & Feeding Of Nicad Battery Packs (Getting The Most From Nicad Batteries). October 1990: The Dangers of PCBs; Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs; NE602 Converter Circuits. July 1993: Single Chip Message Recorder; Light Beam Relay Extender; AM Radio Trainer, Pt.2; Quiz Game Adjudicator; Windows-Based Logic Analyser, Pt.2; Antenna Tuners – Why They Are Useful. August 1993: Low-Cost Colour Video Fader; 60-LED Brake Light Array; Microprocessor-Based Sidereal Clock; Satellites & Their Orbits. July 1994: Build A 4-Bay Bow-Tie UHF TV Antenna; PreChamp 2-Transistor Preamplifier; Steam Train Whistle & Diesel Horn Simulator; 6V SLA Battery Charger; Electronic Engine Management, Pt.10. August 1994: High-Power Dimmer For Incandescent Lights; Microprocessor-Controlled Morse Keyer; Dual Diversity Tuner For FM Microphones, Pt.1; Nicad Zapper (For Resurrecting Nicad Batteries); Electronic Engine Management, Pt.11. September 1994: Automatic Discharger For Nicad Battery Packs; MiniVox Voice Operated Relay; Image Intensified Night Viewer; AM Radio For Weather Beacons; Dual Diversity Tuner For FM Microphones, Pt.2; Electronic Engine Management, Pt.12. October 1994: How Dolby Surround Sound Works; Dual Rail Variable Power Supply; Build A Talking Headlight Reminder; Electronic Ballast For Fluorescent Lights; Electronic Engine Management, Pt.13. March 1995: 2 x 50W Stereo Amplifier, Pt.1; Subcarrier Decoder For FM Receivers; Wide Range Electrostatic Loudspeakers, Pt.2; IR Illuminator For CCD Cameras; Remote Control System For Models, Pt.3. November 1990: Connecting Two TV Sets To One VCR; Build An Egg Timer; Low-Cost Model Train Controller; 1.5V To 9V DC Converter; Introduction To Digital Electronics; A 6-Metre Amateur Transmitter. September 1993: Automatic Nicad Battery Charger/Discharger; Stereo Preamplifier With IR Remote Control, Pt.1; In-Circuit Transistor Tester; +5V to ±15V DC Converter; Remote-Controlled Cockroach. April 1995: FM Radio Trainer, Pt.1; Photographic Timer For Dark­ rooms; Balanced Microphone Preamp. & Line Filter; 50W/Channel Stereo Amplifier, Pt.2; Wide Range Electrostatic Loudspeakers, Pt.3; 8-Channel Decoder For Radio Remote Control. January 1991: Fast Charger For Nicad Batteries, Pt.1; Have Fun With The Fruit Machine (Simple Poker Machine); Build A Two-Tone Alarm Module; The Dangers of Servicing Microwave Ovens. October 1993: Courtesy Light Switch-Off Timer For Cars; Wireless Microphone For Musicians; Stereo Preamplifier With IR Remote Control, Pt.2; Electronic Engine Management, Pt.1. May 1995: Build A Guitar Headphone Amplifier; FM Radio Trainer, Pt.2; Transistor/Mosfet Tester For DMMs; A 16-Channel Decoder For Radio Remote Control; Introduction to Satellite TV. March 1991: Transistor Beta Tester Mk.2; A Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose I/O Board For PC-Compatibles; Universal Wideband RF Preamplifier For Amateur Radio & TV. November 1993: High Efficiency Inverter For Fluorescent Tubes; Stereo Preamplifier With IR Remote Control, Pt.3; Siren Sound Generator; Engine Management, Pt.2; Experiments For Games Cards. June 1995: Build A Satellite TV Receiver; Train Detector For Model Railways; 1W Audio Amplifier Trainer; Low-Cost Video Security System; Multi-Channel Radio Control Transmitter For Models, Pt.1. May 1991: 13.5V 25A Power Supply For Transceivers; Stereo Audio Expander; Fluorescent Light Simulator For Model Railways; How To Install Multiple TV Outlets, Pt.1. December 1993: Remote Controller For Garage Doors; Build A LED Stroboscope; Build A 25W Audio Amplifier Module; A 1-Chip Melody Generator; Engine Management, Pt.3; Index To Volume 6. July 1995: Electric Fence Controller; How To Run Two Trains On A Single Track (Incl. Lights & Sound); Setting Up A Satellite TV Ground Station; Build A Reliable Door Minder. July 1991: Loudspeaker Protector For Stereo Amplifiers; 4-Channel Lighting Desk, Pt.2; How To Install Multiple TV Outlets, Pt.2; Tuning In To Satellite TV, Pt.2. January 1994: 3A 40V Variable Power Supply; Solar Panel Switching Regulator; Printer Status Indicator; Mini Drill Speed Controller; Stepper Motor Controller; Active Filter Design; Engine Management, Pt.4. August 1995: Fuel Injector Monitor For Cars; Gain Controlled Microphone Preamp; Audio Lab PC-Controlled Test Instrument, Pt.1; How To Identify IDE Hard Disk Drive Parameters. September 1991: Digital Altimeter For Gliders & Ultralights; February 1994: Build A 90-Second Message Recorder; 12-240VAC 10% OF F SUBSCR TO IBERS O Please send the following back issues:      ____________________________________________________________ R IF YOU BUY 10 OR M Please send the following back issues: ORE ORDER FORM Enclosed is my cheque/money order for $­______or please debit my: ❏ Bankcard ❏ Visa Card ❏ Master Card Card No. Signature ___________________________ Card expiry date_____ /______ Name ______________________________ Phone No (___) ____________ PLEASE PRINT Street ______________________________________________________ Suburb/town _______________________________ Postcode ___________ 92  Silicon Chip Note: prices include postage & packing Australia ....................... $A7.70 (incl. GST) Overseas (airmail) ............................ $A10 Detach and mail to: Silicon Chip Publications, PO Box 139, Collaroy, NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details or fax the details to (02) 9979 6503. Email: silchip<at>siliconchip.com.au www.siliconchip.com.au September 1995: Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.1; Keypad Combination Lock; The Vader Voice; Jacob’s Ladder Display; Audio Lab PC-Controlled Test Instrument, Pt.2. October 1995: 3-Way Loudspeaker System; Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.2; Build A Fast Charger For Nicad Batteries. November 1995: Mixture Display For Fuel Injected Cars; CB Trans­ verter For The 80M Amateur Band, Pt.1; PIR Movement Detector. December 1995: Engine Immobiliser; 5-Band Equaliser; CB Transverter For The 80M Amateur Band, Pt.2; Subwoofer Controller; Knock Sensing In Cars; Index To Volume 8. January 1996: Surround Sound Mixer & Decoder, Pt.1; Magnetic Card Reader; Build An Automatic Sprinkler Controller; IR Remote Control For The Railpower Mk.2; Recharging Nicad Batteries For Long Life. April 1996: Cheap Battery Refills For Mobile Phones; 125W Audio Amplifier Module; Knock Indicator For Leaded Petrol Engines; Multi-Channel Radio Control Transmitter; Pt.3. May 1996: Upgrading The CPU In Your PC; High Voltage Insulation Tester; Knightrider Bi-Directional LED Chaser; Simple Duplex Intercom Using Fibre Optic Cable; Cathode Ray Oscilloscopes, Pt.3. June 1996: BassBox CAD Loudspeaker Software Reviewed; Stereo Simulator (uses delay chip); Rope Light Chaser; Low Ohms Tester For Your DMM; Automatic 10A Battery Charger. July 1996: Build A VGA Digital Oscilloscope, Pt.1; Remote Control Extender For VCRs; 2A SLA Battery Charger; 3-Band Parametric Equaliser; Single Channel 8-Bit Data Logger. August 1996: Introduction to IGBTs; Electronic Starter For Fluores­ cent Lamps; VGA Oscilloscope, Pt.2; 350W Amplifier Module; Masthead Amplifier For TV & FM; Cathode Ray Oscilloscopes, Pt.4. September 1996: VGA Oscilloscope, Pt.3; IR Stereo Headphone Link, Pt.1; High Quality PA Loudspeaker; 3-Band HF Amateur Radio Receiver; Cathode Ray Oscilloscopes, Pt.5. October 1996: Send Video Signals Over Twisted Pair Cable; Power Control With A Light Dimmer; 600W DC-DC Converter For Car Hifi Systems, Pt.1; IR Stereo Headphone Link, Pt.2; Build A Multi-Media Sound System, Pt.1; Multi-Channel Radio Control Transmitter, Pt.8. November 1996: 8-Channel Stereo Mixer, Pt.1; Low-Cost Fluorescent Light Inverter; Repairing Domestic Light Dimmers; Multi-Media Sound System, Pt.2; 600W DC-DC Converter For Car Hifi Systems, Pt.2. December 1996: Active Filter Cleans Up Your CW Reception; A Fast Clock For Railway Modellers; Laser Pistol & Electronic Target; Build A Sound Level Meter; 8-Channel Stereo Mixer, Pt.2; Index To Vol.9. January 1997: How To Network Your PC; Control Panel For Multiple Smoke Alarms, Pt.1; Build A Pink Noise Source; Computer Controlled Dual Power Supply, Pt.1; Digi-Temp Monitors Eight Temperatures. January 1998: Build Your Own 4-Channel Lightshow, Pt.1 (runs off 12VDC or 12VAC); Command Control System For Model Railways, Pt.1; Pan Controller For CCD Cameras. February 1998: Multi-Purpose Fast Battery Charger, Pt.1; Telephone Exchange Simulator For Testing; Command Control System For Model Railways, Pt.2; Build Your Own 4-Channel Lightshow, Pt.2. April 1998: Automatic Garage Door Opener, Pt.1; 40V 8A Adjustable Power Supply, Pt.1; PC-Controlled 0-30kHz Sinewave Generator; Build A Laser Light Show; Understanding Electric Lighting; Pt.6. May 1998: Troubleshooting Your PC, Pt.1; Build A 3-LED Logic Probe; Automatic Garage Door Opener, Pt.2; Command Control For Model Railways, Pt.4; 40V 8A Adjustable Power Supply, Pt.2. June 1998: Troubleshooting Your PC, Pt.2; Universal High Energy Ignition System; The Roadies’ Friend Cable Tester; Universal Stepper Motor Controller; Command Control For Model Railways, Pt.5. July 1998: Troubleshooting Your PC, Pt.3; 15-W/Ch Class-A Audio Amplifier, Pt.1; Simple Charger For 6V & 12V SLA Batteries; Auto­matic Semiconductor Analyser; Understanding Electric Lighting, Pt.8. August 1998: Troubleshooting Your PC, Pt.4 (Adding Extra Memory); Simple I/O Card With Automatic Data Logging; Build A Beat Triggered Strobe; 15-W/Ch Class-A Stereo Amplifier, Pt.2. September 1998: Troubleshooting Your PC, Pt.5; A Blocked Air-Filter Alarm; Waa-Waa Pedal For Guitars; Jacob’s Ladder; Gear Change Indicator For Cars; Capacity Indicator For Rechargeable Batteries. October 1998: Lab Quality AC Millivoltmeter, Pt.1; PC-Controlled Stress-O-Meter; Versatile Electronic Guitar Limiter; 12V Trickle Charger For Float Conditions; Adding An External Battery Pack To Your Flashgun. August 1997: The Bass Barrel Subwoofer; 500 Watt Audio Power Amplifier Module; A TENs Unit For Pain Relief; Addressable PC Card For Stepper Motor Control; Remote Controlled Gates For Your Home. September 1997: Multi-Spark Capacitor Discharge Ignition; 500W Audio Power Amplifier, Pt.2; A Video Security System For Your Home; PC Card For Controlling Two Stepper Motors; HiFi On A Budget. October 1997: Build A 5-Digit Tachometer; Add Central Locking To Your Car; PC-Controlled 6-Channel Voltmeter; 500W Audio Power Amplifier, Pt.3; Customising The Windows 95 Start Menu. November 1997: Heavy Duty 10A 240VAC Motor Speed Controller; Easy-To-Use Cable & Wiring Tester; Build A Musical Doorbell; Replacing Foam Speaker Surrounds; Understanding Electric Lighting Pt.1. December 1997: Speed Alarm For Cars; 2-Axis Robot With Gripper; Stepper Motor Driver With Onboard Buffer; Power Supply For Stepper Motor Cards; Understanding Electric Lighting Pt.2; Index To Vol.10. www.siliconchip.com.au September 2000: Build A Swimming Pool Alarm; An 8-Channel PC Relay Board; Fuel Mixture Display For Cars, Pt.1; Protoboards – The Easy Way Into Electronics, Pt.1; Cybug The Solar Fly. October 2000: Guitar Jammer For Practice & Jam Sessions; Booze Buster Breath Tester; A Wand-Mounted Inspection Camera; Installing A Free-Air Subwoofer In Your Car; Fuel Mixture Display For Cars, Pt.2. November 2000: Santa & Rudolf Chrissie Display; 2-Channel Guitar Preamplifier, Pt.1; Message Bank & Missed Call Alert; Electronic Thermostat; Protoboards – The Easy Way Into Electronics, Pt.3. December 2000: Home Networking For Shared Internet Access; Build A Bright-White LED Torch; 2-Channel Guitar Preamplifier, Pt.2 (Digital Reverb); Driving An LCD From The Parallel Port; Build A Morse Clock; Protoboards – The Easy Way Into Electronics, Pt.4; Index To Vol.13. January 2001: How To Transfer LPs & Tapes To CD; The LP Doctor – Clean Up Clicks & Pops, Pt.1; Arbitrary Waveform Generator; 2-Channel Guitar Preamplifier, Pt.3; PIC Programmer & TestBed. March 2001: Making Photo Resist PC Boards; Big-Digit 12/24 Hour Clock; Parallel Port PIC Programmer & Checkerboard; Protoboards – The Easy Way Into Electronics, Pt.5; A Simple MIDI Expansion Box. January 1999: High-Voltage Megohm Tester; Getting Started With BASIC Stamp; LED Bargraph Ammeter For Cars; Keypad Engine Immobiliser; Improving AM Radio Reception, Pt.3. April 2001: A GPS Module For Your PC; Dr Video – An Easy-To-Build Video Stabiliser; Tremolo Unit For Musicians; Minimitter FM Stereo Transmitter; Intelligent Nicad Battery Charger. March 1999: Getting Started With Linux; Pt.1; Build A Digital Anemometer; Simple DIY PIC Programmer; Easy-To-Build Audio Compressor; Low Distortion Audio Signal Generator, Pt.2. May 2001: Powerful 12V Mini Stereo Amplifier; Two White-LED Torches To Build; PowerPak – A Multi-Voltage Power Supply; Using Linux To Share An Internet Connection, Pt.1; Tweaking Windows With TweakUI. April 1999: Getting Started With Linux; Pt.2; High-Power Electric Fence Controller; Bass Cube Subwoofer; Programmable Thermostat/ Thermometer; Build An Infrared Sentry; Rev Limiter For Cars. June 2001: Fast Universal Battery Charger, Pt.1; Phonome – Call, Listen In & Switch Devices On & Off; L’il Snooper – A Low-Cost Automatic Camera Switcher; Using Linux To Share An Internet Connection, Pt.2; A PC To Die For, Pt.1 (Building Your Own PC). May 1999: The Line Dancer Robot; An X-Y Table With Stepper Motor Control, Pt.1; Three Electric Fence Testers; Heart Of LEDs; Build A Carbon Monoxide Alarm; Getting Started With Linux; Pt.3. July 1999: Build A Dog Silencer; 10µH to 19.99mH Inductance Meter; Build An Audio-Video Transmitter; Programmable Ignition Timing Module For Cars, Pt.2; XYZ Table With Stepper Motor Control, Pt.3. July 1997: Infrared Remote Volume Control; A Flexible Interface Card For PCs; Points Controller For Model Railways; Colour TV Pattern Generator, Pt.2; An In-Line Mixer For Radio Control Receivers. August 2000: Build A Theremin For Really Eeerie Sounds; Come In Spinner (writes messages in “thin-air”); Proximity Switch For 240VAC Lamps; Structured Cabling For Computer Networks. December 1998: Engine Immobiliser Mk.2; Thermocouple Adaptor For DMMs; Regulated 12V DC Plugpack; Build A Poker Machine, Pt.2; Improving AM Radio Reception, Pt.2; Mixer Module For F3B Gliders. March 1997: Driving A Computer By Remote Control; Plastic Power PA Amplifier (175W); Signalling & Lighting For Model Railways; Build A Jumbo LED Clock; Cathode Ray Oscilloscopes, Pt.7. June 1997: PC-Controlled Thermometer/Thermostat; TV Pattern Generator, Pt.1; Audio/RF Signal Tracer; High-Current Speed Controller For 12V/24V Motors; Manual Control Circuit For Stepper Motors. July 2000: A Moving Message Display; Compact Fluorescent Lamp Driver; El-Cheapo Musicians’ Lead Tester; Li’l Powerhouse Switchmode Power Supply (1.23V to 40V) Pt.2. February 2001: How To Observe Meteors Using Junked Gear; An Easy Way To Make PC Boards; L’il Pulser Train Controller; Midi-Mate – A MIDI Interface For PCs; Build The Bass Blazer; 2-Metre Elevated Groundplane Antenna; The LP Doctor – Clean Up Clicks & Pops, Pt.2. June 1999: FM Radio Tuner Card For PCs; X-Y Table With Stepper Motor Control, Pt.2; Programmable Ignition Timing Module For Cars, Pt.1; Hard Disk Drive Upgrades Without Reinstalling Software? May 1997: Neon Tube Modulator For Light Systems; Traffic Lights For A Model Intersection; The Spacewriter – It Writes Messages In Thin Air; A Look At Signal Tracing; Pt.2; Cathode Ray Oscilloscopes, Pt.9. June 2000: Automatic Rain Gauge With Digital Readout; Parallel Port VHF FM Receiver; Li’l Powerhouse Switchmode Power Supply (1.23V to 40V) Pt.1; CD Compressor For Cars Or The Home. November 1998: The Christmas Star; A Turbo Timer For Cars; Build A Poker Machine, Pt.1; FM Transmitter For Musicians; Lab Quality AC Millivoltmeter, Pt.2; Improving AM Radio Reception, Pt.1. February 1997: PC-Con­trolled Moving Message Display; Computer Controlled Dual Power Supply, Pt.2; Alert-A-Phone Loud Sounding Telephone Alarm; Control Panel For Multiple Smoke Alarms, Pt.2. April 1997: Simple Timer With No ICs; Digital Voltmeter For Cars; Loudspeaker Protector For Stereo Amplifiers; Model Train Controller; A Look At Signal Tracing; Pt.1; Cathode Ray Oscilloscopes, Pt.8. IBM Scan-Codes To ASCII); 50A Motor Speed Controller For Models. August 1999: Remote Modem Controller; Daytime Running Lights For Cars; Build A PC Monitor Checker; Switching Temperature Controller; XYZ Table With Stepper Motor Control, Pt.4; Electric Lighting, Pt.14. September 1999: Autonomouse The Robot, Pt.1; Voice Direct Speech Recognition Module; Digital Electrolytic Capacitance Meter; XYZ Table With Stepper Motor Control, Pt.5; Peltier-Powered Can Cooler. October 1999: Build The Railpower Model Train Controller, Pt.1; Semiconductor Curve Tracer; Autonomouse The Robot, Pt.2; XYZ Table With Stepper Motor Control, Pt.6; Introducing Home Theatre. November 1999: Setting Up An Email Server; Speed Alarm For Cars, Pt.1; LED Christmas Tree; Intercom Station Expander; Foldback Loudspeaker System; Railpower Model Train Controller, Pt.2. December 1999: Solar Panel Regulator; PC Powerhouse (gives +12V, +9V, +6V & +5V rails); Fortune Finder Metal Locator; Speed Alarm For Cars, Pt.2; Railpower Model Train Controller, Pt.3; Index To Vol.12. January 2000: Spring Reverberation Module; An Audio-Video Test Generator; Build The Picman Programmable Robot; A Parallel Port Interface Card; Off-Hook Indicator For Telephone Lines. February 2000: Multi-Sector Sprinkler Controller; A Digital Voltmeter For Your Car; An Ultrasonic Parking Radar; Build A Safety Switch Checker; Build A Sine/Square Wave Oscillator. March 2000: Resurrecting An Old Computer; Low Distortion 100W Amplifier Module, Pt.1; Electronic Wind Vane With 16-LED Display; Glowplug Driver For Powered Models; The OzTrip Car Computer, Pt.1. May 2000: Ultra-LD Stereo Amplifier, Pt.2; Build A LED Dice (With PIC Microcontroller); Low-Cost AT Keyboard Translator (Converts July 2001: The HeartMate Heart Rate Monitor; Do Not Disturb Tele­phone Timer; Pic-Toc – A Simple Alarm Clock; Fast Universal Battery Charger, Pt.2; A PC To Die For, Pt.2; Backing Up Your Email. August 2001: Direct Injection Box For Musicians; Build A 200W Mosfet Amplifier Module; Headlight Reminder For Cars; 40MHz 6-Digit Frequency Counter Module; A PC To Die For, Pt.3; Using Linux To Share An Internet Connection, Pt.3. September 2001: Making MP3s – Rippers & Encoders; Build Your Own MP3 Jukebox, Pt.1; PC-Controlled Mains Switch; Personal Noise Source For Tinnitus Sufferers; The Sooper Snooper Directional Microphone; Using Linux To Share An Internet Connection, Pt.4. October 2001: A Video Microscope From Scrounged Parts; Build Your Own MP3 Jukebox, Pt.2; Super-Sensitive Body Detector; An Automotive Thermometer; Programming Adapter For Atmel Microcomputers. November 2001: Ultra-LD 100W RMS/Channel Stereo Amplifier, Pt.1; Neon Tube Modulator For Cars; Low-Cost Audio/Video Distribution Amplifier; Short Message Recorder Player; Computer Tips. December 2001: A Look At Windows XP; Build A PC Infrared Transceiver; Ultra-LD 100W RMS/Ch Stereo Amplifier, Pt.2; Pardy Lights – An Intriguing Colour Display; PIC Fun – Learning About Micros. January 2002: Touch And/Or Remote-Controlled Light Dimmer, Pt.1; A Cheap ’n’Easy Motorbike Alarm; 100W RMS/Channel Stereo Amplifier, Pt.3; Build A Raucous Alarm; Tracking Down Computer Software Problems; Electric Power Steering; FAQs On The MP3 Jukebox. February 2002: 10-Channel IR Remote Control Receiver; 2.4GHz High-Power Audio-Video Link; Assemble Your Own 2-Way Tower Speakers; Touch And/Or Remote-Controlled Light Dimmer, Pt.2; Booting A PC Without A Keyboard; 4-Way Event Timer. PLEASE NOTE: November 1987 to March 1989, June 1989, August 1989, December 1989, May 1990, December 1990, February 1991, April 1991, June 1991, August 1991, January 1992, February 1992, July 1992, August 1992, September 1992, November 1992, December 1992, January 1993, May 1993, February 1996, March 1998 and February 1999 are now sold out. All other issues are presently in stock. We can supply photostat copies (or tear sheets) from sold-out issues for $7.70 per article (includes p&p). When supplying photostat articles or back copies, we automatically supply any relevant notes & errata at no extra charge. A complete index to all articles published to date can be downloaded free from our web site: www.siliconchip.com.au March 2002  93 MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads: $20.00 (incl. GST) for up to 20 words plus 66 cents for each additional word. Display ads: $33.00 (incl. GST) per column centimetre (max. 10cm). Closing date: five weeks prior to month of sale. To run your classified ad, print it clearly in the space below or on a separate sheet of paper, fill out the form & send it with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details to (02) 9979 6503. Taxation Invoice ABN 49 003 205 490 _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ Enclosed is my cheque/money order for $­__________ or please debit my ❏ Bankcard   ❏ Visa Card   ❏ Master Card Card No. Signature­­­­­­­­­­­­__________________________ Card expiry date______/______ Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ 94  Silicon Chip FOR SALE TELEPHONE EXCHANGE SIMULATOR: test equipment without the cost of telephone lines. Melb 9806 0110. http://www.alphalink.com.au/~zenere KITS KITS AND MORE KITS! Check ‘em out at www.ozitronics.com AMAZING NEW Super Microphone point and listen in 500m away $95. Spy bug 1.2km range $49. Wireless Spy Camera transmits clear picture to TV within 200m $179. Tracking device $89. Professional Bug Detector $269. Camera with VCR, automatic recording, 20m cable, P/S and sensor ready to plug and use only $480. GCS Electronics (02) 4227 9933 gcses<at>aol.com; www. gcselectronics.com UNIVERSAL DEVICE PROGRAMMER: Low cost, high performance, 48-pin, works in DOS or Windows inc NT/2000. $1320. Universal EPROM programmer $429. Also adaptors, (E) EPROM, PIC, 8051 programmers, EPROM simulator and eraser. Dunfield C Compilers: Everything you need to develop C and ASM software for 68HC08, 6809, 68HC11, 68HC12, 68HC16, 8051/52, 8080/85, 8086, 8096 or AVR: $198 each. Demo disk available. ImageCraft C Compilers: 32-bit Windows IDE and compiler. For AVR, 68HC11, 68HC12. $396. Atmel Flash CPU Programmer: Handles the 89Cx051, 89C5x, 89Sxx in both DIP and PLCC44 and some AVR’s, most 8-pin EEPROMS. Includes socket for serial ISP cable. $220, $11 p&p. SOIC adaptors: 20 pin $99, 14 pin $93.50, 8 pin $88. Full details on web site. Credit cards accepted. GRANTRONICS PTY LTD, PO Box 275, Wentworthville 2145. (02) 9896 7150 or http://www.grantronics.com.au WEATHER STATIONS: Windspeed & direction, inside temperature, outside temperature & windchill. Records highs www.siliconchip.com.au & lows with time and date as they occur. Optional rainfall and PC interface. Used by Government Departments, farmers, pilots, and weather enthusiasts. Other models with barometric pressure, humidity, dew point, solar radiation, UV, leaf wetness, etc. Just phone, fax or write for our FREE catalogue and price list. Solar Flair/Ecowatch phone: (03) 5968 4863; fax: (03) 5968 5810, PO Box 18, Emerald, Vic., 3782. ACN 006 399 480. Audio, Video, S-Video and VGA cables distribution amps, switchers, adaptors, price lists at: www.questronix.com.au CCTV EQUIPMENT: Best prices best-tange Cameras from $34. Digital PC Video Recording Dial In/Out Software & much more. www.allthings.com.au Satellite TV Reception International satellite TV reception in your home is now affordable. Send for your free info pack containing equipment catalog, satellite lists, etc or call for appointment to view. We can display all satellites from 76.5° to 180°. AV-COMM P/L, 24/9 Powells Rd, Brookvale, NSW 2100. Tel: 02 9939 4377 or 9939 4378. Fax: 9939 4376; www.avcomm.com.au Need prototype PC boards? We have the solutions – we print electronics! Four-day turnaround, less if urgent; Artwork from your own positive or file; Through hole plating; Prompt postal service; 29 years technical experience; Inexpensive; Superb quality. Printed Electronics, 12A Aristoc Rd, Glen Waverley, Vic 3150. Phone: (03) 9545 3722; Fax: (03) 9545 3561 Call Mike Lynch and check us out! We are the best for low cost, small runs. USB KITS: DDS-HF Generator, 4-channel Voltmeter, 10-Relay Card. Also Digital Oscilloscope and Temperature Loggers. http://www.ar.com.au/~softmark ELECTRONICS RETAIL BUSINESS FOR SALE. Premium dealer for national distributor plus extras. Solid, long established family business with good prospects and potential for considerable further growth. Main road position near beach, excellent lease recently renewed. Good income and comfortable lifestyle. Owners wish to retire. Asking $95,000 + SAV. Phone (07) 5443 4290. TV/VCR SERVICE BUSINESS. Well established workshop located on Queens­land’s Sunshine Coast. Large industrial premises on busy road. Excellent income and plenty of potential www.siliconchip.com.au • • • • • 6 Channels 10kHz frequency separation Size: 55 x 23 x 20mm Weight: 25gm Modular Construction Price: $A129.50 with crystal Electronics PO Box 580, Riverwood, NSW 2210. Ph/Fax (02) 9533 3517 Positions At Jaycar Buy Direct From Manufacturer D.I.Y. PCB SUPPLIES AFORDABLEWEB HOSTING from $11/ month, includes POP/WEB email. Other plans available. Servers In A Box, sales<at> siab.com.au; www.siab.com.au, Phone (02) 4341 6555. Mark22-SM Slimline Mini FM R/C Receiver email: youngbob<at>silvertone.com.au Website: www.silvertone.com.au RCS HAS MOVED to 41 Arlewis St, Chester Hill 2162 and is now open, with full production. Tel (02) 9738 0330; Fax 9738 0334. rcsradio<at>cia.com.au; www.cia.com.au/rcsradio PCBs MADE, ONE OR MANY. Low prices, hobbyists welcome. Sesame Elec­tronics (02) 9586 4771. sesame<at>internetezy.com.au; http:// members.tripod.com/~sesame_elec New New New Pre Sensitized Copper Clad to make your own boards. Developer, Carbide Drills & Mills also manufacturer of Single & double sided boards. Comprehensive details at acetronics.com.au goto shop page ACETRONICS PCBs 5/32 Seton Rd Moorebank NSW 2170 02 9600 6832 Fax: 02 9600 6834 Mail: acetronics<at>acetronics.com.au Credit cards welcome to expand. Over 3500 customers on database, more than 50% are regular clients. Fully stocked and well equipped with test equipment. Owner had 6 weeks off last year! Work only 5 days a week. Suit husband/wife owners. Call (07) 5443 2388 or 0412 708 068. EDDYSTONE 770R RX original condition, collectors item plus spare valves $475 (08) 8347 4593. MOTORBIKE ALARM KITS $49.50 + P&H. Includes programmed micropro- We are often looking for enthusiastic staff for positions in our retail stores and head office at Silverwater in Sydney. A genuine interest in electronics is a necessity. Phone 02 9741 8555 for current vacancies. PCB DRILLING MACHINES BY P.E. PTY LTD SINGLE SPINDLE. NC DRIVEN AND PROGRAMMABLE. CAN ALSO BE USED FOR A VARIETY OF OTHER DRILLING APPLICATIONS. MADE IN AUSTRALIA. For information brochure: Fax (03) 5971 1040; Ph (03) 9545 3722 or (03) 5971 1041. Wanted: we pay up to $60 for Circuit Notebook contributions. Silicon Chip Publications, PO Box 139, Collaroy, 2097. cessor, quality sensor, PCB, heatshrink, miscellaneous and tilt switch. Details at: www.users.tpg.com.au/micwen KIT ASSEMBLY NEVILLE WALKER KIT ASSEMBLY & REPAIR: • Australia wide service • Small production runs • Specialist “one-off” applications Phone Neville Walker (07) 3857 2752 Email: flashdog<at>optusnet.com.au March 2002  95 Silicon Chip Binders Keep your copies safe, secure and always available with SILICON CHIP binders: they’re cheap insurance!  Heavy board covers with 2-tone green vinyl covering Advertising Index Acetronics....................................95 REAL VALUE AT Alltac International.......................75 PLUS P &P Allthings Sales & Services...........95 $12.95 Altronics.....................................IFC Aust. Microelect. Network...............7 Av-Comm Pty Ltd.........................95  Each binder holds up to 14 issues so that you can include catalogs Dick Smith Electronics........... 26-29 eLabtronics..................................67  SILICON CHIP logo printed in gold-coloured lettering on spine & cover Elan Audio....................................11 Price: $12.95 (includes GST) plus $5.50 p&p each (available Aust. only). Price includes GST. Farnell Electronic Components....19 Evatco..........................................79 Grantronics..................................95 Order by phoning (02) 9979 5644 & quoting your credit card number; or fax the details to (02) 9979 6503; or mail your order with cheque or credit card details to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. Harbuch Electronics.....................67 Hy-Q International........................75 Instant PCBs................................95 Jaycar ................................... 45-52 JED Microprocessors..............21,75 Kalex............................................89 Subscribe & Get this FREE!* Microgram Computers...................3 MicroZed Computers...................75 Oatley Electronics........................15 Printed Electronics...................... 95 *Australia only. Offer valid only while stocks last. Polykom..................................... 4-6 THAT’S RIGHT – buy a 1- or 2-year subscription to SILICON CHIP magazine and we’ll mail you a free copy of “Computer Omnibus”. Quest Electronics.........................75 Subscribe now by using the handy order form in this issue or call (02) 9979 5644, 8.30-5.30 Mon-Fri with your credit card details. Robotic Education Products.........11 RCS Radio...................................95 RF Probes....................................75 RTN..............................................55 Silicon Chip Binders.....................96 Silicon Chip Bookshop........... 90-91 NOW AVAILABLE FROM SC Computer Omnibus................96 SC EFI Tech Special................OBC SC Electronics Testbench..........IBC Silicon Chip Subscriptions...........53 www.siliconchip.com.au Project Reprints Limited Back Issues Limited One-Shots If you’re looking for a project from ELECTRONICS AUSTRALIA, you’ll find it at SILICON CHIP! We can now offer reprints of all projects which have appeared in Electronics Australia, EAT, Electronics Today, ETI or Radio, TV & Hobbies. First search the EA website indexes for the project you want and then call, fax or email us with the details and your credit card details. Reprint cost is $8.80 per article (ie, 2-part projects cost $17.60). SILICON CHIP subscribers receive a 10% discount. We also have limited numbers of EA back issues and special publications. Call for details! visit www.siliconchip.com.au or www.electronicsaustralia.com.au 96  Silicon Chip Silvertone Electronics..................95 Smart Fastchargers.....................89 Solar Flair/Ecowatch....................95 VAF Research.........................41,75 Wiltronics.................22,43,75,84,87 _____________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: RCS Radio Pty Ltd. Phone (02) 9738 0330. Fax (02) 9738 0334. www.siliconchip.com.au