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SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings.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.gadgetcentral.com.au Contents Vol.16, No.11; November 2003 www.siliconchip.com.au FEATURES 8 Electronic Noses Smell A Big Future Don’t sniff – electronic noses have a big future, from checking your morning coffee to sniffing out explosives. And they’re here now – by Peter Holtham 14 Logging Your Every Driving Moment Some airbag controllers do more than just trigger the airbags; they also log your speed and a range of other driving actions – by Julian Edgar 85 PC Board Design Tutorial, Pt.2 The basics of component placement and routing, plus a few tips to make your boards look good – by David L. Jones A 12AX7 Valve Audio Preamplifier – Page 24. PROJECTS TO BUILD 24 A 12AX7 Valve Audio Preamplifier And we swore we’d never do another valve audio project. Who was it that said “bottles” were dead? – by Jim Rowe 41 Our Best LED Torch . . . Ever! It’s based on a Luxeon Star/O 1W ultrabright LED, runs off two “D” cells and blasts our previous LED torches into the weeds! – by John Clarke 62 Smart Radio Modem For Microcontrollers This low-cost project will enable your Picaxe, Stamp or other microcontroller to communicate without wires – by Nenad Stojadinovic 74 The PICAXE, Pt.8: The 18X Series Our Best LED Torch . . . Ever – Page 41. You’ve guessed it: the Picaxe 08 chip has several big brothers. Here’s a look at the “18A” version, along with a simple temperature sensor – by Stan Swan 78 A Programmable PIC-Powered Timer This PIC-based timer can be set for any period from one second up to 680 days and even (theoretically) up to nearly 60 years – by Trent Jackson SPECIAL COLUMNS 36 Serviceman’s Log The JVC TV set that whistled – by the TV Serviceman 71 Circuit Notebook Smart Radio Modem For Microcontrollers – Page 62. (1) Making The Flexitimer Cycle On And Off; (2) Low Battery Indicator; (3) A Simple 9-Way Cable Identifier; (4) Clipping Indicator For Audio Amplifiers; (5) 8V DV Supply With Overvoltage Protection; (6) Cheap Switchmode DC-DC Converter 90 Vintage Radio The 1953 4-Valve Precedent Mantel Receiver – by Rodney Champness DEPARTMENTS 2 4 13 59 Publisher’s Letter Mailbag Order Form Product Showcase www.siliconchip.com.au 61 96 98 99 Silicon Chip Weblink Ask Silicon Chip Notes & Errata Market Centre/Ad Index Programmable PIC-Powered Timer – Page 78. November 2003  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.) Peter Smith Ross Tester Jim Rowe, B.A., B.Sc, VK2ZLO Rick Walters Reader Services Ann Jenkinson Advertising Enquiries Leo Simpson 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 Stan Swan 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 The valve circuit we said we would never publish Quite some time ago, in the July 1994 issue to be precise, I wrote an editorial entitled “Valve Amplifiers Are Dead & Buried”. The gist of the editorial was that valve amplifiers were far too costly and poor in performance, relative to even run-of-the-mill solid-state amplifiers. I went so far as to make the statement that “SILICON CHIP will never publish a design for hifi valve amplifier unless it is of academic interest only. In fact, let’s be even more absolute and just say NEVER”. So why are we now publishing a design for a valve preampli­fier? Well, as they say in politics, never say never! I still believe that valve amplifiers are far too expensive and that their performance is mediocre compared to very cheap solid-state designs. In fact, our high quality amplifier designs published in the intervening years since 1994 have continued to widen the gap. That has not discouraged readers and kitset suppliers from periodically suggesting that we do a valve amplifier of some sort or other. In fact, only a month ago, one of the kitset suppliers suggested that we do a 60W valve guitar amplifier with its own speaker, etc. When they did the sums for the likely kit price (over $1000), they quickly back-pedalled. So why do a valve preamp? Again, there have been a number of suggestions from readers and a number of circuits have been published elsewhere, all of which by the way, we have regarded as jokes. There has even been a PC motherboard with an on-board valve preamplifier for the sound section. Again, what a joke. A bad joke at that. But having cast such aspersions, we were then more or less obliged to show we could do better. And we have. The triode preamp circuit featured in this issue is considerably better than anything we have seen published elsewhere, either recently or in the past. The good performance comes about because of three factors, two of which were not available in the days when valves ruled. First, we have run the valve heaters from pure DC. This was sometimes done years ago but it was difficult. Now it is easy, using a 3-terminal regulator. Second, the critical grid resistors are metal film types which have very low noise. Thirdly, and most important, our circuit has a substantial degree of negative feedback to greatly improve distortion and frequency response. It turns a very aver­age performance into something we regard as acceptable (for valve technology, that is). Mind you, some valve fans will turn up their noses precise­ly because we have used negative feedback in the circuit. Perhaps we can reassure them: the amount of applied negative feedback is still nowhere near as much as is commonly used in op amp circuits and the circuit still displays “soft clipping” when driven hard. But does it have “warm sound”? Probably not, because it does not have distortion levels of more than 1% unless it is driven to very high levels. Build it and see for yourself. So there you are. We have changed our stance (slightly) and published a valve preamplifier. It is still a long way from publishing a high-quality valve stereo amplifier which would cost lots of money for fairly average performance and not much power. And let us not mince words. While this mono preamp will probably sell quite well, to people wanting to satisfy their curiosity about valve circuits, its performance is still well below what can be achieved with a common low-noise op amp IC such as the LM833 which costs just a few dollars. Leo Simpson www.siliconchip.com.au Need something more than just computers? 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We’ve got them for Serial, Ethernet, Windows Based and Linux applications MicroGram Computers Ph: (02) 4389 8444 FreeFax: 1800 625 777 Vamtest Pty Ltd trading as MicroGram Computers ABN 60 003 062 100, info<at>mgram.com.au 1/14 Bon Mace Close, Berkeley Vale NSW 2261 All prices subject to change without notice. For current pricing visit our website. Pictures are indicative only. See all these products & more on our website...www.mgram.com.au SHOREAD/MGRM1103 Dealer inquiries welcome MAILBAG Misconceptions about copying music I’d like to raise some points regarding comments made in the October 2003 Publisher’s Letter and related comments in a letter to the editor from the same issue. The editorial questioned “Why buy a disc when you know you can’t make a direct copy for your own personal use?” This implies that it is OK to copy CDs for personal use. However, whereas the USA has “fair use” provisions in their copyright laws, we do not. Under Australian copyright law you are not permitted to make copies of music for any purpose – personal or otherwise – unless you first secure permission from the lyric and music copyright holders and the publishers. Using devices like MP3 players, digital jukeboxes and MD walkmen for their intended purpose is therefore technically illegal even though it’s legal to market and buy them. There is some irony when a large company markets these devices and music – one arm effectively encourages the breaking of copyright law while another aggressively pursues copyright violations. It’s deplorable that ARIA continues to do nothing to address issues created by new technology while providing no assistance to consumers wishing to “do the right thing” within the confines of our outdated laws. Consumers cannot be blamed for ignoring copyright requirements in this context – it’s infeasible to do otherwise. In the same issue, correspondent Simon Kareh stated that CD-R AUDIO discs cost more than “normal” CD-Rs “... due to the royalty factor ... which makes it legal for me to copy my copyrighted audio”. I don’t believe this is correct. There is no legal statement on “CD-R Audio” discs (or anywhere else) which says that, through the royalty factor, their purchase grants the right to put copyrighted material on them. Your editorial also mentioned legal challenges to copy protection overseas. I understand that these are all in the US and the basis of the challenges is that copy protection violates “fair use” 4  Silicon Chip copyright and “freedom of speech”. Unfortunately, since Australian law does not include either of these, any findings overseas will not be applicable here. There is a misconception that “fair use” copyright exists in Australia. At the same time, it’s frustrating that outdated copyright laws continue to be applied to new technology in often inappropriate ways. Lawmakers must be persuaded to initiate much-needed law reform so that new technology products can be legally used, but this will only happen when enough people are motivated to complain. This means that publications like SILICON CHIP should present the reality of the law rather than simply mirroring popular wisdom. Misrepresenting the law merely gives credence to the myths which continue to be accepted unconditionally by a vast majority of Australians. Jonathan Woithe, via email. Comment: you are quite correct in your view on the illegality of all copying in Australia and perhaps we should have alluded to this in the Publisher’s Letter. However, let’s be realistic, lots of people do it. It is the same thing with VCRs – no taping is allowed, but everyone does it. Stopping it will be impossible and if ARIA wish to keep their heads in the sand, then so be it. There have been many situations in the past where technology has made nonsense of the law and we see no reason to pompously tell people that something is illegal (it’s against the law!!!) when the law is ludicrous, inequitable and unenforceable. Until Copyright Law in Australia is changed to allow similar rights to that in the USA, it will remain a joke and most Australians will take no notice of it. Cheap CDs do not have world-class artists I would like to add a few comments regarding the Publisher’s Letter in the October 2003 issue. Two issues were raised, namely falling CD sales and secondly the difference in price between CDs. There are different reasons for declining CD sales. One is the fact that CDs last much longer than tape or vinyl recordings. Also when a fine music collector builds up his or her music collection there is little reason to buy another CD of the same piece. This is a different situation to that which existed before CDs, when a vinyl record was discarded after it developed too much surface noise. The degradation justified the purchase of a new LP. For those buying pop music, the reasons are different. New singers, styles and fashion have produced, in the past, a steady “cash cow.” Downloading pop music is often a financial necessity for the cash-strapped younger generation always being pressured to have the latest consumer fad. Also I have heard it said that many pop CDs only have two or three good tracks and the rest are rubbish. If that is the case, pop music enthusiasts can’t be frowned upon for downloading selected tracks. Therefore both types of music have suffered, but for different reasons. Regarding Naxos and other lowpriced labels versus the expensive labels, Naxos has many excellent CDs and I have many in my collection. However, Naxos do not have internationally famous singers such as Emma Kirkby, Luciano Pavarotti etc. Large recording companies like Decca and Sony compete strongly to sign up famous artists and as such have to pay them large sums of money. This is reflected in the CD prices. If you compare the playing of Bach’s Goldberg Variations from a little known pianist against Murray Perahia or the www.siliconchip.com.au legendary Glenn Gould, the difference is amazing. That is why serious collectors will pay two or three times as much for a CD that is going to give a lifetime of pleasure. Sony and the other major companies also have a budget line; these are ADD recordings from the 60s and 70s. You say that “production costs for a CD, case and booklet are around a dollar or so.” However the retail price of any item is many times the material cost. You must know that from publishing “SILICON CHIP.” It’s not all gloom and doom however. Although CD sales are down by approximately 10%, DVD music and video sales have increased by about 126% (from Australian Record Industry Association data) in 12 months. It remains to be seen whether these sales will be affected when DVD recorders become more affordable. As to your comment regarding the quality of MP3 vs CD, I doubt if sound quality is the prime consideration for many people. For many, but not me, I suspect convenience is the most important factor. On a different subject, keep up the good work on electronic projects, especially those using the Picaxes. John Hamilton, via email. Art approach to PC boards has benefits I read Part I of the PC Board Design Tutorial with interest. I have designed several PC boards for manufacture over the past year – two of them reaching a bestseller list. I have also designed PC boards for five well-known electronics magazines during the year. All of these were done with a simple art program and pen and ink. The reason for this is that I prefer the control that an art program and pen and ink give me over the design process – or perhaps I should say the different form of control they offer. They also give me an effective means of retracing my designs both conceptually and in their layout. The result, admittedly, is not as crisp as it might be but the designs are popular. There is a place – a large place – for a more sophisticated approach and the success of some of the software alone is proof of this. In this regard, the PC www.siliconchip.com.au Board Design Tutorial is a valuable mini-series. It gives a well written overview and no doubt concurs with the methods of most designers. At the end of the day, I believe that what matters is that authors and magazines, designers and manufacturers, are able to “meet each other”. Above all, that concept is not sacrificed for presentation, nor presentation, where it is important, for concept. Rev. Thomas Scarborough, Capetown, South Africa. Comment: designing one-off boards for your own use is fine using your approach. However, all boards featured in SILICON CHIP have to be compatible with a recognised PC board program such as Protel. No local PC board manufacturer would be interested in producing it otherwise. Art programs cannot produce drilling details, etc. DVD aspect ratios are not a problem Am I the only one who finds something wrong with this whole discussion about DVD aspect ratios? I fail to see the problem. If you do not want to see movies filmed for the theatre in their original format, simply zoom the DVD player to full height which will simply chop off the sides of the film. After all, this is what you see on commercial TV. The reason that dual format DVDs are seldom produced is that most, if not all, DVD players have the zoom feature. I would not call myself a purist yet I would rather see my movies in the format in which they were originally shot. I find the black bars above and below the picture a small price to pay for seeing the whole movie. It is not as if the people who designed Cinemascope et al did this to deliberately to irritate the watchers of DVD some 50 years hence. A purist is one who buys a projection TV, a surround sound system and builds a home theatre room. One who desires to see the whole picture is simply a movie lover. John Hancock, Morphett Vale, SA. High definition TV has lots of advantages I was a little disappointed at your editorial regarding digital TV in Australia. With attitudes like that it is little November 2003  5 Mailbag: continued wonder that DTV has been “slow” to get accepted. I have had a HD-STB for the last 12 months now and cannot crow enough about the advantages to family and friends. The picture and sound quality are truly amazing, with perfect recep­ tion (once a quality aerial and coax are used). The quality of the STB is a different issue. The main reasons that DTV does not have greater market penetration are that 95 out of 100 people that I talk to have not even heard of DTV. STBs are very thin on the ground and sales “droids” are not trying to sell them. I don’t think they yet understand the technology and are therefore scared to push the technology in case they get asked a technical question. After setting the wheels in motion and then changing the rules a bit, the government seems to have backed away from DTV. The future is very bright for digital TV, whether it is standard definition or high definition, 5.1 surround sound or stereo and it will be the only FTA TV that you can watch in five years time! I think some positive and informative articles are well and truly needed and you have the perfect forum to get this information to the masses. David Williams, via email. Comment: There is no argument about picture quality. Standard definition is pretty good and HD is even better. However, you need one for each set in the home (most people with multiple sets watch different programs). You also need another decoder for the VCR if you want to record another channel off air. This adds up to a lot of money, even if decoders have now come down a long way in price. Surround sound encoding is another issue which is yet to be properly addressed. Digital TV looks good I agree with Leo Simpson’s Publisher’s Letter in the July 2003 issue, entitled “Digital TV Is A Complete Failure” but only up to a point. Yes, the uptake and functionality of Digital TV may be slow but what he neglected 6  Silicon Chip to say was just how good it is. I have worked in television (ABC) for 38 years and have seen the most incredible changes from valves to transistors, integrated circuits and digital. The change from analog to digital has seen the video signal-to-noise improve by more than 10dB. This produces noise-free pictures (>50dB S/N) for the first time. Putting aside the technical details, I have a decoder (STB) for off-air TV digital reception and a DVD player, both connected to a wide-screen 100Hz 76cm TV. The pictures are stunning. The off-air TV signal, when showing a wide-screen movie, is as good as a DVD. Movies that are originally film-based produce the best results. The picture quality is difficult to fault. Pictures produced from electronic cameras, such as the AFL football, do have some interesting characteristics. For example, green grass does not reproduce too well with its fine detail and tends to look like smooth carpet. It appears that there are limitations with the digital signal when it comes to some fine video detail. In conclusion, wide-screen digital TV with standard definition is very good and I have got used to noisefree, crystal-clear pictures, with no 50Hz flicker. When I see the same picture on a 4:3 analog TV, it is way down in quality. Standard definition wide-screen digital TV is a big winner for me. Will McGhie, Perth, WA. Newsgroups can be good I am 14 years old and I have a great interest in electronics and especially robotics. Ever since I took apart my dad’s old stereo when I was eight years old, I have had a fascination with anything electronic. I have recently set up my own website (www.cbuzz.zapto.org) completely from scratch and I have added a discussion board for people to chat about electronics, robots and computers. I have not had much traffic yet but I disagree with some of the Editor’s comments in the September 2003 issue. I have been on many discussion boards to find answers to problems (or just to trawl for interesting info) and I can say that there isn’t a whole lot of disagreeing going on. Some pages are filled with personal experiences of the same problem, which can make it a little more difficult to find your answer, but most of the time it takes under 10 minutes to find exactly what you need. Also, there are some circuits published on these boards – not many – but I think it is a given that you use it at your own risk. The quote “definitely not to be trusted” is a bit harsh for the people who run the boards, like me. Of course, this is one person’s point of view but I would like to hear some other people’s comments – on my forum perhaps? Thanks for a great magazine – I have read mine until they are dog-eared. You guys publish one of the last good magazines in the world that caters for everyone! Callum Martin, via email. Older DVD players may not work with latest releases I recently picked up my few-yearsold DVD player from the repairer where it had been for the correction of a power supply fault. Almost as a matter of casual interest, he pointed out that this machine would not play recent DVDs, particularly productions such as “Sea Change” and “Rabbit Proof Fence” which as an Austra­lian, I might expect to want to watch. In the ensuing discussion, it appears that changes are constantly being made to the software applied to the DVDs which means that unless you have the latest player, you may not be able to play them at all. This is going to cause a big backlash sure­ly. Even the despised Microsoft offers backward compatibility and keeps some reasonable semblance of control on the software up­dates. Several questions arise from this: (1) Who is responsible for telling buyers that the machine they buy will work up to a certain software release? Who establishes the releases anyway? www.siliconchip.com.au (2) Should buyers be told whether their machines can be upgraded (apparently some can’t), how it can be done (chip change, soft­ware upload) how much and whether it is covered under warranty? (3) Should software changes have backward compatibility so that older players can play newer DVDs without the latest features? (4) Should there be markings on both players and DVDs so that consumers can see when they buy a DVD that they might not be able to play it on the DVD player they already have at home. While the situation may sort itself out ultimately, it could do a lot of harm to the industry. It will assist pirates since there is likely to be a market for DVDs which will run on existing players, thereby saving their owners the need to upgrade their player every year, few months, or whatever. Bob Lions, via email. Comment: this looks like a nasty little problem. Can any reader throw more light on this subject? Krypton bike light approach works with Luxeon Star I found your May 2003 article on the Luxeon LEDs most interesting and purchased the 1W Star/O, the 5W Star V Portable and an extra collimator. As well as for general interest, I wanted to investigate the suitability of these LEDs for bicycle lighting (I often ride morning and night, in the dark), to reduce the battery size requirements. However, while the Luxeons are indeed awesome, I was quite disappointed with the ‘reach’ of the LEDs. My commercial bike light with a 5W bulb totally swamps even the 5W LED (fitted with collimator) illuminated area. There was another unexpected side effect – even though you couldn’t see where you were going, oncoming traffic would be blinded by the glare! The problem is that the beam is much too divergent for my intended application, even with the collimator carefully adjusted (only a small effect). Then your September 2003 Krypton Bike Light article came to the rescue. I happened to have an old plastic lens mounted in a 50 x 50mm square plastic frame (focal length about 125mm) and placed this in front of the 1W LED www.siliconchip.com.au (fitted with collimator). Hallelujah (to use your phrase) – by spacing the lens about 130mm from the face of the Star/O collimator, almost all of the diverging light was captured within the lens area and a bright disk of about 900mm diameter was projected onto a wall 9 metres away! The 1W LED brightness approached that of my 5W (very high quality) bulb light. The 5W Luxeon is a shoe-in. Not only that, virtually no glare at all was evident when approaching the light, unless you enter the direct beam. Actually, this could be somewhat a disadvantage as well. The light is almost invisible from only a few degrees off-axis, whereas my commercial light throws a narrow rectangular horizontal beam together with low intensity side lobes to provide visibility for traffic approaching from the side. Another disadvantage – the lens used creates the need for an excessively long housing but a shorter focal length lens may diffuse the beam too much (a long focal length 3-dioptre inspection lamp lens created a much smaller spot at 9 metres). Anyway, food for thought. By the way, my bike weighs in at 7.5kg, so a 1.4kg battery pack is a bit out of proportion! Ian Thompson, Duncraig, WA. Halogen lighting is very questionable With reference to the Publisher’s Letter in the June 2003 issue, it was gratifying to see someone publicly air the negative side to those wretched domestic halogen lights. I was beginning to think I was the only ELAN Audio The Leading Australian Manufacturer of Professional Broadcast Audio Equipment one who detested them. It is hard to understand their popularity unless the industry has been pushing them as giving better lighting (very questionable), chic (why?), safer (how? – possibly the reverse) and more economical (rubbish). Still, they seem to be the done thing: when my new house was built about three years ago, the electrician seemed quite taken aback when I insisted on not having lots of those piercing little spotlights and a ceiling full of transformers! As you point out, the waste heat from these needlessly complicated setups must at times be enough to affect the comfort of the house occupants. This does seem perverse at a time when authorities are insisting on declared energy ratings for domestic appliances and increased insulation for hot water systems, and when even such relatively small wastage as the stand-by power used by TVs, VCRs, etc has been questioned. Brian Wallace, Dora Creek, NSW. SC480 amplifier is great I wish to compliment you on the new SC480 amplifier design in the January & February 2003 issues. I have put together a stereo amplifier and am completely satisfied with the result. The sound is detailed, clear and “musical”, and with no input signal it is completely silent at full volume. Through speakers it is good but even better through headphones using a resistor network to give 120Ω impedance. Rob Rein, via email. 2 Steel Court South Guildford Western Australia 6055 Phone 08 9277 3500 Fax 08 9478 2266 email poulkirk<at>elan.com.au www.elan.com.au RMA-02 Studio Quality High Power Stereo Monitor Amplifier Designed for Professional Audio Monitoring during Recording and Mastering Sessions The Perfect Power Amplifier for the 'Ultimate' Home Stereo System For Details and Price of the RMA-02 and other Products, Please contact Elan Audio November 2003  7 Electronic Noses Smell a Big Future By PETER HOLTHAM 8  Silicon Chip Of our five senses – sight, sound, touch, smell and taste, the first three are physical in nature. They also have readily available electronic equivalents. You can buy cameras, microphones and pressure sensors off the shelf to convert light, sound and pressure into electrical signals. Soon, smell sensors will be readily available too. www.siliconchip.com.au S mell and taste are chemical senses, so-called because they detect the presence of different chemicals as molecules in the air (smell) or dissolved in liquids (taste). At present, electronic sensors for both are in their infancy. Smells are simply chemical molecules small enough and light enough to vaporise into the air. A smell may be just one type of molecule or a mixture of many different types. Over 600 different molecules wafting into your nose make up the delicious aroma of fresh coffee, for example. Smell is a vital part of our daily lives and it uses more of the brain than any of the other senses. Smell lets us sample our surroundings and check for danger. Think of the smell of smoke, for example. Molecules of smoke can travel long distances on the wind, showing that smell can act as an early warning system. Even though the human sense of smell is poor compared with many animals, we can easily detect just parts per billion of the toxic gas hydrogen sulphide – the smell of rotten eggs. With training and experience, human noses can check products such as wine, cheese, fish and many other foodstuffs, for quality and freshness. Doctors can diagnose certain diseases from their smell alone. Human noses are sensitive and self-repairing but they are not suited to boring or repetitive tasks. They are also subjective, prone to catching colds and cannot be used to check situations that may be hazardous. Humans cannot smell the fatal presence of carbon monoxide, for example. What we need is an electronic or E-nose, to give an objective readout of the smell-scape that surrounds us. Scientists have been working on E-nose development since the 1980s, their first step being to understand how our biological sense of smell works. How do volatile odour molecules reaching your nose trigger recognition of a smell in your brain? Smell molecules swirl past the turbinate bones to reach the human smell sensors. the eyes, lies the nasal epithelium containing about 5 million smell sensor cells. By comparison, the super-sensitive noses of dogs contain over 100 million sensors. At one end of each sensor cell there are 10 to 20 hair-like smell receptors, bathed in watery mucus. Smell molecules attach to the receptor proteins in the hairs, triggering a cascade of chemical reactions inside the cell. The reactions result in the transfer of sodium ions across the cell membrane in a form of biological amplification. At the other end of the sensor cell there is a connecting nerve or ‘wire’ called an axon. The sodium ions pour into the axon, triggering it to fire with an electrical impulse. Chemical information is now an elec- trical signal on its way to the brain for identification. Bundles of axons from groups of sensors thread their way through holes in the base of the skull. The bundles terminate in two olfactory bulbs, one in each nasal cavity. Inside the bulbs, a cluster of neural networks called glomeruli carry out some signal pre-processing. They function much like Internet routers, sending the electrical impulses for specific smells via mitral cells to the brain. The architecture of the olfactory bulbs results in a 1000 to 1 convergence between individual sensors and the mitral cells. A lot of information about individual sensors gets thrown away but sensitivity increases since contributions from many sensors are The Biological Nose Sniffing sucks a sample of air carrying a smell into your nostrils. A mucus layer on their inner surfaces together with a forest of sticky hairs cleans the air of any stray dust particles. The filtered air swirls past the turbinate bones to the roof of each nostril. Here, just below and behind www.siliconchip.com.au Simplified diagram of the biological smell sensing system. November 2003  9 to appear everywhere smell detection is important. Conductivity Sensors There are two types of conductivity sensor: metal oxide and polymer. Both show a change in resistance when exposed to odour molecules. Thick film metal oxide gas sensors (TGS) have been around since the late 1960s; you can buy them off the shelf from component retailers. They are sintered n-type bulk semiconductor devices made of tin dioxide. The sensor changes in resistance in the presence In a conductivity sensor the resistance of the sensing layer changes when a molecule of gases such as hydrogen, reacts on the surface. carbon monoxide, methane, propane etc. added together. Just 0.1% propane by volFinal signal processing occurs deep ume is enough to decrease the resistin ancient parts of the brain concerned ance of a TGS gas sensor up to 20 times. with motivation, emotion and certain This concentration is well below the types of memory. Actual identification explosive limit for propane. of the smell occurs in the brain’s more The trouble with metal oxide senmodern frontal cortex. sors is that they are not particularly selective and are easily poisoned, esE-Noses pecially by sulphur compounds. They Electronic nose designers are fol- also need a continuous power supply lowing Nature’s plan. They use a of over 500mW to heat up the sensor. sampling device to act as nostrils and Nevertheless, they have found wide an array of chemical sensors to mimic use as gas leak detectors. the olfactory epithelium. Signal proThin film metal oxide sensors using cessing hardware and software takes silicon micro machining methods are the place of the olfactory bulbs and now starting to appear. They use oxthe brain. ides of tin, zinc, titanium and iridium, The difficulty lies in the sensor doped with catalysts such as platinum stage. Until recently the only way and palladium. A micro hotplate to analyse a sample of air was by structure reduces heater power by a using complex and expensive labo- factor of 10, compared with thick film ratory-based instruments such as gas devices. Because thin film sensors chromatographs. Routine analysis of are now being made in high volumes smells with this technology is out of (1000-2000 per silicon wafer) the cost the question. But now new smell sen- per sensor is falling rapidly. sor technologies based on conductivity A second type of conductivity or resonance are beginning to appear. If they can be integrated into low cost chips or modules, E-noses will start Conductivity sensors manufactured by AppliedSensor (www.AppliedSen-sor. com) – micro sensor (left) and thick film sensor (right) . 10  Silicon Chip The AppliedSensor quartz crystal microbalance sensor. The diameter of the crystal is 6 mm. sensor is based on polymers. Cyrano Sciences uses this technology in its “Cyranose 320 handheld electronic nose”. Conductive carbon black is blended homogeneously with different non-conducting polymers. The different blends are deposited between pairs of electrodes as thin films on an alumina substrate. The result is an array of typically up to 32 chemiresistors. When odour molecules come into contact with the resistors, the polymers act like a sponge and ‘swell up’. Swelling progressively breaks carbon black pathways and the resistances increase. Once the smell goes away, the polymers ‘dry out’ and shrink, the conductive pathways rejoin and the resistances decrease. The ratio of the smell-on to smell-off resistances becomes the output of the sensor array. Any individual sensor responds to a variety of odour molecules. By varying the amount of carbon black in the polymer or the polymer itself, an array of sensors can be built to yield a distinct pattern of resistances for different odours. The cost of polymers and carbon Internal details of the AppliedSensor micro conductivity sensor (left) and thick film conductivity sensor (right). www.siliconchip.com.au The principle of the QCM sensor. black is low and the electronic interface is simple, making this ideal portable E-nose technology. An array of 32 sensors per chip is a long way short of human sensing capability but still allows reliable smell recognition with suitable software. gram. That amount of methane in a one-litre container gives a concentration of just 1.4 parts per billion. QCMs can be made to respond to different smells simply by changing the polymer coating but they are most sensitive to volatile organic compounds. The Surface Acoustic Wave (SAW) sensor is a cousin of the QCM, operating at a much higher frequency. An AC signal applied to the input creates an Piezoelectric Sensors This family of sensors also has two members: quartz crystal microbalance (QCM) and surface acoustic wave Polymer sensor principle. (SAW) devices. QCM types consist of a quartz crystal disk a few millimetres acoustic wave that ‘surfs’ over the in diameter with metal electrodes on surface of the sensor to the output. each face. The QCM resonates at a fre- Although the AC signal is recreated quency in the range 10-30MHz when at the output, it is shifted in phase. The phase shift depends on the mass excited by an oscillator. During manufacture, a thin polymer of the sensing polymer layer covering coating is applied to one face to act as the sensor substrate. This in turns the sensing material. Odour molecules depends on the odour molecules adsorb onto the polymer, increasing absorbed. A typical SAW sensor operates at the mass of the QCM and reducing its BITSCOPE AD 9/10/03 1:38 PM Page 1 resonant frequency. QCMs can detect 400MHz but its sensitivity is similar mass changes of as little as one pico- to the QCM. Because SAW devices The Electronic Sensor Technology zNose® using fast gas chromatography with a SAW sensor. can be made using standard semiconductor technology, they are cheaper than QCMs. An American company called Electronic Sensor Technology has already developed the zNose, which combines fast (10 seconds) gas chromatography with a SAW sensor. The main disadvantage of this family is that more complex electronics are needed compared with conductivity sensors. Mosfet Sensors Metal oxide silicon field effect transistors (Mosfets) can be also used as odour detectors. The gate electrode is coated with a catalyst such as platinum and exposed to the air through a window. Smell molecules react with the gate, altering the gate charge and thereby varying the conductivity of the device. The gate and drain of the transistor are connected together to form a 2-terminal device. The voltage (around 2V) at constant current (100µA) is recorded as the sensor response to Digital Oscilloscope Logic Analyzer + from 5 $59 ANALOG = DIGITAL Convert your PC into a powerful Scope and Logic Analyzer! Now you can analyze electronic circuits in the analog and digital domains at the same time. BitScope lets you see both analog AND digital logic signals to find those elusive bugs. USB and Ethernet connectivity means you can take BitScope anywhere there is a PC or Network. BitScope Hardware • 100MHz Input BW • 40MS/s Sample Rate • Dual 32K Buffers • 4 Analog Inputs • 8 Digital Inputs • Waveform Generator • SMART POD Probes www.siliconchip.com.au BitScope Software • Windows or Linux • TCP/IP Networking • Advanced DSP • Digital Scope • Analog Scope • Logic Analyzer • Spectrum Analyzer Applications • Electronics Labs • Remote data logging • Engineering students • Scientific research • Robotics and control www.bitscope.com USB or Network connection to Windows and Linux PCs! November 2003  11 The Cyranose® 320 portable E-nose manufactured by Cyrano Sciences (www. cyranosciences.com), photo courtesy of Cyrano Sciences. The AppliedSensor MOSFET sensor construction. An AppliedSensor 1.5mm x 1.5mm MOSFET sensor chip on a TO8 header. the smell. These sensors respond to gases like hydrogen, hydrocarbons, ammonia and carbon monoxide. With a silicon carbide substrate instead of plain silicon, Mosfets can operate at temperatures up to 600°C, as in car exhausts, for example. Processing the Signals Sensors are just part of the E-nose story. Adding the electronic equivalent of olfactory bulbs and the brain turns the raw sensor data into a recognised smell. Two stages are normally required: signal pro-cessing and pattern recognition. Signal processing compensates for baseline drift and reduces sample-to-sample variation. The signals from an array are often also scaled or normalised to cover a similar range. Pattern recognition is the crucial step in identifying a smell from the processed data. Firstly, extracting some features from the data reduces the dimensions of the measurement space. Consider the 32 outputs of a conductive polymer sensor chip. The measurement space will have 32 dimensions. This can cause problems in analysis of the responses, not the least of which for humans is trying to visualise a 32-dimensional hyper-space. Often the sensor responses will overlap, so there is a lot of redundan12  Silicon Chip cy in the 32 dimensions. Complex mathematics are used to project the 32 onto a smaller space, preferably in two or three dimensions which can be visualised by humans. Once in a lower dimensional space, the odour pattern can be classified by comparison with known smell responses stored in a database. Here again, complex mathematical techniques such as artificial neural networks are used. These ensure that an unknown smell is matched to the most likely known smell in the database, even if the match is less than perfect. Applications With new chip level sensors becoming available and abundant computing power to process the responses, where are the E-nose applications? The answer is almost everywhere, your car could soon have several, your home several more. A silicon carbide Mosfet exhaust gas sensor can respond fast enough to monitor the air-fuel ratio of individual cylinders in a car. Thin-film conductivity sensors will soon be monitoring cabin air quality, opening and closing fresh air vents as required. In the home, sensors will also monitor air quality, sniffing out carbon monoxide, an early indicator of a fire. One day soon they might find their way into your coffee machine to check that your morning cup is just the way you want it. E-noses are finding widespread use in the food and drink industry. Customers rely on aroma as an indicator of the quality of the food they buy. E-noses are already monitoring the exact ripeness of fruit and vegetables and the quality of fish, cheese, meat and many other foods. Doctors have used smell as a diagnostic tool for centuries. Commercial E-noses are already being tested for rapid diagnosis of lung cancer. They are also being used to screen bacterial cultures for early detection of lethal bugs. Recent events have made everyone aware of terrorism. A major force behind E-nose development in the USA is the need to replace sniffer dogs checking for explosives. Smell sensing technology is still in its infancy but the hardware and software are now starting to appear. More research and development is required but the day of low cost electronic noses all around us is fast approaching. SC Acknowledgement The assistance of Olivia Deffenderfer, Applications Scientist at Cyrano Sciences and Jan Mitrovics, Executive Director Germany, at AppliedSensor GmbH with the preparation of this feature is gratefully acknowledged. The response of an AppliedSensor MOSFET sensor to exhaust gas composition, showing gas from individual cylinders. www.siliconchip.com.au Order Form/Tax Invoice Silicon Chip Publications Pty Ltd ABN 49 003 205 490 PRICE GUIDE- Subscriptions YOUR DETAILS Your Name________________________________________________________ (PLEASE PRINT) Organisation (if applicable)___________________________________________ Address__________________________________________________________ (all subscription prices INCLUDE P&P and GST on Aust. orders) Please state month to start. 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SUBSCRIBERS QUALIFY FOR 10% DISCOUNT ON ALL SILICON CHIP PRODUCTS AND SERVICES# #except subscriptions/renewals and Internet access Qty Item Price Item Description Total TO PLACE YOUR ORDER P&P if extra Total Price $A 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 11-03 Logging your every driving moment Some airbag controllers do more than just trigger the bags! – by Julian Edgar Did you know that the airbag control module in your car could be constantly logging a range of driving factors – includ­ing your speed? If the proliferation of speed cameras and red-light cameras isn’t enough to make you drive carefully, perhaps that piece of news just might! 14  Silicon Chip C ONSIDER THIS SCENARIO – you’ve just collided with the back of another car because you weren’t paying attention. However, you won’t be able to claim that you were braking hard if an electron­ ic record shows that you didn’t begin to slow down until the moment of impact. Or perhaps you were speeding? Once again, the electronic record will reveal all to crash investigators. Convicted by your car? – it’s more than just a possibility, with one such case having already occurred in the US. There, a driver involved in a double fatality claimed he had been travell­ing at about 100km/h. However, the electronic record logged by his vehicle’s airbag showed that his speed just five seconds before impact was, in fact, 184km/h! So what data is logged and why is it recorded? Do all air­bag-equipped cars have this facility? How can you read it? And who owns the information? The implications – not only for drivers but also for in­surance companies, the police, car rental companies and fleet owners – are profound. But if the thought of your car logging your driving behaviour horrifies you, here’s a let-off – at least for the time being. At this stage, General Motors in the US appears to be the only car company that’s wholeheartedly embrac­ing the technology. www.siliconchip.com.au In fact, GM is publicly releasing details on their systems and also working with a third party provider to make available a dedicated data reader for general purchase. The potential benefits of Event Data Logging (EDL) has also resulted in strong US Government support for adopting universal standards for such systems. In other words, due to the influence of US legislation on car makers, it’s probably only a matter of time before all cars have Event Data Logging recorded in a stan­dard format that can be easily read. Airbags have saved many lives since they were first introduced. [DaimlerChrysler] Automotive logging About 20 years ago, the fuel and ignition control in cars started a move from mechanical systems (carburettors and points) to electronic systems (EFI and electronically con­ trolled ignition). These electronic systems rely on sensors to measure various parameters, such an engine airflow, engine speed and throttle position, with an Electronic Control Unit (ECU) then making decisions about the fuel injection pulse width and igni­ tion timing. Most of these systems have the ability to detect and store faults in memory so that they can be later read out and diagnosed. It comes as no surprise then that the airbag control system not only has the ability to store data but also uses a wide variety of sensors as part of its decision making process. Howev­ er, the use of the controller as an Event Data Recorder (EDR) goes a step further – not only are fault codes stored but in some systems, the outputs from a variety of sensors are also continu­ ally logged. Early development So how did this come about? The story goes back to the early 1970s, when the US National Transportation Safety Board recommended that vehicle manufacturers gather information on vehicle crashes using on-board collision sensing and recording devices. As a result, since 1974, General Motors (GM) systems have recorded data for impacts that resulted in the triggering of the airbag (a “deployment event”), while other systems were also introduced that could additionally record “near deployment” events. Subsequently, in 1999, GM introduced a system that could also record pre-crash data – ie, data is recorded www.siliconchip.com.au to a buffer on a continuous basis and overwriting ceases immediately if a crash occurs. Ford in the US started installing EDRs in one model in 1997 and by 1999 nearly all its US models were so equipped. A range of other manufacturers either admit to some data recording or are looking to implement such strategies. Rather than use airbag control systems to record crash and pre-crash data, some US-manufactured heavy trucks use the engi­ne’s ECU instead. For example, Cummins, Detroit Die- sel and Cater­pillar all use electronic control systems on their diesel engines which also log driving data. The GM airbag system The information recorded by GM airbag systems includes data for both deployment and near deployment events. A near deployment event (ie, one where the airbag doesn’t inflate) is defined as an event that’s severe enough to “wake up” the algorithm within the control unit (an algorithm Airbag control systems read the crash deceleration pulse and decide whether to inflate the airbag(s). However, it is easy for a manufacturer to also implement logging of vehicle speed, the change in speed and other aspects such as whether the brakes are applied. [Bosch] November 2003  15 This GM airbag controller contains a full Event Data Recorder. The data logged just before and during the crash can be read either directly from the module or if the wiring is intact, from the car’s diagnostic port. [Vetronix] is used to analyse the severity of the crash pulse; ie, the control unit uses the shape and magnitude of the deceleration pulse it is undergoing before deciding whether or not to fire the airbag). Two different systems are used by GM; one stores data on the near deployment event which had the greatest change in road speed, while the other stores the most recent near deployment event. In both cases, the following data is recorded: • Driver’s Seat Belt: this is recorded as buckled or unbuckled. However, this may be recorded incorrectly if power to the unit is lost during the crash. • SIR Warning Lamp: the on/off status of the Supplemental In­flatable Restraint warning lamp is recorded. • Change in Forward Velocity: this is determined by integrating the average of four 312μs acceleration samples and is recorded in RAM every 10ms. Depending on the module, either 300ms or 150ms of this data is available. • Time To Deployment: the time in milliseconds between the start of the event (ie, enabling of the algorithm which requires two consecutive acceleration samples of over 2g) and the command for the airbag deployment. • Time Between Events – the time in seconds between a deployment event and a near deployment event, if that time is less than five seconds. • Vehicle Speed: the pre-crash speed, recorded every second for five seconds prior to any event. This information is derived from the vehicle speed sensor. • Engine RPM: engine speed, as derived from the engine manage­ ment system. As with vehicle speed, it is The BMW airbag module. The extent to which various manufacturers are logging real-time data is largely unknown but it’s possible that this unit already has this capability built in. [BMW] 16  Silicon Chip recorded every second for five seconds prior to any event. • Throttle Opening: the percentage that the throttle is open, where 100% is wide open. This information is sent by the engine management system along with engine and vehicle speeds and is again recorded every second for 5s prior to any event. • Brake Status: brakes on/off, as derived from the ABS or engine management unit every second for 5s prior to any event. Braking intensity is not recorded. • Data Validity: a check that none of the four pre-crash parame­ters (vehicle speed, engine rpm, throttle opening or brake sta­tus) is out of range or has logged faults. In addition, the number of ignition key cycles at the time of the events and at the time of download is logged, as is wheth­er or not the passenger-side front airbag has been manually switched off. One of the two GM EDR units is designed so that 150ms after the deployment algorithm has been enabled, all the data stored in the memory is permanently written to EEPROM. It then cannot be erased, cleared or altered, so this type of device must be re­placed after an airbag deployment. As a matter of interest, the Ford system records both longitudinal and lateral acceleration, the deployment strategy for the dual-stage airbag, The same control module that's used to deploy the airbags can also be used to log vehicle data before, after and during a crash. Such systems could be in widespread use in just a few years. [DaimlerChrysler] www.siliconchip.com.au seat-belt use, pretensioner operation and the fore-aft position of the driver’s seat. One reason that data from the GM system is being widely used in crash research is that the company licensed the Vetronix Corporation to build a data retrieval tool for their EDR as far back as 1999. Ford subsequently followed suit for their own EDR system. The Vetronix Crash Data Retrieval (CDR) tool consists of both hardware and software. The hardware component comprises an interface between the vehicle’s diagnostic connector (or the EDR itself where the vehicle wiring has been damaged) and a PC. In operation, the CDR system reads the hexadecimal code stored in the EDR and converts it to engineering units, making it available in both tabular and graphical forms. And the cost of this unit? – about $US2500. Data usefulness EDRs improve crash analyses, both by simplifying and im­proving the accuracy of the reconstruction process. This results in more detailed and more accurate conclusions. Table 1 summar­is­es the information available to crash investigators with and without EDRs. Before EDR, crash investigators could only rely on vehicle damage and other obvious physical signs like skid marks (less likely with ABS) in order to make major judgements. So logged data on vehicle speed and other parameters can be enormously useful. Data validity So how good is the data collected via an EDR? The answers to that question are surprisingly broad; certainly there is plenty of information available for someone who wants to fight EDR evidence in a court of law. However, on the other side of the fence, if used carefully, the data gained from an EDR is invaluable when it comes to determining the events that oc­curred before and during the crash. So just what are the potential problems? They are as fol­lows: • Problem 1: vehicle speed, engine rpm, throttle opening and brake status are logged only once per second – a sampling fre­quency that’s much too low when analysing many types of crashes. For example, did the driver brake at 3.1 or 3.9 seconds before www.siliconchip.com.au Table 1: Information Available without EDR Human Vehicle Pre-Crash Skid marks Crash Calculate change in velocity Post-Crash Crash damage Environment Environment after crash Table 2: Information Available with EDR Human Vehicle Environment Pre-Crash Seatbelt use; Throttle input; Braking Road speed; Engine speed Conditions during crash Crash Airbag data; Seatbelt pretensioners Crash pulse; Measured change in velocity; Airbag inflation time Location Post-Crash Automatic crash notification* Automatic crash notification Automatic crash notification* *Automatic crash notification refers to systems which can automatically alert authorities (eg, by mobile phone) when an accident occurs and give the location. impact? The difference is major. Additionally, this data is not synchronised with the start of the crash data and is potentially offset from the crash data by up to one second. • Problem 2: the recorded data goes back only five seconds before the algorithm enable event occurs. There is no record of vehicle behaviour earlier than this – behaviour which might show erratic driver inputs, for example. • Problem 3: the use of only five data points for each of the speed, rpm, throttle opening and brake status parameters can give a false impression; eg, if the data is plotted on a graph, with the various points connected by a straight line. In reality, the true values of any of these parameters might have been quite different between the discrete points, compared to the values indicated by the graphs. • Problem 4: most EDRs record Potential Benefits of Event Data Recorders (1). Real Time Assistance: the use of EDR data in conjunction with Automatic Collision Notification systems would aid in quick­ly locating crashes and despatching emergency personnel with better crash information in advance. (2). Law Enforcement: obtaining impartial EDR data from a colli­sion would help in more accurately determining the facts sur­rounding the incident. (3). Government Initiatives: the collection of EDR data would enable governments to introduce effective initiatives to help reduce fatalities, injuries and property loss. (4). Vehicle Design: EDRs allow manufacturers to collect accu­rate data to monitor system performance and improve vehicle design. (5). Highway Design: the use of EDR data can assist in assessing highway roadside safety and managing road systems. (6). Insurance/Legal: Additional objective data provided by EDRs advance quicker and fairer resolution of insurance and liability issues (7). Research: EDR data could provide objective data for re­searching driver behaviour and performance, as well as other research related topics. (8) Owners/Drivers: EDRs can help fleet owners and drivers monitor vehicle and driver performance, to ensure the safe and efficient movement of people and cargo. Canadian Multidisciplinary Road Safety Conference, 2001. November 2003  17 Pre-Crash Graph GM Airbag Module This dedicated reader is designed to work with GM and Ford EDR systems. It costs US$2500, putting it within easy reach of pro­fessional crash investigators and researchers. [Vetronix] Fig.1: this is a sample of the pre-crash data that is logged by the GM system, as read out using the Vetronix Crash Data Retrieval tool. Throttle opening, engine and road speed, and the on/off status of the brake switch are logged at 1-second intervals for the five seconds before the crash. [Vetronix] Post-Crash Graph GM Airbag Module Fig.2: during the crash, the change in speed is logged every 10ms, to allow a detailed examination of the impact behaviour. The airbag system’s acc­el­erometer is used in this process. [Vetronix] speed only in a longitudinal direc­ tion. However, many accidents also involve lateral as well longitudinal movement and so the speed recording may give a false impression of the events that occurred. No current original equipment EDRs record vertical accelerations. • Problem 5: where the crash does 18  Silicon Chip not involve a major decelera­tion – eg, when a large truck hits a small car or when a pedes­trian is run over – the EDR may not record the event at all. • Problem 6: vehicle speed, engine rpm, throttle opening and brake status all depend for their accuracy on sensors and/or switches. However, vehicle speed and throttle position sensors can vary by up to 10% in accuracy, a point that seems to have been overlooked by some researchers. Other research A great deal of work has gone into testing the relationship between the data gathered from EDRs and that gained through other logging techniques. One approach is to measure the vehicle’s change of velocity using the EDR and compare that figure with the crash test impact speed. A series of Canadian tests has shown that there is usually fairly good agreement between the calculated and actual speeds – eg, an actual impact speed of 40.3km/h and an EDR-calculated speed of 42.4km/h. Typically, the EDR showed a slightly higher speed because it was affected by the car bouncing back off the barrier after the collision. However, one test involving a 2000 Ford Taurus had a sig­nificantly greater difference between the actual (47.8km/h) and EDR (53.6km/h) speeds. The testers suggested that this discrepan­cy had been caused by a spike in the acceleration/time curve, caused by structural deformation in the area where the EDR was mounted. A major discrepancy also occurred in another test, where a 1988 Chevrolet Cavalier’s EDR lost power during the crash. The independently measured test speed was 64.8km/h but the EDR showed 56.8km/h. Away from the laboratory, the usefulness of the data – even with these reported inaccuracies – can be clearly demonstrated. In one case, an 83-year-old male driver of a 2000 www.siliconchip.com.au Analysing An Accident Table 3: System Status At Deployment SIR Warni ng Lamp Status Off Driver's Bel t Swi tch C i rcui t Status Passenger Front Ai r Bag Suppressi on Swi tch C i rcui t Status Igni ti on Cycl es At Depl oyment Unbuckl ed Ai r Bag N ot Suppressed 187 Igni ti on Cycl es At Investi gati on Time From Al gori thm Enabl e To Depl oyment Command C ri teri a Met (ms) Time From Al gori thm Enabl e To Pretensi oner Depl oyment Command C ri teri a Met (mil liseconds) Time Between Near Depl oyment and Depl oyment Events (seconds) Time (millisceonds) Recorded Velocity Change (MPH) Time (millisceonds) Recorded Velocity Change (MPH) 213 18.75 18.75 N/A 10 20 30 40 50 -1.54 -3.07 -3.51 -5.27 -7.68 160 170 180 190 200 60 70 80 90 100 110 120 130 140 150 -10.09 -12.29 -16.24 -21.50 -27.86 -32.69 -39.93 -42.78 -43.44 -44.32 210 220 230 240 250 260 270 280 290 300 -44.98 -45.42 -46.07 -46.95 -47.17 -47.17 -47.17 -47.17 -47.17 -47.17 -47.17 -47.17 -47.17 -47.17 -47.17 Pre-Crash Data - Electronic Data Validity Check Status = Valid Time Before A lgorithm Enable -5s Vehicle Speed (MPH) Engine Speed (RPM) Throttle Position (%) B rake Switch Status 57 4032 100 Off -4s 65 4160 70 Off -3s 62 2304 2 On -2s 55 1088 2 On -1s 47 896 2 On Buick Century was negotiating a righthand curve when he ran off the road, travelled down an embankment into brush and tall grass, then crossed a level section of lawn and a gravel driveway before finally colliding with two large rocks. The car came to rest approximately 140 metres from where it left the road. Pre-crash data obtained from the EDR indicated that the driver wasn’t operating the throttle or the brakes for at least five seconds prior to the impact with the rocks. At the crash scene, the driver was lethargic and he subse­quently died in hospital. An autopsy showed that he had died from the results of a brain haemorrhage that had occurred while he was driving – a diagnosis well supported by the EDR data. Conclusion If the US success at implementing onboard diagnostics in cars is repeated with EDR, it’s very likely that all new www.siliconchip.com.au cars will have accident crash logging in 5-10 years. So if you are ever involved in a car crash and there’s some debate about Table 3: this is a summary of the data that can be gained from GM’s EDR. Note that the driver’s seatbelt was undone and that the vehicle was travelling at 47mph (76km/h) at impact. This can be seen both in the vehicle speed and also the Recorded Velocity Change figures. [Vetronix] the circumstances, think about the implications of an EDR. It may only be a matter of time before authorities SC can access such data. Who Owns The Logged Data? While the potential benefits of EDRs are highlighted by road safety researchers, many drivers and some vehicle manufac­turers are concerned about the privacy implications. In fact, the US Federal Motor Carrier Safety Administration has stated that the following standards should apply to control­ling access to EDR data: • The vehicle’s owner should also own the EDR data. • Only the vehicle’s owner, or another party having the owner’s permission, may access the EDR data. Exceptions would include instances where a law enforcement official has a warrant for a crash investigation. • One method of assuring that only owners have access is through the use of an EDR password. • The storage and retrieval of EDR data must protect the privacy rights of the individual in accordance with law. At this stage, none of those points has been implemented, although truck owners can deactivate the EDR by setting the deceleration threshold inappropriately, giving them some measure of control over the data being collected. Certainly, there needs to be more public debate about the privacy issues involved with EDR. November 2003  19 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 Who said bottles were dead? By JIM ROWE A 12AX7 valve audio preamplifier After many years saying we would never publish a valve circuit, here is a valve preamplifier for guitars and other musical instruments. However, it is a valve circuit with a number of differences, to give it much better performance than was common in the “olden days”. 24  Silicon Chip W HAT’S THIS? An audio project using a valve, actually described in SILICON CHIP? After all those scathing things our esteemed Editor and Publisher has said in the past about olde-worlde “bottles”? Yes, Leo finally gave in and approved the development of a valve preamp for guitars and other instruments, using the trusty 12AX7 dual hi-gain triode. We had to brush up on valve design to do it but the performance has turned out to be www.siliconchip.com.au quite impressive, better in fact, than was commonly achieved when valves ruled the electronics world. Now you can build one up, so you can hear for yourself just how good “valve sound” compares with that from modern solid state gear. Fig.1: the circuit of a basic commoncathode amplifier stage using a triode valve. It’s quite like a common-emitter transistor amplifier. How it developed Once we had decided to do a valve preamp, the first step was to see what parts were still readily available. This narrowed down the choice straight away, since the only type of low power amplifier valve that is widely available is the trusty 12AX7. Older readers may remember that this is a dual high-mu indirectly heated triode, which was also known by the European type number ECC83 and the military number 7025. It comes in a Noval or “miniature 9-pin” all glass envelope, and has a centre-tapped heater designed to operate from either 12.6V (at 150mA) or 6.3V (at 300mA). The 12AX7 is apparently still being made in Russia and a few other countries and Jaycar Electronics stocks the 12AX7WA made by Sovtek. They’re brand new and they sell for $24.95 a pop (Cat. ZA-6000). Jaycar also stocks matching Noval sockets, as the PS-2082 ($4.40 each). Of course, the valve is only part of the story, because valves not only need heater power to “light them up” and make the cathode emit electrons – they also need to operate from a fairly high voltage to attract those electrons to the anode or “plate”. In fact, for reasonable audio performance, a valve like the 12AX7 really needs to be operated from a “high tension” (HT) plate voltage supply of 250V DC or so. They don’t draw much current from this high voltage supply (only a few milliamps) but the high voltage is necessary because valves are much higher impedance devices than transistors. In the old days we’d usually generate this HT voltage with a simple rectifier circuit, based on a mains transformer with a high voltage secondary. But this sort of transformer is no longer readily available. So the next step in developing our preamp was to come up with a suitable HT power supply, using more reasonably priced parts. Modern technology came to the rescue here, because nowadays it’s easy to generate a high DC voltage with a low power DC-DC www.siliconchip.com.au converter. This type of converter is quite efficient and low in cost thanks to the availability of converter chips like the TL494, fast switching rectifier diodes and high voltage power Mosfets such as the MTP6N60E. So as part of the preamp design, we had to come up with a suitable 12V/250V step-up converter to run it. More about this later, but now let’s explain a bit more about designing the preamp itself. One way in which valves are different from solid state devices is that they have much tighter parameter spreads. So the performance of one 12AX7 is almost exactly the same as any other 12AX7; unlike transistors and FETs, where things like the current gain and quiescent current tend to vary over a wide range. Because of this much more predictable performance, valve amplifier stages are designed in a rather different way. In fact, many valve amplifier stages can be designed using a fairly straightforward graphical method, as we’ll now explain. Fig.1 shows the circuit of a basic common-cathode amplifier stage using a triode valve, such as one section of a 12AX7. As you can see, it’s quite like a common-emitter transistor amplifier or a common-source FET amplifier. In fact, if you to think of the valve as a kind of “depletion mode FET” that operates from high voltage, you’ll soon get the hang of things. The anode (A) or plate of the valve is connected to the +250V HT supply via a load resistor Ra, which is rather like the drain resistor of a FET. And the current the plate draws is controlled largely by the voltage applied between the grid (G) and cathode (K), because the grid works very much like the gate of a depletion mode FET. When there’s virtually no voltage Fig.2: our first attempt at the valve preamplifier. The first circuit stage is a common-cathode amplifier while the second is a “cathode follower” to give low output impedance and avoid the severe performance losses which can occur when driving following stages. The input RC network compensates for Miller Effect high frequency loss. November 2003  25 Fig.3: these are the “characteristic curves” for each triode in the 12AX7. Each curve shows how the plate current (Ia) varies with plate voltage Va, for a different value of grid voltage. With a load line curve drawn in, the gain of a triode stage can be closely predicted. between grid and cathode, the plate draws maximum current. But as the grid is made more and more negative with respect to the cathode, the anode current is “throttled back”. In fact, only a few volts of “negative bias” between grid and cathode are needed to make the plate current fall away and “cut off” the valve’s conduction. It’s this ability for a small voltage change on the grid (relative to the cathode) to control the valve’s plate current that makes it a good amplifier. If you look at Fig.3, you’ll see how 26  Silicon Chip the amplification can be shown graphically using the “characteristic curves” for the valve – in this case, the curves for each triode in the 12AX7. As you can see, there are a number of curves, each one showing the way the valve’s plate current (Ia) varies with plate voltage Va, for a different value of grid-cathode bias voltage Vg. The steepest curve shows how quickly the current increases when there’s no grid bias (Vg = 0). Then the other curves show how increasing levels of negative bias reduce the plate current for the same plate voltages. Each curve is marked with the corresponding level of negative bias voltage: -0.5V, -1.0V, -1.5V and so on. Notice how with -3.0V applied to the grid, the valve only draws about 0.6mA of plate current even with a plate voltage of 300V. Note that these curves only show the behaviour of the valve if it is connected directly to an adjustable DC voltage supply. But this isn’t the situation in our amplifier stage of Fig.1, because here the valve is connected in series www.siliconchip.com.au with a fixed “plate load” resistor Ra, across a fixed 250V DC voltage supply. So in this case the voltage drops of the valve and load resistor Ra always add up to 250V. In effect, they share the voltage according to the ratio of their resistances. For example, when the valve has a small negative bias voltage on the grid (so it’s able to draw more current), its effective plate-cathode resistance is smaller than Ra and as a result Ra drops more of the voltage. Conversely, when the valve has more negative grid bias and can only draw a small current, its plate-cathode resistance rises compared with Ra and it now drops more of the voltage. Because the voltage drops of Ra and the valve must always add up to the HT voltage (here +250V), this also means that the voltage across the valve can always be found by subtracting the voltage drop across Ra from the HT voltage. And since Ra is a fixed resistor, it’s easy to find its voltage drop by Ohm’s law: the voltage drop is simply Ra times the current. We can show this graphically by drawing a “load line” to represent the behaviour of Ra on the valve’s characteristic curves. As you can see from Fig.3, the load line is simply a straight line (shown in green) drawn between two known points. One is the point on the horizontal (voltage) axis representing the full HT voltage, because this will be the voltage on the valve’s plate when no current is being drawn (so there will be no voltage drop across Ra). The other known point is on the vertical (current) axis, showing the current which would be drawn by Ra by itself from the HT supply, if the valve could be fully “turned on” so that it had no voltage drop at all. The load line shown is for a load resistor Ra of 100kΩ, so it’s therefore drawn between the +250V point on the horizontal axis, and the point on the vertical axis corresponding to a current of 250V/100kΩ, or 2.5mA. Now what this load line shows is the way the voltage on the plate of the valve must vary for different current levels, operating from a 250V plate supply and with an Ra of 100kΩ. And since the valve’s own curves (red) show how its current varies with grid-cathode voltage Vg, we can use the two together to see how variations in Vg caused by an AC input signal www.siliconchip.com.au Parts List Preamp PC Board 1 PC board, code 01111031, 125 x 62mm 1 UB3 jiffy box, 130 x 67 x 44mm 1 piece of 1mm aluminium sheet, 125 x 62mm 1 12AX7WA or ECC83 twin triode valve 1 Noval 9-pin valve socket 2 PC-mount RCA sockets 2 2-way PC terminal blocks 6 6mm untapped metal spacers 4 M3 x 12mm machine screws 8 M3 nuts and star lockwashers Capacitors 1 220µF 10/16V PC electrolytic 1 47µF 450V PC electrolytic 1 220nF (0.22μF) 630V metall­ ised polyester (greencap) 1 100nF (0.1μF) 100V metallised polyester (greencap) 1 100nF (0.1μF) 630V greencap Resistors (0.25W 1% metal film) 3 1MΩ 1 8.2kΩ 2 33kΩ 2 1kΩ 2 100kΩ 1W carbon film Power Supply 1 PC board, code 01111032, 122 x 58mm 2 TO-220 mini heatsinks (6073B type) 2 2-way miniature PC-mount terminal blocks 1 1m-length .08mm enamelled copper wire 1 3m-length 0.25mm enamelled copper wire will result in plate current variations and then much larger variations in the plate voltage. In short, the valve will amplify the input signal. After looking at the 12AX7’s curves and the 100kΩ load line together, we can pick a suitable operating point for the two when they’re operating from an HT of 250V. Since the load line intersects the Vg = -1.0V curve at about halfway along, this would make a fairly good operating point for a stage handling fairly small input signals (say ±0.5V or less). As you can see, at this point the valve would have a Va of about 146V, while Ra drops the re- 1 Ferroxcube ETD29-3C90 ferrite transformer assembly (2 ETD29-3C90 cores; 1 CPHETD29-1S-13P bobbin and 2 CLI-ETD29 clips); OR 1 Neosid ETD29-F44 ferrite transformer assembly (2 ETD29 F44 32-580-44 cores; 1 ETD29 59-580-76 bobbin and 2 ETD29 76-055-95 clips) 1 2.5mm PC-mount DC socket 4 6mm untapped metal spacers 2 M3 x 10mm machine screws 4 M3 x 15mm machine screws 6 M3 nuts and lockwashers Semiconductors 1 TL494 switchmode controller (IC1) 1 7812 3-terminal regulator (REG1) 1 BC337 NPN transistor (Q1) 1 BC327 PNP transistor (Q2) 1 MTP6N60E 600V/6A or STP6N50B 500V/5.8A Mosfet (Q3) 1 1N4004 1A power diode (D1) 1 UF4004 400V fast switching diode (D2) Capacitors 1 2200µF 16V PC electrolytic 1 470µF 25V PC electrolytic 1 10µF 450V PC electrolytic 1 10µF 35V TAG tantalum 1 1nF (.001μF) MKT metallised polyester Resistors (0.25W 1%) 3 680kΩ 1W 1 39kΩ 1 220kΩ 1 4.7kΩ 1 47kΩ 1 1kΩ 1 100kΩ horizontal trimpot (VR1) maining 104V (250 - 146V). The resting or “quiescent” plate current flowing through both will be about 1.05mA. Cathode bias By the way, once we decide to make this the valve’s operating point, we can also choose the value of the self-bias cathode resistor (Rk in Fig.1). This will simply need a value which gives a voltage drop of 1.0V (the desired Vg), at the desired plate current (1.05mA). So Rk will have a calculated value of 952Ω, meaning that we can use the nearest preferred value: 1kΩ. It’s now fairly easy to show the valve’s amplification at this operatNovember 2003  27 Fig.4: the final preamp circuit uses two triode common-cathode stages with negative feedback from pin 6 to pin 4, to greatly improve distortion and frequency response. Note the HT filtering network which reduces noise and hash on the 260V supply. ing point, as you can see in Fig.3. If we draw a horizontal line off to the left from the operating point, this becomes the zero axis for our audio input signals fed to the valve’s grid via capacitor Cin. Similarly by drawing a vertical line down from the operating point, this becomes the zero axis for the amplified audio signals that will appear at the valve’s plate and are coupled out via capacitor Cout. So when we draw a sample sine­ wave input signal of say 1.0V peakto-peak (±0.5V) as shown, we can run horizontal lines through from the signal’s peaks to the points where they intersect the load line. Then we can draw vertical lines down from those points, because these must represent the plate voltage and current levels which will correspond to those signal peaks. Then we can reconstruct the valve’s output signal as shown, underneath the curves. Notice that the output from such a 1.0V peak-to-peak input signal will have a peak-to-peak amplitude of about 61V (174V - 113V), showing that the valve should provide an amplification or “gain” of about 61 times. As you can see the output waveform is also `upside down’ with respect to the input waveform (positive input peak becomes negative output peak), showing the way the valve inverts the signal polarity – just like a transistor or FET. 28  Silicon Chip So that’s the basic way a triode valve amplifier stage is designed, using the graphical method. Practical design is a little more involved than that though, because there are a few complications. For example, the gain will never be quite as high as we find from the curves, because whatever AC load we connect to the output capacitor Cout is effectively in parallel with Ra (as far as the AC signals are concerned), which reduces its effective value – and hence the gain we can achieve. Miller Effect high frequency loss There’s also another complication when the stage is amplifying higher audio frequencies, caused by the valve’s internal capacitance between its grid and plate. In each section of Performance Voltage Gain: 61 Frequency response: -1dB at 20Hz and 160kHz (see Fig.5) Harmonic distortion: <0.2% for output levels up to 3V RMS (see Figs.6 & 7) Signal-to-noise ratio: -81dB unweighted (22Hz to 22kHz) with respect to 2V Input impedance: 1MΩ Output impedance: 1.5kΩ at 1kHz the 12AX7, the internal grid-plate capacitance is about 1.7pF, which rises to about 2pF when the valve is plugged into a socket. Now this capacitance is connected directly between the amplifier’s input and output, and because the two are opposite in phase due to the signal’s inversion, the capacitance provides a path for negative feedback. In addition, because of the valve’s amplification, the capacitance tends to pass much more reactive current than it would as a result of the input signal alone. In fact, it draws (A+1) times the current, where A is the stage gain. So this internal capacitance acts as if it was a capacitor A+1 times larger than its real value, a phenomenon known as the “Miller Effect”. As a result, this kind of triode amplifier stage tends to have a fairly poor high-frequency response. For example, due to the Miller Effect our 12AX7’s 2pF of grid-plate capacitance will have an effective value of about 124pF in the circuit of Fig.1, which has a drastic effect on its frequency response. First prototype circuit But enough of theory. Our first attempt at a preamp circuit using the 12AX7 used the circuit shown in Fig.2. As you can see it consists of a voltage amplifier stage just like that in Fig.1, with a 100kΩ plate load resistor, a 1kΩ self-bias resistor and a 1MΩ grid resistor. To try and achieve as high a gain as possible, even when the output of the preamp was connected to a main amplifier or mixing desk with a fairly low input impedance, we used the second triode section of the 12AX7 as a “cathode follower” with its 100kΩ load resistor connected from the cathode to ground rather than from the plate to +250V. This makes the second stage have a gain of slightly less than unity, but at the same time it provides a high AC load impedance for the first stage plus a low source impedance to drive the following amplifier. This means that capacitance effects of the output signal cable will not cause further reductions in the high-frequency response. This arrangement gave an overall gain of about 36 times but the high-frequency response was quite poor, due to Miller Effect in the first stage. The upper -3dB point was only 5kHz but we were able to compensate for that www.siliconchip.com.au Fig.5: the frequency response is very smooth, with -1dB points at 20Hz and 160kHz, measured at 2V into a 50kΩ load. Because the output impedance is low, the frequency response will not be curtailed by an amplifier load. loss by adding an input compensation circuit (shown highlighted in Fig.2). However, this dropped the gain to 34 times, which we judged to be inadequate. The distortion level we achieved with this configuration was also fairly high – about 0.9% with an output level of 3V RMS, and rising to above 5% for an output level of 16V RMS. These are very high levels of distortion compared to good solid-state designs but this was typical of valve stages operating without any negative feedback – which was the usual approach. At SILICON CHIP we have always tried to produce the best available audio performance, so we decided to try a different approach, converting the second preamp stage into a common-cathode amplifier like the first, and then applying a fair amount of negative feedback around the two. The goal was higher overall gain, combined with a much more extended frequency response and much lower harmonic distortion. The negative feedback would also reduce the output impedance of the second stage, to make it easily drive following stages without high frequency loss. To cut a long story short, this new configuration worked much better and as noted at the start of this article, the overall performance is far superior to that normally achieved by valve audio circuits from the “olden days”. Circuit description Fig.4 shows the final circuit configuration. The input signal is coupled www.siliconchip.com.au Fig.6: total harmonic distortion at 1kHz, measured into a 50kΩ load and with a measurement bandwidth of 22Hz to 22kHz. Note that most valve circuits do not have negative feedback and so their distortion is considerably worse. into the grid of triode V1a via a 100nF capacitor, with a 1MΩ resistor to tie the grid at DC earth potential. The idea of using a 1MΩ grid resistor is to achieve the best possible low-frequency input response with the 100nF coupling capacitor (1MΩ is the highest allowed value for the 12AX7’s grid resistor). V1a has a 100kΩ plate resistor, as before, and the cathode bias resistor is also 1kΩ. But the latter isn’t bypassed with a capacitor, because we use it as part of the negative feedback divider. The output from the plate of V1a is coupled to the grid of V1b, the second triode section of the 12AX7, via a second 100nF capacitor. This capacitor is rated at 630V because it has to be able to withstand the full HT voltage. The second stage is almost identical to the first except that its 1kΩ cathode resistor is now bypassed with a 220μF capacitor, to achieve the maximum possible gain. The preamp’s output is taken from the plate of V1b via a 220nF coupling capacitor, which again must be rated to withstand the full HT voltage. The final 1MΩ resistor to ground is to allow the 220nF capacitor to charge up as soon as the HT voltage is applied, rather than running the risk of it only charging later on when we connect the preamp to a load (which would cause a loud “plop” sound). A second 220nF capacitor is connected to the plate of V1b, to couple the negative feedback signal back to the cathode of V1a via the two 33kΩ series resistors. (We use two resistors in series because of the fairly high voltage swings.) The negative feedback divider formed by the two 33kΩ resistors and the 1kΩ cathode resistor has a division factor of 1/(66+1) or 1/67. This gives Fig.7: total harmonic distortion versus frequency, measured at 2V into a 50kΩ load and with a measurement bandwidth of 22Hz to 80kHz. Even the very best valve amplifier circuits (with negative feedback) of the past would have been struggling to match this performance. November 2003  29 Fig.8: the DC-DC converter uses a TL494 switchmode controller to drive Mosfet Q3 in a boost converter running at around 33kHz. T1 is wired as an auto-transformer to step-up the voltage developed in the 12-turn primary winding. the preamp a theoretical final gain of very close to 67. In practice, the measured gain was 61. The performance of this final preamp configuration is shown in the plots, produced on SILICON CHIP’s Audio Technology test system. Fig.5 shows the very smooth frequency response, with -1dB points at 20Hz and 160kHz, measured at 2V into a 50kΩ load. Figs.6 & 7 shows the harmonic distortion performance. Total harmonic distortion (THD) is below 0.2% for output levels up to about 3V RMS (8.5V peak-to-peak). The distortion remains below 1% at output levels up to about 12V RMS and then goes into soft clipping at higher levels. The distortion is mainly second harmonic, as expected. The preamp’s signal-to-noise ratio is better than -81dB unweighted (22Hz to 22kHz measurement bandwidth) with respect to 2V RMS output. Most of the noise is a low-level “frizzle” from the 33kHz switching hash of the DC-DC converter. The preamp’s input impedance is very close to 1MΩ while its output impedance measures very close to 1.5kΩ, thanks to the negative feedback. Before leaving the preamp circuit, note that the HT supply is fed to the circuit via an 8.2kΩ resistor which is then bypassed by a 47μF 450V electrolytic capacitor. This RC network provides a high degree of noise filtering and removes most of the residual high frequency noise and hash super­imposed on the HT line from the DC-DC converter. The voltage on the decoupled line is +250V which means that the DC-DC converter needs to deliver about +260V. DC-DC converter Now let’s look at the DC-DC converter circuit shown in Fig.8. As we Table 2: Capacitor Codes Value μF Code 220nF 0.22µF 100nF 0.1µF   1nF .001µF EIA Code   224   104   102 IEC Code   220n   100n     1n Table 1: Resistor Colour Codes o o o o o o o o o o No.   3   3   1   2   1   1   2   1   3 30  Silicon Chip Value 1MΩ 680kΩ 220kΩ 100kΩ 47kΩ 39kΩ 33kΩ 4.7kΩ 1kΩ 4-Band Code (1%) brown black green brown blue grey yellow brown red red yellow brown brown black yellow brown yellow violet orange brown orange white orange brown orange orange orange brown yellow violet red brown brown black red brown 5-Band Code (1%) brown black black yellow brown blue grey black orange brown red red black orange brown brown black black orange brown yellow violet black red brown orange white black red brown orange orange black red brown yellow violet black brown brown brown black black brown brown www.siliconchip.com.au Fig.9: the parts layout for the preamp board. Make sure that the electrolytic capacitors are installed with the correct polarity and note that the high-voltage components must be covered with neutralcure silicone sealant. mentioned earlier, we have to provide the valve with an HT supply of about +260V in addition to the low voltage needed for its heaters. Current requirements from the HT supply are quite small – only about 2mA for both preamp stages. Since the 12AX7’s heaters can also run from 12V DC, this has the advantage that the complete preamp can be run from either a 12V battery or a suitable 12V DC plugpack. The total drain from the 12V source is only about 250mA. By the way, it’s actually very desirable to run the 12AX7 heaters from 12V DC in an audio preamp, because this removes a major source of hum. When the valve heaters were run from 12.6VAC in the “valve days”, it was very difficult to avoid a small amount of 50Hz hum caused by heater-cathode leakage and capacitance – plus some 100Hz hum caused by thermal modulation. As you can see from the circuit of Fig.8, the power supply is quite straightforward. Regulator REG1 is included so that the preamp can be operated from an unregulated plug pack, while still providing both the valve heaters and the DC-DC converter with smoothly regulated 12V DC. If you want to run the preamp from a 12V battery, the regulator is simply omitted and replaced by a wire link. The DC-DC converter uses a standard “flyback boost” circuit, where energy is first drawn from the +12V supply and stored in the 12-turn primary winding of transformer T1, by turning on Mosfet Q3 (which acts as a high-speed switch). Then Q3 is turned off, so that the stored energy is returned to the circuit as a high voltage “flyback” pulse, induced in both windings of T1. Because the two windings are connected in series, this output pulse is This view shows the fully assembled preamplifier board. When you finish testing the preamp, coat the 100kΩ resistors, the 8.2kΩ resistor the HT connection on the terminal block with neutral-cure silicone sealant – see Fig.9. www.siliconchip.com.au November 2003  31 This is the completed DC-DC converter board. Note the small heatsinks fitted to transistor Q3 and to regulator REG1. WARNING! HIGH VOLTAGES (260V DC) ARE PRESENT ON THIS BOARD WHEN POWER IS APPLIED Fig.10 the component layout for the DC-DC converter board. Fit the flag heatsinks before installing REG1 and Mosfet Q3. added to the +12V input, boosting it still further. Fast switching diode D1 then feeds the pulse energy into the 10μF capacitor, which charges up to about +260V. The capacitor voltage becomes the preamp’s HT supply and we maintain it at a little over 260V by feeding a known proportion back to IC1, a TL494 switching controller. This compares the feedback voltage with an internal reference voltage (5V) and automatically adjusts the width of the switching pulses fed to Q3 (via driver transistors Q1 and Q2). This controls the energy stored in T1 to produce each flyback pulse and hence makes sure the HT output voltage is not allowed to rise higher or fall lower than 260V. The feedback voltage for IC1 is de32  Silicon Chip rived from the HT output via a resistive voltage divider, as you can see. The three 680kΩ 1W resistors in series form the upper arm of the divider, with a total value of 2.04MΩ (we use three 1W resistors to handle the voltage drop rather than the power dissipation, which is only 30 milliwatts!). The lower divider arm is formed by the 47kΩ resistor in parallel with the 220kΩ and 100kΩ trimpot (VR1) which allows the output voltage to be adjusted over a small range. The TL494 has an internal oscillator to generate the switching pulses fed to Q3, and the oscillator’s frequency is set by the values of the resistor and capacitor connected to pins 6 and 5. The values shown (39kΩ and 1nF) give the converter an operating frequency of 33kHz, which is high enough to ensure that any output ripple which finds its way into the preamp (either via the HT line or by radiation) will be inaudible. Transistors Q1 and Q2 are used to buffer the PWM (pulse width modulated) pulses generated by IC1, providing a low impedance high current drive for the gate of Q3. This is to make sure that Q3 is switched on and (especially) off as rapidly as possible, which is necessary to achieve high converter efficiency and minimise Q3’s power dissipation. By the way, this DC-DC converter is capable of supplying up to about 40mA of current at 260V (dependent on plugpack rating), so it’s certainly capable of feeding two preamps if you wish to have a stereo pair. It would also be suitable for running other valve circuits, such as a mantel radio. In that respect, it could substitute for the vibrator in some 12V sets, although we have not checked its performance in this application. Construction All the components for the preamp itself are built on a small PC board which measures 125 x 62mm – just the right size to mount on the top of a standard UB3 size jiffy box. The power supply is built on a slightly smaller PC board measuring 122 x 58mm, which is designed to go down inside the UB3 box and out of sight. The two boards www.siliconchip.com.au Fig.11: this diagram shows how the two boards are stacked together inside the plastic box, with a metal shield plate between them. have the code numbers 01111031 and 01111032 respectively. We designed the preamp and power supply on two separate boards to make it easier for people to build a “2 preamp + 1 power supply” combination, if they wish. It also gives you more options when it comes to physical construction, because you don’t have to build them into a jiffy box. They could be built side-by-side in a metal box, if you’d prefer. Having the power supply separate also makes it easier to use it to power other valve projects. The construction details of both board assemblies should be fairly clear from the wiring diagrams and photos. Fig.9 shows the component layout for the preamp board while Fig.10 shows the layout for the DC-DC converter board. Note that the valve socket for the 12AX7 is mounted above the centre of the preamp board, using two 12mmlong M3 machine screws through the flange holes and the matching board holes. www.siliconchip.com.au A pair of M3 nuts on each screw are used as spacers, with a lockwasher and nut on each screw under the board to hold everything together. Fig.11 shows how the two boards are stacked together, as well as the way the preamp board is mounted to the metal box lid and shield plate. The audio input and output connectors are RCA sockets, mounted directly on the preamp board at each end. The power connections are brought out to board-mounting mini screw terminal blocks, which accept suitable insulated hookup wire. The power supply board has the same kind of screw terminal blocks. All of the parts used in the power supply are also built directly onto the board, including converter transformer T1. This is wound on a Ferroxcube ETD-29 ferrite transformer assembly, which uses two E-cores made from 3C90 ferrite material plus a bobbin type CPH-ETC29-1S-13P, and two clips type CLI-ETD29. The construction details for T1 are shown in Fig.12. The 12-turn primary winding is wound on the bobbin first, using 0.8mm diameter enamelled copper wire (ECW). This is then covered in a couple of layers of PVC insulation tape, over which is wound the secondary winding. The secondary is wound using 0.25mm ECW, as two layers of 40 turns each with a layer of insulation tape between the two layers. Then when the end of the secondary is soldered to the appropriate former pin (Sf), another few layers of PVC tape are applied over the top of the windings to protect them and hold everything in place. The location and orientation of all parts on the power supply board should again be fairly clear from the wiring diagram of Fig.10 and the photos. Note that REG1 and Q3 are both mounted vertically on the board and each is fitted with a TO-220 mini heatsink (19 x 19 x 10mm) like the Jaycar HH-8502. These ensure that they run within ratings. In practice, you will find that the Mosfet (Q3) runs cool, while the 3-terminal regulator gets quite warm or even, depending November 2003  33 power supply to the preamp board are brought out through an 8mm hole in the metal plate, with a grommet to protect the insulation from chafing. Checkout & adjustment The DC-DC converter board is mounted in the bottom of the plastic case, while the valve preamp board is mounted on an aluminium shield plate. The DC supply leads from the converter are fed through a rubber grommet. on the input voltage from your DC plugpack. Take care when you’re fitting all of the polarised parts to the board – especially the electrolytic capacitors, the diodes, the transistors and the IC and regulator. The finished power supply board is mounted in the bottom of the UB3 box using four 15mm long M3 machine screws, with M3 nuts and star lockwashers. Four 6mm long untapped metal spacers are used to provide clearance for the solder joints under the board. Three lengths of insulated hookup wire are used to connect the power supply outputs to the screw terminals on the preamp board. The preamp board itself is mounted above a 125 x 62mm piece of 1mm thick aluminium sheet, which is identical to the alternative metal lid sold with some UB3 boxes. The dimensions of the plate are shown in Fig.13. The aluminium plate supports the preamp PC board as well as providing shielding between it and the power supply board. The preamp board is 34  Silicon Chip spaced above the plate using six 6mmlong untapped metal spacers. It’s attached to the plate initially using two 12mm long M3 machine screws with M3 nuts and star lockwashers, passing through the centre holes on each long side of the board. Then when the plate is placed in the top of the box, the four 4G x 15mm self-tappers supplied with the box are passed through the four corner holes (and the remaining four spacers), to hold the board and plate assembly together as well as firmly in the box. Note that the three lengths of hookup wire used to connect the Where To Buy A Kit A complete kit of parts for this design is available from Jaycar Electronics for $89.95. In addition, Jaycar will be selling a kit for preamplifier board only (includes the preamp PC board, all parts and the valve) for $59.95. Note: copyright of the PC boards associated with this design are owned by Jaycar Electronics. Before you fit the preamp board assembly into the top of the box, it’s a good idea to check that everything is working and also to adjust the HT voltage output via trimpot VR1. Do this by first plugging your 12AX7 valve into the preamp socket. Make sure you orientate the valve correctly, using the gap between pins 1 and 9 as a guide. Also push the pins into the socket clips gently, so they don’t bend and possibly crack the glass envelope. Now set trimpot VR1 to its mid position and then connect a DMM (set to a range such as 0-400V DC) across the HT terminals of either the power supply or preamp boards. After this, connect the power input of the power supply board to either a 12-15V DC plugpack (500mA or better) or a 12V battery, depending on the power source you’re planning to use for the preamp. Note: the converter circuit produces high voltages, so don’t touch any parts on this board when power is applied. Check also that the 10μF capacitor across the output has discharged before touching this board after switch off. A few seconds after you connect the power, you should see the heaters of the valve begin glowing as they heat up. At the same time the DMM reading should rise up to 260V or there­-abouts, as the DC-DC converter output builds up. If the voltage rises higher than 260V or lower than 250V, adjust trimpot VR1 to bring it back to 260V. That’s the only adjustment you may need to make. If you want to make sure that the preamp circuit is working correctly, carefully disconnect the DMM from the HT supply (don’t touch the probes or clips, because 260V DC can give you a nasty shock!) and use it to measure the plate voltage on each section of the 12AX7. You can measure these voltages at the plate ends of each 100kΩ 1W plate load resistor, with the DMM’s negative lead connected to the preamp’s earth. You should measure about +160V on each plate. You can also measure the voltage across each 1kΩ cathode resistor, with the DMM now set to a lower DC range. www.siliconchip.com.au Fig.12: these diagrams show how the converter transformer is wound. The primary is wound on first, followed by two layers of the secondary. Fig.13: this diagram shows the dimensions of the metal shield plate. You should find about 1V DC across each one, verifying that each section of the 12AX7 is drawing about 1mA of plate-cathode current. If all these voltages seem OK, your preamp should be working correctly. High voltage protection Now that you’ve checked all the voltages, it remains to provide a some www.siliconchip.com.au protection against accidental electric shock. Since the HT voltage is around +250V, it is possible to get a bad shock if you simultaneously touch the plate resistors and the earthed RCA connectors. With that in mind, we strongly suggest you put a generous coating of silicone sealant over the two 100kW 1W resistors, the 8.2kΩ resistor and the HT connection on the screw terminal block (be sure to cover both the top and the side entry point). Now all that should remain is connecting its input to the pickup of a guitar or other instrument and its output to your power amplifier, recorder or mixing desk. Then you can hear for yourself what “valve sound” actually SC sounds like. November 2003  35 SERVICEMAN'S LOG The JVC TV set that whistled After many years in the same premises, we recently moved to something newer and bigger so I now have a lot more workshop space than before. And you need plenty of space these days be­cause the TV sets are getting bigger. Moving premises can be a real pain in the you-know-what but the move really has been worthwhile. Among other things, it gave me the chance to throw out a lot junk and other stuff that I didn’t need, so that I can now work in an uncluttered environ­ment. It’s amazing how much stuff you can accumulate in this business over the years and I really welcomed the excuse for a good “chuck out”. Of course, I kept all the real treasure – you never know when it might come in handy! The whistling JVC Mrs Blandford complained that her 59cm JVC AV-G25AU (MZ2 chassis) had no picture and “whistles”. On the face of it, I thought that this might be quite interesting because I had never heard a TV whistle before. In reality, the set was actually pul­sating and gave out a protesting noise that very loosely could be described as whistling. Having repaired a troublesome AVG21AU some months ago, I had a good idea what the problem was. The line output transistor (Q522, 2SD­1878-YD) was short circuit and the usual cause was dry joints on blue ceramic resonator CF561. I dutifully replaced the transistor, resoldered the resona­ tor and, fully confident of the outcome, switched the set on. I then confirmed that all was Mickey Mouse and went to have a cup of coffee. When I returned 20 minutes later (I don’t like to be rushed over sacred rituals), I was mortified to find that the set had rejoined the choir and was pulsating just as before. So what had gone wrong? I installed another expensive tran­sistor and then began resoldering the set in an effort to cure the fault. However, what I didn’t realise was that the switchmode power supply reservoir capacitor (C910) remained charged at +295V for a very long time after the fault had occurred. As I worked on the set, my arm suddenly strayed across this vindictive component and yes, you guessed it – it bit me! That 295V on my otherwise pristine arm was very painful but worse still, the solder I was carrying fell out of my hand and shorted out parts of the power supply. This resulted in a short fireworks display, even though the set had been turned off for quite a while. When the smoke cleared, and after I had checked the obvi­ous, I found that the power supply no longer whistled. It fact, it couldn’t do anything at all – except give me another shock, if I was stupid enough to try. I wasn’t – instead, I discharged the beast using a globe before carrying out a series of DC voltage checks on the circuit. Eventually, I discovered that Q901 (2SD1853-T) and D908 were leaky. The former is a special Darlington pair and the latter a 7.5V zener diode. I had to order the tran­sistor in but after I had fitted them both, the set was still dead. Remembering to discharge the capacitor again, I then re­placed IC901 (STR-S6707), after which the set agreed to fire up. This time, with my hand near the master on/off switch, I waited to see if there was anything untoward that was causing the de­ struction of the line output transistor. A few minutes later, the set started to make noises and the picture began to tear. During this time, the +114V at test point TP91 remained constant on my DMM, so the power supply itself was obviously OK. And that in turn meant that something was affecting the line output stage. My suspicion was again drawn to CR561 which I though might need replacing. However, before doing this, I resoldered all the pins to IC201 (the These emailed pictures proved that one customer’s TV set really did have a problem! 36  Silicon Chip www.siliconchip.com.au jungle IC), paying particular attention to pins 14 & 17 which are adjacent to the crystal. This finally fixed the problem and Mrs Blandford was able to have her “telly” back after a good long soak testing. Email in the fault Amongst all the huge technological changes within this industry that happen daily, a slightly novel approach to report­ing faults has arisen which I suspect will take off and be the way of the future. A 1990 Philips 25GR6765/75R (G110-S chassis) appeared on my bench with a fault description “Intermittently, the top disap­ pears when changing channels”. So I switched it www.siliconchip.com.au on, expecting a vertical linearity fault. This set is well known and, although rather ancient these days, is not considered difficult to repair. In addition, you get used to the terrible and widely varying fault descriptions from clients, so you never quite know what to expect. Well, I waited and waited but nothing happened. The picture was excellent considering the set’s age, so I put it to one side but still within visual range while I got on with other jobs. After three weeks, the set hadn’t so much as blinked incor­rectly and I put the “fault” down to either an antenna problem, or bad connections or interference. And so the set was returned to its owner with a note to that effect. Days later, I got an email with a set of attachments. Apparently, it played up about 24 hours after going home and to prove it, our enterprising client had photographed the effects with his digital camera. The photographs were quite clear, although the cause of the fault wasn’t. Items Covered This Month • • • • JVC AV-G25AU 59cm (MZ2 chassis). Philips 25GR6765/75R (G110-S chassis). Panasonic TX-33V30X (M16MV3 chassis). Grundig M82-4986/9S/PIP (CUC 3840 chassis). November 2003  37 Serviceman’s Log – continued The accompanying email said that it performed perfectly until there was an advertisement or switching from the 38  Silicon Chip studio to an outside broadcast, which seemed to invoke the symp­tom. And according to his email, the TV would sometimes come good when he approached it but would then revert to the fault when he walked away. This was getting “curiouser and curiouser”, as they say in the classics. Anyway, the set was returned to the workshop but again refused to play up. However, the client’s photographs showed horizontal lines of different contrast going up and down the screen, which definitely looked like a vertical timebase fault. The vertical output stage of this set is pretty reliable but I did change C2813 and C2814 (1500µF 35V), as well as C2981 (1000µF), as these are known to give trouble. I also checked the PC board for electrolyte corrosion and dry joints, before putting the set aside to soak test. It was two weeks later that I first got to see – if only momentarily – the fault, which was indeed like the photographs except that there was no colour when the fault occurred. I now suspected a vertical fault that was somehow impinging on the colour decoder, possibly involving the vertical blanking pulses. To check this theory, I connected the CRO to the sandcastle line from IC7705 and monitored the combined vertical and horizontal pulses. However, the sandcastle pulse didn’t vary and so I couldn’t determine if it really was a vertical deflection fault at all. Next, I decided to look at the supply rail voltages to see if problems were occurring there. Nothing showed but I did change a few electros that looked a bit suspect, just in case – espe­cially C2175 (1000µF 50V) on the +32V rail. It made no dif­ference. Fortunately, I own several of these popular sets and so I decided to swap large chunks of the set in order to eliminate these areas. First, I swapped and then removed the Teletext module. I also swapped the stereo decoder and even the CRT socket but the fault gradually became more frequent, which was good because I could measure and check more of the waveforms. However, because it was intermittent, there were many times when the fault would actually stop for days before reappearing, which meant tying up a lot of test equipment for a very long time, waiting for the fault to occur. Next, I socketed and swapped IC­ 7705 (TDA2579A jungle timebase), IC7278 (EEPROM), IC7550 (TDA­ 3562A chroma decoder), IC7355 (TDA5850 video switching) and IC7325 (TDA8341 video IF). The fault continued, even with a generator connected to the AV input SCART socket. And then, by sheer luck, I finally managed to get an idea of where to start when I checked the CVBS video input to pin 8 of IC7550 and saw the waveform vary wildly. Having secured a toehold on the possible cause, I decided to monitor the waveform from pin 12 of IC7325 to pin 8 of IC7355, and from pin 5 (of IC7550) to pin 8 of IC7550. I then tried heating and freezing all the components but was continually thwarted by the fault intermittently coming and going. I even s­wapped over the SVHS module and some of the leads where I thought the problem might be lurking but it was just another blind alley. By this stage, I had been working on this set on and off for about seven weeks. And then one day, an arrogant technician friend who was working with me at the time claimed to have fixed the fault in less than 10 minutes while I was out. Incredulous, I asked him what it was and how he had managed to find www.siliconchip.com.au it – especially as the set was giving a perfect picture again and had been doing so all morning. Seriously, he claimed that he just looked at the circuit and knew straight away where the problem was. He then showed where a lump of clear glue had held a wire link over the PC board. I then asked him where exact­ly on the circuit this was (you know, the one he looked at first) and I wanted to know what components were affected. He proceeded to show me, in a large sweeping circle, an area of the circuit covering about 50 components. By now, he had lost all credibility and I told him he was talking rubbish. The fact is, he would have seen the glue first and the circuit sec­ond, and the glue was a later type used by Philips that no longer conducts with age like the old brown stuff. In short, it was only by luck that the set was working. Anyway, I decided to play along for a while and boxed the set up and left it on display in front of him. An hour later, his luck ran out – the fault was back and he fell extremely and un­characteristically quiet. Not being backward in coming forward, I chose my moment to rub it in further. His grim silence was eventually broken when a new original idea popped into his head. “Ah”, he said, “I was only joking!” Back to the grindstone – the fault, www.siliconchip.com.au when I was able to measure it, seemed to start from near IC7550 but I had already changed that. The signal also went to the Teletext board, which I had removed, and it also went to pin 5 of IC7705 which I had replaced. From there, it went to a surface-mounted emitter fol­ lower transistor (Q7350) and then to the SVHS panel, before going through the luminance delay line to IC7550. I had already changed the panel, so that left the transis­ tor and the delay line. Because it was easier, I changed the delay line first but it was the surface-mount transistor that was causing the trouble and a new one fixed the fault. Sony BG-1s chassis The Sony BG-1S series of chassis are pretty reliable sets which employ a similar switchmode power supply to the JVC set mentioned earlier. However, when the power supply fails, it often takes out several parts. Recently, I have had a series of these where IC601 (STRS6707) fails, disintegrating R629 (33Ω) and taking out D607 and/or D609 (DNL20). I suspect that C624 (1000µF) and C623 (220µF) may be the culprits as they are often also found to be faulty but guessing which failed first is beyond me. When this lot fails, fuse F1610 3.15AT goes black too, though the other day I had a real beauty. The fuse November 2003  39 Serviceman’s Log – continued had melted a gap of about 0.25mm in the middle, which is barely visible to the naked eye. Replacing this fuse was all that was necessary in that particular set. Sometimes R601, R602 and R611 also fail. The BG-2S is more reliable but has a ceramic capac­ itor (C820, 1000pF 2kV) across the line output transistor which sometimes fails. TV set sizes When I refer to a large 80cm or 34inch television, please bear with me, as these sorts of numbers can be confusing. For example, if a picture tube carried a label that read “M78KPH­ 566X”, you used to be able to rely on this as meaning that the viewable diagonal was 78cm. However, the manual for the Panasonic TX-33V­30X set (M16MV3 chassis) that uses this tube states that it is a “type 33 (84cm) measured diagonally”. Other manufacturers use the imperial system and call it a 33-inch set. Because of these differences, I can only generalise and quote the advertised size where I can find it. Anyway, there I was with another large heavy (60kg) “telly” on the bench (what do one-man-show TV repairers do about moving these? No wonder when we get old we all suffer from bad backs and poor eyesight!). The picture and sound were great off-air but on AV there was little colour and no luminance. Instead, there was an effect I can only describe as like “shooting stars”! These appeared as 40  Silicon Chip lines with a bright spot at the end on the lefthand side – very bizarre. I decided to start with the AV input “U Board” and trace the video signal with a CRO into the “C Board” (AV Control). The only trouble was access – basically, there was none! Fortunately, I had a set of extension cables and when I finally had the “C Board” out on the bench with the CRO probe in my hand, I switch­ed the set on. Unfortunately, the fault had now disappeared and the set was showing the colour bars perfectly. After examining it for dry joints, I refitted the module into the set to see if the fault would reappear. This was going to be tricky to get to the bottom of because it really needed to be in the set to give the fault. I persevered again with the module on the bench (with the extensions) and tried to recreate the fault. It looked as though a component on the “C Board” was radiating an interfering cross-modulating signal. I ran my moist fingers all over the board and noticed that when I touched an area near the bottom corner (from IC3003 to the C1 plug corner), the fault began to recur. I tried to nail it down but it wasn’t possible with my big fingers, so I used a small screwdriver instead to pinpoint dif­ferent components. I started at “A/V 3.58/Other” analog switch IC3003 (TC4066) and found pins 6, 8, 11 & 12 to be sensitive, but it got more so when I touched the base of Q3039 and even more so when I got down to Q3046 (UN4213). The latter is a surface-mount NPN transistor (with inbuilt 47Ω resistors in its base and emitter circuits), which controls the switching signal to the IC. Replacing this transis­tor and refitting the module fixed the problem. A slow Grundig A Grundig M82-4986/9S/PIP (CUC 3840 chassis) was brought into the workshop with the complaint that it was slow to come on. Once I got the back off, I connected a true RMS heater meter to the heater filament pins (9 & 10) of the A76­JTS90X03 picture tube and, as I suspected, the voltage was very low (about 3.5V) at switch on. However, there was also a noise coming from the motherboard, which suggested that something was under stress. Next, I measured the main voltage rail (A) from D656k. This was spot on at +152V and as I was watching, the noise stopped and the heater voltage moved up to 6.3V. However, the “A” rail remained constant. This told me that the switchmode power supply was OK and so my attention moved to the deflection stages. This set uses IC550 (TDA­8140) as the horizontal driver and it goes direct to the line output transistor. It is fed by a + 12V rail to pin 2 and right next to it is a 100µF electrolytic filter capacitor (C507). Its cover had peel­ed back and it looked highly suspect. I froze the capacitor when the set was running normally and immediately the noise returned and the picture dimmed. Replacing it fixed the problem SC completely. www.siliconchip.com.au Our LED best TORCH... EVER! By JOHN CLARKE This new LED torch blasts our previous LED torches into the weeds. It is much brighter, gives a beautifully diffused beam and is far more efficient than any torch globe. The batteries will also last much, much longer. It can be easily built into a readily available 2 D-cell torch. O ur new LED torch uses the Luxeon STAR/O 1W white LED which comes with its own collimating lens assembly. We previewed the Luxeon 1W and the truly awesome 5W version in the May 2003 issue and this torch is the first of a series of drive circuits for the 1W version. In the last 12 months LED torches have finally arrived. This white LED torch provides a similar light output to its incandescent bulb counterpart yet uses far less current from the battery. It gives a beautifully soft light beam which maintains a constant colour and similar brightness over the whole battery life. And the LED should never need replacing. www.siliconchip.com.au Compared with a typical conventional torch, this LED torch has a much wider and more evenly distributed beam. Torch bulbs typically have a very small bright spot with weak diffuse light surrounding it. The white LED torch provides a beautifully even distribution of light which can light up a fence gate (or whatever) at more than 15m. At this distance the beam is about 5m in diameter. Apart from its sheer light output, this LED torch provides produces a natural white light instead of the yellowish light from torch bulbs. And it continues to produce this constant white light regardless of the battery condition, until they are virtually flat. High efficiency The heart of the new torch: a Luxeon STAR/O 1W ultrabright LED. These new white LEDs are much more efficient than torch bulbs. The Eveready KPR102 Krypton light bulb November 2003  41 Spot the deliberate mistake in this disassembled photo! Give up? We used carbon cells instead of alkaline. Of course standard carbon cells will work but cannot give the peak current that alkaline can; hence your torch will not be as bright as it could be or should be. used in the torch we are using, is rated to deliver 16 lumens of light output, when drawing 0.7A from a 2.4V battery; equivalent to 1.68W. In effect, the KPR102 bulb produces 9.52 lumens/watt. By comparison, the Luxeon 1W white STAR/O LED is rated at 18 lumens/watt – almost twice as efficient! Consider also that this LED torch will continue to operate when the cells are down to less than 1V (0.5V each). This is long after a conventional torch would have expired. The LED torch also gives you plenty of notice. We estimate that typical alkaline D cells will last for several days before they give up. The Luxeon 1W LED assembly includes a lens which focuses the light into a narrow beam. Heat produced by the LED is dissipated onto a 25mm square aluminium PC board which is an integral part of the LED package. The voltage waveform across the 33 milliohm resistor when the circuit is powered from two fresh D cells. Battery voltage was 2.6V. Efficiency is over 85%. Waveform hash means the frequency readout is wrong – it should be about 60kHz. 42  Silicon Chip Note that this is all the heatsinking required as the maximum heat developed would be less than 1W and the heatsink size is sufficient to maintain the temperature only a few degrees above ambient. In practice, the heatsink runs slightly warm to the touch. Drive requirements The Luxeon 1W LED requires about 3.4V in order to produce its rated output. If we are using a 2-cell torch, this The voltage waveform across the 33 milliohm resistor when the circuit is powered by two D cells which are just about flat, delivering 1.1V. At this point, a conventional torch would have long since given up. www.siliconchip.com.au Fig.1: the complete circuit diagram with a DC-DC converter to power the LED. Note that there are several components which you won’t find “off the shelf” at your local lolly shop. However suppliers are given in the text. means we need to step up the voltage with a DC-DC converter which should be as efficient as possible. After all, we do not want to use an efficient light source and then waste power in the converter. In practice, our DC-DC converter has an efficiency of well over 80% over the likely operating battery voltage range of 3V down to 2V. Below 2V the batteries are essentially exhausted but compared to conventional torch- es, battery life will be considerably extended. The complete Luxeon LED torch circuit is shown in Fig.1. It uses a number of semiconductor devices specially manufactured by Zetex to achieve high efficiency in a DC-DC converter. Heart of the circuit is IC1, a DC-DC converter which can operate from a supply voltage between 0.93V and 3.5V. It includes current sensing and voltage sensing inputs. In operation, IC1 switches base current to a low saturation transistor, Q1 which turns on to build up current build through a 22µH inductor, L1. This current is monitored by the emitter resistor R1 and when it reaches 0.53A, transistor Q1 is switched off and the current flowing in the inductor is diverted to the LED via diode D1. This switching runs at around 60kHz, depending on the battery voltage. The resulting current pulses are filtered by The various components of our LED torch shown here ready for assembly. You may wonder why we have not shown the two electros nor the inductor on the PC board – this is because they have to mount half off the board to fit! www.siliconchip.com.au November 2003  43 Parts List – 1W Star LED Torch 1 Eveready 2 D-cell WP250 waterproof torch (KMart) 1 Luxeon 1W white STAR/O LED (LXHL-NW98) (Alternative Technology Association) 1 PC board coded 11211031, 33mm diameter (RCS Radio Pty Ltd) 1 Ringgrip mains bayonet lamp holder skirt (LH19/RBWE) (KMart) 1 32mm diameter tinplate disk (or brass) 1 22µH 3A axial choke 7mm diameter x 26mm long (Epcos B82111-E-C22) (Farnell 608-671) 1 PC stake 4 M2 x 6mm screws 1 50mm length of red hookup wire 1 50mm length of black hookup wire Semiconductors 1 ZXSC100N8 Zetex DC-DC Converter SO8 package (IC1) (Farnell 384-7962) 1 ZXT13N20DE6 Zetex low Vcesat NPN Transistor (Q1) (Farnell 334-6870) OR 1 ZXT13N50DE6 (Q1) (Farnell 334-6882) 1 BC559 transistor (Q2) 1 ZHCS2000 Zetex Schottky diode (D1) (Farnell 411 5843) Capacitors 2 220µF 10V Rubycon ZL series Ultra Low Impedance electrolytic (Farnell 768-080) 1 1nF ceramic capacitor (code 102 or 1n0) Resistors 1 33 milliohm 1W surface mount resistor (R033) (Welwyn LR series 2010 case) (Farnell 361-0238) 1 22kΩ 0.063W surface mount 0603 case resistor coded 223(Farnell 911-392) 1 3.3Ω 0.063W surface mount 0603 case resistor coded 3R3 (Farnell 357-1130) 1 100kΩ miniature horizontal trimpot coded 105 (VR1) 1 0.1Ω 5W resistor (for setting up); coded 0R1 the 220µF capacitor to provide DC to the LED. Losses in this conversion are mainly in the inductor, the switching transistor Q1, current sense resistor R1 and the diode D1. Efficiency will be high if we can minimise these losses. Since the inductor current is limited to 0.53A (peak) while it is rated at 3A, it will not saturate and will therefore have minimal heating losses. At the same time, transistor Q1 is a low saturation device. Its collector emitter voltage is a maximum of 45mV at 1A which means that there will be little power loss in this device. R1, the current sensing resistor has a value of only 33mΩ (33 milliohms) so the maximum voltage drop when the inductor current reaches 0.53A is 44  Silicon Chip Fig.2 (above): because this is such a tiny PC board, we have shown the overlay above twice normal size. Fig.3 (right) shows the PC pattern at 1:1 scale while the photo below of the nearly-completed PC board is slightly larger than life-size. The trimpot (VR1) needs to have its legs bent under and trimmed to allow it to mount low enough on the PC board, as shown in the diagram below (Fig.4). a mere 17.5mV. Power dissipation in this resistor is so low that even with a constant 0.53A through it, the power would be less than 10mW. In practice, it will be less than 5mW. Losses in diode D1 are kept to a minimum because it is a Schottky type with a rated 385mV forward voltage at 1A. Further efficiencies in the conversion are due to the very low quiescent current drain of IC1 at less than 300µA, and the way Q1 is driven. Transistor Q2 is used to boost the current drive to the base of Q1. IC1 senses the voltage across the 3.3Ω resistor at Q2’s emitter and limits current flow to around 7.5mA into Q1’s base. Q2 therefore operates as a current source providing the base current to This photo is similar to the one above but is now complete with the inductor (L1) and two electros soldered in place. Note that these components are neither vertical nor horizontal –they must be “crammed in” as flat as they can go to allow the PC board to fit in place. www.siliconchip.com.au Fig.5: you’ll need one of these tinplate discs – use this diagram (or the PC board itself) as a template and cut the disc from a tin can. Fig.6: here’s how the LED sits in the reflector. The cathode (black) wire (only!) is soldered to the flange as shown. Q1. When the Vdrive output of IC1 at pin 8 goes to ground, the base drive to Q1 is off and so the transistor switches off, allowing L1 to deliver its power to the load via diode D1. The output power delivered to the 1W LED is related to the peak current in L1, the switching frequency and the difference between the input voltage and the voltage across the LED. The power is regulated using the sense resistor R1 to detect peak current and by sensing the voltage across the LED. VR1 and the 22kΩ resistor divide the LED voltage down and feed it to the FB (feedback) input, pin 6 where it is compared to an internal voltage reference which is around 730mV (nominal). Heavy switching currents drawn from the battery and delivered to the load are smoothed out using low impedance capacitors. Note that good efficiency of the conversion is also dependent on the low effective series resistance (ESR) of the decoupling capacitors. We have specified two 220µF 10V ZL series capacitors from Rubycon. These have an ESR of 130mΩ at 100kHz. You could improve efficiency slightly by using the ZA ultra-low impedance 220µF 10V Rubycon capacitors with 44mΩ impedance instead. However, these cost around ten times more than the ZL series! The 1W LED torch is installed into an Eveready WP250 water-proof torch which uses two D cells. We have designed a PC board (coded 11211031) measuring 33mm in diameter to mount the DC-DC converter components. Note that all components mount on the copper track side of the PC board, opposite to what you would normally do. At the time of writing, none of the kitset suppliers had decided to make a kit available for this project. However, the parts can be obtained from the suppliers mentioned below. You can obtain the 1W LED from Alternative Technology Association, PO Box 2001, Lygon St North, East Brunswick, Vic 3057. Phone (03) 9388 9311; Fax (03) 9388 9322; website: www.ata.org.au Parts listed with a Farnell catalog number can be obtained from Farnell. Phone 1300 361 005; Fax 1300 361 225; website: www. farnellinone.com The PC board can be obtained from RCS Radio Pty Ltd, 41 Arlewis Street, Chester Hill, NSW 2162. Phone (02) 9738 0330; Fax (02) 9738 0334; website: www.cia.com.au/rcsradio Begin construction by checking the PC board carefully. The board should be circular as shown and may need to be cut and filed to shape first. Check for any possible shorts or undrilled holes. The PC board only has five holes, four for the mounting screws and one for the PC stake. The mounting holes can be drilled out to 2.5mm in diameter or you can file the hole in from the edge of the PC board to form an elongated slot. The three main semiconductor devices are small surface mount types which should be soldered in first. The orientation for these is shown in the overlay diagram of Fig.2, with the labelling oriented as shown. To solder these in, you will need a fine tipped soldering iron and a magnifying glass. Place one of these parts in position and solder one outside pin first. Check that it is oriented correctly and that the remaining IC pins lines up with the tracks on the PC board. When correctly lined up, solder the remaining pins. Now solder in the other semiconductor devices in a similar manner. Next, solder in the 33mΩ resistor Start the lens assembly by feeding the LED leads through what was the lamp hole in the reflector. The cathode (black) wire needs to be soldered to the threaded section, as shown above. Next goes the bayonet lampholder skirt which we removed earlier and cut down to 16mm deep. The lampholder (and of course the lamp itself) are not used – that’s the whole point in making this very efficient LED conversion! Finally the assembled PC board is secured into position. This already has the tinplate disc soldered to it, with the whole assembly ready for mounting inside the torch body. The torch switch will still work and battery position will be the same. www.siliconchip.com.au Construction November 2003  45 Fig.7: and finally, here’s how the various pieces fit together in the torch. and the other surface mount resistors. Note that the 3.3Ω and 22kΩ resistors can be standard 0.25W resistors instead of surface mount types and provision has been made to install these with an extra circular pad allocated and spaced for the extra resistor length. All components must be installed on the copper side of the PC board, except for the +3V supply PC stake. Trimpot VR1 is mounted by bending the leads as shown in Fig.4, so that they contact the PC pads allocated for this component and soldering in place. The remaining components are installed by soldering the leads to the copper pads. Keep components below 12mm above the PC board. The capacitors and inductor need to be bent over as shown in the photographs. Cut out a 32mm diameter disk of tinplate from a tin can lid and place this on the back of the main PC board. Fig.5 shows the details. Drill a hole where the PC stake fits through and solder this tinplate disk in place. Cut the PC stake flush against the tinplate. Also drill and file out the four mounting holes. As mentioned, the LED torch is built into a standard Eveready WP250 water-proof torch. The reflector needs to be removed from the lens cap so that the 1W LED can be installed. To remove the reflector, scrape around the inside of the lens cap where the reflector sits, to remove the plastic that has been heat welded to the reflector. We used a flat screwdriver and scraped away till the reflector came loose. The 1W LED assembly will require a small amount of filing at each corner base so that it will sit comfortably within the reflector and no more than 5mm above the reflector lip. This is to prevent the LED assembly making contact with the inside of the torch lens. Fig.6 shows how the Luxeon LED is installed and connected. Note that if you install the LED in a different torch, you may need to drill four holes in the reflector so that each corner of the LED assembly can sit inside the hole. The PC board is installed at the rear of the torch reflector assembly using a 240VAC bayonet lamp holder skirt. This is cut down to 16mm in height from the screw thread end and glued to the plastic flange at the rear of the torch reflector using super glue. The PC board is placed over the rear of the bayonet lamp holder and the four holes are drilled 2mm in diameter for the securing screws. Note that you will need to scrape away a little of the bayonet holder for the solder connections to sit into allowing the PC board to sit flat against the rear of the holder. Also mark the orientation of the PC board onto the bayonet lamp holder so that it will be installed with the same orientation each time. We used a red marking pen to show the correct orientation. Fig.7 shows these details. Setting up Wire the circuit up as shown but with a 0.1Ω, 5W resistor in series with the LED. Set VR1 fully anti-clockwise and connect a multimeter across the 0.1Ω resistor set to read DC millivolts. Using a piece of wire, connect the two D cells to the torch (take care to get the correct polarity) and adjust VR1 for a reading of 35mV. Then remove the 0.1Ω resistor and finish wiring. Attach the PC board to the bayonet lamp holder skirt with the M2 screws. Assemble the torch together, making sure the batteries are placed in with the positive side up. SC It’s finished! This photo is taken “turned off” so you can see at least some of the detail inside the lens. Our modification turns the very nice Eveready WP250 Torch into a sensational model! We thought our previous LED torches were good – but with the newLuxeon 1W LED this is by far the best one ever. 46  Silicon Chip 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. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au 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 PRODUCT SHOWCASE Altronics MP3 Player, Amp Kit If you’re looking for a way to “go mobile” with your MP3 music collection, then check out the new Altronics K2770 MP3 Player kit. It works with a standard IDE hard disk drive, meaning it can store gigabytes of music – up to 10,000 tracks, in fact! The kit comes with a pre-punched and silk-screened metallic silver case, and includes a graphical LCD display along with an array of push-button switches for player control. You can even drive the beast with an infrared remote control! The DIN-sized case can house one 3.5-inch hard drive (not supplied), a pre-assembled MP3 jukebox PC board, LCD display module, front panel PC board and power supply PC board. The MP3 jukebox PC board forms the core of the player. Its main functional components consist of a PIC micro, MP3 decoder and stereo D-A converter. Included on the board are connectors for an LCD module, IDE hard drive, power supply, switch inputs and stereo signal output. Almost all on-board components are surface-mounted, which probably explains why Altronics is supplying this part of the kit pre-assembled and tested. The power supply and front-panel boards are supplied as kits of parts. These boards are relatively simple and assembly should not present too much of a challenge to those familiar with the pointy end of a soldering iron. Internal wiring is surprisingly simple too, with the LCD module mounting “piggy-back” on the MP3 board. Hook-up to the hard disk drive is via a conventional 40-way ribbon cable. The unit should work with most ATA-compliant IDE hard disk drives. For use in a car, a 2.5” laptop drive is mandatory as these are much more shock tolerant. However, you’ll need to purchase a 3.5” to 2.5” adapter kit. One negative is that the kit doesn’t provide an easy way of transferring your MP3s onto the hard disk. You must physically remove the drive and plug it into an IDE port in your PC in order to get the files onto the drive. We would not recommend this to anyone www.siliconchip.com.au unfamiliar with the internals of their PC. Audio output from the player is via twin RCA sockets.The unit can be powered from a 12V DC regulated or 13.8V DC unregulated source. Amplifier add-on Altronics also offer a companion 15W stereo amplifier kit. With this add-on, all you need are two bookshelf-style speakers for a complete, stand-alone jukebox. The amplifier is based around Philips TDA1519 amplifier modules, as used in the SILICON CHIP 12V Stereo Amplifier (May 2001). A single PC board carries all of the components, with the amplifier modules bolting up to a small heatsink at the rear of the case. The kit is supplied with a look-alike pre-punched metallic silver case. Twin RCA sockets and an unregulated DC output is provided at the rear for connection to the player unit. Plug-in screw terminal blocks are used for the speaker connections. Note that unlike the player, this unit is mains-powered. Mains input is via an IEC socket and a small (80VA) toroidal transformer. Summary The K2770 MP3 Player kit boasts a host of features that would make it useful for a variety of applications. With a DIN-sized case and 12V operation, it should work well as part of a monster car audio system. Using the automatic random play mode, it could also be used as part of a “canned music system”, such as in a PA setup or as part of a “music on hold” service. Specs at a glance: ·· · 122 x 32 graphical LCD Shuffle & sequential mode playback Stop/play/pause/next track/prev track/ ·· ·· skip/manual track selection Automatic random playback mode Supports multiple directories, ID3V1 tags and “artist-title” track naming Detailed track statistics shown on LCD Standard DIN sized case Special pricing The K2770 MP3 Player kit normally retails for $329, but is currently available at the special price of $299. This includes an A1013 infrared remote control. The K5101 Stereo Amplifier kit retails for $149. Contact: Altronic Distributors PO Box 8350, Perth Business Centre,6849 Tel: 1300 797 007 Website: www.altronics.com.au AUDIO MODULES broadcast quality Manufactured in Australia Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 9476-5854 Fx (02) 9476-3231 November 2003  59 New DPO family from Tektronix Tektronix, Inc. has announced the TDS700B family of new digital phosphor oscilloscopes (DPO) which feature the most advanced triggering, signal fidelity and analysis capabilities of any oscilloscopes on the market at comparable price points. The 4GHz TDS7404B, the 2.5GHz TDS7254B and the 1.5GHz TDS7154B provide more than 400,000 waveforms per second waveform capture display. Designers can implement data rates up to a Gigabit per second (1Gb/s) and rise times on the order of 100 picoseconds (100ps). The TDS7000B Series DPOs waveform capture rate is orders of magnitude better than existing digital storage oscilloscopes (DSOs) in delivering faster accumulation of signal data for both critical insight into signal behavior and indepth analysis. Qualified triggers help designers hone in quickly on problems due to errors that are considered faults only when they occur after qualifying events or time. Other triggers include a broad selection of edge, timing, setup/ hold, fault, and event triggers. This new trigger system features trigger jitter as narrow as 1.0ps RMS and the circuit can detect glitches as low as 110ps. The new DPOs uniquely address both hardware and software clock recovery by a new, continuously variable (1Mb/s to 3.125Gb/s) built-in Computer/Notebook USB TV box with FM radio Want to watch TV (or receive FM radio) on your computer or notebook? Or play standard (composite) video (eg, from a VCR) on your computer? Just connect this nifty little device from Microgram to your USB port. There are connectors for a TV anten- na, FM antenna, S-video in, composite video in, audio in and audio out. A full function remote control is also included. It supports USB 1.1 on a Pentium computer (166MMX min.) using Windows 98SE/Me/2000/XP. Recommended retail is $179.00. Contact: Microgram Computers PO Box 8202, Tumbi Umbi NSW 2261 Tel: (02) 4389 8444 Website: www.mgram.com.au Tech-Rentals has R&S FHS3 Handheld Spectrum Analyzer Tech-Rentals has recently acquired a number of Rohde & Schwarz FSH3 handheld spectrum analyzers; for short or long term rental or purchase. With small dimensions and a large display, it has an upper frequency limit of 3GHz and numerous measurement functions. It has been specifically designed for mobile applications, including areas of mobile communication such as installation, maintenance, servicing and fieldstrength measurements, as well as use in labs and universities or by electronics hobbyists. The integrated Windows software provides relevant documentation allowing the user to track changes in the case of recurring measurements. The measurement results can be stored in the common graphics formats, as text files or in Excel format, complete with 60  Silicon Chip date and time and all settings. Contact: Tech-Rentals Tel: 1800 632 652 Website: www.techrentals.com.au hardware clock recovery circuit or by integrated software clock recovery tools, embracing the widest range of serial standards. Contact: NewTek Sales Pty Ltd Tel: (02) 9888 0100 Website: www.newteksales.com.au Who said the floppy is dead? Many PCs these days do not have floppy disk drives. That’s fine until you need to read a floppy! Proving that the 1.44Mb/1.4Mb formats are not yet dead, Targus Australia has launched a new “Slimline” external floppy drive that powers up from the USB port. This neat little drive (14 x 10.4 x 1.8cm) is completely plug’n’play. The first time it is connected, the notebook recognises the device and treats it just the same as a built-in. The easy hot-plug installation means it can be connected and disconnected while the notebook/PC is in use and the simple, one cable USB connection means no tangled wires or clumsy ‘power bricks’. With an expected retail price of $109.95, the Slimline can read and write to 3.5-in floppy disks including 720K/1.44Mb Windows (2000, Me & XP) and 1.4Mb Macintosh formats. It carries a full 12-month warranty. Contact: Targus Australia Pty Ltd Tel: (02) 9807 1222 Website: www.targus.com.au 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 . For one low rate you receive a printed entry each month on the SILICON CHIP WebLINK page with your home page graphic, company name, phone, fax and site details plus up to 50 words of description– and this is repeated on the WebLINK page on the SILICON CHIP website with the link of your choice active. Get those extra hits on your site from the right people in the electronics industry – the people who make decisions to buy your products. Call SILICON CHIP today on (02) 9979 5644 Our website is updated daily, with over 5,500 products available through our secure online ordering facility. Features include semiconductor data sheets, media releases, software downloads, and much more JAYCAR JAYCAR ELECTRONICS ELECTRONICS Tel: Tel: 1800 1800 022 022 888 888 WebLINK: www.jaycar.com.au WebLINK: www.jaycar.com.au BitScope is an Open Design Digital Oscilloscope and Logic Analyser. PC software drives BitScope via USB, Ethernet or RS232 to create a powerful Virtual Instrument. BitScope is available built and tested or in kit form. Extensive technical details are available on the website. Great for hobbyists, university labs and industry. BitScope Designs Contact: sales<at>bitscope.com Contact: sales<at>bitscope.com WebLINK: bitscope.com WebLINK: bitscope.com A 100% Australian owned company supplying frequency control products to the highest international standards: filters, DIL’s, voltage, temperature compensated and oven controlled oscillators, monolithic and discrete filters and ceramic filters and resonators. Hy-Q International Pty Ltd Tel:(03) 9562-8222 Fax: (03) 9562 9009 WebLINK: www.hy-q.com.au JED designs and manufactures a range of single board computers (based on Wilke Tiger and Atmel AVR), as well as LCD displays and analog and digital I/O for PCs and controllers. JED also makes a PC PROM programmer and RS232/RS485 converters. Jed Microprocessors Pty Ltd Tel: (03) 9762 3588 Fax: (03) 9762 5499 WebLINK: jedmicro.com.au Free simulator program, tutorial SPLat Controls is an Australian manufacturer of embedded programmable controllers who supply OEM users world-wide with off the shelf and custom control solutions. SPLat have developed a tutorial and companion simulator program for users wishing to implement PID (Proportional, Integral, Derivative) control functions. www.siliconchip.com.au 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°. · Hifi upgrades & modification products - jitter reduction and output stage improvement. · Danish high-end hifi kits - including pre- amps, phono, power amps & accessories. · Speaker drivers including Danish Flex Units plus a range of accessories. Soundlabs Group Syd: (02) 9660-1228 Melb: (03) 9859-0388 WebLINK: soundlabsgroup.com.au Av-COMM Pty Ltd Tel:(02) 9939 4377 Fax: (02) 9939 4376 Tel:(02) WebLINK: avcomm.com.au WebLINK: avcomm.com.au We specialise in providing a range of Low Power Radio solutions for OEM’s to incorporate in their wireless technology based products. The innovative range includes products from Radiometrix, the World’s leading manufacturer. TeleLink Communications Tel:(07) 4934 0413 Fax: (07) 4934 0311 WebLINK: telelink.com.au The program is called PIDassist and simulates a controller and a target process. It can also be used as a data acquisition tool for characterising the process and also includes an automatic code generator that produces the SPLat program code required to implement the control function. The tutorial is located in the online SPLat Knowledge Base and contains a thorough but non-mathematical treatment of the theory of PID controlment of an engineering course in Universities or TAFEs. To access the tutorial and download a free copy of PIDassist, go to the SPLat website at: splatco.com. SC au/splat/pidassist1.htm Contact: SPLat Controls 2/12 Peninsular Bvde, Seaford Vic 3198 Tel: (02) 9878 5544 Fax: (02) 9878 6366 Website: www.splatco.com.au November 2003  61 Communicate without wires . . . Smart radio modem for microcontrollers This cheap and simple radio modem will enable your PICAXE, Stamp or other micro to communicate without wires! L By NENAD STOJADINOVIC OW COST, simple construction and easy interfacing makes this project ideal for a whole range of low-speed wireless data applications. Remote control and sensing are two obvious uses and there are undoubtedly many more. Even if you’re just learning about microcontrollers, you’ll be able to get two PICAXEs talking in no time! 62  Silicon Chip The seeds of this project were sown when I got a call from Mr Vineyard, whose grapes kept freezing during the depths of winter. He said he needed a system that would turn on a misting water spray over the vines when the temperature dropped below a certain level. Apparently, Jack Frost would then freeze the water rather than the grapes. This seemed a bit dubious but I was assured that this is a well-known method of frost damage control. The only complicating factor was that the temperature sensors needed to be amongst the vines which were up to half a kilometre away from the shed that housed the water control valves. Given half a dozen sensors, the amount of wiring needed was clearly impractical. And Mr Vineyard was very keen to have a temperature readout in his home so he could keep an eye on things. Going wireless Wireless networking was an obvious choice for the job. Microcontroller-based temperature sensors placed www.siliconchip.com.au www.siliconchip.com.au November 2003  63 Fig.2: one end of the radio link can also be connected to a PC (or any computer with an RS232 port). As shown here, the receiver includes an RS232 interface on-board, whereas the transmitter requires an add-on interface. Fig.1: a block diagram of the radio modem, showing how two microcontrollers can be linked together. Fig.3: the UHF receiver module uses a “bit slicer” circuit to convert the linear signal into digital format. strategically amongst the vines could transmit their readings back to a central computer, which would then control the pumps. Since commercial wireless networking gear was too expensive for this application, the alternative was to design the wireless network from the ground up, with the aid of pre-built UHF radio modules. These miniature modules operate in the 433.05 - 434.79MHz LIPD band and do not require a license for operation at up to 25mW of output power. The advertising blurbs suggest that it’s simply a matter of pumping serial data into the transmitter module and recovering it at the receiver (“data in - radio out”). Discovering that this was anything but true is what people ruefully refer to as a “learning experience”. As it turns out, the data must be “massaged” (encoded, decoded, error checked, etc) at either end of the link to achieve reliable transfer across the airwaves. This was achieved with the aid of Microchip’s PIC microcontrollers and many hours of program- Main Features • • • • • • Point-to-point, one-way wireless data link Error-checked data transfer Low cost & easy to build 1200 bps serial interface speed 465 bps end-to-end speed 150-200m range in built-up areas ming. The fruits of these labours are presented here. Project overview The radio modem consists of a transmitter and receiver pair. The designs use pre-built “Laipac” brand 433.92MHz UHF modules, with PIC12C508 microcontrollers handling the “smarts”. Both transmitter and receiver include a TTL-level (0-5V) 1200 bps (bits per second) serial interface for data transfer. This makes it very easy to hook them up to your Stamp, PICAXE, or other micro (see Fig.1). In many cases (such as the vineyard application above), one end of the link will need to be connected to a PC (Fig.2). The receiver board includes an RS232 interface for this purpose. As it’s usually the remote part of the link, the transmitter doesn’t include an on-board RS232 interface. This saves space and reduces power consumption. Where required, it can be mounted on an (optional) RS232 interface board which also supplies power. The receiver and RS232 interface can be powered from either a 9V battery or DC plugpack. When used without the RS232 interface, the transmitter must be provided with a +5V supply. This is usually available from the sensor or associated circuitry. Serial data Most of our readers will already be familiar with the basics of asynchronous serial data transfer. Those new to the subject will find lots of useful information on the Internet. Two informative sources can be found at: (1). http://janaxelson.com/serport.htm (2). www.beyondlogic.org/serial/ serial.htm The word “serial” simply refers to the fact that data is transferred from sender to receiver a single bit at a time. At a minimum, this requires only one complete circuit (two wires) between the sender and receiver. With wires and logic signalling levels, it’s all pretty straightforward. But how does it work over the airwaves? UHF radio modules Fig.4: the complete circuit diagram for the transmitter. Not much to it is there? An 8-pin PIC microcontroller (IC1) receives serial data from the host (PICAXE, Stamp, etc) and transmits it over the airwaves using a UHF transmitter module. 64  Silicon Chip The radio modules used in this project transmit data by simply switching the carrier signal on and off. The terms “On-Off Keying” (OOK) and “amplitude modulation” (AM) are used interchangeably to describe this method of transmission. The transmitter module consists of a SAW-stabilised RF oscillator tuned to 433.92MHz. When a logic ‘0’ (0V) is applied to the data input (DIN) pin, the oscillator is off and when logic ‘1’ (+5V) is applied, the oscillator is on. An antenna coupled to the circuit radiates the carrier signal into the ether. Things get a bit more complicated at the receiver side. Unfortunately, the manufacturer’s data sheets don’t reveal www.siliconchip.com.au much about its operation. Of course, we do know that it amplifies and rectifies the narrow-band 433.92MHz (±1.5kHz) signal picked up by the antenna, with the result appearing on the Linear Output (LOUT) pin. Data slicing A digital version of the signal also appears on the Digital Output (DOUT) pin. Conversion between analog (linear) and digital is performed with a “bit slicer” circuit. As the name suggests, the bit slicer looks at the incoming signal and decides whether it should be a logic ‘0’ or logic ‘1’, “slicing” it up accordingly. This is achieved with a circuit similar to that shown in Fig.3. IC1 is configured as a comparator and once the capacitor is charged up, a signal peak at the input will result in a high at DOUT while a signal minimum will result in a low. The frequency of ‘1’s (transmitter on) and ‘0’s (transmitter off) in the data stream determine the accuracy of the slicer. If the time between ‘1’s is too long, the capacitor voltage sags and ‘1’s will be detected as ‘0’s instead. Conversely, if the data stream contains Fig.5: this add-on interface connects the transmitter to an RS232-compatible serial port. The MAX232 chip (IC1) handles the RS232 (±10V) to TTL (0-5V) level conversion, while 3-terminal regulator REG1 also powers the transmitter board. Fig.6: the receiver circuit is almost a mirror image of the transmitter. PIC micro IC1 receives data from the UHF receiver module and after decoding and error checking, passes it on to the host via the DATA output. Unlike the transmitter, an RS232 interface (IC2) is included on-board. www.siliconchip.com.au November 2003  65 Fig.7: follow this diagram when assembling the transmitter. If you’ve opted for a more elaborate antenna (instead of the single length of wire), the coax shield can be soldered to the ground pad right next to the antenna connection point. too many consecutive ‘1’s, a ‘0’ will go undetected. Transmission speed also affects the average voltage on the capacitor. Circuit time constant is optimised for a particular “baseboard” data rate, which for these modules is specified as 3000 bps. As you can see, the ideal situation exists when the transmitter is fed with an alternate stream of ‘1’s and ‘0’s at the prescribed data rate. In fact, data transmission must begin with a preamble of alternating 1’s and 0’s of sufficient length to “initialise” the data slicer at the receiver end. Of course, during “normal” transmission, data can consist of any combination of ‘1’s and ‘0’s. This is easily accommodated by encoding the data before transmission. Manchester encoding A number of encoding techniques can be employed to ensure that the data stream contains a balance of ‘1’s and ‘0’s. This project uses “50% Manchester” encoding, which simply involves sending every bit along with its complement. Thus ‘0’ becomes ‘01’ and ‘1’ becomes ‘10’. It is simple and robust but does take twice the time to send each byte. However, this is not of particular concern for our “lowspeed” link. Error detection With all the potential for lost or corrupted data over a radio link, some kind of error detection system is mandatory. Along with data encoding, error detection is another of the main functions of the PIC microcontrollers in the transmitter and receiver pair. The PIC micro in the transmitter sends data in blocks or “packets”. Before transmission, all data bytes in a packet are passed through a polynomial generator, with the result being an 8-bit number called a “Cyclic Redundancy Check” (CRC). This byte is appended to the end of a packet before transmission. On the receiver side, incoming data is passed through the same polynomial generation algorithm and the result is compared to the received CRC byte. If they match, the data is deemed good. Otherwise, it is assumed bad and the entire packet discarded. If you’re interested in the algorithm and microcontroller code required to generate CRCs, then check out Microchip’s application note AN730, entitled “CRC Generating and Checking”. It can be downloaded from www.microchip.com Bytes & packets As mentioned above, data received from the “host” (your PICAXE, Stamp, Fig.8: receiver assembly is also quite straightforward. The UHF receiver module must be oriented with its inductors (coils) facing the two ICs. The “SPARE” signal line is not used and should be left unconnected. 66  Silicon Chip www.siliconchip.com.au Fig.9: the overlay diagram for the optional RS232 interface. Install all components before mounting the transmitter board. Note that the electrolytic capacitors go in different ways, so make sure that you have their positive leads oriented as shown PC, etc) is assembled into packets before transmission. Each packet is preceded with a preamble, two “authorisation” bytes (FF 00) and a length byte to indicate the number of data bytes to follow. Data length may be from 1-16 bytes, with a CRC byte appended to the end. Of course, the receiver returns only the data part of the transmission to its host; the other bytes are strictly for housekeeping. This means that apart from a certain amount of latency, the radio modem link looks just like a piece of wire between the sender and receiver! So far, we’ve only described the radio side of the link. Let’s now look at how you connect your PICAXE, Stamp or whatever to the transmitter and receiver. Transmitter hook-up Your microcontroller project interfaces to the transmitter via a 3 or 4-wire interface (see Fig.1). For a basic setup, you need connect only the DATA, SEND and GND lines. Serial data must be sent on the DATA line at 1,200 bps using the standard format of 8 data bits, no parity and 1 stop bit. The SEND line is used for handshaking and in the idle state must be held high (+5V). To transmit data, send 1-16 bytes and then bring the SEND line low (0V). Data transmission begins immediately and after an appropriate delay (see the “Radio-Modem Performance” panel), the SEND line can be brought high www.siliconchip.com.au Listing 1 symbol symbol begin: SEND = 1 TX_DATA = 2 high SEND pause 1 serout TX_DATA,T1200,(“A”) low SEND pause 500 goto begin again and the transmitter is ready to accept more data. The PICAXE microcontroller program to transmit a single character at a time might look something like that shown in Listing 1. For maximum transmission speed, the BUSY line can be connected as well. This line is an output from the transmitter and indicates its status. When BUSY is high, the transmitter is sending data, and when low, it’s 'transmitter SEND line on pin 1 'transmitter DATA line on pin 2 'raise the SEND line '1ms delay 'load the ASCII character “A” 'lower the pin to send the data 'wait 0.5 sec while the data goes 'loop to repeat forever ready to accept the next packet of data. Listing 2 shows a simple example. Note that attempting to load more than the maximum of 16 bytes at a time will result in BUSY going high and the additional bytes going into the bit bucket. Receiver hook-up The receiver interface is even simpler and requires only a 2-wire connection. Again, a fragment of PICAXE Listing 2 symbol symbol symbol begin: waitrdy: SEND = 1 TX_DATA = 2 BUSY = 3 high SEND pause 1 serout TX_DATA,T1200,(“Hello”) low SEND pause 1 'transmitter SEND on pin 1 'transmitter DATA on pin 2 'transmitter BUSY on pin 3 'raise the SEND line ‘1ms delay ‘load the ASCII string “Hello” 'lower the pin to send the data '1ms delay if BUSY = 1 then waitrdy goto begin 'loop until not busy (data sent) 'repeat forever November 2003  67 Radio Modem – Performance Range: maximum output power with a 5V supply is listed as 25mW (14dBm) into a 50Ω antenna. This provides a range of 150 - 200 metres in the suburbs and rather more over open terrain. Maximum range is heavily dependent on antenna efficiency and environmental conditions. Speed: data is transferred between the transmitter/receiver and the connected device (PC, PICAXE, etc) at a rate of 1200 bps. However, due to the overheads involved in the radio transmission, actual throughput is slightly less than half that speed. Calculated on a maximum payload of 16 bytes per transmission, the radio link speed is equivalent to about 465 bps. That’s about 343ms per transmission, plus the time taken to load and unload the data at either end (about 8.33ms per byte). Power consumption: with a 9V supply, the receiver consumes about 16mA. More than 10mA of this is used by the MAX232, so for battery-powered receivers, don’t install this chip if it’s not needed. When idle, the transmitter requires less than 1mA. During transmission, this peaks at about 6mA. When plugged into the RS232 board, total consumption increases to 12mA at idle and about 17mA (peak) when transmitting. code illustrates how to receive a byte – see Listing 3. As you can see from this listing, it’s simply a matter of listening on the DATA line for the incoming serial data. PC Connection One end of the link can also be connected to a PC or other computer system with an RS232-compatible serial port (see Fig.2). The receiver board includes an RS232 interface, so it’s a simple plug-n-play proposition. Alternatively, for remote control applications, the transmitter end can have the RS232 connection. A simple add-on RS232 interface board (is required for the hook-up (see Fig.6 and the photos). A PC connected to the receiver board can display and/or capture incoming data with a simple serial terminal program (see the testing procedure below). If the data is in ASCII format, Windows “HyperTerminal” will suffice. However, if you want to see the “raw” binary data, then you’ll need a program like “RealTerm” instead. RealTerm is available free from realterm.sourceforge.net To send data from a PC connected to the transmitter, you need more than a simple terminal program. Your application must take control of the SEND line (RTS), and optionally read the status of the BUSY line (DSR). Note: the radio modem is not intended for PC to PC data transfers. Attempting to move “PC-sized” amounts of data across a 465 bps link would be pointless. Transmitter assembly With only nine parts on the board, you’ll have the transmitter assembled in no time at all. Fig.7 shows the component placement. The three 1kΩ resistors must be mounted vertically rather than horizontally and note the orientation of the 2.2µF capacitor and microcontroller (IC1). In addition, make sure that you have the transmitter module in the right way around – the SAW resonator (in the round metal can) must face towards IC1. Receiver assembly Install the single wire link first, using 0.7mm tinned copper wire. All components can then be installed in Listing 3 Symbol RX_DATA = 2 serin RX_DATA,T1200,B2 68  Silicon Chip 'receiver DATA on pin 2 'wait for a byte & store it in variable B2 order of height (see Fig.8). Again, take care with the orientation of the polarised components, these being diode D1, the 22µF capacitors and the ICs. The receiver module goes in with its coils facing toward the ICs (see photos). If don’t intend connecting the receiver to a PC, you can leave out the MAX232 receiver/driver (IC2). This will save power in a battery-powered setup. However, you may prefer to socket the chip and remove it later, as the test procedure (below) requires a PC connection. RS232 interface assembly As before, install the two wire links first, then all components in order of height. Take particular care with the orientation of the four 1µF capacitors, as they go in different ways around on the PC board. The transmitter board mounts vertically near one edge of this board via 90° header pins. Install the 2-way and 3-way SIL header pins on the transmitter board first and then fit this assembly to the RS232 interface board. Before soldering into place, check that the edge of the transmitter PC board contacts the RS232 PC board and that the whole arrangement is sitting “square”. Antenna For testing purposes and many real-world applications, the antenna can be as simple as a 165mm length of light-duty hook-up wire. Strip and tin one end of the wire and solder to the transmitter’s antenna connection point. Repeat for the receiver board (see Figs.7 & 8). For best results, the antenna wires should be kept clear of large metal objects and human bodies! Testing Both the receiver and RS232 interface boards can be powered from a 9V battery or 9V DC plugpack. The battery clip leads (or flying leads from a panel-mount DC socket) can be soldered directly to the ‘+V’ and ‘0V’ pads. Note: 12V DC unregulated plugpacks are not suitable for this project due to their excessively high output voltages at light loads. If you’re not using the RS232 board, connect a regulated 5V supply to the transmitter’s ‘+5V’ and ‘GND’ pads. Next, connect the receiver to a free www.siliconchip.com.au Where To Get The Parts Kits of parts for this project are available from the author. Kits include the PC board and all on-board components (battery, plugpack, enclosure & antenna are not supplied). At time of writing, prices are as follows: Transmitter............................................................................................... $25 Receiver................................................................................................... $40 Transmitter & Receiver pair...................................................................... $60 RS232 Interface....................................................................................... $25 Programmed PICs can also be purchased separately: PIC12C508A for Transmitter (including 4MHz resonator)........................ $15 PIC12C508A for Receiver (including 4MHz resonator)............................ $15 If you’re interested in a “rubber duck” or other specialised antenna, write and ask for a current price list. All prices include postage within Australia. To order, write or email the author at: Nenad Stojadinovic, PO Box 320, Woden, ACT 2606. email: vladimir<at>u030.aone.net.au The Laipac UHF transmitter & receiver modules are also available from Commlinx Solutions, online at www.commlinx.com.au serial port on your PC using a standard 9-way “pin-to-pin” cable (not a “null modem” type). To be able to “see” the incoming data, launch your favourite serial terminal application. HyperTerminal (supplied with Windows) will do the job. Set the terminal’s communication parameters to match the chosen COM port, with a data rate of 1200 bps, 8 data bits, 1 stop bit and no parity. Right, we’re all set. Make sure that transmitter power is off and place a jumper shunt across the “TEST” pins (JP1). Now power up the transmitter and you should see the characters “0123456789:;<=>?” appear in the terminal window. A built-in test routine transmits this string of characters continuously when the SEND line is held low (0V) at power-up. This, of course, is the purpose of the “TEST” jumper. Fault-finding No go? First, check the supply This view shows the completed RS232 interface with the transmitter board mounted in position. www.siliconchip.com.au rails. To do this, use your multimeter to measure between pins 1 & 8 of IC1 on both the transmitter and receiver boards. On the receiver, expect close to 5.0V, whereas on the transmitter, your reading should be about 4.7V. Next, use a logic probe or oscilloscope to monitor the signal on pin 7 of the transmitter’s micro (IC1). With the jumper shunt (JP1) installed at power-up, there should a burst of pulses each time the 16-character test string is transmitted. If that checks OK, then it’s over to the receiver side. Examine pin 4 of the receiver’s micro (IC1). Normally, background noise picked up by the UHF receiver module appears on this pin as random “garbage”. However, you should see a distinctive change in the pattern whenever the test string is received. Assuming that you see signs of activity, then measure at the micro’s serial data output (pin 7). Again, brief bursts of pulses should appear here if the test string is received successfully. The last link The last link in the chain is the MAX232 (IC2) on the receiver. As shown on the circuit diagram (Fig.6), serial data from the micro (pin 7) is applied to the MAX232 on pin 11. Therefore, it should appear on pin 14 after conversion to the ±10V (nominal) RS232 signal levels. This pin should sit near -8V when idle and pulse to about +9V when sending the test data. One option is to fit the transmitter into a small metal diecast case complete with a “rubberduck” antenna. November 2003  69 Parts List Receiver 1 PC board coded 06111031, 63mm x 55mm 1 Laipac RLP-434 transmitter module 1 PIC12C508A (programmed) (IC1) 1 MAX232 RS232 receiver/driver (IC2) 1 78L05 +5V regulator (REG1) 1 1N4004 diode (D1) 1 4MHz 3-pin ceramic resonator (CR1) 1 D9 female connector, 90° PCmount (CON1) 1 9V battery & battery clip -OR1 9V DC 150mA plugpack & panel-mount DC socket to suit Capacitors 2 22µF 25V PC electrolytic 7 100nF 50V monolithic Resistors (0.25W, 1%) 2 1kΩ Transmitter 1 PC board coded 06111032, 37mm x 29mm 1 Laipac TLP-434 transmitter module 1 PIC12C508A (programmed) (IC1) 1 1N5819 Schottky diode (D1) 1 4MHz 3-pin ceramic resonator (CR1) Capacitors 1 2.2µF 16V tantalum 1 100nF 50V monolithic Resistors (0.25W, 1%) 3 1kΩ RS232 Interface (optional for transmitter, see text) 1 PC board coded 06111033, 51mm x 46mm 1 MAX232 RS232 receiver/driver (IC1) 1 78L05 +5V regulator (REG1) 1 D9 female connector, 90° PCmount (CON1) 1 3-way 2.54mm 90° SIL header 1 2-way 2.54mm 90° SIL header 1 2-way 2.54mm SIL header (JP1) 1 jumper shunt (JP1) 1 9V battery & battery clip -OR1 9V DC 150mA plugpack & panel-mount DC socket to suit Capacitors 4 1µF 16V PC electrolytic 2 100nF 50V monolithic Resistors (0.25W, 1%) 1 1kΩ If you’ve successfully traced the test data from start to finish, then the problem must be related to your computer! Double-check the terminal program settings and the cable connection between the unit and the PC. A good vintage, indeed What of the “radio thermometer” project? Well, I built it into one of those cheap solar-powered LED garden lights. Using ‘sleep’ mode on the micro, the device now sends temperature and humidity readings to the water control unit every minute or so and is working very nicely after six months of totally unattended operation! More reading Technical data on the RLP-434 & TLP-434 UHF modules used in this project can be downloaded from the Laipac Technology web site at www. laipac.com For details on government regulations regarding LIPD radio communications devices, visit the Australian Communications Authority web site at www.aca.gov.au/aca_home/ legislation/radcomm/class_licences/ lipd.htm A high-performance commercial radio modem was reviewed in SILICON CHIP, February 2003. Details on the WM232-UHF modem featured in the review can be obtained from http:// SC www.radiotelemetry.co.uk/ New From SILICON C HIP THE PROJECTS: High-Energy Universal Ignition System; High-Energy Multispark CDI System; Programmable Ignition Timing Module; Digital Speed Alarm & Speedometer; Digital Tachometer With LED Display; Digital Voltmeter (12V or 24V); Blocked Filter Alarm; Simple Mixture Display For Fuel-Injected Cars; Motorbike Alarm; Headlight Reminder; Engine Immobiliser Mk.2; Engine Rev Limiter; 4-Channel UHF Remote Control; LED Lighting For Cars; The Booze Buster Breath Tester; Little Dynamite Subwoofer; Neon Tube Modulator. ON SALE AT SELECTED NEWSAGENTS Mail order prices: Aust: $14.95 (incl. GST & P&P) NZ/Asia Pacific: $18.00 via airmail Rest of World: $21.50 via airmail Or 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. 70  Silicon Chip www.siliconchip.com.au 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. Making the Flexitimer cycle on and off The Flexitimer published in the March 1991 issue of “Electronics Australia” is still a popular project but it has the drawback that it is “once only” timer. Once it has timed out, it is effectively disabled. We have had many requests asking how it can be made to cycle on and off. This can easily done, as shown with this modified circuit. This makes it cycle on and off with a 50% duty cycle, for as long as power is applied. So for example, if it is set for a period of 8192 seconds, it will be off for 8192s, on for 8192s and so on. The modification involves cutting the track connection between pin 4 (reset) of IC1 to the collector of Q1 and tying it to pin 8 (+V). SILICON CHIP. Low battery indicator This simple circuit lights LED1 when the battery voltage drops below the setting set by trimpot VR1. In effect, VR1 and associated resistors bias Q1 on which holds Q2 and the LED off. When the voltage drops below the set value, Q1 turns off, allowing Q2 to turn on and light the LED. The circuit is suitable for nominal battery voltages up to 12V. www.siliconchip.com.au I. Ross, Springwood, Qld. ($30) Simple 9-way cable identifier Here is a simple way of identifying multiple cables (with the aid of a multimeter). The circuit consists of a series of resistors, selected so that they give readings that coincide with the 1-9 numerals on the 10V scale on a multimeter switched to the Ohms x 100 range. In use, a common wire needs to be chosen and this is usual­ly the shield wire. The resistors go to one end of the cables to be identified, while the multimeter is used at the other end to check the values and identify each lead. Up to nine cables can be identified at a time. If a mistake is made in choosing the common lead, the readings will all be wide of the 1-9 numerals on the 10V scale, thus making the mis­take obvious. J. Begg, Heidelberg, Vic. ($20) November 2003  71 Silicon Chip Binders Circuit Notebook – continued REAL VALUE AT $12.95 PLUS P &P  SILICON CHIP logo printed on spine & cover  Buy 5 & get them postage free! Price: $A12.95 plus $A5.50 p&p. Available only in Australia. Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. CONTRIBUTE AND WIN! As you can see, we pay good money for each of the “Circuit Notebook” contributions published in SILICON CHIP. But now there’s an even better reason to send in your circuit idea: each month, the best contribution published will win a superb Peak Atlas LCR Meter valued at $195.00. So don’t keep that brilliant circuit secret any more: send it to SILICON CHIP and you could be a winner! 72  Silicon Chip Clipping indicator for audio amplifiers A clipping indicator is a useful accessory on any audio amplifier. It indicates when the amplifier has reached its limit and is clipping the peaks of the audio signal. In practice, quite a lot of clipping can occur before you can hear it. So why is it necessary to know when an amplifier is clipping if you can’t notice it? The answer is that clipping “squares up” the waveform and square waves contain lots of higher-frequency harmonics which can easily damage the tweeters in loudspeaker systems. This circuit is a true clipping indicator as opposed to the level indicators that are commonly used in preamplifier stages. The problem with level indicators is that an amplifier’s maximum output power is not constant. That’s because the amplifier’s supply rails are not regulated and so the maximum power available at any given instant varies, depending on the applied signal. The circuit is quite simple and is based on two BD140 PNP transistors and zener diode ZD1. During normal operation, Q1 is turned on via ZD1 and R1. As a result, Q2 is held off (since its base is pulled high) and so LED1 is also off. However, if the output signal subsequently rises to within 4.7V of the positive supply rail, Q1 turns off since it no longer has any forward bias on its base. As a result Q2’s base is now pulled low via R2 and so Q2 Philip C is this m hugg o winner nth’s o Peak At f the las LCR Meter turns on and lights LED1. (Note: the 0.6V drop across Q1’s base/emitter is ignored here because ZD1 conducts before its rated voltage due to the very low current in­volved). Why choose 4.7V below the power rail as the turn-on point? The reason is that, due to the drive limitations and the nature of emitter followers, they can be expected to have at least 4V across them when they saturate (ie, clip). ZD1 can be increased to a 5V or 6.2V type if the circuit is to be used with a monster amplifier. The value of R3 should be customised according to the amplifier’s supply rail, so that LED1 operates with the correct brightness. To do that, first measure the amplifier’s positive supply voltage, then use Ohms Law (R = V/I) to calculate the value of R3 for a current of about 20mA. As it stands, this circuit can only be used to monitor the positive-going half-cycles of the audio waveform. If you want to monitor the negative half-cycles as well, you will have to build a second circuit with the following changes: (1) reverse both LED1 and ZD1; and (2) use BD139 (NPN) transistors for Q1 & Q2. Note that, in both cases, you should use the earth inside the amplifier, as the speaker negative may not be earth (such as in a bridged output). Philip Chugg, Launceston, Tas. www.siliconchip.com.au 8V DC supply with overvoltage protection This 8V DC power supply was designed for use with an expen­sive piece of electronic equipment. It features full over-voltage protection as a precaution against regulator failure, either in the supply itself or inside the equipment it is powering. The circuit uses a conventional full-wave rectifier, fol­ lowed by a 3-terminal voltage regulator (REG1) with appropriate filtering. When power is applied and switch S1 is in the “Run” position, REG1’s output is fed to the load via a 500mA fuse and Schottky diode D3. This also lights LED2 (yellow) and LED3 (green), which respectively indicate the presence of the unregulated and regulated voltages. D3 is there to protect the circuit against external voltage sources (eg, charged capacitors). A “crowbar” circuit comprising ZD1 and SCR1 provides the over-voltage protection. It works like this: if a fault develops (eg, REG1 short circuit) which causes the output voltage to rise above 9.1V, ZD1 turns on and applies a voltage to the gate of SCR1. If the voltage then continues to rise, SCR1 turns on (at about 10V) and “blows” the fuse. Zener diode ZD2 provides emergency over-voltage protection in case the “crowbar” circuit develops a fault. Switch S1 is provided so the operator can occasionally test the “crowbar” function. When S1 is switched to the “Test” posi­tion, the load is disconnected by S1b and the unregulated supply voltage is applied by S1a to the “crowbar” circuit, thus causing it to trigger. When this happens, LEDs 2 & 3 (green and yellow) extinguish and LED1 (red) lights to indicate that the SCR has triggered. The SCR turns off again when S1 is switched back to the “Run” position. L. Cox, Forest Hill, Qld. (45) Cheap switchmode DC-DC converter This circuit is based on mobile phone chargers available from bargain stores such as “Silly Sollys” for about $4.99. These chargers are based on the Motorola MC34063 switchmode IC. By changing the values of the feedback resistors (R1 & R2), the output voltage can be varied over a wide range. Just modify R1 and R2 according to the formula: Vout = 1.25 (1+R2/R1). www.siliconchip.com.au The values shown give an output of 3V. Timo Mahoney, Chillagoe, Qld. ($30) November 2003  73 MOVING UP IN THE PICAXE WORLD BIG BROTHER IS WATCHING YOU. . . (Picaxe’s big brother, that is) OK, Picaxe enthusiasts – you’ve diligently followed our “08” articles and can rightly claim your Picaxe “drivers licence”. Time to hit the highway, maybe? by Stan Swan A s hinted during our earlier articles, the Picaxe range in cludes seven big brothers, grouped into 18, 28 and even 40-pin families. Although the baby “08” remains supreme for simple control circuits, it’s rather like using a two-door hatchback for a cross country workout. Consider the 18s as perhaps akin to 4WDs, 28s as Rally cars, while 40s. mmm – well you get the idea! The 40X is so long in fact that it looks like a toy aircraft carrier! These larger devices, although featuring powerful further commands, still obey the key 35 “08” instructions, so all you’ve learnt so far can be immediately put to use – but it’s obviously a waste to spend much more to just flash a few LEDs with them! Although this month’s coverage relates to the 18A, we’ve also shown a summary of the family overall (including the recently-released fire-breathing 18X). All enjoy the usual wide supply voltages (3-5.5V), 4MHz clock and direct ~20mA output drive but larger versions have dedicated Input or Output pins rather than the versatile I/Os of the “08”. Note that the basic 18 and 28 74  Silicon Chip Picaxes, inferior to the “A” and “X” versions, are obsolete and no longer marketed. Incidentally, no “A” or “X” updates are planned for the “08” series. Since Picaxes of course are PIC based, it’s worth comparing the pin compatible 18-pin models with the ubiquitous PIC16F84 – now itself obsolete as replaced by the cheaper and more powerful 16F627 with an internal oscillator as well. The enhanced PIC16F627 (the 16F819 – only released by Micro-Chip in January 2003), is the PIC that the Name Mem I/O Out (Pins) lines pins 08 18 18A 18X 28 28A 28X 40X 40 40 80 600 80 80 600 600 5 1-4 13 8 13 8 14 9 20 8 20 8 21 9-17 32 9-17 In- ADC puts (Low) 1-4 5 5 5 8 8 0-12 8-20 1L 3L 3 3 4 4 0-4 3-7 “18A” (bootstrapped by Rev. Ed of course) is based on. Picaxe-18A features: New features include (with associated commands in italics) – 1) Accurate digital temperature sensor interface for direct Celsius readings using the Dallas Semiconductor (Maxim) “1 wire bus” DS18B20 I.C. – readtemp 2) Direct PC keyboard interface allowing inputs 6 and 7 interface     – keyin, keyled 3) Interrupts to immediately respond Data Polled mem. Interrupt 128-prog 128-prog 256 256+I2C 64+256 64+256 128+I2C 128+I2C Yes Yes Yes Yes Yes PIC type Cost (A$) (approx) 12F629/675 $4 16F627 16F819 $10 16F88 ~$14 16F872 16F872 $15 16F873A $20 16F874 $28 Here’s a summary of the currently-available Picaxe chips which also gives their various parameters, allowing you to pick (no pun intended!) the right one for you. The 18X is the new kid on the block, released only last month. www.siliconchip.com.au Here’s the pinout comparison between the PICAXE-18A and the PIC 16F family, on which it is based. to input changes while otherwise busy – setint 4) Infrared detection to enable remote control from a TV style handset –infrain 5) Accurate clock chip interface for precise time keeping      – readowclk, resetowclk 6) iButton interface to allow electronic keys to be used within projects – readowsn 7) Servo control to directly drive up to eight radio controlled servos     – servo Additionally the readadc command, previously only a low resolution “08” feature, now allows high resolution 256- step ADC inputs on pins 0, 1 and 2. Phew! There’s enough here for such a swag of circuits that you’ll be busy for months. And the new “18X” introduces a further half-dozen features (I2C memory enhancement especially) that’ll keep us happy until Christmas (note we didn’t say which Christmas!). We’ll work up designs each month Circuit diagram and protoboard layout for this month’s PICAXE fun. Again, there are some differences between the photo below and this layout (redrawn for clarity) but electrically they are identical. The normal “08” programming cable is still used. The basic circuit arrangement for a PICAXE-18A and DS18B20 temperature sensor. Getting data in is as simple as connecting them together! www.siliconchip.com.au November 2003  75 DATADS18.BAS (Also downloadable from: http://www.picaxe.orconhosting.net.nz/datads18.bas) ‘PICAXE-18A TEMP. DATALOGGER for Nov 2003 “Silicon Chip” article. Ver 1.00 1/9/03 ‘Use with DS18B20 temp sensor IC etc to Picaxe-18A In 1. Via=> s.t.swan<at>massey.ac.nz ‘DS18B20 reads -10C to +85C to +/- 0.5C,but wider with less accuracy. Supply 3- 5.5V ‘N.B.Subzero “bug”-temps <0 C read as ascending from 128. Ex 129 = -1C, 130 = -2C etc ‘Possibly address by 2’s complement or subtracting value from 128. Thus 128-131= -3 ‘Program is “hi res” enhancement of lo res datalog8.bas as in Sept.’03 SiChip article ‘When “18A” powered up,any prior stored EEPROM values sent as pin 2 serial port data ‘-suit display via any terminal program -LCD,BananaCom,F8,StampPlot- or.csv Excel too. ‘NB-Gives you 30secs to turn unit OFF before fresh storage begins & thus progressively ‘wiping existing values ! For security however this data can’t easily be bulk erased ‘***BUT CARE - BE PROMPT ! REPROGRAMMING/RELOADING “18A” TOTALLY WIPES DATA TOO ****. ‘As set up logs direct Celsius temp every 15 secs for ~1 hr. Alter WAIT value to suit? ‘A further tempting ’18A” enhancement uses DS2415 or DS 1307 clock chip for improved ‘logging times. Both these & DS1820 can now be PICAXE-18A read, but not-sniff- by “08” ‘————————————————————————————————————— ‘PICAXE18A has hi-res data values 0-255(via “readadc” command),but also READTEMP for ‘direct DS18B20 Celsius readings! Values stored in non program space too (unlike “08”) ‘“Data compression” scope that’ll maybe give 512 values ? 18X + I2C better if pushed ‘If power saving needed use SLEEP instead of WAIT ex. 25x2.3secs ~1min delay (+/- 1% ) ‘Alter to suit.Ex. Sleep 391 =256 x 1/4 hr =64 hrs.Some interpreter o’head/drift noted ‘Solderless “PICNIK” breadboard setup pix => www.picaxe.orcon.net.nz/datads18.jpg ‘Sample Excel graph resulting (1 hour run)=> www.picaxe.orcon.net.nz/datads18.gif ‘Program hosted=> www.picaxe.orcon.net.nz/datads18.bas & circuit=> ... /picxds18.gif ‘————————————————————————————————————— ‘ASCII INPUTS 3-5V +supply OUTPUTS DS18B20 pinouts ‘ art + + + + + + + + + + + + + + + + + + (top view ) ‘ | | ‘ DS18B20 | _Serial _Piezo ** ‘ | | ———— | | * * ‘ | 0 1 2 6 7 =| PICAXE |=0 1 2 3 4 5 6 7 * * ‘ | =| 18A |= L * * ‘ |__0V ———— E ———— ‘ | D / / / ‘ ||| | |||||||| / / / ‘Prog. - - - - - - - - - - - - - - - - - - 0V | V+ ‘input Common ground for serial,DS18B20,piezo & supply data ‘————————————————————————————————————— ‘READ/PLAYBACK ROUTINE serout 2,n2400,(12,”PICAXE-18A Temp.Datalogger “)’ASCII values 12=FF(= cls), 44=comma for b0=0 to 255 ‘stored data values readout to terminal or LCD read b0,b1 ‘polls & reads out stored eeprom values ( .csv) serout 2,n2400,(#b1,44) ‘Actual value <at> pin 2,then comma for Excel .csv pulsout 2,500 ‘paralled output 2 LED flashes to confirm data next b0 ‘read next stored EEPROM value serial out serout 2,n2400,(10,13,10) ‘Forces fresh line for new data run(10=CR,13=LF) wait 30 ’30 secs “reading” delay -modify if too short etc ‘——————————————————————————————————— ‘WRITE/DATA LOGGING ROUTINE for b0= 0 to 255 ‘begin 256 data readings at time set by SLEEP sound 7,(75,10) ‘Beep to alert data logging commencing pulsout 2,500 ‘brief flash from pin 2 LED indicates datalogging readtemp 1,b1 ‘direct Celsius reading of DS18B20 temp. returned serout 2,n2400,(#b1,44) ‘Now allows display of data as gathered too ! write b0,b1 ‘sequentially write values to EEPROM locations wait 15 'Checks every 15 secs (max 65)-alter to suit etc next b0 ‘Gathering automatically stops after 256 samples ‘——————————————————————————————————— Note: the “ASCII art” in the middle of this text listing appears scrambled but when downloaded from the website lists perfectly. 76  Silicon Chip to keep you stimulated, with a style that gives command insights to start followed by applications such as the enhanced data logger this month. Let’s go! Right – seat belts fastened? When testing any new micro controller it’s traditional to first flash a LED. Flash a LED – that’s kids stuff for any Picaxe! Let’s do this instead with panache and “get the ice broken” while also measuring temperature. Digital temperature sensors For years the only real practical way of measuring temperature in projects was with “hard to calibrate” non-linear NTC thermistors (as used in the September 2003 article). However, digital temperature sensors, of which the 3-wire Dallas Semiconductor DS18B20 is probably best known, output the exact temperature in degrees Celsius and are now available at much the same price as thermistors. Initial DS1820s (note the missing “B”) were somewhat taller but proved drift-prone and are no longer supported. Incidentally, this “BC547 lookalike” is NOT a transistor. The Picaxe connection is very straightforward indeed – below is a code snippet that switches our pin 2 LED on and off at exactly 25° Celsius. Simplicity itself! And of course you want to try this out right away! But how do you house this 18-pinner for testing? Ideally, it would be with something like the Rev-Ed AXE-30 “18A” Starter Pack (retail A$40), which includes References and parts suppliers . . . (also refer to previous months articles) 1. Revolution Education (www. picaxe.com) gave generous permission to reproduce 18A data and graphics. 2. Australian Picaxe agent Micro-Zed (www.picaxe.com.au) supply most Picaxe parts, including the DS18B20 (~A$3). 3. Dallas Semiconductor (recently merged with Maxim) www. maxim-ic.com/1-Wire.cfm 4. Authors’s Picaxe resource page www.picaxe.orconhosting.net.nz –   includes program listings www.siliconchip.com.au main: readtemp 1,b1 if b1 > 25 then LEDon low 2 goto main ‘read temp at pin 1 via DS18B20 ‘LED on if temp (b1) beyond 25C ‘temp <=25 so LED goes/stays off ‘keep looping and measuring LEDon: high 2 goto main ‘temp >25 so turn on LED output 2 ‘keep looping and measuring If you just want to experiment without loading the complete code opposite, try this little program chunk. cables, CDs, battery box, 18A and PC board. It’s an elegant, if costly, solution – but fortunately our (cheap!) solderless PICNIK box conveniently allows a 300 hole breadboard swap-out that just accommodates an 18A version instead. Not all I/O lines need be fitted (especially if you are not using them!) and even the reset push button at pin 4 may be surplus but it’s suggested the wiring style and colour coding shown is followed to allow versatility for later circuits. Just in case you hadn’t twigged, input and output 0 (zero) are black, 1 are brown, 2 are red, etc, etc . . . Now where have we come across that colour coding before? Note the more usual “supply above, ground below” rails on this breadboard (the “08” had unusual supply pins). Useful development space remains on the breadboard, which easily accommodates the DS18B20 temperature sensor. This could of course be mounted remotely to measure the temperature of something, rather than the air around it! Once all hardware is ready, ensure your Picaxe Editor is a recent one (3.5.1 suggested – popular Ver 3.0.3 was 2002 era and did NOT of course support the 18A) and switched to the 18A mode (View >Options >Mode). The same programming cable and technique is otherwise used, although the larger memory of the 18A results in two “sweeps” as the program transfers. Extension Given the deceptive simplicity of the low resolution “08” temperature data logger detailed in September, it’s naturally tempting to enhance this with the high resolution “18A”/ DS18B20 combo just mentioned. Since up to 256 values can now be directly recorded in the EEPROM in degrees Celsius, with simultaneous display enjoyed as the data is gathered, it presents a serious device for real world data temperature monitoring – and even possible alerts if out of range values arise. Exactly the same layout as used in the test circuit above can be used – refer to the breadboard diagram. SC NEXT MONTH: More 18A (&18X?) magic – PC keyboard interfacing and interrupts, plus a preview of a versatile Picaxe datalogging kitset – ideal for school training or project use. Yikes! That home brew is stewing . . . a sample Excel plot from the DS18B20 and PICAXE-18 circuit used this month. This does have sufficient accuracy to be used for serious applications, www.siliconchip.com.au November 2003  77 A programmable PIC-powered timer This PIC-based programmer can provide timing intervals from one second to over 16,320 hours (680 days) with features such as the ability to produce up to eight separate timing events with loop control, one minute on, then one second off, one hour on, one day off, one week on and more. “I s it accurate?” you ask. You betcha! Hard to program, complicated and expensive to build? Not at all. Most timers seem to be capable of only doing the one same thing, in allowing only one timing duration period with the relay either on or off during the timing cycle. But this PIC-based timer is capable of up to eight individual ON/OFF event times of up to 2040 hours ON/ OFF for each event. Seconds, minutes and hours programming in binary, with a one second resolution to boot, is all possible. Loop control allows all timing events to run in a continuous cycle all year round. All eight timing events are executed in a sequential fashion and therefore can be chained together to give one extremely impressive timing delay of 16,320 hours – or the best part of two years! 78  Silicon Chip A LED bargraph menu display is used when programming the timer, making operation a breeze. It can be powered from eight AA batteries or a 12VDC plugpack. All settings can be saved in EEPROM memory. You can even configure it to automatically open and then run these pre-saved settings on power up. Programming is achieved via a set of eight DIP switches that are used to set the various ON/OFF, seconds/ minutes/hours times in BCD (Binary Coded Decimal). If you don’t know binary, it’s not hard at all. Binary simply consists of BITs, (BInary DigiTs) and in our case we are playing with eight BITs. Each BIT has an assigned decimal value starting at 0 or 1 for BIT 1, 0 or 2 for BIT 2, 0 or 4 for BIT 3, 0 or 8 for BIT By TRENT JACKSON 4 and so on. The BIT values in decimal keep on doubling (ie, 1,2,4,8,16, 32,64 and 128). With eight BITs to play with, we can add their decimal values together to give us any number from 1 to 255. Here’s a simple example. To obtain a decimal value of 3 using our eight switches, we would use the following switch setttings: S1 = ON, S2 = ON, S3, = OFF, S4 = OFF, S5 = OFF, S6 = OFF, S7 = OFF, S8 = OFF. To make life easy, the switch number equals the BIT number. So as you can see we are simply adding the ON/OFF status of the switches together in various combinations to achieve many different decimal numbers. There are 255 possible combinations, thus the maximum number that we can create would be 255. The eight DIP switches are also used to set various options and parameters for the timer during the programming www.siliconchip.com.au mode. We’ll give more info on this later. Circuit description One PIC16F628 microcontroller, a 10-LED bargraph menu display, relay, piezo buzzer, DIP switches and diodes plus a handful of other low-cost components is all it really takes. If you thought that the PIC16F84 was great, the 16F628 is even better, with double the program memory, double RAM and EEPROM and – the best part – it’s even cheaper. The PIC is clocked by a crystal at a rate of 8MHz. Ports RB0 to RB7 on the PIC are used as inputs for collecting data from the DIP switches and as outputs for driving the LED bargraph menu display. This display shows exactly what we are doing during the programming side of things. It indicates whether we are programming the seconds/minutes/hours, ON or OFF times, and so on. www.siliconchip.com.au Ten 680Ω resistors limit the current to the display while eight 47kΩ resistors are used as pull-ups for RB0- RB7 when they are used as inputs. Two momentary pushbuttons are used for selecting the menu fields in the display, and entering data. Port RA1 controls the buzzer and an Acknowledge LED (LED11) which indicates buttons being pushed and data being accepted or rejected while programming. This LED is in series with the buzzer and a 27Ω resistor which can be increased or decreased in order to alter the volume level from the buzzer. The number of times the Acknowledge LED flashes and the buzzer beeps indicates what is going on inside the microcontroller’s brain at any given time. Pressing the Menu button will cause the LED to flash once and the buzzer to issue one single soft & fast chirp. Pressing the Enter button will cause the LED to flash three times and the buzzer to chirp three times as well. Invalid data will give two loud beeps. After pressing the Enter button, the PIC will read whatever data is on the programming DIP switches and then quickly process it. If the data is invalid, there will be two loud beeps and two flashes from the LED. Port RA0 controls the switching of the relay via transistor Q1 which is forward biased via a 2.7kΩ resistor when RA0 goes high. Diode D12 is connected across the relay coil to protect transistor Q1 from back-EMF spikes when the relay turns off. RA2 is used to enable/disable the DIP switches. RA2 goes low when the PIC wants to read the switches. At all other times RA2 is high, to avoid the switches from interfering with the LED display. The eight diodes that connect to PORTB are used to ensure that the DIP November 2003  79 80  Silicon Chip www.siliconchip.com.au switches do not interfere with the LED menu display while PORTB is used as outputs. RA0 on PORTA ensures that these diodes are reverse- biased when PORTB is set to output data to the display. RA0 briefly swings low for a few microseconds to allow correct biasing of the diodes, to enable the switches when they need to be read. Menu programming All programming is achieved by following the menu system described overleaf. It really is quite simple once you get the hang of the BCD BIT values. Massive time duration You may wonder how we can get a time delay of 2040 hours if we are limited to 255 hours of time delay setting. If you look at the programming chart, you will note there is a function under the “Hours ON/OFF” which sets X1, X2, X3, etc. These are the multiplication factors – what ever you set here multiplies the hours set. So if you have 200 hours set with a multiplication factor of five, you’ve got 1000 hours. The highest multiplication factor is eight (X8), and 8 x 255 = 2040. All components mount on one PC board. It is strongly suggested that a socket be used for the PIC chip. There are minor differences in the prototype shown above. But wait, there’s more! If you want even longer periods, you could set a number of events. Say you set four events with 2040 hours, you now have 8160 hours, or 340 days. Want your Christmas Tree lights to come on for the same week each year? OK, it’s crazy but it gives some idea of the flexibility of this timer. The theoretical maximum is 255 events x 2040 hours or 59.383 years. Possible? Yes it is – the PIC micro is guaranteed to retain its flash memory program for forty years, so what’s a few more years between friends? Programming event numbers easy: just get into the “Event Number” field on the menu and then select the appropriate DIP switches to the events required. Special functions Along with the event numbers, there are a several special functions available. Programming in a special function option is also done by setting the DIP www.siliconchip.com.au switches to the binary code that is allocated to the function, then pressing the “Enter” button. If Auto Run is enabled then whatever data is in the non-volatile EEPROM will automatically open, load and execute at power up. Save Data will save the current time durations and configuration data into non-volatile EEPROM. Open Data will replace all the current settings with whatever is in the EEPROM (any data which you have entered before executing the Open Data command will be lost). Reset Events will clear all current data that you have entered, without affecting the EEPROM. Reset All, on the other hand will wipe out everything including the data in non-volatile memory. It will also reset all options back to their defaults. Construction All the circuit parts are mounted on a PC board coded 04111031 and measuring 121 x 78mm. Assembly is quite straightforward. Start with the resistors and diodes (watch the diode polarities!) and then place the larger components. The three shorter links can be made from component lead offcuts. However, the longest link may be too long for this – you’ll probably need a short length of tinned copper wire. The two pushbutton switches must be oriented with their flat sides closest November 2003  81 Parts List – Master of Time 1 PC board coded 04111031, 121 x 78mm 1 2.5mm PC-mount DC power connector 1 12VDC DPST PC-mount 240V 10A relay 2 PC-mount momentary pushbutton switches 1 3-way PC-mount terminal block connector 1 8-way DIP switch 1 8MHz crystal (X1) 1 18-pin IC socket 5 6mm x M3 machine screws 1 M3 nut & washer (for securing regulator REG1) 4 10mm x M3 standoffs 1 set of labels to suit project 1 12VDC 150mA plugpack 1 short length of tinned copper wire (PCB links) Semiconductors 1 PIC16F628 PIC micro programmed with “MOT.hex ver 3.0” (IC1) 1 LM7805 3-terminal regulator (REG1) 1 BC548 or similar NPN transistor (Q1) 1 red 10-LED bargraph display (LED1 - 10) 1 green 5mm LED (LED 11) 10 1N914 silicon signal diodes (D1 - D10) 4 1N4004 power diodes (D11 - D14) Capacitors 1 100µF 25V PC electrolytic 1 10µF 16V PC electrolytic 2 100nF MKT polyester 2 22pF ceramic disc Resistors (0.25W, 1%) 2 10kΩ 8 47kΩ 1 82Ω 1W 5% 1 27Ω to (and parallel with) the edge of the PC board. Leave the semiconductors (especially the PIC chip) until last; indeed, it’s a good idea to leave the PIC chip out of its socket until after checking everything. Again, take careful note of semiconductor polarity and/or orientation. No case or other enclosure details are given – we figure that most timers would be built into whatever they are controlling. The prototype had four 5mm threaded stand-offs to act as “feet” while checking and then as anchor points later on. After giving the completed board a thorough visual check for both component placement and quality of soldering, you’re ready to apply power and check voltages. First, confirm that you have a +5V supply by measuring between the middle and lower legs of the 7805 regulator (this assumes that you have the switches at the bottom as shown in our drawing and photograph). Just make sure you don’t short the 82  Silicon Chip 1 2.7kΩ 1 15Ω 10 680Ω legs out with your multimeter probes. Also confirm that the 5V supply is reaching the PIC chip socket – measure between pins 4 and 5. You should also make sure that the relay is going to work when required by shorting pin 1 of the PIC socket to +5V (without the PIC in place!). This should turn on Q1, pulling in the relay. Some relays give a good “click” when they pull in but others are very hard to hear. If you’re in any doubt, rig up something to switch with the relay contacts, such as a small 12V lamp (or a LED and 1kΩ series resistor) connected across the 12V supply via the contacts. If everything checks out OK, disconnect power, wait a few minutes for any capacitors to discharge, then plug in the PIC chip. (Do we have to mention orientation again?). Now you’re ready to start programming. A programming example Let’s say for example that you have a pool filter that you’d like to have turn on for two hours every day of the year. OK, let’s assume that power is applied and the hours ON/OFF is set to the X1 factor and the Event Number LED is on in the menu. By the way, X1 is the default. First, start by selecting event DIP switch 1. It should be ON; all the rest set to OFF. Press the Enter (S2) button, followed by pressing the Menu button (S1) until the Hours & Relay ON Time LEDs are ON. Now set DIP switch 2 ON and all the rest OFF, press Enter again and then Menu until the Hours & Relay OFF Time LEDS are now ON. 04111031 www.siliconchip.com.au Software Menu System Explained When power is applied, the PIC will initiate a simple self test. All the LEDs will briefly light and the buzzer will chirp. Then the Event Number and Power Applied LEDs will be on. Toggling the “Menu” button allows selection of the various items within the menu system. Pressing the “Enter” button causes the software to read the status of the DIP switches and place the data into the currently selected field. The first item in the menu structure is the “Event Number”, which has a default of 1. Unless we want to program in data for another event, we can skip this menu item by pushing the “Menu” button. Everything except “Event Number” assumes a default value of 0 (zero). There is no need to erase previous settings – you simply write over them with new values. And if you don’t need to use a particular menu item (such as “Hours”), simply leave it set to the default. The basic data entry format is Seconds/Minutes/Hours for both Relay ON and Relay OFF times. www.siliconchip.com.au Here’s what you can expect to see after pushing the “Menu” button for the first time. Use the 8 DIP switches to select the number of seconds (in binary), then press “Enter”, followed by “Menu”. Now enter the number of minutes that you require the relay to be off. Made a mistake, or want to change a value in a field? Simply write over it and press the “Enter” button. Minutes, Relay ON Time field: It is as you did with the seconds, except now enter the number of minutes that you want for the current event, then press “Enter”, followed by “Menu”. Last in the time setting functions is the Relay Off Hours. The hours x option can be used to create enormous delays – up to 2040 hours for each event. Refer to the binary special functions chart for more info. Enter the number of hours that you require. Remember, if you don’t want hours (or any other parameter) simply press “Menu” to skip it. Provided that no data already exists, any field (except “Event Number”) will default to zero. The “Loop Events” function can be used to cycle the events to run continuously. Toggle “Enter” to enable or disable it. When it is enabled, the LED will flash (default is disabled). Next is the “Relay OFF Time”. It is simply the amount of time that the relay stays off until the next event is executed. So if you want an event to occur at the same time tomorrow and your “Relay ON Time” is 3:30:00, the “Relay OFF Time” would be 20:30:00. Press “Enter” then “Menu” to move on. Ready for action? Let’s run this baby! Toggle “Enter” to start/stop execution of your program. The LED will flash while it is running. Stop the timer and press Menu to go back to “Event Number” November 2003  83 Now we need to set in an OFF time of 22 hours. With 24 hours in a day, we want it ON for two hours and OFF for 22 hours. In 8-bit binary that number would be 00010110. BITs 2, 3 & 5 will need to be set, therefore switches 2, 3 & 5 must be set ON, all the rest set OFF. Do that, then press Enter and use the Menu button to scroll down to Loop Events. Toggle Loop Events ON by pressing Enter. Then it’s just a matter of pressing Menu again to go down to Run/Stop, followed by Enter. If all is well, the relay should switch ON for two hours then switch OFF for 22 hours, then repeat the cycle over and over again until you hit the Enter button again to break the timing loop. RELAY RELAY ON / OFF TIME DURATIONS DURATIONS BINARY BINARY PROGRAMMING PROGRAMMING CHART CHART 1 2 3 4 5 OGRAMMING 6 7 CHART 8T (DIP 1 ~ 8Switch ) TIMING EVENT SELECTION BINARY Y PROGRAMMING BINAR PR CHAR Dec Switch Value 16 32 64 128 DIP 11 22 34 48 5 6 7 8 ( 1 ~ 8 ) TIMING EVENT SELECTION BINARY BINARY PROGRAMMING PROGRAMMING CHART CHART DIP Switch 1 2 3 4 5 6 7 8 Dec Value 1 2 4 8 16 32 64 128 Sec/Min/Hr - Select the desired Sec/Min/Hr field on the Led menu display by toggling the menu button. Set the appropriate Dip switch codes in for your desired delay times, then press the “Enter” button. 1 ON OFF OFF OFF OFF OFF OFF OFF 2 OFF ON OFF OFF OFF OFF OFF OFF 3 ON ON OFF OFF OFF OFF OFF OFF 4 OFF OFF ON OFF OFF OFF OFF OFF 5 ON OFF ON OFF OFF OFF OFF OFF 6 OFF ON ON OFF OFF OFF OFF OFF 7 ON ON ON OFF OFF OFF OFF OFF 8 OFF OFF OFF ON OFF OFF OFF OFF 9 ON OFF OFF ON OFF OFF OFF OFF 10 OFF ON OFF ON OFF OFF OFF OFF 11 ON ON OFF ON OFF OFF OFF OFF 12 OFF OFF ON ON OFF OFF OFF OFF 13 ON OFF ON ON OFF OFF OFF OFF 14 OFF ON ON ON OFF OFF OFF OFF 15 ON ON ON ON OFF OFF OFF OFF 16 OFF OFF OFF OFF ON OFF OFF OFF 17 ON OFF OFF OFF ON OFF OFF OFF 18 OFF ON OFF OFF ON OFF OFF OFF 19 ON ON OFF OFF ON OFF OFF OFF ON OFF ON OFF OFF OFF 20 OFF OFF 21 ON OFF ON OFF ON OFF OFF OFF 22 OFF ON ON OFF ON OFF OFF OFF 23 ON ON ON OFF ON OFF OFF OFF 24 OFF OFF OFF ON ON OFF OFF OFF 25 ON OFF OFF ON ON OFF OFF OFF 26 OFF ON OFF ON ON OFF OFF OFF 27 ON ON OFF ON ON OFF OFF OFF 28 OFF OFF ON ON ON OFF OFF OFF 29 ON OFF ON ON ON OFF OFF OFF 30 OFF ON ON ON ON OFF OFF OFF 31 ON ON ON ON ON OFF OFF OFF 32 OFF OFF OFF OFF OFF ON OFF OFF 33 ON OFF OFF OFF OFF ON OFF OFF 34 OFF ON OFF OFF OFF ON OFF OFF 35 ON ON OFF OFF OFF ON OFF OFF 36 OFF OFF ON OFF OFF ON OFF OFF 37 ON OFF ON OFF OFF ON OFF OFF 38 OFF ON ON OFF OFF ON OFF OFF 39 ON ON ON OFF OFF ON OFF OFF 40 OFF OFF OFF ON OFF ON OFF OFF 41 ON OFF OFF ON OFF ON OFF OFF OFF ON OFF OFF 42 OFF ON OFF ON 43 ON ON OFF ON OFF ON OFF OFF 44 OFF OFF ON ON OFF ON OFF OFF 45 ON OFF ON ON OFF ON OFF OFF 46 OFF ON ON ON OFF ON OFF OFF 47 ON ON ON ON OFF ON OFF OFF 48 OFF OFF OFF OFF ON ON OFF OFF 49 ON OFF OFF OFF ON ON OFF OFF 50 OFF ON OFF OFF ON ON OFF OFF 51 ON ON OFF OFF ON ON OFF OFF 52 OFF OFF ON OFF ON ON OFF OFF 53 ON OFF ON OFF ON ON OFF OFF 54 OFF ON ON OFF ON ON OFF OFF 55 ON ON ON OFF ON ON OFF OFF 56 OFF OFF OFF ON ON ON OFF OFF 57 ON OFF OFF ON ON ON OFF OFF 58 OFF ON OFF ON ON ON OFF OFF 59 ON ON OFF ON ON ON OFF OFF 60 OFF OFF ON ON ON ON OFF OFF *Up 255BIT BITcombination combinations codes possible. Should sufficient most cases. Up toto 255 codes areare possible. (1 ~(1~60) 60) Should bebe sufficient in in most cases though. * EventValue Num Dec 1 2 4 8 16 32 64 128 1 Event2 Num 3 14 25 36 47 58 ON OFF ON ON OFF OFF ON ON OFF OFF ON ON OFF OFF ON ON OFF OFF ON OFF ON ON OFF ON OFF OFF OFF OFF OFF OFF ON OFF ON OFF ON ON ON ON OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF ON OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF * * 6 OFF ON ON OFF OFF OFF OFF OFF OFF OFF if no event number is selected, the data will be placed in event “1” location * Event7 “1” Is default,ON ON ON OFF OFF OFF OFF OFF 8 OFF OFF OFF ON OFF OFF * Event “1” Is default, if no event number is selected, the data will be placed in event “1” location SPECIAL FUNCTION OPTIONS BINARY BINARY PROGRAMMING PROGRAMMING CHART CHART DIP Switch 1 2 3 4 5 6 7 8 SPECIAL OPTIONS BINAR PR CHAR Dec ValueFUNCTION 1 2 4 BINARY 8 Y PROGRAMMING 16 OGRAMMING 32 64 CHART 128T DIP Switch - To enter 1 into options 2 mode: 3Select “Event 4 Number” in5 menu, set6all switches7“ON” press 8Enter Function Dec ValueX 1 button, Event Number Led will flash. Now enter in the function codes, Menu button to exit mode. 1 2 4 8 16 32 64 128 ON OFF OFF OFF OFF OFF OFF OFF X2 OFF ON OFF OFF OFF OFF OFF OFF - To enter into options mode: Select “Event Number” in menu, set all switches “ON” press Enter Hours ON X 3 ON ON OFF OFF OFF OFF OFF OFF Function button, Event Number Led will flash. Now enter in the function codes, Menu button to exit mode. Hours ON X 4 OFF OFF ON OFF OFF OFF OFF OFF Hours ON ON XX 15 ON OFF ON OFF OFF OFF OFF OFF Hours ON OFF OFF OFF OFF OFF OFF OFF Hours ON X 6 OFF ON ON OFF OFF OFF OFF OFF Hours ON X 2 OFF ON OFF OFF OFF OFF OFF OFF Hours ON ON XX 37 ON ON ON OFF OFF OFF OFF OFF Hours ON ON OFF OFF OFF OFF OFF OFF Hours ON ON XX 48 OFF OFF OFF ON OFF OFF OFF OFF Hours OFF OFF ON OFF OFF OFF OFF OFF Hours ON OFF X X 51 ON OFF OFF ON OFF OFF OFF OFF Hours ON OFF ON OFF OFF OFF OFF OFF Hours OFF X 2 OFF ON OFF ON OFF OFF OFF OFF Hours ON X 6 OFF ON ON OFF OFF OFF OFF OFF Hours OFF X 3 ON ON OFF ON OFF OFF OFF OFF Hours ON X 7 ON ON ON OFF OFF OFF OFF OFF Hours OFF X 4 OFF OFF ON ON OFF OFF OFF OFF Hours ON X 8 OFF OFF OFF ON OFF OFF OFF OFF Hours OFF X 5 ON OFF ON ON OFF OFF OFF OFF Hours OFF X 1 ON OFF OFF ON OFF OFF OFF OFF Hours OFF X 6 OFF ON ON ON OFF OFF OFF OFF Hours OFF ON OFF ON OFF OFF OFF OFF Hours OFF OFF XX 27 ON ON ON ON OFF OFF OFF OFF Hours ON ON OFF ON OFF OFF OFF OFF Hours OFF OFF XX 38 OFF OFF OFF OFF ON OFF OFF OFF Hours OFF X 4 OFF OFF ON ON OFF OFF OFF OFF ON OFF OFF OFF ON OFF OFF OFF Save Data Hours OFF X 5 ON OFF ON ON OFF OFF OFF OFF Open Data OFF ON OFF OFF ON OFF OFF OFF Hours OFFON X6 OFF ON ON ON OFF OFF OFF OFF Auto Run ON ON OFF OFF ON OFF OFF OFF Hours OFFOFF X7 ON ON ON ON OFF OFF OFF OFF Auto Run OFF OFF ON OFF ON OFF OFF OFF Hours OFF X 8 OFF OFF OFF OFF ON OFF OFF OFF Reset Events ON OFF ON OFF ON OFF OFF OFF Reset Data “ALL” OFF ON ON OFF ON OFF OFF OFF ON OFF OFF ON Save ON * Hours Hours ON * * * * * Open Data OFF values.ON OFFfunctionOFF ONsaved data OFF OFF OFF Denotes default Reset “ALL” deletes all & restores factory defaults Auto Run ON ON ON OFF OFF ON OFF OFF OFF Auto Run OFF OFF OFF ON OFF ON OFF OFF OFF Reset Events ON OFF ON OFF ON OFF OFF OFF Reset “ALL” OFF ON ON OFF ON OFF OFF OFF * If you don’t wish to erase all of the timing data in any Denotes default values. Reset “ALL” function deletes all saved data & restores factory defaults given event, you can just erase what you don’t require in a menu field by setting all the switches to “OFF” and then pressing “Enter”. This effectively sets the timing interval to zero and therefore will not be executed as a delay (the software will see a value of “0” and skip it automatically). Wheredyagedit? This project was developed by the author for Global Unlimited Pty Ltd, who retain copyright in the PIC microcontroller code but have released the PC board and circuit. Global Unlimited have three different kits available which should meet the needs of most constructors. Kit 1 includes all components, the PC board, etc (but does not include a plugpack) for $64.95 including GST. Kit 2 is the same but is pre-built and tested and includes a 12-month warranty, for $89.95 including GST. 84  Silicon Chip Finally, for those who wish to “do their own thing” they have the pre-programmed PIC 16F628 microcontroller available for $24.00 (inc GST). All prices include packing and postage to anywhere in Australia (allow up to 28 days for delivery). Cheques should be made payable to Global Unlimited Pty Ltd. Global Unlimited can be contacted on (02) 4566 3218, or (02) 4566 3168. Their postal address is PO Box 3286, SC Dural NSW 2158. www.siliconchip.com.au Here’s the second part of our short series on designing your own PC bards. This month, we take up from where we left off with component placement and design. Part 2 – by David L. Jones I t’s often said that PC board design is 90% placement and 10% routing. While the actual figures are of no importance, the concept that component placement is by far the most important aspect of laying out a board, certainly holds true. Good component placement will make your layout job easier and give the best electrical performance. Bad component placement can turn your routing job into a nightmare and give poor electrical performance – perhaps not even work at all. It may even make your board unmanufacturable. So there is a lot to think about when placing components! Every designer has their own method of placing components. If you gave the same circuit (no matter how simple) to 100 different experienced designers, you’re likely to get 100 different PC board layouts. So there is no absolute right way to place your components. It’s largely a matter of experience. But there are quite a few basic rules which will help ease your routing, give you the best electrical performance and simplify large and complex designs. Getting down to basics Here are some basic steps required for laying out a complete board: www.siliconchip.com.au  Set your snap grid, visible grid, and           default track/pad sizes. Throw down all the components onto the board. Divide and place your components into functional “building blocks” where possible. Identify critical tracks on your circuit and route them first. Place and route each building block separately, off the board. Move completed building blocks into position on your main board. Route the remaining signal and power connections between blocks. Do a general “tidy up” of the board. Do a Design Rule Check. Check your board thoroughly. Then get someone else to check it! This is by no means a be-all and end-all check list – it’s highly variable depending on many factors. But it is a good general guide to producing a first-class layout. A bit more detail Let’s look in more detail at the procedure described above. We have already looked at the grids and track/pad sizes. These should be the first things that you set up before you start doing anything. No exceptions! Many people like to jump straight into placing all the components into what they think is the most optimum position on the board, all in one hit. While this can work for small circuits, you don’t have much of a The very first step in designing a PC board using any PC board software is to set the snap grid, visible grid and default track/pad sizes. This screen (from the popular “Autotrax” freeware) shows how it is done. Other software packages will have similar settings. November 2003  85 hope when you have more complex circuits with hundreds of components spread across many functional circuit blocks. Why? Because it’s very easy to run out of “routing space” which is the room to lay down all your tracks. If you fix all your component positions and then try to route everything, you can easily paint yourself into a corner, so to speak. Alternatively, if you space the components out too much, you can end up with a large board that does not make efficient use of space. The hallmark of an inexperienced designer is a board that has every component evenly spaced out and then has thousands of tracks and links or vias criss-crossing the board. It might work but it can be ugly and inefficient, not to mention bigger and more expensive to manufacture. The best way to start your layout is to get ALL of your components onto the screen first. If you have a companion schematic package, then the simplest way to do this is to get your PC board program to import your schematic design and select all the components automatically. This will also be discussed later. If all you have is a PC board program, then you’ll have to select each compo86  Silicon Chip nent from the library and place them manually. With all the components on screen, you should get a good indication of whether or not your parts will easily fit onto the size (and shape) of board that you require. If it looks like it’s going to be a tight fit, then you know that you will have to work hard to try and keep the component spacing “tight” and the tracking as efficient as possible. If it looks like you have plenty of room, then you can be a bit more liberal in your layout. Of course, if it looks like you have Buckley’s chance of getting your components on the board, you’ll have to go back to the drawing board. Now analyse your schematic and determine which parts of the design can be broken up into “building blocks”. Often this is fairly obvious. For example, say you have a complex-looking active filter in your circuit. This would typically have a single input line and a single output line but will have lots of components and connections as part of the filter. This is a classic “building block” circuit and one that lends itself well to combining all of these parts together in the same location. So you would grab all of these parts and start to arrange them into their own little layout off to one side of your board. Don’t worry too much about where the actual block goes on your board yet. You will also need to partition off electrically sensitive parts of your design into bigger blocks. One major example is with mixed digital and analog circuits. Digital and analog just do not mix and will need to be physically and electrically separated. Another example is with high frequency and high current circuits; they do not mix with low frequency and low current sensitive circuits. We’ll have more about this later. As a general rule, your components should be neatly lined up: ICs in the same direction, resistors in neat columns, polarised capacitors all around the same way and connectors on the edge of the board. Don’t do this at the expense of having an electrically poor layout or an overly big board though. Electrical parameters should always take precedence over nicely lined up components. Symmetry is really nice in PC board design. If you have something like two identical building block circuits side by side and one is laid out slightly differently, it sticks out like a sore thumb. If you have placed your components www.siliconchip.com.au wisely, 90% of your work will be done. The last 10% is just joining the dots, so to speak. Well, not quite –but good placement is a good majority of your work done. Once you are happy with the component placements, you can start to route all the different building blocks separately. When finished, it is then often a simple matter to move and arrange the building blocks into the rest of your design. The Design Rule Check (DRC) will be covered later but it is an essential step to ensuring that your board is correct before manufacture. A DRC basically checks for correct connectivity of your tracks and for correct widths and clearances. Getting someone to check your board may sound like an overly bureaucratic process but it really is a vital step. No matter how experienced you are at PC board design, there will always be something you overlooked. A fresh pair of eyes and a different mindset will pick up problems you would never see. If you don’t have anyone to check your board over, then you’ll have to do it yourself. Get a printout of your schematic and a highlighter pen. Now, compare every single electrical “net” connection (connection between two points) on your board with the schematic, net by net. Highlight each net on the schematic as you complete it. When you are finished, there should be no electrical connections left that aren’t highlighted. You can now be fairly confident that your board is electrically correct. Basic routing Now it’s time for some basic routing rules. Routing is also known as “tracking”. Routing is the process of laying down tracks to connect components on your board. An electrical connection between two or more pads is known as a “net”.  Keep nets as short as possible. The longer your total track length, the greater its resistance, capacitance and inductance – all of which can be undesirable factors.  Tracks should only have angles of 45°. Avoid the use of right angles and in no circumstances use an angle greater than 90°. This is important to give a professional and neat appearance to your board. PC board packages will have a mode to enforce 45° movements – make use of it. There should never be a need to turn it off. Contrary to popular belief, sharp right angle corners on tracks don’t produce measurable EMI or other problems. The reasons to avoid right angles are much simpler – it just doesn’t look good and it may have some manufacturing implications.  Forget nice rounded track corners, they are harder and slower to place and have no real advantage. Stick to 45° increments. Rounded track bends belong to the pre-CAD taped artwork era.  “Snake” your tracks around the board – don’t just go “point to point”. Point to point tracking may look more efficient to a beginner at first but there are a few reasons you shouldn’t use it. The first is that it’s ugly, always an important factor in PC board design! The second is that it is not very space-efficient when you want to run more tracks on other layers.  Enable your electrical grid, which is sometimes referred to as a “snap to centre” or “snap to nearest” option. Let the software find the centres of pads and ends of tracks automatically for you. This is great for when you have pads and tracks which aren’t lined up to Both of these PC boards are electrically identical; both would of course work the same. But you can see instantly just how much better the board on the right looks with the tracks following the 45° design rule. www.siliconchip.com.au In this case, the bypass capacitors on the power rails are too far removed from the supply pins on the ICs. Notice the difference? It not only looks neater and also takes up a lot less real estate – it will work better! your current snap grid. If you don’t have these options enabled then you may have to keep reducing your snap grid until you find one that fits – far more trouble than it’s worth. There is almost never a reason to have these options disabled.  Always take your track to the centre of the pad; don’t make your track and pad “just touch”. There are a few reasons for this. The first is that it’s sloppy and unprofessional. The second is that your program may not think that the track is making electrical connection to the pad. Third, with surface mount components, an off-centre track-pad connection can again cause solder surface tension to pull the component out of alignment. Proper use of a snap grid and electrical grid will avoid problems here.  Use a single track, not multiple tracks tacked together end to end. It may make no difference to the look of your final board but it can be a pain for future editing. Often you’ll have to extend a track a bit. In this case, it’s best to delete the old one and place a new one. It may take a few extra seconds but it’s worth it. People looking at your finished board may not know but you will know! It’s the little touches like this that set good PC board designers apart.  Make sure your tracks go right through the exact centre of pads and components, and not off to one November 2003  87 side. Use of the correct snap grid will ensure that you get this right every time. If your track doesn’t go through the exact centre then you are using the wrong snap grid. Why do you need to do this? It makes your board neater and more symmetrical and it gives you the most clearance.  Only take one track between 100 thou pads unless absolutely necessary. Only on large and very dense designs should you consider two tracks between pads. Three tracks between pads is not unheard of but we are talking seriously fine tolerances here.  For high currents, use multiple vias when going between layers. This will reduce your track impedance and improve the reliability. This is a general rule whenever you need to decrease the impedance of your track or power plane.  Don’t “drag” tracks to angles other than 45°  “Neck down” between pads where possible. Eg, a 10 thou track through two 60 thou pads gives a generous 15 thou clearance between track and pad.  If your power and ground tracks are deemed to be critical, then lay them down first. Also, make your power tracks as BIG as possible.  Keep power and ground tracks running in close proximity to each other if possible, don’t send them in opposite directions around the board. This lowers the loop inductance of your power system, and allows for effective bypassing.  Keep things symmetrical. Symmetry in tracking and component placement is really nice from a professional aesthetics point of view.  Don’t leave any unconnected copper fills (also called “dead copper”), ground them or take them out.   If you are laying out a non-platedthrough double-sided board, then there are some additional things to watch out for. Non-plated-through holes require you to solder a link through the board on both the top and bottom layer.  Do not place vias under components. Once the component is soldered in place you won’t be able to access the joint to solder a feed through. The solder joint for 88  Silicon Chip Adding a chamfer to a “T” junction doesn’t just look neater, it helps prevent undercutting.  Likewise, “teardrops” added to the joins between tracks and pads looks neater and also helps prevent etching problems. the feed through can also interfere with the component. Try to use through-hole component legs to connect top tracks to bottom tracks. This minimises the number of vias. Remember that each via adds two solder joints to your board. The more solder joints you have, the less reliable your board becomes, not to mention that that it takes a lot longer to assemble. Finishing Touches: Even though you have finished all your routing, your board isn’t yet complete. There are a few last minute checks and finishing touches you should do.  If you have thin tracks (<25 thou) then it’s nice to add a “chamfer” to any “T” junctions, thus eliminating any 90° angles. This makes the track more physically robust, and prevents any potential manufacturing etching problems. But most importantly, it looks nice.  Check that you have any required mounting holes on the board. Keep mounting holes well clear of any components or tracks. Allow room for any washers and screws (especially when it comes to mains voltage clearances).  Minimise the number of hole sizes. Extra hole sizes cost you money, as the manufacturer will charge you based on not only the number of holes in your boards but the number of different hole sizes you have. It takes time for the very high-speed drill to spin down, change drill bits and then spin up again. Check with your manufacturer for these costs, but you can’t go wrong by minimising the number of hole sizes.  Double check for correct hole sizes on all your components. Nothing is more annoying than getting your perfectly laid out board back from the manufacturer, only to find that a component won’t fit in the holes! This is a very common problem; don’t get caught out.  Ensure that all your vias are    identical, with the same pad and hole sizes. Remember your pad-to-hole ratio. Errors here can cause “breakouts” in your via pad, where the hole, if shifted slightly can be outside of your pad. With plated through holes this is not always fatal, but without a complete annular ring around your hole, your via will be mechanically unreliable. Check that there is adequate physical distance between all your components. Watch out for components with exposed metal that can make electrical contact with other components, or exposed tracks and pads. Change your display to “draft” mode, which will display all your tracks and pads as outlines. This will allow you to see your board “warts and all”, and will show up any tracks that are tacked on or not ending on pad centres. If you wish, add “teardrops” to all your pads and vias. A teardrop is a nice “smoothing out” of the junction between the track and the pad and is, not surprisingly, shaped like a teardrop. This gives a more robust and reliable track to pad interface, better than the almost right angle between a standard track and pad. Don’t add teardrops manually though, it’s a waste of time. But if your program supports automatic teardrop placement, feel free to use it. Single-sided PC board design Single-sided design can greatly reduce the cost of your board. If you can fit your design on a single sided board then it is preferable to do so. Look inside many of today’s consumer items like TVs and DVD players, and you will almost certainly find some single-sided boards. www.siliconchip.com.au Just about all of SILICON CHIP’s boards are single-sided. They are still used because they are so cheap to manufacture. And in the case of SILICON CHIP boards, single sided are much easier for those who wish to make their own from the printed patterns or downloaded web files. Single-sided design requires some unique techniques which aren’t required once you go to doubled-sided and multi-layer design. It is certainly more challenging than a double-sided layout. Probably the biggest differences is that some links (jumpers) may be required when it is impossible to avoid tracks crossing over one another. However, links should be avoided if at all possible. In fact, a single-sided board design will be regarded inversely proportional to the number of jumper links used. “No links” earns the admiration of many peers! Component placement can be even more critical on a single-sided board, so it won’t always be possible to have all your components nice and neatly aligned. Arrange your components so that they give the shortest and most efficient tracking possible. www.siliconchip.com.au It is like playing a game of Chess; if you don’t think many moves ahead then you will get yourself in a corner pretty quickly. Having just one track running from one side of your board to the other can ruin your whole layout, as it makes routing any other perpendicular tracks impossible. Many designers will route their board as though it is a double-sided board but only with straight tracks on the top layer. Then when the board is to be manufactured, the top layer tracks are replaced with jumper links. This can be a rather inefficient way to approach single sided design and is not recommended. You must be frugal in your placement, and don’t be afraid to rip everything up and try again if you see a better way to route something. Double-sided PC board design Double-sided PC board design gives an extra degree of freedom for designing your board. Things that are next to impossible on a single-sided board become relatively easy when you add an additional layer. Many (inexperienced) designers tend to become lazy when laying out double-sided boards. They think that component placement doesn’t matter and that hundreds of vias can be used to get them out of trouble. They will often lay out components like ICs in neat rows and then proceed to route everything using right angle rules. This means that they will route all the tracks on the bottom layer in one direction and then all the tracks on the top layer perpendicular to the bottom layer. The theory is that if you chop and change between layers enough times you can route almost anything using a “step” type pattern. This technique can be ugly and inefficient and is a throwback to the old manual tape days. Many basic PC “auto routers” work in this way. Stick to using good component placement techniques and efficient building block routing. Double-sided design can also give you the chance to make use of good ground plane techniques, required for high frequency designs. This will be discussed later. That’s all for this month. Next we will look at more advanced topics like multi-layer boards, ground planes, high frequency design, auto routing and SC design for manufacturing. November 2003  89 VINTAGE RADIO By RODNEY CHAMPNESS, VK3UG The 4-valve Precedent mantel receiver (circa 1953) Designed for those on a budget, the 4-valve Precedent mantel receiver was released onto the Australian market in the early 1950s. It’s a relatively simple set with many costcutting features but it still worked quite well in suburban areas. A. W. JACKSON INDUSTRIES of Sydney produced Precedent radios and B & W TV receivers from the 1950s until somewhere about 1975, when colour TV was introduced into Australia. The receivers were aimed at the lower end of the market. In fact, many people looked down on the brand and would­n’t be seen dead selling or us- ing such receivers. But although they were cheaper than other brands, they were remarkably reli­able, had simple circuitry that worked quite well, and were generally easy to service. However, they certainly were not the Rolls Royce of radios. The 4-valve receiver featured in this article was in a rather sorry state when it first came to me, as can be This is the 4-valve Precedent mantel set before restoration. Its cabinet had a bad crack at the top and was held together by masking tape. 90  Silicon Chip seen in the photographs. The cabinet was cracked, the works were covered in a layer of muck, the power lead had perished and exposed power wires were quite evident at the back of the set. In addition, parts of the chassis and the power transformer were showing extensive rust. However, things were much better under the chassis, with only a number of cobwebs to be removed. Even so, it was obvious that quite a challenge lay ahead of me to restore the receiver. It would never be a valuable set but would be an interesting one just the same. Essential checks The first job was to make sure that the power transformer was in good condition – especially since its case was badly rusted. This was one set that would not be valuable enough to restore if its power transformer was faulty, unless a similar transformer was readily available. As a result, the transformer was carefully tested with my high voltage tester. This involved checking for high-voltage breakdown between the various windings and the transformer frame. It all checked out OK. Next, the audio output transformer windings were checked for continuity. In this case, a replacement would be required, as the primary winding was open circuit. By contrast, the interme­ diate frequency (IF) transformers and the aerial and oscillator coils all had continuity, so the restoration would not require any “hard-to-get” replacement parts. Cleaning up Unfortunately, the cabinet top had www.siliconchip.com.au Fig.1: the circuit for the Precedent receiver is a fairly con­ventional “austerity-model” 4-valve superhet. cracked and it had been “repaired” using masking tape. Obviously, a much better repair was needed and so the cabinet was scraped clean of the masking tape and then placed into the laundry wash tub, together with the knobs. It was then thoroughly cleaned using a scrubbing brush and soapy water. The cabinet was then rinsed in clean water as the cracks needed to be free of any “muck” before being glued together later on. Both the cabinet and knobs looked first class after cleaning and were then set aside so that other work could be done. The valves were also cleaned using soapy water but you have to make sure that the type numbers don’t get rubbed off during this process. This involves holding the valves upside down (to keep water out of the socket) and then gently washing the envel­ opes but completely avoiding the type numbers. That done, the valves were rinsed in clean water and left to dry. Valves really do look good after they have been cleaned! After they had dried, I scratched between pins 1 & 2 of the 6M5 with a screwdriver so that any silver migration between grid and screen would www.siliconchip.com.au This view shows the state of the chassis. It was covered in a layer of dirt, the power lead had perished (exposing the wires) and parts of the chassis and the power transformer were covered in rust. be disrupted. This prevents positive voltage being applied to the grid. It might sound like a strange thing to do but 6M5s have been known to have silver migration between these pins, which means that the valves are often (needlessly) thrown out because they are thought to be “gassy”. The next job was to clean up the chassis. It was quite rusty in spots but I stuck to my usual cleaning techniques. First, the chassis was dusted using a small paintbrush, after which I “huffed and puffed” and blew out as much dust as I could. Of course, a small compressor would be ideal for November 2003  91 Vintage Radio – continued The restored receiver is barely recognisable from the rather sorry mess that arrived in my workshop. The cabinet was repaired using fibreglass mixed with cream craft paint. this job but I don’t have one, unfortunately. The next stage of the cleaning procedure involved using a kerosene-soaked kitchen scourer (or a segment of one) to scrub the chassis as thoroughly as I could. I use a screwdriver to push the scourer into odd corners and the end result, after wiping the chassis down with a rag, was a marked improvement in the ap­pearance of the set. In this case, I decided against painting the chassis, as this set isn’t valuable enough to warrant this type of effort. The fact that it is quite rusty shows that the chassis wasn’t well-plated in the first place. Next, the dial scale was cleaned with a damp rag and it came up quite well. However, the method used to indicate the pointer location on the dial drive system is primitive to say the least. The pointer used is the common slide type, however it cannot normally be seen through the scale. So, in order to in­ dicate the pointer position, a dial lamp is set back by about 50mm behind the scale and the shadow cast by the pointer on the scale indicates the tuning. Unfortunately, because the lamp position is fixed, the shadow is quite hard to see at the extremities of the 92  Silicon Chip tuning range. In addition, parallax error greatly affects the tuning accuracy at the dial extremities. Of course, this probably didn’t matter for a cheap kitchen or garage radio, as most of the time it would simply be left on the favourite radio station. In its favour, the dial drive mechanism is cheap and works reasonably well, although it does suffer from increased resist­ance at the low frequency end of the dial. In my case, I was just getting it all functioning correctly when the cord broke, so I ended up having to re-string the dial drive (not the easiest of jobs). In addition, the globe behind the dial scale had blown and had to be replaced. Overhauling the circuitry Having a circuit to follow always makes servicing so much easier but I couldn’t find this set in any of the Australian Official Radio Service Manuals I consulted. According to the markings on the loudspeaker transformer, it was probably made in 1953 but I was unable to find a circuit anywhere. In the end, I had to trace the circuit out with the aid of a valve data book and a multimeter. Fig.1 shows the details and as can be seen, it is a con­ventional “austerity model” 4-valve superhet. Getting back to the set, the original 2-core mains lead had perished. It was replaced with a 3-core lead, so that the chassis could be earthed in the interests of safety. That done, the valves were all removed and the receiver then plugged into power. A quick check with a DMM showed that all windings on the transformer were delivering the correct voltages and there were no signs of overheating, even after it had been running for some time. This indicated that there were no shorted turns in the windings. As mentioned earlier, the speaker transformer was faulty and so it was replaced with an M1100 “Audio Line Transformer” from Dick Smith Electronics. The plate circuit was wired across the 5kΩ winding, while the speaker was connected to the 2Ω sec­ ondary. This gives a reasonable impedance ratio compromise bet­ween the primary (6M5 plate) and the secondary load (ie, the speaker). Leaky electrolytic A quick check with a DMM showed a high resistance (over 50kΩ) between the high-tension (HT) line and the chassis. That cleared the HT line of any shorts, so the multimeter was switched to the 400V range and one lead connected to chassis via a clip lead. That done, the 6V4 rectifier was plugged in, the set turned on and the voltages across the 24µF (C9) and 8µF (C8) capacitors were checked. This quickly showed that the voltage across the 8µF capaci­tor wasn’t rising to the correct value. And when the power was turned off, the voltage across this capacitor quickly disap­peared. The reason for this was straightforward – the capacitor was leaky and in fact showed 12mA of leakage current after several on-off cycles. Just to confirm it was faulty, I removed it and checked the circuit again. This time, the 24µF capacitor discharged slowly when the power was removed so it was in good condition. A re­placement 8µF capacitor fixed the problem and the power supply then worked correctly. Next, the paper capacitors were all checked but only one was found to be excessively leaky. This time, the culprit was C6, a .03µF audio coupler to the 6M5 grid. It too was replaced. Having done all that, the other three valves were plugged in and the set www.siliconchip.com.au Photo Gallery: Zenith Radio Calstan Receiver (1947) VALVES AUDIO HI-FI AMATEUR RADIO GUITAR AMPS INDUSTRIAL VINTAGE RADIO We can supply your valve needs, including high voltage capacitors, Hammond transformers, chassis, sockets and valve books. WE BUY, SELL and TRADE SSAE DL size for CATALOGUE Manufactured by Zenith Radio Co Pty Ltd (Sydney) in 1947, the Calstan was a medium-sized, 5-valve receiver which was housed in a handsome timber cabinet. It used the following valve line-up: 6A8-G frequency changer; 6U7-G IF amplifier; 6B6-G detector, AVC rectifier and 1st audio amplifier; 6V6-GT audio output stage; and a 5Y3GT rectifier. The Calstan brand was also well-known at the time for a range of test equipment, the word being an abbreviation of the phrase “calibrated-to-standard”. (Photo courtesy Historical Radio Society Of Australia (Inc.). switched on again. It quickly burst into life, with stations appearing right across the dial. Fairly obviously, all the valves were in good order - in fact, I find I have to replace very few valves in these old receivers. Annoying whistle Unfortunately, that wasn’t the end of the set’s problems. It had only been on a short while when it started to whistle on all the stations, particularly those in the middle of the dial. The volume control did have some effect on these whistles and it was obvious that the IF stage was oscillating. OK, so how could the set be made stable? First, I tried installing a new screen bypass capacitor from pin 1 of the 6N8 to earth and while that improved matters somewhat, the instability was still there. And as a matter of interest, the original paper capacitor had been fitted incorrectly, as its outer foil (shield) was connected to pin 1 of the 6N8 instead of to earth. My next suspect was the .0047µF plate bypass capacitor (C7) on pin 7 the 6M5 audio output stage. Its job is to get rid of any IF (455kHz) www.siliconchip.com.au components in the audio, so I tried another capacitor here and the whistle stopped. It’s worth noting that neither of the original capacitors was excessively leaky (electrically) but it would appear that they were more inductive than the later types that were substituted. By now, the little Precedent receiver was bringing in the stronger stations at very good volume. However, the volume con­trol to be advanced quite a bit for the weaker stations so I decided to take a close look at the automatic gain control (AGC) system. The AGC system used in this set is actually quite simple. However, it is a bit strange in that only one fifth of the devel­oped AGC voltage is actually applied to the 6N8 and 6AN7 valves by virtue of the voltage divider formed by resistors R1 and R4. This was done to ensure that the AGC-controlled valves worked at nearly at full performance – even with strong signals – so that good audio volume could be achieved. A few quick checks showed that with R1 in circuit, the AGC voltage at the detector is about -27V on the strongest local station. Conversely, ELECTRONIC VALVE & TUBE COMPANY PO Box 487 Drysdale, Vic 3222 76 Bluff Rd, St Leonards, 3223 Tel: (03) 5257 2297; Fax: (03) 5257 1773 Email: evatco<at>pacific.net.au www.evatco.com.au KALEX PCB Makers! • High Speed PCB Drills • 3M Scotchmark Laser Labels • PCB Material – Negative or Positive Acting • Light Boxes – Single or Double Sided; Large or Small • Etching Tanks – Bubble • Electronic Components and Equipment for TAFEs, Colleges and Schools • Prompt Delivery We now stock Hawera Carbide Tool Bits 718 High Street Rd, Glen Waverley 3150 Ph (03) 9802 0788 FAX (03) 9802 0700 ALL MAJOR CREDIT CARDS ACCEPTED November 2003  93 This 1958 5-valve radiogram chassis shows the quality improvements that Precedent made to its later model sets. Its dial mechanism is light years ahead of the 4-valve mantel set’s dial-drive system. with R1 disconnected, the voltage is only about -9V but the audio output is more even on all stations, with no “blasting” when tuning to a strong station. At the time, this made me wonder if R1 had been added by a serviceman at some stage during the set’s life to boost the audio output for suburban use. However, I subsequently came across another 4-valve set that uses a similar AGC circuit, so perhaps it is original. In my case, I decided to leave out R1 as this gave better performance. Resistor R4 had also gone high in value and was replaced. Unusual effect As an aside, it’s interesting to note that a rather unusual effect would have occurred if C6 had not been replaced. Because it had gone leaky, this capacitor would have passed some of the negative DC output from the detector to the grid of the 6M5 audio output stage. As a result, the 6M5 would have progressively been cut off as the volume control was increased on a strong station, resulting 94  Silicon Chip in decreased or no audio! Note that neither the 6AN7 nor the 6N8 have any bias ap­plied to them in the absence of a signal. This means that the receiver must to be tuned to a station in order for AGC bias to be applied to these valves. However, the set’s designer could have applied delayed AGC and back bias to these two valves by adding just two extra resistors and a 47pF mica capacitor. It would have meant a very small increase in complexity for a better performing AGC system. By now the set was performing quite well and so it was left to run on the bench to see if anything else showed up. As it turned out, it ran OK for several days and then started to motor­boat (ie, it produced a noise from the speaker that sounded like the engine of a motorboat). This usually indicates a faulty electrolytic capacitor and this can be checked by bridging each capacitor in turn with an equivalent value. In this case, the receiver’s operation returned to normal when I bridged the new 8µF capacitor that I’d installed earlier. A faulty new capacitor? No, I’d managed to make a dry solder joint on one of its leads, which was rather embarrassing! Resol­ dering the joint fixed the problem. Alignment This set isn’t easy to align, not because it’s a difficult procedure but because the IF transformer slugs are well sealed. In addition, all the trimmer capacitors marked with an asterisk (*) on the circuit are in fact made from a thick piece of enam­elled copper wire which is overwound with thin enamelled copper wire. Because the set’s performance appeared to be quite satis­ factory, I initially decided it would be too much trouble to try to peak the tuning adjustments. In fact, they obviously weren’t intended to be altered after they had been set by the manufactur­er. In this set, the oscillator is a little different to normal in that it’s shunt fed, with no DC voltage on either of the oscillator coil windings. However, capacitor C3 provides padder feedback to ensure reliable oscillator operation across the band. As it stood, the IF amplifier was peaked at about 460kHz and I decided to leave it alone. However, the high-frequency end of the tuning range www.siliconchip.com.au The component layout under the chassis of the later (5-valve) Precedent receiver was clean and uncluttered. Its chassis is of much better quality than the earlier 4-valve set, although it was still aimed at the lower end of the market. of the receiver only extended to 1580kHz, so some work was needed here. This involved taking a few turns off each of the oscillator and aerial trimmer capacitors, after which the core of the aerial coil was adjusted at the low-frequency end of the dial. The tuning range was then quite satisfactory and all the expected stations were received. The sensitivity of the receiver is good at the high fre­quencies but it’s a bit ordinary at the lower frequencies. Howev­er, any station worth listening to at my location was quite audible. Cabinet repair The techniques described in the article in the July 2001 issue were used to repair the Bakelite cabinet. Fortunately, it was just a matter of fixing the cracks and breaks and no sections had to be fabricated as is sometimes necessary. Unfortunately, I couldn’t get the break in the top of the cabinet to mate, despite using quite a bit of pressure. As a result, I had to glue it first and then apply fibreglass to the underside of the cabinet top. I also scraped out some of www.siliconchip.com.au the glue on the top of the cabinet and then filled the resulting grooves with fibreglass that had been mixed with some craftwork paint. Cream isn’t an easy colour to match but the finished cabi­net looks quite reasonable. And, at least, it won’t fall to pieces. Summary This cheap, little 4-valve set really was designed for the lower end of the market. As mentioned above, the chassis was only lightly plated and it had rusted badly in spots. In addition, the layout both above and underneath the chassis is rough and ready. The cost-cutting is evident everywhere. For example, the IF transformers are each made out of a flat piece of metal which has been rolled into a cylinder and the overlapping ends riveted together. And on a similar theme, the transformer windings are on a plastic former which is fitted with top and bottom plastic plates. The dial system also leaves a bit to be desired. It does work but it’s not up to the standard of most other sets. Does it have any good points? Yes, definitely – it’s cheap, its performance is not far behind that of most 5-valve sets and it’s easy to dismantle. In fact, it takes less than a minute to remove the chassis from its cabinet. Try doing that with an AWA “seven bander” – they take nearly half an hour to dismantle or to reassemble. It’s not a set that I’d crawl over hot coals to obtain, however. Instead, it’s an interesting low-end receiver that’s worthy of collecting, if only to show just how well low-cost receivers can perform. Finally, it’s worth noting that the quality of the Prece­dent receivers improved markedly in just a few years. For exam­ple, I have a 1958 dual-wave 5-valve radiogram chassis and that unit shows a significant improvement in all areas of design and manufacture. The chassis is better quality, the layout of the components and the design is better, the accessibility is im­proved (it was good beforehand), and the dial mechanism is light years ahead of the 4-valve mantel set’s dial-drive system. The later unit also looked far more professional, although it was still aimed at the lower end of the market. A. W. Jackson Industries and Precedent receivers are a small but important part SC of our radio heritage. November 2003  95 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 Active crossover as an audio splitter Would it be possible to use the 3-Way Active Crossover featured in the January 2003 issue so that the “Tweeter out” and “Midrange out” did not have any filters included? I want to use the project as a splitter for one common line in. It will be used to power a DJ system for a club, where there is a set of speakers inside the club (controlled by “Tweeter Out”) and a set of speakers outside the club (controlled by “Midrange Out”). I would leave the “Bass Out” for a stereo subwoofer driver inside the club. I would replace the six trimpots with three 100kΩ (log) dual-gang potentiometers. Then disconnect the leg of the potentiometer that connects to IC1c pin 8 and connect it to IC1a pin 1. Similarly, disconnect the leg of the potentiometer that connects to IC3b pin 7 and connect it to IC1a pin 1. Any suggestions would be appreciated? (D. F., via email). • Yes, you could but you are effectively wasting four op amps in each channel. Your method of connection is OK. You can leave out the 2.2nF capacitors and 10kΩ feedback resistors for IC1d and IC1c and the 47nF capacitors and 10kΩ feedback resistors for IC3c and IC3b. Naughty changes to the SC480 I built two SC480 version 1 modules (SILICON CHIP, January & February 2003) and all is well except for the two BC639s and the BC640 which get very hot even with heatsinks. I’m sure I know the reason and that is that I’ve used a 30-0-30V 300VA toroidal transformer that I’ve had for a while. It is putting out somewhere in the vicinity of 47V DC. The obvious answer is probably that I need to go back to the 28-0-28V transformer recommended but that leaves me again with this as yet unused toroidal transformer. Is there any way I can stop those darn critters overheating by changing resistor values or substituting others in their place? I don’t want to compromise the design, so if it’s no then it’s no. (R. C., via email). • You’ve been naughty by doing that substitution. You could try substituting BD139/140s for the BC639/640 How To Magnetically Shield Loudspeakers I am looking for information on how to protect my television set from an old pair of Pioneer speaker boxes that are obviously not magnetically shielded. Is there a way I can shield the boxes by perhaps lining the inside with something or do I need to purchase new ones? The existing speakers sound great and I would like to keep on using them if possible. (T. B., via email). • There is no easy way that we know of to magnetically shield existing speakers. The system involves an extra magnet and steel cowl assembly to cancel the mag96  Silicon Chip netic field leakage from the main magnet. On the other hand, if your speakers are so old that they use Alnico magnets (rather than the ferrite magnets which have been in use for the last 30 years or more), you may not need any shielding. How to tell? Suspend a steel paper clip from a 300mm length of cotton and dangle it around the outside of the cabinet on the same level as the speakers. If the paper clip is obviously moved by the magnetic field, make sure you keep the speakers at least 1.5 metres from your TV. You can do the same test with a compass. but component spacing will make this difficult and you will need to fit larger flag heatsinks. Note that the two flag heatsinks must be isolated from each other. Oscillator problem with Smart Card project I have built the Smart Card Programmer from the January 2003 issue. I have a problem with the clock timing when set to 3.57MHz. I am using a Metex M-3850D multimeter for all measurements. Can you please advise me why the frequency at pin 8 of IC2, the 74HC00, is double that at pin 9. When set to 6MHz, the frequency at pins 6, 11 & 12 are all 5.99MHz, so presumably the problem is around IC2c and X1. (A. H., via email). • It sounds as if the 3.58MHz crystal in your kit (X1) is especially prone to oscillate on its second harmonic. This being the case, you may need to increase the value of the 1.5kΩ series feedback resistor, to achieve more attenuation at the higher frequency so it is forced to oscillate at the fundamental. Try increasing the resistor to 1.8kΩ or even 2.2kΩ until the frequency measured at pin 8 of IC2 is 3.579MHz. Config files for EPROM programmer I have just finished building the Windows-based Eprom Pro­ grammer described in the November & December 2002 & February 2003 issues. Have you provided any config files? Could you advise how I get them or create them? (M. J., via email). • There were a number of config files included in the software package which is available from the SILICON CHIP website. However, it’s easy to make up your own config files for other devices: you simply set the program on-screen with the pin connections, pro­gramming pulse width, etc from the device manufacturer’s data, and www.siliconchip.com.au Better transistors for the SC480 amplifier Your SC480 amplifier in the January & February 2003 issues could not have come at a more opportune time. I had bought an Australian-made amplifier some 15 years ago (after much read­ing of reviews) with the insurance from a robbery in which my Phase Linear 350W RMS per channel amplifier plus Amcron preamp and other assorted pieces of hifi gear were stolen. The Australian amplifier (approx. $2000) did not last long before one of the channels blew. It was returned to the maker who fixed the problem. The amplifier finally expired a few years later and then the maker was uncontactable. I was faced with the problem of replacing the amplifier boards which were very small and were fixed vertically to the heatsink. I also have a defunct Sugden then save the settings as a config file clicking on File->Save Device Config. The dialog box prompts you for the filename, etc. Endpoint for Nicad/ NiMH discharging I’m looking to build a simple discharger circuit for the NiMH cells I use in my digital camera and am curious (given your past projects on dischargers) whether the 0.9V-1V indicated as the end-point for discharging is the open-circuit cell voltage or the cell voltage under load? (J. L., via email). • The end-point voltage is the voltage under load. Depending on the cell rating, our past discharger circuits would work at around 180mA and measure the cell voltage at this current. Measuring off load gives an erroneous result. which had seen many years of service (with the replacement of various diodes and resistors) until the PC boards became so burnt and brittle that some of the tracks were hanging in space! Needless to say, despite Sugden’s claim of lifetime service, they were unable to replace the ampli­fier boards and suggested that I buy a new Sugden. So I built two of your 1987 design amplifiers and incorporated them into a rack chassis with the Sugden’s huge transformer and capacitor bank. They have given sterling service. The new SC480 design with the plastic power transistors will fit nicely into the expensive Aussie amplifier which has a more than adequate trannie and capacitor bank. However, I have a couple of questions: (1) Can I use the Motorola MJL21193/4 plastics in place of TIP3055/TIP2955 transistors without modifying the circuit? (2) Is there any sonic advantage in replacing the you can suggest that might correctly modify this kit to fit my need? (L. J., via email). • The main limiting factor in frequency response will be due to the 470µF capacitor at the speaker output. Into 8Ω, the rolloff is 3dB down at 42Hz. You probably need to increase the capacitor to 2200µF. Also increase the 22µF capacitor between pins 1 and 8 of IC2 to 220µF. Poor matching in volume control I own a Playmaster power amplifier and preamp which performs brilliantly, with stunning performance 1987 design in my “Sugden” with the new SC480 2N3055/MJ2955 amps? (J. W., Carwoola, NSW). • Yes, you can drop in the MJL21193/4s without any other modification and they will certainly give an improvement in distortion performance. However, they are very expensive and their potential is a little wasted in this circuit because the SC480’s supply voltage is too low to extract the maximum avail­ able power. In the Plastic Power modules featured in the April 1996 issue, we got 125W into 8-ohm loads and 175W into 4-ohms (more with Music Power). As you are aware, the main improvement in performance bet­ween the 1987 design and the SC480 is in the very careful PC board design and wiring layout. You should be able to hear the difference but whether it is worth changing to the SC480 boards in your “Sugden” amplifier is up to you. equivalent to commercial equipment costing 2-3 times more. I do have a question regarding the operation of my preamplifier though. With very high line levels and low volume settings, the righthand channel appears to cut in well before the lefthand channel, even though both channels are very similar in amplitude. Why does this happen? This causes problems when listening to stereo music at very low levels. (D. F., via email). • We assume that you are talking about the operation of the volume control – where rotating it from zero setting causes one channel to cut in before the other. This is caused by poor matching of the resistance tracks of the Personal noise source modifications I’ve built your Personal Noise Source from the September 2001 issue. I’m trying to use it as a test noise source for sub-woofer tuning and calibration but its output level and frequency response is too low in the 40Hz-150Hz range. Is there anything www.siliconchip.com.au November 2003  97 Notes & Errata Frequency Meter, October 2003: VR2 on both the circuit and overlay should be 10kΩ. The parts list is correct. PC Infrared Remote Control, August 2003: Some constructors have reported that the remote power-up function stops working after switching power on and off a number of times. The problem was traced to EEPROM corruption during brownout of the +5V supply to the microcontroller (IC1). To fix the problem, mount an MC34064P-5 undervoltage sensing IC on the bottom (copper) side of the PC board as shown in Fig.1. If you’ve yet to assemble your board, then this should be done after all other components have been installed. Slip a short length of heatshrink tubing over the GND lead of the IC before soldering it. dual-ganged potentiometer. Short of purchasing a much higher quality dual pot with guaranteed tracking, there is nothing you can do about it. Power meter for audio amplifiers I have some queries regarding the usage of the Audio Power Meter (April 1993) with the 175W Power Amplifier from the April 1996 issue and the Altronics 200 watt Mosfet Amplifier. I have used the Audio Power Meter with the Playmaster 200/300 watt amplifier (EA) and set up the unit to suit the resistance setting for trimpot VR1 that was quoted in a reply to “Ask Silicon Chip” in an earlier edition of Fig.1: this diagram shows how to modify existing boards. This ensures that the GND and +5V leads can’t short together. The MC34064P-5 is available from Altronics (cat. Z-7252) and Farnell (cat.703-709). the magazine. I am wondering if the APM can be used with these amplifiers and if so, what would the resistance be for both 8-ohm and 4-ohm loads? I am also building the DiscoLight project from the July & August 1988 issues. I generally have used IC sockets with the majority of the projects that I have built because of the ease of inserting and removal of the ICs. Is it advisable to use IC sockets for this project as my main concern is the high voltage that is present on the PC board and that is required to drive the light system? (D. W., via email). • You can use sockets for the Discolight ICs except for the optocouplers which are best soldered directly to the PC board. Fig.2: this new PC board design includes the extra IC. Note that you only need to do this modification if you’re using the remote power-up function. The power meter can be used for 175W amplifiers and 200/300W amplifiers. Values for VR1 are as follows: 175W into 8Ω, VR1= 57.6kΩ; 175W into 4Ω, VR1= 37.9kΩ; 200W into 8Ω, VR1= 62.5kΩ; 200W into 4Ω, VR1= 41.2kΩ; 300W into 8Ω, VR1= 78.5kΩ; 300W into 4Ω, VR1= 52.9kΩ. For powers in between these figures, you can estimate the resistance value required; eg, for 190W into 8Ω, VR1 should be between the 175W and 200W values of 57.6kΩ and 62.5kΩ. A value of 60kΩ for VR1 should be suitable. Generally, it is best to use a smaller value for VR1 than that calculated so the maximum power will be shown on the meter before the amplifier clips. 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. 98  Silicon Chip www.siliconchip.com.au 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. Alternatively, fax the details to (02) 9979 6503 or send an email to silchip<at>siliconchip.com.au 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______________ Phone:_____________ Fax:_____________ Email:__________________ www.siliconchip.com.au FOR SALE PICAXE LED LIGHTING KITS, Superflux RGB LEDs, RGB sequencing LEDs, LED glow sticks, low cost CR123A lithium batteries. Check out: www.alphalink.com.au/spod UNIVERSAL DEVICE PROGRAMMER: Low cost, high performance, 48-pin, works in DOS or Windows incl. NT/2000. $1364. Universal EPROM programmer $467.50. 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, 68HC­08, 68HC11, 68HC12, 68HC16. $385.00 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 $132.00, 14 pin $126.50, 8 pin $121.00. 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 USB KITS: Stepper Motor Controller, USB PIO Intefface, DTMF Transceiver, Thermometer, DDS HF Generator, Compass, 4-Channel Voltmeter, I/O Relay Card. Also available: Digital Oscilloscope, Temperature Loggers, VHF Receivers and USB Active X (and USBDOS.exe file) to control our kits from your application. www.ar.com.au/~softmark PCBs MADE, ONE OR MANY. Any format, hobbyists welcome. Sesame Elec­tronics (02) 9586 4771. sesame777<at>optusnet.com.au; http:// members.tripod.com/~sesame_elec November 2003  99 New New New Foam surrounds,voice coils,cones and more Original parts for Dynaudio,Tannoy and others Expert speaker repairs – 20 years experience Australian agents for products Trade welcome – email for your user ID Phone (03) 9682 2487 Mark22-SM Slimline Mini FM R/C Receiver Cygnus Logic Systems  Industrial High Speed Automation  Electronic System Design  Custom Software Design  Consultancy  Troubleshooting  Project Management Tel: (02) 9904 3991 Fax: (02) 9904 3993 Mob: 0402 985 574 speakerbits.com.au cygnuslogic<at>iprimus.com.au JACKSON BROS JACKSON OF THE UK IS BACK Highest quality products made by UK Craftsmen • • • • • 6 Channels 10kHz frequency separation Size: 55 x 23 x 20mm Weight: 25gm Modular Construction Price: $A129.50 with crystal Electronics Variable and trimmer capacitors, reduction drives, dials, ceramic stand-offs Full range now available off the shelf in Australia CATALOGUES AND PRICE LISTS NOW AVAILABLE CHARLES I COOKSON PTY LTD GPO BOX 812, ADELAIDE, SA 5001 Tel: (08) 8235 0744 Fax: (08) 8356 3652 FreeFax: 1800 673355 (Within Australia) Email: jackson<at>homeplanet.com.au ALL MAJOR CREDIT CARDS ACCEPTED SOLE AGENTS FOR AUSTRALIA AND NEW ZEALAND PO Box 580, Riverwood, NSW 2210. Ph/Fax (02) 9533 3517 email: youngbob<at>silvertone.com.au Website: www.silvertone.com.au Building speaker boxes? Mounting electrical components onto solid timber? You may need the Carba–tecTOOLS FOR WOOD catalogue!! We have Australia’s largest range of woodworking handtools & machinery. Please contact us for your FREE 220 page colour catalogue or come in & see us at: 32 PERCY ST, AUBURN 2144 9649 5077 www.carbatec.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: 1300 132 251; Fax: (03) 9561 5529 Call Mike Lynch and check us out! We are the best for low cost, small runs. TAIG MACHINERY Micro Mini Lathes and Mills From $489.00 59 Gilmore Crescent Garran ACT 2605 (02) 6281 5660 0412269707 trollers. Low cost, high performance. Programming software and SCADA software free. Heaps of features. Full details and credit card ordering available at www.oceancontrols.com.au WEATHER STATIONS: Windspeed & direction, inside temperature, outside temperature & windchill. Records highs & 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. Eco Watch phone: (03) 9761 7040; fax: (03) 9761 7050; Unit 5, 17 Southfork Drive, Kilsyth, Vic. 3137. ABN 63 006 399 480. Pixel Programmable Controller with 4 analog inputs, 8 digital inputs and 8 relay outputs. Uses a Picaxe 28A. Programmed in basic. 100  Silicon Chip Labjack USB Data Acquisition Module features 8 12bit analog inputs, 20 digital I/O, 2 analog outputs and high speed counter. Free software, Labview driver and ActiveX component. DAS005 Parallel Port Data Acquisition Module features 8 12bit Analog inputs, 4 Digital I/Ps & 4 Digital O/Ps. Free windows software and source code. Dual Relay Modules suitable for TTL and Open Collector Outputs Leader Modbus Data Acquisition Modules analog inputs, RTD, thermocouple, analog outputs, digital input and output modules Programmers for Atmel and PIC micro­ controllers. Switch Mode and Linear Power Supplies and DC-DC convertors. FAB Programmable Logic Con- BUY FROM HONG KONG, PAY IN OZ. Get many common passives, ICs and LCDs direct from Hong Kong but pay in Oz. http://www.kitsrus.com/index.html S-Video . . . Video . . . Audio . . . VGA distribution amps, splitters, standards converters, tbc’s, switchers, cables, etc, & price list: www.questronix.com.au TEST GEAR: Oscilloscope, freq. counter, variacs, avometers etc. All cheap. Phone or email for list and prices (03) 5264 1411 or adamson1951<at>bigpond.com 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 www.siliconchip.com.au Do You Eat, Breathe and Sleep Technology? Management & Sales Positions Advertising Index Acetronics..................................101 We are a rapidly growing, Australian-owned international retailer with more than 30 stores in Australia and we have a growing expansion program to open many more, so we need dedicated individuals to join our team to help achieve our goals. If you are customer focused, have an eye for detail, empathy for the products we sell and have recently completed a TAFE of University degree in electronics, we want to meet you. Career opportunities with full training are available now if you have the drive and ambition to make your future with Jaycar. We offer a competitive salary, sales commission and many other benefits. To apply for these positions please send your C.V. indicating the role you are interested in to the address shown below. Altronics........................ loose insert Jaycar Electronics is an equal opportunity employer and actively promotes staff from within the organisation. Dick Smith Electronics........... 20-23 Retail Operations Manager Jaycar Electronics Pty. Ltd. P.O. Box 6424 Silverwater NSW 1811 Fax: (02) 9741-8524 Email: jobs<at>jaycar.com.au Av-Comm Pty Ltd.........................39 BitScope Designs.........................61 Carba-Tec Tools.........................100 Cygnus Logic Systems..............100 David Hall Electronics..................97 Eco Watch..................................100 Elan Audio......................................7 Evatco..........................................93 KITS KITS AND MORE KITS! Check ’em out at www.ozitronics.com PASCAL for AVR – powerful compiler/ IDE. Includes drivers for LCD, 12C, 7-seg LED, RS232, Stepper, LAN and more. AVR In-Circuit Programmers – serial and USB. SPI and JTAG modes. Support JTAG debug. CHIP PROGRAMMERS – EPROMS, micros, flash, etc. Xeltek universal programmers – ultra high speed, USB, PC and standalone modes – from $1230. Digital Graphics Pty Ltd (02) 9888 3105. www.digitalgraphics.com.au LEDs: High Power and Intensely Bright WANTED EARLY HIFI’S, AMPLIFIERS, Speakers, Turntables, Valves, Books, Quad, Leak, Pye, Lowther, Ortofon, SME, Western Electric, Altec, Marantz, McIn- Grantronics..................................99 • • • Instant PCBs..............................100 diameter Narrow beam angle gives 17Cd at 20mA, more at higher currents. Time to start on this year’s Xmas decorations! Ideal for moving message signs and traffic applications Only $36 (incl. GST) per bag of 100, supplied in original SHARP packaging, plus $9 post delivery. Datasheet on request to: fortytroutelectronics<at>optusnet.com.au or Forty Trout Electronics Pty Ltd 15 Rockliffe St, Eltham 3095 High volume enquiries welcome! Harbuch Electronics.....................59 Jackson Bros.............................100 Hy-Q International........................61 Jaycar ....................... 47-58,61,101 JED Microprocessors................5,61 Kalex............................................93 Microgram Computers...................3 MicroZed Computers...................77 Printed Electronics.................... 100 Quest Electronics..................61,100 RCS Radio.................................100 RF Probes....................................93 & MADE TO ORDER PCBs For more details: www.acetronics.com.au Phone (02) 9600 6832 email: acetronics<at>acetronics.com.au tosh, Goodmans, Wharfedale, Tannoy, radio and wireless. Collector/Hobbyist will pay cash. (02) 9440 1267. johnmurt<at>highprofile.com.au Silicon Chip Binders  Each binder holds up to 12 issues  SILICON CHIP logo printed on spine & cover Price: $A12.95 plus $A5.50 p&p each. Available in Australia only. Buy five and get them postage free. Just fill in & mail the handy order form in this issue; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. www.siliconchip.com.au Gadget Central...........................IFC Red and yellow colours available, in •leaded clear plastic cylinder format, 10mm 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 Forty Trout Electronics...............101 Silicon Chip Back Issues.... 102-103 Silicon Chip Bookshop........104,IBC SC Car Projects Book..............OBC Silicon Chip Subscriptions...........13 Silvertone Electronics................100 Soundlabs Group.........................61 Speakerbits................................100 Switchmode Power Supplies........38 REAL VALUE AT Taig Machinery...........................100 PLUS P &P ____________________________ $12.95 Telelink Communications.............61 PC Boards Printed circuit boards for SILICON CHIP projects are made by: RCS Radio Pty Ltd. Phone (02) 9738 0330. Fax (02) 9738 0334. November 2003  101 Silicon Chip Back Issues August 1994: High-Power Dimmer For Incandescent Lights; 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 Batteries; MiniVox Voice Operated Relay; AM Radio For Weather Beacons; Dual Diversity Tuner For FM Mics, Pt.2; Electronic Engine Management, Pt.12. April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors; 32-Band Graphic Equaliser, Pt.2. December 1991: TV Transmitter For VCRs With UHF Modulators; IR Light Beam Relay; Colour TV Pattern Generator, Pt.2; Index To Vol.4. May 1989: Build A Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference. March 1992: TV Transmitter For VHF VCRs; Thermostatic Switch For Car Radiator Fans; Valve Substitution In Vintage Radios. July 1989: Exhaust Gas Monitor; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; The NSW 86 Class Electrics. April 1992: IR Remote Control For Model Railroads; Differential Input Buffer For CROs; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. September 1989: 2-Chip Portable AM Stereo Radio Pt.1; High Or Low Fluid Level Detector; Studio Series 20-Band Stereo Equaliser, Pt.2. October 1989: FM Radio Intercom For Motorbikes Pt.1; GaAsFet Preamplifier For Amateur TV; 2-Chip Portable AM Stereo Radio, Pt.2. 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. 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. 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. 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. 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. 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. 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. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Active Antenna Kit; Designing UHF Transmitter Stages. 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. 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. 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. March 1993: Solar Charger For 12V Batteries; Alarm-Triggered Security Camera; Reaction Trainer; Audio Mixer for Camcorders; A 24-Hour Sidereal Clock For Astronomers. 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. 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. April 1993: Solar-Powered Electric Fence; Audio Power Meter; Three-Function Home Weather Station; 12VDC To 70VDC Converter; Digital Clock With Battery Back-Up. April 1995: FM Radio Trainer, Pt.1; Balanced Mic Preamp & Line Filter; 50W/Channel Stereo Amplifier, Pt.2; Wide Range Electrostatic Loudspeakers, Pt.3; 8-Channel Decoder For Radio Remote Control. April 1990: Dual Tracking ±50V Power Supply; Voice-Operated Switch With Delayed Audio; 16-Channel Mixing Desk, Pt.3; Active CW Filter. June 1993: AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; Digital Voltmeter For Cars; Windows-Based Logic Analyser. June 1990: Multi-Sector Home Burglar Alarm; Build A Low-Noise Universal Stereo Preamplifier; Load Protector For Power Supplies. 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. 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. 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 1993: Low-Cost Colour Video Fader; 60-LED Brake Light Array; Microprocessor-Based Sidereal Clock; Satellites & Their Orbits. 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 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. 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 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. 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. 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. 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. 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. 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. 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. 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. February 1994: Build A 90-Second Message Recorder; 12-240VAC 200W Inverter; 0.5W Audio Amplifier; 3A 40V Adjustable Power Supply; Engine Management, Pt.5; Airbags In Cars – How They Work. 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. 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. 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. 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. September 1991: Digital Altimeter For Gliders & Ultralights; Ultrasonic Switch For Mains Appliances; The Basics Of A/D & D/A Conversion; Plotting The Course Of Thunderstorms. 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. October 1991: 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. June 1994: 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. November 1991: Build A 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. 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. ORDER FORM 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. 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. 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 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 Trans­verter 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: 125W Audio Amplifier Module; Knock Indicator For Leaded Petrol Engines; Multi-Channel Radio Control Transmitter; Pt.3. May 1996: High Voltage Insulation Tester; Knightrider LED Chaser; Simple Intercom Uses Optical Cable; Cathode Ray Oscilloscopes, Pt.3. June 1996: 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 Fluores­cent 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, Please send the following back issues:________________________________________ 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 ___________ 102  Silicon Chip 10% OF F SUBSCR TO IB OR IF Y ERS OU 10 OR M BUY ORE Note: prices include postage & packing Australia ............................... $A8.80 (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 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; 600W DC-DC Converter For Car Hifi Systems, Pt.1; IR Stereo Headphone Link, Pt.2; Multi-Channel Radio Control Transmitter, Pt.8. November 1996: 8-Channel Stereo Mixer, Pt.1; Low-Cost Fluorescent Light Inverter; Repairing Domestic Light Dimmers; 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. 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. 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. 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. 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 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 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 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. 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. 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; 15W/Ch Class-A Audio Amplifier, Pt.1; Simple Charger For 6V & 12V SLA Batteries; Auto­ matic 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; 15W/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: AC Millivoltmeter, Pt.1; PC-Controlled Stress-O-Meter; Versatile Electronic Guitar Limiter; 12V Trickle Charg-er For Float Conditions; Adding An External Battery Pack To Your Flashgun. 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. 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. 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. 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. 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. www.siliconchip.com.au 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. 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. 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? 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. 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. 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; FAQs On The MP3 Jukebox. 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. 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. 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 IBM Scan-Codes To ASCII); 50A Motor Speed Controller For Models. 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. 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. March 2002: Mighty Midget Audio Amplifier Module; The Itsy-Bitsy USB Lamp; 6-Channel IR Remote Volume Control, Pt.1; RIAA Pre­-­Amplifier For Magnetic Cartridges; 12/24V Intelligent Solar Power Battery Charger; Generate Audio Tones Using Your PC’s Soundcard. April 2002:Automatic Single-Channel Light Dimmer; Pt.1; Build A Water Level Indicator; Multiple-Output Bench Power Supply; Versatile Multi-Mode Timer; 6-Channel IR Remote Volume Control, Pt.2. May 2002: 32-LED Knightrider; The Battery Guardian (Cuts Power When the Battery Voltage Drops); Stereo Headphone Amplifier; Automatic Single-Channel Light Dimmer; Pt.2; Stepper Motor Controller. June 2002: Lock Out The Bad Guys with A Firewall; Remote Volume Control For Stereo Amplifiers; The “Matchless” Metal Locator; Compact 0-80A Automotive Ammeter; Constant High-Current Source. July 2002: Telephone Headset Adaptor; Rolling Code 4-Channel UHF Remote Control; Remote Volume Control For The Ultra-LD Stereo Amplifier; Direct Conversion Receiver For Radio Amateurs, Pt.1. August 2002: Digital Instrumentation Software For Your PC; Digital Storage Logic Probe; Digital Thermometer/Thermostat; Sound Card Interface For PC Test Instruments; Direct Conversion Receiver For Radio Amateurs, Pt.2; Spruce Up Your PC With XP-Style Icons. September 2002: 12V Fluorescent Lamp Inverter; 8-Channel Infrared Remote Control; 50-Watt DC Electronic Load; Driving Light & Accessory Protector For Cars; Spyware – An Update. October 2002: Speed Controller For Universal Motors; PC Parallel Port Wizard; “Whistle & Point” Cable Tracer; Build An AVR ISP Serial Programmer; Watch 3D TV In Your Own Home. November 2002: SuperCharger For NiCd/NiMH Batteries, Pt.1; Windows-Based EPROM Programmer, Pt.1; 4-Digit Crystal-Controlled Timing Module; Using Linux To Share An Optus Cable Modem, Pt.1. 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 2002: Receiving TV From Satellites; Pt.1; The Micromitter Stereo FM Transmitter; Windows-Based EPROM Programmer, Pt.2; SuperCharger For NiCd/NiMH Batteries; Pt.2; Simple VHF FM/AM Radio; Using Linux To Share An Optus Cable Modem, Pt.2. 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. January 2003: Receiving TV From Satellites, Pt 2; SC480 50W RMS Amplifier Module, Pt.1; Gear Indicator For Cars; Active 3-Way Crossover For Speakers; Using Linux To Share An Optus Cable Modem, Pt.3. 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. February 2003: The PortaPal Public Address System, Pt.1; 240V Mains Filter For HiFi Systems; SC480 50W RMS Amplifier Module, Pt.2; Windows-Based EPROM Programmer, Pt.3; Using Linux To Share An Optus Cable Modem, Pt.4; Tracking Down Elusive PC Faults. November 2000: Santa & Rudolf Chrissie Display; 2-Channel Guitar Preamplifier, Pt.1; Message Bank & Missed Call Alert; 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; 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. February 2001: An Easy Way To Make PC Boards; L’il Pulser Train Controller; A MIDI Interface For PCs; Build The Bass Blazer; 2-Metre Groundplane Antenna; The LP Doctor – Clean Up Clicks & Pops, Pt.2. March 2003: LED Lighting For Your Car; Peltier-Effect Tinnie Cooler; PortaPal Public Address System, Pt.2; 12V SLA Battery Float Charger; Build The Little Dynamite Subwoofer; Fun With The PICAXE (Build A Shop Door Minder); SuperCharger Addendum; Emergency Beacons. April 2003: Video-Audio Booster For Home Theatre Systems; A Highly-Flexible Keypad Alarm; Telephone Dialler For Burglar Alarms; Three Do-It-Yourself PIC Programmer Kits; More Fun With The PICAXE, Pt.3 (Heartbeat Simulator); Electric Shutter Release For Cameras. May 2003: Widgybox Guitar Distortion Effects Unit; 10MHz Direct Digital Synthesis Generator; Big Blaster Subwoofer; Printer Port Simulator; More Fun With The PICAXE, Pt.4 (Motor Controller). 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. June 2003: More Fun With The PICAXE, Pt.5; PICAXE-Controlled Telephone Intercom; PICAXE-08 Port Expansion; Sunset Switch For Security & Garden Lighting; Digital Reaction Timer; Adjustable DC-DC Converter For Cars; Long-Range 4-Channel UHF Remote Control. 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. July 2003: Smart Card Reader & Programmer; Power-Up Auto Mains Switch; A “Smart” Slave Flash Trigger; Programmable Continuity Tester; PICAXE Pt.6 – Data Communications; Updating The PIC Programmer & Checkerboard; RFID Tags – How They Work. 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. 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). 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: DI Box For Musicians; 200W Mosfet Amplifier Module; Headlight Reminder; 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. August 2003: PC Infrared Remote Receiver (Play DVDs & MP3s On Your PC Via Remote Control); Digital Instrument Display For Cars, Pt.1; Home-Brew Weatherproof 2.4GHz WiFi Antennas; PICAXE Pt.7 – Get That Clever Code Purring; A Digital Timer For Less Than $20. September 2003: Robot Wars – The Sport Of The New Millenium; Bright & Cheap Krypton Bike Light; Portable PIC Programmer; Current Clamp Meter Adapter For DMMs; PICAXE Pt.8 – A Data Logger & Sending It To Sleep; Digital Instrument Display For Cars, Pt.2. October 2003: PC Board Design Tutorial, Pt.1; The JV80 Loudspeaker System; A Dirt Cheap, High-Current Power Supply; Low-Cost 50MHz Frequency Meter; Long-Range 16-Channel Remote Control System. PLEASE NOTE: Issues not listed have sold out. All other issues are in stock. We can supply photostat copies from sold-out issues for $8.80 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 November 2003  103 REFERENCE GREAT BOOKS FOR ALL PRICES INCLUDE GST AND ARE AUDIO POWER AMPLIFIER DESIGN HANDBOOK PIC Your Personal Introductory Course A handbook for professionals and students from one of the world’s most respected audio auth-orities. New edition is more comprehensive than ever with a new chapter on Class G amplifiers and further new material on out-put coils, thermal distortion, relay distortion, ground loops, triple EF output stages and convection cooling. 427 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, tech-nicians and electronics enthusiasts – perfect for schools and colleges. 270 pages in soft cover. by Douglas Self 3rd Edition 2002 89 $     VIDEO SCRAMBLING AND DESCRAMBLING FOR SATELLITE & CABLE TV by Graf & Sheets $ 87 $ UNDERSTANDING TELEPHONE ELECTRONICS By Stephen J. Bigelow. 4th edition 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. 70 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. Includes both theory and practical servicing informationand is ideal for both students and technicians. 382 pages, in paperback. $$ 46 AUDIO ELECTRONICS By John Linsley Hood. First published 1995. Second edition 1999. 2nd Edition 1998 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. by John Morton – 2nd edition 2001 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. EMC FOR PRODUCT DESIGNERS 3rd EDITION $ By Tim Williams. First pub­­lished 1992. 3rd edition 2001. 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. 103 63 $ 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. 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. Servicing TV Satellite & Video Equipment. By Eugene Trundle. Revised edition 2002. Written by a practising service engineer, the emphasis is on the practical business of fault diagnosis and repair, with chapters on TV power supplies, line timebases, video deck machines, test-gear, intermittent faults, repair techniques and workshop practice. This revised edition also features a completely new chapter on the latest digital equipment – DVD, set-top boxes, digital satellite TV and digital TV sets. 70 $ 89 $ Microcontroller Projects in C for the 8051 by Steve Roberts. 2nd edition 2001. 69 ANALOG ELECTRONICS By Ian Hickman. 2nd edition1999. TELEPHONE INSTALLATION HANDBOOK $ 92 $ by Dogan Ibrahim. Published 2000. $ 73 NEW NEW NEW NEW Through graded projects the author introduces the fundamentals of microelectronics, the 8051 family, programming in C and the use of a C compiler. The AT89C2051 is an economical chip with re-writable memory. Provides an interesting, enjoyable and easily mastered alternative to more theoretical textbooks. 178 pages in paperback. Practical Variable Speed Drives and Power Electronics by Malcolm Barnes. 1st Ed, Feb 2003. An essential reference for engineers and anyone who wishes to design or use variable speed drives for induction motors. As reviewed in SILICON CHIP September 2003. 288 pages. 85 $ BOOKSHOP WANT TO SAVE 10%? 10% OFF! SILICON CHIP SUBSCRIBERS AUTOMATICALLY QUALIFY FOR A 10% DISCOUNT ON ALL BOOK PURCHASES! ENQUIRING MINDS! LOWER THAN RECOMMENDED RETAIL PRICE Power Supply Cookbook Analog Cct Techniques With Digital Interfacing by T H Wilmshurst. Published 2001. by Marty Brown. 2nd edition 2001. An easy-to-follow, step-by-step design frame-work for a wide variety of power supplies. Any-one with a basic knowledge of electronics can create a very complicated power supply design . Magnetics, feedback loop, EMI/ RFI control and compensation design are all described in simple language. 265 pages in paperback. VIDEO & CAMCORDER SERVICING AND TECHNOLOGY 99 $ by Steve Beeching (Published 2001) $ 69 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. 69 $ Antenna Toolkit by Joe Carr. 2nd edition 2001. Together with the CD software included, the reader will have a complete solution for constructing or using an antenna - bar the actual hardware. The software is based on the author’s Antler program, which provides a simple Windows-based aid to carrying out the design calculations at the heart of successful antenna design. 253 pages in paperback. PIC IN PRACTICE by Howard Hutchings. Revised by Mike James. 2nd edition 2001. 63 63 $$ $ 52 O R D E R H E R E ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ by Ian Hickman 3rd Edition 2002 P&P Based on popular short courses on the PIC, for professionals, students and teachers. Can be used at a variety of levels. An ideal introduction to the world of microcon-trollers for hobbyists, students and professionals. 255 pages in paperback. ANALOG CIRCUIT TECHNIQUES W/DIGITAL INT............$69.00 ANALOG ELECTRONICS..................................................$89.00 ANTENNA TOOLKIT.........................................................$87.00 AUDIO ELECTRONICS.....................................................$92.00 AUDIO POWER AMPLIFIER DESIGN...............................$89.00 ELECTRIC MOTORS AND DRIVES..................................$63.00 EMC FOR PRODUCT DESIGNERS.................................$103.00 GUIDE TO TV & VIDEO TECHNOLOGY............................$63.00 INTERFACING WITH C.....................................................$63.00 M'CONTROLLER PROJECTS IN C FOR 8051..................$73.00 PIC IN PRACTICE............................................................$52.00 PIC - YOUR PERSONAL INTRODUCTORY COURSE........$46.00 POWER SUPPLY COOKBOOK..........................................$99.00 PRACTICAL RF HANDBOOK............................................$69.00 PRACT. VARIABLE SPEED DRIVES/POWER ELECT.........$85.00 SERVICING TV SATELLITE & VIDEO EQUIPMENT..........$70.00 TELEPHONE INSTALLATION HANDBOOK.......................$69.00 UNDERSTANDING TELEPHONE ELECTRONICS..............$70.00 VIDEO & CAMCORDER SERVICING/TECHNOLOGY........$69.00 VIDEO SCRAMBLING/DESCRAMBLING..........................$87.00 Orders over $100 P&P free in Australia. AUST: Add $A5.50 per book NZ: Add $A10 per book, $A15 elsewhere Anyone interested in ports, transducer interfacing, analog to digital conversion, convolution, filters or digital/analog conversion will benefit from reading this book. The principals precede the applications to provide genuine understanding and encourage further development. 302 pages in paperback. PRACTICAL RF HANDBOOK by D W Smith Published 2002 $ 87 $ Interfacing With C Electric Motors And Drives by Austin Hughes. 2nd edition 1993. Reprinted 2001. For non-specialist users – explores most of the widely-used modern types of motor and drive, including conventional and brushless DC, induction, stepping, synchronous and reluctance motors. 339 pages, in paperback. Covers all the analog electronics needed in a wide range of higher education programs: first degrees in electronic engineering, experimental science course, MSc electronics and electronics units for HNDs. Text is supported by numerous worked examples and experimental exercises. 312 pages in paperback. A guide to RF design for engineers, technicians, students and enthusiasts. Covers all of the key topics in RF: analog design principles, transmission lines, couplers, transformers, amplifiers, oscillators, modulation, transmitters and receivers, propagation & antennas. 279 pages in paperback. TAX INVOICE 69 $$ Your Name_________________________________________________ PLEASE PRINT Address ___________________________________________________ ___________________________________ Postcode_______________ STD Daytime Phone No. (______) __________________________________ Email___________________<at>_________________________________ ❏ Cheque/Money Order enclosed OR ❏ Charge my credit card – ❏ Bankcard ❏ Visa Card ❏ MasterCard No: Signature______________________Card expiry date PLUS P&P (if applic): $........................... TOTAL$ AU.............................. POST TO: SILICON CHIP Publications, PO Box 139, Collaroy NSW, Australia 2097. OR CALL (02) 9979 5644 & quote your credit card details; or FAX TO (02) 9979 6503 ALL TITLES SUBJECT TO AVAILABILITY. PRICES VALID FOR MONTH OF MAGAZINE ISSUE ONLY. ALL PRICES INCLUDE GST