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www.siliconchip.com.au May 2003  1 $UB UB$ $CRIBING MAKE$ MAKE $ $EN EN$ $E... because it saves you dollars! If you regularly purchase SILICON CHIP over the counter from your newsagent, you can $ave more than 10% by having it delivered to your mailbox. Simply take out a subscription – and instead of paying $9.95 per issue, you’ll pay just $8.75 per issue (12 month subscription) – and we pay the postage! How can we do this? It’s all about economics. Printing enough copies to send out to newsagents, in the hope that they’ll sell, is very wasteful (and costly!). When readers take out subscriptions, we know exactly how many copies we need to print to satisfy that demand. That saves us money – so we pass the savings onto our subscribers. It really is that simple! You REAP THE BENEFIT! But wait, there’s more! Subscribers also automatically qualify for a 10% discount on any purchases made from the SILICON CHIP online shop: books, printed circuit boards, specialised components, binders – anything except subscriptions! So why not take out a subscription? You can choose from 6 months, 12 months or 24 months – and the longer you go, the bigger the savings. You can choose the print edition, the online edition or both! Most people still prefer a magazine they can hold in their hands. That’s a fact. But in this digital age, many people like to be able to read SILICON CHIP online from wherever they are – anywhere in the world. That’s also a fact. NOW YOU CAN – either or both. The on-line edition is exactly the same as the printed edition – even the adverts are included. So you don’t miss out on anything with the on-line edition (flyers and catalogs excepted). OK, so how do you go about it? It’s simple: you can order your subscription online, 24 hours a day (siliconchip.com.au/shop and follow the prompts); you can send us an email with your subscription request and credit card details (silicon<at>siliconchip. com.au), you can fax us the same information (02) 9939 2648 (international 612 9939 2648) or you can phone us, Monday-Friday, 9am-4.30pm, on (02) 9939 3295 (international 612 9939 3295). Don’t put it off any longer: $TART $AVING TODAY with a SILICON CHIPwww.siliconchip.com.au subscription! siliconchip.com.au 2  S ilicon Chip February 2015  2 Contents Vol.16, No.5; May 2003 www.siliconchip.com.au FEATURES 8 Motherboard Capacitor Problem Blows Up Faulty electrolytic capacitors could be a ticking time-bomb in your PC. Here’s how to identify the problem – by Peter Smith 11 HID Car Headlights: How They Work High-intensity-discharge (HID) headlights are now finding their way into many up-market cars. Here’s a look at how they work – by Peter Smith 64 The Brightest White LEDs On Earth So you think the latest 5mm white LEDs are bright? Well, you “ain’t seen nothing” until you’ve seen these – by Julian Edgar PROJECTS TO BUILD 22 WidgyBox – A Guitar Distortion Effects Unit WidgyBox: Guitar Distortion Effects Unit – Page 22. Plug into those great guitar sounds with this unit. It’s cheap, easy to build and can be run from a 9V battery or a plugpack supply – by Peter Smith 32 A 10MHz Direct Digital Synthesis Generator This low-cost function generator offers both sine & square wave output and can be set to any frequency between 1Hz and 10MHz – by David L. Jones 56 The Big Blaster Subwoofer Easy-to-build unit offers thunderous bass, can handle up to 250W RMS and is built into a compact enclosure – by Julian Edgar 80 Printer Port Hardware Simulator Simple circuit let’s you test printers or other hardware that connects to a PC’s parallel port without the need for a PC or software – by Jim Rowe 10MHz Direct Digital Synthesis Generator – Page 32. 84 More Fun With The PICAXE, Pt.4: Motor Controller A few changes to the PICAXE’s output circuit and some new code are all that’s required to build an effective motor controller – by Stan Swan SPECIAL COLUMNS 40 Serviceman’s Log Fix the roof, then fix the TV– by the TV Serviceman 53 Circuit Notebook (1) Single Entrance Vehicle Counter; (2) Test Interface For PC Soundcards; (3) White LED Torch Driver Circuit; (4) Adding Outlets To An Irrigation Controller Big Blaster Subwoofer – Page 56. 75 Vintage Radio The HMV C43B console radio – by Rodney Champness DEPARTMENTS 2 4 69 71 Publisher’s Letter Mailbag Product Showcase Silicon Chip Weblink www.siliconchip.com.au 90 92 93 95 Ask Silicon Chip Notes & Errata Market Centre Advertising Index Printer Port Hardware Simulator – Page 80. May 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 Bob Young SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 003 205 490. ABN 49 003 205 490 All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Hannanprint, Noble Park, Victoria. Distribution: Network Distribution Company. Subscription rates: $69.50 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 8, 101 Darley St, Mona Vale, NSW 2103. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. E-mail: silchip<at>siliconchip.com.au ISSN 1030-2662 * Recommended and maximum price only. 2  Silicon Chip We use too many batteries How many battery-operated gizmos do you have in your house­hold? Ten, twenty, thirty or more? Not even 10, you say. Well think again. You may easily find that you have more than 50. If you have children with battery-operated toys, you might have a lot more. If you answered “less than 10” to the above question, you may have just been thinking of battery-operated tools such as a portable drill or an electric toothbrush but a little thought quickly rounds up many more and the list grows inexorably. Just step into your car for example. You probably have a keyless remote and a control for your garage door. Got two cars? That’s four battery-operated gizmos already. Now you’re in the family room and there are infrared re­motes for your TV, VCR, DVD player, CD player, home theatre receiver, etc. That’s at least another five and then there are the memory backup batteries in the TV and VCR, plus the quartz clock on the wall. And you probably have other quartz clocks and at least half a dozen quartz watches between you and your partn­er, so we’re already up to 20 or so battery devices. Smoke detectors, anyone? Cordless telephone? Mobile (cell) phone? Toothbrush, Shaver, Torches? Count a battery for each plus at least one battery in the burglar alarm. That’s probably anoth­er 10, making around 30 so far. Step into your office. Your computer has a backup battery. And you probably have another entertainment system or TV with remote controls for both. There’s probably an LCD clock on your desk. How about a transistor radio? There are probably a few of those spread around the house. Your battery device count is probably at least 35 by now. OK, step into your son’s or daughter’s rooms. Hell, it’s battery city in there (if you can see any clear space)! There are the remotes for their entertainment systems, TV, games console, Discman player (these eat batteries!), ghetto blaster, mobile phone (again), watches (these are fashion accessories – they need at least five!) and LED jewellery. If you have two teenage child­ren, the battery device count is probably already over 50 and there is still your workshop. Battery-powered tools? Yep, there’s a few of those too. And what about big boys’ (and girls’) toys? Cameras, cam­corders? Radio-controlled cars, boats, planes? Computer-con­trolled telescope? (OK - that’s a rare one!) You see what I mean? By now, if you have a normal household you probably have a count approaching or exceeding 70 or more battery-operated devices in your household. All told, if you took all these batteries out and lined them up, you could easily have well over a hundred batter­ies. Well, now you can see that this is getting to be a really big problem. Not only do they cost a heap to replace but when you throw them away, they present a disposal problem. No wonder mercury is no longer a component of most batteries - just as well. What can you do about it? Not a great deal, but next time you are considering purchasing a new appliance, does it really need a battery-operated remote gizmo? And can you eliminate some of your remotes by just using a universal remote in the family room? Maybe your next watch (do you really need another watch anyway?) can be a non-battery type; they still make them. Naturally, if you can run a battery-operated device from a plugpack, you should do so. That is why we try and make all our published battery-operated circuits able to run from a plugpack, if at all possible. Of course, if you can use re­charge­­-ables, you should do so, although they are not practical in many applications. Finally, a tip: you can recycle some batteries. After your children have “used up” the batteries in their Discmans, etc, they can still be used to power low-current devices like clocks, some remotes and so on. Leo Simpson www.siliconchip.com.au Need a Small PC or PXE Terminal? These compact units are actually barebones PC’s which will run Windows, or PXE boot from Linux Terminal Server Cat 1149-7 $559 Notebook/Splitter Solutions! Use a Notebook Computer? Don’t miss out on these problem solvers! Full Size Keyboard & Mouse on your Notebook via USB Cat 15094-7 $159 Cat 1149 An even smaller PC or PXE Terminal. Runs on 12VDC. Ideal for embedded solutions Cat 1150-7 $749 See… www.ltsp.org Two Mice - one computer Cat 15090-7 $161 Two Keyboards Cat 15091-7 $159 Two Monitors Cat 15092-7 $265 Cat 1150 3 ISA Slots on a P4 Motherboard! 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The DynaPulse measures blood pressure with clinical accuracy and provides visual confirmation on your PC’s screen Cat 16000-7 only $399 (Normally $530) 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 may be indicative only. See all these products & more on our website...www.mgram.com.au SHOREAD/MGRM0503 We have a range of Thin Client Terminals to suit most applications - Serial, Ethernet, Windows Based & Linux MAILBAG Warning about camera flash capacitors I have a warning for readers wanting to experiment with the Neon Scintillator described in “Circuit Notebook” in the April 2003 issue. Several years ago, I was scavenging parts from a camera flash unit. The reason for doing this has been forgotten but the consequences will never be. Seeing the 300V capacitor in the unit, I correctly decided that it should be discharged before proceeding. Shorting the cap’s terminals (as suggested in the Neon Scintillator article) with the tips of a pair of side-cut­ters seemed like a good idea at the time. The bang that followed was like a gun going off next to my ear and the arcing was intense enough to mangle the tips of my nice side-cutters and blow the solder on the board to who knows where. A little imagination will conjure up more serious consequences than ringing ears and ruined tools, so take care and use someth­ing more resistive than side-cutters when discharging these “traps for the unwary”. Adrian Righetti, via email. Comment: we take your point. However, it does seem as though the discharge you obtained was rather more dramatic than we would have expected from a smallish capacitor, even though it might have been charged to the full 300V. AETA formed to fight Queensland electrical legislation As indicated in your Publisher’s Letter in the March 2003 issue, the All Electronic Technicians Association Incorporated has been formed and registered in Queensland under the Associa­ tions Incorporation Act 1981 and our registration number is IA31906. Our sole aim is to oppose the current implementation of the Electrical Safety Act 2002 (Queensland). This act has the poten­tial to ruin many electronic repair businesses as it currently exists and goodness knows how it may evolve if left unchallenged. It most 4  Silicon Chip likely would spread to other states if we do not keep a close watch. We intend to attack the law at its roots by directly tar­geting the politicians who passed it and demanding changes to allow electronic repairers to continue their work without the onerous imposts of this law. The average small business will need to spend more than $1000 per year to comply with this law, not to mention the time spent filling out forms and that’s if they are lucky enough to actually be in a position to comply. Penalties for not having this licence include up to six months jail! AETA has a document from the Electrical Safety Office that says that currently a licence is not required if 100% of your work is done within a workshop but this part of the law refers to manufacturing workshops. AETA believes that it will not be long before this loophole is plugged, requiring all repair workshops to have a licence (if you can qualify for one). The committee is well aware of the campaign SILICON CHIP ran a few years back that met with complete apathy. That is the main reason we are now left fighting after the event. It is important for the survival of every electronic business that we succeed in our efforts and to do that we need numbers. Without a strong membership base politicians will not listen to us. This might be the last chance we all have to put a stop to this outrageous law. Let’s not lose it. I urge everyone involved in any form of electronics to contact us for more detailed information at cairnscomms<at>iprimus.com.au Mike Kalinowski, President AETA. Eprom programmer protection resistors I was pleased to see that at least some form of input pro­ tection has applied to the Eprom Programmer featured in the November & December 2002 and February 2003. With regard to the unit being in program mode when not connected to a PC, I would recommend that constructors replace at least one of the address “pull-up” resistors with a “pull down” resistor of 47kΩ. This will select a safer function when the unit is not connected to a PC. There is nothing magic about “pull-ups” when dealing with high impedance circuits like HCMOS. Pull-downs provide an equally valid defined state. The series input resistors really should have a much higher value than 100Ω and the “pull-ups” should be on the connector side, not the IC side where they cause a voltage drop across the series input resistors. Graham Lill, via email. Comment from Jim Rowe: the points you make are entirely valid. If it had been easier to change the PC board pattern to incorporate the changes you suggest neatly, I would have done so. Reproducing old wireless sound I saw the request from R. W. in “Ask Silicon Chip” (March 2003) about his staging of a play and wanting to have music sounding as though coming from an early radio. This may not solve all his problems but I use Cool Edit Pro, which came on the free CD ROMs attached to the August 2002 issue of PC User magazine. This software has mono, stereo and multi-track recording func­tions and I use it for transferring vinyl LPs to CD. Among the various tools are several filters and numerous effects, including one called “Old Time Radio”, which gives the audio a “thin, strained & tinny” sound, very similar to a “small-speakered” radio. The software can’t add hiss and crackle of course; it’s designed to remove them, but using the graphic and parametric equalisers, www.siliconchip.com.au as well as the DTMF filters and other tools, R. W. may be able to distort the sound to the point where it sounds pretty close to what he wants. Adding some white noise or the recorded sound of chips frying in hot oil (not kidding!) might do the trick. Peter Cahill, via email. Comment: actually, old time radios did not have a “thin, strained and tinny sound”. Depending on the radio’s cabinet, the sound was generally more “mellow” (ie, lacking high frequencies) and often quite bassy. Some of the larger console radios with 12-inch speakers and push-pull output stages sounded very good. “Thin, strained and tinny sound” really only came about with the introduction of tiny transistor portable radios, often poorly designed to cope with the failing voltage from tiny bat­ teries. Loves LED stop lamps I have just completed my own (stop & tail) version of the LED tail light featured in the March 2003 issue. I used 6500mCd 5mm LEDS from Jaycar as they are only 44 cents each, in lots of 100. And after what I saw last night I’ve now got five cars to do (three old stop/tails and two new centre mount stop only conver­sions)! In a word – WOW! For stop/tails, I have four LEDs lit for the parking lamp, while all 12 light for stop (or the other eight if the parkers are on). I fitted one of these to my old ’68 Valiant and did the comparison between the normal stop/tail globe and the LED ver­sion. The old girl had pretty abysmal tail lights from day one but now with the LED version you can plainly see the difference. The parkers are brighter, on par with newer vehicles and the stop, well, that’s awesome. As the “C” section shape of the lens assembly does not allow for side viewing (as with newer vehicles), this is not a problem. The LED assembly has to be mounted lower in respect to the bayonet housing to get an accept­able scatter of light in the reflector but this is no problem as a shorter spacer is used. Similarly, in my ’68 Dodge Phoenix, with four stop/tails on the rear, I will replace the inner lamps with LED www.siliconchip.com.au assemblies as these don’t have a chrome “filler” piece across the centre of the lamps as the outer ones do. The outer lamps need to stay standard as this filler piece doesn’t work well with the LEDs and the cruise control uses a normal lamp to sense whether the brakes have been applied. During my test, it was plainly obvious how slow normal lamps are to light. You are correct. You can actually see the time lag between normal lamps and LED modules if you look at the normal lamp with the LED module in your peripheral vision. I would­n’t have believed it if I hadn’t seen it for myself. All in all an excellent project. Brad Sheargold, via email. Comment: thanks for the wrap-up. We will have more to say about stop/tail LED versions in a future issue. Enthusiasm for PICAXE series After buying the February 2003 issue on spec I got enthu­siastic and ordered a couple of PICAXE-08s. They conveniently came just before a wet Melbourne weekend. I got out the proto­board and chopped the tail off an old mouse, etc. Of course with RS-232 involved my bet was it wasn’t going to work first off. The closest I came was on one of three systems which actually downloaded but gave an EEPROM verification error. I even went and got an RS232 converter MAX232 and that did not work. I then carted the system off to work and tried on my office PC, using short hook-up wire from the port - no go at all! And I know the ports on this machine reliably connect to RS232-equipped balances and voltmeters. After discussion with my work colleague, he made the sug­ gestion of fitting a large low impedance non-electrolytic filter capacitor close to the PICAXE. That did the trick; presumably the internal 4MHz oscillator is feeding enough interference out to cause a problem. I had used the demo program on page 13 and was wondering why the LED was not on. I grabbed the voltmeter and was about to measure when I noticed the power supply had sunk to 2.8V (from The Tiger comes to Australia The BASIC, Tiny and Economy Tigers are sold in Australia by JED, with W98/NT software and local single board systems. Tigers are modules running true compiled multitasking BASIC in a 16/32 bit core, with typically 512K bytes of FLASH (program and data) memory and 32/128/512 K bytes of RAM. The Tiny Tiger has four, 10 bit analog ins, lots of digital I/O, two UARTs, SPI, I2C, 1-wire, RTC and has low cost W98/NT compile, debug and download software. JED makes four Australian boards with up to 64 screw-terminal I/O, more UARTs & LCD/keyboard support. See JED's www site for data. Intelligent RS232 to RS485 Converter The JED 995X is an opto-isolated standards converter for 2/4 wire RS422/485 networks. It has a built-in microprocessor controlling TX-ON, fixing Windows timing problems of PCs using RTS line control. Several models available, inc. a new DIN rail mounting unit. JED995X: $160+gst. Www.jedmicro.com.au/RS485.htm $330 PC-PROM Programmer This programmer plugs into a PC printer port and reads, writes and edits any 28 or 32-pin PROM. Comes with plug-pack, cable and software. Also available is a multi-PROM UV eraser with timer, and a 32/32 PLCC converter. JED Microprocessors Pty Ltd 173 Boronia Rd, Boronia, Victoria, 3155 Ph. 03 9762 3588, Fax 03 9762 5499 www.jedmicro.com.au May 2003  5 Mailbag: continued 5V). I stupidly started to wind up the voltage and it went into current limit at whatever I had last set it. A quick finger test as I switched off confirmed a very hot PICAXE. It appeared that some combination of conditions had caused an internal latch up. The PICAXE survived; glad I didn’t get it working at home with a 5V supply with no current limit. I modi­ fied the program to give a 1-second duty cycle and no problem; I haven’t tried a faster cycle yet. It appears from looking at the Rev_ed forum that the 08 is rather sensitive to the supply voltage. Using 4 x 1.5V batteries did not work for somebody and the “tech support” reply was to use three, thus 4.5V. That does not work programming my PICAXE. So as usual anything new takes three times as long as it should and nobody has the time these days. A nicely presented article with all the facts and references one needed. Keep up the good work. Roger Curtain, Department of Chemical & Biomolecular Engineering, University of Melbourne. Computer service in Qld Are you aware that the new Queensland Electrical Safety Act 2002 not only applies to appliance repairers but also persons doing COMPUTER SERVICE work? Under the new Act anybody doing service to anything that connects to the 240VAC mains now need to have a current Electrical Work licence and an Electrical Contra­ ctor’s Licence. This applies to service to everything from a coffee dispenser to a PC. The relevant sections of the Act are 55, 56, 18 and 14. Section 27 describes the maximum penalty of $35,000 or 6 months JAIL for individuals or $180,000 for corporations. Check out www.eso.qld.gov.au for more information. The general public probably don’t care two-hoots about the state of TV service in Queensland. But with the incredible satu­ ration of PCs in the home, schools and workplace one 6  Silicon Chip would think that this would rouse some interest. As well, computer service people themselves probably think that none of this applies to them when it certainly does. In my area, there are only a handful of TV service people but hundreds of computer people! This ridiculous legislation can only be overturned with lots of popular support. David Dorling, Buderim, Qld. Comment: this topic has been well-canvassed in recent issues. But you are right; computer service is more important to the general public. In the meantime, perhaps you should ensure that all the computer technicians you know join the AETA in Queensland. CD anti-copy: shooting the foot? Invariably, copyright publicity like CD piracy is generated by companies wanting to sell their solutions. Most times, these ‘solutions’ hit loyal customers harder than the criminals. For example, when they introduced copyright protection on videotapes (Macrovision), I had to scrap a $900 enhancer and rewire my video system. Prior to then, it made viewing considerably clearer with less noise and correct colour. Did this stop the pirates? No! I watched less videos, though. Now CDs made with copyright protection do not track on all players and CD purchasers cannot make a copy of their CD for replay in their car. Copying has long been better than using your original, as car thieves invariably steal CDs and cash, plus the original is easily scratched in the car. By their own admission, music suppliers really are aiming to combat illegal net sites. These sites will remain, as they have various sources (especially Asia) and electronic restorers. The only losers, the public, will have an inferior product. The music companies know that mainstream piracy is on the decline. Their reduced sales are due to the quality of the pro­duct and competition. New CDs are over $20, the same cost as a host of movie DVDs. More people are watching movies. The music companies are shooting themselves in the foot, as many customers like me, will stock older CDs and ignore new re­ leases with “protection”. This is not difficult, as new music has less attraction in recent years. I feel just as passionate about computer software. Micro­ soft sells the Office suite for over $900, then doesn’t allow even the original owner to have a copy on his PC and laptop. There is a competitor, “Thinkfree Office”, that sells for $99 and allows copies to be used on any of your computers! Music companies should fight the Internet pirates instead of disadvantaging their customers. It’s not as hard as it seems. Sites are traceable and filters are available to stop reception. Kevin Poulter, Dingley, Vic. LED vehicle lighting article I just read Jim McCloy’s email in the April issue rubbish­ing your March 2003 article on vehicle LED lighting and I wanted to offer my support for your magazine’s stance and response. I agree with your puzzlement over his comments about the front driver bearing responsibility for safe driving distances; if all drivers were to follow this practice, then surely we would all be driving at unsafe speeds trying to escape the drivers behind us! He says he’s never been hit in the rear but how much risk is he placing the resting of us in by using his recommended driving technique? What happens when he reaches the speed limit? Mr McCloy also appears to have overlooked the fact that car and truck manufacturers have been using LEDs in brake light systems for years now, and that companies such as Hella (http://www.hella.com.au/) manufacture the same types of after­market automotive lighting units as described in your article. Perhaps he would like to take them to task for being ‘irresponsi­ble’ as well? Please keep up the great work on my favourite magazine! Paul Sun, SC Crows Nest, NSW. www.siliconchip.com.au www.siliconchip.com.au May 2003  7 Motherboard capacitor problem blows up There have been a number of reports in newsgroups and on-line services about leaky electrolytic capacitors on computer motherboards. Here are the facts and what to do about it if your PC has this nasty problem. By PETER SMITH E ARLY IN 2002, stories began appearing in on-line news services and news groups about the high failure rates of electrolytic capacitors used on PC motherboards. Technicians were reporting that the capacitors were rupturing, leaking and even exploding like never before. Initially, there were only two clues to the mystery. First, the failing capacitors were more often that not to be found in the power supply section of motherboards. The capacitors used in this area are characterised by their need to have very low ESR (Equivalent Series Resistance– see panel). This motherboard stopped working and was returned to the workshop for repair. It wouldn’t have taken the techos long to identify the problem. Check the bulging tops on these suckers! On some boards, up to a dozen capacitors have to be replaced. 8  Silicon Chip Second, most of the failing capacitors were identified as Taiwanese in origin. That’s not too surprising at first glance, as Taiwan manufactures about 30% of the world’s aluminium electrolytics (22.5 billion a year). In September, “Passive Industry Components Magazine” published a story that exposed the reasons behind the unusually high failure rates. They reported that the failures were directly related to the use of faulty electrolytes in the manufacturing process. Industrial espionage? The story describing how the elec- trolytes came to be faulty reads like a lot of fiction. It begins in Japan, at a major capacitor manufacturer. A materials scientist for the Japanese company resigned and went to work for a Chinese capacitor manufacturer. While there, he reproduced one of the electrolytes used in his former employer’s premium (low-ESR) aluminium electrolytic products. Staff working with the scientist then defected, taking the secret electrolyte formula with them. They used the formula to manufacture their own electrolyte, which they subsequently flogged to major Taiwanese capacitor manufacturers at bargain prices. Unfortunately, their reproduction of the formula was flawed and the rest is history. A bad case of the squirts So how does the faulty electrolyte cause early failure? Here we can only speculate. Some stories have stated that the flawed formula causes electrolysis, which in turn generates lots of hydrogen. Eventually, gas pressure ruptures the can or breaches the rubber end seal. We are inclined to think that since the electrolyte is used in www.siliconchip.com.au LEFT: the capacitors in the middle of the photograph are not a pretty sight, especially if found on your motherboard! Notice the bulging tops and the discoloration due to the leaking electrolyte. (Photo courtesy Carey Holzman – www.careyholzman.com). perhaps even before the culprits have showed themselves! Brands affected Unfortunately, there is no certain way of determining whether a particular motherboard is affected by this problem or not – until it fails. However, some of the big name manufacturers have identified their highrisk machines and have notified their customers accordingly. What to do low-ESR capacitors, the typically high ripple currents and resulting heat causes decomposition of the electrolyte. Either way, the result is the same – the capacitor eventually leaks or ruptures. Apart from eventual self-destruction, leakage from these capacitors can also damage nearby components and circuit board copper, as the electrolyte compounds are quite corrosive. Symptoms When these capacitors fail, the signs are generally quite obvious. The top of the case may be split open or “bulged” upward and/or the can may be dislodged from its base (the rubber seal). There may also be an unpleasant smell and signs of electrolyte leakage nearby. Even more obvious is the muffled explosion followed by the blank screen. Thankfully, we’ve heard that this failure mode is quite rare! However, before catastrophic failure eventuates, all kinds of annoying symptoms can occur. These can range from intermittent boot failures to lock-ups in Windows. Eventually, the affected PC will refuse to boot at all, www.siliconchip.com.au If you’ve purchased a PC during the last 18 months or so, especially if it’s not one of the big name brands, then it’s worthwhile doing a quick check for any visible signs of the capacitor problem. We should point out here that any number of other hardware or software problems can cause the symptoms mentioned above. Just because you PC has problem “X” does not mean that it is caused by faulty motherboard capacitors! The capacitors to look for will be the largest (highest capacitance) types on the motherboard. Generally, they’ll be situated somewhere near the power supply connectors. Also, you’ll probably notice one or two toroidal inductors in close proximity. As designs vary so much between manufacturers and models, it’s impossible for us to be more specific. Unless you’re experienced with such things, we don’t recommend that you disassemble your PC. You’ll probably be able to get a pretty good idea whether any of the larger capacitors are swollen or leaking with the board in-situ. A bright flashlight will help you here. It’s important to note that these capacitors are failing within a short period of use. This means that even if you’re unlucky enough to be affected, it should be covered under your system’s warranty! What warranty? OK, so your motherboard is out of 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 May 2003  9 “Normal” Electrolytic Capacitor Failure All electrolytic capacitors have a finite life, measured in thousands of hours. Unlike the exceptional cases discussed in this article, there are usually no external signs that a capacitor is nearing its end of life. However, it is possible to determine whether a capacitor is serviceable or not by measuring it’s ESR (Equivalent Series Resistance). ESR is the sum of in-phase AC resistance, including the resistance of the dielectric, plates, electrolytic material and leads at a particular frequency. As the name implies, ESR acts just like a resistor in series with the capacitance. warranty and you’ve determined that it has faulty capacitors. What do you do? First up, you’ll need access to the appropriate desoldering equipment in order to extract the offending parts without damaging your motherboard. Just as importantly, you’ll need to identify and source suitable replacements. As mentioned earlier, these capacitors are of a specific type; they have very low ESR. To understand the need for this requirement, let’s take a brief look at the circuitry involved. Low-ESR capacitors Probably due to the fact that CPU core voltages change so often, designers have been forced to implement sections of the power supply circuitry on the motherboard. The standard power supply box still provides the usual 10  Silicon Chip Towards end of life, a capacitor’s ESR begins to increase as its dielectric losses increase. To test a capacitor’s ESR, you need an ESR meter; an ordinary capacitance meter usually won’t indicate a problem. These instruments are an indispensable part of any technicians toolbox. Commercial ESR meters are expensive. However, an excellent unit was described by Bob Parker in the January 1996 edition of “Electronics Australia”. Kits for this project are still available from Dick Smith Electronics and of course reprints of the original article can be obtained from SILICON CHIP. 12V, 5V and 3.3V rails, but the lower voltages for the CPU core are provided by further step-down circuitry on the motherboard. This on-board switchmode stepdown circuitry runs at high frequencies (over 100kHz) to minimise the required inductance and filter capacitance. A key ingredient in this recipe is physically small electrolytic capacitors that can handle high ripple currents at high frequencies. In short, they must have very low impedance at the switching frequency. As you can probably imagine, capacitors designed for use in mains filtering applications are not up to the job at all. They are physically much larger for the same capacitance and have high characteristic impedance at high frequencies. This would result in unacceptable amounts of ripple This ESR meter is ideal for checking the health of electrolytic capacitors. You can buy the kit from Dick Smith Electronics. voltage and self-heating, leading to early failure. The “Rubycon” (Japanese) brand ZL and ZA series ultra-low impedance capacitors will be suitable in most cases. They’re available locally from Farnell Electronic Components – see Farnell’s web site at www.farnell.com for more information. Caution: the standard ZL and ZA series may be marginally larger in diameter than the original parts (10mm versus 8mm). Other equipment Any electronics equipment that incorporates high-frequency switchmode circuitry could be affected by this problem, including power supplies, monitors and games consoles, to name a few. SC Only time will tell! www.siliconchip.com.au High-Intensity Discharge (HID) headlights are being fitted on increasing numbers of up-market cars. Some use the HID lights for low beam only while others use it for both beams. Either way, they are much brighter than conventional halogen headlights. HID By PETER SMITH Headlights –– how how they they work work www.siliconchip.com.au May 2003  11 E ven if you haven’t heard of these new headlights, you’ve probably noticed the occasional piercing “bluish” flash on the road at night. HID headlights are already being fitted to up-market European, Japanese and American cars. As you might have guessed, the technology used in these headlights is radically different from conventional tungsten-halogen headlamps. Not only are HID headlights much brighter, they are much more efficient and draw less current from the battery. History in a flash All high-intensity gas discharge lighting is related to the original mercury vapour arc lamp, invented back in 1901 by an electrical engineer named Peter Cooper Hewitt. The original mercury lamps were not very efficient (about 10%) and produced a rather harsh blue-green light. The next major advances came with the inventions of the low-pressure and high-pressure sodium lamps. To this day, low-pressure sodium lamps are the most efficient commercially available lighting source. However, they generate a pure monochromatic yellow light that is 12  Silicon Chip unsuitable for many applications. The high-pressure version retains much of the efficiency (about 50%) and produces a “warmer” light colour, making it an obvious replacement for mercury lamps in street and factory lighting, where it is used extensively today. In a further search for efficiency and whiter light output, the General Electric company experimented with various iodine salts (indium, scandium, sodium, and thallium) in their mercury vapour lamps. The result, born in 1962, was dubbed the “Multi Vapour Metal Hal- A current GE Multi Vapour Metal Halide lamp. The arc tube is suspended inside a familiar bulb-shaped glass enclosure. Overall height is almost 300mm. Notice the third (starting) electrode emerging from the bottom of the arc tube to the left of the main electrode. ide” lamp, after the fact that iodine is one of the halogen elements. Derivatives of the first metal halide lamp can be found wherever an efficient, high-intensity white light source is required. Uses for this type of lamp have until recently been restricted to industrial, high-wattage sizes in the 175W to 1500W range. Now, with a few modifications to lamp chemistry and some electronic circuitry, engineers have been able to adapt them to small, low power applications such as automobile headlights. To understand the need for electron- Sketch of a Philips D2S HID lamp. The arc tube is tiny in comparison to a conventional MH lamp. This lamp is only 76mm high. www.siliconchip.com.au ics, let’s look first at the operation of a conventional metal halide lamp. Metal halide lamp operation A basic lamp consists of two “glass” tubes, one within the other. The inner tube is made from fused quartz or ceramic and houses two main electrodes and a starting electrode. The tube is filled with an inert gas (argon) which has been “spiked” with a tiny quantity of mercury and various halide salts. The outer glass envelope serves a number of purposes. It isolates the hot inner tube (up to 800°C) from the outside world. It also filters out some of the shortwave UV radiation, which if left unchecked is a health hazard and can damage rubber and plastic components. When power is applied, the voltage between the starter electrode and nearby main electrode causes ionisation of the argon gas. Ionisation lowers the resistance between the main electrodes located at opposite ends of the tube, allowing an arc to be struck. Initially, the tube emits a dull bluish discharge but as heat from the arc vaporises the mercury (and other metals) and the pressure increases, it changes to a brilliant white. The heat also activates a bi-metallic strip, which shorts out the starting electrode after about 2-4 minutes. The starting cycle can take up to six minutes. If power to the lamp is interrupted, a cooling-off period of ten minutes or more is required before it can be restarted. All metal halide lamps are designed to be “burnt” in a particular position for longest life. This is generally described as “base up” or “base down”. Typically, high-wattage industrial lamps are powered directly from the 240VAC mains via a simple magnetic constant power ballast circuit. In addition to the starting method described above, some metal halide lamps omit the starting electrode and just use a high-voltage pulse across the main electrodes to ionise the gas and strike the arc. Apart from eliminating the starting electrode, high-voltage starting also allows higher initial gas pressures. This provides faster runup, better burn colour and quicker re-starting. Gas-discharge headlights Engineers had to overcome some major hurdles in order to bring high-intensity gas-discharge lamps to low-voltage, instant-use applications such as automobiles and battery-powered torches. For a start, about 85V is needed for the lamp supply. As well, the lamp needs to start immediately it is switched on and have useable light output within seconds, not minutes. It also needs to be instantly restart-able, with no cool-down period. All this has been achieved by re-engineering the basic lamp, along with some clever electronics. Here’s how. Gassing up In order to obtain higher initial light output, the automotive metal halide arc tube is filled with Xenon rather than Argon. This fact hasn’t escaped car enthusiasts who often use the Fig.1: HID lamp operation is carefully controlled by an electronic ballast. This diagram plots lamp voltage and current against time, showing six distinct phases from turn-on to steady-state operation. www.siliconchip.com.au May 2003  13 How good are HID headlights? These two shots compare conventional halogens with HIDs on low beam. The difference is quite spectacular! Notice how the light/dark cut-off appears about the same, but the view is much whiter and brighter (sounds like an Omo ad!) and there’s a lot more side illumination. (Photo: Hella) name “Xenon” when referring to HID headlamps. Xenon, by the way, is an odourless, colourless, tasteless, non-toxic, monatomic and chemically inert gas. Although having markedly different dimensions, the lamps appear to operate in much the same way as their industrial counterparts. From the diagrams, you can see that the lamps retain all of the elements discussed above. To date, manufacturers have standardised on several lamp styles, code named D1S, D1R, D2S and D2R. All four lamps are rated at 35W but the D1S and D2S versions produce 3200 lumens whereas the D1R and D2R produce 2800 lumens. The “R” versions have lower light output due to a black mask on the outer envelope. This is used to control light dispersion, which we’ll talk about later. To put these figures in perspective, a typical 55W tungsten-halogen lamp develops just 1000 lumens. In addition, HID systems consume less power (about 45W; 35W + 10W in the ballast) than conventional lamps; in other words, about 20% less current drain for three times the light output. The difference between the “D1” and “D2” versions can be seen in the base size. The D1 base is physically larger as it houses the igniter circuitry. In contract, the “D2” lamp requires an external igniter. Lamp life HID lamps are generally expected to last the life of the vehicle. With no filament to burn out, you might expect them to last forever but the arc tube does eventually “wear out” due to several unavoidable reactions. In particular, tungsten from the electrodes gradually blackens the inside of the tube, a process that is greatly accelerated during cold starts. Manufacturers specify tube life at up to 3000 hours, which includes a “typical” number of cold starts. By comparison, tungsten-halogens have a life of between 700 and 1000 hours. Electronic ballasts To power a lamp from a 12V DC Fig.1: HID lamp ballast concept. The controller block generally includes a microcontroller or digital signal processor (DSP) chip. 14  Silicon Chip www.siliconchip.com.au Fig.3: basic igniter circuit. When the breakdown voltage of the switching spark gap (SSG) is reached, it momentarily connects C1 across the primary of the trigger transformer (T1). electrical system an electronic ballast is required. Fig.1 shows the basic layout of a typical 12V DC lamp ballast circuit. The input voltage is first stepped up by a DC-DC boost converter. During normal running conditions, the voltage across the lamp needs to be between about 60V and 110V. However, the open-circuit lamp (no arc) voltage can be as high as 600V. This high voltage is used by the igniter circuit (see Fig. 3) to generate the required 23kV ignition pulse. Two transistor pairs in a H-bridge configuration apply the converter output to the lamp in an alternating fashion, with the resultant drive being a square wave of between 250Hz and 10kHz. Power to the lamp is carefully regulated by the controller during all phases of operation. This is where the “smarts” of the system are to be found. The lamp must be brought up to maximum output in the shortest possible time, while minimising electrode erosion. This is achieved in five distinct phases, as follows: 1) Turn-on. Power is applied to the ballast and the controller commands maximum voltage from the boost converter. Within 30ms, the igniter is ready to fire the tube. 2) Ignition. One or more high-voltage pulses, at 20Hz repetition, are applied to the lamp to ignite the arc. If the arc is not struck after 20 pulses, a serious fault is assumed and the sequence is terminated. 3) Take-over. To maintain the arc but also conserve the electrodes, the controller regulates lamp power to 75W maximum at up to 12A. This high current surge lasts only about 300µs. During ignition and take-over, the H-bridge applies DC to the lamp so as not to “disturb” the arc. 4) Warm-up. The H-bridge performs one switching cycle, first applying a negative half cycle of 10ms duration, then a positive half cycle. Power input to the lamp is regulated to 75W at 2.6A maximum. 5) Run-up. The H-bridge begins switching symmetrically at about 400Hz. Until the lamp voltage reaches 50V, the controller regulates lamp power to 75W at 2.6A maximum. This takes about 6-12 seconds. During this time, lamp intensity rises to near its full rated output. 6) Steady state. Lamp power is regulated to 35W ±2W. Continuing regulation ensures that the light output remains constant, regardless of variations in battery and lamp voltages. Of interest is the need to power the lamp from AC rather than DC. Apparently, applying a symmetrical square wave (ie, average = 0V) prevents electrolysis and other life-shortening effects within the arc tube. A relatively low switching frequency (250Hz-10kHz) ensures circuit efficiency and avoids acoustic reson-ances that can occur at higher frequencies. Igniter To ignite the arc during a cold start, a pulse of about 5kV is required. For a hot start (re-strike), as much as 25kV is required to ionise the highly pressurised gas. This is achieved by a dedicated igniter circuit, as shown in Fig.3. The igniter circuit is positioned in series with the lamp so as not to expose the ballast circuitry to high voltage transients. When power is applied, capacitor C1 charges towards the full open-circuit ballast voltage (up to 600V). When it reaches the breakdown voltage of the switching spark gap (SSG), the SSG “flashes over”, dumping the capacitor’s charge into the primary side of the trigger transformer (T1). The voltage appears on the secondary side of the transformer multiplied many times over, resulting in more than 23kV across the lamp electrodes. Packaging the parts Although the lamps and bases conform to a standard, the same can not be said of the ballast, igniter and wiring harness. Generally, the ballast is (Left): components of a Hella “Mark 4 Xenon” HID headlight system. The large metal box on the left houses the ballast, whereas the smaller box houses the igniter. A PES-type headlight (note the lens) appears at the rear. At right is a complete system, including washer and leveller, ready for installation. (Photos: Hella). www.siliconchip.com.au May 2003  15 sealed in small metal enclosure which is mounted a short distance from the lamp socket. For D2S and D2R lamps, the igniter may be a separate black box or integrated within the ballast housing. Wiring harnesses are fully shielded, usually sealed and include high-voltage connectors for the D2S and D2R lamps. Putting the light on the road Equally important to lamp intensity is the ability to be able to direct the light exactly where it is needed. Conventionally, this has been achieved with large parabolic reflectors and segmented glass lenses. In this simple system, the lens is mostly responsible for light distribution. High beam units also include a metal shield or mask that is used to provide the light/dark cut-off. Also popular is the free-form (FF) reflector, which is characterised by a clear, rather than segmented lens. In this system, a complex-surface (segmented) reflector performs precise light distribution. Highly accurate placement of each individual segment is achieved with the aid of computer design software. PES headlights Recently, manufacturers have team-ed complex-surface reflectors with optical projection technology to come up with the Poly-Ellipsoid System (PES) headlight. This system provides many advantages over other headlight systems. For a start, projection allows precise definition of light/dark cut-offs, transition areas and contrasts with the use of an imaging screen. As well, only a very small light-emission surface is needed in comparison to conventional systems. This equates to smaller headlight enclosures, allowing vehicle designers to weave all kinds of magic with front-end styling. Other tricks, such as signal image enlargement and light rings are used to reduce glare and provide better Fig.4: a poly-ellipsoid reflector and projection lens form the heart of the Bosch PES headlight. Dualbeam systems move the screen up and down with the aid of an electro-mechanical actuator. position marking. HID lamps can be fitted to both reflection and projection systems. The masked HID lamps (D1R & D2R) are designed for reflection systems, whereas the clear lamps (D1S, D2S) go in the projection units. Low/high beam solutions To date, implementation of dual About Lamp Efficie ncy Throughout this article , we’ve listed lamp efficiency in perce ntage points, which is intended as a very rough guide only. The most co mmon measure of lighting efficienc y is calculated by dividing light output (in lumens) by the power input (in wa tts). The result is termed “lumens per watt”. Since the value of lum ens per watt is always greater tha n one, it is a measure of “efficacy”, rather that “efficiency”. beam headlights has varied considerably among manufacturers. In some vehicles, halogen lamps are still used for high beam and HIDs for low beam. However, the trend has been towards more complex systems that use a single HID lamp and some clever mechanical “beam adjustment” devices. For example, the Bosch Bi-Litronic reflection system moves the lamp back in the reflector housing with an electromechanical actuator when low beam is selected. Thus, a completely different projection pattern is obtained for low and high beam positions. Things get even tricker on projection systems. Once again, Bosch have developed a unique electromechanical solution. On their Bi-Litronic system, the position of the imaging screen is shifted to generate low and high beam light patterns. Performance Overseas studies have shown that HID headlights provide considerable safety improvements. In particular, more light to the sides of the road allows drivers to spot pedestrians and potential hazards much earlier, especially during poor weather conditions. The whiter light renders colours better too, making road signs and markings more visible. It seems that drivers are impressed with this new system. A significant (and increasing) percentage of new-car buyers have been willing to part with over $1000 for what has mostly been offered as an optional accessory. In 1997, European research institute Emnid carried out a survey among drivers whose vehicles were equipped with HID headlights. The results of this survey indicate that 94% of all HID users have a positive opinion of the new system. The main features highlighted were brightness (42%) and general illumination (35%). HID controversy? However, some road users have complained about the dazzling effects of these new headlights. Of course, having brighter headlights doesn’t mean that we can “aim them up” to see further ahead; the light cut-off point remains the same. However, up to that point, the light is much brighter and whiter. This means that for on-coming drivers, the familiar gradual fade from dark to Fig.5: the basics of a headlight projection system. Operation is very similar to an overhead projector, with the projected image being a screen used to define the light/dark cut-off. 16  Silicon Chip www.siliconchip.com.au A 3-D model, coloured for clarity, of Hella’s Bi-Xenon projection headlight. The imaging screen (grey, centre) is actuated by the electro-mechanical system in the foreground of the picture. light doesn’t occur. Instead, there’s a sudden jump to “bright” as the cut-off threshold is passed, and this could have a momentary dazzling effect. Doctors have put a slightly different spin on the problem. They say that while the human eye is sensitive to long-wave, red-yellow light during the day, at night the optic nerves are irritated by short-wave light, which is a component of the HID lamp spectrum. European regulatory authorities are aware of the potential dazzling effects and have made automatic headlight levelling and cleaners mandatory on all vehicles fitted with HID headlights. Why cleaners? Well, dirty lenses were found to cause light scatter, another potential dazzler! It appears that local car manufacturers will follow suit and fit automatic levellers and cleaners to Australian vehicles as the technology becomes available on less-expensive mounts. Be warned though – after-market HID headlights are illegal on most on-road vehicles! Factory-approved upgrades to some up-market European cars are possible but the rest of us will have to wait. If you’re hankering to take advantage of this new technology, then you still have a couple of options. HID auxiliary driving lights are available in Australia and can really make a difference to your night driving experience. Check out the Hella web site at www.hella.com.au to see what’s on offer. Still too pricey? The new Xenon-filled tungsten-halogen lamps are a good option for older vehicles. These generate up to 50% more light than the standard parts and are available in plug-in “H” series styles. They’re legal, too. Upgrading halogens to HIDs – is it possible? One of the hottest car upgrades right now has to be HID headlights. A quick search on the net proves our point; there are literally hundreds of retrofit offers and for those that can’t afford the $1000 (or more) price tags, there are cheap HID look-alikes. Even the world’s fastest production car, the Lamborghini Murciélago, gets the HID treatment. (Photo: Hella). More reading? Vehicle lighting is set to become very high-tech. The VARILIS (Variable Intelligent Lighting System) will supposedly enable us to see around corners. Here’s a 3D model of Hella’s VarioX system, depicting how it rotates about its longitudinal axis. Projection optics and special surface contours allow up to five different beam patterns to be projected onto the road. (Photo: Hella). www.siliconchip.com.au If you’d like even more information on discharge lighting, SILICON CHIP has published several articles on the subject in the popular “Understanding Electric Lighting” series. Reprints of these articles are available for $8.80 inc p&p and GST: “HID Lighting” – February 1999 “Metal Halides” – July 1998 “High Pressure Sodium” - June 1998 “Low Pressure Sodium” - April 1998 Credits Thanks to Philips Automotive Lighting and Robert Bosch (Australia) for details of their HID lighting systems; Hella and DaimlerChrysler for photographs. May 2003  17 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 Widgy Distortion effects for y Do you own a guitar but don’t have an overdrive (or distortion or fuzz) box yet? Well your prayers have been answered! This one sounds great, it’s cheap and it’s easy to build! By PETER SMITH I F YOU’RE A GUITAR PLAYER, then you’ll certainly know all about the various “effects” that can be used to enhance guitar sounds. Over the years, many great players have combined these effects with their own unique styles to create unmistakable signature sounds. Some of the most sought-after sounds are produced by deliberate harmonic distortion of the music content. Originally, this type of effect was produced exclusively by over-driving the output stage of valve amplifiers. About overdrive & distortion These days, distortion effects are generated by dedicated electronics equipment. Perhaps in an attempt to capitalise on the success of past 22  Silicon Chip legends more than anything, much of this equipment boasts valve-like distortion qualities. Valve amplifiers have a reputation for soft-clipping the output signal when they are overdriven, at least at moderate levels. If the signal is a pure sinewave, the peaks are simply round­ ed off, with a certain amount of wave shape compression occurring. These rounded peaks create predominantly lower-order harmonics. Essentially, this means that the harmonics are closely related to the fundamentals and therefore tend to sound quite natural. Perhaps we could say that they “resonate” or “ring” with the fundamental tones. Harmonics, by the way, are referred to as “partials” in the music world. They are simply some multiple of the original, fundamental frequencies. Once the input to any amplifier is increased well beyond its design limit, the output signal is either hard clipped or transformed into indistinguishable noise, depending on the amplifier’s overload characteristics. Unlike the rounded peaks of a softclipped waveform, hard clipping is characterised by flat, sharp-edged waveforms. This is due to the output stages driving all the way to the power supply rails, slicing the peaks off and compressing, or “crunching”, the signal. Hard clipping results in many higher-order harmonics of the fundamentals. The resulting sound is often described as “reedy”, “rather harsh” and “more metallic”. A side effect called “intermod­ulat­ ion distortion” occurs when all these harmonics inevitably mix. The product of two frequencies is both the sum and difference of the originals, and they may not necessarily be “musically” related to the content. Therefore, intermodulation distortion is unwanted noise that is quite easily detected by the ear. Ideal distortion? As far as we can discern, there is no easy way of generating the ideal siliconchip.com.au yBox your guitar distortion effect. Why? Primarily because it would be impossible to get broad agreement on what that sound is. It has more to do with music type, personal preference and playing styles than the pure technicalities. Many commercial distortion effects units combine both soft and hard clipping and user-accessible controls are included to provide adjustment between these two extremities, thus accommodating a range of music and styles. Some also include tone controls for increased versatility. The SILICON CHIP “WidgyBox” (like the name?) is based on these ideas. The design criterion was simple: it had to be uncomplicated, low-cost and easy to build. We think it will make a worthwhile addition to any guitarist’s basic effects line-up. Reproducing the sound Now for the $64 question: if valve amplifiers already produce the desired sound, then why bother trying to reproduce it? Why not just use a valve amplifier? Well for a start, valve amplifiers are expensive. In addition, they need to be over-driven to produce the effect. This means lots of volume, which can obviously be a real problem. In the words of one disaffected player, “I have good tone when I play loud but I get kicked out of clubs and bands”. Dedicated effects boxes (also known as “effects pedals” and “stomp boxes”) address these issues. They create the MAIN FEATURES • • • • • • Low cost. Easy to build. Battery-powered. Adjustable distortion. Three tone controls. Optional stomp switch. desired effect before the amplifier input, allowing the musician to play at any volume. They also allow easy experimentation for those in search of a unique sound. What’s more, you don’t need a valve amplifier – a (much) cheaper solid-state amplifier will suffice! How it works Fig.1 shows the details of our design – it’s based entirely around the TL07x series op amps. Like most effects pedals, the circuit is designed to connect directly in-line with the guitar’s output. A 47µF capacitor AC-couples the input to the first op amp stage (IC1a). This capacitor is much larger than you might expect in order to ensure low May 2003  23 24  Silicon Chip siliconchip.com.au Fig.1: the circuit uses three low-cost op amps (IC1-IC3) and operates from a 9V battery. Schottky diodes D1 & D2 provide the soft clipping function, while IC1b provides hard clipping, depending on the setting of VR1. noise performance. As with all the following stages, IC1a’s input is biased to one-half the supply rail voltage (+V/2), in this case via a 220kΩ resistor. The 1kΩ resistor and 10pF capacitor at the input act as a low-pass filter, preventing RF (radio frequency) signals from being coupled into the circuit. IC1a is wired in a non-inverting configuration with a gain of 4.9, as set by the 39kΩ and 10kΩ feedback resistors. The 150pF capacitor in the feedback path rolls off the frequency response above the audio spectrum. IC1a’s output appears at pin 1 and is coupled via a 2.2µF capacitor to Drive pot VR1. This pot controls the signal level into the next stage, for reasons that will become clearer shortly. The signal from the VR1’s wiper is in turn AC-coupled to op amp IC1b via a 15nF capacitor. This capacitor also acts with a 100kΩ bias resistor to form a high-pass filter, to provide a small measure of pre-distortion equalisation. This is necessary to reduce the effects of harmonics from the lower strings. Apparently, these low frequency harmonics tend to sound a little “fruity” during chord work. In addition, cutting the low end response may also help with guitar pickup equalisation. Effects Bypassing: The Different Methods Generally, it’s desirable to be able to switch effects in and out during a performance. A popular means of doing this is via a foot switch built into the same box that houses the electronics. This arrangement is part of all commercial effects pedals. Another common method relies on a dedicated bypass box, which is simply wired in series with the effects input and output leads. In the latter approach, the bypass function physically switches the effects box out of the signal path. This is termed “hard” bypassing, as opposed to “soft” bypassing, where some part of the effects electronics is still in-circuit (usually an input buffer and/or line driver). “Hard” bypassing is a popular approach because it ensures that the effect has no impact whatsoever on the signal, especially in relation to loading or otherwise distorting the signal source. A good example of a do-it-yourself bypass box can be found on the web at www.geofex.com/Article_Folders/ Millenium/millen.htm Alternatively, the WidgyBox has provision for an internal DPDT “hard” bypass switch. It’s simply a matter of removing the two wire links adjacent to the input and output sockets and wiring up switch S2 as shown on the circuit diagram (Fig.1). We envisage an internal switch being used in conjunction with a more robust (“stomp proof”) metal case! IC1b is configured as a non-inverting stage and operates with a gain of 12.8. It has two important roles, the first being to drive a pair of back-toback diodes (D1 & D2) whose job it is to perform the soft clipping function. Clip job The way that this works is quite straightforward. Once the peak signal level exceeds the forward voltage (0.2–0.4V) of the diodes, they start to conduct, thus clipping the highs and Fig.2: moderate soft clipping. The top waveform shows the signal into op amp IC1b, while the bottom waveform shows the signal across the clipping diodes (D1 & D2). Note the smooth waveform peaks. Compression is already quite noticeable, nearing a 2:1 ratio. siliconchip.com.au lows off the waveform. In addition, the non-linear conduction characteristic of the diodes give the peaks a smooth, rounded appearance. Regardless of increasing drive level, the diodes continue to clip the signal to about the same voltage, resulting in even more waveform compression (and distortion). At very high drive levels, IC1b’s second role comes into play – it starts to hard clip the signal. What happens is that the amplified signal level exceeds Fig.3: this is the maximum soft clipping signal, again taken across diodes D1 & D2. Note that the rising and trailing edges are almost vertical now but we still have rounded peaks. The compression is now quite high and this also imparts quite a degree of sustain. May 2003  25 Fig.4: maximum hard (and soft) clipping. The top waveform shows the hard-clipped op amp output. At the bottom, we can see what it looks like across the diodes. The amplitude isn’t much different to Fig.3 but the peaks have been “flattened”. the op amp’s maximum available output swing – so it is abruptly clipped. This is normal behaviour for any over-driven op amp and it’s exactly what we need for our hard clipping function! Fig.5: fiddling with the tone controls has a bigger effect than you might expect, because it’s boosting or cutting the harmonics as well. Here’s what the output of the box looks like (bottom waveform) when we wind up the bass boost. As a matter of interest, the TL072 clips non-symmetrically. This suggests that not only do we get the higher-order harmonics mentioned earlier but also a larger proportion of even rather than odd multiples. Note that we’ve specified Schottky diodes for D1 & D2 as they have a lower forward voltage than the common 1N4148/1N914 varieties. This gives a larger adjustment range between soft and hard clipping, allowing more waveform compression and increasing the “sustain” effect. Tone controls This close-up view shows the final version of the PC board. Take care to ensure that all polarised parts are installed the right way around. 26  Silicon Chip The distorted signal is routed to a Baxandall type tone control network, based around op amp IC2 and potentiometers VR2, VR3 & VR4. These pots and their associated resistors and capacitors form the feedback network between the op amp’s inverting input and its output. Each of the bass, mid and treble networks can be considered separately since they are connected in parallel between the signal input following IC1b and the output of IC2 at pin 6. Furthermore, the wiper of each pot is effectively connected to the inverting input (pin 2) which is a virtual ground. Operation of the bass control is as follows: with VR2 centred, the value of resistance connected between the output from IC1b and pin 2 of IC2 is the same as that between pins 2 & 6 and this sets the gain to -1. The 15nF capacitor has no effect since it is equally balanced across the potentiometer. If we move the wiper of VR2 to the full boost position (ie, rotate the pot shaft fully clockwise), we get 19kΩ (18kΩ + 1kΩ) between the input and pin 2 of IC2 and 119kΩ between pins 2 & 6. In addition, the 15nF capacitor siliconchip.com.au Table 2: Capacitor Codes Value 220nF 100nF 15nF 12nF 2.7nF 1.5nF 150pF 39pF 10pF µF Code EIA Code IEC Code 0.22µF 220n 224 0.1µF 100n 104 .015µF  15n 153 .012µF  12n 123 .0027µF  2n7 272 .0015µF  1n5 152 150pF 150p 150 39pF  39p  39 10pF  10p  10 is across the 100kΩ resistance in the feedback loop. Without the capacitor the gain would be -119kΩ/19kΩ or -6.3 at all frequencies. But with the capacitor, the gain is high only at around 50Hz and as the frequency rises it comes back to -1 (ie, overall unity gain). Thus we have bass boost. Conversely, when VR2 is wound fully anticlockwise, the position is reversed and we get a gain of 19kΩ/119kΩ or -0.16 (-16dB). The capacitor is now on the input side and provides less gain at frequencies below 100Hz but with gain increasing to -1 at frequencies above 100Hz. Thus we have bass cut. Various settings of VR2 between these two extremes will provide for less boost and cut. The midrange section works in a similar manner except that there is now a 12nF capacitor between VR3’s wiper and pin 2. This, along with the 2.7nF capacitor across VR3, gives a band­pass filter, so we either boost or Fig.6: here’s how to install the parts on the PC board. Install the smaller parts first before moving on to the output sockets, the battery holder and (finally) the pots (see text). cut the midrange frequencies. The treble control operates with no capacitor across VR4 but has a 1.5nF capacitor between its wiper and pin 2 to produce a high-frequency boost or cut at 10kHz. A 39pF capacitor between pins 2 & 6 of IC2 provides a high-frequency rolloff to prevent oscillation which could otherwise occur when the treble control is set for maximum boost. Similar­ly, the 1kΩ resistor in series with pin 2 is there to attenuate Table 1: Resistor Colour Codes o No. o  1 o  1 o  2 o  2 o  3 o  2 o  2 o  3 o  1 o  2 o  2 o  1 o  1 siliconchip.com.au Value 1MΩ 220kΩ 100kΩ 47kΩ 39kΩ 18kΩ 12kΩ 10kΩ 3.3kΩ 2.2kΩ 1kΩ 150Ω 100Ω 4-Band Code (1%) brown black green brown red red yellow brown brown black yellow brown yellow violet orange brown orange white orange brown brown grey orange brown brown red orange brown brown black orange brown orange orange red brown red red red brown brown black red brown brown green brown brown brown black brown brown 5-Band Code (1%) brown black black yellow brown red red black orange brown brown black black orange brown yellow violet black red brown orange white black red brown brown grey black red brown brown red black red brown brown black black red brown orange orange black brown brown red red black brown brown brown black black brown brown brown green black black brown brown black black black brown May 2003  27 Parts List 1 PC board coded 01105031, 117mm x 100.5mm 1 110 x 140 x 35mm (L x W x H) plastic instrument case (Jaycar cat HB-5970) 1 DPDT PC mount toggle switch (S1) (Jaycar ST-0365) 2 6.5mm PC-mount stereo switched sockets (CON1 - CON2) (Jaycar PS-0190) 1 2.1mm PC mount DC socket (CON3) 1 9V PC mount battery holder 3 100kΩ 16mm PC mount linear pots (VR2 - VR4) 2 10kΩ 16mm PC-mount log pots (VR1, VR5) 5 knobs to suit pots 20mm length of small heatshrink tubing 70mm length of light duty hook-up wire 320mm length of 0.71mm tinned copper wire 2 1N4004 1A silicon diode (D3,D4) Semiconductors 2 TL072CP dual op amps (IC1,IC3) 1 TL071CP op amp IC (IC2) 1 3mm high-brightness red LED (LED1) 2 BAT43 schottky diodes (D1,D2) (Jaycar ZR-1141) Resistors (0.25W, 1%) 1 1MΩ 3 10kΩ 1 220kΩ 1 3.3kΩ 2 100kΩ 2 2.2kΩ 2 47kΩ 2 1kΩ 3 39kΩ 1 150Ω 2 18kΩ 1 100Ω 2 12kΩ RF signals; it stops radio breakthrough. Being able to boost or cut the distorted signal in three distinct bands gives you a lot of control over your Capacitors 1 100µF 25V PC electrolytic 2 10µF 16V PC electrolytic 2 47µF 16V non-polarised PC electrolytic (Jaycar RY-6820) 1 22µF 16V non-polarised PC electrolytic (Jaycar RY-6816) 2 2.2µF 16V non-polarised PC electrolytic (Jaycar RY-6804) 5 220nF (0.22µF) 50V MKT polyester 2 15nF (.015µF) 50V MKT polyester 1 12nF (.012µF) 50V MKT polyester 1 2.7nF (.0027µF) 50V MKT polyester 1 1.5nF (.0015µF) 50V MKT polyester 3 150pF 50V ceramic disc 1 39pF 50V ceramic disc 1 10pF 50V ceramic disc sound – more, in fact, than is possible with many commercial units, which commonly provide only one or two bands of adjustment. Switch S1 has been included to allow you to quickly bypass the tone circuitry altogether should you wish to control it elsewhere in your setup. Level control & output IC2’s output is AC-coupled via a 2.2µF capacitor to VR5. This pot allows you to set the output level to match the input, thus preventing any noticeable jump in volume when the WidgyBox is switched in and out (see the panel entitled “Effects Bypassing: The Different Methods”). From there, the signal is AC-coupled via a 220nF capacitor to op amp IC3a. This op amp is configured as a voltage follower – it simply buffers the incoming signal and passes it through unchanged. A 150Ω resistor decouples IC3a’s output from any cable capacitance, thereby ensuring stability under all conditions. This is followed with a 47µF capacitor to remove the DC offset. Finally, a 10kΩ resistor terminates the output to ground, ensuring that there are no nasty clicks when the box is hot-switched into the signal path. Power supply In keeping with other popular effects pedals, power for the unit is provided by a 9V alkaline battery. The current drain is only about 12-15mA, so you’ll get more than a days’ continuous use and many days of intermittent use before a swap is required. Alternatively, power can be provided by a 9V DC plugpack. Be aware, though, that most unregulated plug­ packs put out much more voltage than their rating at these low current levels. Fig.7: these full-size artworks can be used as drilling templates for the front and rear panels. Drill small pilot holes to begin with, then carefully enlarge each hole to size using a tapered reamer. 28  Silicon Chip siliconchip.com.au Although this won’t damage your box, the higher voltage will alter the characteristics of the distortion effects at high drive settings. If you have a plugpack with selectable output voltages, you may find that the 7.5V setting provides about 9.5V under light load, which is ideal. Note that the negative terminal of the battery connects to earth via the switch contacts of the DC input socket (CON3) and the middle and common contacts of the guitar input socket (CON1). This means that you’ll need to plug in your guitar to power up the box. It also means that when a plugpack jack is inserted, the battery is disconnected. This feature is very important, otherwise the plugpack would attempt to charge the battery and that could have loud and startling consequences! Finally, the half supply voltage rail (ie, +V/2) needed by all of the bias networks is generated by op amp IC3b and its associated circuitry. Two 47kΩ resistors divide the +V rail in half, after which it is filtered by a 10µF capacitor and then buffered by op amp IC3b. A 100Ω resistor in series with IC3b’s output decouples the large 10µF filter capacitor. Construction With the exception of the power LED, all components mount on a single PC board, coded 01105031. Using the overlay diagram in Fig.6 as a guide, begin by installing the eight wire links using 0.7mm tinned copper wire or similar. Note that the two links adjacent to the input and output sockets (CON1 & CON2) can be left out if you intend fitting a foot switch to the box but more on that later. Install the low-profile components first, beginning with the resistors and diodes (D1-D3). Follow with the three op amp ICs (IC1-IC3). Make sure that you have the pin 1 (notched) end of each IC oriented as per the overlay diagram. In addition, note that IC2 is a TL071 (single) op amp, whereas the others are TL072 (dual) versions. Don’t mix them up! The two jack sockets (CON1 & CON2) and the DC socket (CON3) can go in next. When inserting the jack sockets, push them all the way down until the shoulders of all pins make contact with the PC board surface. Follow with the battery holder, which siliconchip.com.au The assembled PC board fits neatly into a low-profile plastic instrument case. Note that the PC board shown here is a prototype version and differs slightly from the final version shown in Fig.6. should be secured to the PC board with No. 4 x 6mm self-tapping screws prior to soldering. Next, install all the capacitors. The 100µF and two 10µF electrolytic capacitors are polarised and must go in the right way around. The remaining five electrolytics are non-polarised (marked “NP” on the overlay) and can go in either way. Potentiometers VR1-VR5 and switch S1 should be installed last of all. Start with VR1 but solder its middle pin only. Lift the board to eye level and examine the position of the pot from the front and side. It should be sitting perfectly “square”. Why bother? – well, when we eventually fit the front panel, this step helps to ensure that all the pot shafts Fig.8: having heard all the stories about valve distortion, we were consumed with curiosity and had to have a look at it ourselves. A kind gentleman loaned us his valve guitar amplifier and we captured this waveform when it was overdriven. Man, that doesn’t look too soft, does it? May 2003  29 switch (S1), ensuring that it is seated firmly on the PC board surface before soldering Case preparation The rear panel carries the 6.5mm stereo switched sockets and includes an access hole for the DC power socket. Note that the PC board in this photo is the final version, as shown in Fig.6. are aligned, improving appearance and minimising stress on solder joints when the nuts are tightened. Adjust the pot position as necessary and then solder the remaining two pins. Repeat this procedure for the other four pots. Finally, install the tone bypass As supplied, the bottom half of the case contains eight mounting posts. The four outermost posts are used to support the PC board, while the four inner posts are not required and must be removed. This can be done using a chisel or an oversized drill bit. The templates shown in Fig.7 provide the quickest and easiest method of getting all the holes in the right places for the front and rear panels. Photocopy the templates, cut them out and carefully align and tape each one to a blank panel. First, gently centre-punch the holes directly through the templates, then remove them and drill 1mm pilot holes for each mark. Don’t attempt to jump directly to a large diameter drill, as you may split a panel or get the holes off-centre. Instead, drill the holes progressively larger in several steps. Some constructors won’t have fractional drill sizes all the way up to the large diameters of the pot shafts and jack sockets. In this case, a tapered reamer is ideal for enlarging the holes to their final sizes. Trial fit The front panel should not be forcibly fitted over the pot shafts. If the holes are correctly sized for the shafts but the panel is still a tight fit (or won’t fit!), then the holes are obviously out of alignment. Increase the hole sizes as necessary to get an easy fit. This is quite important; a good fit keeps all the pot shafts in alignment. With the drilling done, slide the panels into place and loosely install washers and nuts on all the pots and the two jack sockets. The assembly should now slip home in the case bottom without too much trouble. Check that you can sight the four mounting post holes through the PC board holes and that the posts actually make contact with the underside of the board. If all is well, tighten up the nuts by hand. Grounding the pots Fig.9: this is the full-size etching pattern for the PC board. 30  Silicon Chip To minimise extraneous noise, the metal shells of the pots must be connected to the ground (0V) rail. This is achieved by soldering a single length of tinned copper wire to the metal top of each pot and terminating it to the siliconchip.com.au PC board at either end. The overlay diagram (Fig.6) and the various photos show where to position this wire. In order to get the solder to adhere to the pots, remove a small spot of the cadmium plating on each pot with an ink rubber or scouring pad and clean the area with alcohol. That done, pretin the spot with a fairly hot iron and large gauge multicore solder before attempting to attach the earth wire. Installing the LED Sound Fun: Experimenting With The Circuit Like to experiment a little? Then check out these ideas! As explained in the text, the high-pass filter formed by the 15nF capacitor and 100kΩ resistor at the input of IC1b provides for some pre-distortion equalisation. The 3dB point of this filter is around 100Hz. A higher or lower point may better suit your system. We suggest an upper limit of about 300Hz (no lower limit). Here are some example values: for a 194Hz 3dB point, use 8.2nF instead of 15nF; for 284Hz, use 5.6nF. It is also possible to experiment with the distortion-making section of the circuit. For example, replacing one of the Schottky diodes with a common 1N4148 will create non-symmetrical clipping for quite a different sound. You could also substitute germanium diodes, which have softer turn-on characteristics. Have fun! To mount the LED, first strip and tin the ends of two 30mm lengths of light-duty hook-up wire. That done, shorten the LED leads to about 8mm, solder one end of each wire to a LED lead and insulate the connections with heatshrink tubing. Finally, slip the LED into position in the front panel and solder the two leads to the PC board as shown in Fig.6. Be sure to install the LED with the correct polarity, though. The flat edge on the LED body goes towards the edge of the case (see Figs.1 & 6). If necessary, the LED can be fixed in position with a spot of glue or silicone sealant. and measure between pins 4 & 8 of both IC1 and IC3. That done, repeat this measurement between pins 4 & 7 of IC2. In all cases, the reading should be about 9.2V. Now touch the negative probe of your meter to the negative battery terminal and the positive probe to pin 2 of IC2. Your reading should be very close to half the voltage measured above (about 4.6V). Testing Final touches A few quick voltage measurements around the circuit will help to confirm that your project is ready for use. You’ll need a fresh 9V battery, a mono jack plug and a multimeter. Fit the battery and insert the plug in the input socket (CON1). The plug can be on one end of your guitar lead but don’t connect anything to the other end just yet! As soon as the plug is inserted, the power LED should light. If it doesn’t, then remove the plug immediately and check the orientation of the LED. Also, check that there is continuity through the DC socket (CON3) switch contacts, which can be identified by tracing the negative connection from the battery. If the above checks don’t identify the problem, then suspect a short or low resistance between the +V rail (battery positive) and ground (battery negative). You may have inadvertently reversed one of the ICs or perhaps there is a solder bridge between tracks somewhere. Follow the +V trace around the board to track it down. OK, let’s assume your LED lights up. Next, we’ll check that power arrives at each op amp IC supply pin. Set your multimeter to read DC volts The next step is to secure the PC board to the case posts with four No. 4 x 6mm self-tapping screws. Before tightening the screws, it’s a good idea to temporarily loosen off the pot and jack socket nuts, so that the assembly settles “comfortably” into position. The final job is to shorten the pot siliconchip.com.au shafts to match the knobs. Before doing this, screw the top half of the case into position and tighten up all of the pot nuts. The procedure now is to grip the tip of each pot shaft (in turn) in a vice, starting with VR1. You can then carefully cut off the unneeded section of the shaft using a hacksaw. For our prototype, only 14mm of shaft length (measured from the surface of the panel) was required for the push-on type knobs. Be sure to support the weight of the assembly during the cutting. That’s it – your WidgyBox is ready to rock! Crfedits Many thanks to Tim and Ash who were kind enough to drop in and put the prototype through its paces. SC Help – It Doesn’t Work! Before doing anything else, double-check all component values against the overlay diagram. If that doesn’t turn up anything, then some detective work is in order. If you have no output at all, then a few additional DC voltage measurements may help to narrow the problem down to a particular op amp and/or it’s immediate circuitry. Apply power and wait at least 10 seconds for the bias networks to fully charge. Don’t apply a signal to the input or connect anything to the output socket during these checks. Connect your multimeter’s negative probe to battery negative and touch the positive probe to each op amp output in turn (IC1a pin 1, IC1b pin 7, IC2 pin 6 and IC3a pin 7). Although the readings will vary slightly, they should all be close to one-half battery voltage. A large variation in any reading indicates a problem in the immediate vicinity. Alternatively, if you have output signal but varying the drive pot doesn’t change the distortion level, then suspect a problem with the feedback circuitry around IC1a or IC1b. May 2003  31 Direct Digital Synthesis (DDS) makes it very easy to design a low-cost, high-performance function generator – one of the handiest pieces of test gear you can have. This one can be set to any specific frequency between 1Hz and 10MHz and offers both sine and square wave output. T he 20MHz Low Cost Function Generator I described in the August 96 issue of “Electronics Australia” has proven very popular, with thousands having been built. The low cost, simple construction and wide bandwidth made it a very attractive project. However, there were two problems with that design – the lack of a frequency display and being able to set the frequency to exactly what you wanted. To overcome these, one kit supplier bundled the function generator with another frequency counter kit. So it is not surprising that many people have asked for an updated design with a built-in frequency display. While a frequency display would be relatively easy to add, it would add significantly to the cost and complexity of the project. In addition, the analog 32  Silicon Chip nature of the original design meant that temperature drift would also be an issue. This new design overcomes these problems by adding a frequency display and digital frequency selection, while still maintaining the low-cost approach. The design The design is based on an Analog Devices AD9835­, a complete 50MHz by David L Jones* (clock) Direct Digital Synthesis (DDS) sinewave generator on a single chip. The MAX038 used in the previous design is analog in nature and setting the exact output frequency is difficult unless you have many ranges with fine adjustment. Going digital with the DDS chip is the obvious way to go: it allows you to set the output frequency exactly from 1Hz to 10MHz in 1Hz steps and there is effectively no drift with temperature or time as the output frequency is crystal-locked. As the AD9835 is clocked at 50MHz, in theory it is capable of generating a sinewave up to 25MHz. At this frequency, the output waveform quality is more difficult to control and amplify, so 10MHz was taken as the arbitrary upper limit. This results in a good quality, low distortion, large output signal level over a 0-10MHz range. While 10MHz is not as high as the 20MHz+ in the original design, it is still sufficient for most applications and is way beyond the 2MHz or so of most commercial analog bench generators. www.siliconchip.com.au Low Cost 1HZ –10MHz DDS Function Generator It’s a tiny, tiny chip! It’s nice – but by no means essential. Our frequency display is now oneTo set and display the frequency tenth the cost of an LCD and is easier Unfortunately, the AD9835 DDS to assemble. chip is only available in a 16-pin you really only need to display one To also help reduce the cost, the PC TSSOP (Thin Shrink Small Outline digit at any one time, in which case a single 7-segment LED display can board has been designed to fit into a Package) surface-mount package, be used. standard UB3 Jiffy box, with no wirwhich makes it challenging(!) to solder ing required – everything mounts on You do need some other indication to by hand. A TSSOP package has half the pin tell you what digit you are setting – but the PC board. RCA output connectors were chopitch of your typical SOIC surface a simple LED can do that. sen in preference to BNC connectors, mount IC package, a mere 25-thou as the PC board mounting (0.635mm). Compare it with Specifications: RCA connectors are about the 74HC14 SO14 package one-tenth the cost of the also used in this design. BNC type. Waveform Generation: 32-bit DDS, 10-bit DAC More will be mentioned In fact, you can buy a Distortion: <1% at 1kHz about how to solder this PC board mounting RCA Frequency Range: 1Hz to 10MHz in 1Hz steps device later. connector plus an RCA-toFrequency Display: “Sliding Window” 7 digit There are other DDS chips in BNC convertor for less than (EEPROM frequency retention) the Analog Devices DDS prodthe cost of a BNC PC board User Input: Three push buttons uct range with easier-to-handle mount connector. Sinewave Output: 0-5Vp-p adjustable, 50Ω packages but they are much Squarewave Output: CMOS/TTL compatible, 50% duty cycle bigger, more expensive and Main controller Output Connections: RCA don’t have a nice serial interPower: 9VAC 100mA plugpack A PIC16F628 8-bit miface like the AD9835. cro- controller was chosen My first prototype for this as the main controller. It design used an LCD panel for has 2KB of internal FLASH The end result is a single 7-segment the frequency readout but this would have significantly increased the cost LED display with a row of 3mm LEDs program memory, 224 bytes of RAM of the project. So I thought about it to indicate which digit of the output and 128 bytes of EEPROM. This is for a while and came to the realisation frequency is being displayed and set. adequate for our control program and So the row of LEDs correspond to data storage. that you don’t really need to display This chip serves three purposes. the entire frequency at any one time. X,XXX,XXX Hz. www.siliconchip.com.au May 2003  33 Fig.1: inside the AD9835 DDS IC. Its operation is explained in the text. On the facing page is Fig.2, the circuit diagram. One is to control the display and switches, the second is to send the necessary control commands to the AD9835 DDS chip and the third is to store the output frequency in the internal EEPROM. The frequency set by the user is stored in the internal EEPROM and this same frequency is automatically set when the project is next powered up. The 4MHz internal RC oscillator is used to lower system cost and to free the extra pins for I/O functions. There are no critical absolute timing requirements in the project, so a crystal oscillator is not required. How DDS frequency generation works The internal block diagram of the AD9835 (Fig.1) shows its operation as well as that of a basic Direct Digital Synthesis (DDS) generator. A DDS generator consists of three major components – a phase accumulator, a sine-wave lookup table (usually con34  Silicon Chip tained in ROM) and a digital-to-analog convertor (DAC). The phase accumulator is also commonly referred to as a Numerical Control Oscillator (NCO), although no part of a DDS actually “oscillates”. As sinewaves are non-linear in nature, they are not that easy to generate accurately, even using standard sampling techniques. On the other hand, the “phase” of a sinewave is completely linear in nature, from 0-360°, and thus lends itself to be more easily generated. Using a reference clock and the linear aspect of the phase, a DDS generator can generate very accurate sine- waves of almost any frequency, completely in the digital domain. The phase accumulator basically performs an integration function and generates a linear phase “ramp” in proportion to the desired frequency, which is contained in the 32-bit register FREQ0. The sine (or cosine in the case of the AD9835) lookup table converts the linear phase ramp into a sinewave. As sinewaves are completely symmetrical every 90°, the lookup table only needs to store one quarter of the waveform, with some appropriate control logic to map this over the full cycle. (Different DDS devices have differing ways to do this). Even though the AD9835 contains a 32-bit frequency control register, a 32-bit (232 memory bits) lookup table is not required, as the AD9835 only has a 10-bit DAC. So the (co)sine lookup table does not need to be much more accurate than this; in this case it is only 12 bits. This ensures that the accuracy of the signal is determined entirely by the DAC resolution and linearity. How it works: As you can see from the schematic (Fig.2) there isn’t much to the design. IC3 does all the frequency generation, IC2 handles the control and display, while IC1 and IC4 provide output drive. IC3 is programmed by a custom www.siliconchip.com.au www.siliconchip.com.au May 2003  35 All components mount on the one single-sided PC board, although some are on the back (track side). Note how the LEDs stand up to poke through the case lid. The PIC chip should be socketed to allow for any future firmware upgrades. This pic is of an early protoype – the one presented is V2.0. 3-wire serial control bus from the micro- controller (IC2). Data and commands are transferred in 16-bit words. The serial interface is run asynchronously to the main clock and can be run at any speed determined by the host micro. IC3 has various modes and internal registers that must be defined before it will output a frequency, and these are explained in the data sheet for those who are curious. IC3 is also capable of frequency and phase modulation of the output signal, both of which can be controlled by either the serial bus or an external pin. For the sake of simplicity and cost reduction, these features have not been implemented into this design. The actual output frequency is determined by the value in the 32-bit FREQ0 register. The value in FREQ0 will be equal to F/(50MHz/232), where F is the desired output frequency. From this equation you will see that with our 50MHz oscillator we can get approximately 12mHz resolution and this value will also equal our output frequency uncertainty (ignoring crystal accuracy). In the case of a 1Hz output frequency, the FREQ0 register will contain the value 86 which equates to 1.001Hz, not quite 1Hz but close enough! At the low end of the frequency range the frequency accuracy will be 0.1% worst case, while at the high end the frequency accuracy can be controlled to a staggering one part in four billion. Low distortion was not a major de36  Silicon Chip sign requirement, so for simplicity no measures were taken to improve this. The total harmonic distortion (THD) is around the 1% mark, which is adequate for most general applications. External output filtering can be added to improve this if desired. IC3 is clocked by XTAL OSC1, an industry standard 50MHz TTL/CMOS 8-pin DIP crystal oscillator. The stability of the generated output signal will be dependant upon this clock but for this low-cost application any grade oscillator will suffice. There are many brands of oscillator that match this standard footprint – some come in plastic DIP, while others come in a metal can package. IC3 requires digital and analog power and ground pins. These are individually decoupled at the power pins and run as separate lines from the regulators. IC3 provides a current output on pin 14, which is converted into a voltage by R4. C11 is an optional filter capacitor and is not fitted in the standard design. R2 sets the full scale DAC output signal current level, which in this case is approximately 3.9mA. This is already at a maximum value that will not compromise the performance of the chip. Thus the output voltage across R4 will be approximately 1V p-p referenced above ground, as IC3 is powered from a single power rail. This signal is AC-coupled by C12 and referenced to ground and user adjusted by VR1. The signal is then amplified by IC1 which operates with a gain of 4.9, as set by R5 and R6. This gives an The early prototype board has a capacitor and two resistors strapped on to the back. In the final version these are “on top”. The main purpose of this photograph is to show the components which are soldered to the back of the board, especially the tiny AD9835 TSSOP IC (top, centre) which requires great care. www.siliconchip.com.au Fig.3: front (top) and back (bottom) sides of the PC board showing component placement. It is a single-sided board as far as tracks are concerned; some components are on the track (copper) side. The majority of components are polarised or need to be mounted a certain way (for example, the three pushbutton switches). Note carefully the comments about soldering IC3 (and IC4 for that matter). approximate maximum output signal level (at all frequencies) of ±2.5V peak. Thus the final sinewave output level is adjustable from 0-5V p-p. IC1 provides a low impedance buffered output and R7 provides a nominal 50Ω output impedance. IC1 can be either a National Semiconductor LM6361 or an Elantec EL2044. The EL2044 is the recommended device as it has a slightly higher bandwidth, so will provide a higher signal level output at the high end of the frequency range. IC4 is a hex Schmitt inverter, with C13, R1 and R3 providing a level shift function to bias the ground-referenced sinewave input signal to half the supply rail (suitable for a 5V TTL input). The Schmitt input squares up the sinewave and gives a CMOS/TTL output. The 7-segment display and digital LEDs are multiplexed onto the same output pins on IC2. The common cathode line for both displays goes back to a separate pin on IC2. IC2 is thus able to “switch” alternately between displaying the 7-segment display and the digit LEDs. This is done in firmware and each display is turned on for a 5ms burst at a rate determined by the main loop. As long as it is greater than 50Hz or so you won’t see any flicker – all the LEDs appear to be continuously on. The pushbutton switches are debounced in the firmware by a small delay of a few hundred milliseconds after each key press. The power supply is a typical halfwave rectified AC input with positive and negative 5V regulators (REG1 & REG2). Heat dissipation in the regulators Parts List – 10MHz DDS Function Generator 1 PC board, 123 x 56mm; coded 04105031 1 UB3 Jiffy box (130 x 67 x 44mm) 1 18-way IC socket (for IC2) 3 momentary action PC-mounting switches 2 RCA sockets, PC-mounting (with BNC adaptor if required) 1 knob to suit potentiometer shaft 4 12mm x 3mm tapped spacers 4 20mm x 3mm bolts, nuts and washers www.siliconchip.com.au Semiconductors 1 EL2044 or LM6361 opamp (IC1) 1 16F628 PIC microcontroller, programmed with DDSFRQ20.HEX (IC2) 1 AD9835 DDS generator (IC3) 1 74HC14 hex Schmitt trigger (IC4) 1 LM7805 +5V regulator (REG1) 1 LM79L05 -5V regulator (REG 2) 1 50MHz TTL oscillator (XTAL OSC1) 1 FND500 7-segment LED display (DISP1) 7 3mm red LEDs (LED1-7) 2 1N4001 silicon diodes (D1, D2) Capacitors 2 470µF 10V PC electrolytic (C12,13) 1 470µF 25V PC electrolytic (C14) 1 100µF 25V PC electrolytic (C15) 2 10µF 10V PC electrolytic (C1,2) 2 100nF MKT SMD (0.2p) (C6,7) 5 100nF ceramic (C3,9,10,16,17) 2 10nF ceramic SMD (0.2p) (C4,5) Resistors (1/4W 1% unless noted) 1 47Ω 1 120Ω 1 270Ω (SMD) 3 470Ω 2 1.5kΩ (SMD) 1 3.9kΩ (SMD) 2 470kΩ 1 1kΩ potentiometer May 2003  37 The PC board is connected to the case lid via four tapped spacers. Suitable cutouts and holes in the lid allow the switches, LEDs and pot shaft to poke through, while the 7-segment display can also be seen through a cut-out. will depend on the input voltage level from the plugpack. Ensure that this is not too high – a 9V AC plugpack is recommended as a maximum. The plugpack should be rated at 100mA or greater. Parts availability All of the components are available off-the-shelf for those who wish to con- struct the project from scratch. Farnell carry the “hard to get” bits like the AD9835, AD6361, 50MHz oscillator and surface mount 74HC14. As far as the PC board is concerned, it is not out of reach of home manufacture using good lithography techniques, despite the TSSOP track/pad pitch being extremely small. It is however recommended that a proper solder-masked PC board be obtained as this will make construction a lot easier. The HEX file is available for download for non-commercial use from the SILICON CHIP website (www. siliconchip.com.au) and the author’s website at www.alternatezone.com Short form kits and PC boards may also be available from the author. Given the popularity of the original design, it is probable that kits will be made available by major suppliers in due course. Construction Start construction with the AD9835 TSSOP IC (see separate panel). This way, there will be no other components to obstruct you and the board will sit flat and steady on your bench. This IC is by far the most difficult component to solder in this kit; indeed, it may be the most difficult com- Soldering the AD9835 TSSOP IC Soldering the AD9835 is the most difficult aspect of project construction and unless you have the right tools and experience it is likely that you will have problems. Don’t underestimate how hard this will be: the pin pitch is 1/4 that of a regular IC and half that of a standard SOIC. If you have a solder-masked PC board then your job will be a lot easier, as the solder mask will help stop the solder bridging between pins. As a minimum you will need a good temperature-controlled soldering iron with a fine tip suitable for surface mount soldering, 0.45mm solder and tweezers. A chiselled tip is much better than a conical tip, which will have difficulty making good thermal contact. The ideal tip to use is the “wicking” chisel type which has a small cavity in the middle of the tip to help “wick” the solder back off the joint, this helps to keep the amount of solder on the pins to an absolute minimum. Proper 0.45mm surface-mount solder should be used – anything bigger will be a nightmare. Alternatively (if you have them available), proper surface-mount solder paste and a hot-air surface-mount soldering gun will give you a first class job. A magnifying lamp will come in very handy for this job – in fact, it is probably essential as many people will have to do the soldering under a magnifying lamp. You would need really good eyesight to solder and inspect the job without a magnifying lamp. The best approach is to apply a small amount of solder to one of the corner pads of the chip. Then use tweezers to place the chip over the pad (ensure correct orientation!). You can then reheat this pin and move the chip with the tweezers to get it properly centred. Before you solder any more pins, double check the orientation of the chip: desoldering the chip later is an option you don’t even want to think about. 38  Silicon Chip Once the chip is aligned on the pads correctly then solder the pin on the opposite corner so the chip will hold in place. A “wicking” motion of the soldering iron away perpendicular from the pin is your best shot at avoiding bridges between pins. The regular soldering technique of applying the iron to the pin and pad and then applying the solder on the other side of the joint will not work in this situation. Neither the soldering iron tip nor solder are small enough to allow this. You will find that excess solder will form around the joint no matter how hard you try to control how much you use. So you will have to just try and “wick” it away from the joint. The biggest killer when hand soldering surface mount components is too much heat. Not only can excessive heat lift pads and crack tracks but worse, it can crack or destroy the component internally. Only solder one joint at a time and let the device cool before moving on. Do not apply heat to any joint for more than one or two seconds at most. Patience here could help prevent a big headache later. www.siliconchip.com.au These two ’scope shots show both analog and digital outputs at two different frequencies. The shot on the left is at 1kH and shows a pretty good result on both sine and square waves. The other shot is at 5.736MHz (no, this frequency is nothing special!) and shows a still-quite-usable waveform in both cases. The ringing on the square wave, in particular, is due to the signal being unterminated – it would be significantly better into a load. ponent you will ever have to solder! Having successfully soldered and checked the TSSOP, the other 0805 passive components and the SOIC package will be much easier to solder – but similar rules apply. Watch the orientation of the SOIC. Finish construction with the usual through-hole components. The PIC chip should be socketed to allow for firmware updates. The 7-segment display will require a regular wide IC socket cut to size to stand it off from the PC board. The LEDs should be mounted about 10mm proud of the PC board. The easiest way to do this and to ensure alignment of all the LEDs is to cut a 10mm strip of cardboard and place this between the legs of all the LEDs while soldering. Watch the LED polarity. The PC board is mounted behind the front panel on four 12mm spacers You may notice on the prototype that R1, R3, and C13 are retrofitted on the underside of the board. The published design has these components added to the top of the PC board, as shown on the overlay. escaping from any of the components! Next, measure the outputs of the regulators, they should be plus and minus 5V (respectively). In use When first powered up, the project will most likely be set to 0Hz, so there will be no output waveform. This could vary though, depending on the initial contents of the EEPROM bytes in the PIC chip. In either case, press the SFT (SHIFT) button to select which digit will be displayed on the 7-segment display. Use of the SFT button allows you to quickly determine the output frequency. The INC button will increment the currently displayed digit and will wrap back to zero. There is no ability to decrement the number other than the wrap around. Using SFT and INC does not update the frequency at the output. To do this you must push the SET button. This sets the output frequency and also stores the frequency in the internal EEPROM memory, so this frequency will be automatically reloaded when the project is next powered up. Remember that the output frequency will only change when you press the SET button, so the display will only reflect the actual output frequency when you have not touched the INC button since the last time the output frequency was set. When using the TTL/CMOS output, ensure that the output level control is set to maximum, as this output is generated directly from the amplified sine -wave output. SC Happy generating. * david<at>alternatezone.com Testing Before you power up the project, check for any shorts, especially on the surface-mount devices. Do a visual inspection and a multi-meter check. Don’t try to probe the pins of the TSSOP chip directly; instead probe the other end of the appropriate track on a larger component. Apply power to the project and ensure that the vital smoke is not www.siliconchip.com.au Full-size artwork for the Function Generator front panel can also be photocopied and used as a drilling template for the case lid. May 2003  39 SERVICEMAN'S LOG Fix the roof then fix the TV Discovering a hole in the roof is never good news, especially if you don’t know it’s there until it rains. And if there’s a fancy widescreen TV set sitting directly under the leak, it’s more than the roof that will need fixing. Mr Wilson (not his real name) is a barrister and lives in a beautiful harbour­side mansion. Unfortunately for him, his mansion didn’t have a perfect roof – something he didn’t realise until, one evening, a bad storm forcibly brought it to his attention. There was a leak and it was right over his beloved 7-year old widescreen 32-inch (76cm) Sony KV-W32MN21/ BE32 (SCC-J45A-A AG-1 chassis). This set was the state of the art back in 1995 – the best money could buy – and it was totally consistent with 40  Silicon Chip Mr Wilson’s “elevated” station in life. When faced with this disaster, Mr Wilson moved as fast as he could to (a) switch the set off and (b) move it out of harm’s way. But not knowing the extent of the water damage inside the “telly”, he sensibly left it to dry out for a few days while the leak in the roof was repaired. When he finally thought it was safe to reconnect it and switch it back on, his prayers went unanswered – after all, ap­peals to a higher court don’t always work, not even for bar­risters. Apparently, there was a “phut” noise and a little “unmusical” electrical theatre before it all went silent. The only encore was a trickle of smoke and an unpleasant burning smell drifting up out of the ventilation holes at the rear. Ever the optimist, he thought I could fix this in his home. Unfortunately, at that time, I didn’t even have a circuit dia­ gram. Still, I went through the motions of removing the back and inspecting the damage. It was major – the water had leaked inside on a wide front from the deflection board (D) to the small signal and switchmode power supply board (A), plus a multitude of modules plugged into these along the way. Also, there was older corrosion from sea air along the top of the double-sided PC boards, particularly near the flyback transformer, so there was lots of damage. Because of the likely cost of replacement parts, I was happy to declare the case hopeless and advised Mr Wilson to talk to his insurance assessors. To my amazement, it turned out he didn’t have a policy to cover this. Not only that but he insisted that he wanted it fixed – apparently it had “sentimental” value and it match­ ed his min­ imalist (!) decor and the colour scheme in the room. I found his reasoning unconvincing but mine is not to reason why. And so, reluctantly, I agreed to fix it but I warned him that it could be costly. It was a huge struggle to lug the 73kg (900 x 600 x 584mm) set to my truck but we made it without having to consult a car­ diologist. Back at the workshop, I had another tussle to get it onto the workshop www.siliconchip.com.au bench before I could finally tackle the de­struction wrought by the water. I started by dismantling the chassis, separating it into superficially damaged, severely corroded and damaged, and unaf­fected modules. It was soon clear that the power supply boards F1 and A were blown and that the deflection board was severely corroded and burnt. I removed all the obviously burnt parts and then washed the boards to remove the corrosion. It was a long process, starting with scrubbing the boards with Nifti and then flushing with clean hot water. This was then followed by long periods of drying before using chemicals such as methylated spirits, CRC2-26, PC board cleaner and electrical cleaner to remove any residues and expel any remaining moisture. I also had to “gouge” out areas where the board had deep ruts burnt into it. This process was tackled part time over a period of several weeks while the damage was diagnosed and parts ordered. On the AC rectifier board (F1), R1602 (0.1Ω 0.5W) had vaporised and D1602 – a TF5415 power switching SCR – had gone short circuit. Naturally, the F3401 mains fuse (5AT) on board F2 had failed as well. I wasn’t sure about IC1601 (the STR81159A rectifier switch) but it looked OK so I left it for the time being. Later, I decid­ed it was too risky not to replace it, as it might do more damage to the rest of the supplies, so I ordered a new one. Next, I moved to the A board and took a closer look. The power supply occupies only a small part of this module (towards the front of the set) but it is packed with components on both sides, many being surface mounted. I measured both FETs Q605 & Q606 (IRF1840G-LF, CONV-OUT) as being short circuit and I also checked D601 (a protection diode) and zener diodes D605, D606 and MA8180M. To be on the safe side, I decided to replace them, along with IC601, IC602, IC651 and IC652, plus some of the surface-mounted transistors which didn’t look too good from all the corrosion. On the deflection board there was a nasty mess near plug CN515, which supplies high voltage to the CRT board (C). R540 (a 1.8kΩ feed resistor for the +1000V supply) and R546 (a 0.47Ω feed resistor for the +200V rail) were www.siliconchip.com.au both burnt and were open cir­cuit. The corresponding diodes were OK but the PC board was charred. The whole board had a lot of corrosion on top as well but nothing that wasn’t linkable or fixable. The required parts eventually arrived and I informed Mr Wilson of my estimate. It always amazes me how rich people can whinge so much about bills when no doubt mine would pale into insignificance compared to one of his. Nevertheless, when he got over the shock, he agreed to go ahead. Chinese puzzle I fitted all the parts and reassembled all the boards. This was a bit like a Chinese puzzle and CN101 was hard to find, being tucked up at the back behind all the plastic support brackets. The problem was that the plugs are unmarked and often the colour doesn’t match the socket. In fact, you need the circuit to prev­ent plugging the wrong plugs into the wrong sockets. Finally, I rechecked all my work, braced myself and switched it on. The main thing was that there was no melt-down. Surprising­ ly, I had fixed the major parts of the power supply and the set was working after a fashion. I heard the EHT come up, the sound was good and I measured +135V on R3501 at the rear of the deflec­tion board. However, I still had no picture. It was hard to see the CRT filament heaters, so I measured them with a true RMS meter. I also measured the +1000V and +200V to the CRT board (C). I then momentarily shorted one of the tube cathodes to ground and got a flash of a fully scanned raster. But what was more interesting was that just by touching the cathode with almost anything restored the picture –and it was in colour! The quality wasn’t brilliant though and I began wondering whether the picture tube was suffering from low emission. When I switched the set off Items Covered This Month • • • • Sony KV-W32MN21/BE32 TV set (SCC-J45A-A AG-1 chassis). Panasonic NV-SJ400 VCR. Philips 29SP1698/75R TV set. Selectronics SPI 1200-SS 1200W in­verter. and then on again, the picture disappeared but it could be restored by just touching anyone of the cathodes. This was bizarre but seemed to be consistent with a low-emission picture tube affecting the RGB cut-off circuit via CN703-7 “IK OUT”. This line should be at approximately 2.2V. If the tube was flat, then increasing the heater filament voltage should also increase the beam current enough to overcome the cut-off circuit. I did this and also varied the voltage on the IK-OUT line but nothing made any difference. Next, I removed the CRT board and examined it carefully. It was then that I noticed that it too had suffered from corrosion. I thoroughly cleaned it, replaced some of the transistors, par­ticularly in the red and green amplifiers (Q703, Q709 and Q702, Q708), and thoroughly checked everything else. Nothing changed so I also replaced Q714 (spot suppressor) and zener diode D714 but again drew a blank. So how could touching the cathode of any gun switch on the picture? Was I injecting a signal, was it the extra capacitance or was I somehow increasing the beam current? I was still sure it was the IK-OUT line and I hooked up the CRO on and checked the wave­ forms on it. Without a picture, there was no waveform and its DC voltage was just a fraction lower than normal. Conversely, when the picture was present, there were large line pulses. It really didn’t get me anywhere though and I concluded that I was May 2003  41 Serviceman’s Log – continued looking at the problem the wrong way. Finally, I did what I should have done a lot sooner – I measured the voltage on every pin of the CRT, including the screen voltage to pin 3. This voltage was only at 225V whereas the circuit says the range should be 227-858V. Having established that, I switched the set off and meas­ured all the resistors around the screen control, including the control itself – all were correct. I then switched the set back on and ever mindful of how hard it is to align this control these days (see the service manual set-up adjustments), marked the position of the screen control knob. I then advanced it and as I did, the picture came up much better than before, with none of the colour bleeding that had previously been evident. I experimented with a number of positions and finally set­ tled for a voltage of around 430V, which gave the best picture. So why didn’t I follow the service manual’s alignment in­structions. The reason is that you have to: (1) set the picture to normal (define normal!); (2) set the video input to AV with no signal; (3) set the unit to Service Mode and turn off blue and black; (4) chase the BOF data of item number 1A (Auto Cut Off) from 00 to 01; (5) connect an oscilloscope to each of the cathodes and adjust (range 00-3F) 0E R-G, 0F G-G, 10 B-G Red, Green and Blue gain for a waveform that is 170V 42  Silicon Chip DC each above ground. And then it says “adjust G2 (RV701) volume to make the screen slightly bright”. Good, isn’t it? You make all these careful accurate scien­ tific adjustments to finally adjust it subjectively by eye! I skipped straight to the last line. Anyway, this was finally all that was required to give it a crystal clear picture. I checked all its trick functions such as Text, Picture in Picture and 16:9, Dual Pictures, etc, etc and all were fine. I quite liked the feature where you could have one half the picture of a TV channel and the other half on Teletext (Ch 7 Supertext). Mr Wilson was as happy as a barrister can be with the set – but he didn’t like the bill! So what happened? I speculate that rain water had got into the G2 screen control RV701 and caused a high resistance contact between the wiper and the carbon track, enough to drop the vol­tage outside the beam current circuit’s capture range. Unfor­tunately, I didn’t have the luxury of being able to dissect the sealed control further to find out. Home handyman A young unmarried couple brought in a Panasonic NV-SJ400 VCR for repair. When asked what the fault was, they kind of shuffled nervously and looked at each other before coming up with “no picture”. I didn’t pay too much attention to this display of body language, until she qualified the statement by confessing that “initially there was no picture but now there was a something loose inside and something might be a bit bent . . .” Eventually, after a bit of gentle persuasion, the full story slowly came out. They were watching an old tape and the picture went snowy. They figured out, probably correctly, that the tape had dirtied the heads and so had used a wet-type head cleaner. Apparently, this didn’t work, so they tried it again. When this failed, the boyfriend decided to open it up and “have a look”. All that took place only about an hour or so before they brought it to me! This was going to be good so I decided to have a good look inside while they were both still there. Inside, I found that the automatic head cleaner was at a crazy angle, with part of its lever jammed hard under the master cam. Worse still, the take-up arm was missing altogether – that is, until the boyfriend reached into his pocket and sheepishly handed it to me – “is this important?”. This was already looking close to terminal for such a basic VCR and the end finally arrived when I noticed that one of the video heads was hanging loose from the upper head drum. In the end, I told the couple that they had to go and buy new one. And so they left, wildly making all sorts of allegations at each other. My guess is that they are no longer a couple and that they will remain unmarried for some time yet! Philips TV set The Philips G110S chassis had a long and successful career in Australia in the early 1990s and was subsequently superseded by the G111S and G112. However, I don’t see too many of the G112S, as it is the backbone of the more upmarket models, with advanced options and accessories. However, from my perspective, the three chassis are close enough in similarity to be able to use the same methods when it comes to repairing them. I had a Philips 29SP1698/75R dropped in the other day with the fault marked as “No Sound”. In fact, when I got it onto the workshop bench, the fault was more accurately “dead”. The front LED was flashing rapidly in yellow (red and green). A quick look at the chassis revealed that someone had put a lot of work into changing all sorts of parts (you could tell by the soldering). This meant that I had to be on my toes and look out for unusual problems. When I said that the set was dead, this wasn’t quite strictly true. Initially, you could hear the EHT static build up and then the set would die. It was as though a protection circuit had come on. I checked the main +140V supply rails and the 5V out of the SOPS (Self Oscillating Power Supply) and they were OK. However, based on my experience with the G110S, I mostly www.siliconchip.com.au suspected micro­processor IC7200 and the EEPROM (IC7278). As a result, I decided to replace them both with parts scrounged from a few scrapped chassis in my workshop. The EEPROM was easy and I mount­ ed it in an 8 pin socket for convenience. By contrast, the 42-pin high-density micro­processor was more recalcitrant but neither made any difference. The only real clue I had was the initial complaint of “No Sound”. I followed up on this lead and found that IC7266 (TDA8425) was short circuit on pin 4 – the +12V input. I also I found that R3277 – a 68Ω feed resistor – was open circuit, even though it looked brand new. Replacing both these parts brought the set back to life but only in a very limited way. I could switch the set on with the remote control and the Green LED would stay on constantly. Additionally, there was a raster and there was hiss in the loudspeakers at high volume but apart from that, there was no sound or picture and no on-screen display. Well, I searched high and low trying to find out what was going on. Eventually, some oscilloscope checks showed that signal was getting as far as the analog switching ICs on the AV module but no further. I then replaced the original EEPROM without result but was reluctant to replace the microprocessor because of the delicate work involved. I still really couldn’t comprehend why the set closed down when the sound output IC died. There are no protection circuit sensors in that part of the set – I can only conclude that the SDA and SCL data lines from pins 11 www.siliconchip.com.au and 12 were feeding the information back to the microprocessor which closed it down. By now, I was contemplating changing all the ICs on the AV module when I noticed that the microprocessor actually had G11oS stamped on it. It was then that the penny dropped – I had used a microprocessor from a G110S chassis rather than the real McKoy and they were not interchangeable. Replacing the original microprocessor finally fixed the problem completely. Now here is a contribution from one of our readers. It comes from A. P. of Kuranda, Qld. This is how he tells it . . . DC-AC inverter This story concerns a Selectronics SPI 1200-SS 1200W in­ verter, circa 1992, owned by John and Maria who live in Cooktown in far north Queensland. Their main source of power is a micro-hydro system which charges a bank of deep-cycle batteries and they used the inverter mainly to run their washing machine. This particular model of inverter produces a PWM square wave, so it isn’t really suitable for inductive loads like wash­ ing machines. Because of this, I wasn’t terribly surprised when John told me it had “blown up” the washing machine about two years ago. On that occasion, they had sent the inverter to Sydney to be modified so that it was more suited to the task, although just what had been done wasn’t made clear. Since then, it had operated the washing machine without any problems until recently, when it blew the main fuse (about 100A) on the battery bank. The first problem I encountered when I got the beast into the workshop was how to try it out safely. If it could blow 100A fuses (and the user manual claimed it would limit its current drain to 450A!), I didn’t want to connect it straight across the 12V truck battery I planned to use for testing. I ended up jury-rigging a single strand of 16A household fuse wire in the battery positive connection. I then gingerly connected the negative lead to the battery – there was a brief chirp from the undervoltage alarm, a satisfying click as the reverse polarity protection relays changed over, and the fuse stood its ground. So far, so good. However, when I set the inverter to the demand-start override mode, there was a buzzing noise. It sounded like the circuitry was under strain and the fuse immediately vaporised. Figuring that this thing might need a bit more than 16A just to start up, I tried it again with two strands of fuse wire. Again the fuse was vaporised at switch-on. By now, I had proved to my satisfaction that there was a fault and that it seemed to be persistent. It was time to get serious, so I took the lid off. Inside the case was a whopping transformer, over which was mounted a single large double-sided PC board (component side down). There was also a large heatsink on the back of the case for the main MOSFETs, plus a smaller heatsink mounted on the side of the transformer for the secondary-side “power-recovery” MOS­FETs. I pulled the PC board out and began May 2003  43 Serviceman’s Log – continued looking for obvious problems. However, there was no obvious sign of why the thing was eating 100A fuses for breakfast. The next things to test were the MOSFETs. This inverter uses a total of 26 BUK456-50A MOSFETs to drive the primary of the transformer. As well, there are six further MOSFETs, type BUK437-500B, in a “power-recovery” circuit on the secondary side of the transformer. I wasn’t surprised when all the primary-side MOSFETs checked out OK – if any had gone short circuit, the inverter would be drawing significant current even before the demand-start circuit was activated. Conversely, MOSFETs going open-circuit wouldn’t blow the fuse, although this doesn’t mean that none might not have done so. A more likely cause of the problem, especially considering the inductive load provided by a washing machine, would be that one or more of the secondary side MOSFETs had gone short-circuit. These are all mounted, along with their 10Ω gate resistors, on a tiny strip of PC board nestled in a heatsink mounted on the side of the transformer. Some phenolic insulating material was riveted to the base of the heatsink, hiding the MOSFETs, so I drilled out the rivets and began testing. Minor discovery And here I made a minor discovery. All the MOSFETs and gate resistors were fine but one of the gate resistors had not been properly inserted and one of its leads was only just touching the solder that covered the hole it was meant to go through. This was easily fixed but I could not imagine that this was the cause of the fuse-blowing. Indeed, a quick test showed that there was no change in the inverter’s behaviour. At this stage I suspected that the present problem lay in the circuitry controlling the MOSFETs. I considered verifying this by testing the outputs of the MOSFETs without the transform­er connected but since there would now be no feedback from the secondary of the transformer, I wasn’t sure that this would prove anything. 44  Silicon Chip In addition, even if I found a problem here, I’d still have to find the fault in the control circuitry. The main PC board in this inverter is mostly populated by inexpensive, readily available parts, so in the absence of a circuit diagram which might make a deductive approach possible, I decided on a shotgun approach: check or replace everything on the board. I started with the resistors. This approach bore fruit very quickly when I found that R50, a 68Ω 1W resistor, was open cir­cuit. There was no obvious heat damage to the resistor and I expected that this was the fault. However, when I replaced it and re-tested the inverter, its behaviour was the same as before. I then checked every transistor and diode, the leakage and ESR of every electrolytic capacitor and the breakdown voltage of every zener diode. This revealed nothing so I checked the trimpots. The current limit trimpot, P7, is marked 200Ω but meas­ ured nearly 300Ω. I replaced it but didn’t imagine that this would fix the problem. I was right. Next, I started on the ICs. I was able to verify that the timebase, an M706B1 with a 6.5536MHz crystal, was producing a 100Hz square wave. I also verified the operation of two 4N25 optocouplers which provide isolated feedback from the 240VAC output to the control circuitry. The other ICs couldn’t be tested so easily without a cir­cuit diagram, so I replaced them. There were three CD4093s, an LT3524 PWM controller, an LM335 temperature reference and an NE555 timer. Because the fault was not intermittent, and because these are all inexpensive parts, I replaced them all at once without reassembling the thing each time to test it. If that had fixed it, we still wouldn’t know exactly where the fault was. Fortunately for this story, the fault was still there. By now, there really wasn’t anything left on the PC board to check. So could it be a component that wasn’t mounted on the board? Surely that massive transformer couldn’t have a shorted turn, could it? It was easy to test: I connected the output of a 9VAC 1A plugpack to the primary of the transformer and measured the voltage on the secondary. It was only 1.25V AC and the plugpack was pumping out 1.5A. Voila! I phoned Selectronics and they verified that I ought to be getting a much higher output voltage, with an input current of only 150mA at no load. In retrospect, I should have tested the transformer a lot earlier but I had considered it so unlikely to be faulty that I hadn’t bothered. At that point, I declared the inverter a write-off. The price of new inverters has plummeted recently and a new trans­former would cost almost $400. And after all that, it would still be just a PWM inverter. I have therefore advised John and Maria to save their pennies for a sinewave inverter to run their wash­ing machine. This all happened about two years ago and I have since encountered quite a few faulty high-power transformers, mostly in amplifiers. The humid environment here in the tropics obviously SC doesn’t do them any good. 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 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. Single entrance vehicle counter This simple circuit is ideal for counting vehicles as they enter and exit a carpark; eg, at a commercial premises. The circuit counts up when a vehicle enters and down when a vehicle exits and shows the number of vehicles left in the carpark on a digital display. It can count up to 99 vehicles but this could be ex­ tended by cascading additional counters. The sensing circuit consists of two laser sources plus their associated light dependent resistors (LDRs). Normally, light from the two lasers shines on the LDRs which means that the resistance of the LDRs is low (ie, a few hundred ohms). As a result, the output of XOR gate IC1a is low. However, when a laser beam is “cut” by the moving vehicle, the resistance of its associated LDR changes to several megohms. This in turn places a high on the corresponding input of IC1a and so IC1a’s output at pin 3 also goes high. This high lasts for about 2s – ie, the time it takes for the vehicle to pass. www.siliconchip.com.au This output is then transmitted through a low-cost data cable to the counter section. In practice, the two sensors are set up some distance apart, so that the same vehicle cannot activate both sensors simultaneously. The pulses produced by the two sensors as the vehicle passes are not only fed to the XOR gate but are also used to determine whether the counter section should count up or down. The counter section consists of two cascaded 4510B up/down binary counters (IC2 & IC4). It works like this: if Sensor 1 is activated first, the U/D inputs of the counters are pulled high (by a 100kΩ resistor) and IC1a clocks IC2 & IC4 in the up direc­tion (ie, the count is increm­ e nted). Conversely, if Sensor 2 is activated first, the U/D inputs are held low (by LDR1) and IC1a clocks the counters in the down direction (ie, the count is decremented). IC2 & IC4 in turn drive BCD to 7-segment display drivers IC3 & IC5. These then drive two commonanode 7-segment LED displays via 330Ω current-limiting resistors. Finally, 555 timer IC6 is wired as a monostable with a pushbutton switch S2 connected to its trigger input. This can be used to manually decrement the count from any value by just pressing the switch and is provided to alter the count when the unit is serviced. R. Subramanian, Chennai, India. ($45) May 2003  53 Circuit Notebook – continued Position 1 2 3 4 5 6 7 8 9 10 11 12 Test interface for PCs This circuit is a modification of the “Sound Card Interface for PC Test Instruments”, published in the August 2002 issue of SILICON CHIP. The modification increases both the range and the sensitivity of the instrument. In this circuit, the gain of the TL071 op amp ICs has been increased from 10x to 100x (exactly) and the range switch has been modified from six positions to 12 positions, ranging from 20mV to 100V (instead of the previous 200mV to 10V). The input impedance has been kept at 1MΩ, as before. The existing resistive divider chain is largely unchanged except for the original “earthy” 20kΩ resistor which has been changed 54  Silicon Chip TABLE 1 Range 20mV 50mV 100mV 200mV 500mV 1V 2V 5V 10V 20V 50V 100V Multiplier 100 40 20 10 4 2 1 0.4 0.2 0.1 0.04 0.02 here to 10kΩ (R8). The gain of each position is different though. Additional resistors have then been added to the bottom of the divider chain, to make up the additional six positions. The programmable 6-position range switches (S1 and S2) should have their stop washers removed altogether, to allow all 12 possible positions. The two previously unused switch positions that were earthed on the PC board must also be isolated, as these positions are now used. The 20kΩ resistors that were at the earthy end of the range switch (and located at the extreme left and extreme right of the PC board) must be removed and discarded from the circuit. R8-R16 (on my circuit) were added on the back of the PC board in series/parallel around the six new switch positions, starting with R8 (10kΩ) where the previous­ ly removed 20kΩ resistors were located and ending with R16 (200Ω) which connects to earth. The original 27kΩ resistors between pins 6 & 2 of the TL071s have been replaced with R19 (10MΩ) and R20 (100kΩ) in parallel. These two values alter the gains of the op amp stages to 100. In addition, the 3kΩ resistors from pin 2 of the TL071s to ground are replaced with 1kΩ resistors. Table 1 (see circuit) lists the input voltage range for each switch set­ting and its corresponding multiplier value (assuming a x1 probe). Note that although the greatest input attenuation now takes place on the 100V range (instead of 10V), the maximum input voltage capability of the instrument has not been increased – ie, it is still 100V. The only difference is that now you do not have to use a probe set to divide by 10 to measure voltages up to 100V. The existing shielding should work fine but I fitted a shield to the top of the PC board as well, as the unit is now also 10 times more sensitive to noise. In practice, I used a case that had an aluminium top and this was earthed. Finally, some trivia on computer sound cards. First, back­ground noise or hash is unavoidable when using an internal sound card. This noise is worst on the microphone input because of the higher gain required. A low-impedance microphone is less prone to noise but most cheap sound cards have a high-impedance input only and so a low-impedance microphone delivers little signal. Second, sound cards integrated onto the motherboard are generally noisier than PCI-slot cards. An external sound card (eg, a USB card that’s outside the computer case altogether and away from the noise-generating bits) is the best solution but the most expensive. In any case, try to feed the sound card with the highest input level possible (without distortion). This will help keep the background noise to a minimum. Philip Chugg, Launceston, Tas. ($40) www.siliconchip.com.au White LED torch driver circuit The performance of this 6-component white LED torch driver circuit is as good as that of much more complicated circuits. And because there are so few components, it can be built into the space normally occupied by the bulb and reflector. The LED used in the prototype was an ultra-bright type with a 20° beam width. This gives a beam that’s similar in width and brightness to the original incandescent bulb (but with greatly increased battery life). Alternatively, a 50° LED would be pre­ferable for applications such as map reading. The circuit is a blocking oscillator used as a flyback converter. When power is applied, current flows through the 3.3kΩ resistor and turns Q1 on. Positive feedback via the transformer then forces the transistor into saturation. As it does so, the collector current rises linearly (at a rate determined by the inductance of the transformer’s primary), until the base current is no longer sufficient to maintain satu­ ration. Positive feedback from the transformer then cuts Q1 off and the collector voltage rises rapidly until it is clamped by LED1 turning on. The energy stored in the inductor is then dissi­pated by current flowing through the LED. When the transformer current has fallen to a low value, the cycle repeats. As a result, the circuit oscillates at around 90kHz. The transformer is wound on a type 4C65 ferrite toroid measuring 9.4mm (OD) x 3.4mm high (Farnell Cat. 200-604). The tapped primary winding consists of 5 + 5 turns, while the second­ary consists of 10 turns of enamelled copper wire (the wire gauge is not important but the phasing must be correct). The assembly can be constructed “birds nest” fashion and then potted in silicone rubber for protection, leaving just the LED and battery leads exposed. Tony Ellis, Porirua, NZ. ($30) Adding outlets to an irrigation controller Here’s an easy way to expand the number of outputs from a 6-station irrigation controller. The circuit relies on the use of a commercial irrigation controller that’s capable of providing multiple programs during one day. It’s not suitable for controllers that don’t offer multiple programming. To expand the number of outputs, relay RLY1 is used to switch the common returns of the existing six-solenoid valves plus up to five additional five solenoid valves (Sol. Valve 2A6A). The relay is triggered by output 1 and latched by the “Pump” or “Master” valve output that all controllers have (this output is active when any other output is active and is intended to drive a pump or master valve). In operation, the controller is programmed to activate outputs 1-6 on one program cycle and outputs 2-6 on a second cycle, the latter timed to start after the first cycle has been completed. The short time between program cycles causes the latching contacts to release the relay and the absence of a trigger from output 1 on the second cycle prevents RLY1 from turning on. As a result, RLY1 now selects the added bank of solenoid valves via its www.siliconchip.com.au NC contacts. Diodes D1 & D2 isolate the Master valve output from Output 1, while D1, C1 and R1 allow a common 12V DC 20mA relay to oper­ate from the standard 24V AC supply that commercial controllers use. D3 prevents relay switching spikes from damaging C1. Mike Shaw, Nelson Bay. ($45) May 2003  55 By JULIAN EDGAR Big Blaster Subwoofer Capable of thunderous bass, this easy-tobuild subwoofer can handle up to 250 watts RMS and uses a compact 37-litre enclosure. 56  Silicon iliconCChip hip www.siliconchip.com.au www.siliconchip.com.au The driver used in the subwoofer is 10 inches (25.4cm) in diameter, is rated at 125W RMS and uses a voice coil that’s 50mm in diameter. It costs $99 (you need two for this design) and is available from Jaycar. I N MARCH 2003, we presented the “Little Dynamite” subwoofer – an easy-to-build design that used a single 10-inch driver in a 25-litre ported enclosure. At the time, we said that we’d later be describing a larger, higher-powered subwoofer and this is it. This new subwoofer is a flow-on from the previous design, where many different enclosure variations were modelled using BassBox speaker design software. It uses not one but two 10-inch Jaycar drivers, two 25-litre pre-built sealed enclosures and two ports. The two 25-litre enclosures are combined to make one unit with a capacity of 37 litres and we’ll look at just how this is done shortly. The resulting enclosure is longer than before and this has allowed us to use longer ports. This, in turn, has allowed the box to be tuned to a lower frequency which benefits the bottom-end response. In addition, the use of two drivers in­creases the sensitivity and power handling of the finished sub­woofer. Another benefit of the new design is that if you built the previous unit and want to upgrade, you can do so without starting all over again. The enclosure is constructed by marrying two of these pre-made Jaycar boxes together. Each box has an internal volume of 23 litres and is supplied fully carpeted, with the speaker hole precut and speaker terminals fitted. because of the cheapness and ready availability of the pre-built Jaycar subwoofer enclosures (they’re even carpeted!). These en­ c losures are priced at just $59.50 each and at that price, they’re hard to go past – just assembling the materials to build one would cost you more than that. As mentioned, we combined two such enclosures for a usable internal volume of 37 litres. Apart from the low cost of the two boxes, this approach has a number of advantages over building something from scratch: (1) the panels are all small in area and so the stiffness of the finished enclosure is quite high; (2) very little woodworking needs to be done and any that is required isn’t critical in nature (ever tried to cut out the hole for a loudspeaker? – it’s harder than it looks if you want to do a good job!); and (3) the Main Features • • • • • Easy to build 250 watts power handling Suitable for both home and car Versatile wiring allows both 4-ohm and 2-ohm connections Excellent frequency response long, thin design that results is – while unconventional – very suitable for car and home use. On the latter subject, the overall dimensions of 900 x 340 x 250mm allow the subwoofer to fit up against the back seat in most sedans and hatches (we measured a WRX, a 200SX and a Commo­dore – plus several other cars – and the 200SX was the only Design details Despite considering fancy isobaric bandpass designs and all sorts of other exotic types, we eventually came back to a simple bass reflex enclosure for this subwoofer. This was primarily www.siliconchip.com.au The response of the subwoofer, as predicted by the BassBox speak­er design software program. The yellow line shows the response for an in-car environment, while the red line shows the modelled response within a room. May 2003  57 The end panels of each enclosure are marked and then cut out as described in the text. This opening allows air to freely pass along the length of the enclosure and gives room for the long ports. tight one). In a home application, the long, thin design can be easily slipped behind a chair or it can be fitted with feet and placed upright in a corner (the feet are required to give port clearance). As before, the drivers used in the design are the Jaycar CS-2274. These are 10-inch units with 125 watts RMS power han­ dling, a maximum cone movement of 9mm, a voice coil dia­meter of 50mm and a resonant frequency of 33Hz. They cost $99 each. The boxes that are “siamesed” together are the 25-litre (actually 23 litres) CS-2520 sealed subwoofer enclosures. Note that although ported versions of these enclosures are available, it’s better to start with the sealed boxes and cut the port holes as required, to suit the special ports used. The enclosures are first modified by cutting a panel out of the end of each, then joining them together with sealant and nuts and bolts. This makes a strong, airtight enclosure. The ports are the Jaycar CX-2688 flared ports, which can be easily adjusted in length by adding 65mm-diameter plastic pipe. The flared section is used at both ends of each port, reducing the chance of port noise that could otherwise occur as air flows around the sharp inner edge. Optimising the bass The bass response is optimised by tuning the enclosure to 26.5Hz using two 600mm-long, 63mm internal dia­meter ports. Modelled using the Bass­Box software, this combination of tuned box frequency, 37-litre box volume and specified 10-inch drivers, gives an in-car frequency response that is quite strong down to 20Hz. Inside a home, the modelled bass Once the opening has been cut out, align the two enclosures and drill four holes for the attachment bolts (yes, I did drill one hole in slightly the wrong place!). That done, use a sharp knife to cut away a piece of carpet all around the opening. 58  Silicon Chip Using curved corners in the cut-out gives room for the nuts and bolts which will later join the two boxes – and also makes it easier to use the jigsaw. A food can that’s just the right size makes a convenient hole marker. response rolls off by 3dB at 40Hz. However, there is sufficient cone excursion left that this can be boosted to give bass that is audible down to 30Hz. Even more importantly, the use of the twin drivers and long ports allows much louder bass for the same input power: at 100W input power and at 20Hz, the modelled output is 5dB greater than the previous single-driver design. However, as noted before, these drivers are not very sensitive units – so you’ll still want an amplifier capable of at least 100W RMS per channel (more on this later). Building it The first step is to line up the two enclosures end to end. To do this, place the boxes so that their terminal strips are uppermost, then move them apart again. The sides that were touch­ing are the ones that have to be cut open Once the carpet has been cut away, apply water clean-up Liquid Nails (or a similar building adhe­sive) around the opening. As the two box halves are forced to­gether, this adhesive will seal the gap, in addition to providing more strength for the join. www.siliconchip.com.au This view shows one of the four nuts and bolts that hold the two halves of the enclosure together. Notice how the Liquid Nails that has squeezed from the join has been spread along the internal ribs to ensure an airtight seal. so that when they are later joined together, one large enclosure is formed. On each of these sides mark a line 50mm in from the top, back and bottom and 65mm in from the front edge. That done, drill a hole in each panel to take a jigsaw blade and then cut out the panels, following the lines that you have marked. Note that this will leave a “rib” around each of the openings. This rib not only helps strengthen the final assembly but also accepts the connecting bolts. To join the boxes, first hold them in perfect alignment, then drill four holes – one through each corner of the ribs. That done, good-quality nuts, bolts and washers can be used to rigidly fasten the two enclosures together. However, before you do bolt them together, remove a strip of carpet from around the opening and then run a bead of water clean-up Liquid Nails (or some other similar sealant/ adhesive) around the join. Make sure that you don’t use too much or it will squeeze out from the outside of the join and look ugly. The carpet that’s still present between the surfaces will compress as you tighten the bolts, so go right around them three times, tightening them up. After that, you have to let the adhesive set – preferably overnight. The ports are positioned towards the back of the enclosure with their openings at either end (one at the top and one at the bottom). They require an 85mm-diameter hole and this should be positioned 40mm in from the box edges. The flared plastic vents are connected together using cheap 65mm-diameter plastic pipe (see text). This makes it easy to construct ports of the required size and flow characteristics. that they don’t interfere with each other). The first step is to use a round or half-round file to remove the sharp inside edge from the preformed flared ports (ie, at the non-curved ends). This is done to eliminate any sharp steps between the flared vents and the Cutting the ports The next step is to cut the holes for the ports. Two are used – one at each end of the enclosure. Note that these ports must be at the back of the box so that they clear the speaker magnet assemblies, one positioned at the top and one positioned at the bottom (so www.siliconchip.com.au The sharp “steps” that would otherwise occur in the transition from the flared port to the plastic pipe are smoothed using a half-round file and some fine sandpaper. plastic pipes when they are later joined together. Finish off the job using some fine sandpaper. With these edges smoothed, cut each plastic pipe to the correct length (about 520mm) so that when both flared ends are pushed firmly into it, the total length of each port is 600mm. Don’t be tempted to glue the flared vents to the plastic pipe at this stage, though – that step comes later. Once the ports have been temporarily assembled, spray some black paint inside them to hide any scratches that you have made and to hide the white plastic. The next step is to cut the holes for the ports. An 85mm diameter hole is ideal – we drew the two cutouts with the help of a can of food that conveniently had the right diameter. The holes should be positioned with their edges about 40mm in from the edges of the box. If you place the port opening furMay 2003  59 How To Make The Brackets To Hold The Ports In Place (1) Start by cutting off a surplus length of the 65mm plastic pipe. It should be about 30mm wide. (2) Use a hacksaw to make a long­ itudinal cut along the 30mm pipe section. (3) Use a heat-gun to soften a little less than half the diameter. Flatten this piece out (careful – it’s hot!). ther in from the edge, you will find it easier to miss the internal rib with the long ports – but you’ll also be getting closer to the magnet assemblies of the woofers. A trade-off is to mark where the plastic pipe touches the internal rib and then soften this area on the pipe with a heat gun (done with the port out of the box!). It will then be easy to compress the port pipe a smidgin at this spot to give better rib clearance. The port volume and flow changes will be only tiny but the tweak makes it all a bit easier to fit everything in. Gluing these long ports into place is not sufficient to secure them – you will also require brackets to hold them rigidly inside the box. An effective bracket can be easily made by first cutting off a 30mm surplus length of the 65mm-diameter plastic pipe. That done, square the ends and then make a single cut longitudinally along the section. Next, using a heatgun, soften the pipe to one side of the cut and then bend that section outwards (use oven mitts as the pipe is hot!). With a bit more heatgun work, you should end up with a bracket which wraps itself at least halfway around the port. The other end of the bracket is attached to the inside of the enclosure using short self-tapping screws. You will need one bracket for each port and they can be glued to the port tubes using Liquid Nails (or similar) building adhesive. In addition, a generous amount of adhesive should be placed around the back of each flare that faces out of the enclosure, while additional adhesive is placed on the ports where they sit on the internal rib. Connecting The Drivers The two woofers can be driven in parallel from one amplifier or they can be driven separately by a stereo power amplifier but there are a number of traps here. If you get it wrong, you could blow your amplifier. If you want to drive the woofers in parallel, they will constitute a 2Ω load. Many car subwoofer amplifiers will happily drive a 2Ω load, so that is one option. A second option is to use the two channels of a stereo amplifier to drive each woofer separately (4Ω loads). Or, if you have a 4-channel car amplifier which can be bridged to drive 4Ω loads, then you can use that to again drive each woofer separately. What you must not do is connect a stereo amplifier in bridge mode to drive the two 4Ω woofers in parallel; ie, a 2Ω load. In this case, the separate “bridged” amplifiers will each “see” a 1Ω load – most amplifiers cannot drive a 1Ω load and will blow fuses or be seriously damaged. When running the subwoofer in 2Ω mode, simply connect the two drivers in parallel. To do this, connect the power amplifier to one set of the 60  Silicon Chip speaker terminals and then run more cables to the other speaker terminals, making sure that you connect posi­tive to positive and negative to negative. An amplifier driving a 2Ω load will deliver more power than it does into a 4Ω load. 4-ohm load If you want to configure the sub­ woofer as a 4Ω design, you’ll need a 2-channel amplifier. One channel connects to one set of terminals on the subwoofer, while the second channel connects to the other set. Note, however, that you must feed a mono signal to the subwoofer amplifier; eg, by using a Y-connector lead on the input. In other words, both channels of the amplifier must be driven by the same signal. If you have a single subwoofer output from a head unit or other source, this should be fed into one end of the “Y” cable which then connects to each amplifier channel. Make sure that you get the phasing right – ie, connect positive to positive and negative to negative. If you have the phasing to one of the drivers reversed, there will be a distinct lack of bass. Finishing off Once the ports are in place, acrylic speaker damping material can be cut to size and stuck to the inner walls of the box. We suggest 350 grams/square metre material (Jaycar AX-3690) but any similar material is fine – eg, acrylic quilt wadding. Be careful that you don’t block the entrances to the ports www.siliconchip.com.au (4) Twist the tail to form a mounting foot for the clamp. Each port is held in place by attaching one of these clamps to the centre rib of the enclosure. – in fact, it is wise to be quite sparing in your use of the material around the port entrances. Next, solder some heavy-duty speaker cable to the terminals and attach the other ends to the screw terminals on the drivers. Keep this wiring completely separate – each pair of terminals connects to its nearest driver. Be sure to connect the positive terminals to the positive terminals on the drivers; similarly, the negative terminals go to the negative speaker terminals. Once the wiring has been completed, the drivers can be slipped into their precut holes and the locations marked for their mounting screws. That done, remove the drivers and drill small diameter pilot holes for the screws. If you’re fitting metal grilles, you should also drill the holes for The ports are sealed to the panels by applying Liquid Nails from inside the box. It’s a lot easier if you have small hands, so at this point a helper may need to be press-ganged into action. their mounting lugs and attach the T-nuts under the front panels at this point. Finally, reinstall the drivers and fasten each into place using eight coarse-thread MDF screws. As before, the carpet will compress as you tighten the screws, so go around each driver and re-tighten it at least three times. Phasing This step is very important in this It is important that there are no leaks around the ports, so make sure that the sealing is well done. Any leaks here can cause whistles. Similarly, there must be no leaks around the edges of the drivers. www.siliconchip.com.au design – apply a 1.5V battery across each set of external terminals in turn (positive to positive and negative to negative) and check that the corresponding woofer cone moves forwards in each case. If a cone moves backwards when the battery is applied, open up the enclosure and swap the wiring connections to the relevant driver. The next step is to connect the subwoofer to an amplifier (see panel). This view shows the two ports in place inside the enclosure. Note the supporting brackets – these are in addition to adhesive which is placed directly on the ports to secure them to the internal rib. May 2003  61 The final steps before screwing the drivers and their grilles into place are to solder the cable to the terminals and then place the acrylic speaker filling along the internal walls. Make sure that the port entrances can’t be blocked – hold the acrylic filling in place with a few dobs of adhesive. Parts List As can be seen in this overall view, the ports extend into the opposite ends of the enclosure. The clearance between the ports and the magnets of the drivers is quite tight – make sure that they don’t touch. Once it’s connected, begin by driving the unit quite gently. Moisten a finger and move it around the edge of each driver, to check for any air leaks around the frames. Now do the same around the edge of each port – there will be air movement within the ports but there shouldn’t be any around the edge of the flares. Next, listen carefully for any buzzes, rattles or whistles. If everything is OK, wind up the wick a bit more. Naturally, during this test procedure, all other speakers should be disconnected so that you’re just listening to the subwoofer. This will allow you to easily identify any problems. A good test is to drive the subwoofer from the soundcard in your PC and download some free audio frequency generator software from the Internet – eg, the NCH Tone Generator from www.nch.com.au/tonegen/index.html 62  Silicon Chip 2 10-inch Response Subwoofers (Jaycar Cat. CS2274) 2 25-litre sealed subwoofer enclosures (Jaycar Cat. CS-2520) 1 acrylic speaker damping material (Jaycar Cat. AX-3690) 2 10-inch protective grilles (Jaycar Cat. AX-3522) 4 flared speaker ports (Jaycar Cat. CX-2688) 4 2-inch x 0.25-inch bolts, nuts and washers 1 150cm (approx.) length 65mm-dia. plastic pipe 1 0.5m-length of heavy-duty speaker wire 1 tube building adhesive; eg, Liquid Nails 16 speaker attachment screws Alternatively, you can just download the software and burn some test tones onto a CD so that the subwoofer can be checked in a car. Using the software, you can generate sinewave signals at all sorts of audio frequencies. The first use for this is to determine the range of frequencies that are audible. In the case of the prototype (tested in a 5 x 4-metre room), there was strong bass down to 40Hz and audible bass at 30Hz. It was also clear that the cones became dramatically unloaded at about 25Hz – the exact frequency depending on the power being fed to the sub-woofer. That means that a subsonic filter should be used if the subwoofer is going to be driven hard. The other use of the software is to check for peaks and troughs in the frequency response. This can done by doing a slow sweep across a range of frequencies – eg, from 150Hz down to 25Hz. However, these peaks and troughs will also be affected by the listening environment. In the case of the prototype, there were minor peaks at 67Hz and 100Hz. Note, however, that high SPLs (sound pressure levels) shouldn’t be maintained when using sinewave signals. In other words, be careful that you don’t wreck the drivers by driving them or the amplifier into distortion while doing this testing. Conclusion The use of the pre-built boxes really does make this design dead-easy to make – you should be able to put it together in just a few hours. The end result is an impressive subwoofer, especially considering its cost and overall size. SC www.siliconchip.com.au NO FRILLS PICAXE PROGRAMING KIT NEW KITS OF THE MONTH PIC-AXEALL KIT: This development kit can be used to program or run most PICs and all PICAXE Chips plus other chips. Features includes 28 pin chip socket, large tinned copper pads with component holes, low cost all-in-one programmer, simple and easy to assemble. Kit includes a small PCB, Piezo speaker, 5.5V Plugpack and all on-board components. For more information and softwares check the following website www.picaxe.co.uk. (PAE01)$12.50 VALVE PRE-AMPLIFIER KIT Bring back the warmth of that old valve pre-amp with this simple to build kit. It requires a single 9Vac or 9-12dc supply, The single PCB can be cut to separate the power supply section of the circuit. Kit includes power adaptor, PCB, and all onboard components including RCA connectors & valve. k188A $33 PICAXE-08 CHIPS The PICAXE processors use a R.I.S.C (Reduced Instruction Set Controller ) system, & are easy to program. It is like a Basic Stamp clone in single chip. PICAXE-08 IC: (PIXAXE-08) $3.90 PICAXE-18A IC: (PICAXE-18A) $9.40 PICAXE-28A IC: (PICAXE-28A) $14.40 Lots of info available on the Internet. EXPERIMENTERS BREADBOARD The ideal way to prototype electronic circuits without solder. $9... (bb301) UHF REMOTE CONTROL / UHF REMOTE CONTROLLED SIREN: This very loud siren is remotely controlled by a small key-chain transmitter: Press once for ON press again for OFF. The siren contains two PCB's, 1 x UHF Receiver PCB and 1 x Siren PCB. There are two wires interconnecting these so the siren-UHF receiver can easily be separated to serve as stand-alone units. The Motorola encoder IC used in the transmitter is an MC145026 and its matching MC145028 is used in the receiver. These are both readily available. The whole kit is supplied in its original packing and it also includes a 12V cigarette lighter lead, and suitable Australian power adaptor. The unit is new and guaranteed except for the batteries. In a few units tested the 12V lighter battery in the transmitter was OK but the 8.4V Nicad back-up battery in the siren needed charging. Siren-RX: 30M range, 6-13.8V operation, 1mA stand-by, 120dB output, 500mA consumption when on. SYDNEY 2000 OLYMPIC VIDEO: "16 Days in September - Games Highlights of the XXVII Olympiad" Intro by Ian Thorpe. Juan Antonio Samaranch said "I am proud & happy to proclaim that you have presented to the world, the best Olympic Games ever." It wasn't just the IOC's opinion. Sydney 2000 didn't just receive universal acclaim, it was the games that restored the people's faith in the Olympic movement. A global entourage of 11,000 athletes from 200 nations, were assembled in Sydney, for the quest of Olympic performance supremacy, & the medals that confirmed it. From the glorious backdrop, of Sydney Harbour for the 1st Olympic triathlon, to the WARNING!!! These magnets are so strong they are focus on "Torpedo" the dangerous!!! new neodymium rare earth magnets. biggest star in the pool. Dew to popular request we have introduced some The achievements of smaller magnets to our range similar to those used in Cathy Freeman, Ian Thorpe, magnetic therapy etc. 20 X 10mm$6.00... 10 X Michael Klim, Susie O'Neill, 5mm$1.20... 10 X 3 mm$0.70... 7 X 3mm $0.55... 7 X Grant Hackett, Kieren Perkins, Michael Diamond, & our 2.5mm $0.45... 3 X 2mm $0.25... 3 X 1.5mm$0.20. successes are captured here, in tribute to our outstanding athletes. All this and more as we re-live NEW PRODUCT BARGAINS those 16 Days in September. $9.90 0 $ 12VAC PUMP <---BATTERY---> < SOLAR CELL > - + These kits uses pre-built and pre-aligned (pre-tuned) UHF modules, this means easy assembly and no fiddly tuning or mucking around trying to make it work. We tested these kits at 1.8 Kilometers in an industrial area and we were surprised at the strength of the signal. The 4 push buttons on the transmitter kit can be removed and replaced with a with a connection carrying data from a PC or other device (5V logic). It will accept any single or multiple button press or BCD data, with a BCD decoding chip attached to the receiver kit it could control up to 16 outputs. Kits includes PCB, UHF module and all onboard components. Transmitter K190A $22 Receiver K190B $32 .5 6 2 WIRE JUMPER PACK This 79pc jumper pack contains multiple lengths of pre-striped $7... (wj59) + LONG RANGE 4 CHANEL UHF TRANSMITTER & RECEIVER KITs 12V 7AH SEALED LEAD ACID BATTERY Why spend a small fortune on a new water feature when you could build your own. Comes complete with 2 4 0 V p o w e r a d a p t e r. Pumps a head of up to 500mm at 300L p/h via a 8mm outlet. (PP1) - HOW ABOUT A COMPLETE SOLAR LIGHTING SYSTEM FOR YOUR CAMP, CARAVAN OR WEEKENDER: There are 4 main components to this system, 2W Solar Panel, Switching Solar Regulator kit, Battery and 2 X 10 LED Lamp Kits. This combination of solar panel, charger and battery will power 1 of the LED lamp kits for over 7hrs with only 5hrs of sunlight. Central Australia receives around 10 hrs per day. (SL2W): $99 UPGRADE TO A BIGGER PANEL!!! For just $25 more. You can upgrade from a 2W to a 4W panel in your Solar Lighting System . (SL4W) total price.$124 9 $3 LOTS OF OPTICAL BARGAINS HIGH POWERED LEDS, LASERS POINTERS & LASER DIODES ST JU 6.50 $1 BULK LED SPECIAL 20 or more red LEDs for $0.60ea 20 or more white LEDs for $1.70ea 10cD White...$2.00 ea Red...80c Yellow ...70c Green...$2.10 Blue...$2.20 UV LED's ..$1.60 DON'T PAY A SMALL FORTUNE MINI FOG MACHINE Great for water features and humidifies and ionizes the air. This safe low voltage fogger is fully submersible and comes complete with a 30W, 24vac mains power adapter. It uses ultrasound to agitate the water and generate fog. Features include 12 super-bright LEDs that change colour. Available at the end of May These fantastic little devices will hold much more data than a floppy disk and have much better data retention. How many times have you lost data on a corrupted floppy? Or the file is too big to fit a floppy disk? 16M... $24: (16md)... holds more than11 floppies. 32M... $29: (32md)... holds more than 22 floppies. 64M... $49: (64md)... holds more than44 floppies. 128M... $82: (128md)... holds more than 88 floppies. of kits and surplus electronics to hobbyists, experimenters, industry & professionals. www.oatleyelectronics.com Suppliers Orders: Ph ( 02 ) 9584 3563, Fax 9584 3561, sales<at>oatleyelectronics.com, PO Box 89 Oatley NSW 2223 major credit cards accepted, Post & Pack typically $7 Prices subject to change without notice ACN 068 740 081 ABN18068 740 081 SC_MAY_03 by Julian Edgar U S manufacturer Lumileds Lighting has developed a whole new breed of LEDs – they use new technology, they look quite different and they produce more light than we have ever previously seen coming from a LED. The new LEDs are branded Luxeon. It is almost impossible to photograph either of the Luxeons in action – and do their amazing light output justice. Here the current to the 1W LED has been reduced, the camera has been placed well off-axis – and bad lens flare has still occurred. 64  Silicon Chip The manufacturer’s publicity suggests that the Luxeon LEDs are the start of a lighting revolution – and to an extent we agree. “Luxeon is today’s brightest solid-state light source, producing 10-20 times the output of a standard LED lamp,” suggests the company. “With a white source effi- cacy of 25 lumens/watt]. . . Luxeon is a realistic source for general and directional lighting.” Lumileds claims that the LEDs can be integrated into light fixtures – after all, with a rated life of 50,000 hours (other data suggests “up to 100,000 hours”), the ‘bulb’ probably never needs to be changed. Their publicity material shows the LEDs being used for internal commercial lighting and outside architectural lighting, in addition to emergency and portable lighting. However, Lumiled’s engineers are a little more conservative. “Today there is really no such thing as a commercial ‘solid state lamp’ for use in illumination,” they state in an IEEE paper. “However… differences are beginning to appear in the technologies used for low-power LED indicators and the high-power LED light sources that will evolve into lighting sources.” So what are the new technologies? And do the Luxeon LEDs live up to their publicity hype? We won’t be able to make a judgement on their life for nearly six years www.siliconchip.com.au The Star/O is a 1W LED which has a built-in collimator to provide a focused beam. The resulting package is extraordinarily bright and easy to use. (and only then if they are on continrelate mostly to dissipating heat – a lower than a conventional LED. A uously!) but having bought two difhigh thermal resistance and an epoxy high-temp soft gel inner encapsulant ferent versions of the Luxeon LEDs, limited to a maximum temperature optically couples the LED chip to a we can state categorically that these of about 120°C results in a maximum plastic lens. little beasties are simply awesome. input power of about 0.1W. (Consider In addition, Luxeon LEDs use InGaN Phenomenal. Bright enough to a 5mm white LED that might have a (Indium Gallium Nitride) materials blow away any thoughts you constructed in a so-called might still have that LEDs are ‘flip-chip’ structure that good only for panel indicators, The Luxeon gives the following benefits: LEDs are so bright not for illumination. The bulk of the light that they are officially cat egoThe LEDs can provide so much rised is extracted through the as a Class 2 Laser Prodlight that – with the right optics substrate rather than beuct. You should take great care – a beam with a reach, brightness ing attenuated through a not to look directly into the and whiteness can be created that partially absorbing layer as beam and in any applicatio n tha t is made of the LEDs, shi puts a battery-operated handheld occurs with a conventional elding should be provided spotlight to shame. Yes, that so that end users are similarly protected LED; . When working with the LED make sure bright! ♦ Metallisations within that the LED cannot be ina dvertently turned on when you the LED structure give low are looking closely at it. The technology resistance contact to the GaN Conventional 5mm LEDs are and act as excellent optical not very suited to high light outputs – reflectors; maximum current of 20mA at 3.5V – understandable since their packaging ♦ The thin current-spreading that’s 0.07W). was never designed for this purpose. layer in a conventional LED is reThe Luxeon LEDs use completely These LEDs use a small chip mountplaced with a thick, opaque metallic different packaging. A larger LED ed in a reflector cup, with the entire contact, allowing increased current chip is used and it is mounted on an device encased in an epoxy which is densities; aluminium or copper slug, resulting also shaped to act as a lens. ♦ Wire bonds over the top of the in a thermal resistance about 17 times The disadvantages of this approach device are not used, reducing the ab- Safety! www.siliconchip.com.au May 2003  65 A conventional 5mm LED package has a high thermal resistance and temperature-limited epoxy which help limit the maximum input power. [Lumileds] sorption of light within the package; ♦ The LED can be scaled-up in size without electrical resistance or light extraction losses disproportionately increasing. Lumileds state that the ‘flip-chip’ approach is 1.6 times as efficient as a standard power LED, both over the whole range of visible wavelengths and with forward currents of 251000mA. The Luxeon LEDs use a phosphor-converted approach to generating white light – a blue LED is used to pump visible light-emitting phosphors integrated into the package. However, in the Luxeon white LEDs the phosphor granules are applied in a thin conformal layer – rather than being heaped into place – which gives better colour accuracy. Electrostatic discharge (ESD) protec- The Luxeon high power LEDs use packaging which is much better at shedding heat. A more efficient internal architecture is used and ESD protection is incorporated. [Lumileds] tion is built into the LED – shunt diodes are located within the submount that provide electrostatic protection from up to 16kV (human body model) or 2kV (machine model). Two different groups of LEDs are available: a 1W device that uses a 1mm x 1mm chip and an incredible 5W LED that uses a 2mm x 2mm chip. The 5W LEDs have internal Lumileds’ performance records of a drive current density of 50 amps per square centimetre, an efficiency of 44.3 lumens/watt and a flux output of 187 lumens. The 1W Star/O One of the most useful packages is the Star/O. This is a 1W Luxeon LED mounted on a 25mm square piece of aluminium-core PC board. A collimator (focusing lens) constructed from optical grade acrylic results in a beam narrower than would otherwise be obtained. Wiring connections are made to solder pads placed on the upper surface of the PC board, with the positive connection represented by a small dot or ‘+’ sign. The LED assembly can be mounted by small machine screws placed through the U-shaped cut-outs provided on opposite corners of the PC board. The beam produced by the optics has a viewing angle of 10° (defined as the off-axis angle from the centreline where the luminous intensity is half of the peak value). On axis, the 1W Star/O has a typical brightness of 180 Candela. No, that’s not a misprint: 180 Candela (or 180,000mCd….)! The LEDs use an aluminium heat-conducting PC board. The The collimator is a Total Internal Reflection design made wiring connections are on the other side, allowing the LED to from injection-moulded acrylic. It has an optical efficiency of up to 90 per cent and can be used with both be easily mounted on a heatsink. 1-watt and 5-watt Luxeon LEDs. 66  Silicon Chip www.siliconchip.com.au This heatsink is too small for continuous use of the 5W Luxeon LED – although it’s fine for the short, infrequent use that is being made of this LED. Thermal management of the heat dissipated from the back of the LED is critical to longevity. The 5-watt Luxeon Star V Portable produces a stunning amount of light. It is mounted on a hexagonal-shaped aluminium PC board with multiple mounting holes and connection solder pads available. It must not be operated without being mounted on a heatsink. The absolute maximum ratings for touch – and that’s in an ambient of frightening. Frightening not only bethe 1W units are 350mA forward curonly 24°C. cause of the way that you need to be rent (typically at 3.4V) and a PC board careful to avoid blinding yourself, but At the time of writing the Star/O temperature of 105°C. If that temperaalso because its thermal demands are costs $32 from the on-line shop of the ture raises some eyebrows, stay tuned, very high indeed. Australian Alternative Technology because we’ll come back to thermal Association (www.ata.org.au). Importantly, the 5W white Luxeon management in a moment. also has a much more limited life than Considering the number of convenOut of the box, the Star/O LEDs the 1W design – the 5-watter it is rated tional 5mm white LEDs required to are ideal for directional lighting at only 500 hours. such as torches, reading lights This is in contrast and so on. with the other colours As with conventional LEDs Although the assembly is far available in 5W versions , the forward current throu gh the LED must be regulated bigger than a conventional LED, (green, blue and cyan), . The resistance and powe r of the resistors used to limit the fact that it’s a ‘complete packwhich are all rated at up the current flow are select ed using conventional LED des age’ incorporating the light source, to 100,000 hours. ign procedures, although of optics, solder pads, heatsink and The LED is sold in course the resistor powe r dissipation will often be much a mounting plate make its applia hexagonal aluminihigher than is normally enc ountered! Variations in typ cations easy to implement. um PC board package ical values from LED to LE D must be catered for in the When powered up, the LED design, (shaped in this way to so it’s best to measure act ual cur casts a superbright beam of light allow easy side-by-side ren t val ues wit h the individual Luxeon LE Ds that are being used. Lu – in the room in which I am now stacking) with multiple xeo n technical literature sugges ts that DC (rather than pu working, with the Star/O sitting screw cut-outs and also lsed operation) is the most sim on my desk pointing upwards, a multiple solder pads. ple and efficient way of dri ving LEDs, with pulsed opera pool of light about one metre in Centre-to-centre across tion used only when the LEDs diameter is thrown onto the ceil- need to be dimmable. the mounting cut-outs is ing. The light is clearly visible, 19mm and the assembly even with the room brightly lit stands 7.5mm high. by two windows… The LEDs have a forgain the same output (let alone the When viewed on-axis The LED is ward current of 700ma at a forward difficulty of focusing the resulting uncomfortably bright, even from 10 voltage of typically 6.8V. The maxlight) we think that the Star/O is good metres away – again, that’s inside imum rated temperature of the PC value – despite the sudden intake of with daylight streaming in thorough board is 70°C, however a heatsink breath that occurs whenever someone windows. temperature of less than 35°C is refirst sees that price! quired to retain a 90% lumen output However, despite the presence of after 500 hours. the inbuilt heatsink and the LED’s high 5W Luxeon Star V Portable efficiency, it takes only a few minutes And keeping that PC board temIf the 1W Luxeon is impressive, of operation at its peak 350mA before perature down is damn hard, let us then the 5-watter is perhaps a little the aluminium PC board is warm to tell you! Company literature says, Driving the LEDs www.siliconchip.com.au May 2003  67 “We do not recommend lighting a is kept low. any optics the LED will dimly light a 5W Luxeon Power Light Source for whole room at night; suspended from The Luxeon Star Portable comes more than a few seconds at its rated a high ceiling it would be completely without focusing optics, however the current without first mounting to appropriate as a room illumination if collimator used in the 1W Star/O is an appropriate heatsink” – they’re matched with individual spot lighting available separately. certainly right! for reading, etc. With the use of appropriate glue, it While the 1W LED can be used in With the collimating optics in place, is easily mounted on the more powcool ambient conditions (especially the effective brightness is of course erful LED. on a non-continuous basis) without much higher; we then went a step The acrylic optics can be used further heatsinking, that is certainly further and matched this combination without problems on the 5W not true for the 5W LED. with a coated glass lens to give an extraordinary bright spotAn appropriate recommendlight beam. ed heatsink is a finned extruded did aluminium design with a flat The 5W Luxeon Star V Portere wh gy, olo hn king tec So with such ground-brea face dimension 44mm x 44mm able costs $75 from the ATA y pan com e Th m? e fro the Lumileds company com and with six fins each 38mm while the collimating optics to the Hewlett-Packard long. are $6.50 each. can trace its antecedents of (OED). OED became part The heatsink that we used was Optoelectronics Division divided from Hewlett-Pack Conclusion about half this size and proved Agilent when Agilent was hting was formed Lig s led mi Lu 99 suitable for use when the LED The Luxeon LEDs redefine 19 in n ard, and the ture. ven t join s was used with a low duty cycle the current state of the art in ilip Ph and t as an Agilen (ie, was switched on only for short LED technology. bursts). While the relatively short With the LED continuously life of the 5W Luxeon is disLED; the heat is conducted through running at maximum rated current for appointing (but it is still much longer the rear aluminium PC board, with three minutes, the heatsink temperathan most incandescent bulbs used the optical surface of the LED (on ture became uncomfortably warm – a in torches and the like) and careful which the collimator sits) staying near bigger heatsink is essential! thermal design needs to be carried ambient temperature. In continuous use it’s worth again out when using the LEDs, the sheer And so what is the performance remembering the point that life will brilliance of these devices simply has like of the monster LED? Without be prolonged if the LED temperature to be seen to be believed. SC Lumileds? MicroZed.com.au PHONE (02) 6772 2777 9-5 FAX (02) 6772 8987 24 Hours There is more to PICAXE than just the chips. MicroZed have the whole lot on their shelves 68  Silicon Chip www.siliconchip.com.au PRODUCT SHOWCASE USB PIC Programmer with the lot . . . In the April 2003 issue of SILICON CHIP, Jim Rowe looked at several PIC programmers from Kits-R-Us. While his overall impression was ‘very favourable’ he found a few little ‘niggles’ with the kits. Peter Crowcroft of Kits-R-Us took the criticisms on board and has come up with a new PIC programmer which not only corrected any problems but can also program all DIP Flash PIC’s. No external power supply is needed as it gets its power from the USB port. The software interface and design is by Tony Nixon, who readers may remember designed the astoundingly popular Programmable Ignition Sys- USB cable suitable for your computer. The kit is available in Australia from Ozitronics – price is $110.55 including GST and pack and post. tem back in the March 1996 and revised in the June and July 1999 issues. The kit is complete with the 28-pin ZIF socket as shown above right. The only thing you will need to supply is a Altronics’ PortaPAL kit “Power” from Jaycar Altronics will shortly be releasing their long-awaited kit for the “Porta-PAL” Portable PA System described in the February and March 2003 issues of SILICON CHIP. The kit will be short form; that is, it will have all the amplifier electronics including PC boards, components and silk-screened front panel/chassis but will NOT include the speaker box components (timber, carpet, corner protectors, top hat), nor the speaker itself, power supply or battery. (The power supply kit, Cat K1695, is $19.95). Altronics say they have gone down this route to make the kit as versatile as possible. The Altronics PortaPAL kit (K-5360) will sell for $179.95 inc. GST and should be available from Altronics stores or via mail order from the beginning of May. Looking for “free” power from the Sun? Or maybe 240V when you don’t have mains available? These products from Jaycar Electronics might help. First is a solar charger which opens out like a book and can charge a variety of common rechargeable devices such as mobile phones, digital cameras, hifi gear, etc at a charge rate of about 200mA in good sunlight. 3.6, 6, 9 and 12V outlets are provided. It can also house 4 x AAA rechargeable cells (not included) to become a stand-alone power source. This sells for $59.95 (Cat MB3590). Second is a range of 12V DC to 230V AC inverters. In the “Powertech” range are 400W, 600W, 800W, 1000W and 1500W models, with retail prices ranging from $199.50 to $749.50. All have electrically isolated outputs for safety. Outputs are modified sinewave so they Contact: Kits-R-Us Website: www.kitsrus.com Ozitronics Website: www.ozitronics.com will power most appropriately-rated equipment. The solar charger and inverters are available from Jaycar stores and some dealers or via mail/ website order. Contact: Jaycar Electronics PO Box 6424, Silverwater NSW 1811 Ph: (02) 9741 8555 Fax: (02) 9741 8500 Website: www.jaycar.com.au AUDIO MODULES broadcast quality Contact: Altronics Distributors PO Box 8350, Perth Busn. Centre, 6849 Ph: (08) 9428 2188 Fax: (08) 9428 2187 Website: altronics.com.au www.siliconchip.com.au Manufactured in Australia Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 9476-5854 Fx (02) 9476-3231 May 2003  69 Dedicated automotive multimeter from DSE Dick Smith Electronics have introduced a new multimeter to their already extensive range – this one specifically intended for automotive use. The Digitor Q1585 meter offers a comprehensive range of tests and checks including RPM, duty cycle, dwell, temperature, frequency, continuity and diode check, along with the “expected” AC/DC voltage, AC/DC current and resistance measurements. It can handle any number of cylinders from 2-8; RPM to 12,000 and frequency to 32kHz. DC voltage is auto ranging from 32mV to 1000V, (ACV to 750V) while current measurements are from 320µA to 10A. Along with fully-shrouded “standard” multimeter probes, included are a set of alligator clip probes, a thermocouple probe for temperature sensing and an inductive RPM clamp, eliminating the need to break into high tension leads. The standard probes are housed in the back of the anti-shock outer case. The large-display LCD also includes a bargraph and a “data hold” function is included. The normal price of the meter is $135.00 but for a limited time is available for $99.94, a saving of $35+. It is available through all DSE stores, mail/web order or selected resellers. Contact: Dick Smith Electronics PO Box 500 Regents Park DC NSW 2143 Ph: (02) 9642 9100 Fax: (02) 9642 9111 Website: dse.com.au 70  Silicon Chip TVS for HID lighting This normally wouldn’t get a mention here but we thought it timely given the feature on High Intensity Discharge (HID) lighting in this issue. Vishay has announced several new devices for transient voltage protection in HID and lighting ballast applications, from 220V to 540V depending on package. The single-chip TVS devices are said to have improved surge capacity, lower leakage currents and improved clamping for high-voltage applications. Contact: Vishay Intertechnology Inc Ph: 0011 1 610 644 1300 Website: vishay.com Marantz Golden Jubilee Saul Bernard Marantz founded the Marantz Company in New York in 1953, just five years after CBS introduced the first long-playing (LP) record. As a record collector and amateur musician, he felt that commercial amplifiers were simply not good enough – so he built his own. Strangely enough, Saul Marantz' first commercial product, the Model 1 Mono Preamplifier, included an input for TV audio – thus pre-empting home theatre by half a century! Today Marantz is part of Japanese company D&M Holdings Inc (the “D” part is Denon), which tends to specialise in mainly high-end audio and home theatre equipment. Marantz is distributed in Australia by QualiFi Pty Ltd and is available at leading hifi specialists. Contact: QualiFi Pty Ltd Ph: (03) 9543 1522 Website: qualifi.com.au Sydney public transport to get Smart (card)? A project has been announced for Sydney’s public transport system which will deliver the first major roll-out of Smart Cards to the Australian public. The con-tactless card will ease queues and delays on all public transport methods in the greater Sydney area. The NSW announcement, along with decisions on the Brisbane City Council’s and WA transport projects expected to be made shortly, will expedite the development of interoperability standards currently taking place at Standards Australia. The Standard has included input from all State and Territory governments, and members of Intelligent Transport Systems and Asia Pacific Smart Card Forum. The announcement also flags great opportunities to leverage the system for other applications such as parking, tolling, vending and retail outlets. Contact: Asia Pacific Smart Card Forum Phone: (02) 6247 4655 email: dstanley<at>aeema.asn.au World’s smallest player/referee transmitter Have you noticed the number of players, referees, etc who are now “wired for sound” in the big games shown on TV? Ever wondered where they hide their radio transmitters? A Canadian company, VFGadgets Inc, markets the world’s smallest broadcast-quality transmitter. It can be used by the TV networks to broadcast player’s, athlete’s, or official’s audio at any event. The transmitter has a facility for a microphone to be integral or lavaliere mounted. The transmitter has comp-anding, pre-emphasis and provides high quality broadcast audio. It measures just 52mm x 32mm x 13mm) and weighs only 28g. The QT- 256 has an incredibly small lavaliere microphone only 2mm in diameter. Power output is 100mW, while the frequency is selectable from 690-750Mhz. And yes, they are rather expensive – at about US$1950 each! Contact: VFGadgets Inc 23 Elmer Avenue Toronto, Ontario Canada M4L 3R6 Tel: 0011-1-416-686-1452 Website: vfgadgets.com 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 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. BitScope is an Open Design Digital Oscillos-cope 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 TeleLink Communications Tel:(07) 4934 0413 Fax: (07) 4934 0311 WebLINK: telelink.com.au 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 · Hifi upgrades & modification products - jit- ter reduction and output stage improvement. · Danish high-end hifi kits - including preamps, phono, power amps & accessories. · Speaker drivers including Danish Flex Units plus a range of accessories. · GPS, GSM, AM/FM indiv. & comb. aerials. Soundlabs Group Syd: (02) 9660-1228 Melb: (03) 9859-0388 WebLINK: soundlabsgroup.com.au www.siliconchip.com.au RCS Radio has available EVERY PC Board ever published in SILICON CHIP, EA, ETI and AEM (copyrighted boards excepted). Many late boards are available ex stock, others can be made to order within a few days. Custom & production boards too! RCS Radio Tel: (02) 9738 0330 Fax: (02) 9738 0334 WebLINK: cia.com.au/rcsradio We stock the full range of fischertechnik robotic kits and models plus spare parts, computer interfaces and control software. Learn about industrial automation and robotics with fischertechnik. See our website for the latest news and FREE software downloads.Don’t forget to mention this ad for a 5% discount! Procon Technology Tel: (03) 9830 6288 Fax: (03) 9830 6481 WebLINK: procontechnology.com.au PIC chip specialists – microEngineering Labs and others. Easy to learn, easy to use, sophisticated CPU based controllers & peripherals. See our website for new range of ATOM products! MicroZed Computers Contact: sales<at>bitscope.com Tel: (02) 6772 2777 Fax: (02) 6772 8987 WebLINK: bitscope.com WebLINK: microzed.com.au For everything in radio control for aircraft, model boats and planes, etc. We also carry an extensive range of model flight control modules including GPS, altitude and speed, interfaces, autopilot and groundstation controllers. More info on our website! 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. Silvertone Electronics Tel:(07) 4639 1100 Fax: (07)4639 1275 WebLINK: www.silvertone.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°. Av-COMM Pty Ltd Tel:(02) 9939 4377 Fax: (02) 9939 4376 WebLINK: avcomm.com.au Jed Microprocessors Pty Ltd Tel: (03) 9762 3588 Fax: (03) 9762 5499 WebLINK: jedmicro.com.au We’re one of Australia’s most innovative electronic equipment suppliers. For over 10 years we’ve served Australian industry with an extensive range of electronic components and equipment from the world’s leading suppliers. We ensure our customers have the best selection and service. Clarke & Severn Electronics Tel: (02) 9482 1944 Fax: (02) 9482 1309 WebLINK: clarke.com.au May 2003  71 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au/ SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au/ VINTAGE RADIO By RODNEY CHAMPNESS, VK3UG The HMV C43B console radio Generally considered a “step-up” from mantel radios, console receivers enjoyed an extended period of popularity from the 1930s to the early 1950s. Typical of the era was the HMV C43B console, a 5-valve receiver with an impressive cabinet and per­formance to match. At the height of its popularity, a console receiver was usually the focus for household entertainment, just as DVD play­ers and home-theatre equipment are today. Their reign ended during the late 1940s and early 1950s when they evolved into the popular radiogram of the era. To cater for the demand, domestic receiver manufacturers developed a range of impressive console radios. Consoles always sounded more impressive in terms of volume and audio quality compared to the table and mantel sets of the era. The reasons for this weren’t hard to find – they had adequate baffling for the speakers mounted in them and speaker sizes varied from 6-inch to 12-inch types. By contrast, mantel sets had to make do with speakers rang­ing from three inches to eight inches in size. What’s more, their baffling was either inadequate or there was no baffling at all. The HMV C43B HMV had many fine pieces of furniture produced for them, into which they fitted quality receivers. The C43B is a typical example. The “C” in the model number means it is a 5-valve dual-wave receiver; the “4” means it is a horizontal console (whatever that meant); the “3” means it is an AC-powered receiver; and the “B” indicates that it is a second issue model of this type. Table 1 shows the model number code used by HMV and will help readers to identify other HMV models. The C43B console receiver described here belongs to a fellow vintage radio club member and is one of Jim’s more interesting radios. The set itself is quite attractive and given the right setting, would look quite impressive in the lounge room. As can be seen in the photos, the dial sits horizontally along the top front edge of the cabinet (perhaps that is what is meant by “horizontal” in the identification table). The dial doesn’t impress me as much as some of the early HMV dials but it is still quite functional, It’s also simpler than some of the earlier units, so it is less likely to give trouble with wear over an extended period. Information sheet This rear view shows the C43B receiver chassis mounted in the cabinet. Note the large metal brackets at either end. www.siliconchip.com.au A sheet of paper glued to an inside panel of the cabinet details the dial drive system and indicates the valve type used at each location. This valve location guide is handy for ensuring that the valves are correctly replaced in their respec­tive sockets after they have been removed for testing. It was not an uncommon practice in the 1930s, 1940s and 1950s for set owners to remove all the valves when the radio refused to operate or had some other annoying fault. They would then take them to their local radio serviceman and ask him to test them. The serviceman often did this on his emission type valve tester as a free service to the customer. Any valves that showed “replace” on the meter were consid­ered faulty May 2003  75 76  Silicon Chip www.siliconchip.com.au Fig.1: the circuit is conventional dual-band 5-valve superhet with the following valve line-up: 6J8GA convert­er; EBF35 IF amplifier, detector & AGC stage; 6U7G pentode audio amplifier; 6V6GT audio output amplifier; & 5Y3GT rectifier. It may be a little plain from the front but the cabinet is still an impressive piece of furniture. and the set’s owner would usually buy a new valve in the hope that that would fix the problem. I wonder how many valves were replaced just because the tester said “replace”, when in reality the valves still had quite a bit of life left in them for the job they had to do? On returning home, an owner would then put the valves back into the set and turn it on. Often, of course, it didn’t work and sometimes smoke even erupted from the set. Why? Many owners did not understand the significance of valve type numbers and he (she) may well have installed a 6V6G in a 5Y3G socket, or been responsible for some other equally disas­trous substitution. Valves often survived this rugged treatment but many didn’t. Hence, you can see the value of having the type numbers either on a sheet, as this set does, or painted onto the chassis alongside each valve socket. An episode like this often meant that the radio had to be taken to the serviceman to rectify the damage that had occurred. In short, it pays to be careful when replacing valves, to ensure that you don’t plug the wrong valve into the wrong socket. If in doubt, ask someone with more experience. The tone controls The tone controls on this set are on a separate sub-assem­bly that’s attached www.siliconchip.com.au The large oval-shaped loudspeaker is properly baffled by the cabinet, which contributes to the audio quality. to the front panel of the receiver. They connect to the main chassis via a plug and socket combina­tion. The receiver will operate with the tone controls discon­nected, although it will lack bass performance. That’s because, with the tone controls disconnected, there’s just a 500pF cou­ pling capacitor in the audio chain. Fig.1 shows the tone control circuit (VR1, VR2 & C22) and shows how it is attached to the main circuit. Removing the chassis The chassis is easy to remove and simply involves removing the bolts that fasten the chassis to the mounting shelf, then removing the knobs and disconnecting the loudspeaker and tone controls. The chassis can then be removed and, thanks to the large “roll-over” brackets located at either end, stood on its end for service. Circuit details The circuit is quite conventional – it has a 6J8GA convert­er; an EBF35 IF amplifier, detector and AGC stage; a 6U7G pentode audio amplifier; and a 6V6GT audio output amplifier. The power rectifier is the common 5Y3GT. The set is dual-wave, covering 5401600kHz and 5.9-18.1MHz, and it also features a pickup input (“PU”) so that records can be played through the audio amplifier stage. The converter stage has AGC voltage applied to it on both the broadcast and shortwave bands. On the broadcast band, the con­verter is neutralised and HMV was one of the few manufacturers that took the trouble to do this (neutralisation results in improved 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 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 May 2003  77 HMV Model Number Code Param eter C ode A Performance Type of cabinet Power supply Styling Meaning 4-valve broadcast band receiver B 5-valve broadcast band receiver C 5-valve dual-wave receiver D 5-valve dual-wave non-auto radi ogram E 5-valve dual-wave auto radi ogram F El ectrogram G El ectric record pl ayer H Spri ng record pl ayer J Spri ng acoustic pl ayer K FM tuner L FM/AM broadcast-band receiver M FM/AM dual-wave receiver N Extensi on speaker P 4-valve dual-wave receiver 1 Bakeli te mantel 2 Bakeli te tabl e 3 Wooden tabl e 4 H orizontal console 5 Ver tical consol e 6 Por tabl e 7 Metal case 1 D ry battery 2 DC 3 AC 4 DC/AC 5 6V vi brator 6 12V vibrator A Fi rst issue B Second issue, etc H MV audi o equi pment w as gi ven a 4-di gi t model number, w hi ch spec m i ed the performance, type of cabi net, pow er suppl y and styl i ng. For exampl e, the H MV 5-val ve po r tab l e w as coded B 61A , the 1948 5-val ve tab l e dual -w ave recei ver (formerly 888) was a C33A and the 1949 5-valve bakeli te tabl e dual-wave receiver w a s a C 2 3A . performance and less radiation of the oscillator signal from the antenna system). On shortwave, padder feedback capacitor (C6) is used to ensure that the converter oscillates reliably across the entire tuning range. An unusual feature here is the inclusion of a 2kΩ resistor (R2) in the grid lead circuit of the local oscillator for the broadcast band. Obviously, the oscillator was 78  Silicon Chip quite “lively” on the broadcast band so this resistor was included to reduce its activity and prevent spurious harmon­ ics from being generated. The aerial/antenna input circuit is one that HMV commonly used. Note that the shortwave primary winding (L5) is in series with the broadcast band coil (L1) primary. On the broadcast band, the inductance of L5 is quite low and it actually acts as a This label is attached to an inside panel and shows the dial stringing arrangement and the valve positions. small loading coil in series with the antenna. So, for all practical purposes, the broadcast coil is not affected by the shortwave coil. The broadcast coil primary is tuned by L1 and C1 so that it resonates at a frequency just below the broadcast band. This is done to get the best performance on the lower frequency stations. C2 is a “top-coupling” capacitor and its inclusion ensures good performance at the high-frequency end of the dial. On shortwave, L1 acts as a radio frequency (RF) choke and prevents L5 from operating effectively. However, while L1 acts as an RF choke, C1 has very little reactive effect at shortwave and so the bottom of the shortwave winding is effectively connected to earth. This saves the use of a switch section and is quite effective. The intermediate frequency (IF) amplifier is quite conven­tional, operating on 457.5kHz. As shown, the detector diode takes its signal from a tap on the secondary of the second IF transformer. This gives higher selectivity as opposed to extract­ing signal from the top of the winding. The signal for the AGC diode is taken from the plate of the IF amplifier valve, where the signal is stronger but the selec­tivity is reduced. This method helps to smooth the operation of the AGC system and ensures that it starts to work before the signal is fully tuned in, thereby preventing momentary “blasting” before the AGC becomes fully operational. www.siliconchip.com.au The AGC is delayed by the bias supplied through R11 (at the bottom of Fig.1). Note that about a third of the AGC voltage is applied via R17 to the 6U7G audio valve! This technique is rather unusual but was often favoured by HMV in particular. By doing this, the peak audio volume will remain almost constant for quite wide variations in signal strength. This usually obviates the need to alter the volume control setting when tuning from a strong to a weak station and vice-versa. Howev­ er, it does increase the noise between stations in some circumstances. Photo Gallery: 1940 Tasma Model 710 5-Valve Radio Audio amplifier The audio amplifier is a conventional high-quality, high-gain design with audio AGC as mentioned. There is voice coil negative feedback to the first stage via a tap on the volume control. The audio quality is quite good, being noticeably better than the average mantel receiver. The power supply has an unusual feature in that the filter choke has been placed in the negative lead. The advantage of this is that the voltage between the winding and the frame is quite low. The delay bias for the AGC system is obtained by a voltage divider across this choke. Note that a third of the voltage across the choke is used for this bias. This is dropped by another two thirds by a voltage divider consisting of R11, R7 and R8. Most stages employ quite good decoupling, which accounts for the set’s good stability and performance. However, this receiver, like many others, has minimal decoupling of the audio output stage from the IF stage and audio preamplifier. That said, the set has sufficient filtering to remove the IF signal from the audio circuit. This is necessary to ensure that the audio stages don’t act as IF amplifiers, with the possibility of feeding back into the IF amplifier. Inadequate filtering in this area has led to a number of receivers being unstable in some circumstances. As with most, if not all, HMV receivers of the late 1930s to early 1950s, the wiring is very neat and the set gives the im­pression of being a quality item (which it is). Restoration As with most receivers, there are a www.siliconchip.com.au Manufactured by Thom & Smith Pty Ltd in 1940, this Tasma Model 710 from was a compact 5-valve dual-wave mantel set. It featured an unusual “rust-stained” white bakelite cabinet and this was manufactured using a process that ensured no two cabinets were ever like. Band switching was controlled by a central winged knob, although this became the tone control on broadcast band only models. The valve line-up was as follows: 6J8G frequency converter, 6U7G IF amplifier, 6G8G audio amplifier & detector, 6V6G audio output and 5Y3G rectifier. This particular unit was been fully restored by its owner, Maxwell Johnson, Kingston, Tasmania. (Photo: Ross Johnson). few key components that should be replaced almost without question. These include the AGC bypasses and audio coupling capacitors (unless you can test them under real life conditions with high voltages and when they are quite warm). Note that a normal multimeter (set to an ohms range) rarely gives a true picture when it comes to testing capacitors. Only a few components needed replacement in this receiver. In addition, it is also a good idea to check the shielded wires in sets of this era. In some sets, the rubber insulation inside the shield perishes and often goes “gooey” – sometimes becoming conductive in the process. When this happens, it is necessary to replace it with new shielded cable. Despite the set’s age, Jim found that the valves were all in good condition. What’s more, it required no attention to the alignment. The cabinet also required very little attention, having been well looked after by its previous owner. This is one set that had been kept inside, rather than stored in a damp and dusty shed. Summary This set is one of many HMV receivers that look good and perform well. It’s only real drawback is having the horizontal dial on the top of the cabinet, as it’s always possible for someone to put something on top of it and cause damage. What’s more, the operator still has to reach down the front of the set to tune it, although the arrangement does make it easy to see the stations. That said, if it had been set down a little from the top and at an angle (like most of its contemporaries), the set would have looked better. As it stands, the set looks a little bland when viewed from the front. In spite of this minor criticism, the HMV C43B is a good performer and is well worthwhile having in your SC collection. May 2003  79 The LPT Simulator will take you next to no time to build. Note that the final version differs slightly from this prototype. Ideal for troubleshooting Lets you manipulate the data & control lines Has 6 LEDs for status monitoring Low cost & easy to assemble Printer por t harrdware simula ha imulattor Do you need to test printers or other items of equipment that connect to a PC’s parallel printer port? This low-cost, easy-to-build circuit will let you test them quickly, with­out the need for a PC or test software. By JIM ROWE B ASICALLY, THIS DEVICE is a simple hardware simulator. It allows you to manipulate the port’s data and control lines, monitor the status lines and even send the printer (or other equipment) a ‘strobe’ pulse. The idea for the Printer Port Simulator came about while we was developing our Windows-based EPROM Programmer. We struck a rather tricky timing fault and subsequently wasted a fair bit of time trying to work out whether it was due to a problem with the hardware or a bug in the software. The same sort of problem can occur when you’re trying to track down a 80  Silicon Chip fault in other kinds of PC-driven equipment, of course. It can even happen when you’re getting weird problems with a printer. We ended up resolving our particular problem by lashing up this Printer Port Simulator. This allowed us to send basic con­trol signals to the EPROM programmer and monitor its status lines, without having to worry about software debugging until later. It proved to be very effective and enabled us to track down the cause of the timing error. Later on, we realised that our Printer Port Simulator could also be used as a general troubleshooting tool to solve similar problems. So here it is and there’s really very little in it – just two cheap ICs, a +5V regulator, a couple of DIP switches to set up the data and control bit lines, six LEDs for status indi­cation, a pushbutton to produce strobe pulses and a handful of other components. It all fits on a small PC board measuring 113 x 61mm and runs from a 9V DC plugpack. The maximum current drain with all LEDs on is just 58mA. How it works Refer now to Fig.1 for the circuit details. The simulated “port interface” is provided via CON1, which duplicates the DB25 female connector used to provide the standard printer port on a PC. Pins 2-9 are used for the main data bus (DATA 0-7) to the printer. These pins are connected to a very simple data input circuit which uses eight 10kΩ pullup resistors and an 8-way DIP switch (S3). Each pole of S3 is simply connected between one of the data lines and ground – when a switch siliconchip.com.au Fig.1: the circuit is straightforward – just some DIP switches to set the data bits and control pins, a flipflop to generate the strobe pulse and some indicator LEDs to monitor the status lines. siliconchip.com.au May 2003  81 Fig.2: install the parts on the PC board as shown here, taking particular care to orientate the DIP switches correctly. In addition, switch S1 must be installed with its flat body surface to the left. Fig.3: this is the full-size etching pattern for the PC board. Check your board carefully before installing any of the parts. This means that pin 3 is normally low and so pin 11 (the strobe-bar output) is normally held high. Because pin 3 is low, D1 is forward biased and holds the voltage at the inputs of IC1b low as well. As a result, the output of IC1b (pin 6) is held high, as is the pin 13 input of IC1d. Now when S1 is pressed, the 100nF capacitor is discharged and so a logic low is applied to pin 1 of IC1a. As a result, the flipflop is triggered into switching states – ie, pin 3 goes high and pin 11 goes low. This marks the start of the strobe-bar pulse. When pin 3 goes high, it removes the forward bias on D1 and so it can no longer pull pins 4 & 5 low. As a result, the associated 390pF capacitor begins charging via a 10kΩ resistor. After about 2µs, the voltage on pins 4 & 5 rises high enough to switch IC1b. When that happens, pin 6 of IC1b goes low and because this pin is connected to pin 13 of IC1d, this triggers the flipflop into switching state again. As a result, pin 3 switches low and pin 11 switches high, bringing the strobe-bar pulse to an end. Note that this all takes place only if S2d is open. That’s because if S2d is closed, it holds both inputs of IC1b low permanently and so prevents IC1b from reset­ting the flipflop. Basically, S2d allows you either to produce strobe-bar pulses using S1 (when S2d is open) or to hold the strobe line down continuously after pressing S1. This second mode is handy for troubleshooting. Status LEDs is closed, that line is pulled to ground. Conversely, when a switch is open­ ed, that data line is pulled to logic high (ie, +5V) by the pullup resistor. As a result, the DIP switch can be used to feed any desired extended-ASCII data bit combination to the printer (or other device) – ie, from 00 to FF hex. Similarly, 4-way DIP switch S2 is used to set any desired combination of bits on three of the four control lines of the port: ie, pin 14 (Auto LF), pin 16 (Reset) and pin 17 (Select Out). Note that, in this case, the pullup resistors have a value of 4.7kΩ rather than 10kΩ. The remaining printer control line connects to pin 1 of the DB25 connector. This line is normally used to send the negative-going “strobe” pulse 82  Silicon Chip to the printer, to begin printing each character. For correct printer operation, each strobe pulse should be a single clean pulse about 1-2µs long. In the simulator, we generate this pulse each time switch S1 is pressed. This is done by using a simple oneshot circuit formed from three gates in IC1, a 74HC132 quad Schmitt NAND device. NAND gates IC1a & IC1d are connected as an RS (reset/set) flipflop which is triggered by pressing S1. The associated 2.2kΩ pullup resistor and 100nF shunt capacitor form­a simple “debounce” circuit. Diode D1 and NAND gate IC1b are used to convert the flipflop into a one-shot multivibrator. This works as follows: normal­ly, pin 1 of IC1a is held high by the 2.2kΩ pullup resistor. Most of the remaining circuitry in the simulator is used to drive LEDs 1-5. These are used to monitor the “printer status” lines of the parallel port – Acknowledge (pin 10), Busy/ Ready-bar (pin 11), Paper Out (pin 12), Select In (pin 13) and Error (pin 15). As shown in Fig.1, the LEDs are driven by inverters IC2a, IC2b, IC2c, IC2e & IC2f, all part of a 74HC04 hex inverter. Five of the 10kΩ resistors in SIL1 are used as pullups on the input lines, to prevent them from “floating” at an intermediate level when the simulator is not connected to a printer or other equip­ment. The series 10kΩ resistors are used for additional protec­tion against electrostatic charge damage to the gate inputs. IC1c and IC2d are used to drive siliconchip.com.au LED6, which indicates the status of the strobe-bar line. This LED is illuminated when the line is low (because this line is nominally active low) and is off when it’s high. Of course, the narrow nature of the strobe-bar pulse means that in pulse mode (S2d open), the LED glows so briefly it’s not easy to see. LED6 is therefore used mainly to verify the quiescent level on the line and of course, the level in non-pulse mode (S2d closed). Power supply The only part of the circuit we haven’t talked about yet is the power supply. This is very simple, consisting purely of a 7805 regulator (REG1) to produce a stable +5V rail from an unregu­lated 9V DC plugpack. Series diode D2 provides reverse polarity protection, while the 470µF and 100µF electrolytic capacitors provide filtering and stability. Construction Everything fits on a single-sided PC board measuring 113 x 61mm and coded 07105031. This is possible because we’ve used board-mounting components for DB25 socket CON1, DC input connec­tor CON2 and pushbutton switch S1. In fact, the board is designed to be freestanding, supported by four small screw-on rubber feet (one on each corner). Fig.2 shows the parts layout on the PC board. As can be seen, the display LEDs, DIP switches and pushbutton switch S1 are all arranged along the front of the board, for ease of use. Conversely, the two connectors are at the rear, to allow convenient cable connections. The assembly should take you next to no time. Begin by fitting the two connectors, then the three wire links, the DIP switches and pushbutton switch S1. Note that the DIP switches must all be fitted with their “ON” side towards the front of the board – they may look upside down but this gives the correct switching sense. Take particular care when installing switch S1. It must be installed with its flat body surface to the left –ie, one paral­lel pair of pins to the front and the other parallel pair to the back. If it’s installed incorrectly, you’ll get a permanent short across the 100nF capacitor and the switch won’t work. Next, install the resistors and the SIL resistor array. That done, you can fit the small capacitors and the electrolyt­ ics. Be sure to fit the latter with the correct polarity, as shown on Fig.2. The semiconductors can now all be installed. These include the diodes, LEDs, regulator and ICs. As usual, take care with the polarity of each of these. Note that all six LEDs are fitted with their cathode “flat” side towards the rear of the PC board. Regulator REG1 is mounted horizontally on the top of the board, with its three leads bent downwards at 90°, 5mm away from the body. Its metal tab is then secured to the board using an M3 x 6mm machine screw and a nut underneath. This also provides a small amount of heatsinking, as there’s a rectangle of copper underneath as well (there’s no need for a separate heatsink). Your simulator board should now be complete, apart from fitting the four rubber feet. These are fitted using M3 x 9mm machine screws passing up from underneath and fitted with nuts on the top. Parts List 1 PC board, code 07105031, 113 x 61mm 1 PC-mount pushbutton switch (S1) 1 4-way DIP switch (S2) 1 8-way DIP switch (S3) 1 DB25 female connector, PCmount (CON1) 1 2.5mm DC socket, PC-mount (CON2) 1 9V 150mA DC plugpack 4 small rubber feet 4 M3 x 9mm machine screws with hex nuts 1 M3 x 6mm machine screw with hex nut Semiconductors 1 74HC132 quad Schmitt NAND gate (IC1) 1 74HC04 hex inverter (IC2) 1 7805 +5V regulator (REG1) 6 3mm red LEDs 1 1N4148 silicon diode (D1) 1 1N4004 1A silicon diode (D2) Capacitors 1 470µF 16V PC-mount electrolytic 1 100µF 16V PC-mount electrolytic 3 100nF monolithic or ceramic 1 390pF ceramic Resistors (0.25W, 1%) 14 10kΩ 1 2.2kΩ 3 4.7kΩ 6 330Ω 1 8 x 10kΩ SIL array Check-out time It’s very easy to give the completed simulator a quick check-out. First, set DIP switches S2a-S2d to their OFF positions (ie, towards the rear) and connect a 9V DC plugpack to CON2. That done, apply power and check that the first five LEDs light. If they do, use your DMM to check the supply voltage at pin 14 of either IC1 & IC2 – it should be close to 5.00V. At this stage, LED6 should be off. Now set S2d (the leftmost DIP switch in S2, nearest the pushbutton) to ON and press S1. LED6 should now light and stay that way, unless S2d is turned OFF again. If all of the above happens as expected, your simulator is working correctly and ready for use. If not, turn off the power and look for faulty solder joints and components fitted with reversed polarity. These are the only likely causes of problems with SC such a simple project. Table 1: Resistor Colour Codes o No. o 14 o   3 o    1 o   6 siliconchip.com.au Value 10kΩ 4.7kΩ 2.2kΩ 330Ω 4-Band Code (1%) brown black orange brown yellow violet red brown red red red brown orange orange brown brown 5-Band Code (1%) brown black black red brown yellow violet black brown brown red red black brown brown orange orange black black brown May 2003  83 MORE FUN WITH THE PICAXE – PART 4 A Shop Spinning along Door Minder . . with PICAXE . with attitude! Hopefully you’ve been following our previous “PICAXE-08” articles and by now have tested, tweaked, tortured and tamed diverse circuits. A lthough these initial “PICNIK box” ideas were based around a solderless protoboard, there’s naturally nothing sacred about that! In fact, reader email feedback shows boundless “down under” prototyping initiative at work, such as just a 16pin DIP IC socket wired as a minimal test bed. A “seamail” even detailed an old salt’s “08” control of a diesel generator (using the READADC feature to monitor output voltage) rustled up while cruising off Tasmania. Did he get a controller dropped by seagull? Perhaps the appeal of PICAXE circuits relates to just such an approach, since many of the “usual” electronic components can be organised under software rather than silicon and cop- per hardware. The “08” is certainly shaping up as the little controller that could … Supply voltage As remarked in April (and now confirmed by Revolution Education), some users have found a 6V supply too high. Unreliable programming, or even “bootstrap” wiping, may occur at this voltage, particularly (it seems) with late 1990’s RS-232/USB transition PCs. (However, all my programming, using a full 6V and an AMD 475MHz notebook, has had no problems.) Naturally 4 AA cells will have more energy on tap to keep your circuit running longer, but it appears that 5V should now be the maximum supply. You don’t have to use a “toy” motor: with suitable buffering, this PICAXE project can control motors in a “real” device such as this cordless drill. . . Here we are modifying a cheap calculator to act as a poor man’s counter. 84  Silicon Chip by Stan Swan Several techniques to achieve this may be used: use a dummy shorting cell and so run off a 3 cell (4.5V) supply; drop 0.7V multiples with a series-connected silicon diode or two; or even use Nicad/NiMH cells (4 x 1.2V = 4.8V). Outputs Outputs so far have just driven LEDs or made sounds but could even be used to pull in sensitive relays. When more power hungry loads are driven, the limited PICAXE output current (~20mA) needs buffering if the IC is not to be overwhelmed. For modest loads, drawing just a few 100mA, a simple “electronic relay” bipolar transistor will handle this job nicely. Should you have more ambitious applications in mind, drawing considerable current, then respect all those boring issues relating to separate power supplies, heat dissipation and possibly substantial “back-EMF” and stalling currents. For such uses, the L293D H-bridge motor driver IC is suggested, since it’s capable of forward-reverse-stop twin motor control (to 600mA per channel) and comes with inbuilt spike protecting diodes – all for under about $10. Revolution Education sell the L293D pre mounted on the AXE023 motor driver board, that even includes a PICAXE-08 socket. To ease you into motor control however, this month’s main circuit uses a very efficient DC “solar motor”, typically drawing just 30mA at 3V. Small hobby motors often draw hundreds of milliamps – these so called solar www.siliconchip.com.au motors are normally intended for sun powered photovoltaic projects. Just 30mA – this motor could almost be driven directly from a PICAXE output . . . but let’s not push our luck! Almost any handy small signal NPN transistor can be used to achieve buffering, although the base resistor value may need changing if types other than a BC547 (capable of handling more current) are used. The usual DC motor “hash” is taken care of by a 100nF capacitor directly across the motor terminals and a reverse-connected silicon diode tames any motor “back-EMF”. A small paper flag glued suitably to the shaft indicates rotation and is safe enough should your fingers come too close while spinning. The program The program is again quite self explanatory and simply organises an endless but entertaining “speedup/ slowdown” procedure. Try doing this with a 555! The initial “kickstart” helps overcome motor mechanical friction, although a drop of CRC lubricant (“oilware”?) on the bushings may be just as helpful. Reference to previous month’s LDR/ NTC ADC sensor circuits could stimulate you to modify and enhance this program so motor speeds could now be light or temperature-controlled. Aha – how about a small cooling fan that sped up when the air temperature rose? Of course, more powerful small motors can be used but you’ll need to switch to a beefier transistor such as the TIP41C or BD437 along with a modified base resistor for that. One tempting application, still under exploration, is to PICAXE control an efficient Jaycar “Camping Shower” submersible pump. These run on 12V DC (but draw under 1A) and could pump irrigation or solar heated water only under suitable situations, such as at night or when certain temperatures were reached. Check http://manuka. orconhosting.net.nz/solarh2o.htm for my initial ideas . . . You could also modify the code suitably (use HIGH or LOW of course rather than PWM!) if you wish this transistor to control a sensitive relay such as the DSE P-8005. Simply remove the motor and connect leads to the relay’s energising coil instead, leaving the diode in place. www.siliconchip.com.au Once again, it’s very similar to previous months – we make changes to the output circuit and the code inside the PICAXE itself. Note the supply is no longer 6V – see the comments about the 5V rail in the text. The usual protoboard component layout, with the “PICnik Box” mockup below. As usual, for clarity, we have made a few minor component position changes between this photo and the protoboard layout above. Oh, you noticed the LED, did you? That’s yet another variation . . . one which we have covered overleaf. Note the new use for dead batteries as shorting cells! May 2003  85 As we said previously, even though protoboard is convenient for lashing together experimental circuits, you don’t have to use it. The photos at right show a hybrid approach, with most parts soldered to stripboard, but with IC socket strips (DSE P-4300) used for quick “plug in” component changes. Such a setup offers cheaper and more compact circuits and flexibility when away from a soldering iron. Photos: Andrew <copurnicus<at>paradise.net.nz> PICAXE-08 COMMANDS USED THIS MONTH: symbol SYMBOL The only new (pseudo) command here is “symbol”, which all, symbol doesn’t crib on the PICAXE memory, so you can makes programs much more lucid, since “plain English” now blithely redefine those messy b0, b1s with no program words can be used instead for algebraic variables. Best of overhead – not even on the set-up lines text entry either. BASIC PROGRAM LISTING (This can also be downloaded from http://picaxe.orconhosting.net.nz/motorpwm.bas) ‘ Demo PWM motor demo- PICAXE-08 May 2003 SilChip Ver 1.0 11th Mar.03 ‘ Best assembled & tested with solderless “PICNIK” box as detailed SilChip Feb.03 ‘ Refer http://picaxe.orcon.net.nz for background info & potential of PICAXE-08! ‘ Extra parts=DSE P-8980 “Solar Motor”, 4.7k resistor, NPN BC547 transistor ‘ General Si diode & 100-220nF polyester cap (both to stop motor hash & “back emf”) ‘ Dummy cell for 4.5V use. Optional counter =cheap calculator(!) +LDR & heatshrink ‘ New commands here = symbol ‘ Ref.PICAXE prog.editor.pdf help files,& BASIC Stamp 1 manuals etc for insights ‘ via Stan. SWAN (MU<at>W, New Zealand) => s.t.swan<at>massey.ac.nz <= ‘————————————————————————————————— ‘ Byte variables b0= slowing down, b1 = speeding up, b2= slow spin demo ‘————————————————————————————————— ‘ Lines beginning ‘ are program documentation & could be ignored if need be. ‘ Program available for web download => http://picaxe.orconhosting.net.nz/motorpwm.bas ‘————————————————————————————————— symbol slowdown = b0 ‘redefine variables b0, b1, b2 symbol speedup = b1 ‘ using PICAXE “symbol” command symbol slowspin = b2 ‘ to make easier recall/understanding kickstart: pwm 2,255,8 wait 2 ‘ brief routine to overcome initial motor friction ‘ 8 industrial strength pwm cycles to pin 2 ‘ short wait before main routine begins pwmspin: pulsout 4,3000 for speedup = 70 to 255 step 1 pwm 2,speedup,4 next speedup ‘ main pwm demo routine ‘ pulse LED pin 4 for 3mSec to indicate start ‘ values < 70 found unable to easily spin motor ‘ 4 cycles at pin 2 of increasing pwm duty ‘ continue to full speed (255 = 100%) for slowdown = 255 to 70 step –1 pwm 2,slowdown,4 next slowdown ‘ slow motor down at same rate ‘ 4 cycles at pin 2 of decreasing pwm duty ‘ continue until at slowest reliable speed for slowspin= 1 to 80 pwm 2,70,10 next slowspin ‘ longer slow speed spin demo- repeat 80 times ‘ 10 cycles 70/255 % of 5V at pin 2 ‘ continue loop goto pwmspin ‘ repeat entire motor spin demo routine 86  Silicon Chip Some more references and parts suppliers . . . 1. http://picaxe.orconhosting.net.nz Authors enthusiastic web site – updated with many pictures and DIY details. 2. http://picaxe.orconhosting.net.nz/ motorpwm.bas program listing to copy and paste to PICAXE editor. 3. “ The Robot Builders Bonanza” McComb. TAB Books 2000 (DSE B1599) has outstanding motor inter facing details (particularly Steppers & Servos Ch.19-20). 4. Dick Smith Electronics “Solar Motor” (Cat P-8980; approx $3) (3V <at> ~30mA). The P-8005 relay, under 42mA at 5V, can switch up to 2A at 150V. Other mentioned items (capacitor, diode, transistors, heatshrink, etc) via DSE also. 5. Pocket calculator – most bargain and stationery stores. $2-$4 range. 6. Jaycar Electronics “Camping Shower” (Cat YS-2800; approx. $27). 7. Oatley Electronics (www.oatleyelectronics.com) and Microzed (www.microzed.com.au) now stock PICAXE-08 ICs and many accessories. NEXT MONTH: More motor madness So – your triple fives are now in the bin? Since, with flair, “08”s look certain to win. But – you hanker for more – Motor circuits galore? Next up we’ll “step” and “serve” spin! www.siliconchip.com.au A Poor Man’s Counter To stimulate your lateral thinking, here is a simple enhancement for our earlier circuits that offers optically coupled LCD counting. Forget $$ LCD displays and interfacing: we’re going to use a cheap pocket calculator. Pocket calculators sell for only a few dollars, yet offer tempting counting prospects by just exploiting the old schoolboy “1/+/=/=/=” key stroke routine. The carbon-impregnated pad which normally bridges out calculator key contacts offers about 10kΩ resistance. This is (aha!) a value close to a LDR’s bright light resistance. (LDR dark resistance is many megohms – it can be regarded as virtually open circuit). After disassembly, two neat holes are drilled in the PC board near the “=” key and two thin wires are soldered across the “=” key grid contacts. Solder an LDR to these two wires, then black-heatshrink the LDR inside a suitable tube, so that stray light will be cut and triggering will be just from an LED when in the tube’s other end. A suitable PICAXE-generated flash from this LED is now as good as a key press to the modified calculator, although debouncing circuitry (and LDR dark “settling”) tends to limit response rate to about once a second. Most auto-power-off calculators will shut down after some 10 minutes of inactivity too, so perhaps choose an “always on” type (ie, cheap-n-nasty!) if your counting application has only light traffic. SC OATLEY’S “PIC-AXEALL” BREADBOARD KIT In yet another variation on the protoboard theme, Oatley Electronics have released a breadboard kit especially designed for PICAXE (and PIC) experimenters and developers. More importantly, the kit is very cheap, especially when you consider what it includes (significantly cheaper than going the “protoboard” route and much simpler than going down the stripboard path). The kit (Cat K193) includes: • a specially designed PC board with a 28-pin DIL IC socket, capable of handling all PICAXE and most PIC chips • the PC serial interface (10kΩ and 22kΩ resistor) along with the programming slide switch • a piezo speaker • a 5.5V DC mains plugpack and 3.3V or 3.9V zener diode power supply (there is also provision for www.siliconchip.com.au an optional 7805 regulator if more power is required for higher current outputs). • three different coloured status LEDs (with 2.2kΩ resistors). • a pushbutton switch No chip is supplied with the kit, giving complete flexibility as to which particular chip is used. If the type of PICAXE chip ordered with the kit requires a crystal or resonator, it will be supplied with the chip. The top side of the PC board is screen-printed with both component positions and the tracks, or connection paths, underneath the board. Four mounting holes are also provided The board has power supply (+ & -) rails along both edges (similar to the protoboard arrangement) while each of the pins on the IC socket is brought out to a pad, which can be connected through to other pads, supply rails, etc. Two electrolytic and several 22nF capacitors are spread around the board to ensure a clean DC supply. While intended as a breadboard, there is nothing to stop the board being used for a permanent PIC/PICAXE project. If it is too big (at 80 x 60mm – shown above life size) it can be trimmed to an appropriate size. At $12.50, we believe this kit is very good value for money, particularly as it includes the plugpack supply. It is available from Oatley Electronics, PO Box 89, Oatley NSW 2223 (Phone 02 9584 3563, Fax 02 9584 3561) or via www. oatleyelectronics.com May 2003  87 Silicon Chip Back Issues April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors; 32-Band Graphic Equaliser, Pt.2. May 1989: Build A Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference. July 1989: Exhaust Gas Monitor; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; The NSW 86 Class Electrics. September 1989: 2-Chip Portable AM Stereo Radio Pt.1; High Or Low Fluid Level Detector; Studio Series 20-Band Stereo Equaliser, Pt.2. 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. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Phone Patch For Radio Amateurs; Active Antenna Kit; Designing UHF Transmitter Stages. 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 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 1990: Dual Tracking ±50V Power Supply; Voice-Operated Switch With Delayed Audio; 16-Channel Mixing Desk, Pt.3; Active CW Filter. June 1990: Multi-Sector Home Burglar Alarm; Build A Low-Noise Universal Stereo Preamplifier; Load Protector For Power Supplies. July 1990: Digital Sine/Square Generator, Pt.1 (covers 0-500kHz); Burglar Alarm Keypad & Combination Lock; Build A Simple Electronic Die; A Low-Cost Dual Power Supply. August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Mains Appliances (9 Minutes); Horace The Electronic Cricket; Digital Sine/Square Generator, Pt.2. September 1990: A Low-Cost 3-Digit Counter Module; Build A Simple Shortwave Converter For The 2-Metre Band; The Care & Feeding Of Nicad Battery Packs (Getting The Most From Nicad Batteries). October 1990: The Dangers of PCBs; Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs; NE602 Converter Circuits. 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. 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. 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. 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. 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. 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. October 1991: Build A Talking Voltmeter For Your PC, Pt.1; SteamSound Simulator For Model Railways Mk.II; Magnetic Field Strength Meter; ORDER FORM May 1994: Fast Charger For Nicad Batteries; Induction Balance Metal Locator; Multi-Channel Infrared Remote Control; Dual Electronic Dice; Simple Servo Driver Circuits; Engine Management, Pt.8. June 1994: 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. Digital Altimeter For Gliders, Pt.2; Military Applications Of R/C Aircraft. 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. December 1991: TV Transmitter For VCRs With UHF Modulators; IR Light Beam Relay; Build A Colour TV Pattern Generator, Pt.2; Index To Vol.4. March 1992: TV Transmitter For VHF VCRs; Thermostatic Switch For Car Radiator Fans; Coping With Damaged Computer Directories; Valve Substitution In Vintage Radios. April 1992: IR Remote Control For Model Railroads; Differential Input Buffer For CROs; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. 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. 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. July 1994: Build A 4-Bay Bow-Tie UHF TV Antenna; PreChamp 2-Transistor Preamplifier; Steam Train Whistle & Diesel Horn Simulator; 6V SLA Battery Charger; Electronic Engine Management, Pt.10. August 1994: High-Power Dimmer For Incandescent Lights; Microprocessor-Controlled Morse Keyer; Dual Diversity Tuner For FM Microphones, Pt.1; Nicad Zapper (For Resurrecting Nicad Batteries); Electronic Engine Management, Pt.11. September 1994: Automatic Discharger For Nicad Battery Packs; MiniVox Voice Operated Relay; Image Intensified Night Viewer; AM Radio For Weather Beacons; Dual Diversity Tuner For FM Microphones, Pt.2; Electronic Engine Management, Pt.12. October 1994: How Dolby Surround Sound Works; Dual Rail Variable Power Supply; Build A Talking Headlight Reminder; Electronic Ballast For Fluorescent Lights; Electronic Engine Management, Pt.13. 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. March 1993: Solar Charger For 12V Batteries; Alarm-Triggered Security Camera; Reaction Trainer; Audio Mixer for Camcorders; A 24-Hour Sidereal Clock For Astronomers. 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. April 1993: Solar-Powered Electric Fence; Audio Power Meter; Three-Function Home Weather Station; 12VDC To 70VDC Converter; Digital Clock With Battery Back-Up. 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. June 1993: AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; Digital Voltmeter For Cars; Windows-Based Logic Analyser. April 1995: FM Radio Trainer, Pt.1; Photographic Timer For Dark­ rooms; Balanced Microphone Preamp. & Line Filter; 50W/Channel Stereo Amplifier, Pt.2; Wide Range Electrostatic Loudspeakers, Pt.3; 8-Channel Decoder For Radio Remote Control. July 1993: Single Chip Message Recorder; Light Beam Relay Extender; AM Radio Trainer, Pt.2; Quiz Game Adjudicator; Windows-Based Logic Analyser, Pt.2; Antenna Tuners – Why They Are Useful. August 1993: Low-Cost Colour Video Fader; 60-LED Brake Light Array; Microprocessor-Based Sidereal Clock; Satellites & Their Orbits. 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. 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. 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. 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 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. 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. March 1994: Intelligent IR Remote Controller; 50W (LM3876) Audio Amplifier Module; Level Crossing Detector For Model Railways; Voice Activated Switch For FM Microphones; Engine Management, Pt.6. April 1994: Sound & Lights For Model Railway Level Crossings; Discrete Dual Supply Voltage Regulator; Universal Stereo Preamplifier; Digital Water Tank Gauge; Engine Management, Pt.7. May 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. 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. Enclosed is my cheque/money order for $­______or please debit my:  Bankcard  Visa Card Card No. Signature ___________________________ Card expiry date_____ /______ Name ______________________________ Phone No (___) ____________ PLEASE PRINT Street ______________________________________________________ Suburb/town _______________________________ Postcode ___________ 88  Silicon Chip 10% OF F SUBSCR TO IB OR IF Y ERS OU BU  Master Card 10 OR MORE Y Please send the following back issues:________________________________________ 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 May 1996: High Voltage Insulation Tester; Knightrider LED Chaser; Simple Intercom Uses Optical Cable; Cathode Ray Oscilloscopes, Pt.3. O-Meter; Versatile Electronic Guitar Limiter; 12V Trickle Charger For Float Conditions; Adding An External Battery Pack To Your Flashgun. Video Stabiliser; Tremolo Unit For Musicians; Minimitter FM Stereo Transmitter; Intelligent Nicad Battery Charger. June 1996: BassBox CAD Loudspeaker Software Reviewed; Stereo Simulator (uses delay chip); Rope Light Chaser; Low Ohms Tester For Your DMM; Automatic 10A Battery Charger. 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. 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. 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. 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. 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. 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. 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). September 1996: VGA Oscilloscope, Pt.3; IR Stereo Headphone Link, Pt.1; High Quality PA Loudspeaker; 3-Band HF Amateur Radio Receiver; Cathode Ray Oscilloscopes, Pt.5. 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. October 1996: Send Video Signals Over Twisted Pair Cable; Power Control With A Light Dimmer; 600W DC-DC Converter For Car Hifi Systems, Pt.1; IR Stereo Headphone Link, Pt.2; Build A Multi-Media Sound System, Pt.1; Multi-Channel Radio Control Transmitter, Pt.8. 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. November 1996: 8-Channel Stereo Mixer, Pt.1; Low-Cost Fluorescent Light Inverter; Repairing Domestic Light Dimmers; Multi-Media Sound System, Pt.2; 600W DC-DC Converter For Car Hifi Systems, Pt.2. December 1996: Active Filter Cleans Up Your CW Reception; A Fast Clock For Railway Modellers; Laser Pistol & Electronic Target; Build A Sound Level Meter; 8-Channel Stereo Mixer, Pt.2; Index To Vol.9. January 1997: How To Network Your PC; Control Panel For Multiple Smoke Alarms, Pt.1; Build A Pink Noise Source; Computer Controlled Dual Power Supply, Pt.1; Digi-Temp Monitors Eight Temperatures. 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. September 1997: Multi-Spark Capacitor Discharge Ignition; 500W Audio Power Amplifier, Pt.2; A Video Security System For Your Home; PC Card For Controlling Two Stepper Motors; HiFi On A Budget. October 1997: Build A 5-Digit Tachometer; Add Central Locking To Your Car; PC-Controlled 6-Channel Voltmeter; 500W Audio Power Amplifier, Pt.3; Customising The Windows 95 Start Menu. November 1997: Heavy Duty 10A 240VAC Motor Speed Controller; Easy-To-Use Cable & Wiring Tester; Build A Musical Doorbell; Replacing Foam Speaker Surrounds; Understanding Electric Lighting Pt.1. December 1997: Speed Alarm For Cars; 2-Axis Robot With Gripper; Stepper Motor Driver With Onboard Buffer; Power Supply For Stepper Motor Cards; Understanding Electric Lighting Pt.2; Index To Vol.10. 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 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. 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? 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. August 1999: Remote Modem Controller; Daytime Running Lights For Cars; Build A PC Monitor Checker; Switching Temperature Controller; XYZ Table With Stepper Motor Control, Pt.4; Electric Lighting, Pt.14. September 1999: Autonomouse The Robot, Pt.1; Voice Direct Speech Recognition Module; Digital Electrolytic Capacitance Meter; XYZ Table With Stepper Motor Control, Pt.5; Peltier-Powered Can Cooler. 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. November 2001: Ultra-LD 100W RMS/Channel Stereo Amplifier, Pt.1; Neon Tube Modulator For Cars; Low-Cost Audio/Video Distribution Amplifier; Short Message Recorder Player; Computer Tips. December 2001: A Look At Windows XP; Build A PC Infrared Transceiver; Ultra-LD 100W RMS/Ch Stereo Amplifier, Pt.2; Pardy Lights – An Intriguing Colour Display; PIC Fun – Learning About Micros. January 2002: Touch And/Or Remote-Controlled Light Dimmer, Pt.1; A Cheap ’n’Easy Motorbike Alarm; 100W RMS/Channel Stereo Amplifier, Pt.3; Build A Raucous Alarm; FAQs On The MP3 Jukebox. February 2002: 10-Channel IR Remote Control Receiver; 2.4GHz High-Power Audio-Video Link; Assemble Your Own 2-Way Tower Speakers; Touch And/Or Remote-Controlled Light Dimmer, Pt.2; Booting A PC Without A Keyboard; 4-Way Event Timer. 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. March 2002: Mighty Midget Audio Amplifier Module; The Itsy-Bitsy USB Lamp; 6-Channel IR Remote Volume Control, Pt.1; RIAA Prea­ mplifier For Magnetic Cartridges; 12/24V Intelligent Solar Power Battery Charger; Generate Audio Tones Using Your PC’s Soundcard. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. September 2000: Build A Swimming Pool Alarm; An 8-Channel PC Relay Board; Fuel Mixture Display For Cars, Pt.1; Protoboards – The Easy Way Into Electronics, Pt.1; Cybug The Solar Fly. October 2000: Guitar Jammer For Practice & Jam Sessions; Booze Buster Breath Tester; A Wand-Mounted Inspection Camera; Installing A Free-Air Subwoofer In Your Car; Fuel Mixture Display For Cars, Pt.2. 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. November 2000: Santa & Rudolf Chrissie Display; Build A 2-Channel Guitar Preamplifier, Pt.1; Message Bank & Missed Call Alert; Programmable Electronic Thermostat; Protoboards – The Easy Way Into Electronics, Pt.3. 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. 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. 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. 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. 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. 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. 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. 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. October 1998: Lab Quality AC Millivoltmeter, Pt.1; PC-Controlled Stress- April 2001: A GPS Module For Your PC; Dr Video – An Easy-To-Build www.siliconchip.com.au 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. 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. 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. January 2003: Receiving TV From International Satellites, Pt 2; Reader/ Programmer For Smart Cards; SC480 50W RMS Amplifier Module, Pt.1; A “Tiptronic-Style” Gear Indicator; Active 3-Way Crossover For Loudspeakers; Using Linux To Share An Optus Cable Modem, Pt.3. 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. 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 PLEASE NOTE: Issues not listed are now sold out. All other issues are presently in stock. We can supply photostat copies (or tear sheets) 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 May 2003  89 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 Triac tester wanted Have you ever published a circuit to test Triacs? If not, what is the easy way to test a Triac? (Y. G., via email). • We have not published a Triac tester and nor is there any easy way to test them for parameters such as blocking voltage, holding current, gate sensitivity etc. However, if you want a simple safe check, use a 12VAC supply, a 12V 20W halogen lamp and a 470Ω resistor to connect the gate to A2. Connect the lamp in series with A2 and the +12V supply. Connecting the gate to A2 (via the 470Ω resistor) should turn on the lamp. Curtain motor control wanted I am searching for information on the control of an elec­tric motor for the opening and closing of window curtains. The device would detect a voltage drop or a current increase when the curtain carrier comes to the fully opened or closed position. The operating voltage is 12V at less than 1.5A. (H. B., via email). • Have a look at the circuit for a re- Bigger displays for PIC TOC I would like to substitute the existing LEDs in the PIC TOC Alarm Clock (SILICON CHIP, July 2001) with the super large 7-segment displays which are available from Jaycar (Cat. ZD-1850) for $10.95 each for the common cathode type. What would I have to alter on the circuit for this to be done? Secondly, I have in mind to build the Peltier cooler Esky/fridge from your September 1999 issue and I wish to power it from 240VAC, 12V DC and from solar cells. Can you 90  Silicon Chip mote volume control in the June 2002 issue. It was a low power 5V circuit but could be upgraded to higher current by changing the transistors in the H-pack. The BC328s could be changed to Darlington BD682s and the BC338s to BD681s. The 10Ω current sensing resistor would have to reduced to around 0.5Ω or less. Speed Alarm for FWD cars I recently purchased the Speed Alarm kit (SILICON CHIP, November & December 1999) only to find that it does not work for a front-wheel drive car (Mazda 626) as you do not have access to the drive-shaft, only the wheel shafts which rotate too slowly, hence generating too few pulses. My question is, has anyone produced a modification to the circuit or to the PIC program to overcome this problem? (P. H., via email). • You can use the Speed Alarm on a front-wheel drive car. Just use more magnets on the wheel drive shaft. Eight should be enough, evenly distributed around the shaft. In fact, it is not so much that the Speed Alarm does not work for a frontwheel drive but that the speedometer advise what the solar panel and battery requirements would need to be. (M. S., via email). • Unfortunately, neither of your project suggestions is prac­tical or feasible. Each digit of the giant LED displays has two LEDs and so it is not feasible to drive them in the PIC alarm clock. You would need the drive circuit used in the Large Digit PIC clock featured in the March 2001 issue. As far as the Peltier cooler is concerned, you would need a solar panel capable of at least 4A, depending on the cooler used. That would be a very expensive panel. update time is dependent on the number of pulses provided for a given speed from the pickup sensor. So more magnets on the shaft will in­crease the number of pulses and provide a faster speedometer update. However, there is another way and this has been mentioned a number of times in past issues: don’t bother with magnets and the pickup coil; just use the speed signal from your car’s engine management system. The pulsed speed signal connects to the coil input terminal on the PC board, via shielded cable. The shield connection is left open, ie, no need to connect the shield at the pickup point for the engine management speed signal. Flexitimer does not cycle I have built the Flexitimer published in the August & September 1995 issues of “Electronics Australia”. I find that once the 9V mains adaptor is turned on, the solenoid is energised after about 7s (normal) but will not disengage after a further 7s. Shouldn’t it change output poles on the relay every 7s or is the timer only a straight timer that turns on or off once until the mains is turned off? I have used the Q4 jumper to give the minimum time. (A. S., via email). • If you want the relay to cycle on and off, you must cut the track between the collector of Q1 and pin 4 of IC1, then connect pin 4 to pin 8 of IC1. Motor speed controller reversing I have a 10A Motor Speed Controller kit (June 1997) which I intend to use to drive a 12V DC motor. However, I want to run it in forward and reverse direction. I am thinking of using a relay to switch polarities but I realise this will cause a short circuit across protection diode D2. I would appreciate any ideas to solve this problem. (D. C., via email). www.siliconchip.com.au • The simple way to solve your problem is to use a 2-pole changeover relay. We showed how to use a relay in this way in the L’il Pulser Train controller published in the February 2001 issue. We can supply this issue for $8.80 including postage. Speed control for distributor tester I am in the process of building a car distributor tester using a 12V heater fan motor to drive the distributor. I need to vary the speed of the motor to test the centrifugal advance curve of the distributor. The motor draws in excess of 15A on startup and drops to 6A at full speed. Could you please advise if the high-current speed con­troller for 12V and 24V DC motors featured in the June 1997 issue would be suitable to vary the speed of this motor? (K. W., via email). • The June 1997 design would be suitable for handling your load, although we are surprised that the fan motor draws such a high current (both at start-up and when running). We assume that this is without the fan connected and it suggests that there is something wrong with the motor. As an alternative, you could use a 240V sewing machine motor and control it with the speed control featured in the October 2002 issue. We can supply this issue for $8.80 including postage. Bridge amplifier for subwoofers I am building a subwoofer amplifier using the 50W LM3876T chip from your March 1994 amplifier module. My preamp has the extra output to run two modules in bridge mode, so I decided to build two up for extra power. The first module works perfectly, while the second module is the same as the first except for the output chip. It was only after I had finished, that I noticed the second chip was an LM­3886 (they look identical). The amplifier seems to be working OK except that I noticed that the LM3886 chip was running hotter than the LM3876 chip, so I have switched off for now. The modules are in bridge mode. My question is, what is the difference between the two? Can the www.siliconchip.com.au Extending The 6-Channel Remote Volume Control I have just completed the 6-channel IR Remote Volume Con­ trol project and am very pleased with it, particularly the pro­ fessional appearance of the finished unit. I bought my kit from Altronics. It would be a lot more useful to me if I was able to con­trol the volume of the individual channels, as well as having overall volume control. I noticed in your article that you said that “each of the three channels in each IC is individually addressable and could theoretically be loaded with any attenua­ tion value”. Can you provide information on how to do this? (B. M., via email). LM3886 be used in the March 1994 project without modifica­tion? If not, what modifications are needed? Which chip is best for bridge mode operation when using two? My sub-woofer has two separate drivers running in a three-chambered bandpass enclosure, so is it possible to use one module for each speaker. Would this be better? I strive for perfection, so I hope you don’t mind all the questions. The transformer I am using is a 200VA type with two second­ a ry windings. These are 25V-0-25V and 22V-0-22V, with a switch to select the one you want. Would either of the chips produce more power into 4Ω or even 2Ω in bridge mode if the lower transformer voltage was used? The DC voltage was 33V compared to the normal 37.5V DC for this project. I have built up a 5-channel power amplifier using the LM3876T chips for each channel. A 500VA toroidal transformer and 40,000µF of filter capacitors are used to power them. This amplifier has fantastic quality for music and home DVD movies. I use this 5-channel amplifier with a DVD player with an inbuilt 5.1 AC3, DTS decoder and the new 6-channel IR Remote Volume Control project (SILICON CHIP, March 2002). This setup is much cheaper than buying an allin-one home theatre amplifier and you get to use amplifiers you have built up in the past. (K. S., Morphett Vale, Vic). • We would not use the LM3876 and • While it is possible to individually address the attenuators for each of the 6-channels, the design would be much more com­plex, with more hardware and software. The remote control would need to individually select each channel to be adjusted and you would need more indicators on the front panel, to show what was happening. If you want to pursue this further, you can find the codes to address each attenuator in the LM1973 data on the National Semiconductor website. An alternative approach would be add a trimpot attenuator at the input of each channel to set up the individual volume levels. the LM3886 in bridge mode; use either LM3876 or LM3886 - do not mix them. The LM3886 is a higher rated version of the LM3876. If your subwoofer has separate drivers, it would be much better to drive them from individual amplifier modules rather than in bridge mode. In fact, both the LM3886 and LM3876 are not really all that good in bridge mode because their power output into 4Ω is only slightly more than that into 8Ω. If you drive the woofers separately with the modules, you can use both the LM3876 and LM3886. Use 25V + 25V from your transformer. You will not get much more (if any) more power from these chips by changing the supply rails because the chip has internal power limiting (check the article in March 1994, page 80). They will not drive 2Ω loads. Questions on sound level meter I’m interested in building the Sound Level Meter from the December 1996 issue. It is to be used to help set up speaker levels in a 5.1 home theatre system but as I’m fairly new to all this I have a few questions: An ECM-60P type A electret microphone is called for in the design, however I can’t find one. Can you suggest a suitable alternative? Should the 10kΩ bias resistor and 68kΩ and 10kΩ feedback resistors be changed to match May 2003  91 Boosting the 5A speed control I recently completed the AC Motor Speed Controller from the October 2002 issue. However, I need to use it with an 1850W router. Can the circuit be modified to handle this amount of power? (A. H., via email). • The two main factors setting the maximum current are the current ratings for diode D3 and the speed switch. As far as the switch is concerned, you could either leave it out altogether or substitute a bigger the substitute microphone? I have found a software-based pink noise generator at: http://www. nch.com.au Can this be used in place of the pink noise kit? Also I’m not clear on the calibration procedure. It says to connect the pink noise source to the mic input (I assume with the mic disconnected?). Should this be the line level output from the pink noise source or the speaker level output; ie, should I use the line level output from the sound card or the wires that connect to the internal PC speaker? As the software will only go to -30dB, can I use 700mV as the set point; ie, a 300mV change between 0dB and -30dB? (V. S., via email). • The Jaycar Cat. AM-4011 microphone would be suitable. No resistor changes are necessary. The pink noise generator signal from the computer sound card would be suitable. However, the 60dB attenuator circuit as used in the SILICON CHIP Pink Noise genera­tor (January 1997 issue) would need to be used to calibrate the sound level meter. switch, such as the 10A 240VAC DPDT toggle switch from Jaycar (Cat ST-0575). To get a higher rated diode, you will need to go to a TO-220 package type such as the MUR1560 rated at 15A, 600V (Jaycar Cat ZR-1030). Make sure these components fit comfortably inside the case. Note, however, that these modifications will not let you run appliances with 10A ratings on their nameplates. To do that, you would need to use a larger diecast case or otherwise improve the heatsinking of the Triac. This resistive divider can be added to the output of the sound card. Does auto lock-up confuse Gear Indicator? I am interested in the Gear Indicator project featured in the January 2003 issue. I have a VR Commodore with a 4-speed auto and lock-up converter. What do you set the number of gears to? Four or five? As far as I’m aware, the converter locks up in third under certain conditions, as well as locking up in fourth. This being the case, what would the display indicate, because if you set it for five gears - ie, four plus one for lock-up - and the trans­mission locked up in third, would it confuse the display by showing the wrong gear? (P. B., via email). • The Gear Indicator should indicate the correct gear irres­pective of lockup in the torque converter. This is because the unit is calibrated when driving on a flat road at a steady speed and so the torque converter should have minimum slippage anyway. However, calibration in fourth gear may need to be done with the converter locked. If the unit is calibrated in fourth gear when there is slight acceleration and hence slippage in the torque converter, it may be possible to calibrate this as gear 4, with gear 5 when the converter is locked. That’s if that is what you want. Alternatively, you may be able to calibrate for lock-up in gear 3 (call it gear 4), if gear 3 is calibrated with the con­verter slipping. Then you could use the gear 5 and 6 numbers for fourth gear and fourth gear with lock-up. If we were doing it though, we would set it up just to indicate four gears and not worry about the lock-up condition. Notes & Errata PortaPAL PA Amplifier, February & March 2003: the main PC board (code 01103031) has an error which needs to be corrected. The link near pin 1 of IC5 connects on one side to ground but the other side is disconnected. It should go to the emitter of Q1 via the adjacent track. The end of the 18kΩ resistor adjacent to the open circuit link should be connected instead to the adjacent track which goes to pin 7 of IC5. A revised PC board pattern has been placed on our website and forwarded to kit suppliers. Solar Panel Regulator, March 2002: the PC board component overlay on page 85 shows diodes D1 & D2 mounted with metal sides down. They should be mounted metal side up, the same as the Mosfets. Speed Controller For Universal Motors, October 2002: the PC board diagram on page 17 shows a 5404 fitted as D3. This should be a 6A diode such SC as R250H or PX6007. 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. 92  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. 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New and Secondhand Speaker Drivers. Speaker Repairs and Kits. Projectors and Screens. Delivery anywhere in Australia. Melb. (03) 5986 1128; www.penhometheatre.com.au 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, 68HC­ 08, 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 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. KITS KITS AND MORE KITS! Check ’em out at www.ozitronics.com May 2003  93 Silicon Chip Binders New New New Mark22-SM Slimline Mini FM R/C Receiver REAL VALUE AT $12.95 PLUS P&P These binders will protect your copies of S ILICON CHIP. They feature heavy-board covers & are made from a dis­ tinctive 2-tone green vinyl. They hold up to 14 issues & will look great on your bookshelf.  80mm internal width • • • • • 6 Channels 10kHz frequency separation Size: 55 x 23 x 20mm Weight: 25gm Modular Construction Price: $A129.50 with crystal Electronics PO Box 580, Riverwood, NSW 2210. Ph/Fax (02) 9533 3517 email: youngbob<at>silvertone.com.au Website: www.silvertone.com.au  Buy five and get them postage free! Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. Use this handy form Enclosed is my cheque/money order for $________ or please debit my ❏ Bankcard  ❏ Visa   ❏ Mastercard Card No: _________________________________ Card Expiry Date ____/____ Signature ________________________ Name ____________________________ Address__________________________ __________________ P/code_______ 94  Silicon Chip AV-COMM P/L, 24/9 Powells Rd, Brookvale, NSW 2100. Tel: 02 9939 4377 or 9939 4378. Fax: 9939 4376; www.avcomm.com.au Need prototype PC boards? We have the solutions – we print electronics! Four-day turnaround, less if urgent; Artwork from your own positive or file; Through hole plating; Prompt postal service; 29 years technical experience; Inexpensive; Superb quality. Printed Electronics, 12A Aristoc Rd, Glen Waverley, Vic 3150. Phone: (03) 9545 3722; Fax: (03) 9545 3561 Call Mike Lynch and check us out! We are the best for low cost, small runs. Positions At Jaycar We are often looking for enthusiastic staff for positions in our retail stores and head office at Silverwater in Sydney. A genuine interest in electronics is a necessity. Phone 02 9741 8555 for current vacancies.  SILICON CHIP logo printed in gold-coloured lettering on spine & cover Price: $A12.95 plus $A5.50 p&p. Available only in Australia. Satellite TV Reception International satellite TV reception in your home is now affordable. Send for your free info pack containing equipment catalog, satellite lists, etc or call for appointment to view. We can display all satellites from 76.5° to 180°. Microzed.com.au PIC/AXE CHIP SPECIALIST PO Box 634 ARMIDALE 2350 (296 North Cooke’s Rd) Ph: (02) 6772 2777 – may time out to Mobile 0438 277 634. Fax: (02) 6772 8987 LABJACK USB DATA ACQUISITION MODULE features 8 12-bit 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 12-bit 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. Programmers for Atmel and PIC microcontrollers. Switch Mode and Linear Power Supplies and DC-DC converters. FAB Programmable Logic Controllers. 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 Catalog 17078. Industrial Motherboard. 533MHz Front Side Bus, plus on-board Watch Dog Timer and Ethernet. This is a “well sorted” quality industrial board. For more detail: phone Microgram Computers (02) 4389 8444 or www.mgram.com.au RCS HAS MOVED to 41 Arlewis St, Chester Hill 2162 and is now open, with full production. Tel (02) 9738 0330; Fax 9738 0334. rcsradio<at>cia.com.au; www.cia.com.au/rcsradio USB KITS: Stepper Motor Controller, 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 10-RELAY ROLLING CODE UHF REMOTE CONTROL Expands the 4 Relay version (SC, 7/2002) to its full potential controlling 10 relays. Uses PIC16F628. See it at: www.ozitronics.com www.siliconchip.com.au Advertising Index Acetronics....................................95 Altronics................................. 72-74 Av-Comm Pty Ltd.........................94 BitScope Designs.........................71 Black & White Communications...95 Clarke & Severn...........................71 TAIG MACHINERY Dick Smith Electronics........... 18-21 Micro Mini Lathes and Mills From $489.00 Eco Watch....................................93 Elan Audio......................................9 Evatco..........................................77 Grantronics..................................93 59 Gilmore Crescent Garran ACT 2605 (02) 6281 5660 0412269707 Harbuch Electronics.....................69 Instant PCBs................................94 Hy-Q International........................71 & MADE TO ORDER PCBs Jaycar ................................... 45-52 For more details: www.acetronics.com.au Phone (02) 9600 6832 email: acetronics<at>acetronics.com.au 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 S-Video . . . Video . . . Audio . . . VGA distribution amps, splitters, standards converters, tbc’s, switchers, cables, etc, & price list: www.questronix.com.au HOOKED, BOOKED OR ROOKED? CEPU Communications Division for Technicians with industrial problems. Phone (03) 9419 0000. Website: www.cepu.asn.au JED Microprocessors................5,71 Kalex..............................................9 SCOPE TEKTRONIX 2246A 100MHz 7 probes + 1 high voltage probe P0615 with K212 cart. Excellent condition $1300.00 ONO. Dranetz line disturbance analyser model 606 with printout $250.00. Phone (02) 9559 1634, 0412 212953. Microgram Computers..............3,94 KIT ASSEMBLY Quest Electronics....................71,95 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 MicroZed Computers..............71,94 Oatley Electronics........................63 Printed Electronics...................... 94 Procon Technology.......................71 RCS Radio..............................71,94 RF Probes.................................9,71 Silicon Chip Back Issues..............88 Silicon Chip Binders.....................94 Silicon Chip Bookshop..........96,IBC Silicon Chip TestBench..............IFC NOW AVAILABLE FROM SILICON CHIP www.siliconchip.com.au Project Reprints Limited Back Issues Limited One-Shots If you’re looking for a project from ELECTRONICS AUSTRALIA, you’ll find it at SILICON CHIP! We can now offer reprints of all projects which have appeared in Electronics Australia, EAT, Electronics Today, ETI or Radio, TV & Hobbies. First search the EA website indexes for the project you want and then call, fax or email us with the details and your credit card details. Reprint cost is $8.80 per article (ie, 2-part projects cost $17.60). SILICON CHIP subscribers receive a 10% discount. We also have limited numbers of EA back issues and special publications. Call for details! visit www.siliconchip.com.au or www.electronicsaustralia.com.au www.siliconchip.com.au Silvertone Electronics..................94 Soundlabs Group.........................71 Taig Machinery.............................95 Telelink Communications....71,OBC _________________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: RCS Radio Pty Ltd. Phone (02) 9738 0330. Fax (02) 9738 0334. May 2003  95 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 authorities. New edition is more comprehensive than ever with a new chapter on Class G amplifiers and further new material on output 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, technicians and electronics enthusiasts – perfect for use in schools and colleges. 270 pages in soft cover. by Douglas Self 3rd Edition 2002 89 $ by John Morton – 2nd edition 2001 NEW NEW NEW NEW 46 $$ VIDEO SCRAMBLING AND DESCRAMBLING AUDIO ELECTRONICS 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. 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. By John Linsley Hood. First published 1995. Second edition 1999. FOR SATELLITE AND CABLE TV by Graf & Sheets 2nd Edition 1998 4th EDITION $ 70 87 $ EMC FOR PRODUCT DESIGNERS 3rd EDITION UNDERSTANDING TELEPHONE ELECTRONICS By Stephen J. Bigelow. 4th edition 2001 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. 103 $$ By Eugene Trundle. 3rd Edition 2001 3rd EDITION Eugene Trundle has written for many years in Television magazine and his latest book is right up to date on TV and video technology. includes both theory and practical servicing information and is ideal for both students and technicians. 382 pages, in paperback. Widely regarded as the standard text on EMC, provides all the key information needed to meet the requirements of the EMC Directive. Most importantly, it shows how to incorporate EMC principles into the product design process, avoiding cost and performance penalties, meeting the needs of specific standards and resulting in a better overall product. 360 pages in paperback. 63 $ By Ian Hickman. 2nd edition1999. Essential reading for electronics designers and students alike. It will answer nagging questions about core analog theory and design principles as well as offering practical design ideas. With concise design implementations, with many of the circuits taken from Ian Hickman’s magazine articles. 294 pages in soft cover. by Dogan Ibrahim. Published 2000. by Steve Roberts. 2nd edition 2001. Based mainly on British practice and first published in 1997, this book has much that is relevant to Australian systems as a guide to home and small business installations. A practical guide to installation of telephone wiring, ranging from single extension sockets to PABX, with the necessary tools, test equipment and materials needed by installers. 178 pages in soft cover. 89 $$ Microcontroller Projects in C for the 8051 TELEPHONE INSTALLATION HANDBOOK 69 By Tim Williams. First pub­­lished 1992. 3rd edition 2001. ANALOG ELECTRONICS GUIDE TO TV & VIDEO TECHNOLOGY $ 92 $ $ 73 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. BOOKSHOP ENQUIRING MINDS! LOWER THAN RECOMMENDED RETAIL PRICE WANT TO SAVE 10%? 10% OFF! SILICON CHIP SUBSCRIBERS AUTOMATICALLY QUALIFY FOR A 10% DISCOUNT ON ALL BOOK PURCHASES! 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 framework for a wide variety of power supplies. Anyone 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. 99 VIDEO & CAMCORDER SERVICING AND TECHNOLOGY 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. NEW NEW NEW NEW PIC IN PRACTICE O R D E R H E R E by Howard Hutchings. Revised by Mike James. 2nd edition 2001. 63 $$63 $ Anyone interested in ports, transducer interfacing, analog to digital conversion, convolution, filters or digital/analog conversion will benefit from reading this book. The principals precede the applications to provide genuine understanding and encourage further development. 302 pages in paperback. PRACTICAL RF HANDBOOK by Ian Hickman 3rd Edition 2002 by D W Smith Published 2002 Based on popular short courses on the PIC, for professionals, students and teachers. Can be used at a variety of levels. An ideal introduction to the world of microcon-trollers for hobbyists, students and professionals. 255 pages in paperback. 87 $ Interfacing With C Electric Motors And Drives by Austin Hughes. 2nd edition 1993. Reprinted 2001. For non-specialist users – explores most of the widely-used modern types of motor and drive, including conventional and brushless DC, induction, stepping, synchronous and reluctance motors. 339 pages, in paperback. Covers all the analog electronics needed in a wide range of higher education programs: first degrees in electronic engineering, experimental science course, MSc electronics and electronics units for HNDs. Text is supported by numerous worked examples and experimental exercises. 312 pages in paperback. 52 69 $$ $$ A guide to RF design for engineers, technicians, students and enthusiasts. Covers all of the key topics in RF: analog design principles, transmission lines, transformers, couplers, amplifiers, oscillators, modulation, transmitters and receivers, propagation and antennas. 279 pages in paperback. 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