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Australia’s Electronics Magazine SILICON CHIP AUGUST 2001 6 $ 60* INC GST ISSN 1030-2662 08 NZ $ 7 50 INC GST PRINT POST APPROVED - PP255003/01272 9 771030 266001 siliconchip.com.au Geocaching: YOU become the search engine! DI Box: stops hum & noise 200W Amplifier: uses plastic Mosfets Headlight Reminder: stop flat batteries! Frequency Counter: runs up to 40MHz Linux: Internet gateways Landmine Clearance: www.siliconchip.com.au electronic methods August 2001  1 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings.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.protel.com Contents Vol.14, No.8; August 2001 www.siliconchip.com.au FEATURES   4  Geocaching: Treasure Hunting With A GPS Enjoy treasure hunts the high-tech way. All you need is a GPS receiver (and preferably a 4WD) – by Ross Tester 30  Help Reform Electrical Legislation Want to do your own wiring or repair appliances . . .and remain legal? You can help change the legislation. 57  P-Tag: A Wearable Health Information Card New 8MB flash memory card stores your entire medical history. You wear it around your neck. Direct Injection Box For Musicians – Page 12. 58  The Role Of Electronics In Mine Clearing Abandoned land mines are a big problem in many countries. Here’s a look at the methods used for detecting these deadly devices – by Bob Young 81  1 Billion Transistor Microprocessors Are Coming New research from Intel has made it possible to cram 1 billion transistors onto one chip. Stand by for the 20GHz processor! PROJECTS TO BUILD 12  A Direct Injection Box For Musicians Don’t put up with hum. This versatile DI Box converts an unbalanced input to a balanced output signal and includes a 3-band equaliser – by John Clarke 32  Build A 200W Mosfet Amplifier Module Rugged design is ideal for guitar or PA work or for use as a general-purpose subwoofer or hifi amplifier – by Leo Simpson 200W Mosfet Amplifier Module – Page 32 70  Headlight Reminder For Cars Ever forgotten to turn your car’s headlights off? This device could save you from a flat battery – by John Clarke 76  40MHz 6-Digit Frequency Counter Module Low-cost unit measures frequencies up to about 40MHz – by David L. Jones COMPUTERS 24  A PC To Die For, Pt.3 – You Can Build It For Yourself Updating the BIOS and drivers to squash the remaining bugs. The advice applies to other PCs as well – by Greg Swain 64  Using Linux To Share An Internet Connection, Pt.3 Headlight Reminder – Page 70. How to tweak the settings so that you can log on as a user. We also cover logging and show you how to make it easy to drive – by Greg Swain SPECIAL COLUMNS 44  Serviceman’s Log Some faults can be a real challenge – by the TV Serviceman 90  Vintage Radio Substituting for valves that are no longer available – by Rodney Champness DEPARTMENTS   2  Publisher’s Letter  9 Mailbag 42  Circuit Notebook www.siliconchip.com.au 85  Subscriptions Form 86 Products Showcase 98  Ask Silicon Chip 40MHz 6-Digit Frequency Module – Page 76. 101  Notes & Errata 102  Market Centre 104  Advertising Index August 2001  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 Rick Walters Reader Services Ann Jenkinson Advertising Enquiries Ross Tester Phone (02) 9979 5644 Fax (02) 9979 6503 Regular Contributors Brendan Akhurst Rodney Champness, VK3UG Julian Edgar, Dip.T.(Sec.), B.Ed Jim Rowe, B.A., B.Sc, VK2ZLO 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, Dubbo, NSW. 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 Knowledge nation is a woolly headed wish list Now that the Labor Party has released its report on how to build the “Knowledge Nation” we’ll all sleep more soundly in our beds, won’t we? As spelt out on July 1st, the Opposition Leader, Mr Beasley, has compiled a woolly-headed wish list of things that might be good for us, without spelling out any real detail of how they might be accomplished. He and the Deputy Leader Simon Crean are real good at announcing that they will have inquiries but they don’t really seem to have any ideas or policies at all. The fact that they are the only alternative to the lacklustre mob presently in power is not attractive at all. Let’s face it: the record of successive Labor and Liberal governments on anything to do with technology has been woeful. If it wasn’t so serious, it would be farcical. Witness the present Minister for Communications, Richard Alston’s pronunciations on virtually anything to do with telecommunications, the ABC, Pay TV, free-to-air TV and Digital TV, data-casting, Internet gam­bling or whatever and you have to wonder who is advising him. But the really sad part about the nonsense he spouts for most of the time is that there is apparently no-one in Parliament who can step up and say, “What a load of rubbish!” As to Mr Beasley’s wish to double Australia’s research & development by 2010, let’s hope he’s not proposing a return to the old 150% R&D grants. We’ve been there and done that. Even if the Labor Party is genuine about it, you can depend on the Aus­tralian Taxation Office and the “devil in the detail” of the resulting law to rip back most of the benefits. Several years into the program, the ATO will subsequently back assess companies and tell them “that they didn’t qualify after all and they now need to pay huge back taxes”. It happened to Silicon Chip Publi­ cations Pty Ltd and I dare say it happened to many other compa­nies. No, if any company wants to develop new products or servic­es, it had better do it without the expectation of Government assistance. That way, there will be no need to meet arbitrary and stultifying bureaucratic guidelines and no need to wait forever for assistance or grants that might or might not eventuate. It is far better to get in and do it while the opportunity exists. There are lots of Australian companies which are success­fully developing and producing products and services for local use and export. Let us wish them Godspeed in their efforts. But let them do it without any government assistance or interference. If the Labour Party really wants to do something to help Australian industry do better in IT and electronics manufacture, there’s no need to think about any form of financial assistance. It can do it simply by getting rid of unnecessary legislation and regulation. A particular example: get rid of the need for EMC (Electromagnetic Compatibility) testing and C-tick registration for all electronic products sold in this country. EMC regulations have not resulted in any apparent improvement in most electronic products sold in this country and many of those with C-ticks radiate more interference than ever. Not only that, the present lack of enforcement of EMC stan­dards is unfair to those Australian companies which do everything by the book and produce products which fully comply. Worse, the cost of EMC testing stops many small Australian companies from ever developing products they can sell locally - they will never get to the stage where they can export. If the Liberal Party feel like improving their chances of winning the next election, they are free to take up the idea, as well. They might even get my vote. And can we have a replacement for Richard Alston? Leo Simpson www.siliconchip.com.au Smart Card Reader/Writer Cat. 8899 This Smart Card reader (not to be confused with SmartMedia) connects to a PC via a serial port. The reader is compliant with ISO7816/3/4 with T=0, T=1 and APDU protocols. Cat. 8899-7 Smart Card Reader/Writer - Serial $183 Hot-Swap IDE RAID Array Network Tester with LCD Display Tests a range of Modular Cat. 11519 cables including 10Base-T. The LCD display shows the pin connections as well as the wiring scheme detected eg 100Base / Hub. Cat. 11519-7 Network Tester $227 Mouse Tablet Uses electromagnetic technology to provide high resolution input - there’s no ball to clog. It’s also a stylus pen Cat. 11519 input device which has pinpoint accuracy with writing, drawing & painting capabilities. A nice feature is the absolute reference of the mouse (or stylus) on the pad - no more jumping the mouse to get back on the screen. You can use the mouse and stylus interchangeably. Software is included to make navigating the internet a dream as well as handwriting recognition, signature posting utility, signature identification, screen saver and popup note utility. Cat. 8676-7 Mouse Tablet $205 Turn your PC into a TV Connect a Mouse and a Trackball to Your Computer Use two pointing devices Cat. 15097 on one PC. The dual mouse adapter allows the simultaneous connection of two compatible pointing devices, such as standard mice and trackballs. Connects via a PS/2 port. Cat. 15090-7 Dual Mouse Adapter PS/2 $161 Cat. 15097-7 Dual Mouse Adapter Serial $161 Connect Two Keyboards to Your Computer Allows the simultaneous connection of two keyboards from one keyboard port. Connect a specialised keyboard, eg POS, and a standard keyCat. 15091 board at the same time, or a computer that requires input from two locations. Cat. 15091-7 Dual Keyboard Adapter $158 Connect Two Monitors to Your Computer Avoid downtime delays when your hard drive fails! This unit enables the user Cat. 2808 to replace the hard disk while the PC is operating and it automatically resynchronizes itself to full operation. The RAID unit fits into two continuous 5.25” bays and includes a controller and two removable frames. The array accepts two EIDE hard drives. The controller provides RAID Level 1 disk mirroring. It can also be used as an on-line hard drive copier. Cat. 2808-7 IDE RAID Array $1255 Hard Drive Controllers Ultra DMA100 IDE controllers are available as standard or RAID. Will co-reside with up to 4 additional onboard IDE devices! Cat. 2848-7 Ultra DMA100 RAID Cat. 2827-7 Ultra DMA100 Cat. 3437 Cat. 2848 $154 $129 PC to Video Converter Uses digital processing to enable your PC or laptop / notebook display to be viewed on a TV. Converts VGA Modes - 1024 x 768, 800 x 600, 640 x 480 into NTSC 3.5795 and PAL 4.43, PAL-M 3.57, PAL-N 3.58 Video. Can be used between PC and VGA monitor to watch computer displays and games on a TV or record onto a VCR. Cat. 3437-7 PC to Video Converter $354 Allows the simultaneous connection of two monitors from one VGA port. It’s great for training presentations or No room in the house in situations you need two monitors to display from for a TV and a PC? one computer. An inbuilt amplifier ensures there is Now you can watch TV no reduction in image quality. programs in a window $265 on your PC while you are working in other applica- Cat. 15092-7 Dual Monitor Adapter tions, or switch to full screen TV display. Comes with Connect a Keyboard a remote controller which allows you to switch YOUR and Mouse to Your between PC mode and TV mode, adjust channels, SELF Notebook with PS/2 volume and more. New courses now on line - SAP R/3, Cat. 3399-7 PC to TV Card & Controller $209 Turn your Notebook into from a low WIN2000 MCSE, RPG, Web design, a desktop with one simCat. 15094 $1595 CCDA LAN/WAN, e Commerce. Video Capture Card PCI ple connection. Allows the simultaneous connection Cat. 3358 per month www.tol.com.au Provides smooth, full-motion of a PS/2 keyboard & a PS/2 mouse to a single PS/2 video for applications such port or to a USB port. Alternatively you can connect as Video Mail, Video two mice or two keyboards to your notebook. Phone: 02 4389 8800 email: info<at>tol.com.au Conferencing or Full-Motion Cat. 15093-7 PS/2 to PS/2 Adapter $205 Video Capture to AVI file forCat. 15094-7 PS/2 to USB Adapter $161 We welcome Bankcard, Mastercard and VISA NO SURCHARGE! mat. Utility software provides full screen (640 x 480) Watch TV and or any size window live video display. Phone: (02) 4389 8444 Australia wide Cat. 3358-7 PCI Video Card & Software $143 Videos on your sales<at>mgram.com.au PC monitor express courier Cat. 3393 Video Frame info<at>mgram.com.au $ 12 (3kg max) No room in the Cat. 3399 Cat. 15092 TRAIN ONLINE Training Online Capture - USB Port Easily capture a picture from your analogue video stream. Just plug the capture box into a USB port and load the included software. Cat. 3393-7 Video Frame Capture USB $199 FreeFax: 1 800 625 777 house for a TV and a computer? Cat. 3372 MicroGram Computers This compact unit Unit 1, 14 Bon Mace Close, Dealer turns your monitor into a TV. Comes with an Infra Berkeley Vale NSW 2261 Enquiries red remote control for all standard TV control Welcome! Vamtest Pty Ltd trading as functions. MicroGram Computers ABN 60 003 062 100. Cat. 3372-7 Monitor Adapter $345 All prices subject to change without notice. MGRM0801-7 GEOCACHING:: Treasure Hunting For Techies With A GPS By Ross Tester Did you enjoy treasure hunts when you were a kid? Now you can re-live your childhood in a whole new, high-tech way with the world’s latest game/ hobby/past-time. All you need is a GPS receiver! S omewhere in the picture above is hidden a GPS stash, or cache. What, you can't find it? You need to get into the latest “game” on the planet, Geocaching. Geocaching (pronounced jee-ohcashing) is very new – so new, in fact, it won’t have found its way into dictionaries. It’s also so new that a lot of people don’t even know what it is, hence this article! First and foremost, Geocaching is a treasure hunt. But it’s much more – and much less – than that! Normally in a treasure hunt you 4  Silicon Chip expect to find, well, treasure of some sort. When you find the “treasure” in a Geocache cache you’re more likely to find a few trinkets which are worth next-to-nothing. And what’s more, you’re expected to leave something in return! Sometimes, though, Geocaching can be much more financially rewarding. Despite its youth, Geocaching contests have started to spring up with the winners taking home real dollars – $US5000 is not uncommon. But as we said, it’s much more than a treasure hunt. It’s actually closer to the “fox hunts” which amateur radio operators used to (and occasionally still do) take part in, where they are looking for a well-hidden transmitter with the aid of direction-finding receivers. (Please, no correspondence from irate amateurs telling us foxhunts are alive and well. I are one – amateur that is, not irate. But an amateur radio foxhunt may typically attract ten, perhaps twenty or so enthusiasts. A Geocache hunt may attract thousands of enthusiasts). With Geocaching, you’re looking www.siliconchip.com.au (Left): a typical cache, just before it is hidden. The case is waterproof, it is identified with the person or group who left it and it’s not so big that it cannot be hidden fairly easily. (Below): the contents of that same cache. First to find it would almost certainly claim the piggy and possibly polish off a Freddo frog or two. Actually, this one is a bit naughty because food in caches is not recommended – especially if the area is accessible to wild animals. for a (usually) well-hidden cache with the aid of a GPS receiver and a few clues. It’s sort of a cross between orienteering, treasure hunting, bush-walking, four-wheel-driving, occasional cross-country skiing, perhaps abseiling or rock-climbing, often a lot of undeleted expletives (depending on the company!) and much frustration. Sometimes the cache is not well hidden at all. It’s just there – beyond reach. Up a sheer pole or limbless tree. Down a cliff. A few fathoms under water. And so on. Part of the game is solving the problem of how to get there! The most annoying – and at the same time attractive – feature of a cache is that you could be quite literally standing on it without realising it. Something you’ve spent hours, even days, looking for might be unearthed by someone else, seconds after they get there! It’s one thing to know a cache’s location. It’s another thing completely to know exactly where the cache IS and lay your hands on it! What’s in a cache? About the only thing that’s found in just about all caches is a notebook and a pencil to record the successful finders. As far as the other contents of the cache, almost anything goes. No, that’s not strictly true – the contents are deliberately made to be fairly worthless to discourage looting. But looting and trashing of caches still happens occasionally. (That’s yet another reason why such trouble is taken to conceal, or at least camouflage, a cache). Food is not encouraged because wild animals have much better noses than we humans and have been known www.siliconchip.com.au to destroy a cache to get at the muesli bars or chocolates inside. So what goes into the cache? How about a Barry Manilow CD or cassette (yeah, we know, they’re pretty worthless). Maybe a couple of small toys. A comic book. Some really useful computer parts (memory chips for 8086 machines, perhaps?). Maybe the contents will reflect another of the cacher’s hobbies. Or if they want to convert the world, a Gideon’s Bible. As you can see, there is very little that can’t go into a cache. About the only no-nos are weapons of any kind (including ammunition) and drugs (although a couple of Winfields and a lighter wrapped in foil might save a desperate’s life out in the sticks!). The rules for Geocaching are very simple. When you have found a cache; 1. Note your find in the logbook 2. Take something from the cache 2. Leave something in the cache Most Geocachers are also conservationists. The old adage “take nothing but photos, leave nothing but footprints” almost applies (apart from what you actually exchange). But just as importantly, most Geocachers also take the opportunity to help mother nature out by taking rubbish out with them when they leave. How did it start? Geocaching only became possible on May 1st, 2000, when US President Clinton made the decision to remove the deliberate degradation of signals (called Selective Availability) from the 24-satellite Global Positioning System (GPS). This changed the accuracy of non-military GPS units from within about 30 metres or so to at least 10 metres – and often better. So now when you obtain a “fix” from a hand-held GPS unit (especially one averaged over, say, an hour or so) you can be pretty sure you can find your way back to that exact spot (or at least within a few metres of it). In celebration of the lifting of selective availablility, a chap called Dave Ulmer hid a container of goodies (actually an upside-down bucket) outside Portland, Oregon, USA on May 3. Its GPS co-ordinates were logged on the sci.geo.satellite-nav newsgroup and, by May 6, two people had found the “GPS Stash Hunt” container, as it was first called, and logged it in the book. Mike Teague was one of the two and he started building a web site at www. triax.com/yngwie/gps.html dedicated to this new hobby. In July 2000, Jeremy Irish found Mike Teague’s web site and found his first cache outside of Seattle, Washington. Recognising the potential of the game (but never expecting the growth), Jeremy approached Mike Teague with a new site design, used August 2001  5 Now that’s a bit unusual, isn’t it? A duck sitting up a tree? Yep, you guessed it – it’s a cleverly disguised cache, high enough to dissuade all but the most determined looter (or a determined Geocacher . . .) Here’s one of a Geocacher’s favourite hidey-holes: a hole in a tree-trunk. Just be careful it isn’t occupied by spiders, snakes or other creatures! Inset is the type of cache you’d find in such a place – in this case there is no need for camouflage colours because it’s well hidden from view, even from someone standing right there. But it’s no match for an experienced Geocacher, because he/she knows that’s just the sort of place to look! the name Geocaching, and developed a new web site – www.geocaching. com – adding virtual logs, maps, and a way to make it easier to maintain caches as the sport grows. www.geocaching.com is also the international “repository” of Geo-caches – at the time of writing there were somewhere around 3000 active caches around 50 countries including Australia. In the week before, an amazing 1797 logs had been written by 830 account holders with www.geocaching.com Geocaching is arguably one of the world’s fastest-growing pastimes. All you need to participate is a hand-held GPS unit (around $250 up) and some good bushwalking boots! OK, so some caches require a little more equipment – such as abseiling gear, a boat, a 4WD, perhaps even scuba gear! But equally, there are many caches which require only the basic equipment and some clear, problem-solving thinking. No fancy stories, or smelly locations. No trudging for hours through thick scrubby undergrowth. Just a plain and simple cache to get Geomon-keys on the board. Location is accessible via road, and public transport. Tracks can be water logged, so be prepared to splash a little, after rain. And come prepared for a brisk walk. There are three accesses, any one will do, and you’ll find our barrel south of the junction of the three paths. Have fun finding it, re-hide the cache carefully as eyes are all around.” One other vital piece of information is given about the cache: it’s grade. This is a measure of the difficulty of finding the cache and the difficulty of Gradings Take this one, for example – it’s a current cache hidden somewhere near Sydney: “Location: S33°48.543 E151°10.963 A suburban bush track that not many folks know of, but is rather attractive and interesting. 6  Silicon Chip Another variation on the hole-intree cache: a hollow stump, with just enough old timber piled on top to make it look “natural”. the terrain which has to be traversed, both on a scale of one to five. The above is rated 1/1.5 – almost as easy as it gets. Difficulty: 1 A ten year old could probably figure it out without too much difficulty 2 An average adult would be able to find this in about 30 minutes of hunting 3 An experienced Geocacher will find this challenging, and it will take up a good portion of an afternoon. 4 An extreme challenge for the experienced Geocacher – may require in-depth preparation or cartography/ navigational skills. 5 Mensa or equivalent T­errain: 1 Handicapped accessible 2 Suitable for small children; generally on trail 3 Off trail; requires some risk of getting scratched, wet, or winded 4 Off trail; likelihood of getting scratched, wet and winded. Probably requires special equipment (boat, 4WD, etc.) 5 Requires specialized equipment and knowledge/experience (rock climbing, SCUBA, etc.) An example of the “more difficult” caches? This next one is rated as 5/5 (as hard as it gets) and is located at S www.siliconchip.com.au 33°40.59 E 150°14.57 which puts it near Blackheath in the Blue Mountains, west of Sydney. Then again, you don’t have to be Einstein to work that out because the cache owners tell you that much in the clue. When you read the rest of the clue you’ll start to understand why it is rated 5/5 and also that some Geo-cachers take it all very, very seriously. “The cache is located near Blackheath in the Blue Mountains. The co-ordinates given are the exact location of the cache, but you will find it requires Abseiling/Rock climbing equipment for a 30 metre descent. The Stash is sitting, sheltered and comfortable, somewhere inside an old car that has been pushed to its death and rests on a narrow rock ledge. The ledge is still high above the valley floor so it is not safely accessible by any other means. A rather interesting and challenging place you will agree. In the cache, amongst other things, you will find some energy bars which you may need for the difficult ascent back out. Also the first finder will find some cash to help pay for your petrol or gear hire. This should be an exciting find but don’t attempt it without the proper skills. I have rated the overall difficulty as 5 even though it is easy to find once you get there.” Woh! I think I’ll leave that one to the seriously fit, expert Geocachers, thank you! Just to reiterate, all you really need is a GPS receiver and of course web access, so you can see where the latest (or in fact any) caches are close to you. And they are all over Australia and New Zealand now – you shouldn’t have to travel too far to get to a cache site. The www.geocaching.com site even makes life real easy by allowing you to search by country and even by keywords. It’s worth having a look at, just to see the trouble some people go to hide their caches. Searching for a cache www.geocaching.com has some pretty good tips for beginners. We’ll paraphrase these but if you’re serious, it will pay you to look at the site (you’ll Here’s a listing of Australian caches from www.geocaching.com As you can see, these are only the first 25 of the 96 sites listed in late June. You can bet there are even more now! www.siliconchip.com.au August 2001  7 Sometimes the cache hiders make it nice and simple for you to get to the location, providing maps and routes as part of the clue. Don’t expect finding the cache itself to be quite so simple! need to anyway to find the cache co-ordinates). 1: Research the cache – if you don’t know the area, buy a good map (preferably a topographical map) of the area. Navigating by GPS alone is not recommended, especially for your first cache hunt or if you don’t know the area. 2: Prepare properly. Have the right clothing (including boots) for the terrain and season. Always go with at least one other person and remember to tell someone where you are going and when you’ll be back. 3: When hunting the cache, use your GPS to enter waypoints (including where you left your car!). It’s easy to get within a few tens of metres; the last bit is the hardest. Try to think like the person who hid the cache: “where can I hide this so that noone will easily stumble across it”, and so forth. 4: When you’ve found the cache and noted your find in the book, take something and leave something, then make sure you seal the cache back up again and hide it exactly as you found it. 5: Afterwards: email the person who hid the cache to let them know you found it; go to geocaching.com and log the details there as well. 6: Sit back and congratulate yourself! Hiding a cache So you’d like to hide a cache, would you? Probably your best bet would be to first hunt for a few caches so you get to understand the ground rules. The cache container is all-important because it has to protect the cache 8  Silicon Chip contents from the weather (remember, the vast majority of caches are out in the open). Some people use buckets, others ammo boxes, others Tupperware or similar containers. Whatever you use it needs to be fairly neutral in colour or of a colour which will blend with the surroundings. If it’s easily spotted, it is likely to be raided. You’ll see all these things types of containers – and more – as you look for a few caches. You’ll also find what other people leave in their caches and some of the traps for young players. We’ve already mentioned food items. And we also mentioned a notepad and pencil. Why not a pen? If you leave your cache in country where it snows or frosts in winter, the odds are the pen will freeze up and become useless. Similarly, there’s not a great deal of point putting a notepad in an underwater cache, is there! (Some Geo-cachers have even used waterproof diver’s slates). You must be careful not only where you hide your cache but who owns the property it’s hidden on. Always ask permission from private property owners. If they allow people to bushwalk or hike through their property, the chances are they will be amenable to a cache. But you’re probably going to have to explain all about geocaching first! If it’s public land (eg, a National Park etc) then different rules apply. Beaureaucrats being what they are, the answer will always be “no” (unless you happen to strike a Geocacher!). We didn’t say this, of course, but sometimes its best not to ask! If you hide your cache well enough, it’s not going to be spotted anyway so “out of sight is out of mind”. And when you hide your first cache, you probably want the world to know about it. You can register your cache on www.geocaching.com – needless to say, you’ll have to give the GPS co-ordinates available and also a brief description of how to find it, without giving too much away! After all, there’s not much point in telling someone exactly where it is – that takes all the fun out of the game. Finally, remember that as the owner of the cache, you’re also responsible for it. You’re responsible if it causes damage or injury (that’s why you have to be careful about what’s in it). And if you remove your cache, don’t forget to tell www.geocaching.com so there aren’t millions of people (OK, thousands) trying to find a non-existent SC cache! Yet another variation on the hole-in-the-tree theme, although this one is a bit too obvious unless it’s deep in a forest, possibly with a lot of other obstacles (rivers, cliffs, etc) making access difficult. After all, no-one wants a cache that’s too easy. Incidentally, can you spot the cache inside the trunk? It is there! www.siliconchip.com.au MAILBAG Queensland always has been a closed shop I have an amusing story about getting restricted electrical licence recognition in Queensland many years ago when I worked for Telecom (now Telstra). The inspector came to our site to see whether we had sufficient training to allow us to fit power cords to the battery chargers we were installing. We had set out a wide range of equipment that illustrated that we manufactured, installed and repaired very high voltage, high power and high current equipment at both power and radio frequencies that far exceeded what the restricted ticket covered. I pointed out that the broadcast transmitters had high voltage, high current power wiring and mains voltage control circuits. I even showed the inspector a spectrum analyser we were repairing to give an idea of the technical level of the people in the workshop. Needless to say, I was taken back a bit when he subsequent­ly said “Yes I see all that but do you get taught Ohm’s Law?” I explained that we did and that a technician had at least five years of theory and practical training. Knowing that I had demon­strated that we more than covered all aspects of the restricted ticket, I was absolutely gobsmacked when he finally said, with a straight face, “In all honesty I couldn’t recommend that you people be permitted to fit power cords.” A safety issue or a desire to keep a closed shop? I’ll leave the decision to you. Mark Little, via email. WIA needs to take a business approach The WIA has a great opportunity in the near future to take over functions from the ACA and manage them in the interests of radio amateurs. Examinations are currently being investigated for devolution and there has been talk of devolving licensing at some later date. If the WIA is to carry out these www.siliconchip.com.au functions then good organ­isation and sound management will be required. It is therefore unfortunate that we have recent examples in both Queensland and Victoria of decisions to cease running their WIA divisions as businesses with paid staff. In both cases the decision was accom­panied by a substantial fall in members funds. It would seem the directors involved were anticipating declining rather than improving business, justifying their deci­ sions to accept the costs required to change direction. That this has occurred should in no way affect the percep­tion of what can be achieved nationally with a bigger market and a specific business plan identifying the opportunities. The WIA can only carry out devolved work from the ACA on a national basis. Martin Luther, Willaston, SA. A more detailed paper is available on the ARA website at: www.amateurradio.org.au LP Doctor works well on 78 RPM records I wrote to you some 18 months ago with regard to designing a device to remove clicks and pops from records. Some time later you wrote back to me advising you had designed the LP Doctor which was eventually published in the January 2001 issue. Thank you very much for what obviously has been a great deal of work for you and your staff. I have recently constructed the kit from Dick Smith Elec­tronics and bench-tested it, and I am pleased to say the device does as you claim. Further to this, it provides some good results on 78 RPM records which were my main concern. I actually got a battered old 78 and scratched it quite badly with a screwdriver just to prove the point. The LP Doctor is valuable to my cause with regard to pre­senting nostalgia programs on community radio: “Memories of Yesterday” on Plenty Valley FM – Melbourne 88.6MHz. I have a further request: is there a way in which I can feed the LP Doctor input at line level by bypassing the phono input? Ken Jeffrey, Epping, Vic. Comment: you can feed a line level signal directly into the output level control VR1, in both channels. This will require some switching, so that the output of the preamplifier does not load your line level signal. Digital amplifier article appreciated The article on the digital amplifiers in the July 2001 issue was very interesting and the web contacts for further reading are very useful. I like the way you have cut through the hype, blurb and marketing to explain the basics. I note that a review in “Australian Hi-Fi” of that Sharp $25,000 unit made mention of an impedance switch. If the amplifiers are reliant on a low-pass filter, surely the impedance of the speaker would affect its operation – especially as it varies all over the place (wildly with some speakers). How a digital amplifier would behave around the crossover frequencies and bass resonance peaks would be an interesting thing to find out. Perhaps they will only be suitable for mass market audio gear where the speakers are sold with the amplifier and the responses/filter characteristics can be tailored to the drivers used. All in all, an interesting article. John Richardson, via email. Comment: you could be right about digital amplifiers being tai­ lored to suit certain speakers. Maybe they will never become the amplifier of choice for true hifi enthusiasts. continued next page August 2001  9 Mailbag – continued EMC standards not being policed Several years ago the Spectrum Management Agency (SMA), now the Australian Communications Authority (ACA), promulgated a number of Electromagnetic Compatibility (EMC) Standards and Electromagnetic Immunity Standards (EMI) for electrical/ electron­ic devices. Some people at the top of that organisation believed that these new standards would be embraced by the manufacturers of devices likely to cause interference or likely to be interfered with. With this naive belief in mind, I suggest they believed that experienced interference officers were no longer needed and were made redundant. Did the manufacturers do as expected? Some Australian manufacturers did and still do. Overseas imports? Well, people see the CE sticker on equipment coming into Austra­lia and probably believe the equipment meets some standard. But just because there is a label on a device doesn’t mean it meets the standard or ever has met the standard. Paper CE stickers cost about a dollar per thousand! I have bought equipment (mostly Chinese) that has the CE sticker applied and they are some of the worst generators of radio interference I have ever had the misfortune to own; so bad that the local AM broadcast station (20km away) can just be heard through the interference. My wife and I bought an electronically controlled automatic washing machine that was supposed to meet the interference stan­dards. It was just as noisy as some of the imported junk that had the CE compliance stickers attached to them. I complained and around two years later I had an interference suppressed control panel fitted and now I can hear the radio stations. What did this tell me? It told me that the washing machine probably was tested with the suppressed board fitted but the production line model had the unsuppressed board fitted. Computers – now there is a story. 10  Silicon Chip They are required to comply with the EMI and EMC standards since January 1999. The ones I have seen create more interference and are more likely to suffer data corruption from mains-borne interference than earlier computers. I have not been able to find any seller willing to state that their equipment meets the EMI and EMC standards. There are multitudinous devices causing interference out there and the ACA seems uninterested in policing the standards that they have put in place. They can cry that they don’t have the people to do this – well they did, but they got rid of most of their experienced technical officers. Are we going to let Australia once again be the dumping ground for inferior equipment that could never meet an EMI or EMC standard? Overseas countries and many of our greedy importers are quite happy to sell the cheap and nasty stuff to us, claiming when challenged that they didn’t know there was anything wrong with the equipment that they sell. Pull the other leg! Most cars these days are relatively quiet electrically but some Diesel-engined vehicles generate quite severe radio inter­ ference – not what you would expect. Don’t expect any help from the vehicle manufacturers either. I wonder about interference standards for vehicles. Does anyone know what standards apply to them? Rodney Champness, Mooroopna Vic. Electricians’ closed shop to end I have been a SILICON CHIP reader for years and think your magazine is tops. I have had a bit of a scare recently reading your suggestion that the “closed shop” on home electrical work should be opened. I am very concerned as to what level you are suggesting that people should be allowed to perform their own work on mains appliances and household wiring. I am an electrician by trade and I have recently finished my electrical/ electronic engineering degree. I am horrified at the idea of legally allowing unqualified members of the public to repair or install domestic wiring. Some of the jobs I have had to repair/ upgrade that have been completed by do-it-your-selfers have been really frightening. Knowing Ohms Law is just not enough and unfortunately not everything is obvious to the uninitiated. What really concerns me is safety, for the owner and for the next poor bugger who has to come along and upgrade or repair a job that has been completed with good intentions but has ended up being a death trap. I agree that anyone that has the skills should be able to attempt work in their own home, but they should be tested by an independent body to ensure at least at some time they have a thorough grasp of all the knowledge they require to complete the job safely. I can also appreciate that just because a person is li­censed does not mean that the person is capable. I think that electricians should be re-tested every five years but that is another matter. Matthew Nicholas , via email. Comment: we are not advocating any change to the way in which most electrical work is done. However, we ARE advocating that Australia adopt the same system as in New Zealand and a great many other countries whereby homeowners can do their own wiring, subject to inspection by licensed inspectors. This system works very well. New Zealand’s electrical fatality rate is lower than Aus­ tralia’s. And most of Europe, where homeowners are also permitted to do electrical work, has a much lower fatality rate. Apart from that, it appears that electrical fatalities in Australia due to homeowners doing electrical work is extremely low. Valve amplifiers still wanted Some time ago, the Editor made comments regarding recycling electronic devices, etc and ultimately you produced the Ultra-LD amplifier in an old computer case (March, May & August 2000). Well, it WAS ‘recycling’ but only just! Now the valve brigade (read “Luddites”) are going to continually niggle and annoy you until you give www.siliconchip.com.au in, so you may as well do battle with them now rather than later. Two of the biggest headaches with valve amplifiers are the power supply and output trannies. What about using a monitor PSU for HT as well as the filaments? I recently junked a 14-inch colour monitor and the PSU board had outputs of 140V at 400mA, 80V at 200mA and 5V at many amps; in all, about 150 watts. Now the 140V is a limiting factor but with decent efficient speakers and playing REAL music, 10 or 15 watts ought to be ample. Or how about a high-powered headphone amplifier? Regarding the output transformer: go the whole hog and direct/capacitor couple. This will solve the design/ price problem and the “Valve Brigade” will get so bogged down with faction fighting (transformer vs. direct) that they’ll leave you alone for awhile. Seriously, I don’t know if PSU noise will be a difficult problem but if all else fails, run a competition for the best Universal Filtering Circuit. And you could put the whole thing into ANOTHER old computer case. James Longmire, via email. Comment: your idea about recycling a monitor is intriguing but it doesn’t really stack up unless you only want a couple of watts output. Nor is the idea of capacitor coupling to the output practical unless you have special high-impedance speakers; eg, the 800ohm speakers made about 30 years ago by Philips. We could do a valve stereo amplifier but it would probably leave very little change out of $1000. Even then the performance would be inferior to any of our transistor amplifiers. Feedback on editorial content I really appreciated your editorial in the June issue. While electronic product design and development for me finished some years ago, I remain in touch with the technologies (or at least I pretend I do) by building and experimenting on my workbench. That includes, from time to time, building some of the excellent designs from SILICON CHIP. And I certainly understand how much effort must go in from all of your team, to getting those designs www.siliconchip.com.au and the magazine itself, out on time, each and every month. And I enjoy the mix of articles. I don’t really appreciate Vintage Radio but I do appreciate your articles on the subject. Same for model aircraft and the recent series on UAVs. Not my field but I have enjoyed Bob Young’s material, very much. No complaints about the computer articles. They seem reasonably balanced, to me, with other material in the magazine. These articles often come in handy when I’m trying to sort out my systems and family PCs, etc. The first page I turn to (well, of course, after the edito­rial!) is always the Serviceman. It would be interesting to see a feature on the cartoonist. He deserves a medal for his continu­ ously superb artwork. How does he get his inspiration? Has he ever met the man? What’s his interest in electronics? Is he a freelance artist, or is he actually the marketing manager of Telstra with a secret life? One of the biggest problems in the hobby, and one I think which has some impact on its potential to interest younger read­ers, is the scarcity and cost of components. I know that Dick Smith Electronics and others continue to offer fine service, for which I’m grateful. But if you want something a little out of the ordinary, like a Murata ceramic 455kHz AM IF filter, you’ve either got to junk a cordless phone or buy one from the Web at one-off prices with postal costs that are scary. As for those months when your articles don’t quite seem to make the expected impact: I’m reminded right now of articles such as the command control trains series back in 1998. They didn’t much interest me back then but now with my son suddenly intrigued by an old train set, well, out have come those maga­zines and we’re both into it with keen anticipation. Andrew Woodfield, via email. Comment: thanks for the feedback Andrew. Our cartoonist does know the Serviceman – they meet each year at our Christmas party. Brendan Akhurst is a freelance cartoonist with a number of syndi­cated cartoon strips. We feed him the ideas which he mainly ignores and then comes up with his own crackpot concepts. New computers are not so efficient I know you’ve talked about turning PC monitors off when not in use and now I’m hoping you can enlighten me as to the logic in the ATX computer power supply. The power switch on the front of the box doesn’t turn the mains off. It puts the box in sleep mode or something. What I don’t understand is, when we used to turn off the front or side power switch to our PC, we turned off the mains and it used NO power at all. Now we push the button and it goes to sleep, still connect­ed to the mains and consuming the 5W or so to keep it alive. This is energy efficient, I’m led to believe. It also allows such functions as “wake on LAN” and the like. What I can’t come to grips with is all those PCs that AREN’T used in the above way (ie, standalones with no need for such functions as wake up on LAN) sitting there consuming their 5W whereas before they consumed NOTHING. How many PCs on this planet are consuming their 5W doing nothing and how much generat­ ing capacity, producing greenhouse gas emissions, is required to keep them all going when they are doing nothing? I do not believe folks reach around the back and turn the real power switch off! Do the power supplies last longer due to being on all the time? I don’t think so. Can you please tell me how a device consuming a small amount of power is supposedly more efficient than one which consumes no power at all? Brad Sheargold, via email. Comment: don’t you accept all the good stuff that the companies keep telling you? Of course the new power supplies are more efficient – it is just that they keep using 5W when they go to sleep. If you add all the appliances in your house which are supposedly asleep (ie, on standby) you will probably find that you have a standing power consumption of at least 100W (add em up – VCRs, microwaves, plugpacks, TVs, dishwasher, etc). That costs you around $100 per annum. We still reckon you should switch off your computer and pull the plug out of the wall when not in use. August 2001  11 This versatile Direct Injection (DI) Box incorporates a 3-band equaliser (EQ) and can be powered using battery, plugpack or phantom power. You can use it for DI-ing your instruments and as an in-line equaliser. A DI BOX FOR MUSICIANS By JOHN CLARKE “WOTSA DIRECT injection box?” we hear you ask, so let’s cut straight to the main chase. Basically, a DI Box is a device that accepts an unbalanced mono or stereo input signal from a musical instrument and converts it into a balanced output signal. This signal is then fed into a balanced microphone input on a mixing desk. This has lots of advantages when it comes to minimising hum and noise, especially where long cable runs are involved. We’ll have more to say on this shortly. The “direct injection” bit is a musician’s term. It refers to signals that are directly coupled (or injected) into the audio chain from a musical instrument, rather than picked up by a microphone. The signal can come from an outlet socket on the instrument itself, from a pickup (eg, on an electric guitar), or from any other source such as a CD player or tape player. In a nutshell, a DI-Box allows musical instruments to be coupled to the balanced microphone inputs of a mixing desk. It has a high-impedance input so that it doesn’t load (or 12  Silicon Chip degrade) the signal source and a low output impedance, similar to that provided by a balanced microphone. In fact, it’s fair enough to say that a DI-Box “looks” just like a microphone as far as the mixing desk is concerned. Do you really need it? So do you really a DI-Box? You “betcha” – if you’re into serious sound reinforcement, you generally need one for each instrument. But why use a DI-box? Why not connect the output from the instrument directly into the mixer? The answer is that you’ll almost certainly run into serious hum problems and signal losses if you do. The big advantage of using a DI-box is the balanced output it provides for connection to the mixing desk (all high-quality mixers have balanced inputs). This balanced output has two signal lines and a ground return and these connect to standard 3-pin XLR sockets. Pins 2 & 3 of the XLR socket carry the signal and these operate in anti­ phase to each other. In other words, when one line goes positive, the other line swings negative by the same amount. At the mixing end, the two signals are subtracted to recov­er the original signal. Any hum signal which is picked up along the line is effectively cancelled because the same amount of hum will be present in both signal lines. As a result, the subtrac­ tion process attenuates the hum to very low levels. This hum rejection ability using balanced lines is the main reason for using a DI box. Similarly, other forms of interference (eg, from a lighting control desk) are also rejected, since the interference signal will be common to both lines. Another good reason for using a DIBox is that its high-impedance input prevents loading of guitar pickups. By contrast, if the pickup was to be excessively loaded, the high-frequency response would suffer. Don’t be unbalanced In some cases, the output from an instrument can be con­nected directly www.siliconchip.com.au to a mixer using an unbalanced signal. This involves using either one of the mixer’s unbalanced inputs or by using a specially wired lead which connects the inverted signal line to ground. There will no longer be any hum cancellation but this may not be a problem if lead lengths are kept short or if the output impedance of the signal source is very low. That said, unbalanced coupling is seldom used and there are several reasons for this apart from the lack of noise cancella­ t ion. First, some mixers cannot cope with the line-level outputs from musical instruments, since they are usually set up for amplifying low-level microphone signals (usually only tens of millivolts). As a result, the mixer will overload and the sound will be badly distorted. In addition, “hum loops” can be a real problem, especially when a stage amplifier is also connected to the instrument. In this case, there will be a continuous earth loop because the amplifier and mixing desk are connected together via their mains earths and also via the shield connections in the signal cables. These problems can all be solved by using a DI-Box which provides for signal attenuation and includes a so-called “ground lift” circuit. This “ground lift” circuit is simply a switch which disconnects pin 3 on the XLR socket from ground – ie, it disconnects the signal earth at the DI-Box output to break the earth loop. A ground lift switch can literally make the difference bet­ween a very loud audible hum in the system and virtually no audible hum. The SILICON CHIP DI-Box boasts all the above necessary features, including high input impedance, a low-impedance bal­anced output, an atten­uator control (to prevent signal overload) and a ground lift switch. As a bonus, it also includes a 3-band equaliser (consisting of bass, mid and treble controls), so that you can adjust the sound to suit the venue. Another worthwhile feature is the provision of a stereo input so that it can be used with signal sources such as stereo keyboards, CD players and MP-3 players. Note that this stereo input is mixed internally to provide a mono signal. Genuine stereo operwww.siliconchip.com.au The circuit is built into a rugged diecast case to prevent damage during transport. ation will require two DI boxes – one for each channel – and a stereo mixer. Other uses The DI-Box can be used for other purposes as well. For example, it could be connected in-line between the mixer’s fold­back output and the input to a foldback amplifier. That way, you can adjust the EQ (equalisation) of the foldback signal as op­posed to equalising the sound before the signal is sent to the mixer. Alternatively, you could use it to equalise the effects output from the mixer. Power for the SILICON CHIP DI-Box can come from a 12VDC plugpack, a 9V battery or via phantom power from the mixer. All three supplies are isolated from each other so that no harm can occur, even if all three power sources are connected simultane­ously. A separate power switch is used to turn the unit on and off and there’s also a battery test switch so that you can quick­ly check the condition of the battery. Circuit details With all that magic, you might think that the circuit has to be complicated but it’s not. All the details for our DI-Box are shown in Fig.1. It uses two low-cost op amp packages, four potentiometers, two jack sockets, several switches, an XLR panel plug for the balanced output and a handful Main Features •  High-impedance mono input (for guitar pickup) •  Stereo input mixing for tape, CD or other stereo signals •  Input level control, allowing optimum signal level before over­load •  Balanced output •  Three-band equaliser (EQ) •  Can run from battery, plugpack or phantom power •  Battery check function •  Ground lift switch for hum loop control •  Housed in a rugged metal diecast case August 2001  13 BALANCED OUT 2 10mF BP 620W VCC/2 VCC/2 PHANTOM POWER 680W X Y 27k 680W VR5 VCC/2 10k OFFSET 4 1 100mF 16V OUT A ZD2 12V 1W IN K LED 100mF 16V GND 100k 10mF 16V 7812 100k CUT BOOST TREBLE +9V (12V) 10k VR4 100k LIN .0015mF 10k MID VR3 100k LIN .012mF 12k BATTERY 9V 10mF 16V D4 1N4004 SC Ó 2001 S1 POWER 12V DC INPUT LOOP OUT + _ TIP RING TIP RING MONO/ STEREO IN DIRECT INJECTION BOX 10mF 16V OUT GND IN REG1 7812 220W ZD1 5.1V 1W D1 1N5819 D2 1N4004 1M 10pF 4 2 IC1a TL072 8 10mF BP LED1 l A K 10k S3 BATTERY TEST 10mF BP VR1 1M LOG LEVEL 10mF BP S4 MONO/ STEREO 10k 10pF 1M 3 VCC/2 +9V (12V) 1 2.2mF BP 12k VR2 100k LIN 18k .0027mF 18k BASS D3 1N4004 1k 560pF 2 3 7 IC2 TL071 +9V (12V) 5 6 10k 4.7k 5 6 IC1b TL072 10k 100pF 7 0.47mF Y SHELL XLR PLUG 10mF BP S2 LIFT/ GROUND X 1 3 COLD 620W HOT .015mF Fig.1 (left): the complete circuit for the DI Box. IC1a buffers the incoming signal and drives a 3-band tone control stage (bass, mid & treble). This stage then drives op amps IC2 and IC1b to produce the balanced output signals. 14  Silicon Chip of minor parts. As shown, the incoming mono signal is fed in via the tip connection of a 6.35mm jack socket. This signal is then applied to potentiometer VR1 via a 10kΩ resistor and series 10µF bipolar capacitor. A 10pF capacitor is wired across VR1 and acts with the 10kΩ input resistor to reject RF (radio frequency) signals. The associated “Loop Out” socket is simply wired in parallel with the input socket so that the unprocessed signal can fed to other audio equipment; eg, to a stage amplifier. In the case of stereo input signals, the second channel is fed to the ring terminal on the input socket and then applied to VR1 via mono/stereo switch S4 and a second 10kΩ resistor and series 10µF capacitor combination. The two channels are then mixed together at the top of VR1, to form a mono signal. The 10µF bipolar capacitors are included to prevent DC from being applied to VR1, so that it isn’t noisy in use. VR1 acts as the level control. Its output is AC-coupled via another 10µF bipolar capacitor to the non-inverting input (pin 3) of op amp IC1a. This input is biased to the half-supply rail (Vcc/2) via a 1MΩ resistor. Because of this, a second 1MΩ feed­back resistor is connected to the inverting input (pin 2), to minimise the output offset due to input bias currents. The 10pF capacitor across the 1MΩ feedback resistor prev­ents IC1a from oscillating. In operation, IC1a acts as a unity-gain buffer amplifier. It drives the following equaliser (or tone control) stage via a 2.2µF bipolar capacitor. EQ controls The tone controls are based on op amp IC2 and potentiome­ters VR2, VR3 & VR4. These pots and their associated resistors and capacitors are in the feedback path between IC2’s output at pin 6 and its inverting input (pin 2). Each of the bass, mid and treble stages can be considered separately www.siliconchip.com.au since they are connected in parallel between the signal output of IC1a and the inverting input (pin 2) of IC2. Note that pin 2 of IC2 is a virtual ground. Let’s first look at the bass control (VR2). When VR2 is centred, the resistance between pin 1 of IC1a and pin 2 of IC2 is equal to the resistance between pin 6 of IC2 and pin 2 of IC2 – ie, the input and feedback resistances are equal. As a result, IC2 operates with a gain of -1 (the .015µF capacitor has no effect since it is equally balanced across the potentiometer). Now let’s see what happens when we wind VR2’s wiper fully towards the output of IC1a. The input resistance for IC2 now decreases to 18kΩ, while the feedback resistance increases to 118kΩ. At the same time, the .015µF capacitor is now completely included in the feedback circuit. Without the capacitor, the gain would be -118kΩ/18kΩ = -6.5 (16dB) at all frequencies. In practice, though, the .015µF ca­pacitor rolls off the response above 100Hz, so that the gain quickly reduces towards -1 as the frequency increases. As a result, we have maximum bass boost below 100Hz. Conversely, when the wiper is wound towards IC2, the gain without the capacitor is 18kΩ/118kΩ = -0.15 (-16dB). The capaci­tor is now on the input side so the gain rapidly increases to -1 at frequencies above 100Hz. Thus the maximum bass cut is below 100Hz. Intermediate settings of VR2 between these two extremes provide lesser amounts of bass boost or cut. The midrange section (VR3) works in a similar manner except that there is now a .012µF capacitor in series with the input. This combines with the .0027µF capacitor across VR3 to give a bandpass filter. Finally, the treble control (VR4) operates with only a .0015µF input capacitor; ie, there’s no capacitor across VR4 in the feedback path. As a result, this control produces a high frequency boost or cut at 10kHz. Fig.2 shows the response of the tone controls. Note that the maximum bass boost is 12dB at 100Hz. The maximum boost and cut is lower for the midrange and treble controls. The 560pF feedback capacitor across IC2 provides high fre­quency rolloff to prevent instability. Similarly, the 1kΩ resis­tor at the inverting input acts as a stopper for RF signals to prewww.siliconchip.com.au AUDIO PRECISION FREQRESP AMPL(dBr) vs FREQ(Hz) 20.000 05 MAY 100 23:27:05 15.000 BASS 10.000 MID TREBLE 5.0000 0.0 -5.000 -10.00 -15.00 -20.00 20 100 1k 10k 20k Fig.2: this graph shows the responses generated by the bass, mid-range and treble controls. The maximum bass boost is 12dB at 100Hz, while maximum mid-range boost is about 9dB at 850Hz. The treble boost is limited to about 7dB at 11kHz. vent radio pickup. Trimpot VR5 acts an offset adjustment for IC2 – it allows the DC output of IC2 to be nulled to prevent DC current from flowing in bass control VR2. This is necessary since any DC current flowing in VR2 would make the pot noisy to operate. IC2’s output appears at pin 6 and drives pin 3 (cold) of the XLR plug via a 10µF bipolar capacitor and series 620Ω resis­tor. The resistor provides the requisite 600Ω output impedance while the capacitor prevents the phan- tom supply voltage (if present) from being loaded by IC2’s output. It also prevents the Vcc/2 voltage on IC2’s output from being applied to the XLR plug. As well as driving pin 3 of the XLR plug, IC2 also drives op amp IC1b via a 10kΩ resistor. This stage is wired as an in­verting amplifier with a gain of -1 to derive the in-phase signal. Its output appears at pin 7 and drives pin 2 (hot) of the XLR plug. The remaining pin on the XLR plug is the ground pin (pin 1). This is Specifications Signal Handling: 2.42V RMS at maximum level and equaliser at flat settings with 12V supply (greater at lower level control settings); 1.74V RMS with 9V supply Input Impedance: 470kΩ mono; 10kΩ for stereo Total Harmonic Distortion: .009% at 100Hz and 200mV; .02% at 1kHz; .05% at 10kHz Frequency response: -3dB at 13Hz; -2dB at 20kHz Equaliser response: see graphs Signal-to-noise ratio: 93dB with respect to 1V 20Hz-20kHz filter (96dB A weighted) Phase difference between pin 2 & pin 3 XLR output: 180° at 1kHz; 160° at 20kHz Battery test: LED dims for low battery voltages Battery current: 8.8mA <at>9V August 2001  15 Fig.3: install the parts on the PC board and complete the wiring as shown here. Note that the component shown in purple should not be installed until after the four pots have been soldered to their respective PC stakes. Take care with component orientation. either directly connected to ground via S2 or AC-coupled to ground via a 0.47µF capacitor when this switch is open. Open­ing the Ground Lift switch prevents hum loops if the input to the DI-Box is separately grounded to earth (eg, via a foldback amplifier). Power supply As mentioned earlier, power for the circuit can come from a DC plugpack, a 9V battery or via phantom power. Diode D4 provides reverse polarity protection for external DC power sources such as plugpacks. The DC supply rail is then filtered and applied to 3-terminal regulator REG1 to derive a +12V rail. This is then applied to the op amps IC1 & IC2 via diode D2. The internal 9V battery supply (if present) is fed to the op amps via Schottky diode D1. A Schottky diode has been used here because it has a much lower voltage drop across it than a standard diode and this extends the 16  Silicon Chip useful battery life. Note that the negative return of the battery goes via the DC power socket as well as via power switch S1. As a result, the battery is automatically disconnected when ever a plug is insert­ed into the DC power socket. Phantom power is delivered via pins 2 & 3 of the XLR plug and is applied via two 680Ω resistors to diode D3. Zener diode ZD2 regulates the voltage to 12V before it is applied to the rest Table 1: Capacitor Codes  Value IEC Code EIA Code  0.47µF   470n   474  .015µF   15n  153  .012µF   12n  123  .0027µF   2n7  272  .0015µF   1n5  152  560pF   560p   561  100pF   100p   101  10pF   10p   10 of the circuit. Note: phantom power is usually produced from a source of either 48V with a 3.4kΩ impedance or from 24V and a 600Ω im­pedance. This means that we can draw up to about 9mA from each supply, or 18mA in total at 12V. Diodes D1, D2 & D3 isolate each supply so that only one source can deliver power to the circuit. Essentially, where more than one supply is connected, it is the highest voltage source that powers the unit. The half-supply rail (Vcc/2) is obtained using two 100kΩ resistors connected in series across the power supply. The half-supply point is de­ coupl­ed using a 100µF capacitor to prevent any supply ripple. S3, LED1, ZD1 and the series 220Ω resistor form a simple battery test circuit. If the battery voltage is 9V, the voltage across the 220Ω resistor will be 9V - 5.1V - 1.8V (the voltage across the LED), or about 2.1V. As a result, www.siliconchip.com.au about 9.5mA will flow through LED1 when S3 is closed and the LED will glow brightly. As the battery voltage goes down, the current through the LED drops accordingly and so its brightness also decreases. For example, a battery voltage of 7.5V will leave about 0.6V across the 220Ω resistor and so just 2.7mA will flow through the LED which will now be quite dim. Putting it together Building it is easy because most of the parts are mounted on a PC board coded 01108011 (102 x 84mm). This is housed in a metal diecast box measuring 119 x 94 x 57mm. The diecast case serves two purposes: (1) it provides the necessary shielding for the audio circuitry; and (2) it makes the unit extremely rugged – a necessary requirement for stage work. Fig.3 shows the PC board assembly and wiring details. Begin by checking the PC board for any shorts or breaks in the copper tracks. Check also that the PC board fits neatly into the case. If it doesn’t, file the corners and edges of the board, so that it fits when seated on 9mm standoffs (these can be temporarily attached for testing the board fit). Note that the case tapers in slightly towards the base. The board doesn’t have to go all the way down – just to within 9mm. Now for the board assembly. Install the three wire links first, then fit the resistors. Table 2 shows the resistor colour codes but it’s also a good idea to check each one using a digital multimeter, as the colours can be hard to recognise. The diodes can go in next but make sure that D1 is the 1N5819. Be careful not to mix up the two zener diodes – Inside the completed prototype. The two 6.5mm jack sockets (at left) have to be wired before they are attached to the side of the case. Similarly, you will have to complete the wiring to the PC board before fitting the other hardware items. ZD1 is the 5.1V zener, while ZD2 is the 12V zener. The 5.1V zener will probably be marked “1N4732”, while the 12V zener can carry a “1N4742” marking. The two ICs can now be installed, taking care to ensure that IC1 is the TL072 (or LF353). This done, install the capaci­tors, using Table 1 to identify the low-value units. The bipolar electrolytic capacitors can be installed either way around but make sure that the “normal” electrolytic capacitors (ie, the polarised types) are installed with the correct polarity. The capacitors marked in purple should be left out for the time being – see Fig.3. VR5, REG1 and the DC power socket can go in next, followed by the PC stakes. You will need PC stakes at all the external wiring points, including three stakes for each of the pots. LED1 should be installed with its body about 20mm above the board. It is later bent over and pushed into a bezel mounted on the side of the case. Table 2: Resistor Colour Codes  No.   2   2   1   2   2   6   2   2   1 www.siliconchip.com.au Value 1MΩ 100kΩ 27kΩ 18kΩ 12kΩ 10kΩ 680Ω 620Ω 220Ω 4-Band Code (1%) brown black green brown brown black yellow brown red violet orange brown brown grey orange brown brown red orange brown brown black orange brown blue grey brown brown blue red brown brown red red brown brown 5-Band Code (1%) brown black black yellow brown brown black black orange brown red violet black red brown brown grey black red brown brown red black red brown brown black black red brown blue grey black black brown blue red black black brown red red black black brown August 2001  17 These two views shows the locations of the RCA input sockets, the 3-pin panel-mount XLR socket and the Ground-Lift and Stereo/Mono rocker switches. The Power and Battery Test rocker switches are mounted on the rear panel, along with the battery test indicator LED. Finally, complete the board assembly by securing the battery holder using three M2.5 screws. Don’t forget to solder its leads. Final assembly OK, now for the final assembly. First, position the PC board inside the case and mark out the four corner mounting holes. This done, drill these holes to 3mm and countersink the holes on the underside of the box. Next, attach the four 9mm tapped spacers to the underside of the PC board using M3 screws and secure these into the box using countersunk M3 screws. Now mark out the po- sitions for the pot shafts – these are mounted directly above their corresponding stakes on the PC board, with the shaft centres about 28mm above the base. Once the centres have been marked, remove the board and drill the holes for the pots. It’s best to start with a small pilot drill and then carefully enlarge the holes to size using a tapered reamer. Once this has been done, use a rat-tail file to elongate the holes vertically – this will make it easier to insert the pots through the holes when they are later attached to the PC board. Now mark out and drill mounting holes for the 6.35mm jack sockets, the XLR panel plug, the DC socket entry, the LED and the switches. You can use the front panel artwork and the photographs to guide you in positioning these holes. The switch cutouts can be made by first drilling a series of small holes around the inside perimeters, then knocking out the centre-pieces and carefully filing the edges. Note that all three switches must be a snug fit, so that they are held in position by their plastic retaining lugs. Don’t make the holes too big, otherwise the switches will fall out. The four pots can now be attached to the PC board by sol­ dering their leads to the front of the PC stakes (make sure that VR1 is the 1MΩ pot). Install them so that their shaft centres are about 17mm above the top of the board. It’s best to lightly tack solder one of the pots first, then test the assembly to make sure it fits in the case before finally installing the remaining pots. This done, install the capacitors marked on the overlay (Fig.3) in purple, then reinstall the board and secure the pots to the case by doing up the nuts. Internal wiring Fig.4: this full-size front panel artwork can be used as a guide when positioning the switches and sockets. 18  Silicon Chip All that remains now is to fit the remaining hardware items and complete the wiring. You will find that it’s easier to run the wiring from the PC board to several of these items before they are attached to the case (eg, to the XLR plug, the 6.35mm jack sockets and the power switch). The panel-mounting XLR plug is secured using M3 x 9mm screws, star www.siliconchip.com.au washers and nuts. The lower nut can initially be held in place using some adhesive tape, to make it easy to attach the screw. The LED is inserted into its adjacent bezel on the side of the case by bending its leads over and clipping it into position. Finally, complete the assembly by fitting the front panel label to the lid of the case and sliding the knobs onto the pots. Testing Now for the smoke test. Apply power using a 9V battery or 12VDC plugpack (or a DC power supply set to about 15VDC) and check that the LED lights when the Battery Test switch is on. This done, check that for +9V (or +12V) on pin 8 of IC1 and on pin 7 of IC2. The voltage should be around +9V when a fresh battery is used and +12V for a plugpack supply. Now connect your DMM across bass pot VR2 and adjust VR5 for 0V DC. This stops DC current flowing through VR2 which might make it noisy. Further testing can be made using your DI source. This can range from a guitar pickup through to high-level inputs such as keyboards. Set the input level control to maximum when using low-level sources such as guitar. Conversely, it may be necessary to wind the input level control down for high-level sources to prevent clipping, particularly when equaliser boost is applied. Make sure that you select mono for high output impedance sources such as a guitar pickup. This is because the input im­pedance of the DI box in mono is 470kΩ but only 10kΩ for stereo. The stereo selection is used only with stereo sources and, as explained previously, mixes the signal to a mono output. Parts List 1 PC board, code 01108011, 102 x 84mm 1 diecast box, 119 x 94 x 57mm 1 front panel label, 100 x 87 1 XLR metal panel plug 2 6.35mm stereo jack panel sockets 3 SPST mini rocker switches (S1-S3) 1 1MΩ 16mm log pot (VR1) 3 100kΩ 16mm linear pots (VR2-VR4) 1 10kΩ 16mm linear pot (VR5) 4 knobs to suit pots 1 DC socket (PC-mount) 1 216 9V battery or 12VDC 200mA plugpack 1 9V battery holder 1 5mm LED bezel 4 9mm long M3 tapped spacers 4 M3 x 6mm screws 4 M3 x 6mm countersunk screws 4 M3 x 9mm countersunk screws 2 M3 nuts and star washers 3 M2.5 x 9mm screws 23 PC stakes 1 400mm length of green hookup wire 1 300mm length of black hookup wire 1 200mm length of blue hookup wire 1 200mm length of yellow hookup wire 1 200mm length of 0.8mm tinned copper wire Semiconductors 1 TL072 dual op amp (IC1) 1 TL071 op amp (IC2) 1 7812 12V 3-terminal regulator (REG1) 1 5.1V 1W zener diode (ZD1) 1 12V 1W zener diode (ZD2) 1 5mm red LED (LED1) 1 1N5819 Schottky diode (D1) 3 1N4004 diodes (D2-D4) Capacitors 2 100µF 16VW PC electrolytic 3 10µF 16VW PC electrolytic 5 10µF bipolar electrolytic 1 2.2µF bipolar electrolytic 1 0.47µF MKT polyester 1 .015 MKT polyester 1 .012 MKT polyester 1 .0027 MKT polyester 1 .0015 MKT polyester 1 560pF ceramic 1 100pF ceramic 1 10pF ceramic Resistors (0.25W 1%) 2 1MΩ 6 10kΩ 2 100kΩ 2 680Ω 1 27kΩ 2 620Ω 2 18kΩ 1 220Ω 2 12kΩ XLR-to-jack plug lead If you are using the DI Box as an inline equaliser, you may need to make up an unbalanced XLR line socket to jack plug lead. It is wired with the pin 3 connection open, the signal connected to pin 2 and the lead shield connected to pin 1. Ground lift (S2) should only be selected if there is a ground loop that’s causing hum. The hum should cease when S2 is opened. Finally, make sure that the DI Box is switched off when not in use to conserve battery life. You can test the battery with the Battery Test switch at any time when the power is on. SC www.siliconchip.com.au Fig.5: this is the full-size etching pattern for the PC board. Check your board for defects before installing any of the parts. August 2001  19 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.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.dse.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.dse.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.dse.com.au COMPUTERS: Do-it-yourself & learn A PC TO DIE FOR Part 3: squashing some more bugs and updating the BIOS & drivers By GREG SWAIN Computer lock-ups and system crashes are annoying. Don’t put up with them. If you’ve been tearing your hair out over stability problems, this article will show you how to squash the bugs. It describes how we solved the problems in our new PC but applies to lots of other PCs as well. A CTUALLY, WE TORE out quite a bit of our own hair recent­ly, battling instability in our new 1GHz Athlon PC. And although this article describes how we solved the problems, the basic approach described here applies to lots of other PCs as well. That’s because there’s nothing unique about our hardware. Lots of motherboards use the Via chipset, while video cards based on the nVidia GeForce2 and TNT chips are commonplace. And of course, lots of PCs are fitted with sound cards, network cards and other devices. So although your particular machine mightn’t exactly match ours, a lot of the advice given here still applies. It’s common practice for the AGP (video card) slot to share its IRQ with the first PCI slot (arrowed). However, many AGP video cards don’t like sharing an IRQ, so it’s standard practice to leave the first PCI slot empty. 24  Silicon Chip Our problems with our new PC really started when we decided to convert it for use as a desktop publishing machine. There were several things we had to do to: (1) convert the operating system to Windows NT; (2) install a 250MB ZIP drive; and (3) install a network card so that the new machine could be plugged into the SILICON CHIP network. We cheated when it came to the Windows NT conversion by using Power Quest’s “Drive Image” to clone the installation from my old machine (the old machine was later converted to Windows Me). Before doing that though, we changed over to a standard VGA driver so that there would be no problems with the new video card. The 250MB ZIP drive was also pinched from the old machine and slaved with the DVD-ROM drive on the primary IDE port. Did it work? Umm, no – it wouldn’t boot initially because it couldn’t find the drive (no driver for the on-board Promise Ultra ATA100 controller, you see). That was solved by temporarily transferring the hard drive to one of the “normal” IDE ports. This then allowed us to install the Promise driver from the motherboard CD-ROM, before swapping the drive back to the Primary Ultra ATA100 IDE port. www.siliconchip.com.au Go To These Websites For The Drivers & BIOS Upgrade Device Website Download Asus A7V133 BIOS Upgrade www.asus.com.tw/index.html avu1005a.awd (BIOS); afl ash.exe (Fl ash Memory Wri ter) Geforce2 MX Graphi cs Card www.nvidi a.com 12.41-W9x.exe or Win98_Me(12.41).exe for Win98/Me 12.41-W2K.exe or Win2000(12.41).exe for Windows 2000 12.41-NT.exe or WinNT4(12.41).exe for Windows NT4 Via 4-In-1 Dri vers www.viatech.com 4in1432v.zip Promi se Ul tra ATA100 Controll er www.support.promise.com/status.asp ul tra100b35.zip (beta build 35 driver) Note: final dri ver may now be available Iomega ZIP250 www.iomega.com/software/ioware28pc.html ioware-w32-x86-28.exe SoundBlaster Li ve Soundcard www.soundblaster.com/drivers/ Driver to sui t your soundcard Note: download the correct BIOS for your motherboard and the correct drivers for your hardware (sound cards, network cards, etc). You don’t have to do this with a new NT install, by the way. You just connect the hard disk to the primary Ultra ATA100 port from the beginning and install the “SCSI” driver when prompted to do so during the installation procedure (Windows NT labels all disk drives as SCSI devices). Next, the Via 4-In-1 drivers were installed, followed by the video card driver. These all went without a hitch, so the machine was powered down and the network card installed in the first PCI slot (ie, the slot adjacent to the video card AGP slot). Initially, the network card wasn’t recognised, despite being exactly the same as in the old machine – that would make things too easy, wouldn’t it? This problem was solved by deleting and reinstalling the driver. The network then came up OK after we had re-entered the network settings and it appeared to be all systems go. The lockup bug Well, it was all systems go for the first few hours – then the machine “locked up” and would not respond to either the keyboard or mouse. Even the customary three-fingered salute (Ctrl-Alt-Del) brought no joy and there was nothing for it but to press the Reset button. Unfortunately, this wasn’t a one-off event and the machine subsequently continued to lock up, seemingly at random. There just didn’t seem to be any pattern to it. Sometimes it would go for hours before locking up; at other times it would lock up again after just a few minutes. So just where do you start in tracking down a problem like this? Well, www.siliconchip.com.au it’s really just a matter of eliminating the likely suspects one-by-one until you nail the culprit. But what are the most likely possibilities? On the hardware front, it could be a crook memory module, a faulty video card or motherboard, a compatibility problem or something as simple as a resource conflict. Alternatively, it could be a software problem; eg, a buggy device driver, an incor­rect BIOS setting or even the BIOS itself. The memory was quickly cleared by swapping over memory from another machine. Choosing conservative performance settings in the BIOS didn’t help matters either and nor did turning off the Norton AntiVirus Auto-Detect utility that normally ran in the background. That left either a resource conflict or a buggy device driver – possibly involving the video card – as the most likely suspects. Why the video card? Well, buggy video drivers are a common source of problems and in this case the machine appeared to sometimes “trip” over the splash screens that are commonly displayed when an application is launched. As a result, we decided to download and install the latest drivers for the video card. While we were at it, we visited the Viatech website and grabbed the latest Via 4-In-1 drivers and installed these as well. These drivers are necessary to support the Via chipset on the motherboard and include an AGP VxD driver, so it’s important to use the latest version. By the way, don’t go to the Prolink website for video card drivers. You’ll find the most up-to-date drivers for GeForce2 MX cards on the nVidia website (www.nvidia.com). Just click the download driver button when you get there, select your operating system and grab the Detonator2 v12.41 drivers. In common with many other AGP video cards, this Prolink GeForce2 MX card doesn’t like sharing an IRQ. August 2001  25 Fig.22: the Systems Properties dialog box is opened by double-clicking its icon in Control Panel or by right-clicking My Computer and selecting Properties from the drop-down list. Fig.23: double-clicking the computer entry in Fig.22 lets you check the system resources. Make sure that the video card doesn’t share an IRQ with any other device (IRQ Holder For PCI Steering excepted). You have a choice here – you can either download the self-extracting installer or you can download a self-extracting zip file. If you have self-extracting installer, you just double-click the file to begin the driver installation and choose “GeForce2 MX/MX 400” as the display adapter when prompted – assuming, of course, you are using the PixelView GeForce2 MX video card. Unfortunately, the new video card and Via 4-In-1 drivers didn’t cure the lock-up problem, although they did appear to alleviate it somewhat (or perhaps that was just our imagination). OK, what next? Read the manual, dummy It turns out that the answer is in the FAQ section in the video card manual. 26  Silicon Chip That’s right, when all else fails read the <at>#%^&<at>! manual. According to the manual, this particular video card doesn’t like sharing its IRQ (interrupt request setting) with any other device. However, the Asus A7V133 motherboard forces the AGP slot (which accommodates the video card) to share its IRQ with the first PCI slot – a feature that’s common to many other mother­boards as well. So what was in the first PCI slot? Answer – the network card that we had installed earlier. This meant that the video card and network card were both grabbing IRQ11 (as indicated by the on-screen boot messages) and it was this that was causing our lock-up problems. The cure was simple – move the network card to the second PCI slot and leave the first PCI slot free (this also improves the airflow around the video card). The network card now happily shares its IRQ with the mass storage controller (IRQ10), leaving the video card with exclusive use of IRQ11. In case you are wondering, manually assigning a different IRQ to the first PCI slot doesn’t help matters. If you do manual­ly assign an IRQ to the first PCI slot, the AGP slot follows and grabs the same IRQ. So that’s not a solution – at least not in this case. The easiest way out is to leave the first PCI slot free if you are using the Prolink GeForce2 MX video card. Also, don’t allow any other expansion cards in any other slots to share the video card’s IRQ. If you are using Windows 98 or Windows Me, you can check the IRQ assignments in the System Properties dialog box (right click My Computer, click Properties, click the Device Manager tab and double-click Computer). Many other video cards, especially those using GeForce2 and TNT chips, are just as fussy. So, if you strike this sort of problem, make sure that the video card has exclusive use of an IRQ (the only exception here being the “IRQ Holder For PCI Steering”). Kick in head time Normally, my advice to anyone who strikes this sort of problem is to strip the machine down to its bare minimum (ie, eliminate unnecessary expansion cards) and troubleshoot from there. If only I’d followed my own advice – I’d have solved the problem Fig.24: the latest video card drivers (Detonator 2 v12.41) can be down-loaded from the nVidia website. much sooner than I did. That said, it’s still a good idea to download and install the latest drivers. Sometimes there can be more than one factor that’s contributing to system instability and you really have to cover all the bases. Upgrading the BIOS Moving the network card proved to be a complete cure for our instability problems – well, almost. System lockups were now quite infrequent but they still happened so we weren’t quite out of the woods. Adelong Computer’s advice was to upgrade the system BIOS, as there have been several revisions since our motherboard was made – some of them apparently involving issues with the AGP slot. Our Asus A7V133 motherboard came with Award Bios version avu1002a.awd, whereas the latest version (at the time of writing) is now avu1005a.awd. Upgrading the BIOS is a simple enough procedure. First, you need to go to the Asus website and download the latest BIOS file (avu1005a.zip for the A7V133). You also need to grab the Award Flash Memory Writer Utility (aflash.exe) and print out the instructions. Next, you need to make a bootable floppy disk (type format a:/s at a DOS prompt) and copy the aflash.exe file across to this disk. You also need to unzip and copy across the new BIOS file (avu1005a.awd). It’s a good idea to write down the name of this file, since www.siliconchip.com.au Squashing The Bugs – Follow These Steps The following steps are necessary to ensure a stable sys­tem. Carry out the steps in the order listed but before you do, make sure that any critical data is backed up. The Tiger comes to Australia (1) Leave the first PCI slot vacant to avoid IRQ conflicts with the video card. If you have a sound card, plug it into PCI slot 3. The network card can then go into slot 4. (2) Upgrade the motherboard BIOS to the latest version (to avu1005a. awd in the case of the Asus A7V133). Note: BIOS upgrades carry some risk – see text. (3) Download and install the latest video card driver from the nVidia website. (4) Download and install the latest Via 4-In-1 drivers from the Via Technology website. Install any service packs first if you are running Windows NT4 or Windows 2000. (5) Download and install the Beta Build 35 driver for the Promise ATA100 controller if you are running Windows 98 (this step is optional for other operating systems). (6) Download and install the latest drivers and utilities for any other devices that you have – sound cards, network cards, ZIP drives, scanners, etc. (7) Don’t install DOS emulation for the sound card if you don’t intend on running DOS games. If you do require DOS emulation, in­stall the sound card in PCI slot 3 and assign IRQ5 to this slot in the system BIOS (under PCI/ PNP IRQ Resource Exclusion). It may also be necessary to reserve IRQ5 for a legacy device. Note: you cannot run DOS emulation under Windows NT4. you have to type it in later. This done, it’s simply a matter of booting from the floppy and typing aflash <Enter> at the A:\ prompt to run the Flash Memory Writer Utility. You then follow the on-screen prompts to save the motherboard’s current BIOS to a file (eg, oldbios.awd) and update to the new BIOS. You don’t really have to save the current BIOS to a file but it’s a good idea to do so. That way, you can reinstall the old BIOS if you get error messages when you attempt to flash the latest version. When it’s finished programming, the message “Flashed Suc­cessfully” will be displayed and you hit Esc twice to exit the Flash Memory Writer. You then remove the floppy disk, restart the computer, enter the BIOS setup and choose Load Setup Defaults at the Exit Menu. After that, it’s just a matter of going back over the BIOS settings before saving the changes and exiting. If you get an error message when you attempt to flash the new BIOS, go back to the Main Menu and try writing it www.siliconchip.com.au again. If this doesn’t work, it’s possible that the new file is corrupt and you should reinstall the old BIOS. What ever you do, DON’T turn the computer off if you get an error message – it may no longer boot if you do and you will need to go back to the dealer to get the BIOS re-flashed. Similarly, if the power fails while you’re flashing the BIOS, you’re right up that proverbial creek. Re-flashing the BIOS is a simple enough procedure but it does carry some risk – don’t blame me if it all goes pearshaped. In our case, the BIOS upgrade put an end to our instability problems. We haven’t experienced a single lock-up (or any other crash) in four weeks now, so the problem is finally cured. Just one more thing here – when you go to the Boot Menu in the BIOS setup, the default for the “Other Boot Device” entry will now be “[INT18 Device (Network)]” (ie, a network drive). All you have to do here is select this device, press <Enter> and then select “[Onboard ATA100 Boot]” 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 2 UARTs, SPI, I C, 1-wire, RTC and has low cost W98/NT compile, debug and download software. JED makes four Australian boards with up to 64 screw-terminal I/O, more UARTs & LCD/keyboard support. See JED's www site for data. RS232RS485 Converter This small plastic case (100mm by 55mm by 25mm) is an Australian-made RS232-RS485 opto-isolated converter. It connects a PC or PLC RS232 serial port to a multi-drop RS485 network up to 4000 ft in length. Several models are available with RTS or automatic control. The J995X uses an internal microprocessor to turn the TX on byte-by-byte. $176 plus $22 for plug pack. $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 August 2001  27 Fig.25: Windows NT4 labels all disk drives as SCSI devices. Fig.26: clicking the “Drivers” tab lets you check which drivers are installed and confirm that they are started. from the drop-down list. This device can then be moved to the top of the boot order. www.softsynth.com/jsyn/support/ removed_error.html The Promise controller bug If you’ve already upgraded the system BIOS and/or installed the latest VIA 4-In-1 drivers, you won’t have to worry about this problem. The 686B data corruption bug only occurs with VIA chipset motherboards using the 686B Southbridge chip (eg, the Asus A7V133) and usually only if there is also a SoundBlaster Live soundcard installed. Basically, it prevents you from copying more than 100MB of data from one IDE drive to another and also causes problems when burning disks on CD writers. If you have an Asus A7V133 motherboard, it would appear that this problem is only possible if you have one or more drives connected to a conventional IDE port. Apparently, it’s caused by an incorrect BIOS registry setting that was made by many motherboard manufacturers in an attempt to fix a conflict with the SBLive card. This problem has since been corrected by motherboard manu­facturers and it’s probable that the latest BIOS upgrade for the A7V133 fixes the problem. If not, the fix is to install the latest Via 4-In-1 4.32 drivers. No harm will result if you up­grade both the BIOS and the VIA drivers – in fact, it’s a good idea to do both. If you want to find out more, take a look at: www.viahardware.com/686bfaq.shtm This particular bug only occurs if are using the Promise Ultra ATA100 controller and you are running Windows 98. When present, it sometimes causes a fatal error during boot up with a blue-screen message that says: “The volume that was removed had open files on it. Next time please check first to see that the volume can really be removed”. The user then has no option but to do a hard reset, which is hardly the way to go. This problem apparently occurs when using version 1.60 Build 34 (or earlier) of the Ultra ATA100 driver. Promise Tech­nology’s recommended cure is to download and install the latest Beta Build 35 driver – called Ultra100b35.zip from their website. Note that this driver is only a beta version (we tested it without problems) but Promise will probably have a final version on their website by the time you read this. In Windows 98/Me, you can update the driver via Device Manager in the System Properties dialog box. Windows NT users should double-click the SCSI Adapters icon in Control Panel, then click the Drivers tab to bring up the dialog box shown in Fig.26. The old Promise Ultra ATA100 controller can then be deleted and the new one installed. For further information on this problem, point your web browser to: 28  Silicon Chip The 686B data corruption bug Installing an IDE ZIP drive If you have an internal IDE ZIP, the best approach is to slave it with the CD-ROM drive (or DVD-ROM drive) on the conven­ tional primary IDE port. Alternatively, you can configure it as a master and run it by itself on the secondary IDE port, although this involves running an extra cable. Don’t choose auto detect for the ZIP drive in the system BIOS, as this can cause problems. Instead, choose “None” in the BIOS setting if you have a ZIP250 or select the ZIP100 option if you have a ZIP100 drive. Finally, don’t forget to install the Iomegaware software that was supplied with your ZIP drive. Even better, download the latest version from the Iomega website (see table). If you don’t do this, you won’t have any of the Iomegaware utilities; nor will you be able to read 100MB ZIP disks if you have a ZIP250 drive. Do it logically If you’ve feeling confused by now, the accompanying panel sets out all the things that you have to do in a logical order, so that your machine behaves the way it should. Apart from re­flashing the motherboard BIOS, the job simply involves download­ing and installing the latest drivers for your motherboard, video card and any other devices that you may have. This advice not only applies to our particular hardware combination but to any other hardware combination as well. The web is your weapon here – just be sure to get the correct drivers for your hardware and don’t upgrade the BIOS unless you have to. After all, SC why take unnecessary risks? 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.dominion.net.au Want to do your own home wiring and be legal? Repair appliances? Replace a power point or light fitting? YOU can help make it happen! You should know that all Australian states have legislation which effectively bans you from doing any home wiring (even temporarily undoing a power point of light switch to paint around it). In Queensland, the relevant legislation is the Electricity Act (1994) and the Electricity Regulation Act (1994). This is used to maintain a “closed shop” for electricians. It is not about main­taining safety for users or homeowners. In Queensland it can effectively stop anyone who is not a licensed electrician from working on any mains-powered appliance, including TVs, VCRs, computers, amateur radio equipment, vintage radios – any equip­ment powered from the 240VAC mains supply! Our campaign is appealing to parliamentarians in each state to direct their electrical licensing authority to: (a) remove any restrictions which may prevent people from working on mains-powered equipment, whether it is for the purpose of assembly, service, repair or restoration; (b) produce legislation which is based on the New Zealand Elec­tricity Act and Regulations, which allows householders to do their own “electrical work”, including appliance repairs and the installation of fixed wiring. See our website at www.siliconchip.com.au for more infor­mation on the relevant legislation. Electrical fatalities in Australia Electricians have generally opposed this campaign on the grounds of safety. This is not a problem in this country. In Australia, the overall fatalities are currently about 51 per annum or 2.7 persons per million. In Queensland, the state with the most restrictive regulations, the fatality rate is about 4 per million. By contrast, in the UK which allows homeowners to do wiring, the death rate is about 1 person per million. We’re not doing too well on the face of it. Just about all of the Australian fatalities each year are not due to homeowners doing wiring. Very few homeowners are electrocuted because they have modified or worked on electrical wiring. So the current restrictions against homeowners (and particularly electrical engineers) doing their own home wiring and working on electrical appliances and projects are completely unnecessary. You can do you bit to change the legislation by signing the “Statement of Will” in this issue and sending it to us. PLEASE DO IT NOW! Leo Simpson Send the completed forms to SILICON CHIP and we will forward them to the relevant state Ministers, along with copies of published correspondence, editorials, etc. The Ministers will be informed that their response, or a report that they apparently decided not to respond, will be published in SILICON CHIP! While in some ways similar to a petition, it must be our aim that it is not treated as a petition. If you have access to the Internet, go to http://www. rag.org.au/rag/petqld.htm and study the onerous requirements that must, by law, be observed in order to produce a petition that a state parliament will accept. Then click on Creative Petitioning at the bottom of the page to learn how easily parliaments can disregard petitions. Our state parliaments have refused to accept petitions that had many tens of thousands of signatures on them, simply because the form of the petition was not exactly correct. If you don’t have access to the Internet, suffice to say that conventional petitions to our state and federal parliaments are largely a waste of time. In addition to circulating the “Statement of Will” form, write an individual “MY WILL” letter, similar to the one below, to your local state member of parliament and encourage others to do the same. Don’t forget to date the letter and provide your name and address so the parliamentarian can confirm that you are a constituent. Dear Sir (or Dear Madam), I know that it is my duty to keep you informed of MY WILL on any matter that comes before Parliament, or that should come before Parliament. IT IS MY WILL that you take immediate action to end the “closed shop” that electricians enjoy in relation to “electrical work”, and that you promote the replacement of current electricity related legislation with legislation that is essentially equivalent to the New Zealand Electricity Act and Regulation, which allows householders to do their own “electrical work”, including appliance repairs and the installation of fixed wiring. Yours Faithfully, (signed) Above all, don’t enter into written argument with a politician. Politicians 30  Silicon Chip are masters in the art of avoiding what they don’t want to face up to, and become experts in manipulating words to their own benefit. Should your parliamentary member try to sidestep (and they are extremely adept at doing so) taking positive political action on your behalf (ie, they rattle on about what his/her party is or is not doing instead of agreeing to act in accordance with your WILL), you simply write back and state: Dear Sir (or Dear Madam), Further to my letter of (insert date of your original letter) and your reply of (insert date of their inadequate or fob-off reply), and in accordance with my lawful obligation to keep you informed of MY WILL, I again inform you that IT IS MY WILL that you take immediate action to end the “closed shop” that electricians enjoy in relation to “electrical work”, and that you promote the replacement of current electricity related legislation with legislation that is essentially equivalent to the New Zealand Electricity Act and Regulation, which allows householders to do their own “electrical work”, including appliance repairs and the installation of fixed wiring. Yours faithfully, (signed) If you have access to the internet, go to http://www.rag.org.au/rag/ mywillet.htm and learn about the background and potential power of the “MY WILL” letter. For each “MY WILL” letter you send to your parliamentary member, send a copy to SILICON CHIP so we can monitor the level of involvement in the campaign for reform. If your local parliamentarian shows interest in the issue, provide them with copies of relevant SILICON CHIP published correspondence and editorials, etc, or ask them to contact SILICON CHIP directly. Come on SILICON CHIP readers, you asked us to help you with this one – if you don’t want more and more restrictions, get those signatures rolling in! This information (including a copy of the "MY WILL" form) may also be downloaded from the SILICON CHIP website, www.siliconchip.com.au www.siliconchip.com.au Statement of Will: Reform of Electrical Legislation The primary responsibility of parliamentary representatives and governments is to do the will of the people. Electors must make their will known to their parliamentary representatives and governments. We, the undersigned, hereby assert that it is our will that the government of *_________________________________ acknowledge that current electrical safety legislation unjustifiably discriminates against ordinary householders as well as electrical and electronic engineers, technical officers, and technicians and that the effect of its enactment has been, and continues to be, to protect a monopoly for licensed electricians. We also hereby assert that it is our will that the government of *___________________________________ acknowledge that the potential dangers of “electrical work” are grossly exaggerated by the state electrical licensing boards and that the New Zealand electrical fatalities and accidents statistics belie these claims of dangers. We further assert that it is our will that the government of *_________________________________________ repeal, in a timely manner, all current electrical safety legislation to replace it with legislation that is essentially equivalent to the New Zealand Electricity Act and Regulation, which allows ordinary householders to do their own “electrical work”, including appliance repairs and the installation of fixed wiring. * (insert state or territory)     Name           Address    Signature  1. ........................................................................ .......................................................................................................................................... .............................................................  2. ........................................................................ .......................................................................................................................................... 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............................................................. 10. ........................................................................ .......................................................................................................................................... ............................................................. 11. ........................................................................ .......................................................................................................................................... ............................................................. 12. ....................................................................... .......................................................................................................................................... ............................................................. 13. ........................................................................ 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.......................................................................................................................................... ............................................................. www.siliconchip.com.au August 2001  31 A compact audio powerhouse This rugged, single channel amplifier module comes complete with power supply and a fan-cooled heatsink. It is based on the once-popular “Pro Series One” originally featured in “Electronics Australia” magazine and now re-designed by Altronics. 200 Watt Mosfet by LEO SIMPSON W e have had quite a few en- power output of 140W into 8Ω and TO-3 metal cases. These are no longer quiries from readers who 200W into 4Ω. Frequency response available and their plastic equivalents want to build a Mosfet am- is within 1dB from 20Hz to 80kHz are quite difficult to obtain as well. (Fig.1). Total harmonic distortion is Altronics looked at this situation plifier with a rating of about 200W. We had not designed such a module rated at less than 0.1% up to full power and have used essentially the same (Fig.2) and signal-to-noise ratio with circuit designed around some equivand as has been mentioned previalent plastic Mosfets made by Exicon ously in SILICON CHIP magazine, our respect to 200W is better than 100dB of the UK. This preference has been to has necessitated design high performance Performance of Prototype a re-design of the amplifier circuits around PC board so that all bipolar transistors rather Output Power (RMS):.... 140W into 8 ohms; 200W into 4 ohms the Mosfets and the than Mosfets. Frequency Response:.. 20Hz – 80kHz at -1dB points (see Fig.1) driver stage tranHowever, many people sistors all line up prefer Mosfets because Input Sensitivity:........... 830mV for 200W into 4 ohms along one edge, alof their legendary rugHarmonic Distortion: .. <0.1% (20Hz – 20kHz) (see Fig.2) lowing them to be gedness. Altronics had a mounted vertically Mosfet amplifier module Signal-to-Noise Ratio:.. >102dB unweighted; 105dB A-weighted on the heat-sink. which produced 200W             with respect to 200W into 4 ohms Apart from usinto a 4Ω load and so we Stability:........................ Unconditional ing plastic power decided to take a look it. transistors which It turned out to be based greatly simplify on the “Pro Series One” as mentioned unweighted. mounting compared to metal TO-3 above, although this version by AlOriginally, the “Pro Series One” power transistors, Altronics have emtronics has been derated and adapted was based on Hitachi Mosfets with ployed spring clips to mount adjacent to different Mosfets. It has a rated 32  Silicon Chip www.siliconchip.com.au Amplifier Module Ideal amplifier for:  ✪ hifi   ✪ subwoofer  ✪ public address  ✪ guitar transistor pairs, to make things simpler again. The spring clips apply just the right amount of tension to the transistors and there is no danger of damaging a transistor due to over-tightening a mounting screw. The heatsink is a black-anodised aluminium extrusion with fins on one side. It measures 300mm long and is fitted with a cover which allows it to be cooled by an 80mm 24V DC fan. The fan runs continuously and this means that the heatsink is always cool (or at least, at little above ambient temperature). A really attractive feature of the module is that it comes with its own power supply, consisting of a 300VA toroidal power transformer and accompanying power supply board. The bridge rectifier is mounted on the same vertical heatsink as the amplifier and so it also gets the benefit of continuous fan cooling. The whole assembly is mounted on www.siliconchip.com.au a sheet of black enamelled steel measuring 300 x 214mm. This could be built into a larger chassis for a PA system, stereo system, active sub-woofer or whatever. Easy connections Both the amplifier and power supply boards are designed for easy connection to supply wires, input and output lines and so on, by virtue of the insulated terminal blocks lined up along one edge. The particular advantage of this feature is that it makes it very easy to connect and disconnect the boards, without any need to resort to the soldering iron. Circuit details The circuit of the amplifier appears to be loosely based on an original Hitachi design produced about 20 years ago but it still rates as a very good design today. Fig.3 shows the circuit. Q3 & Q4 are the input differential pair with the input signal applied to the base of Q3 via a 0.47µF capacitor and 1kΩ resistor. Negative feedback is applied to the base of Q4. Q3 and Q4 amplify the “difference” between the input and negative feedback signals and the output signals appear at their collectors. Q1 & Q2 form a constant current “tail” circuit for the differential pair, ensuring that it has high gain and good common mode rejection ratio. Following the input differential pair of Q3 & Q4 is the voltage gain stage involving differential pair Q5 & Q6 and their balanced current mirror load of Q7 & Q8. The bases of Q5 and Q6 are driven from the collectors of Q4 & Q3 respectively and their collector loads are provided by Q7 & Q8, the current mirror. Current mirror loads for differential gain stages are widely used in op amps as they give very good linearity (ie, distortion free). In fact, most of the August 2001  33 AUDIO PRECISION SCFREQRE AMPL(dBr) vs FREQ(Hz) 10.000 06 MAY 100 05:15:08 AUDIO PRECISION SCTHD-W THD+N(%) vs measured LEVEL(W) 10 06 MAY 100 04:52:33 8.0000 6.0000 1 4.0000 2.0000 0.1 0.0 -2.000 0.010 -4.000 -6.000 -8.000 0.001 -10.00 .0005 10 100 1k 10k 100k 200k Fig.1: as measured in the SILICON CHIP laboratory, frequency response is a very wide 20Hz-80kHz (-1dB). distortion in this amplifier will be generated in the Mosfet output stage although most of this is then corrected by the negative feedback applied back to the base of Q4. The output of Q6 drives the gates of Mosfets Q9, Q10, Q11 & Q12 which 0.5 1 10 100 300 Fig.2: maximum power output before it “hits the wall” is about 220W into 4Ω at <0.1% distortion. operate as complementary source followers, ie, with a voltage gain of a little less than unity. It may appear that Q6 drives Q11 & Q12 while Q8 drives Q9 & Q10 but Q6 is the driver while Q8 is merely part of the current mirror load for the second differential amplifier stage. The gates of Q9 & Q10 are “separated” from the gates of Q11 & Q12 by the 200Ω trimpot RV1. The trimpot actually provides a small amount of forward bias to the gates of the Mosfets so that they are always conducting Viewed from a steeper angle than the previous photo, this gives a good idea of the layout of all the major components in the amplifier. Note the insulated cover over the fuse in the foreground: this is essential for your safety. 34  Silicon Chip www.siliconchip.com.au Fig.3: the circuit is relatively conventional, using four power Mosfets in the output stages. Q13 and 14 form an overload indicator, detecting the large spikes generated at the onset of clipping. to some extent. This is done so that the effects of crossover distortion are minimised. Readers may wonder why trimpot RV1 does not have an associated NPN small signal transistor across it to function as a “Vbe multiplier”. This is required in Class A, AB and Class B amplifiers using bipolar output transistors to ensure that the quiescent current is thermally stable. Without such a transistor to monitor and continually adjust the bias setting, the quiescent current just www.siliconchip.com.au continues to rise until eventually, the output transistors get so hot that they are destroyed. This is called “thermal runaway”. So why don’t Mosfet amplifiers need this same transistor? It is not true to say that Mosfet circuits cannot experience thermal runaway in particular circumstances but generally the power Mosfets used in high-quality audio power amplifiers have a negative temperature coefficient for currents above a particular level, typically 100mA. Above that current, if the Mosfet gets hotter, it tends to throttle back its operating current and thus reduce its dissipation and so there is no tendency to thermal runaway. We’ll discuss the quiescent current setting later in this article in the section on testing and setup. The drive signal to the gates of the four Mosfets is limited to about 12.6V peak-to-peak by the diode network consisting of D1, D2, ZD1 & ZD2. This limiting is included because Mosfets can be destroyed if they have excessive August 2001  35 Fig.4: there are two parts to the power supply; a centre-tapped bridge to give the main plus and minus rails, along with a conventional bridge fed by a 6.8µF capacitor, stabilised with a zener diode for the 24V fan supply. Note that the voltages are nominal, being “off load” and the type of figures you would expect to measure with a digital multimeter. gate drive. In normal signal conditions this does not occur but if the output of the amplifier is shorted or fed into a very low impedance, the negative feedback action causes the amplifier to compensate by increasing the gate drive. Also part of the circuit of each Mosfet is a 220Ω resistor in series with the gate. This is referred to as a “stopper” resistor because it is there to prevent (ie, to stop) spurious or parasitic oscillation at very high frequencies. Mosfets can oscillate at much higher frequencies than bipolar transistors and it is not unheard of for a badly designed Mosfet amplifier to oscillate at 100MHz or more (ie, in the middle of the broadcast FM band). So those stoppers are vital for stable amplifier operation. By the way, amplifiers with bipolar transistors often have stopper resistors as well but the potential frequency of oscillation is much lower than for power Mosfets. Another interesting feature of the Mosfet output stages in this amplifier is the presence of 47pF capacitors between Drain and Gate of Q9 & Q10. These are incorporated to equalise the gate capacitance of the N-channel Mos36  Silicon Chip fets (ie, Q9 & Q10) to the higher gate capacitance of the P-channel Mosfets (Q11 & Q12). Each Mosfet has a 0.22Ω 5W source resistor. This is included to improve current sharing in each pair of Mosfets and it also contributes to overall thermal stability. Right at the output of the amplifier, at the junction of the four 0.22Ω source resistors, is a Zobel network consisting of a .022µF capacitor and 6.8Ω resistor. This is necessary in virtually all solid-state amplifiers to ensure that a predictable load impedance (ie, around 6.8Ω) is presented at high frequencies where the inductance of typical speakers means their impedance is becoming very high. The overall gain of the amplifier is set by the negative feedback network consisting of C4, C6, R8 & R12. R12 and R8 set the overall gain to 34 while C4 sets the low frequency rolloff to 3.3Hz. However, the main determinant of the amplifier’s low frequency response is the 0.47µF input capacitor C1 and the 33kΩ input resistor which together set the -3dB point at 10Hz. The high-frequency response of the amplifier is mainly determined by the 1kΩ input stopper resistor R2, in conjunction with the .001µF input shunt capacitor C2. They set the high frequency -3dB point to about 160kHz. Overload indicator Finally, an interesting feature of the amplifier is the overload indicator involving transistors Q13 & Q14. It depends on the fact that, at the onset of clipping, large spike signals appear at the collector of Q5. These are fed via the voltage divider comprising R25 & R26 to the base of Q13. Each time a positive spike is fed to Q13, it charges capacitor C20 in its collector circuit. As the capacitor subsequently discharges, it turns on Q14 and lights LED1, the overload indicator. Thus Q14 and C20 function as a pulse extender so that each momentary signal overload is made visible on the overload indicator. Power supply The power supply (Fig.4) is fairly conventional, employing a 300VA toroidal transformer with 45V secondaries feeding a bridge rectifier, BR1. Each diode in the bridge rectifier is bypassed with a 0.22µF capacitor to provide suppression of rectifier hash. The bridge rectifier feeds four 4700µF 80VW capacitors to provide balanced supply rails of ±67V (nominal). On www.siliconchip.com.au O P T O PA C K 1 0 4 D E V I C E S : various colours & types. Top brands. Siemens etc. just $10 VISIBLE LEDs...5mm...14X Yellow clear, 6X Red (clear) 24deg, 2X Yellow (clear) 24deg, 16X Red (clear) 24deg,38X Green (clear) 24deg.VISIBLE LEDs... 3mm...14X Red diffused 70deg. 4X 3mm or rect. Yel. diffused 70deg SPECIAL...1X 5mm IR,3X 3mm Clear Phototransistor, 3X 5mm Phototransistor, 1X IR RX module. 2X DIL rect. black PIN Photodiode. PELTIER EFFECT DEVICES. 4A T 65deg. Qmax 42W $24 6A T 65deg. Qmax 60W $26 8A T 65deg. Qmax 75W $28 Comes with info to build cooler / heater All 40 X 40mm. PELTIER CONTROLLER KIT this kit is a switch mode design and correctly controls the temperature of peltiers to 10A using a very efficient design. Inc PCB, all on-board components . (k140) $19 (NEW) MULTI FUNCTION BATTERY CHARGER / DISCHARGER: New in original box with instructions. This unit was designed to charge NI-CD & NIMH mobile phone batteries of 4.8V, 6.0V and 7.2V. Operates from 12-24V DC input. Features include processor control & multi stage charge indicator. By changing the value of one resistor it can charge higher voltages, although a higher voltage plugpack is required for 9.4V or higher. Includes cigarette lighter lead, 12V / 1A DC plugpack & instructions for modifications for higher voltages. The unit has battery charging terminals but the user will have to make their own adaptor to interface to a battery. The plugpack supplied alone is worth around $30 retail. Weight is 0.9kg. $29... 15V DC / 1A Plugpack for charging batteries 9.4V or higher: (ZA0055) $6 If you ask when ordering you will receive a free 6-pack of batteries. CFL INVERTER KIT our very popular inverter. Very Efficient Driver kit can drive a number of CFL’s from 12vdc$25. QUALITY AUSTRALIAN MADE FEATURE PACKED MINI ALARM SYSTEM CONTROL Features inc. boot release, central locking output, imobiliser output, indicator flash relay. With 2 key-fob transmitter keys. $99 12V AUTOMOTIVE RELAY: Has 30A SPDT Contacts with 73ohm relay coil. These are the standard size and normally retail for around $7 each: (RL3) $3 each SUBSCRIBE TO NEW KITS FROM “OATLEY’S” We are constantly developing many electronic projects, but there is only a limited amount of these that the electronics magazine can publish. If you wish to receive a regular Email and be informed about these projects just send a blank Email with the following text in the subject heading: newkits-subscribe<at>oatleyelectronics.com Where possible our Emails will include descriptions, PCB overlays, parts lists and pictures. We will also offer you regular kit specials and where necessary, additional notes and or errata. In the future you will be able to access this same information at www.newkits.com but for the moment the ONLY WAY you can do this is by subscribing to the above Email address. As an example if you do it now you would be Emailed the following two projects within the next few weeks. MULTI PURPOSE INVERTER This modified square wave inverter can be used to convert 12-24V DC to 120V AC or 240V, or any other voltage. Power and voltage O/P’s depend on transformer. O/P freq. is adjustable between 50 and 60Hz and a beat indicator cct. is included (LED) so you can easily adjust the freq.. to be the same as the mains freq..With one pair of MOSFETS and no additional heat sinks 100W power O/P is possible, 200W with two pairs of MOSFETS and no H/S’s, 400W+ with two pairs of MOSFETS and additional H/S’s, etc…PCB plus all on-board components kit (No transformer):$18...Two additional MOSFETS: $6...US Plugpacks with a 30VA transformer: $2.50Ea. We will include notes on how these can be rewound for 120V O/P (1 needed) or 240V o/p (2 needed) FINALLY IT'S HERE!!! THE RIGHT WAY TO DRIVE STEPPER MOTORS. Now stepper motors can give high torque at high revs with our new 2 part kit driver system K142C Constant Current Source and K142B New Stepper Motor Driver. As a stepper motor's speed increases the current drawn and the power output slowly drop until it reaches a certain speed (varies greatly with motor type) then suddenly drops to almost nothing. Some drives like "Chopper drives" try to overcome this with a linear response to a non-linear problem. Our new K142C Constant current source drive senses the drop in current and increases the voltage to the motor and thus the current as speed increases. This gave similar torque at around 290 RPM as at 1 or 2 RPM (this is as high as we tested with a 200 step motor) Because of the wide voltage output range of the constant current source we had to re-design our stepper motor driver to cope. K142C: features easy construction, kit inc. PCB, heat-sink with fan and all onboard components. K142B: features inc. 4 or 6 wire motor drive, Opto Isolation to protect your computer, MOSFET placement for ease of heat-sink installation (if required) (heat-sink not supplied). Kit inc. PCB and all onboard components inc. high power MOSFET's. Both kits inc. full instructions, component ID and orientation printed on PCB for easy assembly. All Circuit boards (PCBs) are solder masked for easy soldering. GENUINE MAGLITE TORCHES So new it’s hard to tell that they are used, (during the Olympics). The same type as used by police, security guards etc. Complete in original box with booklet, rechargeable batteries, charger and charger clip /wall bracket etc. $150 SOLAR PANELS: Quality SIEMENS brand Polycrystalline cells. Open circuit voltage 5.7V, Short circuit current 0.22A, Peak power 1W <at> 100mW per square cm. 4 panels req. to charge 12V batteries. 160 x 55 x 5mm. Terminated with a 25cm long figure eight cable. $10 ea. or 4 for $36. SONY UNIVERSAL CAMCORDER BATTERY + CHARGER: Brand new in original packing Less than 1yr. old. 7.2V 1500mAh lithium-ion As commonly used with SONY digital cameras, camcorders, SONY and some other brand products . US made OPREX brand. Charger has an unusual plug that is easy to adapt. Requires power plug-pack (not supplied) 9V 1A (2A peak for 5 minutes)...$39. SERIAL SERVO CONTROLLER KIT: This kit is ideal for robotics kits etc, it controls up to 5 servos via the serial port of your computer. A lot of shareware and support for this kit on the Internet. Features inc. small kit size & hi servo resolution. Kit inc. software, PCB & all ELECTRONIC HOT WATER BOTTLE This kit would be ideal for sports injuries, pets, home-brewing etc Features include onboard com-ponents.:$24 insulated heating wire & thermostatic control. Some suitable power supplies may be GEARED AC MOTORS available, check when ordering. Kit inc. PCB, all onboard components & heating wire. Brand new small mains operated BOOK SHELF LIGHT SHOW K170 This 4 channel light controller is ideal for processional musicians or DJs. It is sound geared motors, triggered with adjustable gain or it will change through lots of different patterns at very strong, random by its self when its quiet. It is designed with 4 high powered MOSFETs to made for generate minimal heat while switching high loads and easily switches 4 12/50W rotating microwave halogen down lights. Kit inc. PCB, all onboard components inc. 4 MOSFETS. turntables, 240V/ Some suitable transformers may be available, check when ordering. 50Hz/3W/5RPM., SOOPER SNOOPER / STETHOSCOPE $4Ea. or or 4 for $12. This amazing parabolic microphone can listen in on all sorts of things from a distance, like bird calls and wildlife sounds, etc. Or by attaching the microphone to a metal rod NEW 500W Tungsten Halogen Lamps or screwdriver handle it can be used to listen to white ants chewing on your house! It is (All are new but packing may be shop also ideal for detecting engine knocks and worn bearings etc. We even heard water soiled) Ideal replacement or spare bulbs rushing through a radiator hose! Kit inc. PCB, all onboard components, stethoscope for yard and security lights. $2ea pickup, electret microphone and 300mm parabolic dish. SOLAR FURNACE /PARABOLIC REFLECTOR This is the same 300mm dish as used in our Sooper Snooper project. It is mill finished ie. unprotected aluminum and is reflective enough to ignite paper allmost instantly, With the use of some automotive cutting compound / polish it could easily be made W e h a v e m o r e u s e d t e s t equipment. we need to clear some highly reflective:$25 ea. VIDEO SYNC. STABILISERS Various forms of copy protection are used on video tapes & DVDs, that may cause playback problems like the jitters. This device removes the copy protection. thus cleaning the ONE / TWO CHANNEL UHF REMOTE picture. It has CONTROL On freq. of 304MHz, been transmitter is suggested to us that assembled, receiver is a these units could be used to copy commkit, inc. 2 12V/ ercial videos & DVDs but we do not 12A relays, 1Tx + condone any breach of copyright. This 1Rx kit:$45, additional Tx: $15 item comes as a ready built PCB with a I CHANNEL Kit just $25 new recycled metal case to suit. Just...$29 NEW 80mm 12V FANS WE HAVE TOO MANY ITEMS TO Ideal replacement for ADVERTISE HERETHE ONLY WAY TO computer power supply fans. SEE IT ALL IS TO CHECK OUT OUR 12V <at> 0.15A..$4 or 4 for $12 WEB STIE oatleyelectronics.com NEW SHIPMENT to make way for the next lot. But you may have already missed it. The only way to make sure you don’t is to subscribe to our bargain corner and receive advanced notice of what’s comming... Just send us a blank E-Mail to.... bargaincorner-subscribe MONOCHROME CCD VIDEO CAMERA <at> o a t l e y e l e c t r o n i c s . c o m VIDEO CAMERAS The output of these cameras below is std video & can be plugged into the "VIDEO IN" socket of any Australian std VCR, video monitor or TV, or via an RF Modulator to an Ant. Input. The B/W cameras are Infra Red responsive & can be used in total darkness with IR Illumination. B&W Camera built on a PCB with auto iris. (0.1 lux). Can be focused sharply down to a few mm(useful for people with visual impairment). Spec.: Power req.: 10V to 12V <at> approx. 50mA.CCD: 1/3", 30grams: $89, with 92° lens: www.oatleyelectronics.com Orders: Ph ( 02 ) 9584 3563, Fax 9584 3561, sales<at>oatleyelectronics.com, PO Box 89AOatley NSW 2223 www.siliconchip.com.au ugust 2001  37 major cards with ph. & fax orders, Post & Pack typically $7 Prices subject to change without notice ACN 068 740 081 ABN18068 740 081 SC_AUG_01 Fig.5: the component side of the PC board. The eight large empty holes are for the 5W resistors – see below. Fig.6: the four 5W resistors mount on the underside (copper side) of the PC board and should be 3-4mm away from the surface to avoid heat damage to the tracks or board. the amplifier board, further filtering is provided for the early stages via diodes D3 & D4 and associated 100µF capacitors. Another bridge rectifier, BR2, is fed from the two 45V secondaries (90V total) via a 6.8µF capacitor to supply a zener stabilised 24V for the fan. The high impedance of the 6.8µF capacitor throttles back the voltage to the bridge rectifier so that little power is wasted in zener diode ZD1. Assembly details Three PC boards need to be assembled: one for the amplifier, one for the power supply and one for the bridge rectifier. The amplifier PC 38  Silicon Chip board measures 159 x 65mm while the power supply board measures 122 x 65mm. We suggest you start on the amplifier board first, placing all the small components, then the insulated terminal blocks, followed by the power transistors and Mosfets along one edge. Use the component overlay diagram of Fig.5 as a guide to the assembly. When soldering the transistors along the edge, you will need to make sure that each Mosfet is pushed right down onto the board while the four other transistors are mounted with a lead length of about 11mm. This is not really critical though because spring clips are used to mount these transistor packages to the heatsink. The four 5W source resistors are mounted underneath the PC board, as shown in Fig.6. They should be mounted so that the resistor bodies are clear of the copper tracks by about 3 or 4mm. The rectifier is attached to the heatsink with a long screw and nut and a small PC board is fitted over the four rectifier lugs and soldered to them, as shown in the diagram of Fig.7. Before you do that though, make sure you mount and solder the four 0.22µF 250VW capacitors onto the rectifier board. The power supply board is also quite straightforward – see Fig.8. Mount and solder the insulated terwww.siliconchip.com.au Fig.7: the bridge rectifier and its associated capacitors are mounted on this small PC board which mates with the board at right. minal blocks first, followed by the small components, the 6.8µF capacitor and finally, the four 4700µF capacitors. Make sure that all electrolytic capacitors, diodes and zener diodes are mounted the right way around, as shown on the component overlay diagrams of Figs.5 & 8. Note that the 2A fuse is a slow-blow type. When all the boards are finished, check your work carefully and make Fig.8: the main power supply board holds the rest of the power supply components. sure that you have not missed any solder connections or have made any solder splashes to short between tracks. The next step is to mount the power transistors and Mosfets to the heatsink. Line up the board so that its lower edge is about 4mm above the lower edge of the heatsink channel. Each transistor is mounted using an appropriately sized mica heatsink washer and this is coated on both sides with heatsink compound. Then it is a matter of attaching the heatsink clips to secure each pair of transistors in place. The heatsink is then attached to the chassis plate with two self-tapping screws and the forward edge of the amplifier board is secured with metal spacers and screws. Fit the tunnel plate and the 24V fan to the heatsink at the same time. A heatsink-side view of the amplifier showing the fan and the way the heatsink is assembled and all mounted on the “chassis”. www.siliconchip.com.au August 2001  39 Fig.9: follow this inter-board wiring diagram when you’re assembling the amplifier and you shouldn’t have any problems. The chassis is designed to be mounted “as is” into other equipment, such as a PA or guitar amplifier. 40  Silicon Chip www.siliconchip.com.au The power supply board is also mounted on the chassis plate with four metal spacers and screws. Next the power transformer can be mounted using a large bolt, nut, flange washer and rubber washer. All the transformer leads, with the exception of those to the main bridge rectifier (BR1) are connected to the insulated terminal block along one end of the power supply board. All the inter-board wiring is shown in Fig.9. Solder the two 45V windings to the AC inputs on the bridge rectifier on the heatsink, together with two white wires which become the AC input to the bridge rectifier (BR2) on the power supply board. The white wires are connected to the relevant 45V terminals on the power board. Don’t forget to scrape the varnish (enamel) off the ends of all the transformer wires, to make sure you make good connections before soldering or terminating them. Make all the input connections to the power board but don’t connect any of its DC outputs to the amplifier. Do connect the 24V output to the fan. The green/yellow wire of the 3-core mains flex is terminated to the solder lug on the chassis adjacent to the transformer. Also connected to this lug is a 0.1µF capacitor which connects to the 0V line and centre-tap of the transformer. This is done instead of directly earthing the amplifier as it can help to avoid hum and buzz due to earth loops. The Active and Neutral wires in the mains cord connect to the relevant insulated terminals on the power supply board. Note that the slow-blow mains fuse should be fitted with a plastic shroud to stop any possibility of accidental contact. Initial power up Before connecting the amplifier supply rails, it is a good idea to check out the power supply operation. So carefully check out all your power supply connections and then apply power. The fan should immediately run and you should be able to measure around ±70V at the DC outputs of the board. Turn off the power and discharge the main filter capacitors with a 5W resistor of 100Ω or higher connected across the DC outputs. Now connect the DC supply rails Winning Gold . . . . . .After the Games EX OLYMPIC GENUINE MAG LITE TORCHES Made in USA, complete with 240V battery charger kit and in car battery charger kit. As used by Police, Navy & RTA from the power board to the amplifier, each via a 10Ω 5W resistor. Rotate RV1 fully anticlockwise – this is to set minimum quiescent current. Do not connect any signal source or a speaker load. Then apply power. If the fuses go up in smoke or get red hot, turn off the power and recheck your work. If all is well, check the ±67V rails and the DC voltage at the speaker output; it should be within ±30mV of 0V. To set the quiescent current, monitor the voltage across one of the 10Ω 5W resistors and adjust RV1 for a reading of 0.8V. Leave the amplifier running for a period of ten minutes and if necessary, readjust RV1 for the correct reading. Then turn off the power, remove the 10Ω resistors and directly connect the supply rails from the power supply board to the amplifier. The signal leads and loudspeaker can be connected to the relevant terminals on the connector strip and then you are ready to roll. Where to buy the kit This 200W amplifier is exclusive to Altronics (Cat K-5172) and is priced at SC $349. Phone 1 800 999 007. HURRY! This is your LAST CHANCE to grab some of the equipment left over from the Sydney 2000 Olympic Games at never-to-be-repeated prices! CALL NOW! PH: (02) 9879 6782 FAX: (02) 9879 6993 180 ea $ EX OLYMPIC SECURITY DURACELL 9 VOLT BATTERIES Brand new (expiry dates 2004) Boxed lots of 48 1 00 $ 79 ea $ 80 ea EX OLYMPIC TOA MEGAPHONES Complete with shoulder harness and alkaline batteries www.siliconchip.com.au ALL PRICE INCLUDS E GST ® DON’T MISS OUT! ® Registered Trade Mark Australian Video Systems August 2001  41 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. Vibrating VU meter This circuit was designed to enable a visually impaired person to work as a presenter at the local community radio station. It vibrates when the signal level in either of the stereo channels exceeds 0VU. Even if you aren’t visually impaired, it’s a handy device to monitor recording and broadcast levels, as it frees you from watching level meters or overload lights. The circuit is designed to fit into the case of a surplus pocket pager. This makes it comfortable to hold, put in a pocket, or clip to a belt. The pager also provides the vibrating motor and an easy-to-access battery compartment for a single AAA cell (or AA cell in some models). The circuit design was constrained by the supply voltage of only 1.5V, virtually forcing the use of discrete transistors. The left and right channel signals cannot be simply added together, be- cause a negative swing on one channel could then mask an overloading positive swing on the other channel. Hence separate transistors, Q1 and Q2, are used to detect overload in each channel. The collectors of Q1 and Q2 are connected together, wired-OR fashion, to give a signal that goes low when there is an overload in either channel. The signal from each input channel is attenuated by a 100kΩ trimpot, adjusted so that a 0VU signal will just turn on the appropriate transistor. The threshold is referenced only to the turnon voltage of the transistor, making it independent of the supply voltage. Transistor Q3 provides extra gain to square up the response to input signals near the threshold. The 1µF capacitor and parallel 470kΩ resistor extend the response to brief overloads to a minimum of about 1/3 second. Transistors Q4 and Q5 form a Schmitt trigger which ensures clean transitions as the 1µF Andrew Partrid ge capacitor charges and is the inaugura l w discharges. Transis- inner of a Wavetek tors Q6 and Q7 act Meterman 85XT true RMS multimet as current amplifiers er to drive the pager motor, which needs about 60mA for reliable starting. Switch S1 and the series 1M resistor provide an optional battery test facility. Pressing S1 will activate the pager motor, provided the battery voltage exceeds about 1.2V. There is no power switch because all transistors are off when the input signal is below the trigger threshold, giving negligible quiescent current drain. Andrew Partridge, Kuranda, Qld. Digital Trainer using 4000 series chips This circuit is a simple cheap way of teaching the basics of digital electronics and the functions of different types of gate. The basic circuit is the same for all gate types; one gate has its inputs initially tied low. Two switches allow you to change the level on an input and therefore change the output which drives a LED to show the output state; on is High. You can use this circuit to 42  Silicon Chip demonstrate the functions of AND (4081), OR (4071), NOR (4001), Exclusive-OR (4030, 4070) and Exclusive-NOR (4077) gates. The use of a socket allows convenient changing between chips. Only the first gate of the chip is used, with all the other inputs being tied to ground (0V) via a 100kΩ resistor. The circuit will run on supplies between 5V and 12V DC. Owen Klan Rathdowney, Qld. ($40) www.siliconchip.com.au Thermistor addition for heat controller This circuit is essentially the Heat Controller published in the July 1998 issue of SILICON CHIP with the added feature of thermistor control. As originally published, the Heat Controller circuit used a 1MΩ potentiometer to control the power delivered to the load. This circuit modification employs comparator IC3 and a thermistor to provide temperature control and gates the Triac control signal on and off with IC2, a 4001 quad NOR gate. When the temperature is lower than the setting desired by trimpot VR2, the thermistor’s (relatively) high resistance will mean that pin 2 of IC3 will be high and so pin 1 will be low. This signal is fed to three gates of IC2 so that the pulse signal from IC1 is fed through to IC4 and the Triac to drive the heater load. Once the temperature rises sufficiently, the thermistor’s resistance will drop, pulling pin 2 of IC3 below pin 3 and sending pin 1 high. This will cause the NOR gates of IC2 to block of signals and so the Triac will not be pulsed on and off. Jeff Griffin, Bairnsdale, Vic. ($40) $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ As you can see, we pay good money for $ $ $ each of the “Circuit Notebook” contributions $ $ $ $ $ published. But now $ $ there’s an even better $ $ $ $ reason to send in $ $ your circuit idea: $ $ $ $ each month, the $ $ $ $ best contribution $ $ published will $ $ $ $ win winone oneofof $ $ these superb $ $ $ $ Wavetek Meterman $ $ $ 85XT true RMS $ $ $ multimeters - valued $ $ $ $ at around $380! $ $ So don’t keep that $ $ $ $ brilliant circuit secret $ $ $ $ any more: send it to $ $ SILICON CHIP and $ $ $ $ you could be a winner! $ $ $ Contributions must be your own original work or a major $ $ adaptation and not published elsewhere nor submitted for $ $ $ publication elsewhere. SILICON CHIP’s decision is final. $ $ $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ CONTRIBUTE AND WIN! 1 meter to win every month! www.siliconchip.com.au August 2001  43 SERVICEMAN'S LOG Some faults can be a real challenge Although most servicing jobs are routine, some faults can be a real challenge to track down and fix. There were several such jobs that caused me a great deal of grief this month. Mrs Dawson is very proud of her TV set and its features. This is not just any Akai set; this is the “Jet Reflex” model (CT2590A-T) because of its “Super Bass Woofer System” and its comprehensive dubbing facilities. She also had an Akai hifi video but unbeknownst to her, she wasn’t getting the full effect of this as it wasn’t connected to the sound system via the AV leads. As a result, when she replayed it via the RF lead, she was only getting duo-mono! Anyway, it was a rainy day when her beloved machine died shortly after its fourth birthday and I was asked to give it first aid in her home. I hadn’t actually ever seen this model before but by good fortune, I al- 44  Silicon Chip ready had an original service man­ual. Judging by the quality of its picture it looked as though the set was designed and built by Akai in Japan but I was surprised to discover that the set was actually made in China. I was also disappointed to find that the set was crammed inside a black home entertainment unit in the darkest corner of the room, with tight leads connect­ed to the rear of the set. Anyway, I persevered, straining my kryptonite vision night glasses and really struggled to get the back off. The black screws are in deep dark recessed holes in the black cabinet but I finally succeeded, to realise I had just opened a Pandora’s box. The set was almost completely dead; it would only switch the red LED power on light to green, which would then fade off to nothing. Access inside the set wasn’t brilliant and with the way it was installed, it was difficult to get to the underside of the PC board. But despite this, I managed to determine that the power supply was working OK and that there was 150V on R508 (interest­ ingly this 59 cm set has a higher HT than the 68cm model, which has an HT of +135V). I also managed, again with great difficulty, to measure the 8V, 5V, 27V, 33V and 38V rails and found nearly 150V on the collector of Q52, the horizontal driver transistor. This meant that this transistor was well and truly switched off (normally it is 63V) and so there was no horizontal drive from the jungle IC (IC201). There was only one other thing left to check before I called a halt and that was whether there was any power getting to IC201. I measured 8V on pin 35 of this IC, so that wasn’t the problem. It was time to take this baby back to the workshop but Mrs Dawson was not happy with this news. However, I had already spent at least an hour on the set and so I insisted. When she finally agreed, I partially replaced the back on the set (I have a life – I think?) and got out as fast as I decently could. Back at the workshop, I was able to relish what space and light were all about and could at last examine the set more carefully. Though the service manual is good, both it and the set can only be described as “bitty” – with lots of flying leads, plugs and sockets and small modules. The main board is screwed onto one of those black plastic support brackets which always make large parts of the circuit inaccessible – usually, the very parts you are trying to inves­tigate. In this case, there was also an annoying control board screwed onto the front of the bracket. This was all removed until, finally, I could analyse the naked board for hairline cracks and dry joints. This also allowed me to use the CRO to check that the crucial crystal clocks - X201, X202 and X301 on 3.58MHz, 4.43MHz and 8MHz – were all work­ ing. They were which led to a quick analysis of where I was going with this. We had all the voltages correct (well, nearly all), we had an oscillator but no drive and we had limited control (the set would switch on and off with the remote). To me, it left three major areas to investigate – the jungle IC, the micro and EEPROM and the signal paths between them, especially the I2C (Two-line Inter IC bus), SDA (Serial Data) and SCL (Serial Clock) www.siliconchip.com.au pulses. The latter turned out to be extremely interesting, as this is the first set I have come across that has two sets of data­ lines (which is surprising because I thought the whole idea was to keep it simple by having only one set). As far as getting the set going though, we only needed SCL1 and SDA1 from the jungle IC (IC201; TDA8366), the EEPROM (IC302; XL24C04P) and microprocessor IC301 (TMP87CM39N). The SCL2 and SDA2 lines control the small signal circuits only. There is not much you can do to check data lines other than to check that they are at 5V and that there is data on them. The CRO confirmed that everything was OK here, so I then checked for continuity between the ICs and the line driver transistor (Q052). Again, everything was OK, so there was nothing for it but to replace the ICs themselves. This also meant inflicting pain on the old overdraft, be­cause they are invariably expensive. Basically, because I didn’t have a clue, I decided to replace the ICs in order of their expense, starting with the cheapest – the EEPROM. This 8-pin device is an enigma – you can buy them from a couple of dollars up to over fifty dollars each for what is essentially the same device. Like so many other aspects of the devices used in TVs, I wish there was more information available on them and what their numbers mean. But basically, it is whether the EEPROM is sold preprogrammed or not that decides its cost. I socketed the new IC and slipped it in when it eventually arrived. To my relief, this fixed the problem instantly and the set burst into life. However, despite paying the price for what surely must be a preprogrammed IC, I still had to reprogram it. The service manual describes this as presetting the MCU option code for the E2 P-PROM. First, you engage the TEST MODE by pressing the volume + and - button on the front panel while switching the set on. Nothing happens except that the set comes on in the Standby red LED mode. Next you switch on the power button on the remote control. Next we get a “TEST MODE” written on the screen with a list of five digits starting at 000 00. The first three are addresses and www.siliconchip.com.au the last two data. From a table in the service manual, the Akai CT-2590AT model requires address 3A0 to have data 3A and address 3A1 to have data CE. When you have finally learnt how to navigate this list and edit it, you find that the replacement KS24CO4P, which has a white paint spot on it, is set for the CT-2990AT model as a default, which meant changing only the 3A0 from 2A to 3A. The secret of doing all this, I find many lifetimes later, is to save the data imme­diately after you have entered each digit by pressing the centre button on the remote. Not quite the end I thought that this would be the end but wait, there is more – quite a lot more. Despite setting the MPU option for this model, I found that the geometry was incorrect, especially the east-west pincushion. This meant finding the address for the EWPW (E-W parabola/width to you in Akai talk) which is 369 and changing it from 33 (29-inch) to 19 for the 25-inch set for pincushion, and finding address 368 and changing it from 25 to 33 for the width. When the job is done, you have to Items Covered This Month •  Akai CT2590A-T “Jet Reflex” TV set. •  Deitron CTV74ST TV set. •  Akai TV2570 TV set. •  Philips 25PT448A/75A PV4 TV sets (2). turn the set off and on to get back to an operating mode. After that, it is just a matter of using the on-screen menus to do the channel presetting. The set was now working perfectly – all I had to do was reassemble the boards, replace the back and return it to Mrs Dawson. Pretty simple stuff, eh? Well, unfortunately it wasn’t meant to be. Putting the boards back together again was fine but fitting the chassis back into the front shell of the cabinet wasn’t quite so easy. The problem was the on-off power switch and its dog-leg extension and trying to line this up with the push­button knob in the front. After several attempts, ducking the degaussing coils and other leads, I finally got it in and checked its function before putting the back on. To digress just a moment, the back has two red round tur­bine adjusting bass reflex holes which look like jet engines – hence (I assume) the name “Jet Reflex”! Then it was on to getting the back on. It is long overdue, but everyone should give the manufacturers a treatise on how to make backs that can be removed and replaced easily. Half my grey hairs are directly attributable to the problems of poorly fitting backs. Nowadays, they are even worse because they are heavy with the sub­ woofers and even more difficult with their flying leads to disconnect and rejoin. Well, I did fit the back only to then find the on/off switch wouldn’t work. It was only on my third attempt after I had lubricated the latch mechanism that I finally got the on/off switch to August 2001  45 work. I then left the set on soak test for two days, switching it on and off regularly before arranging to return it. Mrs Dawson was very excited that her set was back – she had been phoning every two minutes for the last three weeks to find out when it would be ready. And now it was. After climbing the stairs, getting it down the narrow passage and past all the chairs, I steered it gingerly into its tight home. I finally got everything plugged in and ship-shape before switching it on. And would you believe it – it was giving exactly the same fault symptoms as when I picked it up! Actually, I lie a bit – at least the set was trying to fire up momentarily before going back into its standby state. And the reason was that that wretched on/off switch wouldn’t latch into place again. The only way I could get the set to work was by using a piece of paper to jam the switch into the on position. 46  Silicon Chip Considering the strife this set had caused us both, I think we were both pretty restrained in our language and demeanour. However, there was nothing for it but to take it back, order and fit a new switch. All I can say is come the revolution, I am going to be out looking for the designer of this set and won’t be satisfied until Madame Guillotine is! Deitron CTV74ST I had never heard of Deitron before (except for an old English brand many years before), until suddenly there was a 68cm stereo TV sitting right plumb in the middle of my workshop table. I had no idea how it got there but there it was with a scrap of paper stuck to the screen which said “dead”. At the time, I was the only one in the shop and I had fin­ished my coffee and so I figured I had to be the one to fix it. The set was a Chinese-built Deitron CTV74ST employing an RCA picture tube. I soon found out the cause of the problem. Q302 (2SD1556) was short circuit and the flyback transformer had been arcing. The former was easy to fix but getting hold of the latter was harder. However, a Samsung FCR2SA015 was an exact replacement and I soon had a pink raster and sound. Finding and replacing Q57 (JC558) with a BC558 and changing the pin orientation got me nearly there. All I had left to do now was fix the uncontrollable bright white raster and retrace lines. First, I tried adjusting the screen control on the new fly­back transformer but it could only reduce the intensity slightly. Next, I measured the 180V video B+ to the CRT board and for good measure replaced C57, a 10µF 250V smoothing electro. I also measured the 12V rail and replaced C51 (470µF 16V) as well. Neither of these steps made any difference at all but I did notice that unplugging the plug to the colour decoder board removed the raster completely. Finally, I did the sensible thing and measured the voltage to the three cathode guns to find they were all at nearly 0V. The three colour amplifiers are from transistor push-pull amplifiers driven directly from IC824 (TDA3505) on the colour decoder board. I fitted a socket for the 28-pin IC and before putting a new one in, switched the set on. This time the screen was dark but after fitting a new IC I was back to square one. By now, I was desperate for a circuit diagram and just by chance I found that an AWA 6990S was extremely similar and so I used that. I then decided to investigate the beam-limiting contrast and brightness circuits and noticed a negative voltage rail was developed from the flyback transformer (EM301, pin 8) via R345, D309, C332 and R346 - except of course there was no voltage getting to the destination of R90 and Q65 on the CRT board. I found a 220kΩ resistor (R346) that was covered with brown glue to be open circuit and felt sure that replacing it would be the panacea for all my problems. Unfortunately, it made no difference at all except apart from putting a negative voltage on the SK line to the CRT board. It was only then that I paid attention www.siliconchip.com.au to a mysterious 3-transistor circuit on the CRT board. It consisted of Q65 (BF423), Q51 (BC547) and Q52 (BC558) - plus D51, a 10V zener diode. 12V is applied to the emitter of Q65 and a negative voltage to its collector, which is also connected to G1 of the picture tube. This apparently forms part of a brightness stabilisation control circuit but I can’t quite see how it is all meant to work. I decided to check each transistor out of circuit and even­tually found Q52’s collector-emitter junction to be leaky. Re­placing this and readjusting the screen control finally restored the picture. One of the main problems I had with this repair was being unable to measure the screen G2 voltage accurately, getting extremely low voltages (100V) with all sorts of meters, making me suspect the new flyback transformer again. However, I now think that this was so low because the intense white raster on the tube was loading the voltage. (S2000AF) with them. Recently I had a case where D514 BY218-400 was also short circuit, giving no east-west correction. The problem is getting general-purpose equivalent replace­ m ents for these diodes, because you just cannot stock every diode known to man and genuine replacements are often no longer avail­able anyway. I’ve written before about the huge variety and types of diodes available. I chose to fit a BY228 diode as a replacement but it didn’t fix the problem. I also replaced T63 (BD237) which measured fine with an ohmmeter but had totally lost its gain (ie, hfe = 0). Next, I replaced C781, C548 and C546 but this made no dif­ ference. I could see the waveforms arrive at T562’s base but disappear on the collector of T561. I replaced these transistors and checked all the components around them but got nowhere. I tried freezing and heating but only managed to blow D513 (BY448), which made the set go dead. I even Akai TV2570 tried replacing the EW tank coil. The Akai TV2570 is an ITT/Nokia However, once or twice, the width did European-designed and built digital come good with the freezing treatment set and I have seen quite a few over but only for a few seconds. the years. By and large, it has been Finally, I managed to crack it with pretty reliable and is a good performer another set in for re­pair, swapping but the remote and panel controls are the components over one after the difficult to comprehend and not at all other. The culprit was D514 – which user friendly. measured perfectly. BY218s are hard The most common fault has been to come by and I solved the problem by flyback transformer (TV53 4515 using a BYX55-600 General Purpose 10344) problems and for a while, there Switching Diode (600V 3A) instead 80x181mm.qxd 11:37 AM 1 was a shortage of3/5/01 replacements. And Page of my first choice of a BY228 (a TV more often than not, they take T511 damper diode rated at 1500V 1.75A). The silly thing is I have seen similar TVs with a BY228 fitted in this position. I even tried replacing the BY228 with another but it made no difference. The set has been working fine with the BYX55-600 ever since. Mr Sandman’s Philips Mr Sandman is a wealthy man, consequently he can afford to live right on the ocean waterfront. He had two 4-year old Philips sets (25PT448A/75A PV4 chas­sis) which weren’t working and though he could easily afford new ones, he asked me to fix them. I guess he wouldn’t be where he is if he did not appreciate the value of money. Both would try to start and then go into standby mode with the red LED pulsating. Both sets were also somewhat corroded inside but not excessively. I already had a service manual for the PV 4.0AA chassis (4822 727 20962) and the first thing I did was to measure the main HT rail. The service manual – as is Philips’ wont – is fairly confusing, giving the VBATT voltage as 95V for 14-inch sets, 100V for 21inch sets and (120) in brackets at point P1 across C2551 or D6550 K. Well, I was getting 134V, so I felt it was fairly obviously in a protection mode because the VBATT line was so high. I also figured that once I’d fixed one set, the other would be very easy since the fault would probably be the same. In order not to inflict damage, I shorted the base and emitter leads of the line output transistor (7448) and Meterman. The Working Man’s Meter. Meters that fit your job. Meters that fit your wallet. Introducing Meterman, a hot new brand of test and measurement tools that gives you the performance you need at a price you can afford. Meterman is a line of more than 60 meters, clamps, and testers. Each one designed with the right combination of features, functions and accuracy to fit your application. You work hard on the job. Get the tool that’s easy on your wallet. Ask your local test and measurement supplier for the Meterman products or contact Meterman on Locked Bag 5004 Baulkham Hills NSW 2153, phone 02 8853 8812 or fax 02 8850 3300, or visit metermantesttools.com TM www.siliconchip.com.au August 2001  47 Serviceman’s Log – continued hung a 100W globe across the HT line. The power supply looked pretty conventional, though Philips love to put some SMD parts under­neath the chassis, making circuit tracing just that bit more difficult. I tried adjusting VR3540 and noticed that although the voltage changed, it was still too high and remained so – even in the standby mode. I spent a lot of time investigating the power supply and could find nothing seriously wrong. I replaced all the small electros and IC7520 (MC44603P) and checked all the resistors. Obviously all the voltages were out – but not by much. I tried this with both the sets but just wasn’t getting anywhere. I was fooled by the circuit involving Q7510, especially when I found resistor R3510 (39kΩ) to be high in value. Actually, a 56kΩ resistor was fitted in both sets but one was still too high at nearly 80kΩ. Fitting new ones and various variations made no difference and in any event, this circuit is part of the degaussing circuit. It’s obviously provides a soft start-up to reduce surges but I am not sure how it works. In the end, I decided to fudge it by altering the value of the pot (VR3540) 48  Silicon Chip but even with the right voltage output the set was still closing down. As a result, I decided to concentrate on the line output stages. Accordingly, I removed the dummy load and base-emitter jumper and found a whole stack of faulty components: (1) R3482 and R3329 were open circuit, preventing the +165V rail being applied to the CRT output stages; (2) D6444, D6447 and D6497 weren’t even shown on my circuit diagram but all were short circuit; and (3) L5479 was open circuit on the +13V VDEF line. When I replaced the latter, the new one started to get hot which was consistent with the HT being too high. The set was still almost immediately going to standby, so measuring voltages on the secondary was extremely difficult. It was about this time that I had the good fortune to meet and talk to a Philips technician who was familiar with these sets. (Because Philips has produced well over 5000 models since 1974 it is hard to be that familiar with any of them). He informed me that although I did have a service manual for this chassis, it was still the wrong one. Instead, there is a separate manual for the 25-inch model and being an extremely obliging fellow, he gave me a photocopy of the circuits I needed. This breakthrough informed me that VBATT is actually +134V at P1 and the circuits also showed me all the differences I had already noticed, including the location and detail of D6444, D6447 and D6497, as well as their values. It also meant I had to write off a huge amount of time spent investigating a total red herring. I reset the power supply and could see the +13V VDEF rail was under stress. Following the rail along, I could see it mainly fed the vertical output IC (IC7960, TDA­9302H). Replacing this restored the sound and picture and I now had everything working except that there was no east-west correction. I put the set into the Service Default Mode SDM by shorting M25 (pin 1 of the EEPROM) to ground and switching the set on. I checked out the Options Code Address/Data with the list stuck on the inside of the back of the set. The East West data was differ­ent to that in the list but varying it made no difference to the picture geometry. I then spent another huge chunk of time investigating hard­ware failure in the east west circuit, which is half on the motherboard and half on a separate module J. I soon discovered – oh joy! – that leaving this module unplugged destroys the line output transistor! Eventually, I conceded that it had to be a faulty jungle chip (IC7200, TDA8375) and ordered one in. This IC fixed the first set completely. I just needed to set up the east-west geometry, so I went back into the Options table (which inciden­tally told me this was an Anubis-PV4 PM4.3) and reset address 111 (width), 112 (para), 113 (corner), and 114 (trap) for the best square picture using a test card. Address 246 (height) needed adjustment as well. I also had to tune in the set using the installation menu afterwards. Having finished the first set, I got back onto the other one, hopefully wiser than I was before. Thankfully, it had very similar problems, with the vertical output IC (IC7960 TDA9302H) being the main culprit. Replacing it and the other coils and resistors restored the picture and sound but there were no east west problems this time. These sets certainly caused me grief SC but I’ll know better next time. 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 World’s first trials of a wearable health info card A ustralian health organisations are watching a US study involving three Texas hospitals and 34 Health Maintenance organizations with great interest, as the outcome could have a bearing on the health record card which will ultimately be introduced in this country. The study involves the first public use of SanDisk Corporation's (Sunnyvale, CA. www.sandisk.com) “P-Tag” flash memory card, the industry's first wearable storage device for the health care market. More than five thousand patients in the Dallas, Texas area will have their complete medical records stored on the small 8-megabyte P-Tags. Information stored on the P-Tags will include drugs being currently taken, drug reaction histories, physical exam reports, allergies and allergic reactions, vaccinations, previous injury history, blood type and even compressed images of X-rays, CAT scans and MRIs. Various levels of security can be built into the cards. A 8MB P-Tag can store two hours of recorded voice or 6,000 double-spaced pages of text P-Tags weigh two grams and are the size of a postage stamp. Most patients will wear them around their neck or keep them on a key chain. Doctors participating in the study will each have a P-Tag reader connected to their computer. P-Tags do not need a battery to retain data and they are expected to have a lifetime of more than 100 years. Patient information also will be stored in doctors' computers to ensure that medical information is retained if a P-Tag is lost. Officials at Matrevic Data Systems Inc (www.matrevic. bigstep.com), the Dallas-based company that has organised the project and provided the software, believe the trials will demonstrate how the P-Tags can save lives and deliver medical care more quickly, efficiently and inexpensively. Ed Cuellar, director of marketing at SanDisk, said, “P-Tags will give tremendous comfort and convenience to patients because they will have their medical records with them at all www.siliconchip.com.au times. As this technology gets more widely used, emergency medical technicians and paramedics will be able to quickly read the information on the P-Tags and possibly save lives by having critical information at their fingertips.” Dr. Fred Maese, a cardiologist at the Ferris Heart Center in Dallas, said, “We're very excited to be a part of this case study and I can see lots of benefits for my own specialty. The cardiology specialty is the largest specialty in the US health care system and I am looking forward to the day when all my patients are P-Tag carriers.” More than 1,000 of the patients in the trials belong to 34 different health maintenance organizations (HMOs). Carr said the HMOs will be closely monitoring the results of the study to determine if they should start equipping more of their patients with P-Tags. He added “P-Tags can play a role in reducing medical errors. According to a 1999 study by the US Institute of Medicine, up to 98,000 people in the USA die annually from medical errors, making medical errors the fifth leading cause of death in the country. Some 11 percent of medical tests, over $1 billion annually, are redundant because doctors cannot find initial test results or don't know if the tests were ordered.” Carr cited one of many possible scenarios where a patient would benefit from having a P-Tag. “A pregnant woman is travelling on business and isn't feeling well. She goes to an urgent care clinic where her blood pressure is measured at 130/85 and a urine dipstick shows 1+ protein, a little above normal but the physician isn't overly concerned and she is released. The doctor is not aware that her blood pressure is normally as low as 90/70, she has gestational diabetes and she in danger of pre-eclampsia, a condition that can be fatal to the woman and child if it is not treated promptly.” “If the woman had a P-Tag with her medical information,” explained Carr, “she would have been treated immediately. Patients don't always tell physicians everything about their medical condition during office visits.” SC August 2001  57 The The role role of of electronics electronics in in MINE ACHTUNG! CLEARING In many parts of the world there is a vast problem with mines. In some cases these have been in place since World War I – yet they are still lethal. Huge numbers of civilians are still being killed or maimed by mines, years after hostilities have ceased. In this article, we investigate the role of electronics in mine clearing and discuss the many different types of mines which have to be dealt with. By BOB YOUNG W A second more sinister reason takes Australian veterans of the Korean hen dealing with this subinto account the fact that the sight of War can tell chilling stories of standing ject we enter into one of the maimed men can be quite demoralisin the face of Chinese human wave most ghastly fields of human ing for their friends and other soldiers. attacks, where it was virtually imposendeavour imaginable. Just read the sible to fire their guns fast enough to two accounts in the breakout panels However, in defence of military slow or stem the onslaught. A mineif you need any proof – and these “Chyeng was fetching field between such an enemy are about civilians! the cow from our field wh en adds greatly to the firepower The laying of vast fields of he stepped on a mine,” explained his father, Nyeng, in of a defending force, as the anti-personnel mines with the hospital with him. “We did not know there was any following descriptions of express purpose of maiming sol- danger there. I ran into the field to rescue him, but then mines clearly indicate. diers rather than killing them is I stepped on a second mine and lost my leg. I am a quite diabolical, as the following widower with eight other children. But in virtually every I am very fearful for all my children as I have no quote will illustrate quite clearly; case, the military forces money and now I canno t “Research has shown that it is work the land.” have callously walked away better to disable the enemy than from the battlefield and left to kill him” (Advertisement for their silent sentinels to Pakistani mines.) continue their grisly work thinking, there is another side to long after hostilities have The thinking is that injured men this story. ceased. require more resources than dead men. ilicon Chip hip 58  Silicon www.siliconchip.com.au As a result, minefield clearance is left mainly to civilian agencies to organise. This is largely because it is civilians who are suffering the agony of living with these lethal devices. With approximately 120 million mines scattered throughout 71 countries, few people in the western world have any idea of the immensity of the task facing the mine disposal teams. And nor do they have any real idea of the cost in terms of human suffering. There are up to 800 deaths and 1200 maimings each month – a tragedy of colossal proportions. danger of mine clearance can be gleaned from the following summary of information contained in the Norwegian People’s Aid landmine database at www.angola.npaid.org This is another very extensive landmine database, here discussing the Russian PMN blast mine. “The PMN has a circular bakelite body with a rubber plate on the top. The rubber plate is secured to the mine body by a thin metal band. The detonator/booster well is placed on the side of the mine body, opposite the fuse assembly well. The booster housing is made of plastic and the A plethora of mines detonator is fitted into the booster. To understand mine detection it is A plastic plug is screwed into the necessary to understand mine design detonator/booster well to close it. The Blast mines and construction. The designers of fuse assembly is screwed into the well these diabolical devices go to exThese are the most commonly on the opposite side of the detonator/ traordinary lengths to make them as booster well. The fuse is secured difficult to detect as is huwith a safety pin to prevent the t las o can vol r the Guazapa nea d die gs lin manly possible. Given the striker from moving forwards. sib ree “Th during pped on a mine planted human capacity to devise The fuse is delay armed. A thin d weekend when they ste ha ents re. Ironically, their par ways to kill people, they metal wire is attached to the back en the period of civil warfa ldr chi ys earlier. The have succeeded beyond returned to the area only a few da part of the striker enclosing a ee thr the m ars old. Parts fro ye ht eig d an six measure. lead strip.” r, fou were far as 30 metres from Land mines are composed children’s bodies were found as “When the safety pin is reof an endless array of diffi- the explosion site.” moved, the spring-loaded striker cult-to-detect materials such is released, causing the steel wire as plastic, Bakelite, phenolic to start cutting through the lead encountered type of land mine. The fibreglass, rubber, cardboard, delay strip. After the delay strip is Soviet PMN, also known as the Black neoprene and on occasions when the cut, the striker is allowed to move Widow, is one of the most widely designers really mean business, sheet forward until it stops on a step in used. Its large explosive content, 240g metal and steel. the actuating plunger. The mine is of TNT, is often fatal. It has probably now armed. The delay arming time is To detect, defuse and clear these killed and maimed more civilians from 15 to 37 minutes depending on grisly gadgets taxes human ingenuity than any other type of mine. It is the temperature. Pressure on the rubeven further. Sadly, the designers of pressure-activated, generally buried ber plate will depress the actuating the detection equipment to date have by hand and is deployed in vast plunger until the striker is released. fallen behind in the race, for the task numbers in Afghanistan, Cambodia, The striker fires the detonator and the has proven extraordinarily difficult. North Iraq/Kurdistan, Iran, Nicarabooster, which in turn detonates the Nor is it made any easier by the fact gua, Angola, Mozambique and many main charge.” that in many cases cleared fields are other countries. “The mine cannot be neutralised re-laid with a new stock of mines as because the forward motion of the soon as the clearance teams depart. PMN striker when the safety pin is reThe Mines Advisory Group has Some idea of the complexity and moved prevents the safety pin being documented more than 300 identified replaced. To disarm, hold the mine by the bakelite sides only. Unscrew and remove the detonating plug. Remove the detonator and booster from the mine. After disarming the mine, the striker can be removed by depressing the pressure plate to fire the striker out through the hole for the detonator plug.” “The Iraqi version of the PMN is named PMN HGE. It is black in colour This is the PMN landmine in cut-away and fully assembled. It has probably and is known to be extremely unstable killed more people than any other type of mine. Incidentally, we must apologise after years in the ground therefore no for the standard of photographs in this story: needless to say, mine manufacturattempt should be made to disarm ers are not all that forthcoming when asked for press photographs. Most of these this mine.” photos came as low-res pictures direct from the various websites mentioned. www.siliconchip.com.au land mines and even this is not a comprehensive list of the different devices. There is a very comprehensive landmine database at www.de-mining.brtrc.com/minesearch.asp This database includes all known mines, type, description, general information, characteristics, components, performance, analysts’ information, neutralisation and detecta-bility. This information is given so that people who have to live with these mines can clearly identify and deal correctly with the type of mine confronting them. However many mines have similar characteristics and a brief summary of common anti-personnel mines is given below: August 2001  59 TECHNICAL SPECIFICATIONS – PMN MINES Height........................................ 56mm Diameter.................................... 112mm Mine weight................................ 600 grams Explosive weight........................ 240 grams of TNT Casing material and colour......Brown body with black rubber plate or olive green body with green rubber plate. Fuse type................................... Integral cocked striker with delay arming. Sensitivity................................... 8-25kg pressure Detectability............................... Yes Anti-handling.............................. No Butterfly mines Millions of these small green mines were scattered from helicopters or launched from artillery throughout the war in Afghanistan. They became so familiar that children began to call them “green parrots”. One ‘wing’ contains liquid explosive. When pressure is applied, the explosive is forced into contact with the fuse. The amount of explosive is small but it can still take off a child’s hand. Fragmentation mines Developed in World War 2, these consist of a cast iron body on a wooden stake. Often known as ‘stake’ mines, they are triggered by trip-wire, causing jagged metal fragments to spray over a 100-metre radius. Anyone within 25 metres is likely to die. These were used extensively in Cambodia. Directional mines Often known as Claymore mines, these propel 700 steel balls forward in a 60° arc. They kill at up to 50 metres and maim at up to 100 metres. 70 percent remain lethal for over 20 years. This type of mine is often used in peri-meter defence. Usually activated by trip wire, some designs incorporate radio remote triggering. It requires no great imagination to envisage more exotic forms 60  Silicon Chip of triggering, such as passive infrared, sound, etc. Bounding mines Arguably one of the more sinister mine types, when triggered, the bounding mine leaps 45 centimetres in the air before shattering into more than 1000 metal splinters. The killing radius is at least 25 metres. A common example, the Italian Valmara 69 (illustrated above right), can be found all over northern Iraq. Detecting and clearing mines Minefield clearance is a tedious, costly and a very dangerous undertaking. By and large the work involves people locating and removing mines by hand and even “cleared” fields present their dangers. Thus we see a proliferation of research projects into automated mine clearance in order to remove the human dimension, but it is proving to be a difficult task indeed. Electronics plays a prominent part in experimental automated clearance systems and they are not meeting the challenge at all well. In the meantime, aid agencies are using older, well-proven methods such as “flail” machines (first used in WWII) and sniffer dogs. Although there are high investment costs related to mechanical mine clearance, the running costs are moderate compared with manual clearing. The distinct advantage of being able to clear areas faster than even large manual de-mining operations makes mechanical mine clearance cost effective. Used in conjunction with dogs and manual de-mining, rapid clearance rates can be achieved. For example Norwegian People’s Aid (NPA) purchased two refurbished Aardvark flail machines that had earlier seen service in the Gulf War, for Angola in October 1996. In July 1998, NPA increased its mechanical mine clearance capacity with two of the more powerful Hydrema flail machines. A third Aardvark machine was also donated to the organisation and arrived in Angola in October 1998. NPA is generally satisfied with its Aardvark and Hydrema machines. In Balombo, in Benguela province, the machines effectively identified the boundaries of a large minefield www.siliconchip.com.au and cleared base lines for the manual de-mining teams. This made it possible to deploy 150 de-miners in a targeted area at the same time. Without mechanical support the job would have taken 3-4 weeks and the boundaries of the minefield would still be unknown. In Ucua, a road which was de-mined mechanically would have taken 6-8 months to de-mine manually. Aadvaark in action In action the Aardvark is driven in reverse and a gyroscope is used to guide the driver, as it is sometimes at the GCS. This machine operates in vertical takeoff and landing modes, so there is no need for launch or recovery equipment. Modular in design, the Camcopter is transported to a field site via a light utility vehicle and can be carried into the field and set up by a single individual. It has integrated fail-safe mechanisms that reduce the Camcopter; a small unmanned helicopter fitted with sensors to locate and mark various mine types. The Camcopter’s primary payload is a dual-sensor gimbal system. It consists of an azimuth-over-elevation gimballed turret with integrated thermal imaging and monochrome television sensor modules. Groundstation impossible to see due to the dust from the flails and exploding mines. A strong crosswind is a great help in this job, as well as nerves of steel. It is not unknown for flail drivers to die in the line of duty. For the flail concept to be successful ground conditions have to be suitable. Flails can work well in areas with vegetation and high grass but high vegetation causes the loss of chains and reduction of the clearance speed. By now the reader will have gained some appreciation of the complexity and danger involved in mine clearing. There is a great need for more effective methods of mine detection and clearance but developing these systems is proving to be very difficult indeed. To illustrate just how difficult, the following is a summary of several experimental systems. This list is by no means exhaustive but serves to demonstrate the complexity of the task facing engineers designing these systems. Camcopter Perhaps the most novel idea is the www.siliconchip.com.au The Ground Control Station allows operators to program flights and monitor the Camcopter throughout the mission. Aimed at providing an aerial platform to be used for identification, detection, digital mapping and marking, and mission planning of mines and minefields, the Camcopter is a remotely controlled, fully autonomous aerial platform for use in locating and detecting individual mines and minefields. It is designed to carry equipment that can be used for data gathering, minefield mapping and de-mining mission planning. The Camcopter system consists of the Camcopter aerial platform, currently configured with a dual sensor gimbal assembly consisting of a CCD camera and infrared sensor, a dedicated Ground Control Station (GCS), a Flight Control Unit and a Sensor Control Unit. The Camcopter can be operated manually or automatically by programming preselected routes or way-points risk of injury or inadvertent damage and is simple to operate. Performance During testing, the Camcopter perfor-med at cruising speeds up to 90km/h and altitudes up to 1700 meters. With ideal conditions, the Camcopter may be operated within a 10km radius of a remote operator. The dual-sensor gimbal system, with its InSb-based 256 x 256 thermal imager and monochrome CCD camera, demonstrated the ability to locate mine-like objects. These objects were digitally marked using the on-board DGPS. The video tapes produced can be used for de-mining mission planning in previously unmapped areas. Hopefully the digital map could be used to determine the size and location of new mine-fields as well as individual mines when the system is fully developed. The limitations are that Camcopter must fly above the tree-line of heavily Camcopter Aerial Platform: vegetated areas and Power Plant: .......11kW (14.8 hp) two-stroke engine urban environments Cruise Speed: .............................. 90km/h (56 mph) can be difficult to fly Mission Radius: ................ 10km (6 miles) standard in because line-of-sight Data Link: ............................. S-Band, bi-directional communication is reVideo Link: ................................. C-Band (downlink) quired. Tracking: ..................... Fully-autonomous, remotely Navigation: ................ INS-based and DGPS-based Mini flail tank Climb Rate: ...........................300m/min (990 ft/min) The Mini-Flail is a Hover Ceiling: ..............1700m (weather permitting) remotely controlled Length: ......................................... 2500mm (98.43") utility vehicle that Main Rotor Diameter: ................ 3020mm (118.76") clears AP mines from Payload: ................................... Up to 25kg (55 lbs.) off-road areas that are August 2001  61 not accessible to large-area mine clearers. The Mini-Flail system uses chains attached to a spinning rotor to beat the ground and will detonate most AP mines. The Mini-Flail is effective against bounding, tripwire-fused and simple pressure-activated AP mines. found most AT mines but had difficulty identifying AP mines and proved very complicated to operate. Vehicle Mounted Mine Detector (VMMD) Completed Detection Projects Much of this work, as the reader can quite easily sense, is purely experimental or under development. The following section contains descriptions of completed detection projects and a brief description of the outcome from testing. Additional results are documented in the FY1995 test report, Countermine Technologies for Humanitarian Demining, Test Results Report, December 19, 1995, available from the Defence Technical Information Centre (DTIC A310061). Vehicle Mounted Detection System (VMDS) The VMDS concept is based on a commercial skid steer chassis modified to incorporate a remote control capability. The VMDS sensor package consists of a 2-metre wide Schiebel metal detection array, a Thermal-Neutron Analysis (TNA) sensor and an infrared sensor. The 2-metre array detects metal objects in the vehicle’s path, while the TNA indicates those targets that contain explosives. In testing, the 2-metre array performed extremely well. The TNA The VMMD is also a small modified utility vehicle. The VMMD sensor package consists of ground penetrating radar, infrared and ultraviolet cameras. The VMMD did well in detecting AT mines but had difficulty identifying AP mines and proved very complicated to operate. Ground Based Quality Assurance The Ground Based QA prototype was an assembly of four cameras (3-5 micron and 8-12 micron IR, UV and normal video). The concept was to feed the signals from all four cameras which are aimed at the same spot, to a computer software program that would analyse the images and use an automatic target recognition (ATR) algorithm to mark suspected mine locations on the operator’s screen. Although the system showed potential, the prototype did not consistently discriminate mines from clutter. Humanitarian Innovative Mine Sensor (HIMS). In 1997, the Humanitarian De-min62  Silicon Chip ing Program investigated the use of polarised IR cameras to detect mines. The advantages of polarimetric imagery over conventional radiometric IR for detection of mines were not demonstrated. K9 program In 1995, the Humanitarian De-mining R&D Program demonstrated the effectiveness of using dogs for mine detection. The program evaluated two systems, free leash, which used a dog and handler in a mined area and the Mechem Explosive and Drug Detection System (MEDDS), which collects air samples in suspected mined areas for dogs to smell at a remote location. The program also investigated what effects burned areas and explosive material scattered on the ground had on the dogs’ ability to detect buried mines. Both dog programs performed well. In fact, after a great deal of research, sniffer dogs are still more effective overall than electronic methods for mine detection. So there you have it, a brief excursion into one of the less edifying SC aspects of human creativity. www.siliconchip.com.au SILICON $ 95* 10 CHIP’S PSST! WANT A FREE Electronics Electronics Electronics inc GST ISBN 0 958522 9 2 8 TestBench TestBench? .a .. ” E V A H “MUSuTr library in yo A selection of from the page the best test equipment s of SILICON C www.silic HIP magazine onchip.c . om.au Subscribe to SILICON CHIP and we’ll give you a copy, just to say “thanks”! Or, if you prefer, a copy of SILICON CHIP’S “COMPUTER OMNIBUS” Or a SILICON CHIP Data Wallchart. The choice is yours. We value your support. In fact, we cannot exist without it. That’s why we want to say “thanks” with our gift to you. Subscribing to Australia’s only electronics magazine will also save you money, you’ll get it earlier than it appears on the news-stands, you get a 10% discount on any other SILICON CHIP merchandise (books etc) . . . and your support is vital to ensure your magazine remains strong. 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Payment by: 1 Cheque Enclosed OR Card No: l l l l ll l l l 1 ll l 1 l l ll Signature: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S ILICON CHIP PUBLICATIONS www.siliconchip.com.au MAIL ORDERS: PO Box 139 Collaroy NSW 2097 l l l 1 l Expiry: l l l-l l l & (Aust rates include GST) YES! I want to become a SILICON CHIP subscriber for Please copy form if you don’t want to cut your magazine Test Bench, Computer Omnibus and Wall Chart can also be purchased separately Phone orders: (02) 9979 5644 (9-5, Mon-Fri) Fax orders: (02) 9979 6503 (24 hrs, 7 days)2001  63 August Email orders: silchip<at>siliconchip.com.au (24 hrs, 7 days) Using Linux To Share An Internet Connection; Pt.3 In Pt.2, we showed you how to configure your Linux box to function as an Internet gateway with demand dialling and a firewall. This month, we show you how to tweak the settings so that you can log on as a user (rather than as root). We also describe logging and show you how to make it really easy to drive. By GREG SWAIN So far, you’ve done all the work on your Linux box while logged on as root. This is necessary in order to access certain files and to perform other administrative tasks. However, even with a firewall, it’s a really bad idea to be connected to the Internet while logged on as root. If someone cracks your firewall, they can not only take over your machine but can also read any sensitive files, such as your pap-secrets file which contains your username and password. Similarly, logging on as root enables anyone who has easy access to the machine to pry on sensitive information. At the very least, you want your Internet password to be Tip 1: Mounting Devices In Linux Unlike Windows, Linux doesn't use drive letters. Instead, external disk drives and other resources (such as network shares) are “mounted” by attaching them to the file system. If you don’t do this, the files won’t be visible. The point at which the device is attached is referred to as the “mount point”. For example, on most systems, floppy disk drives and CD-ROM drives are attached to the /mnt folder (automatically set up during installation), so that they become /mnt/floppy and /mnt/cdrom. To mount a CD-ROM or floppy disk in KDE or Gnome, insert the disk, then right-click its icon on the desktop and choose “mount” from the drop-down list. Alternatively, left-clicking the icon mounts the device and opens the file manager to display the files. Similarly, a device should always be unmounted before the disk is removed; ie, right-click the device icon on the desktop and choose “unmount” from the menu. You can also mount and unmount devices from the terminal prompt. Type man mount for more details. 64  Silicon Chip kept secret, to prevent someone else from running up a big bill at your expense. In short, connecting to the Internet while logged in as root is like playing “Russian Roulette”. Your machine could end up being “owned” by someone else – perhaps from another country. Running pppd as a user The way around this is to log onto your Linux box as a user (you did write down your user account name and password when you installed Linux, didn’t you?). This allows you to keep sensitive setup files hidden. It also prevents you or anyone else from accidentally altering or deleting critical system files, which could wreck your Linux setup. That’s one of the advantages of Linux. Because it’s de­ signed as a multi-user system, you can restrict the privileges that any one user has while granting special privileges to cer­tain users or groups. By default, only root has access to the entire system and we need to make a few changes in order to run pppd as a user. What we’re going to do now is change the permissions of certain files to allow this and to increase security. We do that using the chmod (change mode) and chown (change ownership) com­ mands. We won’t get sidetracked explaining file permissions here; just remember that Linux can set different permissions for the same file – one set for the file’s owner, another set for members of a group and another set for everyone else (others). Because pppd requires root privileges to run, we are now going to change its permissions so that it can be executed by both “root” and members of the “pppusers” group. This is done as follows (you will need to be logged on as root): www.siliconchip.com.au Aaaaarggghh! It Doesn’t <at>#$%^&* Connect The /var/log/messages file is your starting point if you have problems getting your modem to connect. Here are a few trou­bleshooting clues: (1) Modem Drops Connection: if the modem dials in but disconnects before the log-in procedure is complete, try increasing the second timeout value in /etc/ppp/ chat-script. A value of 40 seconds should be sufficient in most cases but you may have to increase this to 60 seconds or more. If the modem drops the connection immediately, check the telephone number. Also, check your scripts for typing errors, particularly /etc/ppp/options and /etc/ppp/chat-script. It only takes one error to crash and burn. (2) LCP Timeout Errors: if the modem fails to complete the connec­tion and you see “LCP: timeout sending Config Requests” in the log, add the following line to /etc/ppp/ options: lcp-max-configure 30 This increases the number of lcp requests from the default value of 10 and may be necessary if the server at the ISP’s end is a bit slow to respond. In fact, you might like to add this line by default, to avoid any possible problems. For a really slow server, you may have to use an even higher value. Alternatively, try adding the line asyncmap chown root:pppusers /usr/sbin/pppd chmod 4750 /usr/sbin/pppd Note: Linuxconf users should do this from within Linuxconf, otherwise it will cancel these changes the next time you run it. To do this, launch Linuxconf and go to Control -> Control files and systems -> Configure file permission and ownership. The first line changes the ownership (chown) of pppd so that it now belongs to the pppusers group. The second line chang­es the permissions and gives pppd a set user identification (SUID) number – it’s the “4” that sets the SUID bit. The “7” makes pppd readable, writable and executable by the file’s owner (in this case, root), while the “5” makes pppd readable and executable by the group. The final digit (0) makes pppd inaccessible to everyone else; ie, they can neither read, write or execute the file. You can check that the correct permissions have been set by entering the command: ls -l /usr/sbin/pppd You should get this response: -rwsr-x— 1 root pppusers www.siliconchip.com.au 0xa0000 to the /etc/ppp/options file. (3) IP-Compress Errors In Log: if you see ip-compress errors in the log when a connection is made, add the following lines to the bottom of /etc/modules.conf (this mainly applies to Caldera usrs): alias ppp-compress-21 bsd_comp alias ppp-compress-24 ppp_deflate alias ppp-compress-26 ppp_defl (4) Port Speed Is Too High: don’t set the port speed too high in the /etc/ppp/options file. If you do, you may find that your modem doesn’t connect reliably or may drop the connection for no apparent reason. Use 115200 for 56Kb modems and 38400 for 33.3Kb modems. (5) Modem Doesn’t Respond Correctly: if the modem fails to respond, dials on every second attempt only or often fails to hang up, you need to include some initialisation strings in the /etc/ppp/chat-script file. Take a look at the revised chat-script file shown in the accompanying panel – it will probably be all you need or you can include you own initialisation string. (6) Modem Doesn’t Respond: if there’s no activity from the modem at all, check to ensure that you’ve specified the correct serial port. You can do that using the “modemtool” utility, as described last month in Pt.2. This indicates that only “root” and members of the “pppus­ers” group can execute pppd. Having done this, you need to edit /etc/group and add your user name to the “pppusers” group. So if your user name (or login name) is “greg”, the line would read: ppppusers:x:44:greg What this does is make greg a member of the pppusers group, which means that greg can now log on and run pppd. By the way, the user name here refers to the user name chosen for logging onto your Linux box; not the “username” used for logging onto the Internet. Don’t confuse the two. You now have to run the command: newgrp pppusers from your user account for the change to take effect. Of course, you could also reboot but hang on ... this is Linux – you really don’t have to do that. Permissions cleanup We now need to change the permissions of some files to improve security. Basically, this involves restricting access to them so that they cannot be altered, executed or even read by unauthorised users. August 2001  65 First, let’s look at the /etc/ppp/chat-script file. By default, this is readable by everyone and that’s not good if this file includes your username and password details. To restrict access, we need to change the ownership and permissions for this file as follows: chown root:pppusers /etc/ppp/chat-script chmod 640 /etc/ppp/chat-script This changes the ownership of this file so that it now belongs to the pppusers group. As a result, only “root” and members of the pppusers group have read access to /etc/ppp/chat-script and only “root” can edit it. The next three files – /etc/ppp/options, /etc/ppp/ pap-secrets and /etc/chap-secrets – can be locked down as follows: chmod 600 /etc/ppp/options chmod 600 /etc/ppp/pap-secrets chmod 600 /etc/ppp/pap-secrets This makes them readable and writable by “root” but denies access to everyone else. Note that we don’t have to provide read access for any of these files to members of the pppusers group. That’s because they are read when we run /usr/sbin/pppd and this always runs with root privileges. Now, complete the permissions clean-up as follows: chmod 700 /sbin/ipchains chmod 700 /etc/rc.d/rc.local chmod 644 /etc/resolv.conf The first two lines make ipchains and rc.local readable, writable and executable by root and deny any access to all other users. The third line makes resolv.conf readable and writable from “root” and readable by everyone else (security is not really an issue with this file, so we can silchip<at>penguin: /home/silchip relax the access rules). It’s time to test this – reboot, log on as user, open a terminal window and type: /usr/sbin/pppd It should all work exactly as before, when you were logged on as root. You can test this by triggering a dial out from one of your Windows boxes. The only thing that probably won’t work is issuing killall pppd as a user (to manually disconnect from the ISP). This does­n’t matter if you always plan to let the connection time out when traffic ceases. However, if you do wish to manually disconnect, you’ll need the “PPP Kill SUID Wrapper” – see panel. By the way, if there are multiple user accounts on the machine, only those users who are members of the pppusers group will be able to run pppd (ie, they must have their names added to the pppusers group in /etc/group). This means that a Linux box is great for restricting Internet access – you might want to stop your children from accessing the Internet without your permis­ sion, for example. Just keep the appropriate user name and password details secret and you’ve got it all locked up. Logging the connection By default, pppd logs messages in /var/log/messages, so check this file first if you strike problems. Fig.19(a) shows the logs recorded when a successful dial-out connection is made. Note how the local and remote IP addresses are changed. Fig.19(b) shows the log from an unsuc­cessful connection attempt. This was made with the phone line disconnected and results in the message: “Failed (NO DIALTONE)”. Look at the error logs carefully if you can’t make a con­nection. They will often indicate exactly where the problem lies. As well as debugging, logging is also useful for indicating any unauthorised connection attempts to your Linux box via the Internet. Port scans, Telnet requests and other access requests are all logged, so it’s easy to check that the firewall is doing its job. Each time something is filtered out, /var/log/messages will show that an incoming packet has been denied and will list the IP address that it came from. silchip<at>penguin: /home/silchip Fig.19a (left): you can watch the session logs go by in a terminal window. This screen grab shows the logs recorded for a successful connection attempt using the revised /etc/ppp/chat-script file described in this article. Fig.19b (right) shows the log for an unsuccessful connection attempt (the attempt was made with the phone line disconnected). 66  Silicon Chip www.siliconchip.com.au Hanging Up – Fixing The Killall Problem Hanging up while logged on as root involves issuing the command killall pppd. This shuts pppd down and drops the DTR line to the modem, forcing it to hang-up. Unfortunately, this command may not work for you if you are logged in as a user. One way around this is to log on as root and then run the killall pppd command but that’s a bit of a hassle. An easier method is to use the “PPP Kill SUID Wrapper” (fancy name, ain’t it?) written by W. G. Unruh from the Universi­ty of British Columbia, Vancouver, Canada. This “wrapper” runs the killall pppd command but does so without giving the user root privileges. Basically, this file consists of about 20 lines written in the C programming language. You’ll find it at: http://axion.physics.ubc.ca/ppp-kill-wrapper.html First, you have to save the code to a file called pppoff.c, as instructed. You then have to compile the code but don’t sweat this – Linux comes with a built-in C-compliler (gcc). All you have to do is log on as root, open a terminal window and change to the folder where you saved the file. This can also be useful for tracking down any problems with your firewall – eg, if it’s blocking something that it should let in. Note that if you open /var/log/messages, you only see the logs that were recorded up until the file was opened. Want to see the logs go by in real time? Do this – open a terminal window and type: tail -f -v /var/log/messages The messages will now scroll by in the terminal window as they are continually updated – see Fig.19(a). Making it easy to drive Well, actually, it’s already easy to drive. Provided you’ve followed all the instructions, your Linux gateway will be ready for demand dialling as soon as it’s booted. What’s more, it will work whether you’re logged in as a user or as root (user is best for security). Note that it isn’t necessary to start X Windows for the gateway to function. In fact, you might want to leave the box running in terminal mode if it’s used only as a gateway, since this minimises the load on system resources – something that might be important if you’re running an old 486. Actually, you don’t even have to log in for the gateway Fig.20: /var/log/messages logs any unsuccessful connection attempts. This shows an unsuccessful attempt by a user (us actually) with an IP address of 210.10.178.105 to Telnet into a Linux box on 210.10.188.232. www.siliconchip.com.au You then issue the following commands: gcc -o pppoff pppoff.c chmod a+x pppoff chmod +s pppoff This compiles a binary file called pppoff, makes it execut­able and sets the SUID (set user ID) bit. Copy pppoff into the /bin directory and you are in business. All users can now kill pppd and force the modem to hangup by issuing the command pppoff. You can also create a linked icon to /bin/pppoff on the desktop – just drag the file to the desktop, release the mouse button and choose “Link” from the resulting menu. You can now hangup with just a single mouse click. A better scheme is to create a single executable script file (called hangup) that includes both the pppoff and startpppd commands, as described in the main text. This will automatically restart pppd each time you force the modem to disconnect. Note that you don’t have to restart pppd if the modem dis­connects due to an idle timeout. to function. The system is ready for use as soon as it boots and will automatically dial on demand and disconnect 10 minutes after traffic ceases. Inevitably, there will be occasions when you want to manually disconnect from your ISP, rather than wait for an idle disconnect. However, if you do that, you then have to restart pppd to enable demand dialling again. But who wants to type long command lines in a terminal window each time you wish to disconnect (hangup), restart pppd or monitor the message logs? Not me, that’s for sure, so let’s create some script files to make the job easy. We’ll begin by writing some script files so that we can disconnect and automatically restart pppd – either by single-clicking an icon on the desktop or by typing “hangup” at a termi­nal prompt. First, create a new text file and put the following into it (you should be logged on as root): Script 6: /bin/startppd #!/bin/sh # Start Demand Dialling (startpppd) # /usr/sbin/pppd silchip<at>penguin: /home/silchip August 2001  67 Modem Initialisation And A Revised Chat Script The basic chat-script file listed on page 64 of the June 2001 issue should work with most modems . However, some modems require an initialisation string to work properly with Linux (under Windows, the initialisation string is included in the driver). Try using the basic chat-script first but if you strike problems, modify the /etc/ppp/chat-script file as follows: TIMEOUT 5 ABORT "BUSY" ABORT "NO CARRIER" ABORT "NO DIALTONE" ABORT "ERROR" ABORT "NO ANSWER" "" AT OK-+++\c-OK ATH0 OK "AT&F&D2&C1&K3" TIMEOUT 40 OK ATDT[dialup number] CONNECT "" Let’s take a look at what this does. Following the abort error lines, the script sends the AT (attention) command to the modem (the "" means expect nothing from the modem). Provided the modem is in command mode, it should respond with OK. The next line tells the script to expect this OK. If this isn’t received (OK-), the script then sends +++ (a standard Hayes modem string) to force the modem into command mode. The c-OK says don’t send a carriage return and to wait for OK again. When it arrives, the script sends ATH0 which is the modem hang-up string. This is done so that the script can cope with the Save this file as /bin/startppp and change its permissions as follows: chown root:pppusers /bin/startpppd chmod 750 /bin/startpppd This makes the file readable, writable and executable by root, and readable and executable by members of the pppusers group. Next, create a /bin/pppoff file (this hangs up the modem), as instructed in the accompanying panel: “Hanging Up Fixing The Killall Problem”. Finally, create a new text file with the following: Script 7: /bin/hangup #!/bin/sh # Hangup and restart pppd for demand dialling /bin/pppoff sleep 3 /bin/startpppd 68  Silicon Chip modem being stuck on-line – something that should happen only rarely (if at all). If this is a problem, you can remove this line until you’ve determined the cause (or get rid of the OK ATH0 from the end of the line to give OK-+++\c-). The next line says to expect OK (in response to the ATH0 command) and send the initialisation string: AT&F&D2&C1&K3. As usual, this command string begins with AT to get the modem’s attention. The &F sets the modem to the factory default; &D2 ensures that the modem hangs up when DTR goes low (taking DTR low is the usual method of getting a modem hang up); &C1 ensures that carrier detect follows the carrier signal; and &K3 instructs the modem to use RTS/CTS hardware flow control. After that, the timeout is reset to 40 seconds and the modem instructed to dial the number. Note that the dialling command line begins with OK, since this is expected from the modem in response to the initialisation string. Finally, chat-script is told to expect CONNECT (the modem sends this when the remote modem answers) and to send nothing in reply. This chat-script file should work with the vast majority of modems. In fact, you might like to use it as a matter of course, in place of the version described last month. If you still have problems, use the initialisation string listed in your modem’s manual or at the manufacturer’s website. You can also extract the ini­tialisation string from the Windows 98/Me .inf driver file sup­plied with the modem. Just open up the .inf driver file using Notepad on a Windows box and search for “Init” (without the quotes). You’ll see the initialisation string at the end of one of the Init lines. Save this file as /bin/hangup and do the following: chown root:pppusers /bin/hangup chmod 750 /bin/hangup That’s it – issuing the command “hangup” at a terminal prompt will now force the modem to hangup (if it’s connected) and then automatically restart pppd. The system is then ready for the next dial-out request. The “hangup” command can also be used to restart demand dialling if pppd has exited due to four successive unsuccessful connection attempts. Note the “sleep 3” line. This inserts a delay of three seconds between hanging up the modem and restarting pppd, to give the modem time to reset. You can see this if you watch the terminal log. What about that desktop icon? Easy – just open the file manager, left-click the /bin/hangup file and drag it onto the desktop. Release the mouse button, then click “Link” from the drop-down menu that appears. This creates an icon that’s linked to the original file (just like a Windows shortcut). www.siliconchip.com.au Fig.21: creating shortcuts on the desktop makes it easy to manually hang up and view the messages log. You can force the modem to hang up (and automatically restart pppd) by clicking once on the hangup icon, or by issuing the hangup command at a terminal prompt. Tidying Up The Previous Stuff (1) Chat-script file On page 64 of the June 2001 issue, it states that some modems may require an initialisation string in the /etc/ ppp/chat-script file. If you do place the line "" +++[initialisation string] into this file, change the next line to read: Single-clicking this icon is now all it takes to disconnect the link and automatically restart pppd for demand dialling. What could be easier? There’s another option here – if you want to separate the disconnect and restart pppd functions, just create links to /bin/pppoff and /bin/startpppd by dragging them to the desktop in exactly the same manner. You can also type pppoff and startpppd at a terminal prompt to disconnect and to restart demand dia­lling, respectively. Be careful if you adopt the latter approach though – it’s easy to forget that you have to restart pppd if you disconnect by using pppoff. Using a single command (hangup) is the easiest, since it automatically restarts pppd for you. Note that you will have to repeat the above procedure for creating the desktop icon shortcuts when you subsequently log on as a user. Now let’s make it easier to following the logging. Create a new file and place the following lines it: Script 8: /bin/logit #!/bin/sh # logit - for logging in real time # tail -f -v /var/log/messages Save this as /bin/logit and set the permissions as follows: chown root:pppusers /bin/logit chmod 750 /bin/logit Now all you have to do is issue the command “logit” in a terminal window and you can watch the logs go by in real time. You can test that it’s working by disconnecting the phone line from the modem and clicking the hangup icon on the desktop a few times. OK, I’ve probably now got a few Linux gurus frothing at the mouth, since the /bin directory is normally reserved for binary files only. However, one of the files (pppoff) is a binary file and by placing them all in /bin, all the files are kept in one place. More importantly, we don’t have to type in the complete path to the file when we want to execute a command. That’s it – your Linux Internet gateway is complete. As far as your Windows clients are concerned, it should look as though it isn’t there. Next month, we’ll take a look at SC the steps you can take to improve security. www.siliconchip.com.au OK ATDT[dialup number] Better still, if your modem does require an initialisation string, we suggest that you modify the chat-script file as shown in the accompanying panel: “Modem Initialisation & A Revised Chat Script”. (2) Modifying /etc/rc.d/rc.local On page 68 of the June 2001 issue, the lines “logger Firewall up” and “logger Demand dialling started” in the /rc.d/rc.local file should read “echo Firewall up” and “echo Demand dialling started” (without the quotes). Alternatively, these two lines can be omitted. (3) Cleaning up /etc/rc.d/rc.firewall The full path was left out of the last two lines of the firewall script. Change these lines as follows: # Log everything else to syslog and drop the packet /sbin/ipchains -A input -s $ANY -d $ANY -l -j DENY /sbin/ipchains -A output -s $ANY -d $ANY -l -j DENY Also, rule (6) under the section headed “# Set up rules for Internet (ppp0) traffic” can be changed to read: /sbin/ipchains -A input -p tcp -s $ANY -d $ANY auth -i ppp0 -l -j REJECT This denies and logs any incoming authorisation requests. (4) Fixing /etc/ppp/pap-secrets & chap-secrets Use tabs instead of a spaces before and after the asterisk (some systems won’t work with spaces); ie, [username][tab]*[tab][password] Tip 2: Improving Security Here’s a quick way of denying access to any services that have been left running on your Linux box to outsiders on the Internet. First, open up the /etc/hosts.deny file and add the following rule to the end of the commented section: # /etc/hosts.deny ALL: ALL This tells the “TCP wrappers” to deny connections to all services from all hosts. It will also stop local machines on your network from accessing any wanted services, so we need to weaken the rules by adding some exceptions to /etc/hosts.allow. Open this file and add these lines: # /etc/hosts.allow ALL: 127.0.0.1 ALL: 192.168.0. August 2001  69 Ever turned your headlights on in the early morning gloom... and forgotten to turn them off? Talk about frustrating! Here’s a little project that will put an end to the angst by letting you know that the lights are on as soon as you open the door. No more bat flatteries! by JOHN CLARKE W e’ve all done it – left the lights on, that is – and it’s one of the best ways to unintentionally immobilise your car. And Murphy’s law says it will always happen at the most inconvenient time. The double whammy Murphy also says that it will always happen in the worst possible location – you know, the part of town you’d never be seen dead in after dark . . . Sure, you can call road service, only to find out the delay is a couple of hours or more because there were dozens of other motorists out there who did exactly the same thing. (Road service organizations say that flat batteries are far and away the highest reason for call-outs). But even worse than the delay, when you use jumper leads to start a modern car with an engine management computer you risk doing real (expensive!) damage – sometimes to both vehicles. And even if you don’t, you’re prob70  Silicon Chip ably going to have to reset your car radio’s station memory, reset the clock – and don’t forget rescheduling your appointments because you’re now a couple of hours late! Other options such as clutch starting may briefly spring to mind, only to be dismissed when you realise that your car is (a) parked in, (b) in a very busy Features ✪ Compact unit ✪ Uses inexpensive parts ✪ Modulated alarm on ✪ Monitors lights and igniti tion ✪ Optional door switch detec sounds ✪ Short delay before alarm ✪ Time-out of alarm road, or (c) is an automatic! Fit this Headlight Reminder and you should never have such a problem again. How it works While it’s true that many modern vehicles have a headlight reminder built in, it’s just as true that the vast majority of older cars – especially the “standard” models in the range – do not. And of those that do have them, they’re often just a simple device which cannot be over-ridden or stopped. That can be annoying if you want to have your headlights on for some reason without the engine running. Headlight reminders require a certain degree of logic so that the alarm will not sound under “normal” headlight use. To do this we monitor the headlights, the ignition and also the door switch. In its most basic form, the headlight reminder will only sound the alarm if the headlights are on and the ignition is switched off. While headlight reminders will usuwww.siliconchip.com.au ally sound immediately the ignition is switched off if the headlights are on, this is a bit of an over-exuberance on the headlight reminder’s part. We need a bit of grace when we do remember to turn off the lights. A refinement to this system is to add a delay before the alarm sounds or to add in door switch detection. With this last inclusion, the alarm will not sound when the engine is switched off and the lights are on but will wait until the door is opened. There is another wrinkle: different methods of light and door switching. It is usual to have the headlight/ parker switch supply power to the globes which are earthed on the other side, thereby completing the circuit. But some cars don’t earth the globes – they are powered at all times and the headlight/parker switch connects them to earth. Conversely, it is usual to have the car door switches connect a permanently-powered interior light to earth, with the interior light switch doing the same thing (in parallel). But some cars do the opposite – supply power via the door switches. They’re rare, but they do exist. Sensing of the light’s state is taken from between the switch and the light. If we think in terms of logic “highs” and “lows”, Fig.1 shows earth-side switching gives a high when the light is off and a low when the light is on. www.siliconchip.com.au Battery-side switching gives a low when the light is off and a high when the light is on. The SILICON CHIP Headlight Reminder caters for the different wiring and switching possibilities of car headlight and door switch operation. The headlight reminder is a very compact unit and can be fitted into a small plastic utility case measuring 84 x 54 x 31mm. The circuit The circuit for the Headlight Reminder is quite simple and uses only three low-cost CMOS integrated circuits (ICs) plus a transistor, a few diodes, capacitors and resistors and a piezo buzzer. The inputs for the ignition, lights and door switch are monitored via gates IC1a, IC2a and IC2b respectively. Outputs from these gates are sent through a series of gates which control the alarm signal. These gates simply prevent the alarm signal unless the ignition input is low and the lights are on. The use of the door switch input is optional. Let’s take a look at each of these inputs and see how they control the action of the alarm. IC1a (a Schmitt NAND gate wired as an inverter) monitors the ignition switch state. When the ignition is on, IC1a’s output is low and the output of IC1c is high regardless of the logic level of its other input (pin 5). As we shall see later, this prevents the alarm from sounding. If the ignition is off, IC1a’s output is high and the output of IC1c can go low if its pin 5 input is also brought high by the action of the signals from the lights and door switch gating. IC2a monitors the lights’ input. It can be configured to accept either polarity of headlight switching. If link LK1 is in position (and LK2 out), the circuit suits vehicles with headlight switching on the “earthy” side. Conversely, with LK2 in position and LK1 out, the circuit suits vehicles whose headlights are switched on the battery side. Fig.1: the two types of headlight switching with their equivalent logic states: the top circuit switches power from the battery; the bottom connects the “live” globes to earth. Our circuit caters for both types via movable links. August 2001  71 Fig.2: the circuit is based on only 3 low-cost IC’s and a handful of other components. 72  Silicon Chip In the first case (LK1 in), IC2a’s pin 1 is high, while pin 2 is high when the lights are off and low when they are turned on. If the lights are off, the output of IC2a will be low. This is because the output of an exclusive OR (XOR) gate is low unless one of its inputs is at a different logic level to the other. If the lights are switched on, pin 2 will be low and so IC2a’s output will be high. Similarly, if LK2 is in position and LK1 out, the pin 1 input will always be low. With the lights off, pin 2 is low and the output of the gate stays low. When the lights are switched on, the pin 2 input goes high and so the output goes high. A similar circuit operation occurs with IC2b which monitors the interior light, controlled by the door switches. Here the links are designated LK3 and LK4 for normally high or normally low door closed switching possibilities. The only difference is that we have provided an extra link option with LK5 which can tie the door switch input at pin 5 low if you don’t want to use the door switch feature. High inputs at both pins 1 & 2 of IC1b will produce a low output at pin 3 which is subsequently inverted via IC2c If the ignition is off (IC1c pin 6 input high), a high at pin 5 of IC1c will set a low output at pin 4. In turn, IC2d inverts this low so that the high output at pin 10 allows operation of the oscillator, based around IC1d, another Schmitt NAND gate. When its pin 12 is high (driven by pin 10 of IC2d), IC1d oscillates at about 1Hz, as determined by the 1µF capacitor and 470kΩ resistor connected to pin 13. Ignore diode D2 for the moment – we’ll get to that later. So as IC1d is oscillates its pin 11 goes high and low alternately, turning Q1 off and on to sound the piezo buzzer. So the buzzer turns on and off at once a second. OK, so you’ve left the lights on, the ignition’s off and you’ve opened one of the car doors. Result: the buzzer is sounding on and off. But what if you do want to have the door open and the lights on. This is where IC3 comes into the picture. It provides a timeout facility so that the buzzer stops after 10 seconds or so. The same low at the output of IC1c which is responsible for triggering www.siliconchip.com.au Parts List – Headlight Reminder Reproduced same size, here is the completed project immediately before connecting it to the car wiring. The header pin sets (left side of board) are used to modify the input triggering so the circuit will work with all vehicle types. Fig.3: and here’s the component overlay, viewed as if you were looking through the PC board with X-ray vision. The copper tracks are on the opposite side of the PC board. (Compare this with the PC board pattern shown later). the alarm also triggers the timer, IC3, via the 0.1µF capacitor. This applies a short low trigger voltage to pin 2 of IC3 which sets this timer running. The pin 3 output of IC3 goes high and pulls the cathode of diode D2 high. This reverse biases the diode which means it has no part to play in the charging/discharging of IC1d’s capacitor. However, the 10µF capacitor from pins 6 & 7 of IC3 to ground charges via the 1MΩ resistor towards the +12V supply. When this voltage reaches two thirds the supply, pin 7 and pin 3 both go low. The 10µF capacitor discharges through the IC via pin 7. The low pin 3 output forward biases D2, which in turn pulls pin 13 of IC1d low. So the output of IC1d is forced high, turning off Q1 and the buzzer. Thus the alarm only sounds for the duration of the IC3 timer. The length of time can be varied by increasing (for longer time) or decreasing (for shorter time) the values of the above resistor and capacitor. Power for the circuit is derived www.siliconchip.com.au from the car battery via the automotive fusebox. The 10Ω resistor provides isolation from the automotive supply, while the 16V zener (ZD1) suppresses transients across the supply. With a “normal” vehicle supply of around 13.8V this zener would never conduct; it is only when spikes generated by other electrical equipment in the car or even such things as mobile phones and two-way radios exceed 16V that the zener conducts to shunt the spike safely away. The supply is decoupled with a 47µF capacitor. Inputs to IC1a, IC2a and IC2b are 1 PC board coded 05108011, 78 x 49 mm 1 plastic utility case, 83 x 54 x 31mm 1 100mm length of 0.8mm tinned copper wire 1 12V PC-mount piezo buzzer (Altronics S 6104) 1 3-way PC screw terminal block, 5mm pitch (Altronics P 2039) 1 2-way PC screw terminal block, 5mm pitch (Altronics P 2038) 2 3-way pin headers 1 2-way pin header 3 link pins for (LK1-LK5) (DSE P 2730) 1 150mm length of 0.8mm tinned copper wire Semiconductors 1 4093 quad Schmitt NAND gate (IC1) 1 4030 quad XOR gate (IC2) 1 7555 timer (IC3) 1 BC328 PNP transistor (Q1) 1 16V 1W zener diode (ZD1) 2 1N914 signal diodes (D1,D2) 1 1N4004 diode (D3) Capacitors 1 47µF 16VW PC electrolytic 2 10µF 16VW PC electrolytic 1 1µF 16VW PC electrolytic 1 0.01µF (code 10n or 103) Resistors (0.25W, 5%) 4 1MΩ z 470kΩ 3 100kΩ 2 10kΩ 1 10Ω protected against transient voltages using the internal transient protection diodes and the series 100kΩ resistance at each input. The 1MΩ resistors at the lights, door switch and ignition inputs to IC2a, IC2b and IC1a tie these either high or low via the links LK1-LK4 for IC2a and IC2b and low for IC1a. This RESISTOR COLOUR CODES    No. Value   4  1MΩ    1   470kΩ    3   100kΩ    2   10kΩ    1   10Ω 4-Band Code (1%) brown black green brown yellow violet yellow brown brown black yellow brown brown black orange brown brown black black brown 5-Band Code (1%) brown black black yellow brown yellow violet black orange brown brown black black orange brown brown black black red brown brown black black gold brown August 2001  73 The PC board fits snugly inside the specified case, albeit upside down and with its corners filed away as shown here. There is nothing to hold the board in the case – it is rigid enough once the lid is screwed on. prevents floating inputs before they are connected to the car’s wiring. Construction The Headlight Reminder components are installed onto a PC board coded 05108011, measuring 78 x 49mm. Our design was housed in a small plastic utility case measuring 83 x 54 x 31mm. Before you start construction, inspect the PC board for shorted tracks or breaks in the copper. Compare the PC board against the published pattern to make sure it is correct. Also check that the holes are large enough for the component leads, particularly for the screw terminals. These might have to be drilled out larger because many automated PC board production processes drill all holes the same size. The corners of the PC board must be shaped as shown on the PC pattern so that it can be fitted into the box. A small “rat tail” file is ideal for this purpose. Start construction with the links and resistors, using the resistor colour code table as a guide to finding each value. You could use a digital multimeter to measure them as well. The diodes can then be inserted making sure they are installed the correct way around. IC1 and IC2 can be inserted ensuring they too are oriented correctly. SILICON CHIP And here’s how it all looks assembled, with the cut-out shown here for the five external connections. Naturally, these must be made before the board is placed inside the case and the lid and panel secured! The capacitors can be installed taking care with the electrolytics which must be oriented with the polarity as shown, as must the piezo buzzer. Now solder in transistor Q1 and the pin headers. Finally, install the screw terminals with the wire entry side facing the edge of the PC board. Testing Ensure that all the parts are installed and soldered correctly. Install the links LK2 and LK4. Now connect a 12V power supply to the +12V input and ground. Apply power and check that there is 12V between pins 14 and 7 of IC1 and IC2. IC3 should have 12V between pins 8 and1. At this stage, the outputs of IC2a and IC2b at pins 3 and 4 should be low and pin 10 of IC1a should be high. Connect up short lengths of wire to the lights, door switch and ignition inputs. Now connect the ignition lead and the door and light inputs to +12V. If you lift the ignition input connection, the alarm should sound at a 1Hz rate for about 10 seconds. Installation Before installation you will need to check how your car is wired with regard to the headlights and door switches. Gain access to the lights switch and a door switch and check the polarity when the lights are on and www.siliconchip.com.au 74  Silicon Chip +12V Lights Door Ignition Chassis when the door is opened. For the lights switch measurement, if the voltage is 12V when the headlights are on, use LK2. If the voltage is zero when the headlights are on use LK1. Similarly, for the door switch: if the measured voltage is 12V when the door is open use LK4. If the voltage is 0V when the door is open use LK3. If you do not intend to use the door switch connection use LK5 and LK3. A small rectangular cutout in one end of the case will allow the leads to enter the screw terminals. A large hole at the opposite end will be required to allow the buzzer sound to be heard. The PC board can be installed into the box by simply placing it component side down. The PC board will rest on top of the side mouldings and be held in position by the lid. When wiring use automotive wire and automotive quick connectors to make the tappings into the wiring. You can mount the headlight reminder unit anywhere under the dashboard but do not obstruct the sound outlet hole in the side of the box. Note that the circuit is powered all the time but its standby current is quite low at 200µA and this will not cause the battery to go flat. Neither, now, will leaving your SC headlights on! Full-size artwork for the front panel and PC board pattern. These can also be downloaded from the SILICON CHIP website. www.siliconchip.com.au MORE FROM YOUR EFI CAR! Own an EFI car? Want to get the best from it? You’ll find all you need to know in this publication EFI TECH SPECIAL Here it is: a valuable collection of the best EFI features from ZOOM magazine, with all the tricks of the trade – and tricks the trade doesn’t know! Plus loads of do-it-yourself information to save you real $$$$ as well . . . HERE ARE JUST SOME OF THE CONTENTS . . . n Making Your EFI Car Go Harder n Building A Mixture Meter n D-I-Y Head Jobs n Fault Finding EFI Systems n $70 Boost Control For 23% More Grunt n All About Engine Management n Modifying Engine Management Systems n Water/Air Intercooling n How To Use A Multimeter n Wiring An Engine Transplant n And Much More including some Awesome Engines! AVAILABLE DIRECT FROM SILICON CHIP PUBLICATIONS PO BOX 139, COLLAROY NSW 2097 - $8.95 Inc GST & P&P To order your copy, call (02) 9979 5644 9-5 Mon-Fri with your credit card details! www.siliconchip.com.au August 2001  75 FROM THE PUBLISHERS OF “SILICON CHIP” By DAVID L. JONES This low-cost 6-digit frequency counter module uses readily available components and can measure up to 40MHz with a resolution of 1kHz. It is ideal for adding a digital frequency display to a function generator or to some other project. A 6-Digit Frequency Counter Module M OST SIMPLE frequency counter designs are based on the 74C926 integrated counter chip. Unfortunately, this device is now quite expensive and can only handle four digits which means the resolution isn’t all that great. By contrast, this alternative design is much lower in cost and has six digits for improved display resolution. As presented, the circuit features two signal inputs. The first of these is fed directly to the main counter circuit and this gives a direct readout in Hertz (Hz) up to a maximum of 999999Hz (ie, just under 1MHz). The second input is fed to the counter circuit via an on­board divider circuit or prescaler. This prescaler divides the input frequency by 1000, which means that the display now 76  Silicon Chip shows the measured frequency in kHz. As a result, the circuit can now measure frequencies up to about 40MHz. Because the display reads directly in Hz or kHz, there is no need for decimal point switching and the associated complexity that this involves. There are no switches or controls – you simply feed the signal into the appropriate input for a direct readout in Hz or kHz. BCD output multi­plexer with an internal oscillator. That’s quite a lot in one package and makes the 4553 ideal for a frequency counter applica­tion. The basic principle behind the frequency counter is to count the number of input pulses that occur within a precise one-second window. The value stored in the counter chip will then equal the exact frequency in Hertz and this is then displayed on the How it works Let’s now take a look at the circuit details – see Fig.1. At the heart of the design are two 4553 triple BCD (binary coded decimal) counters (IC4 & IC5), which are wired in cascade fash­ion. Each of these ICs contains three synchronously cascaded BCD count­ers, three output latches and a 3-channel Fig.1 (right): the circuit is based on two 4553 triple BCD counters, which are wired in cascade. The drive the displays via 7-segment decoder drivers IC6 & IC7 and transistors Q1-Q3. IC2 provides the clock signal, while IC1 & IC8 form a divide-by-1000 prescaler. www.siliconchip.com.au www.siliconchip.com.au August 2001  77 Specifications Frequency Readout: 6-digit 7-segment LED display. Frequency Range: 1Hz-1MHz (1Hz resolution); 1kHz-40MHz (1kHz resolution). Can be easily modified for other ranges and resolu­tions. Input Signal Level: 5V TTL/CMOS compatible. Decimal Point Switching: Optional. Size: 116mm x 35mm x 25mm x 30mm. Supply Requirements: 5V DC <at> 90mA. 6-digit display. Lets take a look at how this works in de­tail. IC2 is a 24-stage binary divider and oscillator. It divides the 4.194304MHz crystal (X1) frequency by 8,388,608 (223) at its Q23 output, to give a precise 0.5Hz clock signal. This signal then drives the DISABLE input (pin 11) of the first 4553 (IC5). Let’s initially assume that IC4 and IC5 have both been reset and that the DISABLE line has just gone high. This stops input pulses from clocking the counter and is the Latch/Display phase of the operation. At the same time, the DISABLE signal is differentiated by a .001µF capacitor and 10kΩ resistor (to form a short positive-going pulse) and fed to IC3a. IC3a inverts this signal and the resulting negative-going pulse on its pin 3 output drives the latch enable (LE) pins of ICs 4 & 5. This latches the current counter value into the output registers and this is the value that’s displayed on the 7-segment LED read­outs. Pin 3 of IC3a also drives a second differentiating circuit, again consisting of a .001µF capacitor and 10kΩ resistor. The resulting signal is then squared and buffered by IC3b and IC3c to provide a master reset (MR) pulse. This resets the counters in ICs 4 & 5, so that they are ready to start counting again. After that, the DISABLE signal line goes low and the counters count the input pulses for precisely one second until the DISABLE line returns high again. This is the counting phase of the operation. This Counting & Latch/Display sequence continues indefi­nitely while ever power is applied. As a result, the display is updated every two seconds with the current input frequency. The OVF output (pin 14) of IC5 provides the means to cas­ cade the second 4553 counter (IC4). It connects to the CLK input of IC4, so that we effectively have a 6-digit BCD counter. IC5 has an internal free-running oscillator between pins 3 & 4. Its frequency is set by the .001µF capacitor between these two pins. Pin 3 also directly drives pin 4 of IC4 to keep it in sync and this also sets the multiplexing rate for the 7-segment displays. As shown in Fig.1, the BCD outputs from ICs 4 & 5 (ie, at pins 5, 6, 7 & 9) Fig.3: this scope shot shows the latch enable (LE) signal (top), the master reset (MR) signal centre and the 0.5Hz clock signal (bottom). 78  Silicon Chip each drive 4511 BCD-to-7-segment decoder/driver ICs (IC6 & IC7). These in turn each drive the a-g display segments of three displays. IC7 drives the seg­ments of displays DISP1-DISP3, while IC6 drives the segments of DISP4-DISP6. Note that the corresponding segments of DISP1-DISP3 are all connected in parallel. The same goes for the segments of DISP4-DISP6. The DS1-bar, DS2-bar and DS3bar lines from counter IC4 control the display multiplexing – ie, they control which dis­plays are turned on at any given instant. When DS3-bar goes low, PNP transistor Q3 turns on and “sinks” the current for DISP1 and DISP4. Similarly, when DS2-bar goes low, transistor Q2 turns on and enables DISP2 & DISP5. And when DS1-bar is low, transistor Q1 switches on DISP3 & DISP6. Prescaler circuit IC1 and IC8, both dual 4-digit decade counters, form the divide-by-1000 prescaler circuit. The first thing to note here is that the MR line also drives the CP1-bar input (pin 12) of IC1b. This may look puzzling at first glance because IC1b doesn’t appear to do anything. And that’s exactly what it does – nothing! This was just a convenient way to tie the CLK input on the PC board layout. After all, there’s no point adding extra links or tracks if you don’t have to. It’s the three remaining 4-bit decade counters (IC1a, IC8a & IC8b) that do all the prescaling work, with each stage dividing by 10 to give an overall division of 1000. As shown in Fig.1, the input signal is fed to the CP0-bar (pin 1) input of IC1a and the divided output appears at the Q3 output (pin 7). This then drives the CP0-bar input of IC8a which in turn drives decade counter IC8b. Finally, IC8b drives the clock input (pin 12) of IC5. The maximum frequency that can be displayed depends on the upper limit of the 74HC390 chips, which is around 40MHz. Note that this circuit will only accept TTL-level signals although signal-conditioning circuitry could be added to cater for other signal levels if required. The 4553 BCD counter chips will handle input frequencies up to about 1MHz. The 7-segment LED displays are LT313 0.3-inch common-cathode types. Compatible types are the www.siliconchip.com.au Parts List 1 PC board, code 04108011, 35 x 116mm 1 PC board, code 04108012, 35 x 116mm 4 15mm M3 tapped spacers 8 M3 screws 5 PC board stakes Fig.2: install the parts on PC boards as shown here, taking care to ensure that all polarised parts are correctly orientated. The two boards are stacked together on spacers and joined at both ends using wire links (see photo). Agilent 5082-7613 and the smaller HDSP7303/HDSP7803 units. These were used in favour of the more popular FND500 displays (which have a different pinout) to simplify the PC board layout and to minimise the size. The module requires a single +5VDC supply rail and this could come from any well-regulated source. The current consump­tion is around 90mA. output of IC8a to the clock input (pin 12) of IC5. The decimal point is just as easy. All you have to do is connect a 470Ω resistor between pin 7 of DISP5 and the +5V rail. So it’s quite easy to “customise” the display to your own requirements. If necessary, you could even add a switching ar­ rangement so that you could easily select different ranges. Possible modifications Construction The circuit can be easily modified to display any resolu­tion and direct readout you require within its 40MHz capability. For example, let’s say that you wanted a direct readout in MHz with a display resolution of 100Hz – ie, the display must be capable of showing 99.9999MHz (if the circuit could handle frequencies that high). This requires two things: a divide-by-100 prescaler and a decimal point between DISP4 and DISP5. The divide-by100 prescaler is easy – just bypass IC8b by connecting the pin 7 The design is built on two PC boards measuring 116 x 35mm. These are stacked together on 20mm spacers to form a single compact module. The two boards are joined at both ends using straight wire links running directly from one to the other. Alternatively, flexible ribbon cable could be used to join the two boards and this could be left long enough so that the two boards could be easily separated at a later stage (eg, for modifications). Straight wire links are much neater, however. Semiconductors 2 74HC390 dual 4-bit decade counters (IC1,IC8) 1 4521 24-stage divider/oscillator (IC2) 1 74HC132 quad NAND gate (IC3) 2 4553 3-digit BCD counters (IC4,IC5) 2 4511 BCD to 7-segment decoder/driver (IC6,IC7) 3 BC557 PNP transistors (Q1-Q3) 6 LT313 or equivalent 8mm 7-segment LED displays (DISP1-DISP6) 1 4.194304MHz crystal (X1) Capacitors 1 10µF 10VW tantalum 3 .001µF ceramic 1 82pF ceramic 1 22pF ceramic Resistors (0.25W, 1%) 1 3.3MΩ 2 10kΩ 1 4.7kΩ 3 1kΩ 2 470Ω 7-way DIL resistor packs or 14 x 470Ω resistors Fig.2 shows the assembly details for the two PC boards. Begin the assembly by installing the ICs and 7-segment LED dis­plays on the display board, taking care to ensure that the dis­plays are correctly orientated (ie, decimal point to bottom right). Don’t The prototype used sockets for the ICs on the logic board but we suggest that you solder the ICs straight in. Note that two resistors adjacent to IC2 are mounted “end-on”. www.siliconchip.com.au August 2001  79 A short length of insulated wire can be used to join the “Divider Output” to the “Freq Input” if the counter is to be used in divide-by-1000 mode. use sockets for the display board ICs – this would raise the ICs above the level of the displays and could lead to mounting problems later on. The displays can be mounted in sockets to increase their height above the PC board if desired (eg, you might want them to protrude through the front panel of an instrument case). Normal­ l y, however, the displays would be mounted directly on the PC board and would sit behind a Perspex window. Additional holes are provided in each PC board to make mounting easy. Note that the prototype used two 470Ω DIL resistor packs which look just like (gold-coloured) ICs. Alternatively, you can fit individual 470Ω resistors here, as shown in Fig.2 You are now ready to build the logic board. Begin by fit­ting wire links to the locations shown, then fit PC stakes at the five points marked with a “star”. This done, you can fit the resistors and capacitors, crystal (X1) and the three transistors (Q1-Q3). The crystal should be a low-profile HC49/4H type to reduce its height. You can now complete the logic board assembly by installing the six ICs. Make sure that each IC is in Resistor Colour Codes       No. Value 1 3.3MΩ 2 10kΩ 1 4.7kΩ 3 1kΩ 14 470Ω 4-Band Code (1%) orange orange green brown brown black orange brown yellow violet red brown brown black red brown yellow violet brown brown 5-Band Code (1%) orange orange black yellow brown brown black black red brown yellow violet black brown brown brown black black brown brown yellow violet black black brown Fig.3: here are the full-size etching patterns for the two PC boards. The extra corner holes make it easy to mount the module on a panel or bracket. 80  Silicon Chip its correct location and is correctly orientated. The use of sockets is optional here – they were used on the prototype but you can save money by directly mounting the ICs on the PC board. Once the board assemblies are complete, they can be stacked together on the 20mm spacers and secured using machine screws, nuts and washers. Finally, complete the assembly by installing the connecting links between the two boards. There are 13 links in all, seven at one end and six at the other. Note that once the two boards are joined together, it can be difficult to access the top of the logic board for trou­bleshooting. For this reason, you might like to temporarily “patch” the two boards together using rainbow cable, so that they can be powered up and tested before the final assembly. Using the module The module can be mounted on the front panel of your pro­ject by using another set of spacers or by gluing it in position. All external connections are made via the PC stakes on the logic board. Be careful when you connect the 5V DC power supply – there’s no reverse polarity protection, so if you get the leads the wrong way around, something’s bound to fry. If you want the display to read in “Hz”, connect your input signal directly to the “Freq Input” terminal. This configuration can be used for signal frequencies up to 999,999Hz. Alternatively, if you want the display to read in kHz, connect the input signal to the “Divider Input” terminal instead. You will also have to connect the “Divider Output” terminal to the “Freq Input” terminal using an insulated lead (see photo). As previously stated, this configuration allows measurements up to about 40MHz. The frequency accuracy of the module will be dependant on the crystal used and the values of the two associated capacitors (22pF and 82pF). If necessary, these can be tweaked to “cali­brate” the module. An accurate function generator or another frequency meter of known accuracy will be required for this task. That’s all there is to it – your module should accurately indicate the input frequency and update the display every two seconds. Its application is limited only by your imagination. SC www.siliconchip.com.au 20GHz, 1 Billion Transistor Microprocessors Are Coming Citius . . . Altius . . . . Minimus? (With apologies to the Olympic motto!) F While featuring capabilities that are generations beyond the or a while there, it looked as though Moore's law was about to be overturned. Moore's law says that the number most advanced technologies used in manufacturing today, it is of transistors packed onto a sliver of silicon will double significant that these experimental transistors were built using the same physical structure and materials used in today's chips. every two years. Packing more transistors into a processor has become the Intel plans to use a different class of gate oxide material by the time these new chips go into production. Holy Grail of semiconductor manufacturing: more transistors The future processors will operate at 1V or less, consuming equates to to more computing power and if you can make significantly less power per transistor than today's processors. them faster at the same time, you obviously get a faster, more This will make them ideal for powerful computer. battery-operated devices such But with transistors already too as mobile computers and handsmall to be seen except through held devices. a very powerful microscope, Intel also plans to introduce Moore's law looked to be in a 45 nano-metre (0.045 mijeopardy. Until Intel researchers cron) manufacturing process, stepped in, that is! four process generations more Intel has now developed the advanced than their current world's fastest – and smallest – 0.18 micron technology. This transistors, ready to incorporate will rely on extreme ultraviolet into the super microprocessors of (EUV) lithography, allowing tomorrow. At just 20 nanometres Intel to print ever-smaller feawide, there will be almost a biltures on a wafer. Today's most lion crammed into the one chip, advanced method uses deep compared with the 42 million ultraviolet (DUV) technology. transistors on the current chip, the The two methods can be Pentium 4 processor. compared to drawing two lines The new (experimental) tranon a piece of paper with feltsistors are 30% smaller and 25% tipped pens – EUV is equivalent faster than the industry's current fastest transistors, also developed An electron microscope image of a single transistor (the to the finest pen available while by Intel last year. mushroom-looking thing in the top half of the photo). It DUV is more like a broadtipped fat marker pen. Let's get this into some sort of is so small that it would fit inside a strand of DNA. By And Intel's Dr Robert Chau, perspective: a nanometre is a 2007, Intel expects to put about 1 billion of these trandirector of transistor research billionth of a metre. Some of the sistors into a processor the size of a fingernail. at Intel Logic Technology Detransistor's structures are only velopment, claims that there is three atomic layers thick – a stack of 100,000 would be as thick as the page you're now reading. still a way to go. “We still have not found a fundamental limit And in the 20GHz processors (which Intel expects to build for making silicon transistors smaller,” he said. “The pace of silicon development is accelerating, not deby 2007), in the time it takes you to blink they would have celerating.” completed close to one billion calculations. But the X-factor might change all that again . . . Until now, the majority of chips have been made using “Manhattan” architecture, so called because the interconnections between chip elements are at right angles, resembling a city grid. Now a consortium of major players has been formed to develop a new semiconductor design, called “X” architecture. In “X” factor, the interconnects can be routed in any of eight directions. “X” factor designers Toshiba and Simplex say that their www.siliconchip.com.au www.siliconchip.com.au system, the result of two years of development, reduces power consumption by 20% (because of shorter signal paths) and allows chips to be about 30% smaller. Toshiba’s senior vice-president Susumu Kohyama said that most chip designs with five or more layers are expected to convert to the new format. Toshiba should have chips available from 2002 with other manufacturers later in the year. UGUST2001  81 2001  81 AAugust 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. 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Folded: $A5.95 inc p&p within Australia; elsewhere $A10 inc p&p. *BOOKSHOP TITLES: Please refer to current issue of SILICON CHIP for currently available titles and prices as these may vary from month to month. SUBSCRIBERS QUALIFY FOR 10% DISCOUNT ON ALL SILICON CHIP PRODUCTS AND SERVICES* *except subscriptions/renewals and Internet access Item Price Qty Item Description P&P if extra Total Price Spec i SUB al Offer SCR IBE & COM PUTE GET R OM FO N Aust R FREE! IBUS ralia Only* Total $A TO PLACE YOUR ORDER Phone (02) 9979 5644 9am-5pm Mon-Fri Please have your credit card details ready OR Fax this form to (02) 9979 6503 with your credit card details 24 hours 7 days a week OR Mail this form, with your cheque/money order, to: Silicon Chip Publications Pty Ltd, PO Box 139, Collaroy, NSW, Australia 2097 * Special offer applies while stocks last. 08-01 PRODUCT SHOWCASE New components distributor is 50 years young A “brand new” electronics components distributor in Australia, ELECTUS Distribution Pty Ltd, has actually been trading for the past 50 years. And unlike many suppliers, it is 100% Australian owned and operated. Initially set up in 1950 to provide high quality thermal and electrical insulation materials to Australian industry, John Carr & Company this year celebrates its Golden Jubilee. It has traded continuously but no longer sells insulation materials. John Carr & Co was acquired in 1981 and used as a vehicle to supply electronic components and equipment to resellers, manufacturers and other commercial users including the Jaycar Electronics chain of stores In keeping with the changing times, the company is to change its name to ELECTUS Distribution Pty Ltd. ELECTUS will have a greater focus on distribution of high quality electronic components & equipment to OEMs, resellers and other commercial users. Its prime focus will be as a stocking distributor. It carries over 5,500 items off-the-shelf and offers 24 hour delivery on orders filled from the $A10 million inventory. The company operates from a new 7,000 square metre distribution centre in Silverwater in Sydney’s inner west. Contact: Electus Distribution Pty Ltd 100 Silverwater Rd, Silverwater NSW 2128 Phone: (02) 9741 8567 Fax (02) 9741 8558 Dual-bander HF/UHF Uniden CB from DSE A new Uniden CB combines both the UHF and HF CB bands into one easily-mounted, compact unit. Along with 5W of output power on both bands, the Uniden UH-090 provides extensive scanning facilities including open scan and group scan. There is also a separate priority channel and one-touch instant recall channel on each band. There is a 38-tone CTCSS system on the UHF band allowing selective calling when talking to other CTCSS equipped radios. An optional headset allows VOX operation with 10-step mic sensitivity on the UHF band. A separate antenna socket is provided for each band on the rear panel. There are two different ring tones, UHF repeater access, a busy channel lockout on the UHF band and a variable squelch control on the HF CB band. Price of the dual bander is $498 which compares very favourably with the price of two individual sets offer86  Silicon Chip World-first DVD player with hard disc recorder Perth-based Ashburton Minerals Ltd has unveiled takeover plans for a Singapore company which has developed the world’s first DMR, or Digital Multimedia Recorder. Ashburton Minerals claim the takeover is one of the very few examples where an Australian-owned company will take offshore technology to the world, keeping the profits and shareholder benefits at home. The DMR incorporates a combination DVD player and hard disk recorder and enables movies to be recorded in digital format direct to the disk. It will play back DVD, SVCD, VCD, CD and MP3 discs and the developers claim it will replace the average home’s separate VCR, CD and DVD players. Contact: Ashburton Minerals Ltd 3/2 Richardson St, West Perth, WA 6005 Phone: (08) 9321 6600 Fax (08) 9321 6633 AUDIO MODULES broadcast quality ing similar features. As with all CB radios, no licence is required in Australia. The Uniden UH-090 is available from all Dick Smith Electronics stores, DSE PowerHouse stores, by mail order (1300 366 644) or via the DSE website. Contact: Dick Smith Electronics 2 Davidson St, Chullora NSW 2190 Phone: (02) 9642 9100 Fax (02) 9642 9153 Website: www.dse.com.au Manufactured in Australia Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 9476-5854 Fx (02) 9476-3231 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 David Polkinghorne today on (02) 9979 5644 Dick Smith Electronics is the largest electronic component and equipment retailer in Australia and New Zealand, with more than 200 outlets including company owned stores, franchises and authorised stockists. Jaycar Electronics is Australian owned and our stores are staffed by electronics enthusiasts who know their products and will give you the right advice. Jaycar has stores in most capitals and dealers in most areas of Australia. For components, go to Jaycar Electronics DICK SMITH ELECTRONICS PTY LTD JAYCAR ELECTRONICS Tel: (02) 9642 9100 Fax: (02) 9642 9153 WebLINK: www.dse.com.au Tel: (02) 9741 8555 Fax: (02) 9741 8500 WebLINK: www.jaycar.com.au VGS2 Graphics Splitter NEW! HC-5 hi-res Vid eo Distribution Amplifier DVS5 Video & Audio str Di ibution Amplifier JED designs and manufactures a range of single board computers (based on Wilke Tiger and Atmel AVR), as well as LCD displays and analog and digital I/O for PCs and controllers. JED also makes a PC PROM programmer and RS232/RS485 converters JED Microprocessors Pty Ltd Tel: (03) 9762 3588 Fax: (03) 9762 5499 WebLINK: www.jedmicro.com.au MicroZed Computers GENUINE STAMP PRODUCTS FROM Five identical Video and Stereo outputs plus h/phone & monitor out. S-Video & Composite versions available. Professional quality. For broadcast, audiovisual and film industries. Wide bandwidth, high output and unconditional stability with hum-cancelling circuitry, front-panel video gain and cable eq adjustments. 240V AC, 120V AC or 24V DC High resolution 1in/2out VGA splitter. Comes with 1.5m HQ cable and 12V supply. Custom-length HQ VGA cables also available. Check our NEW website for latest prices and MONTHLY SPECIALS www.questronix.com.au Email: questav<at>questronix.com.au Video Processors, Colour Correctors, Stabilisers, TBC’s, Converters, etc. QUESTRONIX All mail: PO Box 548, Wahroonga NSW 2076 Ph (02) 9477 3596 Fax (02) 9477 3681 Visitors by appointment only ite web s o k c e h f C ore in for m Scott Edwards Electronics microEngineering Labs & others Easy to learn, easy to use, sophisticated CPU based controllers & peripherals. PO Box 634, ARMIDALE 2350 (296 Cook’s Rd) Ph (02) 6772 2777 – may time out to Mobile 0409 036 775 Fax (02) 6772 8987 http://www.microzed.com.au Most Credit Cards OK Programmable arms, walkers and mobiles from robot-Oz “Hexapod 1” BASIC Stamps® and ® Muscle Wire www.robotoz.com.au Ph: (08) 9370 3456 www.siliconchip.com.au www.siliconchip.com.au Fax: (08) 9370 2323 UGUST2001  87 2001  87 AAugust ...and the . Following the review of tiny two-way radios in the March issue of SILICON CHIP, we conducted a competition to find the uses our readers would put these radios to. The prizes were: TWO PAIRS OF UNIDEN MINI UHF TWO-WAY RADIOS COURTESY OF First of all, we have to say a big “thank you” to all those who entered this competition. A trickle at the start of July turned into a flood at the end and picking the overall winners was very, very difficult indeed. There were several dozen entries from people who wanted to use the little Unidens in rural applications. In fact, just reading those entries made us realise how lucky we are in the big cities with conditions on the land now so difficult. Most, if not all, told a similar story: they desperately needed to keep in touch on the farm but conditions were so bad many simply couldn’t afford to outlay even the couple of hundred dollars required to buy a pair of the Unidens. To single out any one of these entries as more deserving than another was impossible, so we decided to group all similar entries and then pick one of those out as a winner. Then there were the “offbeat” entries. Yes, we did say that they were allowed – it’s just that we didn’t quite expect to be taken quite so literally. In deference to the sensibilities of many readers (young and old!) and in the interests of decorum and good taste, we haven’t reproduced some of those entries here. Suffice to say that we had never even dreamed possible some of the more unusual applications suggested! Again, our thanks to all those who entered and, of course, to Dick Smith Electronics for sponsoring the prizes. 88  Silicon Chip www.siliconchip.com.au winner s is are Here are the winning entries: From John O’Grady, Frankston, Victoria: "Sailing a tall ship presents challenges. In ad- dition to the usual ship/shore ad ship/boat communications, a real need exists for reliable comms between foredeck, masthead crew and bridge, especially on our 44m brigantine where wind, waves and particularly movement make other forms of communication (currently shouting!) unrealistic From Victor Tarhanoff, Blantyre, Qld: "I suffered from a stroke in January and my side was paralysed. Should I have an accident on the farm and be unable to get up promptly, I need Uniden 2-ways to contact my wife for help. Ants, snakes and aggressive animals are always around.” Your two Uniden UH-040XR transceivers will be on their way to you both shortly. But wait, there's more! We received quite a few entries from our younger SILICON CHIP readers – but this one really caught our attention! It was from Petah Chapman, a young lady who lives right up in north Queensland and she not only sent us the entry below, she also attached a letter telling us that her Mum had filled in the entry because her writing wouldn't fit. But she also sent us this beaut drawing illustrating how she would be using them. . . We admit it! We’re suckers when someone goes to a bit of effort. So we grovelled a bit (lot!) to Dick Smith Electronics PR department and they agreed to give us a third pair of Unidens. Thanks, Nicola! So Petah, your entry is also a winner: your two Uniden UH-040XR CB radios will be on their way to you shortly. Oh yeah . . . what did Petah want to do with the Unidens? What any self-respecting kid would do, of course: play! "I saw the radios in SC months ago. I showed them to my brother (9) and sister (7). We're saving up to buy three. We want them for communicating between the house, our forest cubby and pontoon at the river. We’ll use them like phones and when we play “spies” and when we are camping out bush.” Now you’ll only have to save up for one, Petah! Two Unidens will be on their way real soon. But it was the P.S. on the entry at right that we really enjoyed. Hopefully you can read it! Onya, Dad! Ross Tester www.siliconchip.com.au August 2001  89 VINTAGE RADIO By RODNEY CHAMPNESS, VK3UG How to substitute for valves that are no longer available A big problem for anyone restoring vintage radios is obtaining new valves, particularly for very old sets. In this article, we describe how it is possible to substitute valves with similar characteristics and even eliminate rectifiers while still maintaining an original appearance. From time to time, vintage radio buffs find that they don’t have a particular valve that is used in a very old, little known model made by an obscure manufacturer. For example, where would you get an A141 valve? Never heard of it! They are very rare and some others are even rarer. A 49 MAY be able to replace it, although its characteristics are quite different and so the result of replacing the A141 with a 49 is uncertain. Having exhausted all practical avenues to obtain a valve, what do you do? The only practical alternative is to fit a close relative of the valve. This may involve some modifications to the set, although it is desirable to keep these Many valves had a host of near equivalents which may have come in a different envelope and required different heater, plate current and bias settings and so on. This photo shows a 6V6GT and some near equivalents. 90  Silicon Chip to an absolute minimum to maintain originality. Selecting a replacement Manufacturers had the habit of designing many types of valves which had similar but not identical characteristics. One manufacturer would produce an XYZ valve with specific character­istics and then another manufacturer would produce valve ABC, similar but not the same – either the base wiring was different or the characteristics varied just a little. Toward the end of the valve era though, manufacturers used a lot more sense and built virtually identical valves but with their own label (AWV, Philips, Mull­ ard, etc). I imagine they had some sort of licensing agreements to cover this. Some valves were still only available from one manufacturer, such as the 6BV7 from AWV. Even some “identical” valves from different manufacturers are not the same under certain circum­stances. Take the 6DQ5, for example. This was used in early American colour TV sets as the horizontal output valve. Certain characteristics were designed into the valve and one of the most important was its ability to draw many hundreds of milliamps in pulse mode – which its function as a horizontal output valve requires it to do. Now single sideband (SSB) radio transmitters operate virtu­ally in pulse mode due to the peaky nature of the human voice. An American manufacturer of amateur radio transceivers decided to use the 6DQ5 as the power amplifier (PA) valve in some of its early single sideband (SSB) transmitters. The 6DQ5 was consider­ably cheaper than similar transmitting valves and its www.siliconchip.com.au ability to draw high current for short periods was ideal for use in SSB transmitters. The transmitters worked well until the 6DQ5 needed replacement. If replaced with the same brand all was well but if another brand of 6DQ5 was substituted, the output power was low and the valves had a short life. If they were “identical” why was one valve so much better than the other? The reason for the difference was that the valves were designed for horizontal output (flyback) in a TV set running at roughly 16kHz and each brand met those design parameters. But while one particular brand of 6DQ5 might have been adequate for SSB use (by good fortune), others were only suitable for TV use. Valve data books The best way to find out which valve can be used as a re­placement for an unobtainable valve is to look up a valve data book. Preferably, the data book will have all the performance graphs so that the characteristics of all the likely replacement valves can be compared. To the average vintage radio buff that is a lot of hard work and in most circumstances, it is not neces­sary. A valve data book such as the “Miniwatt Technical Data” (7th edition best) gives abridged specifications and this data is usually enough to determine whether any particular valve can replace another. However, it doesn’t have much on very old valves. If you think that you may have to do much substitution work, get as many valve data books as you can, particularly early ones or reprints of early ones. The 6V6 and equivalents Now let’s look at some comparisons. Take the ubiquitous octal-based 6V6, for example. Checking in the data book, it can be seen that the 6V6 has the same ratings as variants 6V6G, 6V6GT, 6V6GT/G and 6V6GTA. These are plug-in equivalents but due to the shape of the glass envelope, some may not physically fit into the set. (GT stands for glass tubular envelope). Now consider the 6BW6. This is a 9-pin miniature type and the data says “* For data and notes refer to type 6V6G”. But it is not likely that you will replace a 6V6G with a 6BW6 as it is less common than the 6V6G, having been used almost exclusively www.siliconchip.com.au Photo Gallery: The Radiolette Model 47 Console The Model 47 Console was manufactured by Amalgamated Wireless Australasia, (AWA), in 1934 and sold for £21/18/6. The set used the same chassis as the companion table Model 27 but was fitted with an 8-inch speaker, in place of the 5-inch unit used in the table model, which resulted in improved audio quality. A “local-distance” switch was fitted to the rear of the chassis to reduce overload in strong signal areas. The 47 was small by comparison with many other console sets of the day, measuring 910mm(H) x 510mm(W) x 260mm(D). The circuit was a 5-valve reflexed superheterodyne with an Intermediate Fre­quency (IF) of 175kHz. The valves used were: 78, RF amplifier; 6A7, frequency changer; 6B7, reflexed IF amplifier, detector, AVC rectifier and audio amplifier; 42, audio output and 80, rectifi­er. Picture & text, courtesy Historical Radio Society of Australia (Inc). August 2001  91 Fig.1: this circuit can be used to replace a defective rectifier valve. If the defunct valve has no faults other than loss of emission it may be left in the socket to preserve the original appearance. by STC. The 7C5 is also identical in characteristics to the 6V6G – but where would you get a valve socket for it? Then we could consider the 6AQ5 and 6AQ5A. The first few lines of information are the same as for the 6V6G but following data is different. The differences are mainly due to the fact that the 6AQ5 is physically a smaller valve and is derated so that it doesn’t get too hot and melt down. So there we have four physically different valves that are electrically identical in many ways but may or may not be suit­able for substitution, depending on the set and its circuit. Most restorers would rather use valves that look similar to the originals if at all possible. Let’s see what octal-based valve could be used to replace the 6V6. The following could be considered: •  6EY6 plug-in, greater heater current and requires more bias; •  6F6G plug-in, greater heater current, requires more bias and a higher impedance plate load; •  6K6G plug-in, less heater current, requires more bias and a higher impedance plate load; •  6L6G plug-in, greater heater and plate current, lower impedance plate load; •  6W6GT plug-in, considerably more heater current but approximate­ly the same bias and plate impedance; •  6Y6G plug-in, considerably higher heater current, higher plate current, lower plate voltage and plate load impedance. So there are six possible plug-in valve types that could possibly be used in place of the 6V6GT. Some would have to be crossed off the list as the extra heater current may stress the power transformer too much. 92  Silicon Chip Bias would need to be altered in most cases and the audio output speaker transformer impedance may need to be altered. In another example, the 42 valve can be replaced by the 6F6G if the socket is replaced. And with slight alteration of the operating conditions, the 6V6GT could replace the 42. So by doing a bit of research backwards and forwards through the data, it is possible to determine if and what valve could replace that “hard to get” one. Alternative RF and IF valves RF (Radio Frequency) valves are another area where alterna­tive types may need to be used. This time we’ll look at possible octal replacements for the remote cut-off 6U7G. For those new to valves, “remote cut-off” means that the gain of the valve is gradually reduced as the negative bias on the grid is increased. The 6U7G valve can be considered to be cut off and not amplifying when a bias of -50V is applied to the grid. Valves such as the 6U7G are very suitable for use in circuits that have automatic gain control (AGC). The 6K7G is a plug-in closely similar to the 6U7G, with the 6S7G being somewhat similar. The 6AR7GT, 6B8G and 6G8G are all duo diode RF remote or semi-remote pentodes but the socket would need rewiring to suit. The 6SF7, 6SG7, 6SK7 and 6SS7 are all single-ended valves but could be worth considering too. Of course, the large 7-pin 2B7 and 6B7 valves may need replacement too. They are electronically the same as the 6B8G but the heater of the 2B7 is 2.5V. If you are really hard up and have suitable valve sockets the 7V7, 7R7, 7H7, 7E7, 7B7, 7A7 and 7AH7 would also be possible replacements. Perhaps the set uses one of the duo-diode/pentodes with all elements in use and you only have a straight pentode to replace it. The straight pentode can be put in the rewired socket but it would then be necessary to use either a couple of germanium or silicon signal diodes to do the work of the diodes from the defunct valve. Sharp cut-off octal and large 7-pin base RF pentodes are sometimes used in receivers but are not usually connected to AGC lines. Once again, by going through the data book, various re­ placement valves will be found. The 6J7 and the 6SH7 octal valves are probably the most common of this type, although there are a few others to consider such as 6SE7GT and 6W7G. Replacement converter valves Converter valves are probably more of a worry, as they tend to become faulty more regularly, being a family of valves with quite complex internal structures. A common converter valve is the 6J8G and 6J8GA triode-heptode. Note that the GA version has a 0.45A heater filament whereas the G version requires only 0.3A. The only other relatively common triode-heptode is the 6AJ8 9-pin miniature, arguably the best of the converter valves. The 6K8G triode-hexode can be plugged in place of the 6J8G and works satisfactorily even though it is slightly different internally. In 9-pin miniature triode-hexodes, the options are 6AN7(A), 6AE8 and 12AH8. The 12AH8 may be used on 6V or 12V heater lines. Pentagrid converters are noticeably different to the tri­ ode-heptode and triode-hexode converters and therefore use dif­ ferent circuitry. If you compare the circuit around a 6BE6 penta­grid converter and that of a 6AN7 triode-hexode and you will see what I mean. Here is a list of common and not so common pentagrid con­ verters. 2A7*, 6A7*, 6A8G+, 6D8G+, 6L7G+, 6SA7GT+, 6SB7+, 6BA7# and 6BE6!. * = Large 7-pin base, + = octal base, # = 9-pin minia­ture base and ! = 7-pin miniature base. Electrically, the 2A7, 6A7 and 6A8G are identical. If you cannot get a 2A7 or a 6A7, a 6A8G will do the job if you change the valve socket. However, when replacing the 2A7 it will be necessary to fit a 6.3V filament transformer as the 2A7 has a 2.5V heater. www.siliconchip.com.au The 6SA7GT and the 6SB7 are somewhat similar and have the same socket pinouts. The 6BE6 miniature is similar to the previous two valves. Finally, the 6BA7 has similar character­istics to the 6SB7. So while the list of converters is not extensive, it should be possible to find one that will do the job with some modifica­tion. If an octal or large 7-pin socket converter has a valve shield around it, it is always possible to substitute a miniature equivalent inside the shield if you are really stuck. The same applies to RF/IF valves too. Photo Gallery: The Astor GR “Football” Mantle Radio Duo-diode/triode substitutes There is quite a variety of octal and pre-octal valves that are duo-diode/ triodes as used in the second detector and first audio stage of most receivers. Electrically, the 2A6, 6SQ7GT, 6B6G and the 75 are the same except for their bases and some heater voltages. A few others that can be considered are 6Q7, 6R7, 6SR7GT, 6ST7, 6SZ7, 6T7G, 55 and 85. In each case, it will be necessary to check their characteristics, particularly whether they are high or low-gain valves as the bias and plate resistors may need to be changed. If a higher gain valve is fitted, feed­back may occur. Miniature duo-diode triodes that are somewhat similar are the 6AQ6, 6AT6, 6AV6 in 7-pin and 6BD7 in 9-pin form. Rectifier replacements Replacement of rectifier valves is in some ways easier than any other valve because if a replacement cannot be found, you can always resort to silicon rectifier diodes. The circuit of Fig.1 shows how two 1000PIV diodes, such as 1N4007s, can be wired across the valve plates and common cathode. If the transformer secondary voltage is above 250V per side, two 1000PIV diodes in series must be used to replace each section of the valve rectifier, otherwise the peak inverse vol­ tage (PIV) rating of the diodes may be exceeded, particularly if the mains supply has any spikes on it. Catastrophic failure may occur with the diodes shorting and causing the transformer to burn out. A 6X4 has a peak inverse voltage rating of 1250V and a 5Y3GT a rating of 1400V. Since silicon diodes are much more efficient than rectifier valves like the www.siliconchip.com.au This is the highly sought after Astor “Football” radio. It is commonly called this because its size, shape and colour is sug­gestive of a football. Its model number is GR or GRP and was a basic TRF circuit produced around 1948. It has three valves including the rectifier, so has a rather limited performance despite its use of a reflex circuit. They sell at auction for up to $300, depending on condition and colour. 5Y3GT and 6X4, it is necessary to put a resistor in series with the diodes. This keeps the DC voltage of the supply at much the same level as that produced by the valve rectifier. The value of the resistance will need to be determined by experiment but 300Ω at 5W is a good starting point. Provided the defunct valve has no faults other than loss of emission, it can remain in circuit and the set will then look to be in original condition. Surge voltage ratings There is one more point to be considered if you substitute silicon diodes for a valve rectifier. Because they don’t have filaments which take time to heat up before the cathodes can start to emit electrons, when a silicon diode rectifier is used, the HT (high tension) voltage is immediately applied to the filter and bypass capacitors at switch-on. And because it takes time for the other valves to heat up and start drawing current, the initial HT may be substantially higher than when all the valves are drawing current. It is there­fore prudent to check that the voltage at switch-on does not exceed the voltage ratings of any of these capacitors. In this case, we can take advantage of the “surge voltage” ratings of the capacitors, provided they are new. Typically, the surge voltage rating of a new electrolytic capacitor is 15% higher than the “working voltage” (WV or VW). However, if the set has the original capacitors in it, they will have to be “formed up” to the higher voltage, with no valves in the set, as de­scribed in the December 2000 issue. August 2001  93 Vintage Radio – continued Note that, if you exceed the surge voltage rating of any electrolytic capacitor, even for a very short period, it is likely to break down immediately and spray its contents all over the inside of the set, with disastrous results. Miniature valve equivalents I deliberately haven’t discussed miniature valve equival­ ents to any extent as they are much more common than octal and pre-octal valves and shouldn’t be too hard to obtain. One valve that appears to be not particularly common is the 6M5. It can be replaced with the 6BQ5, with a slight rewiring of the socket. The pentode section of a 6BM8 could also be used in place of a valve such as the 6M5. Rewiring of the socket and alteration of the bias will be necessary. 6BM8 valves are as common as mud after a flood. A common problem with 6M5 valves concerns migration of metal between the screen and grid (pins 2 and 1) which causes them to appear to be gassy. Scrape between these two pins with a metal scriber and in many cases the valve will again work well, saving it from the rubbish bin. Battery valves Battery valves from the early to mid 1930s onwards usually had 1.4V or 2V filaments. Prior to this, a variety of voltages were used. A number of octal and pre-octal valves are identical except for the base. Several valves had sub-models like the 1B4, 1B4P and 1B4T pre-octals. Electrically they are not sufficiently different to warrant a different number and are similar to the 1E5GT and 1E5GP octal valves. Valves with 2V filaments draw 0.06A, 0.12A or 0.24/0.26A filament current. In some cases, where parallel filament wiring is used with a 2V battery, the amount of filament current drawn is not critical. However, where series/parallel wiring is used from a 6V battery, replacement valves need to draw the same filament current unless a careful redesign of the filament cir­ cuit is undertaken. The same requirement applies to 1.4V valves, although they tend to draw either 0.05A or 0.1A of filament current. Output valves such as the 3S4 have a 3V filament that is centre-tapped, which makes it easy to use on either 1.4V or 2.8V. The typical valve line up of a 5-valve battery set using 2V valves is as follows, with possible alternatives in brackets. They are certainly not all direct equivalents: •  Converter 1C7G (1C6, 1A6, 1D7G); •  RF/IF remote/medium cutoff 1M5G (1D5*, 1A4*, 1C4, 34); •  Sharp cut-off 1K5G (1K4, 1B4*, 1E5*, 15, 32); •  Detector/audio pentodes 1K7G (1K6, 1F7*, 1F6); •  Triodes 1H4G (30, 1H6); •  Audio output 1L5G (1D4, 33, 49, 1G5G, 1F4, 1F5G); •  Twin triodes 1J6G (19, 31); •  Twin pentode 1E7G. * means that there are several minor variants of this type number. Subscribe & Get this FREE!* *Australia only. Offer valid only while stocks last. THAT’S RIGHT – buy a 1- or 2-year subscription to SILICON CHIP magazine and we’ll mail you a free copy of “Computer Omnibus”. Includes articles on troubleshooting your PC, installing and setting up computer networks, hard disk drive upgrades, clean installing Windows 98, CPU upgrades, a basic introduction to Linux plus much more. Subscribe now by using the handy order form in this issue or call (02) 9979 5644, 8.30-5.30 Mon-Fri with your credit card details. 94  Silicon Chip The equivalents for a receiver using 1.4V valves is as follows: •  Converter 1R5 (1A7GT, 1AC6, 1L6); •  RF/IF amplifiers, sharp and remote cutoff 1T4 (1L4, 1N5G, 1P5G, 1U4); •  Diode first audio 1S5 (1U5, 1G4G, 1H5G); •  Audio output 3V4 (3S4, 1S4, 1Q5GT, 1T5GT, 3Q4, 3Q5GT, 1C5G, 1A5G). One valve that has no equivalent is the 1D8GT, diode/tri­ ode/pentode (output). Miniature dry battery valves universally used the miniature 7-pin base, whereas a miniature 1D8GT would have needed a miniature 9-pin base. What a shame, as I believe it would have been a popular valve. Summary While I haven’t given you a blow-byblow description of which valves can replace which, I trust I have given you some ideas on how to find a substitute when the correct one is una­vailable. If you are in a quandary of not being sure if a partic­ular valve will do what you require, consult a fellow collector – particularly if they have a valve data book – and work out what valve will do the job. It can be a lot of work but it can also be fun figuring out how to solve the problem and save money into the bargain. When checking the compatibility of various valves, it is necessary to look at the heater/filament volts and current, the HT volts and current, screen volts and bias voltages. For exam­ple, if a possible replacement valve draws too much HT current, it may be made to suit by lowering the screen volts and/or in­ creasing the negative bias on the grid. It is also important not to replace a low gain valve with one that has considerably higher gain, as oscillation and other strange symptoms may appear which may not respond to remedial attention. Some valves have an internal shield – others don’t, so if replacing a valve with an internal shield with one that hasn’t a shield, an external earthed shield may be necessary. An example of this problem is discussed in my article in the February 2001 issue. I found that a 6BE6 (un­ shield­ed con­struction) needed to be shielded for optimum performance SC of the receiver. www.siliconchip.com.au REFERENCE BOOKSHOP GREAT BOOKS FOR ENQUIRING MINDS! AUDIO POWER AMP DESIGN HANDBOOK AUDIO ELECTRONICS By John Linsley Hood. From one of the world’s most respected audio authorities. 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It includes chapters on standards, measurement techniques and design principles, including layout and grounding, digital and analog circuit design, filtering and shielding and interference sources. The four appendices give a design checklist and include useful tables, data and formulae. 299 pages, in soft cover. By Tim Williams. First published 1991  (reprinted 1997). 99 $ $ UNDERSTANDING TELEPHONE ELECTRONICS By Stephen J. Bigelow. Third edition published 1997 $ 59 A very useful text for anyone wanting to become familiar with the basics of telephone technology. The 10 chapters explore telephone fundamentals, speech signal processing, telephone line interfacing, tone and pulse generation, ringers, digital transmission techniques (modems & fax modems) and much more. Ideal for students. 367 pages, in soft cover. 65 By Ian Hickman. 2nd edition (1999). Essential reading for electronics designers and students alike. 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TAX INVOICE Your Name__________________________________________________________ PLEASE PRINT Address ____________________________________________________________ ___________________________________ Postcode_______________ Daytime Phone No. (______) __________________________________ STD  GUIDE TO TV & VIDEO TECHNOLOGY............................$59.00  Cheque/Money Order enclosed  THE CIRCUIT DESIGNER'S COMPANION........................$65.00  Charge my credit card   –    Bankcard   Visa Card   MasterCard  UNDERSTANDING TELEPHONE ELECTRONICS.................$65.00                BOOK TOTAL: $...................... PLUS P&P (if applic): $................... ORDER TOTAL$ AU................ Orders over $100 P&P free in Australia. AUST: Add $A5.50 per book NZ: Add $A10 per book, $A15 elsewhere www.siliconchip.com.au OR No: Signature______________________Card expiry date POST TO: SILICON CHIP Publications, PO Box 139, Collaroy NSW, Australia 2097. OR CALL (02) 9979 5644 & quote your credit card details; or FAX TO (02) 9979 6503 ugust 2001  95 ALL TITLES SUBJECT TO AVAILABILITY. PRICES VALID FOR MONTH OF MAGAZINE ISSUE A ONLY. ALL PRICES INCLUDE GST 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 (Uses MC13024 and TX7376P) Pt.1; High Or Low Fluid Level Detector; Studio Series 20-Band Stereo Equaliser, Pt.2. September 1993: Automatic Nicad Battery Charger/Discharger; Stereo Preamplifier With IR Remote Control, Pt.1; In-Circuit Transistor Tester; +5V to ±15V DC Converter; Remote-Controlled Cockroach. October 1993: Courtesy Light Switch-Off Timer For Cars; Wireless Microphone For Musicians; Stereo Preamplifier With IR Remote Control, Pt.2; Electronic Engine Management, Pt.1. May 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 1989: FM Radio Intercom For Motorbikes Pt.1; GaAsFet Preamplifier For Amateur TV; 2-Chip Portable AM Stereo Radio, Pt.2. October 1991: Build A Talking Voltmeter For Your PC, Pt.1; SteamSound Simulator For Model Railways Mk.II; Magnetic Field Strength Meter; Digital Altimeter For Gliders, Pt.2; Military Applications Of R/C Aircraft. 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. November 1991: Colour TV Pattern Generator, Pt.1; A Junkbox 2-Valve Receiver; Flashing Alarm Light For Cars; Digital Altimeter For Gliders, Pt.3; Build A Talking Voltmeter For Your PC, Pt.2. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Phone Patch For Radio Amateurs; Active Antenna Kit; Designing UHF Transmitter Stages. December 1991: TV Transmitter For VCRs With UHF Modulators; Infrared Light Beam Relay; Colour TV Pattern Generator, Pt.2; Index To Volume 4. 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. January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V 8A Power Supply, Pt.1; Baby Room Monitor/FM Transmitter; Experiments For Your Games Card. 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. March 1992: TV Transmitter For VHF VCRs; Thermostatic Switch For Car Radiator Fans; Coping With Damaged Computer Directories; Valve Substitution In Vintage Radios. April 1990: Dual Tracking ±50V Power Supply; Voice-Operated Switch (VOX) With Delayed Audio; 16-Channel Mixing Desk, Pt.3; Active CW Filter; Servicing Your Microwave Oven. April 1992: IR Remote Control For Model Railroads; Differential Input Buffer For CROs; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. June 1990: Multi-Sector Home Burglar Alarm; Build A Low-Noise Universal Stereo Preamplifier; Load Protector For Power Supplies. 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. 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. December 1990: 100W DC-DC Converter For Car Amplifiers; Wiper Pulser For Rear Windows; 4-Digit Combination Lock; 5W Power Amplifier For The 6-Metre Amateur Transmitter; Index To Volume 3. \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. 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 1994: Fast Charger For Nicad Batteries; Induction Balance Metal Locator; Multi-Channel Infrared Remote Control; Dual Electronic Dice; Simple Servo Driver Circuits; Engine Management, Pt.8. June 1994: 200W/350W Mosfet Amplifier Module; A Coolant Level Alarm For Your Car; 80-Metre AM/CW Transmitter For Amateurs; Converting Phono Inputs To Line Inputs; PC-Based Nicad Battery Monitor; Engine Management, Pt.9. 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. August 1992: Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; 1kW Dummy Load Box For Audio Amplifiers; Troubleshooting Vintage Radio Receivers; The MIDI Interface Explained. 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 1992: 2kW 24VDC - 240VAC Sinewave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal Stereos; A Regulated Lead-Acid Battery Charger. October 1994: How Dolby Surround Sound Works; Dual Rail Variable Power Supply; Build A Talking Headlight Reminder; Electronic Ballast For Fluorescent Lights; Electronic Engine Management, Pt.13. January 1993: Flea-Power AM Radio Transmitter; High Intensity LED Flasher For Bicycles; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.4; Speed Controller For Electric Models, Pt.3. 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. 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. 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. March 1993: Solar Charger For 12V Batteries; Alarm-Triggered Security Camera; Reaction Trainer; Audio Mixer for Camcorders; A 24-Hour Sidereal Clock For Astronomers. 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. April 1993: Solar-Powered Electric Fence; Audio Power Meter; Three-Function Home Weather Station; 12VDC To 70VDC Converter; Digital Clock With Battery Back-Up. February 1995: 50-Watt/Channel 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. June 1993: AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; Digital Voltmeter For Cars; Windows-Based Logic Analyser. 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. 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. April 1991: Steam Sound Simulator For Model Railroads; Simple 12/24V Light Chaser; Synthesised AM Stereo Tuner, Pt.3; A Practical Approach To Amplifier Design, Pt.2. August 1993: Low-Cost Colour Video Fader; 60-LED Brake Light Array; Microprocessor-Based Sidereal Clock; A Look At Satellites & Their Orbits. March 1995: 50 Watt Per Channel 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; Simple CW Filter. 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. ORDER FORM Please Pleasesend sendthe thefollowing followingback backissues: issues:      ____________________________________________________________ Enclosed is my cheque/money order for $­______or please debit my:  ❏ Bankcard  ❏ Visa Card  ❏ Master Card Card No. Signature ___________________________ Card expiry date_____ /______ Name ______________________________ Phone No (___) ____________ PLEASE PRINT Street ______________________________________________________ Suburb/town _______________________________ Postcode ___________ 96  Silicon Chip 10% OF F SUBSCR TO IB OR IF Y ERS OU 10 OR M BUY ORE Note: prices include postage & packing Australia ....................... $A7.70 (incl. GST) Overseas (airmail) ............................ $A10 Detach and mail to: Silicon Chip Publications, PO Box 139, Collaroy, NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details or fax the details to (02) 9979 6503. Email: silchip<at>siliconchip.com.au www.siliconchip.com.au 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. 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. Speed Alarm For Cars, Pt.1; Multi-Colour LED Christmas Tree; Build An Intercom Station Expander; Foldback Loudspeaker System For Musicians; Railpower Model Train Controller, Pt.2. 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. 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. 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. December 1997: A Speed Alarm For Your Car; Two-Axis Robot With Gripper; Loudness Control For Car Hifi Systems; Stepper Motor Driver With Onboard Buffer; Power Supply For Stepper Motor Cards; Understanding Electric Lighting Pt.2; Index To Volume 10. December 1999: Electric Lighting, Pt.16; Build A Solar Panel Regulator; The PC Powerhouse (gives fixed +12V, +9V, +6V & +5V rails); The Fortune Finder Metal Locator; Speed Alarm For Cars, Pt.2; Railpower Model Train Controller, Pt.3; Index To Volume 12. 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 Bass Reflex Loudspeaker System; Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.2; Fast Charger For Nicad Batteries; Digital Speedometer & Fuel Gauge For Cars, Pt.1. November 1995: Mixture Display For Fuel Injected Cars; CB Trans­verter For The 80M Amateur Band, Pt.1; PIR Movement Detector; Digital Speedometer & Fuel Gauge For Cars, Pt.2. 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 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. 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; Build A One Or Two-Lamp Flasher; Understanding Electric Lighting, Pt.3. 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; Marantz SR-18 Home Theatre Receiver (Review); The “Hot Chip” Starter Kit (Review). 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; Understanding Electric Lighting, Pt.4. March 2000: Doing A Lazarus On An Old Computer; Ultra 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; Multisim Circuit Design & Simulation Package (Review). 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. April 2000: A Digital Tachometer For Your Car; RoomGuard – A LowCost Intruder Alarm; Build A Hot wire Cutter; The OzTrip Car Computer, Pt.2; Build A Temperature Logger; Atmel’s ICE 200 In-Circuit Emulator; How To Run A 3-Phase Induction Motor From 240VAC. 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. 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. 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. June 1998: Troubleshooting Your PC, Pt.2; Understanding Electric Lighting, Pt.7; Universal High Energy Ignition System; The Roadies’ Friend Cable Tester; Universal Stepper Motor Controller; Command Control For Model Railways, Pt.5. April 1996: Cheap Battery Refills For Mobile Telephones; 125W Audio Amplifier Module; Knock Indicator For Leaded Petrol Engines; Multi-Channel Radio Control Transmitter; Pt.3; Cathode Ray Oscilloscopes, Pt.2. July 1998: Troubleshooting Your PC, Pt.3 (Installing A Modem And Solving Problems); Build A Heat Controller; 15-Watt Class-A Audio Amplifier Module; Simple Charger For 6V & 12V SLA Batteries; Automatic Semiconductor Analyser; Understanding Electric Lighting, Pt.8. 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; Say Bye-Bye To Your 12V Car Battery. May 1996: Upgrading The CPU In Your PC; High Voltage Insulation Tester; Knightrider Bi-Directional LED Chaser; Simple Duplex Intercom Using Fibre Optic Cable; Cathode Ray Oscilloscopes, Pt.3. August 1998: Troubleshooting Your PC, Pt.4 (Adding Extra Memory); Build The Opus One Loudspeaker System; Simple I/O Card With Automatic Data Logging; Build A Beat Triggered Strobe; A 15-Watt Per Channel Class-A Stereo Amplifier. August 2000: Build A Theremin For Really Eeerie Sounds; Come In Spinner (writes messages in “thin-air”); Loudspeaker Protector & Fan Controller For The Ultra-LD Stereo Amplifier; Proximity Switch For 240VAC Lamps; Structured Cabling For Computer Networks. September 1998: Troubleshooting Your PC, Pt.5 (Software Problems & DOS Games); A Blocked Air-Filter Alarm; A Waa-Waa Pedal For Your Guitar; Build A Plasma Display Or Jacob’s Ladder; Gear Change Indicator For Cars; Capacity Indicator For Rechargeable Batteries. 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. June 1996: BassBox CAD Loudspeaker Software Reviewed; Stereo Simulator (uses delay chip); Rope Light Chaser; Low Ohms Tester For Your DMM; Automatic 10A Battery Charger. July 1996: Build A VGA Digital Oscilloscope, Pt.1; Remote Control Extender For VCRs; 2A SLA Battery Charger; 3-Band Parametric Equaliser; Single Channel 8-Bit Data Logger. August 1996: Introduction to IGBTs; Electronic Starter For Fluores­cent Lamps; VGA Oscilloscope, Pt.2; 350W Amplifier Module; Masthead Amplifier For TV & FM; Cathode Ray Oscilloscopes, Pt.4. September 1996: VGA Oscilloscope, Pt.3; IR Stereo Headphone Link, Pt.1; High Quality PA Loudspeaker; 3-Band HF Amateur Radio Receiver; Cathode Ray Oscilloscopes, Pt.5. October 1996: Send Video Signals Over Twisted Pair Cable; Power Control With A Light Dimmer; 600W DC-DC Converter For Car Hifi Systems, Pt.1; IR Stereo Headphone Link, Pt.2; Build A Multi-Media Sound System, Pt.1; Multi-Channel Radio Control Transmitter, Pt.8. November 1996: Adding A Parallel Port To Your Computer; 8-Channel Stereo Mixer, Pt.1; Low-Cost Fluorescent Light Inverter; How To Repair Domestic Light Dimmers; Build A Multi-Media Sound System, Pt.2; 600W DC-DC Converter For Car Hifi Systems, Pt.2. October 1998: Lab Quality AC Millivoltmeter, Pt.1; PC-Controlled Stress-O-Meter; Versatile Electronic Guitar Limiter; 12V Trickle Charger For Float Conditions; Adding An External Battery Pack To Your Flashgun. 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; Protoboards – The Easy Way Into Electronics, Pt.2. 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; Setting Up A LAN Using TCP/IP; Understanding Electric Lighting, Pt.9; Improving AM Radio Reception, Pt.1. November 2000: Santa & Rudolf Chrissie Display; 2-Channel Guitar Preamplifier, Pt.1; Message Bank & Missed Call Alert; Electronic Thermostat; Protoboards – The Easy Way Into Electronics, Pt.3. December 1998: Protect Your Car With The Engine Immobiliser Mk.2; Thermocouple Adaptor For DMMs; A Regulated 12V DC Plugpack; Build Your Own Poker Machine, Pt.2; Improving AM Radio Reception, Pt.2; Mixer Module For F3B Glider Operations. 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; Electric Lighting, Pt.10. 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 Volume 9. February 1999: Installing A Computer Network; Making Front Panels For Your Projects; Low Distortion Audio Signal Generator, Pt.1; Command Control Decoder For Model Railways; Build A Digital Capacitance Meter; Build A Remote Control Tester; Electric Lighting, Pt.11. 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. March 1999: Getting Started With Linux; Pt.1; Build A Digital Anemometer; 3-Channel Current Monitor With Data Logging; Simple DIY PIC Programmer; Easy-To-Build Audio Compressor; Low Distortion Audio Signal Generator, Pt.2; Electric Lighting, Pt.12. February 1997: Cathode Ray Oscilloscopes, Pt.6; PC-Con­trolled Moving Message Display; Computer Controlled Dual Power Supply, Pt.2; The Alert-A-Phone Loud Sounding Telephone Alarm; Build A 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; Colour TV Pattern Generator, Pt.1; Build An Audio/RF Signal Tracer; High-Current Speed Controller For 12V/24V Motors; Manual Control Circuit For A Stepper Motor; Cathode Ray Oscilloscopes, Pt.10. 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. www.siliconchip.com.au 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. 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; Electric Lighting, Pt.13; Autopilots For Radio-Controlled Model Aircraft. 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: Automatic Addressing On TCP/IP Networks; Autonomouse The Robot, Pt.1; Voice Direct Speech Recognition Module; Digital Electrolytic Capacitance Meter; XYZ Table With Stepper Motor Control, Pt.5; Peltier-Powered Can Cooler. October 1999: Sharing A Modem For Internet & Email Access (WinGate); Build The Railpower Model Train Controller, Pt.1; Semiconductor Curve Tracer; Autonomouse The Robot, Pt.2; XYZ Table With Stepper Motor Control, Pt.6; Introducing Home Theatre. November 1999: Electric Lighting, Pt.15; Setting Up An Email Server; December 2000: Home Networking For Shared Internet Access; Build A Bright-White LED Torch; 2-Channel Guitar Preamplifier, Pt.2 (Digital Reverb); Driving An LCD From The Parallel Port; Build A morse Clock; Protoboards – The Easy Way Into Electronics, Pt.4; Index To Vol.13. January 2001: LP Resurrection – Transferring 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; Wireless Networking. February 2001: How To Observe Meteors Using Junked Gear; An Easy Way To Make PC Boards; L’il Pulser Train Controller; Midi-Mate – A MIDI Interface For PCs; Build The Bass Blazer; 2-Metre Elevated Groundplane Antenna; The LP Doctor – Clean Up Clicks & Pops, Pt.2. March 2001: Driving Your Phone From A PC; Making Photo Resist PC Boards At Home; Big-Digit 12/24 Hour Clock; Parallel Port PIC Programmer & Checkerboard; Protoboards – The Easy Way Into Electronics, Pt.5; More MIDI – A Simple MIDI Expansion Box. April 2001: A GPS Module For Your PC; Dr Video – An Easy-To-Build Video Stabiliser; A Tremolo Unit For Musicians; Minimitter FM Stereo Transmitter; Intelligent Nicad Battery Charger; Computer Tips – Tweaking Internet Connection Sharing. May 2001: Powerful 12V Mini Stereo Amplifier; Microcontroller-Based 4-Digit Counter Modules; Two White-LED Torches To Build; A Servo With Lots Of Grunt; PowerPak – A Multi-Voltage Power Supply; Using Linux To Share An Internet Connection, Pt.1; Computer Tips – Tweaking Windows With TweakUI. June 2001: Fast Universal Battery Charger, Pt.1; Phonome – Call, Listen In & Switch Devices On & Off; L’il Snooper – A low-Cost Automatic Camera Switcher; Build a PC Games Port Tester; Using Linux To Share An Internet Connection, Pt.2; A PC To Die For, Pt.1. July 2001: The HeartMate Heart Rate Monitor; Do Not Disturb Tele­ phone Timer; Pic-Toc – A Simple Alarm Clock; Fast Universal Battery Charger, Pt.2; A PC To Die For, Pt.2; Computer Tips – Backing Up Your Email; Digital Amplifiers Are Here (Feature). PLEASE NOTE: November 1987 to March 1989, June 1989, August 1989, December 1989, May 1990, February 1991, June 1991, August 1991, February 1992, July 1992, September 1992, November 1992, December 1992, May 1993, February 1996 and March 1998 are now sold out. All other issues are presently in stock. For readers wanting articles from sold-out issues, we can supply photostat copies (or tear sheets) at $7.70 per article (includes p&p). When supplying photostat articles or back copies, we automatically supply any relevant notes & errata at no extra charge. A complete index to all articles published to date is available on floppy disk for $11 including p&p, or can be downloaded free from our web site: www.siliconchip.com.au August 2001  97 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. Are there X-rays from light globes? dangerous because they are positioned so close to the user’s eyes. Some enthusiasts on the Internet have raised issues about harmful emissions of Gamma and X-rays from certain mixtures of ionised gases. In particular, one experimenter suggests that the nitrogen rich mixture of gases found within common incandescent globes might emit such rays in substantial quantities. Do you see this as a legitimate concern or simply unin­formed hysteria? If it is a concern, what kind of position would the magazine take on such matters? (M. M., via email). •   We doubt whether X-rays and Gamma rays could be emitted from ordinary incandescent lamps – you need a very high voltage to get X-rays in a discharge tube – that is why large TV CRTs DO emit X-rays. By the same reasoning, a plasma display could also emit low level X-rays. However, halogen lamps and most gas discharge lamps do emit UV and this can be at quite high levels. So much so that the high intensity lighting in some sports arenas can give bad sunburn after a few hours! We also regard halogen desk lamps as poten­tially Theremin is mute TV pattern generator has no colour I have recently made up the Colour TV Generator kit de­scribed in the June & July 1997 issues of SILICON CHIP. It per­forms perfectly at the video output but I can’t get colour when using the modulator output. The modulator provided in the kit is a “Wittis” MM0002V-A12, replacing the original “Astec” suggested in the 1997 article. The circuit was modified to include a 5.1V zener diode, leaving the 180Ω resistor in circuit. Flexible leads connect the modulator to the main board. On connecting the 98  Silicon Chip I bought a Theremin kit from Dick Smith Electronics (de­scribed in August 2000). I have built the PC board but I cannot get my Theremin to produce a tone. I have checked very carefully that I have not created any short-circuits with my soldering. I am at the stage of tuning the voltage between the transformer coils and pin 1 of IC2 to 4.3V but I cannot get a reading on the multimeter between these two parts. I would appreciate any advice you can give me. (S. M., via email). •  If you have a power supply which can deliver 9 to 12VDC, try the Theremin operation with this or use a 9V battery. This will check whether the plugpack you are using is working. Other tests would include checking the various supply rails in the circuit with respect to the ground. Check for about 6V at pin 6 of IC3 and pin 8 of IC2. IC1 does not have a power supply pin (as it is a collection of transistors) but the various pins should have voltmodulator on Channel 1 to a TV set, the bars present well (without colour) and all the patterns (except the Red Raster) are well defined with a mid-range setting of VR2. Varying the input level to the modulator and shorting out the 470µF coupling capacitor will not produce colour. Have I missed some later technical advice to correct the problem? I am tempted to change the modulator. (G. P., via email). •  Some modulators require a resistor between ground and the input to set up the internal DC conditions. You can use a value of 1kΩ. We recall that the Wittis type requires this resistance. ages on them. The drains of Q1 to Q3 should have about 5V. Testing the rest of the circuit without an oscilloscope could be difficult. You could disconnect the 1kΩ and 100Ω supply resistors for the separate oscillators, so that you have only one oscillator operating at a time. Bring an AM broadcast band radio close to the Theremin. Check that you can hear a whistle which is varied when you tweak the relevant oscillator coil. This will indicate whether or not each oscillator is working. Apart from that, check your soldering very carefully for missed joints or solder splashes. Most project faults are due to soldering problems. Running the white LED torch at 1.2V I constructed the White LED Torch, described in the Decem­ber 2000 issue, from a Dick Smith Kit. It works brilliantly. I have two questions. Is it possible to run the LED at 20mA+ from a 1.2V rechargeable cell with minor changes to the circuit? This would make the unit more useful on long trips away from services. Secondly, can it run, with modification, from a 3V source, allow­ing incorporation into combined radio/torch setups? (H. B., via email). •  The White LED Torch can be operated from 1.2V by shorting out resistor R1. This will increase the current drive to the LED. Essentially the current is limited by the DC resistance of inductor L1 since this determines the saturation current. We do not know the characteristics of the commercially wound inductor used in the Dick Smith kit. Winding your own using the Xenon tube transformer former will enable you to increase the LED current when using a 1.2V supply. You would need to use 250 turns of 0.25mm enamelled copper wire (rather than the 0.16mm wire speci­fied) on the bare former. You could run the torch from 3V but R1 should be increased to 4.7Ω. www.siliconchip.com.au Increased brightness for Video Doctor I recently built your Video Doctor kit from the April 2001 issue and I am very pleased with it. However, as an experiment I attempted to make a copy of my video of Star Wars, to see how effective the kit is at removing the protection. It worked well, except that it was apparent that the picture from the copied video was not as bright as the original. This is the same, with or without the Video Doctor. Unprotected videos are not affected in this way. Is this a function of the copy protection and if so, can I do anything about it? (D. M., via email), •  The brightness level of the output from the Dr Video unit can be adjusted but it does involve a bit of ‘fiddling’ and component substitution on the PC board. You can try replacing one or both of diodes D4-D5 with germanium diodes or ‘hot carrier’ diodes, which will give a lower voltage drop and hence lower the black level given to the video in the input DC restorer. This should do the trick but if it makes the picture darker rather than lighter, try adding a germanium diode in series with D4 and D5 instead. Calibrating the LED Bargraph Ammeter Can you please help me with the LED Bargraph Ammeter de­ scribed in the January 1999 issue. When calibrating it on my car with VR1 fully anticlockwise I am able to adjust VR2 until the green and yellow LEDs are lit. But when the parking lights are turned on to adjust VR1, the LEDs go off the board, not towards the centre. Also, when the engine is started, nearly all LEDs light and twinkle. Pin 6 of IC3 is showing +4.4V but all other voltages seem OK. (J. C., via email). •  Check that you have -5V at pin 4 of IC1. The +4.4V at pin 6 of IC3 is normal since the 555 is oscillating and this is the aver­age voltage, as measured with a multimeter. Also check the wiring between battery (-) and the cable earth. Perhaps these connections are transposed. You can increase the filtering to stop the LEDs from flickering by changing the 0.1µF capacitor between pins 1 & 2 of IC1a to a 1µF bipolar (non polarised) electrolytic. Note that VR2 may need readjusting after you have set VR1. www.siliconchip.com.au When is a watt a WATT? Are there many different ways of measuring power consump­tion for compliance labels in various countries of the world? Being involved with hifi equipment, I often see completely illogical and obviously plain wrong power consumption figures on amplifiers. I have numerous examples but one to hand is a giant 26.5kg Sony N77ES power amplifier which is rated to consume 490W for the UK model, 510W for the multi-voltage model, 950VA for the Canadian model and 380W for the US model. These are the various country models, all rated the same output of course, as listed in the service manual. The amplifier delivers in excess of 200W continuous into 8Ω per channel, 270W+ into 4Ω per channel and over 540W as a bridged mono amp. So, is a watt a WATT or not? Is power conserved or do these Driving fuel injectors from the hot chip I have the Investment Technologies Hotchip miniboard as reviewed in the February 2000 issue of SILICON CHIP. I have written a program for it that enables the A-D converter and follows voltages until a predetermined (and variable) point and then switches port B (only one pin is currently used) on and off very fast; ie, pulses of between 4V and 5V at 20mA of current. I have designed this program to read the voltages from a typical 0-5V MAP sensor as found in most turbocharged cars (mine includ­ed). What I have done is set the chip up so that it pulses port B on and off in the manner of a fuel injector. I would now like to run a fuel injector off these pulses. What sort of relay system do I need to run one injector solely from the hotchip and switched 12V? Do you know of a relay that can be switched by only 20mA <at> 4.5V yet handle 400mA <at> 14.4V to drive the injector? Will a relay switch fast enough and be able to handle the continuous on and off cycles and yet remain reliable? (R. W., via email). •  No relay is suitable. Injectors are amplifiers actually manufacture their own power? Only kidding. As Pauline would say, “Please Explain”. (J. R., via email). •  We have no idea why the various country ratings are differ­ent. In fact, at maximum power into 8Ω the amplifier would con­sume in excess of 700W and over 900W at maximum power in bridge mode, assuming normal power supply and class-B efficiency. However, this would virtually never occur in normal use so perhaps the various countries derate the power consumption. The 950VA rating for Canada probably also recognises power factor as part of the equation. Given maximum power output, the Canadian rating looks the most realistic (and conservative). We actually reviewed that amplifier in February 1988. Given the exaggerated PMPO ratings of many ghetto blasters, we think they MUST manufacture their own power out of thin air. usually driven by Dar­lington transistors designed for just that purpose. Some later model cars are also using Mosfet or IGBTs (insulated gate bipolar transistors). We suggest you try using the IRLZ44NS/L logic level power Mosfet from International Rectifier. You can get it from Farnells (Cat 637-488). Phone 1 300 361 005. Revised software for speed alarm I purchased your speed alarm kit from the November 1999 issue and am about to build it but I noticed on the SILICON CHIP website software page that there is a revised program for the microcontroller. I purchased the kit from Jaycar and I need to know which version the chip may be and what the revision actually does. Can you help? (S. G., via email). •  The original software for the Speed Alarm (first version) allowed speeds on the alarm and speedo function up to 155km/h. The newer software (second version) called speed255.ASM allowed the alarm and speedometer function to reach 255km/h. Both ver­ sions are suitable for road use. August 2001  99 12V version of battery charger I refer to the Automatic Battery Charger published in the June 1996 issue. I wish to build this as a dedicated 12V charger, without the 6V or 24V options. I assume that I won’t need IC1a, IC1b, IC1c, Q5, Q6, Q7, LED5, LED6, LED7 and associated components. However, I still need to obtain a stable 2V on pin 2 of IC2 for the 12V battery function. I have a few questions relating to this. Can I obtain the 2V for pin 2 of IC2 via a voltage divider from the reference voltage (5V) at pin 14? Can I do away with Q1, D1, D7 and S2? Can I simplify the RC network around D2 and IC2, and is D2 needed? Is the battery sense line down to IC1a able to be used to turn off IC2 when no battery is connected, as The second version was produced for those wanting to use it for racing purposes. The software in your speed alarm is probably the first version. You can check which version you have by check­ing how far the speed alarm settings can go. If they can go higher than 155km/h then it is the second version. Water cure for noisy power pole At times I was getting atrocious TV reception of Channel 2 due to power pole interference – sometimes the set was reduced to a blue screen. The interference seems to mess up the TV and VCR AGC function as well as the picture signal. I traced it to a particular power pole using a transistor radio as a direction finder. I thought it was a bad insulator or cross-arm. That was fine but what could I do about it other than fruitlessly complain to the power authority? Anyway I planted some flowers at the base of this pole and I found that the con­stant watering made the interference sharply less. Clearly it is something to do with the pole having a bad earth. So, problem solved. I have the flowers there to explain to the neighbours my need to water my power pole. If TV interference 100  Silicon Chip per the original circuit? I realise that one approach is to simply leave it the way it is, but I don’t want to have to use the override switch when the 12V battery is very low in voltage. With my changes, I will connect the leads to the 12V battery, turn the charger on and forget it. Any assistance will be much appreciated. (G. D., via email). •  To obtain the 2V for pin 2 of IC2 use a 2.2kΩ to ground and 3.3kΩ to the 5V reference. Yes, you can do away with Q1, D1, D7, and S2. To simplify the RC network around D2 and IC2, you need to connect the 100kΩ and 4.7kΩ resistors to ground where they pre­ v iously connected to the anode of D2. D2 can be omitted. The battery sense line down to IC1a cannot be used to turn off IC2 as the Mosfet and driver circuit is disconnected. climbs I water the power pole and the interference disappears! Others in similar trouble may be interested in this. (R. D., Salisbury Heights, SA). •  We assume that you have very low rainfall and that the ground is very dry. However, you should know that constantly watering around the base of the pole may promote rot and make the pole unsafe. In Sydney, the relevant authorities discourage planting around poles for that reason. Do you have the option of UHF reception? (Editor’s note: upon receiving our reply, our correspondent phoned to say that the offending power pole was made of rein­forced concrete). On making an electric wheelchair Could you please tell me if you think a 12V motor/gearbox from a windscreen wiper would be powerful enough (using two) to drive a wheelchair that I intend to build. It would be lightweight and used mainly around the kitchen. The commercial ones are too large, heavy and expensive. Also would a computer joystick (modified) be robust enough to handle the voltage and current required to steer it, etc? (S. G., via email). •  12V windscreen wiper motors will do the job but the joystick will not handle the current. You will have to do the switching/speed/direction via a switchmode H-bridge circuit. Have a look at the Railpower train controller circuit we published in October 1999 as the basis for the switching circuit – it has been used in electric wheelchairs before. Stereo preamplifier lacks bass I just built the magnetic cartridge version of the stereo preamplifier based on the LM833 (see SILICON CHIP, April 1994). To my surprise the circuit is acting like a pure amplifier with no RIAA compensation. When playing through the tuner inputs on my amplifier, the sound is all treble, but if I turn my treble right down and bass right up, it sounds about right. Conversely, if I plug into the cartridge input, the frequency balance is about right although it overloads easily. I have looked carefully at the way I put the kit together and I can’t see anything wrong. In any case, both channels exhib­it the same behaviour, which surely eliminates a bad soldering job, mixed up components, or a faulty component. Is there a possible explanation that I have overlooked? (G. B., via email). •   It seems extremely likely that you have not put the RIAA feedback components in or you have some bad solder joints. Check that R1 (16kΩ), R2 (200kΩ), C1 (.0047µF) and C2 (.015µF) are all in place and properly soldered. Using a retired video monitor What about a means of utilising spare (usually 14-inch) comput­ er monitors for video cameras – using those little ‘cameras-on-a-PCB’ things that sell for around $100 for B&W. Some of the better ones seem to have a reasonable degree of resolution when dis­played through a good TV. I know you could “play” them through a video card but that’s like using the Roller to round up the sheep. (J. L., via email). •  Unless you are talking about a preVGA monitor with a com­posite video input, it won’t work because it will not be compat­ible with the sync signals www.siliconchip.com.au from typical NTSC or PAL cameras. We published a project featuring a miniature camera and old monitor in the June 1995 issue and revisited the subject in the October 2000 issue. 500W amplifier for subwoofer use I’m considering building the 500W amplifier, described in the August, September & October 1997 issues of SILICON CHIP, for use in a subwoofer application that needs to be flat down to at least 10Hz. The specs printed in the relevant issues give a frequency response between 20Hz and 20kHz but no farther. Can you tell me the -3dB point at the bottom end, or better still, provide a frequency plot? (N. N., via email). •  The frequency response is quoted as 20Hz to 20kHz at the -0.3dB points so you can expect that the response at 10Hz is less than -1dB down. By the way, 10Hz is not audible (it can be felt at high levels) and there is no sub­woofer that goes to 10Hz – most don’t even go below 25Hz. Coil-based electric fence wanted I seem to recall you did a project for a home-made electric fence based on an automotive coil. I am trying to find this kit and have checked all my local electronics shops to no avail, so was wondering if you could give me details of this kit please. (M. P., via email). •  We published the coil-based electric fence kit in July 1995. Kits are no longer available but an almost identical kit, using the same PC board, is available for the Jacob’s Ladder, published in September 1995, from Jaycar. Cat KC-5191. We can supply the back issues for $7.70 including postage. Capacitance in house wiring Perhaps you can shed some light on house wiring voltages and leakage with regard to neon indicator lights in switch plates and power points. I have a double power point with inbuilt neons, and with nothing plugged into it and the switches off, the neons glow very faintly (only visible in the dark). I assume it cannot be leakage due to faulty wiring, as the neons are integral to the power point. Secondly, I have two neons connected to switches in one room that turn off lights in another room. If both switches are off, the neon glows very faintly but if the one nearest the light (a fluoro) is on and the other one near the neon is off, the neon does not glow at all. A similar problem occurred with the other neon when the other light was installed. The switch and neon went in first, then the wiring and light a week or so later. Once again, this neon glowed very faintly in the dark with the switch Notes and Errata Li’l PowerHouse, June/July 2000: some constructors have not been able to calibrate the current reading successfully, finding that the current reading is too high and cannot be adjusted low enough with VR2. If you encounter this problem, try reducing the value of the 15kΩ resistor connected to pin 2 of IC2. We suggest a value of 7.5kΩ. The final paragraph on page 60 of the June 2000 issue states that “IC2 is specified as an OP77GP which has off. Once the light (also a fluoro) was wired up, this neon does not glow faintly when the switch is off. The wiring to both is correct, with neutrals and earths going back to the switchboard. I assume it is the same problem as the power point neons. I also saw this problem at my father’s house. He had an external light with a neon at the switch. No problems, until he had an extension added and an electrician removed the light but temporarily left the wiring with connectors on it. Then this neon also glowed faintly in the dark with the switch off. This house had been fully rewired a few years before. In all of the above, with the switches on the neon glows fully as you would expect. Any idea as to why? (J. B., via email). •  Without devoting the time to fully analyse your letter, the explanation for your observations is almost certainly due to the capacitance of the wiring. If you have a capacitance meter, try measuring the capacitance of a 10m length of mains cable. You will be surprised. the required low input offset voltage (typically 50mV).”. This should read “(typically 50µV)”. The last paragraph of the first column on page 61 of the June 2000 issue states “In operation, VR2 sets the voltage on pin 4 of IC2 at between 0V and 1.25V”. This should read “pin 6 of IC2”. The final paragraph on page 64 of the July 2000 issue states “Note that the wire connecting the pole of S4b to the PC board (and to the 100kΩ resistor at pin 2 of IC4) . . .”. This should read SC “pin 3 of IC4”. 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. www.siliconchip.com.au August 2001  101 MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. FRWEEBE YES! Place your classified advertisement in SILICON CHIP Market Centre and your advert will also appear FREE in the Classifieds-on-the-Web page of the SILICON CHIP website, www.siliconchip.com.au And if you include an email address or your website URL in you classified advert, the links will be LIVE in your classified-on-the-web! S! D E I F I S C LAS EXCLUSIVE TO SILICON CHIP! CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads: $11.00 (incl. GST) for up to 12 words plus 55 cents for each additional word. Display ads: $27.50 (incl. GST) per column centimetre (max. 10cm). Closing date: five weeks prior to month of sale. To run your classified ad, print it clearly in the space below or on a separate sheet of paper, fill out the form & send it with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details to (02) 9979 6503. Taxation Invoice ABN 49 003 205 490 ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ Enclosed is my cheque/money order for $­__________ or please debit my ❏ Bankcard   ❏ Visa Card   ❏ Master Card Card No. Signature­­­­­­­­­­­­__________________________  Card expiry date______/______ Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ 102  Silicon Chip FOR SALE BLEMISH FREE & LOW BLEMISH CCDs * UP TO 5 YEARS WARRANTY * OVERNIGHT DELIVERY * PC DIGITAL VIDEO RECORDER - Alarm Inputs & Outputs - Dial-In Remote Viewing – Auto Dial-Out to Pagers – Telephones – PC – WWW from $599 * VCR Controller use a home VCR for Surveillance Event Recording Wireless IR Control only $39 * EXTRA High 600 + H-Line Modules – Domes – Covert in PIR Case with SONY Super HAD CCD & SONY Chipset from $122 * Mini Cameras from $61 COLOUR from $85 * TIME LAPSE 24 hour VCRs from $599 National Service Centers * Multinational Manufacturer ! * QUAD 1024 H-Pixels from $175 * COLOUR QUAD only ! $389 * DOME VIDEO CAMERAS from $53 ! COLOUR from $77 ! BULLET from $97 TWO YEAR WARRANTY * DIY PLUG-IN 20 m AV Cables from $20 * DOME 480 Line 0.05 Lux SONY CCD & ChipSet from $81 * COLOUR DSP DOME: 400 Line from $139 * 600 + Line from $164 * COLOUR DSP PIN in PIR CASE from $152 * MINI CAMS from $67 * DSP COLOUR from $133 * PC W98/W2000 REMOTE VIEW, PAGING, WEB-CAM, DVR System High 768 x 576 Resolution from $219 * MULTIPLEXER 4 Ch from $633 * 4 Ch / 8 Ch Switchers only $79 / $99 ! COLOUR Bullet Cameras from $122 * Digital PC 4 Ch Video Recorder System from $119 * www.allthings. com.au TELEPHONE EXCHANGE SIMULATOR: test equipment without the cost of telephone lines. Melb 9806 0110. http://www.alphalink.com.au/~zenere 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 www.siliconchip.com.au KITS KITS AND MORE KITS! Check ‘em out at www.ozitronics.com SEE-in-the-DARK Camera with inbuilt IR LEDs in Water Resistant Case for disturbance-free Baby - Bird - Animal observation from $147 * NEW Wireless Version available NOW ! *from www. allthings.com.au GO TO www.questronix.com.au for video equipment, information, techo links and monthly specials. UNIVERSAL DEVICE PROGRAMMER: Low cost, high performance, 48-pin, works in DOS or Windows inc NT/2000. $1320. Universal EPROM programmer $429. Also adaptors, (E) EPROM, PIC, 8051 programmers, EPROM simulator and eraser. Dunfield C Compilers: Everything you need to develop C and ASM software for 68HC08, 6809, 68HC11, 68HC12, 68HC16, 8051/52, 8080/85, 8086, 8096 or AVR: $198 each. Demo disk available. ImageCraft C Compilers: 32-bit Windows IDE and compiler. For AVR, 68HC11, 68HC12. $396. Atmel Flash CPU Programmer: Handles the 89Cx051, 89C5x, 89Sxx in both DIP and PLCC44 and some AVR’s, most 8-pin EEPROMS. Includes socket for serial ISP cable. $220, $11 p&p. SOIC adaptors: 20 pin $99, 14 pin $93.50, 8 pin $88. Full details on web site. Credit cards accepted. GRANTRONICS PTY LTD, PO Box 275, Wentworthville 2145. (02) 9896 7150 or http://www.grantronics.com.au ROLA AUSTRALIA PH/FAX (08) 8270 3175   WEB SITE WWW.BETTANET.NET.AU/GTD Model Flight Control Modules CHECK OUR WEBSITE FOR DETAILS ON KITS AND COMPONENTS •  TRANSMITTER KITS AND MODULES •  AUDIO MODULES •  COMPUTER INTERFACE KITS •  RADIO STATION AUDIO SOFTWARE NEW: Our MP3-CD player in short form for $169 inc GST. Includes the following: processor board, front panel display and tactile keypad; just add a case, cables, 12V power supply and a CD-ROM drive. Play CDs and up to 2600 MP3’s from a CDR. Great for car or home. Satellite TV Reception International satellite TV reception in your home is now affordable. Send for your free info pack containing equipment catalog, satellite lists, etc or call for appointment to view. We can display all satellites from 76.5° to 180°. AV-COMM P/L, 24/9 Powells Rd, Brookvale, NSW 2100. Tel: 02 9939 4377 or 9939 4378. Fax: 9939 4376; www.avcomm.com.au PDC 01 SERIAL INTERFACE $198.60 PDC 10 GPS INTERFACE MODULE $398.00 PDC 20 ALTITUDE HOLD MODULE $498.00 PDC25 SPEED HOLD MODULE $498.00 PDC 400 ALTIMETER AIR-DATA SENSOR $398.40 PDC 450 AIRSPEED-AIR DATA SENSOR $398.00 PDC1200 VIDEO OVERLAY (PAL-D) $698.60 TRACKER GPS TELEMETRY SOFTWARE $198.60 PDC 3200 AUTOPILOT AND GROUNDSTATION: PRICE ON APPLICATION (PRICE DEPENDS ON CONFIGURATION). (ALL PRICES INCLUDE GST) Silvertone Electronics, PO Box 580, Riverwood 2210. Phone/Fax (02) 9533 3517. www.silvertone.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. by GE, USA $55.00. Rectifier valve for AVO valve tester VR92 $5.50. D. Dauner Ph (02) 4982 9847, fax (02) 4982 9505. Buy Direct From Manufacturer D.I.Y. PCB SUPPLIES write for our FREE catalogue and price list. Solar Flair/Ecowatch phone: (03) 5968 4863; fax: (03) 5968 5810, PO Box 18, Emerald, Vic., 3782. ACN 006 399 480. Pre Sensitized Copper Clad to make your own boards. Developer, Carbide Drills & Mills also manufacturer of Single & double sided boards. Comprehensive details at acetronics.com.au goto shop page ACETRONICS PCBs 5/32 Seton Rd Moorebank NSW 2170 02 9600 6832 Fax: 02 9600 6834 Mail: acetronics<at>acetronics.com.au Credit cards welcome 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. DPDT. Trimpots, 16mm 10k linear, spline shaft. All $1.20 each plus postage. Please email tparkerwati<at>gias.net.au DIGITAL OSCILLOSCOPE, USB, VHF Receiver; temperature/voltage measurement via phone kits. www.ar.com.au/~softmark DIY CCTV PAKS 4 Cameras & Switcher .................$354 as above COLOUR ......................$466 4 Cams, Switcher/Monitor ...........$495 4 Cams & QUAD .........................$478 4 COLOUR & QUAD ....................$752 Time-Lapse 24 hr VCR only $599 with CCTV Systems! MORE at: www.allthings.com.au Fully Plug-In DIY Paks with Cables & Power Supplies * PC W98/W2000 Digital Motion/Sound detection & activat­ ed Video/Audio Recording systems. AUDIO POWER VALVE 6550A made SWITCHES, miniature toggle, 3A 250V continued next page HOME CCTV Mono / Colour PAKS only ! $119 / $151 Full DIY Plug-In to TV / VCR 20 metre Cable, Plug Pack & Camera www.allthings.com.au AEM, EA, ETI, SC every edition from 1974 onwards half price. 0428888985. www.siliconchip.com.au VALVE AUDIO AMPLIFIER REPAIR and modification. Audio Research, Quad Leak, etc. Prototypes constructed. Audio Design OTL 03 9822 1116. August 2001  103 DON’T MISS THE ’BUS Advertising Index Acetronics..................................103 Altronics................................. 82-84 Aust. Video Systems....................41 Allthings Sales & Services..102,103 Do you feel left behind by the latest advances in com­puter technology? Don’t miss the bus: get the ’bus! Includes articles on troubleshooting your PC, installing and setting up computer networks, hard disk drive upgrades, clean installing Windows 98, CPU upgrades, a basic introduction to Linux plus much more. Av-Comm Pty Ltd.......................103 Dick Smith Electronics........... 20-23 Dominion Electronics...................29 Emona.......................................IBC Grantronics................................103 Harbuch Electronics....................87 Price: $12.50 (incl. GST) Order now by using the handy order form in this issue or call (02) 9979 5644, 8.30-5.30 Mon-Fri with your credit card details. Special subscription offer available only while stocks last. RCS HAS MOVED to 41 Arlewis St, Chester Hill 2162 and is now open, with full production. Tel (02) 9738 0330; Fax 9738 0334. rcsradio<at>cia.com.au; www.cia.com.au/rcsradio PCBs MADE, ONE OR MANY. Low prices, hobbyists welcome. Sesame Elec­tronics (02) 9586 4771. sesame<at>internetezy.com.au; http:// members.tripod.com/~sesame_elec VIDEO amplifiers, Stabilisers, TBCs, Converters, Mixers, etc. QUESTRONIX (02) 9477 3596. FREE DELIVERY, new release colour dome camera pan/tilt via remote control. Only $790. Colour camera 600+ lines $99. Wireless audio-video transmitter $65. Bug 1.2km $59. BUY DIRECT AND SAVE. GCS: 0410 739 317 OR (02) 4227 9933. KIT ASSEMBLY NEVILLE WALKER KIT ASSEMBLY & REPAIR: · Australia wide service · Small production runs · Specialist “one-off” applications Phone Neville Walker (07) 3857 2752 Email flashdog<at>optusnet.com.au WANTED Early Hifi's, Amplifiers, Speakers, Turntables, Valves, Books; Quad, Leak, Pye, Lowther, Ortofon, SME, Western Electric, Altec, Marantz, McIntosh, 104  Silicon Chip Instant PCBs..............................103 Jaycar ................................... 49-56 JED Microprocessors..................27 Good­mans, Wharefdale, Tannoy; radio and wireless. Collector/Hobbyist will pay cash. (07) 5449 1601. johnmurt<at>highprofile.com.au PERSON WITH EXPERIENCE/APTITUDE to fault find & repair PCBs – without diagrams. GENEROUS PKG NEG. Tel John<at>AER (03) 9482 4958 or 0415 305 470. Meterman....................................47 MicroZed Computers...................89 Microgram Computers..........3,OBC Oatley Electronics........................37 Printed Electronics.................... 103 Protel International....................IFC Questronix............................89,103 RCS Radio.................................103 Silicon Chip Binders RF Probes...................................89 RobotOz......................................89 Rola Australia............................103 R.T.N............................................87 Silicon Chip Back Issues....... 96-97 Silicon Chip Binders..................104 REAL VALUE AT $12.95 PLUS P & P Silicon Chip Bookshop.................95 SC Electronics Testbench............63 SC Computer Omnibus.............104 Silicon Chip Subscriptions...........75   Each binder holds up to 14 issues    Heavy board covers with 2-tone green vinyl covering   SILICON CHIP logo printed in goldcoloured lettering on spine & cover Price: $A12.95 plus $A5.50 p&p each (Australia only; not available elsewhere). Buy five and get them postage free. Just fill in & mail the handy order form in this issue; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. Silvertone Electronics................103 Smart Fastchargers.....................41 Solar Flair/Ecowatch..................102 _____________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: •  RCS Radio Pty Ltd. Phone (02) 9738 0330. Fax (02) 9738 0334. www.siliconchip.com.au 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.tek.com