January 1999 - Silicon Chip Online

Outer Front Cover
Contents
Publisher's Letter: Wind power and marketing hype
Feature: The Y2K Bug & A Few Other Worries by Bob Dyball & Greg Swain
Project: High Voltage Megohm Tester by John Clarke
Feature: Satellite Watch by Gary Cratt
Project: Getting Going With BASIC Stamp by Ross Tester & Bob Nicol
Feature: 4.8MW - Blowing In The Wind by Leo Simpson
Product Showcase
Order Form
Project: A LED Bargraph Ammeter For Your Car by Rick Walters
Project: Keypad Engine Immobiliser by John Clarke
Serviceman's Log: How long is a couple of months? by The TV Serviceman
Feature: Electric Lighting; Pt.10 by Julian Edgar
Back Issues
Feature: Radio Control by Bob Young
Feature: How To Listen To Community AM Radio by Rick Walters
Vintage Radio: Improving AM broadcast reception, Pt.3 by Rodney Champness
Notes & Errata: Use Your old PC Power Supply For High Current Outputs / Thermocouple Adaptor for DMMS / Improvements to AM Broadcast Band Reception
Book Store
Market Centre
Advertising Index
Outer Back Cover

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SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au Contents FEATURES The Y2K Bug 4 The Y2K Bug & A Few Other Worries Vol.12, No.1; January 1999 The Y2K Bug & Other Worries – Page 4. You’ve got more to worry about than January 1st, 2000 – by Bob Dyball & Greg Swain 40 4.8MW – Blowing In The Wind A look at Australia’s first grid-connected wind farm – by Leo Simpson 73 Electric Lighting; Pt.10 The design and construction of lights in cars – by Julian Edgar 86 How To Listen To Community AM Radio Have you heard of these new radio stations? – by Rick Walters PROJECTS TO BUILD 18 High Voltage Megohm Tester Resistance measurements far beyond where a DMM will go – by John Clarke 32 Getting Going With BASIC Stamp HighVoltage Megohm Tester – Page 18. Our experimenter’s board makes it easy – by Ross Tester & Bob Nicol 54 A LED Bargraph Ammeter For Your Car It’s easy to build and even easier to connect – by Rick Walters 62 Keypad Engine Immobiliser There’s no need for a hidden “kill” switch – by John Clarke SPECIAL COLUMNS 29 Satellite Watch The very latest on satellite TV – by Garry Cratt 68 Serviceman’s Log How long is a couple of months? – by the TV Serviceman 80 Radio Control Operating model R/C helicopters – by Bob Young Getting Going With The BASIC Stamp – Page 32. 88 Vintage Radio Improving AM broadcast reception, Pt.3 – by Rodney Champness DEPARTMENTS 2 13 30 43 53 Publisher’s Letter Mailbag Circuit Notebook Product Showcase Order Form 90 92 94 96 Ask Silicon Chip Notes & Errata Market Centre Advertising Index LED Bargraph Ammeter For Cars – Page 54 January 1999 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.) Robert Flynn Ross Tester Rick Walters Reader Services Ann Jenkinson Advertising Manager Brendon Sheridan Phone (03) 9720 9198 Mobile 0416 009 217 Regular Contributors Brendan Akhurst Rodney Champness Garry Cratt, VK2YBX Julian Edgar, Dip.T.(Sec.), B.Ed Mike Sheriff, B.Sc, VK2YFK Philip Watson, MIREE, VK2ZPW Bob Young SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. A.C.N. 003 205 490. All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Macquarie Print, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $59 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 and maximum * Recommended price only. 2 Silicon Chip Wind power and marketing hype This month we feature a short story on the new wind farm at Crookwell in New South Wales. This was opened in August last year but for a number of reasons the story had to be delayed until this issue. It is a good development for the electricity industry in this country but it is nowhere near as significant as the marketing people have tried to make it out to be. To hear the speeches on the opening day, you would think the management people at Pacific Power had invented wind power! The truth turned out to be somewhat more prosaic, as I found when talking to the Danish commissioning engineer from Vestas Wind Systems A/S; it was a straightforward turnkey project. In fact, on the opening day, in spite of there being hordes of people from the various power companies, I could not find one Australian engineer who could give me any technical background on the project. Years ago, Australian engineering would have had a very significant part in a project of this type and it probably would have been much larger. Crookwell was promoted as the first “grid connected” wind farm in Australia. The publicity handout was very careful about that point “grid connected”. But at no time did they mention other wind power installations in Australia and especially not the one at Esperance, WA which has nine turbines, compared with Crookwell’s eight. The reason that the two power companies involved, Pacific Power & Great Southern Energy, were heavily promoting the Crookwell wind farm was to publicise their commitment to “Green Power”. This concept of Green Power has been heavily promoted to their customers and it has been very successful. At last count, over 30,000 people had agreed to pay more for their electricity, quite a few in the mistaken belief that they were going to somehow be supplied with the “green stuff” through their electricity mains. The fact is that a wind farm with a total capacity of 4.8MW is tiny indeed compared with the total generating capacity of New South Wales or any of the other states. We’re talking of tens of Gigawatts here, not megawatts. Of course, half the trouble is that the public doesn’t know what a megawatt is, let alone a Gigawatt. A Gigawatt is equal to 1000 Megawatts. Nor has it probably dawned on these enthusiastic green power customers, that while it might be a windy place at Crookwell, it doesn’t blow all the time and when it doesn’t, there is no “green power” being generated from that source. In any case, all the Crookwell wind power is supposedly going to the Great Southern customers and Pacific Power customers won’t get a look-in. To get some idea of how small 4.8MW is, you have to think in terms of two medium-powered railway locomotives, or perhaps 12 large semi-trailers. Throughout Australia there are many hundreds of such locomotives and many thousands of semi-trailers. If we wanted one Gigawatt of wind power, we would need 1,666 wind turbines, each rated at 600kW. At Crookwell, we’ve got eight. Isn’t that exciting! If Australians are really concerned about greenhouse gases, they should not be hoodwinked by marketing hype about green power. They should be getting serious about energy conservation. It is clear to me that most people don’t even know what energy conservation is! It means not driving your car when you can take the train and a whole host of other measures. And it means not wasting electricity. If every Australian could turn off one 60W electric light bulb, or in other words, permanently reduce their electricity consumption by that amount, Australia’s generating capacity could be reduced by one Gigawatt. That makes 4.8MW of wind power seem puny indeed. Reckon it will happen? Leo Simpson £ £ ¢ ¢ *Full details at www.tol.com.au ¤ ¢ ¥ ¡ ¢ ¢ ¢ ¢ E & OE All prices include sales tax MICROGRAM 0199 Come and visit our online catalogue & shop at www.mgram.com.au Phone: (02) 4389 8444 Dealer Enquiries Welcome sales<at>mgram.com.au info<at>mgram.com.au Australia-Wide Express Courier (To 3kg) $10 FreeFax 1 800 625 777 We welcome Bankcard Mastercard VISA Amex Unit 1, 14 Bon Mace Close, Berkeley Vale NSW 2261 Vamtest Pty Ltd trading as MicroGram Computers ACN 003 062 100 Fax: (02) 4389 8388 Web site: www.mgram.com.au FreeFax 1 800 625 777 The Y2K Bug And A Few Other Worries The Year 2000 bug is not the only bug that computer users have to worry about as we approach the end of the millennium. There are other problems lurking in the background as well. By BOB DYBALL & GREG SWAIN Suppose someone mentioned these dates: 1st January 1999, 21st August 1999, 29th February 2000, 1st July 2000 and 18th January 2038? Would they mean anything to you? No? –then how about an easy one? What about the 31st December 1999? Of course, the latter will immediately evoke a response. It’s the end of the century and the end of the millennium; a time for parties and revelry. OK purists, the 31st December 2000 is really the end of the millennium (not 31st December 1999) but guess when the big party is going to be held. The rollover from the year 1999 to the year 4 Silicon Chip 2000 seems far more significant than from 2000 to 2001, so let’s not be too pedantic. It will also be far more significant to those who own and operate computers. The concern is that not all computers will continue to operate correctly when the year 2000 ticks over, due to hardware and/or software limitations. Indeed, if you listened to some of the doom and gloom merchants, you could be forgiven for wondering if the Earth will stop spinning at midnight of the 31st December, 1999. Certainly, if you work as a computer programmer, you could well be left wondering if the patches you’ve put in place in the computer system will do the job when the year 2000 ticks over. Some IT (information technology) workers in critical industries may even have to remain at work on 31st December 1999 to monitor the rollover, just in case problems are encountered. However, there are a few other dates that are likely to cause problems as we approach the year 2000 and in the years immediately afterwards. Let’s find out what those dates are and what effect they might have on our computer systems. 1st January 1999 The first critical date that might cause problems is 1st January 1999. Yes that’s right, 1999! This year sees the introduction of a new currency – the “Euro” – in the European Union, although the coins and notes aren’t due for release until 2002. If you deal with Europe or European currencies and need to handle the Euro, then you may have to upgrade your software to handle this new currency. This could include both your operating system, plus other software such as spreadsheets, accountancy packages and even word processors. According to Microsoft’s website, Windows 98 already has support for the Euro and Windows NT5 will have it when it’s finally released. Meanwhile, users with NT4 can update using the “NT4 Service Pack 4” or the “NT4 Euro Update Pack”. Windows 95 users should also check the Microsoft website for a special update patch. In addition, replacements for the Comic Sans MS and Monotype.com fonts with the Euro symbol, as well as some of the more common True Type fonts (Arial, Courier New and Times New Roman), are available by following the links from the Euro section of Microsoft’s website. Registered MS Office users may also download an updated Euro-ready Tahoma font. However, even if you have the correct fonts, this won’t make your software work in Euros. Check with your software supplier to find out what will best suit your needs or whether you can upgrade existing software. But do you really need to update? As with most things, look before you leap. If you don’t deal in Euros, then there’s no need to act. Instead, you can wait and take care of the problem as your software is progressively upgraded in the normal manner. As a matter of interest, estimates of costs to companies and banks in Europe range from 25% of the year Fig.1: Microsoft’s year 2000 website includes detailed compliance information on operating systems and applications. It also includes Y2K fixes that can be downloaded and applied to problem programs. Fig.2: the Microsoft year 2000 web site has links to numerous “Year 2000 Tools” that can be used to assess Microsoft products. There are also links to numerous third party suppliers with Y2K diagnostic utilities, some of which can be downloaded for free. 2000 costs to as much as two or three times the cost of year 2000 conversion. 21st August 1999 What’s the significance of this seemingly innocuous date? Well, this date is the week zero rollover for GPS Fig.3: Dell’s website has some excellent material on the Y2K problem. There’s a complete product list of Dell machines, a number of Y2K test tools that can be downloaded, and a several easy-to-follow articles on the Y2K problem. navigation systems. In greater detail, the 21st August 1999 is the last day of week 1023 of the GPS system. However, the system was only designed to count from 0 to 1023 in the first place. This means that on the 22nd August 1999, the Fig.4: if you have a Dell computer, you can check its Y2K status and, if necessary, download a BIOS update or software patch. January 1999 5 What About Apple Computers? If you’ve got an Apple Mac, you can afford to be a little smug here. According to Apple, the Mac OS (operating system) has always correctly handled dates between 1st January 1904 and 6th February 2040. What’s more, the current Mac OS date and time utilities correctly handle dates between 30,081 BC and 29,940 AD. Apple also state that all applications which use the Mac OS date and time utilities will have no problems when the year 2000 rolls around. However, there could be GPS satellites will be broad casting that it is week 0. Some GPS ground systems will just stop working, having severe problems with the rollover. Others may need only a simple modification, often back at the factory, to make sure that they continue working properly and display 22nd August 1999 instead of 6th January 1980, or something worse. Most GPS systems made over the last couple of years should have no problems but be sure to check with your supplier that yours will work properly. If you have a GPS mapping system for your computer, it might also pay to check with the supplier (as well as the supplier of the GPS) for any updates. 9th September 1999: 9/9/99 This could be a real sleeper in some applications. That’s because software writers occasionally used 9/9/99 to indicate unknown information. Basically, this was a date that was never supposed to happen during the life of the program. It means that some applications will fail before the year 2000 is reached. 31st December 1999: Y2K Bug Given the publicity, there must be few people who haven’t heard the “Year 2000 Bug”, also known as the “Millennium Bug” and the “Y2K Bug”. It refers to the fact that many computer systems will not roll over correctly from 31st December 1999 to 1st January 2000, but will roll over to 1900 or 1980 instead. The older the computer, the more 6 Silicon Chip problems with applications that don’t do this. Once again, it’s best to check with the company that supplies the software. One issue affecting the Apple Mac is that the Date and Time control panel only allows the year to be set in the range from 19202019. However, it’s possible to set dates beyond 2019 using the SetDateTime toolbox. There are a few other issues and owners are best advised to visit the Apple website for further details. likely it is that it has the Y2K bug. Many applications will break down as well and again, the older the application, the more likely it is that it will suffer year 2000 problems. So how did it begin? Basically, the problem can be traced back to the early days of computing and the practice of using only two digits to represent the year. That practice, possibly introduced to save storage space, was Embedded Controllers It’s not only computers that could strike problems in the year 2000. Many of today’s so-called “high-tech.” systems contain embedded controllers and these are commonly used in medical equipment, car computers, traffic lights, industrial process control, office equipment, PABXs, airconditioning plants, building access controls and alarm systems, to name just a few. Of course, only some of these controllers are date dependent but those that are could cause problems in the year 2000 if not replaced or modified. The effects, of course, will depend on the equipment. In some cases, the equipment will continue to operate normally (although it will report the wrong date) but in other cases, the equipment could malfunction or cease working altogether. subsequently carried over into the age of the PC. If you “dig down” into the hardware of a PC, you’ll find a real-time clock (RTC) chip. This RTC keeps track of the time and date and updates the CMOS memory which is backed up by an onboard battery when the machine is off. The year information in the CMOS is passed on to the system BIOS in 2-digit format each time the machine boots. What happens is that the BIOS receives the 2-digit count from the RTC, adds this to 1980 (Microsoft’s base date) and stores the year as four digits (eg, 1980 + 18 = 1998). This all works fine until we get to the year 2000. At this point, the RTC rolls the year from 99 to 00 but the century field remains fixed at 19. As a result, the RTC rolls over to 1st January 1900 instead of 1st January 2000. The next step depends on the system BIOS itself or more specifically, on what type of BIOS is built into the PC. When the machine is rebooted, some BIOSes will simply reflect what is in the system clock and will show 0101-1900. Other BIOSes will interpret year 00 as 01-01-1980. As a result, the system rolls over from either 1999 to 1980 or from 1999 to 1900. However, there’s a complicating factor. Microsoft operating systems (Windows and DOS 6.22) don’t recognise 1900 as a valid date. Instead, when the operating system boots, it automatically resets the system clock to 4th January 1980; or at least, this is what happens with DOS 6.22, Windows 3.1x and Windows 95. Windows 98, Windows NT 3.51 (Service Pack 5) and Windows NT 4 behave differently. According to Microsoft, these operating systems include a BIOS “fix” which automatically resets the year 1900 to 2000. However, some BIOSes will revert to 1900 every time the system reboots. In that case, Microsoft’s BIOS fix will only work until the year 2001 is reached. When that happens and the system BIOS rolls over to 1901, the fix will not work and the operating system will revert to 1980. Now let’s inject an air of reality here. Generally, it’s older machines that have BIOSes with this type of problem. You’re not likely to be running Windows NT or Windows 98 on a 486 and if you are, it’s probably time for an upgrade anyway. Check Out These Websites The Year 2000 Problem www.mi crosoft.com/year2000/ Mi crosoft's year 2000 websi te. Lots of information on operating systems and appli cations plus numerous links to various dianosti c utili ti es, etc. www.novel l.com/year2000/ Information on Novell products and Y2K compatibi li ty. www.year2000.com Lots of i nformation on the Y2K probl em plus links to manufacturers. www.y2k.gov.au/ The NSW Government's year 2000 information websi te. Lots of information plus links to other state government websi tes and the Commonweal th Government's websi te. www.sba.gov/y2k/ Year 2000 website for the US Government Small Business Administration. www.bug2000.co.uk The Bri tish Government's Action 2000 websi te. www.garynorth.com/ The Year The Earth Stands Stil l - an interesting vi ewpoint on the year 2000 problem. Read i t wyou're sti ll compl acent. Some Use ufl Y2K Diagnostic Utilities www.ourworld.compuserve.com/homepages/saphena/year2000/ Saphena Computing's DOSCHK.EXE diagnosti c utili ty. www.precise.co.uk/T2000.htm Preci se Publi shing's Y2000RTC.zip diagnosti c uti li ty. www.nstl.com/html /nstl_ymark2000.htm NSTL's YMARK2000 diagnosti c utili ty. www.RighTime.com RighTime's Test2000 diagnosti c utili ty. Computers Suppliers & Y2K Lets you check your Dell system for compliance. Bi os updates and dri vers can be downloaded wnecessary. www.del l /com/ap/au/year2000/index.htm www.gateway.com/year2000/ www.ibm.com/IBM/year2000/ www.compaq.com/year2000/ Euro Information www.europa.eu.int/euro European Union's official Euro websi te. www.mi crosoft.com/euro Mi crosoft's Euro websi te. www.bitstream.com/news/what/pi Bitstream Fonts Euro websi te. Global Positioning Satellite (GPS) Navigation System www.amsa.gov.au/ns/dgps/eow.htm Austral ian Mari time Safety Authori ty. www.navcen.uscg.mil /gps/geninfo/y2k/defaul t.htm GPS date rollover issues pl us a list of GPS manufacturers. www.navcen.uscg.mil US Coast Guard Navi gation Information Centre. Donating Old PCs To Schools www.typequick.com.au Note that if a non-compliant machine is left running during the rollover, the DOS date will be updated correctly to 01-01-2000. However, that doesn’t necessarily mean that all applications will work correctly. Some applications take the date from the BIOS rather than from the operating system. Typequick's link to put business in contact wi th school s that need PCs. What’s more, if the BIOS date reverts to 01-01-1900 or 01-01-1980, the operating system date will also be incorrect when the machine is next booted. However, if you manually correct the date in the CMOS setup, many machines will maintain the correct setting from that point on and even re-booting will not cause any problems. The Award 4.50g BIOS can pose particular problems. Some versions of this BIOS will not allow any year that’s less than “94”, which means that 1900 becomes 1994 and 2000, 2001, 2002, etc become 2094. This January 1999 7 Fig.5: DOSCHK.EXE is a small utility that can automatically test your PC for Y2K compliance. It starts by saving the current date and time, then resets the time to 5 seconds before midnight on 31/12/1999. Fig.6: next, the program counts down to midnight on 31/12/1999. An on-screen display shows the progress. Fig.7: finally, the program displays the results and offers advice on a fix. As can be seen, this PC has gone back to 1900-01-01. means that the machine will roll over from 1999 to 1994 and you cannot correct the situation by manually resetting the BIOS clock. Although many RTCs in recent machines are still technically non-compliant, a “fix” is incorporated into the BIOS to overcome the Y2K problem. Basically, the BIOS corrects the date in the CMOS at bootup time and this is subsequently passed on to the operating system. Most (but not all) of the later Pentium machines fall into this category and so will correctly roll-over to the year 2000. In greater detail, the CMOS RTC almost always fails to increment from 1999 to 2000 (except for the very latest RTCs) but this usually doesn’t matter – very few programs access it directly (and these would now usually be considered obsolete). What does matter is that the BIOS fixes the problem so that 8 Silicon Chip both the BIOS and operating system dates are correct. Testing your system So how can you check to see if your system rolls over to the year 2000 correctly? Again look before you leap; if you rush in and change the date and time on your PC to a few minutes before the year 2000, there could be unforeseen consequences. For example, if you have a program that is only registered for a certain period of time, it may stop working. In addition, anything that schedules events, including e-mail delivery, could cause lots of problems. Even year 2000 compliant applications could cause problems if you move the clock forward to the year 2000, run the program, then change the clock back again. The best way to test your system is to use a bootable floppy disc (created using DOS 6.22 or later). That way, you can avoid writing any information to the hard disc, which may alter vital files. Make sure that the machine on which you create the bootable floppy is clean of viruses, then change the boot order in your BIOS (CMOS) setup to A: C: (normally it should be on C: A: or C: only, to prevent accidental infection if a virus-infected disc is left in the A: drive). Although not considered totally reliable, a manual check can give a good indication as to how your system will behave when the year 2000 ticks over. The basic procedure involves setting the system clock to one minute before midnight on 31/12/1999 and then observing what happens when the system rolls over into the year 2000. However, to properly determine the system’s behaviour, you need to test two conditions: (1) what happens if the machine is switched off during the rollover; and (2) what happens if the machine is left switched on during the rollover and then rebooted. First, boot from the floppy disc to the A: prompt and change the date and time to one minute before midnight on the December 31st 1999. You do this by first typing “date” (without the inverted commas) at the A: prompt and then typing in the new date (ie, 12-31-1999). This done, type “time” and change the time to 23:59. Note that this procedure not only changes the operating system clock but also changes the date and time in the BIOS and RTC as well. Now turn the PC off, wait a couple of minutes, then switch the machine back on and check the date, day and time in the BIOS (ie, CMOS) setup. PCs with non-compliant BIOSes will usually drop back to 01-01-1980 or to 01-01-1900 but some will go to 01-01-1994. Now exit the BIOS setup without making any changes, boot from the floppy disc and check the date – just type “date” (without the inverted commas) at the DOS prompt and hit the Enter key. If the BIOS previously indicated 01-01-1980, then this date will also be shown when you type “date” at the DOS prompt. However, if the BIOS previously reverted to 0101-1900, DOS 6.22 will change this to 4th January 1980 (04/01/1980). You can now check to see what Fig.8: Y2000RTC is another free diagnostic utility. You can either run Y2000.exe from DOS or Y2000W.EXE from Windows 3.1x or Windows 95/98. These three screen grabs show the test results from a typical 486 PC. happens when the machine is left on. Once again, boot from the floppy, change the date and time to a couple of minutes before midnight on 31st December 1999 and leave the machine running during the rollover. Now reboot the machine and check the date. If the machine is non-compliant, you will find that the DOS date will be incorrect after the reboot. Assuming a non-compliant system, try manually setting the date to the year 2000 (eg, 1/1/2000) in the BIOS setup, then switch the PC off and reboot from the floppy disc. Recheck the date in the BIOS setup, then allow the machine to boot to the A: prompt and check it again. If the year is still 2000, this means that you should only have to reboot the PC and manually alter the date in the BIOS setup once when the year 2000 arrives. After that, the machine should be OK. Finally, don’t forget to reset the date C-Time Rollover Talk to anyone with Unix, or a Unix related system, and they’ll probably be laughing while we PC and Windows users are sorting out the Y2K problem. Why? Well they usually (but not always) write software using a special date/time library (CTIME), in which dates start from 1970 and don’t run out until 18th January 2038. After that, they have a real problem, because the date resets to 1970 again! People using Unix can still have problems, as their appli cations might deal with dates in a 2-digit manner – so not all of them will be laughing at us. and time to the correct values before booting from the hard disc. TSRs & BIOS cards As indicated previously, some machines can revert to the year 1900 each time they are turned on. The only way around this problem is a BIOS upgrade, a TSR “fixup” routine or a new motherboard (it’s probably time to upgrade anyway). A TSR (terminate and stay resident) patch is basically a software routine that’s loaded via the autoexec.bat file when the machine boots. In operation, the TSR fix checks the date in the BIOS and applies a correction if a date prior to 1980 is returned. A TSR isn’t exactly foolproof though and might not work with some programs. It will also be lost if you reformat the hard disc drive (unless you remember to reinstall it), or can be inadvertently bypassed if you boot from a floppy disc or CD ROM. Alternatively, an add-on BIOS card which plugs into an expansion slot on the motherboard can be used to solve the problem in most machines. Its advantage is that the fix is permanent but it costs more than a TSR fix. Basically, the add-on card acts as an extension to the existing BIOS. It works by changing the century register in the RTC to 20 if a value of less than 80 is returned from the year register. However, as with TSR fixes, a BIOS card might not work with some programs. If your motherboard has flash BIOS, you may be able to download and upgrade the BIOS yourself. Just be sure to get the correct BIOS for your particular motherboard from the manufacturer’s web site. A word of warning, though – updating the BIOS is not a job for the novice. If you make a mess of things, you could end up with a machine that won’t boot. Another approach is to replace the BIOS chip itself. However, that may only be feasible if your machine is less than two or three years old. Test software A more reliable (and easier) way of testing your machine is to use one of the many commercial software packages that are now available. “Check How To Manually Test Your PC For The Year 2000 Step 1: Boot from a floppy disc created using DOS 6.22 or later. Step 2: type “date” (without the inverted commas) and change the date to 31-121999. Step 3: type “time” and change the time to 23:59 (ie, to one minute before midnight). Step 4: switch off, wait for two minutes, then reapply power and enter the BIOS setup. Check the date. If the year isn’t 2000, then your machine is non-compliant. Step 5: exit the BIOS setup without saving and allow the machine to boot from the floppy disc. Step 6: type “date”. Machines with non-compliant BIOSes will usually show either January 1st 1980 or January 4th 1980. Step 7: Reset the date and time to the correct values. January 1999 9 Fig.9: File Manager will display a garbled year for files created on or after 1st January 2000 if your version of winfile.exe is dated earlier than 11/3/97. A fix is available from Microsoft but be sure to download the correct version for your operating system. 2000 PC” from Greenwich Mean Time is one such example. This comprehensive package not only checks your PC for year 2000 compliance but can also fix any BIOS problems it does find using a BIOS fix utility (for most BIOS types, that is). It can also scan your applications and data files and offer advice on fixing any problems. Other commercial Y2K auditing tools include McAfee 2000 Toolbox, OnMark 2000 Access, Norton 2000 and Express 2000 Suite. There are also lots of utilities available on the Internet for checking whether your computer will correctly roll over to the year 2000. Many of these are free for personal use and are quick and easy to use. As well as checking for year 2000 rollover, many check other critical dates as well. One example is “DOSCHK.EXE” from Saphena Computing in the UK. The archived file can be downloaded from their website in less than a minute (see table for website address) and you simply copy the unzipped files to a directory on your boot floppy before running the program. Basically, the program takes the tedium out of having to manually reset the time and date and reboot the computer on several occasions. It’s also more comprehensive than the manual reboot test, since it separately tests the RTC, the BIOS and the operating system. A panel summarises the results at the end of the test (see Fig.7). Do You Really Have To Fix Year 2000 Problems? If you only use your PC at home to play games and/or for letter writing, you probably don't really need to worry about the Y2K problem. On the other hand, if the PC is used in business and to run date sensitive applications, then you really must take action to ensure Y2K compliance. If you don’t, you can run into all sorts of problems, particularly with accountancy, payroll, database and spreadsheet applications. In fact, the impact of non-compliant systems and applications 10 Silicon Chip on businesses could be extremely serious. Many businesses rely on the integrity of their data to function correctly and, unless Y2K problems are fixed, could lose money and even end up with financial difficulties. There are also the legal aspects to consider. In fact, this is a potential minefield that ranges all the way from companies taking action against suppliers to shareholders taking action against company directors that fail to adequately address Y2K issues. Another interesting millennium checker is Y2000RTC from Precise Publishing, another UK company. You can download Y2000rtc.zip (around 90KB) from their website and, after unzipping, run Y2000.exe from DOS or Y2000W.EXE from Windows 3.1x or Windows 95/98. Fig.8 shows the test results from a typical 486 PC. If problems are discovered, you can install a driver file which, according to Precise Publishing, solves the problem by correcting the RTC. Precise Publishing even state that it can fix the “94” problem associated with Award 4.50G BIOSes. This driver file isn’t included in the free test program but has to be purchased separately. YMARK2000 from NSTL (USA) is also well worth downloading. This interesting utility does more than just check the year 2000 rollover. It also checks for correct leap year support for the years from 2000-2009 and checks the RTC for compatibility with the Motorola MC146818 chip (if the RTC isn’t compatible, non-DOS operating systems and programs that read the clock directly may fail). In addition, YMARK2000 checks to see if the date can be set manually if the rollover to the year 2000 fails. By the way, all the above diagnostic programs test the RTC, which invariably fails except on the very latest machines. Howev e r, as discussed above, the CMOS RTC date is unimportant unless you have one of those rare programs that accesses it directly. It is the BIOS date that really matters. Yet another interesting diagnostic program is Test2000 from RighTime in Miami. This program first carries out a real-time BIOS rollover test. It then resets the date to 29-02-2000 and reboots the machine to see if valid year 2000 BIOS dates are retained (the BIOS retention test). The results are shown on-screen and are also written to a text file called Test2000.tst on the root directory of the hard disc. If the machine is non-compliant, Test2000.tst indicates whether the problem can be fixed using a proprietary utility program (Y2KPCPro). 29th February 2000 The year 2000 is a leap year but apparently not all systems or applications will recognise it as such and will miss the day altogether. Such systems will incorrectly roll from 28th February 2000 to 1st March 2000. The reason for this confusion is that the year 2000 is a special case that occurs once in every 400 years. The rule is that a year is a leap year if it is divisible by four but not by 100. However, there is an exception – if the year can be divided by 400, then it is a leap year. Confused? Let’s look at the year 1900. This is divisible by four and by 100 but not by 400, so it wasn’t a leap year. However, the year 2000 is divisible by 400, so it is a leap year. As a result, many sources suggest that the system be checked to ensure that it rolls correctly from the 28th to the 29th February 2000 and from there to 1st March 2000. In fact, most year 2000 diagnostic utilities automatically check the system to ensure that the leap year will be handled correctly. That said, there’s a wealth of opinion that states that the leap year problem doesn’t exist since the standard RTC automatically provides for a leap year if the year is divisible by four. This means that the year 2000 will be correctly interpreted as a leap year but it won’t hurt to check anyway. Y2K web sites There’s a wealth of information on the World Wide Web on the Y2K problem and it’s well worth visiting some of the sites listed in the accompanying panel. In addition, you will be able to obtain a list of other suspect dates. It’s also a good idea to check out the web sites for your BIOS supplier and your computer (and/or motherboard) supplier. They will have tested many more dates and times than you would normally be able to check and may have patches or BIOS updates available for older PCs. One site that’s well worth checking out is www.microsoft.com/year2000 This large site hosts detailed infor mation on Microsoft operating systems and applications and includes Y2K fixes that you can download and apply to any problem programs. It also has links to year 2000 “White Papers”, a sec tion with frequently asked questions (FAQs), and links to external suppliers and companies offering Y2K diagnostic utilities. Yo u s h o u l d a l s o c h e c k o u t www.year2000.com and the NSW Government’s site at www.y2k. gov.au If, after all this, you still feel complacent about the prob- Year 2000 BIOS Card From Microgram Computers: All You Have To Do Is Plug It In The “FIX-IT 2000/CI-5050 Millennium Card” from Microgram Computers is designed to solve the year 2000 rollover problem in PCs with non-compliant BIOSes. It features it’s own real time clock (RTC) and an enhanced BIOS chip to ensure that the year 2000 rolls around correctly. The card is easy to install – it simply plugs into a spare ISA slot on your PC’s motherboard. Onboard jumpers allow you to set the I/O port and ROM BIOS addresses but in most cases the default settings will be OK. A nifty feature is an on-board lem, check out Gary North’s site: www.garynorth.com Operating systems Fortunately, Microsoft’s operating systems are either year 2000 compliant or compliant with minor issues. They all store and manipulate dates in 4-digit formats and all correctly recognise 2000 as a leap year. What this means is that Microsoft operating systems won’t break down when the year 2000 rolls around, although you may discover a few CMOS backup facility. This allows you to save the CMOS settings from the motherboard and restore them later if necessary. The settings may either be restored manually or automatically each time the system is powered up. This is designed to overcome corruption of the CMOS settings, either due to viruses or end-user mistakes. The FIX-IT 2000/CI-5050 Millennium Card costs $129 (incl. tax) and is available from Microgram Computers, Unit 1, 14 Bon Mace Close, Berkley Vale 2261. Phone (02) 4389 8444; fax (02) 4389 8388; or email sales<at>mgram.com.au. quirks. For example, the File Manager included with Windows 3.1x, Windows For Workgroups and the early releases of Windows 95 will display a garbled year for files created on or after 1st January 2000. The year 2000, for example, displays as 19:0, while 2020 displays as 19<0. Note, however, that these are only display artefacts; the underlying system date is handled correctly. Basically, your File Manager will have the garbled date problem if your winfile.exe file is dated earlier January 1999 11 There’s Lots More To The Year 2000 Problem! This article is intended as a general guide to the Year 2000 problem only and is by no means exhaustive. Because of the wide variations that exist in computer hardware, operating systems and applications, it is impossible to offer specific advice that covers all situations. If you are involved in any sort of business that operates computers, then you cannot afford to ignore the year 2000 problem. In particular, it’s vital that you seek than 11/3/97. A fix is available from the Microsoft year 2000 website – just be sure to download the correct version for your operating system, as follows: w31filup.exe for Windows 3.1x, wfwfilup.exe for Windows For Workgroups, and w95filup.exe for Windows 95. Even Windows NT Workstation 4.0 has some quirks and various fixes are available. However, the problems are all of a minor nature and most users won’t even notice them. What ever your operating system, visit the manufacturer’s web site and check out the details for yourself. Applications This is where the fun really begins. Just because your hardware is Y2K compliant, it doesn’t mean that your applications will behave as expected. professional help in overcoming year 2000 problems and that all systems and applica t ions be thoroughly tested well before 2000 rolls around. Please note that Silicon Chip Publications Pty Ltd makes no claims as to the reliability or completeness of the various test procedures described in this article. Nor do we make any represent ations regarding the suitability of the diagnostics utilities referred to for your particular situation. In particular, applications that specify the year using just two digits can cause problems and that particularly applies to spreadsheet, accountancy, payroll and database programs. As an example, if a date in a spread sheet is specified as 21/10/27, how is this interpreted? Is the year 1927 or 2027? It all depends on the application but the wrong result could easily make a mess of superannuation calculations or of any calculations that rely on future projections. In fact, a file can even give different results when opened in different versions of the same application. It’s important to ensure that your applications are year 2000 compatible and that the data is interpreted correctly. Many spreadsheet and data base programs rely on Windows itself to set the default date display format. Fig.10: many applications rely on Windows itself to set the default date display format. For this reason, it’s a good idea to set the Windows short-date display to “d/MM/yyyy” via the Regional Settings applet in the Control Panel. 12 Silicon Chip For this reason, it’s advisable to set the Windows short-date display to “d/MM/yyyy” using the Regional Settings applet in Control Panel – see Fig.10. Check with the software supplier. Do they have a certificate of compliance or some other guarantee that your software will work correctly? Do you need to upgrade? Answers to these questions are best provided by the company that produced the software. Once again, check the manufacturer’s web site for Y2K information; it may be possible to make your software compliant by downloading and applying patches. Often, however, it will be better to upgrade your applications to the latest versions and apply any patches (if necessary) from there, particularly for applications that are used in business. What if things don’t comply? If you’re running outdated software on an old 486 machine, it’s probably best to go for a completely new system. You might even consider donating the old 486 to a school so that students can learn valuable computer skills. The Typequick website (see panel), includes a link to help you get in touch with schools that are interested in receiving “retired” PCs. It’s not sufficient just to bring individual computers and applications up to speed. If you are in business, you must con sider what happens when you exchange data with others, either via a local network, via email or by some other means. You also have to consider what happens if you exchange data between different applications. Look out for all the small things –things like third party add-ons, mac ros and formulae in spreadsheets and other applications. These can all have problems, especially if you’ve been using a 2-digit year format. They can even cause problems with applications that are, by themselves, year 2000 compliant. Finally, it’s important to realise that there’s no magic cure-all for the Y2K problem. Each site must be tested on its own merits and the appropriate solutions implemented. But even though most of the problems are wellknown, not many of the thousands of individuals specialising in the Y2K problem will give a 100% guarantee that their solutions will work without SC any hiccups. MAILBAG Antennas for UHF & VHF TV reception the socket to the pencil proved too much and we just put up with the poor picture and waited (apparently in vain) for the change to UHF. Then along came your article on the FM antenna in the March 1998 issue. As this would cover the bandwidth of Channel 3 it seemed an ideal solution. I constructed it as per your instructions and erected it with a diplexer above the bow-tie. Low and behold we get a perfect, interference-free reception of Channel 3 and, with a splitter, every FM station within 100km roars in. J. Lowe, Heatherbrae, NSW. Radio interference from power lines When I retired and moved to Heath erbrae (NSW) some 11 years ago, it was stated that all local TV channels telecasting from Mount Sugar loaf would move to the UHF band. Due to the stupidity of a previous government, or their advisers, Channels 3, 4 and 5 were allocated bandwidth in the international FM band. The first to move out was the ABC which moved from Channel 5 to the then new Channel 5A. Then very shortly afterwards they established a new UHF channel. Station NBN also was to vacate their spot in the FM band and move to UHF. On the strength of all this I built your bow-tie reflector UHF antenna which gave perfect results on UHF. I have been waiting ever since for NBN to close down their VHF transmitter and re-establish in the UHF band. The main reason is that there is some interference with their VHF signal here. My wife “discovered” that if the coax lead was removed from the wall socket and a pencil placed so that the pencil “lead” made contact with the inner socket, an excellent picture could be obtained if the setup was placed on the floor. The mind boggles! However, the nuisance of moving the coax lead back and forth from I must make a clarification of the Vintage Radio article in the November 1998 issue. I am referring specifically to the comment regarding interference from high voltage power lines. It is the mistaken belief by the majority of people within the trade that interference on high voltage power lines is caused by arcing. Whilst I was employed in the Department of Transport and Communications and its other names over a period of 23 years I did quite a bit of research on interference to radio, TV and radio communications reception, and methods of improving reception. The only time that an arc creates interference is at the instance the arc is established and when it is extinguished, not during the time that the arc is present. High voltage power line interference is caused by sparking, much the same as the spark coil in a car causes sparks. Arcs may well be produced as well but because of the oscillatory nature of the waveforms, there are many sparks. On HV power lines, there are both capacitive and resistive currents flowing over and through insulations, pins, cross arms, braces, nuts and bolts, etc between phases. If this current is constant, no interference is produced. However, interference is produced if within this leakage path there is a spot/area that has a high re- sistance but a low dielectric strength. Sparks will be produced across or through this area once the breakdown voltage is exceeded, towards the peak on each half wave. Interference will be produced where there is any abrupt change in the current flowing. The harmonics of the basic 100Hz mains interference (every half cycle) can extend to hundreds of megahertz in many cases. Generally, the majority of interference occurs where wooden high voltage transmission poles are used. As the wood dries out it shrinks and the hardware becomes loose, which often gives a discontinuous leakage path between phases. Instances like the high insulation resistance but weak dielectric strength areas as mentioned in the previous paragraph occur. These sparks are often inside the cross arms and initially when dew or rain falls, the conductivity on the outside of the pole and its hardware struc t ures increases, resulting in increased interference as the area with the weak dielectric has a greater amount of sparking across it. This will continue until the area with the weak dielectric is completely wet and then all the discontinuities that cause the interference will be removed. It is usually found that the interference increases as the dew settles then suddenly ceases late in the evening once these discontinuities are wet. To overcome these discontinuities the hardware on the high voltage section of the wooden pole is tightened and the problem usually disappears. The interference is more likely in the summer and autumn periods where the pole hardware is dry and has shrunk. With sustained rain, interference is rare except where cracked insulators or faulty high voltage surge diverters are evident. With salt-encrusted HV hardware and insulators, the resistive current is greater than what it would be on inland installations. There can be a substantial loss of power in some locations due to this high leakage. R. Champness, Benalla, Vic. January 1999 13 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 Build this: High-Voltage Megohm Tester This high-voltage insulation tester can measure resistances from 1-2200MΩ. It is battery powered and displays the readout on a 10step LED bargraph display. By JOHN CLARKE Y OU CAN USE this Megohm Tester to check the insulation of your 240VAC mains appliances, high voltage capacitors and high value resistors. As well, it can be used as a Go/No Go Tester for testing Voltage Dependent Resistors (VDRs, also known as MOVs or metal-oxide varistors). In a pinch, it could also be used to check SCRs and Triacs (high voltage blocking test). It uses an inbuilt inverter to generate a high voltage which can be selected as 100V, 250V, 500V, 600V & 1000V and the insulation reading is indicated on a bargraph display (dot mode) using an LM3914 display driver. These days, virtually all appliances are operated from the 240VAC mains supply, either directly or stepped down to a lower voltage using a transformer. However, for all its 18 Silicon Chip Fig.1: this block diagram shows the basic building blocks of the Megohm Meter. It uses a step-up converter to generate the test voltage. A voltmeter with a LED bargraph display shows the results. advantages there is a downside to electricity and that is its potential to kill. Under normal circumstances, if appliances are well-insulated and correctly earthed, there should not be any cause for concern about safety. However, should there be an insulation breakdown within an appliance, there is the possibility that the appliance can become dangerous. This is particularly true for earthed items where this connection has failed, which is why safety switches are a good idea. There is, however, no substitute for an appliance which has excellent insulation between Active and Earth and between Neutral and Earth. This is where the SILICON CHIP Megohm Tester comes into play because it allows you to check the integrity of the appliance insulation under high voltage conditions. It operation, the tester applies a high voltage (up to 1000V) between the terminals being checked and accurately displays the insulation resistance up to 2200MΩ. You could of course use an ordinary multimeter to check the insulation but this isn’t a valid test. This is because a multimeter only produces a very low test voltage (around 1.5V) and most insulation breakdown occurs at much higher voltages. By applying a high voltage between the test points, the Megohm Tester overcomes this problem. Another problem with a multimeter is that it will only show overrange for “good” insulation measurements rather than an actual value of the resistance. This is because insulation resistance measurements usually result in readings of hundreds of Meg ohms rather than the nominal 20MΩ maximum value for a multimeter. So an ordinary multimeter cannot really tell you how good the insulation is and nor can it test under high voltage conditions. Naturally, the appliance being tested must be unplugged from the mains socket during the test procedure. Note, however, that the on/off switch on the appliance itself may have to be switched to the ON position, in order to get a valid reading. If this isn’t done, the mains switch will effectively isolate the Active and Neutral wiring inside the device from the Main Features • • • • • • • • • LED bargraph display Five test voltages from 1001000V Measures from 1MΩ to 2200MΩ (2.2GΩ) Can test VDRs and MetalOxide Varistors (MOV) Battery operated Overrange indication External voltage indication Discharge path for charged capacitors Overcurrent trip-out at 10mA test leads and give misleading results. Note also that the Megohm Tester only checks the integrity of the insulation between Active and Earth and between Neutral and Earth. It doesn’t check the integrity of the Earth connection itself. This means that if the Earth connection has failed (eg, there’s a break in the Earth lead), the unit will usually in dicate the overrange (OR) condition. The point here is that if you are checking a mains ap pliance, you should always independently check the integrity of the Earth connection itself by some other means, either a multimeter switched to a low Ohms range or a continuity tester. Main features As can be seen from the photos, the SILICON CHIP Megohm Tester is a self-contained unit with just a few self-explanatory controls. It can measure high values of leakage resistance for six different DC test voltages: 100V, 250V, 500V, 600V and 1000V. In addition to checking mains insulation, it can also test capacitors for leakage. A 10-LED bargraph display is used to indicate the leakage resistance, while a 3-position range switch selects either x1, x10 or x100 scale readings, thereby allowing measurements from 1-2200MΩ. The measurements are made via insulated external test leads. The front panel also includes an indicator which shows whether there is an external voltage present between the two test points. The output impedance is low enough to discharge any capacitors which may pose a nasty shock hazard after the test procedure – see panel. The Megohm Meter is also fitted with an overcurrent trip circuit. This immediately shuts down the high voltage supply if the current through the probes exceeds 10mA. This current setting is sufficiently high to prevent nuisance tripping when measuring insulation resistance but low enough to prevent the probes causing a bad shock if you accidentally get across them. Block diagram Refer now to Fig.1 for the block diagram of the Megohm Tester. It is powered by a 9V battery and this is stepped up to the required high voltage using a transformer in a January 1999 19 Fig.2: this is the full circuit diagram for the Megohm Meter. IC1, a TL494 switchmode converter IC, is used to drive step-up transformer T1 via Q1, Q2 and Q3 to produce the test voltage. IC2a provides the 10mA overcurrent trip feature, while IC3 functions as a high-impedance buffer amplifier stage for the LED bargraph display driver (IC4). 20 Silicon Chip switchmode configuration. The high voltage output is then applied to the Test switch (S4) and is also monitored via resistors on switch S2a to derive a feedback voltage. This feedback voltage controls the switchmode supply so that it automatically maintains the selected output voltage. Test switch S4 (a pushbutton type) is wired so that it normally selects the external voltage indicator circuit. This means that LED13 lights if an external voltage is present across the test points. This indicator circuit will also discharge the external voltage if it has been stored in a capacitor. When S4 is pressed, the high voltage supply is switched through to the positive test terminal instead. Any leakage current between the positive and negative test leads is then fed to a current-to-voltage converter which is simply a resistance selected via Range switch S3. The resulting voltage is then fed to a high input impedance voltmeter circuit which is calibrated to display the resistance across the test terminals. This voltmeter circuit consists of an amplifier stage based on op amp IC3 plus a LED bargraph display based on IC4. Note that this is no ordinary voltmeter since it cannot draw any significant current via the test terminals, otherwise false readings will occur. In fact, a simple calculation will tell us just how small the currents flowing between the test terminals are. Let’s assume a 1000V test voltage and a 2000MΩ (2GΩ) resistance between the test terminals. In that case, the current will be only 500nA (500 x 10-9). The same resistance at 100V will give a current of just 50nA. Op amp IC3 provides the high input impedance for the voltmeter circuit, while IC4 drives the LED bargraph display. This display uses 10 LEDs to form the bargraph plus an overrange LED which indicates that the next range should be selected. Finally, the 10mA trip circuit monitors the current through the current-to-voltage converter. If the current exceeds 10mA, the trip circuit shuts down the high voltage supply. Pressing Reset switch S5 restores the supply to normal operation. Circuit details Fig.2 shows the full circuit of the Megohm Tester. It uses four ICs, a Fig.3: the top trace of this scope readout shows the gate drive to Mosfet Q1 when the 100V test voltage range is selected, while the lower trace shows the waveform for the 1000V range. Note how the pulse width increases for the higher test voltage. small transformer, Mosfet Q3 and a handful of other components. The high voltage output is produced by using IC1 to switch step-up transformer T1. It does this via Mosfet Q3 and buffer transistors Q1 & Q2. IC1 is a TL494 switchmode controller which incorporates a nominal 5V WARNING! This Megohm Meter is capable of charging capacitors to very high voltages (up to 1000V). Depending on their value, such capacitors are capable of providing a severe electric shock which, in some circumstances, could even prove fatal. For this reason, always allow the capacitor to fully discharge via the External Voltage LED after releasing the Test switch. This involves leaving the test leads connected to the capacitor until the LED has fully extinguished. Finally, use your multimeter to confirm that the capacitor has fully discharged before disconnecting the test leads. reference, an internal oscillator, two op amp error amplifiers and two output drivers. The outputs can be used in either push-pull or single-ended mode but in our application, we have used the latter configuration. The RC components at pins 5 & 6 set the oscillator frequency to around 22kHz. The outputs appear at pins 9 & 10 and drive buffer transistors Q1 & Q2 which in turn drive Mosfet Q3 to switch T1. The step-up converter uses the two windings in transformer T1 to produce up to 1000VDC. When Q3 is turned on, current flows through the primary winding via the 9V supply. When Q3 is subsequently switched off, the voltage across the primary is stepped up in the secondary winding and delivered to a .0056µF 3kV capacitor via diodes D1-D3. These diodes are rated at 500V each and so together provide greater than the required 1000V breakdown voltage. The voltage across the .0056µF 3kV capacitor is sampled via a voltage divider consisting of two series 4.7MΩ resistors and a resistor selected by S2a. The sampled voltage is then fed to pin 16 of IC1. This pin is the non-inverting input (+IN2) of an internal error amplifier which monitors the sampled voltage. The gain of this op amp stage is set January 1999 21 Parts List 1 PC board, code 04301991, 87 x 135mm 1 front panel label, 90 x 152mm (note: two versions available – see text) 1 plastic case, 158 x 85 x 52mm 1 SPDT toggle switch (S1) 1 2P6W rotary switch (S2) 1 2P3W slider switch or 1P3W (S3) 1 SPDT momentary pushbutton switch (S4) (Altronics S1393) 1 SPDT momentary pushbutton or SPST push-to-close switch (S5) 1 red banana panel mount socket 1 black banana panel mount socket 2 insulated test leads with banana plugs and insulated probes 1 10kΩ horizontal trimpot (VR1) 1 9V alkaline battery 1 9V battery holder 1 EFD30 transformer assembly (T1) 1 150mm length of red hookup wire 1 150mm length of blue hookup wire 1 150mm length of yellow hookup wire 1 150mm length of green hookup wire 1 400mm length of mains rated wire 1 5m length of 0.25mm ENCW 1 100mm length of 0.8mm tinned copper wire 1 19mm knob 16 PC stakes Semiconductors 1 TL494 switchmode controller (IC1) 1 LM358 dual op amp (IC2) 1 TL071, LF351 op amp (IC3) by the 4.7kΩ resistor between pins 15 & 14 (the +5V reference) and by the 4.7kΩ and 1MΩ resistor in series between pins 15 & 3. The associated 0.1µF capacitor rolls off the response above about 1.5Hz, while the unfiltered 4.7kΩ resistor allows the op amp to respond quickly to sudden changes. The op amp output is at pin 3 and is 22 Silicon Chip 1 LM3915 log bargraph driver (IC4) 2 BC337 NPN transistors (Q1,Q4) 1 BC327 PNP transistor (Q2) 1 MTP6N60E 600V N-channel Mosfet (Q3) 1 BC557 PNP transistor (Q5) 2 3mm red LEDs (LED11,LED12) 1 10-LED bargraph (LED1LED10) (Jaycar ZD-1700 or 2 x Altronics Z 0179) 1 bi-colour LED (LED13) 3 1N4936 fast recovery diodes (D1-D3) 4 1N4148, 1N914 switching diodes (D4-D7) Capacitors 3 100µF 16VW PC electrolytic 5 10µF 16VW PC electrolytic 1 0.22µF MKT polyester 1 0.1µF MKT polyester 1 .001µF MKT polyester 1 .0056µF 3KV ceramic Resistors (0.25W 1%) 2 4.7MΩ 1 W 1 15kΩ 1 1MΩ 1 12kΩ 1 820kΩ 4 10kΩ 1 430kΩ 1 9.1kΩ 1 180kΩ 3 4.7kΩ 2 100kΩ 2 2.2kΩ 1 91kΩ 1 1.8kΩ 1 82kΩ 1 1.2kΩ 1 75kΩ 3 1kΩ 1 56kΩ 1 680Ω 3 47kΩ 1 180Ω 1 43kΩ 3 100Ω 1 39kΩ 1 27Ω 2 33kΩ 1W 1 1Ω 1 22kΩ Test resistors 2 10MΩ 1 x 3.9MΩ 1W (see text) 1 15kΩ also compared internally with a sawtooth waveform which operates at the oscillator frequency. This frequency is set by the 47kΩ resistor on pin 6 and by the .001µF capacitor on pin 5. The resulting pulse width modulated signal appears at pins 9 & 10 (E1 & E2) of IC1. This drives pushpull pair Q1 & Q2, which in turn drive the Mosfet (Q3). If the voltage on pin 16 of IC1 rises above the +5V reference, the duty cycle of the pulse width waveform reduces to lower the output voltage across the .0056µF capacitor. Conversely, if the voltage on pin 16 goes below 5V, the duty cycle increases to increase the output voltage. As a result, the high voltage output is regulated so that the voltage on pin 16 of IC1 equals the voltage on pin 14 (ie, +5V nominal). Thus, when S2a is in position 1, the division ratio is 43kΩ/(4.7MΩ + 4.7MΩ + 43kΩ) = .00455. So if the reference voltage is 4.75V (minimum value) the output voltage will be regulated to 4.75/.00455 = 1043V. Note that we offer a method of reducing this value later on in the article should the voltages be more than 10% high. Similarly, the other four switch positions give regulated output voltages of (nominally) 600V, 500V, 250V and 100V. The 10µF capacitor at pin 4 of IC1 provides a “soft” start for the high voltage converter circuit. When power is first applied to the circuit, pin 4 is initially pulled to the +5V reference via the capacitor. This prevents any pulses from appearing at pins 9 & 10. The pulses then begin to appear and gradually widen as the capacitor charges via the 4.7kΩ resistor to ground. Full regulation of the output voltage occurs once the capacitor has fully charged. 3V supply A +3V reference is required for the remainder of the circuit and this is derived from the +5V reference via a voltage divider consisting of 10kΩ and 15kΩ resistors. The resulting +3V rail is filtered using a 10µF capacitor and applied to pin 3 of op amp IC2b which is wired as a voltage follower. Its output appears at pin 1 and is decoupled using a 100Ω resistor. A 100µF capacitor provides further filtering for the resulting +3V reference. When Test switch S4 is pressed, the test voltage is applied to the positive (+) test terminal. As a result, a leakage current will flow between the positive and negative test terminals (ie, between the test points) and through one of three pairs of resistors selected by Range switch S3. This leakage current also flows through the 100Ω resistor between the wiper of S3 and the +3V refer- The PC board can accommodate either two 5-LED bargraph displays (as shown here) or a single 10-LED display. Make sure that all parts are correctly oriented and note that Mosfet Q3 (near transformer) is bent over so that it will clear the front panel. ence. The voltage developed across this resistor (and thus the current through it) is monitored by pin 5 of op amp IC2a (via the associated 47kΩ and 2.2kΩ series resistors). Pin 6 of IC2a is biased to +4V by the 10kΩ and 39kΩ voltage divider network between the +5V rail and ground. If the current through the 100Ω resistor rises above 10mA, the voltage across it will be greater than 1V. When added to the 3V reference, this means that the voltage on pin 5 of IC2a rises above +4V. IC2a is wired as a comparator and so its pin 7 output now switches high. This does three things. First, it turns on transistor Q4 which in turn lights LED11, the overcurrent indicator. Second, it pulls pin 16 of IC1 high via diode D4, which shuts down the high voltage supply. And third, it pulls pin 5 of IC2a high via D5 so that the comparator (IC2a) is latched with its output high. Normal circuit operation can now only be restored by pressing the Reset switch (S5). This pulls the voltage on pin 5 of IC2a below the voltage on pin 6 and so pin 7 switches low and the switchmode converter starts working again. Voltmeter circuit As indicated previously, IC3 and IC4 form a high-impedance voltmeter. IC3 (TL071) functions as a buffer amplifier which monitors the voltage across the resistors selected by S3. This op amp offers a very high input impedance of about 1,000,000MΩ (1TΩ) and has a nominal 200pA input current. The gain of IC3 is x10 for the 1000V position of S2b and x100 for the 100V setting. The remaining test voltage positions (250V, 500V & 600V) give gains between these two figures. These gain adjustments are necessary to compensate for the different currents that flow through the selected detector resistors when different ranges are selected. The 0.22µF capacitor between pins 2 & 6 rolls off the frequency response above about 0.8Hz, thereby filtering out any hum pickup. The 100kΩ input resistor at pin 3 protects the input from damage if the test terminals are shorted (even at the 1000V setting), Specifications Test voltages................................................... 100, 250, 500, 600 & 1000V Test voltage accuracy after adjustment...............................................<10% Display readings......................................1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22 Reading ranges...................................................x1MΩ, x10MΩ & x100MΩ Current drain................................................................ 50mA <at> 1000V out January 1999 23 Fig.4: install the parts on the PC board as shown on this wiring diagram. Note that the leads from the test terminals are terminated on the copper side of the PC board. Fig.5: (left) the wiring details for the step-up transformer. The 10turn primary is wound on first, followed by the 70-turn secondary – see text. 24 Silicon Chip while diodes D6 & D7 limit the input voltage swing to 0.7V above and below the 3V supply. VR1 is the offset adjustment. It allows the output at pin 6 to be trimmed to 3V under no-signal conditions. S3 is used to switch one of three series resistor pairs in series with the 100Ω resistor on its wiper, to give the x1, x10 and x100 ranges. Position 1 selects a total of 128Ω, position 2 selects 1.28kΩ and position 3 selects 12.78kΩ. At first glance, these may appear to be unusual values. However, they have been selected to correspond to the 1.28V full-scale reading for the LM3915 LED bargraph driver (IC4). IC3’s output is applied to the pin 5 input of IC4 via a 1kΩ resistor. IC4 is a logarithmic LED bargraph display driver, connected here to drive LEDs 1-10 in the dot mode. Each step represents 3dB (ie, a 1.41 ratio), giving a total range of 30dB. The internal reference is 1.28V and this sets the maximum sensitivity of the display. The overrange indicator circuit relies on the fact that when IC4 overranges, all the LEDs are off. By including a 100Ω resistor in series with the commoned LED anodes, the voltage across it can be monitored using PNP transistor Q5. When a LED is on, the voltage across the 100Ω resistor is greater than 0.7V and so Q2 is biased on. This shorts out LED12 and so the overrange indicator is off. However, if all the LEDs are off (ie, when IC4 overranges), the voltage across the 100Ω resistor is zero and Q5 is off. This removes the short from across LED12, which now lights via its 1.8kΩ current limiting resistor. LED13 is the “External Voltage” indicator. This bicoloured LED is wired in series with two 33kΩ 1W resistors between Test switch S4 and the +3V reference. Normally, one side of LED13 is directly connected via S4 to the positive test terminal. If there is an external voltage at the test terminals, current can flow from the positive test terminal, through LED13 and the 33kΩ resistors, and back to the negative test terminal via the resistors selected by switch S3. The LED glows red for DC voltages of one polarity and green for DC voltages of the opposite polarity. If an AC voltage is present, both colours will come on together to display orange. Note that the LED will begin to glow SMART FASTCHARGERS® 2 NEW MODELS WITH OPTIONS TO SUIT YOUR NEEDS & BUDGET Now with 240V AC + 12V DC operation PLUS fully automatic voltage detection Use these REFLEX® chargers for all your Nicads and NIMH batteries: Power tools  Torches  Radio equip.  Mobile phones  Video cameras  Field test instruments  RC models incl. indoor flight  Laptops  Photographic equip.  Toys  Others  Rugged, compact and very portable. Designed for maximum battery capacity and longest battery life. AVOIDS THE WELL KNOWN MEMORY EFFECT. SAVES MONEY & TIME: Restore most Nicads with memory effect to capacity. Recover batteries with very low remaining voltage. CHARGES VERY FAST plus ELIMINATES THE NEED TO DISCHARGE: charge standard batteries in minimum 3 min., max. 1 to 4 hrs, depending on mA/h rating. Partially empty batteries are just topped up. Batteries always remain cool; this increases the total battery life and also the battery’s reliability. DESIGNED AND MADE IN AUSTRALIA For a FREE, detailed technical description please Ph: (03) 6492 1368 or Fax: (03) 6492 1329 2567 Wilmot Rd., Devonport, TAS 7310 Fig.6: check your PC board for defects before mounting the parts by comparing it with this full-size etching pattern. for external voltages of about 30V and will be fully lit at 240V. Basically, this circuit is intended to discharge any residual voltages that may be left following the test procedure. This can commonly occur when testing capacitors for leakage or if an internal capacitor in the appliance being tested is charged to the test voltage. Power for the circuit comes from a 9V battery via switch S1. There are several 100µF and 10µF capacitors across the supply and these are used to decouple the 9V rail. Construction The SILICON CHIP Megohm Tester is built on a PC board coded 04301991 and measuring 87 x 135mm. Fig.4 shows the assembly details. Begin construction by checking the PC board for any defects by comparing it with Fig.6. This done, install PC stakes at the external wiring positions. These are located at the (+) and (-) battery wiring points, the wiring points for S3 and the (+) and (-) output terminal points. Next, install the links and resistors. Table 2 shows the resistor colour codes but we recommend that you check each value on your digital multimeter just to make sure. The ICs and diodes can now be installed, taking care to ensure that each part is correctly oriented and that it is in the correct location. This done, install trimpot VR1 and the capacitors (the electrolytics must be correctly oriented), followed by the transistors. Note that transistors Q1, Q2, Q4 January 1999 25 Use medium-duty hook-up wire for the leads to the test terminals and keep them separated as shown here. The leads from the 9V battery holder are also terminated on the underside of the board. and Q5 should all be mounted close to the PC board. Just push them down onto the PC board as far as they will comfortably go before soldering their leads. Don’t get these transistors mixed up – there are three different types involved here. Mosfet Q3 is mounted using its full lead length so that it can be bent horizontally over transistors Q1 and Q2, to allow clearance for the case lid (see photo). Note that its metal tab faces transformer T1. Now for the switches. First, cut the shaft for S2 so that the knob can be pushed down close to the threaded collar. This done, lift the locking tab located under the nut and star washer and rotate it to position 5. Finally, solder the switch to the PC board and check that there are now only five positions available for this switch. Switches S1, S4 & S5 are also directly mounted on the PC board. Note particularly that S4 and S5 Table 1: Capacitor Codes ❏ ❏ ❏ ❏ ❏ Value 0.22µF 0.1µF .0056µF .001µF IEC 220n 100n 5n6 1n 26 Silicon Chip EIA 224 104 562 102 must be oriented correct l y, with their common (COM) pins located as shown (S4 goes in with its COM terminal towards the bottom edge of the board, S5 with its COM terminal towards the top). If you are using a 2-pin push-toclose switch for S5, then solder it in with its pins in the COM and NO positions. Transformer winding Fig.5 shows the winding details for transformer T1. It is wound on an EFD30 former using 0.25mm enamelled copper wire (ENCU). The primary winding goes on first. Strip back the insulation on one end of the wire using a hot soldering iron and terminate this end on pin 1 of the former. Now wind on 10 turns side-by-side in the direction shown on Fig.5 and terminate the free end on pin 5. Cover the primary winding with a layer of insulating tape. The secondary begins at pin 9 and must also be wound in the direction shown. You will need to wind on the 70 turns in several layers. Cover each layer with insulating tape before winding on the next and terminate the winding on pin 6. The transformer is now completed by sliding the cores into each side of the former and securing the assembly with metal clips. Finally, install the completed transformer on the PC board, making sure that it is oriented correctly; ie, pin 1 to top left. The LEDs can now all be installed at their appropriate locations but don’t solder them just yet – that step comes later. Once again, these must be oriented correctly (the anode lead is the longer of the two). The exception is LED13 which can really be installed either way around. Two different bargraph displays can be used in this cir cuit: (1) a single 10-LED bargraph from Jaycar; or (2) two 5-LED bargraphs from Altronics. Which ever type you use, be sure to install the bargraph with its LED anodes to the left, as shown on Fig.4. Splay the leads slightly so that the bargraph remains in position but again leave the leads unsoldered. Final assembly The Altronics bargraph is slightly longer than the Jaycar bargraph, so we have designed two different front panel labels to suit. Just choose the appropriate front panel for your bargraph. Affix this panel to the lid of the case, then drill and file the holes for the LED bargraph, LEDs11-13 and switches S1-S5. You will also have to drill two holes in one end of the case for the output terminals. These should be positioned near the bottom of the case, to provide clearance for the PC board. Table 2: Resistor Colour Codes ❏ No. ❏ 2 ❏ 1 ❏ 1 ❏ 1 ❏ 1 ❏ 2 ❏ 1 ❏ 1 ❏ 1 ❏ 1 ❏ 3 ❏ 1 ❏ 1 ❏ 2 ❏ 1 ❏ 1 ❏ 1 ❏ 4 ❏ 1 ❏ 3 ❏ 2 ❏ 1 ❏ 1 ❏ 3 ❏ 1 ❏ 1 ❏ 3 ❏ 1 ❏ 1 Value 4.7MΩ 1MΩ 820kΩ 430kΩ 180kΩ 100kΩ 91kΩ 82kΩ 75kΩ 56kΩ 47kΩ 43kΩ 39kΩ 33kΩ 22kΩ 15kΩ 12kΩ 10kΩ 9.1kΩ 4.7kΩ 2.2kΩ 1.8kΩ 1.2kΩ 1kΩ 680Ω 180Ω 100Ω 27Ω 1Ω As shown in the photos, the PC board is mounted on the lid of the case and is secured by nuts on the switch collars. Before mounting the board, it will be necessary to first run short lengths of hookup wire to slide switch S3. This done, secure S3 to the lid using its mounting screws and install one nut on each of S1, S4 & S5. The lid can now be fitted over the switches and secured by installing the nut on rotary switch S2 and by fitting extra nuts to S1, S4 & S5. If necessary, adjust the nuts on the underside of the lid so that the lid is parallel to the PC board. Once the lid has been secured, push the LED bargraph and the separate LEDs into their respective holes, then solder their leads. All that remains now is to fit the battery holder and the test terminals to the case and complete the wiring. The battery holder can either be glued to the base of the case using epoxy ad- 4-Band Code (1%) yellow violet green brown brown black green brown grey red yellow brown yellow orange yellow brown brown grey yellow brown brown black yellow brown white brown orange brown grey red orange brown violet green orange brown green blue orange brown yellow violet orange brown yellow orange orange brown orange white orange brown orange orange orange brown red red orange brown brown green orange brown brown red orange brown brown black orange brown white brown red brown yellow violet red brown red red red brown brown grey red brown brown red red brown brown black red brown blue grey brown brown brown grey brown brown brown black brown brown red violet black brown brown black gold gold hesive or secured with small screws. Use 250VAC-rated cable for the leads to the positive and negative test terminals and keep the leads separate to eliminate leakage between them. Note that the leads from the test terminal and from the battery holder terminate on the underside of the PC board. Testing It will probably be easier to check voltages on the PC board if it is detached from the lid. A word of warning here – don’t touch any part of the circuit during the test procedure otherwise you could get a nasty shock from the high-voltage converter. To test the unit, install the battery, apply power and check that either a bargraph LED or the overrange (OR) LED lights. If this doesn’t happen, check that the LEDs are oriented correctly. Now check the supply voltages. 5-Band Code (1%) yellow violet black yellow brown brown black black yellow brown grey red black orange brown yellow orange black orange brown brown grey black orange brown brown black black orange brown white brown black red brown grey red black red brown violet green black red brown green blue black red brown yellow violet black red brown yellow orange black red brown orange white black red brown orange orange black red brown red red black red brown brown green black red brown brown red black red brown brown black black red brown white brown black brown brown yellow violet black brown brown red red black brown brown brown grey black brown brown brown red black brown brown brown black black brown brown blue grey black black brown brown grey black black brown brown black black black brown red violet black gold brown brown black black silver brown There should be about 9V across pins 1 & 8 of IC1, pins 4 & 8 of IC2, pins 4 & 7 of IC3 and pins 2 & 4 of IC4. In addition, check for about 3V between TP2 and the negative side of the battery. Now switch the unit off, select the 1000V or higher range on your multimeter and connect the positive lead of the meter to the cathode of D3. Reapply power and check for the correct test voltages as selected by rotary switch S2. If the voltages are all high by about 10% or more of the correct value, substitute a 3.9MΩ 1W resistor for one of the 4.7MΩ resistors. Assuming that all is correct so far, switch off again, connect your multimeter between test points TP1 & TP2 and select the DC mV scale. Set the Range switch on the Megohm Meter in the x1 position and slowly adjust VR1 until you obtain a 0mV reading. You can now check the calibration January 1999 27 Fig.7: here are the full-size front panel artworks for the Megohm Meter. The panel at left suits the Altronics 5-LED bargraph displays, while the panel at right suits the Jaycar 10-LED display. by connecting the test terminals to a 20MΩ resistor (ie, two 10MΩ resistors in series). Select the x1 Range and press the Test switch. The display should indicate either 16MΩ or 22MΩ. Check that you get the same reading for all the test voltages, as selected by S2. The current trip circuit can be tested by connecting a 15kΩ resistor across the test terminals. Select the 100V position and press the Test switch; the display should read below 1MΩ. Now select the 250V position and press the Test switch again. This time, the overcurrent trip LED should light. The display should also show a reading but this should be ignored. 28 Silicon Chip Pressing the Reset switch (Test switch released) should extinguish the overcurrent LED and restore normal operation. Once all the tests have been completed, attach the lid and install the unit in the case. Testing capacitors If a capacitor is being checked for leakage, be sure to select the correct test voltage (ie, do not exceed the capacitor’s voltage rating) and always wait until the capacitor charges before taking the reading. If necessary, hold down the Reset switch if the overcurrent trip LED lights, to override this feature. Note that the lowest test voltage is 100V. This means that the Megohm Meter is not suitable for testing low-voltage electrolytic capacitors. Take care with fully charged capacitors since they can give a nasty electric shock. Always discharge the capacitor after testing by releasing the Test switch with the probes still connected. When you initially release the Test switch, the External Voltage LED will light to indicate that the capacitor is charged. Wait until this LED has extinguished before removing the test probes. When checking appliances, always check that the earth is intact by measuring with your multimeter between the earth pin on the mains plug and the metal body of the appliance. You SC should measure zero ohms. SATELLITE WATCH Compiled by GARRY CRATT* Panamsat will enhance Pacific coverage PANAMSAT 8 Panamsat 8 was successfully launch ed November 4 and com m enced testing late November from 166°E longitude. Although there were a few anxious moments when the much publicised live video coverage of the launch failed, the Proton launch was a complete success from the Baikonur Cosmodrome in Russia. The satellite will greatly enhance the coverage offered by Panamsat in the Pacific, though K band coverage appears to exclude PNG and New Zealand. LENOID METEOR SHOWER This much publicised meteor shower, caused by the close proximity of the Earth and the tail of Comet Tempel-Tuttle every 32 years, threatened to disrupt world satellite communications on November 17. Military satellite operators moved satellites out of regular orbits in order to avoid possible damage, whilst the rest of the world waited for news of communications disruption. Fortunately, only 1000 or so particles entered the Earth’s atmosphere, far short of the previous estimates of 4000-5000 meteorites, providing viewers in New Zealand with a spectacular sight of “shooting stars”. Elsewhere in the Asia-Pacific region, cloud obscured the view from most locations. PANAMSAT 2 There have been many changes during the last few months on this satellite. NHK’s analog service finally ceased on October 30, leaving CNN as the only remaining analog service on this satel lite apart from several itinerant services. The BBC commenced operations on 3743MHz, vertical polarity, SR 21800, FEC 3/4, in preparation for their move from the California bouquet last December. A bouquet of 4 channels (LBC Latest Aurora Timetable For ABC & SBS Digital Services OPTUS B3 The latest Aurora timetable for the introduction of replacement digital ABC and SBS services are as follows. The project has been delayed many months by equipment incompatibility but these problems now appear to be resolved. Central Australia: December 10: Imparja, ABC NT, ABC SA commence digital operation. February 9: ABC NT BMAC service ends. February 26: ABC SA and Imparja BMAC service ends. North Eastern Australia: February 26: QSTV, ABC Qld and SBS Qld commence digital operation. May 6: QSTV, ABC and SBS NE beam BMAC service ends. South Eastern Australia: March 12: ABC and SBS commence digital operation. May 20: ABC and SBS SE beam BMAC service ends. Replacement ABC and SBS digital services are about to be introduced on Optus B3 – see panel below. Australia, RAI International, ART Australia and ANT 1 Greece) commenced early November on 3778MHz, vertical polarity, SR 13331, FEC 3/4. The service is due to be encrypted this month, as part of a commercial service. This bouquet replaces earlier tests conducted with an SR of 6619. ASIASAT 2 A new service called the “Fashion Channel” appeared late November on 3799MHz, vertical polarity, SR 2533, FEC 3/4. This is a weak signal and requires a very carefully adjusted dish system for good reception. Although testing at present, the service will bring MCM Rock and MCM Classical and one Jazz channel to Asiasat 2 sometime in the first quarter of 1999. This channel was previously carried on Hotbird 5, located over Europe. Viewers have also noted the demise of TVSN on this satellite. SC *Garry Cratt is Managing Director of AvComm Pty Ltd, suppliers of satellite TV reception systems. Phone (02) 9949 7417. http://www.avcomm.com.au January 1999 29 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. 9V battery checker This battery checker gives a simple Go/NoGo test for the common 9V battery in its alkaline and carbon-zinc forms. The advantage of the device is that, unlike a conventional DMM, there is no need to switch on, select the appropriate range, handle probes, interpret the reading and then switch off. It also applies a reasonable load current, something that does not happen when you test a battery with a multimeter. Yes, there is a simple battery checker with a visual display on the market but its display is imprecise. The circuit described here can be adapted to a wide range of voltages but is presented to suit a standard 9V type such as an Eveready 216. IC1 is an ICL7665 under/over voltage detector in an 8-pin package. It has two internal comparators, essentially independent of each other but sharing the same reference voltage (1.3V). Each comparator has two outputs which can change state, depending on the actual voltage being measured. The input for comparator 1 is at pin 3 while the input for comparator 2 is pin 6. Trimpots VR1 and VR2 are used to set the battery voltage above and below which the respective comparator outputs will turn on their associated LEDs. In practice, VR1 is set so that LED1 turns on for battery voltages of 8V or more. VR2 is set to turn on LED2 for battery voltages below 7.5V and LED3 comes on at times when the battery voltage is between 8V and 7.5V. Naturally, you can select lower set voltages for VR1 and VR2, depending on your battery requirements. Resistor R3 sets the load test current at around 20mA, to which must be added the current drawn by LED1, LED2 or LED3. The ICL7665 itself draws only a few microamps. Another version of this circuit was used to test 9V nicad batteries but the load test current was increased to 0.5A. This is far too heavy for a pushbutton switch, so the load test button was used to apply base current to a power transistor with an 18Ω 5W resistor in its collector circuit. Ben Critchley, Elanora, NSW. ($25) lates at about 0.5Hz, as set by trimpot VR1, and alternately flashes LED1 and LED2. IC2, an LM3905, commences its timeout cycle as soon as power is applied and its pin 7 output goes high to apply power to the positive side of the buzzer. However, the buzzer can only sound when pin 3 of IC1 is low; ie, only at those times when LED1 is alight. After about 45 seconds, as determined by the setting of trimpot VR2, IC2’s pin 7 output (NPN emitter) goes low and so the buzzer is turned off. Reverse current through the buzzer is prevented by diode D1. R. Sewell, Annandale, NSW. ($25) Timed audible alarm This simple alarm circuit could be used with the 12V SLA battery charger featured on page 20 of the December 1998 issue. Alternatively, it could be used anywhere an audible alarm needs to be sounded for a defined period, after which a visual alarm indication continues. Once triggered, the alarm will sound for about 45 seconds and continues to alternately flash two LEDs until the power is removed. The circuit consists of a 555 timer (IC1) operating as an astable mul tivibrator. This is used to alternately switch red and green LEDs. An LM3905 timer (IC2) operates in the timeout mode to switch off the audible alarm. In normal operation, the 555 oscil30 Silicon Chip Balanced input & bridging module This circuit can be used for bridging both channels of a stereo amplifier or two mono amplifiers. The circuit uses a TL074 quad op amp and 1% metal film resistors should be used throughout to ensure simultaneous clipping levels and identical overall response from both outputs. Op amps IC1a and IC1c provide the balanced to unbalanced conversion, while IC1d is an inverting stage. Switch S1 provides selection from a stereo or mono source. If unbalanced input operation is required, simply ground the inverting (-) input terminals and connect the signal between the non-inverting (+) terminals and GND. S. Williamson, Hamilton, NZ. ($30) PC stake crimper the PC board, crimp the end and presto – it won’t fall out. You then solder it and it will not fall out when you attempt to solder wires to it. This PC stake crimper was made out of a worn-out pair of long-nosed pliers. The noses were ground off using an electric grinder first and the remaining noses were given a flat edge. While doing this job, it is important to regularly dip the pliers in water to keep them cool, otherwise the steel will lose its temper. The accompanying photo and diagram shows the tool and how the stakes should be crimped and soldered. The stakes should be crimped to about twice their original diameter, not paper-thin. Alex Mattill, Hampton Park, Vic. ($30) Here is a solution to a problem that many electronics enthusiasts have with PC stakes. You solder it in, but when you go and solder a wire onto it, nine times out of ten the heat causes the solder on the stake to melt and it either comes off, or ends up askew to the board, looking rather unprofessional. Worse still, you may get a dry solder joint on the stake or the wire. The solution is this PC stake crimper. You insert the stake into Low current shunt regulator This circuit will provide a reference voltage adjustable between 0.9V and 2.5V. Apart from the lower voltage, the regula tion is much better than a 3.3V zener and its operation starts at only 1µA. The “knee” characteristic is also quite sharp. If the voltage is set to 1.1V at 2µA, it rises to 1.11V at 250µA up to 2mA, 1.12V at 8mA and 1.16V at 70mA. A BD140 could replace Q4 if higher Circuit Ideas Wanted power was needed. D1 provides temperature compensa t ion and should be thermally bonded to Q1. A. March, North Turramurra, NSW. ($25) Do you have a good circuit idea. If so, why not sketch it out, write a brief description of its operation & send it to us. Provided your idea is workable & original, we’ll publish it in Circuit Notebook & you’ll make some money. We pay up to $60 for a good circuit but don’t make it too big please. Send your idea to: Silicon Chip Publications, PO Box 139, Collaroy, 2097. January 1999 31 Getting Going With BASIC Stamp In these days of 32-bit microprocessors handling millions of instructions per second and running at speeds in the hundreds of MHz, why on earth would anyone want to use a strange 14-bit processor which can only handle BASIC programs no bigger than 256 bytes . . . and screams along at just 2000 BASIC instructions per second? The answer is simple: because you CAN! Or is it because YOU can! To program most microprocessors you need to be an expert in machine language code. Not so with the BASIC Stamp. If you know BASIC, you should be able to program it to do, well, whatever you want to (as long as you can do it in 256 bytes!). Even if you don’t know BASIC, it’s not too hard to learn. You’d know what D-I-Y stands for, of course. Now the BASIC Stamp lets you T-I-Y (think it yourself) before you D-I-Y. But what is this BASIC Stamp, anyway? You’ve probably heard of PIC microcontrollers. Made by Microchip (USA) and intended for control use, they’re found in countless applications and sold in the millions upon millions (bet your computer mouse even has one in it!). In normal applications, they’re programmed once and that’s it. As versatile as they are for original equipment manufacturers, though, PIC chips are not particularly useful for hobbyists and experimenters; at least not in their own right. That’s where the BASIC Stamp comes in. Back in 1993, Chip Gracey (no kidding, his name is Chip!) of the US company Parallax combined a 16C56 PIC microcontroller with a 93LC56 electrically erasable PROM, loaded in a BASIC interpreter, enabled 8 input/output ports and a few other goodies... and the BASIC Stamp was born. The version of the BASIC Stamp 1 we are using is supplied as a self-contained module, housed on a tiny (36 x 10mm) PC board and terminated to a row of 14 header pins at 0.1-inch spacing. These mate with either a standard 14-pin header socket or even half of a by ROSS TESTER & BOB NICOL* 32 Silicon Chip 28-pin IC socket. Components are all surface mount types which means it’s just as well you don’t have to do any assembly (no pun intended) on the BASIC Stamp PC board. The reason it is called the BASIC Stamp is that the original design fitted onto a PC board the size of a postage stamp. Today it’s just a tiny bit larger with a few more components. Fig.1 shows the circuit diagram of the BASIC Stamp. In fact, this is slightly different to the model we are using because ours also has an onboard 5V regulator, allowing supplies of up to 15V or even higher. Because of its very low drain (1-2mA, ignoring input/output or I/O requirements), it is eminently suitable for battery operation (a 9V battery will last for weeks). In real-world applications the I/O current cannot be ignored, so a 9VDC plugpack of a few hundred milliamps or so is generally preferred. Speaking of I/O, any of the eight pins will source up to 20mA or sink up to 25mA, with the proviso of a total loading of 40mA (source) or 50mA (sink). This makes the BASIC Stamp capable of directly driving LEDs, piezo buzzers, speakers and even some sensitive relays. With buffering, of course, much more can be driven. For programming, the BASIC Stamp connects to the parallel port of any IBM-compatible personal computer running good, ol’fashioned DOS. That’s right, you don’t need Windows – 1, 2, 3, 95, 98, NT, 2000 or any other derivative. And when we say any PC, we mean any PC – here’s a good reason to fire up the old XT or 8088-based machine that’s been languishing in the garage for 10 years! (Of course, if you want to use the latest Pentium II 450, go right ahead. Better still, we’ll swap you a perfectly good XT and throw in a Sydney Harbour Bridge ...) Sure, the BASIC Stamp will only handle 256 bytes of programming (around 80-100 instructions). But in these days of long-winded and often superfluous coding, that teaches you to be efficient, even miserly! We mentioned before that it is programmed in BASIC. That’s not strictly true; it’s Parallax’s own version of BASIC called PBASIC. The structure is much the same except that lines of code are not numbered, they’re labelled. However, if you know good old garden variety BASIC (in any of its forms) you shouldn’t have too much difficulty with PBASIC. PBASIC has a suite of 33 commands. The usual BASIC ones such as GOTO, FOR-NEXT, IF and so on are there but there are a few new ones necessary for the Stamp’s role as a logic controller chip. Any command works with any I/O pin. If you don’t know BASIC, here’s the perfect opportunity to learn. It’s a lot simpler than trying to learn machine language, C or other more recent languages. (BASIC, including a detailed manual, was supplied with most computers up until about the ’386 days. If you don’t have a copy, it can be picked up for a song or even a few notes). The BASIC Stamp PC Board Having waxed eloquent about the BASIC Stamp’s features, the way it is supplied is rather inconvenient to use, not to mention risky. Taking the latter point first, the BASIC Stamp sells for around $80 yet, as far as we can tell, contains no reverse polarity protection (despite the on-board regulator). Our first reaction was how we would feel if we’d just spent eighty bucks and saw it disappear in a wisp of smoke . . . As far as incovenience goes, you obviously have to be able to interface to the microprocessor board – somehow. In the past, we’ve seen a number of designs in magazines using perforated strip board. We shudder. If you’re building up a $10 circuit, strip board might be good enough but remember, the BASIC Stamp is worth $80! To use strip board you have to cut tracks and it’s easy to miss one or more. It’s also very easy to short between tracks with copper swarf, especially using the old “big drill in small hole” track-cutting routine. No! Strip board is a definite no-no as far as we are concerned – especially for this type of project. The only logical solution was to design our own PC board which would not only accommodate the BASIC Stamp module, it would also allow us to include some other components which would make the whole thing that much more user-friendly. That includes reverse polarity protection and some on-board supply decoupling Fig.1: a somewhat simplified circuit diagram of the BASIC Stamp, with the or smoothing. actual module shown bottom right, same size. IC1 is a PIC microprocessor, Because of the previously-mennormally one-time-programmable but in this configuration receives its data from tioned limitations on the BASIC IC2, a 256-byte EEPROM (electrically erasable, programmable, read-only memory). Stamp I/O, we have included a An on-board 4MHz ceramic resonator sets operating speed. The ‘‘brownout’’ circuit ULN2003 buffer. This is a 7-way shown top left automatically resets the device if the supply falls below 4V. January 1999 33 The SILICON CHIP version of the BASIC Stamp experimenter's kit. The thicker lead ending in the DB-25 plug connects to the parallel port on any IBM-compatible PC. The thin lead is for power – in this case a 9VDC plugpack. The close-up photo of the PC board itself reveals a 16-way pin header (which allows connection to all BASIC Stamp pins), reverse-polarity protection diode and power supply decoupling capacitor, the BASIC Stamp module (end-on in its 14-way header socket), the ULN2003 buffer IC and a variety of input sensor devices and output devices – LDR, 10-turn trimpot, piezo buzzer, LED and DPDT relay. Also provided are plenty of I/O pads for further experimentation. open-collector Darlington driver which has a maximum collector current of 350mA or 500mA (depending on brand) for each buffer so it can drive significantly larger loads. We’ve also included a double pole change over (DPDT) relay, driven by one of the ULN2003 outputs. And before anyone thinks we’ve forgotten the usual suppression diode across the relay contacts, each of the ULN2003 outputs has one built in. Jumping ahead of ourselves, the ULN2003 gets quite hot – no, very o hot. But it's rated at 150 C so there's no great problem. Just thought we'd warn you in advance! There’s also a LED, an LDR, trimpot and piezo buzzer mounted on the board. These will be used in some simple programs which you can use to try out the BASIC Stamp – before you start writing your own! Into the bargain, we’ve also included some spare tracks and pads which would accommodate other components for uses as yet undreamed of. Putting it together Assembly of the PC board is very simple, as it should be with just a handful of components. Start with the PC stakes (the relay outputs) then the Parts List for Timer Projects 1 BS1-IC BASIC Stamp module with stamp1.exe operating software, PC parallel port connection cable and power connection cable (see text) 1 ULN2003 7-way peripheral driver 1 1N4004 or similar diode 1 LED, any type 1 1kΩ 1/4W resistor 1 20kΩ, 10-turn vertical trimpot 1 light-dependent resistor 1 100µF 25VW electrolytic capacitor 34 Silicon Chip 1 12V mini relay with DPDT contacts 1 small piezo buzzer 1 PC board, 103x55mm, coded SC11301991 1 16-way header pin set, 0.1in spacing 1 14-way header socket, 0.1in spacing 3 (or 6) PC stakes (as required) 1 plugpack supply, approx 9-12V DC <at> 400-500mA output (to suit application) resistor, LDR, LED and diode – their pigtails will give you the wire you need for the link and the two connection wires for the piezo buzzer. It’s probably a good idea to fit the socket terminal strip and pin header next, before any of the larger components start crowding the board. The socket can go either way around. Ideally, the pin header and the sockets on the power and output leads should be marked some way so that they will never be incorrectly connected. We used some bright red nail polish to paint a red stripe on the base of the third pin in from one end of the header, and some quick-drying paint to put a stripe on the next (fourth) pin. We used yellow ’cause we had some. We painted matching stripes on the output lead socket (a red stripe on the + lead) and on the output lead socket (a yellow stripe on the end of the socket with the green wire attached. In retrospect, green would have been a better colour to use!). If you don’t have any paint, try coloured correction fluid. When later connecting the sockets to the pin header, it’s just a matter of connecting colour to colour. Having marked the pin header in this way, it must be mounted with the marked pins closest to the diode (the red pin, marking the positive supply, actually lines up with the diode). The pins are closely spaced, so check very carefully between each pad after soldering for dags shorting out pads. If necessary, use a multimeter or a magnifying glass. Next the large components – the relay, trimpot and electrolytic capacitor – can be soldered in place, followed by the piezo buzzer. As the photograph shows, this is mounted edge-on to the PC board with the pins connected to vertical wires soldered to the appropriate PC pads. After checking thoroughly, carefully insert the BASIC Stamp module into the 14-way socket. Take care that all pins actually go into the socket and mate properly – it’s easy to bend them. It’s also easy to insert the module backto-front: make sure the components on the module face the input socket. STAMP EXPERIMENTER'S BOARD Figs.2 & 3: the circuit (above) and PC board layout (below) for BASIC Stamp experiments and circuit development. With the components shown either the simple or complex timer can be built but the large number of spare pads make adapting this exclusive SILICON CHIP design very easy. What else do you need? Now that you’ve finished the BASIC Stamp PC board you’re just itching to get going, right? Whoa! It’s simple, but not quite THAT simple. There are a few more things you'll need. First and foremost, you need software that will allow your PC to communicate with (and program) the BASIC Stamp. For BASIC Stamp 1 (which we are using) the software is stamp1.exe. You’ll also need connecting cables and, unless you’re already a wizz at PBASIC and programming, some form of driving instructions. Fortunately, there’s an easy way to get all this in one package. Dick Smith Electronics stores stock the BASIC Stamp Development kit which contains all of the above for less than $150. It also includes a certificate entitling you to three months free technical support. The BASIC Stamp manual, by the way, is more than 460 pages thick so it’s no lightweight. It contains 23 application notes to try out and also contains information on the higher spec’d BASIC Stamp II. Fig.4 (below): use this PC board layout to make your own board or to check commercial boards. The pattern is also available for download (in Adobe PDF format) from the SILICON CHIP website: www.siliconchip.com.au January 1999 35 Both these books from Dick Smith Electronics will be invaluable for anyone interested in the BASIC Stamp. A Few Stamp FAQs Before we conclude our look at the BASIC Stamp, we’ll try to answer a few FAQs (for those not into webspeak, that stands for frequently asked questions). ‘‘Programming and Customizing the BASIC Stamp Controller’’ (left, $77.95) has nearly 300 pages with many BASIC Stamp projects to try. It also includes a CD-ROM with a variety of software tools and the BASIC Stamp applications, along with the stamp1.exe software. “Can the program storage memory be increased?” No, the PBASIC interpreter only addresses 8 bits of program space, which results in the 256-byte limitation. Using a larger EEPROM won’t make any difference. It is possible to use external memory for storing lookup tables and extra data – you’ll find information on this in the BASIC Stamp manual. “Can the BASIC Stamp support floating point maths?” No, it only works with integer maths, which means fractions are out. If your program required the BASIC Stamp to divide 7 by 2, it would give you the answer 3, not 3.5. “Speaking of maths, how does the BASIC Stamp evaluate maths expressions?” Strictly left to right – not, as you might expect, following maths conventions. For example, a BASIC Stamp would evaluate 1+2x3 as 9, not 7. That is, it would work it out as (1+2)x3, not 1+(2x3). “What is the BASIC Stamp’s life?” Hard to say! A program is guaranteed to stay in memory for 40 years but there is a finite limit to the number of times the EEPROM can be reprogrammed. Fortunately, that limit is about 10 million times so you’re hardly likely to reach that in a hurry. However, swapping files to and from the EEPROM (in an effort to overcome the 256-byte limitation) could reach this limit much more quickly, so this is not recommended. “How do I get more than 25mA output current from the I/O lines?” You don’t – that’s one of the quickest ways to blow up the processor. That is precisely the reason we added the ULN2003 buffer: it can sink up to 350mA collector current per output (not 500mA as you might see claimed). If you drive all seven ULN2003 inputs gates from the BASIC Stamp I/O you'll still be under the 40mA maximum output limit. 36 Silicon Chip The ‘‘BASIC Stamp Manual’’ (below) is part of the BASIC Stamp Development Kit ($149) which also includes the cables and software. If you already have a working knowledge of the BASIC Stamp and don’t want to buy the Development Kit, an alternative would be to buy the programming cable (also available from Dick Smith Electronics – Cat K-1407 <at> $19.95). Another very handy reference is the Scott Edwards book, “Programming and Customizing the BASIC Stamp Computer” (you guessed where from – Cat B-4807 <at> $77.95). It contains a host of very detailed information, projects and even a CD-ROM of software tools including the stamp1. exe program. Meanwhile, back at the ranch ... Let’s assume you have the BASIC Stamp board completed, the programming cable to connect to your PC and copies of the experimental software. Ah! Experimental software – we haven’t mentioned that yet, have we? The experimental BASIC programs (as distinct from the executable stamp1.exe) are all listed overleaf. Simply type them as a text file in any word processor or text editor and save them with the names shown. But if you don't feel like doing all that typing, don't! All listings are available from the “Software Downloads” page on the SILICON CHIP website – www.siliconchip.com.au – and the best part of all is they are free! So before we get too much further down the track type out the software or log on to the website and download it. There are four programs – adjust. bas, test.bas, simple.bas and complex. bas. All four files come to less than 6kB so they’ll only take a few moments to download. That is, unless you want to explore the SILICON CHIP website while you’re there! OK, so we’re ready to go. The first step is obvious: connect the programming cable to the BASIC Stamp and to your PC’s parallel port. About now you’ll be starting to think "Perhaps I should have put the paint spots on those cables. Which way around do they go?" Plug in power and turn on the computer (the IBM compatible, that is). We mentioned a moment ago that the software is tiny. Even stamp1.exe is only 14kB. Therefore it is perfectly practical to run the BASIC Stamp software from a floppy-disc-only computer. Yes, we really did mean any IBM compatible! If you have a hard disc, of course, it’s preferable to run it from that, if only because you’ll never misplace the floppy disc. Create a directory called STAMP1 and copy stamp1.exe and the four BASIC programs into it. It makes sense to include the STAMP1 directory in your DOS “path” statement, especially if you’re going to be doing a lot of experimenting with files. Which ever you choose, floppy or hard disc directory, go to your DOS prompt and log on to that disc or directory. Load the operating software for the BASIC Stamp 1 module, stamp1.exe. Once stamp1.exe is loaded, you should have an almost blank, blue screen as shown overleaf. Fear not! You haven’t loaded one of Mr Gates’s blue screens of death. Your next step is to load the experimental BASIC programs which you downloaded. Just a reminder – these are just ideas to get your creative juices flowing. Once you’ve played with the BASIC Stamp, you could come up with a whole host of ideas! Where to get help The BASIC Stamp project described here and the accompanying software is, of necessity, very elementary – just enough to whet your appetite to develop bigger and better applications using this simple, yet clever little module. Because of its simplicity, we imagine that very few constructors will have any difficulties with this project as published but that may not be the case as you expand your horizons. So where do you go when you need help? If you buy the Dick Smith Electronics development kit, you will receive a certificate entitling you to three months software support through the Australian distributors, MicroZed Computers. This is available by phone (02) 6772 2777; fax (02) 6772 8987 or email – support<at>microzed.com. au Note that support is available for STAMP product and software obtained only through Dick Smith Electronics or MicroZed. You can also obtain information and support through the Microzed web site, www.microzed.com.au A great deal more information and backup support is available from the Parallax website, www.parallaxinc. com There’s even an evaluation copy of stamp1.exe to help you decide if you want to buy the real thing. As mentioned before, if you don't feel like typing them out the four PBASIC programs – adjust.bas, test. bas, simple.bas, and complex.bas – are all available from www.siliconchip. com.au; however technical support is not available from this website nor SC from SILICON CHIP magazine. * Bob Nicol manages MicroZed Computers, authorised Australian distributors of Parallax Inc's products. OVERLEAF: HOW TO LOAD THE SOFTWARE PLUS COMPLETE PBASIC LISTINGS January 1999 37 LOADING THE SOFTWARE Loading BASIC Stamp software is a three-part process: first load the application software (stamp1.exe) into your IBM-compatible PC; second load the PBASIC program (*.bas) from disc into your PC; third download it to the BASIC Stamp module. Load stamp1. exe from the DOS prompt (it doesn’t matter whether you do it from DOS itself or from a DOS Window. Our screen shots show the latter). A nearly blank blue screen should appear as above. Type ALT L (ie, hold down the Alt key and touch the L key at the same time). This will bring up a menu of the *.bas software in your STAMP1 directory. In this case we are choosing adjust.bas. Type ALT R to run.The program takes about a second (or less) to download to the BASIC Stamp and if all is OK, will run immediately. The histogram which appears shows how much BASIC Stamp memory is taken from total memory, the red or dark portion showing memory used. Once loaded, it stays until another is loaded. If there are ‘‘debug’’ lines in your PBASIC program they will show up on the first loading. 38 Silicon ilicon C Chip hip 38 S Setting the LDR – adjust.bas ’adjust.bas - LDR threshold setting - Silicon Chip January 1999 ’This short program allows setting of the LDR to an appropriate level ’LED is on pin 6 via ULN2003 Solenoid driver chip ’LDR is on pin 5, adjust the potentiometer, when LDR is in light ’then hold finger over LDR adjust so that LED goes off LOOP: LOW 6 IF PIN5 = 1 THEN LED GOTO LOOP ‘this segment looks at LDR ‘turn LED off ‘Goto subroutine named LED ‘go back to beginning, to look again LED: HIGH 6 ‘this segment turns LED on ‘this line does just that GOTO LOOP ‘go back to look at LDR again First of all, load the “adjust.bas” program. This lets you set the threshold of the LDR between light and dark. Now you can adjust the trimpot. If the LED is on, turn the pot anticlockwise to the point where it just turns off, then back again until it just turns on. Put your finger over the LDR and the LED should turn off. Note that this setting applies to the light levels in that room at that point – if you change locations you might need to run adjust.bas again. One point to keep in mind: the BASIC program loaded into EEPROM is going to stay there for a long, long time – it’s guaranteed for 40 years, even with power removed. It will also keep operating even if the PC which programmed it is turned off and/or disconnected. You can erase the contents of the EEPROM by loading another program – which is exactly what we are going to do now. The simple timer – simple.bas ’Simple.bas - Simple Timer - Silicon Chip January 1999 LDR: ’this segment looks at LDR LOW 0 ’turn relay off LOW 6 IF PIN5 = 0 THEN RELAY ’Goto subroutine named RELAY GOTO LDR ’go back to beginning, to look again RELAY: ’this segment turns relay on HIGH 0 ’this line does the job ’ HIGH 6 ’this line turns LED on too, to enable ’line remove first apostrophe in line PAUSE 20000 ’Stamp marks time for 20 seconds GOTO LDR ’go back to look at LDR again The simple timer is an example of a BASIC Stamp application which may or may not be particularly useful – but it’s an interesting example nevertheless. Do you have a deep cupboard or storeroom which doesn’t have a light of its own, or where the light can’t reach into the furthest corners? This BASIC Stamp program might solve that problem. It is designed to sit in a cupboard or room and sense when the cupboard or storeroom door is opened, allowing some light in. The LDR in the circuit senses the light and the microprocessor pulls in a relay (via the interface chip). This can then be used to turn on an additional light (battery operated?) in that dark corner. Overkill, when you can do the same thing with an LDR and transistor? Probably. But these applications are not intended to be so much practical as examples of what can be done with the BASIC Stamp. You will have noticed that no details are given for the connection to the light – that’s the easy part! Once again, follow the “adjust.bas” steps to load the software. Note that the additional light must not be in the field of view of the LDR, otherwise the system becomes a closed loop and the additional light will be locked on all the time. With the software as it stands, the light will stay on for 15 minutes. The BASIC Stamp test – test.bas ’Test.bas - test components on timer PCB - Silicon Chip January 1999 SOUND 7,(100,1000) ‘beep piezo sounder for 1 second HIGH 0 ‘relay on HIGH 6 ‘LED on TEST_LOOP: DEBUG “pin 5 getting logic “, #PIN5, “ from LDR”,CR IF PIN5 = 0 THEN ALL_OFF ‘turn everything off IF PIN5 = 1 THEN ALL_ON ‘turn everything on GOTO TEST_LOOP ‘tedious, but let’s do it again ALL_OFF: ‘this section of the program turns all devices off & beeps LOW 6 ‘LED off LOW 0 ‘relay off SOUND 7,(100,10) ‘one beep each time around GOTO TEST_LOOP ‘back to the tedious bit ALL_ON: DEBUG “ * * * * * * “, CR ‘separates DEBUG lines on screen HIGH 6 ‘LED on HIGH 0 ‘relay on SOUND 7,(120,5,120,5) ‘two short beeps each time around GOTO TEST_LOOP ‘back to the tedious bit This little routine puts all of the on-board components through their paces just to make sure everything is working properly. Apart from that, it doesn’t do very much except demonstrate how the program interacts with the hardware! Loading the program is exactly the same as loading the adjust. bas above, with the obvious exception of the program name! What this will do is sound the piezo buzzer for 2 seconds, light the LED, close the relay and pulse the piezo buzzer. It will stay in that state until you block the light to the LDR, when the LED goes out, the relay drops out and the buzzer tone drops and quickens. The complex timer – complex.bas (listing at right) Aunty Maud has left you with her much loved but rather delicate pot plant with strict instructions to water it every evening. Alas, you’ve forgotten it for the last three days and the pot plant is looking, well, not well. Wouldn’t it be nice if you had another brain to do it for you? BASIC Stamp has a brain! With the complex timer software loaded it will sense dusk, turn on the relay for a minute (or whatever other time you set from about 1/1000 of a second (!) right up to a minute – or more correctly, 65,535 milliseconds). That’s as the program is written – but if you wanted to, you could add extra “pause” statements and eventually drown the poor plant, the dog and the next door neighbour’s oak tree. The timer doesn’t trigger again until the next dusk. The program takes into account that night time is just a bit longer than the normal watering cycle of the system. And if you’re really clever in setting the LDR threshold and writing code, it could even detect full cloud cover and skip those days. It also takes into account daylight but will ignore a torch or car headlights flashed on it. It really does have a lot of features but there are many more which could be incorporated – it just depends on how clever you want to be at adapting the complex.bas program. Exactly how you water Aunty Maud’s pot plant is left up to you – there’s a relay output to turn on your ingenuity, we’re sure (or is that a mixed metaphor?). A windscreen washer pump or a valve connected to an overhead bucket are both ideas that spring to mind. But the purpose of this software is not so much to demonstrate what to do but how it can be done and modified to suit your requirements. Now, who's into hydroponics . . . These program listings are also available for downloading free of charge at the SILICON CHIP website: www.siliconchip.com.au COMPLEX.BAS - COMPLEX TIMER LISTING ’Program for Complex Timer - Silicon Chip January 1999 ’by Bob Nicol, MicroZed Computers ’DEBUG statements are used in this program. They show on your PC screen the first time 'you load the program and NOT when program is run again. ’DEBUG statements should be disabled with an apostrophe, and the program loaded to the 'Stamp again when you have finished editing and checking the program to suit your needs ’pin assignments and settings, plus some startup fiddles: ’PIN 0 output to pin 7 of ULN2003 to drive relay on pin 10 LOW 0 ’Make sure pin 0 is low LOW 1 ’PIN 1 Not used set low LOW 2 ’PIN 2 Not used set low LOW 3 ’PIN 3 Not used set low LOW 4 ’PIN 4 Not used set low INPUT 5 ’sets pin 5 as an input to accept LDR level ’PIN 6 output to pin 4 of ULN2003 to drive LED on pin 11 of ULN HIGH 6 ’turn LED on PAUSE 1000 ’leave LED on for 1 second LOW 6 ’Then turn LED off and make sure pin 6 is low ’PIN 7 output to piezo sounder SOUND 7,(100,200) ’make a noise on start up ’Variables ’B2 accumulates number of times LDR (PIN 5) is low ’B3 accumulates number of times LDR (PIN 5) is high ’B4 accumulates count for reset B2 ’W4 accumulates darkness events ’B5 Flags ACTION already done WAITING_FOR_CHANGE: ’This program module keeps looking at LDR ’and initiates action when LDR is dark ’long enough to be a valid condition DEBUG “PIN 5 IS “,#PIN5,CR ’shows if LDR on pin 5 is in dark(0) or light(1) DEBUG “LDR HAS SEEN DARK “,#B2,” TIMES”,CR ’shows on PC screen DARK / LIGHT DEBUG “LDR HAS SEEN LIGHT “,#B3,” TIMES”,CR ’counts in B2(DARK) & B3(LIGHT) PAUSE 1000 ’wait one second IF PIN5 = 0 THEN INCREMENT_D ’goto increment_D to add 1 to B2 IF PIN5 = 1 THEN INCREMENT_L ’goto increment_L to 1 to B3 B4 = B4 + 1 ’add 1 to B4 DEBUG “LDR has been looked at “,#B4,” times”,CR,CR PAUSE 1000 ’wait one second IF B4 > 5 THEN DECREMENT ’B2 hasn’t increased, go to DECREMENT ’to reset B2, B3 & B4 GOTO WAITING_FOR_CHANGE ’keep going around this loop INCREMENT_D: ’LDR has seen darkness DEBUG “INCREMENT DARK B2 “,CR,CR ‘PC screen shows we are in increment B2 = B2 +1 ’B2 gets one more added to it IF B5 = 1 THEN HOLDOFF ’intercept Action, already done IF B2 > 10 THEN ACTION ’LDR has seen at least 10 Dark signals GOTO WAITING_FOR_CHANGE INCREMENT_L: DEBUG “INCREMENT LIGHT B3”,CR,CR B3 = B3 +1 IF B3 > 10 THEN RESET_B5 GOTO DECREMENT DECREMENT: DEBUG “DECREMENT”,CR DEBUG “RESETING LDR STATUS”,CR,CR B2 = 0 B4 = 0 GOTO WAITING_FOR_CHANGE ACTION: SOUND 7,(60,100,80,100,100,100,120,100) DEBUG “ACTION, RELAY ON, LED ON”,CR,CR HIGH 0 HIGH 6 PAUSE 2000 LOW 0 LOW 6 B2 = 0 W4 = W4+1 B5 = 1 DEBUG “Darkness has occured “,#W4,” times”,CR GOTO WAITING_FOR_CHANGE HOLDOFF: DEBUG “ HOLD OFF UNTIL LIGHT SEEN” B2 = 0 GOTO WAITING_FOR_CHANGE RESET_B5: DEBUG CR,CR,” R E S E T B5 & B3",CR,CR B5 = 0 B3 = 0 GOTO WAITING_FOR_CHANGE ’get back to looking at LDR signal ’LDR has seen light ’B3 gets one more added to it ’seen enough light to make change ’reset dark and light variables ’there has been no valid darkness ’show on PC screen decrease happened ’set darkness count to zero ’set false counts to zero ’go back to looking at LDR signal ’Darkness criteria met, do something about it ’audible warning of action ’show on PC screen we are doing it ’turn relay on via ULN2003 ’turn LED on via ULN2003 ’stay that way for 2 seconds ’turn relay off ’turn LED off ’reset B2 ’keep count of times turned on ’show on PC screen count of events ’go back to looking at LDR signal ’this is a loop to stop action already taken ’show on PC screen ’reset B2 ’go back to keep looking at LDR ’Stop HOLDOFF cycling ’Show on PC screen ’when B5 is 1 HOLDOFF is used ’reset light counts ’go back and keep looking at LDR ANUARY 1999 39 1999 39 January WIND POWER On August 26th, 1998, Australia’s first grid-connected wind farm was officially opened near Crookwell, NSW. Using eight 600kW wind turbines, the $10 million wind farm can produce up to 4.8MW of electricity, enough to meet the average demand of several thousand homes and save up to 8000 tonnes per year of carbon dioxide emissions. by LEO SIMPSON Crookwell,on onthe theSouthern Southern Tablelands Crookwell, Tablelands in in Vestas Vestas Systems more or less a turnWindWind Systems A/S A/S more or less as aasturn-key NewSouth SouthWales, Wales,isis reputedly one of the most installation. New reputedly one of the most key installation. This company supplied the eight This company supplied the eight wind consistentlywindy windyplaces places in Ausconsistently wind turbines, the computerised turbines, the computerised montralia,which whichis iswhy why it it was chosen tralia, monitoring system oversaw itoring system andand oversaw the forthis this assembly assembly of of eight 600kW for the entire project. entire project. wind turbines. turbines. Calling Calling it it a wind wind The wind turbines turbines have have been been farm possibly possibly makes makes it it sound a farm installed on aa privately privately owned owned muchlarger largerproject project than than it really much grazing property carrying carrying sheep sheep butlet letus us hope hope it it is a precursor isisbut and cattle and will will not not affect affectthe the forthe the installation installation of of many more for farming activities activities in in any any way, way, windturbines turbinesin inAustralia. Australia. wind with the bottom of of the the blade blade arc arc Theentire entire project more than 20 metres The project has has beenbeen supmetres above above the the supplied byDanish the Danish company ground. plied by the company 40 Silicon Chip Fig. 1: this cut-away diagram shows the main components inside the nacelle of the Vestas 600kW wind turbine. By any standard, these 600kW wind turbines are large and stately machines. They are installed on a 45-metre high tubular steel tower and they have three blades with a rotor diameter of 44 metres. The choice of rotor diameter depends on the prevailing wind conditions at the site. For any given power rating, higher wind speeds mean a smaller rotor diameter while lower wind speeds require a larger dia meter, to enable the optimum output to be obtained. While consistently windy, the Crookwell site has relatively low wind speeds so it required the largest size rotors. The 3-bladed rotor drives a planetary gearbox which steps up the nominal rotor speed of 28 revs per minute to drive the 3-phase alternator at around 1560 rpm. The alternator’s output voltage is 690V AC and this is fed to a transformer near the base of the tower where it is stepped up to 11kV AC. The generated electricity is then sent to a substation where it is stepped up to 66kV for connection to the New South Wales grid. When seen from a distance, the large rotors seem to be rotating quite slowly. After all, 28 rpm is just a little less than one revolution every two seconds. However, when you see them up close, the reality is different. Since the rotor diameter is 44 metres, the blade tips are moving at no less than 230km/h. In fact each blade makes a very audible swish as it whizzes round. From further away, say 200 or 300 metres, the wind turbines are eerily silent, any slight noise they make being drowned out by the wind that drives them. Interestingly, the wind turbines require a certain minimum wind speed before they start generating. For this Vestas model, auto start-up occurs at a wind speed of about 15km/h but the turbine does not reach full power output until the wind speed hits about 54km/h. Above that speed, the generator output stays constant until the wind speed hits 72km/h (which is a real gale, 8 on the Beaufort scale). When the wind speed exceeds 72km/h, the blades are feathered, cutting out the generator to prevent damage. Fig.2 Technical data Vestas V44-600kW Wind Turbine Diameter 44m Swept area 1,521m2 RPM 28.5 Number of blades 3 Power regulation Pitch + OptiSlip Air brake Full-feathering Hub height 45m Start-up wind speed 4m/s Cut-out wind speed 2m/s Generator Asynchronous, 1500 - 1560 rpm Nominal power output 600kW, 50Hz, 690V AC 3-phase Transmission Planetary gear/parallel shafts Control Microprocessor-based monitoring of all turbine functions, plus OptiSlip regulation of output and OptiTip pitch regulation of the blades January 1999 41 Other wind turbine installations Crookwell is not the first wind farm in Australia although it is the first to be connected to the state grid. The first Australian wind farm was installed at Esperance in Western Australia some years ago. It consists of nine 225kW wind turbines, giving a maximum output of 2MW. There is also a pair of 225kW wind turbines installed on Thursday Island and a 150kW machine is running at Coober Pedy in South Australia. We have also seen a large wind turbine running near Newcastle. By the standards of other parts of the world, the Crookwell wind farm is a small project. In Europe in particular, wind farms with ratings of many megawatts are the norm. For example, in Denmark, the 24MW Rejsby Moor wind farm employs 40 wind turbines while in Carno in Wales, 56 wind turbines are installed. There are even large offshore installations. For example, Denmark has two offshore installations with 10 wind turbines installed off the east cost of Jutland. Presently, Vestas is involved in the commissioning of a large wind farm on the northernmost tip of the North Island in New Zealand, employing 48 660kW wind turbines. This is one of the windiest sites in the world, with average wind speeds of 11m/s (40km/h). Further information on wind power around the world can be obtained from CADDET, the Centre for the Analysis And Dissemination of Demonstrated Energy Technologies. This organisation was founded in 1988 by the International Energy Agency. They have two websites: (1). www.caddet-ee.org (2). www.caddet.co.uk Further information on Vestas wind turbines can be obtained at www.vestas.dk 42 Silicon Chip Fig. 2: the power curve for the 600kW wind turbines installed at Crookwell. Computer control prevents them starting up until the windspeed, measured by an anemometer mounted on the turbine body, reaches 15km/h. They are shut down (blades feathered and braked) when the speed exceeds 72km/h. shows the power curve of the 600kW turbine. Even with the auto cut-out system for high wind speeds, wind gusts still present a big problem for a large wind turbine. Sudden gusts are extremely tough on the mechanical components of wind turbines and can cause undesirable fluctuations on the grid. This problem has been solved by Vestas with a system called “Opti Slip”. Combined with the “OptiTip” pitch adjustment system, this allows the speed of rotation of both generator and rotor to vary by as much as 10% during a gust of wind. This not only helps eliminates flickering but also minimises the strain on the main components of the wind turbine.  If you would like to view the Crook well Wind Farm, it is on the left side of the Goulburn to Crookwell road about half-way between Pejar Dam SC and Crookwell. Minimising the effect of windspeed changes Harnessing wind power to generate electrical power has always had to face the practical reality that the wind doesn't always blow – and when it does, it is forever changing both strength and direction. Variations are not welcome in any generating system, especially one connected to the power grid. Electricity authorities go to great trouble to keep the supply voltage as constant as possible. The mini "weather station" on the tur- bine's tail keeps the blades facing the wind, while Vestas' proprietary "OptiSlip" design can compensate for a variation in blade rotational speed of up to 10%. The graphs above show actual measurements from a Vestas 600kW Wind Turbine demonstrate the varying relationship between windspeed and generator rpm over time. Note, though, that the output remains constant at 600kW, minimising fluctuations on the electricity grid. PRODUCT SHOWCASE New Fluke multimeters: rugged & affordable Philips has released two new rugged, reliable and affordable digital multimeters from Fluke, designed for the Asia-Pacific electronics market. Apart from the usual voltage-current-resistance-diode ranges, the Fluke Model 17 and 19 DMMs offer several of the most-wanted features for the electronics technician such as Min/Max/Average Record that captures the lowest and highest readings for recording power supply drift, line voltage changes or circuit performance while parameters are being changed. The DMMs have a wide AC voltage input bandwidth of 100kHz for accurate measurement of audio, video, monitors, and switching power supplies. They also feature autoranging, a frequency counter (0.5Hz-200kHz) and duty cycle measurement. Both meters are supplied with Fluke TL-19 test leads, a 9V battery and a User’s Manual. The new DMMs are designed and manufactured to the latest safety standards of IEC 61010-1, 1000V Overvolt-age Category I, 600V Overvoltage Category II. The Fluke 17 and 19 have been submitted for independent testing and certification to CSA and UL standards. For more information, contact Philips Test & Measurement, 34 Waterloo Rd, North Ryde, NSW, 2113. Phone (02) 9805 4486; fax (02) 9805 4170; E-mail TMI_Inquiry<at>philips.com.au You can also visit Fluke’s website at http://www.fluke.com Keep those cords tidy! Over the years many methods have been tried to contain messy cords. Most have failed. Now a new Australian product – Clipaway – claims to provide an easy and convenient solution to the problem. Clipaway clips come in a variety of sizes to suit all types of cord (even rope) up to 12mm dia-meter. They're available from Woolworths/Big W, BBC/Hardwarehouse and other leading retailers. Hybrid panel meters from Yokogawa This analog/ digital hybrid LCD meter from Yokogawa Australia features a bargraph consisting of 31 segments for representing 0-100% of full scale plus a 31/2 digit, 8mm 7-segment digital readout. Accuracy is 0.25% of indication, plus one digit. The display, model no 2302, is housed in a standard 96mm DIN package with a depth of only 48mm. It is backlit by a 12V halogen bulb for long life, uniform colour and brightness. Models are available as DC and AC voltmeters and ammeters, measuring mV to kV and mA to kA and a variety of other units. Special models are available on order. For more information contact Yokogawa Australia, phone (02) 9805 0699; fax (02) 9888 1844; email measurement<at>yokogawa.com.au Duratech soldering station from Jaycar This 60W Duratech Soldering Station, now available from Jaycar Electronics, has an adjustable temperature range of 150-450oC + 3 oC. For process applications the temperature dial can be locked in place with the Allen key supplied. The soldering pencil is of lightweight construction with a ceramic heater and has an extremely flexible silicone rubber cord. The robust case includes a stainless steel tray for storing spare tips (seven tips are supplied). It sells for $189 and comes with a 12-month warranty. For further details contact any Jaycar Electronics store or call the head office at 8-10 Leeds St, Rhodes, NSW 2138. Phone: (02) 9743 5222 fax: (02) 9743 2066 Radio frequency counter This lowcost 10MHz3GHz counter has no connections. All the operator needs to do is extend the telescopic antenna of the Aceco FC1001 and the 8-digit LCD shows the frequency of any transmitter in range with 100Hz resolution. Enquiries to Computronics Corp Ltd, Locked Bag 20, Bentley Business Centre, WA 6983. Phone (08) 9479 1177, fax (08) 9470 2844. January 1999 43 21-inch professional monitors from Hitachi Intended for high-end applications such as DTP, imaging, CAD and engineering is the new range of CM81X high-accuracy monitors from Hitachi. With up to 1856 x 1392 resolution, they offer Windows PnP setup. For further information contact Hitachi Australia Ltd, 13-15 Lyonpark Rd, North Ryde, NSW 2113. Phone (02) 9888 4100, fax (02) 9888 4188 NATA directory The National Association of Testing Laboratories (NATA) has released its 1998/99 Annual Directory of laboratories for companies wishing to test, calibrate, inspect or measure their materials, products or equipment. Almost 2500 NATA-accredited labs are listed. NATA accreditation is recognised worldwide. The A4-sized publication is priced at $140 and is available from NATA, 7 Leeds St, Rhodes, NSW 2138. Phone (02) 9736 8222, fax (02) 9743 5311. Fluke T2 Electrical Tester Safety Recall Philips Test & Measurement is recalling some Fluke T2 Electrical Testers to repair a potential product malfunction which may present a safety hazard to users. The malfunction is caused by corrosion of the battery contact to the PC board inside the Tester which can lead to intermittent operation. If the malfunction occurs, users may believe that no voltage is present when the reverse is true. This represents a safety hazard. Only Fluke T2 units with serial numbers less than 70524051 are affected and only then if they do not have the letter “R” stamped after the serial number. Those units have already been repaired. Customers with affected units should return them to the service/ calibration centre at Philips Test & Measurement (phone 02 9805 4486 for shipping arrangements). A sealant will be applied to the battery contact to prevent corrosion and the “R” will be stamped after the serial number. Philips Test & Measurement urges all owners to return their Fluke T2 instruments as soon as possible, even if they have not experienced any malfunction. For further information, contact Philips Test & Measurement Business Electronics Service Centre, 2 Green-hills Ave, Moorebank, NSW 2170. Phone (02) 9805 4486. Central Coast Amateur Radio Field Day One of the most-anticipated annual events in the radio and communication area, the Central Coast Field Day, is on again next month, on Sunday, February 28 at Wyong Race Course, Howarth Street, Wyong. Wyong is approximately one hour from Sydney via the Newcastle freeway with free off-street parking, or an electric train from Sydney stops only 5 minutes walk from the site. Admission is $10 or $5 concession. Organised by the Central Coast Amateur Radio Club Inc, the Field Day is Australia’s largest, with new and used radio and communications equipment for sale. The flea market and disposals areas are always popular, with bargains from both traders and other amateur enthusiasts. Many commercial communications organisations arrange special displays for the field day and there are also displays from clubs and groups with special interests ranging from vintage radio to satellite communications. For further information, contact the Central Coast Amateur Radio Club’s website, www.ccarc.org.au, or call the club on (02) 4340 2500. Upgrade Your Analog Phone to Digital For Minus $1.00 Dick Smith Electronics have come up with a pretty compelling argument for those who have not yet upgraded their analog mobile phone to digital. They will upgrade your analog phone to a new Philips ‘Twist’ digital, charge no connection fee, keep you on a $10 per month plan if you wish, automatically divert calls from your old analog number . . . and give you a dollar! It’s all part of a move designed to get existing analog users to upgrade to digital before the analog network is scrapped on January 1, 2000. According to DSE, there are more 44 Silicon Chip than 1.8 million analog phones still in use and even though extensive publicity has been given to the close-down, the changeover to digital needs a boost. In conjunction with Telstra's Budget 10 plan, Dick Smith Electronics will give $50 trade-in on a working analog phone. And with phone prices under this deal starting at $49 you could actually walk away with a new phone and a dollar in your hand! Other models available under the plan include a Motorola Jazz for $59, Panasonic G450 or Ericsson GA628 for $79 and a Nokia 5110 for $129 – all less the $50 trade-in. The most important feature of this plan, though, is the $10 monthly charge. It’s the first time digital phone users have had access to this low fee. Apparently this has been one of the main reasons low-usage analog phone owners have not converted to digital. To take advantage of this offer, contact any Dick Smith Electronics store. Users must stay connected to Telstra Mobilenet for a minimum of 24 months. Some other conditions apply to this offer. Further information is available at any Dick Smith Electronics store. 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 ORDER FORM BACK ISSUES MONTH YEAR MONTH YEAR PR ICE EACH (includes p&p) TOTAL Australi a $A7.00; NZ $A8.00 (airmail ); Elsewhere $A10 (airmail ). Buy 10 or more and get a 10% discount. Note: Nov 87-Aug 88; Oct 88-Mar 89; June 89; Aug 89; Dec 89; May 90; Aug 91; Feb 92; July 92; Sept 92; NovDec 92; & March 98 are sol d out. 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Please have your credit card details ready OR Fax (02) 9979 6503 Fax the coupon with your credit card details 24 hours 7 days a week Mail order form to: OR Reply Paid 25 Silicon Chip Publications PO Box 139, Collaroy 2097 No postage stamp required in Australia January 1999 53 A LED bargraph ammeter for your car Keep an eye on the charging and discharge of your car’s battery with this LED ammeter. It has 10 rectangular LEDs and will indicate charge and discharge currents up to 25 amps. No alterations need to be made to your car’s wiring as it monitors the voltage drop across the negative strap to the battery. Design by RICK WALTERS Very few cars these days have a “proper” ammeter; they just have a single idiot light to indicate that the battery is being discharged. But when it goes out, you have no idea of how much current is going into the battery and nor, for that matter, do you ever 54 Silicon Chip know how much current is being pulled out. Even when cars did have ammeters they were not what you would call a precision meter movement; they gave a very rough approximation of what was happening. Well, now you can im- prove on this situation with this LED ammeter. It has 10 rectangular LEDs, five green to indicate that the battery is being charged, and one yellow and four red to show discharge conditions. Each LED covers a range of 5A, so the display indicates from -25A (discharge) to +25A (charge). We used a yellow LED for the 0-5A discharge indicator as this will most likely be the one normally illuminated when the motor is not running or at idle. Every ammeter needs a shunt which is placed in the current path. In effect, the ammeter measures the voltage drop across the shunt which is a very low resistance. The question is “How do you install a suitable shunt in series with the battery?” The answer is that you don’t. There is already a shunt there in the form of the negative lead Fig.1: the circuit of this LED Ammeter works by monitoring the voltage drop across the negative battery strap. This will have a resistance of a few milliohms and so a current of say 20A will produce a voltage of around 40mV or so. This is amplified by IC1a and IC1b and then fed to the LM3914 to produce a LED dot display. from the battery to the car’s chassis. This lead will typically have a resistance of only a couple of milliohms but this is enough to produce a voltage to be measured by our circuit. It amplifies the voltage across the “shunt” and feeds it to a LED bargraph driver IC. Circuit details Fig.1 shows the circuit. Op amp IC1a monitors the voltage across the negative battery strap and amplifies by a factor of between 10 and 210, depending on the setting of trimpot VR1. The amplified voltage at the output of IC1a is fed to the inverting input of IC1b via a 2.2kΩ resistor. This op amp stage has a gain of 10 and the output is fed to the input of IC2, an LM3914 LED bar/dot linear display driver. IC2 needs an input voltage increasing from zero to 1.25V to sequentially light each LED at its outputs (pins 1 & 10-18). With that voltage range, the LEDS will switch for every 125mV increase in input voltage. The only problem is, we want to measure positive and negative currents so we effectively need a centre-zero display. This would correspond to the voltage where the fifth LED is about to turn off and the sixth LED is about to turn on. This “centre-zero” voltage corresponds to +625mV (ie, 5 x 125mV) so we need the output of IC1b to be sitting at this voltage when the battery is not being charged or discharged. This is done by feeding a portion of the 1.25V internal reference of IC2, which is available at pin 7, to pin 5, the non-inverting input of IC1b. The amount of this input offset to pin 5 is set by the voltage divider resistors, 22kΩ, 1kΩ and 160Ω. Another offset voltage which must be dealt with is the DC voltage at the output of IC1a when it has no input voltage (ie, no charge or discharge current to the battery). This output voltage will change over a wide range as trimpot VR1 is altered. Accordingly, trimpot VR2 is included to inject an equal and opposite voltage into the inverting input of IC1b (pin 6) to cancel this effect. To recap, with the battery receiving no charge or discharge, the input to IC1a will be zero volts and the voltage at the non-inverting input of IC2 will be half the reference voltage at pin 7 of IC2. This will cause LEDs 5 and 6 to light. When the battery is being charged, one of LEDs 6 to 10 will illuminate depending on the charging current. Conversely, if the battery is being discharged, one of LEDs 1 to 5 will light, depending on the current being drawn. Actually, there will be times when there is a transition from one LED to the next and so two adjacent LEDs can be on. At night the LED display is dimmed, whenever the car’s headlights are turned on. PNP transistor Q1 has its 8.2kΩ base resistor connected to the headlight switch. When the headlights are turned, Q1 turns off to reduce the current flowing through the LEDs. The initial brightness of the LEDs is set by the 680Ω resistor from pin 6 of IC2 to the emitter of Q1. The night-time brightness is reduced by switching off Q1, which puts the 2.2kΩ resistor in series with the 680Ω resistor. Negative supply rail So far, the circuit should seem relatively straightforward but you may wonder why the 555 timer is included. Does it really need to be there? Well, yes it does. Since the current into or out of the battery can be negative or positive, it stands to reason that the input voltage to IC1a can be negative or positive as well. This means that the output of IC1a and IC1b can swing below the 0V line and for this to be possible, IC1 needs a negative supply rail. This is what the 555 is used for. IC3 is set up as an oscillator running at around 9.5kHz and its output at pin 3 drives a “diode pump” consisting of diodes D1 & D2, together with the two 10µF capacitors. The circuit produces January 1999 55 a negative rail of about -5V which is adequate to run IC1. Assembling the PC board Fig.2: this is the component overlay for the PC board. Do not get the colours of the LEDs mixed up. LEDs 1-4 are red, LED5 is yellow and the remainder (LEDs 6-10) are green. The entire circuit, including the 10 LEDs used in the display, is accommodated on a PC board measuring 74 x 59mm and coded 05101991. The component overlay is shown in Fig.2. Before you install any components, check the PC board against the artwork of Fig.4 for any defects such as broken tracks, shorts between tracks or undrilled holes. Fix any faults and then proceed by inserting and soldering the resistors and diodes, then the ICs and the 10 LEDs followed by the capacitors. The diodes, LEDs and capacitors are polarised and must be inserted the correct way, so double check them before soldering. Finally, fit and solder the five PC stakes. We used thin figure-8 flex to connect to the battery and the car electrics. This flex had a striped black lead which is handy when wiring DC circuitry. When wiring the input, you can use the plain lead to the battery negative pole connection and the black striped lead for the connection to the earth strap at the car’s chassis. For the 12V supply, you can use the plain lead for the connection to D3 and the striped lead for the earth connection. The DIM connection can be a single length of hookup wire. Make one final check of the diode and capacitor polarities, before the big test. Bench-testing the ammeter Fig.3: here’s how two adjustable DC power supplies can be used to bench-test the LED Ammeter. Effectively, what we are doing is to use supply one (PSU1) to simulate the voltage drop across the negative battery strap while the second power supply (PSU2) provides power to the circuit in place of the 12V battery. PSU2 should be set to deliver 12V while PSU1 can be set to provide anywhere between 0V and 12V. 56 Silicon Chip If you have two DC power supplies it is far easier to do the initial test in your workshop. If you don’t, then skip to the in-car test. If you do have two DC supplies, Fig.3 shows how to connect them for the bench test. Effectively, what we are doing is to use supply one (PSU1) to simulate the voltage drop across the negative battery strap while the second power supply (PSU2) provides power to the circuit in place of the 12V battery. PSU2 should be set to deliver 12V while PSU1 can be set to provide anywhere between 0V and 12V. Connect the accessories switch wire to the positive terminal on the PSU2 supply and connect the other wire of the pair to the common or negative terminal of PSU2 (depending on how the supply is marked). Set the output to +12V. Fig.4: this is the actual size artwork for the PC board. Check your board carefully before installing any of the parts. You can either mount the LEDs directly on the PC board as shown here or you can mount them separately and connect them via rainbow cable. Wire the resistors across PSU1 as shown in Fig.3 and connect the leads as shown. You will need to connect the negative terminals of the two supplies together with a length of hookup wire. Set the output voltage of PSU1 to 12V, turn the supply on, and adjust VR2 until the leftmost red LED (LED1) is illuminated. Wind the output voltage of PSU1 down and the LEDs should light in sequence. Connecting the DIM wire to the accessories lead should reduce the LED brightness. In-car testing Connect the plain lead marked ‘to accessories switch’ to the battery positive, the black lead of the pair to the chassis. Connect the plain lead of the other pair to the battery negative terminal and the striped We mounted the unit in a small plastic case but you will probably want to mount the LEDs on the dashboard. Resistor Colour Codes  No.  1  2  1  1  1  1  2  3  1  1 Value 100kΩ 22kΩ 10kΩ 8.2kΩ 6.8kΩ 2.7kΩ 2.2kΩ 1kΩ 680Ω 160Ω 4-Band Code (1%) brown black yellow brown red red orange brown brown black orange brown grey red red brown blue grey red brown red violet red brown red red red brown brown black red brown blue grey brown brown brown blue brown brown 5-Band Code (1%) brown black black orange brown red red black red brown brown black black red brown grey red black brown brown blue grey black brown brown red violet black brown brown red red black brown brown brown black black brown brown blue grey black black brown brown blue black black brown January 1999 57 Table 1: Typical Lamp Ratings In Cars Parking lights (front)............................................................................... 5W Tail lights................................................................................................ 5W Licence plate.......................................................................................... 5W Dashboard parking indicator............................................................... 1.4W Reversing lights.................................................................................... 21W Brake lights.......................................................................................... 21W High level brake light......................................................................... 18.4W Dashboard brake indicator.................................................................. 1.4W Headlights (high beam/low beam)................................................ 60W/55W Dashboard high beam indicator.......................................................... 1.4W Table 2: Total Load When Lights On Parking Lights + licence plate.................................................26.4W (2.2A) Reversing Lights.........................................................................42W (3.5A) Brake Lights............................................................................61.8W (5.2A) Headlights (low beam + parking + licence plate)................136.4W (11.4A) Headlights (high beam + parking + licence plate)...............256.4W (21.4A) ground lead to the chassis end of the battery strap. Turn trimpot VR1 fully anticlockwise and adjust trimpot VR2 until the green and yellow LEDs are both alight. Turn on the parking lights and adjust VR1 until the yellow LED is illuminated. Now turn on the headlights and the second or third red LED should illuminate (depending on the current drawn by them and the setting of VR1). Connect the DIM lead to the battery positive and the LED’s brightness should reduce. Turn off the headlights. Final calibration To do the final calibration, you will need to know the wattage of the various lights in your vehicle. You should be able to find this information in your owner’s handbook or in the service manual. For example, find out the total wattage drawn by You don’t have to modify the car’s wiring to monitor the current. Instead, the unit operates by monitoring the voltage across the main earth strap between the negative terminal of the battery and the vehicle chassis, as shown in this temporary lash up. 58 Silicon Chip the parking lights, brake, reversing lights and headlights (low and high beams). Knowing the wattage, you can calculate the current drain for various light combinations. For example, you can operate the reversing and parking lights separately and together and then you can add the headlights, in low and high beam settings. Do not forget that when you switch to high beam, low beam will still be on. Current calculations Typical lamp ratings in cars are as shown in Table 1. Except for the dashboard indicators, these lamps come in pairs, so the total load for the following lights on is as shown in Table 2. From this, you can see that if you switch on the headlights to low beam, as well as the reversing lights, you will get a total current drain of 14.9A and this is close enough to 15A to be used as a load current for the 15A indication. Similarly, if you switch the headlights to high beam, as well as the reversing lights, you will get a total current drain of 24.9A and this is close enough to 25A to be used as the full load current for the 25A indication. Naturally, the current can be expected to vary depending on the battery’s charge but it will be close enough for this calibration job. The Ammeter will have to be installed in the car and the five wires connected as indicated in Fig.1. You may mount the PC board directly behind the dashboard, or elect to fit it in the small plastic box we have specified in the parts list. If you do use the box, mount the PC board on the lid using a 3mm nut as a spacer and bring the leads out through the hole. VR1 will have to be adjusted to get the correct LED lit for the particular load. Don’t forget that the currents are only nominal and can probably vary by ±10% or more depending on the battery voltage. There is no need to step the LEDs in 5A increments, as the setting of VR1 will determine the step size. Once VR1 is set, VR2 must be readjusted to light the two centre-scale LEDs with no battery drain; ie, with all lights off. Troubleshooting If your unit doesn’t appear to work properly, check the following voltag- Parts List 1 PC board, code 05101991, 75 x 60mm 1 plastic case, Jaycar HB-6075 or equiv. 3 6mm x 10mm countersunk screws 6 3mm hex nuts 3 3mm spring washers 5 PC stakes 1 200kΩ multiturn trimpot (VR1) Altronics R-2390 or equiv. 1 10kΩ multiturn trimpot (VR2) Altronics R-2382 or equiv. Semiconductors 1 LM358 dual op amp (IC1) 1 LM3914 LED bar/dot linear display driver (IC2) 1 555 timer (IC3) 1 LM7808 or LM7809 TO-220 voltage regulator (REG1) 1 BC558 PNP transistor (Q1) 2 1N914 silicon diodes (D1,D2) 1 1N4004 silicon diode (D3) 4 5mm x 2mm red LED (LED 1-4), Jaycar ZD-1760 or equiv. 5 5mm x 2mm green LEDs (LED 6-10), Jaycar ZD-1765 or equiv. 1 5mm x 2mm yellow LED (LED 5), Jaycar ZD-1770 or equiv. 14 Model Railway Projects Shop soiled but H ALF PRICE! Our stocks of this book are now limited. All we have left are newsagents’ returns which means that they may be slightly shop soiled or have minor cover blemishes. Otherwise, they're undamaged and in good condition. SPECIAL CLEARANCE PRICE: $3.95 + $3 P&P (Aust. & NZ) This book will not be reprinted Yes! Please send me _____ copies of 14 Model Railway Projects at the special price of $A3.95 + $A3 p&p (p&p outside Aust. & NZ $A6). Enclosed is my cheque/money order for $A__________ or please debit my  Bankcard  Visa Card  MasterCard Card No. Capacitors 2 100µF 25VW PC electrolytic 2 10µF 16VW PC electrolytic 1 0.1µF MKT polyester 2 .01µF MKT polyester Signature___________________________ Card expiry date______/______ Resistors (0.25W, 1%) 1 100kΩ 1 2.7kΩ 2 22kΩ 2 2.2kΩ 1 10kΩ 3 1kΩ 1 8.2kΩ 1 680Ω 1 6.8kΩ 1 160Ω Suburb/town_________________________________ Postcode_________ Name ______________________________________________________ PLEASE PRINT Street ______________________________________________________ Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number (Bankcard, Visa Card or MasterCard). Silicon Chip Binders es. IC1a pin 8 +8V (or +9V with 7809), IC1a pin 4 -5V, IC2 pin 3 +12V, IC3 pin 6 +1.25V. If you are within 20%, everything is probably fine. If the negative voltage is missing or low then the problem is around IC3.  Heavy board covers with 2-tone green vinyl covering Dimming  SILICON CHIP logo printed in goldcoloured lettering on spine & cover If the dimmed LED intensity is not to your liking vary the value of the 2.2kΩ resistor at the emitter of Q1. Making it smaller will increase the dimmed brightness, increasing it will SC do the opposite.  Each binder holds up to 14 issues REAL VALUE AT $12.95 PLUS P &P Price: $12.95 plus $5 p&p each (Aust. only) 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. January 1999 59 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 More protection for your car with the . . . Keypad Engine Immobiliser This project takes the Engine Immobiliser described last month and adds a keypad. When you stop your car and turn the engine off, you hit any key to enable the Immobiliser. To start the car again, you must enter the correct 4-digit code, otherwise the car will stall every time it is started. By JOHN CLARKE For good protection against car thieves the Engine Immobi liser described last month works well but you do need a concealed switch to operate it and this can be a drawback. Using a keypad to enable the Immobiliser is much more elegant. The design uses a standard 12-button keypad, labelled 62 Silicon Chip from 0 to 9 plus asterisk (*) and crosshatch (#) keys. Four buttons must be pressed in the correct sequence before you turn on the ignition. The car can then be started in the normal way. You can program in any 4-digit code, including the “*” and “#” buttons, by means of links on the PC board. This means that you can set the combination to say, #123, 1223 or whatever. You cannot trick the keypad circuit into disarming the Immobiliser by pressing all keys at once, by disconnecting the battery and reconnecting again or any other jiggery-pokery. The code must be entered in the correct sequence. If you enter the wrong code, you can start again by pressing any key which is not used in the code sequence, followed by the correct code sequence. The Immobiliser is armed by pressing any key which is not used in the combination code. A LED flashes to indicate when the Immobiliser is active and it goes out when the correct code is entered. The keypad can only be used when the ignition is turned off. It does not Fig.1: this circuit has two parts. IC2 and diodes D3, D4 & D5 detect when a key is pressed while IC3, IC4 & IC5 detect when the code is entered in the correct sequence to deactivate the Engine Immobiliser via the output at pin 10 of IC4. respond to any buttons when the ignition is switched on. This means that you can only arm the Immobiliser once you have switched off the engine. Similarly, to disable the Immobiliser, you must enter the correct code before switching on the ignition. The reason for this approach is so that the Immobiliser cannot be activated by the keypad when the car is in motion; if this happened the car could possibly be stopped in a dangerous situation if any of the keypad buttons was inadvertently touched. As with the basic Engine Immobiliser described last month, the keypad version becomes active when power to the ignition is switched on, provided it has already been armed. If the ignition is off, the Immobiliser circuit is off and the only current drain from the battery is that drawn by the keypad Main Features • • • • • • • • Keypad operation to restore normal ignition. 4-digit code entry. Any of 12 keys can be used for the code. Any order, sequence or duplication of code is allowed. LED flashes when ignition is disabled. LED is off when correct code entered to enable normal ignition. Keypad disabled when power to ignition is switched on. Normal ignition cannot be restored by disconnecting and reconnecting battery supply. • System is armed by pressing a key when the ignition is off (which is not part of the code). • Can be used in unarmed mode by not pressing a key. January 1999 63 Fig.2: this is the modified circuit of the Engine Immobiliser published last month. Q4 responds to the high signal from the keypad circuit and disables IC1. circuit itself. This draws about 6mA which should not be a problem for the car battery. Circuit details The keypad circuit is shown in Fig.1. The keypad itself has 12-keys which are connected in a matrix of three columns and four rows. As shown on the circuit, the columns are labelled C1, C2 & C3 while the rows are marked R1, R2, R3 & R4. If, for example we press the “1” key, then there will be a connection between row R1 and column C1. Similarly, if the “9” key is pressed, row R3 is connected to column C3, and so on. The keypad circuit has two functions. First, it must detect when buttons are pressed and second, it must detect if they are pressed in the correct order. The first part, detecting when buttons are pressed, is relatively easy and is accomplished with the 4017 decade counter, IC2. This chip is clocked at about 100Hz by a Schmitt trigger oscillator, IC6a, and four of its outputs are connected to the four rows of the keypad matrix. As IC2 is clocked, its outputs cycle high and low and nothing happens until a key is pressed. The column associated with the key is then connected to that key’s row and when that row goes high, perhaps a millisecond later, the key column goes high as well. Each of the three columns is monitored by a diode and so the “high” signal is fed via diode D3, D4 or D5 to the “clock enable” line (pin 13) of IC2. This stops IC2 and so the key just pressed will have its column and row both high. IC2 will not start counting again until the pressed key is released. Key detection Four 2-input AND gates, in IC3, are used for key detection. Why only four, considering that there are 12 buttons on the keypad? The reason is that only four digits are used in the code. Each 2-input AND gate has one input connected to a row and one connected to a column, depending on the “hard wire” programming. If we consider IC3a, for example, its inputs are shown connected to row R1 and column C2 and so if key “2” is pressed, both inputs of IC3a will be pulled high and its output at pin 3 will also go high. So far then, we have described how each correct key-press is detected and the four outputs of IC3 will go high if the correct keys are pressed. But the circuit must also detect if the those keys have been pressed in the correct sequence. This is where IC4 and IC5 come into the picture. Sequence detection Fig.3: this is the modified component layout for the Engine Immobiliser, with Q4 and three resistors added in. 64 Silicon Chip IC4 is another 4017 decade counter but it is not clocked in the same way as IC2. It is clocked each time a correct button in the code sequence is pressed. Let’s see how this happens. Say, for example, button 2 is pressed. This will cause the output of AND gate IC3a to go high and pull pin 13 of NAND gate IC5a high as well. At the same time, pin 12 of IC5a will be high because the “0” output of IC4 (pin 3) is high. This will cause pin 11 of IC5a to go low and pull pin 14 (the clock input) low via diode D6. But nothing happens until you take your finger off button 2. This kills the column signal to IC3a, takes pin 3 of IC3a low and so pin 11 of IC5a goes high. It is this “low to high” transition that causes IC4 to be clocked and its “1” output, pin 2, goes high. The next button in our sample 4-bit code is 4. Provided this button is pressed, pin 4 of IC3b goes high, as does pin 9 of IC5b. Its pin 8 will already be high, since it is connected to pin 2 of IC4 and so pin 10 will go low, again pulling pin 14 of IC4 low via diode D7. Again, when button 4 is released, pin 10 goes high and IC4 is clocked by one count, so that its “2” output, pin 4, goes high. By now, you should see how the sequence is going. The next button in the 4-bit code is 5 and pressing it causes pin 3 of IC5c to go low and pull pin 14 of IC4 low via diode D8. The end of the correct sequence is when you press button 9 and then take your finger off the button. This again causes IC4 to be clocked and its “4” output, pin 10, goes high. This has two results. First, its high output is fed to the Engine Immobiliser board, to disable its operation. Second, it disables Schmitt trigger oscillator IC6d and LED1 stops flashing. This view shows the Engine Immobiliser PC board with the extra parts added in the bottom lefthand corner. You have to add one transistor and three resistors, with the 10kΩ resistor to the left of the IC replacing a wire link. Invalid keys So far we have seen what happens when you press the correct buttons in sequence. But what happens when someone else has a go and gets it wrong? Previously we noted that each time a key was pressed, a column is connected to a row and when the row output from IC2 went high, one of the three diodes D3, D4 or D5 would feed the high signal to the CE pin and stop the counter while ever the key was pressed. That same high signal is also fed via an RC delay circuit (10kΩ and .01µF) to the reset pin of IC4 but if a correct key has been pressed, this reset signal is suppressed by diode D10 and one of the four diodes D6-D9. The RC delay in the reset signal line ensures that when a “correct” key is pressed, IC4 is not reset. So if keys are pressed in the correct sequence, IC4 is clocked forward with each key press. On the other hand, if a couple of correct keys are pressed and then Fig.4: the component layout for the keypad. The 4-digit code is programmed by installing links on the board to the left of IC2. a wrong key, IC4 will be reset and its “0” output goes high. The correct sequence must now be entered in full for the Immobiliser to be deactivated. Ignition monitoring Transistor Q5 and gate IC6b monitor the +12V line from the ignition keyswitch. With the ignition switch off, Q5 is off and pins 1& 2 of IC6b are high and so pin 15 of IC2 is held low. Hence, IC2 is continually clocked by IC6a and the circuit is waiting for buttons to be pressed. When the ignition is turned on, Q5 turns on and pulls pins 1 & 2 of IC6b low. Thus, pin 15 of IC2 is pulled high, which is the reset condition. IC2 is prevented from clocking and so the circuit cannot respond to any buttons being pressed. By the way, we have used the “2”, “6”, “7” and “3” outputs of IC2 to drive the keypad switch rows and so the rows are not scanned in sequence. The reason for doing this was to make the layout of the PC board more convenient. Power for the circuit is derived from the car battery and this is decoupled via a 39Ω resistor and a 100µF electrolytic capacitor. This effectively filters any hash on the supply line. The 16V zener diode ZD6 clamps any voltage above 16V to protect the ICs from damage. Immobiliser circuit The Engine Immobiliser circuit published last month is modified by the addition of one transistor to make it work with the keypad circuit. The January 1999 65 header for the ribbon cable to the keypad. Next, insert the links which can be made using the tinned copper wire or component pigtails. Before you can insert the links associated with the keypad, you need to decide on the 4-digit code. Have a look at the component overlay diagram in Fig.4. You will notice that there is an area on the board to the left of IC2 which has seven tracks labelled R1-R4 and C1-C3. These correspond to the four rows and three columns of the keypad. Each of the four keys to be programmed has two link connec tions, with the lefthand side link connected to one of the four rows and the right-hand connected to one of the three columns. In our example code shown on the circuit, key 2 is pro grammed as row 2 and column 1; key 4 key is programmed as row 1 and column 1; key 5 is row 2 and column 2; and key 9 is The keypad board in the prototype was mounted above the Engine Immobiliser board row 3 and column 3. Table 1 in a standard plastic case, with the keypad attached to the lid. Alternatively, you can shows the coding needed for mount the keypad separately on the dashboard. all keys. Having installed all the modified circuit is shown in Fig.2. the Immobiliser PC board is shown links to program the 4-digit code, you The circuit operation is as de- in Fig.3 while the component layout can now install the resistors, followed scribed last month, since the addi- for the keypad PC board is shown in by the diodes. Then install the 16V Fig.4. This board is the same size as zener diode and the transistor. tional transistor is off at all times unless a valid 4-digit code has been the Engine Immobiliser board and is The ICs must be inserted with the fed into the keypad. When that hap- coded 05401991. correct polarity as shown and make pens, the base of Q4 is pulled high sure that you insert the correct type in Construction and it turns on to pull pin 4 of IC1 each position. Finally, the capacitors low. This causes IC1 to stop oscillatYou can begin construction by can be installed, taking care that the ing and its output at pin 3 goes low. checking the PC board for shorts electrolytics are oriented with the This causes all transistors, Q3 to Q1, between tracks, breaks in the tracks, correct polarity. The 0.1µF capacitors to turn off and the Immobiliser circuit or undrilled holes. Fix any defects (if may be marked as “100n” or “104” then has no further effect on the car’s any) and then fit PC stakes into the while the .01µF capacitor may be ignition system. holes for the external wiring points marked as “10n” or “103”. The modified wiring diagram for on both boards. We used a 7-way pin The assembly procedure for the En- Resistor Colour Codes       No. 1 1 9 1 1 66 Silicon Chip Value 220kΩ 100kΩ 10kΩ 2.2kΩ 39Ω 4-Band Code (1%) red red yellow brown brown black yellow brown brown black orange brown red red red brown orange white black brown 5-Band Code (1%) red red black orange brown brown black black orange brown brown black black red brown red red black brown brown orange white black gold brown Parts List 1 plastic case, 130 x 67 x 43mm 4 M3 screws x 6mm 2 15mm long tapped spacers 1 1m length of heavy duty black automotive hookup wire 1 1m length of heavy duty red automotive hookup wire 1 1m length of light duty red automotive hookup wire 1 1m length of heavy duty yellow automotive hookup wire 1 150mm length of hookup wire Fig.5: actual size artwork for the PC board. Table 1: Programming Links Key 1 2 3 4 5 6 7 8 9 * 0 # Row 1 1 1 2 2 2 3 3 3 4 4 4 Column 1 2 3 1 2 3 1 2 3 1 2 3 gine Immobiliser board was featured last month and we expect that most users will assemble and get it going on its own before making it work with the keypad board. Installation The two boards can be housed in several ways. We stacked the PC boards in a plastic case measuring 130 x 67 x 43mm and mounted the keypad onto the lid. However, you could mount both boards underneath the dash and mount the keypad on the dash itself. We’ll leave that up to you. If you want to take our approach, the PC boards are stacked on top of each other using 2 x 15mm spacers. Note that the integral side ribs in the case will need to be removed using a chisel and a hole drilled in the end of the box for the wiring. The keypad was secured to the lid with four small (M2.5) screws or selftappers. Note also that if the keypad is mounted on the lid as shown in the photo you will need to cut slots for its mounting feet in the sides of the case, so that the lid can later be placed in position. Wiring & testing The boards can be wired up using automotive hookup wire. We used light duty wires for all wiring except for the wires to the ignition coil and ground. Connect the circuit boards to a 12V battery or DC supply. Check that the LED flashes at a one second rate and that the LED stops when the 4-digit code is entered into the keypad. Press any other key (ie, not one included in the code) and check that the LED flashes again. The keypad should now be inoperative. Connect up the ignition wire to the supply positive. You can verify that the high voltage transistor Q1 comes on by measuring the resistance between its emitter and collector. The transistor will be on when the resistance is low. If the circuit operates properly you are now ready to install it into your vehicle. Find a suitable position under the dashboard to mount the unit and then locate the fused side of the ignition circuit and the fused side of the battery supply. The wiring to these points should be made using automotive connectors. Also you will need a chassis point to connect the ground supply of the circuit to the battery negative Keypad 1 PC board, code 05401991, 106 x 60mm 1 12-switch keypad with 4-row and 3-column addressing 1 5mm LED bezel 6 PC stakes 1 7-way pin header 1 60mm length of 7-way rainbow cable 1 400mm length of 0.8mm diameter tinned copper wire Semiconductors 2 4017 decade counters (IC2,IC4) 1 4081 quad 2-input AND gate (IC3) 1 4011 quad 2-input NAND gate (IC5) 1 4093 quad 2-input Schmitt NAND gate (IC6) 1 BC337 NPN transistor (Q5) 1 16V 1W zener diode (ZD6) 8 1N4148, 1N914 signal diodes (D3-D10) 1 5mm red LED (LED1) Capacitors 2 100µF 16VW PC electrolytic 1 10µF 16VW PC electrolytic 1 0.1µF MKT polyester 1 .01µF MKT polyester Resistors (0.25W, 1%) 1 220kΩ 1 2.2kΩ 1 100kΩ 1 39Ω 9 10kΩ terminal. This can be an existing screw in the metalwork or a separate self-tapping screw which secures the eyelet terminal for the ground lead in place. The connection to the ignition coil should be made with an eyelet terminal. This wire should be concealed as much as possible. SC January 1999 67 SERVICEMAN'S LOG How long is a couple of months? How long is a couple of months? This may not seem to be very important, until an irate customer disputes the time and details of your last service job. A properly kept record system could then prove vital but more on that later. It’s been rather quiet as far as work goes during the last month. Either not much has failed or I need to change my brand of breath freshener. However, as well as the normal boring repairs there have been a few interesting cases. First, there was a Casio SF-7900 Digital Diary which had been literally drowned in shaving cream (not too sure whether I can fix that one yet). This was followed by an NEC remote control that had been 68 Silicon Chip savaged by a dog (not much of that left), in turn followed by a dropped Hitachi 34cm TV set sporting a smash ed tube (its only remaining function being landfill). Difficult repairs take time, impossible ones take a little longer. One set was delivered in a van, with two very fit young men visibly straining under the weight of a Philips Matchline 83cm TV set. Fortunately, I had a trolley available – and where they put this set down was where it was going to be when they picked it up! This monster was a model 33CE 7538/42R, employing a 3A chassis (circa 1986-1988), which had been bought at auction. Ironically, I already had seen this very set at a competitor’s secondhand store and I knew the tube was virtually defunct, which was why the proprietor had put it back to auction. A new tube costs over $2000. Anyway, the new owner also had this information but because he had bought it so cheaply, he wanted a few other supposedly simple faults fixed. These included a blue line at the top and east-west distortion in the corners. He was prepared to live with the washed out picture. To make things more difficult, there was no remote control and no instruction booklet but, on the bright side, I did have the service manual on this 3A chassis. At switch-on there was nothing except the blue line at the top. After 15 minutes or so, a very dingy picture appeared, with four vertical kinks in the left and righthand sides about 10cm from the corners. The picture tube carried no label and was already running flat out, with the heater filaments glowing like torches. Someone had shorted the two series inductors feeding them in an attempt to extract extra performance. The line at the top of the picture and the delay in coming on was reminiscent of the Philips 2B chassis described last month. And, in fact, the circuits are very similar. I removed the chassis (not easy) and, with the help of the service manual, set about replacing as many electros as I could around the eastwest circuitry and vertical output stage (especially C2555). I also fitted an 82kΩ resistor from pin 26 to pin 6 on IC7355 (TDA4580), in the multi-standard decoder module. As mentioned last month, this is a standard modification to cope with tube ageing. When I switched on, the picture came on much faster than before but the east-west geometry was still a mess. It was time to delve deeper into the likely causes. The geometry adjustments of this set are performed using a remote control but not necessarily the one that comes with the set. The remote control must have a Print or Sleep Timer function on it which, when pushed simultaneously with the mono button on the front panel, will bring up a display of four bars. You then select two numbers corresponding to the geometry control you wish to adjust (e.g. 08 for east-west pincushion) and then adjust the value with the remote volume control. Of course, I didn’t have one. But while I waited to see if I could beg, borrow or steal a remote control (models RC5991, RC5275, RC5375, RC53, RC5, RC5610 are the only ones that can do the job), I tried my hardest to fix the other problems. I found that by varying the screen preset pot (R3472) on the neck of the tube, as well as the greyscale, I could vary the colour and shape of the line at the top of the picture. I also found that freezing the components around the east-west output stage, along with an increase in the beam current, also varied the corner distortions. I spent a long and fruitless time replacing everything in the east-west circuitry and found that the only way to achieve any worthwhile improvement was to fit a 10kΩ resistor across C2602. However, this still left a pincushion effect which would have to wait until a remote control became available to see if it could be corrected. In the meantime, I came to the conclusion that some attempt to rejuvenate the picture tube might be worthwhile. And so it was that I dug out my old home-made monochrome picture tube booster and analyser. This basically consists of a 15W lamp in series with the cathode and grid of the CRT across 240V AC. The heater filaments are powered from a separate variable multitap transformer and when current starts to flow, it is limited by the lamp. I connected the tube pins directly to this and switched on, not expecting very much action. To my surprise, the globe flashed quite vigorously on each gun in turn, telling me that AC current was indeed flowing healthily between the grid and the cathode, even with the filament at the normal 6.3V. Next, I removed the shorts across coils L5466 and L5465 and reconnected the CRT base. At switch-on, the picture came up quickly and strongly with a high-definition picture. I reset the greyscale tracking and the picture was excellent. The blue line and the vertical kinks in the horizontal scan on the left and right had all gone but the east-west fault remained. I needed the correct remote control. Three weeks later, I finally managed to obtain one and dialled in the digits. Not all the controls displayed the value of the adjustment but apart from that, the east-west pincushion command (08) did function properly, without any modifications to the set. I did find it necessary to set up the horizontal EHT Compensation (11) as well as controls 07, 09 and 10, and then save the settings with the remote control’s PP and Standby buttons on program 1 (PR1); the default condition when the set is switched on. Summing up the repair, it was really just a matter of rejuvenating the tube and adjusting the controls. Of course, I cannot guarantee how long the rejuvenated tube will last, as the procedure knocks off the oxide on the poisoned cathodes. Nor can one tell how much material is left behind, nor how long before it, too, becomes poisoned. Anyway, the new owner has, for the time being at least, acquired a cheap large-screen TV set. The Akai video My next story concerns an Akai play-only video machine, model VP170. This set was only just out of warranty and the problem was that a cassette had jammed inside it and it was switching off. When I shook the unit, I could hear loose components rattling around inside – not a good sign. I took the cover off and a small piece of white plastic fell out but the cassette couldn’t be moved. There was nothing for it but to dismantle and remove the entire deck. Once it was out, the cassette ejector mechanism was disengaged from the loading gears and removed. The fault causing this mess was the righthand loading arm on the ejector; a fault which is well known to Akai service agents but not to lesser mortals such as I. A replacement was ordered, now modified with a fourcoil spring instead of three-coil type (BL438155C). After a lot of fiddling around, I managed to remove a sliding gear rack and the mode select switch, to free the cam gear. The ejector was then reassembled. This is not for the fainthearted or “mechanically challenged” the first January 1999 69 time one is confronted with this operation. However, after reassembling everything I was relieved to find it all worked properly. Badged sets With so many TV sets now manufactured in Asia, it is sometimes only the badge which really distinguishes different brands. I had two such sets this month with vicious faults. The first was an Akai CT1406A, while the other was badged as a JVC C-14K1AU but was exactly the same set electrically. The CT1406A sounded straightforward enough, with the words “went dead” written on the job sheet. Having done many of these by now, I found the usual ZD402 12V zener short and resistor R425 (5.6Ω) burnt open on the secondary of the horizontal output transformer (pin 3 of T402). These failures were caused by two electros – C911 and C909 in the power supply – drying out and allowing the two DC supply rails to go high. It was at this stage that I found I had no vertical deflection. I replaced IC401 (LA7830) but that wasn’t it. I then re placed tantalum capacitors C417 and C416, along with C409 for 70 Silicon Chip good measure – still no difference. Some quick voltage checks showed that I had 29V on pin 6 of IC401 and 24V on pin 3 but the CRO indicated no vertical drive from pin 31 of IC301 to pin 4 of IC401. I replaced IC301 – an AN5601K jungle IC – and finally restored the vertical timebase. But now all I had was a distorted blue raster and none of the front controls were working. A visual inspection revealed that IC802, a TMS73047 microprocessor, had been corroded by some liquid that had dried there, so I replaced that as well. By now, you would have thought that all this hard work would have delivered some decent results but my misery continued. I couldn’t believe how much was wrong with this 3-year old TV set which still looked brand new from the outside. Should I call it quits and write off all the work done so far? I decided to continue. At this juncture, I still had the distorted blue raster and limited intermittent control of everything. The distortion was hard to describe but the top quarter of the picture was black with retrace lines and the remaining three quarters was all blue as though there was severe “hum” in the picture. I went back to the jungle IC (IC301) with the CRO and checked the RGB colour outputs on pins 21, 24 and 25. The CRO showed large square pulses to all guns. I checked diodes D307, D308 and D309 and disconnected the CRT socket (CN302) in case something was dragging it down. However, after a lot of mucking about, it turned out that diode D306 was leaky. I found this only by comparing the voltages and waveforms with the second set of this story, as I had to literally fix them side by side. D405 measured OK and the “hum” was a distorted vertical pulse going into pin 14 of IC301. By now I had a good picture and sound but still only had intermittent control of the set, especially when switching on. Eventually, I noticed that flexing the board near the micropro cessor (IC802) varied the symptoms and it didn’t take long to find a hairline fracture in one of the copper tracks. Resoldering this fixed the last problem. Now for the second set – the JVC C-14K1AU. As already noted, I was actually working on both sets together, alternating between the two. And the JVC also suffered from no vertical deflection. I followed the same search pattern sequence as on the Akai, and was beginning to suspect the jungle IC (IC301) again. In addition to the three capacitors I had already changed, I also had a go at C321 and C326 but to no avail. I was just about to remove the IC and was comparing the impedance of each pin with respect to chassis when I noticed a sizeable difference on pin 33. On the working set (the Akai) it measured about 100kΩ but on the non-working JVC set it was 1MΩ. The soldering on this pin didn’t look too crash hot so I reworked it, after which it read the same as the Akai. I fired it up and found to my relief that it was working perfectly. Fortunately, there were no other faults and I sat back sipping my coffee and contemplating why I ever became a TV technician. A surly customer And now about that matter of service records, mentioned earlier. My next customer was a surly Mr Borland (not his real name) who brought in his Sony VTX-100M (this is a multisystem TV stereo tuner, part of an expensive modular Profeel TV System, COLOUR CCD CAMERAS (42X42mm) 2 lux. colour with one of these lenses 3.6mm-92 deg./4.3mm -78 deg.5.5mm-60 deg. Special introductory Price of just $189 + $8 for audio module B/W cameras also available. PARROT VOICE RECOGNITION DIARY Access up to 350 names and their Ph./Fax No’s just by the sound of your III voice. Easy to use ,small pocket sized unit. Also up to 13 min of vocal memo notes, appointment book, clock, Ph assistant etc. Quality product made by IBM, retails for $300, we Parrot have limited quantity at: $130 IR SWITCH KIT: Ref: EA March 96. Uses a commercial coded IR TX & a RX kit. The Tx has one button & req. 9V. Size 115 x 33 x 22mm. The Tx uses an UM3750 (code/decode chip). The Rx uses a RX module to pick up the 40KHz IR signal. This demodulated code is detected & not decoded. The detected level switches a 4013 (wired as a toggle flip flop) then a relay. Can be used as a high security remote. With UM3750 IC in the Tx PCB as a decoder, a second IR Tx is used. UM3750 has 12 coding inputs. Use your own PIN in the Tx & Rx. Note: you two TXs & one Rx kit for high security remote. * IR Switch Kit (with 1 TX):(K66S) $20 *Secure IR Switch Kit (with 2 TXs): (K66C) $28 IR RECEIVER FRONT END MODULE Contains an IR receiver diode, amp tuned to 38KHz, a bandpass filter, an AGC section & detector circuit. $2 Ea or 10 for $15 WIRED IR REPEATER KIT: Ref: EA March 96. Simple kit which uses a commercial IR Transmitter and a Rx kit which works with most remote controls. The receiver uses a receiving module to pick up the 40KHz IR signal. The output of the receiver module is connected to the IR LED driving circuit of the IR Tx. This retransmits, giving an extension in range of up to 15 metres: (K66R) $20 CIGARETTE LIGHTER LEAD & PLUGS Heavy duty 1.6M lead Removable 4A fuse $1.50 DRIVER/ RIDER COMMS SYSTEM Ideal for rally driver/co-driver communications or bike intercom. This is a new (surplus) professionally made unit and requires some minor wiring & a cheap pair of head phones for this & many more applications. With 2 high quality unidirectional electret Noise Cancelling Microphones with wind filters &mounting clips. Appears to have been designed for a comm unications system. (AP3)$18 NEW STEPPER MOTORS 30 oz./in. torque, 2.5 deg. 144 step, low voltage, compact 57 x 38mm: $14 POWERFUL 80 IR ILLUMINATOR With strong universal swivel mount & 50X50X50mm housing:$36 Just $30 With any camera purchase X-RAY MACHINES, HEART MONITORS, SATELLITE TV EQUIPMENT, OSCILLOSCPOES, OTHER TEST EQUIPMENT These are some of the items that may still be for sale at our Web Site. See our BARGAIN CORNER, TRADERS CORNER & FREE ADS FREE ADS should be E-mailed with “FREE ADS” in the subject window KITS OF THE MONTH NEW DESIGN 110W CFL INVERTER This kit is a redesign of our extremely popular inverter kit. The new improved design uses a larger transformer and a SG3525 switch Mode Chip.This very Efficient Driver kit can drive up to 11 X 10w CFL’s from 12vdc. And would be great for lighting the weekender or caravan Kit inc. 1 inverter & 1 CFL: $30 Extra CFLs $12 NOW TRY OUR PROFESSIONAL PIC MICRO PROGRAMER Programs up to 39 different types of PIC chips, Software works under DOS, WIN 3.xx and WIN 95, Quick Easy construction, Connects to Pc’s parallel port. Download fully functional evaluation software from the Internet register for a small fee. More details on our web page $35 WE BUY NEW & USED SURPLUS OR STOCK COMPONENTS, MODULES, PCBs, MOTORS, GEAR BOXES, HOUSINGS, PLUGS, SWITCHES, METERS, ASSEMBLIES. CALL OR FAX WITH DETAILS. LARGE OR SMALL QUANTITIES Gosford Amateur Radio & Electronics Field Day On Sun Feb 28,1999. Wyong race course 830am. This is the biggest sale day of new, used & new surplus electronics, radio and computer equipment in Australia. Don't miss out. If you can't attend on the day some Gosford bargains will be posted on our web site from Fri Feb 26th until Mon Feb 29th and orders can be placed via the normal method on those days only. Just take the F3 to the Alison Rd. turn-off in to Wyong or a 300M walk from Wyong train station. More at.... www.terrigal.net.au/~rosser/fieldday.htm BARGAIN PACK HIGH QUALITY 1.6 / 5.6 SERIES SIEMEMS CONNECTORS, 92 date code, See Siemens web site. Compatible with new series. Some gold plating. High Quality co-axial connectors.. Just.$19 for 24. You get..... 2x...43 - Panel or Line Push on Female 5x...106 - Straight Line Male Push On 2x...172 - Line Male Push On 45 Deg 7x...169 - Panel or Line Female 3x...171 - Line Female 90 Deg 2x...173 - Straight Line Male 2x...105 - Line Male 90 Deg 1x...30 - 90 Deg Line Male An international supplier Lists similar connectors for more than 10 times The price!!! ENCODER / DECODER CHIPS As used in remote control devices AX5326 encoder, AX532-7 decoder with 4 bit latched outputs, AX532-8 with Valid Data output. These chips could be used to control up to 16 items (relays etc.) down one wire all with brief application sheet: $3.50 or combo. of any 10 for $25 EXPERIMENTERS LENS SET: Set of 4 high quality Military spec. lenses. Experiment with convergence, divergence and magnification. Could be used to extend the range of infra-red systems, like IR communicators, PIRs & lasers. $7 12VDC - 240AC INVERTER Features include modified square wave output, Auto start with load sensing, Uses six power MOS-FETS with minimal heatsinking required. 200 - 600VA. Dependant on trans former size. To save money you can use an rewind your own transformer. Basic kit includes pcb & all on-board components + 4 X 60A MOSFETS. $35 Requires 240V to 8-0-8 V Transformer.. Ring or E-Mail for More Details. BEST VALUE $1 for our famous wiring kit with any order COMPUTER CONTROLLED STEPPER MOTOR DRIVER KIT can drive larger motors, Has optoIsolation. Inc. Software & notes: $40 Or $50 with two Used 23 frame 200 step 1.8 Deg. motors!! NEW DIGITAL BAR CODE WANDS: USA made, with 2.5m curly cord & 5pin 240° DIN plug. With an Optical sensor, visible Red LED, a photo IC detector & precision aspheric optics. Converts bar codes to digital pulses. Uses a Sapphire tip, pot size 0.19mm. TTL / CMOS compatible open collector output. Req.5Vsupply: KEY-CHAIN LASER POINTER Very bright 650Nm laser pointer in a high quality machined metal housing $20 FOR SALE TO ADULTS ONLY VERY BRIGHT LASER MODULE 650Nm laser module as used in the above pointer. (Lm2) FOR SALE TO ADULTS ONLY **************NIGHT VISION*************** IMAGE CONVERTER TUBES Hard to find deep IR tubes As used in night viewers. Tube plus EHT power supply kit plus suitable eyepiece: $50 UNIDIRECTIONAL ELECTRET MICROPHONE New quality product with clip, 3M lead, 2.5mm plug: $4 Make a stage quality wireless microphone by combining it with our FMTX MK2 transmitter kit: $16 for the kit plus the microphone ************ OPTICAL PRISMS *********** Series I, 3,4 CHANNEL UHF RECEIVER: Ref: EA Mar 94. Control up to 4 output These are military spec. optically pure glass prisms relays. Uses a pre-built and pre-aligned set in a diecast mount UHF (304MHz) receiver module & security (removable).They are in coding ICs. Output relays have 5A contact A1 condition and stored in PO Box 89 Oatley NSW 2223 ratings and can be configured for toggling plastic (no scratches) Ph ( 02 ) 9584 3563 Fax 9584 3561 They will show colours operation at each press of a Tx button or orders by e-mail: oatley<at>world.net of the spectrum on a wall momentary operation when Tx button is www.oatleyelectronics.com pressed. 1 X 3ch transmitter plus 1 X4ch when placed in sunlight $12.50 major cards with ph. & fax orders, We also have a small Quantity of very receiver:$50 extra Tx $15 is req. to access the fourth relay. 12V operation. (K39) $70 large prisms “RING FOR DETAILS” Post & Pack typically $6 OATLEY ELECTRONICS $35 $18 NICAD CHARGER & DISCHARGER: Professional, fully assembled & tested fast NICAD battery charger & discharger PCB. Switch mode circuit. Has 6 ICs, 3 indicator LED's, 3 power MOSFETS, a toroidal inductor & many other compon-ents. Nominal unreg. input 13.7V DC, 900mA charge current. Appears to use volt slope detection to end charge, also a timer (4060) to end charge. We supply a thermistor for temp sensing. Probably for fast-charging 7.2V AA nicads. 3 trimpots for adjustment + Basic info. $9 or 3 for $21 LARGE LED DISPLAYS 70mm HIGH 7 SEG. STANDARD TYPE DISPLAY . (no data available) JUST $20 FOR 7 (Dl2) TELESCOPE Build your own, with our high quality components: 1 X eyepiece lens worth $5 + 1 X prism (to invert the image) worth $12.50 + 1 X large object lens worth $27 + construction plans all for the price of just $35 NEW SUPER LOW PRICE + LASER AUTOMATIC LASER LIGHT SHOW KIT: MKIII. Automatically changes every 5 - 60 secs, & is adjustable. Each motor has 8 speeds, one motor is reversible, & one can stop. Countless great displays from single to multiple flowers, collapsing circles, rotating single and multiple ellipses, stars, etc. Easy mirror alignment with “Allen Key”. Kit inc. PCB, all on board components, three small DC motors, mirrors, precision adjustable mirror mounts: (K115) + very bright 650nM laser (LM2) module. $59 UHF DATA TRANSMISSION Stamp sized Xtal locked 433.9MHz superhetrodyne receiver module $25 Small matching transmitter kit: $12 (K122) SOLID STATE 4-6A PELTIER EFFECT COOLER / HEATER 3.3A<at>14V(GP1) PELTIER: $27, 6A<at>15V(GP2) Peltier: $35, both approx. 40X40X4mm, temp. Control via supply voltage /current, will even work from a 1.5V battery!! With data sheet, diagram & circuit for a Fridge / Heater. OVERSPEED MONITOR KIT Ref EA Feb. 97.Gives a pulsed tone signal when preset speed is exceeded. 12V operation. A small PCB is provided for a Hall Effect pick-up sensor. This assembly is mounted near the drive shaft and connected to the main PCB by three wires. Kit inc. two PCBs & all on-board components, a small speaker, & two small powerful 'rare earth' magnets: (K99) $22 MEGGER METER / INSULATION TESTER For testing for insulation breakdown or moisture ingress etc. of cables or connectors etc. This kit will deliver a genuine 500Vdc in to a 1M ohm load!!! This means that unlike other cheap kits it performs to AUSTRALIAN STANDARD AS-3000. Kit inc. PCB, all onboard components, surplus meter movement plus instrument case for just $50 *** NEW *** NEW *** NEW *** HIGH POWER IR FENCE / DRIVEWAY / DOOR MINDER Uses include powerful Passive IR detector, invisible fence / gate & doorway monitor. Range: with 5 IR LEDs 40m (can drive 50 LEDs), can be boosted with a torch reflector. The kit has on board relay + active HI & active LO outputs for relays etc Simple to construct PCB can be cut into two for active mode Kit inc. PCB, all on-board components, 5 IR LEDs + salvaged new plastic case All for $18 Extra box + swivel mount $3 SC-JAN-99 Serviceman’s Log – continued circa 1986). His manner was aggressive from the start. “Remember this?, he said. “I brought it in a couple of months ago? Well, it’s doing the same thing again”. “And what was that, Mr Borland?” “You know, it doesn’t work. There’s no picture – just like before”. Summoning up as much poise and dignity as I could, I booked the job in without further comment. When he had gone, I looked up its service history. It was just as I thought. The unit was last in some three and a half years ago for a “no stereo” problem, caused by IC203, C251 and C253. Hmmm! – that’s a bit different from being in a couple of months ago for no picture. When I had a chance to look at it, the fault was no off-air reception. Once the lid is off, access is easy and I started by checking the four voltage rails from the power supply, which were all OK. Next, I checked the voltages to the tuner, TU101, while in the search mode. There was 12V at this point and the band switching was all OK, as indeed was the tuning voltage, varying from 0-30V. The only clue was that the RF AGC didn’t seem to vary at all. I checked the video output from pin 13 of IC201 while still searching on all bands. There was no output at any time. This brought me to IC201, a TDA– 4429T. In view of all the symptoms, it was the most likely culprit. This IC ran very hot even though it was fitted with a heatsink. However, it was also possible that either the tuner or IF circuits were at fault. To be certain, I substituted a test tuner that I keep for just such occasions. This is a freestanding rotary VHF tuner with its own manually adjustable AGC. There was still no picture and I was now virtually certain that it had to be IC201. When I checked the price of this device, I was horrified to be quoted a trade figure of $86. The real problem now was informing Mr Borland. I phoned him and presented the facts. His response was typical: “But you replaced that part before and I haven’t used it since then – I don’t think much of your guarantee”. 72 Silicon Chip I couldn’t make much sense out of his claim that the unit had not been used since I last serviced it and said so. I also calmly pointed out that it had in fact been 31/2 years since I last serviced it – not two months as he claimed – and that I had replaced entirely different components for an entirely different problem. And I couldn’t resist pointing out that in 12 years, this was only his second problem with the unit. It all washed right over him. He abused me for a few minutes but I was past caring what he thought. I told him that that was my price for the work that had to be done and that I guarantee only the parts I fit and the work I do, and nothing else. He could either take it or leave it. Finally, and ungraciously, he decided to accept the estimate and I placed the order for the IC. Three weeks later it arrived, I installed it and tuned in the stations; my diagnosis was correct, much to my relief. However, I was dismayed to find that the pictures were very poor and distorted, with severe “pulling”. Adjusting the tuner RF AGC pot, RV201, varied the quality of the picture, which suggested an AGC problem. There were three electros near the IC that could have dried out from the heat. I thought it worth a shot and replaced C216, C215 and C214 in that order. It wasn’t until I got to the last one that I fixed the problem. I installed 105°C capacitors instead of the original 85°C types and mounted C214 underneath the board on the copper side, away from the heat source. Mr Borland was still firing broadsides when he unappreciatively picked the set up a few days later, despite the extra work I had done at no further charge. I guess there’s no pleasing some people. Sony monitors In striking contrast, my last story concerns a small firm of accountants who have a fleet of Sony PD-1704S computer monitors. These are rather nice 17-inch SVGA multiscan monitors but are now getting long in the tooth – they were made in 1992. So far I have had four of them in, mostly suffering from east-west distortion problems. The difference between this firm and my last client was entirely in their attitude. These accountants were in no way pushy, understood that the equipment was complex, and understood that the faults were intermittent and required time to soak test. They also appreciated the costs involved. The problems were nearly all confined to a plug-in module DA(DC-1) on the righthand side of PBG-626-S (looking at the rear). This board has nearly all the 23 preset controls mounted on it and it didn’t take a mental giant to determine the cause of the faults. There are no less than 20 subminiature surface mount ed electrolytic (CHIP) capacitors mounted on this board, some of which are now leaking electrolyte and causing corrosion. There is a very simple test to determine whether a capacitor is faulty or not and that is to heat its terminals. If faulty, it will produce a pungent fishy odour from the vaporising electrolyte. However, it is an expensive exercise to replace all these capacitors at one time, even though it probably makes more sense in the long run. (The capacitors are expensive and it is extremely time consuming and fiddly to replace them). So which are the critical ones? The most common fault I had experienced was a trapezoidal picture. By heating and freezing the board, I eventually concluded that C349, C331 and especially C334 were the worst culprits and so I replaced them with ordinary 105°C 35V electros. When the old capacitor is removed, it is necessary clean off the electrolyte and repair any corrosion to the PC tracks. When freezing these capacitors, slightly misleading results can sometimes occur due to water vapour condensing on the electrolyte that has oozed onto the PC board. One fault I encountered caused the set to come on, intermittently go off horizontal frequency and then shut down. This turned out to be C110 on pin 5 of IC101, plus C311 and C309. Anyway, the fault in this unit responded to the replaced capacitors and to a general clean up of the leaked electrolyte. And the accountants were extremely happy and better still, paid SC on the spot. Electric Lighting Pt.10: Automotive Lighting The design and construction of lights used in cars – especially headlights – has changed considerably over the years. This month we look at current headlight designs, while in the next issue we will examine automotive High Intensity Discharge lighting. JJANUARY anuary 1999 73 Sealed beams reduced the problem of glass blackening and being pre-focused assemblies, gave more consistent results than earlier designs. the whole lamp body with systems using manual levers and even pneumatics to do this. Electric switching of filaments to dip the beam was introduced in the 1930s. However, this was different to the present system – in the dipped position one headlamp was extinguished and the other mechanically dipped by means of a solenoid. Twin filament bulbs allowing the pure electrical dipping of lights were introduced in the 1940s. Sealed Beams Since vehicles have been driven at night there has been a need for effective illumination of the road ahead. Very early cars used lamps of polished brass and copper that contained a single candle. However, they could scarcely light the way of the man walking in front carrying the red flag! This type of lamp was replaced with lamps burning oil and in some cases petrol, common until about 1910 when acetylene designs became popular. Early Lamps The acetylene lamp used two containers mounted one above the other. The lower one was filled with carbide in solid form; the upper one contained water which was dripped onto the carbide, with the flow regulated by a needle valve. The ensuing chemical reaction released acetylene gas which was transferred to the lamp itself through a tube. Here it burnt with a bright green flame. Some models of this type of lamp even had a primitive dipping function! The first electric headlights were powered by non-rechargeable batteries with quite limited life. The light output of these lamps was little better than oil or candle lamps, which meant they made little headway against acetylene lamps. Only the introduction of the generator saw the popularity of acetylene lamps begin to wane. Early automotive electric lighting systems used a constant current dynamo complete with a magnetic cutout which disconnected the dynamo from the battery when it rotated too slowly to charge. A typical battery of the time was described as a “12 volt 40 Actual Ampere Hour Accumulator”. Headlights ranged in diameter from 12.7cm (5-inch) to 33cm (13-inch), with systems normally incorporating a switchboard complete with ammeter and voltmeter. Some lamps were even available with sealed, gas-filled reflectors plated in either silver or gold. The brightness of these lights meant that a dipping system was needed. This generally took the form of moving Many low beam headlights use a capped bulb. The cap shades the bottom half of the reflector, preventing light from being reflected in an upwards direction. The edge of the cap demarcates the light/dark cut-off on the road surface. 74 Silicon Chip It is the luminaire design (comprising the bulb, reflector and lens) that is critical to headlight performance. Early reflectors used a system where it was possible to vary the position of the bulb in relation to the reflector, leading owners to adjust the focus of the light beam with, in some cases, poor results. To overcome this (and other) problems, the sealed beam was introduced. This consisted of an integral lens, filament and reflector – effectively a large bulb with an inbuilt reflector and diffuser. A further advantage of sealed beams over conventional bulbs was in reduced glass blackening. This occurs as the tungsten of the filament vaporises and is deposited on the inside of the bulb. In a sealed beam there was a very large area of glass on which the tungsten could be deposited, resulting in less blackening than previously occurred when using small bulbs. The sealed beam design also protected the reflector from physical damage and corrosion. Some Citroen vehicles have used swivelling headlights that turn in conjunction with the steering. The inner light that can be seen here is so equipped. (1) low beam filament (2) cap Fig. 1: a low beam headlight using a capped bulb. Note how the lower half of the reflector is not used in this type of lamp. (Bosch) The 17.8cm (7-inch) headlight was standardised in the 1940s and remained current until the 1970s. The change in the style of cars then required a smaller size and the 12.7cm (5-inch) headlight was introduced. Aerodynamic development of cars in the 1980s reduced the popularity of discrete round headlights and together with the introduction of halogen bulbs, meant that some of the previous advantages of sealed beams were no longer valid. This resulted in the widespread adoption of headlights unique to each model of car, using commonly available interchangeable bulbs. A bit like 40 years ago, really! Current Headlight Design The majority of headlight use, especially for city driving, is on low beam. This requires lamps with sharply defined, bright beams giving extended range on the passenger’s side of the road without creating glare for oncoming drivers. Many low beam headlights use a light source mounted forward of the parabolic reflector’s focal point. A cap The JE Holden Camira uses a homofocal headlight reflector. From left to right: the high beam inner light, the homofocal combined high/low beam and the indicator. (1) Basic reflector; (2) Supplementary reflector. Fig. 2: this graph shows the luminous intensity on the passenger side, as a function of the horizontal reflector diameter. As can be seen, wide headlights can have high luminous intensities. (Bosch) Fig. 3: a homofocal headlight uses two reflectors within the one housing. (Bosch) within the bulb keeps the lower portion of the beam from being reflected from the bottom half of the reflector in an upwards direction. Fig.1 shows this approach. Other low beam headlights mount the low beam filament above and slightly to one side of the reflector focal point. This causes almost all of the effective luminous flux to be directed downwards and to the left (in righthand-drive countries!). However, this approach does not give the clearly defined light/dark cut-off of those headlights using a capped bulb. The edge of the cap in bulbs so equipped demarcates the light/dark cut-off on the road surface. While it first might appear that this should be as sharp a cut-off as possible, this is not the case. For practical driving reasons, the light/dark contrast must not exceed a prescribed value. An extremely high contrast will produce unfavourable dynamic contrast of the road surface during vehicle pitching, leading to disorientation as the road is alternately plunged into darkness and then well lit. To achieve a maximum visual range with a minimum of glare, the light distribution close to the vehicle is critical. For example, there must be sufficient illumination of both the lefthand and righthand edges of the road to allow cornering. In the past, some manufacturers have mounted headlights on swivels such that they turned in conjunction with the steering. Citroen and Maserati did this on some models. More recently “turning” lamps that operate when the indicators are on have been introduced. As one would expect, the larger the reflector and the higher it is mounted, the more effective is the illumination for a given power. Unfortunately placing two 20cm headlights a metre above the ground is practical only for large trucks, not modern sleek and aerodynamic cars! This has meant that other strategies have needed to be adopted to improve illumination. Increasing the size of the reflector is normally achieved by fitting wider headlights. This is advantageous because the horizontal diameter of the reflector is a major determining factor Variable foci reflectors can be optimised to produce whatever light distribution is required, with the entire reflector surface being employed. This type of reflector is used with a clear lens Some headlight clusters incorporate a variety of lamp designs. From left to right – indicator, parking light, projector style low beam, homofocal high beam. January 1999 75 (1) Bulb; (2) Basic reflector; (3) Supplementary reflector. (1) Lens; (2) Shield; (3) Reflector; (4) Bulb. (1) Lens; (2) Shield; (3) Reflector; (4) Bulb; (5) Auxiliary beam. Fig.5: a projector headlight uses an elliptic reflector and imaging optics ahead of the bulb. (Bosch) Fig.6: an auxiliary short-distance version of the projector light uses a stepped reflector and a shortened shield. (Bosch) Reflectors are available in a number of different types. Stepped reflectors consist of paraboloid sections of different focal lengths, allowing a shorter effective focal length without the disadvantage of a tall reflector. Stepped reflectors are available in two configurations – homofocal and bifocal. A homofocal reflector uses a supplementary reflector which has a shorter focal length than the main reflector. This increases the effective luminous flux with the supplementary reflec- tor improving near-field and lateral illumination. Fig.3 shows this type of reflector, which is normally made from plastic to accommodate the large steps between the different parts of the reflector. The Holden Commodore VL and some Camiras used this design in a combined high/low beam application. Bifocal reflectors use reflector sections with different focal points. Used only in low beam applications, the design makes use of the lower portion of the reflector which normally receives no light. This section of the reflector is shaped such that light from this area is directed downwards, improving near-field illumination. Fig.4 shows this type of design. Note that the two reflectors do not have a common plane surface behind the bulb –they are indeed stepped. With computer aided design it is possible to have reflectors with variable foci. The shape of the reflector can be optimised to produce whatever light distribution is required, with the entire reflector surface being em- ployed, even for low beam applications. This approach has been recently adopted with multi-faceted reflectors used with a clear lens. Projector headlights use imaging optics located in front of the light source. Fig.5 shows this type of design. A light opening area of only 28cm2 (the equivalent of a 6cm dia-meter round headlight) allows light distributions of the type only previously achievable with much larger headlights. A CAD-calculated elliptic reflector is used in conjunction with a convex lens. The light/dark contrast can be defined with either a high degree of sharpness or with an intentional lack of sharpness, depending on the pattern required. Alternative designs of this type of lamp are also available. Fig.6 shows an auxiliary short-distance lamp which uses a stepped reflector. This taller unit (130mm versus the previous design’s 80mm) has improved near-field illumination. Both types of projector lamp are used only in low beam applications. Placing a translucent plastic panel in front of the assembly shows the beam pattern of each lamp. The projector lens low beam has its highest intensity in the middle, with a sharply defined spread left and right. The homofocal high beam is much deeper, to light the near-field as well as distant objects. On this car, this is required because the low beam light does not remain illuminated when high beam is selected. An H1 halogen bulb. This type is used in fog lamps, supplementary high beam and the low beam in 4-headlight systems. Fig.4: a bifocal reflector uses two reflector sections with different focal points. (Bosch) in the achievable luminous intensity. Data from Bosch indicates that if the width of the reflector is doubled from 130mm to 260mm, the luminous intensity is approximately doubled at the lefthand edge of the road surface at a distance of 50 metres from the vehicle. Fig.2 shows this. Reflectors of the same size but with different focal lengths perform differently. A reflector with a shorter focal length develops a broader beam with better close and lateral illumination. Reflector Types 76 Silicon Chip The problems of light/dark cut off and glare are not experienced with high beam designs. Instead, the light source is always situated at the reflector’s focal point, resulting in a beam parallel to the reflector’s axis. Fig.7 shows this type of design. Reflectors can be made from sheet steel or plastic. Steel reflectors are galvanised or powder coated to protect against corrosion. A coating is then applied to smooth the surface, after which a reflective aluminium layer is applied by evaporation. A protec- Bulbs As in other forms of high intensity lighting, the type of incandescent bulb used in automotive applications has moved from tungsten to tungsten halogen. Halogen bulbs have a far higher luminous efficacy than tungsten designs, with associated advantages in alternator loading and cable thickness. To preclude inappropriate fitting, automotive bulbs have differently shaped bases. Common categories are R2, H1, H2, H3, H4 and H7. The table below shows a variety of bulbs used SC in headlight applications. Application Category Nominal Power (Watts) High/low beam R2 45/40 Specified Luminous Flux (Lumens) 400/550 Fog lamps, supplementary high beam, low beam in H1 4-headlight systems 55 1550 High beam 55 1800 H2 Fog lamps, H3 supplementary high beam High/low beam H4 55 1450 60/55 1650/1000 Shape SILICON CHIP This advertisment is out of date and has been removed to prevent confusion. ELECTRONIC COMPONENTS & ACCESSORIES • RESELLER FOR MAJOR KIT RETAILERS • • PROTOTYPING EQUIPMENT • FULL ON-SITE SERVICE AND REPAIR FACILITIES • LARGE RANGE OF ELECTRONIC DISPOSALS (COME IN AND BROWSE) CB RADIO SALES AND ACCESSORIES Croydon Ph (03) 9723 3860 Fax (03) 9725 9443 Mildura Ph (03) 5023 8138 Fax (03) 5023 8511 M W OR A EL D IL C ER O M E Fig.7: in a headlight used only for high beam the light source is always situated at the reflector’s focal point, resulting in a beam parallel to the reflector’s axis. (Bosch) tive layer is then evaporated onto the aluminium, hermetically sealing the sheet steel. The reflective surface typically has a residual roughness of only 1/10,000mm. Plastic reflectors are produced by injection or compression moulding. Lenses are made from glass or polycarbonate. During construction, particular care is paid to surface quality to ensure light is not deflected upwards, causing glare problems. The shape, number and location of the prisms in the lens depends on the type of reflector design used. Truscott’s Low beam in 4-headlight systems, fog lamp H7 55 1500 ELECTRONIC WORLD Pty Ltd ACN 069 935 397 30 Lacey St Croydon Vic 3136 24 Langtree Ave Mildura Vic 3500 January 1999 77 Silicon Chip Back Issues December 1991: TV Transmitter For VCRs With UHF Modulators; Infrared Light Beam Relay; Colour TV Pattern Generator, Pt.2; Index To Volume 4. 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 1992: TV Transmitter For VHF VCRs; Thermostatic Switch For Car Radiator Fans; Coping With Damaged Computer Directories; Guide Valve Substitution In Vintage Radios. September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Build The Vader Voice. 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. April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors; 32-Band Graphic Equaliser, Pt.2; The Story Of Amtrak Passenger Services. November 1990: How To Connect 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; Build A Simple 6-Metre Amateur Band Transmitter. May 1989: Build A Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; The Burlington Northern Railroad. July 1989: Exhaust Gas Monitor; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; The NSW 86 Class Electrics. December 1990: The CD Green Pen Controversy; 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. 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. January 1991: Fast Charger For Nicad Batteries, Pt.1; Have Fun With The Fruit Machine; Two-Tone Alarm Module; LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers of Servicing Microwave Ovens. October 1989: FM Radio Intercom For Motorbikes Pt.1; GaAsFet Preamplifier For Amateur TV; 2-Chip Portable AM Stereo Radio, Pt.2; A Look At Australian Monorails. February 1991: Synthesised Stereo AM Tuner, Pt.1; Three Low-Cost Inverters For Fluorescent Lights; Low-Cost Sinewave Oscillator; Fast Charger For Nicad Batteries, Pt.2; How To Design Amplifier Output Stages. 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 Disc Drive Formats & Options; The Pilbara Iron Ore Railways. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Phone Patch For Radio Amateurs; Active Antenna Kit; Designing UHF Transmitter Stages. February 1990: A 16-Channel Mixing Desk; Build A High Quality Audio Oscillator, Pt.2; The Incredible Hot Canaries; Random Wire Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs, Pt.2. March 1990: Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC; The Australian VFT Project. 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. June 1990: Multi-Sector Home Burglar Alarm; Build A Low-Noise Universal Stereo Preamplifier; Load Protector For Power Supplies; Speed Alarm For Your Car. 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; Inside A Coal Burning Power Station. 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 Simple Shortwave Converter For The Lifestyle Music System (Review); The Battery Packs (Getting The Most From Counter Module; Build A 2-Metre Band; The Bose Care & Feeding Of Nicad Nicad Batteries). March 1991: Remote Controller For Garage Doors, Pt.1; 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. April 1991: Steam Sound Simulator For Model Railroads; Remote Controller For Garage Doors, Pt.2; Simple 12/24V Light Chaser; Synthesised AM Stereo Tuner, Pt.3; A Practical Approach To Amplifier Design, Pt.2. 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. June 1991: A Corner Reflector Antenna For UHF TV; Build A 4-Channel Lighting Desk, Pt.1; 13.5V 25A Power Supply For Transceivers, Pt.2; Active Filter For CW Reception; Tuning In To Satellite TV, Pt.1. April 1992: IR Remote Control For Model Railroads; Differential Input Buffer For CROs; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. May 1992: Build A Telephone Intercom; Electronic Doorbell; Battery Eliminator For Personal Players; Infrared Remote Control For Model Railroads, Pt.2; Aligning Vintage Radio Receivers, Pt.2. June 1992: Multi-Station Headset Intercom, Pt.1; Video Switcher For Camcorders & VCRs; IR Remote Control For Model Railroads, Pt.3; 15-Watt 12-240V Inverter; A Look At Hard Disc Drives. 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. 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. 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. 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. March 1993: Solar Charger For 12V Batteries; Alarm-Triggered Security Camera; Reaction Trainer; Audio Mixer for Camcorders; A 24-Hour Sidereal Clock For Astronomers. April 1993: Solar-Powered Electric Fence; Audio Power Meter; Three-Function Home Weather Station; 12VDC To 70VDC Converter; Digital Clock With Battery Back-Up. May 1993: Nicad Cell Discharger; Build The Woofer Stopper; Alphanumeric LCD Demonstration Board; The Story of Aluminium. 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. June 1993: AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; Digital Voltmeter For Cars; Build A Windows-Based Logic Analyser. 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. 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. 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 1991: Build A Colour TV Pattern Generator, Pt.1; A Junkbox 2-Valve Receiver; Flashing Alarm Light For Cars; Digital Altimeter For Gliders, Pt.3; Build A Talking Voltmeter For Your PC, Pt.2; Build a Turnstile Antenna For Weather Satellite Reception. August 1993: Low-Cost Colour Video Fader; 60-LED Brake Light Array; Microprocessor-Based Sidereal Clock; Southern Cross Z80-Based Computer; A Look At Satellites & Their Orbits. September 1993: Automatic Nicad Battery Charger/Discharger; Stereo Preamplifier With IR Remote Control, Pt.1; In-Circuit Transistor Tester; +5V to ±15V DC Converter; Remote-Controlled Cockroach. ORDER FORM Please send me the following back issues: _____________________________________________________________________ _______________________________________________________________________________________________________________ _______________________________________________________________________________________________________________ Enclosed is my cheque/money order for $______or please debit my: ❏ Bankcard ❏ Visa Card ❏ Master Card Signature ___________________________ Card expiry date_____ /______ Name ______________________________ Phone No (___) ____________ Note: all prices include post & packing Australia ....................................................... $A7 NZ & PNG (airmail) ...................................... $A8 Overseas (airmail) ...................................... $A10 Street ______________________________________________________ Detach and mail to: Silicon Chip Publications, PO Box 139, Collaroy, NSW, Australia 2097. Suburb/town _______________________________ Postcode ___________ Or call (02) 9979 5644 & quote your credit card details or fax the details to (02) 9979 6503. PLEASE PRINT 78 Silicon Chip ✂ Card No. October 1993: Courtesy Light Switch-Off Timer For Cars; Wireless Microphone For Musicians; Stereo Preamplifier With IR Remote Control, Pt.2; Electronic Engine Management, Pt.1. November 1993: High Efficiency Inverter For Fluorescent Tubes; Stereo Preamplifier With IR Remote Control, Pt.3; Siren Sound Generator; Engine Management, Pt.2; Experiments For Games Cards. December 1993: Remote Controller For Garage Doors; Build A LED Stroboscope; Build A 25W Audio Amplifier Module; A 1-Chip Melody Generator; Engine Management, Pt.3; Index To Volume 6. January 1994: 3A 40V Adjustable Power Supply; Switching Regulator For Solar Panels; 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; 12240VAC 200W Inverter; 0.5W Audio Amplifier; 3A 40V Adjustable Power Supply; Engine Management, Pt.5; Airbags In Cars – A Look At 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; Simple LED Chaser; 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 Antenna; PreChamp 2-Transistor Preamplifier; Steam Train Whistle & Diesel Horn Simulator; Portable 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; Engine Management, Pt.11. September 1994: Automatic Discharger For Nicad Battery Packs; MiniVox Voice Operated Relay; Image Intensified Night Viewer; AM Radio For Weather Beacons; Dual Diversity Tuner For FM Microphones, Pt.2; Engine Management, Pt.12. October 1994: How Dolby Surround Sound Works; Dual Rail Variable Power Supply; Build A Talking Headlight Reminder; Electronic Ballast For Fluorescent Lights; Build A Temperature Controlled Soldering Station; Electronic Engine Management, Pt.13. November 1994: Dry Cell Battery Rejuvenator; Novel Alphanumeric Clock; 80-Metre DSB Amateur Transmitter; Twin-Cell Nicad Discharger (See May 1993); How To Plot Patterns Direct to PC Boards. December 1994: Dolby Pro-Logic Surround Sound Decoder, Pt.1; Easy-To-Build Car Burglar Alarm; Three-Spot Low Distortion Sinewave Oscillator; Clifford – A Pesky Electronic Cricket; Remote Control System for Models, Pt.1; Index to Vol.7. January 1995: Sun Tracker For Solar Panels; Battery Saver For Torches; Dolby Pro-Logic Surround Sound Decoder, Pt.2; Dual Channel UHF Remote Control; Stereo Microphone Prea mpl ifier. 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. 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 Darkr ooms; Balanced Microphone Preamp. & Line Filter; 50W/ Channel Stereo Amplifier, Pt.2; Wide Range Electrostatic Loudspeakers, Pt.3; 8-Channel Decoder For Radio Remote Control. May 1995: What To Do When the Battery On Your PC’s Mother board Goes Flat; Build A Guitar Headphone Amplifier; FM Radio Trainer, Pt.2; Transistor/Mosfet Tester For DMMs; A 16-Channel Decoder For Radio Remote Control; Introduction to Satellite TV. June 1995: Build A Satellite TV Receiver; Train Detector For Model Railways; 1W Audio Amplifier Trainer; Low-Cost Video Security System; Multi-Channel Radio Control Transmitter For Models, Pt.1; Build A $30 Digital Multimeter. July 1995: Electric Fence Controller; How To Run Two Trains On A Single Track (Incl. Lights & Sound); Setting Up A Satellite TV Ground Station; Build A Reliable Door Minder. August 1995: Fuel Injector Monitor For Cars; Gain Controlled Microphone Preamp; Audio Lab PC-Controlled Test Instrument, Pt.1; Mighty-Mite Powered Loudspeaker; How To Identify IDE Hard Disc 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: Geiger Counter; 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 Transv erter For The 80M Amateur Band, Pt.1; PIR Movement Detector; Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.1; 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; Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.2; Knock Sensing In Cars; Index To Volume 8. January 1996: Surround Sound Mixer & Decoder, Pt.1; Magnetic Card Reader; Build An Automatic Sprinkler Controller; IR Remote Control For The Railpower Mk.2; Recharging Nicad Batteries For Long Life. February 1996: Three Remote Controls To Build; Woofer Stopper Mk.2; 10-Minute Kill Switch For Smoke Detectors; Basic Logic Trainer; Surround Sound Mixer & Decoder, Pt.2; Use your PC As A Reaction Timer. March 1996: Programmable Electronic Ignition System; Zener Diode Tester For DMMs; Automatic Level Control For PA Systems; 20ms Delay For Surround Sound Decoders; Multi-Channel Radio Control Transmitter; Pt.2; Cathode Ray Oscilloscopes, Pt.1. April 1996: Cheap Battery Refills For Mobile Telephones; 125W Audio Power Amplifier Module; Knock Indicator For Leaded Petrol Engines; Multi-Channel Radio Control Transmitter; Pt.3; Cathode Ray Oscilloscopes, Pt.2. May 1996: Upgrading The CPU In Your PC; High Voltage Insulation Tester; Knightrider Bi-Directional LED Chaser; Simple Duplex Intercom Using Fibre Optic Cable; Cathode Ray Oscilloscopes, Pt.3. June 1996: BassBox CAD Loudspeaker Software Reviewed; Stereo Simulator (uses delay chip); Rope Light Chaser; Low Ohms Tester For Your DMM; Automatic 10A Battery Charger. July 1996: Installing a Dual Boot Windows System On Your PC; 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: Electronics on the Internet; Customising the Windows Desktop; 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; Feedback On Prog rammable Ignition (see March 1996); 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. July 1997: Infrared Remote Volume Control; A Flexible Interface Card For PCs; Points Controller For Model Railways; Simple Square/Triangle Waveform Generator; Colour TV Pattern Generator, Pt.2; An In-Line Mixer For Radio Control Receivers; How Holden’s Electronic Control Unit works, Pt.1. 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; How Holden’s Electronic Control Unit Works, Pt.2. 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; Win95, MSDOS.SYS & The Registry. October 1997: Build A 5-Digit Tachometer; Add Central Locking To Your Car; PC-Controlled 6-Channel Voltmeter; 500W Audio Power Amplifier, Pt.3; Customising The Windows 95 Start Menu. November 1997: Heavy Duty 10A 240VAC Motor Speed Controller; Easy-To-Use Cable & Wiring Tester; Build A Musical Doorbell; Relocating Your CD-ROM Drive; Replacing Foam Speaker Surrounds; Understanding Electric Lighting Pt.1. December 1997: A Heart Transplant For An Aging Computer; Build 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. 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 1998: Hot Web Sites For Surplus Bits; Multi-Purpose Fast Battery Charger, Pt.1; Telephone Exchange Simulator For Testing; Command Control System For Model Railways, Pt.2; Demonstration Board For Liquid Crystal Displays; Build Your Own 4-Channel Lightshow, Pt.2; Understanding Electric Lighting, Pt.4. 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; Jet Engines In Model Aircraft. May 1998: Troubleshooting Your PC, Pt.1; Build A 3-LED Logic Probe; Automatic Garage Door Opener, Pt.2; Command Control For Model Railways, Pt.4; 40V 8A Adjustable Power Supply, Pt.2. June 1998: Troubleshooting Your PC, Pt.2; 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. July 1998: Troubleshooting Your PC, Pt.3 (Installing A Modem And Sorting Out Any Problems); Build A Heat Controller; 15Watt Class-A Audio Amplifier Module; Simple Charger For 6V & 12V SLA Batteries; Automatic Semiconductor Analyser; Understanding Electric Lighting, Pt.8. August 1998: Troubleshooting Your PC, Pt.4 (Adding Extra Memory To Your PC); 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. December 1996: CD Recorders – The Next Add-On For Your PC; Active Filter Cleans Up CW Reception; Fast Clock For Railway Modellers; Laser Pistol & Electronic Target; Build A Sound Level Meter; 8-Channel Stereo Mixer, Pt.2; Index To Volume 9. September 1998: Troubleshooting Your PC, Pt.5 (Software Problems & DOS Games); A Blocked Air-Filter Alarm; A WaaWaa Pedal For Your Guitar; Build A Plasma Display Or Jacob’s Ladder; Gear Change Indicator For Cars; Capacity Indicator For Rechargeable Batteries. January 1997: How To Network Your PC; Control Panel For Multiple Smoke Alarms, Pt.1; Build A Pink Noise Source (For Sound Level Meter Calibration); Computer Controlled Dual Power Supply, Pt.1; Digi-Temp Monitors Eight Temperatures. October 1998: CPU Upgrades & Overclocking; 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. February 1997: Cathode Ray Oscilloscopes, Pt.6; PC-Controlled Moving Message Display; Computer Controlled Dual Power Supply, Pt.2; Alert-A-Phone Loud Sounding Alarm; Control Panel For Multiple Smoke Alarms, Pt.2. November 1998: Silicon Chip On The World Wide Web; The Christmas Star (Microprocessor-Controlled Christmas Decoration); A Turbo Timer For Cars; Build Your Own Poker Machine, Pt.1; FM Transmitter For Musicians; Lab Quality AC Millivoltmeter, Pt.2; Beyond The Basic Network (Setting Up A LAN Using TCP/IP); Understanding Electric Lighting, Pt.9; Improving AM Radio Reception, Pt.1. 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: Avoiding Win95 Hassles With Motherboard Upgrades; 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: Teletext Decoder For PCs; Build An NTSC-PAL Converter; 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: Tuning Up Your Hard Disc Drive; 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; Fail-Safe Module For The Throttle Servo; Cathode Ray Oscilloscopes, Pt.10. 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; GM’s Advanced Technology Vehicles; Improving AM Radio Reception, Pt.2; Mixer Module For F3B Glider Operations. PLEASE NOTE: November 1987 to August 1988, October 1988 to March 1989, June 1989, August 1989, December 1989, May 1990, August 1991, February 1992, July 1992, September 1992, November 1992, December 1992 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 $7.00 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 disc for $10 including p&p, or can be downloaded free from our web site: www.siliconchip.com.au January 1999 79 RADIO CONTROL BY BOB YOUNG Operating model R/C helicopters This month, we will take a look at some of the technical aspects related to the operation and flying of model R/C helicopters. They are not easy to fly, as we will find out. September 19th, 1971. Place, Doylestown Pennsylvania, USA and a very much younger Bob Young was standing engrossed, contemplating the gruelling events of the last four days. Today was the last day of the 1971 World Aerobatic Championships and scheduled for demonstration flying, which simply meant fun and lots of it. Suddenly all pain was forgotten as a magical sight suddenly commanded complete attention. Here was a sight that made the entire trip worthwhile. Gone were all thoughts of the winter months of early morning practice sessions, the long nights of preparation and the strain of competing in a contest alongside some of the best R/C fliers in the world. There in front of my eyes, drifting inches above the ground, was not one but two quite large model helicopters. I was about to witness what was billed as the first public demonstration of a model helicopter. Looking back at the flying from a 1998 viewpoint, Dieter Schluter (the designer) and his friend put on a quite tame demonstration that day, with coordinated stall turns as the highlight of the aerobatic routine. But we were all stunned. In 1971 this was an amazing feat of model aerodynamic engineering. Dieter had gone where no other modeller had been before and not content to demonstrate one machine, floored us with a synchronised display featuring two helicopters. The display brought the sky down. Flown with great authority, Dieter and his mate gave us a never-to-be-forgotten show. The difficulties facing the engineers developing the model helicopter were enormous. Not only were they faced with scale effect and Reynolds numbers, they faced problems with inadequate engines, incredibly involved mechanical linkages and finally, keeping this untested mechanical nightmare in one piece while learning to fly at the same time. They had no teachers because they were entirely on their own. It was a truly difficult task and the modern modeller owes a great debt to the people who made it all happen. The fact that these models didn’t make an appearance until 1971 Fig.1: the major components of a model helicopter. (Diagram courtesy of Max Tandy R/C Helicopters Australia). 80 Silicon Chip is a measure of the scope and difficulty of the task. My first helicopter I knew of all of these difficulties but I was hooked! I had to have one of these machines and when I returned to Sydney arrangements were made to procure one of the Kalt (45 powered) Huey Cobras, a smaller Japanese licence built version of the Schluter (60 powered) Huey. By modern standards they were a primitive machine. Fitted with a fixed pitch Hiller type head with swash plate for pitch and roll, throttle for climb/descend and tail rotor pitch control for yaw/torque compensation, they were simple indeed. There were no gyros or computer radios in those days! But they flew and they flew well. Cooling was a major problem with the motor buried deep inside a slab-sided fuselage. Very large extra air vents had to be cut into the sides and covered with fine mesh and air ducting from the dummy air scoop brought in cool ram air once the helicopter started to move forward which it rarely did for the first two months. For those first two months of learning to hover, the motors sat inside that fuselage bathed in their own hot, oily exhaust fumes, and in the Huey they sometimes choked on these stale gases. Fresh clean air is a must and lots of it. Because the motors ran at a higher temperature, there was a much denser smoke haze generated. I remember one dead still, cool evening right at dusk. The local baseball team was practising in the park where I was flying and I heard “Strike, talk about pollution!” I looked up and found the whole park covered in what looked like stage smoke. It was an eerie sight. For one hour every day after work I religiously toiled at mastering the hover. It was all very new and very difficult; made even more difficult by the fact that I had no-one to turn to for help. I was one of the first in Australia and very much on my own in Sydney at least. However I was fortunate to have as my teacher from time to time, Yuri Oki, the man who built the models under licence in Japan. Oki insisted that before an out-and-return flight could be attempted I had to be able to hover at eye level and over the same spot, for an entire tank of fuel, about 15-20 minutes. This Hughes 300 model helicopter was built by Mike Zimmerman. (Photo courtesy “Airborne” magazine). This was advice that I was very grateful for when I did eventually undertake my first out-and-return flight. Now Oki was a wild man and he loved to fly helicopters. He flew one inside my factory when it was a bare shell just after I moved into those premises in February 1972. We nearly gassed ourselves that night and in the end we were all hanging out of windows gasping for breath. We flew the model in the street outside my factory and again over the factory from the local park about 500 metres away. I shudder when I think of all of this now, for just after that flight I had my first motor cut out and with no auto-rotation there was only one way to go and that was down and not very nicely at that. Fortunately, I was quite low in the park at the time and little damage was done. Oki gave demonstration flights at the Royal Easter Show on several occasions and on one such occasion he asked me to call for him while he did a flight around the clock tower at the far end of the main arena. It was the most January 1999 81 Fig.1: the main rotor blades in a helicopter are arranged so that the pitch can be changed in each quadrant of the main rotor disc. This is called the “cyclic pitch control” and is used for the main pitch (fore and aft) and roll (lateral) control functions. Fig.2: when a helicopter hovers close to the ground in still air, the air is forced down from the rotor, hits the ground and rebounds. This upward moving air is then drawn back down into the rotor disc and accelerated further, hitting the ground and rebounding with even more energy than before to create a dangerous ground effect. Fig.3 another dangerous situation. Air moving down through the disc on the cliff side will reduce the lift on that side of the disc and the helicopter will gradually begin to bank towards the cliff. Any attempt on the part of the pilot to increase the lift on that side of the disc will only serve to increase the velocity of the vortex, further exacerbating the problem. The only answer once this situation arises is to move forward into clear air and come around again after the vortex has died away. difficult pylon call I have ever made. I still have visions of that model disappearing out of sight behind the tower. It only took moments to reappear but it seemed like an eternity. They were fun days and we could not get enough of it. Rumour has it that Oki was asked to leave his hotel one night after he flew a helicopter 82 Silicon Chip in his room. As I said, he was a wild man and loved flying. He was also very good at it. It is typical of the man that these days he is knee-deep into model turbines. I subsequently flew helicopters for about three years after that and eventually gave it away to return to my first love, aerobatic flying. One interesting aside here: when I returned to aerobatics I was a far better pilot because I had gained complete mastery of my left thumb as a result of flying with no gyro on the tail rotor. Helicopters demand constant attention to the tail rotor, hence the modern helicopter with tail-rotor gyro. With no gyro you become very adept with your left thumb, a most important movement in multi-point rolls on fixed wing aircraft. I do not agree with all of the modern gadgets. It is like a concert pianist using an electronic piano. However, the modern crop of gadgets has made life much easier for the tyro helicopter pilot and it does not take anywhere near as long to learn to fly now as it took us. How they work So how do these fabulous machines work? A helicopter is classified as a rotary winged aircraft and the aerodynamics of this type of machine are quite different to that of a fixed-wing aircraft. Helicopters, both full size and models, are very difficult to learn to fly, as they require a great deal of dexterity and coordination. Basically, the controls are as follows. The main rotor blades are arranged so that pitch can be changed in each quadrant of the main rotor disc – see Fig.1. This is called the “cyclic pitch control” and is used for the main pitch (fore and aft) and roll (lateral) control functions. The lateral cyclic pitch control corresponds to the aileron stick in a fixed wing aircraft and the forward and aft cyclic pitch control corresponds roughly to elevator. “Cyclic pitch”, as the name suggests, alters the pitch of the main rotor blades on a cyclic basis. Thus to bank left, the pitch on each rotor blade is reduced in the left quadrant and increased in the right on each cycle of the main rotor blades. To move forward the pitch is reduced in the forward quadrant and increased in the aft. Collective pitch control is used to increase or decrease the pitch angle of all blades over the entire cycle and serves as the climb or descend control in conjunction with the throttle. The linkages required to achieve all these pitch variations are very elaborate and took a long time to develop. There is also the problem of the This Eurocopter “Tigre” model helicopter is 1.9 metres long and weighs just 7kg. (Photo courtesy “Airborne” magazine). increase and decrease of lift on the advancing and retreating blade in forward flight. This creates an unbalanced lift distribution across the transla tional lift disc and was one of the biggest problems facing the pioneers of model helicopters. The solutions to this problem are outside the scope of this article and we may deal with this one later. The torque of the main rotor is counteracted by the small tail rotor. By increasing or decreasing the collective pitch on this small propeller, yaw control can be effected. Loss of tail rotor control is a serious business and many helicopters have crashed as a result, so routine maintenance on this seemingly insignificant item is very important. The Americans lost over 5000 helicopters in Vietnam and one of the favourite tricks of the Viet Cong was to shoot at the tail rotor. There was an interesting exhibit in the Canberra War Museum of a tail rotor assembly of an Australian helicopter that was riddled with bullet holes. The controls in a helicopter are highly interactive and learning to fly one of these models may become a long drawn out affair. Great strides have been made in transmitter and gyro design and mixers and gyros have simplified learning significantly. Flying hazards Flying helicopters is difficult and fraught with hazards unknown in fixed wing aircraft. To begin with, there are two forms of lift equations; one for hover and one for forward movement. In the hover, lift is a function of blade area, rotor speed and angle of attack of the blades. In forward motion, the blade area becomes the total swept area of the blades; in other words, the total rotor disc. This is referred to as translational lift and is a very important factor in helicopter operations. Heavy-lift helicopters are almost always fitted with wheels and a fully loaded takeoff is usually carried out in much the same manner as a fixed wing aircraft, with the machine running along the ground to gain flying speed before lifting off. In this manner the extra lift obtained from translational effects can be fully utilised. Hover and vertical takeoff are an inefficient and somewhat risky pair of manoeuvres and used only when circumstances dictate. Great care must be exercised at all times in hovering flight because of the problems arising from vortex generation. Because they shift such huge volumes of air, strange STEPDOWN TRANSFORMERS 60VA to 3KVA encased toroids Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 9476-5854 Fx (02) 9476-3231 January 1999 83 to the ground. Too late and the speed will not be washed off sufficiently to effect a safe landing. Helicopter pilots are an intrepid lot. Dangerous situations A close up view of the Eurocopter “Tigre” model helicopter pictured on the previous page. (Photo courtesy “Airborne” magazine). things can happen when hovering around obstacles. Refer now to Fig.2 which shows a helicopter hovering in still air and in ground effect. Air is forced down from the rotor, hits the ground and rebounds. This upward moving air is then drawn back down into the rotor disc and accelerated further, hitting the ground and rebounding with even more energy than before. In time, this doughnut-shaped ring of air may obtain such a velocity that the speed of the downgoing air entering the rotor disc may exceed the climb rate of the helicopter and the helicopter will gradually sink to the ground, even with full power applied. Now you will notice that I particularly stated that this happens in still air. In a strong wind, the aircraft is actually travelling forward relative to the airstream to maintain hover over a fixed spot. As a result, the dirty air is swept away behind the helicopter and it is almost impossible for vortexes to form in strong winds. Which leads us to an interesting observation. One of the things that make learning to fly a helicopter so difficult for an experienced fixed-wing pilot are the radically different emergency procedures. In a model fixed-wing aircraft, in an emergency, more often than not the best procedure is to cut the throttle 84 Silicon Chip and pull full up. This lifts the nose, slows the model and settles it into a glide, giving time for the pilot to stabilise the model and see what should be done next. By contrast, in a helicopter the procedure is usually to go straight to full power and give down elevator (full forward cyclic). This lifts the model away from the ground and moves the model into clean air (away from vortexes) and increases translational lift – all of which gains the pilot height and time to think. The two reactions are exactly opposite. Chopping the throttle on a helicopter is catastrophic because they come down like bricks, especially in the days before auto-rotation. Auto-rotation, by the way, is the ability of the helicopter to convert height into rotor RPM. In an auto-rotative descent, the main rotor blades are put into free wheeling mode and the pitch moved to a slightly negative angle of attack. The downward motion of the helicopter is used to spin up the main rotor and this stored energy is converted to lift at the last moment before touch down. The pilot must gauge the correct moment to engage positive angle of attack on the main rotor and this is a very delicate operation. Too early and the rotor will slow below minimum lift RPM and the helicopter will crash Moving back now to vortexes, Fig.3 shows an interesting variation on the theme. Here we have a typical rescue scenario, where someone has fallen down a cliff into a difficult to reach crevice. The air on the cliff side of the chopper is trapped and will vortex readily. By contrast, the air on the open side is free to move away and now we have a really dangerous situation on our hands. Air moving down through the disc on the cliff side will reduce the lift on that side of the disc and the helicopter will gradually begin to bank towards the cliff. Any attempt on the part of the pilot to increase the lift on that side of the disc will only serve to increase the velocity of the vortex, further exacerbating the problem and if the situation gets out of hand the helicopter could ultimately crash into the cliff face. The only answer once this situation arises is to move forward into clear air and come around again after the vortex has died away. Hovering in still air near trees, buildings and cliffs is fraught with danger and must be undertaken with great care. I once got caught with a tail rotor vortex in the early days, after hovering for a long time in still air at about 100 feet. I gradually lost tail rotor control until even full opposite tail rotor control would not stop the tail from spinning around. I thought the tail rotor servo had packed it in so I had no alternative (or so I thought) but to gradually bring the model down and plonk it unceremoniously on the ground with the fuselage slowly rotating around the main rotor axis. Fortunately, Oki was there that day and he recognised it for what it was and told me how to deal with it correctly. The answer: full throttle and full forward cyclic, thus moving the chopper into clear air and establishing a weather vane effect on the side area of the fuselage until the tail rotor control re-established itself. It never occurred again so I never had the opportunity to put his instructions into practice. So there you have it: a look at the SC art of flying model helicopters. Community AM radio: how do you listen to it? Do you wish to listen to your local community AM radio station but find that its frequency is “off the dial”? You can buy a cheap radio to cover the extended band or you can tweak your existing radio. We show you how. By RICK WALTERS The frequency range of the Australian AM band is from 531kHz to 1602kHz but recently a range above the top of the band (from 1611kHz to 1705kHz) has been allocated to “narrow band area services”. Community radio stations have been allocated frequencies in this new band. They operate on low power and are only meant, as the name implies, to cover a small area within a radius of 20-25km. They operate on a restricted bandwidth (narrow band) of ±3kHz and because of this, they do not transmit This Digitor AM/FM radio costs $12.95 from Dick Smith Electronics. It already covers all the new community stations without modification. Alternatively, you can tweak an old AM receiver if you have one lying around. wideband hifi sound. (Other AM stations do broadcast hifi sound but you’d never know it because most AM radios produce poor quality sound). For their intended use, community news and information, the narrow audio bandwidth is not a major drawback. The problem is that normal AM receivers, and especially AM/FM tuners with digital displays, will not cover this additional range. The same comment applies to car radios. So why not design a down-converter which would translate these stations into frequencies which can be tuned by a standard receiver? When we looked at the cost of a small AM/FM radio, we realised that the “converter” would cost many times more than the radio. We therefore decided that, in view of the cost of a down-converter and the relative difficulty in connecting it to an AM/FM tuner or car radio, the project was not really viable. OK then, could we convert an “offthe-shelf” AM radio to cover this extended band? Being the last of the big spenders (and having to get the money back from the boss), we bought a $12.95 Digitor AM/FM pocket radio from Dick Smith Electronics. When we got it back to the lab and opened the box, one of the interesting things about the radio was its dial coverage. It was scaled from 520kHz to 1710kHz, which meant it should already cover all the new stations. Checking this range using a signal generator showed that it actually tuned from 537kHz to 1720kHz. So who needs a converter? Just buy this radio and the problem is solved. Tweaking your own radio Maybe you have an old AM radio lying around and would like to try to 86 Silicon Chip extend its high frequency coverage. We can only give you a broad outline of the procedure involved as the location of the components you have to adjust will vary from one unit to another. The simplest way to move the tuning range higher is to reduce the inductance of the local oscillator coil (we are assuming that any set you adapt will be a superheterodyne). Now before we go any further we should state the drawback of this sort of modification. It will upset the tracking of the gang over the tuning range of the dial and so if you rely on stations appearing at particular parts of the dial, they will inevitably be shifted. However, the aim of the modification is to receive community radio stations. Identifying the oscillator coil Which one’s the oscillator coil? If the receiver uses small metal can coils, the oscillator will probably have a red spot on its slug. To decrease the inductance you need to rotate the slug anticlockwise. Once this is done, the aerial input coil should be peaked for maximum volume on the new frequency. If there is no red dot then you face a dilemma. If you are not the adventurous type, put the back on the radio and put it back on the shelf. After all, if you don’t twiddle anything, the radio will still work as it did. On the other hand . . . The oscillator coil is the only one that will move the received frequency dramatically when the slug is moved. Tune the radio to a local station around 1500-1550kHz and rotate the slugs 1/4 turn anticlockwise, one by one. If the volume changes but the audio stays clear, return the slug to the original position and try the next coil. The effect should be similar to tuning slightly off frequency, where the sound becomes slightly distorted or sibilants become pronounced. One of our photos shows the position of the oscillator coil in the radio we purchased. Once you have identified the oscillator coil, set the tuning pointer right against the high frequency end stop, then move it back a fraction. This allows you to easily find your local community station. Now adjust the oscillator slug until the station is heard at maximum level. Keep backing off the volume control The Digitor AM radio covers the range from 520kHz to 1710kHz and it uses a single surface mount IC which is soldered on the copper side of the PC board. OSCILLATOR COIL This photo shows the position of the oscillator coil in the Digitor AM radio that we purchased. Often, the oscillator coil will be identified by a red dot on its slug. If there’s no red dot, try rotating the coil slugs 1/4 turn anticlockwise, one by one, and observe the effect (see text). as you turn the slug as it is easier to distinguish this peak at low volume levels. The final step is to peak the aerial trimmer on the gang. This tunes the aerial coil on the ferrite rod to the new frequency. There may be three or four trimmers, so again follow the same procedure. Move each in turn and if it appears to have no effect, move it back to the original position and try the next one. While these adjustments may upset the tracking and sensitivity a little at other frequencies, we feel that the main aim is to get the best possible reception on the new channel. If you want a list of the broadcasting frequencies of community radio stations in your area, contactthe Australian Communications Authority by phoning (02) 6256 5555. Alternatively, you can get this information via their SC website at www.aca.gov.au January 1999 87 VINTAGE RADIO By RODNEY CHAMPNESS, VK3UG Improvements to AM broadcast band reception; Pt.3 In our final article this month, we look at making a practical antenna booster for AM transistor radios. The circuit is basically a separate broadcast-band tuned circuit. Last month, mention was made of the problems that occurred when antenna/earth connections were made to the cheaper transistor radios. Often, the reception will be made worse by these connections due to the poor selectivity of such sets. So what can be done to make these sets quite useable with improved antennas and earths? This was a problem that exercised my mind for quite some time. The solution turned out to be relatively simple and very effective. I reasoned that if I could improve the front-end selectivity of such receivers, their response to shortwave transmissions would diminish, if not completely disappear. But how could this be done without delving into the internals of the sets? The answer is to connect the antenna and earth to a separate broadcast-band tuned circuit. By placing this circuit near the set, sufficient signal is then inductively coupled into the receiver’s loop-stick antenna to give a worthwhile improvement. The tuned circuit arrangement is virtually the same as for a crystal set but without the detector and headphones. A crystal set coil and tuning capacitor tend to be rather bulky, so a ferrite loopstick antenna coil and a small tuning capacitor were wired You can make a simple antenna booster using a ferrite rod antenna and a tuning capacitor to tune the AM broadcast band. 88 Silicon Chip up instead. This was connected to an antenna and earth and when the receiver’s loopstick and the booster were lined up a few centimetres apart, a significant improvement in the performance was observed. Measurements confirmed that the improvement in set perfor mance, when used with the booster and a reasonable antenna/earth system was of the order of 14-20dB. Many have been sceptical about the performance of such a simple device but I can assure you that it really does work well. For this reason, I call it the “AM Radio Reception Booster”. It can even be demonstrated that sitting a transistor set with a large (eg, 200 x 13mm) ferrite rod antenna alongside a mediocre set with a small ferrite rod antenna will boost the performance of the latter (provided that the two sets are tuned to the same station. This even applies when the larger set is turned off. Naturally, the improvement is nothing like that obtained with an outside antenna and earth attached to the booster but it does prove that sets with bigger rod antennas tend to be better performers. The booster can be built into a small plastic project box. A ferrite rod antenna (either prewound or one which you wind the coils yourself), a tuning capacitor, a knob and a 2-way screw terminal strip are all the major parts required. The circuit of the “deluxe” version of the booster is shown in Fig.9. Here’s how to build it. First, obtain a 100mm length of 9.5mm diameter ferrite rod and wind on 70 turns of 0.5mm diameter enamelled copper wire towards one end of the rod. This tuned winding is tapped at 7 turns from the earthy end. Next, you need to wind on a bifilar winding consisting of 15 + 15 turns of 0.5mm enamelled copper wire. This must be spaced 20mm from the end of the tuned winding. To make the bifilar winding, first put one end of two 500mm pieces of the wire into a vyce. Place the other ends into the chuck of a small hand-drill and rotate the drill whilst keeping modest tension on the wires, until the wires are wound together with a twist every 2-3mm. These two wires are then wound onto the rod (15 turns) and are connected together so that they are in series. The junction of the start of one winding and the end of the other becomes the centre tap, which may go to earth in some instances. The start of each winding is shown by a dot on the circuit diagram. Nail polish or other “plastic” glues will hold the windings in position. You may care to slip the first and last turns of each winding under the adjacent one to make it just that bit firmer. One of the accompanying photographs shows a couple of variations of the booster. If you are using a plastic case, the ferrite rod can either be glued in position or tied to the lid using short lengths of spaghetti sleeving (this passes through holes drilled in the lid). The tuning gang needs to have a maximum capacitance of 300pF and is attached to the lid using machine screws. The commonly available twin-gang plastic capacitors are quite suitable for this job, if both sections are paralleled and the trimmers set at minimum capacitance. A few more turns may be required on the tuned winding if one of these is used, in which case the antenna tap should also be moved up the winding. Make sure that a knob comes with the capacitor otherwise it will be difficult to find a knob to suit. If you really want to keep costs down, you can make a booster using the parts from a defunct AM pocket portable transistor set. could also be connected across these two terminals. However, better results with a loop may be obtained by using the “Ant 1” and “Ant 2” terminals at the top of the diagram. An earth is optional but in a noisy situation may give sufficient improvement to be worthwhile. With the booster connected to the antenna and earth, move it close to a transistor radio and adjust the tuning knob for an improvement in the received signal. Initially, the set and the booster can be close together while you adjust the tuning. However, if your antenna system is large, the amount of signal coupled into the set from the booster may be enough to cause overload. If this happens, just move the booster away from the set. Make sure that the booster is oriented for best performance - the loop Testing it Having assembled the AM Radio Reception Booster, now is the time to try it. The deluxe version gives the user several options for obtaining the best noise-free reception. First, the booster may have an ordinary antenna and earth connected to the terminals shown on the bottom of the circuit in Fig.9. A loop antenna Fig.9: the circuit of the AM Radio Reception Booster. stick in the receiver and the booster should both be horizontal. Although the deluxe version gives the user a variety of options, it is usually not necessary to go to that amount of trouble. For example, instead of winding your own ferrite coil, try using a prewound ferrite loop antenna. These have four wires coming out of the windings and the pair with the greatest resistance, as measured using an ohmmeter, are attached to the tuning capacitor. The other two wires go to the antenna system. Adjust the coil on the rod so that complete coverage of the broadcast band is achieved (you may also have to connect both sections of the tuning gang in parallel). Note that the perfor mance of this simple version will not be quite as good as the deluxe version. If you really want to keep costs down, you can make a booster using the parts from a defunct AM pocket portable transistor set. Open up the set, remove the speaker and the battery carrier, and mount a terminal strip near the ferrite rod antenna. Next, undo the PC board mounting screws so that you have access to the antenna leads where they connect to the base circuit of the converter transistor. Unsolder these and connect them to the new terminal strip. Finally, reassemble the set, connect the external antenna system to two terminals on the front (or back) of the set as shown in the photo, and your booster is complete. This is surely one of the most inexpensive methods ever to improve radio reception. It costs just one terminal strip and two self-tapping screws, plus a defunct set that you SC already own! January 1999 89 ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. Digital tachometer not an easy rider I have recently purchased a Digital Tachometer kit as described in the August 1991 issue of SILICON CHIP. It features a 4-digit, 7-segment LED display which indicates zero to 9900 rpm. I’ve installed it on a Harley Davidson motorcycle with billet machined housing for the LED display which is connected to the circuit board via ribbon cable. My problem is that I had to change RX to 170kΩ to get correct calibration to suit a 2-cylinder engine. It works fine but the count rate is too slow (ie, 0.6 seconds). In the lower gears the engine will beat the tachometer update time. Is there a simple or practical way of reducing the count rate time by modifying the circuit? Or is it possible to multiply the input signal by two or three? (B. V., Bateman, WA). • There is no easy modification to shorten the update time of the circuit as it stands. The alternative is to increase the input frequency and then reduce the update time. The frequency could be multiplied using the frequency doubler circuit from page 44 of the October 1998 issue. The multiplication factor can be increased to x16 or x32 by using the Modifying the multipurpose charger I would like to add an extra voltage setting to charge a 15.6V battery pack for my cordless drill. Could you please supply me with the resistor values. Would it be possible to feature a project or circuit for a tacho for tuning chainsaws? (D. G., via email). • The multipurpose charger is not capable of charging a NiCd battery with a nominal 15.6V output. The total of 13-cells within this battery pack require a supply voltage of 90 Silicon Chip Q5 (pin 5) or Q6 (pin 4) output from IC2, a 4020 divider. The capacitor between pins 6 & 7 of the 4046 (IC1) should be reduced to about 120pF. The divider resistors at the pin 4 output of IC1 are not required. A multiplication circuit is also used in the digital tachometer from the October 1997 issue. The multiplier circuit is inserted between the pin 4 output of IC3f on the digital tachome ter and the pin 1 input to IC4b. Connect pin 4 of IC3f directly to the pin 14 input of the 4046 multiplier and the pin 4 output of the 4046 to the pin 1 input of IC4b. Note that the 4046 and 4020 can be operated from the 9V supply via the digital tachometer. The update time for the 555 timer (IC1) can then be reduced by changing the 2.2µF capacitor on pins 6 & 7. If you multiply by 16, use a value of 0.15µF, or use .068µF if you multiply by 32. Magnetic shielding for loudspeakers I am looking for an easy way to magnetically shield my speakers and I was wondering if it is possible to use ordinary off-the-shelf magnets glued to the back of the speaker. If at least 26V in order to provide a full charge. The transformer only delivers 18V RMS or 25V peak. At this stage we cannot suggest using a higher voltage transformer since there are a significant number of other changes that would need to be made to the circuit for satisfactory operation. We have not published a simple tachometer which would directly be suitable for tuning a chainsaw. However, the Digital Tachometer described in the October 1997 issue of SILICON CHIP could be suitable. it is possible what kind of magnets would you use and would it matter what size the magnet was? (S. L., Ringwood East, Vic). • We do not think your method will work. You need a complete mildsteel shield to go around the existing magnet structure and this must be magnetised by a permanent magnet to completely cancel the field from the main magnet. Electrolytic capacitor polarity This may seem silly but could you please explain what criteria governs the polarisation of input\output coupling ca pacitors in AC circuits (amplifiers, etc)? I understand why they are there but have seen circuits with differing polarisation. I am particularly mystified by the “Guitar Limiter” project in the October 1998 issue but the question could apply to any of your power amplifier projects. As far as the Guitar Limiter is concerned, could you ex plain the polarisation of the following capacitors: input to IC1a (10µF); IC1a to IC2 (2.2µF); IC2 to VR5 (1µF); VR5 to IC1b (1µF) and IC1b to output (1µF). Why is the 3.3µF capacitor from the output of IC2 to the input of the rectifier stage a non-polarised type? And are C1 and C2 connected negative to negative because of the forward biased diodes D3 and D4. (M. B., Lawson, NSW). • The reason the input capacitors to the LM833 op amps are positive to pins 5, 3, etc is that the internal input transistors are PNP and their bias currents cause a positive voltage to be impressed across the input bias resistors. Hence pin 3, pin 5, etc will be positive with respect to GND. Similarly, the outputs of the LM833 op amps can be expected to be slightly positive with respect to GND. The 3.3µF and back-to-back 100µF capacitors (C1,C2) have been included because pin 11 of IC2 can be positive or negative, depending on the control Current limit setting for ignition I have recently installed the ignition kit in my 1975 VW Passat and I am very impressed that your design worked well first time (responsive engine, less pollution!) but with the following reservation which I hope you can clarify for me. In following the instructions for “current limit adjustment”, VR1 from fully clockwise to fully anticlockwise gives a reading from 200mV to 225mV respectively (not approaching the suggested 250mV). Do I have a problem with this? Should the 33Ω resistor be increas ed in value to obtain a better balance? The engine is 4-cylinder 1500cc with a points type distributor, a 1Ω ballast resistor, a single coil, a new 12V heavy-duty bat tery, negative earth and water cooling! I took considerable care to heatsink each semiconductor lead during solder- setting produced by IC2. Also, VR2 and VR4 can affect the DC polarity – it can be positive or negative, therefore NP capacitors must be used. Resurrecting the 40V 8A supply I have built the 40V 8A power supply described in the April and May 1998 issues of SILICON CHIP. Unfortunately, it expired during testing and I was wondering whether you could shed any light on a possible cause. To start at the beginning, it was built from an Altronics kit and initial testing seemed OK – well almost. Unloaded, I discovered that adjusting it to a lower voltage (say from 20V to 10V) would result in the supply output dropping to 0V. A bit of probing revealed that the cause appears to be the 7812 input voltage going too high and the regulator shutting itself down due to overvoltage. I assume that when the output voltage is wound down, the switching regulator effectively stops for a bit while the output voltage falls to the desired level. Because it is now unloaded, the 12V rail current is insufficient to drop enough voltage across the 470Ω dropping resistor ing. (M. K., Albury, NSW). • Some ignition coils may have too high a resistance to allow the maximum current of 5A to be obtained. To test this possibili ty, try shorting out the 100Ω resistor from pin 8 of IC1. This will prevent the current-limit feature from working. Now try measuring the voltage across the 0.1Ω resistors as described in the article (with the ballast resistor shorted out). If you still get less than 250mV, then your coil is one of those (with higher resistance). In that case, you don’t need or want the current limit feature. The 100Ω resistor should be replaced with a shorting link and so should the 0.1Ω current limit resistors. You can then pull the 33Ω resistor and VR1 out of circuit. On the other hand, if you now measure more than 250mV, try replacing the 33Ω resistor with a lower value, such as 10Ω, and do the adjustment again. before the regulator. (A telling point is 30 seconds or so after turning the supply off once this happens, the supply will briefly restart as the voltage on the main filter caps falls to a level where the regulator restarts). I fixed this behaviour by adding another 470Ω 5W resistor from the input of the regulator to ground. This stabilises the input voltage to the regulator at around 25V (instead of the 35V or so before). Actually that’s all a bit of preamble – I don’t believe it to be the cause of the eventual failure. During load testing the power supply would “growl” at any current over about 1A. I assumed that was just winding vibration. Anyway I dutifully cal ibrated the ammeter at a current of 4A, growl notwithstanding. However, there was about 1V p-p ripple on the output –this was decidedly not within specs (I was using a 2Ω dummy load). I decided to push the current up to the maximum 8A (OK it was dumb!) and practically as soon as the current was increased to this level, there was a puff of smoke as Q1’s gate resistor expired. Q1 was shorted Gate to Drain and its 47Ω gate resistor was open. I figure that Q1 shorted and the resistor let Looking for an old valve? or a new valve? BUYING - SELLING - TRADING Australasia's biggest selection Also valve audio & guitar amp. books SSAE DL size for CATALOGUE ELECTRONIC VALVE & TUBE COMPANY PO Box 381 Chadstone Centre VIC 3148 Tel: (03) 9571 1160 Fax: (03) 9505 6209 Mob: 0411 856 171 email: evatco<at>mira.net go as it didn’t like trying to dissipate 50 odd watts! I have replaced Q1 and its gate resistor and the 4049 driver. During subsequent testing I have discovered that the power supply output has substantial 1kHz “ripple” at certain voltages and current; eg, with a 2Ω dummy load and currents from 400mA to 1A, there is about .050.1V peak-peak sinusoidal “ripple” on the output. From 1A to about 1.5A the output is clean with no ripple. Above 1.5A, the 1kHz ripple returns at around 0.1-0.2Vpp, with audible buzzing from the supply. I haven’t pushed the current past 1.5A as I don’t wish to kill another Mosfet. Below 1A, touching a CRO probe to pin 1 of the TL494 will reduce the ripple level by over half, and sometimes remove it entirely. Curiously, using a 4Ω dummy load, the ripple is present from 800mA through to 1.5A. I have confirmed that the Mosfets are switching at about 22kHz, checked the 12V rail and the TL494 5V reference, double checked all components and wiring, etc. Any ideas on a course of action? January 1999 91 Notes & Errata Use Your old PC Power Supply For High Current Outputs, December 1998: the circuit diagram on page 75 incorrectly shows the nega tive terminal of the bridge rectifier as being connected to earth. It should go to negative side of the bottom 220µF electro lytic capacitor instead. Fig.1 (above right) shows the correct circuit arrangement. Thermocouple Adaptor for DMMs, December 1998: the 4.7kΩ resistor from ZD1 to the 2kΩ trimpot VR2 is incorrectly shown as 47kΩ on the wiring diagram of page 34. A 15kΩ resistor has been omitted from the parts list. The current limiting and current limit LED don’t agree too well. Pulling 4A say and winding the current limit back would result in the current dropping appreciably (say to 2A) before the current limit LED would light. The power supply would growl even worse during current limiting. Aren’t the main filter caps a bit underrated voltage wise? My supply measures 52V on the caps. I’m fearful of a bang – or five! (A. W., Grange, SA). • An audible squealing from the power supply is normal when in current overload or when current draw exceeds the output setting. This was mentioned on page 57 of the April 1998 issue. The 470Ω resistor at the input to The accuracy of the current limit LED can be adjusted by altering the bias voltage on pin 10 of IC5b. You may wish to use a trimpot (100kΩ) in place of the 220kΩ and 100Ω resistors. Adjust the trimpot so that the Overcurrent LED lights when the supply just begins to current limit. The 50V rating for the filter capacitors is satisfactory. Troubleshooting an amplifier Fig.1: the corrected power supply circuit. Improvements To AM Broadcast Band Reception (Vintage Radio), December 1998: the diagram on page 67 shows the two twin flex leads as being joined where they connect to the antenna loop. This is incorrect – there should be no connection between the leads at this point. REG1 should be sufficient to reduce its input voltage to below 35V. This is because the combined regulator and IC standby currents will total more than 35mA to produce a 16.5V drop from the 50V supply. However, it will do no harm to add the extra 470Ω resistor in series to reduce the voltage even further. You will be able to reduce the output ripple from the power supply by adding a small amount of capacitance between pin 1 of IC1 and ground. This will filter the feedback voltage from the output of the supply before it is applied to the pulse width modulation circuitry. Try 100pF or a larger value until the squealing noise and excess ripple disappears. I have built an audio amplifier and it was working OK but now isn’t. It uses two MJL21194 and MJL21193 Mosfet transistors and I am afraid that these might have blown but I am not sure. Do you have any extra information you could send me about these transistors, such as how to test them? I have checked the voltages that were given in the instruction manual and the negative side is fine, but the positive side reads as 0.2V instead of 55.8V! The positive (NPN) transistors get extremely hot and the PNP transistors stay cold. (S. E., St. Ives, NSW). • Just a small point, the two transistors you mention are bipolar types, not Mosfets. You also did not mention when the circuit was published so we can’t be too specific in suggestions. From your description, it appears that you might have blown the positive rail fuse. If you are lucky, this might be all you have damaged. If the transistors are damaged they will usually have a direct short between collector and emitter and you can check this with your multimeter (switch to a low ohms range). You should check the other transistors in the circuit to make sure that SC they have not blown too. WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Trade Practices Act 1974 or as subsequently amended and to any governmental regulations which are applicable. 92 Silicon Chip Silicon Chip Bookshop SUBSCRIBE AND GET 10% OFF SEE PAGE 53 Guide To Satellite TV* Installation, Reception & Repair. By Derek J. Stephenson. First published 1991, reprinted 1997 (4th edition). This is a practical guide on the installation and servicing of satellite television equipment, including antenna installation and alignment. The coverage of the subject is extensive, without excessive theory or mathematics. 383 pages, in hard cover at $60.00. Understanding Telephone Electronics* By Stephen J. Bigelow. Third edition published 1997 by Butterworth-Heinemann. This is 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 machines) and much more. Ideal for students. 367 pages, in soft cover at $55.00. Guide to TV & Video Technology* By Eugene Trundle. First published 1988. Second edition 1996. Eugene Trundle has written for many years in Television magazine and his latest book is right up date on TV and video technology. Includes both theory and practical servicing information. Ideal for both students and technicians. 382 pages, in paperback, at $55.00. The Art of Linear Electronics* By John Linsley Hood. Published 1993. This is a practical handbook from one of the world’s most prolific audio designers, with many of his designs having been published in English technical magazines over the years. A great many practical circuits are featured – a must for anyone interested in audio design. 336 pages, in paperback at $80.00. Digital Audio & Compact Disc Technology* Produced by the Sony Service Centre (Europe). 3rd edition, published 1995. This is the best book on compact disc technology that we have ever come across. It covers digital audio in depth, including PCM adapters, the Video8 PCM format and R-DAT. If you want to understand digital audio, you need this reference book. 305 pages, in paperback at $90.00. Servicing Personal Computers* By Michael Tooley. First pub lished 1985. 4th edition 1994. Computers are prone to failure from a number of common causes & some that are not so common. This book sets out the principles & practice of computer servicing (including disc drives, printers & monitors), describes some of the latest software diagnostic routines & includes program listings. 387 pages in hard cover at $90.00. Radio Frequency Transistors* Principles & Practical Applications, By Norm Dye & Helge Branberg. Published 1993. This book strips away the mysteries of RF circuit design. Written by two Motorola engineers, it looks at RF transistor fundamentals before moving on to specific design examples: eg, amplifiers, oscillators and pulsed power systems. Also included are chapters on filtering, impedance matching & CAD. 235 pages, in hard cover at $105. Title Price EMC For Product Designers $95.00 Understanding Telephone Electroni cs $55.00 Guide to Satell ite TV $60.00 Daytime Phone No._______________________Total Price $A _________ Audio Electroni cs $79.00  Cheque/Money Order  Bankcard  Visa Card  MasterCard Digital Audio & Compact Di sc Technology $90.00 The Art Of Linear Electroni cs $80.00 Servi cing Personal Computers $90.00 Guide to TV & Vi deo Technology $55.00 Your Name__________________________________________________ PLEASE PRINT Address_____________________________________________________ ______________________________________Postcode_____________ Card No. Signature_________________________ Card expiry date_____/______ Return to: Silicon Chip Publications, PO Box 139, Collaroy NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details; or fax to (02) 9979 6503. *All titles subject to availability. Prices valid until 28th February, 1999 Postage: add $5.00 per book. Orders over $100 are post free within Austral ia. NZ add $10.00 per book; el sewhere add $15 per book. TOTAL $A FJebruary anuary 1999 93 MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads: $10.00 for up to 12 words plus 50 cents for each additional word. Display ads (casual rate): $25 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. ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ ___________ Enclosed is my cheque/money order for $__________ or please debit my ❏ Bankcard ❏ Visa Card ❏ Master Card Card No. Signature__________________________ Card expiry date______/______ Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ 94 Silicon Chip FOR SALE SPEAKERWORKS: specialist in speaker repairs and par ts. DIY refoam kits: 3 1/2 ", 4", 5", 6", 7", 8", 9", 10", 11", 12" and 15" $39.95. Includes shims, dustcaps and adhesive. Largest inventory of cones, surrounds, gaskets, spiders, dustcaps, grilles, foam and cloth and 4,700 custom voice coils. Phone 02 9420 8121, Fax 9420 8131. C COMPILERS: everything you need to develop C and ASM software for 68HC08, 6809, 68HC11, 68HC12, 68HC16, 8051/52, 8080/85, 8086 or 8096: $145.00 each. Macro Cross Assemblers and Disassemblers for above CPUs + 6800/01/03/05, 6502 and 68HC12 now combined at the new low price of $75. Debug monitors: $75 for 6 CPUs. All compilers, XASMs and monitors: $480. 8051/52 Simulator (fast, now incl. 80C320): $75. Try the C-FLEA Virtual Machine for small CPUs, build a “C-Stamp”. Demo desk: FREE. All prices + $5 p&p. Atmel Flash CPU Programmer: Handles the 89Cx051, the 89C5x and 89Sxx series, and the new AVRs in both DIP and PLCC44. Also does most 8-pin EEPROMs. Includes socket for serial ISP cable. $199, $37 tax, $10 p&p. SOIC adaptors: 20-pin $90, 14-pin $85, 8-pin $80. Credit cards accepted. GRANTRONICS PTY LTD, PO Box 275, Wentworthville 2145. Ph (02) 9896 7150 or Internet: http://www.grantronics.com.au WEATHER STATIONS: Windspeed & direction, inside temperature, outside temperature & windchill. Records highs & lows with time and date as they occur. $420.00 complete plus sales tax if applicable. 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., etc. Just phone, fax or * TOP QUALITY VIDEO CAMERAS * UP TO 730 DAYS WARRANTY * HiRes SILICON CCD MODULES only $59! COMPLETE PACKAGED CCTV SETS see p31 EA Feb 98 only $249! ** PREMIUM QUALITY MODULES 400 + Line x 0.05 Lux SONY H.A.D. CCD & CHIPSET from $91 ** CAMERAS: Mini 36 x 36 from $88! Dome from $91! COLOUR DIGITAL SIGNAL PROCESSING CAMERAS & MODULES: ** 400 + Line from $180 ** DOME from $185! 480 + Line DOME with SONY CCD from $246! 600 + Line from $346! ** OUR CAMERAS PRODUCE “NEAR SUPER-VHS” TO “BETTER THAN SUPER-VHS” QUALITY IMAGES ** 50 LED DIY Infra-Red Illuminators only $19! ACCESSORIES: 30 + Lenses 2.1 to 16mm. FILTERS: Polarising, Coloured, Temperature Conversion, Infra-Red Cut & Pass for Image Enhancement, Colour Correction, Focus, Glare & Exposure Control. ANCILLARY EQUIPMENT: QUADS 4 pix 1 screen from $280. PACKAGED SETS! QUAD + FOUR CAMERAS + Power Supplies from $689! SWITCHER + FOUR CAMERAS + REG Power Supply from $508! MULTIPLEXERS FULL-SCREEN FULL-RESOLUTION VCR Recording/Playback from $826! SWITCHERS 4 & 8 Ch from $126! ALSO: Monitors, Outdoor Housings, Brackets, Dummy Cams, CCTV-TV/ VCR Interface Modules, Motorised Pan Units etc. CCTV-TV/VCR 48 + Channel Crystal Locked Modulator/ Mixer/Booster Modules from $14. CCTV Technical Reference Manual 400+ Pages $95 or FREE! DISCOUNTS: Based on ORDER VALUE, BUYING HISTORY, for CASH/ CHEQUE & NZ BUYERS! BEFORE you BUY Ask for our Illustrated Catalogue/Price List with Application Notes & Special New Enquiry Offer. Allthings Sales & Services 08 9349 9413 Fax 08 9344 5905. 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 76.5F to 180F. AV-COMM P/L, 198 Condamine Street, Balgowlah NSW KITS-R-US PO Box 314 Blackwood S.A. Ph/fax 08 8270 3175 FMTX2A Universal Stereo Coder $49 FMTX2B 30mW Xtal Locked 100MHz Transmitter $49 FMTX1 1-3 Watt Free Running Transmitter $49 FMX1 200mW Full Broadcast Transmitter, built & tested $499 FM220 10-18 Watt FM BGY133 Philips Linear $499 FM1525 25 Watt Discrete Linear FM Band $499 FM2100 110 Watt Discrete Linear FM Band $699 FM3000 300 Watt Discrete Linear FM Band $1499 Philips 828E/A VHF Receiver Boards (6 metres) $9 AWA 721 VHF Receiver Boards (2 metres) $9 AWA 721 VHF transmitter boards 1 watt (2 metres) $19 Philips 323 UHF transmitter boards 500mW (70cm) $19 AEM 35 Watt Little Brick Audio Power Amp $15 Digi-125 200W RMS Audio Power Amp $39 CA Clipper Compiler, new in box $49 6dBd Gain Colinear FM Band Antenna $999 Roll Smart-1 FM Station Audio Processor $999 Free catalog on disk of discounted surplus components Same day shipping, credit cards OK, circuits supplied. SPECIAL STEAM BOAT KITS $14 write for our FREE catalogue and price list. Solar Flair/Ecowatch ph: (03) 5968 4863 fax: (03) 5968 5810, PO Box 18, Emerald, Vic., 3782. ACN 006 399 480. 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. Ph: (03) 98306288 Fax: (03) 98306481 Positions At Jaycar We are often looking for enthusiastic staff for positions in our retail stores and head office at Rhodes in Sydney. A genuine interest in electronics is a ‑necessity. Phone 02 9743 5222 for current vacancies. 651 Forest Rd, Bexley 2207 makes all the project PCBs published in SILICON CHIP and other Australian magazines Tel +61 2 9587 3491 Fax 9587 5385 http://www.cia.com.au/rcsradio/ 2093. Tel: 02 9949 7417 or 9948 2667. Fax: 9949 7095; www.avcomm.com.au A NEW address for Acetronics http://www.acetronics.com.au On-line PCB quotes, free software, DIY PCB supplies plus many other items & services. 02 9743 9235. 1A LASER DIODE DRIVER, 3W head laser power monitor, IR laser diode with housing, greatly reduced price, e-mail lmatthee<at>perthpcug.org.au for details and pictures. HOMEBUILT DYNAMO, engineering dreams into reality. “An absolutely marvellous book for the true ex perimentalist!” Elektor Electronics. (www.onekw.co.nz) TEKTRONIX 100MHz 1GS/s Digital Oscilloscope plus FFT Module (near new), manuals and software. $2850 o.n.o. (08) 8244 5857. TELEPHONE EXCHANGE SIMULATOR, SC February 1998. Test equipment without the cost of telephone lines. $190. MAGNETIC CARD READER, SC January 1996. Holds up to 8 cards. Use as a door lock. $65. Melbourne 9806 0110. continued next page WANTED: TECHNICAL ASSISTANT We are looking for a motivated person with an interest in electronics/ communications to work in our Balgowlah office. Emphasis is more on practical aptitude rather than academic qualifications. Duties are varied and range from dish installations, equipment evaluation and repair, and providing technical advice to customers. Necessarily, this means dealing with the general public. Applicants must have good verbal communications skills, possess a drivers licence and be neatly presented. Specific training relating to satellite TV will be provided on the job. Applicants undertaking part-time studies will be considered. This position will become available in Feb. 1999. Please send written applications to Av-Comm Pty Ltd, PO Box 225, BALGOWLAH, NSW 2093. January 1999 95 Circuit Ideas Wanted Do you have a good circuit idea. If so, why not sketch it out, write a brief description of its operation & send it to us. Provided your idea is workable & original, we’ll publish it in Circuit Notebook & you’ll make some money. We pay up to $60 for a good circuit but don’t make it too big please. Send your idea to: Silicon Chip Publications, PO Box 139, Collaroy, 2097. SOLAR PANELS: buy by mail and save! 75 watt from $590.00, unbreakable s/steel 64 watt $555.00. Largest manufactured: 120 watt $995.00, flexible 32 watt $475.00. Limited stock 22 watt $195.00. All other sizes available, top brands, lowest prices. INVERTERS: budget inverters from $110.00 (12V 140W). High quality pure sine wave inverters from $390.00. Call with your requirements. WIND GENERATORS: wide variety available, call with requirements. TASMAN ENERGY Free call 1800 226626 RAIN BRAIN AND DIGI-TEMP KITS: 8 station sprinkler controllers, 60 channel temp monitor uses DS1820s over 500 metres. Has PC Data logging. Mantis Micro Products, http://www.home.aone.net.au/mantismp RTN Australia Parallax distributor: Basic Stamps, SXKey develop ment tools and SX chips. Wireless RF modules, serial LCD modules, Basic Stamp Bug, etc, etc. FerretTronics >R/C servo control chips. NEW: HandyScope 2 from Europe, 2 channel/12 bit portable measur i ng instrument, it’s a voltmeter, digital storage CRO, transient recorder and spectrum analyser. All in a very small box powered off a parallel port. DOS and Windows software provided. Ph/ Fax (03) 9338 3306. email: nollet<at>mail.enternet.com.au http://people.enternet.com.au/~nollet PICTUTOR: Programmer board + 32 tutorials for PIC84. Other models available. E.S.T. (02) 9789 3616. Fax (02) 9718 4762. Advertising Index Altronics................................. 60-61 Av-Comm Pty Ltd.........................95 Dick Smith Electronics..................... ................................ IFC,OBC,14-17 Evatco..........................................91 Harbuch Electronics....................83 Instant PCBs................................95 Jaycar .............................. 45-52,95 KIT ASSEMBLY Kits-R-Us.....................................95 ANY KITS assembled/calibrated: professional, speedy service. Phone Neville Walker (07) 3857 2752. Microgram Computers...................3 WANTED Oatley Electronics........................71 WANTED: A Z-80 trainer that works, preferably with manuals. Would prefer a Microprofessor or similar. Phone Colin Turner (02) 6231 7249. Printed Electronics.......................95 ANNOUNCEMENTS DON’T MISS AUSTRALIA’S BIGGEST AND BEST EXHIBITION and sale of new and used radio and communication equipment at the Central Coast Field Day, Sunday 28th Feb, Wyong Race Course, just 1 hour north from Sydney. Starts 8.30 a.m. Special Field Day bargains from traders and tons of disposals gear in the flea market. Exhibits by clubs and groups with interests ranging from vintage radio, packet radio, scanning, amateur TV and satellite comms. www.ccarc.org.au; Ph (02) 4340 2500. MicroZed Computers...................37 Procon Technology......................95 Quest Electronics........................25 RCS Radio...................................95 Scan Audio..................................77 Silicon Chip Back Issues....... 78-79 Silicon Chip Bookshop.................93 Silicon Chip Subscriptions...........53 Silicon Chip Binders/Wallchart....85 Smart Fastchargers.....................25 Solar Flair/Ecowatch....................95 Solis.............................................96 Truscott’s Electronic World...........77 HELP SAVE THE NIGHT SKY! We are losing our heritage of starry night skies. Poor, inefficient outdoor lighting is causing glare and “light pollution”. This wastes energy and increases greenhouse gas emissions. You can help by joining SYDNEY OUTDOOR LIGHTING IMPROVEMENT SOCIETY (SOLIS). SOLIS aims to educate and inform about quality outdoor lighting and its benefits. We also lobby councils, government and other bodies to promote good lighting practice. SOLIS meetings are held third Monday night of each month at Sydney Observatory. Individual membership is $20 pa. Donations are also welcome. Cheques payable to “SOLIS c/- NSAS”, PO Box 214, West Ryde 2114. Email: tpeters<at>pip.elm.mq.edu.au 96 Silicon Chip Zoom EFI Special......................IBC _____________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 9587 3491. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone (09) 828 5730. Own an EFI car? Want to get the best from it? Youll find all you need to know in this publication