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www.siliconchip.com.au February 2003  1 Contents Vol.16, No.2; February 2003 FEATURES 8 PICAXE: The New Millennium 555? www.siliconchip.com.au PICAXE: An Easy-To-Use PIC For Every Man . . . And His Dog – Page 8. Simple to use, even for old-timers, the PICAXE-08 is the PIC for everyman. Here’s how to get started – by Stan Swan 32 Review: WM232-UHF Wireless Modem Reliable short-range wireless links for remote control and data acquisition. And it’s licence free – by Peter Smith PROJECTS TO BUILD 14 The PortaPal Public Address System It’s packed with features, is easy to build and rivals commercial systems costing much more – by John Clarke & Leo Simpson 36 240V Mains Filter For Hifi Systems The PortaPal Public Address System – Page 14. Get rid of clicks, pops, spruigles and sundry other noises in your hifi system – by Ross Tester 54 The SC480 50W RMS Amplifier Module; Pt.2 Everything you need to know to put together this outstanding new power amplifier module (covers both versions) – by Peter Smith & Leo Simpson 72 A Windows-Based EPROM Programmer; Pt.3 Final article presents the Windows-based software and details a few modifications to improve performance. – by Jim Rowe SPECIAL COLUMNS 24 Circuit Notebook (1) 12V Lead-Acid Battery Desulphator; (2) Low Supply Rail Detection Circuit; (3) Fifth Channel For Code-Hopping Remote Control; (4) Two Simple Headlight Reminders; (5) In-Situ Battery Test Probe; (6) Engine Immobiliser 40 Serviceman’s Log Servicing can be frustrating – by the TV Serviceman 80 Vintage Radio Aligning TRF & superhet radio front-ends – by Rodney Champness 240V Mains Filter For Hifi Systems – Page 36. COMPUTERS 69 Using Linux To Share An Optus Cable Modem; Pt.4 Firewall logs, operating with a keyboard or monitor & automatic shutdowns – by John Bagster 86 Tracking Down An Elusive Fault In Windows XP Don’t reinstall the operating system when things go wrong. Here’s a logical approach to tracking down system faults– by Stephen Davis DEPARTMENTS 2 4 63 64 79 Publisher’s Letter Mailbag Book Review Product Showcase Silicon Chip Weblink www.siliconchip.com.au 89 92 93 95 Ask Silicon Chip Notes & Errata Market Centre Advertising Index Building The SC480 50W Amplifier Modules – Page 54. February 2003  1 PUBLISHER’S LETTER www.siliconchip.com.au Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Production Manager Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Peter Smith Ross Tester Jim Rowe, B.A., B.Sc, VK2ZLO Rick Walters Reader Services Ann Jenkinson Advertising Enquiries Leo Simpson Phone (02) 9979 5644 Fax (02) 9979 6503 Regular Contributors Brendan Akhurst Rodney Champness, VK3UG Julian Edgar, Dip.T.(Sec.), B.Ed Mike Sheriff, B.Sc, VK2YFK Philip Watson, MIREE, VK2ZPW Bob Young SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 003 205 490. ABN 49 003 205 490 All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Hannanprint, Noble Park, Victoria. Distribution: Network Distribution Company. Subscription rates: $69.50 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 8, 101 Darley St, Mona Vale, NSW 2103. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. E-mail: silchip<at>siliconchip.com.au ISSN 1030-2662 * Recommended and maximum price only. 2  Silicon Chip Queensland TV repairs need a safety check, not a licence Predictably, the Publisher’s Letter in last month’s issue has brought forth howls of anguish from all those affected by the new Queensland legislation requiring electronics servicemen to take out an electrical contractor’s licence. I have had quite a few people phone me to rant about how unreasonable the new re­quirement is, how they might avoid it (they can’t) and whether there are any sanctions (fines of up to $30,000). In every case, I have agreed that the requirement is unrea­sonable (stupid, ridiculous and ludicrous are other words that come to mind) and advised the person concerned to log on to relevant website (www.eso.qld.gov.au) and wade through what they must do. In some cases people have said that they could not understand the requirements on the website. Yes, I’m not sur­prised. The trouble with these people is that they think it might be logical and sensible – it isn’t and nor is the language and presentation of the website. I have also advised every caller to contact their local Member of Parliament and make their feelings known in the stron­gest possible fashion. That is what they should have done some time ago when we were campaigning for the right of everyone to do their own electrical wiring and related issues. Interestingly, on January 8th, the Brisbane “Courier Mail” ran a story stating that only 11 of an estimated 1000 repairs has applied for the licence, in spite of the new regime taking effect on 1st February 2003. A spokeswoman for Industrial Relations Minister Gordon Nuttall said that “the Government had done all it could do to alert repairers to the new licensing requirements”. Yeah, yeah. Funny that they did not take out any adverts in SILICON CHIP or other relevant magazines. No, whether you are a repairer or just a consumer, you should get onto your local member of parliament and tell him or her that the situation is ridiculous. Furthermore, tell them that if the Electrical Safety Office was really interested in safety, they would not require electronics repairers to take out an irrele­vant licence. At this stage the politician might be wanting an intelligent alternative. You can give them this: If the ESO is really concerned about the safety of repaired electrical and electronic appliances, why don’t they require that a standard safety check be done and each appliance be fitted with a sticker to say it has passed. The safety test could include physical and electrical checks of the power cord, insulation resistance and so on. Wouldn’t that make more sense? The relevant portion of the Electrical Safety Act should immediately be sus­pended, repealed or otherwise nullified, to allow some common­sense to be brought to bear. But again, I’m not hopeful. Leo Simpson Special note: due to a printing problem, many readers in Western Australia have had difficulty obtaining a fault-free December 2002 issue. We arranged for the issue to be reprinted and sent to WA but evidently many readers were still unable to get copies from newsagents. To help those readers, we can supply the December 2002 issue for $6.60, including postage, until the end of March 2003. www.siliconchip.com.au USB Printing on NT4 Network!!!! Cat 11362 At last Multiple Serial Ports from USB! Cat 2852-7 USB to 2 serial (RS232) Cat. 2852 $169 Cat 2851-7 USB to 4 serial (RS232) $499 Cat 2853-7 USB to single RS 422/485 $249 Cat 2854-7 USB to 2 x RS422/485 with opto-isolation $499 Now you can connect USB printers to an NT4 network. Our new print server will work in any TCP/IP network & has 2 USB ports & 1 parallel port Cat 11362-7 $399 Wireless LAN Access Point Cat 11339 Roll-Up Keyboard PC (PCMCIA) drive for your desktop This front access drive provides a single PCMCIA slot mounted in the spare “floppy drive” bay Cat 6668-7 $139 Training-OnLine If you need a value-for-money training solution then check out this well established company. T.O.L. offers a comprehensive range of quality courses at prices that students will appreciate. On line now at.....www.tol.com.au High Performance Barcode Scanners Laser Scanner PS/2 K/b wedge Cat 1008039-7 $399 Laser Scanner USB Interface Cat 1008042-7 $429 Laser Scanner Serial Interface Cat 1008043-7 $429 These high performance scanners all use the same “head” unit; you simply change the cable for the different interfaces. ADSL Internet Router Video Conversion Cat 3431 Video signal conditioner for stabilizing your video signal when backing-up DVD’s and video tapes. 1 input and 3 outputs Cat 3431-7 $159 NTSC/PAL/SECAM to PAL/NTSC system converter. This handy unit will also stabilize the Cat 3486 video signal when duplicating DVD’s or videos Cat 3435-7 $539 Semi-professional version Cat 3486-7 $1099 Cat 3497 Video to VGA. Watch TV/Video etc on your high resolution monitor Cat 3497-7 $279 Need a new Cash Drawer? Cat 8906-7 Cash Drawer – Serial $269 Cat 8897-7 Cash Drawer – Printer connected $220 Until end February 2003 or... ...while stocks last! Cat 6710 Cat 6711 Game Console Wireless Link Got a PlayStation 2, X-Box or GameCube? This Compact 2.4 GHz device lets you link without wires! Multi-Player links let you compete head-to-head with your archrivals Cat 11372-7 $359 USB Device Sharing Hubs Cat 12053-7 2 PC’s share a single USB device Normally $89 NOW ONLY $44 Cat 12051-7 2 PC’s share 3 USB devices. 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Cat 12054 External Hard Drive Cases USB 2.0 2.5” Cat 6710-7 $109 USB 2.0 3.5” Cat 6711-7 $ 159 USB 2.0 5.25” Cat 6689-7 $199 Cat 1008074 Here’s a full size USB Keyboard that you can put in your pocket!!! Cat 1008074-7 $89 Provides fast reliable connectivity from your 2.4 Ghz wireless equipment to your LAN Cat 11339-7 $449 Industrial P4 motherboard with ISA slots as well as a Watchdog Timer, DiskOnChip, Digital I/O & more Cat 17078-7 $999 A PCI Bus A/D - D/A card with programmable I/O control Cat 17077-7 $599 Cat 17078 Cat 17077 Satellite TV on your Computer!!! Digital Satellite TV Card with CI (Common Interface) Receive Satellite TV on your computer! Our satellite card also includes a smart card socket to allow reception of encrypted programs Cat 3510-7 $459 We have a range of terminals to suit most emulations - Serial, Windows based & Linux MicroGram Computers Ph: (02) 4389 8444 FreeFax: 1800 625 777 sales<at>mgram.com.au info<at>mgram.com.au Vamtest Pty Ltd trading as MicroGram Computers ABN 60 003 062 100, 1/14 Bon Mace Close, Berkeley Vale NSW 2261 All prices subject to change without notice. Pictures are for illustrative purposes only. SHOREAD/MGRM0203 MAILBAG Active 3-Way Crossover project acknowledgement Thanks for the presentation of my Active 3-Way Crossover in the January 2003 edition. However, I neglected to acknowledge that much of the design configuration came from Rod Elliot’s website, and in particular, the configuration for feeding the LPF stage from the low-pass section of the midrange stages. Rod’s site has a wealth of information on all kinds of audio and other projects. It can be found at http:// sound.westhost.com Mick Gergos, via email. TV repairers may cause lethal appliance faults Your Publisher’s Letter in the January 2003 issue appears to have missed the point regarding TV and appliance repairers needing to have an electrical contractor’s license. Your negative view begs the question, “Do you have an electrician’s license?” Because if you did you would well understand the bureaucrats’ and unions’ viewpoint. Imagine your appliance or TV being repaired by someone unlicensed: a fault may be created or develops after the repair. This places you or your family at risk. An accident occurs and someone is injured. You sue for compensation and the repairer claims on his insurance. The insurance company asks if the re­pairer is a licensed contractor and receives the reply “No”. Where do you stand? Do you sue the repairer (who has no effective insurance) and send him bankrupt? Would you sue the bureaucrat for allowing the repairer to operate without a contractors li­cense? Perhaps the government in their wisdom have set a benchmark where all involved will be protected, both the repairer and the consumer. If the electronic or electrical repairer is so highly skilled why would it be difficult to obtain an electrical contra­ctor’s license that only mere electricians can possess. You may also try to fathom the at- 4  Silicon Chip titude of the manufactures in making throw-away appliances. Perhaps it is far better the appliance or device be discarded than be repaired when the origi­nal manufacturer has no control over who does the repair, regard­less if it is in or out of warranty. Would the manufacturer be prepared to wear litigation because of faulty workman­ship or inferior parts used by any repairer? In regard to your comments about persons knowing the “true situation”, please do not make remarks that will leave your readers assuming this is fact without qualification. Not all accidents or injuries are the direct result of electrocution. Many accidents and injuries can be from indirect means but at­tributed to electrical faults. Paul Betteridge, Port Macquarie, NSW. Comment: believe us, the bureaucrats have set the “benchmark” too high. Few servicemen will be able to meet the require­ ments for the electrical contractor’s licence. The only real way to do it is to do a course lasting several years. We will go out on a limb and state that there probably never has been a fatality because of an appliance wiring fault caused by a repairer. In fact, we challenge anyone to come up with such a case. Improving the damping factor of the SC480 module I refer to page 26 of the January 2003 issue of SILICON CHIP. In the list of performance figures for the SC480 amplifier, you give the damping factor without the PTC thermistor. A small design change may be worth trying. It involves taking the majority of the negative feedback from the speaker side of the PTC. Obviously, there would be problems if the present 22kΩ feedback resistor was connected to this position and a fault occurred. However, an improvement in the performance of the amplifier may well result with the following changes: (1) For the present 22kΩ feedback resistor, substitute a higher value such as to bring the gain down to a controllable level with no load connected. (2) From the base of the BC557 to the speaker side of the PTC, connect another resistor of value such that (1) & (2) in parallel present 22kΩ. I note in the introduction you say “It also sounds much better”. I would have thought, in amplifiers of this order, there would be no observable “sound” or “coloration” contributed by the amplifier when used in conjunction with other parts of an audio system. Maurie Findlay, MIEAust, via email. Comment: it is true that you could improve the damping factor by taking a portion of the feedback from the output side of the thermistor. However, it could cause further problems in the event of a fault condition which operated the PTC; the re­sulting voltage gain in the unloaded amplifier would be much higher. As far as the comment about sound quality is concerned, we can assure you that the SC480 definitely does sound a lot better than the ETI480. CDs programmed to deteriorate In your response to John Tingle and his letter concerning CD deterioration in the January 2003 issue, you say “the heat does it.” Well, he keeps his collection in a “cool, dry room”. The real culprit is the chemicals still present in both the packing materials and the environment. Chemicals known as “plas­ticisers” are added to plastic materials to make them flexible and easier to process. Over time this leaches out and can attack other nearby plastics. www.siliconchip.com.au The foaming agents used to produce foamed plastics and rubber can also be destructive and corrosive. In addition, trace elements in the environment will cause long-term deterioration of plastics, especially foams. Ozone is one of the most destructive elements. The problem of protecting valuable assets is a major con­cern to libraries, museums and archives. There are long-life, non-corrosive packing and filing materials available from spe­ cialist archival materials suppliers. Otherwise, advice can be sought from National Archives because they have to deal with the problem all the time and have produced guides to safer storage of archives. Check them out at: www.naa.gov.au/recordkeeping/ On a related point, the politicians are keen to get on the “we are green” bandwagon and want to force biodegradable plas­tics into the market. So, how do manufacturers comply? By making plastic packing that contains chemicals that cause it to break down. The pollies can beat their breasts because they have done something “good” for the environment. Of course, nobody thought about what would happen to the precious goods packed within this smorgasbord of chemicals or that the products of decomposition might be worse than the original plastics! Colin MacKinnon, via email. Geostationary satellites do not fall to Earth I have a few corrections to the article on satellite TV reception in the December 2002 issue of SILICON CHIP. Geostation­ary satellites do not fall to Earth once they have run out of fuel. They are far enough out that they are beyond the slowing effect of the Earth’s atmosphere. The fuel they burn occasionally is to keep them “on station” at the correct position. When they run out of fuel, they start drifting into a wob­bling orbit, pulled by the gravity of the Moon and Sun. It would take a great amount of resistance, or a great amount of fuel (neither of which they have) to slow them enough to bring them down. They can effectively be considered permanent artificial satellites. Evenwww.siliconchip.com.au tually the Clarke belt will have so many birds up there, that the chances of old ones bumping into active ones will increase. Fortunately, they are far enough out that there is a lot of space between them. From the animation at the site mentioned below, you will see that there are many ‘retired’ geostationary satellites in wandering orbits near the tight ring of satellites that are ‘on station’. Some of these are actually at slightly higher and faster orbits than the geostationary orbit. It probably depends on which way they were nudged by a last fuel burn but most are still at the same height, just wobbling. GPS satellites are not low-earth orbiting satellites. They orbit at around 20,000km (about half the geostation­ary height) and have an orbital period of 12 hours. Also, some weather satel­lites (usually the ones used for ‘satellite photos’) are geosta­tionary, while others are low-earth orbiting, depending on their particular role. Low-earth orbiting satellites have altitudes between 300km and 1000km, with orbital periods of 1.5-2 hours. These are low enough that they are significantly affected by the Earth’s at­mosphere, so they will eventually fall back to Earth. For an interesting exploration of many of the satellites out there, where they are, and the way they behave, check out: http://liftoff.msfc.nasa.gov/RealTime/ JTrack/3d/JTrack3D.html Noel Bachelor, via email. The Tiger comes to Australia The BASIC, Tiny and Economy Tigers are sold in Australia by JED, with W98/NT software and local single board systems. Tigers are modules running true compiled multitasking BASIC in a 16/32 bit core, with typically 512K bytes of FLASH (program and data) memory and 32/128/512 K bytes of RAM. The Tiny Tiger has four, 10 bit analog ins, lots of digital I/O, two UARTs, SPI, I2C, 1-wire, RTC and has low cost W98/NT compile, debug and download software. JED makes four Australian boards with up to 64 screw-terminal I/O, more UARTs & LCD/keyboard support. See JED's www site for data. Intelligent RS232 to RS485 Converter The JED 995X is an opto-isolated standards converter for 2/4 wire RS422/485 networks. It has a built-in microprocessor controlling TX-ON, fixing Windows timing problems of PCs using RTS line control. Several models available, inc. a new DIN rail mounting unit. JED995X: $160+gst. Www.jedmicro.com.au/RS485.htm $330 PC-PROM Programmer Publisher’s letters are not so bad It’s not often that my normal state of torpor is disturbed by a letter to the editor but I cannot allow to pass the strange comments penned by Doug Thwaites in the December 2002 issue of SILICON CHIP. The extraordinary suggestion that one should, by right, enjoy the whole of any magazine (or any other composite produc­tion, for that matter) cannot surely be made by anyone living in the real world. There are heaps of things which we can truly enjoy but there are always other things which will not be so acceptable. So far as the Publisher’s Letters are This programmer plugs into a PC printer port and reads, writes and edits any 28 or 32-pin PROM. Comes with plug-pack, cable and software. Also available is a multi-PROM UV eraser with timer, and a 32/32 PLCC converter. JED Microprocessors Pty Ltd 173 Boronia Rd, Boronia, Victoria, 3155 Ph. 03 9762 3588, Fax 03 9762 5499 www.jedmicro.com.au February 2003  5 Mailbag: continued concerned, I don’t believe that there has ever been a bad one and I think anyone who has the temerity to suggest this would need to have a pretty good command of his subject. I must say that I have not infrequently disagreed with the argument but the Publisher’s Letters are always well reasoned and well expressed. Anyone who believes the world overall was a better place 30 years ago has suppressed the bad memories and exalted the good. Things are a lot more compli­cated now but I still have hopes that human beings may one day become civilised if we or nature doesn’t destroy us first! Probably, Doug Thwaites would get more of the sort of infor­mation he wants by searching the web. I doubt if there would be enough interest even to support a department in SILICON CHIP to suit Doug Thwaites or G. J. Wilson, let alone support a magazine. In my view, Leo Simpson and the staff of SILICON CHIP are doing an excellent job and I will continue to subscribe so long as both the magazine and I are extant. Alan March, Turramurra. NSW. CRT video monitors not obsolete yet I would like to make a few comments regarding your December editorial about CRT video monitors. First of all, I don’t think LCDs are the complete answer yet, although they certainly have their advantages. We use a mixture of LCD and CRT monitors at work and for straight picture quality, the CRT units win hands down every time. I don’t think your statement “CRT monitors have not drasti­cally reduced in price” is really correct. Defying inflation, the ticket price of computer monitors has steadily declined over the past decade, while the quality of the actual CRTs fitted has increased enormously. Of course, the same applies to ordinary TV sets. Just yes­terday, I saw excellent quality 67cm “true flat” screen TVs in my local Aldi store for $699! A bit bulky, true, but compare 6  Silicon Chip that with the price of a plasma display! Incidentally, whatever hap­ pened to the 16 x 9 CRT “revolution”? However, what I mainly wanted to point out is that every­body seems to be overlooking what will almost certainly be the dominant display technology of the future: Light Emitting Polymer (LEP) displays. There are already laboratory prototypes of com­ pletely flexible full-colour displays and it can only be a matter of time before this becomes the dominant technology. Not only does it combine the thinness of LCDs with the picture quality of CRTs, it also holds the promise of allowing the manufacture of cheap and practical wall-sized displays for the first time. The biggest problem at the moment is the relatively short life of the polymers but this is being improved all the time, to the point where they are beginning to appear in mobile phone screens, where the short operational lifetime is less of a con­sideration. Adrian Kerwitz, via email. Publisher’s letter should be broad ranging I do not think you should restrict your editorials to just matters electronic. Industry and politicians always need stirring up, even if they usually still go off and do what they were always going to do in the first place. Oh, and I do not think you need to cover the radio world. I think your appeal lies with the broad base of people who want to know and understand a bit about everything, especially if it borders on the edge of their understanding or knowledge at the time. Most radio people I know are dedicated specialists who are very tunnel-visioned. Michael Hill, Heathridge, WA. Leaky motherboard capacitors I writing to you to bring the topic of leaky and exploding capacitors to the attention of fellow readers. I work in the computer service industry and have come across, just recently, an increase in motherboard failures due to leaky or exploding ca­pacitors. Doing a search through the “Google” search engine for “Leaky Capacitor Motherboard” will list a couple of forums and websites dedicated to this subject. According to these websites, it is not a isolated problem. It is across all brands and makes of motherboards. But I have only ever seen it in mother­ boards with late-model Pentium II CPUs and later. If the problem can be addressed in time, the replacement of the offending capacitors with higher ratings is usually a cure but in all cases I have come across, the problem has not been discovered early enough. The capacitors and other components, usually the regulators around the CPU, have failed as a follow-on effect. These regulators fail in a big way. All the boards I have seen have had the copper tracks severely discoloured and lifting. Also the PC board was charred from excessive heat. I have had a couple that have actually melted the solder holding them to the PC board. What prompted me to write was the mention in “The Serviceman’s” notes, December 2002 issue, about a JNL Digi-vision TV that was only two years old and had exploded capacitors in the power supply. I thought this could be a similar thing. Mark Robin, via email. Comment: it appears that designers of switchmode supplies in many recent model video monitors and domestic TV sets are pushing the technology too hard. As a result, many recent model TVs and monitors are not as reliable as previous models. Apparently, the same applies to PC motherboard as well. Macro viewer is a vision boon I thought some readers might like to see an idea that grew from your Video Microscope project published in the October 2001 issue. This macro viewer was built for my mother-in-law, who is suffering from macular degeneration, which almost robbed her of most all her reading www.siliconchip.com.au ability. The viewer has proved to be a lifeline for her. I have constructed two units, one for Sydney and one for her home in Taree which is set up at a permanent reading station. With a 50mm lens, a multiplication of about 4:1 displayed on the monitor seems to be optimum for close reading on the screen. While similar commercial devices are available at upwards of A$2500, these cost in the order of about $150. My thanks to SILICON CHIP for the basic idea, plans and inspiration. Chris Williams, via email. De-glitching the EPROM programmer I wonder if I might make a few constructive comments about your EPROM Programmer project without appearing to be excessively negative? Over the years, the various electronic hobby magazines have published many innovative projects but also numerous cir­cuits which feature “de­ glitching” filters to ensure “correct” operation. All logic chips, with the exception of ripple counters, are designed to interact without suffering from “decoding glitches”. If this were not the case, then products as complex as computers would never work at any speed, let alone at the mind-boggling speeds we presently see. Intuitive design methods can readily make one of anything work but when large numbers of identical products are required without individual www.siliconchip.com.au adjustment, a rather more rigorous design discipline is necessary. For example, the 74HC138 (1-of-8 decod­ er) you use as an address decoder, really requires a control strobe signal on the enable lines to conform to its intended use. Your design has used up all the available output signals and seems to have no other choice but in fact it is easy to free up several lines by simply using edge-triggered latches (74HC­ 374) instead of level-triggered latches. Simply use those inverters (IC5) to clock one set of data in on the falling edge and another on the rising edge. You already have the required inverters in your circuit. The trigger PGM pulse can now be connected to the free select line from the 74HC138 and the printer strobe signal on pin 1 of CON1 can be used to strobe pins 4 & 5 of the 74HC138 as intended by the manufacturers. The glitch filters are then no longer needed as software generates the strobe while the address is steady. Similarly, in the Program pulse length timer, the 74HC161 can be used much more elegantly to avoid the “glitch” problem you refer to. Where possible, it is best to avoid level-triggered flipflops (IC4a & IC4b) in favour of edge-triggered units, as these give you more choice as to when you wish the output state to be read. In this case, simply clocking the IC13 terminal count into a “D” flipflop (such as 74HC74) with inverted clock gives clean glitch-free operation. If the program pulse is started with the clear line, then an extra half cycle is added to its duration but this is probably of little consequence in this application. Using the 74HC74 as a divide-by-2 can be dangerous and unpredictable. This is because when the clock reads in the data on the “D” input, it is actually possible that the input changes state before the hold time expires. Happily, the HC logic family have extremely short hold times and will generally operate this way, however it is a close call and one with a less favourable outcome when TTL or LSTTL are involved. Using J-K flip­ flops for dividing is a better proposition, being free from such “race” conditions. HC family chip manufacturers rec- ommend that any chip with inputs derived off the immediate circuit board have a pull-up resistor of typically 47kΩ to 100kΩ at the connector and then a 10kΩ series resistor mounted very close to the IC input pins. If “bus termination” properties are required, then individual RC terminators can be used at the board connector as well. If the inputs are left open circuit as in your design, then the inputs can readily assume any voltage as they represent an extremely high impedance. They can easily assume a voltage of 2.5V and drive both output FETs on and cause cross conduction and overheating. Open-circuit inputs are also rather more vulnerable to ESD damage. In general, CMOS and HCMOS inputs should never be exposed to an open circuit. At the high end of the speed scale it may be necessary to reduce the 10kΩ series resistor. In EPROM Programmers I have designed, I have always put a resistor in series with each data pin to cover the case when someone puts in an EPROM back-to-front. This error can allow the Vpp supply to punch through a data pin and find its way into the programmer circuits and possibly right through to your printer card or even motherboard! The HC ends of these resistors are individually clamped to a 4.7V zener diode. Naturally the Vcc and Vpp pins have no resistor but do have a current-limited power supply. I hope you can accept these observations in the spirit that they are offered. I spend quite a deal of my time solving prob­ lems for other people. Simple issues like those outlined above are all too often the cause. I wonder if there might be any interest in an article on logic design methods by a professional electronic design engineer? If so I would be willing to put some material together. In any event, keep up the good work, there’s a lot of people out here relying on you as the last real electron­ ics magazine. Graham Lill, via email. Comment: thanks for the feedback. Readers are also referred to the comments about pullup resistors in the third article on the EPROM ProgramSC mer in this issue. February 2003  7 PICAXE – the new millennium 555? Stan (the man) Swan, electronics lecturer from Massey University in Wellington (NZ), leads the charge with the innovative PICAXE-08, the PIC for everyman. Stan reckons this PIC is really easy to use, even for old-timers! T he legendary electronic industry workhorse IC, the 8-pin 555 timer, was first introduced (unpatented!) by Signetics in 1972. It subsequently featured in countless circuits. Virtually every monthly electronics magazine (SILICON CHIP included) continues to have further tips, hints and innovative tweaks for them. In fact, entire “555 Cook Books” have evolved. In today’s silicon chip age, the 30-year endurance of such a humble device is a remarkable tribute to its sound initial design, reliability and cheapness. It’s been the largest volume IC sold every year and the original design, although enhanced with lower powered CMOS versions, remains unmodified. To put this in historical context, consider that the 555 dates from the first pocket calculators, VCRs and colour TV sets, and that today’s 21st century electronic appliances (DVDs, mobile phones, home PCs, GPS, etc) were then the stuff of science fiction. Given its white-hot rate of change, thirty years in electronics compares to perhaps three hundred in normal engineering fields (steam engines to space shuttles?) and by any measure the 555 seems due for a successor. Enter the PIC The 1990s arrival of the Microchip PICs (Peripheral Interface Controllers or Programmable ICs), with their PC interfacing, cheapness and non-volatile RAM, initially showed most promise. PICs abound in modern electronic devices, including bread makers, washing machines, sewing machines, PCs, mobile phones, digital cameras and even toys. Most PICs now are Flash RAM, with the “F” (rather than an earlier “C”), indicating block memory cell erasure when electrons pierce a thin dielectric under Fowler-Nordheim tunnelling. Phew! Data remains in the IC without any battery backup, yet can be easily be edited or retrieved. An irksome trade-off between cost and programming difficulties exists however. Bare PICs (such as the popular PIC16F84) are cheap and powerful but too complicated for many enthusiasts and educators. They may be great for controlling smart washing machines and ideal for mass production but they intimidate beginners simply wanting to flash a few LEDs! In contrast, the Parallax BASIC “Stamp” variations were better suited to education and developmental work, since they were easy to high-level program in BASIC. But their costs were usually much Although both the 555 and PICAXE too high to justify production work are 8-pin DIP, their internals differ and their large footprint was – well radically. Note that the “I/O pin” num– postage-stamp sized. bers are NOT the same as the chip More recently, high level editors “leg” numbers (especially 3 & 4!). Part 1: Introduction to the PICAXE – by Stan Swan* 8  Silicon Chip www.siliconchip.com.au It’s a PIC that even your dog could understand. . . and PIC intro kits have also abounded but with costs or assembly complexity still rather daunting for newcomers. In an admirable blend of industry and education, akin perhaps to Victorian ventures when schools aligned with local firms, the UK Oil and Gas Industry recently funded a West Country firm, Revolution Education, in a remarkable PIC venture. The firm already handles a more powerful and larger PICAXE “18” and “28” range but it’s their new 8-pin PICAXE-08 that looks set to take the “555 successor” mantle. PICAXE-08s are bubble-gum cheap, powerful, have non-volatile memory and are delightfully easy to use. They PC-connect via a 3-wire D9 serial cable and program under a free Windows high level editor using 35 BASIC “plain English” commands such as “high, low, nap, goto, sound, if…then, sleep” etc. Even your dog could understand these! The command set is intentionally similar to that of BASIC “Stamps”, meaning that circuits and code already produced The Revolution Education Starter Pack board uses soldered contacts and although allowing neat assembly, can be heat damaged and is inconvenient for prototyping. A suggested layout on 300-hole protoboard is shown at right – much more convenient for the hobbyist and experimenter. The PICAXE-08 has unusual supply voltage positions: Pin 1 is +ve and pin 8 is ground. The jumper allows one channel to be used for I/O as well as normal programming. Wire colours follow normal resistor colour coding to help identify channels, ie, black 0, brown 1, red 2, orange 3, yellow 4. Lo, the PIXAXE! www.siliconchip.com.au February 2003  9 PICAXE-08 COMMANDS (Note similarity to Parallax BASIC Stamp PBASIC) Several “pseudo” commands too, especially SYMBOL (assigns new word to a value) and INPUT = pin Rem, semicolons (;) or apostrophe (‘) precede remarks/comments, & also colons (:) as usual in BASIC. DIGITAL OUTPUT. HIGH Switch an output pin high (on). Example: High 2 turns pin 2 on. LOW Switch an output pin low (off). Example: Low 3 turns pin 3 off. TOGGLE Toggle (alter) the hi/lo state of an output pin. OUTPUT Set a pin as an output. Example: Output 1 makes pin 1 an output. INPUT Set a pin as an input. REVERSE Reverse the I/O state of a pin. PULSOUT Output a timed pin inverted pulse. Example: Pulsout 0,3 - pin 0, 30 microseconds. ANALOG OUTPUT PWM Provide a pulse width modulation output. Example: Pwm 1,20,8 - pin 1,20/255 duty,   8 cycles. SOUND Make sound(s) 0 = quiet, 255 = hiss. Example: Sound 4,(100,10) - sound pin  4,~5kHz,~100ms. DIGITAL INPUT IF...THEN Jump to new program line, depending on condition. Example: If b3 < b2 then ledoff PULSIN Measure input pulse duration (µs). Example: Pulsin 4,0,w2 - pin 4 input,   logic low triggered. ANALOG INPUT READADC Read analog channel (0 - 160) into a variable. Example: Read 1,b2 - read channel 1 into b2 PROGRAM FLOW FOR...NEXT Establish a for-next loop. Example: For b2=0 to 100 step 2   counts even numbers. BRANCH Jump to address specified by output if in range (akin to ON x GOTO). GOTO Jump to address. Example: If b0=5 goto daylight   goes to daylight routine if b0=5. GOSUB Jump to subroutine at address specified. Example: Gosub test heads to test subroutine. RETURN Returns to main program from gosub routine. 10  Silicon Chip VARIABLE MANIPULATION (LET) Assigns a value to a variable & does limited L-R maths. Example: Let w0=b2*22/7 – Pi LOOKUP Lookup indexed data specified by offset & store. Example: lookup 1,(6,7,8) - takes 7 LOOKDOWN Search values for a target’s match number & store in variable, akin to $trings RANDOM Generate a pseudo-random number. SERIAL I/O SEROUT Serial data output (to 2400bps). Example: Serout 0,n2400,(65) - sends    ASCII 65 (=A). SERIN Serial data input - many qualifiers! Example: Serin 0,n2400,(“A”) - waits for    ASCII 65. INTERNAL EEPROM ACCESS (program & data storage; take care since program overwriting may occur). EEPROM Store data in EEPROM before download. Example: eeprom 0,(“hello”) - starts <at>   location 0. READ Read data EEPROM into variable. Example: Read 255,b2    get location of last program instruction. WRITE Write variable into data EEPROM. Example: Write 220,b3 - stores byte b3 into   address 220. POWER DOWN NAP Enter low power 20µA mode for short period ( <2.3 secs). Example: Nap 3 - sleeps for 144ms. SLEEP Enter low power mode long period (±1%). Example: Sleep 3600 - sleeps for 1 hr   (max 65535s). END Power down until reset (indefinite sleep). MISCELLANEOUS PAUSE Wait up to 65535ms (65.5 ) ~ 1ms overhead. Example: Pause 100 - pauses ~100ms = 0.1s. WAIT Wait for up to 65 seconds. DEBUG Displays variable value on attached PC screen. Example: Debug b0 - shows b0 value on screen. Ch.0 Ch. 3 Ch.1 PROGR or switchable OUT IN only Low res. Analog I/O www.siliconchip.com.au A typical 555 oscillator circuit to flash a single LED. As you can see, even this simple circuit requires more components than the PICAXE. And that’s all this circuit can do! may readily convert to PICAXE use. PICAXE-08s are based on the new Microchip 8-pin PIC12-F629s but with the BASIC interpreter squeezed on-board. Such interpreters allow easy code tweaking, since the program doesn’t need compiling before each run, although a slight execution overhead (about one millisecond) exists. They have in-built 4MHz oscillators, 1K code space, 64 bytes RAM, 128 bytes EEPROM (enough for about 40 lines of code), five I/O pins and valuable low-resolution analog-to-digital conversion (ADC). Battery needs are a flexible – 2.5V to 6V at just 2mA, yet they’re able to supply 20mA at each pin to drive LEDs or piezo speakers, etc. Perhaps the PICAXE name represents a miner’s digging tool with “Silicon – I’ve struck Silicon!” the cry, instead of “Gold!” Gold prices are irrelevant however, since PIXAXE08s sell for an astound- On the left is the classic 555 oscillator, very cheap but with all aspects hardware-dependent. Contrast this with larger footprint and much more costly BASIC “Stamp” approach at right. In the centre is the smaller PICAXE approach which offers the best of both worlds: software control and “bubble gum” cheapness. ingly low $3 each. Being so cheap, they can be even left in the final soldered circuit. Later software tweaking can be attended to with a 3-wire serial connection if need be. It’s recommended that all PICAXE circuits have such a simple inclusion and the associated 10kΩ and 22kΩ resistor pair. Folks, if you’ve been meaning to get into PICs but thought the process akin to unravelling DNA sequences, then PICAXE chips are the answer. Although Revolution Education (UK) market a $25 “Starter Pack” Introducing the PICNIK box – the “Peripheral Interface Con-troller Nifty Intro Kit.” The protoboard fits neatly into a parts box and along with the battery pack and sundry other components, offers a one-stop PICAXE experimenter’s kit. www.siliconchip.com.au (along with other project boards) that could be ideal for dedicated circuits, this involves fine soldering and inconvenience when away from the workbench. For more flexibility, solderless protoboards are better, since these allow easy component swapping and reuse, neater circuit layouts, and no burnt fingers! It’s a PICNIK! With increased productivity in mind, I’ve developed the PICNIK (Peripheral Interface Controller Nifty Intro Kit?) box. Emily, a Year 11 student, uses her notebook PC and a PICNIK to create an instant solderless PIC workshop. It’s suitable for education, non-specialist workrooms or home use. February 2003  11 What are the goodies in the PICNIK Box . . . PICAXE-08 IC Revolution Education, UK (see website) Approx. $3 each in a tube of 5 Small solderless “Wish” protoboard Sold by most electronics outlets. 4 AA battery holder and battery snaps Ensure PICAXE is not run from 9V! 4 AA cells (Power demands are very light, so cheap non-alkalines should do). Solid core hookup wire Multi-coloured (avoid stranded wire on protoboards). Wire snips & strippers Even fingernail nippers can be used! Small piezo speaker Allows direct sound production. (Don’t use a normal 8Ω speaker). Assorted LEDs Easily driven by the PICAXE. 330Ω dropping resistors LEDs can be driven directly but it’s wise to use these. Light Dependent Resistor (LDR) Allows easy ADC action via a simple voltage divider with further resistors. 3-wire serial cable Perhaps from an old serial mouse and PC motherboard header pins. Other tools & materials Hot-melt glue gun, wide heatshrink tubing (clear), photocopied labels. PICAXE Editor and .PDF manuals from CD, or free download from Rev-Ed (also at www.picaxe.orconhosting.net.nz). The protoboard neatly fits into a semi-transparent parts box and along with the battery pack and sundry other components, offers a one-stop PICAXE experimenter’s kit. Few of its items are exotic, and with junk box fossicking, the total bill of materials shouldn’t set you back more than $30. Both educational users and experienced circuit developers should find this a most cost effective approach. We hope to use the PICNIK box over the next few months to get you as enthusiastic about these new chips as we are! What’s this? No serial port? Don’t have a serial port in that spiffy new notebook? The computer industry has perhaps been rather TOO keen to run with USB ! Although wonderfully convenient and well supported now by modern peripherals, USB-only machines leave serial RS-232 “legacy” devices in limbo – including our PICAXE. This may also be frustrating for GPS, data logging and PDA applications. Help is at hand, however, since USB to serial adaptors ( but NOT vice versa) are available, althought they may be quirky and costly (A$60 range) and need software drivers. Undemanding “3 wire” serial needs, such as this PICAXE-08 ,should be supported by almost any such adaptor but if conversion problems arise it’s suggested you just rescue that older serial-port-fitted Win95 PC from the broom cupboard! 12  Silicon Chip References and updated material For convenience these are hot-linked at website http://picaxe.orconhosting.net.nz/refs.htm http://picaxe.orconhosting.net.nz Author’s pictorial page outlining PICAXE-08 features http://picaxe.orconhosting.net.nz/progedit Free program editor and PDF manuals (6 .cab files ~ 8.5 MB) www.hippy.freeserve.co.uk/picaxe.htm Overview of entire PICAXE family www.rev-ed.co.uk Revolution Education, Bath UK, microcontroller products www.picaxe.co.uk Rev-Ed’s PICAXE products and programming editor www.techsupplies.co.uk Rev-Ed’s online technical products shop – global sales! www.jpixton.dircon.co.uk/pic/history.html PIC history page www.microchip.com Microchip PICmicro products and data. Who is Stan Swan? We first met Stan Swan in his "WiFi" article in SILICON CHIP back in November 2002. Stan is a New Zealander who first wrangled electrons with 1960s valve-era ham radio. He is a career educator teaching Electronics and Computer Technology at the Wellington (NZ) campus of Massey University. His enthusiasm for “hands on” appropriate technology covers such diverse fields as PC interfacing, alternative energy resources, wireless data comms, digital photography and Internet applications. He credits Ray Doty’s “Wordless Workshop “ and the lucid electronics articles of US writer Forrest M. Mims III as especially formative influences. * Stan’s email address is s.t.swan<at>massey.ac.nz www.siliconchip.com.au Your first PICAXE application: a simple LED flasher The 555 timer oscillates under time periods established by external resistor and capacitor values. If a LED is used at the output, perhaps on a battery-powered bike light, the flash rate, duty cycle and battery drain can be juggled by changing these components. This may be very inconvenient, especially if only physically larger capacitors are available! In contrast, a PICAXE LED flasher uses software tweaks for fine tuning. Flash rates that are the most attention-getting or duty cycles that prolong battery life are simply “cut and tried” at the PC keyboard. Not only is this more versatile but the parts count, cost and circuit size are all reduced. First attach the programming serial cable, connect a LED (plus suitable dropping resistor (see below) to output 2 and power up the PICAXE-08. Run the editor (download free from www.rev-ed. co.uk or http://picaxe.orconhosting.net.nz) on the PC, enter the following code and send it to the PICAXE. The comments (preceded by ‘) are not saved on the IC but are essential documentation for your future reference. Colons (:) identify the defined routine – helpful names are best. ledflash: high 2 pause 5 low 2 pause 50 goto ledflash ‘LED flash rate & mark/space experiment ‘turn on output pin 2 – LED lights up ‘keep it on for 5 milliseconds ‘turn off pin 2 – LED goes out ‘keep it off for 50ms ‘repeat routine The value of RD, the series resistor, depends on the supply voltage and the type of LED you are using. In fact, it may not even be required as there is a 20mA limit on the PICAXE output. But we are used to using current-limiting resistors with LEDs so let’s keep it that way and avoid accidents! For a red LED (which requires about 2V <at> 10mA), with a 6V supply, RD = (6-2)/.01, or 400Ω (330Ω would be fine). For a white LED (3.6V <at> 25mA), RD = (6-3.6)/0.025 = 100Ω. With an ultra-bright white LED, normally taking 25mA at 3.6V, this DIY serial leads can be made using 10:1 duty cycle pulsing still gave the header pins rescued from old impression of a steady light, yet avermotherboards or modems. First, age current dropped to just a few mA. solder the three serial wires, then This means batteries should last 10 dribble hot-melt glue onto them. times as long. The inbuilt slight interAllow this to cool somewhat and preter overhead could mean the timing while still warm and pliable, work it is stretched by a millisecond or so. with your fingers into a neat “plug”. NEXT MONTH: www.siliconchip.com.au The D9 serial plug has its pins 5, 3 & 2 going to PICAXE legs 8 [ground], 2 (via a 22kΩ resistor) [serial in] and 7 via a jumper (S1) [serial out]. A small photocopied label slid under protective clear heat-shrink tubing will identify the plug after final hot-air shrinking. A more ambitious application of the PICNIK box. Build your solderless kit up now and get to know its features in anticipation! February 2003  13 E R U FEAT ECT PROJ The PortaPAL A State-Of-The-Art Portable Public Address Amplifier Features d unit with safe plugpack charger • Portable, 12V battery-powere • High power output eaker with tweeter ut • Inbuilt 200mm (8") loudsp s 6.35mm guitar or aux inp m microphone inputs plu • 2 combined XLR/ 6.35mwit stereo to mono mixer • Stereo RCA line inputs hRCA and 6.35mm jack outlets • 2 line outputs with stereo ut • Level control for each inp • Bass and Treble controlsto extend battery charge with power-down indication • Automatic power-down indication arger on and charging • Ch 14  S ilicon hip re leads ce forCspa rage spa Sto • and corner protectors dle, speaker stand socket han ry • Box includes car siliconchip.com.au Part 1: by JOHN CLARKE & LEO SIMPSON T HIS PORTABLE PA amplifier can be powered from the 240VAC mains or its inbuilt 12V SLA battery. It delivers up to 70 watts and pulls a number of tricks to keep battery current low while still maintaining very high performance. Back in March 2002, we published the “Mighty Midget”, a 70-watt class-H audio amplifier module based on the Philips TDA1562Q power IC. This ground-breaking IC uses special techniques to deliver up to 70 watts from a 12V battery and does away with the need for a DC-DC inverter. At the time, we said the “Mighty Midget” was ideal for use in a portable PA system and now we have followed up with the PortaPAL: a complete system, including mixing for two 600Ω balanced or unbalanced microphones, guitar input and line inputs for a CD player or a cassette deck. This new circuit makes use of the TDA1562Q’s muting feature, to further reduce battery drain and keep hum and noise very low. We’ve also taken advantage of the inbuilt 12V SLA (sealed lead acid) battery to eliminate a heavy transformer and large and expensive electrolytic filter capacitors from the power supply – leading to a considerable cost saving. No DC-DC inverter needed Up until the release of the Philips TDA1562Q IC, if you wanted more than about 16 watts from a 12V-powered PA system, you had to resort to a DC-DC inverter to provide power supply rails of, say, ±40V, to get around 50 watts into an 8-ohm load. Not only are DC-DC inverters relatively complex but even the most efficient designs inevitably lead to a reduction in overall circuit efficiency. With its special class-H operation and bridged amplifier operation, the TDA1562Q not only eliminates the need for an inverter but its class-H operation is considerably more efficient than a normal class-B amplifier which is what would be normally used. So enough of the rave about the TDA1562Q – if you want more information, refer to the March 2002 issue of SILICON CHIP. Now let us have a look at the other features of this great little (actually, not so little) portable PA amplifier. Features Housed in a timber cabinet meas- uring 450 x 280 x 240mm, the PortaPAL amplifier uses a coaxial 200mm speaker which is rated at 50W and has relatively high efficiency of 92dB/ 1 watt <at> 1 metre. It is a 4Ω speaker which incorporates a separate concentrically mounted miniature dome tweeter; that’s where the “coaxial” term comes from. The speaker is specified as a 4Ω model because the amplifier is designed to deliver maximum power into a 4Ω load. All the controls are at the rear of the cabinet. There are two XLR sockets for connection of low impedance (600Ω) balanced microphones. These special XLR sockets also accept standard 6.5mm jack sockets so that unbalanced microphones can be used as well. There is also a pair of RCA phono sockets for connection of a CD player or cassette deck and RCA sockets are also provided for line out signals to a cassette deck, if the proceedings need to be recorded, or to another PA system. This output is also duplicated at a 6.35mm stereo jack socket. There are four mixing knobs for the microphones, guitar and line inputs but there is no master level control, to keep things simple. Bass and treble tone controls are provided and automatic VOX is built in. There are four LEDs on the panel, PortaPAL Specifications 33W RMS into 4Ω (depending on battery voltage) 70W RMS into 4Ω (depending on battery voltage) Line -3dB at 26Hz and 40kHz Guitar and microphone -3dB at 42Hz and 20kHz Tone Controls +13dB and -14dB at 100Hz (see graphs) +11dB and -13dB at 10kHz Input Sensitivity: Line 340mV RMS (for 30W into 4Ω) Guitar 16mV RMS (1.9V RMS overload) Microphone 1.3mV RMS (130mV RMS overload) Signal-to-Noise Ratio: -83dB unweighted (20Hz to 20kHz); input level controls all off (all figures with respect to 33W) -71dB unweighted with microphone level set at maximum sensitivity (-73dB A-weighted) Muting Threshold: <7mW output power Time: 15 seconds (typical) after signal drops below threshold 100ms (typical) unmute when signal applied Battery Consumption Standby (mute) 26mA No signal (unmute) 160mA Battery Charger Charge rate: 1A maximum Charge voltage: 13.8V maximum Dimensions: 500 x 295 x 250mm (including handle and corners/feet) Mass 13kg (including charger plugpack) Output Power Music Power Frequency Response siliconchip.com.au February 2003  15 Fig.1: all of the functional areas of the PortaPAL are shown in this block diagram, with the exception of the mains power supply/SLA battery charger. two at the top righthand corner and two lower down, adjacent to the plugpack charger input socket. At the top, one of the LEDs flashes about twice a second to indicate that the unit is on while the other is the “Fault” indicator. We’ll talk more about this and the charger LEDs later. The only other control is the On/Off switch. Also on the rear panel is the lid for the 12V battery compartment and the battery can be quickly changed over if that is necessary. Power comes from the battery or an external 16VAC 1.5A plugpack. While the plugpack has relatively low power rating (24VA) with respect to the maximum output of the PA amplifier, it is quite adequate to keep the battery fully charged in normal PA operation. In fact, the power supply is really just a battery charger with the battery permanently connected. The inbuilt VOX operates to mute the power amplifier if there is no signal for more than 15 seconds, reducing the standby battery consumption from 16  Silicon Chip 160mA to around 26mA. While it is hard to be precise, we estimate that the inbuilt 12V 7Ah battery should be good for about five to six hours use. In practice, that means you could typically use the PortaPAL all day on battery power. Circuit overview Fig.1 shows the simplified block diagram. Apart from the TDA1562Q power amplifier IC, there are eight low-cost ICs and not a lot else. The microphone signals are amplified in op amps IC1a and IC1b, while the guitar signal is amplified by op amp IC3. The microphone, guitar and line signals levels are set by VR1, VR2, VR3 & VR4 and then mixed and fed to the tone control stages and to the muting circuit involving IC6, D1 & D2. This circuit provides a mute signal to the power amplifier when the audio signal levels are below a certain threshold. Circuit details As already noted, the Portable PA uses two special XLR sockets which also accept stereo or mono 6.5mm jacks. For simplicity, these sockets are shown on the circuit of Fig.2 as separate XLR and jack sockets but remember that they are combined into what look like ordinary 3-pin XLR sockets. In normal operation, using a microphone with an XLR plug, the balanced microphone signals are fed to the inputs of op amps IC1a & IC1b. These provide a gain of 22 from a 600Ω microphone. Both microphone preamps are identical except that the MIC1 preamp has provision for a bias voltage (phantom power) for electret microphones, if required. The use of 1% resistors in the balanced microphone circuits ensures good rejection of common mode signals such as hum and hash. High frequencies above 50kHz are rolled off by the 150pF capacitors across the 22kΩ feedback resistors. The 390pF capacitors shunting the balanced input lines, in conjunction siliconchip.com.au with the microphone impedance, also roll off the high frequencies. Should you insert a 6.5mm stereo jack plug from a balanced mike into the XLR socket it will again be accepted as a balanced signal and converted to a single-ended output. But here is the clever part. We have wired it so that if you insert a mono jack into the socket, the non-inverting input (pin 3 of the XLR) is grounded and IC1a (or IC1b) operates as a normal non-inverting amplifier with a gain of 22. Thus we cater for both balanced and unbalanced low impedance microphones. The unbalanced outputs of op amps IC1a & IC1b are each fed to level potentiometers VR1 & VR2 via a 150Ω resistor and 1µF capacitor. The signals from VR1 and VR2 are then applied to op amps IC2a and IC2b, both of which have a gain of 11. This means that maximum gain for microphone signals is 242. Guitar input The guitar input stage involving the TL071 Fet-input op amp IC3 looks like a straightforward non-inverting amplifier but there are a number of interesting wrinkles. First, the guitar signal is coupled in via a relatively large value of capacitor, 47µF, especially when the input load resistor is also high at 470kΩ. This is because are aiming for two separate outcomes. We have specified the high load resistance of 470kΩ to ensure optimum high frequency response with the relatively high inductance of typical guitar pickups. With such a high load resistance, you might wonder why we have used such a large input coupling capacitor. After all, to maintain a flat response to below 20Hz, all you need is a 15nF (0.15µF) input capacitor. Why use 47µF, 300 times bigger? The answer is that the inductive guitar pickup represents a low source resistance at low frequencies. In order to minimise noise, op amp IC3 needs to see as low a source resistance as possible. Ergo, we use a big capacitor. IC3 is set for a gain of just two. This is adequate for any guitar (when the following gain is accounted for) but it also means that this input can handle line input signals of up to 1.9V before overload occurs. Following potentiometer VR3, the siliconchip.com.au Construction will be fully described next month but to whet your appetites, at top we show the completed amplifier assembly ready for mounting in the box, while immediately above is the separate SLA charger board. By the way, this could be built independently as a high performance SLA battery charger. guitar signal is fed to op amp IC4a, which has identical gain to IC2a & IC2b. Stereo line inputs Stereo line inputs (eg, from a CD player) are mixed to a mono signal with 2.2kΩ resistors and fed to potentiometer VR4. All of the signals from the four potentiometers are then mixed in IC5a which has gain of unity. Note that the input resistor from VR4 is 10kΩ rather than 15kΩ to make up for a slight gain loss in the resistive mixing of the stereo line inputs. IC5a drives the tone control stage involving IC5b and this has its output signal fed to three places: the line outFebruary 2003  17 18  Silicon Chip siliconchip.com.au siliconchip.com.au February 2003  19 Fig.3: total harmonic distortion versus frequency at 12W using the microphone input. put to RCA and 6.35mm jack sockets, the muting stages involving IC6 and the power amplifier involving IC8 and IC9. All of the op amps in the circuit, with the exception of IC4b and IC6, have their non-inverting (+) inputs biased from the Vref line which is at +6V. This is derived from the +12V line by a voltage divider consisting of two 10kΩ resistors with the centre point bypassed by a 100µF capacitor. The bypassed supply is then buffered by op amp IC4a to provide the Vref line. This means that all op amps will have symmetrical clipping at overload, to maximise the output signal. All op amp outputs, with the exception of IC6b, will sit at +6V (or half the battery voltage). Muting stages As noted above, we have incorpo- rated VOX into the circuit to mute the amplifier and cut current consumption when no signal is present. This muting function is provided by dual op amp IC6. Op amp IC6a is a non-inverting stage with a gain of 471 by virtue of the 470kΩ and 1kΩ feedback resistors. The 22pF capacitor rolls the gain off above 15kHz, while the 10µF capacitor in series with the 1kΩ resistor rolls off signals below 16Hz. The amplified signal from IC6a is then fed to a diode pump circuit consisting of diodes D1 & D2 and 1µF & 10µF capacitors. Hence, the peak level of the signal from IC6a will be stored in the 10µF capacitor which is continuously being discharged via the 1MΩ resistor across it. The 10µF capacitor is monitored by IC6b which is connected as a Schmitt trigger. A 10MΩ resistor between pin 5 and pin 7 applies a degree of positive Fig.5: distortion versus frequency at 30W but using the line input. 20  Silicon Chip Fig.4: total harmonic distortion versus frequency at 30W using the microphone input. feedback to give hysteresis. This makes the comparator output switch cleanly between high and low, to prevent the possibility of parasitic oscillation at the switching points. The inverting input of IC6b is set at +3.4V using the 100kΩ and 39kΩ resistors across the 12V supply. When power is first applied to the circuit, the 10µF capacitor between the 12V supply and the inverting input to IC6b is initially discharged and therefore pulls pin 6 high, causing pin 7 to be low. Pin 7 of IC6b is connected to the mute (mode) input, pin 4, of the power amplifier, IC9. So at power-up, the amplifier is muted. Once the audio signal monitored by IC6a is of sufficient level, IC6b’s output will go high and the power amplifier will be unmuted. Muting indication is provided by Fig.6: power versus distortion when driven by the mic input. Maximum power here is 42W at 10% distortion. siliconchip.com.au Fig.7: power versus distortion when driven by the line input. The distortion is lower than Fig.6 because of the lower gain from the line input. IC7, a CMOS 7555 timer, which drives LED1, the power/ standby indicator. Initially when power is switched on, transistor Q1 is off and so pin 4 of IC7 is pulled high via the 10kΩ resistor connecting to the 12V supply. This allows the 555 timer to run and it flashes LED1 on and off. The rate of flashing is set by the 10µF capacitor connected to pins 2 & 6 and the associated 100kΩ and 10kΩ resistors. Note that the 10µF capacitor is tied to the +12V supply rather than 0V, as in a normal 7555 timer setup. The reason for doing this is so that pin 3 of the 7555 will be low when power is first applied and the LED will light immediately and then flash. If the capacitor was connected to 0V (as in a conventional 7555 circuit), the LED would be off for almost one second before flashing on. In effect, the 10µF capacitor is charged via the 10kΩ and pin 7 and then discharged to +12V via the 10kΩ and 100kΩ resistors. Since the ratio of the charge/discharge resistances is 1:11, the LED flashes with about the same duty cycle (on for 70ms, off for 740ms) and thereby keeps current drain to a minimum when the amplifier is muted; LED1 draws about 400mA. Fig.8: the tone control action in the “flat”, “max boost” and “max cut” settings. siliconchip.com.au February 2003  21 The main PC board includes most of the electronics: the power amplifier (the large IC attached to the heatsink), the mixer, tone controls and so on. Input “daughter boards” attach to this main board. The power supply is also on a separate board. When pin 7 of IC6b’s output goes high to unmute the power amplifier, transistor Q1 is switched on and it pulls pin 4 of IC7 low. This forces the pin 3 output low and LED1 is lit continuously. So LED1 is on continuously in normal operation and it flashes when the amplifier is muted. Power amplifier IC9 is the TDA1562Q power amplifi- The specified 200mm 4Ω woofer from Altronics has a separate concentrically mounted plastic dome tweeter and has quite a wide overall frequency response. 22  Silicon Chip er which can deliver up to 70W under music power conditions, depending also on the state of battery charge. The circuit presented here is very similar to that first presented in the March 2002 issue of SILICON CHIP. The main difference is that here we are using the mute (pin 4, Mode input) facility, as described above and the diagnostic output at pin 8. This is used to drive LED2. It will show when the amplifier is clipping, if there is a short at the output, if there is an open circuit load and if the amplifier has gone into thermal shutdown. If you want a full description of the TDA1562Q, you will need to refer back to the March 2002 issue. For those readers who have not seen that issue, we will briefly the describe the circuit operation. The TDA1562Q actually contains two power amplifiers which drive the 4Ω speaker in bridge configuration and its inputs are balanced. So we drive these balanced inputs (pins 1 & 2) with signals that are 180° out of phase. Hence, pin 1 of IC9 is driven directly from the output of IC5b (albeit via two capacitors) while pin 2 is driven from the output of IC8, a TL071 op amp connected as a unity gain inverter. The two 4700µF capacitors at pins 3 & 5 and pins 13 & 15 of IC9 are “lift supply” reserves for when momentary high power levels are required. Both amplifier output terminals pass through Zobel networks, each comprising a 2.2Ω resistor and parallel inductor shunted via a 220nF capacitor. The components are included to guarantee stability (ie, stop any tendency to supersonic oscillation) when driving reactive loads. Power for the circuit comes from a 12V 7 amp-hour battery which is fed via switch S1 and a 7.5A fuse. Diode D3 is included should the battery be connected the wrong way around. If that happens, the diode will conduct and blow the fuse. Next month In March, we will present the charger circuit for the PortaPAL. This can be built as a general-purpose charger, as well as the power supply for this amplifier. We will also present the full construction details of the PortaPAL PA SC amplifier. siliconchip.com.au 110mm NEAR HALF PRICE SOLAR PANELS $199 2W 315 X 162 X 19 ... $29 4W 315 X 315 X19... $59 14W 315 X 925 X19... 199 I A RG 3 A B $3 77mm N 28mm $29 All of our panels are amorphous, aluminium framed, backed and water-proof. COOL NEW ITEM HEATER / COOLER This new cooler / heater assembly includes a 90mm fan, heat-sink, 65deg. thermal cut-out switch (used when heating), spacer block and a 50W Peltier device. Just cut a hole in your ESKI or insulated cooler box & fit an aluminum plate or heat-sink (not supplied) to this assembly to turn your ESKI into a fridge for the car or boat. requires 12VDC Special intro price of only $33 (pelt1). SWITCHING SOLAR REGULATOR KIT: This easy to assemble kit is designed to efficiently charge batteries from solar cells. It has charge / discharge indicator LEDs. Kit contains PCB plus all on-board ( N E W ) 4 3 3 . 9 2 M H z M I N I T R A N S M I T T E R components. KIT PRICE: (K008B) $15 AND RECEIVER MODULE: 10 LED LAMP KIT: NEAR ACTUAL This kit uses 10 Ultra-bright LEDs t (equivalent to around 6W incandescent) with SIZE superhetrodyne surface mount transmitter far less current drain than normal incandescent light bulbs but with a brighter, Pre-built module which is saw resonator locked at 433.92MHz. whiter light, It uses a constant current circuit and draws 100mA. (This means is Operates from 3 ~ 12V DC and has 7 connections. When your get many more hours of light with a smaller & cheaper battery & solar cell. Kit use in conjunction with RX434, the pair can give a range of up to 2km when the transmitter is powered by 12V DC. contains a small PCB, 10 White Ultra-bright LEDS & all on-board components. Dimensions: 20mm (L) x 8mm (W). (Same diameter as a 5c coin). Click here for data: (TX434) $11 Easy to assemble. K199 Kit price $20 (NEW) 433.92MHz MINI RECEIVER MODULE: 12V / 7AH SEALED LEAD ACID BATTERY: (RX434) $21 Fresh stock batteries, now is the time to pick up a real bargain, 2.6kg, 150 x 65 x "LOOK NEW KIT" 92mm.(PB6) $25 each STEREO FM TRANSMITTER KIT professionally designed stereo transmitter HOW ABOUT A COMPLETE SOLAR LIGHTING SYSTEM FOR YOUR CAMP, This uses a special IC that produces the MPX CARAVAN OR WEEKENDER: There are 4 main components to this system, 2W signal only plus a stable transmitter uses discrete components: Solar Panel, Switching Solar Regulator kit, Battery and 2 X 10 LED Lamp Kits. that $22.50 for a complete kit inc. case. (k094b) This combination of solar panel, charger and battery will power 1 of the LED lamp The following items are in good condition!!!! If you kits for over 7hrs with only 5hrs of sunlight. Central Australia receives around 10 have not subscribed to our E-mailing list you may have missed them, small quantity only!!! hrs per day. (SL2W): $99 ( U S E D ) TO P WA R D 7 0 4 6 D U A L C H A N N E L OSCILLOSCOPE: UPGRADE TO A BIGGER PANEL!!! For just $25 more. 40Mhz Portable Dual Channel Oscilloscope are in You can upgrade from a 2W to a 4W panel in your Solar Lighting System . excellent condition. It features Dual channel with Delayed (SL4W) total price.$124 sweep, Vertical sensitivity is 5mV/div - 5V/div in 10 calibrated steps, X5 magnification (1mV/div-1V/div), and Time Base 0.1µS/div - 2S/div in 23 calibrated Steps, X10 Magnification (10nS/DIV-200mS/DIV). Dimensions are 352(W) x 167(H) x 430(H) mm. Weight: 8Kg: (ZC0210) $290 LOTS OF AMAZING OPTICAL MINI FM TRANSMITTER KIT K189 This kit is easy to build with BARGAINS HIGH POWERED LEDS, just a few simple steps to LASERS POINTERS & LASER complete and test it. It measures only 32mm X DIODES 13mm X 24mm and draws AMAZINGLY BRIGHT MINI KEY-CHAIN LED only 5.8mA from it's 1.5V TORCHES, ALL ARE AROUND 8 TO 10 Cd. LR44 button cell (supplied). ...$7 RED ...$4 BLUE ...$6 Kit comes complete with a GREEN ...$6 metal case, battery, prebuilt PCB and double sided tape YOU HAVE HEARD OF SUPER BRIGHT LEDs?... for quick and easy installation. ARE THESE THE NEXT GENERATION LED?... (K189) $39 All of the following are up to 10cD, 20mA max and narrow angle. ***LOOK***LOOK***LOOK*** 10cD White...$2.00 ea Red...80c Yellow ...70c Green...$2.10 Blue...$2.20 WARNING!!! UV LED's ..$1.60 These magnets are so strong they Less 10% for 10 or more of any mix Money Detector Pens are dangerous!!! These use a very bright UV LED. Check Australian currency for counterfeits by looking at the hidden UV Look at the prices on our new printing on them. ...$4.50 neodymium rare earth magnets Extra AG13 batteries ...15c as used in the key-chains, 3 req. Extra AG3 batteries...6c as used in pens, 4 req. Don't forget our bargain OPTO PACK...K147 Pack inc. total of 103 opto semiconductors. 91 various colours & types of visible LED's, 1 x IR LED, 6 x Phototransistors, 2 x high speed PIN photodiodes, 1 x HC312 IR Receiver Module. KIT PRICE: (K147) $10 each pack 10mm 10mm X X 3mm 5mm $0.70 $1.20 (USED) BWD 603B FUNCTION GENERATOR MINILAB: This single unit includes a 0.1Hz to 1MHz Function Generator, a power differential amplifier with an adjustable gain of 1 to 100 <at> 1A output current capability, a bi-polar power supply / power amplifier with an output voltage range of -15 to +15V <at> 1A, a positive voltage power supply with an output voltage range of 1 to 15V <at> 1A, a negative voltage power supply with an output voltage range of 1 to 15V <at> 1A, a 0 to 200V positive power supply and a 12.6V center tapped 50Hz AC voltage source (6.3V 0 6.3V). Units are in excellent condition: (ZC0211) $250 20mm X 10mm $6 of kits and surplus electronics to hobbyists, experimenters, industry & professionals. www.oatleyelectronics.com Suppliers Orders: Ph ( 02 ) 9584 3563, Fax 9584 3561, sales<at>oatleyelectronics.com, PO Box 89 Oatley NSW 2223 major credit cards accepted, Post & Pack typically $7 Prices subject to change without notice ACN 068 740 081 ABN18068 740 081 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. 12V lead acid battery desulphator Lead acid batteries often fail prematurely due to over-charging, under-charging, deep discharging and low electrolyte level. All of these can lead to sulphation of the plates which leads to high internal resistance and eventual failure. Normally, this process is regarded as irreversible but this circuit is claimed to reverse the process by applying high vol­tage pulses to break down the lead sulphate compounds. The cir­cuit is essentially a high-voltage pulse generator which is powered directly from the battery in question. If the battery is badly sulphated, it will be necessary to connect it to a low power charger as well, say 2A. We have strong doubts about whether battery sulphation can be effectively reversed but we are publishing this circuit be­cause the subject is of particular interest. This circuit has been submitted to us from a number of sources so we do not know who is the original designer. More information can be found at http://shaka. com/~kalepa/desulf The 555 timer is connected as an astable oscillator with its output frequency set by R1, R2 and C2. Its output pulses drive the gate of Mosfet Q1 which turns on to charge inductors L1 and L2. At the end of each pulse, Q1 turns off and the inductors develop a high-voltage high-current pulse which is applied across the battery via fast recovery diode D1 and the 100µF capacitor. The 555 is protected from the high voltage pulses via its isolated supply, by virtue of the 15V zener diode ZD1, the 47µF capacitor and the 330Ω resistor R3. SILICON CHIP LED1 just comes on at the desired low-voltage point. The current consumption is typically less than 2mA when LED1 is off. Finally, the value shown for RLED is suitable for 6-12V operation. For other voltages, RLED can be calculated using the formula RLED = (Vcc - 1.8)/0.01 (this equates to a current of about 10mA). Trent Jackson, Dural, NSW. ($30) Low supply rail detection circuit Here’s a simple low supply rail detection circuit that costs peanuts and takes just 20 minutes or so to make. Its power consumption is quite low, so it could easily be built into bat­terypowered devices. Instead of using an op amp, the circuit is built around three low-cost transistors (Q1-Q3). Diodes D1-D3 form a 1.8V voltage reference (Vref) for the emitter of Q1. If the voltage across the voltage divider formed by R1 and VR1 is less than this, Q1 turns on and supplies Q2 with base bias current. This turns on Q3 in proportion to this bias current which then drives LED1. The brightness of the LED gives an indication of the sever­ity of the low voltage condition. The brighter the LED, the lower the supply voltage. Trimpot VR1 is adjusted so that 24  Silicon Chip www.siliconchip.com.au Fifth channel for codehopping remote control This circuit was developed as a refinement to the Code-Hopping 4-Channel Remote Control featured in the July 2002 issue of SILICON CHIP. As mentioned in the article, code-hopping prev­ents code-cracking of the transmission but you still have a problem if someone steals your remote transmitter. This circuit adds a fifth hidden channel with its own entry code entered via the four existing buttons. This involves adding three low-cost CMOS ICs, a transistor and several resistors and capacitors (plus an extra relay and relay driver circuit). The extra ICs include a hex Schmitt trigger IC1, a 4016 quad bilateral switch (IC2) and a 4017 decade counter (IC3). The existing 4013 dual D-type flipflops are retained. The idea is to input a “sequential code” to the counter (by pressing the correct sequence of buttons on the transmitter), without switching the regular channels. This is achieved by www.siliconchip.com.au delaying the rising edge of the receiver’s output pulses by 0.6s, before they trigger the flipflops which activate the relay driv­ers. In other words, both the on/off and momentary functions work as before but are delayed by 0.6s. To activate any of the regular channels, the relevant transmitter button must now be held down for about 1s or longer. Alternatively, to activate the “sequential code” fifth channel, the code must be rapidly entered in the correct sequence, with each button press less than 0.4s. Here’s how it works: initially, IC3 is held reset by the voltage across the 1µF capacitor. When the code is entered, the high on pin 3 of IC3 is applied, via CMOS switch IC2, to the enable pin (pin 13). As a result, Q1 turns on and discharges the 1µF capacitor, thus releasing the reset on IC3. When this first button is released, pin 13 of IC3 goes low, advancing the counter by 1. Similarly, when the second button is pressed, pin 2 of IC3 goes high and the process is repeated. After the last button has been pressed and released, the ‘O4’ output goes high for 0.8s while the 1µF capacitor charges Manfred Schm idt and resets the coun- is this mon th’s winter. This high in turn ner of the Wavetek Meterman 85XT clocks flipflop IC5a. tru e RMS digital Note that only multimeter. three channel buttons have delay networks, to keep the IC count low. This means that one button has to be used twice to get a 4-digit code. And that in turn means that their corresponding counter outputs must be fitted with blocking diodes. The code for the circuit shown here is 3424 – ie, output O3 from the receiver module goes to the first switch in IC2, output O4 goes to the second and fourth switches, and output O2 goes to the third switch. As a result, blocking diodes are fitted between the O1 and O3 outputs of IC3 and pins 1 & 11 of IC2. Manfred Schmidt, Edgewater, WA. February 2003  25 Circuit Notebook – continued Simple headlight reminders These two headlight reminder In-situ battery test probe This item describes a simple probe that allows in-situ AA and AAA battery voltage and current drain measurements without removing the cells from the holder. circuits are easy to install and operate on the KISS (Keep It Simple Stupid) principle. The simple circuit involves add- ing just a 12V piezo buzzer between the lights circuit and a door switch. The buzzer sounds if the lights are left on and you open a door. The disadvantage of this simple circuit is that it’s annoying to have the buzzer sound continuously if you want to leave the door open while the lights are on. The improved circuit overcomes that problem by adding a 1000µF capacitor and a parallel 100kΩ resistor in series with the buzzer. Now, when a door is opened, the buzzer gives a brief burst of sound only, while the 1000µF capacitor charges. The 100kΩ resistor discharges the capacitor when the lights are switched off. Andrew Gibbs, Jindalee, Qld. ($30) In use, the probe is simply pushed between the positive end of one cell and either the negative end of the adjacent cell or the battery holder terminal. The probe leads are then plugged into a multimeter set to a voltage range and the device switched on so that the no-load voltage can be read. Switching the multimeter to a current range allows the device to power up so that the current drain can be read. Warn­ing: be sure your meter has a fuse in its current metering cir­cuit, in case the device being tested has an internal short. The prototype probe was made by gluing strips of brass shim (using plastic adhesive) to both sides of a strip of tough, flexible plastic. Robin Stokes, Armidale, NSW. ($25) Automatically armed engine immobiliser Most immobilisers, once armed, do not allow the vehicle to be started. By contrast, this design is automatically armed each time the ignition is switched on and allows the engine to be started. The engine will then continue to run for about 9 seconds but will stop unless the immobiliser is disarmed using a small transmit­ter. Alternatively, the immobiliser can be disarmed after the ignition has been turned on but before the engine is started. The logic behind this approach is to fool the thief into thinking that the car is faulty and abandon it. When the ignition is switched on, 26  Silicon Chip the LED in optoisolator OPTO1 is turned on (D1-D3 and R1 limit the voltage across the LED to about 1.8V). The tran­ sistor in the optoisolator then conducts and resets IC1b, part of a 4013 dual-D flipflop, via a 10nF capacitor. As a result, pin 13 of IC1b is initially low. At the same time, the 10nF capacitor on pin 3 of flipflop IC1a charges via a 10kΩ resistor and causes pin 2 of IC1a to go low. This in turn triggers both sections of IC2, a 556 dual timer. As a result, pins 5 & 9 of IC2 both go high. Pin 9 turns on LED1 (a flashing LED fitted in the dashboard) to indicate that the immobiliser is armed and also supplies +5V to the emitter of Q1. During this time, Q1’s base is also www.siliconchip.com.au at +5V (pin 5 of IC2a is high) and so Q1 is off. By contrast, Q2 is biased on by the high on pin 9 of IC2b (via D5). This activates the relay and allows the vehicle to start. Both sections of IC2 now start their timing sequence. After about 6s, pin 5 of IC1a goes low (as set by the 5.6MΩ resistor and 1µF timing capacitor) and this turns on Q1 and sounds the warning buzzer. This alerts the driver that the immobiliser is still active. If the immobiliser isn’t disabled, pin 9 of IC2b goes low after about 9 seconds. When that happens, LED1 stops flashing, the buzzer stops and the relay turns off, stopping the engine. Because IC1b is reset when the ignition is switched on, its Q output is low. As a result, the circuit will remain in this condition, even if the ignition is turned on and off repeatedly. The vehicle is thus effectively immobilised and cannot be restarted without the transmitter. Pressing the button on the keyring transmitter (Oatley Electronics TX2) before the timing sequence is complete resets the timers (and holds them in the reset condition). It works like this: when the UHF receiver (Oatley Electronics RX4) receives an encoded signal, its output is fed to decoder IC3 (Oatley Elec­tronics A5885M). If the code is valid, IC3’s output goes high and clocks IC1b. As a result, IC1b’s Q output (pin 13) goes high to ensure that Q2 and the relay remain on. At the same time, pin 12 of IC1b goes low and resets both timers via a 10nF capacitor, causing their outputs to go low. This in turn causes LED1 to stop flashing and silences the buzzer (if it is sounding), ready for the next timing sequence. IC3’s output also resets IC1a, so that it is ready to change state next time the ignition is turned on. The contacts of the relay can be connected in various ways to disable an engine. These include interrupting the +12V supply to any of the following: the ignition coil, fuel and gas cutoff solenoids or fuel injectors. In addition, you can open the con­nection to the starter motor solenoid to prevent the engine being cranked. Note that the relay should be a heavy-duty automotive type with 30A contacts. Don Adamson, Mt. Duneed, Vic. ($50) www.siliconchip.com.au February 2003  27 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au product review WM232-UHF Short range, high-performance wireless modem The applications for radio as a medium to connect devices is virtually unlimited. Some applications demand wireless connection, due to difficult access or for mobility reasons. Others, such as metering and data acquisition systems can benefit greatly from wireless technology. No network cabling and no direct access to equipment is needed, reducing costs right from the installation stage and beyond. T he WM232-UHF, an Australiandesigned and manufactured radio modem, is a low-cost, plug’n’-play connectivity solution for devices that communicate via serial links. It supports on-air data rates of up to 14.4kbps and features data encryp32  Silicon Chip tion, error checking and acknowledged data transfer. The basics The modem is housed in a small ABS plastic case, measuring about 103mm (L) x 62mm (W) x 24mm (D). Antenna hookup is via an SMA connector that protrudes through one end of the case. A tiny (60mm) helical stubby antenna can be mounted directly onto the SMA connector, making a very tidy little package. Power for the unit can be provided www.siliconchip.com.au by Peter Smith Fig.1: Point to Point mode allows simple, transparent connections between any two devices with RS232 ports. by either an internal 9V PP3 battery or around 500m line-of-sight. Of course, dressing system, composed of “unit” an external 7-15V DC source. A 9V DC you could also fit a more elaborate and “site” addresses. plugpack was supplied with our evalu“gain” antenna for much greater range, Up to 16 pairs of modems can operation unit. The average current drawn but that wouldn’t be legal, now would ate within a single site address, with during transmit/receive is quoted at it? up to eight possible site addresses. 40mA, falling to 15mA when idle. This corresponds to a maximum of 127 Wireless simplicity This means that an external power possible point-to-point links. source will be necessary for most In their simplest configuration, two Site addressing effectively partiapplications. In power-down mode, WM232-UHF modems can function as tions groups of modems for repeating consumption drops to a more respecta reliable two-way wireless link. purposes. Any WM232-UHF can able 400µA. operate as a dedicated repeater unit. Apart from a certain amount of Connection to the modem is made latency in the data exchange, the Up to three repeaters can be used via a 9-pin female ‘D’ connector. modems appear transparent to the within a network to extend the opPin assignments conform to the PC connected devices, functioning just erating range. A repeater retransmits modem (DCE) standard, so for conas they would if they were hard-wired any data it receives with the same nection to a PC (DTE) serial port all together. This mode of operation is site address, allowing very flexible that’s required is a 9-way pin to pin called “Point-to-Point”. networks to be constructed. cable (supplied). For more demanding applications, It is important to note that effecThe unit operates in the 433.920MHz multiple pairs of modems can operate tive data throughput for any pair in a LIPD (license-free) band, with transmit within the same air space. network will decrease as the network power limited to is expanded, as the available airtime This is achieved with a two-tier ad10mW (ERP) to satalways remains constant. isfy the regulatory An LBT (Listen requirements. Before Transmit) √ Easy configuration via PC, laptop or PDA Receiver sen scheme is employed √ Point to point or multip sitivity is quoted to minimise the inoint network capability at -100dBm for a √ Repeater support terference that ocfor increased range 1ppm BER (Bit Er- √ Se curs when multiple rial port speeds of 600 to 115200 baud ror Rate), giving modems attempt to a range of about √ On-air data speeds of 600 to 14400 transmit simultanebaud 300m line-of-sight √ On-air data encryption ously. and error checking and 50m indoors √ Diagnos tic “Radar” and “Ping” More about netfunctions with the helical √ DTR-controlled “slee stubby fitted. p” mode working A n o p t i o n - √ Internal 9V battery or externa A common requirel DC plugpack a l c o a x - f e d , √ Range of up to ment within a wire500m with coax-fed ha lf-wave antenna ground-inde- √ less network is to CE & Australian C-Tic k approval for use on pendent halfbe able to monitor licence-free UHF Band wave dipole exand control multiple tends the range to nodes from a central Features www.siliconchip.com.au February 2003  33 product review (continued): Telelink Communications WM232-UHF Fig.2: before data exchange can occur in Point-to-Multipoint mode, the host first programs the desired slave address into the master modem. location. This is the purpose of the “Acknowledged-Point-to- Multipoint” mode, where a single modem is configured as the master and all other modems as slaves. Each slave is assigned a unique address, using the same addressing scheme employed in Point-to-Point mode. In order to communicate with a particular slave modem, the host must first program the desired slave address into the master modem. In Acknowledged-Point-to-Multipoint, the master modem must initiate a link with a slave before data transfer to or from that slave can occur. By contrast, “MultiMaster” mode allows up to 15 slave modems to initiate connection with a single master unit. In this mode, data transfers must be kept as short as possible to prevent “hogging” of available airtime. Design your own network If none of the above modes suit 34  Silicon Chip your requirements, then it is possible to design your own network from the ground up using “Broadcast Multi-drop” mode. In this mode, all aspects of network management, including routing, node addressing and error recovery, are assumed to be host-controlled. Data sent to a modem over its RS232 link is transmitted (broadcast) to all modems within range. Receiving modems simply decode the data and pass it on to their hosts. Configuration Modem configuration is accessible, strangely enough, via configuration mode. A PC, laptop, or PDA with an RS232 port and suitable terminal software (such as HyperTerminal) are required for the job. Normally, modems automatically enter data transfer mode at power up. To exit data transfer mode and enter Fig.3: any modem can function as a dedicated repeater. Up to three repeaters can be added to a network, greatly extending the operating range. www.siliconchip.com.au short range wireless modems configuration mode, it’s just a matter of sending an “escape” sequence from the terminal program. The factory default sequence is three consecutive “+” characters. Typing “help” at the configurator prompt displays all possible commands, whereas “list” displays current settings (see Figs. 4 & 5). A variety of useful commands allows mode and address selection and fine-tuning of network parameters. It’s also possible to modify most of these settings remotely, from a second modem via a wireless link. Of course, this feature can be disabled for security purposes if so desired. Link testing Two diagnostic commands have also been included to aid network setup and testing. The “ping” command looks for a modem within range with the specified address and returns its status. This is a useful “go-no go” test and it allows verification of which unit addresses are in use. The “radar” command allows link range and reliability to be quickly determined. This mandatory feature will help to eliminate most of the guesswork from a simple network installation. Impressions Setting up a simple, reliable wireless network with these modems should be a painless exercise. And if you have something more elaborate in mind, the WM232-UHF can probably handle that too. Getting more information Fig.4: configuring the WM232-UHF is dead easy. Here, we’ve used the “list” command to show all configurable parameters. The WM232-UHF Wireless Modem is manufactured and sold in Australia by Telelink Communications, phone (07) 4934 0413 or email sales<at>telelink .com.au You can reach them on the ’net at http://www.radiotelemetry.co.uk/ SC WM232-UHF Modem and Accessories Prices (inc. GST) WM232-UHF Modem:......$361.90 WM232-PSU Power Pack..................................$ 27.50 ANT-UHF-H SMA Helical Antenna.............................$ 26.40 ANT-UHF-Q SMA 1/4 Wave Antenna.............................$ 28.60 ANT-UHF-D 3dB Industrial Dipole................................$ 42.90 Fig.5: the “ping” command is a handy “go-no go” test and allows quick verification of modem addresses. www.siliconchip.com.au A PC Board only version of the WM232-UHF is available for OEM’s. (prices on application) February 2003  35 FOR HI FI SYSTEMS Are you irritated by clicks, pops, spruigles and sundry other noises in your hifi system? Chances are they are getting in via the mains wiring. Here’s an easy-to-build mains filter which should put an end to those annoyances. By Ross Tester W hat we have done here is taken a commerciallydesigned mains filter kit and modified it ever-soslightly to make it more acceptable – not only for Australian wiring rules and practices but also more acceptable as far as the end user is concerned. As well as making a few mechanical changes to the circuit (which we will cover shortly), we also added a four-way powerboard so that the filter goes between the mains plug and the four outlets. That way, all (or at least four!) devices could be plugged into clean mains. Incidentally, there is nothing to stop you using a six-way or even eight-way power board if you wish. But four-ways are now really cheap – often less than four bucks each at Woolies (and no doubt other stores!). 36  Silicon Chip The documentation and PC board both state a maximum loading of 2300W – this would be more likely 2400W in Australia with our 240V system. But if your hifi system draws anything like 2kW, please let me know before you turn it on so I can leave town! Where’s it from? The kit came to us from Leon Gross of the Soundlabs Group, a purveyor of high-end sound equipment. The actual design (and kit) is marketed by LC Audio Technology, of Denmark, as the “NETfilter”. On first inspection, we were quite impressed with the layout and quality of the kit. As our circuit (Fig.1) shows, it is an LC design with the chokes formed on toroids and www.siliconchip.com.au Fig.1: the circuit consists of two LC filters and a voltage-dependent resistor. All sections of the circuit are at 240V so take extreme care. pre-potted. We imagine that these chokes might contribute a significant portion of the overall kit cost. Similarly, X2-rated capacitors are used, giving a high margin of safety. The kit includes a cleverly-designed PC board which mates with a snap-together (“clamshell” type) plastic case. No mounting screws or bolts are needed to hold the board in the case – once the board is mounted in the case (it will only go one way due to various cut-outs on the board) the case is closed and fully encloses the bitey bits. Just a word of caution before we go any further: yes, this device operates directly from the 240V mains and could therefore be lethal if used outside of the case. Never work on a live board either outside the case or with the case not snapped closed. dissipate around 0.05W). Two 1nF capacitors, each rated at 3kV, connect between the Active and Neutral lines and the Earth line. These are responsible for getting rid of any high-frequency garbage which might be on the line. Following a second pair of inductors in series with the Active and Neutral lines, there is another 100nF X2 capacitor forming a second LC circuit, along with a voltage-dependent resistor (VDR – also known as a MOV) . The VDR offers a high resistance at the normal mains voltage (240V) but when the voltage rises significantly above this (as it could with a spike on the mains), its resistance drops, effectively shunting the spike away from the output. The circuit One area where we had to make changes to the circuit involves the earth lead. While the documentation which came with the kit went to great pains about not using the mains earth but instead running a separate earth lead to a “ground stake”, we The filter is a traditional LC type. The graph of Fig.2 shows the attenuation achieved (in dB) vs frequency. This was measured using a 75Ω input and 75Ω output HF generator and AC millivoltmeter. There are four inductors in the circuit, all 1.8mH. The inductors are supplied pre-wound and potted. A 100nF capacitor is connected across the Active/Neutral after the inductors. The “X2” after the value doesn’t mean there are two of them – it means that the capacitor is an X2-type. These have ratings sufficient enough to cope with this role. Immediately following the first capacitor and in parallel with it is a 1MΩ resistor. This is to bleed off any charge on the capacitors when not in use – to save you getting a not particularly dangerous but nevertheless annoying bite, if you touched the 3-pin plug Active and Neutral pins. This resistor is a 1W type – not because it must dissipate that amount of power but to get an acceptable voltage rating. (The resistor would in fact only The earth lead Fig.2: this graph shows the filter’s attenuation in dB vs frequency. www.siliconchip.com.au February 2003  37 The completed PC board, ready for insertion in the case. Here’s what the kit of parts looks like. This shot also gives a good idea how the PC board slots into the clamshell case. The arrows on the PC board go from mains in to mains out. Here’s how to cut and strip the mains cable between the plug and powerboard. Just where you cut it is up to you – you could even make it a longer cord if you wished. believe this would be illegal under Australian wiring rules. (Their rationale, by the way, is that the mains earth is often noisy in itself. This may or may not be true, depending mainly on how well the earth wire is actually earthed). But many overseas countries do not have the “multiple earth neutral” or MEN system used in Australia, where every building must have its own earth and the earth is bonded to the neutral at the switchboard. Unless a device is manufactured – and specifically labelled – as “double insulated, do not earth” an earth wire must be supplied to that device – hence the Australian 3-wire mains lead (Active, Neutral and Earth). Sometimes people get into trouble with earth loops, causing hum, because of this multiple earth system and cut the earth lead to one or more of their hifi devices. Sure it works – until something goes wrong and a tiny signal earth lead is required to carry fault current. It fails, and the device is live. This can kill (and indeed has done so in the past). Therefore, we made some mechanical changes to the circuit to ensure that the earth lead was not only used but stayed intact from input to output. problem. Despite trying several times, we could not get the mains cords (input and output) to grip properly with the anchorage and terminal blocks supplied. Our test was simple: two people pulled on the cords to see if they would separate. Unfortunately, they invariably did. Not happy, Jan! Fortunately, the answer was really simple: scrap the mains terminal blocks, drill out the holes they were supposed to sit in so they would accommodate the mains wires and solder them in. This also gave us more “meat” on the outer cable for the cord clamps to grip to. Cord anchorage This was the other area of concern – and it was a real What about the earth wire? On the input side, we drilled a new 2.5mm diameter hole in the space between the two now unused holes, right in the centre. We passed the earth wire (including insulation) right through this hole, then snaked it across the back of the board to the point marked “true earth connection”. We soldered the input earth wire to this point. Then we repeated this for the output side – exactly the same process, with the “output” earth wire also soldered to the “true earth connection” point. Now when we repeated our tug-of-war test, no problems. Even when tugging much harder than we would reasonably You need to make a couple of modifications to the PC board – drilling out four holes and drilling two new ones, to accommodate the different mains cord attachment method we use. This back-of-board diagram is approximately 1:1 scale. 38  Silicon Chip www.siliconchip.com.au expect, or applying short, sharp tugs, the mains wiring never moved. Happy, Jan! Construction We’ve already detailed the process for the mains lead connections – just follow the diagrams for the cable cuts and lengths. Where you make the cut on the cable depends on your circumstances – it can go nearer the 3-pin plug, nearer the 4-way powerboard, or in the middle. If you wish, you could even use a new piece of 3-wire mains cord with a 3-pin plug and extend the length of your powerboard/filter assembly to save using extension cords. The rest of the construction is pretty straightforward, especially if you refer to our photos and PC board overlay diagram. As usual, start with the low-profile components (resistors, 1nF capacitors) Don’t mix up the VDR with one of those capacitors. Next fit the two 100nF capacitors and finally the two potted chokes. The chokes are identical and symmetrical – they can go in either way and in either position. It’s impossible to get them wrong! Check out your soldering and component placement very carefully (even though it’s hard to make a mistake on this board, solder bridges could prove briefly very spectacular!). Now place the assembled board in the plastic case – it can go either way up but logically the components should face upwards. Make sure the three small notches on the edge of the board line up with the three pins in the case. Fold the top of the case over and squeeze very tightly – the case will snap closed – and that’s all there is to it. Note that once the case is closed, it is (deliberately) quite difficult to open up again. It can be done, but . . . Using it All of your hifi devices (amplifier, tuner, cassette, CD, DVD, etc) should be plugged into the filter, otherwise mains-borne noise may get in elsewhere. It may be even better to attempt a cure at the source of the noise rather than at the hifi end. In the past, we have used filters which made little or no difference at the amplifier end but stopped noise from a refrigerator completely when the ’fridge was operated via the filter. It’s basically a matter of experimenting for the best results. SC Where from, how much? The complete kit of parts, (minus the powerboard of course), is available from Soundlabs Group, PO Box 307, Surry Hills, NSW 2010, for $99 inc GST (not including p&p). Please note this is a special price, exclusively for SILICON CHIP readers – normal retail price is $125.00. You can order the kit direct from the Soundlabs website – www.soundlabsgroup.com.au; by phone – (02) 9660 1228; or by fax – (02) 9660 1778. Don’t forget to mention that you are a SILICON CHIP reader to get that special price! We have been advised that Soundlabs Group intend to modify future kits according to this article, so the PC board drilling may already be done for you. www.siliconchip.com.au Fig.3: the complete wiring diagram of the filter, from the beginning (the three-pin-plug) to the end (the power board). February 2003  39 SERVICEMAN'S LOG Servicing can be frustrating Yes, frustration would seem to be the name of the game this month. Of three tricky jobs tackled, only one was success­ful. It took a contributed story to brighten the scene. When a 10-year old 80cm Philips Matchline 33FL1880/75R (FL1.1-S AA) TV set came into the workshop I thought it would be routine. Considering my experience with the Philips Match­line FL1 series of TV chassis, I consider myself to be someth­ing of an expert on these. Unfortunately, I soon learnt the meaning of the phrase “pride goes before a fall”. Truly, this came close to being one of my worst disasters yet. The set came in with an “intermittent dead” label attached to it. But for the first two weeks, it behaved faultlessly, producing an excellent picture. Then, during the third week, I saw the problem for the first time. The set would start OK in stand-by but wouldn’t come on. All the front seven LED display indicators were flashing, in turn, in various combinations. Sometimes the set would come on and then later stop with the same flashing indicators. Supposedly, each of these flashing indicators represents an error code but when they all flash, what does one do? Not every single circuit can be faulty! I obtained a service manual for the FL1.1 chassis. Unfor­ tunately, large chunks of the manual were completely different to the set I was looking at. In the end, I settled for a mix­ture of the FL1.0, FL1.0S, FL1.1 and FL1.1S (and even the FL1.2). However, this particular model still had differences that weren’t covered in any of them (eg, the bridge rectifier is a single D5SBA60SIN block and not four separate diodes as all the service manuals showed). The next thing was to engage the 40  Silicon Chip SDM (Service Default Mode), which provides microprocessor diagnostics. This is done by shorting inaccessible test points S24 and S25 deep in the bowels of the small signal panel. I have given up trying to kill myself and the set by reaching these parts; I now always mount a self-centring toggle switch on the rear so I can go easily into Service Mode S23 and S24, as well as the SDM. That done, I examined the SDM figures on the OSD (On Screen Display): “SERVICE. 08 10 99 23 09”. I interpreted these to represent the fault codes for the last five breakdowns, 08 being the first and 09 being the last. 08 means a PSI/Control fault and 23 means System/Ident fault. Code 09 means a video control fault. These are matched by front-panel LED display combinations. On paper, this looked great but I couldn’t find what 10 and 99 meant. Supposedly, the SDM is meant to override the LED flashing but in this case, it didn’t always do this. Anyway, to refresh the error code list, I switched the set to stand-by with the remote control and put the back on before reapplying the SDM. This now gave a row of zeros, “SERVICE 00 00 00 00 00”, ready for the next time the Items Covered This Month • Philips Matchline 33FL1880/ • • • 75R (FL1.1-S AA) TV set Shamrock SRC2102L tech. monitor. Teac CT-M5928 TV set. Audioline FF895 cordless telephone. set faulted. It wasn’t too long before it did, giving “SERVICE 00 00 00 09 99”. I examined IC7430 (TDA4680) in the video control for 09 code but couldn’t see anything wrong. The 99 code made no sense at all. By now I noticed the code most often given on the front panel was the “mute”, “stand-by” and “stereo” LED displays and so, as a last resort, I followed a fault-finding flowchart in the manual. This eventually suggested I check (Test Point) TP56 at Plug L401, which I did. This measured 4.4V which implied I had a SOPS (Self Oscillating Power Supply) fault. Getting this chassis into a suitable position for servicing is precarious at best. Basically, the chassis slides out after releasing plastic catches on either side of the boards. It can then be pulled back, along with the control modules, until it clears the runners. That done, I balanced it vertically on the bench with the two boards at an angle to each other. I could­n’t find brackets F, nor were the leads long enough to use the service position shown in the manuals. Thus far, the diagnostic system wasn’t really making much sense so I started making voltage measurements to see what was happening. I had 18V (TV START) on (Test Point) TP60 and 5V (STBY) on TP50. TP56 was mostly at 4.4V but sometimes at 0.79V. However, when the set was working, it was 17.5V. I also had 280V on V1 and, in the fault condition, there was 141V on TP57. In an effort to make life easy, I replaced the SOPS drive unit module from a good working set but it made no difference. Next, I decided to examine the protection circuits but before I could get very far, one final indignity occurred. Though the set had been completely off for quite a while, I accidentally re­ceived an electric shock from the collector of chopper tran­sistor 7216. But that wasn't the end of it. Withwww.siliconchip.com.au out thinking carefully, I decided to discharge the main electro through the powerful chopper transistor by biasing this transistor on using my multimeter – ie, by setting the meter to the x1 ohms range and connecting it between base and emitter. This worked really well – the voltage was removed from its collector immediately. What I didn’t realise was that this had also damaged the transistor, so that when I switched the set on the next time, there was an almighty bang followed by a deafening silence. Well, I had done really well for myself. I not only had the original intermittent fault to deal with but a much more serious fault as well. The explosion had destroyed the main fuse, the on/off switch, the bridge rectifier (a massive 25A job), the chopper transistor (7216), two diodes (6217 and 6218) and the SCR (6228) – not to mention my ego, which was left crushed and bruised. Perhaps I should retire now? Patiently, I diagnosed and replaced each destroyed part but some of these items were no longer available. The 2SC3973B had to be replaced by a lower tolerance 2SC3973A, and I had real trouble matching up the two 1N5602 diodes. I was lucky with the bridge rectifier but I had no hope with the SCR, which was an S0824NH (the circuit called this a BT150). Neither is available anywhere. I tried a variety of substitutions but all I achieved was a momentary picture, before it closed down with R3227, a posistor in parallel, getting extremely hot. I discovered that the original SCRs are high-voltage high-current “sensitive gate” devices, which are now an extinct species. I must confess that, until now, I had never heard of these components! Fortunately, I was saved by a SILICON CHIP staff member, whose modesty prevents me from naming him. He designed a little circuit that used a sensitive gate SCR (C106D) to trigger a main SCR (TYN816) substitute. I made up this neat little circuit, mounted it underneath the main PC board and it worked really well. So now I was back at the beginning, ready to tackle the six protection circuits. There is only one way to deal with these and that is to disconnect them one at a time and monitor the base voltage to transistor 7381, which should be 0V. www.siliconchip.com.au It sounds simple but it’s not, especially when the fault is intermittent and operating on three protection circuits. The first was the sound protection circuit, which I am sure I would have picked up earlier had I been provided with the external loudspeakers needed for this set. The problem here turned out to be IC7000 (TDA1521Q) and C2071 (which I changed to 330µF). The second fault involved the over-voltage protection and this turned out to be D6375 (LL4148) and D6376 (LLZC18V), the latter a surface-mount zener. The third problem had me really stumped. It was the EHT protection line off pin 13 of the horizontal output transformer, and it was very intermittent, sometimes taking several days to show. In desperation, I changed every part of the circuit and it still played up. Someone suggested desensitising the circuit by changing some of the values but in the end, I was so fed up with it that I just dis­connected it and left it on test. Well, of course, two weeks later the inevitable happened and the set died again. This time, one of the horizontal output transistors (7504) was short circuit. This device can be either a BU508AF, ON4673A, 2SD1884 or 2SC4288A but the important thing is to check tuning capacitor C2504 (470pF) and C2523 (8.2nF). This time, I didn’t stuff up – C2523 measured only 6.7nF. I replaced this and upgraded C2504 to a 3kV ceramic type I then found that the east/west output transistor (7610, 2SA1359) had also been taken out. I replaced this and reconnected the EHT pro­tection line. My persistence was rewarded – the set now fired up correctly and was still working four weeks later. It was just as well, as it was either me or the set. I had already written the note and loaded the gun! But I still don’t know what fault code 99 means. Can anyone enlighten me? Shamrock revisited The Shamrock story, which started back in December 2002 but was left February 2003  41 Serviceman’s Log – continued in limbo, has progressed – just a little. A friend who specialises in monitor repairs very kindly offered his services and, working without a circuit, fixed the east/west pin­cushion problem. He also located the smoking device that I couldn’t trace. It turned out to be R495 which feeds ZD404, Q417c, U405 pin 4 and much more. Unfortunately, the smoke had also discoloured the resistor’s colour code. He guessed it to indicate 100Ω but checking in his own set suggested this could be a common fault as that, too, had been replaced with a 180Ω 5W resistor. I was thrilled about this but sadly a new fault had developed which has brought me full circle. When the set warms up, the beam current rises and the power supply makes “chirruping/squealing” noises, and then closes down. Using freez­er, I traced this to an area in the power supply 42  Silicon Chip around Q108/D107 (the FET driver) and IC U102, but I was unable to find the offending part. (I changed all the electros). Yes – it’s all very frustrating but I am still hopeful that someone out there might have a circuit diagram. Teac CT-M5928 TV set Unfortunately, that wasn’t to be the end of my frustration this month. I had another Chinese built 5-year old Teac CT-M5928 come in with the repair docket saying it was dead, and that it was really urgent, as its owner was moving interstate. As usual, I felt pretty confident this was going to be quick and easy; after all, I had a circuit diagram and plenty of experience with these models, plus lots of parts in stock. With the back off, it didn’t take long to find that the problem was due to no horizontal drive from pin 26 of IC102 (TDA8305A) to transistor Q401. Actually, it wasn’t strictly true that there was no drive but the oscilloscope showed only a brief burst before the signal died almost immediately. Waveforms were also present on the horizontal driver and output stages but, as expected, they too collapsed along with the drive. All the voltages from the separate power supply were cor­rect at 143V, 18V and 18V, as were all the 12V and 5V rails. Ob­viously, as I had no horizontal output stage operation, I could not yet check the voltages emanating from there. All I had to do, it seemed, was find out why there wasn’t a consistent output from the jungle IC. This is a very popular Philips IC and is also used in their sets, notably the GR1 AX. Being a jungle IC, I was only really interested in about a dozen pins pertaining to the horizontal drive output circuit. I had a very similar model soak-testing in the workshop (AWA6850SH) and I quickly jotted down all the pin voltages of this IC and then compared them with the faulty set. Naturally, because the faulty set wasn’t working, not all voltages could be compared. Pin 7 was for the 12V input, which was correct, with no appreciable ripple. This 12V also supplied the vertical oscillator on pin 2 and the horizontal drive on pin 26. I established that the horizontal drive was still present on the good set , even when its horizontal output stage was disa­bled. This was important because it may have been that the 12V from the secondary of the horizontal output transformer may have affected the horizontal phase on pin 28 which it eventually sup­plies. I then found that the faulty set couldn’t supply substantial output with or without the horizontal drive circuit being connected to the horizontal driver transistor (Q401). I removed the 28-pin jungle IC and fitted a socket in its place. I then swapped it with the IC in good set but it made no difference. Back to the drawing board. Just in case there was something wrong with the 12V supply (I didn’t really think there was), I connected an external power supply to R125 and then added the 12V supply from the horizontal output transformer. Again, nothing changed. By now I was beginning to feel nervwww.siliconchip.com.au 100 95 Audioline cordless telephone 25 www.siliconchip.com.au 5 0 Most low cost microcontroller boards give you only half the solution, namely a processor and some solder points. SPLat controllers are ready to use out of the box, with real-world interfaces, easy programming language and a huge amount of support materials. No soldering required! SPLat controllers are an Australian innovation that is being used by major companies world-wide. 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Newsletter subscription Resource Kit Version 3 August 2001 © 2001 SPLat Controls Pty Ltd      SL99 controller 8 digital inputs 8 digital 400mA outputs 1 analog input 1 analog output And more, much more $180* inc software & matching connectors XBIO16 expansion Add 16 digital I/O points to MMi99 or SL99 connecting cable & matching connectors $159* inc * All prices are for 1-off developer’s kits, and include GST. All major cards accepted. Substantial discounts are available for quantity purchases. FREE delivery in Australia if you quote this ad when ordering! Made in Australia by SPLat Controls Pty Ltd 2/12 Peninsula Blvd Seaford VIC 3198 Ph 03 9773 5082 tA in ussie nova Visit our website for much more information, free software, our renowned training course and complete February 2003  43 online product documentation sc1.splatco.com.au n tio Following a recent electrical storm in our area, I ended up with an Audioline FF895 cordless phone on my bench. This is an upmarket phone, with multiple handsets and lots of features. The reported 100failure was that the it would not connect to the phone line. Apparently, it had been taken to two other repairers who had declined to repair it. 95 Examination revealed that the handsets appeared to be work­ing OK 75 and that the base station had most of its functionality, the main problem being that it could not get a dial tone. I had no circuit information about the phone and Controllers for the real world Gre a ous and time was ticking by. I measured every component (15) attached to pins 23-28 and also replaced all 75 five electrolytic capacitors around the IC. Once more I drew a blank. It was at this point that I had some good luck. I was about to check 25 all the waveforms around the IC and was in the process of winding up the external power supply when 5I noticed that, in the range from 7-9V, the horizontal drive would come on and actually stay on! I then reconnected the horizontal output stage and 0 repeated the operation. This gave sound and a picture, complete with colour – in fact, almost everything was working. But this was all quite unexpected and had me really con­fused. I spent some considerable time experimenting with the power supplies to pins 7, 2, 28 & 26, as well as to pin 11. In the Philips set, the latter is used to start the horizontal oscillator but in this set, there is only a resistor to chas­sis. Unfortunately, none of this was leading anywhere. The best I could do was fit a 33Ω resistor from the 12V supply to pin 7 to make the set work. If the voltage increased beyond 9.5V it stopped. And I did start to notice other deficiencies with the set’s operation. First, the sync was somewhat weak. Second, the AGC was prone to make the tuner IF stages overload and the RF AGC control apparently did not have any effect. Third, the automatic tuning system did not stop after a station was tuned in. And finally, the colour would occasionally change its phase – even when using a colour bar generator con­nected to the AV input sockets. However, all this could be be­cause the rest of the IC was underpowered. But time was up – the client just had to have the set back. I told him of the developments and, somewhat disappointed, he just collected the set and left. I was equally disappointed – I had given it my best shot but it wasn’t good enough. Afterwards I went over my notes to try to see if I had overlooked something on the sandcastle line to pin 27. This was a 2-way connection, with sandcastle pulses going out and horizon­tal output pulses coming in from R419, R420, and C433 to the horizontal output transistor (Q402). It’s too late now of course; the set has gone but I sure would like to know what I missed! Now, on a brighter note, here is a contribution with a happy ending. It comes from J. B. of Hampton Vic. This is how he tells it. Serviceman’s Log – continued not being very familiar with their workings, simply carried out a few basic checks. The plugpack was OK but I thought I was on to something when I measured the input resistance (DC) of the phone line connection and found it open circuit. At this point I suspected that what ever had failed was the cause of the open circuit. And when I say open circuit there was no reading on my multimeter. As this device has a mixture of surface mount and through- hole compon­ents, I had to use a couple of pins on my multimeter to probe for some of the connections. Tracing the circuit, I found my way through various chokes and filter components, all of which checked out OK. When I started to find various 10MΩ and higher value resistors, I was starting to think this high impedance was normal. I tested several diodes and some transistors but was having no luck at all. I have a theory, which I call the "black box syndrome", which states that if you do not understand any component, or what it does, then 44  Silicon Chip that is the component you are most likely to suspect as being faulty. This, of course, is questionable and really means that if you don’t know what the part does, you won't know how to test it and thus eliminate it as a suspect. I try at all costs not to apply this theory as it is usually wrong but I was staring at a TEA1110AT IC and had no idea what it does; only that it was in the right area. This is a Philips device, so I got straight onto their website and downloaded the data sheet for this chip. At least I could find out what this device does and work out whether it was causing the problem. It turned out to be a “Low Voltage Versatile Telephone Transmission Circuit With Dialler Interface”. What a mouthful. Still, it sounded like a good culprit. What's more, Audioline appeared to have used a circuit configuration that was very close to that shown in the data sheet. This IC is powered from the phone line via a bridge recti­fier, 10Ω resistor and a 10V zener. With the base station in the stand-by condition, there was no power to the IC but when the handsfree speaker was selected, I had 10V on pin 1 (LN). There were a couple of transistors controlled by another section of the phone between the bridge rectifier and 10Ω resistor. These were switched in when the base station was off-hook. The data sheet suggested 619Ω between pin 1 and pin 14 (Vcc) but in this case, it was 1kΩ. When the voltage at pin 14 was measured, there were only a few millivolts. A check to chassis found about 25Ω at pin 14. Maybe there was something in the black box syndrome after all. There were several other components connected to this pin and I wanted to isolate the IC from these components. The IC is a surface mount type, so with the aide of a magnifying lamp I was able to unsolder pin 14 and check the resistance without the IC. This turned out to be 80kΩ or so, so the problem was in the IC. I phoned several suppliers and soon found that the TEA1110AT is not stocked by anyone I normally deal with. A call to Philips lead me to a few of their agents who either did not want to know me (I'm not a manufacturer) or would only sell me a reel (1170 pieces). The next problem was that there were none in the coun­try. Maybe those other repairers have seen this problem before and knew that the necessary parts were unobtainable. After making further calls, I eventually found a very helpful lady at Philips who was able to help. As a result, I decided to remove the faulty IC and now have great sympathy for anyone who has to repair devices with surface-mount components. However, I eventually managed to remove it without any damage to the PC board. With the IC on the bench, I checked each pin and found only 5Ω between pins 14 & 2. Because pin 2 has a 20Ω resistor to chassis, that accounted for my measurement of 25Ω. A look at the internal circuit for the IC suggested that there was a very convoluted path between pin 14 and pin 2. I was feeling confident as there is no way it should be so low, so things were looking good. All I had to do was sit back and wait for the replacement part. While waiting for the part, I had an opportunity to measure the line resistance of another FF895 and found it to be open circuit (higher than I could measure), so this was the normal condition. When the IC turned up all I had to do was solder it in – sounds easy doesn’t it? I tinned each of the PC board pads, then gently held the device in place with tweezers and tacked one pin, aligned it, then removed it, tacked it again and realigned it! Once in location, soldering the remaining pins wasn’t all that difficult but I did spend some time checking each pin with a magnifying glass to make sure I didn’t have any solder bridges. Reassembly involved holding one’s mouth correctly to align the circuit board and I have to admit to being relieved that the phone now worked correctly. Weakest link I thought the failure was interesting in that the component that failed was not the first stage – there was a lot of hardware in between. The surge had obviously come down the phone line but this phone has various chokes and filters, so it appeared to be well protected. Like all things I suppose, it is always SC the weak­est link that fails. www.siliconchip.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au www.siliconchip.com.au February 2003  53 Building PART 2 – By LEO SIMPSON & PETER SMITH The SC 480 Putting together our new high performance amplifier modules Last month, we presented the circuit and performance details of the modules which effectively replace the very popular, but ancient, ETI480 amplifier. This month, we show how to assemble the PC board(s) and connect them for the very best performance. A s discussed last month, there is a choice of two modules; one with plastic power output transistors (Version 1) or with TO-3 metal encapsulated output transistors (Version 2). At this stage, it is likely that Version 2 will be available from all major kitset suppliers, while at least one supplier has indicated that they will be selling both versions. Both modules are straightforward to assemble but the transistor mounting details differ considerably between the versions. Therefore, we’ll begin by describing the assembly of parts common to both versions. Common assembly Before installing any components, check the PC board for defects such as shorted or open-circuit tracks or undrilled holes. Fix any defects before proceeding further. Referring to the overlay diagram in Fig.1 (for Version 1) or Fig.2 (for Version 2), install the wire links first, using tinned copper wire. Then you can install the resistors, followed by the three diodes. If not sure of the resistor values, use your multimeter to check each one’s value before soldering it in place and make sure that the diodes are installed the right way around. The four 0.22Ω 5W resistors and the 6.8kΩ 0.5W resistor should be mounted about 1mm proud of the PC board surface to improve heat dissipation. All six small transistors (Q1-Q6) can go in next. There are three different transistor types in this group (BC557, BC639 & BC640), so be particularly careful with placement. Install the four fuse clips and five 2-way terminal blocks next. Note that the small retaining lug on each clip must be positioned to the outer (fuse end) side, otherwise fuse installation will be impossible. These components must be seated firmly on the PC board surface before soldering. By now, your board should be starting to take shape! Continue the good work by installing all the capacitors, 54  Silicon Chip starting with the smallest devices and working up to the largest. The two 470µF 50V electrolytics are polarised components and must be installed the right way around. Note also that they’re oriented differently to one another. If you get either of them the wrong way around, they will be damaged when power is applied and may even explode. Just to confuse the issue, there are two other electrolytic capacitors on the board, 1µF and 47µF, and both are non-polarised and can go in either way around. By the way, some manufacturers call these bipolar (BP) and some call them non-polarised (NP). We intend to standardise on the term “NP”. Note that the 68pF ceramic capacitor, between collector and emitter of transistor Q5, must have a rating of 100V. Similarly, the 150nF (0.15µF) capacitor at the output of the amplifier should have a minimum rating of 250V. Continue construction by installing the multi-turn potentiometer (VR1), 6.8µH choke (L1) and “Polyswitch” thermistor (PTC1). We understand that some kits may not include the optional Polyswitch thermistor, so install a wire link in its place if necessary. Winding the choke If you’ve building your amp module from a kit, the 6.8µH choke may have been supplied pre-wound. If so, all you’ll need to do is scrape the enamel insulation off the wire ends, tin them and solder the part in place. Alternatively, it’s a relatively simple matter to wind the choke yourself. You’ll need a 13mm I.D. plastic former (bobbin) and about three metres of 1mm enamelled copper wire. Begin by bending the wire at right angles, about 10mm from one end. This will be the starting end. Slip it into the bobbin and position the end in one of the slots. Now wind www.siliconchip.com.au FEA P RO T U R E JEC T The two versions of the SC480 amplifier: on the left is what could be called the direct replacement of the ETI-480, with the same TO-3 output transistors (2N3055/2955). Performance, though, is streets ahead. On the right is the “plastic” version using TIP3055/2955 output transistors. These are easier to mount to a heatsink than the TO-3 variety. on 23.5 turns as evenly and tightly as possible. Pass the remaining wire length out through the opposite slot and cut off any excess, leaving about 10mm protruding. Wind on a couple of turns of insulation tape to hold everything in place. Scrape the enamel insulation off the wire ends with a scalpel blade or similar and tin with solder. Don’t worry if the result is less than perfect. An extra turn or a small deviation in the wire will have little effect on the performance of your completed module! With a bit of minor adjustment, the assembly should slip neatly into position in its PC board holes. Press down firmly so that the bobbin contacts the PC board surface and solder in place. Well, that completes the assembly of the parts common to both versions of the amplifier. Now we’ll describe how to mate the power transistors to your chosen heatsink, starting with Version 1. Mounting the output transistors (Version 1) As depicted in the various photographs, the four plastic power transistors and three driver transistors all mount along one edge of the PC board. Transistor spacing is arranged so that the assembly will bolt up to many commonly available heatsinks. Our prototype is shown attached to an Altronics H-0552 heatsink. Other suitable types include the Dick Smith Electronics H-3406 and the Jaycar HH-8546. To begin, fit 10mm tapped spacers to the two remaining PC board holes using M3 x 6mm screws. Notice how this leaves the PC board sitting in a rather lop-sided attitude, with one side higher than the other. We slipped a second, temporary pair or 10mm spacers under our board to bring it back to the horizontal and therefore make the remaining assembly tasks easier. Next, fit the seven transistors (Q7-Q13) into their respective holes, but do not solder or cut their leads short just yet! www.siliconchip.com.au Butt the assembly up against your chosen heatsink and centre it roughly within the available space. If you’re using one of the heatsinks mentioned above, then you should be able to line up the transistor mounting holes with the spaces between the heatsinks fins. This makes life much easier; there’s no need to drill into fins or tap threads in blind holes! In the horizontal plane, the transistors should be mounted as close to the centre of the heatsink as practical. Obviously, this will be limited by available transistor lead length. Once you’re happy with the positioning, mark off and drill 3mm holes for each of the seven devices. After drilling, remove all burrs from around the holes so that the mounting surface is entirely smooth. That done, loosely attach the transistors to the heatsink using the mounting hardware shown in Fig.3. Check that the PC board is sitting horizontal and at right angles to the heatsink and tighten up the screws. Flip the assembly over, taking care not to disturb the PC board position, and solder all transistors in place. Finally, it’s a good idea to make sure that all transistor collectors are indeed isolated from the heatsink. To do this, set your meter to read Ohms and measure between the heatsink and the metal tab (collector) of each TO-218 device. Also, measure between the heatsink and centre lead (collector) of each TO-126 device. You should get a high resistance (open circuit) reading in all cases. Mounting the output transistors (Version 2) In most cases, kit suppliers will provide a predrilled heatsink or heatsink bracket with the Version 2 module. However, if you’re building yours from scratch, here’s how to get all the holes in the right places. To begin, position the PC board on the smooth side of the heatsink surface. If you’re using the recommended heatsink, then the board should be a good fit on the 35mm shelf. February 2003  55 Fig.1: component overlay and matching photo below of the plastic transistorequipped SC480 amplifier (Version 1). It’s very easy to build when you use these to help you. The complete circuit diagram and description were presented in last month’s SILICON CHIP. In this version, the transistors can bolt directly to just about any heatsink. It is definitely the easier form of construction. 56  Silicon Chip www.siliconchip.com.au Fig.2: similarly, Version 2 of the SC480 amplifier with TO-3 transistors. While more robust (and also very similar in appearance to the original ETI-480), mounting the TO-3 transistors does require more care and skill in drilling the heatsink. In the ETI-480, the transistors were attached to a bracket which then attached to the heatsink. While a practical alternative, the heat transferrance is not as effective. www.siliconchip.com.au February 2003  57 Fig.3b (below): the smaller (TO-126) devices mount in a similar way to the larger transistors but no insulating bush is required as there is no metal tab. The back of the transistor must still be insulated from the heatsink. Fig.3a (above): detail showing how the plastic (TO-218) transistors are mounted on the heatsink, with their insulating washers and bushes. Not shown here is the PC board because it does not fasten to the heatsink. Clamp in place and use a sharp scriber or pencil to mark through the holes of all seven transistor positions as well as the two heatsink alignment holes (see overlay diagram). Make sure that you’ve marked all 21 holes before unclamping the board. Gently centre-punch your marks before drilling. Start with a small drill size (about 1mm) and work up to the final size in several stages for best results. Note that a drill press is mandatory for this job. Drilling accurate holes in thick aluminium with a hand drill is almost impossible. The TO-3 transistor holes (four for each device) should be drilled to 6mm. All other holes should be drilled to 3mm. After drilling, remove all burrs from around the holes so that both top and bottom heatsink surfaces are completely smooth. Note that the holes sizes in the PC board do not match the heatsink hole sizes. This is as intended; do not enlarge the PC board holes! On the PC board, all transistor mounting holes as well as the two heatsink alignment holes should be precisely 3mm in diameter. In addition, the TO-3 transistor emitter and base lead holes should only be large enough to accept the respective device leads. OK, let’s put it all together. Figs.4a (top) and 4b (bottom): here’s how the transistors mount to the heatsink (or heatsink bracket) in Version 2. All of the nuts and bolts which hold the transistors on the heatsink also hold the heatsink on the PC board. 58  Silicon Chip Position the PC board beneath the heatsink shelf and insert the two M3 x 12mm alignment screws through from the top. Fit M3 washers and nuts (on the PC board side) and wind up but don’t fully tighten just yet. Now take a moment to admire your work. Looking through from the top, the PC board holes should be centred within the heatsink holes. If any deviate by more than about a millimetre from centre, then you may have problems. The heatsink holes are sized so that the TO-3 transistor mounting screws can pass right through without making contact. If there is any chance of the screws shorting to the heatsink, then you should consider insulating them with high-temperature tubing or similar. Assemble the transistors to the heatsink and PC board as shown in Fig.5, starting with the smaller (TO-126) devices. We've recommended nickel-plated brass screws www.siliconchip.com.au Parts List – SC480 Amplifier Module(s) Parts common to both versions Parts specific to Version 1 (plastic) Semiconductors 3 BC557 PNP transistors (Q1-Q3) 2 BC639 NPN transistors (Q4, Q5) 1 BC640 PNP transistor (Q6) 1 BD139 NPN transistor (Q7) 1 MJE340 NPN transistor (Q8) 1 MJE350 PNP transistor (Q9) 3 1N4148 small-signal diodes (D1-D3) Parts specific to Version 2 (TO-3) 1 6.8µH air-wound choke (L1) (see text) 1 Raychem RXE250 Polyswitch (IH=2.5A, IT=5A, 60V) (PTC1) 3 TO-126 silicone-impregnated insulating washers 4 M205 PC mount fuse clips 2 M205 3A slow blow fuses Capacitors 2 470µF 50V PC electrolytic 1 47µF 16V non-polarised (bi-polar) PC electrolytic 1 1µF 16V non-polarised (bi-polar) PC electrolytic 4 220nF (0.22µF) 63V metallised polyester (MKT) 1 150nF (0.15µF) 250V metallised polyester (MKT) (10 or 15mm lead pitch) 1 100nF (0.1µF) 63V metallised polyester (MKT) 1 12nF (.012µF) 63V metallised polyester (MKT) 1 330pF 50V ceramic disc (or plate) 1 68pF 100V ceramic disc (or plate) or polystyrene 1 10pF 50V ceramic disc (or plate) Resistors (0.25W, 1% unless specified) 2 22kΩ 1 18kΩ 1 15kΩ 2 4.7kΩ 1 2.2kΩ 1 1kΩ 1 680Ω 1 470Ω 8 100Ω 1 10Ω 1 6.8kΩ 0.5W 5% 1 6.8Ω 1W 5% 2 560Ω 5W 5% wire-wound (for calibration, see text) 4 0.22Ω 5W 5% wire-wound 1 200Ω 0.5W 25-turn trimpot (VR1) Connectors 5 2-way 5.08mm pitch 10A terminal blocks Miscellaneous 230mm (approx.) 0.7mm tinned copper wire (for links) and nuts (not steel) for securing the TO-3 devices. This gives a measurable, albeit small, performance improvement. Tighten up all screws but don't solder the transistors leads just yet. Set your meter to read Ohms and measure between the heatsink and the metal can (collector) of each TO-3 device. Also, measure between the heatsink and centre lead (collector) of each TO-126 device. Obviously, you should get a high resistance (open circuit) reading in all cases. If everything checks out, then solder all transistor leads to complete the assembly. Of special note here is that the TO-3 transistor mounting screws must be tightened up before soldering the base and emitter leads. If this is done in reverse order, then stress will eventually crack the solder joints and perhaps even delaminate the PC board copper. www.siliconchip.com.au 1 PC board coded 01201031, 119.4mm x 90.2mm 4 TO-218 silicone-impregnated insulating washer sets (with bushes) 1 Heatsink (1.2°C/W or lower) (eg. Altronics H0552) 2 TIP3055 NPN power transistors (Q10, Q12) 2 TIP2955 PNP power transistors (Q11, Q13) 2 M3 x 10mm tapped spacers 2 M3 x 6mm pan head screws 7 M3 x 15mm (or 16mm) pan head screws 7 M3 nuts 7 M3 flat washers 7 M3 star washers 1 PC board coded 01201032, 149.8mm x 118.7mm 4 TO-3 silicone-impregnated insulating washers 1 Heatsink with 35mm flange (eg. Jaycar H-8550) 2 2N3055 NPN power transistors (Q10, Q12) 2 MJ2955 PNP power transistors (Q11, Q13) 2 M3 x 12mm pan head screws 11 M3 x 15mm (or 16mm) pan head screws (nickelplated brass) 13 M3 nuts (nickel-plated brass) 16 M3 star washers (stainless steel) 8 M3 flat washers Power Supply 1 4 2 1 2 4 4 PC board coded 01201033, 90.2mm x 54.6mm 1N5404 3A power diodes (D1-D4) 4700µF 50V PC electrolytic capacitors 56V/2.4A centre-tapped mains transformer 3-way 5.08mm pitch terminal blocks M3 x 10mm tapped spacers M3 x 6mm pan head screws Parts for optional preamp supply section 2 2 4 1 15V 1W Zener diodes (ZD1, ZD2) 100µF 16V PC electrolytic capacitors 2.2kΩ 1W 5% resistors 3-way 5.08mm pitch terminal block Heatsink brackets As mentioned previously, some Version 2 kits will be supplied with pre-drilled heatsink brackets (as was the ETI-480). The assembly details listed above should still apply, with the main difference being that once assembled, the bracket must be bolted to your heatsink of choice. When attaching a bracket to a heatsink, make sure that you have good mating across the entire facing surfaces, and use heatsink compound to maximise heat transfer. Power supply assembly All secondary-side power supply components, apart from the transformer, are contained on a single small PC board, coded 01201033. Referring to the power supply circuit in Fig.5 and overlay diagram in Fig.6, you can see that the supply incorporates February 2003  59 Fig.5: the power supply for the SC480 is simple enough but adequate for the job. As explained in the text, if you don’t need a ±15V preamp supply, all components within the dotted box can be left out. Fig.6: the power supply PC board overlay, again with a matching photo below. This supply suits a single module – if you want to build a stereo amplifier, you will need two supplies (and either two transformers or one rated at around 5A <at> 56V AC). a ±40V section and an optional, regulated ±15V section. The ±15V supply is handy for those assembling a complete system and can be used to power a preamplifier module, for example. If you have no need for the low-voltage supply, then there is no need to install the associated components. For added flexibility, we’ve designed the PC board so that you can cut off the low-voltage end if you so desire. Begin assembly by fitting an M3 x 10mm tapped spacer to each corner of the PC board. Follow with the four diodes (D1-D4) and two 3-way terminal blocks, making sure that they’re seated firmly on the PC board surface before soldering. Be very careful with the orientation of all of these components, as mistakes here can result in major fireworks at power up. If required, all components in the optional ±15V section should be installed next. Note the zener diodes (ZD1, ZD2) go in different ways around. Last of all, install the two 4700µF 50V filter capacitors. Wiring Housing and wiring of the amplifier modules is totally up to you. However, we’ve outlined a Insulated TO-126 packages Transistors Q7-Q9 are manufactured in plastic TO-126 packages that usually include a small rectangular metal area on the rear. This area is electrically connected to the collector and thus must be isolated from the heatsink with an insulating washer (see Figs.4 & 5). However, some packages that we’ve seen do not have this metal area – they’re plastic (epoxy, actually) on both sides. This ‘isolated’ type package should be mounted without an insulating washer. Simply smear with a small amount of heatsink compound and bolt directly to the heatsink. 60  Silicon Chip www.siliconchip.com.au few important points below that Table 1: Resistor Colour Codes will help you to get the most from your project. No. Value 4-Band Code (1%) 5-Band Code (1%) Fig.7 depicts the most important    2 22kΩ red red orange brown red red black red brown elements of any wiring layout.    1 18kΩ brown grey orange brown brown grey black red brown Note in particular the position    1 15kΩ brown green orange brown brown green black red brown of the +40V & -40V wiring as it    1 6.8kΩ blue grey red brown blue grey black brown brown passes under the PC board. Posi   2 4.7kΩ yellow violet red brown yellow violet black brown brown tioning the wires exactly as we’ve    1 2.2kΩ red red red brown red red black brown brown shown helps to cancel the fields    1 1kΩ brown black red brown brown black black brown brown resulting from currents flowing    1 680Ω blue grey brown brown blue grey black black brown in the PC board tracks. This pro   1 470Ω yellow violet brown brown yellow violet black black brown duces the lowest possible signal  8 100Ω brown black brown brown brown black black black brown distortion.    1 10Ω brown black black brown brown black black gold brown To reduce radiated noise and    1 6.8Ω blue grey gold brown blue grey black silver brown to improve overall appearance, tightly twist the power supply and Earthing is one of the most important and perhaps conspeaker wires as shown. Use a medium to heavy-gauge tentious issues in system design. As we’ve shown in Fig.7, multi-strand wire for both of these connections. Connections to the modules are terminated in 2-way all ground (0V) lines must be returned to a single earth terminal blocks. Only one position (hole) of each of the point. If you’re building a stereo system, then its ground terminal blocks for the +40V, -40V and 0V (GND) connec- (0V) line must also be connected to this point. By the way, you’ll need two power supply modules for tions should be used. a stereo setup, as a single module is just not up to the task. Do not connect anything to the remaining position. Fig.7: here’s how to wire up your completed amplifier module and power supply boards. We’ve shown Version 2 here but wiring to Version 1 is identical. The mains wiring at right would be typical of most installations – but ensure that all exposed terminals are fully shrouded/insulated. www.siliconchip.com.au February 2003  61 You’ll also need two transformers, although it is possible to upgrade to a single, larger, unit of appropriate capacity. Setup & testing No doubt you’re keen to try out your new amp. But hold on a minute; there are a couple of checks and adjustments that must be made first! With nothing connected to the output terminals of the power supply module, apply mains power and measure both positive and negative rails. You readings should be Fig.8: PC board pattern for Version 1, coded 01201031. This board is the smaller of the two, measuring 119 x 90mm compared to the Version 2’s 150 x 119mm. Fig.9: PC board pattern for the power supply (01201033). Fig.10: PC board pattern for Version 2, coded 01201032. The “empty” sections of the board on the left and right side (shown dotted) were removed for aesthetic reasons (as our photos also show) but we imagine most kit and board suppliers will leave these sections in place, making it a rect-angular (and therefore cheaper) board. Performance-wise, it doesn’t matter either way. 62  Silicon Chip www.siliconchip.com.au close to the 40V mark, depending on With your multimeter set to read 50V Table 2: Capacitor Codes mains fluctuations. or more, measure across one of the A word or two of caution: avoid resistors and rotate VR1 clockwise Value IEC Code EIA Code contact with the ±40V DC supply until you get a reading of 28V. This  220nF  220n   224 rails. Although you may get less gives a total quiescent current of  150nF  150n   154 than a “tingle” from the positive or 50mA.  100nF  100n   104 negative rail, getting yourself across Give the amplifier about 5 minutes  12nF   12n   123 both of them simultaneously could to warm up, then readjust if necessary.  330pF  330p   330 be a shocking experience! You’ll probably find that the voltage  68pF   68p    68 If you have installed the optional across the other resistor differs by a  10pF   10p    10 ±15V section of the power supply volt or two; this is normal. module, then the large filter caps will Finally, measure across the output discharge to a safe level quite quickly at power off. (speaker) terminals. The reading should be within ±30mV However, without the low-voltage section, the ±40V rails of the 0V rail. will decay at a slower rate, so it’s wise to check the rails with your meter before touching anything. Problems? OK, the next step is to set the amplifier’s quiescent curIf you can’t adjust VR1 for the correct reading or the rent level. To do this, remove both fuses from the board output voltage is more than ±30mV, then there is a fault and solder a 560Ω 5W resistor across each fuse clip pair. on the board. You may find it easier to tack solder the resistors on the We’ve provided voltage readings for various points rear (copper) side of the PC board. in the circuit (see Fig.10, part 1 [SILICON CHIP January The purpose of the resistors, by the way, is to limit fault 2003]) that may help you to track down the problem. current should there be a problem with the board, as well Your readings should fall within ±10% of our listed as to simplify current measurement. values. Note that nothing should be connected to the input or Once everything checks out OK, switch off power, output terminals until these checks are complete. remove the resistors and plug in the fuses. You’re ready Set VR1 fully anticlockwise and then apply power. SC to rock! Book Review: Motor Home Electrics & Caravans Too!, by Collyn Rivers. Self-published 2002. Spiral bound, 296 x 210mm, 102 pages. ISBN 0 9578965 14. $42.50 Anyone who has been an electronics enthusiast over the past 30 years or so will be well aware of Collyn Rivers. He was the founding editor of “Electronics Today International” (ETI) magazine which went on to have a number of very successful editions in the UK and elsewhere, as well as being very successful in Australia. With that sort of background you can expect that he has put together a comprehensive but succinct guide to caravan electrics. The subject is not rocket science but there are a lot of myths and wrong information afield and Collyn has done a good job of setting the record straight. There are 30 chapters in all, plus four appendices. Collyn starts out by defining the essence of the problem – storing and extracting the maximum amount of energy from lead acid batteries, while ensuring that they give as many years of use as possible. The problems are the same whether you are running a solar-powered home in a remote location, a motor home, caravan or boat. Collyn also goes on to discuss alternators, voltage regulators, solar panels, wind generators and regulators. The book also defines how much power typical appliances require – far more than most people expect – and devotes a chapter to 240V inverters. A short (one-page) chapter is devoted to lighting and compact fluorescents and 12V halogen lamps are the recommended types. And while I found that I agreed with all the rest of the book, I disagree with a number of points in this chapter. First, it states that 12V halogens are intended to run on AC – ideally at 11.8V. Supposedly their life is reduced by 50 – 80% if run on DC. This flies in the face of evidence to contrary. Car headlamps have always run on 12V DC and their life is excellent – usually lasting for the life of the vehicle. Secondly, the book recommends the use of a 12V-to-240V inverter www.siliconchip.com.au to run 12V transformer-driven halogen lamps. “Their 11.8V output extends globe life and reduces consumption, making up for the converter’s 5-10% loss”. Well, not in my book! Typical inverters are around 70% (or less) efficient and typical 12V halogen light transformers are notorious for running hot and would be unlikely to run at more than 75% efficiency. Multiply the two efficiencies together and the result is that almost 50% of your battery power is lost if you take this inverter/transformer drive approach. In my opinion, you’re better off sticking with battery power to run 12V halogens. However, the chapter is redeemed by a recommendation against halogens and plumping instead for warm white compact fluorescents. Here again, for mobile home use, I would suggest the much brighter “cool white”. Other very useful chapters are devoted to refrigerators, water pumps, electric toilets, TV antennas, communications, low voltage and mains voltage wiring. Perhaps the most useful is the chapter entitled “Suggested solutions” which gives good information on real setups. All told, this is a very practical and informative book, written in an informal style which is very easy to read. To purchase the book, contact the publisher, Collyn Rivers, PO Box 3634, Broome, WA 6725. Phone 08 9192 5961. Email: collynr<at>bigpond.com.au (L.D.S.) February 2003  63 PRODUCT SHOWCASE Free on-line controller programming course SPLat Controls is an Australian manufacturer of programmable controllers. They have a very large website, with product information, technical documentation and other support materials for their world-wide customer base. One of SPLat’s significant online resources is a free interactive training course covering the programming of real-world controller applications. The course will take you 10-25 hours to complete depending on your prior knowledge. When you have completed the course you will have acquired the following skills: * The ability to understand and identify inputs and outputs. * Understanding the workings of sequential program functions, with programmed decision made through testing and branching. * The ability to define and analyse a moderately complex control requirement and define a solution in diagrammatic form. * The ability to translate the diagrammatic solution into a programming language. * Using timeouts for fault detection. * Counting off events and actions. * Programming Boolean (logical) functions. * Program debugging. * Good programming practice. The course is easy to follow, with lots of explanations and examples. It is used by a number of educational institutions in Australia and overseas, including RMIT Universtity but requires absolutely no prior skills other than a logical mind. You will benefit from it even if you are not planning to use SPLat in the near future. You can run the course on-line or download the files and run it off-line. One of these was just about to be a project . . . Do you curse the designer of your computer for putting all the inputs and outputs on the rear panel? Thought so! If you’re anything like us, you’re continually pulling the PC out of its space or fossicking around under or behind desks to access USB ports, sound card ins & outs, game ports, etc. A few months ago someone here came up with the scathingly brilliant idea of a simple project which brought those sockets – and maybe a few others – out to a plate on the front panel which occupied an unused drive bay. Time goes by, as time does – and then the January issue of SILICON CHIP came out with a Jaycar advertisement featuring . . . a “Multi-Function Transfer Panel for PCs”, which “transfers the USB, firewire, audio line in/out and an infrared IrDA connection” to a plate which occupies an unused drive bay space on the front panel . . . And just for good measure, the Jaycar model (XC5171) also includes a temperature probe to let you know 64  Silicon Chip how things are cooking inside your PC case. Aah well, there goes a project . . . One of the most difficult hurdles we had to overcome in our project was sourcing all the input and output plugs and connectors – but the Jaycar unit includes all of these, along with any mounting hardware required. At a recommended retail price of $99.95, we reckon it’s great value and will save hours of poking around. And in this issue, it’s on special at just $79.95 – sensational value! Contact: Jaycar Electronics PO Box 6424, Silverwater NSW 1811 Ph: (02) 9741 8555 Fax: (02) 9741 8500 Website: www.jaycar.com.au You can access the course by going to the SPLat website at sc2.splatco. com .au then selecting “Support” and “Online training” from the menu. Contact: SPLat Controls 2/12 Peninsular Boulevarde, Seaford Vic 3198 Ph: (03) 9773 5082 Website: sc2.splatco.com.au World’s first Wi-Fi and Flash Memory Cards SanDisk Corporation has introduced a line of wireless Wi-Fi (802.11b) cards with the world’s first card products to include both memory and wireless communications technology at the Las Vegas Consumer Electronics Show. The “Connect” product line includes four products – dual-function 128MB CompactFlash (CF) and 256MB SD cards that combine Wi-Fi and flash memory as well as single-function CF and SD cards with Wi-Fi connectivity. SanDisk plans to add 256MB cards to the CF Connect product line by the middle of 2003. Retail prices are between $US99 and $US149. Contact: Sandisk 140 Caspian Ct Sunnyvale, CA 9408 Ph: (00111)408 542 0500 Website: www.sandisk.com www.siliconchip.com.au TRANSFORMERS manufactured in Australia by Yokogawa ScopeCorder Yokogawa’s new DL750 is the latest in the DL700 series of waveform measuring instruments that can be used for observing a wide variety of waveforms from physical to electric signals. The DL750 ScopeCorder has incorporated 1 gigaword of memory, the largest for this class of device, and is half the size of previous generation products. It is also equipped with the GIGAZoom function, which uses a specially developed ASIC to instantaneously display data stored in the large memory. The DL750 ScopeCorder can act as an oscilloscope for capturing instant events, as well as a data recorder for prolonged trend measurement. Control of the DL750 can be done by Wirepuller software – down-loadable from Yokogawa’s web site – while complete data analysis including waveform analysis, cursor functions, file conversion to ASCII format, etc, can be performed by the Waveform Viewer software. New Gadget Central Store Where do you get a ballpoint pen that doubles as a head massager? Or a motorised Pepper Mill? Not to mention JamesBond style pens with lasers in them... All this and over 1000 more products can be found at Sydney’s newest “must see” Gadget shop. Gadget Central specialises in providing that unique gift for the person who “has everything” or loves to be the first kid on the block with the new toy. Prices range from $5 to $300 so all budgets are catered for. Now what about a pair of spectacles that bend your vision by 90° so you can watch TV while lying flat on your back, or a spring loaded fly swatter that really works? Gadget Central Stores are located at – 225 Macquarie St, Liverpool; 314 Victoria Ave, Chatswood; 95 Burwood Rd, Burwood. Yokogawa Australia Pty Ltd USB Print Server from Microgram USB and NT4 don’t mix?? They do now. If you need to connect a USB printer to an NT4 network, all you need is Micro-gram’s new USB printer server. It will host two USB printers and one parallel printer and simply connects by attaching a UTP cable to the nearest hub. It supports pretty well everything, including Windows 95/98/98SE/ME/NT 4.0/2000/ XP, Mac OS 8.1 or higher, UNIX/ Linux, NetWare (Bindery/NDS). Contact: Microgram Computers Ph: (02) 4389 8444 Website: www.microgram.com.au www.siliconchip.com.au STEPDOWN TRANSFORMERS Toroidal – Conventional Transformers Power – Audio – Valve – ‘Specials’ Medical – Isolated – Stepup/down 60VA to 3KVA encased toroids Encased Power Supplies Harbuch Electronics Pty Ltd Encased Power Supply 9/40 Leighton Pl. HORNSBY 2077 www.harbuch.com.au Ph (02) 9476-5854 Fx (02) 9476-3231 Harbuch Electronics Just a reminder . . . Pty Ltd 9/40 Leighton Pl, HORNSBY 2077 Ph (02) 9476 5854 Fax (02) 9476 3231 Psst . . . wanna copy some DVDs? Contact: Private Mail Bag 24, PO North Ryde NSW 1670 Ph: (02) 9805 0699 Website: www.yokogawa.com/au Harbuch Electronics Pty Ltd harbuch<at>optusnet.com.au Verbatim Australia have recently updated their range of CopySmartPlus manual-load DVD copiers. Using a high-speed Pioneer DVD-R drive capable of recording at 4x DVD-R, 2x DVD-RW and 16x CD-R, the towers can copy from and record 3, 5 or 7 new discs depending on the model. A feature of the CopySmartPlus range is their ease-of-use. Note that they will not duplicate copyrighted discs (such as movies). Up to 28 4.7GB DVDs can be produced per hour and the stand-alone towers do not need a PC to drive them. Priced between $5000 and $10000 depending on model, they are built in Australia by Verbatim. Contact: Verbatim Australia Ph: (03) 9823 0905 Website: www.verbatim.com.au On Sunday 23rd February 2003 the Central Coast Amateur Radio Club hosts the Southern Hemisphere’s largest amateur radio and communications show, the Central Coast Field Day. More than 2000 people from 40 clubs and organisation from all over Australia and the Pacific will converge on Wyong Racecourse to display and trade the latest radio communications equipment. Plenty of off-street parking is available within Wyong Racecourse grounds. Tea, coffee and biscuits will be available from 8.30 am to 3.00 pm at no charge in the Dining Room. Hot and cold food can also be purchased within Wyong Racecourse. Gates to the Racecourse will be open to the public from 8.30am Entrance fee: adults $10.00, seniors card, pensioner concession, students $5.00, children under 12 free. Anyone with an interest in radio communications or electronics can contact the event organisers, The Central Coast Amateur Radio Club, by phoning 02 43402500 for more information. There is an extensive and informative web site covering the Field Day at www.ccarc.org.au February 2003  65 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au/ SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au/ COMPUTERS: Linux firewall logs Using Linux to Share an Optus Cable Modem Internet Con­nection Pt.4: firewall logs, operating without a key­board or monitor & automatic shutdowns In this final article, there’s a useful script file to enable easy viewing of the firewall log plus further advice on Internet security. We also describe how you can operate your Linux box without a keyboard or monitor and shut the system down correctly just by pressing the power switch! By JOHN BAGSTER A USEFUL SCRIPT FILE I wrote called zplog is available for free download from the SILICON CHIP website. In case you’re wondering where the name came from, I have convention of starting all my programs and scripts with “z” so I know that they are “home grown” (not many commercial programs start with “z”). The “plog” bit stands for “packet log”. I will not attempt to explain how it works as it contains a lot of diabolical “awk” code. However, if you read the “man” pages on “awk”, you should be able to make some sense of it. The script can be run with or without arguments. The optional arguments are: zplog [-a] [-e string] [-f fn] [-i] [-m nm] [-n] [-p] [-s] [-v] Basically, running the zplog command displays ipchains packet logs. The optional command line switches can be in any order and using no arguments will display packet logs using defaults (where applicable). Here’s what it all means: -a – show ACCEPTs and MASQs (these are excluded by default). -e string – gives a string to search for (ie, only include lines containing it). If -e is used more than once, then the patterns from all of them are matched (ie, www.siliconchip.com.au a line must contain all the patterns). Matches are done before the site names, services or ICMP type names from any of -i -n -p arguments are included, so you cannot match any of these (you can match numeric IP ad­dresses, services and ICMP types). -f fn – is the messages file; eg, messages.fn (the default if -f missing). This is useful if the (syslog) messages file has recen­tly been cleared. -i – show ICMP type names. -m nm – sets number of messages to display (default is 10 if -m is missing). -n – show the site name by doing a host command on IP addresses. This slows up the log output. Ignored if followed by -p. -p – do a ping on IP addresses to try to get the site name. This is slower than using -n but shows you if the site is still on-line when the log is output. Ignored if followed by -n. -s – show the service (port) name for TCP and UDP if it is in /etc/services. -v – match all but the -e strings (ignored if no -e’s). Example logs In the following examples, there are only five messages shown instead of the expected 10. That’s because five duplicates have been removed. February 2003  69 COMPUTERS: Linux firewall logs Beefing Up Security On Your Linux Box Apart from having a good firewall, there are a few other things you van do to beef up security. First, edit the /etc/hosts.deny and /etc/hosts.allow files so that only PCs on your internal network can access the Linux gateway. That’s done by first opening /etc/hosts.deny and adding the following rule at the end of the commented section: # /etc/hosts.deny ALL: ALL This tells the “TCP wrappers” to deny connections to all services from all hosts. So we need to weaken this rule by adding some exceptions to /etc/hosts.allow, as follows: #/etc/hosts.allow ALL: 127.0.0.1 ALL: 192.168.0. This tells the “TCP wrappers” to allow connections to serv­ices from the local machine (127.0.0.1) and from the local net­work (192.168.0.). And yes, you must include the full stop at the end of the second line. Another very effective way to improve security is to shut down any services that you don’t need and restrict access to any that you do need. Have a look at the articles published in June 2001, August 2001 and September 2001 issue of SILICON CHIP if you require detailed information on how to do this. Note also that these logs were produced by a “stronger” firewall (cablefirewall.unfriendly) than the one presented in Pt.3 – one that rejects a lot of outgoing UDP to stop spyware sending things out (the simple firewall presented in Pt.3 doesn’t stop outgoing Internet traffic). Cablefirewall.unfriendly is too long to publish here but can be downloaded from the SILICON CHIP website. The script is fully commented and experienced Linux users should have little trouble adapting it to their needs. Please note, however, that neither SILICON CHIP nor the author are in a position to offer any further advice on this firewall. Here are some typical tail /var/log/messages packet logs (grep -e “Packet log:” /var/log/messages|tail): Aug 22 17:17:15 fire-wall kernel: Packet log: output REJECT eth1 PROTO=17 210.49.34.215:61499 67.233.33.88:1214 L=1341 S=0x00 I=54295 F=0x0000 T=127 (#15) Aug 22 17:58:50 fire-wall kernel: Packet log: input DENY eth1 PROTO=6 217.225.157.216:2634 210.49.34.215:21 L=48 S=0x00 I=8952 F=0x4000 T=113 SYN (#18) Aug 22 18:13:55 fire-wall kernel: Packet log: in70  Silicon Chip You should also only set up users that you need. If you connect via SSH, you will need one user who can log in (other than root). If you require other users for email, etc, create them with a shell of /bin/false and a login directory of /dev/null so they cannot log in. Do not remove the existing root access restrictions to allow root to log in via SSH (or similar). Instead, log in as a normal user and then use su to log in as root. If you use Samba to transfer files back and forth, then don’t set up home shares. Restrict access to one share limited to one directory and have a password on it. Make sure you include an interfaces command in your smb.conf file to stop Samba using the cable modem interface, as Samba by default uses all interfaces. If you are using a terminal utility to connect to your Linux box, use SSH instead of Telnet and disable the Telnet service. That’s because SSH encrypts all data, while Telnet sends plain text (including passwords). Having said that, I have been using Telnet on my internal network for months and have not had any security problems, because the firewall rules and hosts.allow and hosts.deny files stop any would-be crackers anyway. Finally, having a good firewall doesn’t mean you can become complacent. Be sure to keep an eye on your log files and remember to install any security updates as the come along. Just remember this: human beings are clever and resourceful little blighters and no protection system or firewall can be guaranteed to be foolproof. put DENY eth1 PROTO=6 210.244.158.43:22 210.49.34.215:22 L=40 S=0x00 I=31977 F=0x0000 T=122 SYN (#18) Aug 22 18:14:54 fire-wall kernel: Packet log: output REJECT eth1 PROTO=17 210.49.34.215:62017 68.17.240.77:1214 L=1341 S=0x00 I=29821 F=0x0000 T=127 (#15) Aug 22 18:50:48 fire-wall kernel: Packet log: input DENY eth0 PROTO=17 0.0.0.0:68 255.255.255.255:67 L=328 S=0x00 I=0 F=0x0000 T=128 (#18) Here are the same messages via zplog: Aug 22 17:17:15 output REJECT eth1 udp eth1:61499 67.233.33.88:1214 (#15) Aug 22 17:58:50 input DENY eth1 tcp 217.225.157.216:2634 eth1:21 SYN (#18) Aug 22 18:13:55 input DENY eth1 tcp 210.244.158.43:22 eth1:22 SYN (#18) Aug 22 18:14:54 output REJECT eth1 udp eth1:62017 68.17.240.77:1214 (#15) Aug 22 18:50:48 input DENY eth0 udp 0.0.0.0:68 255.255.255.255:67 (#18) www.siliconchip.com.au using a graphical interface like Gnome or KDE, so you don’t need a mouse either! A word of warning though: if you do have a mouse plugged in and remove it, Linux will prompt you about its removal the next time the system restarts. So if you want to remove the mouse, unplug it and restart the system and follow the screen prompts before you remove the screen and keyboard. Switching off Here’s a cunning idea: you can make a dummy keyboard by scrounging the circuit board inside a “real” keyboard that’s been discarded. The circuit board can then be housed inside a small plastic case, or even hidden inside the main system case (see SILICON CHIP, February 2002). And with zplog -n -i -s, we get: Aug 22 17:17:15 output REJECT eth1 udp eth1:61499 67.233.33.88 (1Cust88.tnt1.valparaiso2.in.da. uu.net):1214 (#15) Aug 22 17:58:50 input DENY eth1 tcp 217.225.157.216 (pD9E19DD8.dip.t-dialin.net):2634 eth1:21=ftp SYN (#18) Aug 22 18:13:55 input DENY eth1 tcp 210.244.158.43 (c43.h210244158.is.net.tw):22=ssh eth1:22=ssh SYN (#18) Aug 22 18:14:54 output REJECT eth1 udp eth1:62017 68.17.240.77 (adsl-17-240-77.jax.bellsouth. net):1214 (#15) Aug 22 18:50:48 input DENY eth0 udp 0.0.0.0:68=bootpc 255.255.255.255:67=bootps (#18) Apart from the fact that zplog only returns packet logs, the format it returns is a lot easier to interpret. It displays the internal network (192.168.0.x for example) as eth0.x and the external IP address as eth1 (these will be swapped around if you have eth0 and eth1 swapped) to make interpretation easier. No keyboard or monitor If you have a method of communicating with the Linux PC other than via the keyboard and screen (eg, a terminal utility such as SSH), you can dispense with the keyboard and screen. The February 2002 issue of SILICON CHIP explained how to do this, by making up a dummy keyboard. In my case, I had to make up a dummy keyboard in a small box but depending on your BIOS, you may be lucky and not have to do this. My Linux PC also made several annoying beeps when booting if it didn’t have a monitor – but it would boot. I found that the “three 75Ω resistors in the dummy SVGA plug” trick cured this (see SILICON CHIP, February 2002). If you aren’t using a screen or keyboard, you won’t be www.siliconchip.com.au It’s all very well to run your Linux box without a mouse, keyboard or monitor but how do you shut it down in an orderly fashion without these components? Well, if your Linux PC has an ATX power supply, you can download a utility called “Powerswitch” from http://deadlock.et.tudelft.nl/~joris/powerswitch/ and in­stall it. The instructions that come with it are easy to follow and once installed, the driver automatically shuts Linux down and powers off the machine when ever the power switch is pressed. Since the standard Linux modules are in directories within /lib/modules, I created a directory called /lib/ modules/3rdparty and put powerswitch.o in that but you could put it anywhere. It needs to be loaded on system start up and this can be done by including the appropriate entry (eg, /lib/modules/3rdparty/pow­erswitch in /etc/rc.d/rc.modules file (see Pt.2 of this series in last month’s issue). This module works by trapping the suspend mode and execut­ing shutdown -h now. Apart from that, there are just a few BIOS settings to tweak. First, the BIOS must be configured so the power switch enables suspend mode when it is briefly pressed (ACPI support = yes in mine). Second, I found that I had to set the CPU and monitor entries to suspend for powerswitch to activate. And third, it is important to disable all suspend timers in the BIOS, otherwise the PC will shut down when one of these activates! If you cannot get powerswitch to do a shutdown (or if the system shuts down incorrectly), play around with the power set­tings in the BIOS. Provided everything is OK, pressing the power switch will now result in Linux shutting down correctly before the PC switch­es off. The powerswitch module is very handy and does make one lazy! Why log in to shutdown when you can simply turn the PC off? It is also a nice safety feature, as Linux doesn’t like being switched off without being SC shut down in the correct manner. DISCLAIMER Although the two firewalls mentioned in these articles should make for a reasonably secure system (especially if unwanted services are turned off), neither Silicon Chip Publications nor the author can offer any guarantees. If security is vital to your organisation, be sure to seek expert professional advice when it comes to setting up a firewall. February 2003  71 FEATURE PROJECT: EPROM PROGRAMMER; PT.3 In this final article, we’re presenting the Windows-based software for controlling our new EPROM programmer. We also detail a few modifications which have been made to the circuitry to improve its performance. Pt.3: By JIM ROWE 72  Silicon Chip www.siliconchip.com.au D URING THE SOFTWARE development, we encountered a number of problems which delayed its release until now. Some of these problems were caused by timing errors that were encoun­ tered when using different settings for the “en­ hanced” printer port. They were fixed by adding a couple of RC filters. The rest were fixed by adding a few pullup resistors on the data input lines and by eliminating one capacitor. This means that we are now able to present the software and it’s the Windows-based version – not just a clunky interim ver­sion written in VBDOS, which looked a strong possibility when the second article was published. Before I start talking about the software though, let’s take a look at the modifications which have been made to the programmer hardware. Incidentally, the revised PC board pattern has been sent to board manufacturers, so the boards you buy or receive in programmer kits should have all the modifications included. Hardware modifications The first modification involves adding pullup resistors to the input lines from the printer port connector (CON1) to data buffer IC1 and mode decoder IC3. This prevents the chip inputs from “floating” at indeterminate voltage levels when the program­mer isn’t connected to the printer port. Leaving the inputs floating makes them prone to induced cable crosstalk and noise (and could even result in damage). The extra parts involved a SIL (single in-line) array of eight 10kΩ resistors for the data inputs of IC1 and discrete 2.2kΩ pullup resistors on the three inputs to IC3. These are shown at upper and lower left in Fig.11, which shows the modified input and decoding circuitry. There is one small complication with these changes: if the programmer is now powered up when it isn’t connected to a PC, the fact that IC3’s inputs are all pulled high sets the programmer into programming mode. This means that if an EPROM is also plugged into the ZIF socket, it will be subjected to the program­ming voltages continuously. So it’s now important that an EPROM should not be plugged into the ZIF socket until the programmer is connected to a PC’s printer port, www.siliconchip.com.au Fig.11: the modified EPROM Programmer circuitry. The modifications involved adding extra pull-up resistors on the data lines to IC1 & IC3, plus RC filters to the READ & PROG* lines. A capacitor is also deleted from another section of the circuit (see text). powered up and set to read mode by the software (which does this as soon as it starts). Another modification involved adding a couple of RC filter networks. The original circuit showed low-pass RC filters on five of the outputs from mode decoder IC3 (LAL*, LAM*, LAH*, LCF* and LPD*). They were necessary to suppress narrow glitches from IC3, for reliable address and configuration downloading. Similar RC filters have now also been added to the remain­ing two mode February 2003  73 This revised version of Table 1 shows the corrected entries for the CF1 configuration bit. lines (READ and PROG*). They provide small time delays which match those caused by the existing RC filters. Both these extra filters are shown in Fig.11 and have exactly the same component values as the originals. The remaining hardware modification involves removing a component. The original circuit showed a 100nF bypass capacitor from pin 24 of the ZIF socket to ground. However, this line cannot be fitted with a bypass capacitor because it’s the EPROM OE* line (output enable/disable) and must be toggled rapidly during programming and data verification. A bypass capacitor slows down the voltage changes quite seriously, so it can’t be used here. The solution to this one was easy – remove the capacitor. It was originally mounted at the very front of the PC board, just below the ZIF socket – see Supplementary Parts List Capacitors 2 1nF metallised polyester Resistors (0.25W 1%) 3 2.2kΩ 2 100Ω 1 8 x 10kW SIL resistor array, pin 1 common (SIL1) Delete 1 100nF multilayer monolithic capacitor (near ZIF socket) 74  Silicon Chip the PC board overlay (Fig.8) on page 34 of Pt.2. It was also shown on the original circuit diagram (Fig.3) on page 27 of Pt.1 and should be deleted. The revised PC board overlay is shown here as Fig.12 and includes all the corrections. Most of the added components are just above IC1, IC2 & IC3, with the remaining components just to the left of IC1. Note that to fit in SIL1 (the 8 x 10kΩ pullup resistor array), I had to reduce the mounting centres for nine of the 100Ω input suppressor resistors. This means that these no longer mount horizontally but are instead tilted at about 45°, so their leads mate with the board holes. Note too that SIL1 is fitted with its “common” pin to the left, just above pin 19 of IC1. If you fit SIL1 the other way around, you’ll almost certainly get rather strange problems. So that’s the story on the hardware modifications. Just follow the revised layout shown in Fig.12 and you won’t have any problems. Configuration table error There was also an error in Table 1 (Pt.1, p23), which showed the functions of the CF1 bit transposed. As a result, a corrected version of Table 1 has been reproduced in this article, to avoid any possible confusion. Any port won’t do! Before moving on to the software, let’s first take a look at the various printer port configurations and see how the differences between them can affect the operation of the EPROM programmer and its software. When the IBM PC first appeared in the early 1980s, it was provided with a fairly basic parallel printer port conforming to the standards originally specified by printer maker Centronics. This “Centronics” type of printer port became the standard for quite a few years but as processors and printers both became faster, various “enhanced” printer port configurations came into use. These provided both faster operation and fully bidirectional parallel data transfer. When the American IEEE came out with its IEEE-1284 stan­dards (see side panel), PC makers began incorporating multi-mode ports directly into their motherboard chipsets. That’s why the CMOS setup program in modern PCs gives you a number of options for configuring the onboard printer port(s) – usually as a “legacy” Centron­ ics port or SPP (standard parallel port), an enhanced EPP port or an enhanced ECP port with DMA options. We wanted the new EPROM Programmer to be backward compat­ible with older PCs having only an SPP, so that it could be used with just about any PC. As a result, I originally tested the design using an old 66MHz 486 machine, running a quick-and-dirty test program written in VBDOS (and running under DOS). This machine has only a bog-standard SPP/Cen­ tronics port and every­thing worked fine. However, when it came to developing the final software using Visual Basic 6, I used a Pentium 3 866MHz machine running Win98SE. This machine allows the onboard parallel port to be set to one of several different modes, so I automatically went into the CMOS setup and configured it as an SPP which seemed like the logical choice. Unfortunately, I was wrong! It turned out that on both this machine and a Pentium 2 266MHz machine which I tried as well, setting the port for SPP/Centronics mode operation gave all kinds of weird timing problems. In this mode, the ports couldn’t toggle the various bit lines in synchronism in response to soft­ ware instructions. It was only when I tried setting the port to ECP mode (or www.siliconchip.com.au Fig.12: this is the parts layout for the modified PC board. Most of the added components are just above IC1, IC2 & IC3, with the remaining components just to the left of IC1. The deleted 100nF capacitor was originally installed just below the ZIF socket (see text). “EPP+ECP” mode for the P2 machine), that these timing problems suddenly disappeared. This means that if you’re planning to use the EPROM pro­grammer with a PC that has a multimode parallel port, you’ll almost certainly have to set it for ECP or ECP+EPP operation. By contrast, you probably won’t be able to change the port mode on an older PC (eg, a 486) but this shouldn’t be a problem – it will almost certainly have an original SPP/Centronics type port which should work OK. Windows complication There’s another trap for the unwary in using devices like the EPROM Programmer which communicate with the PC via the print­er port – especially when the PC is running one of the many versions of Windows. This is because Windows and its printer drivers are very possessive about the port and simply won’t let another program www.siliconchip.com.au talk to it after they have previously used it for printing (during the current session, that is). This means that if you use the PC’s parallel port to print out from a Windows program during your current session, you can’t then simply connect the EPROM Programmer to the port and fire up the software to read or program an EPROM. The software simply won’t be able to communicate with the programmer if you try! Instead, you have to reboot the PC to unlock Window’s steely grasp on the port and allow the software and hardware to talk to each other. The software OK, let’s now look at the actual software. As mentioned earlier, the software is Windows-based and was written using Visual Basic 6. It makes use of a freeware DLL (dynamic link library) called IO.DLL to directly access the parallel port hardware. This DLL was written by Fred Bulback and works with Win95, Win98 and Windows NT/2000/XP. The DLL file can be downloaded from Fred Bulback’s website located at www.geekhideout.com and has also been made available in the software package on the SILICON CHIP website. Thanks to IO.DLL, the VB6 software can send data out via one of the parallel port registers by calling the added subrou­tine: PortOut (ByVal PortAddress As Integer, ByVal Data As Byte) and can retrieve input data nibbles from the port’s status reg­ister by calling the added function procedure: ReadVal = PortIn (ByVal PortAddress As Integer) In each case, PortAddress has a value corresponding to the address of the port register in I/O space. So that’s how the software actually passes data out to the EPROM programmer and fetches it back again. Software interface A screen grab of the software’s main February 2003  75 Fig.13: the main interface for the software that’s used to drive the EPROM Programmer. It shows all the critical settings and includes a large “list box” that’s used to view a data file loaded from disk or read back from an EPROM. interface is shown in Fig.13. It has the standard Windows appearance, with a menu bar at upper left and a bunch of display windows and option button controls. There’s also a fairly large list box at lower left which can be used to view a data file loaded from disk or read back from an EPROM. The two small display boxes at top right are used to show the I/O base address of the selected parallel port (ie, the one that the programmer is connected to) and the current setting for the programming pulse width in microseconds or milliseconds. Beneath these boxes are eight pairs INSTALLING THE SOFTWARE On the SILICON CHIP website, in the software folder, you’ll find the following files: EPROMP1.CAB (1,283KB), EPROMP2.CAB (373KB), SETUP.EXE (137KB), SETUP.LST (4KB) and DEVCFGS.ZIP (1KB). Download these files and save them in your PC’s C:\Temp folder. Then from the Start menu, select Run, Browse to C:\Temp\Setup.exe and click OK to run this file. It’s then just a matter of following the simple instructions. Setup will unpack and install the executable EPROMProg.exe in the C:\ Program Files\EPROMProg folder, together with IO.DLL and all other files needed to run the program. It will also add a shortcut called “Silicon Chip EPROM Programmer” to your Start->Program Files menu. After the setup program has finished, open the file DEVCFGS.ZIP with Winzip, and extract the sample device config files in it to the C:\Program Files\EPROMProg folder, so that they’re ready for accessing by the program. The programming software is now installed, and ready to run. The compressed installation files can be deleted from the C:\Temp folder if you wish, or saved on floppy disks or a CD-ROM if you want to keep a backup. Incidentally, along with the EPROMProg.exe program and its associated files, the setup program also installs an uninstall log file, ST6UNST.LOG. This file is used by the Windows uninstall utility to uninstall all files, if you later choose to remove the software from your computer. 76  Silicon Chip of option buttons, which are used to set up the programmer’s configuration to suit each different type of EPROM. In the screen grab shown here, these have been set up automatically by opening the configuration file for a Microchip 27C256 device. Incidentally, I have produced a few of these configuration files for different EPROMs and these will be made available along with the software on the SILICON CHIP website. However, you’ll find that it’s also easy to produce other device configuration files yourself, using the software and information from the EPROM manufacturer’s datasheet. Basically, you only have to set the pin connections, the supply voltage levels for reading and programming, and the pro­ gramming pulse width. That done, you simply select File -> Save Device Config (from the menu) and the software guides you through saving the configuration as a file. Once the device configuration data has been saved to disk, you can set up the programmer for working with that type of EPROM at any time in the future simply by opening that configuration file again. This is done by selecting File -> Open Device Config from the menu. Two other options in the File menu allow you to open and save an EPROM data file (as you might expect). The software will not only load and save EPROM data in raw binary form but can open files in Intel and Motorola S-record hex formats as well. These latter formats are often used for saving EPROM data. The final option in the File menu is used to exit the pro­gram. Incidentally, when you do exit, the program automatically saves two handy pieces of information to a set-up file: the parallel port address currently in use and the device configura­tion file currently in use (if any). This information is then loaded by default the next time you fire up the program. The next main menu option (along from File) is Set. This gives you two options: the ability to set the parallel port base address and the desired programming pulse width in microseconds. There are three standard base addresses (278h, 378h or 3BCh) to choose from and a dialog which allows you to set the programming pulse width to any value from 1µs to 50ms. www.siliconchip.com.au Next along in the main menu options is Test. There’s just one option here and that’s to confirm that the software can communicate with the EPROM Programmer hardware – ie, that you have selected the right port base address and the programmer is powered up and ready to go (and that Windows hasn’t locked up the port)! It does this by making the programmer’s LED3 glow and then asking you to confirm that it is glowing. It then turns LED3 off again. The fourth of the main menu options is View, which again has only one option: to display the currently loaded data which has been either opened from a disk file or read from an EPROM in the programmer. The data is displayed in hex in the viewer wind­ ow, in lines of 16 bytes, with the address offset shown at the start of each line. The viewer window has a scroll bar so that you can examine every part of the data at your leisure. Read options The next main menu option is Read, which gives you two choices. One is to read the contents of any desired address range in the EPROM in the programmer, so you can view the data and/or save it to disk. This option asks you for the start and end ad­dresses for the range to be read but offers the EPROM’s own start and end addresses as defaults, in case you want to read all of its content (this depends on you having opened the right device configuration file, though). The second Read option is Check Erasure, which is provided so that you can quickly check if an EPROM has been properly erased. When this option is selected, the software quickly reads the contents of all addresses in the EPROM, checking to see if they all contain FFh (this is the sign of complete erasure). It’s always a good idea to use this option after you’ve wiped an EPROM in your UV eraser, to make sure it’s ready for reprogramming. The final main menu option is Program, which provides a list of three options. The first programs the complete EPROM with the data currently in memory – (ie, from opening a disk file or reading another EPROM). The second option programs just a range of addresses in the EPROM, again using the data currently in memory. You can specify just one EPROM address location if you wish, which is good for testing purposes. With both of these Program options, the software controls the programmer to perform a “fast” programming algorithm at each device address. This kind of programming algorithm does a “verify read” after each programming pulse, to check if the programming was successful. If it was, the address is regarded as properly programmed and the software sends the next address to the pro­grammer. On the other hand, if the verify read shows that pro­gramming wasn’t successful, the software directs the programmer to try again with another programming pulse. This “try again” routine continues until either that ad­dress has been successfully programmed, or a total of 10 program­ming pulses have been used without success. In the latter case, the software stops the programming operation and lets you know that programming failed at the EPROM address concerned. Fig.14: this oscillogram shows the key data and control line waveforms during a read operation – in this case, the read sequence for a single EPROM address at 7FFEh. www.siliconchip.com.au Don’t Skimp On The Programming Cable Be sure to use a good quality round DB25M-DB25M parallel data cable to connect the EPROM Programmer to your PC’s parallel port. Don’t use a 25-way ribbon cable with IDC connectors on each end if you can avoid it, because this type of cable has no shielding and degrades the noise and crosstalk performance of the programmer-PC link. A good-quality round cable, preferably one manufactured to conform to the IEEE 1284 specification, will give you virtually error-free EPROM reading and programming. I found this out the hard way, so be sure to follow this advice. In short, don’t skimp on the cable. This type of fast programming algorithm is now recommended by virtually all EPROM manufacturers, for most modern devices. Each manufacturer tends to call it by a different name, though – eg, “Turbo Programming”, “Programming Express”, “Flashrite”, “Presto II” and so on. The basic idea is that each address is only given just enough short programming pulses to ensure that the data is reliably stored. As you can see, this type of programming algorithm has built-in data verification while the programming is taking place. Despite this, the third option in the soft­ware’s Program menu Fig.15: the key data and control line waveforms during a programming operation. In this example, the address programmed is 1FE8h and the data is E8h. February 2003  77 About The Various PC Parallel Printer Ports The parallel port used in IBM’s original PC of 1981 – and in just about every clone made during the following few years – was very similar to the Centronics printer port. This in turn had been used on most of the earlier 8-bit computers like the Tandy TRS-80 and allowed 8-bit parallel data transfer from the PC to the printer. However, there were only five lines for transfer of “status” information the other way. This made it capable of transferring outgoing data fast enough to keep up with a dot-matrix or daisywheel printer but it could only be used for transferring data back into the PC in 4-bit “nibbles” – ie, at less than half the speed. This type of parallel port is now known as the “legacy”, “Centron­ ics” or “standard parallel port” (SPP) and is probably the only type found on every model of PC. When IBM subsequently released its PS/2 models in 1987, it provided them with an improved version of the SPP which allowed fully bidirectional 8-bit data transfer on the eight main data lines. This type of paral- lel port was adopted by other makers as well and became known as the “PS/2 parallel port”, “simple bidi­rectional port” (SBP) or “byte mode parallel” (BMP) port. Not long after this, when Intel produced its 386 processor and its associated chipset, it collaborated with computer makers Zenith and Xircom to produce an enhanced parallel port which would allow much faster bidirectional data transfer than the SPP or SBP. This new port became known as the “enhanced parallel port” or EPP and was designed to speed up both printing and communication with peripherals like scanners, memory, tape drives and even external disk drives. The EPP specification allowed for fast byte-wide transfer of both data and address information in both directions and was widely adopted in computers based on the 486 and later proces­sors. Then in the early 1990s, yet another type of enhanced parallel port appeared: the “extended capability port” or ECP. Originally proposed by Hewlett-Packard is Verify, which allows you to do a complete re-read of an EPROM and have its contents compared with the data currently in memory. This option might seem unnecessary but it has two uses. The first is obvious: it allows you to make doubly sure that an EPROM has been correctly programmed with the data. The second use is for re-reading an EPROM you’ve just read, to make sure the Read operation did indeed retrieve a faithful copy of the EPROM cont­ents. If Verify gives the “all clear”, the re-read data compares exactly with the data you read the first time. OK, so that’s a quick rundown on the EPROMPrg.exe program, the features it provides and how it’s used. Signal Oscilloscope/Logic Analyser. They show key data and control line waveforms during a read operation (Fig.14) and a programming operation (Fig.15). In Fig.14, you can see that a read sequence for a single EPROM address (here address 7FFEh) takes about 40µs. The first 15µs are taken by the address downloading (high bits, middle byte and low byte in that order), while the high data nibble is read after the address has stabilised and then the low data nibble at the end of the sequence. Fig.15 shows a programming sequence which is successful after a single 100µs pulse, so it is complete after about 160µs. The address programmed is 1FE8h and the data programmed into it is E8h. You can see the address download at the start, the 100µs long programming pulse in the centre (PGM_N and CE_N lines) and Key waveforms Figs.14 & 15 are screen grabs from SILICON CHIP’s Agilent 54622D Mixed 78  Silicon Chip and Microsoft, this soon became incorporated into the new IEEE 1284 standard specification entitled “Standard Signalling Method for a Bidirectional Paral­ lel Peripheral Interface for Personal Computers”, which was released in March 1994. As well as establishing a full standard for very fast byte-wide transfer using an ECP, IEEE 1284 also formalised the speci­ fications for the existing EPP, SBP and SPP port configurations. At the same time, it also established standards for the cables and connectors to be used with each type of port, for optimum performance. In most PCs manufactured in recent years, the primary parallel port is incorporated inside one of the motherboard chipset ICs. Many of these onboard parallel ports can be config­ured by the BIOS firmware to emulate any of the types of port we’ve mentioned above – or at least some of them. This configura­tion is done using the CMOS setup utility, which can usually be entered during bootup by pressing the <DEL> or <F2> key. then the verify read operation at the end (far right). Note that during EPROM Read, Check Erasure, Program and Verify operations, the software displays a graphical “progress” bar at lower left (just below the viewer window). This lets you observe the progress of the selected operation. Finally, the program is available for download from the SILICON CHIP web-site (www.siliconchip.com.au), together with IO.DLL and some sample EPROM config files to get you going (see panel). We are also providing the VB6 source code for the program, for those who’d like to see for themselves just how it does what it does. Hotshot programmers might also want to improve it in vari­ous ways –feel free to modify it to meet your needs. Happy EPROM programming! SC www.siliconchip.com.au SILICON CHIP WebLINK How many times have you wanted to access a company’s website but cannot remember their site name? Here's an exciting new concept from SILICON CHIP: you can access any of these organisations instantly by going to the SILICON CHIP website (www.siliconchip.com.au), clicking on WebLINK and then on the website graphic of the company you’re looking for. It’s that simple. No longer do you have to wade through search engines or look through pages of indexes – just point’n’click and the site you want will open! Your company or business can be a part of SILICON CHIP’s WebLINK . For one low rate you receive a printed entry each month on the SILICON CHIP WebLINK page with your home page graphic, company name, phone, fax and site details plus up to 50 words of description– and this is repeated on the WebLINK page on the SILICON CHIP website with the link of your choice active. Get those extra hits on your site from the right people in the electronics industry – the people who make decisions to buy your products. Call SILICON CHIP today on (02) 9979 5644 · Hifi upgrades & modification products - jitter We’re one of Australia’s most innovative electronic equipment suppliers. For over 10 years we’ve served Australian industry with an extensive range of electronic components and equipment from the world’s leading suppliers. We ensure our customers have the best selection and service. RCS Radio has available EVERY PC Board ever published in SILICON CHIP, EA, ETI and AEM (copyrighted boards excepted). Many late boards are available ex stock, others can be made to order within a few days.Custom & production boards too! Tel:(07) 4934 0413 Fax: (07) 4934 0311 Tel: (02) 9482 1944 Fax: (02) 9482 1309 WebLINK: clarke.com.au Tel: (02) 9738 0330 Fax: (02) 9738 0334 Syd: (02) 9660-1228 Melb: (03) 9859-0388 SPECIALISTS in AUDIO, VIDEO, CD, DATA Media and Multimedia manufacturing & wholesale. We also specialise in DVD Production & editing. We can produce Short Run or Bulk CD Audio, CD Rom & DVD projects. Distributor of Emtec (by Basf) TDK, HHB and Quantegy Professional Products. JED designs and manufactures a range of single board computers (based on Wilke Tiger and Atmel AVR), as well as LCD displays and analog and digital I/O for PCs and controllers. JED also makes a PC PROM programmer and RS232/RS485 converters. 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WebLINK: soundlabsgroup.com.au For broadcast, audiovisual and film industries. Wide bandwidth, high output and unconditional stability with hum-cancelling circuitry, front-panel video gain and cable eq adjustments. 240V AC, 120V AC or 24V DC. VGS2 Graphics Splitter High resolution 1in/2out VGA splitter. Comes with 1.5m HQ cable and 12V supply. Custom-length HQ VGA cables also available. Check our NEW website for latest prices and MONTHLY SPECIALS www.questronix.com.au Email: questav<at>questronix.com.au Video Processors, Colour Correctors, Stabilisers, TBC’s, Converters, etc. QUESTRONIX www.siliconchip.com.au All mail: PO Box 348, Woy Woy NSW 2256 Ph (02) 4343 1970 Fax (02) 4341 2795 Visitors by appointment only February April 2003  79 2003  69 VINTAGE RADIO By RODNEY CHAMPNESS, VK3UG Aligning the front-ends of TRF & superheterodyne receivers In the last two issues, we’ve looked closely at the IF stage in superhet receivers. This month, we take a look at the RF (radio frequency) circuits in TRF receivers, the local oscillator stage in superhets and at receiver alignment. TRF (tuned radio frequency) sets were the most common re­ceivers in the 1920s but their popularity rapidly decreased as the superhet became dominant in the mid 1930s. However, some manufacturers still produced cheap and simple TRF sets that could be used in high-signal strength areas. A typical set of this type is the Astor “Football” from the 1940s. TRF radios had from one to four tuned stages. Initially, it wasn’t nec- essary to have the stages track one another as individ­ual variable capacitors were used to peak each station. However, this was quite a chore and the radio manufacturers soon decided to mechanically couple all the variable capacitors together in the more elaborate receivers – eg, by using brass straps and dial drums. This made tuning much easier but it also meant that the sets had to be designed so that each stage tuned to This photo shows two different twin-gang tuning capacitors. The one on the right is a padderless type. 80  Silicon Chip the same frequency across the dial – ie, the stages had to track each other. However, in many cases, no attempt was made to accurately align each stage for best performance. Later on, a trimmer capacitor was placed across each tuning capacitor. This meant that all tuned circuits could be set to the same frequency at the high-frequency end of the dial, thereby ensuring the best performance possible. By contrast, accurate tracking at the low-frequency end of the tuning range relied heavily on the accuracy of the winding of the tuning coils. This was helped by the fact that distributed and stray capacitance around the tuned circuit was less of a problem than at the high-frequency end of the tuning range. And as time progressed, manufacturers were able to wind the coils with quite high accuracy, which meant that it wasn’t really necessary to later adjust the inductances. However, I have found that almost all air-wound RF and antenna coils give improved performance at the low frequency end of the dial if an adjustable slug is incorporated in the coil design. Some older coils suffer from moisture ingress over the years and this causes the inductance to alter and the quality factor (“Q”) to decrease, thereby lowering the gain of the stage. In order to assess alignment accuracy, it is best to meas­ure the effect of any adjustments on the receiver. If the set has AGC, a digital multimeter (DMM) connected across the diode load or AGC line will indicate peak performance, as described in the previous two articles on IF amplifiers. However, many sets do not have diode detectors or AGC, so measuring www.siliconchip.com.au the audio level across the speaker terminals is one of the few options left. Note that this can only be done if a signal generator with tone modulation is used. If the alignment is done only on the apparent aural difference, the accuracy will be limited, so it’s best to measure the output if possible. It’s also important to realise that a receiver front-end that’s been aligned with a signal generator connected to it will no longer be correctly aligned when connected to an antenna. To overcome this problem, I adjust the signal generator output to a high level and wrap the test lead around the antenna lead. That way, the signal generator does not detune the antenna tuned circuit to any extent and the signal level into the set is rela­tively low. PEAKING AIR-CORED TUNING COILS IN TRF SETS These coils are usually wound solenoid fashion on coil formers ranging from 25-75mm in diameter. Some of these coils are in aluminium cans while others are left unshielded. Invariably, they don’t have iron dust cores to adjust their inductance, to ensure accurate tracking across the band. It is fairly easy to determine whether the tuned circuits do track accurately. To do this, first tune to the high-frequency end of the tuning range and adjust the trimmer capacitors for best reception, with the trimmers nominally at half capacitance. It doesn’t matter whether the stations are tuned at the correct spot on the dial for this test. Now tune to a low-frequency station. Make a note of where each trimmer is set, then vary the trimmer capacitance up and down in each tuned circuit and note the position where peak performance occurs. Return each trimmer to its start position before adjusting the next trimmer. Note whether more or less capacitance is needed to peak the performance in each case (sometimes, you may need more ca­pacitance, in other cases less capacitance). If the trimmer has to be screwed further out (less capacitance) for peak perfor­ mance, it indicates that the tuned circuit has too much induc­tance and a turn or two of wire may need to be removed to improve the tracking. Conversely, if the trimmer has to be screwed in www.siliconchip.com.au Two broadcast-band oscillator coils (left) and one shortwave band oscillator coil are shown here. further, it indicates that the inductance is insufficient and a turn or two of wire will need to be added. As a matter of fact, I had a 1931 Operatic TRF with this problem. In that case, removing two turns from one coil allowed the two tuned circuits to track each other. Another method of checking the tracking is to get a small length of ferrite rod and with the set tuned to the low-frequency end of the dial, insert the rod into each coil and observe wheth­ er the performance improves or deteriorates. If it improves, more turns are needed and if it gets worse, fewer turns are needed. If there is no change in the performance, it is accurately tuned. Some later receivers with air-cored RF and antenna coils can be converted to slug tuning for improved sensitivity. I’ve done this to several receivers by placing a small-diameter slugged coil former inside the air-cored coil. This is held in place by soldering the coil former lugs (no winding on the form­ er) to the larger coil lugs, so that the former sits quite se­curely inside the air-cored unit. This works well and will noticeably lift the performance of some sets. ALIGNING TRF RECEIVERS TRF receivers are relatively easy to align, as we shall see. First, if the coils have no iron-dust cores, no alignment adjustments can be done at the low-frequency end of the dial – unless you are prepared to Fig.1: circuit of “front end” of Kriesler 11-90. Note the use of a pad­derless tuning gang (VC1a & VC1b). February 2003  81 set that has all the stations displaced by a similar amount is likely to be reasonably well aligned. However, it will still have to be peaked for best performance. Starting at the low frequency end of the dial, adjust the coil cores until the sought after station (about 600kHz) appears at the correct spot on the dial. That done, tune to a high-fre­quency station (about 1400kHz to 1500kHz) and adjust the trimmers for best performance. Note that some adjustment may be necessary to get the station to appear at the correct spot. If you find that you have wound the iron cores right into or out of the coils and the trimmers right in or out and the performance is still poor, reset them all to half-way and try again. However, it’s also possible that one or other of the tuned circuits has a fault and no amount of adjustment will overcome the lack of alignment. Alignment of TRF receivers on shortwave bands involves the same principles as those used on the broadcast band. However, there aren’t many shortwave TRF sets about and those that do exist tend to have fewer tuned circuits (often only one in a regenerative detector circuit). THE SUPERHET RECEIVER This photo shows the dual-wave coil assembly from a wrecked receiver. The two coils can be seen at top-right of the metal sub-chassis. try the techniques previously men­ tioned to match the inductances in the various tuned circuits. If the inductances do prove to be matched, it’s a matter of adjusting the dial scale so that the tuned station appears at the right spot on the dial. This is done by loosening the dial scale pointer or grub screws holding the dial drum to the tuning ca­pacitor and adjusting its position, while still listening to the station. It’s then just a matter of retightening the screws. Now tune to the high-frequency end of the dial and note where a particular station appears. If it tunes with the gang further out of mesh than it should be, adjust the trimmers for less capacitance until the station appears in the correct position. Conversely, if the gang is further in mesh than it should be, increase the trimmer capacitance. Note that it is necessary to check the tuning at the low-frequency end of the dial following any adjustments 82  Silicon Chip at the high-frequency end, and vice versa, until the stations appear in the correct positions. Aligning a TRF with slug-tuned RF and antenna coils is straight forward. In this case, it isn’t necessary to muck about with adding or subtracting turns on the coils as occurs with some older sets. Generally, the frequencies at the ends of the dial travel are marked in some way. If not, just assume that later receivers tune from 540-1620kHz, while older sets tune from about 5501500kHz. First, tune the receiver across the band and note where stations appear on the dial. Alternatively, if you have access to a signal generator, check the entire tuning range. If stations are consistently displaced (eg, by 10mm) from the correct posi­tions on the dial, it is necessary to adjust the dial pointer by a similar amount in the opposite direction to correct this inaccu­racy. A The RF and antenna circuits of a superhet receiver are identical with those used in TRF sets of the same era. Instead, the big difference between the two types of sets is in the vari­able tuned circuits, due to the addition of a local oscillator in the superhet. This local oscillator is tuned to a frequency that’s offset from the antenna and RF circuits by the intermediate frequency (IF). In most sets, the IF is 455kHz and the local oscillator must accurately maintain this offset right across the band. This is not an easy task. Receivers using tuning gangs with identical capacitance ranges (plate shape) will usually only have the local oscillator displaced exactly 455kHz from the signal fre­quency circuits at three spots across the tuning range. This means that the tuning of a superhet receiver can vary sufficiently for differences in sensitivity to be apparent across the band. However, this is mainly a problem in earlier sets –later receivers use automatic gain (volume) control (AGC) and therefore these inaccuracies are hardly noticed. www.siliconchip.com.au Another view of the dual-wave coil assembly from the wrecked receiver. On some “broadcast band only” receivers, it became reason­ably common to use a twin or triple section tuning gang which had one section specifically for the oscillator tuning. This section usually had fewer plates and they were shaped differently to achieve accurate tracking. These are called “padderless tuning gangs” as no padder was required. The miniature tuning gangs used in broadcast-band transis­tor sets are of this type too. One such tuning gang can be seen in one of the photos, where one section is noticeably smaller than the other. The smaller section is used for the oscillator. The maximum capacitance for each section is 210pF for the signal frequency section and 90pF for the oscillator section. By the way, I have several transistor sets (different brands) that use the 3-gang version of this tuning capacitor (MSP). Unfortunately, I have found that the oscillator and the antenna and RF tuned circuits do not track, not matter what I try do to overcome the problem. Whether this was just a faulty batch or is due to some other problem, I don’t know. On the other hand, my Kriesler 11-90 and 11-99 sets use another brand of padderless gang and they track perfectly. As a result, their performance is very good. www.siliconchip.com.au Padderless tuning gangs are only suitable to use on the broadcast band and in sets with a 455kHz IF. They can be designed for other bands and IFs but I’ve not seen any. Where multi-band operation is required, all sections of the tuning gang are iden­tical. ALIGNING THE FRONT-END OF A SUPERHET WITH A PADDER Early superhet receivers used aircored coils in both the RF/antenna circuits and the local oscillator. This meant that it was necessary to have some means of adjusting the oscillator at both the low and high frequency ends of the dial, so that the stations were at their correct locations on the dial. This was achieved by having an adjustable padder (mounted on the chassis) to align the circuit at the low-frequency end of the dial, plus a trimmer capacitor to align the high-frequency end. There was only one adjustment for the antenna or RF coil and that was done at the high-frequency end of the dial. The first step is to shift the dial pointer (if necessary) so that it has equal overlap at either end of the dial scale. Then, with the receiver operating, check that the stations are received at the correct dial locations KALEX PCB Makers! • High Speed PCB Drills • 3M Scotchmark Laser Labels • PCB Material – Negative or Positive Acting • Light Boxes – Single or Double Sided; Large or Small • Etching Tanks – Bubble • Electronic Components and Equipment for TAFEs, Colleges and Schools • Prompt Delivery We now stock Hawera Carbide Tool Bits 718 High Street Rd, Glen Waverley 3150 Ph (03) 9802 0788 FAX (03) 9802 0700 ALL MAJOR CREDIT CARDS ACCEPTED February 2003  83 (1) Do the same as (1) above (ie, by overwinding the coil), except the turns must now be in series opposing; or (2) Adjust the padder to higher values of capacitance so that the tuning capacitor plates are further out of mesh for a given oscillator frequency. That done, continue to adjust the circuits in the same way as mentioned above, except that the padder is continually increased in value. Do this until the performance is at its best. ALIGNING FRONT-ENDS WITH IRON DUST/FERRITE CORED COILS This assortment includes one 13mm ferrite rod and one 9.5mm rod (both without windings), plus an antenna assembly from a wrecked set. (they probably won’t be at this stage). Next, at the low frequency end (around 600kHz), adjust the padder so that a known station appears at the correct dial loca­tion. That done, go to the high-frequency end (around 1400-1500kHz) and adjust the oscillator trimmer so that a known sta­tion appears at the correct spot. For best results, double check these two adjustments. Next, adjust the antenna/RF circuit trimmer(s) at around 1500kHz for best performance. Now if all is well, the set is correctly aligned. In some cases, however, the alignment may not be correct for the antenna and RF circuits at lower frequencies. To check this, slide a small ferrite rod into these coils and observe any differences in performance, as described earlier for TRF receiv­ers. If the performance improves, this indicates that the anten­ na/RF coils have insufficient inductance. In that case, there are three ways in which the alignment can be improved: (1) Overwind a few turns (experiment with the number) of enam­elled copper wire onto the coil. That done, connect one end in series with the grid end of the coil and the other end to the point in the circuit where the grid connection had originally been made. (2) Install a small amount of ferrite material inside the coil. (3) Reduce the “apparent” induct84  Silicon Chip ance of the oscillator coil by reducing the padder value. This means that the tuning capacitor plates have to be more in mesh for a given oscillator frequency. Method three is the easiest to implement. First, tune to a weak station at the low-frequency end of the dial. Now adjust the padder so that the station appears closer to the end of the dial and note any improvement in signal strength. Keep doing this until no further improvement can be obtained. It is then necessary to alter the dial pointer so that it points to the appropriate frequency or marking on the dial scale. That done, readjust the oscillator alignment at the high frequen­cy end of the dial and peak the RF/antenna circuit(s). However, in some cases, it many no longer be possible to receive all the stations that should be received. The receiver may now only tune from (say) 600-1600kHz instead of 550-1600kHz. If this proves to be the case, then this particular method of obtaining the best performance at the low-frequency end of the band isn’t appropriate. Instead, one of the other methods must be used – or you can just forget about getting the best performance at the low-frequency end of the dial. If the antenna/RF coils have too much inductance, there are only two ways of improving the low-frequency alignment: It is much easier to adjust the frontend of a receiver if all the coils have iron-dust or ferrite cores, plus trimmer capacitors. However, you must use a non-metallic alignment tool to make the adjustments if the core is inside the coil. The first step is to adjust the dial pointer so that it travels from about the 520kHz mark (ie, maximum capacitance) to about the 1620kHz mark (the exact frequencies at either end of the band will vary from model to model). That done, tune to a frequency around 600kHz and adjust the oscillator so that the station appears at the correct spot on the dial, then tune to around 1400kHz or 1500kHz and do the same by adjusting the oscil­lator trimmer. Repeat this procedure until the stations appear in the correct positions on the dial (or as near as practical). Now do exactly the same thing for the antenna and RF coils but use a frequency nearer 1600kHz for the high frequency adjust­ment. Note that these adjustments should be carried out with the set coupled to the antenna. In each case, you adjust the coils and trimmers for a signal peak by measuring the AGC or detector output voltage, as mentioned earlier in the article. When ferrite rod loop antennas are used, the coil (or a small auxiliary coil) is simply slid along the rod for best performance at the low-frequency end of the dial. It’s then locked in position with some bees wax (or similar). The nominal value of the padder capacitor for the broadcast band and a 455kHz IF is 425pF. For a 175 kHz IF, it is around 550pF or higher. On the shortwave bands, the padder value can vary from upwards of 2200pF to 4500pF. In some cases, the manu­ facturers didn’t worry about tracking www.siliconchip.com.au Photo Gallery: National Panasonic R-100 4-Band 9-Transistor Radio Purchased at a charity bazaar a few years ago for the princely sum of $10, this National Panasonic R-100 4-band 9-transistor radio was the top-of-the line model from Matsushita in the late 1960s. Covering the range from 525kHz to 26.1MHz, the R100 has an IF of 470kHz. Most of the transistors are on a tightly-packed PC board but the oscillator and antenna coils are chassis-mounted, as are the band switch and trimmers. Weight without batteries is 4.2kg. This unit has been modified to run from a 9V DC plugpack and still performs very well. (Note: if anyone has a manual, please contact Leo Simpson). on the shortwave band and dispensed with the padder altogether. RECEIVER ALIGNMENT ON SHORTWAVE BANDS On the shortwave bands, the local oscillator operates above the received frequency – with a few exceptions. The alignment procedure is the same as for the broadcast band. However, the problem of image breakthrough is quite evident, as discussed in the earlier articles on IF alignment. Assuming that the IF is 455kHz, a station on 17MHz will be heard on the receiver dial at both 17MHz (or close to it) and at 16.09MHz (the image frequency). For this reason, make sure that the antenna/RF coil(s) are peaked on the 17MHz frequency. Unfortunately, shortwave stations are often difficult to iden­tify. Several frequencies often carry the same www.siliconchip.com.au program and fading is common, all of which makes alignment rather difficult. It’s best to use a signal generator for this job, as this eliminates any ambiguities in the results. Once again, tune the receiver to about 17MHz, then adjust the signal generator to 17MHz. Adjust the receiver for a response on or near 17MHz, then shift the signal generator frequency until the receiver responds to another frequency. It should respond when the generator is shifted to 17.910MHz if the receiver is reasonably well aligned. However, if it is badly out of alignment, the response will be at 16.09MHz instead. The correct alignment frequency is the lower generated signal. If the response is at 16.09MHz, the oscillator trimmer will have to be reduced in value so that the receiver can respond at 17MHz, as marked on the dial scale. The RF/antenna coil trim­mers are adjusted for peak performance on this frequency, if the tuning range is 6-18MHz. Shortwave bands are very approximately aligned, with few receivers having accurate dial calibrations. In fact, shortwave bands on many sets were purely a selling point, with poor perfor­ mance, poor dial calibrations and inadequate alignment facili­ties. SUMMARY So that’s it – a comprehensive alignment procedure for most TRF and superhet receivers. In summary, the general procedure is to adjust the coil cores (or padders) at the low-frequency end of each band and the trimmers at the high-frequency end for peak performance. That said, you should be guided by the alignment procedure for SC each model if this is available. February 2003  85 COMPUTERS: tracking down elusive problems Tracking down an elusive fault in Windows XP By STEPHEN DAVIS Tracking down an elusive fault in your PC’s operating system can be a frustrating and time-consuming exercise. Although used to solve a particular problem, the approach described here can be applied to tracking down other faults as well. When a fault or a glitch appears in your PC’s operating system, the first question you must ask yourself is “How far am I willing to go to fix this problem?” After all, many problems can be fixed simply by reinstalling the operating system and provided you have backed up important files, there is noth­ing wrong with this. However, this method does have two important drawbacks: (1) it leaves you none the wiser as to what actually caused the problem in the first place; and (2) you risk losing settings and software updates that you may have spent a lot of time getting right. As a result, many people prefer to trou­bleshoot any problems as they arise, if only to satisfy their own curiosity or to meet a challenge. And – dare I say it? – fixing a crashed computer can actu­ally be a lot of fun. Desktop folders won't open In this article, I am going to give you the step-by-step process I used to fix a strange fault in my own computer. This fault would always appear after what appeared to be a normal boot-up. Quite simply, folders on my desktop wouldn’t open when double-clicked. Instead, the cursor would bring up the “hourglass” icon and just “hang” there. What’s more, when ever I gave the computer the three finger salute (Ctrl-Alt-Del) to bring up the Task Manager, Fig.1: checking the Device Manager will quickly reveal if there are any resource conflicts or hardware problems. 86  Silicon Chip there would be no application running in the foreground to turn off. And the taskbar at the bottom indicated that CPU utilisation was running at 100%! So what was causing this problem? I hadn’t added any new software lately; nor had the comput­er recently crashed or done anything else unusual. Safe mode Initially, I decided to restart the computer in safe mode (by pressing F8 during the boot) to see if this gave any clues. Fortunately, the folders now opened up normally, so I was not hampered by that particular problem. I had been on the Internet the night before and although any downloaded material is automatically checked by a virus scanner, I decided to do a thorough virus scan as a first step. That step quickly excluded a virus infection as being the cause of my problems. Next, I had a cursory look in Device Manager (Fig.1) to see if any obvious faults were present. However, having had a stable system running for quite some time (and with no new hardware recently added), I wasn’t surprised to see that everything was normal. Registry rollback The next consideration has to be a corrupt registry, so I rebooted into safe mode and “rolled back” the registry to a date when I knew the folders opened normally (see Fig.2). That’s one very worthwhile feature of XP – you can easily rollback the registry to an earlier time. Unfortunately, the problem was still present in normal mode, so I rebooted into safe mode again and ran Scandisk and Defrag to exclude the possibility that file allocation or disk corruption errors were causing the problem. The hard disk was given a clean bill of health and, as I quickly found out, the problem remained. The next step was to get back into normal mode and use the Windows Configuration Utility so that the normal startup runs in diagnostic mode. Typing “msconfig” in the “Run” dialog box brought up the configuration utility and I selected “Diagnostic Start Up”. www.siliconchip.com.au al-up connection. It obviously didn’t need the WebClient service. System file checker Fig.2: Windows XP’s System Restore utility lets you roll back the system to an earlier date when everything worked normally. This utility is accessed through the Start menu. After rebooting, the folders now opened normally but of course, I now had none of the services that allow the computer to be usable. By a process of elimination, I was then able to quickly show that the problem was in the “services” area and not in the “start-up” or “.ini” files. This was done by selecting “Selective Startup” (Figs.3 & 4) and enabling one group but not the other before reboot­ ing, then doing the reverse. By using the same process of elimination within the “Serv­ices” group, I found that the folders would open normally if “WebClient” was disabled. To check what this service actually does, I went into Start, Control Panel, Administrative Tools, Services, and looked up “WebClient”. This is what I found there: “WebClient enables Windows-based programs to create, access and modify Internet-based files. If this service is stopped, these functions are no longer available. Services that depend on it will fail to start”. It also showed that the executable for this service was svchost.exe in the system32 folder. As a result of disabling this service, programs such as Acrobat Reader, Eudora and Internet Explorer would no longer load. However, Netscape Navigator continued to work perfectly and could access the Internet via a di- Fig.3: the System Configuration utility lets you load only selected services and devices at start-up. www.siliconchip.com.au A corrupt file now looked a distinct possibility so the next step was to run the System File Checker. This was done by booting into normal mode and typing “sfc /scannow” in the “Run” dialog box. I had been fairly confident that this would fix the prob­lem, so you can imagine my frustration when, at the end of the file check, the original fault was still there. Perhaps not fully accepting the result, I then used the “repair” option available during the Windows XP reinstallation procedure, using the origi­nal CD to replace the system files in the Windows directory. But again, there was no joy. Incidentally, I was impressed by the fact that this proce­ dure apparently changed none of my settings or hardware configu­ rations. However, anyone who has Windows XP preinstalled by an OEM should look at Microsoft’s Knowledge Base article on this subject before attempting this procedure. Safe mode vs diagnostic mode My next step was to think about the difference between safe mode and diagnostic mode in normal startup. The folders opened normally in safe mode and Acrobat Reader, Internet Explorer and Eudora all worked normally. At this point, I enabled logging during both safe mode and diagnostic mode boot up. By then reading the ntbtlog. txt file in the Windows directory and highlighting the differences between the two boots, I found that non-Microsoft files were present in diagnostic startup but not present in safe mode. These non-Microsoft files included port drivers, sound drivers, modem drivers, an Nvidia video card driver and Nor­ton’s Internet Security filter. Next, I uninstalled the video and sound drivers and in­ stalled the latest updates (why waste the opportunity?). I also disabled the Norton filter file, along with the modem and port drivers (by going into the driver Fig.4: in this case, disabling WebClient allowed all folders on the desktop to open normally. February 2003  87 COMPUTERS: tracking down elusive problems physical memory. Event Viewer Fig.5: you can quickly find out what a particular service does by going to Start/Control Panel/Administrative Tools/ Services. In this case, the WebClient description is shown. directory and renaming them). The problem was still present! However, one thing I did notice was that those programs that refused to load when the system was in normal mode would, in fact, finish loading as the system was shut­ting down. In addition, a window would appear to indicate that an error had occurred. In Windows XP, “dwwin.exe” is the Microsoft error reporting utility and this puts the error message into a format that can be sent to Microsoft. In my case, I disabled this file (by renaming it), so that any errors would be reported in readable format on the screen as they occurred. I then rebooted the computer in normal mode (with “WebClient” disabled) and tried to start Inter­net Explorer, which I knew would fail to load. I then clicked Start, Turn Off Computer, Restart and as the computer was shutting down, Internet Explorer started to finish loading. And as it did so, up popped the following message just before reboot: “The instruction at 0x7621a4ca referenced data at 0x0176d000. The required data was not placed into memory because of an I\O error status of 0xc0000010”. Exactly the same error occurred at the same memory location when I rebooted and did the same thing with Adobe Acrobat Reader. I then did an Internet search on this error but could find very little information about it. Furthermore, there was no information about the error in Microsoft’s Know­ledge Base. Of course, I didn’t really know whether this error was due to the original fault or because I had disabled “WebClient”. Howev­er, it did cause me to think about the possibility of a physical memory fault. It occurred to me that either the physical memory was faulty or that this error was the result of a memory allocation problem for some reason. To test the physical memory, I downloaded the memtest. exe utility from www.memtest86.com and allowed this to thoroughly test the machine’s memory. This ran for some 12 hours and tests both the SDRAM and on-board caches. The result was clean bill of health for the system’s 88  Silicon Chip By this stage, I was running out of ideas so I went to the Administrative Tools section in the Control Panel and opened the Event Viewer. Of course, errors here would probably be the result of disabling “WebClient” but I was getting desperate. In the System section of the Event Viewer, there were two error messages that had been repeated a number of times. These were: (1) “The SYMTDI service depends on the TCP/IP protocol driver service which failed to start because a device attached to the system is not functioning”; and (2) “The IPSEC Service de­pends on the IPSEC driver service which failed to start because a device attached to the system is not functioning”. Yet another message appeared in the Application section: “Faulting application explorer.exe, faulting module wininet.dll”. In order to make absolutely sure that neither wininet.dll nor explorer.exe were corrupted, I renamed both files (in the system32 and windows folders respectively) and did another file check by typing sfc /scannow in the Run dialog box. This forced the System File Checker to install new versions of these files on the hard disk, direct from the CD but the problem remained. The SYMTDI service is the Norton Internet Security Filter and I had checked this previously. Similarly, the IPSEC service is the Microsoft Internet Security Service and was included in the operating system files that had already been checked for corruption. So what was left? By now it was obvious that the fault was connected with the Internet modules in the operating system, because it disappeared when “WebClient” was disabled. In addition, the faults listed in Event Viewer all pointed to Internet modules, wininet.dll being the Internet extensions dll for win32. And the fact that Netscape Navigator could still be used, despite Internet related software problems, pointed the finger at Internet modules that were asso­ciated with Microsoft. The thought dawned on me that Internet Explorer itself could be the problem, since this has files deeply embedded in the operating system. As a result, I started poking around at the folders associated with Internet Explorer and quickly found that I couldn’t open the “Temporary Internet Files” folder. Despite the fact “WebClient” had been disabled, this one folder wouldn’t open but instead caused the computer to hang. The conclusion was almost an anticlimax. After booting into Safe Mode, I deleted the offending folder, then rebooted into Normal Mode again to regenerate the “Temporary Internet Files” folder. The operating system then behaved normally again. So that was it – the Temporary Internet Files folder was corrupt and for some reason (probably known only to God and to Microsoft), it affected every other folder. I was lucky that I had enough time to track down this fault but I now appreciate more fully why so many people chose reinstallation as a first option when strange SC faults appear. www.siliconchip.com.au ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097; or send an email to silchip<at>siliconchip.com.au 240VAC electricity distribution I’ve always wondered why there are four electrical wires on top of the power poles but only two wires come into our house, and my neighbour has three wires going into their house. What are the reasons? Does it mean my neighbour uses more electricity than I do? Someone told me that 3-phase electricity supply requires four wires; is that the reason? (K. W., via email). • Electricity distribution in the street is three phases of 240VAC and the neutral connection. Most houses only have two; ie, 240VAC (one phase) and neutral. Some houses have two phases (three wires) while some have all four because they are running a pool heater or some other big appliance which needs 3-phase 415VAC. Revox A78 amplifier for cannibalisation My trusty and much-used Revox A78 40+40 watt stereo ampli­fier has recently suffered a catastrophic blowup. It is built like a tank but since it is Increasing the range of the 0-80A ammeter I have just built the 80A ammeter from the June 2002 issue of SILICON CHIP and it appears to work extremely well. I have also built two digital voltmeters for the two batteries in my main vehicle. Because of the vehicle wiring I can only display the discharge cur­rent from the battery and not charge. Discharge is via a separate cable while charge comes through the main starter cable. My question is can the ammeter be upped to 120A? Both my vehicles are Landrovers, a 3.9-litre petrol V8 and a new TD5 diesel. The main vehicle is the diewww.siliconchip.com.au over 20 years old, no serviceman will accept it for repair. I was advised that one of the power lines failed but that the power transformer is in good order. At the moment it lan­guishes in my garage since I am reluctant to throw it on the tip. I have the user’s manual but no circuit data. If any reader can find a use for it as a source of spare parts they are welcome to contact me at juniper1<at>tpg.com.au (I. J., via email). aware that the headphone output can be plugged into the RCA aux input of the amplifier (with the volume control set to a suitable level), is it possible to take an output from the circuit board (at an appropriate level) which bypasses the volume control? (R. C., via email). • You can operate the noise source from 9V instead of 12V. You can take an output for connection to a stereo system from across the volume control potentiometer. Pink noise for environmental masking Capacitors for RIAA preamplifier I have just completed the Personal Noise Source for tinni­ tus sufferers from your September 2001 edition. It worked first time I powered it up! I do have two questions though: first, the specs define the external power supply to be 12V but I did not notice any components between this input and the 9V battery. Does this mean that the device can also be powered by an external 9V source as well? Second, I want to use the device with a hifi system to provide environmental noise masking. Although I am I am about to build the RIAA preamplifier described in the March 2002 issue but am having troubles sourcing some capacitors. Can you help me with their supplier? The capacitors I need are 2 x 270pF MKT polyester, 2 x 100pF MKT polyester and 2 x 33µF 16V PC bipolar electrolytics. (F. P., via email). • You can use polystyrene capacitors from Dick Smith Electron­ics or ceramics (available most kitset suppliers) for these small values. Tolerance is not critical in these circuit positions. 33µF BP capacitors are available from Jaycar Electronics. sel and this has an electronic injection 5-cylinder motor. Both vehicles run alter­nators of between 100A and 120A. Both vehicles also run fairly decent lighting as well, so the 80A ammeter goes into overload. (J. G., via email). • The ammeter cannot be changed to show over 99A since the leftmost digit is only there to provide a minus sign. You could, however, divide down the Hall effect sensor output by a factor of two. This would then show readings which are half of the true value; eg, 120A would show as 60A. This could be done by connecting a 47kΩ resistor across the 10µF capacitor at pin 2 of IC2a. High energy ignition problems I assembled the High Energy Ignition kit (June 1998) for use on a points-triggered Nissan Patrol. On completion I found that Q1 would not switch. After checking component values and the circuit, I found that pin 7 of IC1 was not dropping low. I fur­ ther found that Q2 was not dropping the collector low. On investigation, I found that pin 5 of IC1 would not drop low when Q2 was biased on. The circuit shows DC blocked by a 10nF (.01µF) capacitor. This is the problem. If that capacitor was jumpered, the system worked OK except of course, the dwell delay February 2003  89 Tone control mods for guitar preamp I have some queries concerning the November 2000 guitar preamp kit. I noted the modifications proposed by a reader in the October 2002 edition to lower the turnover frequencies for the mid and treble tone controls for use with a bass guitar. The treble was originally set at a 10kHz turnover frequency. For use with a regular electric guitar, isn’t this frequency too high? I don’t know the highest frequency an electric guitar can produce but note that most guitar speakers have a range no higher than around 5kHz. I built this amp for my son, who commented that it is not as bright as his smaller commercial combo unit. The treble adjustment on this kit is barely audible – the mid has a more profound effect and the bass is terrific. I also built the reverb kit and note that at volume set­tings on the preamp any higher than moderate would not work. The capacitor was replaced to no effect. Even if the collector of Q2 was jumpered to earth, the circuit would not work. A link was inserted from the “points” position on the cir­ cuit to the “coil” position provided for the programmable igni­ t ion module. I could find no mention of such a link being re­quired in the circuit or circuit description. I would like confirmation that my modification will not effect the dwell timing. I don’t think it will. (C. H., via email). • As always, if you are building the Programmable Ignition Timing module and the High Energy Ignition system, you should get the ignition system properly working on your vehicle before linking it to the PIT module. Shorting out the .01µF capacitor between the collector of Q2 and the 22kΩ resistor going to pin 5 of IC1 will disable the dwell extension facility. Since you are able to measure the switching of Q1 when the points are open and closed with the dwell extension out (shorted .01µF capacitor), it is most likely that the circuit does work correctly with the .01µF dwell 90  Silicon Chip (>1/4 turn of the input level pot), the unit produces a “metallic” sounding rever­beration. It is hard to describe in writing – the sound is par­ ticularly noticeable on the bass strings, does not appear with lower volume settings and is triggered when the string is plucked, and sounds, well, imagine that the perforated steel speaker grill has a bundle of aluminium cans hanging off it. My son thinks it sounds great – I think I have done someth­ing wrong. Can you confirm it is normal? (B. R., via email). • The treble action will depend on the guitar. You can reduce the frequency of boost and cut in the same way as described for the bass guitar modification. You may not want to reduce the frequency as far for a lead guitar and so an intermediate capaci­tor value may be more appropriate. The metallic sound with the reverb is normal and is due to too much reverb effect being applied. exten­sion capacitor in circuit. This is because the switching of Q1 will not be noticeable when using a multimeter, as it switches off for only 0.9ms. You should be able to monitor this switching with an oscilloscope. If no oscilloscope is available, test the circuit on your vehicle with the dwell capacitor in circuit. It is highly likely that it will work correctly. Then you can hook up the PIT module. Multi-Spark CDI substitution questions I have a couple of questions regarding the Multi-Spark Capacitor Discharge Ignition featured in the September 1997 issue of SILICON CHIP. I live in the Netherlands and am having trouble finding some of the parts for this project. My first question concerns Mosfets Q6 & Q7, which are IRF822. I was wondering if I could substitute IRF820 or IRF830? Their specs look much the same but they are able to handle bigger currents. My second question is about IC1 and IC2, which are both IR2155. Is there any substitute for those ICs? There isn’t a lot of information on the Internet about this IC. Is International Rectifier the only manufacturer? (D. G., via email). • The IRF820 or IRF830 can be used. The IR2155s are made only by International Rectifier. They are available from Farnell Maarssen in the Netherlands. Phone 31 30 241 7373 or log on to www.farnell.com 5-chime diesel horn wanted I would love to have a diesel horn sound on my train layout but can’t find one anywhere. There are plenty of engine simula­ tors but no horns. Would it be possible for SILICON CHIP to come up with one, preferably a 5-chime horn rather than 3 or 2. (R. B., via email). • We described a 3-chime diesel horn in the July 1994 issue in an article entitled Steam Train Whistle and Diesel Horn Simula­tor. Each of the chimes used an op amp oscillator, with one ca­pacitor determining the chime frequency. It would be a simple matter to add another two chime op amps if you wished. Provided you know the chime frequencies you want, it should be a simple matter to scale the capacitor values accordingly. If you don’t have it, we can supply the July 1994 issue for $8.80, including postage. Water level indicator for turbo cooler I would like to adapt the water level indicator, described in your April 2002 issue, for use in monitoring the water level of a turbocharger cooler tank in a car engine. I hope you can answer some questions I have. (1) The sensor probe will only be 30cm long x 5mm OD. I am look­ing to have three sensors to indicate contents. Will the turns ratio and wire diameter have much effect on the efficiency of the sensor? (2) For 3-LED operation, can I simply omit appropriate resistors at the voltage divider of Q1 and LEDs from IC1? (3) The DC supply for vehicles ranges from 12V to 13.8V. A 12V regulator would be inappropriate. Would connecting a 12V zener be a better solution? If so, what would be the best connection method? Also, would any addi­ tional filtering be www.siliconchip.com.au needed (ferrite beads, rings, etc)? (G. T., via email). • The number of turns and gauge of wire will not affect the readings of water depth. For a 3-LED indicator, LED1 and LED2 can be omitted as well as R1 and R2. The circuit can be powered from a lower voltage regulator instead. A 9V type would be suit­able (78L09) or (7809). The diode bridge (D1-D4) is not necessary and you can place a link and resistor in their place. In other words, use a link for D4 and delete D3 and D2 on the overlay. Replace D1 with a 10Ω 0.25W resistor. A 16V 1W zener should be placed between the input and ground of the regulator, with the cathode (striped end) towards the input. If you want to use a 12V zener, use this in place of the 16V zener described above, delete the regulator and short the ‘in’ and ‘out’ holes on the PC board for the regulator. Use a 68Ω 0.25W resistor instead of the 10Ω resistor described above. You may also wish to use the coolant sensor featured in the coolant alarm from the June 1994 issue of SILICON CHIP instead. This provides a single level alarm indication. 24V operation for fluorescent inverter The 40W fluorescent inverter described in the September 2002 issue appears to be almost exactly what I am looking for. However, I need it to run just as efficiently from 24V (mobile workshop). Is it possible to make some mods to allow it to oper­ate from 24V? (I. C., via email). • 24V operation could be achieved by (1) changing ZD1 to a 12V 1W zener; (2) increasing the 10Ω resistor feeding ZD1 to 330Ω 1W; (3) increas- Wideband AM radio for rural areas A recent question about a circuit diagram for an Allen Wright Wide­ band AM tuner sent me looking through my articles on quality AM radio. I found an EA review on it and also reviews of the Audiosound AM 100, the EA HiFi AM tuner and your own AM stereo Walkman radio. I also found on the Internet details of Motorola’s AM stereo chips, Toko coils and Murata wideband AM filters. Some years ago I built a Playmaster 138 tuner (EA December 1972) but unfortunately it tended to drift over several hours. ing the 100Ω resistor feeding IC3 to 1kΩ 0.5W; (4) using 3 turns for the primary of T1 instead of 4 turns; and (5) using 48 turns for the secondary instead of 134 turns on T1. You will also need to include the other modifications listed on page 92 of the January 2003 issue. Check that IC1 and IC3 receive nominal 12V and 15V supplies respectively, when operating. Applications for Megger tester I am trying to gather some information on Megger (insula­tion) Testers. So far all I’ve come across is specifications and where I can purchase them. What I’m trying to find out is what the main purpose is, how they work, and a few examples of when they would be used in an application? (B. F., via email). • Meggers are widely used in industry Which brings me to the point of my missive. In the capital cities, the ABC is on the AM band (country folk get the ABC on FM!) and there are no plans to move it to FM. Is a new wideband AM tuner a possibility? I did think that something similar to the AM 100, tuned by varicap diodes with an IF of 450kHz, using Toko coils and a notch filter at 9kHz, a signal meter and simple frequency counter may be a possibility. (I. F., via email). • You may want to consider our wideband AM stereo tuner de­ scribed in the February, March and April 1991 issues. We can supply these issues for $8.80 each, including postage. to test the insulation of appliances at a specified high voltage (typically 500V). For example, it is essential that washing machines have a good insu­ lation against the incoming 240VAC otherwise they present a big electrocution hazard to users. We published a high voltage insu­lation tester in the May 1996 issue. We can supply the issue for $8.80 including postage. Chaser lights for fountain I have an outside pond with re­ circulating water and a foun­tain head. With the aid of Waterproof Bostick epoxy, I have positioned four high brightness LEDs in red, blue, green and yellow colours. I have coupled these to a kit purchased from Dick Smith Electronics that has four outputs that can act as a chaser, sequencer, etc. What I really want to do is have WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Trade Practices Act 1974 or as subsequently amended and to any governmental regulations which are applicable. www.siliconchip.com.au February 2003  91 Notes & Errata so that the correct connections are made. 5A Universal Motor Controller, October 2002: Fig.4, the overlay diagram on page 17, shows the device installed for SCR1 as an MCR100. If you fit a C103B, remember to reverse the device so that the flat on the package faces down; ie, towards the edge of the PC board. Capacitor Leakage Adaptor for DMMs, December 2002: the maximum supply voltage to this circuit should be limited to 30V DC. Fig.1: this circuit shows how to hook a smart card to a PIC programmer. Reader/Programmer for Smart Cards, January 2003: this project can only be used to read and program the EEPROM in a card where the PIC microprocessor has already been programmed. Howev­ er, the PIC in a blank card can be programmed quite easily using a standard PC-driven PIC programmer, such as the one published in the March 2001 issue of SILICON CHIP. All that is needed for this is to make up an adaptor so that the card can be connected to the programmer’s 18-pin PIC socket. To make up an adaptor, mount a card socket identical to the one used in the January 2003 programmer each colour turn on for say 30-45 seconds (by itself), switch off and at the same time the next colour turn on – sort of a sequencer situation but with each colour staying on for at least 30 seconds. Are you able to suggest a way to modify the kit for longer ‘on’ times? (K. J., via email). • We assume you are referring to our design published in the March 1994 issue. It is quite simple to slow it down. Just change the 2.2µF capacitor to 47µF tantalum and change the 100kΩ trimpot to a 680kΩ resistor. Interfacing the stepper motor controller I have read and thoroughly enjoyed 92  Silicon Chip (ICA-7000, Jaycar Cat No. PS-0012) on a small piece of matrix board, so you can make con­nections to its card contact pins. Then using the above diagram (Fig.1) as a guide, connect the pins to an 18-pin DIL plug using a short length of rainbow ribbon cable. The DIL plug can then be plugged into your PIC programmer’s ZIF socket. Note that if you can’t obtain an 18-pin DIL plug, you can use a 16-pin wirewrap DIL socket and change the pin connections as shown. Then the ‘tails’ of the socket can be plugged into the programmer’s ZIF socket. Just make sure you plug it in at the pin1/18 end, the articles on the Stepper Motor Controller (May 2002) and the Rolling Code 4-Channel UHF Remote Control (July 2002). My interest is in regards to interfacing these two projects so that I can use the UHF remote to control the direction of a stepper motor. The project is intended to revolve a car amplifier from the roof (laying horizontal) down 90° to a vertical position and reverse, using one channel each of the UHF remote output relays to switch the driving stepper motor forward and reverse (that’s the plan). Obviously, this would only be done when the car was parked and the intention is to use these circuits from your magazine for car shows. The other two channels on the UHF remote control system are to be connected to Gear Indicator, January 2003: the parts list should include 2 x 4.7kΩ resistors. Also the 400mm of 0.8mm tinned copper wire can be 100mm in length. The 2.2kΩ resistor shown on the overlay diagram to the right of VR1 should be 4.7kΩ. Midi-Mate Interface for PCs, February 2001: it has been found that the MIDI-in port does not work with all PC sound cards. The simplest solution is to increase the value of the resistor in series with LED1 to 680Ω (from 330Ω) and then fit a 470Ω resistor on the underside of the PC board so that it is in parallel with the series combination of LED1 and the 680Ω resistor; ie, from the +5V rail directly to pin 13 of IC1. 12V solenoids mounted in a frame so as to lock the subwoofer boxes into the car boot area and prevent them from being stolen. One channel would fire two solenoids into the locking position and the 4th channel would unlock them. So, my question is what do I need to do to interface these two projects in order to be able to remotely control the stepper motor direction? (R. W., via email). • The relays of the UHF remote will do the job directly. Use them to control direction. Connect the DIR input to +5V via a 10kΩ resistor and then pull this input low via a relay to change direction. Use the other relay to link the OSC and SC Step terminals for stepping. www.siliconchip.com.au MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads: $20.00 (incl. GST) for up to 20 words plus 66 cents for each additional word. Display ads: $33.00 (incl. GST) per column centimetre (max. 10cm). Closing date: five weeks prior to month of sale. To run your classified ad, print it clearly in the space below or on a separate sheet of paper, fill out the form & send it with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details to (02) 9979 6503. Taxation Invoice ABN 49 003 205 490 _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ Enclosed is my cheque/money order for $­__________ or please debit my ❏ Bankcard   ❏ Visa Card   ❏ Master Card Card No. Signature­­­­­­­­­­­­__________________________ Card expiry date______/______ Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ www.siliconchip.com.au FOR SALE WEATHER STATIONS: Windspeed & direction, inside temperature, outside temperature & windchill. Records highs & lows with time and date as they occur. Optional rainfall and PC interface. Used by Government Departments, farmers, pilots, and weather enthusiasts. Other models with barometric pressure, humidity, dew point, solar radiation, UV, leaf wetness, etc. Just phone, fax or write for our FREE catalogue and price list. Eco Watch phone: (03) 9761 7040; fax: (03) 9761 7050; Unit 5, 17 Southfork Drive, Kilsyth, Vic. 3137. ABN 63 006 399 480. UNIVERSAL DEVICE PROGRAMMER: Low cost, high performance, 48-pin, works in DOS or Windows incl. NT/2000. $1364. Universal EPROM programmer $467.50. Also adaptors, (E)EPROM, PIC, 8051 programmers, EPROM simulator and eraser. Dunfield C Compilers: Everything you need to develop C and ASM software for 68HC08, 6809, 68HC11, 68HC12, 68HC16, 8051/52, 8080/85, 8086, 8096 or AVR: $198 each. Demo disk available. ImageCraft C Compilers: 32-bit Windows IDE and compiler. For AVR, 68HC­ 08, 68HC11, 68HC12, 68HC16. $385.00 Atmel Flash CPU Programmer: Handles the 89Cx051, 89C5x, 89Sxx in both DIP and PLCC44 and some AVR’s, most 8-pin EEPROMS. Includes socket for serial ISP cable. $220, $11 p&p. SOIC adaptors: 20 pin $132.00, 14 pin $126.50, 8 pin $121.00. Full details on web site. Credit cards accepted. GRANTRONICS PTY LTD, PO Box 275, Wentworthville 2145. (02) 9896 7150 or http://www.grantronics.com.au CENTRAL COAST FIELD DAY, SUNDAY 23rd FEB: Don’t miss Australia’s biggest Amateur Radio exhibition and sale of new and used radio and communication equipment at Wyong Race Course, just 1 hour north from Sydney. Gates open 8.30am. Special Field Day bargains from traders and tons of disposals gear in the flea February 2003  93 Silicon Chip Binders New New New Mark22-SM Slimline Mini FM R/C Receiver REAL VALUE AT $12.95 PLUS P&P These binders will protect your copies of SILICON CHIP. They feature heavy-board covers & are made from a dis­ tinctive 2-tone green vinyl. They hold up to 14 issues & will look great on your bookshelf.  80mm internal width • • • • • 6 Channels 10kHz frequency separation Size: 55 x 23 x 20mm Weight: 25gm Modular Construction Price: $A129.50 with crystal Electronics PO Box 580, Riverwood, NSW 2210. Ph/Fax (02) 9533 3517 Or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. Use this handy form Enclosed is my cheque/money order for $________ or please debit my ❏ Bankcard ❏ Visa   ❏ Mastercard Card No: _________________________________ Card Expiry Date ____/____ Signature ________________________ Name ____________________________ Address__________________________ __________________ P/code_______ 94  Silicon Chip 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. For price list, write Acetronics 5/32 Seton Rd, Moorebank 2170 or email acetronics<at>acetronics.com.au Phone (02) 9600 6832 www.acetronics.com.au  Buy five and get them postage free! Silicon Chip Publications PO Box 139 Collaroy Beach 2097 AV-COMM P/L, 24/9 Powells Rd, Brookvale, NSW 2100. Tel: 02 9939 4377 or 9939 4378. Fax: 9939 4376; www.avcomm.com.au email: youngbob<at>silvertone.com.au Website: www.silvertone.com.au  SILICON CHIP logo printed in gold-coloured lettering on spine & cover Price: $A12.95 plus $A5.50 p&p. Available only in Australia. Satellite TV Reception International satellite TV reception in your home is now affordable. Send for your free info pack containing equipment catalog, satellite lists, etc or call for appointment to view. We can display all satellites from 76.5° to 180°. Microzed.com.au PIC CHIP SPECIALIST PO Box 634 ARMIDALE 2350 (296 North Cooke’s Rd) Ph: (02) 6772 2777 – may time out to Mobile 0438 277 634. Fax: (02) 6772 8987 market. Exhibits by clubs and groups with interests ranging from vintage radio, packet radio, scanning, amateur TV and satellite. www.ccarc.org.au Ph (02) 4340 2500. RCS HAS MOVED to 41 Arlewis St, Chester Hill 2162 and is now open, with full production. Tel (02) 9738 0330; Fax 9738 0334. rcsradio<at>cia.com.au; www.cia.com.au/rcsradio KITS KITS AND MORE KITS! Check ’em out at www.ozitronics.com LABJACK USB DATA ACQUISITION MODULE features 8 12bit analog inputs, 20 digital I/O, 2 analog outputs and high speed counter. Free software and ActiveX component. DAS005 Parallel Port Data Acquisition Module features 8 12bit Analog inputs, 4 digital I/Ps & 4 digital O/Ps. Free windows software. FAB Programmable Logic Controllers. Low cost, high performance. Programming software and SCADA software free. Heaps of features. Full details and credit card ordering available at: www.oceancontrols.com.au USB KITS: Stepper Motor Controller, DTMF Transceiver, Thermometer, DDS HF Generator, Compass, 4-Channel Voltmeter, I/O Relay Card. Also available: Digital Oscilloscope, Temperature Loggers, VHF Receivers and USB Active X (and USBDOS.exe file) to control our kits from your application. www.ar.com.au/~softmark PCBs MADE, ONE OR MANY. Any format, hobbyists welcome. Sesame Elec­tronics (02) 9586 4771. sesame777<at>optusnet.com.au; http:// members.tripod.com/~sesame_elec Audio, Video, S-Video and VGA cables distribution amps, switchers, adaptors, price lists at: www.questronix.com.au continued next page www.siliconchip.com.au Subscribe & Get This FREE!* *Australia only. Offer valid only while stocks last. Positions At Jaycar We are often looking for enthusiastic staff for positions in our retail stores and head office at Silverwater in Sydney. A genuine interest in electronics is a necessity. Phone 02 9741 8555 for current vacancies. OSCILLOSCOPE Hitachi Dual 20MHz $250.00, Ango Eprom Eraser $30.00, three 16x2 LCD $20.00. Sydney 0411 965 960. KIT ASSEMBLY Contact: Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097 Phone Orders: (02) 9979 5644 Fax Orders: (02) 9979 6503 Email Orders: office<at>silchip.com.au Classifieds: continued from p.92 ROBOT KITS, books, accessories. Check them out at: www.robotics.com. au Free catalogue 1800 000 745. HALF RETAIL PRICE! Used Solar Panels, Inverters, Batteries, Surplus Components and more. See our specials pages at www.kcsolar.com.au NOW AVAILABLE FROM Acetronics....................................94 Altronics................................. 66-68 Av-Comm Pty Ltd.........................94 ADD SPEECH, SONAR OR DIRECTION SENSING to your next project. Fully contained modules. Full specs on website www.robotparts.com.au Ph 0412 350671 THAT’S RIGHT! Buy a 1- or 2-year subscription to SILICON CHIP magazine and we’ll mail you a free copy of “Electronics TestBench”, just to say thanks. Advertising Index NEVILLE WALKER KIT ASSEMBLY & REPAIR: •  Australia wide service •  Small production runs •  Specialist “one-off” applications Phone Neville Walker (07) 3857 2752 Email: flashdog<at>optusnet.com.au WANTED PARAMETERS OSCILLOSCOPE for parts. Clinton 02 9817 2543 or email wongcl<at>ozemail.com.au Clarke & Severn...........................79 Dick Smith Electronics........... 28-31 Eco Watch....................................93 Elan Audio....................................83 Emona Instruments......................21 Grantronics..................................93 Harbuch Electronics.....................65 Instant PCBs................................94 Hy-Q International........................79 Jaycar .............................. 45-52,95 JED Microprocessors................5,79 Kalex............................................83 Microgram Computers...................3 MicroZed Computers..............79,94 Oatley Electronics........................23 Printed Electronics...................... 94 EARLY HI FI’S AMPLIFIERS, Speakers, Turntables, Valves, Books ; Quad, Leak, Pye, Lowther, Ortofon, SME, Western Electric, Altec, Marantz, McIntosh, Goodmans, Wharfedale, Tannoy, radio and wireless. Collector/Hobbyist will pay cash. 02 9440 1267. johnmurt<at> highprofile.com.au Procopy........................................79 Quest Electronics.........................79 RCS Radio...................................94 RF Probes...............................79,83 Silicon Chip Binders................53,95 Silicon Chip Bookshop..........96,IBC Silicon Chip TestBench..............IFC www.siliconchip.com.au Silvertone Electronics.............79,94 Soundlabs Group.........................79 Splat Controls..............................43 Telelink Communications....79,OBC Project Reprints – Limited Back Issues –Limited One-Shots If you’re looking for a project from ELECTRONICS AUSTRALIA, you’ll find it at SILICON CHIP! We can now offer reprints of all projects which have appeared in Electronics Australia, EAT, Electronics Today, ETI or Radio, TV & Hobbies. First search the EA website indexes for the project you want and then call, fax or email us with the details and your credit card details. Reprint cost is $8.80 per article (ie, 2-part projects cost $17.60). SILICON CHIP subscribers receive a 10% discount. We also have limited numbers of EA back issues and special publications. Call for details! visit www.siliconchip.com.au or www.electronicsaustralia.com.au www.siliconchip.com.au _________________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: RCS Radio Pty Ltd. Phone (02) 9738 0330. Fax (02) 9738 0334. February 2003  95 REFERENCE GREAT BOOKS FOR ALL PRICES INCLUDE GST AND ARE AUDIO POWER AMPLIFIER DESIGN HANDBOOK PIC Your Personal Introductory Course A handbook for professionals and students from one of the world’s most respected audio authorities. New edition is more comprehensive than ever with a new chapter on Class G amplifiers and further new material on output coils, thermal distortion, relay distortion, ground loops, triple EF output stages and convection cooling. 427 pages in paperback. Concise and practical guide to getting up and running with the PIC Microcontroller. Assumes no prior knowledge of microcontrollers, introduces the PIC’s capabilities through simple projects. Ideal introduction for students, teachers, technicians and electronics enthusiasts – perfect for use in schools and colleges. 270 pages in soft cover. by Douglas Self 3rd Edition 2002 89 $ by John Morton – 2nd edition 2001 NEW NEW NEW NEW 46 $$ VIDEO SCRAMBLING AND DESCRAMBLING AUDIO ELECTRONICS If you've ever wondered how they scramble video on cable and satellite TV, this book tells you! Encoding/decoding systems (analog and digital systems), encryption, even schematics and details of several encoder and decoder circuits for experimentation. Intended for both the hobbyist and the professional. 290 pages in paperback. For anyone involved in designing, adapting and using analog and digital audio equipment. It covers tape recording, tuners and radio receivers, preamplifiers, voltage amplifiers, audio power amplifiers, compact disc technology and digital audio, test and measurement, loudspeaker crossover systems, power supplies and noise reduction systems. 375 pages in soft cover. By John Linsley Hood. First published 1995. Second edition 1999. FOR SATELLITE AND CABLE TV by Graf & Sheets 2nd Edition 1998 4th EDITION $ 70 87 $ EMC FOR PRODUCT DESIGNERS 3rd EDITION UNDERSTANDING TELEPHONE ELECTRONICS By Stephen J. Bigelow. 4th edition 2001 Based mainly on the American telephone system, this book covers conventional telephone fundamentals, including analog and digital communication techniques. Provides basic information on the functions of each telephone component, how dial tones are generated and how digital transmission techniques work. 402 pages, soft cover. 103 $$ By Eugene Trundle. 3rd Edition 2001 3rd EDITION Eugene Trundle has written for many years in Television magazine and his latest book is right up to date on TV and video technology. includes both theory and practical servicing information and is ideal for both students and technicians. 382 pages, in paperback. Widely regarded as the standard text on EMC, provides all the key information needed to meet the requirements of the EMC Directive. Most importantly, it shows how to incorporate EMC principles into the product design process, avoiding cost and performance penalties, meeting the needs of specific standards and resulting in a better overall product. 360 pages in paperback. 63 $ By Ian Hickman. 2nd edition1999. Essential reading for electronics designers and students alike. It will answer nagging questions about core analog theory and design principles as well as offering practical design ideas. With concise design implementations, with many of the circuits taken from Ian Hickman’s magazine articles. 294 pages in soft cover. by Dogan Ibrahim. Published 2000. by Steve Roberts. 2nd edition 2001. Based mainly on British practice and first published in 1997, this book has much that is relevant to Australian systems as a guide to home and small business installations. A practical guide to installation of telephone wiring, ranging from single extension sockets to PABX, with the necessary tools, test equipment and materials needed by installers. 178 pages in soft cover. 89 $$ Microcontroller Projects in C for the 8051 TELEPHONE INSTALLATION HANDBOOK 69 By Tim Williams. First pub­­lished 1992. 3rd edition 2001. ANALOG ELECTRONICS GUIDE TO TV & VIDEO TECHNOLOGY $ 92 $ $ 73 Through graded projects the author introduces the fundamentals of microelectronics, the 8051 family, programming in C and the use of a C compiler. The AT89C2051 is an economical chip with re-writable memory. Provides an interesting, enjoyable and easily mastered alternative to more theoretical textbooks. 178 pages in paperback. BOOKSHOP ENQUIRING MINDS! LOWER THAN RECOMMENDED RETAIL PRICE WANT TO SAVE 10%? 10% OFF! SILICON CHIP SUBSCRIBERS AUTOMATICALLY QUALIFY FOR A 10% DISCOUNT ON ALL BOOK PURCHASES! Power Supply Cookbook Analog Cct Techniques With Digital Interfacing by T H Wilmshurst. Published 2001. by Marty Brown. 2nd edition 2001. An easy-to-follow, step-by-step design framework for a wide variety of power supplies. Anyone with a basic knowledge of electronics can create a very complicated power supply design . Magnetics, feedback loop, EMI/RFI control and compensation design are all described in simple language. 265 pages in paperback. 99 VIDEO & CAMCORDER SERVICING AND TECHNOLOGY by Steve Beeching (Published 2001) $ 69 $ $ Provides fully up-to-date coverage of the whole range of current home video equipment, analog and digital. Information for repair and troubleshooting, with explanations of the technology of video equipment. 318 pages in soft cover. 69 Antenna Toolkit by Joe Carr. 2nd edition 2001. Together with the CD software included, the reader will have a complete solution for constructing or using an antenna - bar the actual hardware. The software is based on the author’s Antler program, which provides a simple Windows-based aid to carrying out the design calculations at the heart of successful antenna design. 253 pages in paperback. NEW NEW NEW NEW PIC IN PRACTICE O R D E R H E R E by Howard Hutchings. Revised by Mike James. 2nd edition 2001. 63 $$63 $ Anyone interested in ports, transducer interfacing, analog to digital conversion, convolution, filters or digital/analog conversion will benefit from reading this book. The principals precede the applications to provide genuine understanding and encourage further development. 302 pages in paperback. PRACTICAL RF HANDBOOK by Ian Hickman 3rd Edition 2002 by D W Smith Published 2002 Based on popular short courses on the PIC, for professionals, students and teachers. Can be used at a variety of levels. An ideal introduction to the world of microcon-trollers for hobbyists, students and professionals. 255 pages in paperback. 87 $ Interfacing With C Electric Motors And Drives by Austin Hughes. 2nd edition 1993. Reprinted 2001. For non-specialist users – explores most of the widely-used modern types of motor and drive, including conventional and brushless DC, induction, stepping, synchronous and reluctance motors. 339 pages, in paperback. Covers all the analog electronics needed in a wide range of higher education programs: first degrees in electronic engineering, experimental science course, MSc electronics and electronics units for HNDs. Text is supported by numerous worked examples and experimental exercises. 312 pages in paperback. 52 69 $$ $$ A guide to RF design for engineers, technicians, students and enthusiasts. Covers all of the key topics in RF: analog design principles, transmission lines, transformers, couplers, amplifiers, oscillators, modulation, transmitters and receivers, propagation and antennas. 279 pages in paperback. 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