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Publisher & Editor-in-Chief Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Rick Walters Reader Services Ann Jenkinson Advertising Enquiries Leo Simpson Phone (02) 9979 5644 Regular Contributors Brendan Akhurst Garry Cratt, VK2YBX Marque Crozman, VK2ZLZ Julian Edgar, Dip.T.(Sec.), B.Ed John Hill Jim Lawler, MTETIA Philip Watson, MIREE, VK2ZPW Jim Yalden, VK2YGY Bob Young Photography Stuart Bryce SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. A.C.N. 003 205 490. All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Macquarie Print, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $49 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 34, 1-3 Jubilee Avenue, Warrie­ wood, NSW 2102. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. PUBLISHER'S LETTER Have you had your house wiring checked? Let’s face it, because we are all familiar with electricity, we take it for granted. We seldom think about the safety aspects of electricity. This thought was prompted by a recent change of home that I have made. My “new” house is older than my previous home, having been built prior to 1950. With this in mind, I made a cursory check of the switchboard before I purchased the house. I was encouraged by what I saw. Instead of the old fuseholders, there was a bank of modern circuit breakers which had evidently been fitted in recent years. And the cables behind the board were in double sheathed plastic so I thought everything was apples. How wrong can you be. The first event to shake my equanimity occurred when I attempted to change over a light fitting. This was to be a straightforward job one Saturday afternoon, requiring no modifications to the wiring; just whip out the old fitting, connect the new one and the job should be finished in under 10 minutes. Ha ha! Two minutes after I started I discovered that the wiring to the light fitting was old, very old. It was the original “tough rubber” insulation and it had long ago perished and then gone crumbly. Even undisturbed, it was in a dangerous state. To cut a long story short, I now have an electrician replacing most of the wiring in the house. To say that I had been deluded is to understate the case. That was bad enough. Having discovered one booby-trap, I instructed the electrician to check every light fitting, switch and power point and rewire/ replace as necessary. I naturally thought that he would just find dicky switches and old wiring. I did not expect that he would find original wiring which was downright illegal and dangerous. But that is just what he found. And this very afternoon he found that the power point in my study had been wired without any earth. The earth had not become disconnected – there was no earth wire at all and never had been! It is the same power point that my computer is connected to. If one of the mains interference suppression capacitors in the computer’s switchmode power supply had shorted to chassis I would have had no way of knowing and the computer would continue to work, only its case would have been live and lethal! Now perhaps you live in a new house and you think “This can’t happen to me because all my wiring is new.” Well perhaps you should think again. Was your house wiring thoroughly checked by an electricity authority inspector when the dwelling was completed? Of course, it wasn’t. From my observations of the wiring in many houses under construction, at least some of the wiring will be suspect. If you are completely certain that all your wiring is new and safe, then sleep well. If not, do what I have done – call an electrician in and prepare to spend some money to make your home safe. It will be money well spent. Leo Simpson ISSN 1030-2662 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. 2  Silicon Chip