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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) 979 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) 979 5644. Fax (02) 979 6503. PUBLISHER'S LETTER Computers can be a fire hazard Yes, computers can be a fire hazard. There have been a number of serious domestic fires reported in the media recently and these have pointed up the risk of leaving computers on and unattended for long periods. My advice to anyone with a computer is don’t leave it on any longer than necessary. This applies equally to computers used at home and in industry. I am amazed at the number of companies who leave their computers running all the time, whether anyone is on the premises or not. Maybe they do this because of a belief that computers are more reliable if left running continuously but they are mistaken. It is bad practice, from a number of points of view. First, there is the considerable cost of running these machines all day, every day. Even if there was an improvement in reliability, the cost of the energy to run each computer continuously would easily out­weigh the cost of a breakdown. Second, the longer computers are left running, the sooner they will fail and this applies particularly to the monitor and to hard disc drives which run all the time, whether there is hard disc activity or not. Third, the longer a computer is left run­ning, the more likely it is to experience a power interruption or worse, a voltage surge. Such events can easily cause damage. Think about the occurrence of thunderstorms. They usually occur in the late afternoon or evening and they often cause blackouts or power surges. The risk is greatly increased if the machine is connected to a telephone line via a modem. Many fax machines and modems are damaged during thunderstorms, and so are computers. If it is good practice to disconnect your computer during a thunderstorm, particularly if it has a modem connected, then it is also good practice to have computers turned off and discon­nected, while no-one is on the premises. If the computer is disconnected, it can’t be damaged by power surges and it certain­ly can’t catch fire and cause the premises to be burnt down. If a computer must be left running all the time, then the monitor should be turned off when not needed. Colour TVs are a known fire risk in homes and should not be left running unattended for long periods. They should not even be left on standby for long periods, because of this risk. And nor should computers. As with colour TVs, they employ switchmode power supplies which are directly connected to the 240VAC AC mains, and their monitors employ high voltage (EHT) supplies which can arc over and start a fire. By all means, leave your computer on during the day, even if you are using it only intermittently. But don’t trust it when you are not there. Turn it off. 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