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SILICON CHIP Publisher & Editor-in-Chief Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Advertising Manager Paul Buchtmann Regular Contributors Neville Williams, FIREE, VK2XV Bryan Maher, M.E. B.Sc. Jim Yalden, VK2YGY Garry Cratt, VK2YBX Jim Lawler, MTETIA John Hill David Whitby Photography Bob Donaldson Editorial Advisory Panel Philip Watson , VK2ZPW Norman Marks Steve Payor, B.Sc., B.E . SILICON CHIP is published 1 2 times a year by Silicon Chip Publications Pty Ltd. All material copyright (c). No part of the contents of this publication may be reproduced without prior written consent of the publisher. Kitset suppliers may not photostat articles without written permission of the publisher. Magazine Printers Pty Ltd, Waterloo, NSW 2017 . Printing: Masterprint Pty Ltd, Dubbo, NSW 2830. Distribution: Network Distribution Company. Typesetting/makeup: Subscription rate: currently $42 per year ( 12 issues) inside Australia. For overseas rates, refer to the subscription page in this issue . Liability: 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. Address all mail to: Silicon Chip Publications Pty Ltd, PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 982 3935. ISSN 1030-2662 * Recommended and maximum Australian price only. 2 SILICON CHIP PUBLISHER'S LE't-lER Those wonderful infrared remote controls Ever stopped to consider just how wonderful some electronic products are? My favourites are the remote controls for my VCR and TV set. And I know that anyone who has a remote control for their TV set loves it too. Don't like that program or that advert? Just zap it and something else is on the screen. Have you ever stopped to watch how people use their remotes? Some people have it on the table in front of them and they stab the buttons viciously to erase the offending images. Others hold the remote control in their hand and derisively thrust the unit at the TV as they zap the program off the screen. Or perhaps they just casually render the talking head voiceless so that adverts can be ignored. And consider how handy it is to be able to "fast forward" through the commercials when you are watching a videotape. So attached to the remote am I that I become irritated if I can't immediately reach it while I am watching the Teev. But aside from the utter convenience, remote controls are a wonderful piece of technology. First of all, they employ one or two infrared light emitting diodes which are pulsed on and off at a rate of around 10kHz or so. The pulses are actually a serial data stream corresponding to the button you've pushed. Each button, and there may be 40 buttons or more on some complex remotes, has its own special data code. These pulses of infrared light from the remote transmitter (you could almost think of them as pulses of heat) are received by an infrared detector (diode or phototransistor) inside the appliance and converted to an electrical signal. This is fed to an amplifier which filters out all the noise and then passes it to a decoder. Normally the decoder is a dedicated microprocessor which puts out digital signals in response to your commands. Some of these digital signals will be converted to analog signals, to change the volume setting or the DC voltage to the varicap tuner in the VCR or TV set or to do some other task. All this happens within a few tens of milliseconds of you pressing a button. And when you're not pressing a button, the encoder chip inside the control is quiescent, draining perhaps only a fraction of a microamp from the batteries. No wonder the batteries last a long time. We've come to accept this wonderful technology as nothing special. It's just one of the features of electronic appliances. But next time you pick up your remote control to zap an advert, think about the complex series of electronic events you set in motion as you push the button. And we just take it all for granted. Leo Simpson