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SILICON SILIC CHIP www.siliconchip.com.au Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Production Manager Greg Swain, B.Sc. (Hons.) Technical Editor John Clarke, B.E.(Elec.) Technical Staff Ross Tester Jim Rowe, B.A., B.Sc Nicholas Vinen Photography Ross Tester Reader Services Ann Morris Advertising Enquiries Glyn Smith Phone (02) 9939 3295 Mobile 0431 792 293 glyn<at>siliconchip.com.au Regular Contributors Brendan Akhurst David Maddison B.App.Sc. (Hons 1), PhD, Grad.Dip.Entr.Innov. Kevin Poulter Dave Thompson 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 is copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Hannanprint, Warwick Farm, NSW. Distribution: Network Distribution Company. Subscription rates: $105.00 per year in Australia. For overseas rates, see our website or the subscriptions page in this issue. Editorial office: Unit 1, 234 Harbord Rd, Brookvale, NSW 2100. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9939 3295. E-mail: silicon<at>siliconchip.com.au ISSN 1030-2662 Recommended & maximum price only. 2  Silicon Chip Publisher’s Letter QuickBrake: an idea whose time has come This month, one of our featured projects is the QuickBrake which has the potential to substantially reduce the incidence of rear-end collisions. Now you might not think that is a big deal but there are Australian statistics which indicate that some 26% of all road accidents are rear-end collisions and almost half of those result in injury. Any device which can substantially reduce those statistics must be very worthwhile. And yet, this idea is not new. In fact, this month’s article is our second version of this project, having been first featured in the March 2004 issue, 12 years ago. This second iteration is very similar to the first, with the major change being to make it able to be used if the brake lights are changed over to LED equivalents when it is installed. So how does it work? It senses when you are about to make an emergency stop because you lift off the accelerator much more rapidly than when you are about to make an ordinary stop. It does this by monitoring the voltage from your car’s throttle position sensor (TPS) which is normally a potentiometer coupled to the accelerator pedal at its pivot. Without going into the description (you can read it on pages 55 & 56), the circuit senses the rapid change of the TPS voltage and uses it to briefly operate a relay whose contacts are in parallel with the brake pedal switch contacts. So the QuickBrake circuit switches on the brake lights even before your foot has actually left the accelerator and moved over to depress the brake pedal. Typical driver response times, having realised the need to make an emergency stop, are from 250 to 750 milliseconds. So even if we allow that the QuickBrake turns on the brake lights some 250ms before you can manage it, that is a major safety improvement. If the following driver is travelling at 110km/h at the time your brake lights come on, that gives him (or her) more than a car length extra to come to a full stop. That could be the difference between a safe but panic stop for the following driver (and possibly some heavy breathing afterwards) or perhaps a severe accident and injuries. Even if the following driver does not manage to stop in time, the resulting prang should be less severe than if the early warning did not occur. Now if you are driving a largish modern car with active head restraints you might not be too worried about the consequences of a rear-end collision. Don’t be so complacent. A few years ago my Honda Accord was subjected to quite a severe rear-end collision. I was stopped at traffic lights and heard the screech of tyres from a car behind me. A glance in the mirror showed it approaching rapidly with smoking tyres. I knew it would be a severe collision and there was nothing I could do about it. I was a sitting duck. In the event, I was not injured but the driver in the car behind was – severely. Fortunately for the injured driver, the accident happened outside Mona Vale Hospital. But I was very lucky and the outcome could have been much worse. I could have been killed, you see, because my car was booted right across the intersection, into the path of cars coming in from the right. The gods must have been smiling on me that day because my car was not T-boned and the only damage was to my car’s rear bodywork. The other car would have been a write-off. I report this because I intend installing the QuickBrake on my car. While I very rarely need to make an emergency stop, I like the idea of giving a following driver more warning. And think about this; if you do have a collision but you have the QuickBrake fitted to your car, that might mean that your accident is not made much worse by a pile-up in the rear. Leo Simpson siliconchip.com.au