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SILICON
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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
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