On Fri, 28 Aug 2009 17:01:09 +0100, Fleetie
wrote:

At night I find the on/off flickering of LED brake lights particularly
annoying, why not have interleaved arrays of LEDs that turn on at
different times to give the effect of a constant light?

Why not just make them flash about 100 times faster, i.e. about 100kHz
rather than about 1kHz or thereabouts that a lot of them currently do?

It really is not hard to make LEDs flash on and off. Tens or hundreds
of MHz is easy and routine. So 100kHz should not be a problem at all.

No, I suspect the flash rate is *kept* down to MAKE the flash just
noticeable, to make the car look "flash" by standing out conspicuously
from those cheaper cars with mere incandescent brake lights that do NOT
flash. It's for posing.

I very much doubt it. More likely so as to make them CE compliant. A
high current square wave creates a lot of EMI at frequencies way above
the square wave frequency. To prevent it, you have to round off the
square edges by slowing the rise and fall times of the pulses. The
higher the frequency, the less the rise and fall times can be slowed,
and so the more difficult it is to suppress EMI.

--
Cynic