31 Oct
2011
31 Oct
'11
6:47 a.m.
On Oct 31, 2011, at 5:51 AM, Benjamin S?lberg wrote:
Joke-a-side.. If multiplexing really did save power
then just pulsing a
single led would do the same..
It might be true... think bicycle lights ?
Pulse width modulation is generally considered the "proper" way of dimming an
LCD, since varying the voltage just doesn't work well (the threshold area is highly
non-linear and inconsistent across devices) and current variation also produces
inconsistent results across devices. Running about a 1KHz pulse to the LED and varying
the duty cycle works quite well.
Unfortunately, some car manufacturers (in the US, I'm thinking of Cadillacs
especially) got hold of this idea and decided to drop the PWM frequency down from about a
KHz (where the human eye can't see the flicker) to just a handful of Hz, so that on a
dark night, as you move your eyes, the tail lights scatter themselves across your field of
view like animation frames. It's very distracting and irritating, and I doubt the
lower frequency saved them more than a few cents per $30,000 car in drive electronics.
- Dave