On Tue, 23 Apr 2013 11:10:27 +0100, Dave Plowman wrote:

In article ,
wrote:
On Mon, 22 Apr 2013 19:44:38 +0100
"Major Scott" wrote:
Surely they can design LED lights on cars to have a higher frequency
PWM= ? Even =A3100K cars flicker dramatically, especially when filmed.
It m= akes them look really cheap. All it would take is a higher
frequency PW= M, or a smoothing capacitor?

They flicker for a reason. If they smoothed the current they might just
as well use DC direct from the battery. I don't know the technical
reasons why but apparently using the equivalent DC voltage required to
get the same brightness as you can get by strobing them would burn them
out. I'm sure some electronics guru on here can explain more. But it
does lead to interesting effects on video as you say )

Pulsing an LED is a way of getting a higher light output from it without
overheating. Overheating an LED kills it in short order.

Take for example the brake/tail lights. These are often pulsed for tail and on for brake. So what you said doesn't make sense. Anything less than full voltage on (as for brake) will be lower heat.

Seeing a flicker
from them on a video is the same effect as wagon wheels appearing to turn
backwards on old cowboy and indian films - stroboscopic effect.

It's way worse than that - the duty cycle is quite a lot less than 50%, so you see them off, with the occasional on.

--
Peter is listening to "Eagles - Hotel California"