On 17/11/2016 15:24, Dave Plowman (News) wrote:
Asking here in the hope someone has come across this and may have an
answer.

Car interior lights have an auto 'dimmer'. They do a graceful fade in and
fade out when switched on and off. On a Merc. Owner wanted some slightly
brighter lights so changed from tungsten to LED. The auto system still
does a graceful fade out - but sort of leaps to on, rather than fading up.
Later Mercs have got LED lighting which does fade in and out OK - but it's
not just a case of changing the module which on the later cars is part of
other things too.

On this model the module is stand alone, so would be possible to modify it.


I wonder if the tungsten module is doing it by varying the voltage
whereas the LED one is PWM/current control?
Should be easy to check and then maybe knock up a voltage controlled
PWM? I note there are a few old school 555 designs for that