On Friday, November 18, 2016 at 2:00:13 PM UTC, Dave Plowman (News) wrote:
In article ,
Lee wrote:
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?

That's a good guess, I'd say.

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

Not seen any that do the fade in fade out when powered up and down, though.

As was said, it might be easier to use a microprocessor for this. Above my
pay grade, sadly.

PWM won`t quite make it to zero theres a slight step down to zero , but usually close enough, current control is usually smoother.

Arduino and output transistor, cheaper than building it in discretes

http://arduino.stackexchange.com/que...h-arduino-nano

http://www.ebay.co.uk/itm/like/262459320226



--
*I wished the buck stopped here, as I could use a few*

Dave Plowman London SW
To e-mail, change noise into sound.