On Sep 11, 10:13*am, "Dave Plowman (News)"
wrote:
In article ,
* *D Yuniskis wrote:

I've got a (Vellerman) PWM device which is DC controlled. I'd like to
use it such that it fades up to max when a simple DC switch is made,
then fades out when it is broken. I can get it to do this using a
simple RC circuit - but the 'law' of the fades isn't as linear as I'd
like. Any clever way of doing it?
Constant current source into a cap.

The constant current source into the cap is easy enough - but the constant
current load?

--
*I used to have an open mind but my brains kept falling out *

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

OK you don't like that. How about an up/down counter and a DAC?

G²