[sdiy] A simpler LED/Optocoupler/Vactrol dimmer

[Justin Owen]

Hello,

Thought I'd post this here because I know a few of you use LDRs/Vactrols in your projects.

I've been using the H11F3 optocoupler as a modulation destination/controller. Very cool little IC - but I've still got the age old problem that controlling the brightness of the internal LED with a regular pot gives me a very uneven taper. i.e. approximately 90% of the taper gives a very small increase in brightness and the last 10% or so jumps right up - which doesn't make for a very even control curve.

I know the standard way of improving this is to use PWM to control the brightness - and the couple of circuits I've tried have definitely been an improvement...

...but - I was wondering if there was simpler way - somewhere between just a pot and a full-blown PWM circuit? (On this project I've got the equivalent of 11 LEDs to control - so that's a lot of extra components).

I was sure I saw something about adjusting the taper of a pot somewhere - but for the life of me a I can't find it now.

Any clues would be most appreciated.

Thanks much - J