[sdiy] PWM, Vactrols & Opto-Isolators

[jays at aracnet.com]

One issue I would be concerned with is how accurate the conversion (PWM > Volts) needs to be.  Yes, LEDs can have their brightness controlled by PWM, but the the PWM -> brightness is not a linear function. Also a number of photo/optical sensors are not linear either.

Jay S.

Dustin Withers wrote:

> Hello All,
> 
> I think this maybe my first post here. I guess I should introduce
> myself a bit? I've been in and out of Synth DIY for the past 10 years
> and have also purchased some modular equipment (specifically Modcan
> A). My system is about 1/2 Modcan and about 1/2 things I've built. I
> keep a semi regular blog @ http://www.fadeddata.com . Lately I've been
> getting into hobby CNC and I've been engraving my own PCB's. I'm going
> to begin engraving aluminum panels soon as well.
> 
> Most of the things I'm up to are pretty boring compared to the rest of
> what some of you are doing :)
> 
> Anyhow, enough of that!
> 
> I'm curious about what the differences are between Opto-Isolators and
> Vactrols. I think they are the same thing, right?
> 
> Also I'm interested in converting PWM to a voltage. I know this can be
> done with a low pass rc circuit. I remembered that you could also
> control the brightness of an LED with PWM. Couldn't a
> Vactrol/Optoisolator be used to convert PWM to a voltage? What are the
> pros/cons vs the RC circuit?
> 
> Thanks for your time,
> -dustin
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