[sdiy] PWM, Vactrols & Opto-Isolators

[Jerry Gray-Eskue]

<<I'm curious about what the differences are between Opto-Isolators and
Vactrols. I think they are the same thing, right?>>

You are almost correct, they all fall in the device family of opto-couplers.
Opto-Isolators are specifically designed for high degrees of isolation
especially electrically.
A Vactrol may or may not be designed for high levels of isolation, all
opto-coupler devices tend to isolate, but some are not designed for high
voltage isolation levels.

I believe that the Vactrol device is characterized as having an output that
acts as a symmetrical resistor typically a cadmium sulfide device under
control of the photon emitting side of the device, other types of
opto-couplers have output side devices such as transistors, FETs, SCRs,
Triacs etc.

The use of cadmium, considered a hazardous substance, has led to cadmium
based devices being discontinued.

-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl]On Behalf Of Dustin Withers
Sent: Wednesday, January 13, 2010 10:33 AM
To: synth-diy
Subject: [sdiy] PWM, Vactrols & Opto-Isolators


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
_______________________________________________
Synth-diy mailing list
Synth-diy at dropmix.xs4all.nl
http://dropmix.xs4all.nl/mailman/listinfo/synth-diy