[sdiy] Vactrols

[Paul Perry]

----- Original Message -----
> Has anyone tried ultra-sonic pulse width modulation of an LED / LDR
combination
> instead of varying the current through an LED?
>

If you mean, trying to use PWM to drive the diode, I expect that would work
very
well (and I suspect that is done in certain microprocessor controlled
compressors).
But it opens another possibility, if you go PWM, normally one drives CMOS
switches,
but maybe something could be done with (very common & cheap) digital
optocouplers,
using the opto output as a switched resistor for example (the output stages
vary
widely).
paul perry Melbourne AUstralia