>A quick follow on question,
>
>        I seem to remember a device which allow one to apply some
>percentage of the AC waveform similar to pulse width modulation.  That
>is:
>        full power = full waveform
>        half power = 180 degrees of waveform
>        X% power   = appropriate % of the waveform
>
>I do not remember what that device is.  Any help?

I don't know the correct English name, but you find that in (most)
so-called dimmers for lamps. It's basically a triac, a
zero-crossing-detector, and some sort of delay device (might all boil down
to a RC and a trigger diode). If you want to use it with a PIC, you'll have
to detect the time of the zero-crosing of your AC, wait
(1 - X%) * (1/ACfrequency), and then trigger your triac (or opto-coupler
*without* zero-crossing detector) (basically).


>
>Thanks Markus for your quick reply.

You're welcome. Any distraction appreciated (at that moment :-) )

Bye
  Markus