>Fellow PIC users,
>
>        I am using a 16C57 in a project driving nitinol "muscle wires"
>which contract when heated.  I believe that I will use alternating
>current to heat the wires so that I don't have to regulate the all that
>power just for heating wires.
>
>        1)  Would someone suggest an efficient way to switch A/C power using
>PIC outputs.

Hi Martin,
I don't know about your power/space/money limits, but there are a few
optocouplers capable of AC-switching, with integrated zero-crossing
detection.

>
>        2)  I have been looking into using a triac but I have little
>experience with them and I am not sure just how they work.  Does a triac
>switch on and off with it's control or does it stay triggered as long as
>the A/C power is applied?

Not that easy. I'm no expert either, but a Triac will stay conducting
unless the next zero crossing of the AC (control removed). You might apply
a continouus trigger signal to the triac, but some of them don't like it if
they are triggered at the wrong time with respect to the AC phase (don't
ask me about that - that's about all I know). In addition, triggering away
from the zero crossing will (might, if you are lucky) produce HF
distortions, which might interfere with the rest of your equipment.

>
>Thanks all,
>
>Martin Kirk
>Arizona State University
>mlk@asu.edu
>(602) 263-9270


Hope that helps
  Markus