pic microcontroller discussion list wrote:
> I haven't try this myself , but it is an idea. Build a zero crossing
> circuit that trigger one of the Pic's port pinns. (interrupt on port
> pin) The Pic can then do the delay part. The pic wait for ???ms
> before trigering the Triac. This happens 50 times per second. Your
> delay must not be longer than 10ms if you use both half cycles.
>
> Riaan
>

I have done this using H11AA814 for the zero-crossing, fed into INT0
of a 12F629. The basic idea is to use TMR0 as a delay. when INT0
fires, it loads a value into TMR0. when TMR0 fires, it turns on a triac.
The larger the value loaded into TMR0, the shorter the delay from
zero crossin. You can think of the value loaded into TMR0 as
'effective power level' The larger the value, the more power delivered
to your load.

Effectively all interrupt driven, leaving your code free to do other
processing, such as accepting user input to increase/decrease power
levels.

There are several discussions in the archive on this, including one
by me. search on "zero crossing idea" for that thread, or try "zero
cross" for other posts.


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