The original application for the thread was to control
AC mains lights
There is another way to control AC mains that does
involve zero crossing
It does require a few more components but the results
are superb
It's suitable for lights, motor control and many other AC
mains apps

The components that follow are for 220V

You run the AC through your load, in series with a bridge rectifier.
The +/- you connect to a cap (1 or 2 microFarad 400V, parallel up some
.47's )
in parallel with a transistor (eg. TIPL 760 )with a 220 Ohms 50W
(depends
on the power you want to draw) in series (in the collector)
to limit the current to a safe level.
A MPSA 42 to drive it, a BC 549 to drive the MPSA, which is driven buy
an opto
Power for the "hot side" is taken from the mains via a 22k 1 watt
resistor

The opto is driven non from syncronised PWM direct from the Pic.
The TIPL 760 works in switch mode and shorts out the bridge via the 220
Ohms
resistor the entire circuit is very efficent
and should handle at least 100 Watts probabaly more

--
Peter Cousens
email: peter@cousens.her.forthnet.gr
snailmail: Peter Cousens, karteros, Heraklion, Crete, 75100, Greece,
phone: + 3081 380534,    +3081 324450   voice/fax

After Bill Gates announced to the world that he was Microsoft,
his wife was asked to comment. She said that as his wife, she
had been the first to notice this problem