On Feb 5, 2:05*pm, default wrote:
On Tue, 05 Feb 2008 18:08:12 GMT, "James Sweet"



wrote:

The lash up works. *I can control a 120 VAC lamp with the dimmer
triggering the external triac.

Two things might be worth worrying about: first, the trigger
of the new triac might be incomplete or unreliable (might
miss some cycles); if you have an oscilloscope, it would
be worth checking this. The current that triggered the old
triac could trigger the new one only 90% of the time, or could
miss negative half-cycles, or misbehave in lots of ways
that wouldn't fail the lightbulb test.

Second, triacs have a dI/dt limit, so a heavy load should
always be turned on/off at zero crossings (also for RF noise,
but that's not tihe big issue). The failure mode if your
phase-control trigger does too much switching at full
current from a dead stop, is short circuit of the triac.
Beware scorched wort! Solid state relays aren't terribly
expensive, and include the desirable zero-voltage-switching.