How to trigger triac gate with optocoupler


Joined Aug 21, 2008
You will notice that in both this thread and your previous thread that we think the MOC3043 is a much better couple for your purpose than the PC817. Turning on traics handling any real power well is a little more complicated than you seem to imagine and the MOC3043 give you a solution with all the hard work (extra circuitry) already inside.


Joined Aug 7, 2020
If you put a current that is greater than the trigger current into the gate (in either direction*) the triac will turn on and AC current can flow between MT2 and MT1.
The triac will turn off when the current between MT2 and MT1 falls below the holding current or when the trigger current is removed.
That's all there is to it.

It looks very much like an AC version of a transistor with MT1=emitter, MT2=collector and gate=base

*trigger current may be different values for positive and negative, and some triacs will only trigger with negative voltage on the gate.
[and you might be in trouble for hijacking an old thread - if you want to ask a question start a new thread]