Triac Pin Diagram. Pin 4 is a triac pin of the optocoupler. The circuit above shows a simple dc triggered triac power switching circuit.
From the equivalent circuit diagram shown earlier one might think that main terminals 1 and 2 were interchangeable. The gate current could be positive or negative with respect to a1 terminal of the triac. The circuit above shows a simple dc triggered triac power switching circuit.
This causes a gate current to flow across gate and terminal a1.
The diagram below shows pin outs for most common transistors thyristors scrs and triacs. With switch sw1 open no current flows into the gate of the triac and the lamp is therefore off. The diagram below shows pin outs for most common transistors thyristors scrs and triacs. For this to happen the gate pin of the triac should receive a voltage greater than the threshold gate voltage and should also get a current that is greater than gate trigger current.
