DC Control for Triacs

If a circuit is to switch a mains voltage, a relay is a simple solution in cases where switching times are long and high currents are involved. However, at lower currents, and in particular where rapid switching is required, such as in sound-to-light systems, a relay no longer fills the bill. Electrical isolation is often a requirement, which rules out driving a triac via a transistor. Here we use the MOC3041 optocoupler, which is specially designed for such applications, to drive a power triac. The control circuit therefore remains galvanically isolated from the mains.