Triac-output optoisolator with zero-crossing for AC load switching
The MOC3042SR2M is an onsemi optoisolator that integrates a triac output with a zero-crossing detection circuit, designed to switch AC loads such as solenoids, relays, motors, and lamps from a low-voltage control side. The zero-crossing circuit ensures the triac turns on only when the AC line voltage is near zero, which limits inrush current and reduces conducted EMI at the switching instant. This is a single-channel device in a 6-SMD gull wing package rated for surface-mount assembly.
Isolation and off-state voltage rating for mains applications
With a 4170Vrms isolation voltage and a 400 V off-state voltage rating, this part can reliably switch 240VAC loads with a healthy margin above the peak line voltage. The minimum static dV/dt of 1kV/µs provides immunity against false turn-on from fast line transients — a common concern when driving inductive loads like contactor coils or small motors. The typical LED trigger current (Ift) is 10 mA max, and the forward voltage is 1.25V typ, so a standard 5V or 3.3V logic output with a series resistor can drive the input LED.
Active production status and sourcing
The package option is Bulk, which is typical for engineering samples or small-run production.