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 MOC3042SR2M carries an Active product status from onsemi. The package option is Bulk, which is typical for engineering samples or small-run production.