4170 Vrms isolation and zero-crossing drive
The MOC3043M: Rated for 4170 Vrms isolation and 400 V off-state blocking voltage, this optoisolator drives a triac directly from a low-voltage logic signal. The zero-crossing circuit gates the triac on only near the AC mains zero — that cuts inrush and EMI when switching resistive or lightly inductive loads like heaters, lamps, or solenoid valves. The 1 kV/µs minimum static dV/dt means the output triac stays off during fast voltage transients — important when the load is a motor or contactor that kicks back noise onto the line. Without that margin, the triac can self-trigger and the load never turns off.
LED drive — what the MCU side needs to deliver
The LED trigger current (Ift) is 5 mA max, and the forward voltage is 1.25 V typical. The LED can handle up to 60 mA continuous, so there is headroom for derating over temperature or for driving the LED harder to guarantee turn-on at cold start.
Through-hole 6-DIP — field-swappable, socket-friendly
Housed in a standard 0.300-inch 6-DIP through-hole package, the MOC3043M is easy to hand-solder or install in a DIP socket. No reflow profile, no hot-air station — a technician with a soldering iron can swap it on site. The tube packaging keeps the leads aligned for automated insertion too.
UL and ROHS3 — compliance for mains-connected gear
UL recognized and ROHS3 compliant — the approvals cover North American mains isolation and EU lead-free assembly.