62. Triac Output Optocoupler for AC Load Control

To switch a 230VAC heater, the controller uses a main power triac. But the controller is 5V logic — it cannot drive the triac gate directly at mains potential.

A triac-output optocoupler bridges this gap. The 5V controller drives the internal LED; the optocoupler’s built-in triac output triggers the main power triac’s gate, all with complete galvanic isolation from the mains.

Zero-crossing detection is critical for heater control. It ensures the triac only fires when the AC waveform crosses zero, which dramatically reduces EMI and inrush current on resistive loads.

Required: Triac Output · Zero-Cross · 1-Ch · ≥4170Vrms · Voff ≥400V · dV/dt ≥600V/µs · 6-SMD

Go to DigiKey.com → Isolators → Optoisolators → Triac, SCR Output

Apply these filters:

• Output Type → Triac
• Zero Crossing Circuit → Yes
• Number of Channels → 1
• Voltage - Isolation → 4170Vrms or higher
• Voltage - Off State → 400V or higher
• Package / Case → 6-SMD
• Part Status → Active

Tip: Check the LED trigger current (Ift) in the datasheet. It must be ≤15mA so your 5V GPIO can reliably trigger it through a series resistor.

The filtered list will show matching parts. Before you pick one, check: Is it Active? Is stock available? Is the manufacturer reputable? Is a datasheet available?

Full checklist: How to Select a Safe, Production-Ready Component — EWskills Guide

➡ View Matching Parts — Triac, Zero-Cross, ≥4170Vrms, ≥400V Off-State, 6-SMD