MOC3021Random-phase optotriac driver

MOC3021 is an optically isolated triac-driver family. An infrared LED transfers a command to a bilateral output switch without a conductive signal connection between the two sides. The selected onsemi MOC3021M has a 400 V peak off-state output rating. It has no zero-cross detector, allowing the controller to choose the trigger point. The 15 mA maximum input trigger-current test is specified at 3 V across the main terminals and 25°C; it does not guarantee the same margin at every temperature. Both DIP MOC3021M and gullwing MOC3021SR2M SMD versions retain all six physical pins. Pin 3 is unused and pin 5 is a substrate connection that must remain open. The example uses a small isolated AC source and resistor load to explain optical switching without a mains connection.