Explore MOC3021 pins, signal names, electrical functions and connection guidance for each package.
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Click a lead or use the arrow keys. Top view · dot marks LED anode pin 1
Positive terminal of the optical input emitter.
Use a buffered 5 V source through 220 Ω.
Drive above the required trigger current with temperature and tolerance margin.
Input-side return for the emitter current.
Return to GND_A.
Do not join the input return to the isolated output domain.
No intended internal connection.
Leave unconnected.
One terminal of the light-triggered bilateral switch.
Connect to the isolated AC source return in the example.
This is a triac driver, not a high-power load switch.
Internal triac substrate lead.
Leave open; do not route a signal through this pin.
NC in the manufacturer symbol does not authorize connecting this substrate lead.
Other terminal of the light-triggered bilateral switch.
Connect through the pulse/load resistor to the isolated AC source.
No zero-cross detector: trigger timing follows the optical input and available output voltage.
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