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A comprehensive guide on using the MOC3021 optoisolator in digital-AC interfacing. Schematics, wiring tips, troubleshooting, and South African sourcing - all in one resource from Communica.
Learn what the MOC3021 does and where it fits in SA circuit builds.
Guided circuit diagrams, resistor selection, and AC load control examples.
Find MOC3021 stock, compatible triacs, and support at Communica branches.
The MOC3021 is a popular optically isolated triac driver, designed to interface low-voltage digital signals (like microcontrollers or logic circuits) safely with high-voltage AC loads. It is widely used across household appliance controls, industrial automation, and hobby projects in South Africa for switching lamps, fans, or relays from an Arduino, Raspberry Pi, or PLC.
| Parameter | Typical Value |
|---|---|
| Isolation Voltage | 5000 Vrms |
| Input Forward Voltage (VF) | 1.15V (at 10mA) |
| LED Trigger Current (IFT) | 15mA max |
| Output | Phototriac, drives external triac |
| Package | 6-pin DIP |
Microcontroller Output (e.g. Arduino) 230V AC (Load, e.g. Lamp)
| |
[Rin] (Pins 1-2) MOC3021 (Pins 4-6) [Gate R]
|------->|---[LED]----+---[PhotoTriac]-----+----|>|-------+------
(1) (2) (6) (4) (Triac)
In this setup, an Arduino output pin triggers the MOC3021 LED via a resistor (Rin), activating the internal triac output. This, in turn, gates an external TRIAC (such as the BT136 or TIC206M) to control the AC load.
To reliably trigger the internal LED, Rin must be sized for at least 15mA forward current:
For a 5V Arduino:
Rin = (5V - 1.15V) / 0.015A = ~257Ohm. Round to 270Ohm standard (0.5W min).
Free shipping for orders over ZAR 1,000.00.
Get a full refund if you had the product for less than 7 days.
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Communica supplies semiconductors and electronic components to industries such as automotive, electrical, automation, mining, and education.
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