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Random-phase optotriac driver

MOC3021 Working Principle

Learn how MOC3021 works with an illustrated explanation and practical readings.

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MOC3021 at a glance

Follow the labeled connections and functional stages

MOC3021 working principle: illustrated functional stages, basic circuit and connections
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How it works

3 stages · Explore one step at a time

Step 1 / 3

Drive the emitter

The buffered source and resistor set infrared LED current.

Step 2 / 3

Transfer the trigger

The optical detector activates the bilateral output without zero-cross inhibition.

Step 3 / 3

Allow current commutation

The output remains conducting until current falls sufficiently; removing LED drive prevents later retriggering.

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