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Topic: Resistor for optocoupler (Read 329 times) previous topic - next topic


To save component costs and space:
You can probably just ground pin 4 (the output emitter) and wire pin 3 (the collector output) directly to a arduino input pin, then just enable the internal pull-up resistor for the input pin. Then reading a LOW means opto in on and reading a HIGH means opto is off.

You can save another resistor by wiring the visible led (if being used) in series with the opto's input and adjust the resistor size downward accordingly.



Would a resistor be needed to limit the current?

Look to the datasheet. Most of the times, people try to set them to work at the highest current transfer ratio, or flatest current transfer ratio. Typically that's 1 - 10ma.

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