Optocoupler module pin functions
• Pin-2: The Cathode (-) pin is connected to the common ground with the circuit and power supply Phototransistor Output • Pin-3: The Emitter pin is similar to the Cathode pin. These PC817 optocoupler isolation modules provide a convenient, pre-built breakout board that handles the supporting circuitry for you. In this pinout diagram of PC817, pin1 and pin2 are parts of the input side and pin3 – pin4 are output pins. INPUT_PULLUP means, the pin's signal is HIGH, if there is no connection to the GND pin (circuit.
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