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Phototransistor optocoupler

PC817 Basic Circuit

Build a basic PC817 circuit with labeled pins, component values and connection guidance.

Package view

PC817 in a circuit

Physical package, two supplies and two separate grounds.

5V_A through switch and750ohm resistor to PC817pin1; pin2 toGND_A. Separate3.3V_B through10kohm pull-up to pin4andMCUinput; pin3toGND_B. Grounds not connected.
Low-voltage teaching circuit. LED on pulls the output low when there is enough collector drive; LED off lets the pull-up restore high.

Connect it, step by step

Follow the component values and pin connections

Limit input current

Drive the anode through 750 Ω; return the cathode only to GND_A.

Power the output side

Pull the collector up to the independently powered 3.3 V_B rail through 10 kΩ.

Read the inverted signal

Connect the collector to the receiving logic input and the emitter to GND_B. Check the receiver’s logic thresholds.

Component view