Easy

Optocoupler Isolated Switch

An optocoupler passes a control signal across an internal beam of light, with no direct electrical connection between the control side and the switched side — essential protection whenever two parts of a circuit must be kept electrically separate.

Circuit Diagram

INPUT SIDE OUTPUT SIDE (isolated) +5V PC814 1 (LED anode) 2 (LED cathode) 330R BUTTON +12V Q (phototransistor) C E 330R LED GND (output side, separate rail) GND (input side)

How to Build It

  1. Place the PC814 optocoupler on the breadboard.
  2. On the input side: connect a resistor from the positive rail (5V) to the internal LED's anode (pin 1), and the cathode (pin 2) to a push button, then to GND.
  3. On the output side (fully electrically separate): connect the internal phototransistor's collector (pin 4) through a resistor to an LED, then to a second positive rail (can be a different voltage, different circuit).
  4. Connect the emitter (pin 3) to the output side's GND.
  5. Press the input-side button — the output-side LED should light up, even though the two sides share no electrical connection.

Bill of Materials

ProductCodeQty
LED (3/5/10mm, SMD, power) l-934ID-12V 1
Optocoupler — 1
Push button 10100565(ALX-5A025) 1
Resistor DR47K-8/9 1
Resistor DR100R-418 1
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