Test with a multimeter

Optocoupler (PC817)

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Now: LED forward: red on pin 1

LED CircuVanta 6000 counts · auto range DCAUTO•)))HOLDFUSE− HOLD LIGHT OFFV⎓V~Ω•)))FmA⎓ mA400 mACOMVΩ Anode (a), pin 1 1 a Cathode (k), pin 2 2 k Emitter (e), pin 3 3 e Collector (c), pin 4 4 c
Pin 1: Anode (a), pin 1 (a) Pin 2: Cathode (k), pin 2 (k) Pin 3: Emitter (e), pin 3 (e) Pin 4: Collector (c), pin 4 (c)

Red probe Not connectedBlack probe Not connected

Hold the probe and drag it to the tip of a leg. Tapping works too: first pick the probe, then the leg.

Set the range to diode test.

Test setup: Setup: it drives the LED through a resistor. While it is driving, do not make Ω or diode measurements on the LED pins; measure the output.

Measure step by step

An optocoupler’s input is an LED and its output is a phototransistor; the two are isolated from each other. Measure the input like a diode and the isolation in Ω. To see the output’s response you need a rig: when you drive the LED, the output transistor conducts.

In the setup, drive the LED only through a series resistor. Never connect it directly to a battery or power supply.

  1. 1LED forward direction: red probe on leg 1
  2. 2LED reverse direction
  3. 3Insulation: input to output
  4. 4C → E with the output not driven
  5. 5LED driven, C → E