Optocoupler tester

[darkoford]

It is my fault that I did not record of the defective optocouples.

Cheers

[hegefer]

Would you be so kind to provide schematics which is suitable to test both of the failure states you mentioned of an optocoupler?
Thank you.

[DIYSwede]

No big deal, hegefer:
-Just hook the (normally open) push-button between the opto-couplers Pin 2 to ground (instead of as per the schematic).
Then the +voltage will feed the opto-transistor at all times, or rather as long as the +supply is on,
but the button will draw current through the coupler's LED only when pushed.

Thus you check that:
1) The transistor won't lead when the internal LED is off (No push: External LED OFF),
2) That it'll lead when, and only when PB is pushed (Push and hold: LED lights up), and
3) That the transistor also shuts off when PB is released (Release PB: LED goes off,
thus eliminating that no stray, internal current keeps it ON,
an indeed very rare, but still possible fault mode)

2 cents

[hegefer]

Dear DIYSwede,
Thank you for your quick and detailed answer.
hegefer

[darkoford]

Circuit with ground switch:

[hegefer]

Circuit with ground switch:

Thank you! I am just about to make one. Very useful tester.

[darkoford]

Thank you! I am just about to make one. Very useful tester.

I don't know if there is another way to check. This is easy to do.

[hegefer]

I don't know if there is another way to check. This is easy to do.

Why one would need another method? It works perfectly!
Thx

[darkoford]

It would be easier if it could be tested directly on PCB.