Electrical – How did I break this optocoupler


I'm trying to use an H11AA1 (datasheet) optocoupler to test when my doorbell is pressed (I'm in an apartment building):


simulate this circuit – Schematic created using CircuitLab

It worked when I first tested it, but then it stopped working less than a day later. I have a second optocoupler (which I bought with the idea that I would almost certainly break the first one somehow), and if I swap it in it works. The input part is supposedly rated for 230VAC, so I don't think the issue is there.

I've disconnected it all for now out of fear of breaking the second optocoupler. What did I do wrong?

Best Answer

What might you be missing: -

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The raw input has just internal diodes and these get messed up from anywhere between 1 volts and 3 volts. Use a resistor. 8 V AC is too much to put on the input. +/- 60 mA is the current limit into the device - stay away from this limit.