audio signal for "activate" GPIO?

Hi all,
My doorbell ringer is a 8ohm 0.5 W speaker. Is there a way to use the signal reaching it during dorbell button push to activate a GPIO ? ( like a rele or octocoupler )

thank you

The Arduino can be damaged by negative voltages or voltages greater than +5V.

An opto-coupler could work, but since you have an unknown voltage and audio signals normally swing positive and negative, use an [u]over-voltage protection circuit[/u].

You can increase the resistance to between 1K and 10K. Also, and add a "pull down" resistor about 10 times that value between the Arduino input and ground.

Then, start [u]Digital Read Serial Example[/u] to see if you can detect the doorbell ringing. (Of course, connect the doorbell instead of the switch circuit, and connect the common grounds.)

If you don't get anything or if it's not reliable try the Analog Read Serial Example. That will work because even if the signal is weak you can set a threshold in software. (Again with the doorbell signal instead of the pot.)

You can take the delay() out of both examples.

Thank you very much for your answer, I bought the components I'll give feedback :slight_smile: