What I would like to do is wire up my Arduino/Raspberry Pi to this doorbell, detect when the doorbell speaker is ringing, and then do some other stuff.
What potential options do I have to detect if the speaker is currently ringing? Can I wire up the speaker in parallel with the right amount of resistance to one of the GPIO pins?
Opto coupler with opto transistor from pin (collector) to ground (emitter) and pull up enabled on the pin.
Opto Led with reverse protection diode across and current limiting resistor in series. 1-2mA should be enough.
Leo..
Since the voltage from the speaker is AC, the negative swings could damage the input LED. I would use a series resistor of 1K and a diode antiparallel to the input LED to protect it. See below. Reduce the 1K if needed.
You do not connect "Arduino 3.3V" to OUT1. Connect it to "HV" instead.
jremington:
Since the voltage from the speaker is AC, the negative swings could damage the input LED. I would use a series resistor of 1K and a diode antiparallel to the input LED to protect it.
One quick snag I've run into: I can't seem to determine the voltage coming out of the speaker.
I've soldered on extra wires onto the speaker contacts, but when I set my multimeter to AC it just displays 0. On the speaker is clearly printed: "20 Ohm, .5W" so if I trust that I know I'm working with ~3v. Is that good enough for me to start wiring things up? Reason for it not working could be:
Is my multimeter not sensitive enough to register the low voltage?
Did I mess up my soldering? (Unlikely, I've inspected it and it looks like a normal joint)
thr33:
I've soldered on extra wires onto the speaker contacts, but when I set my multimeter to AC it just displays 0. On the speaker is clearly printed: "20 Ohm, .5W" so if I trust that I know I'm working with ~3v.
Not necessarily as your speaker is an inductive load, not a resistive. So the resistance is highly dependent on the frequency of the signal applied.
For measuring the voltage with your multimeter, do make sure that you're measuring AC not DC.