I'm building an electro-mechanical doorbell as a gift. An arduino controls 4 servos which actuate 4 mallets on 4 chimes to play a melody. I have the arduino and servos operating as expected, interfacing a standard doorbell button is the trick I just can't seem to figure out.
My goal is to make it a drop-in doorbell, using the same wiring as any door bell you might buy at home depot. This means I have 5 wires to interface (7 if using a button for back door chime). 3 wires for AC power, 2 wires pe r doorbell button.
For power, I have a 12v2a/5v6a regulated power supply.
Doorbell buttons come in two flavors, lighted and non-lighted. Interfacing to a non-lighted button is trivial. It's just a regular switch and I can push 5v to capture that input. Lighted buttons normally run on 12vac, but will also light on 12vdc. Unfortunately, the bulb is wired in parallel wit h the button - so there's constant current. Additionally, the arduino can' t take 12v on the inputs - so there's no way for me to use a lighted button without some magic.
I have an alternative that I really don't want to pursue. I could reconfig ure the lighted button with a resistor and LED and run the whole thing on 3 .3v from the arduino. The reason I don't want to do this is because - as a gift - I want this to be as transparent to the recipient as possible. If at some point the button needs to be replaced, the new button would need to be made compatible.
Another issue I've run into is, when the arduino and button are connected t o the same source - pressing the button drops voltage to the arduino - caus ing it to reset. So the button circuit needs to be isolated from the ardui no.
So, if you were forced to use a 12v lighted doorbell button as trigger to a 5vdc device - what would you do?