I've built a 418MHz RF receiver into a Radio Shack project box together with a couple of relays. When I push one of the button on the transmitter, one of the relays closes.
My intent is to wire this into the doorbell circuit, so I can ring the doorbell remotely, when no one is there. I can then use this to desensitize the dog to the doorbell - teach him to not get so excited every time he hears it ring.
I have a clip for a 9V battery inside the box, but I also included a set of binding posts so that I could power it from an external source. I'd thought that I might be able to power it from the doorbell circuit. But the truth is I don't know beans about what sort of power doorbell circuits carry.
I know they run at a low voltage. That's clear from the wiring used. And I can see the step-down transformer.
I also know that the solenoids in the doorbell itself have to be powered by a DC current. Applying AC to a solenoid accomplishes nothing.
But I don't know whether the current is rectified at the transformer or inside the doorbell. If the former, I might be able to connect it straight to the 7805 voltage regulator inside the box. If the latter, I need a rectifier circuit.
So - can anyone tell me exactly what sort of current I can expect to find in a doorbell circuit? And what I would need to condition it before feeding it to a 7805 voltage regulator?