I want to send a signal between 2 isolated DC-powered circuits using only single wire connecting them. If possible, I'd like to avoid wireless solutions.
I have a broken doorbell installation which I'm trying to fix. Doorbell itself operates on rather low voltage (around 6V). This is a weird custom installation, which most likely doesn't work, because something happened years ago to the initial power supply. I wasn't able to trace the cables to any useful culprit.
What I was able to deduce so far:
- There's a switch outside the apartment with 2 dead cables coming from inside of the wall,
- There's a doorbell inside the apartment with different 2 cables coming from inside the wall,
- I know for sure that 1 cable is going through the wall directly to the doorbell.
In the simplest form, the circuit must have looked in the past somewhat like that:
What I want to do is to make 2 separate circuits with 2 separate power sources. First one for the swtich outside the apartment and the second one for the bell inside the apartment. I want the first circuit to notify the second circuit that someone pressed the button via 1 existing cable. I guess it is possible, but I'm not sure what components do I need to use to make it work.
At first I thought about 2 microcontrollers (even something arduino–like like DigiSpark USB). The first microcontroller would send a
HIGH signal through that 1 wire to the second microcontroller — then the second one would turn on a doorbell.
Then, I though that maybe I can use less dark magic and make use of basic components like... transistors?
In the end I want to have something like the following:
What magical components can I use in a place of
Magic 1 and
PS. Yes, I marked a doorbell as an LED.