Grabbing power from a garage door wall controller

[larrybud]

I have a Chamberlain Whisper Quiet + garage door, about 10 years old, and I'm making and ESPHome controller to monitor and control the door. This particular door opener is a 2-wire connection, and it has two way communication between the motor and the door controller. The wall controller has a backlit LCD screen, and monitors the battery backup level for the garage door motor, has the time, temp, and will control the door open/close, the interior light, and you can lock the controls of the door, so it's not just a simple on/off or "doorbell" type controller. There's 18V going to the controller.

I put my scope on the two wires and you can see the communication happening with some pulses between the wall controller and motor. I wasn't able to decode this communication to control the door, and instead just decided to solder a couple of wires to the PCB where the open/close switch is, and I can easily mimic the manual switch with a relay that's connect to the ESP Home.

Now comes time for powering my ESPHome. I made a couple of attempts to try to tie into the 18V to the wall controller by using a buck converter, but the converter interferes with the signals that come across the line, and I'm no longer able to open and close the door, because the signals are smoothed out over the wire. I took the input cap off the buck converter to see if that would help any, but still no result.

Could there a *simple* way to tie into this without affecting the signals? I certainly can run a separate 5v supply to my ESPHome device, it's not a really big deal, but this is as much of a learning exercise as it is a useful project.

[edavid]

The best way would be to tap power from inside the wall unit, since it will already have the necessary filter to avoid disrupting the communications.

I doubt you will be able to tap enough power for WiFi though.  Maybe Bluetooth.

[larrybud]

That's a good idea, thanks!