[SOLVED] Control Hörmann Promatic 3 with a Sonoff SV


i want to control a Hörmann Promatic 3 garage door opener with a Sonoff SV.

Therefore i used a 9 V DC Power Adapter and removed the resistors of the Sonoff to use it in isolated mode.

I connected the relay on the input of my garage door opener (see page 25)

This works already fine. I can open and close my garage door via openhab.

The unit has a 24 V DC output which is signalling an closed door.

How can i connect the 24 V DC output of the door opener to an GPIO-Pin (4,5 or 14) to control the state of the garage door?

Thanks a lot!

Convert the 24V to 3.3V with a step down or a voltage divider


i’ve tried it with a step-down-converter and a 5-V-relay. This won’t work, because the Hörmann could only provide 25 mA @ 24 V. This seems to be to less power. I’ve tried it with the relay, because i don’t know the stability of the 24 V.

If i connect the step-down converter directly to the GPIO-Pin, i didn’t know how to do this.

The GPIO-Pin has pulled to low, right?


As i wrote above, the solution with a relay didn’t work.

Therefore i took the risk of destroying the Sonoff-SV an added a voltage divider.

Now i have a voltage level of 3.1 V on the GPIO-Pin when the garage is open. This solution is now working for three day now… Seems to be that the 24 V signal is clean…