Home Assistant Community

Intercom Buzzer Sonoff SV and Home Assistant


Hello, I am planning to interface my home intercom with home assistant through a Sonoff SV, but I really need your help because I have never opened an intercom since yesterday.
My intercom is a Siedle HT 511-01, I found a PDF containing the schematic (page 10) here:

I have a Sonoff SV with the Tasmota firmware and Home Assistant running on my RaspberryPi 3
I attach also a picture of my intercom opened and of my buzzer, as soon as I know the model I will write it here, but on it it’s written 8V - 6V

My goal would be that when someone rings the bell i receive a notification and then I can open the door through HomeAssistant

Do you think it’s doable? Can I connect the buzzer to the GPIO14 of my Sonoff SV and then open the door throught the relais of the Sonoff SV?

Thank you very much in advance for your support!!



3.3V is the maximum you can put on the GPIO pins. You will need a relay in between the buzzer and Sonoff.


Hello again, I measured with a Voltmeter what happens to my doorbell when it rings and it gets 11V AC. I was thinking of using a rectifier and then a then a voltage divider in order to get my 3.3V in the GPIO pin. Does it make sense?
Moreover you say that I need a relay in between the buzzer and the Sonoff (SV), does it mean that I could use a Sonoff Basic as a Relay? Or do you mean a normal relay?
Thanks in advance for your answer!


A voltmeter wont show up voltage spikes that could very well be present from this sort of mechanical doorbell.

If you use the rectifier/divider method, add some sort of voltage clamping to the GPIO as well, a 3.3V Zener diode, or better yet, a 3.3V transil diode (faster acting, flatter cut off voltage).

Or just use a 12V AC relay. Relay coil connected in parallel with the bell, voltage free contacts connected to short the GPIO to ground, with a 10k pullup resistor connecting 3.3V to the GPIO.