I automated my intercom with a 10€ aqara humidity sensor ^^

It’s really silly, I’m posting this just in case it’s useful for somebody.

On the one hand, I have an old intercom in my rented house.

If you open any intercom there usually are a bunch of cables in parallel, each one serving a different purpose. Through one of them (calling cable) flows a 1.8V current (that voltage is device dependant, I found out in the manual of my device) every time somebody rings the intercom from the outside of the building.

On the other hand I had this xiaomi humidity sensor paired to HA with ZHA and a conbee II


The battery on this device works at 3V. I noticed, listening to state_changed events, that every time I extracted the battery from the humidity sensor and placed it back in, the sensor was instantly sending a state_changed event to HA.

So I wondered whether the 1.8V from the intercom’s calling cable were high enough as to mimic the same behaviour.

I extracted the battery, bound the calling cable to the aqara’s positive pole and the negative pole to the intercom’s neutral cable and there you go. Now every time somebody rings from the outside the sensor reacts as if somebody had put a battery in and therefore instantly sends a state_changed event to HA.

The original ring of the intercom (which was pretty annoying) is no longer working and I set my ringing sound of choice which now sounds more softly and throughout the whole house. I can choose which rooms it sounds in depending on whether somebody’s sleeping, taking a shower or whatever… On top of that, I can disable/enable it at please. It doesn’t require battery replacement nor any power source to operate plus the sensor itself is so tiny it easily fits inside the majority of the intercoms (mine is actually quite small). If watching a movie, pause it, send notification to mobile phone, etc, etc.

There’s not much one can do with this workaround compared to devices like the Nuki opener, but there’s not much one can demand either after all ^^.


This kind of tinkering makes me happy lol! Job well done I’d say hahahah


VERY nice idea, thank you for sharing!

1 Like

There are a number of RF sensors with various batteries and working voltages in Ali (1.5V, 1.8V, 3V, 12V, etc), enough variety to fit adecent amount of intercoms I guess. Those RF sensors paired with a Sonoff RF bridge might do the trick as well.

I personally tried with an aqara doors sensor and there was too much delay. A push of the button wouldn’t fire the event, only after having the battery sitting for 10 seconds would make it react which translates in somebody pushing the button for an unacceptable length of time.

Very nice idea !

1 Like

This might prove to be super useful to me. I have gotten into Home Assistant with the goal of being able to automate a scene when someone drives past my magnetic driveway sensor. Its a mighty mule brand unit that lights up an LED and also squaks a speaker. People have used the voltage going to the LED to “import” a signal into Home Assistant by triggering external sensor poles on a door sensor. One problem is, you have to reset the unit each time, as the LED remains lit.

I think that I could use your approach with the speaker, maybe. Perhaps I wire the speaker voltage with a voltage buck to knock it down into the battery range and use the humidity sensor like you did ?

Let us know :smiley:. Not sure if your automation requires to be triggered instantly like the intercom. If so, bear in mind not all sensors react instantly. It will take some trial and error.

If you have a power source nearby, you can use the sonoff pow r2 for example.

Hey there, glad that i found this Post. I have the Same Situation. I live in a House with a few Families and the House has Intercom for the Doorbell. Tried a aquara Vibration Sensor for Notification but didnt Work even with sensitive settings it noticed No vibration

When i saw your Post Here i thought finally i can make use of this Sensor in a different way to get it to Work.

So could you Tell me how far you teared down your Sensor for being able to Connect to +/- ?

Im a Bit unsure how much Teardown needs to be done to the Sensor to solder the Cables.

Help appreciated

No teardown no soldering, though you might better solder it. I just curled the cables around the battery’s compartment positive and negative poles and stuck the sensor whithin the intercom. It’s been working flawlessly so far.

Meanwhile i already soldered it and tested it to function :nerd_face:

Since i used an aquara Vibration Sensor my entities may differ a little bit.
Could you help me out with your Automation based on Trigger “Changed_State”?

I got the following Entities available for my Device which could possibly be useful as a Trigger to Setup an Automation?


Are you using NR or YAML? I haven’t been using YAML for some time now so I’m sorry if there are errors… I hope you at least get the idea.

- alias: Chime
  - platform: state
    - sensor.devicename_battery
    - sensor.devicename_power_outage_count
  - "{{ trigger.to_state.state not in ['unavailable','unknown'] }}"


  - delay: 10

By setting a platform: state trigger without any to or from field you are basically listening to events. The condition is to avoid the chime triggering after a few hours of inactivity, since it will go unavailable. The delay is there in order to throttle your actions since you have two entities, and it’s good to have more than one entity triggering this particular automation.

If you want to easily turn on and off your intercom through lovelace you may also want to create and input boolean and do this:

  - "{{ trigger.to_state.state not in ['unavailable','unknown']  and is_state('input_boolean.your_input','on')}}"

Or maybe just set the automation in lovelace and toggle it ^^.

Yeah thx i get the Idea. Had to go a little different cause its not an Intercom as i thought at first. Its a “Ritto” which needs a little relais to add my prepared Sensor.
The Procedure should be the same when it finally arrives.

Will add my Results here If its okay