Apartment intercom buzzer detection without power

I would like to get a notification when someone rings our intercom from the street.

I would like to send the notification to Homeassistant via a modified openclose door sensor as I don’t have power where my intercom is.

See some photos of the actual buzzer that vibrates when the button is pushed, I assume it has AC current going through it.

Any ideas would be much appreciated :slight_smile:

Why do you assume? Why not just use the multimeter and find out?

Also can’t you just add a wire with 5 volt in there to add an ESP? That should give you lots of possibilities

Hi @Hellis81 I assume because the buzzer looks like some sort of electromagnet as it rapidly pulls the thin piece of metal towards it and let’s is spring back.

I put a digital multimeter on it but it didn’t give me a reading. This may be due to my lack of understanding so I will give it another go.

I didn’t find any continuous voltage on the intercom.

Makes sense that it’s a coil.

I just added a wire in like this:

I might end up putting another cable in somehow :slight_smile:

How do you do the detection of the button pushing?

I don’t have a detection of when the phone rings. I only have ability to open the door downstairs.
I know the system will be replaced in september so I didn’t bother adding more than needed.

I used an ESP and a optocoulper to “short” the connections where the button is to open the door downstairs.

Use an INA219.Intercom with ESP

I use a Zigbee door sensor (the two piece ones where one of the parts is a magnet) to detect both my doorbell and my intercom ringing since both of them have the buzzer as an electromagnet (as you have in the picture). When it rings, it generates a magnetic field that triggers the magnetic switch on the door/window sensor. No power needed since the sensor it is battery operated and it lasts for a very long time.

Could you share some photos also which ZigBee sensor are you using?

I’m using much the same solution as @butuletz, mine is an Aqara Door and Window Sensor - well the innards of it. Funnily enough with almost exactly the same Siedle intercom as @kiwinol has.

Looks like a bit of band aid, but has been attached and working like that for several years now, it’s only really to hold it until the cover is back on :wink:

I am using a Sonoff SNZB-04 Door/Window Sensor (very small circuitry board if you remove the case). Unfortunately I am not home for a couple of weeks and I do not have any pictures. But looks like @DigiH uploaded a picture (thanks you!). It is very similar to what I have. :+1:

I am particularly interested in exactly how the sensor is located as I didn’t manage to get my aqara door window sensor to trigger :frowning:

@kiwinol Can you see the CR1632 battery of the Aqara Door sensor in my picture, as it is in the holder of the circuit board?

This is how the whole circuit board is positioned and fixed to the buzzer coil, so that the hall sensor of the circuit board (which is on the other side to the battery holder) is directly centred over the coil.

The only difference I can see from my coil and yours is that mine is encased in a plastic enclosure, while yours is metal, so that might negatively affect the magnetic/hall sensitivity to some extend.

Is your metal enclosure part somehow removable by any chance? As inside it also looks like a black plastic enclosure is holding the coil.