Contact Sensor for Doorbell

I tried setting up a video doorbell but it was to much hassle do to the position of the button outside the house and since I already have a camera setup. What I would like to do with HA is use my regular doorbell and add a contact sensor that gets triggered when the chime rings and eventually be able to pull up my camera feed automatically.

I’ve seen some old youtube videos of this working, but what hardware should I buy now? At the moment i do not have anything, so will need a contact sensor as well as a compatible z wave or zigbee usb stick.

Are the Ring or Wyze contact sensor a good buy and work with HA?

How exactly does the doorbell work? It may be as simple as connecting an esp8266 to the wires in parallel to the existing “bell”.

that’s cool and plan to do that for the garge, but overly complicated as I do not have an outlet next to my mechanical door chime.

The contact sensor integration seems like it is the easiest.

Something like this

I did exactly that, interface my existing button:

how did you solve powering the esp? i don’t have a power source near by

If you have z-wave you can consider using this:

by Nexia Home Intelligence

Ties right into the doorbell. Powered by batteries. They last about 2 years.

Last I checked DB100Z from Nexia is rather difficult to find. Do you guys have any luck to find any DB100Z these days?


Also I found this from Shelly forum, using a Shelly UNI and the existing transformer that is powering your regular doorbell.

I understand in the US, a typical doorbell transformer is to bring 120VAC into 10-20VAC.

Would this work as an alternative? Comments? Questions? Anything we should be careful of?

Should be ok, just read shelly uni can use 12v ac as source.
I intended to do the same with my esp01, which didn’t work, as the transformer didn’t have enough power. The voltage dropped too much when activated, causing the esp01 to reboot :wink:. So i am using an additional powersupply for the time being.
Wil sort it out some day (maybe🤔)

nahh that is simple, THIS is overly complicated:

Is the chime powered by a transformer? If so you can convert that to DC to power an ESP or Shelly device

Do you have a mechanical chime? I jammed contact sensors next to the plunger for my doorbell, I have an Ecolink Zwave Contact Sensor DWZWAVE25 (reed switch) for the front door and an old Iris (Centralite) Zigbee sensor 3320-L (Hall effect) for the side door… they pick up the magnetic field when the solenoid is energized… positioning was a bit finicky especially with the Iris one… I ended up adding a separate reed switch on a wire because the Ecolink has dry contact terminals and it let me get it exactly where it needed to be… I’ll see if I can find a picture

We have huge warehouse and have multiple doors so here is what I did.

Installed homeassistant
Setup zigbee2mqtt with zigbee cc2538 dongle for long range (now switching to cc2652p)
Modified zigbee door contact sensor (removed reed switch and added push button wires)
Added automation if button pressed play custom mp3 files on Sonos speakers for example someone at front door.

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I have integrated in my dumb doorbell this board which has an optocoupler and can handle 36v DC PSU.
Very cheap and no soldering needed. Only other part you need is a little bridge rectifier to rectify AC from 9-20V AC to DC to power the WiFi board. I have wired the doorbell button through relay in NC so I can disable the doorbell when I need. The optocoupler is configured as binary sensor for the button

Please do. I’m interested.
Also maybe a wiring diagram would be even better…? And does it work well enough to detect short ding-dong?

Sorry about the bad picture… only had a minute… there is no wiring involved… the one contact sensor sits on top for the side door and
The zwave one was originally just balanced in the button area on a screw and with some foam tape… lol. But it occasionally moved so thats why I added the separate reed switch so I could get it right next to the coil without it moving from the right spot… the other white wires you see are part of a video doorbell and have nothing to do with the sensors…
and yea it works with a short ding… even the door that does ding dong is actually just a ding and the dong is the solenoid returning to its normal spot on return…it is a very quick action and as long as it is in the right spot it hasn’t missed one. Anytime it has missed is because I had been up there fiddling with something and didn’t get it in the correct spot.
I can tell you for sure my family hated me for about a day while I tried different spots and made my kids go ring the doorbell over and over.


Sorry… had to come back for more questions.

Per the photo you had, how do you link / position the wires (from Ecolink) to the chime exactly? Is the black wire attached to the metal case that houses the strike bars (those silver bars that would move to strike the bronze cylinders when energized), and then the white wire being attached to… the strike bar itself? Is that how you detect the movement, when the white wire moves and completes the circuit with the black wire? So… normally open contact? (Or maybe I missed the mark by a mile?)

You mentioned you had a reed switch - is that in the photo above? They come in different shapes and packages and size. So which type / spec of the reed switch you are using? Do you actually attach a small magnet to your strike bar? Is the orientation of the reed sensor matter?

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This was the reed switch Cylewet 10Pcs Reed Switch Normally Open (N/O) Magnetic Induction Switch Electromagnetic for Arduino (Pack of 10) CYT1004

As far as positioning it, those two plungers you see are wrapped in the magnetic coils so where the white circle is in top picture the reed switch is placed right up next to the coil and between the back of the frame that holds them. (Just sticking up right next to the coil) so when the doorbell is rang it energizes the coils and makes a magnetic field around the coil… so the reed switch is just placed right up against/next to the coil. If I remember this afternoon after work I’ll see if I can’t get a better picture of the reed switch. But in this picture that is the edge of the reed switch… one black wire and one white wire just goes to each side of the reed switch (DuPont wires with reed switch stuck inside, and stripped and placed in Ecolink terminals on other end)

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Ah! thank you so much!

I thought that was some sort connector we had to do, so that to keep the black wire in contact to the metal frame of those 2 plungers. :rofl:

You can use any standard door sensor up against the coil. Depending on the doorbell and the space you have to work with. The aqara ones are pretty small. No wiring at all if you can get it next to the coil.

I tried a Aqara door sensor, was able to get it to trigger but it would either stay triggered or not trigger at all

My doorbell is a cheap RF (wireless) one. (one battery powered button, battery lasts about a year, and a number of simple mains powered receivers that look like a usb power adapter) I just catch the RF signal with a sonoff RF bridge and act on the event in homeassistant. No screwdriver or soldering needed.