Great minds…
Pi Zero W is a good choice, as it already has inbuilt wifi also an ESP8266 is possible to use. I just plugged it into the socket next to the doorbell (which is obviously inside my appartment). But a Pi needs 5V/2A, so may be you can hook it up there
Right, ESP8266 is great solution and way cheaper then the pi (and smaller).
With this solution, I have 1 big problem to solve: how to send/transform the signal of the ring to the input of the ESP
I will ask in some electronics forum where is more on topic.
Nevertheless I try also here: I just checked the instruction of my receiving doorbel which has two pins for an additional buzzer (one pin for the “signal” and one pin for the “negative”), may I connect it to the PI and/or ESP8266 without the need of diodes/resistors/capacitors and all that jazz for which I understand nothing? 
I’m doing this with a relay & a fibaro z-wave doorsensor (which has a binary sensor input, could also work with a dedicated binary zwave sensor Universal Binary Sensor FGBS-001). So all ‘analog’ stuff/doorbell still works, it just also switches the relay and the relay switches the binary sensor. All easy to build in in your existing bell housing without a change in wiring. I have automation setup to send notifications/Google home/picture etc.
Example project here: (it’s in Dutch but you can use Google translate) https://www.robbshop.nl/domotica/projecten/z-wave-deurbel#
that’s another great idea: I could use also a Xiaomi door sensor (see below). PArdon my ignorance, but when the external doorbell is pressed, in the internal unit you think should have two pins and receive a relay-like signal (close on press or open on press)?
The above would solve the size problem (the xiaomi are very small, even smaller then the fibaro) and the power supply (they are battery operated and last easily a year)
Nifty! I don’t have anything from Xiaomi and don’t want to add another hub (I think this is Zigbee?) but sounds like a good alternative.
That’s the Xiaomi door sensor opened, if you short circuit the little fuse at the bottom it triggers the sensor
I connected a relay to my doorbell.
Checked the doorbell with a DVM, and it puts out something like 15-16 VAC. There is a transformer in my garage that generates this voltage.
So the relay is connected to the doorbell so it sees a voltage when you push the button, and this closes the contacts. The contacts are connected to an ESP, and causes an input on the ESP to change state, and send a MQTT switch message to HA.
So you would need to measure the voltage to your doorbell, find a relay that changes state at that voltage, and then figure out how to wire the relay up to your doorbell. My doorbell wires are available in my garage, so this was pretty straightforward.
With this scheme, pretty much all you need is a relay, some wire, and an ESP with a power source for the ESP.
Randy
I use a Xiaomi door sensor - I have a traditional wired doorbell pusher outside, then I just disconnected the doorbell ringer in the house, and soldered the wires onto the Xiaomi door sensor.
This way, when the bell pusher is pressed outside, it completes the door sensor circuit and triggers my HA automations.
mmhh so if that’s my case I would probably fry my Xiaomi … ? Sorry pretty newb about electronics here
Ohh interesting, but why you disconnected the ringer, because you would have problem for the Xiaomi sensor? I rather keep the ring, since its good to have.
Other question, you have the Xiaomi first version or the Aqara version, in case is the second would you mind sharing where to solder the 2 pins?
EDIT: nevermind, its the same as fdirst version: desolder the reed switch and solder 2 wires)
In the US, I think an ac voltage like this is pretty common for doorbells, not sure about other places.
Do you have a meter? They are cheap these days, and really helpful for these projects.
You could measure the voltage going to the chime when you push the button too.
I didn’t desolder any reed switch on mine, it had some contacts that I connected to which i assume gives the same result.
I disconnected the traditional ringer since it was just a bell, but now I can use automations to have my own bell via speakers etc… it means for some fun at Halloween with spooky door bell sounds, and Xmas etc…
Ahh ok, I thought was needed, while seems its not. Now wioll have to see which two wires are triggering the bell (i.e. external door button press) in my doorbell internal unit
well if someone passes with a magnet near your doorbell internal unit it will trigger it, but I guess its a unlikely event
The luxury of power to the doorbell is not readily available for me, so I’m currently using a Flic button. This works okay, and the battery lasts for months, but has two disadvantages: it takes 2-3 seconds before a notification occurs, and it connects to an iPad which can fail if the iPad is upstairs. As a result, I’m thinking of changing plans.
I also have some mcModules from the original mcThings Kickstarter. They operate for years from a battery, and you can write fairly simple code using a VB-like language to send MQTT messages on button push. I just have to get the soldering iron out and find a suitable doorbell enclosure. That’s the main stumbling block.Currently I’m just using them as temperature sensors, but they also have an accelerometer and reed switch. The downside is they’re only cheap if they’re already lying around the house.
I tried this too. In one position its ok (when pressing the button i.e. door closed), when idle it receives some not clean signal and the Xiaomi sensor is erratic (on/off/on/off very quickly, totally unusable).
I guess it needs some electronics to “clean” the signal when the button is not pressed. But how is beyond my electronics knowledge
I have a traditional 12VAC doorbell. Into the bell housing on the wall, and only there, I added (from AliExpress):
An Esp-01 (£1.30)
a KY-025 reed switch (£0.29)
LM317 AC - DC Adjustable converter (£3.42)
a few wires (~£0.20)
a mini breadboard (~£0.16)
I installed sonoff tasmota on the ESP-01 (total overkill), using atom. secured the reed switch to the bottom of the internal solenoid ringer. set the ac/dc to 3.2V. Powered the ESP (on EN and VCC) and the Reed from the breadboard. Connected ESP to WIFI, Chose generic18, set GPIO2 to Switch1 in Tasmota, hooked the reed switch up to GPIO2. Subscribed to MQTT server running on HASSIO Pi with ‘doorbell’ topic. Set up an automation to send me a HTML5 notification including photo snap shot of security camera covering my front door.
Result; sub £6 ‘Smart Doorbell’.
No Two Way comms and I have to take action to see a live camera feed, but I can see instantly if its a particular delivery company, or a visitor.
Config.yaml
- platform: mqtt
name: "Doorbell"
state_topic: "stat/doorbell/POWER"
Automations.yaml
- id: '1535928645329'
alias: Doorbell
trigger:
- payload: 'ON'
platform: mqtt
topic: stat/doorbell/POWER
condition: []
action:
- data:
data:
image: https://'myurl'.duckdns.org:'port'/api/camera_proxy/camera.approach?api_password='password'
message: The doorbell has rung
title: Doorbell
service: notify.homeassistant
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Inspired by this thread, I added a ‘smart’ door sensor to my dumb wired doorbell without other electronics or wiring.
The catch is the doorbell has to be using electromagnet to ring the bell so the reed switch of the sensor will be triggered when doorbell button is pushed. If you have the digital kind that play different ring tones, I image it’s still possible to wire a electromagnet to it for this purpose.
The door sensor behaves like a momentarily switch sensor, shows “off/close” when the button is pushed and then switch back to “on/open” after 1 second or so (bell done ringing).
Also, since our doorbell has front and back door buttons which ring different bells (i.e. 2 electromagnets), I’ll be adjusting the sensor position so it will be triggered by both buttons.
If you have the electromagnet-style doorbell like mine, give it a try, find the magnet(s) inside the bell housing and place the sensor as close to it as possible, that’s it. Remember to set up automation/trigger like for a momentarily sensor.