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.homeassistantInspired 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.
Hi
I did almost the same thing, works fine 
I took an old electromechanic doorbell, the type that says “ding dong” and glued the xiaomi door sensor to the side of magnet. When the magnet moves (for the ding-dong), the doorbell triggers
Wireless push button on the outside. No fuzz with contacts or cables. I didnt even have to dismount any casing, just tried a few positions of the door sensor before it worked 100%
I am the only one with an electronic doorbell 
Should be able to use a mimo lite if you have a traditional doorbell.
Do you have any pictures? which part of the door sensor are you using the ‘bigger’ one i assume?
I was about to order the Mimolite to use for this, as in the video, but the specs on it say 0-16vdc, and doorbells (in the US, at least mine) is something like 24v and AC. Am I missing something how this would be used? Do you need to rectify and divide the voltage and count pulses? Or is there a way to wire this I am missing?
I thought it could do up to 120vac and 24vdc? in the video I can see 120v and 24v on the relay and he even states as such.
I’m looking at the specs for input (not relay):
Input Signal 1 (SIG1): Digital or Analog Input 0 to 16V DC or 16 Hz Max for pulse counting (minimum 32 ms high or low time). The trigger levels and hysteresis can be set via the Configuration Command Class for the two endpoints.
I’ve decided to go back to the reed switch. I had a zwave contact switch, but it would not respond fast enough to a quick push of the doorbell. Instead I took an esp8266 and a reed switch and that seems to work just fine, I can’t hit the doorbell fast enough to miss it, though I need a debounce time or sometimes it senses the same push twice (debounce on off not on).
I used it for a bunch of testing on a breadboard, and now am wiring it up on a little PCB in a case. Debating between a hot glue gun or just tape to attach the reed switch in the chime housing while I wait for amazon to deliver cases. hardest part is getting power to it without the wires showing, debating actually adding a couple of outlets above the kitchen cabinets, that might be handy for lights as well. But the doorbell aspect seems to work nicely with esphome, only requires the twi wires going to the reed switch, a lot simpler than all the other things I tried.
frenck has a really nice write up for a smart doorbell. It does not have the two way audio from the original request, but is really well written and can give some ideas for anyone interested. I have one programmed, but have not yet installed it.
My doorbell does use ~16vAC, so I need an additional piece to convert this to 5vDC to power the esp01s, but I plan to just tie this into the transformer.
DeadEnd
@DeadEnd I built the Frenck doorbell, works great. I also had an AC 16V transformer in my door bell and just bought an AC to 5VDC converter based on a 7805 regulator off eBay.
I decided to solder this up and go without a case and just use gaffer tape and put everything inside the chime box.
Reed switch is just stuck up near the coil on the front door actuator: It’s on the end of the blue/blue-white wires and just hanging in space (the wire is UTP solid copper so fairly stiff.
Then it’s attached between ground and D4 on the ESP8266:
And stuck to the inside of the chime box, and fed from a USB adapter.
binary_sensor:
- platform: gpio
pin:
number: D4
mode: INPUT_PULLUP
inverted: True
name: doorbell_pushed
filters:
- delayed_off: 200ms
MQTT feed to Home Assistant as a binary sensor, and automation to speak the words “Doorbell - Someone at the door”.
Works great. About as simple as it can be. If the gaffer tape doesn’t hold well I will probably give hot glue a try for the reed swtich and maybe PCB.
- alias: "Doorbell was run"
trigger:
- platform: state
entity_id: binary_sensor.doorbell_pushed
to: "on"
action:
- service: media_player.volume_set
entity_id: media_player.all_minis
data:
volume_level: 1.0
- service: tts.google_say
entity_id: media_player.all_minis
data:
message: 'Doorbell, Someone at the door'