Smart Door Opener with Legacy (1970s) Intercom

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Whole project documentation: https://github.com/raphis/koch-esp-door-opener

In our multi-apartment building we have a 1970s Koch K933UP/K3 intercom system installed.
The goal of my project to be able to open the building’s main door from any of my Aqara Zigbee buttons. This should be done via the legacy intercom system without interfering too much with the installation.

The hardware is based on the Wemos D1 mini with a relay shield on top. I didn’t want to take the risk of interfering with my neighbors intercom so I decided to have a dedicated power-supply for my project.

The D1 stays usually in deep sleep mode and only wakes up and connects itself to HA when somebody ringed the bell. HA is then informed via a webhook that something happened.

The interaction looks as follows:

Untitled (1)
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Schematics:

Schematic_Door-Opener-ESP D1_2021-02-28
Schematic_Door-Opener-ESP D1_2021-02-281169×827 40.6 KB

Hardware:

download
download768×1024 46.2 KB

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There are a lot of people want to do this kind of stuff, or even tryed it.
I for my self had a hard time to figure out, how to do this.

The biggest Problem for the most people is, to deal with the electrical parts, because every doorbell is different and deals with different powers. Some using AC, some DC, What works for some people, goes terrible wrong to others.

I’m not good in these electrical things, but was thinking about how to help people to calculate the needed parts, like resistors and diodes.

For my old Siedle, im getting 10V AC if someone is ringing. Im using a very big Buck Converter Modul, AC-DCto bring this down to 1v DC for the ESP. And a Relais for the door opener.

But this is a big bulky solution which could be much slimmer, if i would now how to calculate the z-diode/resistory and choosing the right parts.

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btw: i found a nice solution to open the door with actionable-notifications. The script sends a push with the actuall camera live-stream and i only have to hold the image to get the door open. Maybe this could be an update for you.

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Thanks for your inputs. Indeed the resistor needs to be adjusted based on the voltage on the speaker. I added a section to the documentation on how to calculate the value of the resistor: https://github.com/raphis/koch-esp-door-opener

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Hope this makes it more clear and helpful to others as well. Regarding AC/DC: in general this could be done with DC as well - no problem. The diode in the opposite direction won’t be needed then anymore. And obviously for DC you have to connect + and - the right way.

For your use case: I think you’d be fine just using a bigger resistor instead of the bulky DC converter :wink:

Thanks for the actionable-notification recommendation - I will have a look into that as soon as I can. Currently I used my Aqara Button to open the door. 1-click is usually turning the light on/off - if the ESP is online the behavior switches and 1-click opens the door for 3 seconds.

alias: Aqara Button 1 - Living Room
description: ''
use_blueprint:
  path: SeanM/zha-aqara-wireless-mini-switch.yaml
  input:
    aqara_mini_switch: 67d31d244b0472b931e95d849a968761
    button_single_press:
      - service: input_boolean.toggle
        data: {}
        entity_id: input_boolean.livingroom_1click_button

alias: 'Living Room 1 Click: Door Opener ESP'
description: ''
trigger:
  - platform: state
    entity_id: input_boolean.livingroom_1click_button
condition:
  - condition: state
    entity_id: input_boolean.door_opener_esp_online
    state: 'on'
action:
  - service: script.door_opener_esp
    data: {}
mode: single
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See, thats the experience i don’t have to play around with electronics.
Thanks for the infos.This makes sense. :slight_smile:
Im going to try it again on the weekend.