Hack your Intercom for remotely open the door

This article will explain how to add the ability to remotely open your door having a not smart/connected Intercom (Bticino 366821) using a Sonoff RE5V1 relè.

Sonoff RE5V1

Sonoff RE5V1 is a nano size wifi relè with dry-contact output, also known as a volt free contact. It means that no energy is applied to the two OUT pins: the power/voltage for the load is not provided from the relè but is instead supplied by another source, the Intercom in this example. OUT pins only closes the circuit like the manual micro button would do in the standard intercom, and being soldered in parallel to the button both will keep working. Sonoff RE5V1 is instead powered by a different 5V source, like an USB charger.

Following the wiring diagram:

Before proceed: implement this procedure at your own risk, it works for me, it’s up to you the decision to modify or not your own devices.

Prepare the Sonoff

Sonoff wiring is pretty simple:

  • Cut a spare USB cable and soldered the 5V and GND wires to the Sonoff power source
  • Solder other two wires the the OUT pins
  • 3D Print a little enclosure to secure everything together.
  • The most tricky step is to solder the two OUTPUT wires from the Sonoff to your Intercom Micro Switch button that normally is pressed to open the door.
  • To Identify the right pins on your device, try connecting the micro switch pins using a jumper wire until the door is opened.

3D Print Eclosure

STL files for 3D printed enclosure available here

Sonoff setup

To enable your Sonoff relé you can follow the standard procedure for all ITead products:

  • Power the sonoff device with 5V
  • Long press (5 secs) Reset button on the back until it start to blink
  • Open eWelink app
  • Click plus icon on bottom side of the app
  • Click Quick pairing
  • Click Add new device
  • Wait some seconds until the device is discovered
  • Assign a name, for example “Smart Door Opener”

If the device is not founded be sure to have a 2.4 Ghz wifi enabled ( temporary disable 5.0 Ghz channel if you have it)

Go to you Device Setting from the eWelink app and enable Inching feature with 1 second timer.

At this point you are already able to switch on and off the relè from the eWelink app, if you want to integrate it also with Home Assistant server go to next chapter.

Home Assistant Add-on for Sonoff

There is an official add-on to integrate sonoff devices that support also LAN mode.

The steps are so easy and very well described in the official site, so I’m not going to repeat anything here, just use following link: Sonoff Home Assistant add-on

At the end you will obtain a switch entity:

Click on it to set the Inching timing, so that after 1 sec pulse the relè is automatically turned off.

Do not forget that Alexa will automatically detect the device, so you could also open your door with a voice command!