Door lock sensor in home assistant

by Erik · 2024-03-13

A little project I put together to easily see if the door is locked or not.

The background

I don’t want any smart locks (yet) but still get reminders if the door is unlocked or be able to double check “did I really lock the door?”

Implementation

The solution was a Fibaro door/window sensor (version 1) which has dry contact points for external switches. This can of course be done with any device that allows screwing/soldering on external switches. Ex Aqara’s door/window sensor. In this case I wanted a small sensor and then Fibaro’s oblong design was perfect.

First, I removed the plastic cover for the sensor to slim it down a bit, it will sit in a 3D-printed housing so the cover is not needed as protection.

In the door frame I drilled a hole for the Fibaro sensor. The hole is extra deep to be able to house a full-sized 3.6V battery, which I replace with the next time the battery needs replacing.

Size comparison of the 3,6V batteries

3,6V full size AA, 2400mAh

3,6V, ½ AA, 1200mAh
This is the default one for the sensor.

A simple microswitch is mounted in the lockbox, which is then connected to the Fibaro sensor via a diagonal hole up through the frame/wall.

The 3D printed plastic tube has a recess so the tube can go further in than where the diagonal hole meets. Everything is assembled easily and the hole is covered with a 3D-printed cap.

How this is used in everyday life

Reminders via the Home assistant app to lock the door where you are the last to leave the “home zone”
A light in the bedroom that changes color when the door is unlocked but the “sleeping” scene is activated
Be able to double check the status of the lock when you leave home.

Next step

Next up is the same installation in another front door. This is usually locked and the solution is upgraded with an LED embedded in the door frame that lights up if the door is unlocked, so that you can quickly see if the door is unlocked or not.