All I wanted to achieve was to see in my HomeAssistant dashboard if the deadbolts on four doors (front, balcony, office, patio) were locked at the end of the day - and trigger some automation when I go to bed, e.g. tell me which deadbolt isn’t locked when I check if the house is ready for the night…
For a while, I was looking into buying a smart look (or better: 4) to be able to see the status in Home Assistant, but couldn’t get myself to go that route because:
- I only want to see, if the deadbolts are in place, I don’t actually want to lock them remotely,
- my general approach is to NOT have functionality/data in the cloud if I can keep it local at all, and
- my CFO wouldn’t have approved the budget for four smart locks at the current price point, i.e. the well-known WAF wasn’t there.
So I came up with another idea - here it goes:
All I need is to know when a deadbolt is in place, so why not use a mechanism in the lock itself that closes a circuit when the deadbolt is locked and transmit that information wirelessly either to HomeAssistant directly or via my alarm system.
I previously extended my ADT/Honeywell alarm setup with additional door/window sensors (Honeywell 5816WMWH Wireless Door Window Contact Sensor Transmitters) and thought this would be a better route to go that experimenting with ZWave units I had experience with - and from what I’ve read, I’m not too keen on gaining any either. Given that I have an Envisalink module in place already, the connection between the alarm system and HomeAssistant is available already.
In the worst case, I thought I could bridge the Reed Switch in the sensor/transmission unit by soldering in a pair of wires and connect them with a microswitch placed in the door frame. Turns out that the unit has a pair of connectors that can be used with a wired switch directly, so a secondary set of information - in addition to the Reed Switch being open or closed - can be utilized.
When I put the kit into the first door frame it seemed to work fine at first - until the evening came and the sun stopped shining on the door and deadbolt. This caused the pieces to contract slightly so that the microswitch disengaged. Bummer - a design improvement was required!
As I had a bunch of Metal Battery Spring Plates lying around from another project, I now use one of them to provide just enough pressure on the microswitch to keep the circuit closed even if the deadbolt moves away from the switch slightly.
So far, so good!
I installed it on two of the four doors and it is working fine so far and I spent only $15 per lock.
Here are some pics:
I thought I might have to take the Reed Switch (2) out, but I could use connectors (1) instead - the programming of the alarm system is just slightly different.
Couldn’t get exactly the wire I wanted at my local HW store so I decided to double up the wires from a normal telephone cord when soldering it to the switch.
In one lock my contraption fit straight away without impacting the security of the deadbolt, the other one needed a little ‘help’
The cables are all hidden in the door frame or the weather stripping, not much to be seen apart from the Honewell transmitter:
I’m sure this is not something that works for all locks or for all climates, but I thought I share it with the community.