How I made my dumb locks a little smarter!

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’ :wink:
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.


Hello OP,

I like your idea so I used it to!



Nice to see some ideas! I was thinking of doing this the other day as I’m not completely sold on doing some door locks, the dealing with batteries, security, etc. But it would be cool to have an automation that would alert me that I armed the alarm with doors unlocked. Looking at little contact switches right now as that is really the only stumbling block, running wires, connecting them to a wemos d1 or a nearby Sonoff in wall switch is easy as cake.

Thanks for some pics of this!

I used a similar, though I kept it as simple and cheap as I could think: I simply ran a wire to the deadbolt, “stuff” some metal scourer in it, connected a wire to it, and connected the wire to the metal part of the door.
When I lock the door, it closes the circuit wire-scourer in the frame-lock in the door-wire.

Connected the wire to a GPIO on my Pi, with a pull-up resistor, et voila

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I like it! No button to wear out. I’ll have to see if there is continuity between the hinge and the deadbolt on my doors. I know one isn’t as it is a wooden door, but the others are.

for a bit more details, I simply put a bit of plastic sleeve to ensure the top and bottom part of the frames don’t touch each other.
I have metal scourer stuffed in the deadbolt and one of the additional security anchors. Locking the door makes the connection between the 2 scourers

Because I hooked my not-so-dumb locks up to my alarm system, I can’t even arm the system with the deadbolt unlocked - just like if a door or a window were still open.

I’m using an Envisalink to connect my ADT system to HomeAssistant, but I’ve seen other solutions discussed here as well.
Like this one that just came with V0.70:

That’s even lower tech than mine - I like it.
But I wouldn’t get away with something like that - not ‘clean’ enough; the WAF, you know :wink:

lol it’s near invisible to the naked eye. Enough that the WAF didn’t find anything against it :smiley:

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As long as I don’t have the wires showing or boxes hanging off the wall/door it would be all good. But I’m not going to have any wires showing on projects in the first place.

Did something similar with my dumb Schlage keypad deadbolt; I’m using the microswitch that is built into the deadbolt to pull down the Garage Door Sensor switch input. Not the greatest integration job; didn’t bother isolating the signal; just tied the two grounds together. Works fine though.

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Is that a ZWave unit you’re using there?


Nice… I did almost the exact same thing at

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I used these… 12" drill bit right into the wall cavity to meet an ESP8266… second larger bit to countersink the nut… looks nice, works great… $1.50 per door ( already had the rest done for Reed Switches for open/closed)


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Hi @CountParadox. That’s a Xiaomi door sensor, right? Any tips or photos of how you wired it up? I tried both removing the red switch and just using the contacts, but I couldn’t get it to work reliably. Thanks.

it was just using tapped off the reed switch, it was still inside

ive since changed to having an external reed switch mounted near the turning handle, and a magnet stuck to the handle, so when its in the locked position it moves near to the reed switch

Thanks you the reply. My application needs a mechanical switch as a reed switch is proving too sensitive. Did the Xiaomi work reliably while you had it running?

yes it did, but the spring and button mechanism didnt work very well. the reed switch worked more reliably for me…

Cheers, @CountParadox . I may give it another try.

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