Hello OP,
I like your idea so I used it to!
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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 
lol it’s near invisible to the naked eye. Enough that the WAF didn’t find anything against it 
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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 https://www.reddit.com/r/homeautomation/comments/77x2lw/i_made_a_diy_contact_sensor_to_monitor_a_normal/
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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)
Enjoy!
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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…
Hi all 
Just wanted to share my take on the idea, this is such an awesome idea! 
First I took my Xiaomi door sensor and soldered on the contacts.
Then I soldered the ends of the wire on to two battery springs which are glued on to a piece of cardboard. Also had to glue a piece of tinfoil of the deadbolt to make the contacts trigger.
Ran the wires and stuffed the board back into it’s case.
NOTE 
My sensor was being really unresponsive/reporting the wrong state at first. I had to try all sorts of position for my sensor, and finally found a spot where it works.
Now it works! Huge thanks to everyone for sharing the idea 
!
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