Aqara contact door lock sensor

This print will allow you to build a small sensor to place within your UK uPVC door latch to report lock/unlock state without needing any changes to the lock or requiring a smart lock.

I have two different UK uPVC doors and this design fits in both perfectly so I assume they're fairly standard but I can't promise it'll fit in yours. The opening of mine measure "14mm x 66mm with a maximum depth of 25mm" and given these are a tight fit I'd say you'll need the same to use this. 

I created v1 of this model two years ago and have been using it on my back/front doors daily since. I'm still by no means a 3D designer so it's pretty basic but they've been nearly 100% reliable over that time. Over the years I've had to change the batteries once or twice and on one occasion the glass reed switch had suddenly smashed so I thought it was time for a slight improvement to the design.

This version changes the glass reed switch out for a plastic encased one which should hopefully provide much more protection and also removes the base of the casing allowing you to easily swap the battery/reset button without having to remove the board from the casing which can be difficult once assembled. I've had this installed for the past week and it's operating just as well as the v1 which is no surprise given the similarity.

The design choices are a combination of: My basic design skills, what fit within my door whilst allowing the lock free movement, the perfect distance between the magnet and the sensor and ease of build.

Printing: 

• Inverted files are provided depending on how your door opens, I use one on my back door and one on the front but hopefully it's clear by looking at your door and the stls which is required.

• The stl files are correctly oriented to print

• Use supports on the main frame, I used tree.

• No other specific print settings required, I printed at 10% infill, 0.16mm layer height on my K1C.

You'll need:

• An Aqara contact sensor (https://amzn.eu/d/0exv02C5)

• Plastic Reed Switch (https://amzn.eu/d/05teoK43)

• Some short wires, I've used solid core which I'd recommend for nearly everything (https://amzn.eu/d/0g075TC8)

• 10mm x 3mm x 2mm neodymium magnet. Measure this fits on your lock, try to keep it on the tinner side if picking a different one (https://ebay.us/m/ysrIT8)

• Epoxy glue (https://amzn.eu/d/04MLiOHj)

• Some double sided tape to stick the print to the inside of the door latch (https://amzn.eu/d/05fRk8EO)

• A soldering gun

Assembly steps:

1. Print the correct orientation for your door. The main frame is required and the extra friction fit casing sections are optional depending on if you'd like more covering around the sensor/reed contacts.

2. Pop open the Aqara sensor and cut off the existing reed switch with some flush cutters. 

3. Cut a couple lengths of wire slightly longer than expected and solder one to each of the old reed switch contact points. 

4. Fit the reed switch into the gap on the frame (this should be a tight fit) and place the aqara sensor into the printed case. This should now give you a good indication of how long the wires need to be and how to route them to the ends of the reed switch. You can see where mine are routed in the pictures.

5. Solder the ends of the wires to the reed switch, ensuring the wires are tucked into the grooves on the print so they don't protrude from the back of the casing. Now is a good time to test everything works before fitting with a magnet. 

6. Optionally now you can put on the extra casing sections to mostly cover the switch contacts/aqara board. These were a bit of an after thought so sort of slot into place.

7. Place a couple of small strips of tape against the back of the frame, squeeze the sensor into the door latch and press against the side to secure it in place. At this point test that you can close and lock the door as before, there should be no noticeable difference. 

8. I used epoxy glue to secure the magnet to the lock bolt as I didn't want any chance of it coming free, follow the instructions on your chosen method to secure this on. 

9. Done! When I need to replace the battery I just grab the top of the frame with a set of needle nose pliers, pull it out, replace the battery and tape and secure it back in. I tend to get around a year per battery, HomeAssistant automations alert me if the door has opened (another aqara sensor) without the lock changing to signal something is wrong with the sensor/battery.