A list of door sensor / reed sensor hacks! (Aqara, Xiaomi, others)

There’s so many cool little door sensor hacks floating around that I thought it might be useful to have a meta thread? Like this one.. I really like the Aqara ones, which are small, cheap, and reliable in my experience.

I’ll add the one’s I know about, and add one I’m just playing with.

  1. Chair Occupancy Sensor
  2. Door Lock Sensor
  3. Rain Drop Sensor
  4. Weber BBQ on/off detection
  5. Gas Meter

Edit: Added from this thread. This may not be well maintained so scan the thread too.
6. Rain Gauge
7. Water Level
8. Bed Occupancy
9. Smarter ding-dong-doorbell
10. Power loss sensor
11. Kidde smoke alarm interconnect sensor
12. State sensor for dumb air con
13. Chair Occupancy Approach #2

My new (?) sensor:

Tilt sensor (using ball switch):

  • Yes Xiaomi have proper multi axis tilt sensors.
  • This one is a bit dumber, a bit smaller, a bit cheaper.
  • I’ll use it for my blinds up/not up state.

Sure you could figure out a tidier solution, but not too bad like this. It doesn’t quite fit inside.

Have you seen others around?

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I will add my contribution to the list:)

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Does it have to be Aqara based? I have an old Qurky tripper that I use as a loss of power to the house sensor and a Zwave sensor attached to my kiddie interconnected smoke alarms.

Both of these could easy be used with an Aqara sensors though.

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I’m using one with an FSR for bed presence detection.

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Using a door sensor to detect door bell / chime with mechanical ding-dong strikes:

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I reckon whatever brand. I’ve adjusted to title to reflect.

I “kind of” get your examples, but I suspect if you elaborate a little more, others may replicate your success;)


Power loss sensor setup
Door/window sensor of your choice
5v usb power supply
USB cable you can cut or is damaged
5vdc single pole relay (https://a.co/0C8jUhC)
Maker box or something to hold the relay
Soldered wires to each side of the reed switch of the sensor and attached those to the Normally Closed side of the relay.
Connect postive RED from USB power to DC+ and jumper that over to the IN
Connect negative BLACK to the DC-


@Cbarth3 thanks for sharing this sweet setup. I was thinking about just this same sort of thing in order to get an instant power off trigger in HA, especially for the blips of outage that happen in storms at night.

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Kidde smoke alarm interconnect sensor
I made this when I first had Wink, moved it over to SmartThings, and now have it in Home Assistant.
Kidde SM120X Interconnect Accessories Smoke Relay Module https://a.co/hov76Yx
I would imagine there is a first alert version also.
Door/window sensor of your choice
Mine is a Go-control and I have had this setup since I started with Wink in 2016. At the time they didn’t see the external contacts so I removed the reed switch and Soldered wires to the pads.
Drywall box to put the relay in
Blank wall plate to install sensor on
Some wires to connect relay to smoke alarm wires

I added an up close of the relay module as it has the wiring printed on it.

Caution the smoke alarm beeps in this video


@Cbarth3 just ordered my parts for this project on AliExpress for cheap and will be tackling this when the items arrive. Is there any reason that you didn’t put the door/window sensor inside the project box?

@timnolte No just figured it would be easier to change the battery when needed.

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I have a Sonoff SNZB-04 sensor with the magnet mounted on the flap of my dumb Daikin air conditioner to give me a indication that it is on.


Nice. I do the same actually. Forgot about it;)

And as occasionally the ir signal from my broadlink ir/rf hub is not received first attempt by the air con, I retry if the door sensor state hasn’t changed to the correct position.

Another chair occupancy approach.

My parts arrived and I finally tackled the build tonight. Got everything added into Z2M/HA and my automation built. This is perfect and will see how my automation works out during the next power outage.

I did end up moving things around slightly in the project box from that picture as the relay and sensor were too thick to be on top of each other. My project box didn’t come with screws so I’ve currently got it kept closed with rubber bands.

I setup a Template Sensor based on the door/window sensor state as a clear way of seeing the “Power Service Status” as either “In Service” or “Outage”.


Hi guys,

Hi everyone, since all you guys seem to be gurus at this, though I’d ask here.
I’ve accidentally damaged the reed switch on one of my old Xiaomi contact sensors MCCGQ01LM

Does anyone know what specs I need to confirm when buying a new reed switch? Looks like there are different diameters

I would go for the Aqara door sensor, that’s what I’ve used for my projects, and they work perfectly.

My Rain Gauge is running two years already, on the same battery!

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Do you want to replace just the actual glass reed switch?

I would measure the length and diameter of an unbroken one with a caliper if possible?

I suspect you may still be able to solder, fit and position an oversized one in the casing if required?

I’m guessing N/O normally open is what you want?

Yeah great point, I measured with calipers and it’s 2mm x 14mm

I would assume it’s N/O yes

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