What's the smallest door/window sensor that you know of?

[sacred badge]

I keep forgetting to fill up the clean water tank on my Dreame X40 Ultra (running Valetudo) before I leave for the weekend and so, my bot doesn't end up mopping when I'm out.

My solution to this skill issue is to install a door/window sensor on the clean water tank and set an automation up that gives me a visual reminder using my kitchen LED strips if the water tank has not been removed at least once in 7 days. I am looking for a sensor that will fit in the space that's available in the X40 Ultra's water tank compartment. As the picture shows, the space in there is pretty dang tight, so I need as small a sensor as is possible. I'm entirely Protocol agnostic.

I'm open to alternative ideas as well. My original plan was to install the sensor all the way at the bottom and to have the magnet connected to a float sit inside a PETG tube that I glued inside the tank so that I could have the sensor trigger when the water level was low.

[ivory dragon]

Personally I'd just use a capacitive water level sensor - either a single low level one or something more involved like this https://thepihut.com/products/grove-water-level-sensor - can just stick it on the outside of the tank wherever there's space to be found

[sacred badge]

I didn't even know this existed! A single, low level sensor would be totally fine, actually. Anything that you can recommend? Having wires there would be a bit of a problem since there's not a lot of space to get wires into the compartment when it's closed.

[ivory dragon]

You could get some "FFC/FPC ribbon cable" to get it out of the lid and to a controller which is like half a mm thick at most - but you'd likely need to use adaptor boards like this (https://thepihut.com/products/adafruit-touch-screen-breakout-board-for-4-pin-1-0mm-fpc) to convert to/from normal wires to connect it up

[vague siren]

You wont find a thinner door sensor than these. They are about 1/2 " wide 7 3/4" long and < 0.2 inch thick. They are Z-wave . I use these because I hate door warts. A little pricy and batteries are not replaceable but should last 10 years for your use case

https://sensative.com/sensors/strips-zwave/strips-guard-800/

[sacred badge]

That thinness is unreal. What do they cost? It won't tell me unless I log in :/

[ivory dragon]

not cheap - bloody hell

£60-70

[blissful rain]

Those thin strips are pretty cool! For small sensors I like the Fibaro, they are very reliable for me (I have quite a few) and aren't too big.

[sacred badge]

Yeah, that's mega pricey. I don't think I'm willing to shell out that much that is essentially a disposable sensor :/

Found a video where a guy used an Aqara leak sensor with some wires to achieve what I'm trying to do. I might try this out. Looks cheap and compact enough.

[ivory dragon]

A leak sensor would work if you've got space for it, yeah

[ivory dragon]

If it doesn't.. i recommend sticking something to the outside of the lid you can easily detect

[sacred badge]

It's hard to tell whether or not it would fit just based on pictures. I've ordered one - let's see. I noticed that this sensor is submersible as well - I could just install it inside the tank and see if that works.

[vague siren]

$40 Amazon US. For what your use is, open <1 /day, the battery will probably last 10 years. I'm going on one year on front door and battery is still at 100%

[sacred badge]

It's €60 out here in the EU 😦

[vague siren]

VAT is great == $64.69 🤑

[marble warren]

Could the sensor be installed to detect the outer cover being opened rather than the lid of the clean water tank?

Here's a mockup. If you look (and listen) carefully you can see the sensor being triggered about the 45 degree point, and hear a remote socket responding to it.

[smoky thistle]

Doesn't someone make tilt sensors too, where you just get a binary ON when an angle is reached? Some are just a ball bearing on a track

Stick that to the lid so it goes off when it's opened

[ivory dragon]

Yeah most things sold as vibration sensors can give you tilt

so long as they aren't tuya

[sacred badge]

I'll look this up. Might actually be a better solution than the leak sensor

[vague siren]

You may be able use a THIRDREALITY tilt sensor . Designed to detect garage door opening but would detect lid opening .
Zigbee. I use one my garage door. In your case it the sensor would be open until lid is lifted then it would detect closed using least sensitive setting, 45 deg from vertical
https://3reality.com/product/smart-garage-door-tilt-sensor/

[distant zenith]

The Ikea PARASOLL door sensors are pretty small and only $12
https://www.ikea.com/us/en/p/parasoll-door-window-sensor-smart-white-70504318/