Hacker News Reader

Comment by Gigachad | Hacker News Reader

I put the Ikea Thread sensor in my fridge a while back and it's been a lot more useful than I expected. My fridge had been periodically getting too cold or too hot, I suspect the issue is that the captive touch buttons that control the temp get occasionally bumped, changing the set temperature. With the thread sensor I can have Home Assistant send me an alert when the fridge leaves the safe zone for too long so I can manually correct it.

It's also been interesting to see when placing hot food in the fridge how long the temperature stays elevated for. I put the sensor in a ziplock bag and sucked the air out of it so it has weatherproofing.

View on HN

And it communicates OK to outside the fridge? I would have thought a fridge is pretty close to a Faraday cage

For me, the Zigbee ones (generic ones from AliExpress) have been great inside both fridge and freezer. Bluetooth ones occasionally dropped off (and were much worse re: battery life.)

What happen to the batteries when inside the freezer ? Sensors seems to be fine at -20°C, but is it the case for standard AAA or CRC32 batteries ?

I can't speak as to what happens with the chemistry but the Zigbee sensors do seem to be fine on standard (not rechargeable) AAA batteries at ~-18ºC.

Rechargeables were worse for me and thus I haven't used them at low temperature for a couple of years - maybe things are better now.

Yeah I thought this might be an issue but it's been running flawless for months without ever dropping out.

It does, though in my case I've purposefully put an IKEA smart plug (which acts as a Thread/Matter router) in the kitchen, too, so the signal only needs to reach 2-3 meters out.

I did the same and just added zigbee repeater outside the fridge.

Works great.

The door seal is plastic/rubber and is RF transparent.

I had issues with my garage fridge last year. Took a while to figure out, but there was a small box at the bottom that was occasionally keeping the door from closing completely. The Zigbee sensor was great tracking what happened when and helping me narrow down the cause.

Did the exact same thing, which is how I discovered our fridge was actually staying around 10-15 deg Celsius inside for half the summer.

Recommend this exercise to everyone.

Thats a cool (!) idea. A zigbee knob + a PID loop would be a nice complement.

The controls engineer in me just vomited at the thought of a PID loop with 6 hr feedback

Did you make sure those hot peaks are not your fridge's defrost cycle?

What would normally happen is I’d start seeing things freeze so I’d adjust it hotter until one time some things went mouldy sooner than I’d expect so I put the sensor in the fridge to get a better idea what is going on. Seeing the data, the fridge seems to once every couple months just move to a colder temp and stay there until I adjust it back again which is why I think it’s just the button getting bumped.

Being able to see the fridge temp to a tenth of a degree and getting alerted when it’s wrong has been much more useful than I expected. The safe fridge temp is a fairly narrow band that’s basically impossible to hit without a proper temp sensor.

Sounds like, in your case, this narrow temperature band is impossible to hit without a proper refrigerator.

PS: You have seen Alec's unbelievably detailed encounter with the cheap red refrigerator, right?

I've worked in grocery retail, and this is exactly the boring problem that quietly eats money: a fridge drifts a couple of degrees overnight and nobody notices until the stock has to go in the bin. a cheap sensor with an alert for "out of range for 20+ minutes" pays for itself the first time it fires. the "too long" part matters more than precision, door openings make single readings useless

Reply on news.ycombinator.com