How do I use a temperature probe in a freezer?

August 20, 2015 7:06 PM

I'm trying to use a DS18B20 probe with this super rad Reed Kumosensor inside this upright freezer. Is it safe to just start drilling holes in the side of the freezer, or is there a way to fish the probe in somehow?

I've had great luck with Wireless Sensor Tags, but the poor sensor is having a heck of a time transmitting through a metal box. Additionally, the cold is super hard on the battery. Since the freezer is in a detached garage, it's pretty far away from the receiver, as well.

Putting a temperature probe on this reed sensor seems like a good solution to a lot of problems. The radio doesn't have to transmit through a metal box, the batteries are kept warmer, and as an added bonus I get to use the reed sensor to tell me when the freezer is open. The only problem is actually getting the probe in there.

I'm reticent to just have the wire loose in the door - I hear this is asking for condensation problems. So can I get away with drilling a hole in the side or top, or will I hit a coil? If so, is there a way to snake the probe in somehow?

posted by cr_joe to Technology (8 answers total)

You could splice some flat wire to the sensor and feed that through the door seal. Much less leakage than drilling a hole through the insulation. Maybe put some putty around to help it seal.
posted by notsnot at 7:20 PM on August 20, 2015 [1 favorite]

I think you are safe drilling a hole in the door.
There could be cooling coils anywhere in the box, so I wouldn't drill there without calling the manufacturer.
Seal the hole with caulk or putty.
Try to position it where someone won't whack it with their knee.
posted by H21 at 7:30 PM on August 20, 2015

Best answer: I'm considering doing just the same thing (though with a different freezer). Given the door is detached, I'd drill through that, and fill any gap with some putty.

Alternatively, is the seal between the door and the body of the fridge thick enough that you could drill just through that and thread your sensor wire in?
posted by pompomtom at 9:55 PM on August 20, 2015

I would try just threading it in through the door first to see if there are any condensation problems--it seems like you're more likely to have cooling problems by drilling through areas not designed to deal with it. We do this with a few fridges and freezers in my lab (though with a flatter wire) and the effects are minimal.
posted by tchemgrrl at 5:02 AM on August 21, 2015

I'd crimp three lines of kitchen foil to the sensor wires and run the foils out under the door seal, stuck down with a piece of packing tape which I'd also use to tape the crimp joints to the inside wall.
posted by flabdablet at 6:03 AM on August 21, 2015

Don't drill through the cabinet; there are both refrigerant lines and electrical wiring hiddened between the walls. Drilling through the door should be safe but check for wires fed through the hinges.
posted by Mitheral at 6:23 AM on August 21, 2015

Best answer: Dear lord don't drill holes in your freezer.
My thermometer-geek husband just closes the door over the wire when he wants to check the fridge or freezer temp. Any leak in the seal is pretty insignificant for short checks. A flat wire is probably a good idea if you want to leave it there permanently.

If you really want a hole, drill a hole in the seal, run the wire through it--or run the wire under the seal-- and then seal up the hole somehow, although that may leave a bigger bump than the wire alone.
posted by SLC Mom at 8:07 AM on August 21, 2015

I used to work at a biotech that had about eighty lab freezers. They just threaded the tiny temperature probe wire thru the door seal.
posted by LoveHam at 12:54 PM on August 21, 2015