Where to place temperature sensor in a chest freezer

I want to place a DS18B20 sensor (waterproof, with long cable) that I want to mount in a chest freezer.

[arduino based project] The arduino will send me emails if the temp goes high, and a "I am alive" email every few hours. I also have a watchdog program running on my computer.

Where is the best place to place the sensor, and the best way to attach it? I'm thinking of wire clips held in by hot glue (will hot glue work at 0°F or lower?) to attach it to the plastic inside of the lid.

The inside of the freezer is plastic, and the "food" area is a dimpled metal. Ice sometimes builds up on the metal, and I don't want the sensor in a layer of ice - it would not be sensing temperatures accurately - just the temp of the ice!

Any help would be appreciated!

Insufficient information to even offer a guess. What is the size of your freezer, length, with and particularly the depth. What type of cooling? Regular refrigeration system or electronic using Peltier devices?

Where is the cooling done(coils)? Keep the sensor as far away as possible from this area as it will always be the coldest.

How often is the freezer opened? If seldom opened, then anywhere away from the cooling system will work. If opened regularly, then the sensor near the open top will see the warmest air.

Paul

It is a 3.5 cubic foot freezer, powered by 110V. I believe the coils are underneath the metal "food" section, or to the right side of the freezer. Alarm to basically alert me if the freezer has lost power, or is not working anymore, or if kids left it open.

The freezer is in a garage, and may be opened 1-2 times a day. It is used for foods I buy in bulk.

If sensor is on top door, I can add a delay, ie if temp is too high, wait 5 minutes and take temp again. If temp did not go down, alarm - something like that.

Use a cable tie to hold sensor to the grill.

BigBird0000: It is a 3.5 cubic foot freezer, powered by 110V. I believe the coils are underneath the metal "food" section, or to the right side of the freezer. Alarm to basically alert me if the freezer has lost power, or is not working anymore, or if kids left it open.

The freezer is in a garage, and may be opened 1-2 times a day. It is used for foods I buy in bulk.

If sensor is on top door, I can add a delay, ie if temp is too high, wait 5 minutes and take temp again. If temp did not go down, alarm - something like that.

That would sure work. All the "cold" is in the products you have in the freezer, not the air. Suggest you find an ice bag, like you freeze and put in a picnic basket to keep stuff cold. Attach a sensor to the bag and keep the bag on top of everything.

Paul

Sensor need to be at the top, monitoring the warmest part of the freezer. Some of those waterproof DS18B20's don't last forever as they aren't actually hermetically sealed (epoxy is permeable to moisture).

Hot melt glue will be very brittle at those temperatures, will crack I suspect.

I’d use one of these ( you could make your own) and use a self tap screw into the lid insulation.

Getting cable out is another issue . You might try sending a temperature around the compressor ( hot or cold) to indicate it’s running ( or a vibration sensor on it) . Less invasive that making holes

https://www.pegasusparts.co.uk/ourshop_90073/prod_4312998-41379-Clip-for-316-Brake-Pipe-Metal-type.html

From #3: Use a cable tie to hold sensor to the grill.

This may be the best approach. I couldn't get any kind of tape to stick to my freezer.

From #4 That would sure work. All the "cold" is in the products you have in the freezer, not the air. Suggest you find an ice bag, like you freeze and put in a picnic basket to keep stuff cold. Attach a sensor to the bag and keep the bag on top of everything.

Another good idea. I have my probes in pill containers filled with glass beads or RV (non-toxic) anti-freeze. These are stuck down among the contents of the freezer.

From #6 Getting cable out is another issue . You might try sending a temperature around the compressor ( hot or cold) to indicate it's running ( or a vibration sensor on it) .

Not such a good idea since a refrigerator that has lost its coolant will run constantly and not get very cold. I splice a few feet of ribbon cable onto my probe wires and run the flat ribbon out through the gasket.

Don

Something you may want to consider as to your sensor placement and temperature set point for an alert is not placing the sensor too deep in frozen cold. Especially in a smaller chest freezer where things are stacked if they are stacked. If I place a sensor in the midst of 50 Lbs of ground beef there will be quite a thaw before I know about it. I would think the idea is to know about potential thaw before it happens.

Ron