Going to monitor garage freezer, and have ???


Active Member
We just got a new freezer for the garage, and I want to be able to monitor it's temp with HS. I would hate to have it die, trip a breaker or just go bad and loose hundreds of dollars of food.

I already have a Temp08, 1-wire network and sensor within inches of the freezer, so I plan on extending that to an extra sensor inside the freezer.

This 'should' be rather easy, I just have two issues/questions.

1> Where can I get cheap, flat wire to go into the freezer without leaving a leak at the lid. I have seen the stuff but can't find anything cheap, they all want me to buy 100' rolls and I only need 6" - I need to run the wire through the lid seal as there is no other easy, read 'non-warranty violating' methods, to get inside.

2> Has anyone had an experience with 'potting compound' ? I want to 'pot' the circuit board to protect it, but again I am unable to find anything cheap and I don't know if standard epoxy would work. I want something electrically insulating but thermally conductive. I only need a very small amount and hate to purchase $50 worth and end up with an extra gallon, although I could 'pot' the cat... oh wait that would get me into even more trouble... ;)

My wife would kill me if this turned into another of my $100+ automation projects, heaven knows I already have too many of those! (although I have a killer doorbell) :)


Well I was all over this until you threw in that warranty voiding talk. :) I simply drilled a hole right through the back of mine and used clear silicone to mount the sensor nearly flush with the back. On my fridge I found a plastic popoff that could be used to route into the freezer via the ice maker tube. Do you have any plastic popoffs on the rear of the freezer?

Radio shack sells flat phone cord that should work no further than you need to route.
I've fiddled with some of that flat phone cord and found that it was still thick enough to break the seal of my refrigerator. If you use it, you may still need to build up either side of the cord.
I like Rupps idea about the phone cord. Another choice would be to use a regular wire, but bring it through the corner of the door where the gasket breaks.
Not to sound to simplistic, but why not just use an old ribbon cable from a computer that you have lying around? Would this still be too thick?

As far as the PC board I would just make a mold with some carboard and silicon the heck out of it..
How much of a circuit board do you have? Since you just need wires connecting to the DS1820 (or variation) a little silicone and heat shrink tubing should cover the connections. Just leave the "black part" of the DS1820 exposed. You shouldn't need to cover it at all.

If you use a circuit board, just cover everything except the DS1820 with silicone. If the sensor is exposed, it should be ok and accurate.
Thanks for all the ideas... My freezer is a chest type so I am figuring on going in through the lid/door and attaching my circuit board to the lid, this should keep it out of the way. I was looking at potting it for protection, both impact and from the moisture.

I did find some 'flat wire' from here: http://www.21st-century-goods.com/page/21st/CTGY/FW
I like these as they are really flat, and adhesive backed. These should seal.
I will see if they can send some 'samples' as I only need a little bit.

The only temp sensor I have left is already mounted on a circuit board, and I can remove if needed, but I think the board may be easier to mount. Although I will probably cut the board down a bit as it is a lot bigger than needed. I also want the temp sensor to be a bit 'isolated' so I don't see the door open spikes, I think potting will help this.
Your going to miss out on some good "data" if you do not want to see the temp spikes. It's kind of neat to be able to see when the door was opened and closed.
OK, now I'm going to mentioned the REALLY simplistic method.

Why not just put an LED monitor on the Freezer's status light? Why? That way you can tell exactly when it loses power, and not when the temperature rises above a threshold.

I've considered monitoring my Freezer after a recent indicent... (The wife was trimming the hedges and cut the extension cord in half with the trimmer, fortunately it was connected to a GFI outlet, so she did not get hurt, The GFI outlet was on the same circuit as the freezer and I did not know that the freezer was without power until about 20 minutes later, after I had repaired the extension cord). I hit the reset button (which was located where the freezer was plugged in) and restored power to all the affected outlets).

Anyway, had I an LED detector on the Freezer's status light, I would have known instantly what had happened.

Of course, if the freezer malfunctions (or is left open), and the light stays on, this won't help, so maybe you need both (LED detector for instant notification of power problems and temp sensor for other incidents).

Also, as tightly packed as my freezer is, I imagine positioning the sensor is important - because I could see the stuff in my freezer insulating the sensor and the temperature where the sensor is differing greatly from other parts of the freezer.
Good point Dan. I thought it would draw enough power just being plugged in but it would be variable. A relay plugged in would work as well wouldn't it?
I already do quite a bit of power monitoring with those CRMagnetics sensors, they're great (I have one on almost every piice of Home Theater equipment I have). What Dan said about the variable draw of the freezer is why I suggested the LED-type power detector instead. They sell them somewhere at Smarthome, but you have to use a digital breakout box (Smarthomes' BOB, or buy/follow akit/plan available from a fellow who frequents the ADI board) in order to convert it's analog output to digital output (and be able to use it more easily with an SECU16, or other device that detects open/closed relays).

Rupp, I'd guess that if you were able to get the number of wire windings on the current sensor to where they'd trip when the freezer was at its loweest draw, you could still use it. I'msure it could be done through expirementation.
I use my washer machine status LED to monitor when it is turned on, it works great, and didn't cost much at all, just a few bucks in a package of photo cell sensors, bought at Radio Shack. I hooked them up directly to my ocelot, and after installing another resistor, it works 100%. I'll try to finish the How-To today or tomorrow.

I was forced to go this route after BSR finding out that the CR magnetics sensors aren't the best solution, due to the various cycles a washer machine goes through, each having different power requirements, making it harder to detect accurately what is going on.