Freezer monitor ideas

[Bridges-PdP]

We run everything off of generators. We have between 6 and 8 big freezers (like you might have in your garage or basement) that I would like to monitor the temperature of. I have a solid Arduino project (that I found here on the forum) for monitoring the outlet the the freezer is plugged into for power loss, but I'd also like to monitor temp inside the freezer. We periodically have one or more of our generators down for maintenance and during those times the power would certainly be off, but it would be nice to know what's happening inside the freezer as well. This week one of our freezers died quietly and without warning. The power was still on, but the freezer's compressor failed. Had we some warning that the temp what changing, we could have moved food to another freezer.

So, my first couple of questions are:

Would the TMP36 be suitable if it was moisture proofed? or is there a better sensor?
Could a single Arduino monitor the temperature in three or more big freezers simultaneously?

I don't have to have exact temperatures, I just need to be able to see if the temp is rising toward zero. Sort of an 'if temp > -5C then do something meaningful (turn on some LEDs, turn on a buzzer)

I would appreciate any ideas, code, help, links, etc.

Scott Bridges
Port-de-Paix, Haiti

[Sparky]

TMP 36 datasheet says it works down to -40C.
http://www.analog.com/static/imported-files/data_sheets/TMP35_36_37.pdf
So it seems like that would work. Adafruit also has a one wire temp sensor that comes waterproofed. http://adafruit.com/products/381

[adafruit_support_bill]

The DS18B20 would probably be the better choice since it is already waterproofed and the digital interface is less susceptible to picking up noise with a longer cable run. With the TMP36, you can monitor up to 6 freezers on an Arduino. With the DS12B20, you can do as many as you want.