mazzmn in the Element 14 community posted this great project that he made and a tutorial showing how to do one yourself!

I’ve been blogging about my experience in Road Test reviewing the Ultimate Raspberry Pi Bundle. As a part of this Road Test I’m creating a Fridge/Freezer Temperature Alarm system for our local food shelf, Channel 1. You can see where this Road Test started for me here

Background info:
Last Christmas vacation, I volunteered for a local food shelf called Channel One. I was chatting with the warehouse manager and he mentioned that their large freezer and cooler rooms are protected by commercial monitoring systems, but he’d really like a temperature monitor for their walk-in display-case cooler and freezer. The food shelf is closed from Friday Noon until Monday at 8am, they’ve had several cases where the unit has blown a fuse and food has been ruined. My goal was to use the Ultimate Raspberry Pi Bundle to build a low cost temperature monitoring system that can send free text messages when the temperature in the fridge or freezer is outside of the acceptable range.

Project Objective:

• Monitor the temperature of the Freezer and the Fridge Unit – the valid temperature target is 33F in the fridge unit, and -10F in the freezer unit. However, during business hours, the doors are opened by customers and stocking personnel, so the the fridge could possibly fluctuate to 60F. So allow for a wider temperature range during Business Hours vs Off Hours.
• Audible temp range alarm. Make some noise when the temperature is out of range.
• Snooze Alarm – If the temperature range is out of whack, support a button that stops the noise.
• Text message – when the temperature is out of range, send a text message to someone who can either fix the problem, or move the food.
• LCD Temperature display -make the unit wall mountable, we’ll mount it outside of the cold of the fridge/freezer unit but the temperature will be visible to staff.

See the full tutorial here.

Featured Adafruit Products!

Adafruit RGB Positive 16×2 LCD+Keypad Kit for Raspberry Pi: This new Adafruit Pi Plate makes it easy to use an RGB 16×2 Character LCD. We really like the RGB Character LCDs we stock in the shop. (For RGB we have RGB negative and RGB positive.) Unfortunately, these LCDs do require quite a few digital pins, 6 to control the LCD and then another 3 to control the RGB backlight for a total of 9 pins. That’s nearly all the GPIO available on a Pi! Read more.

Waterproof DS18B20 Digital temperature sensor + extras: This is a pre-wired and waterproofed version of the DS18B20 sensor. Handy for when you need to measure something far away, or in wet conditions. While the sensor is good up to 125°C the cable is jacketed in PVC so we suggest keeping it under 100°C. Because they are digital, you don’t get any signal degradation even over long distances! These 1-wire digital temperature sensors are fairly precise (±0.5°C over much of the range) and can give up to 12 bits of precision from the onboard digital-to-analog converter. They work great with any microcontroller using a single digital pin, and you can even connect multiple ones to the same pin, each one has a unique 64-bit ID burned in at the factory to differentiate them. Usable with 3.0-5.0V systems.