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

 

After the success of my first Raspberry Pi Project The Pi Powered Joke Machine - The Ultimate Raspberry Pi Bundle Blog post

I documented that fun little educational project on Instructables (since they are running a Raspberry Pi contest)

 

And now it's back to the Temperature sensor. I need to figure out what type of temp sensor I should use. Previously I found this resource on Element 14 that lays out the types of temp sensors I could use

Hints for selecting the correct temperature sensor for your application

 

For a project I worked on a few years back, we used an Arduino and a TMP36 IC and I also had access to an LM34 and LM35, but I believe those would all require analog ports which the Pi doesn't have.

I thought a thermocouple might work, but a friend tells me they put out a very low level signal that requires a lot of analog processing (hmm again analog port required)


He recommended a digital output sensor like the Dallas Semi DS18B20 and found a prepackaged version that looks like what I want. It is pre-wired, waterproof, is meant to go long distances (I'll have to run the sensor out 25ft from where I mount the Pi) and they have included some documentation / examples on how to use it.

http://www.adafruit.com/products/381#Description

Reasonably priced at $9.95 (although I could have saved money and bought just the ICs...but...then I would have to try to wrap them up to stand up to the cold of the freezer and buy cable and cable wrap....) Another good sign is that according to my research Raspian (which I've installed on my Pi) supports this type of temp sensor

Here is a link to the tutorial on how to use the sensor Adafruit's Raspberry Pi Lesson 11. DS18B20 Temperature Sensing

 

And here is a little bonus too, I happened to notice Adafruit was having a few live events....Demos of Wearable tech, a Show and Tell session and Ask an Engineer. I participated in the Show and Tell (showing off my Pi Powered Joke Machine) and then while watching the Ask an Engineer session they provided a discount code worth 10% off all orders for the evening...so my temp sensors are on the way!

 

Next step...while waiting for the Temp Sensors I'm going to crack in to some of the other items in the bundle....hmm possibly the Gertboard and or the Pi Camera....say cheese!