No, don't misread that (although a colleague of mine is working on something more 18 rated). This small bot is the beginning of (hopefully) even tastier meats. Its a hacked slow cooker that can hold a temperature reliably for a long period of time. Its called Sous Vide cooking and I got quite interested in it after seeing The Cooking for Geeks Talk at the Next Hope Conference. It seemed quite interesting.
This is probably the most hacking thing I've actually done. All the parts except for the Arduino are second-hand or scavenged. The slow cooker came from eBay,the case was given to me from another hackspace member and the major relay I took from a board that was being thrown out. Thats the main key of the circuit - a large relay capable of switching a mains voltage.
To flip that relay we need to send almost 5 volts to it from the arduino. Now these pins are rated at 5 volts and the relay was actually rated at 12V. We got quite lucky we could switch it at all. However we added a transistor and a couple of resistors with a flyback diode and job was a goodun.
To measure temperature, I used this probe from Earthshine electronics. It works quite well and with a pull up resistor, it works quite well out of the box. There are some Arduino libraries for this which makes it a doddle.
It looks good and holds reasonably well but will it be good enough for Sous Vide? We shall have to see. I'll do the egg test tomorrow and we shall see :P