I wrote this for another forum un-related to brewing, thought you might like. Feel free to chime in.
I have been brewing for about 2 years now but not consistently. I was having a major problem with temperature changes in my house as it is 90 years old and drafty. These temp changes were a bane to my poor little yeasties which in turn would make them puke out some horrible flavors. So through some scrounging around and careful procuring of essential materials I built this.
The temperature probe will sit directly in the middle of solution as the turbulence created by yeast farts brings the sludge to the top it cools and drops to the bottom. This will keep the solution circulated and will pull the heat off a heating pad attached to the side of the carboy.
All in all I spent about $68 dollars on the whole setup. If I were to buy something equivalent it would cost me $180-$230. Hope it works as I have about a 30% failure rate of my beers.