Due to a lack of viable options, I decided awhile back to create my own thermostat for my fermentation chamber.
After looking at the options available, I wasnt too excited about any of the temperature controllers I could find. The thought of having to update the temperature manually on a daily/hourly basis during a lager process doesnt really excite me or my ADD tendencies too much. So I set about making one of my own with the help of a temperature reading IC, a microcontroller and a relay to control a power outlet.
Despite getting a little carried away on some of the options/features, Im pretty excited about the resulting product. I essentially come up with a digital controller that has an LCD screen on it to show the current stage of the fermentation process, number of days at the current stage, the actual temperature inside the chamber and the temperature you have it set to. It has the ability to control a fridge/freezer as well as a heating element of some sort.
The best part of the controller is that it has the ability to setup and change fermentation programs. For instance, I can setup a lager fermentation program that will set the temperature at 52 degrees for 10 days, then slowly bring it up to 68 degrees over 2 days for a diacetyl rest, then gradually lower the temperature to 34 degrees for lagering.
You can create a program by adding stages. Each stage has a start temperature, a duration and a gradient. If you want to set a temperature and keep it, set the gradient to zero. If you want to lower the temperature 1 degree per day, you set the gradient to -1/day, or you can set the rate to drop 1 degree every 6 hours or whatever your heart desires.
Im just now finishing up programming the code to store new programs. Outside of that, its about ready to go. I have a chest freezer (thanks craigslist) with a fresh coat of paint on it and ready to go. I hope to be brewing my first lager here very soon!
Here are a pic of what it looks like:
I have also posted blog entries during the building process of the controller. Lots more pics and information can be found there.
You can check it out at this address if you like: ohmbrew.blogspot.com
**Disclaimer: There's plenty of geeky vernacular on there.