Build A Robot Brew A Real Ale
A Rasberry Pi, a BeagleBone Black and some Arduinos.
The BeagleBone has two Arduinos attached to it, one monitors the beer temperature, another controls a heater.
The photo below shows an earlier incarnation where the Raspberry Pi was controlling the Arduinos. Sadly the Pi's USB system appears to be a nonsense and tends to send the USB serial driver into a nosedive when you send traffic over it. A more up to date photo is forthcoming.
The primary and secondary fermentation vessels sit inside a rubber trug surrounded by water. An aquarium heater sits in the water, along with a temperature sensor.
The effect is sort of like a beer ban-marie.
The aquarium heater is turned on and off via a relay in the plug box controlled by one of the Arduinos.
The finished article:
apt-get install avahi-daemon avahi-utils libavahi-compat-libdnssd-dev couchdb