Sparmatic is a thermostat that is relatively cheap and quite easy to mod. It costs from 13 to 25 EUR. It contains a simple AVR ATmega169/ATmega169PA. However, as there are different microcontrollers mentioned in the last sentence, there are several revisions of the device.
Alternative Firmware
We are currently writing an alternative Firmware for one one of these revisions. You can get it by cloning this git repository:
git clone http://www.0x53a.de/git/sparmatic
Features
Motor control:
Readout of the motor's rotation sensor (and counting)
Current measuring and automatic switch-off
return to home
move to specified position
Readout of the temperature sensor (including some calibration)
Some simple PI controller
LCD
Bargraph
Day column
4 digit numbers (e.g. for temperatures, position counts...)
All symbols (mostly untested :)
Planned Features
LCD
Convert characters to 14 segment display (if needed)
Onewire slave support
Buttons & Rotary encoder
Temperature sensor value to temperature conversion or at least some limits
An actual temperature controller (maybe ;) )
Window open switch
Measurement and inclusion into regulation of return temperature (to get maximum efficiency of the heating)
