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Project: Sparmatic
Opened sparmatic with ISP connector

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

(This repo might not have the latest state...)


  • 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 row
    • 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
  • Window open switch
  • Measurement and inclusion into regulation of return temperature (to get maximum efficiency of the heating)