Controlling the heater, the goal of this paper is to set and maintain temperature on a referent value. The whole system consists of a temperature sensor, controlling set, and a heating drive. Microcontroller Arduino Uno was chosen for the controlling set, and for the temperature sensors where used Dallas DS18B20, as off-the-shelf components. Regulators would be achieved developing program support for the microcontroller. In the beginning the whole system was tested on a model of a thermal chamber made out of aluminium foil and styrofoam as thermal insulators, so the effectiveness of the two chosen regulators could be confirmed, the proportional gain regulator and relay regulator. Although the power of the model was small, it was enough to demonstrate one system on which measurements could be made. The work was continued on a much bigger thermal chamber with the power of 0,8 kW. Temperatures that could be achieved where around 80 °C but could also go a little above 100 °C. First goals where reached and systems overshoot was taken care of, and the measured temperature was staying inside tolerated temperature values. Software developed was written and used on the Arduino Uno microcontroller which was integrated with the PCB developed for the system. Besides programming for Arduino, a script was used in Matlab to collect data, and for easier processing and interpretation od the data. The PCB was developed in an open source program called KiCad.