With the figure circuit it is possible to control the amount of heat generated by the heating element. The heating element can operate with voltages up to 25 V and maximum current of 3 amps. The maximum input voltage of this circuit is 35 V, and for normal operation it must be at least 2 volts more than the voltage required by the heating element. The sensor of the circuit is an LM334 that must be placed next to where the heater is to detect the temperature of its environment. The circuit can be used in greenhouses, incubators and biology experiments. The circuit is set to the 100 k ohm potentiometer for the temperature to be maintained.