Thermostatic control circuit three using 555 time base integrated circuit

It is an electronic thermostat circuit for plastic injection molding machines. It uses the intermittent heating principle. A multivibrator with variable duty cycle is composed of a
555 time base integrated circuit . The signal controls the electric heater EH through the relay KA and changes
the power-on time to achieve temperature control. By adjusting the potentiometer RP, the pull-in time of the relay
KA can be changed from 0 to 67 seconds, so that the length of the energization time of the electric heater EH can be easily changed to achieve temperature control.