Temperature control circuit with temperature dependent resistor for power control - is part of feedback loop around operational amplifier with 2nd operational amplifier coupled as comparator between reference voltage and first amplifier output drives output transistor for switching power relay for heating current

摘要

The temperature control circuit uses a temperature dependent resistor (PT500) to control the supply of power to a consumer. The resistor forms part of a negative feedback network surrounding an operational amplifier (IC1). A voltage divider is connected to the positive input terminal of the operational amplifier. The divider is supplied with a current derived from the current through the resistor in such a way that the output voltage of the divider can be compared with the output of the smplifier in a further comparator amplifier (IC2). The output of the this comparator controls the power supply to the consumer.