Electronic heater control circuit - has saw tooth generator connected as quasi-feedback to electronic control circuit

摘要

The temp. dependent control circuit is for the heating medium feed- and return room temp. and for the heating energy. A separate saw-tooth generator with adjustable pulse width, is connected as a constant quasi-return to an electronic temp. dependent heater control circuit. The heater control circuit consists of a Wheatstone bridge with an external temp. dependent resistance; and of an operation amplifier with three-point characteristics. The resulting impulse width-proportional control voltage actuates a servo unit via switch elements. The generator has a field effect transistor (11a), with two variable resistances (8a, b) and a capacitor (10). This permits the periodic length of the servo tooth impulses to be adjusted between one second and thirty minutes. The amplitude of the impulses is limited by a diode.