Electric heater temperature detection control circuit

Electric heater temperature detection control circuit

Shown is a common electric heater temperature detection control circuit. The circuit is mainly composed of a power supply circuit and a temperature detection control circuit
.     In the circuit, the power circuit is mainly composed of the AC input part, power switch K, step-down transformer T, bridge rectifier circuit (VD1-VD4),
resistor Ri, power indicator light VD1, filter capacitor cl and Zener diode VS1. The temperature detection circuit is composed of the thermistor
RT, integrated circuit IC (NE555), potentiometers RP1 ~ RP3, relay K, light-emitting diode VD2 and peripheral related components.
    The AC 220 V voltage is stepped down by the transformer T, rectified by the bridge rectifier circuit, filtered by the capacitor, and stabilized by the diode to produce a DC
voltage of about 12 V, which provides the operating voltage for the integrated circuit IC. When the circuit detects that the ambient temperature is low, the resistance value of the thermistor RT becomes larger, the
voltage of pins ② and ⑥ of the integrated circuit IC decreases, pin ③ outputs high level, VD2 lights up, and relay K draws electricity.
When the ambient temperature rises to a certain temperature, the resistance value of RT becomes smaller, and the ② pin of the
integrated circuit IC , The @ pin voltage increases, @ pin outputs low level, VD2 goes out, relay K is released, and its normally open contact
cuts off the working power of the electric heater, causing the ambient temperature to gradually drop.