Infrared heater temperature control circuit

In the severe cold winter, infrared heaters become household heating equipment. Most of their heating tubes are composed of three to four. Each heating tube is controlled by a switch. The temperature is controlled by a selector switch. The temperature control is extremely uneven. This circuit can enable all heating tubes to be used at the same time and achieve stepless adjustment. Working principle: The circuit is as shown in the figure above. IC (555) is connected as a low-frequency oscillator. Adjusting RP can change the charge and discharge time constant of C3. The output pulse duty cycle of pin ③ of the IC changes accordingly, that is, the thyristor's The ratio of turn-on and turn-off times controls the average power obtained on the heating tube RL to achieve the purpose of temperature control. When RP is adjusted to the uppermost end, the IC output pulse duty cycle is approximately "0", and the power obtained on RL is the smallest; when RP is adjusted to the lowest end, the IC output pulse duty cycle is approximately "1", and the power obtained on RL is Maximum power. Therefore, adjusting RP can make the IC output pulse duty cycle continuously change between "0" and "1". What is obtained on RL is the average power that continuously changes between the maximum and minimum, and the LED brightness changes accordingly as the average power. Size indication. This thermostat can also be used as a power regulator in other resistive heating appliances without generating electromagnetic field interference. The choice of the power of the thyristor depends on the power of the heating tube. Generally, the heat extractor of 1KW ~ 1.5KW can use the thyristor of BTA12/600, and it is better to add a heat sink.