The temperature control circuit is composed of a special intelligent temperature sensing integrated circuit. It has high and low temperature light tube function, no mechanical contact, wide temperature control range. Safe and reliable, high temperature control accuracy.
(1) Circuit composition and working principle The circuit composition is shown in Figure 13-30, which mainly consists of rectifier filter, temperature control circuit 1C1, optical coupler IC2, bidirectional thyristor VTH and heater RT.
Switch on the power supply, the transformer T-secondary wire winding through the AC 220V, the secondary output 12V AC voltage, after the bridge rectifier filter. The electronic temperature control circuit IC1 is supplied. The 1, 2 ~ 3 and 4 pins of IC1 are provided with RP1 and RP2 potentiometers respectively to set the constant temperature.
When the ambient temperature is lower than the set temperature, the ⑥ pin of the temperature control Icl outputs a high level, the infrared light-emitting diode shines, so that the photosensitive bidirectional switch of the output stage of IC2 is turned on, the internal LED light of IC2 is turned on, the touch thyristor VTH is turned on, and the heater RT begins to heat up.
When the ambient temperature exceeds the set temperature, the ⑤ pin of the circuit IC1 jumps from a high level to a low level, so that the optical coupler two-way switch of the output stage is turned off, the LED light is turned off, and the VTH two-way crystal tube is cut off, so that the heater is powered off and the heating is stopped.
At this time, the @ foot of IC1 will remain low, and only when the ambient temperature drops below the set temperature, the high level will be output, thus enabling the heater to work again. In this way, the above control process is repeated constantly to achieve the purpose of automatic temperature control.
Post time: Jan-09-2025