High-precision non-contact temperature control circuit 4a

It is a high-precision temperature control circuit that utilizes temperature-frequency conversion . That is, the temperature change
signal is converted into a frequency signal, and then decoded by the audio decoder to drive the electronic switch to control the temperature. Because the temperature change is converted
into a frequency signal, only a slight change in temperature will cause the frequency signal to change, so the temperature control accuracy is high.
    Working principle: The 555 time base integrated circuit Ai, semiconductor temperature sensor B, resistor Ri, and capacitor Cl form a
multivibrator whose frequency changes with temperature changes, that is, a temperature-frequency converter. LM567 integrated circuit
Az, potentiometer RP, capacitor C4, etc. form an audio decoder.
    Adjust the potentiometer RP to change the temperature set value.
    Temperature sensor B can be T-312 or T-121.