Humidity control circuit using transistors

It uses composite transistors VTi and VT2 as the control circuit and a humidity sensitive resistor RS
as the moisture detection element. When the ambient humidity is high, the relay KA is closed and the hot air blower M works to dehumidify. When the humidity drops to the
set value, KA is released and M stops working. At the same time, the microammeter PA (the panel scale is changed to humidity) can directly indicate the humidity
value.
    Adjust the potentiometer RP to adjust the humidity set value.