By two NAND gates Di, Dz and resistor Rz, capacitors Cl etc. RC self-excited multivibrator oscillation frequency 2. 5Hz, the oscillation amplitude is 4V. Using as probe tempera
ture humidity resistance RS element. VTi ~ VT4 composed by transistors control circuit. When the humidity drops to the set value (adjusted by potentiometer RPi), relay KA2 release, cut off the power supply dryer; at the same time, KAi pull, turn the humidifier off. When the humidity rises, RS resistance decreases when the humidity reaches the set value. KA2 pull, repeat the process, so that the indoor humidity is maintained around the set value.