Humidity control for greenhouse flower seedlings with bird chirping alarm circuit (MS01-B)

As shown in the figure, the circuit is composed of a humidity sensor, a detection circuit, a temperature indicator, a comparison circuit, a thyristor controlled heating circuit, a birdsong sound circuit and an AC step-down rectifier circuit. RH is a humidity sensor, using MS01-B type. When the relative humidity in the greenhouse changes from 20% to 90%, its resistance can vary from a few kΩ to hundreds of kΩ.