Automatic ventilation and verbal warning circuit for excessive humidity in grain and cotton warehouses

As shown in the figure, the circuit is composed of a humidity-sensitive bridge network, a comparison circuit, a relay control ventilation circuit, a speech sound circuit and an AC step-down rectifier circuit. When the humidity in the warehouse is too high, the circuit will automatically turn on the ventilation fan and issue a warning statement to remind the personnel on duty to pay attention. RH is a humidity sensor, which forms a bridge humidity measurement network with RP1, R1, and R2. When the ambient humidity is within the normal range, the sensor RH shows a large resistance value.