Rain Sensor Module with Nickel-Plated Detection Board (FC-37)

This sensor is designed to detect moisture, specifically rain. It comes with a large, nickel-plated board that acts as a variable resistor. When the board is dry, resistance is high, and no electricity conducts. When water droplets fall on it, they bridge the nickel tracks, lowering the resistance. The separate blue control board (Comparator) reads this change. You can use the blue potentiometer to set a threshold—for example, to trigger an alarm only when it is raining heavily, or immediately upon the first drop.