In-Depth: How Rain Sensor Works and Interface it with Arduino

The rain sensor system relies on a two-part setup: a sensing pad and a control module powered by an LM393 voltage comparator. The sensing pad consists of exposed parallel copper traces. When dry, electricity cannot easily flow across the traces, resulting in a high resistance state. When raindrops fall onto the pad, they bridge the gap between the conductive traces, lowering the electrical resistance and allowing a small current to pass. This creates a variable analog voltage drop across the sensor. The LM393 comparator on the module continuously compares this incoming analog voltage against a reference threshold voltage set by an onboard potentiometer. Depending on whether the sensor voltage crosses this threshold, the module outputs either an analog signal corresponding to the moisture level or a digital high/low signal. By connecting the module's output to an Arduino board, the microcontroller can read these signals using its analog or digital pins. Through programmed logic in the Arduino IDE, the system can interpret the sensor data to trigger alerts, control mechanical relays, or execute automated tasks whenever precipitation is detected.