Arduino robot kits rain rain sensor can be used for all kinds of weather monitoring and go down to set the output signal and the AO. The code download https://app.box.com/s/yvfdhs4179izn32szgse. When connect with 5V power supply the light on. When there is no water droplets on induction plate the DO output for the high level switch lights off drop water-drop DO output is low level indicator light on. Brush away the water droplets return to again the output high level state. AO analog output can be connected to the microcontroller AD mouth drops of rainfall in the above size. DO TTL digital output can also be connected microcontroller detecting whether it will rain. Size: 3.7 x 2 x 0.6cm.