Rain Sensor Circuit Schematic Diagram

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This circuit will sound an alarm when the rain falls. The rain sensor used in this circuit is a simple one consists of winding wires. If the wires touch by a drop of water, the current will flow from wire A to wire B. This circuit uses 3 volts power supply. The current won’t flow if the sensor is dry, therefore the battery will long last. If the sensor touched by the water, the alarm will sound for 1 minute. The buzzer sound can be prolonged by rising the capacitance value C1. Here is the schematic :

Rain sensor schematic diagram

Component List :

Resistor R1 : 10k ohm
Resistor R2 : 1k ohm
Resistor R3,R4 : 1M ohm
Capacitor C1 : 1 uF
Capacitor C2 : 0.1 uF
Q1 : 2N2222
Q2 : 2N2906
3V buzzer
3V battery
Estimated price : $1