Transistor Based Rain Detector Device

The purpose of the project is to provide an alarm at the instant it starts to rain giving enough time to close the windows or bring in possessions.

The circuit is being powered by batteries where a couple of AA cells will last a long time because the circuit current consumption is low when the buzzer is activated and it virtually draws no current when the sensor is dry. An alternate way is a molded power supply using a simple voltage regulator to maintain the voltage to 3V. Using ordinary silicon transistors, the circuit is basically a handy flasher circuit that operates well on only 3V.

The buzzer is pulsed about once per second for a very short time when the circuit is triggered giving a dripping water sound. By increasing the capacitor value, a longer and slower beep may be obtained. For a longer beep time without decreasing the beep rate, the resistor may be increased depending on the gain of the transistor.

Any number of ways can be used to build the rain sensor wherein simply two conductors are bridged by the rain water. The two conductors are bare copper wires.

Rest of the project