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Rain Alarm Project

Rain Alarm Project

The main purpose in designing this Rain Alarm project is to provide proper irrigation system in the field of agriculture. It is mainly used to reduce human intervention.  Rain Alarm comprises of soil moisture sensor, a transistor driver and a fan motor indicating a pump.

When soil moisture condition is fully wet, sensor changes the output logic to de-energized driver to make pump motor OFF. When soil moisture condition is dry sensor changes the output logic to  turn the pump motor ON.

Kit Contents: Sensor, Solderless Multipurpose breadboard, Set of Components, Accessories, Connector, Motor, Wire.

With this solderless breadboard approach none of the component is soldered, hence all the components can be used again and again to try such multiple circuits.


Water is a conductor of electricity. When water is in contact with the probe then there is a flow of current toward the base of  NPN transistor (BC548), which conducts. With the conduction of NPN transistor, electron reaches to Q2, which is a PNP transistor . PNP transistor (BC558) also conducts and current flows through the speaker. In a speaker there is inductive coil which causes motion in one direction and after that produces induce current, which is in opposite direction to the flow of current this induced current in the form of pulse, flows through a capacitor, resistance and makes 1st transistor BC548 off for an inter-well and after-that it relaxes to previous state. This process repeats again and again till probe is in contact with water and an oscillation is created in the circuit. Speaker diaphragm vibrates and gives a tone.

Block Diagram

Rain Alarm Project

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