Hi friends, today we are going to make a simple mini project which is rain detector with alarm. This mini project generates sound using speaker whenever rain starts. The circuit diagram of this mini project is very simple and you can make this project as your first or second year engineering project for electronics and electrical students.
- Resistor: 10K, 330K
- Transistor: BC548, BC558 (other equivalent transistors can also be used)
- 3V DC supply (you can also use two 1.5V normally used cells in series)
- Probe (it is nothing but a set of two open ended wires)
Working Principle of Rain Detector
The working of this rain detector mini project is very simple. In this mini project, we are using a probe placed in a small plastic container. Whenever raining starts water get collected in that plastic container. As water is the conductor of electricity the contact between two open ended wires (probes) takes place and current start flowing towards the base of NPN transistor BC548. Here collector of BC548 NPN transistor is connected to the base of BC558 PNP transistor. Therefore when NPN starts conducting PNP also starts conducting.
Due to conduction of PNP transistor current starts flowing through the speaker and it generates an alarm. As in this mini-project, we have used a resistor and capacitor in series it causes the first transistor to turn on and off continuously till there is rain water present in the plastic container. This on and off period depends on the values of the capacitor, resistor and inductive coil of the speaker. Because of capacitor charging and discharging period it continuous to turn on and off continuously. This on and off condition of the transistor causes to generate a siren-like alarm from the speaker.
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