INTRODUCTION: The rain detector is used to give a head up at the moment the rain starts occurring informing you to close your doors and windows and to save your possessions. The circuit latches an alarm as the water came in contact with two aluminum rods. The speaker is used to produce the sound indicating falling of rain.
|1) Transistors||n-p-n transistor (BC 147)
|2) Resistor||2K,330K & 1K|
|3) capacitor||10 Nf|
|4) 4 diode ( as rain sensor)||SCRS|
|5) speaker||5 TO 8 OHM|
|6) battery||3 VOLTS|
Working: This battery powered circuit usually draws no current in dry conditions it works well with 3volts supply and ordinary silicon transistors. The circuit is based on the idea that “water is a good conductor of electricity” On triggering of circuit the buzzer is pulsed for a very short period of time per second producing a “dipping water” sound. As the water comes in contact with Rain sensors a flow of current is generated towards the base of npn transistor as the conduction starts in a npn transistor due to flow of electrons the pnp transistor also begins to conduct thus the path of current through speaker completes. The speaker generates an induced current opposite to the real current which is in form of pulses flows through capacitor,inductor and resistor causing first transistor to become off and then leaves it in its previous state. This process continues to occur until the sensors comes in contact with water generating oscillations in the circuit which vibrates the speaker’s diaphragm and it gives a tone. Thus an alarm is generated indicating raining.
APPLICATIONS: This circuit can be used as:
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