06-02-2015, 04:56 AM
construction and working of rain alarm mini project
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Rain Alarm is an application that detects rainwater and shock alarm. They are useful devices and play an important role in various industries such as automobile, irrigation and wireless communication. Desiging a rain alarm system is quite simple and we have designed here a demonstration rain alarm project with the help of 555 Timer IC.
Components
- Rain sensor (You can buy or build yourself)
- 555 IC Timer
- NPN Transistor BC547
- Resistors (470, 100k and 1k ohms)
- Condenser (10uf)
- Buzzer
- 9v Battery
The main component of this rain alarm is rain sensor, I have bought one, but we can also build it at home. It is very easy to create a rain sensor. Take a sheet of Bakelite or mica, and glue the aluminum wire in it according to the diagram below. The separation between the cables should be around 3-5mm. It can be seen that every time the rainfall falls on the rain sensor, the point A and B is cut off and a voltage is applied to the base of the transistor, and it will turn ON. We can also use copper wire for rain sensor but copper usually reacts to oxygen to form oxide, so it needs to be cleaned on a regular basis.
Circuit Diagram and Explanation of Work
Rain alarm circuit diagram with timer IC 555
It is a very simple rain alarm circuit that is designed using mainly a transistor, water sensor and an IC of 555 timers. Whenever there is rain, raindrops fall on the rain sensor, and as you can see from the rain sensor diagram, the water in the rain sensor would short-circuit point A and B. As soon as the points A and B are shortened, the voltage would be applied to the base of the transistor Q1, through the resistor R4. Due to the voltage at the base, the transistor is turned ON (initially it was in OFF state), and the current began to flow from the collector to the emitter.
Now reset the PIN 4 of timer 555, get a positive voltage and the timer IC 555 turns on and the buzzer beeps. Here we must take into account that initially there was no positive voltage in the Replacement PIN 4 of 555 IC, since it was connected to the ground through resistor R5 (4.7k) and IC 555 only works when the reset pin receives voltage positive.
Here we can see that the 555 Timer IC has been configured in the Astable mode so that Buzzer generates an oscillating sound (means that it is switched on and off periodically). This oscillation frequency can be controlled by changing the value of resistor R2 and / or capacitor C1. Pin Control pin 5 must be grounded through a .01uf condenser. Resistance R3 and R4 have been used to control the collector of the transistor and the base current respectively.
Rain sensor should be kept at 30-40 degrees from the ground, so the water can not remain in it for a long time, this will prevent the alarm to continue for a long time.