It is a rain alarm presentation which includes the video of its working and the components and the working of thee rain alarm.

2. Presented By:
• Salman Mughal
Presented to:
Prof. Bin Yameen

4. Rain alarm is an application which detects the rain
water and blows alarm. They are useful devices and
play an important role in various industries such as
automobile, irrigation, and wireless communication.
Designing a rain alarm system is quite simple and we
have designed here a demo rain alarm project with
the help of 555 Timer IC.
What is Rain Alarm :

5. Components
1. Rain sensor (Either you can purchase or build yourself)
2. 555 Timer IC
3. NPN Transistor BC547
4. Resistors (470, 100k and 1k ohm)
5. Capacitor (10uf)
6. Buzzer
7. Battery 9v
8. Animated LED
9. Voltmeter

6. 555 Timer IC

7. Circuit Diagram and Working Explanation

8. Working of circuit diagram
It is a very simple rain alarm circuit which is designed using mainly a transistor, water
sensor and a 555 timer IC. Whenever there is a rain, rain drops falls on the rain sensor,
and as you can see in the diagram of rain sensor, water on rain sensor would short the
Point A and B. As soon as Point A and B become short, a positive voltage would get
applied on the base of Transistor Q1, through the resistance R4. Because of the voltage at
the base, transistor becomes ON (initially it was in OFF state), and current started flowing
form collector to emitter.
Now Reset PIN 4 of the 555 Timer, gets a positive voltage and 555 timer IC becomes ON
and Buzzer starts beeping. Here we should note that initially there was no positive
voltage at Reset PIN 4 of 555 IC, as it was connected to the ground through resistance R5
(4.7k) and 555 IC only works when Reset pin gets positive voltage.
Here we can see that 555 Timer IC has been configured in stable mode so that Buzzer
generate a oscillating sound (means periodically on and off). This oscillation frequency
can be controlled by changing the value of resistor R2 and/or capacitor C1. Pin 5 control
Pin, should be connected to ground through a .01uf capacitor. Resistor R3 and R4 has
been used to control the transistor’s collector and base current respectively.
Rain sensor should be kept at 30-40 degree from the ground, so that water cannot stay
on it, for the long time, this will prevent the alarm to going on for a long time.

9. Video of rain alarm

10. Advantages
 1. It is very cheap.

 2. The battery last very much.

 3. Not risky.

 4. No harmful effect.

 5. The circuit can be made by everyone

11. Disadvantages
 It doesn’t tell about the speed of the rain which is fallen on the roof.
 It will send signal or the led will be glowing until the detector becomes wet.
 It something is over that then the detector will not work until it gets wet.
 There are so many problem that you will face when you will make this circuit.

12. Schematic Capture

13. PCB Layout

14. 3D Visualization