Project: Basic electronics Rain Alarm

1. Basic Electronics Project
Subject : Basic Electronics
Project : Rain Alarm
Prepared by :Kelvin Parmar(160110116027)
Tanmay Jani (160110116015)
Bhavik Vashi (160110116061)
Submitted to Neha D. Upadhyaya

2. Circuit Diagram

3. Components:-
1) Bread Board
2) Connecting Wires
3) 9V Battery
4) IC 741 – Op Amp
5) Transistor : BC 547
6) Red LED
7) 10kohm Resistor *3
8) 100ohm Resistor
9) Buzzer

4. Working :-
• Op-Amp IC 741 is designed as a voltage
comparator.
• Its inverting input pin2 receives half supply voltage
(4.5V) through the potential divider R1 and R2. Its
non-inverting input pin 3 is connected to touch
pads and variable resistor VR1.
• Output of the comparator becomes high only when
its pin3 gets a higher voltage than pin2. Normally
pin 3 is low because it is not getting current from
the positive supply. So output remains low. This
inhibits transistor T1 and buzzer remains off.
• When the contacts of the touch pad gets water,
current passes through the contacts to the pin 3 of
the comparator.
• This higher voltage at pin 3 causes the output to
go high. LED lights and transistor
conducts.Buzzer then starts beeping to indicate
rain.

5. Applications:-
• This is a simple circuit that can be used to detect
rain. It will give a loud beep when the first drop of
rail falls on the sensor. So it useful to detect rain
where sun drying is carried out.
• In the irrigation , it will detect the rain and
immediately alert the farmer.
• In automobiles , when the rain detector detects the
rain it will immediately active the wiper.
• It is also used to detect chemical rain.