a mosquito repellent circuit to generate a frequency range between 20-38 kHz. As this particular frequency is known as ultra sound it distracts the female mosquitoes .To make this circuit we are using here IC-555 timer, variable resistor, capacitor and to generate this ultrasound frequency we are using piezzo buzzer.

1. ABACUS INSTITUTE OF ENGINEERING & MANAGEMENT
MOSQUITO REPELLENT CIRCUIT TO GENERATE A FREQUENCY RANGE
BETWEEN 20-38 kHz
BY
RAHUL NANDY, ROLL NO : 24000311034,REGISTRATION NO : 112400110096
REGISTRATION NO: 112400110107SOUMYAJIT DE, ROLL NO: 24000311034,
DEBJYOTI BISWAS, ROLL NO : 24000311015,REGISTRATION NO : 112400110077
REGISTRATION NO: 112400110096
REGISTRATION NO: 112400110096
ROLL NO : 24000311034,
ROLL NO: 24000311046,SOUNAK MAJUMDAR,
SAGNIK DASGUPTA,

2. Under The Supervision of
Assistant Professor
ABACUS INSTITUTE
OF
ENGINEERING & MANAGEMENT
Mrs. SUCHANDANA ROY

3. ACKNOWLEDGEMENT
First of all we would like to thanks all the member of Abacus
Institute of Engineering & Management for helping us for the
project and for her continuous guidance and support. We
would like to thank others faculty members of our
department.
We would also like to thank everyone in the list. The
developers of this project was also very helpful. Finally we
would like to thank our family and friends for putting up with
our constant moaning about the project and supporting us
through the difficult times.

4. CONTEXT
1. Abstract
2. Acknowledgment
3. Theory behind the circuit
4. Circuit Diagram
5. Equipment
6. Theory
7. Use of 555 timer
8. Astable Multivibrator
9. Capacitor
10. Resistor
11. Mosquito Repellent Circuit Limitations

5. Principle Behind Mosquito Repellent Circuit:
THEORY BEHIND THE CIRCUIT :
* Human beings can hear sound in the range of 20 Hz to 20 kHz
* Sound of any frequency above 20 kHz is termed as ultrasonic sound. Several
animals like cats, insects, mosquitoes have the feature of being able to hear this
ultrasonic sound.
*Usually ultrasound is transmitted by male mosquitoes and received by female
mosquitoes
*After breeding, female mosquitoes generally avoid the ultrasound and this fact
can be used to produce ultrasound in a range similar to that produced by male
mosquitoes and repel away the mosquitoes.
*In other words, a simple circuit is designed which can produce ultrasound in
the frequency range of 20 kHz to 38 kHz, which can scare away mosquitoes.

6. Mosquito Repellent Circuit Operation:
1.Once the switch is closed, the 555 timer gets the power supply.
2.The inner circuit, initially the capacitor
voltage will be zero and hence voltage at threshold
and trigger pin will be zero.
3.The capacitor charges through resistors Ra
and Rb, at a certain point voltage at threshold pin is
less than the capacitor voltage.
4.This causes a change in timer output.
5.The capacitor now starts discharging
through resistor Rb, i.e. the discharge pin and
continues so until the output voltage is back to
the original.
6.Thus the output signal is an oscillating signal
with frequency 38 KHz.
7.The output from this astable multivibrator circuit drives a 38 KHz piezo
buzzer, producing ultrasound at regular repetitions.

7. Circuit Diagram of Electronic Mosquito Repellent Circuit:

8. Mosquito Repellent Circuit Design:
*The basic idea behind developing the circuit is to use a buzzer to produce
ultrasound. The buzzer is driven by an oscillator circuit
*A 555 Timer based astable multivibrator circuit as the oscillator circuit.
* The frequency of output signal produced by a 555 astable multivibrator
is given by:
F = 1.44((Ra+Rb*2)*C)
Ra =resistor between pin 7 and Vcc , Rb =resistor between pins 7 and 6
C =capacitor between pin 6 and ground.
Let C = 0.01 microFarad ,F = 38 kHz
Let Duty Cycle, D = 60%
This gives,Ra = 1.44(2D-1)/(F*C)And Rb=1.44(1-D)/(F*C)
Substituting values of C, F and D, we get
Ra = 0.758 K Ohms, i.e. 758 Ohms and Rb = 1.52 K Ohms

9. Equipment:
•An electrolyte capacitor of 0.01 micro Farad
• A ceramic capacitor of 0.01 micro Farad
•A resistor of 760 Ohms
•Another resistor of 1.5 K
•A 38 kHz pizzo buzzer
•A SPST switch
•A 5 V battery
•C.R.O

10. Theory:
*A multivibrator is an electronic circuit producing a pulsed output signal.
Generally multivibrators are classified based on the nature of stability of
output
*A multivibrator with one stable state is known as monostable
multivibrator and is used as a pulse generator.
*A multivibrator with no stable state is known as an astable multivibrator
and is used as an oscillator.
*A multivibrator with two stable states is known as a bistable multivibrator
and is used as a Schmitt Trigger.
**Astable multivibrators do not require any external
triggering and hence can be used as oscillators.

11. Use of 555 timer:
The most common form of Astable multivibrator
is 555 Timer IC. It is basically an 8 pin IC with the
following pin description:
Pin1 – Ground pin, which is directly connected
to the negative terminal of the battery.
Pin2- Trigger Pin. It is an active low pin. The
timer is triggered when signal at this pin is less
than one third of supply voltage.
Pin 3 – It is the output pin.
Pin 4 – It is the reset pin. It is an active low pin. It is usually connected to positive
rail of the battery
Pin 5 – It is the control pin and is seldom used. For safety purpose, this pin is
connected to ground through a 0.01microFarad ceramic capacitor.
Pin 6 – It is the threshold pin. The timer output is back to its stable state when
voltage at this pin is greater than or equal to two-third of supply voltage.
Pin 7 – It is the discharge pin and provides the discharge path for the capacitor.

12. Astable Multivibrator (AMV):
*In the 555 Oscillator circuit above,
pin 2 and pin 6 are connected together
allowing the circuit to re-trigger itself
on each and every cycle allowing it to
operate as a free running oscillator.
*During each cycle
capacitor, C charges up through both
timing resistors, R1 and R2 but
discharges itself only through
resistor, R2 as the other side of R2 is
connected to the discharge terminal,
pin 7.
*Then the capacitor charges up to
2/3Vcc (the upper comparator limit)
which is =0.693(R1+R2)C combination
and discharges itself down to 1/3Vcc (the
lower comparator limit)=
0.693(R2.C) combination.
*Output waveform whose voltage
level is approximately equal to Vcc –
1.5V and whose output “ON” and “OFF” time
periods are determined by the capacitor and
resistors combinations

13. BATTERY:
*An electric battery is a device consisting of two
or more electrochemical cells that convert stored
chemical energy into electrical energy.
*Each cell contains a positive terminal,
or cathode, and a negative terminal, or anode.
*Electrolytes allows ions to move between the
electrods & terminals,which allows current to flow out of
the battery to perform work.
Resistors:
There is always some resistance in every circuit.
• A circuit is always made up of some wire, so there will be some resistance there.
• Even the battery has parts that offer resistance to the flow of electrons.
• The only circuits that come near to zero resistance are superconductors.
This resistance that is from the parts of the circuit itself (especially the battery) is
called internal resistance.

14. Capacitor:
*A ceramic capacitor is a fixed value capacitor in which ceramic
material acts as the dielectric.
*It is constructed of two or more alternating layers of ceramic and a metal layer
acting as the electrodes.
Ceramic capacitors are divided into two application classes:
• Class 1 ceramic capacitors offer high stability and low losses for resonant circuit
applications.
• Class 2 ceramic capacitors offer high volumetric efficiency for buffer, by-pass, and
coupling applications.
*Ceramic capacitors, especially the multilayer style (MLCC), are the most produced
and used capacitors in electronic equipment
*Ceramic capacitors of special shapes and styles are used as capacitors
for RFI/EMI suppression, as feed-through capacitors and in larger dimensions as power
capacitors for transmitters.
ceramic capacitor:

15. Electrolytic capacitor:
Electrolytic capacitors is the generic term
for three different capacitor family members:
• Aluminum electrolytic capacitors, Tantalum electrolytic capacitors and Niobium
electrolytic capacitors
All electrolytic capacitors (e-caps) are polarized capacitors
whose anode electrode (+) are made of a special metal on which an insulating oxide
layer originates by anodically oxidation (forming), which acts as the dielectric of the
electrolytic capacitor
The large capacitance of electrolytic capacitors makes them
particularly suitable for passing or bypassing low-frequency signals up to some mega-
hertz and storing large amounts of energy.
Electrolytic capacitors are polarized components by the
manufacturing principle and may only be operated with DC voltage. Voltages with
reverse polarity, or voltage or ripple current higher than specified, can destroy the
dielectric and thus the capacitor.

16. SPST switch:
A Single Pole Single Throw (SPST) switch is a switch that only has a
single input and can connect only to one output. This means it only has one input
terminal and only one output terminal.
A Single Pole Single Throw (SPST) switch serves in a circuit as on off
witchs.

17. 38 kHz piezo buzzer:
*Piezo buzzer is an electronic device commonly used to produce sound.
*Light weight, simple construction and low price make it usable in various
applications like car/truck reversing indicator, computers, call bells etc
*It is the phenomena of generating electricity when mechanical pressure is
applied to certain materials and the vice versa is also true.
*Such materials are called piezo electric materials.

18. Mosquito Repellent Circuit Limitations:
•It requires a lot of frequency setting.
•Ultrasound signals travel at an angle of 45 degrees from the source. In
case of any obstacles in the path, the signals get reflected or diverted.
•It shows effect for lesser mosquito population.

19. Progress of The Project :
IN PROJECT I :
we had collect all the information of the project and the
equipments then we design the circuit using pspice and run it and got the
graph which generate frequency near about 38khz.And we also made a
power point presentation on our project and displayed it in PROJECT I
lab. Exam.

20. IN PROJECT II:
This semester we make the circuit in hardware using
Resistor,Capacitance,555 timer,SPST Switch,Power supply 5V,CRO.we obtain
the frequency using CRO using make the circuit in bread board.

21. CONCLUSIONS:
We conclude that the experimental values is near
about the theoretical values. the frequency
generate near 38khz not properly. the circuit is
successfully done and get the expected result
approximately.

22. References:
All the information about the circuit ,equipment ,theory behind
the circuit and the circuit diagram we got from the book
“ELECTRONICS Fundamental and Applications” written by
D.Chattopadhyay and P.C.Rakshit.
Also our respective mam Mrs. Suchandana Roy and all
the assistant professors of ECE department of Abacus Institute
of Engineering and Management help us to get success in our
project.