We usually get irritated when mosquito bite.When mosquito bites we also get fever at sometimes.We cannot do our work with concentration ,in a place where mosquito are present.This mosquito repeller will make your home and work place mosquito free environment.

Step 1: Components Required

IC 555

Resistor

820Ω
1.5KΩ

IC BASE

8 Pin IC Base

Capacitor

0.01μF
0.1μF

BUZZER

Buzzer

PCB

General Purpose PCB

Connectors

2 Pin screw terminal---------2

Power Supply

5V Charger Board from MOBILE Charger and you can use any type of charger board

Step 2: Materials Required

Calling Bell Box

I had taken my home calling bell box which was not in working condition.So,i choose to enclose the Mosquito Repeller circuit with this calling bell box.

Step 3: Principle Behind Mosquito Repellent 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, dogs, insects, mosquitoes have the feature of being able to hear this ultrasonic sound. In mosquitoes, this feature is attributed to the presence of sensory structures in their antennae. Usually ultrasound is transmitted by male mosquitoes and received by female mosquitoes. However 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. The ultrasound produces a stress on the antennae of the mosquitoes and repels them away.

In other words, a simple circuit is designed which can produce ultrasound in the frequency range of 36 kHz, which can scare away mosquitoes.

Step 4: Schematic Diagram

Step 5: Designing the 555 Oscillator

The basic idea behind developing the circuit is to use a buzzer to produce ultrasound. The buzzer is driven by an oscillator circuit. Here, we are using a 555 Timer based astable multivibrator circuit as the oscillator circuit.

Designing the circuit involves designing an astable multivibrator circuit. Generally, frequency of output signal produced by a 555 astable multivibrator is given by:
F = 1.44((Ra+Rb*2)*C)

Here Ra is the value of resistor between pin 7 and Vcc, Rb is value of resistor between pins 7 and 6 and C is value of capacitor between pin 6 and ground.

Let C = 0.01 microFarad

F = 36 kHz

Let Duty Cycle, D = 60% (It is not possible to get 555 timers to produce signal with 50% duty cycle.

Formula to Calculate Ra and Rb Resistors

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 = 0.818 K Ohms, i.e. 818Ohms and Rb=1.52KOhms

Thus, we can use a resistor of 820Ohms and another resistor of 1.5 K.

The another capacitor at 5th terminal of IC555 is used to terminate the 5th terminal.Because in order to avoid any noise in frequency and also we need not use 5th terminal of IC555 so,we generally connect this terminal to ground with 0.1uF capacitor.