Saturday, 16 January 2016

Electronic mosquito repelent ultrasonic frequency generator circuit


Dear friends today we are going to learn how to make a circuit which act as mosquito repellent.

This circuit is very much easy to understand and use. A circuit with minimum components repel mosquito. Large number of things like coils, creams, oils is available in the market to repel mosquito. But these replant is also harmful for the humans . Oils and creams can led to skin disease, while coils or mats produces toxic fumes which can lead to breathing problem and lung cancer.

Our circuit do no harm for human being as it produces frequency which human being can not hear. Mosquito repellent generates a frequency ranges from 20-38 KHz. And mosquito runs away from your house as they irritates from these range of frequency.
Humans are only able to hear frequency which has a range from 20Hz to 20 KHz. All the rest frequency above this is considered as a ultrasonic frequency. Many animals and insects are able to hear this range of frequency. Usually in mosquitoes ultra sound is generated by the males and female one receives that one. While after breeding female mosquito usually used to avoid this frequency. And this circuit produces the same frequency as the male one generates, and these creates a stress on the antennae of the mosquito and these keep them away.
Here the basic principal of this circuit is to connect a such type of buzzer which can produce ultrasonic frequency range. With the help of oscillator in the circuit, buzzer is driven. And in the circuit oscillation is generated by 555 timer IC which is linked as a astablemultivibrator.

The circuit is connected in the closed mode and thus power is received by the 555 timer. In the starting stage voltage in the capacitor is zero volts.

So the voltage at the threshold `as well trigger pin is at zero volts. Now the capacitor starts charging via a resistor R1 and R2.There will be one point when the voltage of capacitor will be higher as compared to threshold voltage. At this stage capacitor starts discharging with the help of resistor R2, which is a discharging pin and it keeps of going downward till it reaches to its original state. Thus the signal at the output pin of IC will be an oscillating signal having 38 KHz frequency. With the help of pin 3 of timer IC 555 which is out pin of IC 38 KHz frequency drives to 38 kHz piexo buzzer. This buzzer will produce a ultrasound at a regular interval.
By altering the value of resistor R2 we can alter the output frequency.
By changing the value of resistor and capacitor, it can also use as an insect replier as insects are also able to hear ultrasound.
From the source ultrasound are transportable only at 45 degree. So in the situation when there is any hurdles in the track signals get diverted. Also it works on the place where population of mosquito are not much more.

Component Description:-

1. Power supply (12V)

2. Resistors (2.7kΩ x 2)

3. Capacitors (0.01µF x 2)

4. NE 555 timer

5. IC Diode (1N4007)

6. Piezo Buzzer



Working principle:-

(1) Here the 555 timer is configured in astable multivibrator mode , specifically devised for generating sound at the ultra frequency levels.

(2) The frequency of this circuit is set to 25 kHz, this frequency falls in the ultrasound region and it is not audible to human beings.
The 1N4007 diode is used to get 50% duty cycle for the frequency generator.

(3) The piezo buzzer converts the output of 555 astable to ultrasonic sound that can be heard by the insects.

(4) This ultrasound frequency cause some irritations and uneasiness to the insects such as mosquitoes. However it will not disturb you if you have installed this circuit of insect repellent for your home.

How to design this circuit:-

We need 25 kHz signal, so the time period will be 40µseconds .
Then T =T =20µSeconds .
use R= 2.7kΩ standard.
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