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Mosquito Repellent using IC555 Mini project


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Product Description


Mosquito repellents like coils, mats, liquid vaporizers, creams are often used at various places. However they are prone to be fatal and can cause harm to human beings. For instance, mosquito repellent creams and oils can cause adverse affects on the skin like allergic reactions. Coils, mats can produce toxic fumes when heated and cause breathing trouble, whereas liquid vaporizers can also produce fumes when heated. For efficient results without any side effects, the most optimum solution is building a simple electronic circuit with minimal components which can produce output so as to repel the mosquitoes.

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 antenna.

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 20 kHz to 38 kHz, which can scare away mosquitoes.


  • Resistor 1k.
  • 7805 voltage regulator
  • LED
  • Buzzer
  • 555 timer IC
  • 10uf capacitor.

Circuit diagram



Once the switch is closed, the 555 timer gets the power supply. As per the inner circuit, initially the capacitor voltage will be zero and hence voltage at threshold and trigger pin will be zero. As the capacitor charges through resistors 1k and 1k2, at a certain point voltage at threshold pin is less than the capacitor voltage. This causes a change in timer output. The capacitor now starts discharging through resistor 1k2, i.e. the discharge pin and continues so until the output voltage is back to the original. Thus the output signal is an oscillating signal with frequency 38 KHz.  The output from this astable multivibrator circuit drives a 38 KHz piezo buzzer, producing ultrasound at regular repetitions. On varying the value of potentiometer, the output frequency can also be varied.

What is 555 Timer???



Basically, 555 timers is an 8-pin integrated chip which has capable of producing accurate time delays or oscillation. By connecting different values of resistor and capacitor to a 555 timer we can use it for countless applications.

  • 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. For astable operation this pin is connected directly to pin no.6
  • 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. For astable operation, this pin is shorted to pin 2 and connected to pin 7 using a resistor.
  • Pin 7 – It is the discharge pin and provides the discharge path for the capacitor.



As described, this circuit can be used as a mosquito repellent. By certain modifications and changes in the value of resistors and capacitor, the circuit can also be used as other insect repellent. Further, it can also be used as a simple buzzer alarm circuit.



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