Mosquito Repellent Circuit Using 2N3904 Transistors

A Mosquito repellent is important for every household and there are different kinds of them. Mosquito repellants like coils, mats, lotions, and creams can have adverse effects on health. Electronic mosquito repellents are safer and more efficient. These circuits are simple and can be built easily at home by following this tutorial.

The basic principle on which these circuit works is by producing high-frequency sound waves. These sound waves are inaudible to humans but can be heard by certain animals and insects. Humans can listen to sounds having 20 Hz to 20KHz frequency, any sound below or above this frequency is inaudible to them. In this circuit we are producing sound waves having frequencies greater than 20KHz which can be heard by mosquitos, it will produce stress on their antennae and repel them away.  

Hardware Components

The following components are required to make Mosquito Repellent Circuit

S. No	Component	Value	Qty
1.	Transistor	2N3904	2
2.	Resistor	1.5K, 100K	2, 2
3.	Piezo element	–	1
4.	Ceramic Capacitor	560pF, 2nF	1, 1
5.	Battery	1.5V-3V	1
6.	Battery Clips	–	1
7.	Breadboard	–	1
8.	Connecting Wires	–	1

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2N3904 Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of 2N3904

Mosquito Repellent Circuit

Working Explanation

By looking at the circuit diagram it’s visible how the circuit works. Two transistors are connected as a multi-vibrator. They both alternately start conducting immediately after the supply is turned on. The alternate switching takes place because the two capacitors connected with transistors, both get alternately charged and discharged. Both capacitors and transistors complement each other to sustain the oscillations.

The value of base resistors and capacitors decides the frequency of the oscillations. The generated frequency drives a piezo element connected with the circuit. It generates these high-frequency sounds. This circuit only needs 1.5 to 3V DC voltage to operate.

Applications and Uses

• This circuit works as a mosquito repellent circuit. It can also function as a repellent for other insects, through some modifications and changes in the value of resistors and capacitors. Another use of this circuit is a simple buzzer alarm circuit.