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Working of Electric Mosquito Killer Racket / Fly Swatter Bat

Circuit Diagram and Working of Mosquito Killer Racket, Fly Swatter Bat, Bug Zapper etc.

Mosquitos are small but very annoying little insects that are present in every corner of the world. These annoying little insects may look small but cause itching in the bite area as well as carry and spread diseases such as malaria, dengue, etc.

There are several ways to get rid of mosquitos such as the use of mosquito repellent, insecticides and of course electric fly swatter and bugs zapper racket and bats.. This bad boy can instantly electrocute these tiny vampires in the most creative way with a spark.

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This article explains how the electric fly swatter or mosquito killer racket works with its circuit diagram.

What is Electric Fly Swatter / Racket Bat?

An electric fly swatter is a household device used for killing mosquitos. It is designed in the shape of a badminton or tennis racket having an electrical mesh. When a fly comes in contact with the mesh, it is instantly electrocuted and incinerated with a spark.  It is also known as a fly zapper, mosquito-killing racket, etc.

It has an electrical circuit inside the handle containing several components and a rechargeable battery. The circuit amplifies the DC voltage of the battery and oscillates it at a very high frequency to generate the necessary spark of around 3000 volts. It generates a very low current and enough heat to fry these flying insects.

Good to know: An Electric mosquito killer racket works on the same bases used for similar functions using different products such as electric fly swatter, bug zapper bat, electronic Fly and Insect Swatter etc.

Working of Electric mosquito killer racket electric fly swatter bug zapper electronic Fly & Insect Swatter

Working Principle of Electric Racket Bat / Fly Zapper

The electric fly swatter works on the principle of electrocution. There are two types of grid meshes: inner mesh and outer mesh. The inner mesh is sandwiched between the two outer meshes. The grid mesh is electrically charged when the button is pressed.

High voltage appears between the inner and outer mesh. When a mosquito flies between the inner and outer mesh, it completes the circuit. The high voltage difference generates an arc through the mosquito’s body and burns it in microseconds.

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Electric Bug Swatter Circuit Diagram & Working

The circuit of the electric fly swatter is concealed inside the handle of the racket. It consists of four major parts: a charging circuit, oscillator, transformer, and voltage multiplier. The circuit diagram for the electric fly swatter aka mosquito killer racket is given below.

Mosquito Killer Racket Circuit Diagram

Charging Circuit

An electric fly swatter is a mobile device therefore it requires a rechargeable battery. Since it is a rechargeable battery, it requires a charging circuit to charge from the mains. The charging circuit inside the electric fly swatter is transformer-less or capacitive power supply. It is also known as a capacitive dropper since it reduces the AC voltage from the mains down to low-voltage DC as shown in the figure below.

Mosquito Killer Racket Charging Circuit

This transformer-less charging circuit reduces the 220/110 volts AC from the mains down to 3V DC for the battery. It consists of a capacitor, diode rectifier bridge and smoothing capacitor. The high AC voltage from the mains is reduced down to low voltage using the capacitive reactance of the capacitor. The rectifier bridge then converts the AC into pulsating DC. The smoothing capacitor filters the ripples from the pulsating DC and provides a smooth DC output for the battery.

The benefit of transformer-less power supply circuits is to have low cost, save space and have a very simple circuit.

Rechargeable Battery

At the output of the charging circuit, a rechargeable battery is connected which stores the charge. The battery provides mobility and is easy to use in any place. Once fully charged it can last up to 7 days depending on the ratings of the battery.

Oscillator Circuit

The battery provides DC and we know that DC cannot be stepped up using a transformer. Therefore the DC is converted into AC using an oscillator circuit. An NPN transistor is used to oscillate the DC voltage between positive and negative DC voltage turning an AC signal. This AC signal can be easily stepped up using a center tap transformer.

Mosquito Killer Racket High Voltage Circuit


The next stage after the oscillator circuit is the step-up transformer. A center-tap step-up transformer is used to convert the oscillator output which is a low-voltage AC into high voltage up to 200 V.

Voltage Multiplier

The next stage is the voltage multiplier. The output voltage of the transformer is in the range of 220 volts which is not enough to generate the arc. Therefore the voltage is further increased using a voltage multiplier circuit.

Mosquito Killer Racket Voltage Multiplier

A voltage multiplier circuit is made of diodes and capacitors. Where each stage is made of a diode and capacitor. Each stage doubles the voltage of the preceding stage. Therefore a 3-stage voltage multiplier increases the voltage by 8 times.

The voltage multiplier increases the transformer output which is 220v up to 2k – 3k volts.


A capacitor is used at the output for storing the charge and discharging while in use. The capacitor discharges through the mosquito in the form of an arc.

Grid Mesh

The output from the capacitor is supplied to the grid mesh. There are two meshes i.e. inner mesh and outer mesh. The inner mesh is connected to one of the terminals while the two outer meshes are connected to the other terminal of the capacitor.

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How Many Volts is in an Electric Fly Swatter?

The output voltage depends on the design but it is usually between 500 – 3000 volts with a frequency of up to 200 kHz

Is Electric Fly Swatter Dangerous for Humans?

The electric fly swatter has inner mesh and outer mesh on both sides. Both outer meshes are at the same potential. It electrocutes a fly once it touches both the inner and outer mesh i.e. when it completes the circuit.

For safety reasons, the grid mesh is designed in such a way as to prevent touching both the inner and outer mesh at the same time.

Even if you touch both electrodes, it will only shock you. The charge stored in the capacitor is not enough to electrocute any human. It may not directly hurt you but it may indirectly become dangerous. The tiny spark can generate enough heat to ignite any alcoholic solutions or any other flammable products you have applied to your skin. Therefore it is necessary to keep it away from flammable materials.

Precautionary Measures

There are some precautionary measures taken while using the electric fly swatter.

  • Do not use it near any flammable surface or materials.
  • Please do not use it near food material as the food may get contaminated.

Benefits of Electric Fly Swatter

Here are some advantages of electric fly swatter over other mosquito-killing methods.

  • There are no insecticides or any other toxic chemicals involved.
  • The grid mesh is designed to have enough charge to incinerate a fly but not any human.
  • It is easier to handle and its operation is very simple.
  • It provides visual confirmation of a confirmed mosquito kill with a spark. Therefore clearing the doubt on the spot.

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