Mosquito Killer Bat Circuit Working Explanation

Mosquitoes are like tiny vampires and are present in every corner of the world. They are truly a nuisance, as they not only cause painful itching in the bite area but also have the potential to spread horrible diseases such as malaria. No matter how much you try to reduce their population, mosquitoes just keep growing in numbers. A cool way to eliminate these "devilish" insects is through electrocution.

A mosquito killer bat is designed just for this purpose. It is also called an electric flyswatter, mosquito bat, racket zapper, or zap racket. These devices are handheld and resemble a badminton racket or tennis racket in appearance. The device is activated by pressing and holding the button. The grid of the device is electrically charged; when a fly nearly bridges the gap between electrodes, a spark jumps through the fly and high voltage burns it. Inside the handle of a mosquito killer bat contains an electric rechargeable battery and a circuit board.

Mosquito Killer Bat Circuit Diagram

The schematic of a mosquito killer bat circuit is shown below. This circuit is similar to the circuit in an electroshock weapon or stun gun. However, the output voltage of the mosquito bat is much lower, typically about 500 to 3000 volts of direct current.

Working Principal of Mosquito Killer Bat Circuit

The mosquito killer bat, also known as a mosquito flyswatter, works through the combination of three main circuits: the battery charging circuit, the inverter circuit, and the voltage multiplier circuit.

Battery Charging Circuit

A mosquito killer bat circuit board receives power from a rechargeable 4V electric battery. Therefore, a charging circuit is needed to charge the battery. Typically, a Transformer-less or capacitive power supply is used. After a full charge, the battery provides service for 5 to 8 hours (depending on the user).

Inverter Circuit

The inverter circuit is the most crucial component of the mosquito killer bat circuit. This circuit converts the low DC voltage to high-voltage AC voltage, about 200 to 230 volts. The blocking oscillation concept is utilized in this inverter circuit, where only a single NPN transistor, a resistor, and a step-up transformer are employed.

Transformer Details -
Models: EE16 Transformer
Dimension: 17mm x 16mm
Type: High Frequency Transformer
Phase: Single
Winding Structure: EE
Bobbin Material: Thermal insulation board
Working Frequency: 1 kHz-200 kHz

Here is a small EE-type ferrite core transformer typically used with no air gaps between them. The primary winding (L1) has 35 turns of 0.2mm copper wire, the feedback winding (L2) has 13 turns of 0.2mm copper wire, and the secondary winding (L3) has 1250 turns of 0.05mm copper wire.

Voltage Multiplier Circuit

Due to the low inverted voltage, which could not build up the required voltage to create the spark between the two electrode grids in the mosquito killer bat, a voltage multiplier circuit is needed to Step up the voltage to the required level. The maximum continuous flow of most electric flyswatters is less than 5 milliamps (mA) of current after the initial discharge. This current level is safe, even when flowing from one arm to another, but not for mosquitoes.

Flashlight Circuit

Nowadays, some mosquito zapper bats come with single or multiple LED flashlights to be used as emergency lights. The light can be turned on using the ON/OFF switch on the bat handle, which allows the switch to select three modes: turning the flashlight on, turning it off, and activating the mosquito killer bat circuit.