Mosquitoes are tiny in size but they come in big numbers, and no matter how much we try to eliminate them, these micro pests keep growing with their population.
Today you will find plenty of techniques available in the market that provide us with the options of getting rid of these insects, some are in the form of sprays, some are in the form of coils and mats that need to be burned. Most of these variants are chemical based which either drive away or kill pests due to their toxic nature.
Needless to say if these chemicals have the potentials of harming the pests they would do the same to us in a smaller scale, but nevertheless in the long run they could cause significant health hazards.
However there's an innovative method of killing mosquitoes by electrocution which doesn't involve chemicals and also the procedures are clean, without any mess.
Moreover the electrocuting equipment being in the form of a tennis racket makes the swatting playful and provides an opportunity to avenge ourselves from these pests.
The proposed mosquito swatter bat or mosquito zapper circuit can be seen in the diagram given below, the functioning may be understood with the following points:
The shown configuration employs a blocking oscillator concept as used in joule thief circuits, wherein only a single transistor and a center tapped transformer execute sustainable oscillation across the two winding of the transformer.
R1 along with the preset and the C1 determine the frequency of oscillation. R1 ensures that the transistor never comes within an unsafe zone while adjusting the preset.
TR1 here is a small ferrite core transformer built using the smallest EE type of ferrite core.
The winding inside the coil is calculated for working with 3V DC supply, meaning the circuit becomes compatible with a 3V battery pack made by putting a couple of AAA cells in series.
When power is applied to the circuit, the transistor and the center tapped transformer instantly start oscillating at the specified high frequency. This forces the battery current to pass across the TR1 winding in a push pull manner.
The above switching generates a proportional induced high voltage across the secondary winding of TR1.
As per the winding data, this voltage could be somewhere around 200V.
To further enhance and lift this voltage to a level which may become suitable for generating a flying spark, a charge pump circuit involving a Crockcroft-Walten ladder network is used at the output of TR1.
This network pulls the 200V from the transformer to about 600V.
This high voltage is rectified and applied across a bridge rectifier where the voltage is appropriately rectified and stepped up by the 2uF/1KV capacitor.
As long as the output terminals across the 2uF capacitor are held at some specified distance, the stored high voltage energy inside the capacitor is unable to discharge, and stays in a standby condition.
If the terminals are bought at a relatively closer distance (about a couple of mm) the potential energy across the 2uF capacitor becomes capable enough to break the air barrier and arc across the terminal gap in the form of a flying spark.
Once this happens, the arcing momentarily stops, until the capacitor charges fully to execute another spark, and the cycle keeps repeating as long as the gap distance is kept within the saturable distance of the high voltage.
When this circuit is applied as a mosquito swatter, the end terminals of the 2uF capacitor are appropriately tied or connected across the internal and the external bat mesh layers.
These metal mesh layers are woven and positioned tightly over a sturdy plastic frame in such away that these are held apart at some distance. This distance prevents the high voltage spark from arcing across the meshes while the bat is in a stand by condition.
The moment the bat is swatted over a fly or a mosquito, the insect gets bridged itself between the bat meshes and allows the high voltage to find and easy conducting path through it.
This results in a crackling sound and a spark through the insect, killing it instantly.
The circuit of the mosquito zapper explained here also includes an small transformerless charger circuit which may be connected to mains for charging the 3V rechargeable battery when the bat stops generating sufficient arcing voltage while swatting the mosquitoes.
TR1 winding details can be found in the following image:
Warning: The above design is not isolated from mains input voltage and therefore will be floating with lethal mains AC, the user is advised to exercise extreme caution while handling or testing the circuit in open and powered condition.