Earl

user Electronics Engineer

city Innovuze Solution Inc.


  • Electric Fly Swatter Circuit

  • Created: Mar 12, 2017

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Summary

Flies and mosquitoes are important to the food chain and serve a purpose in the ecosystem. Despite their purpose, we cannot deny that they are one of the common pests in the households. They bit that can cause itch and they are also potential carriers of diseases. Most common way of getting rid of them is through chemicals, which can also cause health hazard in long-term exposure. A way of eliminating them without the use of chemical is to use fly swatters. A much cooler way of eliminating flies that doesn’t need force in swatting flies is by zapping them. The design is an electric fly swatter circuit that looks like a tennis racket.


The circuit is powered by a 3V supply made from series of AAA batteries. The switch has a built in LED indicator when the circuit is powered. This is to have visual indicator that the device is turned ON to protect the user from being electrocuted when zapping flies. A blocking oscillator circuit is used to produce a free-running signal. This is done using a single transistor, resistor, and a center-tapped transformer to execute sustainable oscillation across the two winding of the transformer. The resistor R1, R2, and capacitor C1 are the component responsible for the blocking oscillator circuit. Resistor R1 provides forward bias for the base of the transistor. The frequency of oscillation is determined by C1 and T2. The transformer T2 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. The voltage after the transformer must be around 200V. To increase the voltage a Crockcroft-Walten ladder network is used at the output of the transformer, which multiplies the low-voltage to a high voltage. The network makes 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. 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. The meshes are placed on a plastic tennis like racket, the inner mesh if where the positive connection is connected is places in between the two outer mesh, while both the outer mesh are connected to the ground. The distance of the inner and outer mesh prevents high voltage spark from arcing across the meshes when the bat is turned ON but not in used.


The electric fly swatter is helpful in dealing with flies in the household. The advantage of using an electric fly swatter compared to a normal fly swatter is that there is no need to mechanically crush the fly against a hard surface to kill it and also there are no chemicals involve. The Outer mesh are used as guards from the electrified inner mesh but caution is still advised with the mesh when using the electric fly swatter.

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