In one of my earlier posts I discussed a simple mosquito zapper circuit, in this article we study a similar design which is commercially used in all mosquito rackets, or mosquito bat units.
How this electronic mosquito racket circuit works
The article was originally posted in one of the Chinese electronic sites and I found it quite interesting and an easy design, and therefore decided to share it here.
When the power switch SA is pressed, the high-frequency oscillator composed of the transistor VT1 and the step-up transformer T is energized using the 3V DC supply generating a high-frequency alternating current of about 18kHz, boosted by T to about 500V.
This high voltage ranging at 500V is then further stepped up using a ladder network, which is made up of three 1N4007 Diodes, capacitors C1- C3.
This network steps the T output to approximately three times its original value and we get around 1500V which gets stored inside a high voltage PPC capacitor positioned at the extreme end of the ladder network.
This stepped up 1500V is then terminated to the mosquito racket net, which now becomes armed with this high voltage and when ever a mosquito tries to get past the racket net, it instantly gets electrocuted through this high voltage discharge from the PPC capacitor.
An Led can be seen included in the design, it is used for indicating the ON/OFF states of the circuits and also the how much power is left inside the battery. The series resistor R1 decides the intensity of the LED which can be tweaked as per preference to maximize battery life
The oscillator transistor used in this Chinese mosquito zapper circuit is a 2N5609, which is an NPN BJT, having a current handling capacity of around 1 amp, however other similar variants such as 8050, 2N2222, D880 etc can also be tried instead of the original number in the design.
The LED can be any 3mm tiny 20mA type of LED, the diodes can be 1N4007 type although fast recovery would work much better, therefore you can also try replacing them with BA159 or FR107 type of fast diodes. The resistors could be 1/8 watt rated or even ¼ watt can be used without issues.
The capacitors must be strictly PPC types rated not less than 630V.
How to Build the High Voltage Transformer
This is ideally constructed using a 2E19 type ferrite cores and the respective matching plastic bobbin.
L1 consists of φ0.22mm enameled copper wire or magnet wire with around 22 turns
L2 is identically wound using φ0.22mm enameled copper wire or magnet wire with around 8 turns
Finally, L3 which constitutes the secondary winding uses φ0.08mm enameled copper wire and has around 1400 turns.
The above discussed mosquito bat circuit can be also used for killing various kinds of bugs through electrucution using some other suitable format. For example this design could be integrated with a mesh over a dish having a mosquito/bug bait, which might attract the mosquito/bugs and eventually electrocute them as soon as they try to enter the dish through the electrified mesh.