Production of electric mosquito killer

Electric shock mosquito killing is more environmentally friendly, safer and more convenient than traditional mosquito killing methods. In addition, it has good mosquito killing effects and is becoming more and more popular. It uses ultraviolet light emitted by ultraviolet light tubes to lure mosquitoes. When mosquitoes touch the circular high-voltage power grid, the electrodes are short-circuited and the mosquitoes are killed. The following is an analysis of an electric shock mosquito killer with a simple circuit, low cost and easy to make.

1. Circuit and working principle

The circuit schematic is shown in Figure 1. It consists of a UV lamp light-emitting circuit, a high-voltage DC generator, a high-voltage circular power grid, etc. The UV lamp light-emitting circuit consists of a UV lamp H and a capacitor C1, and the DC high-voltage generator consists of diodes D1, D2, a potentiometer W, resistors R1, R2, and a capacitor C2. The unidirectional thyristor SCR, a pulse transformer T, and a current-limiting resistor R3, etc.

When the power supply is connected to 220V AC, the UV lamp H will light up. Its wavelength is about 253.7nm. It uses the phototaxis of mosquitoes to lure mosquitoes. When mosquitoes fly towards the UV lamp, they will inevitably touch the circular high-voltage power grid first. As a result, they will be electrocuted to death.

After the circuit in Figure 1 is powered on, the positive half cycle of the power supply is rectified by the diode D1, and then the positive voltage is provided to the anode and control electrode of the unidirectional thyristor SCR through the step-down current limiting resistors R1, R2 and the potentiometer W. Adjust the potentiometer W. When the voltage of the path reaches the trigger voltage of the control electrode, the unidirectional thyristor SCR is turned on, and the capacitor C2 is discharged through the primary coil of the pulse transformer T and the unidirectional thyristor SCR. The larger the capacity of C2, the higher the voltage induced by the secondary coil of the pulse transformer T. When the power supply voltage changes from positive to zero, the unidirectional thyristor SCR is turned off because the current flowing through it is less than the holding current. After that, the unidirectional thyristor SCR bears the reverse voltage of the power supply. It will not turn on again until the trigger pulse of the next cycle is added to the control electrode again. Change the value of the potentiometer W. The size of the conduction angle is changed, that is, the output voltage can be changed. Due to the frequent conduction and cutoff of the unidirectional thyristor SCR, high-frequency oscillation is formed, and a high voltage of 10000V to 15000V is induced on the secondary coil of the pulse transformer T. After rectification by the high-voltage silicon stack D2, a DC high voltage is formed on the circular power grid.

2. Selection of components

The pulse transformer T can be selected from the horizontal output transformer of a 12-14 inch black and white TV.

The power of the UV lamp H can be 3W. The high-voltage circular power grid needs to be made by yourself. The power grid can be made of iron wire of about φ0.5mm isolated and wound on a plastic frame, as shown in Figure 2. Note that the two iron wires A and B cannot have any contact, otherwise it will cause a short circuit. The distance between the two wires is more suitable to be 2mm.

3. Production and precautions

Except for the printed circuit board and the high-voltage circular power grid, the rest of the components of this electric mosquito killer can be purchased and assembled. When making it, the lamp tube is installed in the circular net, and the other components are installed in a box. If the components are good and installed correctly, turn on the power and adjust the potentiometer, and the electric mosquito killer can work normally. Although the voltage of this electric mosquito killer is relatively high, the current is at the microampere level, so it is safe to use. Even if you accidentally touch it, it will only feel like a needle prick, so there is no need to panic. When using it, plug in the power plug and rotate the potentiometer with the power switch to turn on the power. Continue to rotate and you can hear the high voltage generated, and the ultraviolet lamp in the circular net will glow. At this point, the electric mosquito killer is successfully made. When not in use, turn the potentiometer in the opposite direction to turn off the power.

When using, please note the following:

(1) During normal use, the round net should be hung high to achieve a good mosquito killing effect and prevent children from touching it.

(2) It is best to use it without other light sources to avoid affecting the mosquito killing effect. It can usually be used after going to bed.

(3) Do not touch the device within 2 minutes after it is turned off, as the charge on the network has not been completely discharged and may cause electric shock to your hands.

(4) As ultraviolet rays are harmful to the human body and eyes, the lamp power should not be too large and do not look directly at the lamp.