Simple and easy-to-make electronic mosquito repellent

Circuit and working principle

The circuit schematic is shown below. 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. It also consists of a unidirectional thyristor SCR, a pulse transformer T, and a current-limiting resistor R3.

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, and then be electrocuted to death.

After the power supply is turned on, the positive half cycle of the power supply is rectified by the diode D1, and the positive voltage is provided to the anode and control electrode of the unidirectional thyristor SCR respectively through the step-down current limiting resistors R1, R2 and the potentiometer W. When the potentiometer W is adjusted so that 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. Changing the value of the potentiometer W changes the size of the conduction angle. That is, the output voltage can be changed. Due to the frequent conduction and cutoff of the unidirectional thyristor SCR. The high-frequency oscillation is formed, and a high voltage of 10,000V to 15,000V is induced on the secondary coil of the pulse transformer T. After being rectified by the high-voltage silicon stack D2, a DC shock high voltage is formed on the circular power grid.