Mosquito Repeller

Summer comes, and with it mosquitoes and all sorts of other midges appear. Everyone knows how annoying mosquitoes are, especially at night. The proposed device allows you to protect yourself from all insects, and if you increase the frequency of the generator to ultrasound, then also from dog barking. The device diagram is shown in Fig. 1, and the printed circuit board is shown in Fig. 2.

Let's consider the operation of the device. Diode VD1 is necessary to protect against incorrect power connection to the circuit. The device is powered by +1.5 V galvanic cells (the supply voltage can be increased to +9 V). As the voltage increases, the radiation power of the device increases. The sound-reproducing element of the device is a piezo emitter ZP-1 (ZP-3, ZP-22) or any other, for example from a wristwatch. Resistors R2...R4 and R5, R6 set the operating point of transistor VT1 and VT2. When voltage is applied to VT1, C1 is charged, a pulse from C1 briefly opens VT2, VT2 charges C2, which briefly opens VT1, and the operating cycle is repeated again. The frequency of the generator depends on the values ​​of capacitors C1 and C2 and resistance R6. You can connect several more emitters in series with BQ1, then the output power will increase.