Summer comes, and with it mosquitoes and all sorts of other midges appear. Everyone knows how mosquitoes annoy, 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 from dog barking. The device diagram is shown in Fig. 1, and the printed circuit board - in Fig. 2.
Consider the operation of the device. The VD1 diode is necessary to protect against incorrect power supply to the circuit. The device is powered by galvanic cells +1.5 V (the supply voltage can be increased to +9 V). With increasing voltage, the radiation power of the device increases. The sound-reproducing element of the device is the piezoelectric transducer ZP-1 (ZP-3, ZP-22) or any other, for example, from a watch. Resistors R2 ... R4 and R5, R6 set the operating point of the transistor VT1 and VT2. When voltage is applied to VT1, C1 is charged, the pulse from C1 briefly opens VT2, VT2 charges C2, which briefly opens VT1, and the operation cycle is repeated again. The frequency of the generator depends on the capacitances C1 and C2 and the resistance R6. You can turn on several more emitters in series with BQ1, then the output power will increase.
In the device, in addition to KT361B, you can use any similar transistors. It is advisable to use ceramic capacitors. The device hardly needs to be set up. It is only necessary to select the elements (R2, R4, C1, C2) that set the frequency of the generator. Next, a frequency meter is connected in parallel with R1 and the generation frequency is measured. It should be around 20 kHz. If the frequency is less, it is set by adjusting R6. The device consumes a very small current (about 1.5 mA), so one battery lasts for several months of operation. It is advisable that during operation the device be located as close to the ceiling as possible. mosquitoes prefer higher places for day and night parking.
Mosquito repeller 2.