Summer comes, and with it come the mosquitoes, and all sorts of other midges. Everyone knows how annoying mosquitoes, especially at night.
The proposed device allows to be protected from all insects, and if you increase the frequency of the generator to the ultrasound, then a dog barking. Diagram of the device shown in Fig.1, a printed circuit Board in Fig.2.
Fig.1
The sound reproducing device element is a piezo oscillator SN-1 (SN-3, SN-22), or any other, such as watches.
Consider the operation of the device. The VD1 diode is needed to protect from wrong connection of power to the circuit. The device is powered by galvanic cells +1.5 V (the voltage can be increased to +9 In). With increasing voltage increases the radiation power of the device.
Resistors R2...R4 and R5, R6 set the operating point of the transistor VT1 and VT2. By applying voltage on VT1 C1 is charged, a pulse with short-C1 opens VT2, VT2 charges C2, which briefly opens VT1, and the cycle repeats again.
The oscillator frequency depends on the values of capacitances C1 and C2 and R6.
Can consistently with BQ 1 to include several emitters, then the output power will increase.
Fig.2
In the device, except CTB, you can use any similar transistors. Capacitors it is desirable to use ceramic.
In commissioning the device is practically not needed. You just need to pick the elements (R2, R4, C1, C2), which specify the frequency of the oscillator. Further connected in parallel with R1 the frequency and measure the frequency of oscillation. It should be about 20 kHz. If the frequency is less, it put up by adjusting R6.
The device consumes very low current (approximately 1.5 mA), so one battery is enough for several months of operation.
It is desirable that when the device was located as close as possible to the ceiling, because mosquitoes prefer the higher spot for daytime and night "Parking".
Author: K. Churasco, Brest; Publication: N. Bolshakov, rf.atnn.ru