Electronic mosquito repeller

Here is the circuit diagram of an ultrasonic mosquito repeller.The circuit is based on the theory that insects like mosquito can be repelled by using sound frequencies in the ultrasonic (above 20KHz) range.The circuit is nothing but a PLL IC CMOS 4047 wired as an oscillator working at 22KHz.A complementary symmetry amplifier consisting of four transistor is used to amplify the sound.The piezo buzzer converts the output of amplifier to ultrasonic sound that can be heard by the insects.
Circuit diagram :

Main Parts Used:
IC CD4047 ( a Phased Lock Loop) - 1
4 Transistor ( 2 NPN (SL100) and 2 PNP (SK100))
Capacitors ( 4.7 nF, 22uF 16V)
10K Potentiometer - 1
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Note

• Assemble the circuit on a general purpose PCB.
• The circuit can be powered from 12V DC.
• The buzzer can be any general purpose piezo buzzer.
• The IC1 must be mounted on a holder
• R1 and C1 are deciding the frequency of Ocillator.

Posted in: Electronics,Mosquito Repellent,PLL