1 electronic mosquito repellent circuit using 555

This circuit will emit sound around 22kHz, this frequency is very high that we can’t notice or hear it. According to some sources (to be confirmed) that sound at this frequency is annoying, disturbing noise for insects specially mosquitoes, and can drive them away.
The heart of the circuit is the 555 time IC that is adjusted to output  high frequency pulses  to the speaker. You can adjust the output frequency of the circuit by changing the values of R1, R2, and C1 using the formula   freq =1/[(ln(2)(C1)(R1+2R2)] or just use 555 timer calculator operated in astable mode.

insect repellent circuit

555 timer pins

Part list:
R1 - 1.2 kilo-ohms
R2 - 2.7 kilo-ohms
C1 - 10nF
C2 - 10nF
C3 - 470nF
SPK - piezo diaphragm or just use  a 16-ohms speaker 1/2W
        - 8 ohms speaker for high frequency is still okay
DC - 6V to 9V DC source or battery