Simple NE555 ultrasonic dog walking machine

1206RGB (single)

Single chip microcomputer STM32L151CCU6

Filter 18.432M

It is said that many animals are particularly well-developed in hearing and can hear higher frequency sounds that humans cannot hear. Many commercial pest drivers are manufactured according to this principle, usually with a frequency range of 30 to 50 kHz.
The principle of this design is also the same, but it is different. This is a powerful audio/ultrasonic generator that can be used to drive dogs. With it, you can let your dog quiet down at midnight, no longer screaming or surrendering other people's dogs (probably the thieves would like this thing very much).
Therefore, I decided to redesign a circuit (of course, based on the most commonly used 555), using a variable resistor to change the frequency and using a piezoelectric buzzer that emits a relatively large enough sound - 82dB.
The circuit is very small and can be assembled in half an hour. The parameter values ​​for most components are not required to be accurate, but you should be aware that these values ​​may change the frequency of the generation. Adjustment of the variable resistor: A larger resistor makes the frequency lower. Since different dogs will react to different frequencies, you may need to make constant experimental adjustments to the circuit.
The circuit is very simple and may be a trivial matter for you. The 10nF (0.01uF) capacitor is very critical, it determines the frequency, most of the ceramic capacitors work very unstable, the error is about 20%, it is very difficult to use, so it is best to use a stable polyacrylic capacitor. A larger capacitance value means a lower frequency.

An oscilloscope is necessary during the adjustment process. Since I don't have an oscilloscope, I used Winscope (winscope is an analog oscilloscope software developed by Russian scientist Konstantin Zelidovich for electronic experiments on the computer for frequency analysis. It uses the sound card to sample the waveform and display the result. In addition, winscope also has storage facilities and powerful FFT (Fast Fourier Transform) routines that make winscope a spectrum analyzer. Although its measurement range is limited to 22 kHz, you can just see how the circuit works. Test if the circuit works at different frequencies. The 4k7 variable resistor and 10nF capacitor produce a frequency of 11K to 22kHz, which is just right.
This circuit does not require etching the board, and the board is ready. If necessary, you can install the circuit into a small plastic box, or you can add a light tube as an indicator light. The circuit consumes very little power and a 9v battery can work for a long time.
Further experiment: I used an enlarged version of this circuit to make a louder sound. Further attempts have not been successful, mainly because the high frequency characteristics of 555 have deteriorated. Probably I have to use a multiplier circuit - I don't know if my thoughts are a bit wrong. Another use of the circuit is "a simple device to prevent dog screaming", adding a sound trigger to the circuit, set to: as long as your dog screams in the dark, it emits an ultrasonic hum. After a period of training, your dog won't scream at night.