The electronic dog repeller circuit produces a discomforting but not harmful, high frequency sound, audible to dogs but not to humans. Help stop the approach of unwanted dogs at up to 15 feet. It uses 555 circuit at is easy to build, this is a dog chaser schematic that you can do it yourself.
From R3 adjust the resonance frequency of the Ultrasonic Ceramic Transducer. 100Vpp were obtained at 30 kHz. Without piezo the output voltage is 200 Vpp.