Ultrasonic Dog Repellent device. It generates Ultrasound not audible to Human and repels Dogs.
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To build an ultrasonic dog repeller you will need the following: The first operation is to open the alarm. Make sure you buy one that can be handheld if you plan to take it with you when out walking. Using the fine hacksaw, cut very carefully into the casing of the alarm, but not any deeper. You are cutting the alarm in two but only the casing, so cut a circle around the base until it separates. When the casing separates you should have two halves, one with the speaker and one with the electronics.
Ultrasonic Cannon Dog Repeller by cinidavide is licensed under the  license.
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While the gap between dogs (45,000 Hz) seems pretty far from the mouse level (up to 60,000 Hz), do commercially-available ultrasonic repellers fall in the "safe range" for dogs? Now you have an ultrasonic dog repeller to keep those barking dogs at bay.
Photo provided by PexelsUltrasonic Dog Repeller Anti Bark Training Device Sound Trainer
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Dog Repeller mainly based on producing an ultrasonic waves with frequency annoying dogs and be strange for them so they scare from this sound and ran away .basic ...Another ultrasonic dog repeller, the Dog Dazer works by emitting that high frequency which canines utterly dislike. It comes with a clip so you can attach it to any part of your clothing and take it with you, and it’s effective for a distance up to twenty feet.When we hear the word “Ultrasonic" we often refer it to bats and dolphins communication. Technically, “Ultrasonic" applies to sound that is anything above the frequencies of audible sound, and includes anything over 20kHz. Frequencies used for medical diagnostic ultrasound scans extend to 10 MHz and beyond. This dog repellent ultrasonic circuit will chase away angry dogs. It comprises of a 555 timer IC, a speaker/piezoelectric and a little ferrite transformer.

The main part of this circuit is a 555 timer IC. A 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation, and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-flop element. Derivatives provide up to four timing circuits in one package. You can use the 555 effectively without understanding the function of each pin in detail. Frequently, the 555 is used in astable mode to generate a continuous series of pulses, but you can also use the 555 to make a one-shot or monostable circuit. The 555 can source or sink 200 mA of output current, and is capable of driving wide range of output devices.

To use this circuit adjust R3 at resonance frequency of the piezo transducer for maximum amplitude of the repeller ultrasonic sound. At 30 KHz this can reach a value of 108 Vpp. Without the piezo the output voltage is around 200 Vpp.
Many people are interested in their safety when it comes to aggressive dogs, and an ultrasonic dog repeller emits a sound that is out of the human hearing range. This type of device is intended to effectively startle and confuse the aggressive animal to stop its pursuit. Although this type of device has had some success, there are other options available that may prove to be more effective.There are two major problems with an ultrasonic dog repeller. For one, there’s no telling when the device is actually working, as humans can’t hear it. It’s possible, even with some kind of indicator, that the device isn’t producing a single sound when activated. These devices are also difficult to aim, as they emit in a narrow angle. When under attack by a rushing canine, this can be a serious liability, and it might be part of the reason why these devices can be less effective than those that use audible tones.The volume of an ultrasonic dog repeller and the sound it emits also seems to be a factor. The louder the sound, and the more amplified and repulsive it may be. Sounds within an animal’s sensitive hearing range will be perceived as louder to the animal than sounds of the same decibel level outside the animal’s sensitive hearing range. Ultrasonic sounds are far outside dog’s sensitive hearing range.