Shoo Dog !

Description: Annoyance often arises from inconsiderate dog owners whose pets relieve themselves on private property. This issue is challenging to resolve through verbal or physical means, making an electronic solution more effective and amicable. The circuit begins with a commercially available passive infrared (PIR) sensor, commonly found in low-cost motion detectors. The relay contact of the PIR activates the power supply for the circuit depicted. This power supply produces approximately 15 V after rectification by diodes D1-D4 and filtering through resistors R1 and R2, along with capacitors C2 and C3. This voltage powers a square-wave oscillator consisting of IC1a, R3, and C1, with IC1b functioning as a buffer. The two additional gates are connected in series with the buffer to ensure defined operational levels. The resistor-capacitor network is designed to achieve an oscillation frequency exceeding 20 kHz, with the amplitude adjustable via potentiometer P1. An integrated circuit power amplifier follows the oscillator to boost this tone to a level that is particularly disturbing for dogs and other small animals. The ST Microelectronics TDA2030 is employed for this purpose. The peripheral circuitry adheres to the specifications outlined in the data sheet. With a supply voltage of 15 V, the TDA2030 can produce approximately 5W into a 4-ohm speaker. The data sheet indicates that the supply voltage can be increased to 30 V, which allows for an output of 16W into 4 ohms (or 11W into 8 ohms). However, the 4093 must remain at a maximum supply voltage of 15 V, which is the upper limit for this CMOS IC. Any cost-effective piezoelectric tweeter with a frequency response exceeding 20 kHz can be utilized for the speaker, with a preference for the highest possible sound pressure level (greater than 100 dB). A suitable example can be found on page 626 of the Conrad Electronics catalog. The impedance of such speakers typically rises to around 40 to 50 ohms at 20 kHz, making it impossible to achieve the power specified in the data sheet using this circuit. Nonetheless, the output should be sufficient to deter both the dog and its owner.

The circuit utilizes a PIR sensor to detect motion, triggering the activation of the power supply circuit. The power supply comprises a bridge rectifier formed by diodes D1-D4, which converts AC to DC, followed by a filtering stage that smooths the output voltage. This voltage feeds into a square-wave oscillator built around a CMOS IC, which generates a high-frequency square wave. The output from this oscillator drives a power amplifier, specifically the TDA2030, which is designed to deliver significant audio power. The amplifier's output is connected to a piezoelectric tweeter capable of producing high-frequency sounds that are unpleasant to dogs, thereby serving as a deterrent.

The design considerations include ensuring that the oscillator operates at a frequency above 20 kHz, which is generally inaudible to humans but can be perceived by dogs. The adjustable amplitude allows for fine-tuning the output level to maximize effectiveness while minimizing potential disturbances to nearby humans or other animals. The choice of a piezoelectric tweeter with a high sound pressure level ensures that the generated sound is loud enough to achieve the desired deterrent effect. Overall, the circuit presents an innovative and humane solution to the issue of dogs relieving themselves on private property.We`ve all had occasion to be annoyed at inconsiderate dog owners whose animals relieve themselves on the private property of others. This problem can hardly be solved in a lasting manner using verbal (or even physical) means, so recourse to an electronic remedy is better and friendlier.

The starting point for this circuit is a ready-made passive i nfrared sensor (PIR), such as can be found in inexpensive movement detectors. The relay contact of the PIR energizes the power supply of the circuit shown here. The power supply generates a voltage of around 15 V after rectification by D1-D4 and filtering by R1/C3 and R2/C2. This voltage powers a square-wave oscillator comprising IC1a, R3/C1 and IC1b (acting as a buffer). The two unnecessary gates are simply connected in series with the buffer, so that they work with defined levels.

The R-C network is dimensioned such that frequency of oscillation is greater than 20 kHz. The amplitude can be set using P1. An IC power amplifier follows the oscillator to amplify this tone to a level that will be deafening for dogs (and other small creatures). We use the ST Microelectronics TDA2030 ( The peripheral circuitry corresponds to the specifications in the data sheet.

With a supply voltage of 15 V, the TDA2030 can generate around 5W into a 4 speaker. According to the data sheet, the supply voltage of the TDA2030 can be increased to as much as 30 V, at which level it generates a hefty 16W into 4 (or 11W into 8). However, the 4093 still must be operated at 15V, which is the maximum allowable supply voltage for a CMOS IC.

In principle, any inexpensive piezoelectric tweeter whose frequency response extends past 20kHz can be used for the speaker; it should have the highest possible sound pressure level (>100dB). A suitable type is listed on page 626 of the Conrad Electronics catalog. The impedance of such speakers rises to around 40 to 50 at 20 kHz, so it is naturally not possible to obtain the power listed in the data sheet using this circuit.

Nevertheless, it should be more than enough to scare off dog and master.