The electronic dog repellent circuit diagram below is a high output
ultrasonic transmitter which is primarily intended to act as a dog and
cat repeller, which can be used individuals to act as a deterrent
against some animals. It should NOT be relied upon as a defence against
aggressive dogs but it may help distract them or encourage them to go
away and do not consider this as an electronic pest repeller. The
ultrasonic dog repellant uses a standard 555 timer IC1 set up as an
oscillator using a single RC network to give a 40 kHz square wave with
equal mark/space ratio.
This frequency is above the hearing threshold for humans but is known to be irritating frequency for dog and cats. Since the maximum current that a 555 timer can supply is 200mA an amplifier stage was required so a high-power H-bridge network was devised, formed by 4 transistors TR1 to TR4. A second timer IC2 forms a buffer amplifier that feeds one input of the H-bridge driver, with an inverted waveform to that of IC1 output being fed to the opposite input of the H-bridge.
Cat And Dog Repellent Circuit diagram:
This frequency is above the hearing threshold for humans but is known to be irritating frequency for dog and cats. Since the maximum current that a 555 timer can supply is 200mA an amplifier stage was required so a high-power H-bridge network was devised, formed by 4 transistors TR1 to TR4. A second timer IC2 forms a buffer amplifier that feeds one input of the H-bridge driver, with an inverted waveform to that of IC1 output being fed to the opposite input of the H-bridge.
Cat And Dog Repellent Circuit diagram:
Cat And Dog Repellent Circuit Diagram
This
means that conduction occurs through the complementary pairs of TR1/TR4
and TR2/TR3 on alternate marks and spaces, effectively doubling the
voltage across the ultrasonic transducer, LS1. This is optimised to
generate a high output at ultrasonic frequencies. This configuration was
tested by decreasing the frequency of the oscillator to an audible
level and replacing the ultrasonic transducer with a loudspeaker; the
results were astounding. If the dog repellent circuit was fed by a bench
power supply rather than a battery that restrict the available current,
the output reached 110dB with 4A running through the speaker which is
plenty loud enough!
The Dog and Cat repellant was activated using
a normal open switch S1 to control the current consumption, but many
forms of automatic switching could be used such as pressure sensitive
mats, light beams or PIR sensors. Thus it could be utilise as part of a
dog or cat deterrent system to help prevent unwanted damage to gardens
or flowerbeds, or a battery powered version can be carried for portable
use. Consider also using a lead-acid battery if desired, and a single
chip version could be built using the 556 dual timer IC to save space
and improve battery life.
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