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Dogschaser - a scarecrow for dogs - a dog repeller

Dogecheiser - "horror story for dogs"

V.V. Bannikov, G. Oskva

Dogcezigerom ( from the English , dogchaser - dog pursuer ) is called a portable electronic device, capable of frightening off aggressive dogs. Such a device is useful not only for rural postmen, for whom it was originally intended, but for any passer-by, especially in the dark night time, not to mention defenseless women and weak children.

The action of the dogcezer is based on the emission of ultrasonic messages inaudible by man, but well perceived by the dog in the form of a kind of "silent" barking. In general, the dogmaker reminds of the device " Antilay ", but it is much simpler than it.

So, the simplest version of the dogmaster (Fig. 1) is assembled with only one digital microcircuit ( DD 1) and five transistors ( VT 1 ~ VT 5). On the logical elements DD 1.1, DD 1.2, resistors R 1, R 2 and capacitors Cl , C 2 an infrasonic generator is made. It is a symmetrical multivibrator, which forms rectangular pulses with a frequency of about 1.5 Hz. The second symmetrical multivibrator, built on the elements DD 1.3, DD 1.4, resistors R 6, R 7 and capacitors C 5 , C 6 , is an ultrasonic generator whose frequency of rectangular pulses is 20 kHz and periodically (every 0.66 s) is increased approximately 4 times. A comparatively smooth periodic "withdrawal" of the ultrasonic frequency upward is performed by the node containing the resistors R 3- R 5, the capacitor S3, the transistor VT 1 and the diodes VD 1. VD 2.

Formed at the output terminals 10 and 11 of DD 1, ultrasonic vibrations of directly carbon form have a small power. Therefore, they are amplified by the power of a two-stroke bridge amplifier assembled on transistors VT 2- VT 5. The emitter load of this amplifier is a piezoceramic radiator BF 1. Ultrasonic vibrations ( modulated by infrared sound ) are excited in it after pressing the button SB 1, which functions as a conventional power switch. The power supply circuit of the DD 1 chip is protected against accidental " reverse polarity " of the GB 1 battery by the VD 3 diode , and the C 4 and C 7 filter capacitors ensure that the power supply passes respectively high frequency and low frequency oscillations.

If instead of piezo - emitter SP-1 apply car piezo siren ACT- 10, the range of the dogmezer will noticeably increase. The GB 1 battery can be made up of six to ten galvanic cells (316), D-0.25 batteries or a ready-made 12-volt L 1028 battery, or the worst-end 9-volt Cronu or Korund. The chip K561LA7 can be replaced with K176LA7, K1561LA7 or 564LA7. Diodes VD 1- VD 3 - any silicon small-sized, transistor VT 1 - any silicon low-power with a base current gain of at least 30. Transistors VT 2, VT 4 and VT 3, VT 5 are replaceable by any of the series KT3102 and KT3107, respectively.

When manufacturing a dogmaker, you can do without microchips at all, however, then the number of transistors will increase to nine. Thus, Fig. 2 shows the scheme of the second version of the device, or rather its fragment (the rest is shown in Fig. 1), in which the infrasonic generator is assembled on transistors VT 6, VT 7, capacitors C 1 , C2 and resistors R 1- R 4 , and ultrasonic transistors VT 8, VT 9, capacitors C 4, C 5 and resistors R 7- R 10. The ultrasonic frequency "retraction" circuit contains resistors R 5, R 6, capacitor SOC, transistor VT 1 and diodes VDI , VD 2 .

In order to adjust the dogcezer , which mainly consists in selecting the resistance of the resistors R 3 (Fig. 1) or R 5 (Fig. 2), you can control its operation by hearing, for the time in parallel, the capacitor C 4 and C 5 are connected by soldering two capacitors a capacity of at least 6800 pF each.