Of course, for a real Parking locator, perhaps it is too simple device. But it can be used in any toys or other purposes, perhaps just as interesting experiment.
The device consists of a housing, the front panel of which there are two of piezoelectric sound projector. They settle down on a soft surface (thin tight foam), glued to the frame. They are in the same plane and directed forward. If ahead in the distance more than 30 cm's nothing there, "machine" is silent. When approximation of the object begins to occur acoustic feedback between piezoelectric sounders, and is generated. Approaching the object of the sound increases and changes the tone. This can be judged the degree of approximation to the object.
Schematic diagram shown in the figure, is just a few details.
Foster acoustic node (microphone) is the piezoelectric sound projector B1. He connected between the input circuits A1. This allows to obtain the greatest sensitivity. Capacitor C1 adds positive feedback summing mode of the amplifier closer to the excitation. On the output is on another piezoelectric sound projector B2.
Powered locator from the source of DC voltage 9-12V. This may to be Krona rechargeable battery or car battery.
Piezoelectric sounders type 3P-22, or any other, without built-in the generators. It is desirable that they were in plastic housings
The capacitors can be of any type, for example, C1 - K10-7V. and C2 - C50-35
Almost all parts are assembled on a printed circuit Board of foiled fiberglass. Piezo-sounders can also be placed on the Board, but previously under them stick the foam pad that nebylo acoustic feedback via the Board material.
If when you turn right you hear the sound, but within 20-30 cm no there is no obstacle, this indicates the occurrence of AOC through the material of the PCB. Can B1 to connect the wires and place it away from the Board, placing it on the table on a piece of foam.
When approaching obstacles (hands book), should begin sounding.
Author: L. V. Skorohodov