How to construct your own Ultrasonic Motion Detectors

This project involves constructing ultrasonic motion detectors device at 40 kHz frequency and are used to detect any moving object where this device is installed. The printed circuit board (PCB) measures only 1-1/2 by 3 inches.
The device detects motion from 4 to 7 meters away. Once that occurs, a red LED turns ON, butwith additional circuitry attached to the output, the detector can turn on lights, sound buzzers,trip a recording device, or even call the police. Also, the circuit can be made to sound off with a message when anyone moves within its field of detection.
Using various voice recording and playback circuits, you might even have the device provide a pleasant greeting or snarl with a barking dog sound when someone approaches the front door. As you can see, the project can be put to work in a variety of ways.
You can place it in the driveway, on the porch, garage, basement or any place where you need to be informed of any object that comes near the location. A detailed explanation of how the circuit works is described here. First timers who construct this project will learn a great deal about ultrasonic frequency application, its concept and the difficulty encountered when installing the completed device.
Download the project PDF file here. You will need adobe reader to open the file. If you do not have one, you can download the free reader from http://get.adobe.com/reader website.