This project refers to an Arduino sketch which uses an ultrasonic sensor for calculating the time return of the ultrasonic signal emitted by the sensor and the object reflecting the signal back. Then, with the help of appropriate physicomathematical formulas, it performs calculation of the distance between the sensor and the object causing the reflection signal. Also, the system includes a piezo speaker used to produce a tune when an object is detected too close nearby. This system could be used in security doors, on cars as a helper to park or anywhere else where distance at close proximity is important.

For more information you can get the project itself:


Below the image of the application: