Instead, it relies on an ultrasonic distance sensor to detect a hand (or foot) waved in front of the door. An Arduino Leonardo runs the show, sounding a buzzer when the ultrasonic sensor is triggered.

If you have one ultrasonic sensor and a microcontroller, you can detect plenty of useful things, like the water level in a rain barrel or the distance traveled by a tablet along a rail.

An Oakville high school student is developing new type of white cane to assist the blind and visually impaired. The concept includes vibration-based GPS navigation, ultrasonic proximity sensors ...