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.

A low-cost (~$100), do-it-yourself (DIY) ultrasonic water level sensor/datalogger has been designed, constructed, and tested for use in education, citizen/community science, and research settings. The ...

This one is an unusual smart home project, potentially - how to monitor a fish tank’s health with an AI-enabled ultrasonic sensor system. The detailed project is highlighted on Hackser.io and features ...

Ultrasonic sensors work using ultrasound to build up an image of your fingerprint (yes, really) and work better with messy fingerprints - if your hands are wet or oily with sun cream, for example.