40-KHz ultrasonic transmitter and receiver pair (40T/R-B/W) Schematic of the HC-SR04 module Get to the point In truth, my intent is not to provide a new translation of some well-worn “Arduino & ...

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 ...

Basing knowledge from a Lady Ada tutorial on PIR sensors, the additional Arduino code slides into place and some loose ends from part one are cleaned up.