A simple Theremin using a HC-SR04 Ultrassound Sensor and a Arduino.
You will need: • an Arduino; • a HC-SR04 Ultrassound Sensor; • a speaker, buzzer or anything that can reproduces sound.
For this application you will need the Tone.h library, besides the comon Ultrassonic.h. You can find Tone.h in: https://github.com/andrebahiense/PolyphonicPiano And Ultrassonic.h you can add through the Arduino IDE.