At the end of every semester, we get a bunch of amazing and well-documented trainee jobs from Cornell’s ECE4760 class. [Scott] and [Alex]’s infrared theremin is no exception.
The classic theremin design employs each of the player’s hands as the grounded plate of a variable capacitor in an LC circuit. For the pitch antenna, this circuit is part of the oscillator. For the volume antenna, the hand capacitor detunes another oscillator, changing the attenuation in the amplifier.
[Scott] and [Alex] put a twist on the theremin by utilizing two IR sensors to manage volume and pitch. The sensors compute the place of each hand and output a voltage inversely proportional to its distance from the hand. An ATMega1284P converts the signal to an 8-bit binary number for processing. They developed four voices into it that are accessible with the push-button switch. The different voices are produced with wave combinations and modulation effects. In addition to classic Theremin, you can play in pure sine, sawtooth, and FM modulation.
If you’re just not that into microcontrollers, you could build this digital IR theremin instead. If you find IR theremins soulless or plebeian, try this theremincello.
[Thanks Bruce]