The Light Theremin: Turning Light Into

Sounds

By: Scott RobbinsSenior Project for the Ithaca College Department of

Physics and Astronomy

History of the ThereminLeon Theremin lived in Soviet Russia, and was a young

physicist researching how to make proximity sensors for the military.

Lenin saw his device and wanted him to go around the world showing it off, with the Caveat that he act as a spy.

In America, he patented his device in 1928, and signed with RCA (Radio Corporation of America)

He was eventually kidnapped by the KGB and forced to return to Russia, but his instrument was already huge.

How does the Light Theremin Work?Using a phototransistor, you occlude light to

manipulate a voltage. This voltage is converted into a pitch with an

Arduino. This pitch is sent out as digital square waves. The volume of this signal is controlled by a second

photo transistor, and is sent through an amplification circuit, and connected to a speaker.

The Design and Final Product

Analyzing the Device: Pitch Control

Data AnalysisOn the left is the modulation of digital square waves. Below that we see the buffer circuit output, and to the bottom right we see the amplifier output.

Theory Behind Square Waves

The creation of square waves relies on using a Fourier series of increasing frequencies to approximate the square wave shape.

Photo Credit: Rice University

External Sound Analysis

Using Raven, I analyzed the sound coming from the speaker!

Challenges and ErrorsNeeded whole circuit to run on the same 5V. This

required ordering special op amps (TVL2362). Pitch control worked extremely well, however the

volume control circuit uses a lot of feedback, and exhibits strange behavior.

The device operates very differently depending on the ambient lighting in the performance space.

The additional frequencies produced by Fourier Series were too powerful at low frequencies.

Thank You!I’d like to thank Matt Sullivan for helping with my

writing,motivating me throughout the course and suggesting I use Raven for external sound analysis.

I’d like to thank Jennifer Mellot for being patient with me and helping me order parts.

I’d like to thank Dan Briotta for encouraging me to follow my weird ideas, and for teaching me so much about electronics and computer programming.

Thank you to the Ithaca College Department of Physics and Astronomy for enabling me to do this project!