1. The Light Theremin:
Turning Light Into Sounds
By: Scott Robbins
Senior Project for the Ithaca College Department of Physics
and Astronomy

2. History of the Theremin
 Leon 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.

3. 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.

4. The Design and Final Product

5. Analyzing the Device: Pitch Control

6. Data Analysis
On 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.

7. 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

8. External Sound Analysis
Using Raven, I analyzed
the sound coming from
the speaker!kU
S
-20
-10
10
20
30
0.000
5 10 15 20 25 30 36.052
kHz
S
1.000
1.500
2.000
2.500
3.000
3.500
0.000
5 10 15 20 25 30 36.052
kHz
S
1
2
3
4
5
0.000
2 4 6 8 10 12 14 16 18 20 22 24 26 28 29.6

9. Challenges and Errors
 Needed 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.

10. 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!