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Theremillusion
Steven Bennett, Imen Ben-Neticha, Snigdha Jonna, Sandra Jenkins,
Advisor: Paul Siqueira
ABSTRACT
The end goal in the design and implementation of the Theremillusion has been the notion of creating a user
friendly interface that would teach people how to play a theremin. The theremin is an instrument that has existed for
many decades. It can be played easily by moving your hand through the electric field, disrupting the electric field
and outputting a note. However, due to lack of a reference, it is very difficult to master playing the theremin,
especially those new to music instruments in general.
The initial goal of the Theremillusion is to make the theremin more accessible to everyday people by creating a
friendly interface that would serve as a guide to the user. As mentioned above, the Theremin is lacking a reference.
To address this shortcomming, the Theremillusion is designed with Electro-Luminescent (EL) wires to lead the user
through playing a song. The wires are positioned to match specific notes needed to play a song.
The Theremillusion allows the user to pick what song they would like to learn. It then teaches the user to
play the song on the theremin by lighting up the wire one note at a time. The next note will only appear after the user
has played the current note successfully. After the song has completed, the user is shown their score on the
Theremillusion. The score is based on how many notes the user has received correctly within a specific time.
I. INTRODUCTION
A theremin is a musical instrument first designed
and demonstrated by a Russian physicist named Leon
Theremin in 1921 (Oddmusic). The pitch of the sound
from the instrument is produced by two beat frequency
oscillators that operate in the radio frequency. One
oscillator frequency is fixed while the other’s frequency is
modified by a change in capacitance when a person’s hand
enters the magnetic field of an antenna. The difference
between the two oscillators creates a “beat frequency”
which is what creates audible the music note pitch
(Dawson). The volume of that pitch is also controlled by a
similar system.
The Theremin is one of the earliest electronic
instruments and thus it received a lot of attention when it
was first created. Recently there has been a resurgence of
interest in the Theremin and its unique properties as a
musical instrument; the instrument is played without
physically touching anything and it has a continuous range
for both pitch and volume. These aspects make it an
instrument that is extremely easy to make sound with, but
very difficult to play well. The player cannot tell if the note
is correct or not until hearing it played, thus making the
technique akin to a negative-feedback mechanism
(Skeldon). Consequently, the user must already have
extensive ear training; knowledge of not only exactly what
pitch they want to play but also the ability to hear the
difference between a correct note and one that is slightly
off pitch. This has made the device very hard for
beginners to learn how to play, and thus has limited its
popularity.
Our project is focused on making the Theremin
easier to play for beginners by incorporating a visual
reference and feedback for where the player will place their
hand. This feedback will allow players to not only learn to
play the Theremin, but to improve their ability to hear
tones. We are focusing specifically on the western scale,
however further research for this project might include a
way to teach different methods for categorizing notes and
music besides the western view.
II. REQUIREMENT SPECIFICATION AND
DESIGN
A. System Overview
The user should be able to play the
Theremillusion and receive feedback. The aim of this
project is to have bidirectional communication between
theremin and the software designed. The user interacts
with the theremin and receives feedback through a display.
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potentiometer but by the changing capacitance associated
with the antenna. The frequency of 172 kHz may seem
Figure 1a. Theremin and Discrete Mode Overview
The basic system architecture is as follows. The
Theremillusion is broken down into two major components,
the construction of the Theremin and the software for the
sound output and the construction of the display and the
software integration of a teaching mode.
In figure 1a, it is apparent that there is switching
capability. This allows the Theremillusion to play in two
modes: Continuous and Discrete. The Theremin is
naturally a continuous instrument meaning that there is not
a defined range as to when a note ends and begins. This
creates a continuous sweep noise. To many, this means that
they have a hard time hearing when notes played are in
tune or not as the notes are not distinct. The theremin is
associated with a very eerie sound and a high level of
difficulty to play. In the Theremillusion, the Discrete mode
enables the user to play distinct notes, presenting the user
with more familiar sounds. This mode is easier for
teaching because there is an audible difference between the
notes and these notes actually correspond to where they
should normally place their hands when playing in
continuous mode. Consequently the user can learn the
different note types and in turn learn to play the Theremin.
B. Traditional Theremin
For our discussion of the how the Theremin works,
we are using the example Theremin design we began
building to deepen our understanding of the instrument.
The Theremin is built with three main parts, the pitch
control, the volume control, and the output control.
fairly arbitrary to some extent it is. As long as the two
oscillators operate at the same value when there is no
human interference the circuit will work. The frequencies
do have to be high enough to give the right offset for
changing the audible tone. It is important for the audible
range of the Theremin’s sound. In order to fully understand
this, an explanation of how the system works is required as
follows.
The pitch circuitry is made up of beat frequency
oscillators (BFO) which are directly used to generate the
tone of the instrument. This BFO contains two independent
oscillators each with their own angular frequency. The
schematics for these two oscillators can be seen in figures
two and three.
The outputs of these two oscillators are put
through a mixer (a heterodyne mixer) which multiplies the
two signals together (Skeldon). The schematic for this can
be seen in figure four. This has two frequency components:
one that is the sum of the two frequencies and another that
has the difference. For our purposes, we only want the
differences between the frequencies of the two oscillators,
so the signal is then passed through a low pass filter .
The way the Theremin produces audible
frequencies is through altering very slightly the frequency
of the Variable Pitch Oscillator in figure three so that the
beat frequency (the frequency that results from the
difference of the two oscillators’ frequencies) changes.
This is done through the interaction of an antenna, or even
just interfering with the inductors on the circuit with your
hand. Your hand acts like a capacitor, however its effect is
not very significant (only around a few picofarads) so the
frequency of the oscillator needs to be arranged very high;
so that this small change in capacitance results in a big
change in the beat frequency. This leads to a trade-off. The
higher the frequencies the bigger the range, but the harder
are more precise the player must be to stay playing a single
pitch.
After looking at a number of different circuits and
understanding how a beat frequency oscillator works, the
circuits were constructed and tested. We were able have a
frequency similar to the fixed oscillator.
Pitch Control:
The Pitch control for the Theremin is composed of
a reference pitch oscillator and a variable pitch oscillator .
The reference oscillator is designed to operate around 172
kHz and has a potentiometer which can fine-tune the
circuit to the correct frequency. The variable oscillator also
runs around 172 kHz; it is fine-tuned not by a
Example circuit design:
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Oscillator and a Volume Resonant Circuit and Voltage
Controlled Amplifier. The system is very similar to the
pitch circuitry and the basic concept is that by changing the
frequencies of the oscillators by moving your hand you
change the gain on an amplifier.
Figure 2. Fixed Pitch Oscillator
There are much simpler ways to control the gain
of an amplifier, however these involve turning dials .
Inexpensive Theremins often opt to have a simpler volume
control method than that of the traditional Theremin
(namely, one with both a pitch and volume antenna) . We
have decided to keep with the traditional method of the
Theremin which will allow the user to control both the
pitch and volume of the instrument without touching
anything.
Volume Variable Oscillator:
Figure 3. Variable Pitch Oscillator
Figure 4. Mixer
Volume Control:
Volume control is composed of a Volume Variable
Choice of circuit design:
The circuit design for the volume variable
oscillator along with Volume Controlled Amplifier is used
to vary the volume of the final output level of the Theremin.
This is achieved when the player moves his hand in
relation to the volume antenna. As the player approaches
the volume antenna, the capacitance of his hand changes
the set frequency of the volume oscillator. This produces a
DC signal which oscillates at a high frequency of 440kHZ.
The circuit that we used in building a Volume Variable
oscillator is given below. This overall design of this circuit
is similar to the pitch circuitry. The potentiometer in the
circuit is used to fine tune the frequency of the volume
oscillator. When the circuit is tuned correctly, the
frequency from this oscillator will match the tuning of the
volume resonant circuit.
The gain of the VCA is controlled by the input
signal by resistors. The circuit as shown in Figures 5 and 6
were constructed and we were able to achieve the right
audio signal.
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The basic understanding of the Theremin we
gained from building our own simpler version
has proved useful in trouble shooting and
building the kit and integrating it with the rest of
the project.
C. Software Design
Software to run the Discrete Mode:
Figure 6. Voltage Resonant Circuit and Voltage Controlled
Amplifier
The Arduino IDE software is used to read
the frequencies outputted by the Theremin in
order to run the Continuous Mode and the
Discrete Mode of the project. The
microcontroller on the Arduino board is
programmed using the Arduino programming
language. The Arduino board consists of a simple
hardware design along with Atmel AVR
processor and input/output support on the board.
After coding in Arduino, the board is connected
to the computer using a USB cable and the code
is uploaded onto the microcontroller. Once the
frequencies are read from the Theremin using the
code (in which we use peak detection to mesure
the period and from this obtain the frequency),
this information is used to display the notes on a
seven segment LED display. A frequency-to-note
chart is used as a reference to correspond the
frequencies to the appropriate notes. The
frequencies and the corresponding notes are
stored in two arrays. With the help of these
arrays, if the frequencies fall within a specific
range, the appropriate notes will output on the
display using the code.
Decision to use a kit:
Software to run the Discrete Mode:
After building the simple Theremin
described above, we concluded that there was too
much noise and instability which hindered the
implementation of the Discrete Mode. The
volume and pitch circuitry were temperamental
due to the weak breadboard connections and
excess noise. After careful research we found
that the most cost effective and efficient solution
was to order the Theremax Theremin kit and
construct it. This kit had the advantage of not
only being fairly inexpensive but also
customizable.
The Arduino IDE software is used to read
the frequencies outputted by the Theremin in
order to run the Continuous Mode and the
Discrete Mode of the project. The
microcontroller on the Arduino board is
programmed using the Arduino programming
language. The Arduino board consists of a simple
hardware design along with Atmel AVR
processor and input/output support on the board.
After coding in Arduino, the board is connected
to the computer using a USB cable and the code
is uploaded onto the microcontroller. Once the
Figure 5. Volume Variable Oscillator
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frequencies are read from the Theremin using the
code (in which we use peak detection to mesure
the period and from this obtain the frequency),
this information is used to display the notes on a
seven segment LED display. A frequency-to-note
chart is used as a reference to correspond the
frequencies to the appropriate notes. The
frequencies and the corresponding notes are
stored in two arrays. With the help of these
arrays, if the frequencies fall within a specific
range, the appropriate notes will output on the
display using the code.
The Arduino software is also used to run the
Discrete Mode which will eliminate the sweep between
two notes.
Using a frequency-to-note chart, the
frequencies within a range are grouped together to output a
specific frequency. By doing this, the frequencies are
distinct and the sweep between two notes can be
eliminated. Such a Discrete Mode is desirable to teach the
user to play the Theremin and to implement glowing wires
which will direct the user to the right position to play
accurate notes.
A PIC32MX795 microcontroller is used in addition to the
Arduino. The PIC32 is used to control the glow wire
visual interface. Binary signals are sent from the PIC to
the EL Sequencer board which drives eight glow wires.
The PIC uses binary encoded signals which are decoded by
the EL Sequencer to represent which of the eight glow
wires to activate. The PIC32 contains in it "songs" which
are C structures used to represent the information needed
to model a sing to be played. Notes are mapped to a look
of table which is encoded into different bit fields such as
sharp, flat, octave and note. This Allows for high
performance lookups and ease of use in software. As
songs are read on the PIC, the notes will be extracted along
with a delay which is sent to the EL Sequencer. In addition
to the EL Sequencer illuminating the space that occupies
the note, a seven segment display will tell the user which
note is to be played. The player can then try to match the
note they are playing, with the note being asked for. From
here, the PIC will take an analog sample of the audio signal
being played by the Theremin user. That sample is then
broken down into FFT components and passed to an
optimized FFT library function. This function returns the
frequency spectrum from which the highest magnitude
frequency is extracted. This frequency is compared to a
lookup table which maps frequencies to musical notes.
Depending on how close that musical note is to the desired
note, the PIC will update the Theremin player's score with
various penalty points. Each song contains a letter grading
cutoff table which, at the end of the song, will be iterated
through to see which grade range the player belongs in.
That grade is the outputted to the seven segment display
for the user to see.
The EL Sequencer is a glow wire control board
based on Arduino programming. It uses an Atmega 328
chip which can be programmed through the Arduino development environment. This board drives 8 glow wires
and has 6 analog pins. The 6 analog pins have been configured as inputs for the Theremillusion project. Binary
signals are sent to pins 3 through 6 to represent 0x0 to 0xF.
These signals are decoded in software by the EL Sequencer's Atmega 328 which will choose which of the 8 output
glow wire drivers to enable. The software on the EL Sequencer is kept to a basic decode table to simplify the control elements of the interacting micro controllers.
Electroluminescent Wires:
Choice of Electroluminescent Wires for
Theremillusion
As the implementation of the project
progressed, the decision to abandon the fiber
optics for the visual interface was made. This
was due to the fiber optics loosing brightness as
the length of the fiber was increased. This is
because the Fibers are not closed at the end, and
therefore the light is not reflected back into the
fiber. For this reason, electroluminescent wire
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was chosen as an alternative.
Electroluminescent wire (EL wire) is a
thin copper wire that is coated with
phosphor.This wire glows when an alternating
current is applied. EL wire produces a 360 degree
unbroken line of visible light. It is also very thin
and flexible which is very ideal for this project as
it would allow more precision as to the location
of the notes on the Theremin.
The EL wires need 120 volts of
alternating current (VAC) in order to glow. The
PIC32 however only emits power of 3 volts of
direct current (VDC). For this reason a power
inverter or driver had to be acquired. At first, the
idea of building a 12VDC – 120VAC driver
seemed like a good idea. The plan was to get a
transformer from a microwave, and then rewire it
and connect it to a circuit board to create the
driver. After acquiring a microwave transformer
by carefully taking apart a microwave, it was
discovered
that
the
transformer
was
dysfunctional. Due to lack of other resources
with transformers and time, it was decided to
purchase a driver. This would ensure that the EL
wires would be powered correctly and remove
any hazards of the team getting electrocuted.
Figure 8. Electroluminescent wire
Figure 9. Soldering EL wires and Heat shrink
tubes
To connect the EL wire, it must first be stripped
very carefully. After stripping the wire, there are
three wires exposed: two thin radial wires and
one core wire. The core wire is covered with
white phosphorous coating. While being very
careful not to tug at the two radial wires, the
white phosphorous coating must be removed by
using a sharp knife. The next step is to solder the
core wire to a black wire, and the solder the two
radial wires to one red wire. This is difficult
because the radial wires are very frail and can be
easily broken if tugged at. If this occurs, the EL
wire must be re-stripped etc. Also, it is important
to cover the connections between the core wire
and the black wire, as well as the radial wires
with the red wire with heat shrink tubes. This is
important for two major reasons: the first reason
is so that the connections are strong and so that
the wires will not move and break. The second
reason is so that there is no connection between
the core wire and the radial wires. If they touch,
it can cause the wire to short circuit itself.
Preparing the EL wires is a long and tedious
process that requires a lot of finesse and attention
to detail. After the EL wires were all ready and
connected to the red and black wires, the next
step was to control them.
To control the EL wires, many microcontrollers were researched, and instead of
recreating the wheel, a special EL microcontroller was found. The EL sequencer is an
ATmega based control board that allows the user
to program any sequence of blink, on/off, and
even pulse width modulation (PWM) pulsing of
EL wire. This was a perfect choice because it can
light up to eight EL wires on one board, and the
project would require a decent amount of wires
to match with the number of notes the theremin
can generate. Not only this, but it can be
programmed using an Arduino interface and
programming. Also, the EL sequencer has a set
of analog inputs that can be used to control the
EL sequencer from another micro-controller.
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This was a great aspect because the PIC32 can
interface with the EL Sequencer and control it.
Another great aspect to buying the EL sequencer
was that it cut our costs by eight because one
driver sufficed for the equivalent of eight drivers.
Although more than one EL sequencer was
purchased, this micro-controller was relatively
inexpensive for all of its functionality. The EL
sequencers were bought on sparkfun.com for
$24.95 a piece.
Figure 10. EL Sequencer
To program the EL sequencer, Arduino was used.
This was because the board uses the Atmega328
chip which can be easily controlled using
Arduino language. To program the EL sequencer,
an FDTI cable was used to connect the EL
sequencer to the computer's USB port. Once this
was done, the appropriate FDTI cable drivers,
and Arduino software was installed. Then coding
begins.
First the pins needed to be defined and
named so that coding the program to blink on
and off would be easier. However this process
took longer than normal because all of the
websites that contained the EL sequencer
datasheets were faulty. This was because the
sequencer purchased was the latest version,
however the datasheets were of the original EL
sequencer which is a couple of years old. To fix
the problem, all of the analog to digital converter
pins, as well as all of the EL wire input pins were
defined in the code. They were then tested by
inputing VCC power from the EL sequencer to
the analog inputs and checking the serial monitor
for a signal. Although this process was long and
tedious, an accurate result of data pins were
attained.
After attaining the correct data pins, the
code was written so that each EL wire (one by
one) turned on for two seconds, and then turned
off. This was done as an extra test to make sure
that the EL pins work as well as the functionality
between the EL wires, the EL sequencers and the
EL drivers.
First the EL driver had to be connected to
the board as well. Since the driver purchased was
not fabricated to work with the EL Sequencer,
some adjustments had to be made. The wires
connecting the driver had to be cut and resoldered into jumper wires with JST connections
so that the drivers could be inserted into the
board. Also, since the EL Driver was battery
operated, the battery had to be removed and
soldered onto the EL sequencer in a similar
manner to the EL driver re-soldering. Once this
step was complete, the EL wires were placed into
the EL pins. After switching the EL sequencer to
BAT power, and the turning the driver on, the EL
wires illuminated.
The next step after getting the EL wires to
light up was to control them according to an
analog input. This is important because it would
simplify the code as well as keep the PIC32 and
the EL sequencer synchronized. To do this,
Arduino code was written onto the EL sequencer
that would read the analog input, and detect
which input was on. Since the EL sequencer has
eight EL wires, the best way to approach the
analog inputs is to make them into binary
numbers. This means that the ADC1 corresponds
to 0001, and ADC2 is 0010, ADC3= 0100 and
ADC4 =1000. Since there are only eight EL
wires, only four analog inputs are enough (since
1000 is 8 in binary).
To do this, the EL sequencer read the
inputs, and then shifted them together into one
number. This would simplify the code because it
allows the code to compare one number. To
compare the numbers, switch statements were
used. In these switch statements, the code turns
all the EL wires off except for the one being
played. For example, if EL wire six was to be
played, then the code would compare the signal
to check that it corresponds to 0110, and then
turn off all the wires except for wire six. In the
code used, the EL wires were named A-H. The
following is a part of the code:
case 6:
digitalWrite(A, LOW);
digitalWrite(B, LOW);
digitalWrite(C, LOW);
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digitalWrite(D, LOW);
long and 1'' wide. It has also got two mounting holes to
digitalWrite(E, LOW);
secure it to a casing.
This board is particularly attractive since it is easy
to program for fast prototyping. Unlike many traditional
microcontrollers, the USB 32-Bit Whacker development
board doesn't require a hardware programmer. Instead, the
firmware can be quickly rewritten on the board using the
USB bootloader. Each project can be developed in
Microchip's MPLAB IDE which compiles code to PIC32
native object files with Microchip's MPLAB C Compiler.
As each project is built, there must also be a procdefs
linker file which tells the C32 linker not to write into the
range of code needed to engage the bootloader at the
powering up of the board. These firmware sections are
essential so that the bootloader method can keep being
used to quick updates to the board. If this code is
overwritten, a hardware programmer can still make further
edits to the onboard firmware.
The PIC32MX795 development board is a great
selection for the Theremillusion project. There are plenty
of options for I/O needed to control lighting elements for
the guide interface. The number of I/O ports also allows
digitalWrite(f, HIGH);
digitalWrite(G, LOW);
digitalWrite(H, LOW);
break;
After coding this onto the EL sequencer and
seeing that the PIC32 did infact accurately
interface with the EL sequncer, the code for the
EL sequncer was finished.
III. FPR PROTOTYPE IMPLEMENTATION
A. Choice of Microcontroller for Theremillusion
The PIC32MX795 32-bit CPU from Microchip
will be used to control the Theremillusion.
More
specifically, Sparkfun's USB 32-Bit Whacker PIC32MX795 Development Board is being used to
prototype the Theremillusion. This board has 73 usable
I/O pins along it's edges which allow for easy breadboard
mounting to prototype quickly. The large amount of I/O
gives plenty of headroom to control the lighting elements
and offers room for expansion. The PIC32MX795F512L
CPU runs at 80 MHz and is more capable than typical 8-bit
or 16-bit hobbyist boards like the Arduino, an initial choice
for prototyping. With respect to storage the board has
for the possibility of many switches. These could be
implemented as input for song selection or any other
parameters as needed for the project. The USB port is a
great expansion option since the project could later on be
adapted to include a MIDI interface with a PC. Since a
512K Flash and 128K RAM. This allows work with large
datasets such as FFT samples and I/O maps. This CPU is a
MIPS based RISC core so it will be student friendly and
there is a good source of documentation available for low
level routines. The board offers many power options, one
of which is power by miniUSB. This means that a separate
power supply won't be needed when uploading and testing
code while already connected to a PC. The board also
features a 3.3V power regulator and a 5V power regulator
which allows for a higher voltage (battery) input. The
power source can be set easily through an onboard switch
and is protected with a 500mA input fuse. External power
can also be used and it is protected as well using an
integrated diode. There are 5 LEDS on board; one is for
power, and the other four are programmable. These can
provide debugging at the stages where the USB cable and
programming overhead is undesirable. There are three
hardware push buttons; one reset and two programmable.
Another advantage to using this board is it's small form
factor. The board is very thin at 0.28'' high as well as 4.4''
major component of the project is realtime frequency
Figure 11. PIC32MX795
analysis, the PIC32MX795's high execution
speed of 80 MIPS will be taken advantage of as
well. Finally, the PIC32 also brings more
memory to the table compared to the earlier
PIC16 models so there will be 512K of flash to
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work with our large datasets without the worry of
slow external memory access.
Prototype for Theremin:
After constructing the Theremin kit by using the
knowledge gained from designing our own Theremin, the
Arduino software is used to obtain frequencies and output
the continuous mode and discret mode. To run the
continuous mode, the output from the Theremin is
connected directly to the amplifier. On the other hand, to
run the Discrete mode, the Arduino code reads the input
frequencies, groups them together and outputs discrete
values.
These different discrete notes will be delineated by a
programming aspect that will organize the different sounds
from the theremin into notes based off of a main chromatic
western scale. This programming aspect from the discrete
mode will be integrated with the glowing wires
programming and expanded on. These distinct notes will
create the Discrete playing mode of our project.
As mentioned before, the glowing wires will now
be implemented using electroluminescent wires. The next
steps to implement these EL wires in the Theremillusion is
to successfully build a power inverter. This is so that the
EL can be powered by the PIC32 micro-controller.
IV. PROJECT MANAGEMENT
V. SUMMARY AND CONCLUSIONS
The project was divided into two major
subsystems. The first subsystem was the construction of
the Theremin and the second half was integrating a
teaching mode along with a visual interface. Each member
chose to work on components of the project that interested
them. Two members of our team were responsible for
Throughout this semester, we have successfully
designed and built the different modules of the theremin
including the pitch reference oscillator, the pitch variable
oscillators, the mixer, the volume variable oscillator, and
the volume reference oscillator - voltage controlled
amplifier. We have also successfully implemented the
PIC32 micro-controller as well the fiber optics with the
LEDs. Through experimentation and reseach , the design
has now changed to using electroluminescent wires to
make the project more efficient, cost effective, and
appealing.
We will be integrating the different modules of the
theremin so that by implementing all these parts together
will create a functional Theremillusion.
building the Theremin. Sandy and Snigdha worked on this
component and also did all the programing for the discrete
mode. The remaining two members, Imen and Steven,
worked on creating a user friendly Visual interface for
assisting the player and programming for this teaching
mode respectively.
The group worked together in integrating these
components. The pitch circuitry is designed so that when
the player brings his hand closer to the antenna, the pitch
rises and when the player moves his hand away from it, the
pitch falls. Similarly the volume circuitry is built so that
the volume changes according to the position of the
player’s hand to the antenna.
Glowing and side emitting fiber optics are used in
order to assist the player to play the right notes. The
programming is written so that the user can pick a song of
their choice and also get their score on the number of right
notes being hit. This feedback will serve as a guidance to
better improve their score in the future.
VI. REFERENCES
"Bildr » Getting Started with Your SparkFun EL
Sequencer." Bildr. Web. 23 Jan. 2012.
<http://bildr.org/2011/06/el-sequencer/>.
Dawson, C. "Theremin: A Weird Music Machine."
Electronics Australia 44.6 (1982): 86-91.
Holloway, Barry. “Theremin.” 2011.
<http://www.strangeapparatus.com/
Theremin.html>. (11/29/11).
a. Outlook on Next Steps:
Our next steps would be to make the oscillators
more stable, work on troubleshooting of the different
components and integrating the parts together so that they
are not only functional modules but a complete working
theremin. After this is accomplished we will start working
on the Discrete Playing Mode. In this mode, the user will
be able to play the instrument without having a continuous
sweep of music when they go from one note to the other .
"Home | Product Categories | EL | COM-09203." EL
Sequencer. Web. 04 Jan. 2012.
<http://www.sparkfun.com/products/9203>.
"MAKE | Programming EL Wire Fashion." MAKE. Web.
24 Feb. 2012.
<http://blog.makezine.com/2010/04/27/programming-elwire-fashion/>.
NeonString EL Wire Electroluminescent Wire and Drivers.
Web. 1 Dec. 2011.
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<http://www.neonstring.com/index.php?
tasket=solder>.
Oddmusic. “The Theremin: What is a Theremin?” 2007.
<http://www.oddmusic.com/theremin/
what_is_a_theremin.html>. (11/27/11).
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American Journal of Physics 66.11 (1998): 94555.
"12V to 120V Inverter." Aaron's Homepage. Web. 01 Dec.
2011. <http://www.aaroncake.net/circuits/
inverter.asp>.
APPENDIX
A. Application of Mathematics, Science and Engineering
The areas of math, science, and engineering that
apply to our project are computer systems engineering,
hardware organization, data structures and algorithms,
circuit analysis, electronics, signal analysis and signal
theory. Our project involves a significant programming
portion which will be written using the C programming
language. Programming practice and theory has been
covered extensively through the undergraduate ECE track
through the following courses: ECE 122, ECE 242, ECE
353, ECE 354 and ECE 373.
Our project will be using a microcontroller from
the PIC32 MCU family. Microcontrollers have been
thoroughly explored in ECE 353 and ECE354 and we used
that knowledge to choose an appropriate chip for the job.
Theremin construction and engineering is no
small task and this is where the electrical engineering and
circuit understanding comes into play. Circuit analysis
techniques like those learned in ECE 211 and ECE 212 are
essential to analyze our schematics and the parts available
to us. The design skills from ECE 323 and ECE 324 have
also proven very necessary to understand how to design an
analog circuit from a high level and bring it down to a low
level implementation.
B. Design and Performance of Experiments, Data
Analysis and Interpretation
11
C. Design of System, Component or Process to Meet
Desired Needs within Realistic Constraints
The system requirements of our design are such
that our device should be capable of providing anyone with
an intuitive guide to theremin playing. A prospective
player should be able to approach our theremin, easily
calibrate it and then produce music when the provided
visual cues from the illuminated fibers are followed. The
underpinnings of the system should be transparent to the
user. The system must have the capacity to respond to the
capacitance of any individual who would like to participate.
The system should also be transparent with respect to any
delays associated with performing frequency analysis.
Hardware delays should not be perceived by the user.
Our design must also be safe. Working with
proximity sensors is a nonhazardous way to achieve an
invisible magic element. There is no radiation. Socially,
our design preserves privacy with volume control so
minimize disturbance in whatever environment the system
may be used in.
As the implementation of the project
progressed, the decision to abandon the fiber
optics for the visual interface was made. This
was due to the fiber optics loosing brightness as
the length of the fiber was increased. This is
because the Fibers are not closed at the end, and
therefore the light is not reflected back into the
fiber. For this reason, electroluminescent wire
was chosen as an alternative.
Electroluminescent wire (EL wire) is a
thin copper wire that is coated with
phosphor.This wire glows when an alternating
current is applied. EL wire produces a 360 degree
unbroken line of visible light. It is also very thin
and flexible which is very ideal for this project as
it would allow more precision as to the location
of the notes on the Theremin.
The EL wires need 120 volts of
alternating current (VAC) in order to glow. The
PIC32 however only emits power of 3 volts of
direct current (VDC). For this reason a power
inverter or driver had to be acquired. At first, the
idea of building a 12VDC – 120VAC driver
seemed like a good idea. The plan was to get a
transformer from a microwave, and then rewire it
and connect it to a circuit board to create the
driver. After acquiring a microwave transformer
by carefully taking apart a microwave, it was
discovered that the transformer was disfunctional.
Due to lack of other resources with transformers
and time, it was decided to purchase a driver.
This would ensure that the EL wires would be
powered correctly and remove any hazards of the
team getting electrocuted.
D. Multi-disciplinary Team Functions
 Imen Ben-Neticha, EE:
– Visual elements and EL Wire circuitry
– Discrete Circuitry
 Sandra Jenkins, EE:
– Pitch Circuitry
– Discrete Circuitry
 Snigdha Jonna, EE:
– Volume Circuitry
– Discrete Circuitry
 Steven Bennett, CSE:
– PIC32 Microcontroller Programming
E. Identification, Formulation
Engineering Problems
and
Solution
of
To program the EL sequencer, Arduino
was used. This was because the board uses the
Atmega328 chip which can be easily controlled
using Arduino language. To program the EL
sequencer, an FDTI cable was used to connect
the EL sequencer to the computer's USB port.
12
Once this was done, the appropriate FDTI cable
drivers, and Arduino software was installed.
Then coding begins.
First the pins needed to be defined and
named so that coding the program to blink on
and off would be easier. However this process
took longer than normal because all of the
websites that contained the EL sequencer
datasheets were faulty. This was because the
sequencer purchased was the latest version,
however the datasheets were of the original EL
sequencer which is a couple of years old. To fix
the problem, all of the analog to digital converter
pins, as well as all of the EL wire input pins were
defined in the code. They were then tested by
inputing VCC power from the EL sequencer to
the analog inputs and checking the serial monitor
for a signal. Although this process was long and
tedious, an accurate result of data pins were
attained.
After attaining the correct data pins, the
code was written so that each EL wire (one by
one) turned on for two seconds, and then turned
off. This was done as an extra test to make sure
that the EL pins work as well as the functionality
between the EL wires, the EL sequencers and the
EL drivers.
First the EL driver had to be connected to
the board as well. Since the driver purchased was
not fabricated to work with the EL Sequencer,
some adjustments had to be made. The wires
connecting the driver had to be cut and resoldered into jumper wires with JST connections
so that the drivers could be inserted into the
board. Also, since the EL Driver was battery
operated, the battery had to be removed and
soldered onto the EL sequencer in a similar
manner to the EL driver re-soldering. Once this
step was complete, the EL wires were placed into
the EL pins. After switching the EL sequencer to
BAT power, and the turning the driver on, the EL
wires illuminated.
F. Understanding
responsibility
of
professional
and
ethical
One of our professional responsibilities as
electrical engineers in accordance with IEEE is to treat
fairly all persons regardless of such factors as race, religion,
gender, disability, age, or national origin. This idea of
ensuring any human gets equal treatment from our product
is one of the central tenants not only in the design of our
Theremillusion, but is also one of the fundamental ideas in
the construction of the original Theremin. The Theremin
was designed to be a simple classical instrument to be
played
by
all
(http://www.pavekmuseum.org/theremin/index.html). Our
design is one that keeps this thought of universality in
mind. We are aiming to make the Theremin easier to play
for all people. Our Theremin will offer tuning so each
person customize the tune to both their own unique
capacitance and to their liking.
G. Team Communication
Our team is close and we love each other very
much. We maintain a schedule of weekly meetings each
Monday to communicate with our Advisor about the status
of our project. We also meet later in the week to catch up
on any group critical topics that we're unable to cover
adequately through our regular email discussions. These
regular email discussions are where we share work or
notify the group about how our individual work is going .
Our group maintains a working set of documents on our
shared workstation computer in the SDP lab. We also
utilize a “dropbox” (http://www.dropbox.com/) we can
each access from our SDP workstation computer as well as
our personal computers. The dropbox is a synchronized
shared folder dedicated to managing up to date copies of
our project files. These project files can include our
reports, presentation slides, research, code, website data
and media. Finally, we also keep in contact through phone
messages to coordinate meetings or exchange information
that may break the usual established routines. We are all
able to be reached by each other to help, give advice, share
ideas and organize meetings.
H. Understanding of the impact of engineering solutions
in a global, economic, environmental and societal
context
Our group has gotten in contact with Professor
Karpinski of the university music department to discuss
our project. Our meeting gave us a more broad view of
our project's implications with this additional musican's
perspective. Professor Karpinski communicated to us
many ideas from a music professional's standpoint. We
left with a better understanding of why the Theremin is
unpopular, yet fascinating as an instrument. He also
recommended several techniques of how to tune a unique
instrument like the Theremin. Lastly, he left us with some
resources to explore such as the list of books and websites
13
to help us build on the musical foundation of the product .
The Theremin is traditionally a very difficult instrument to
not only build but to play as well. We can see now that our
design is one that would be appreciated by music students,
hobbyists and laypersons alike.
I. Application
coursework
of
material
acquired
outside
of
Theremillusion applies material from many
sources including those outside our traditional engineering
coursework. We have held a meeting with one of the
music professors who took an interest in our project. He
enlightened us with many ideas of how malleable the
frequency to musical note scale is. He proposed the ideas
of
equal
temperament
(http://en.wikipedia.org/wiki/Equal_temperament) which
would make our Theremin scale it's notes logarithmically
with respect to frequency.
In addition to this help we've received from the
university music department, we've also gotten project help
from the PIC32 development community. Brian Schmalz's
UBW32 website (http://www.schmalzhaus.com/UBW32/)
in particular has many applications of the PIC32
Development board we're using. We've been able to use a
lot of the framework code provided on the website through
it's tutorials. This made quickly rolling out a prototype
possible and also helped in the understanding of how to
program the PIC32 MCU family.
J. Knowledge of Contemporary Issues
Music is a part of human culture. It can be easy
for people today to be so caught up in their work they may
feel they don't have the time needed to invest in learning an
instrument. That is in itself a great loss. Our project aims
to make this plunge into the world of music an easier one.
By reducing the learning curve to playing the Theremin,
we hope to aid in the understanding of music. This simple,
intuitive teaching interface will let anyone play the
instrument. Over time players will not only learn some
songs, but also learn an appreciation for music which could
otherwise be left undeveloped.
K. Use of modern engineering techniques and tools
1) Eclipse is a multi-language expandable integrated
development environment and has proven invaluable for its
aid in quickly rolling out C projects.
2) Microchip MPLab, is the development suite for coding,
debugging and simulating PIC code.
3) MPLAB C32, compiles C code to native PIC32 machine
code.
4) PSPICE, an analog circuit and digital logic simulation
software.
5) Circuits analysis and design as learned from our core
ECE courses. This includes the trouble shooting of
breadboards.
6) Arduino, an open-source electronics
prototyping platform based on flexible, easy-touse hardware and software. It's intended for
artists, designers, hobbyists, and anyone
interested in creating interactive objects or
environments.