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University of Massachusetts Amherst
Theremillusion
The Thereminators: Imen Ben NetichaSnigdha JonnaSandra JenkinsSteven Bennett
Advisor: Professor Siqueira
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Team Members
Snigdha JonnaEE
Steven BennettCSE
Imen Ben NetichaEE
Sandra JenkinsEE
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Responsibilities – Reallocations
Imen
− EL Wires and EL Sequencer
− Visual Output Control
Sandy
− Theremin Integration and Troubleshooting
− Discrete Mode (digital to voltage)
Snigdha
− Theremin Troubleshooting
− Discrete Mode (voltage to frequency)
Steven
− Displaying note accuracy programming
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Invented by Léon Theremin in 1920
Background
Originally got the idea while working on short wave ratio equipment and capacitive sensing during the Civil War in Russia
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Motivations for Theremin Modification
No Reference
Continuous Pitch and volume
Need to have extensive ear training
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How Does it Work
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Theremin Principles
Beat Frequency Oscillators
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Wire Wrapping the Theremin
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Theremin Kit Theremax Theremin
− Volume and Pitch Antennas
− Volume and Pitch field adjustment knobs
− Timbre control: useful for external signal processing (aka Discrete Mode)
− Manual for general operation and tuning
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Discrete Mode-Theremin
SWITCHAnalog-to-Digital Converter in a PIC Controller
Digital-to-Analog Converter
Voltage to Frequency Converter
SPEAKERS
Frequency from the Theremin
Discrete Signal Processing in MicroController
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Analog to Digital Converter in PIC
The Microcontroller PIC32 has a 10-bit Analog-Digital- Converter in it.
PIC32 has a range of 0 to 5.5V input voltage.
The PIC takes in frequency and converts it into a binary number.
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Software in PIC32
The Analog-to-Digital converter displays the frequencies that it reads from the Theremin.
These frequency values are grouped together to output a specific frequency based on a frequency-to-note conversion table.
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Conversion table Calculation for Equal-Tempered tuning [A4 = 440Hz]
Hertz Octave=1 Octave=2 Octave=3 Octave=4 Octave=5 Octave=6
0 A 55.000 110.000 220.000 440.000 880.000 1,760.000
1 A#/Bb 58.270 116.541 233.082 466.164 932.328 1,864.655
2 B 61.735 123.471 246.942 493.883 987.767 1,975.533
3 C 65.406 130.813 261.626 523.251 1,046.502 2,093.005
4 C#/Db 69.296 138.591 277.183 554.365 1,108.731 2,217.461
5 D 73.416 146.832 293.665 587.330 1,174.659 2,349.318
6 D#/Eb 77.782 155.563 311.127 622.254 1,244.508 2,489.016
7 E 82.407 164.814 329.628 659.255 1,318.510 2,637.020
8 F 87.307 174.614 349.228 698.456 1,396.913 2,793.826
9 F#/Gb 92.499 184.997 369.994 739.989 1,479.978 2,959.955
10 G 97.999 195.998 391.995 783.991 1,567.982 3,135.963
11 G#/Ab 103.826 207.652 415.305 830.609 1,661.219 3,322.438
12 A 110.000 220.000 440.000 880.000 1,760.000 3,520.000
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Digital to Frequency Conversion
DAC5675A chip: D/A converter
LM331 Voltage-to-Frequency Converter The equation that
relates the frequency
to voltage:
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PIC32 DSP
16 Channel 10-Bit ADC
80 MHz, 1.56 DMIPS/MHz, 32-Bit M4K Core
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FFT Demonstration
Configure IO Registers
Allocate and Prepare buffers.
256 Samples of Analog Signal at 10 KHz
Call Microchip Library Fuction:mips_fft16(dout, calcbuffer, fftc, scratch, log2N)
Meaningful Results: Magnitude/Frequency
Transmit Blocks of Data to USB
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What’s Next
Analog Audio can be compared to a Musical Note Lookup Table
Derive a Score fromPlayed Note vs Expected Note
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Results
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Why the EL Sequencer● Easy to use, no need to re-invent the wheel
● Relatively inexpensive for the amount of hardware (in comparison to building one from scratch)
● Incorporates programming into the software
● Using a microwave transformer is more labor, more bulky, and not as accurate (results)
● Safer. EL wire is 100+V at 4000hz, but very low power. Instead of a shock, you will feel a small tingle if touched in the wrong places
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EL Sequencer
● Board can be powered from USB or LiPo
● Switch chooses source and acts as on/off
● Compatible with Arduino (8MHz LilyPad)
● On-board 8MHz external resonator
● 8 TRIACs can handle up to 600V
● Control 8 channels of EL
● Runs on 3.7V LiPo
● Footprint for connection to FTDI Basic for downloading code
● Footprint for connection to Nordic nRF24L01 2.4GHz wireless module
ATmega328 based control board that allows the user to program any sequence of blink, on/off, even pulse width modulation (PWM) pulsing of EL wire
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TRIACs in the EL Sequencer
● While EL wire requires very little power, you can't use normal transistors to turn on/off a string of it
● So we use TRIACs → nifty 'switches' that allow you to turn on/off an AC source
● Triode for Alternating Current
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Integration with PIC32
● The EL Sequencer will guide the user with a series of lights.
● three levels (easy/medium/hard)
● PIC32 will compare and grade the user
● PIC32 interfaces with EL sequencer to display score on the EL wires
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Timeline
Feb 24th – Finish Theremin Assembly
March 2nd – Finish integrating PIC32 FFT and EL Sequencer for light control
March 9th – Finish integrating PIC32 and discrete mode
March 16th – Finishing integrating parts
March 23rd – Week for trouble shooting
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SDP Day
Working Theremillusion will look similar to a harp.
Glow Wires
The glow wires will light up to teach the use how to play the theremin.
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END
Thank You!!!
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References Kenneth D. Skeldon, et al. Physics of the Theremin. Department of Physics and Astronomy,
University of Glasgow, Glasgow G12 8QQ, Scotland. Received 15 May 1998; accepted 12 June 1998.
Way, Beng Koay; Douglas Beard, Micah Caudle, and Jeffrey Jun-Fey Wong. Theremin. Department of Electrical and Computer Engineering at Mississippi State University. <http://www.ece.msstate.edu/courses/ece4522/projects/2001_spring/theremin/>.
Holloway, Barry. Theremin. Strange Apparatus. 2009-2011. <http://www.strangeapparatus.com/Theremin.html>.
Sparkfun Electronics. “USB 32-bit Whacker – PIC32MX795 Development Board”.<http://www.sparkfun.com/products/9713>.
PAiA, “Theremax FAQ.” <http://www.paia.com/ProdArticles/therefaq.htm>.
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Physics of Theremin
Antennas
Difference between Analog/digital theremins
Physics of the variable capacitance and how that changes the oscillators (how oscillators change sound)
Sandy email about finding theremin player
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Powering the theremin
Theremin can be powered by 12 volts.
This can be done by building a step-down transformer that will convert the normal house voltage or buy a power cord with a built in converter.
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Design Requirements
Visual Display
− Will display current note being played and if in teaching mode, indicate how close the note is to target note.
Visual Reference (Fiber Optics)
− Lights will indicate the general location the hand has to be in to play a particular note.
− (tentative) A light will change color depending on how close or far away the sound is from the target note.
Continuous and Discrete Playing Mode
− Device will be able to be switched between playing in the traditional continuous range and playing only discrete notes in specific frequency ranges.
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Software Interface
Modular Design
Visual Interface
Optical Fibers
Display
Output Processing
Frequency to Voltage
Tuning
Learning Mode
Output control
VCA
Audio Amplifier
Pitch Control
Variable Oscillator
FixedOscillator
Mixer/ Detector
Volume Control
Variable Oscillator
Knob
Volume Tuning
Voltage to Frequency
Voltage Comparison/Discrete
Output
Switch
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FFT Complexity
FFT lengthMultiplies (real) Adds(real) Mults + Adds
Radix 2 1024 10248 30728 40976
Split Radix 1024 7172 27652 34824
Prime Factor Alg 1008 5804 29100 34904
Winograd FT Alg 1008 3548 34416 37964
TABLE 1: Representative FFT Operation Counts
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Reasons for the Theremin Kit
Building the Theremi
Comparable to creating an acoustic guitar for a woodworker
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