Transcript theremin - Courses

Theremi
n
THEREMIN
Department of Electrical and Computer Engineering
Theremin
Background
• Created by the Russian Inventor Leon Theremin in 1919.
•First electronic instrument influencing Moog and pioneers
in musical electronics.
• The thereminist does not actually touch the theremin except
to mute it.
•Controlled by capacitance between hands to antennas.
Placement of the hands relative to antennas controls pitch
and volume.
Theremi
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Motivation
Continuous Pitch: The theremin is a continuous pitch
instrument like trombone or violin which makes staying
in tune difficult. Also the lack of any physical reference
makes playing difficult to learn.
Continuous Volume: Staccato playing or quick stops and
starts are difficult with the theremin because of continuous
volume control.
Lack of Reference: Since the thereminist does not actually
touch the theremin, he has no point of reference for tuning
notes and nothing to steady his hand.
Theremin
Solutions
Dual Mode Theremin: A more versatile theremin will be
able to switch from the original continuous frequency mode
and a new discrete frequency mode that produces scales
automatically.
Foot Pedal: A foot pedal will allow instantaneous mute and
unmute in order to produce easier staccato.
Tuning: A reference for tuning will be provided for silently
locating starting pitches and pitch verification during
practice. Theremin will interface with common tuners.
Theremin
Design Requirements
• Discrete Frequency Accuracy
–Switchable between playing the traditional continuous range and playing
only distinct frequencies in twelve selectable major scales with error < 0.1%.
• Precise Articulation
–A footswitch will connect to the theremin to enable the performer to
quickly and easily articulate notes.
• Tuning
–A signal will always be present at the 1/4" tuner out jack to enable the
performer to locate starting pitches and for pitch verification during
practice.
• Frequency Range
–A frequency range of four octaves with a center frequency at 440Hz.
Theremi
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Design
1. Software Simulation
• PSPICE, MATLAB
2. Hardware Testing
• Breadboard circuits
• Analyze differences between simulation and lab results.
3. Update Simulations
Theremin
Theremin Modular Design
Variable
Oscillator
Fixed
Oscillator
Detector
Freq-Voltage
Converter
PIC controller
with A/D
14-bit D/A
V/F
Converter
Discrete Frequency Controller
Pitch Control
Variable
Oscillator
Freq
Switch
Voltage Controlled
Amplifier
Audio Out
Tuner Out Signal
Volume
Tuning
VCA
Processor
Volume
Control
Output Control
Footswitch
Theremin
Front Panel: Frequency Controls
Key
Continuous
A
Chromatic
B
G
#
C
F
Discrete
b
E
D
Discrete Mode
Continuous Mode
Discrete Mode
B Flat Scale
Traditional Operation
Chromatic
Key Circuitry Bypassed
Bypass Right
Selector Switch
Bb
C
D
Eb
F
G
A
Theremin
Tuning
FLAT
A
.
IN TUNE
B C
.
D
.
SHARP
E F
Sabine STX-1100
Theremin
.
G
.
Theremin
Conclusions and Future Work
• Our .1% pitch error limit may be more stringent than
needed. Some common tuners accept up to .2% pitch error.
• The discrete frequency output may have a different timbre
than the continuous frequency output. A wave-shaping
circuit could be added to give them similar quality.
Theremin
Time Line
Semester One
Month 1
Requirements
Month 2
Month 3
Test Specification
Month 4
Test Certification
Design Document
Simulation
Semester Two
Month5
Month 6
Month 7
Month 8
Final Design Document
Documentation Design/Simulation
Hardware Verification
Packaging
Presentations
Theremi
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THEREMIN
Department of Electrical and Computer Engineering
Test Specification
Requirements
Circuit
Simulation
Fixed Pitch
Accuracy

Foot Switch

Frequency
Range

Physical
Attributes
Antenna
Test
Excel
Oscilloscope
Tuner






Prototype
Testing




Power
Signal Output

Tuner Out



Theremi
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Discrete Mode Overview
Frequency/Voltage
110-1760 Hz
continuous beat
frequency from
detector
Binary
representation of
selected output
level
PIC controller
with 10 bit A/D
Converter
0.3-5 V
continuous
voltage range
14 bit
D/A Converter
Voltage/Frequency
Resulting discrete
voltage level
Converter
Desired note
within 0.045%
error