THEREMIN

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THEREMIN
Theremin

• Mississippi State University
• Department of Electrical and Computer Engineering

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Theremin Team
Theremin
Douglas Beard dtb4_at_ra.msstate.edu
Way Beng Koay wk4_at_ece.msstate.edu
Dr. Raymond Winton Faculty Advisor
Jeffrey Jun-Fey Wong jw5_at_ra.msstate.edu
Micah Caudle Msc1_at_ece.msstate.edu
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Responsibilities
Theremin

• Micah Caudle
• Oscillators.
• Beat frequency extractor.
• Voltage to Frequency

• Way Beng Koay
• Frequency to Voltage Conversion
• Voltage to Frequency

• Douglas Beard
• Analog to Digital
• Digital to Analog
• Microprocessor

• Jeffrey Jun-Fey Wong
• Output Stage
• Footswitch Circuit
• Tuner Out

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Motivation
Theremin

• Theremins are hard to play because they are
  continuous frequency instruments like violin or
  trombone.

• Quality theremins are too expensive.
• 350-3,500

• Limited playing style currently prevents broad
  use. A more versatile theremin will expand use.

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Problems
Theremin

• Continuous Pitch The theremin is a continuous
  pitch instrument like trombone or violin which
  makes staying in tune difficult. This fact makes
  theremin difficult to learn, but it also produces
  some desired effects.

• Continuous Volume Staccato playing or quick
  stops and starts are difficult with the theremin
  because of continuous volume.

• Lack of Reference Since the thereminist does
  not actually touch the theremin, the thereminist
  has no point of reference for notes and nothing
  to steady his or her hand.

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Design Requirements
Theremin

• Discrete Frequency Accuracy
• Switchable between playing the traditional
  continuous range and playing only distinct
  frequencies in selectable scales with error lt
  0.1.

• Frequency Range
• A frequency range of four octaves with a center
  frequency at 440Hz.

• Precise Articulation
• A footswitch will connect to the theremin to
  enable the performer to quickly and easily
  articulate notes.

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Design Requirements
Theremin

• Cost
• The theremin will not cost over 80.00. If sold
  for a 33 profit margin at 106.40, our theremin
  will still provide considerable savings relative
  to comparable theremins. This will greatly
  enhance the marketability of the unit.

• Tuning
• A small amplitude 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.

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Theremin Modular Design
Theremin
V/F Converter
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Capacitance Test
Theremin
2 pF to 6 pF Range
Comfortable Range of Motion
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VPO and FPO Circuits
Theremin
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Detector Circuit
Theremin
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Beat Frequency Output Range
Theremin
CMAX 6 pF gives fMAX of 1765.4 Hz
f 1 / T 1765.4 Hz T 0.566 msec
CMIN 2 pF gives fMIN of 109.9 Hz
f 1 / T 109.9 Hz T 9.1 msec
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Discrete Mode Overview
Theremin
110-1760 Hz continuous beat frequency from
detector
0.3-5 V continuous voltage range
Voltage/Frequency Converter
Binary representation of selected output level
Resulting discrete voltage level
Desired note within 0.045 error
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Percentage Error Calculation
Theremin
D/A
x MIDI note number A reference note
frequency (440Hz)
Voltage level
Voltage/ Frequency Converter
Ideal Note Frequency
Percentage Error
Frequency level
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Percentage Error
Theremin
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Output Note
Theremin
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Component Cost Analysis
Theremin
Design Requirement 80.00 Leaves 80.00
41.61 38.39 for packaging costs.
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Conclusions and Future Work
Theremin

• To get the desired discrete frequency accuracy
  within a four octave range, we need 14 bits, and
  accurately converting this to analog is expensive
  in relation to other operations.

• 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.

• Lastly, build it!

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Questions?
Theremin

• Mississippi State University
• Department of Electrical and Computer Engineering