theremi n design review ii. douglas beard [email protected] micah caudle [email protected] u...
TRANSCRIPT
![Page 1: Theremi n Design Review II. Douglas Beard dtb4@ra.msstate.edu Micah Caudle Msc1@ece.msstate.ed u Jeffrey Jun-Fey Wong jw5@ra.msstate.edu Way Beng Koay](https://reader035.vdocuments.net/reader035/viewer/2022062720/56649f0c5503460f94c201ff/html5/thumbnails/1.jpg)
Theremin
Theremin
Design Review II
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Douglas [email protected]
Micah [email protected]
Jeffrey Jun-Fey [email protected]
Way Beng [email protected]
Dr. Raymond Winton Faculty Advisor
Theremin
Theremin Team
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Theremin
Responsibilities
Douglas Beard:
Analog to Digital
Digital to Analog
Microprocessor
Micah Caudle:
Oscillators.
Beat frequency detector.
Volume Circuit
Way Beng Koay:
Frequency to Voltage Conversion
Voltage to Frequency Conversion
Jeffrey Jun-Fey Wong:
Output Stage
Footswitch Circuit
Tuner Out
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Lack of Reference: Since the thereminist does not actually touch the theremin, he has no point of reference for playing certain notes and nothing to steady his hand.
Continuous Volume: Staccato playing or quick stops and starts are difficult with the theremin because of continuous volume control.
Theremin
Continuous Pitch: The theremin is a continuous pitch instrument like trombone or violin which makes playing in tune difficult, especially for beginners.
Motivation
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Theremin
Tuning: A reference for tuning will be provided for silently locating starting pitches and pitch verification during practice. Theremin will interface with common tuners.
Solutions
Foot Pedal: A foot pedal will allow instantaneous mute and unmute in order to produce easier staccato.
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.
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Theremin
•Footswitch for staccato articulation
Design Requirements
•Tuner signal independent of volume control
•Box dimensions of 18”x6”x4” and weight under 8 lbs.
•Four octave frequency range: 110 Hz to 1760 Hz
•Automatic scales with error < 0.1%
•Parts cost less than $80
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VariableOscillator
FixedOscillator
Detector
Pitch Control
VariableOscillator
VolumeTuning
Volume Control
FreqSwitch
Theremin
Tuner Out Signal
Footswitch
Audio Out
Freq-VoltageConverter
PIC controllerwith A/D
Discrete Frequency Controller
14-bit D/AV/F
Converter
VCAProcessor
Voltage ControlledAmplifier
Output Control
Theremin Modular Design
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ThereminTheremin
Pitch ControlVariableOscillator
FixedOscillator
Detector
Pitch Control
Requirements:
(1) Output an audible sinusoidal frequency between 110Hz and 1760Hz.
(2) Achieve the change in frequency with 1 to 17 inches hand distance from antenna.
VariableOscillator
FixedOscillator
Detector
290 – 288 kHz
292 – 288 kHz
Audio:110 – 1760Hz
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Theremin
Oscillators
VPO and FPO schematic
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Theremin
Variable Pitch OscillatorSimulation result
VPOMAX 291 kHz VPOMIN 288kHz
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Theremin
Fixed Pitch Oscillator
FPOMIN 288kHz
Simulation result
FPOMAX 292 kHz
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Theremin
Detector
Requirement:
Extract beat frequency from variable and fixed oscillators
(heterodyning)
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Theremin
Detector
Simulation
Simulation result Circuit output
Beat frequency range 70 Hz – 1850 Hz
Sensitivity 104.5 Hz/inch (from 1 – 17 inches)
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Theremin
Volume Control
•Functioning on breadboard circuit
•Not working in box
•Needs more testing and debugging
Volume vs. Distance
0
0.20.4
0.6
0.8
11.2
1.4
1.6
0 2 4 6 8 10 12 14 16
Distance (inches)
Au
dio
(p
k-p
k)
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Theremin
Oscillator DriftProblem:Temperature induced drift cause unstable oscillator frequency
Factor: Temperature sensitive components in the oscillator circuit
Solution:
(1) Adjust FPO on the fly with potentiometer
(2) Improve temperature stability by up-grading temperature sensitive components
(3) Insert a feedback loop into circuit to reduce drifting
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Theremin
Discrete Frequency Controller
Frequency/Voltage
Converter
PIC controller with 10 bit A/D
14 bit
D/A Converter
Voltage/Frequency
Converter
110-1760 Hz continuous beat frequency from detector
0.3-5 V continuous voltage range
Binary representation of selected output level
Resulting discrete voltage level
Desired note within 0.1% error
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Theremin
Frequency-Voltage Converter
Requirements:
(1) Take input of sinusoidal frequency between 110Hz and 1760 Hz and output DC voltage between 0.3V and 5 V
(2) Sensitivity 2.5mV/Hz ± 1mV/Hz.
(3) Convert the sinusoidal signal to pulse signal to meet the requirement of the LM331, slew rate < 0.05V/us.
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Theremin
Frequency-Voltage Converter
Problem: Slew rate of the opamp comparator > 0.05V/us
Design factor: time, space and cost
Solution: LM 239 comparator
General purpose opamp – LM 741 Integrated circuits comparator – LM 239
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Theremin
Frequency-Voltage Converter
Requirement Sensitivity(to allow PIC control)
2.5mV/Hz ± 1mV/Hz
Achieved sensitivity 1.6mV/Hz
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Theremin
PIC controller and A/D
• Correct table values still need to added to code
• The microcontroller now takes in a voltage and outputs a corresponding stepped number.
• Microcontroller then needs to be connected to the other portions of the Discrete Frequency Controller.
Weeks 1 2 3
Discrete Frequency Controller Debug
Micro-codeTesting
Assemble on Board
Projected timeline for meeting all requirements
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Theremin
Microchip Program
Flow Chart of the Microchip Program
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Theremin
Voltage-Frequency Converter
Requirement:
In order to achieve the 0.1% frequency error, the voltage-frequency converter has to meet the following requirement.
Sensitivity: 146.67 Hz/V ± 25Hz/V
Linearity: ± 0.11Hz worst-case
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Theremin
Voltage-Frequency Converter
Required Sensitivity 146.67 Hz/V ± 25Hz/V
Achieved sensitivity 160.31 Hz/V
Required linearity ± 0.11 Hz worst case (0.1% of 110 Hz)
Achieved linearity ± 20.7 Hz (std deviation)
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Theremin
Voltage-Frequency Converter
Problem: Error exceeds 0.1% frequency accuracy
Musical sinusoidal output signal
Solution: Re-design using a more accurate sine wave generator
• Voltage controlled oscillator
• Numerical controlled oscillator
Lowest frequency Highest frequency
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Theremin
Tuner Out Circuit
Requirement:
Provide signal for common tuner (frequency discriminator)
Gain = -RF / R1 = -46k / 13k = 3.54 V/V
To
Tuner
Detector
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Theremin
Tuner Out ResultsSimulation Circuit Output
Actual Gain = Vo / Vin = 1.4154 / 0.4 = 3.54 V/V
The output signal meets the requirement for common tuners
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Theremin
Footswitch
Footswitch
Tip
Ring
Amplified Audio Out
Audio InControl Signal
Normally Open
Requirements: (1) Stepping on footswitch enables Audio Out.
(2) Releasing footswitch disables Audio Out.
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Theremin
Cost AnalysisPart Quantity Cost
Inductors 11 $16.50
AD7538 1 $10.92
Resistors/Capacitors 81 $3.66
LM331 2 $3.02
PIC16F870 1 $2.74
Pitch Antenna 1 $2.00
Transistors 8 $0.72
Volume Antenna 1 $0.30
Diodes 5 $0.10
LM239 1 $0.25
LM13700 1 $0.53
Voltage Regulator 2 $2.30
Box 1 $10.00
Miscellaneous --- $1.06
Total --- $54.10
Requirement: cost< $80.00
Actual cost = $54.10
Retail price = labor + manufacturer + marketing
= 400% of part cost
= $216.40
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Theremin
Design Summary
Requirement Objective Achieved
Frequency Range 110 – 1760 Hz 110 – 1760Hz
Automatic scales < 0.1% No
Footswitch Staccato articulation
Tuner Signal Always active
Cost < $80.00 $54.10
Size 18” x 6” x 4” 22” x 7” x 3”
Weight < 8 lbs 7.5 lbs
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Theremin
Market Possibility• Currently, the cheapest quality theremin is the Big Briar Etherwave Theremin. (cost US$369.00)
• Able to compete with this model. Extra features includes tuner out, footswitch and discrete mode.
• Has capability to match medium-range theremin in market with price.
• Currently there are no dealers in the state of Mississippi. Possibility of marketing it here.
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Theremin
Senior Design II
• divide and conquer (solve the requirement by breaking it to a smaller requirement)
• importance of staying on schedule
• work in team
• presentation practice
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Theremin
Future Work
• 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.
• A switch can be added to enable/disable the footswitch option. This would prevent the player having to connect the footswitch every time he wants to play.
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Theremin
Acknowledgements
We wish to acknowledge Dr. Ray Winton of Mississippi State University for his assistance and guidance with this project. We also would like to acknowledge Dr. Joseph Picone for his advice and providing access to many resources necessary to complete this project.
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Theremin
Demonstration