ECE 445 Automatic Guitar Tuner

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					              ECE 445
Automatic Guitar Tuner
                    Group 14

               Ryan Freeberg
                 Darren Pocci
           Tiffany Kasettratut
Introduction
   Our project will detect the fundamental
    frequency of a plucked string and compare
    that to a predefined tuning set that the user
    specifies
   Automatically pluck string and turn tuning
    pegs to adjust string tension
Similar Devices
   Tronical PowerTune
    System
       Gibson Robot Guitar
       Requires modification to
        guitar
Similar Devices
   String Master
       Handheld device
       One tuning style
       No modification
        necessary
Objective
   Create a guitar stand such that user can:
       Put guitar in tuner
       Attach tuning motors
       Select desired tuning style
       Start tuning process
       Remove tuned guitar when tuning complete
Original Design
   Modified standard guitar stand
       Tuning Motors
       Auto-Plucker
   Works with multiple makes and models
       Adjustable tuning motor placement
   Tunes guitar within 2 minutes
The Automatic Guitar Tuner
                       Data Acquisition Board
   Signal
 Processor
                  Tuning
                  Motors


                  User
                Interface



             Auto-Plucker
Features
   Different tuning configurations to choose from
       Standard, Drop D, Open G
   Auto-Plucker component
       User does not need to pluck string
   Works with most electrical guitars with six
    tuning pegs on same side
    Block Diagram

                                            Tuning Motors




                        LabVIEW           BasicX-24
                     Signal Processor   Microcontroller
LCD User Interface
                                                            Guitar

                                          Auto-Plucker
    Block Diagram

                                            Tuning Motors




                        LabVIEW           BasicX-24
                     Signal Processor   Microcontroller
LCD User Interface
                                                            Guitar

                                          Auto-Plucker
User Interface
   Displays tuning style
    and progress of tuner
    to user
   Communicates to
    Signal Processor and
    Motors when to begin
    and which tuning style
    is chosen
User Interface: Schematic
User Interface: Parts
   PIC16F877A
       Communicates buttons with LCD, Signal Processor,
        and Motors
   Samsung UC-20102-GNARS 20x1 LCD screen
       Displays current state of tuner
   Five Push Button Switches
       Standard, Drop-D, Open-G, Start, Reset
    Block Diagram

                                            Tuning Motors




                        LabVIEW           BasicX-24
                     Signal Processor   Microcontroller
LCD User Interface
                                                            Guitar

                                          Auto-Plucker
Signal Processor
   Done in LabVIEW 8.2
   Uses PCI-6036E DAQ Card
       Allows easy input and output of analog and digital
        signals
       Only 7 working Digital I/O lines
Signal Acquisition
   Used PCI-6036E Card
    with TBX-68 Adapter
   Low amplitude
       Upper limit ~2V
       DAQ limit ±10V
   Multiple harmonics and
    overtones
       Good and bad
Sampling
   Want at least 10
    harmonics
   Need to satisfy Nyquist
       Know highest frequency
        we will look for is 330 Hz
       Minimum sampling
        frequency is 6600 Hz
       Used 10,000 Hz for
        added harmonics
Frequency Detection
   Used Harmonic
    Distortion Analyzer VI
    for final version
   Looks for highest peak
    in FFT
   Utilized advanced
    search function
    Block Diagram

                                            Tuning Motors




                        LabVIEW           BasicX-24
                     Signal Processor   Microcontroller
LCD User Interface
                                                            Guitar

                                          Auto-Plucker
BasicX-24 Processor
   BASIC programmable
    microcontroller
   Outputs PWM signals to control
    motors
   Reads signal processor inputs
   Calculates when tuning is
    complete
    Block Diagram

                                            Tuning Motors




                        LabVIEW           BasicX-24
                     Signal Processor   Microcontroller
LCD User Interface
                                                            Guitar

                                          Auto-Plucker
Parallax Servo Motor
   Adjustable potentiometer to
    center the servo
   Continuous rotation
       Required for turning guitar pegs
   Average Speed 60 rpm (with
    no torque)
   Torque 3.40 kg-cm/47oz-in
       Sufficient to turn guitar pegs
Functionality of Servo Motor
                                                                                Pictorial
       Rotation                                       Pulse Input to Motor   Representation
                                 1.5 ms


                         5V

      No Rotation

                         0V

                                              20 ms




                              1.0 to 1.5 ms



                         5V
        Clockwise
         Rotation
                         0V

                                              20 ms



                              1.5 to 2.0 ms



                         5V
     Counter-Clockwise
         Rotation
                         0V


                                              20 ms
Tuning Motors
   Needed bracket
    attached to motor to
    turn guitar pegs
       Modified guitar winders



   Aligned in linear array
    to match six pegs
Control of Guitar Tuning
   Sharp and Flat signals
                                  Signal is Sharp
    read from signal
    processor
       Signals read when Auto-
        Plucker is stationary
       Sharp rotates motors
        CCW
       Flat rotates motors CW
    Block Diagram

                                            Tuning Motors




                        LabVIEW           BasicX-24
                     Signal Processor   Microcontroller
LCD User Interface
                                                            Guitar

                                          Auto-Plucker
Auto-Plucker
   Specialized threaded
    dowel
       Mounted motor
       Guitar pick holder
   Motor rotation direction
    determines linear
    direction of pick
    movement
   Velcro attachment
Control of Auto-Plucking
   Individual String Plucking
       BasicX outputs pulses controlling pick movement
       Guitar pick moves until tunable signal acquired
   Re-Plucking String
       Signal decays below tunable level for duration
           Auto-Plucker plucks string twice moving back to
            original position
BasicX – Tuning Motors –
Auto-Plucker Schematic
                                               +5V

                                                     Parallax Continuous
                                                     Rotation Servo Motor
                                                      Model #900-0008



                                                                            Auto-Plucker
                                                                               Motor
             1                24

             2                23

             3                22

             4                21

     Sharp   5                20

      Flat   6                19
                  BasicX-24   18
                                                                            6th String
             7
                              17
                                                                              Motor
     Pluck   8
   RePluck   9                16

     Start   10               15
                                                                            5th String
   Restart   11               14
                                                                              Motor
     Done    12               13   StopPluck


                                                                            4th String
                                                                              Motor

                                                                            3rd String
                                                                              Motor

                                                                            2nd String
                                                                              Motor

                                                                            1st String
                                                                             Motor
    Block Diagram

                                            Tuning Motors




                        LabVIEW           BasicX-24
                     Signal Processor   Microcontroller
LCD User Interface
                                                            Guitar

                                          Auto-Plucker
Unforeseen Challenges
   Frequency detection robustness
       Assume string within certain frequency range
           If not, tuner detects wrong fundamental frequency
   Auto-Plucker and signal processor miscue
       Signal processor would advance to next string
        while Auto-Plucker would not
Unforeseen Challenges
   Guitar pick hits more than current string
       Results in noise, though little effect in frequency
        detection
   Changing tension of current strings changes
    tension of tuned strings
       Changed tuner to tune strings twice
       Lengthened tuning process (~5 minutes)
Unforeseen Challenges
   Minimize lateral guitar movement due to
    Auto-Plucker
       Two guitar wall mounts
   Floating Ground
       Wrong input would be acquired
Recommendations for
Unforeseen Challenges
   Plucking and reading states of signal
    processor
       Would be fixed if 8th digital output was available
   Introduce better frequency detection algorithm
   Build device to hold other strings while current
    string is being plucked
How well did it work?
Tuning Results
   Standard tuner shows difference in cents
       1,200 cents = 1 octave
       Each tick is 5 cents



   Frequency of note = N
   Number of cents away from N = C
   Frequency = F         C
                    F  N *2     1200
Tuning Results – Standard
Note        Note        Calculated             Error* (Hz)
       Frequency (Hz) Frequency (Hz)
 E          82.4          82.07                    0.33
 A          110             109.5                   0.5
 D         146.8           146.04                  0.76
 G          196             194.9                   1.1
 B         246.9            246.3                   0.6
 E         329.6            328.8                   0.8
                       *Tuned string to ±2 Hz of correct frequency
Improvements
   Adjust tuner to adapt to multiple makes and
    models of guitars
       Adjustable tuning motor placement
   Flexibility of tuning styles
   Increase portability
       Use DSP chip opposed to LabVIEW
   Increased Speed
Credits
   ECE Machine Shop
   Professor L. Haken
   Tony Mangognia
   Professor S. Carney
   Gary Pocci
   CV Lloyde
Thank You

Questions?
Ethical Issues
   Minimize damage when setting and removing
    guitar from tuner
   Warn about possible broken strings
       Due to assumed frequency range of guitar
   Standalone guitar tuner
       Wall mount → User Injury
Alternate Frequency Detection
Techniques
   Extract Single Tone Information VI
   SINAD Analyzer VI
   Cepstrum Analysis
Tuning Results – Drop D
Note        Note        Calculated             Error* (Hz)
       Frequency (Hz) Frequency (Hz)
 D          73.4           72.8                     0.6
 A          110             109.3                   0.7
 D         146.8           146.99                  0.19
 G          196             195.1                   0.9
 B         246.9            246.5                   0.8
 E         329.6            328.9                   0.7
                       *Tuned string to ±2 Hz of correct frequency
Tuning Results – Open G
Note        Note        Calculated             Error* (Hz)
       Frequency (Hz) Frequency (Hz)
 D          73.4           73.6                     0.2
 G          98               99.2                   1.2
 D         146.8            147.4                   0.6
 G          196             197.5                   1.5
 B         246.9            246.1                   0.8
 D         293.7            294.0                   0.3
                       *Tuned string to ±2 Hz of correct frequency

				
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posted:11/25/2011
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