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Auto Tuner

Auto Tuner. Background. Manual tuning a string instrument to reference tones takes skill, and is often a time consuming and error-prone process. Problem. Develop a hand held system that automatically tunes a string instrument quickly and effectively. Solution. ¼ jack to listen

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Auto Tuner

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  1. Auto Tuner Brian Crosby Final Presentation

  2. Background Manual tuning a string instrument to reference tones takes skill, and is often a time consuming and error-prone process. Brian Crosby Final Presentation

  3. Problem Develop a hand held system that automatically tunes a string instrument quickly and effectively. Brian Crosby Final Presentation

  4. Solution • ¼ jack to listen • Filter to clean signal • Comparator to convert signal • Micro-controller to measure and decide • Gear motor to correct and adjust Brian Crosby Final Presentation

  5. What a Signal is Brian Crosby Final Presentation

  6. System Overview Filter Comparator High Gear Motor Micro Controller Microphone Instrument is plucked Low Brian Crosby Final Presentation

  7. What It Looks Like Tuning peg Heads ON / Off Six position Switch LCD Display Mode Selection Brian Crosby Final Presentation

  8. Presentation Breakdown • Electrical • filter, converter, micro controller, motor driver • Software • Frequency comparisons, overall functions • Mechanical • Torque, motor, gears Brian Crosby Final Presentation

  9. Auto Tuners Electrical Concepts Brian Crosby Final Presentation

  10. Electrical Overview On/OFF BUTTON MODE BUTTON BATTERY DISPLAY DISPLAY PIC COMPARATOR H BRIDGE MOTOR DRIVER INPUT ¼” JACK SIX POSITION SWITCH FILTER Circuit GEAR MOTOR Two Circuit Boards Brian Crosby Final Presentation

  11. Input Filter • Guitar freq. Ranges. • 330hz to 1.3khz. • Low passed freq. • R=1k, C=.05uf. • Filters out frequencies above 2 kHz. Brian Crosby Final Presentation

  12. Comparator Circuit for Strings Voltage divider set comparator reference voltage to 100mv for the E,A,D,G strings Parallel combination of resistors lowers comparator reference to 75mv for the B and High E strings Brian Crosby Final Presentation

  13. Guitar and Comparator Signals Set Trigger Point for comparator Brian Crosby Final Presentation

  14. Micro-Controller • 16f877 Pic • Voltage range • 3.0V to 5.5v • Power consumption 2.0ma @ 5.0v Brian Crosby Final Presentation

  15. Motor Driver Brian Crosby Final Presentation

  16. Power • 6 AA batteries • 9Volts • Current draws • 200ma @ full load • 60 ma @ no load • 30ma@power down Brian Crosby Final Presentation

  17. Auto Tuners Software Concepts Auto Tuner Brian Crosby Final Presentation

  18. Start UP Auto tuner Welcome Power UP Choose Tuning Standard Drop D Eb Select string Pluck String Brian Crosby Final Presentation

  19. Signal Process Master Clock System Shut Down Signal from guitar Motor OUT High Low Capture Clock Memory Check Tuning keys are turned Brian Crosby Final Presentation

  20. Master Clock • Used • LCD Backlight, Off Button, Power down • Overflow interrupt • 13ms • Counts, coin in the bucket • Resets • buttons, switch, captures • Example: • Power down in 2 minutes • 2min = 120 sec = 9231 coin in bucket Brian Crosby Final Presentation

  21. Capture Clock • Overflow • 26ms, 38.46hz. • Signal resets timer • Rising edges • Capture used • 400ns blocks Brian Crosby Final Presentation

  22. 400ns Blocks Brian Crosby Final Presentation

  23. call LCD_Init ;Display the splash screen for 3 seconds. call Delay10ms movlw MSG1 call LCD_PrintString call LCD_NewLine movlw MSG2 call LCD_PrintString call Delay1sec call Delay1sec call Delay1sec Main: call LCD_ClearScreen ;Put the current capture value on the screen. call Delay10ms movlw MSG3 call LCD_PrintString call LCD_NewLine Software sample Brian Crosby Final Presentation

  24. Software Main Loop Main_Loop: call Delay100ms bcf PIR1, CCP1IF ; Clear the Capture module interrupt flag bcf PIR1, TMR1IF bsf T1CON, TMR1ON ; Turn on the timer1 ; Wait for the next Capture event. Main_Loop_Wait: btfss PIR1, CCP1IF goto Main_Loop_Wait clrf TMR1L clrf TMR1H btfsc PIR1, TMR1IF ; check if timer 1 overflows and skips next command if not GOTO Main_Loop Brian Crosby Final Presentation

  25. Auto Tuners Mechanical Concepts Brian Crosby Final Presentation

  26. Input / output circuit board LCD Pic Circuit Board Mechanical Overview Gripper for E,A,D strings Gear Gear Battery Pack Gear Motor Gripper for G,B,E strings Brian Crosby Final Presentation

  27. Torque and Gear Motor • Guitars Tuning Keys • Highest , tightening = 10.8 oz / in • Lowest loosening = 1.8 oz / in • Matching gear motor • 41.7 oz / in @ 12 volts • Less @ 9 volts • Estimated torque = 31.3 oz / in Brian Crosby Final Presentation

  28. Gears • Considerations • 30 RPM • No change • Torque 31 oz / in • No change • Spur Gear • Two of the same size • 1:1 ratio Brian Crosby Final Presentation

  29. Prototype Cost Estimated manufacturing cost $90.00 Suggested retail $160.00 Brian Crosby Final Presentation

  30. Schedule Brian Crosby Final Presentation

  31. For More Information Visit the Auto Tuner web page: www.vtc.edu/elm/projects/2002-2003/auto tuner/webpage Brian Crosby Final Presentation

  32. Thank You • Sam Colwell • Mike Weidman • Roger Howes • Andre St. Denis • Paul Johnson Brian Crosby Final Presentation

  33. Any Questions ??? Brian Crosby Final Presentation

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