Senior Projects
Elm-4701
Auto
Tuner
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By Brian Crosby
Background:
Problem:
Develop a handheld system that automatically tunes a string instrument quickly and effectively.
Solution:
Use a microphone to listen, filter to clean, comparator to convert, micro controller to measure and decide what to do with the input guitar signal and a gear motor to correct and adjust signal.
Diagram:
System Overview:
The system overview above starts with the musician plucking on a guitar. The signal is then fed into microphone and then filter with a low pass filter to cut off all frequencies above 2K-Htz. After filtering the signal it is then converted into a digital signal using a LM-339 comparator. This is done to help the microcontoller to understand the signal. The microcontoller then sends a signal out to the gear motor turning it clockwise or counter clockwise to adjust the pitch of the string.
System Concepts:
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Electrical Concept
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Software Concept
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Mechanical
Concept
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Electrical:
The general electrical functions of the unit are to filter, correct and display. All of these will be covered in this electrical section.
First is the electrical system layout of the Auto Tuner. Six AA batteries produce 9 volts of power for the motor is reduced to 5 volts by a To-7805 voltage regulator for the rest of the circuitry. The main circuitry can be found on two circuit boards connected by a 20 pin ribbon cable. The upper circuit board contains components that are for user input, such as the on/off button, mode selection button and six position switch. These buttons and switch are for the user to navigate and communicate to the micro controller when using the unit. On\off button powers unit up and shut the unit down. The mode selection button allows the user to scroll through the different tunings. The six position switch allows the user to select between the different strings. The upper circuit board also contains the low pass filter, lm-339 comparator to clean and convert in-coming wave forms and the A3968SA motor driver chip for driving the motor.
The bottom circuit board connected by the 20 pin ribbon cable is a programming board for the micro controller. This board also has the TO-7805 voltage regulated that steps the 9 volt battery supply to 5 volts. The 9 volts is to drive the motor only and not for the rest of the circuitry. The micro controller is the brain of the entire unit. This is where the software executes and corrects incoming signals. The micro controller used on this board is a PIC 16F877. The PIC has 8k of flash memory and 5 I\O ports. The last part of the electrical system is the LCD display. This is the menu and instructor to the user. The LCD used is a model DMC 16202N-LY-AME. This LCD runs off from 5 Volts. One of the features of this LCD is the backlight. Although this is a nice feature it increases the current draw considerably. This is why the LCD backlight turns off after three seconds, to save on battery life.
Software:
The software of the system is the heart of the entire Auto Tuner. The software looks at in coming signals and decides on how to correct them. This can be seen in the software concept diagram above. The signal is feed from the guitar then captured and check against a value in memory then corrected through the use of the motor. At the same time, the master clock is reset stopping the unit from shutting down and keeping the LCD on for only three seconds.
The software also writes to the LCD, and turns its backlight on and off. The software even takes input from the user and executes functions such as turning unit off and choosing the right tuning.
The software for the PIC micro controller is written in assembly language. This software is a special kind of assemble for use with PIC micro controllers and only has a 35 instructions in its set. These instructions are written in over 1500 lines commands that help the Auto Tuner to function.
Mechanical:
The mechanical parts of the Auto Tuner consist of the motor, gears, grippers and enclosure. A quick glance at the mechanical concept drawing above, will give you a general sense of where the parts are laid out in the enclosure. The 30 RPM gear motor runs on 9 volts and delivers about 31.3 oz \ in’s of torque to equally sized spur gears. This is a 1:1 gear ratio. The reason for the two of the same sized gears is to not change the RPM or torque. The grippers are machined out of metal for durability and are mounted on a shaft that passes through the enclosure. The reasoning for two grippers is, ease of placement on guitars having tuning pegs on both sides of their head stock.
For some more information about the project to date please check out the following links below:
The general electrical functions of the unit are to filter, correct and display. All of these will be covered in this electrical section.
First is the electrical system layout of the Auto Tuner. Six AA batteries produce 9 volts of power for the motor is reduced to 5 volts by a To-7805 voltage regulator for the rest of the circuitry. The main circuitry can be found on two circuit boards connected by a 20 pin ribbon cable. The upper circuit board contains components that are for user input, such as the on/off button, mode selection button and six position switch. These buttons and switch are for the user to navigate and communicate to the micro controller when using the unit. On\off button powers unit up and shut the unit down. The mode selection button allows the user to scroll through the different tunings. The six position switch allows the user to select between the different strings. The upper circuit board also contains the low pass filter, lm-339 comparator to clean and convert in-coming wave forms and the A3968SA motor driver chip for driving the motor.
The bottom circuit board connected by the 20 pin ribbon cable is a programming board for the micro controller. This board also has the TO-7805 voltage regulated that steps the 9 volt battery supply to 5 volts. The 9 volts is to drive the motor only and not for the rest of the circuitry. The micro controller is the brain of the entire unit. This is where the software executes and corrects incoming signals. The micro controller used on this board is a PIC 16F877. The PIC has 8k of flash memory and 5 I\O ports. The last part of the electrical system is the LCD display. This is the menu and instructor to the user. The LCD used is a model DMC 16202N-LY-AME. This LCD runs off from 5 Volts. One of the features of this LCD is the backlight. Although this is a nice feature it increases the current draw considerably. This is why the LCD backlight turns off after three seconds, to save on battery life.
Software:
The software of the system is the heart of the entire Auto Tuner. The software looks at in coming signals and decides on how to correct them. This can be seen in the software concept diagram above. The signal is feed from the guitar then captured and check against a value in memory then corrected through the use of the motor. At the same time, the master clock is reset stopping the unit from shutting down and keeping the LCD on for only three seconds.
The software also writes to the LCD, and turns its backlight on and off. The software even takes input from the user and executes functions such as turning unit off and choosing the right tuning.
The software for the PIC micro controller is written in assembly language. This software is a special kind of assemble for use with PIC micro controllers and only has a 35 instructions in its set. These instructions are written in over 1500 lines commands that help the Auto Tuner to function.
Mechanical:
The mechanical parts of the Auto Tuner consist of the motor, gears, grippers and enclosure. A quick glance at the mechanical concept drawing above, will give you a general sense of where the parts are laid out in the enclosure. The 30 RPM gear motor runs on 9 volts and delivers about 31.3 oz \ in’s of torque to equally sized spur gears. This is a 1:1 gear ratio. The reason for the two of the same sized gears is to not change the RPM or torque. The grippers are machined out of metal for durability and are mounted on a shaft that passes through the enclosure. The reasoning for two grippers is, ease of placement on guitars having tuning pegs on both sides of their head stock.
For some more information about the project to date please check out the following links below:
| Use Microsoft internet explorer to view the
latest presentations |
Final
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Status Report
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Software
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Electrical Report
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| Check out the Auto Tuners operating instructions. |
user manual
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| Time lines and progress. |
Project schedule
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| Use Microsoft internet explorer to view
research done. |
Research
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