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The Auto-Chromatic Instrument Tuner
Erin Smith
Advisor:  Dr. James Irwin
Functional Description

Overview
 The purpose of the auto-chromatic instrument tuner is to help musicians match the intonation of  their instrument with a reference pitch, or concert pitch, which may be best described as matching the notes on a piano. To maximize the usefulness and practicality of the tuner, there will be three different ways in which to tune:  automatic tuning mode, manual tuning mode, and audible reference pitch mode.  In automatic tuning mode a note is  played, and the tuner matches the input pitch to the closest reference pitch. The manual tuning mode allows the user to select the reference pitch to be compared against.  An advantage of manual mode is faster operation, since the tuner does not have to search for a reference pitch before making the comparison.  Finally, the audible reference pitch allows the user to tune the instrument by ear.  This mode is particularly useful in tuning large ensemble groups.

Inputs
· DC Power Supply
· Microphone:  Converts pitch into an electrical signal
· Power/Mode Switch:  Switches between Off mode, Automatic Tuning mode, Manual Tuning mode, and Audible Reference Pitch Tuning mode
· Pitch Selector:  Selects pitch and octave in Audible Reference Pitch mode and selects tuning note in Manual Tuning mode

Outputs
· Pitch Indicator:  Three character 7-segment display which indicates the letter name, whether it is natural or flat, and the octave of the pitch that is to be detected.  For example- En5, Gb2 would indicate E natural, fifth octave and G flat, 2nd octave.
· Analog Tuning Display:  An analog meter which will demonstrate how close the note is to a reference pitch.  The meter will range from -50 cents to +50 cents, indicating a range between half-way to the next highest chromatic pitch or half-way to the next lowest chromatic pitch.
· Digital Tuning Indicator:  A series of LED’s which will give a discrete minimal error of how close the user is to the desired reference pitch.  A central green LED will indicate a perfectly matched pitch.  Two yellow LED’s outside of the center LED will indicate if the pitch is within 10 cents (or 10%) of the central pitch.  Finally, two red LED’s surrounding the yellow LED’s will exhibit that the pitch is more than 10 cents away from the indicated pitch.
· LED/LCD Bar Indicator:  May replace the Digital and Analog Tuning Displays by displaying a light or marker at the place the input pitch is in relationship to the reference pitch.
· Speaker:  Will produce the reference pitch as an audible sound to the user.
 
 
 

Modes of Operation
· Off:  No power is input into the system
· Automatic Tuning Mode:  Based on the pitch received by the microphone and transmitted into the tuner, the closest reference pitch is found and subsequently indicated on the display along with both the analog and digital indication of how close the received pitch is to the reference pitch.
· Manual Tuning Mode:  The user selects the reference pitch, indicating its octave, and the pitch received by the microphone is then compared to this pitch.
· Audible Reference Pitch Mode:  Again, the user selects the reference pitch and octave, and the output is an audible tone which may be used as a point of reference for obtaining that desired pitch.

Figure 1: Front Panel of Auto-Chromatic Tuner
 
 
1 Power Supply
2 Microphone
3 Power Mode/Switch
4 Pitch Selector
5 Pitch Indicator
6 Analog Tuning Indicator
7 Digital Tuning Indicator
8 Speaker

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