02/12/03 Brian Crosby Electrical Report Auto Tuner Brian Crosby

02/12/03 Brian Crosby Electrical Report Background Manual Tuning a String Instrument to Reference Tones Takes Skill, and Is Often a Time Consuming and Error-prone Process.

02/12/03 Brian Crosby Electrical Report Problem Develop a Hand Held System That Automatically Tunes a String Instrument to Its Standard Tuning Quickly and Effectively.

02/12/03 Brian Crosby Electrical Report Solution Microphone to listen Microphone to listen Filter to clean signal Filter to clean signal Comparator to convert signal Comparator to convert signal Micro-controller to decide Micro-controller to decide Gear motor to correct and adjust Gear motor to correct and adjust

02/12/03 Brian Crosby Electrical Report System Overview Microphone Filter Comparator Gear Motor Instrument is plucked High Low Micro Controller

02/12/03 Brian Crosby Electrical Report What it looks Like ON / Off Six position Switch Mode Selection LCD Display Tuning peg Heads

02/12/03 Brian Crosby Electrical Report Auto Tuners Electrical Layout

02/12/03 Brian Crosby Electrical Report Electrical Overview LOW PASS FILTER PIC COMPARATOR H BRIDGE MOTOR DRIVER GEAR MOTOR INPUT ¼” JACK On/OFF BUTTON MODE BUTTON BATTERY DISPLAY SIX POSITION SWITCH Circuit Board

02/12/03 Brian Crosby Electrical Report Input Filter Guitar freq. Ranges.  330hz to 1.3khz. Low passed freq.  R=1k, C=.05uf.  Filters off frequencies above 2 kHz.

02/12/03 Brian Crosby Electrical Report Comparator for first 4 strings Voltage divider set comparator reference voltage to 100mv.

02/12/03 Brian Crosby Electrical Report Comparator for last two strings Parallel combination of resistors lowers comparator reference to 75mv

02/12/03 Brian Crosby Electrical Report 0 to 4.5 Volt Square Wave

02/12/03 Brian Crosby Electrical Report Micro-Controller 16f628 Pic Voltage range  3.0V to 5.5v Power consumption 5.0v

02/12/03 Brian Crosby Electrical Report H Bridged Motor Driver

02/12/03 Brian Crosby Electrical Report Six Position Switch Power in From Micro Controller Divided voltage Sent back to Micro Controller

02/12/03 Brian Crosby Electrical Report 3 AA Alkaline 4.5V

02/12/03 Brian Crosby Electrical Report Auto Tuner Schematic 16F628

02/12/03 Brian Crosby Electrical Report For More Information Visit the Auto Tuner Web Page /AutoTuner/WebPage

02/12/03 Brian Crosby Electrical Report Any Questions ???