Automatic Guitar Tuner TRENTON AHRENS, ALEX CAPO, ERNESTO WONG GROUP 1

Goals Design a guitar that will automatically tune to a selected tuning preference Interact with an android application Gain necessary skills required to succeed in the engineering field

Motivation Tuning can be time consuming Difficult without extra equipment especially for beginners The interest in music

Specifications Tune within 30 seconds Within a noticeable difference of +/- 5 cents (100 cents/semitone) Small profile 5 tuning preferences At least 50 cycles per battery charge Operate outside with moderate humidity

4-String Bass

Overall System Block Diagram

Division of Labor Ernesto Android app development Code for tuning algorithm Trenton Signal Processing Pickups Mounting Alex Power supply Mounting Code for tuning algorithm

Mobile Application User Interface Android Platform Version 4.4.X+ Android Studio Java Bluetooth communication with microcontroller

Android Studio

Bluetooth Communication Built in Bluetooth capabilities on phone HC-05 Bluetooth module

Microcontroller ATMega328p chip 6 analog inputs 10-Bit ADC 6 PWM outputs 20 MHz operating freq.

Pickups Magnetic field seen by the pickups will induce an analog voltage that will be read by the ADC inputs Polyphonic Extracted from a Power Gig controller

Analog-Digital Conversion Threshold crossing Fast Fourier Transform StringNoteFrequency (Hz) 1 (thinnest)G98 2D A55 4 (thickest)E41.2 Standard Tuning For a 4 String Bass Guitar

DC Offset & Amplification Guitar signal from pickups is about 20mV-40mV ADC 0-5V

Tuning Mechanism Atmega328P controls the tuning algorithm Reflective sensors to determine number of turns H-Bridge for bi-directional rotation QTR-1RC Reflective Sensor (Pololu) L293DNE Dual H-Bridge (Texas Instruments)

Motor Mounting Bracket

Power Battery Power – NiMH (Nickel Metal Hydride) rechargeable batteries 6xAA battery holster (Adafruit) = 7.2 V 2500 mAh

Components to be Powered Atmega328P (Amazon) 1.8-5V Operating voltage 0.2mA current draw while active 4x ROB Standard Gear Motor (Sparkfun) 3-12V operating voltage 95mA current 12 V 4xMotor(95mA) + Atmega328P(0.2mA) = 380.2mA 2500mAh/380.2mA = 6.57 hours battery life 2500mAh/95.2mA = hours battery life (realistically)

Component Decisions 6-String Electric Guitar vs. 4-String Bass Guitar Polyphonic vs. Single Coil ATmega328p Gearmotor vs. Stepper vs. Servo NiMH vs. Li ion IC H-Bridge vs. DIY H-Bridge Android > Apple

Difficulties Mounting of motors Emulating the code Reading signals

Budget PartCost 4-String Bass Guitar$0 Pickups$ x Gear motors ROB-12472$ Arduino Uno$25.75 HC-05 Bluetooth module$8.40 Shaft couplers & motor mounts$ x Sensors (QTR-1RC)$ x H-Bridge (L293DNE)$14.49 Total: $ Funding provided by Boeing : $200

Progress

Future Plans 1. Design adequate motor mount 2. Signal processing/motor tuning algorithm implementation 3. Finish and test Android application functionality 4.Design and order PCB 5.Combine all subsystems into final product and test

Questions?