School of Mechanical Engineering

Project number 180:Design and Build of a self

tuning stringed instrument

Andrew Leonard Colin Love

Project Outline

• Based around conventional 6 stringed electric guitar

Consists of 3 main components• Data acquisition• Control system • Mechanical tensioning system

Design Specifications

• Lightweight• Keep structural integrity• Keep existing manual tuning• Remain tuned without power supplied to system• Quick and Accurate• Cheap (less than $1500)• Retain existing size and shape

Existing Designs

Transperformance– Price >$4500– Alternate tunings– Open loop / Closed loop control

© Transperformance 2004 www.transperformance.com

Rochester Institute of Technology– Student group to design self tuning guitar– Utilised a FFT algorithm– Incremental control– Extremely unreliable

Existing Designs

Our Solution

• Completely internal• Used for fine tuning• Levers to adjust tension• P- control

Data Acquisition system

Midi Pickup

Each signal generated in separate coils

Conventional Pickup

All signals combined in one coil

Micro

Micro

Micro

Micro

Control system

• Pulsed information from signal refining circuit

• Used 6 PICs; one for each string– Existing knowledge base– Cheap– Easy to program

Control Algorithm

T1 T2

•Time between consecutive rising edges measured

•Valid signals are stored in an array

•Motors activated when 8 consecutive valid signals are received

•Predefined set-point

•Last 8 set-point errors averaged and P-control utilised

Motor Control

Speed controlled by pulse width modulation

Micro

PWM

Direction

Motor Driver

DC Motor

Mechanical System

In-body Design– Motors with low speed/high torque gearboxes– Threaded rod – linkage – lever

How it works

Questions?