The pedal relies on an Arduino Uno SMD R3
single-board microcontroller. Diagram below
illustrates a basic signal modification.
Multiple codes were adapted for the pedal
and can be loaded onto the board via USB.
Some of the coded effects include clean,
booster, tremolo, and distortion.
Metal to the Pedal:
Digital Signal Processing Methods for Guitar Effects
Kathryn Pinkerton, Mitchell Fountain, and Christopher Aul
Department of Physics, Engineering, and Astronomy; Stephen F. Austin State University
Kathryn Pinkerton or Mitchell Fountain
Christopher J. Aul, Professor
Email: engineering@sfasu.edu
Phone: (936) 468-3001
Contact
1. B. Hammoud, G. Daou, and N. Wehn, “Multidimensional Minimum Euclidean Distance Approach Using Radar Reflectivities for Oil Slick Thickness Estimation,” Sensors, vol. 22, no. 4, pp. 1431, 2022.
2. C. Benedek, A. Majdik, B. Nagy, Z. Rozsa, and T. Sziranyi, “Positioning and perception in LIDAR point clouds,” Digital Signal Processing, vol. 119, pp. 103193, 2021.
3. M. Taskiran, N. Kahraman, and C. E. Erdem, “Face recognition: Past, present, and future (a review),” Digital Signal Processing, vol. 106, pp. 102809, 2020.
4. P. Sharma, “DSP in image processing,” International Journal of Advanced Research in Computer and Communication Engineering, vol. 4, no. 1, pp. 46, 2015.
5. W. Mousa, Advanced Digital Signal Processing of Seismic Data, Cambridge, UK: Cambridge University Press, 2019.
References
Digital signal processing (DSP) is generally defined as modifying an incoming
signal by way of using computer code or specialized digital processors.
Research into the use of DSP is ongoing in many applications like RADAR [1],
LIDAR [2], face recognition [3], image processing [4], and seismology [5] to
name a few. For this project, DSP is utilized in the creation of guitar effects
through an adapted, open-source guitar pedal design. Elements of computer
science and both electrical and mechanical engineering are used throughout
making it a unique, multidisciplinary project.
Introduction
A Finite Element Analysis (FEA) was preformed on the enclosure designed to
house the pedal components using SOLIDWORKS CAD software. A maximum
loading of 40 lbs is applied at the location of the footswitch. The largest
stresses are shown in red near the application of the force.
Design of Enclosure
• Continue development of code to improve efficiency and functionality.
• Transition to a more robust microcontroller to eliminate need for Arduino.
• Add new components such as potentiometers for extended control.
• Adapt new codes for various effects like delay, chorus, reverb, etc.
• Create modules for keyboard and/or synthesizers.
Future Work
Signal Processing Code
A Printed Circuit Board (PCB) was designed using an open-source, Computer
Aided Design (CAD) software called Kicad 6.0. Shown left to right is an
evolution from CAD model to the final PCB with components.
Printed Circuit Board (PCB)
Prototype Development
Guitar
Signal
Analog
Filtered Input
Arduino w/
DSP
PWM to
Analog
Output
Amplifier
SFA Axe Grinder Pedal
Output
Signal
SFA Axe Grinder Pedal
Specifications:
• Input and output jacks (1/4” Mono)
• Two press buttons
• Toggle Switch (2 place)
• Footswitch
• USB (Arduino)
• Power Supply (9V 1A)
A testbed for the effects pedal wired on an electrical breadboard
Early prototype (v 0.99) with enclosure
Enclosure design of version 1.0 of the guitar effects pedal
Power Supply
Function
Generator
Oscilloscope
• An Arduino-based guitar effects pedal was designed and fabricated.
• A prototype platform for future use was developed.
• Deeper knowledge of DSP and microcontroller systems was gained.
• A custom enclosure was tested and built using in-house manufacturing.
Conclusions
Oscilloscope display with yellow wave as guitar
input and blue wave as pedal output
Prototype on breadboard
Analysis of high-stress points in acrylic joint under compression
Acknowledgements
This research was supported by the Department of Physics, Engineering, and Astronomy and the College of Sciences and Mathematics
as part of the Summer Undergraduate Research Experience at Stephen F. Austin State University. We would also like to acknowledge
the help of Mr. Timmons and Dr. Ochoa who have assisted us throughout the course of this project.
Arduino
