GOSSHOUSE GUITAR PEDALS: Senior Thesis
I am building guitar pedals that integrate and interact with Arduino microcontrollers. Instead of using the standard rotary potentiometers that, for instance, control an effect or volume on an effects pedal, I want to be able to manipulate the values on a circuit using a variety of sensors that make the experience of using the pedal more interesting and interactive.
Last semester, I began learning the basics of electronics and the fundamentals of circuitry. Then, moving on to the actual assembly of a printed circuit board for a simple boost pedal, soldering and wiring the components accordingly. After getting this first go at an effects pedal to work, I created a unique wooden enclosure using a CNC machine, laser engraved the outer design and 3D printed a knob I modeled in Fusion 360 for the potentiometer.
Surpassing the milestone of actually finishing a working pedal, I began my attempts at ‘hacking’ into a pedal. After plenty of failures trying to get a kit chorus pedal I built to function properly and the AIMM After Dark Showcase approaching faster than anticipated, I needed a quick alternative to display this coveted ‘hacking’.
I ended up taking apart my father’s old phaser pedal from the 1980’s — I cut the potentiometer off of the board used for phase rate and took its leads to a breadboard. In order to successfully manipulate values on this analog circuit with Arduino though, a digital to analog converter was necessary — the MCP41100 was the solution.
By connecting the old potentiometer leads to three of the eight pins on the chip, one to ground, one to power and the remaining three as serial connections to the Arduino, an interface between the pedal and the Arduino is formed. For this demo’s sake, I used a MMA8452Q accelerometer to track changes in X, Y and Z, mapping these values to the necessary 0–255 values needed to be sent to the chip. By using the Serial Peripheral Interface (SPI) built into Arduino’s IDE, with a simple digitalWrite() function utilizing a given value and address, I was able to map the X values to change the rate on the phaser.
This ‘hacking’ into an old phaser pedal and controlling the rate of the phaser with an accelerometer proves the point that it’s possible to digitally manipulate the values within an analog circuit.
Knowing this, a world of opportunity opens up. Stealing the three leads from any pedal’s potentiometers and connecting them via the MCP41100 to a breadboard to then communicate with an Arduino and any existing sensor creates a ton of options. A microphone with a given threshold could trigger a specific type of reverb output, the fuzz on a distortion pedal could be controlled by a proximity sensor attached to the instrument itself, or a bluetooth sensor that would allow an interface between a phone and the pedal, making it possible to control a guitar pedal without even physically touching it. The possibilities are endless and increasingly exciting.
