When playing the guitar, working the fretboard is only half of the equation. The other half is plucking or strumming the strings. But some people, particularly those with disabilities, may find it difficult to do both. To help with the strumming part of the equation, Jacob Stambaugh designed this DIY AutoStrummer device.

Stambaugh’s AutoStrummer fits into the sound hole of an acoustic guitar, so that it sits over the strings. A guitar pick, attached to an arm actuated by a stepper motor, swings back and forth to strum the desired strings. An Arduino board controls the movement of the stepper motor through a DRV8825 stepper motor driver chip. 

The guitarist uses an array of six tactile push buttons to select which strings to strum. If both the high E and low E buttons are pressed, then the device will strum all six strings. If the D and G buttons are pressed, then it will only strum those two strings. A potentiometer lets the guitarist set the strumming tempo and the strumming pattern is configurable through a menu system.

A 3D-printed case houses all of those components. Stambaugh designed it to fit his specific guitar, so you may need to tweak the size to fit your own guitar. He created the device for the University of South Florida’s Makecourse, and uploaded build instructions and the necessary files to Instructables so that anyone can build their own AutoStrummer.