We all know that people who can play guitar are very cool, but it takes a lot of dedication to practice to actually get good at it. It's easy enough to play power chords for some punk rock head banging, but learning all of the finger positions for the real chords requires perseverance. Strumming is usually considered the easy part of playing the guitar, because you just need to make sure you're hitting the right strings. But even that can be tricky if the strumming pattern is complex. Fortunately for aspiring folk rock stars that lack strumming skill, Jacob Stambaugh designed a DIY guitar AutoStrummer.
Stambaugh designed this AutoStrummer for the Makecourse at the University of South Florida. His Instructables tutorial provides thorough instructions on how you can build your own AutoStrummer. But he designed the device specifically for his guitar and you may need to tweak the size to fit your own guitar. The device should clamp into an acoustic guitar's sound hole. The only modifications you may need to make to the guitar itself are to the bridge, where Stambaugh had to place spacers under the strings to make their height level. That ensures that the device can strum all size strings smoothly.
Most of the AutoStrummer is 3D-printable and an Arduino Pro Mini board controls the strumming. The player pushes on six tactile buttons to tell the Arduino which strings to strum. A potentiometer adjusts the strumming speed and strumming patterns are selectable through a simple menu system. The Arduino uses those parameters to determine when and how to move a small stepper motor, which has a guitar pick attached to an arm. The guitarist places their fingers on the fretboard in the usual chord positions and then presses the buttons on the device. The AutoStrummer will then begin strumming just like a Mumford or son. It would probably be a lot easier to learn how to strum manually, but this is still a cool project. It could also be useful for guitarists that have disabilities which prevent them from strumming.