ukulELI

A wireless ukulele strummer for one-handed playing

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Inspiration

Coming from a musical family, Eli wants to be able to play ukulele with his young daughter. He does not have full mobility in his left side, so he needs to be able to play with only his right hand. We designed an automatic strummer attachment with Eli that allows him to strum the ukulele by tapping his foot on the ground and finger chords with his right hand.

What it does

To strum, Eli taps his foot on the ground in our foot "pedal." Each tap is wirelessly communicated to the strummer attached to the ukulele. By tapping his right foot to the rhythm and fingering chords with his right hand, he has full control over the tempo and frequency with which he strums.

How we built it

Our strummer is controlled wirelessly using radio communication, giving him flexibility in playing while sitting or standing. Eli taps his foot on the floor in our foot "pedal", which detects his tap through a break in the laser beam sensor. Each time his foot breaks the beam, the strummer moves down and up once to strum the ukulele. The strummer is made with a small servo and custom-made pick arm made of sheet metal and compliant plastic.

We built a mounting fixture of acrylic to hold the strummer and electronics, which follows the natural curve of the ukulele. We used adjustable clamps to attach this to the ukulele so that the mount and strummer can be easily detached from the ukulele in one motion. The foot pedal is made of acrylic and the beam breakers are fixtured on either side.

Documentation

Laser cutting files for the ukulele mount and foot pedal: ukuleli files

Assembly of Ukulele Mount:

  1. Laser-cut the top and base files out of 1/4" black opaque acrylic
  2. Thread the four center holes on the base with 10-32 tap
  3. Thread the clamp holes on the base with 6-32 tap
  4. Attach the servo in the servo hole
  5. Drill clearance 6-32 holes in the clamps and attach the clamps to the base with 6-32 screws
  6. Attach the top and base together.

Assembly of Foot Pedal:

  1. Align the two beam breakers so that the beam is connected.
  2. Secure using epoxy.
  3. Contain the electronics in a black box.

Sizing and length of the ukulele pick can be adapted to your ukulele size and desired strumming location.

Advised: obtain external battery packs that do not time out with low power draw.

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