Tune On A Stick


A Shiny Thing, made with Anton and Russ for EMFcamp 2014.

Jonty wanted some shiny things to make EMF2014 more entertaining, and very generously offered to fund the parts for a suitable project.

What could we do ? We are helpless in the face of that kind of offer. We made a thing.

Here it is outside the First Aid tent, where it ran happily for two whole days.

It generally had a bit of an audience:

It spins continuously, and as it spins it measures the range to the nearest object (generally a person) with an ultrasonic ranger. Those ranges are converted into musical notes in a prechosen scale, the closer the person the higher the pitch.

So, by arranging themselves correctly, the audience can play a tune.

It also improvises a melody line from the audience's notes, and plays a simple percussion line to tell them where the beats are.

Whenever it is idle - when no people are in range for a few rotations - it picks a different scale and different MIDI instruments, so the music changes a lot from run to run.

Here's what's inside - lasercut MDF decks, and a bit of old laser printer drum for a bearing mount:

Power is all from an ATX power supply

Range sensing is handled by a Maxbotix XL-MAXSONAR EZ1. It got a lot better when I put a foam-lined tube over it.

The thing's attention is shown by a focused 3W RGB LED. Focusing is via a 5 degree LED lens from eBay. The three FETs there are doing PWM for the three channels. LED current is set with series resistors.

Drive is an old Audi wiper motor from Russ's hoard:

Driving via MDF cogs:

Mains comes in via a slip ring from eBay (240v, 2A/ring, 6 rings).

Rotation index is via a magnet stuck to the nonrotating shaft and an A3144 Hall effect switch:

Sound is thanks to a 3 pair of charity-shop speakers and a car amplifier:

Processing is all done on an Arduino with a Music Maker shield in Midi mode, The code and CAD files are all in github if you want to play with them, Please let me know if you do!

The music generation is derived from the World'O'Music's code, which had musical cleverness from Phill, subsequently tinkered with by Anton and I.

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