Paper Tape Drive for a Live Performance Music Box

Music is a mystery to some of us. Sure, we know what we like when we hear it, but the idea of actually being able to make it baffles us. And the idea of being able to build new instruments to create it, like this paper-tape programmable music box (YouTube, embedded below), is beyond impressive.

You’ll no doubt remember [Martin Molin] of the group “Wintergatan” and his astounding marble madness music machine. This instrument is on a much more modest scale and is centered around an off-the-shelf paper tape music box. But the cheap plastic drive gears kept failing under performance conditions, so [Martin] headed to what appears to be his cave-based workshop and started grinding. He prototyped a new paper drive from Lego Technics, and while it worked, it needed help to pull the paper. What followed was an iterative design process that culminated in a hybrid of plastic and metal Technic parts that drive the paper reliably, and a musical instrument that’s much more than just a tinny wind-up music box. Hear it in action below with another new instrument, the Modulin, which sounds a little like a Theremin but looks like – ah, just watch the video.

The build video hints at more details to come, and we’re hoping for a complete series like that for the marble machine. We’d also love to see details on the Modulin too – if there ever was a hacked musical instrument, that’s it.

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Simple to build programmable foot switches


Your hands do a lot of work between the keyboard and the mouse, why the heck are you letting your feet be so lazy? [Dossier van D.] is putting an end to the podiatric sloth. He built this set of three foot pedals which have gone through two versions of functionality.

The buttons themselves are made from a base plate of plywood with a smaller piece on top for each ‘key’. The two parts are separated with some foam carpet pad, with a tactile push button in between to register a click. The only thing we’d change about this is adding a couple of wooden spacers next to the switch so that accidentally sanding on a button doesn’t break that electronic component.

Originally each button was soldered to a gaming controller. This worked just fine using button mapping, but recently [Dossier] made the switch to using an Arduino Leonardo. This is a perfect choice. Unlike input devices made with older Arduino versions the Leonardo board can natively register as a keyboard, making it a snap to programmatically map any key to the switches.

If you like this project you should check out [Dossier’s] foot mouse as well.

PIC programmable power supply

This programmable power supply is the perfect addition to your bench tools. [Debraj Deb], who previously built a whole house power monitor, designed this build around a PIC 18F4520 microcontroller. The desired voltage is set with an attached keypad, resulting in a digital output on the 8-bits of port D. The port connects to another protoboard with an R-2R digital-to-analog converter resulting in the target voltage. A set of transistors amplifies the current and a power transistor then takes care of the final output. After the break you’ll find two videos, the first walks us through the hardware and the second demonstrates the device in action, along with measurements of its performance. This certainly provides a lot more functionality than an ATX power-supply conversion.

Update: A big thanks to [Debraj] who sent us a code package as well as the schematic (PDF) used during testing. We’re having trouble getting the code package up for download right now. Check back later, hopefully we’ll have it up soon.

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