Easel controller: some background

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Instrument creation! I've always been fascinated by hackerspaces and the incredible things I've seen people create with microcomputers, but I never thought device creation would be something I could/would do. For the first Christmas in a long time, I had a moment of clarity when my dad asked me what I wanted for Christmas. Haven't I always wanted to try an Arduino?

And to my delight, he got me one of the Arduino Uno starter kits! Just enough to get your feet wet - wires, LEDs, a small breadboard, moment buttons, photoresistors, and a whole mess of normal resistors (buyable via MakerShed, if you have a hankering). After playing around with it, I got obsessed with the idea of turning it into a MIDI controller. After all, most MIDI controllers connect via USB, and the Arduino has a USB connection already for uploading Processing patches. Shouldn't that work?

Long story short, it does, though not quite as directly as you might want. Since I haven't purchased new components yet, I have it set up so that pressing the moment button controls note on/off messages, and a photoresistor controls pitchbend (dark room = lowered pitch, brighter room = raised pitch).

But to me, the goal of making my own MIDI controller is creating something unique and visually interesting, for the instrument to be fascinating in its own right. So I did some research.

Kobakant's How to Get What You Want is a fascinating website all about wearable technology experimentation. They explore creating sensors and actuators, and all the different kinds of materials used to put technology in clothing. Good examples to start with are fabric potentiometers, their knit stretch sensor shootout, and embroidered cloth speakers (!!).

When I first found this website, I was overly excited about the possibility of turning a jacket into a MIDI controller, using a zipper as a potentiometer, all of it. There's even an Arduino model specifically designed for use in clothing! But many of these materials are a bit pricey, conductive thread is known to tarnish over time, and I am not an experienced seamstress. So, while the excitement is still palpable, I'll table my foray into e-textiles for now.

I kept looking around, until I had a thought - would graphite work? A quick Google search turned up a video, which inspires a number of exciting possibilities. First, it's possible to draw on paper and have a circuit - that's awesome! Second, since graphite is a much better resistor than it is a conductor, drawing a line of graphite naturally makes it a variable resistor, which also naturally makes it a potentiometer. That's exciting too! Further digging turned up an instructable on making a four-channel mixer on paper, though it seems a little difficult to control. Also, check out these circular graphite sequencers! Though some of the sounds are a bit chirpy, they remind me of the beat to Hazey by Glass Animals.

As far as testing graphite circuits, I haven't gotten it to work yet. I've been working with just lighting LEDs separate from the Arduino (I haven't short-circuited anything on the Arduino yet, but I'd rather not if I can avoid it). Some troubleshooting things I'm going to try:

  1. Get a multimeter (someone nicked mine), and check if the resistance of my graphite lines is too high. Or, if I need a better 6B pencil!
  2. Get a 9V battery. Most of these experiments/devices use 9V batteries, while the Arduino puts out signal at a 5V, and the battery pack I've been using is 6.5V. It's possible the resistance is too high to light LEDs in my tests, even though LEDs light at 3.3V. This opens up the issue of needing to step down the voltage from the 9V to the Arduino, but I'll cross that bridge if it's necessary.
  3. Get alligator clips. Though this is probably less of an issue, pressing wires down to paper isn't necessarily the most sure-fire way of completing a circuit. With bigger leads that would attach to paper, it would leave my hands free to test other things.

Written by Becky on Wednesday January 28, 2015

Permalink - Category: programming - Tags: Arduino, MIDI controllers

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