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The Bee and the Express

Express: back panel test mount I’m finally back to working on some electronic projects. First up, the Express, an analog-to-MIDI converter built around a Bare Bones Board, an inexpensive Arduino clone.

I’ve been making up some patches for my Evolver synth to use it as an effect on guitar or bass, and thought it’d be nice to have some sort of pedal to control it, along the lines of a wah or volume pedal. The desktop model of the Evolver lacks a pedal input, hence the Express (for “expression”, both of the musical and genetic kind - evolution, geddit?). Currently, it reads one analog pin and spits out continuous controller data. Nothing particularly spectacular there, but it did fit wonderfully into the sturdy steel case from a computer keyboard A/B switchbox. There’s room for lots more inputs, and eventually I figure it’ll sport an additional analog in and some footswitch inputs which will send things like note on/off messages.

I’m still new to making enclosures, and to working metal in particular - instead of grinding out a hole that was slightly too narrow, I used a drill, which grabbed hold of the edges and warped the heck out of the front panel. Panic set in for a moment, but I managed to bash the thing back into shape using a busted old hard drive(!) as an anvil.

Word to the wise: there are two incompatible standards for the wiring of expression pedals:

1/4” - tip to wiper / ring to +5V / sleeve to ground: Clavia, CME, Electrix, Emu, Kurzweil, Oberheim, Roland/Boss
1/4” - ring to wiper / tip to +5V / sleeve to ground: Kawai, Korg, Yamaha

The former arrangement allows you to use a standard normalling jack to connect the tip to ground by default, so the input doesn’t float if nothing’s plugged in. I’m using a Boss pedal now, but my other pedal is a Yamaha, so if I want to use it as a second input, I’ll have to wire up something to cross those connections.

Arduino (and Tarquin) Being easily distractible by possibilities - giant trackball! LED matrix! stepper motor-controlled time-lapse photography! - I’m desperately trying to focus on a couple of projects at a time. Arduino project number two at present is using it for ultra-cheap and dirty sound generation, with piezo disc speakers plugged directly into the digital outputs. A little hacked-together code, and voilà:

The Bee (MP3, 640k)

I call it the Bee, though “Mosquito” might have been more appropriate. Modulating the pulse width creates some nice motion, but there’s a lot more to do, like getting R/C filters to tame some of the harshness - it really is annoying after a while. Oh yes, and putting a switch on it to shut it up between tests. And, of course, buttons and knobs to play it with… maybe even some sort of acoustic treatment, like a resonating soundbox or a spring reverb.

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