Blog: entries tagged with "electronics"

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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One of Stan Krzyzanowski's pine conesDorkbot Toronto, the local chapter of the network of “people doing strange things with electricity”, has a new slate of presentations, and last night was the first.

Patricia Rodriguez presented some of her video work using all sorts of cameras - film, video, digital - and taking advantage of each one’s unique features and most interesting ways of failing.

Cary Peppermint and Christine Nadir’s work is about breaking down the perceived borders between nature and the human-made world, using electronic media installations in unexpected places. Wild Information Network, a solar-powered streaming audio server installed deep in the woods of the Catskills, plays sound pieces submitted by various artists, all with the notion of humans broadcasting to the broader environment, or vice versa. It and other pieces are catalogued on their site:

Stan Krzyzanowski showed his time-lapse work, ranging from handheld still camera shots, to mesmerizing animations created from successive sections of wood and other materials (notably vegetables and marbled cheese), to his recent projects involving cones from various sorts of tree. Pine cones, see, open up as they dry and fold closed again if you get them wet. And when sped up, the waving of a big pine cone’s scales takes on an eerie, almost animal aspect.

It’s beautiful stuff. Interval is a rather huge archive of all his experiments - click some of the “special sets” on the lower right. Most of the best stuff is on the “Favorites” page.

The sessions are held at InterAccess, a gallery at Queen and Ossington devoted to electronic media art. They offer a very cool series of workshops on topics like microcontroller programming, introductory electronics, pinhole photography, and hacking your bike to turn it into a mobile piece of sound art. I’m hoping to attend the ones on Pure Data and creating “resilient outdoor works”.

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Many hands make light (art)work

Three pieces. The first two were passed along by a fellow DIYer who’s working on interactive electronic public art (thanks Gabe!):

GRL's Laser Tag system in operationFirst up, the Graffiti Research Lab and their collaborators have produced a laptop / camera / projector setup that lets you paint on the side of a building.

Their software lets you define the contours of the wall you’re projecting onto, then tracks the position of a laser pointer beam using video fed from the camera, and draws the resulting lines - with some simulated paint dripping, for added effect. Naturally, it’s open source, complete with instructions.

IMAGENext, Body Movies by Rafael Lozano-Hemmer. Portraits are projected on a huge scale on walls surrounding a public square, revealed in the shadows thrown by passers-by. If people in the square arrange themselves in a matching pose, the projections switch. But much more interesting is the ways that people spontaneously interact, given the possibility of casting gigantic shadows of radically different sizes. It turns into instant mimed improv.

Hello from Pika PikaAnd finally, PIKA PIKA, a “lightning doodle project”. Doodler Takeshi explains:

We took a photo of each image using long exposures and put them together to make them look like one animation.

To work on this project,we went out to various places in Japan:parks,under the train track,the Tokyo Bay,school hallways,and so on.

We got all sorts of friends in different fields together to work on this project.
During the process,they got to know each other and discover new things. This is also about “communication”.
People can meet new friends as they create a piece art very easy which brings every one happiness.
We spend a very enjoyable evening at the workshop and the party through this animation.

The results are delightful to watch, too - it’s like a live performance of a Norman McLaren scratch-animation film, with luminous creatures and designs running riot through real physical spaces. I love how the “performers” are often faintly visible, but obscured, like bunraku puppeteers.

The beauty of these projects is how intuitive they are to use. Casting shadows, drawing with light… even if they’re a little tricky to get the hang of, the concept is utterly simple and inviting. And they let people think and interact with their whole bodies.

Now we need to make “computers for the rest of you.” GUI technology allows you to drag and drop, but it won’t notice if you twist and shout.
— Dan O’Sullivan and Tom Igoe, Physical Computing

The body is the large brain.
— Brian Eno

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Musical interfaces 2

the displayBehold the two-digit display for the Box-O-Knobs (also seen here with its breadboarded ancestor). Each digit is run by one 74HC595 IC. Resistors everywhere. The reverse of the board is a bit hideous, I’m afraid, thanks to my still-amateurish soldering skills.

The vacated breadboard now sports five knobs (50k rotary pots), a MIDI socket and a photocell, which I’ve got controlling the sixth analog pin on the Arduino. A change on any input sends a MIDI controller message. The Evolver already has provision for reading in mod wheel, channel pressure (aftertouch), breath controller and foot pedal information, so I’ve got those wired in along with pitch bend and volume.

Next steps:

  • figure out how to cut the appropriate slots in the top of a case
  • wire up six slide pots as controls
  • external input jacks that override the faders
  • buttons!
  • calibration and MIDI settings editable by the user, without having to recompile and upload new firmware.

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Arduino 7-segment output

I hit the electronics store the other day - sadly, they didn’t have any opto-isolators, so no MIDI input experiments this time round. But I scored some 74HC595 ICs, for the driving of LED displays and other digital outputs.

Here’s some code to run a common-cathode 7-segment display using the 595 (the Arduino site has a tutorial on how to hook up the 595, send data to it, and daisy-chain multiple ICs). I’ve included a list of which pins to connect to which anodes on the display in the character set file, below. Displays differ in their pinouts, so if you’ll likely need to do some testing to figure out how the pins are arranged.

charset_7seg.h - I spent a few minutes scribbling out a character set, and here it is as an #includeable file. (I put it in lib/targets/libraries/LED7Segment for the compiler to find.)

And here’s a test sketch. It lets you flip through the characters using a potentiometer on analog pin 0, but if you don’t have one handy you could easily adapt it to display the characters one by one.


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Musical interfaces

We have MIDI!After a good deal of poking and prodding, I got my Arduino board to speak MIDI! The current program reads a potentiometer and sends pitch bend messages down the pipe.

Had a bit of worry when it just sat there doing nothing, but it turned out that I just had the signal and +5V leads reversed. Bonus: if your computer isn’t talking to it via USB, it’s just fine with being plugged into USB and MIDI at the same time. Makes for much, much easier programming.

Invaluable resources in this effort: circuits and code from Tom Igoe, of the Interactive Telecommunications Program at NYU, and Sebastian Tomczak’s blog little-scale, which includes news of his Arduino / MIDI projects.

The more I think over that guitar string ribbon controller idea, the less it strikes me as a permanent solution. I like that it’s quick and cheap, but it’s going to rub the oxide off the tape (or whatever I use as a resistance). So the design will have to take replacement of the tape into consideration. The guitar string method may be useful for building multiple controls - I’d love to have something you could play like the fingerboard of a bass. No rush there, though.

A capacitive position sensor would be a better alternative - that’s what computer touchpads / trackpads use, and among other advantages, they can be placed inside a case so you never have to touch the actual sensor element. Durable is good, especially where musical instruments are concerned. And they generally feature serial output, which I can feed to the Arduino.

Cirque make some promising-looking devices, including some standalone models. Of course, most of the ones I’m interested in are OEM and hard to come by for someone who’s not designing laptops for a manufacturer.

But why buy new when they’re going for scrap all over? A quick search on eBay turns up masses of laptop frames - just the panel that goes around the keyboard, and including the touchpad. I’ll have to hit some local surplus and computer stores too.

Code and sounds to come.

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Two new toys

Desktop EvolverTwo new toys, and no time to play with them…

One is that Evolver I mentioned. It’s the desktop version, a monosynth with no keyboard. First impressions:

Sturdy metal case. Knobs are rotary encoders, i.e. the clicky digital kind, and are a little dodgy - maybe this will improve with time? Cleverly designed interface cuts down costs and space by packing dozens of parameters into a matrix so you can adjust them all using eight knobs: hit a button to select a row, then turn the corresponding knob. It takes a little getting used to, especially since half of the parameters also require you to hit the Shift button to get at them.

It can make pretty analogue sounds, and glittering digital sounds, and frightening noise. It has two audio inputs for use as a signal processor, and it can do some wonderful spacy things to a fretless bass. Here’s one minute of me goofing around, using it as a bass synth, a ghostly lead, a crunchy bit-hacked rhythm, and some other effects. A bit of echo, reverb and compression added in Logic.


Arduino USB boardThe other toy: an Arduino USB board.

Essentially, it’s a little computer processor on its own board. You can program it from a Mac, Windows or Linux box using a simple language based on C. It has a whole bunch of digital input/output lines, and six analog inputs that can double as pseudo-analog outputs (pulse-width modulated and not suitable for audio, but they work fine for dimming LEDs, for example). If you don’t need the USB interface, there’s a tinier, even cuter version.

More sounds and updates to come.

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theology cobra

Ahh, I needed that. New song-a-day track.

Bassline first: Fury thru POD, then software auto-filter; various loops processed to death; drums (Roland); FM pad; guitar thru POD; Alesis lead; rattling metal, treated, in place of a fill.

2007_0531_theology_cobra.mp3 (1′29)

I’ve been thinking: next time I get paid, it’s really time I got that Evolver I’ve had my eye on. But then I thought: wouldn’t it be more interesting to get a kit to build my own Paia 9700 system, for about the same amount of money?

Evolver: cute, tiny, patch editor allows “evolutionary” programming, can be used as a processor for external sound sources, doesn’t have to be assembled by hand

9700: insanely customizable, immediate and hands-on, has MIDI-to-CV outputs, can be used as a processor, external devices could be used to generate or modify control voltages

Something to think about.

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On the Make

15 minutes to a ribbon controller. Oh, rock on. I’d all but given up looking for an anti-static plastic bag with the right resistance (as suggested by the article from PAiA). Sadly I don’t have an SVHS tape to sacrifice at the moment, but I’m wondering if the tape in a DAT cassette will work.

[Edit: I tried the DAT. No dice. But graphite works! I scribbled a big black line on a piece of paper using a soft pencil, put a clip on either end, and used a bare wire as a wiper. Down side: it does get on your fingers. Go for the SVHS tape.]

Shark bassFound the link on the companion blog to Make, O’Reilly’s wondrous gonzo DIY-tech magazine. Recent links include knitted fruit, the latest add-ons for your favorite microcontrollers, a gorgeous “steampunk” keyboard and a photo-gallery of some of the freakiest basses ever.

I did have a subscription to ReadyMade, the other big magazine on the DIY scene, but I won’t be renewing. Make gets a bit technical, but I like its philosophy better. It’s much more about hacking - finding out how everything works, and adapting it to your own purposes. ReadyMade is much more about household stuff, and so much of it is about cute-looking furniture that you can buy, er, ready-made. There are quite a few neat articles, and I certainly don’t mind the household angle, but I wish they’d go deeper: what sort of materials to use, designing for longevity, the philosophy behind everyday objects, that sort of thing.

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Greener computing

I’ve been pondering getting a big second monitor - in particular for the studio, where old CRT monitors create heaps of magnetic interference and AC buzz. But which manufacturers are the best, in terms of environmental impact? I’m talking cutting down on the hazardous chemicals, design for easy disassembly and recycling, take-back policies and so forth.

EPEAT A bit of web-searching turned up EPEAT, the United States EPA’s Electronic Product Environmental Assessment Tool. I note that no one in any of the categories yet meets EPEAT’s Gold standard.

Also, Greenpeace recently published their own Green Electronics Guide, and they’ve been pushing hard to get Apple to green its computers. (To me, they make sense as a target, since Mac devotees are something of a captive market, and may be a tad more likely to pay more for a greener computer.)

So the verdict? NEC’s MultiSync series and Apple’s Cinema Displays top EPEAT’s present list, but they’re ass-kickingly expensive for a monitor I’m not going to be using for high-end design. Dell’s more affordable, and as a company they’ve got one of the better environmental track records out there, so that’s how I’m leaning at present. Not that I’ll be dropping that much on anything for a while yet, but it’s good to know.

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