Electronics, music, electronic music! general geekery


RoboGlitch 2011: It Begins!!!

As excited as I am to complete the Monome kit, it's difficult for me not to tinker with the other project I have going. My circuit-bent SK-1 is about to get a new friend in RoboGlitch 2011. It started out as a patchbay, but it's going to be much more than that. The final plan is to have a traditional patchbay, augmented by computer-controlled relays and pots. Kind of a small musical robot in a clear plastic enclosure, allowing up to eight patch points to be programmatically altered, and the rest to be abused in the traditional fashion. I want to use an Arduino to control various glitch connections by using MaxMSP. I'm implementing everything using my trusty Duemilanove, but the final project will house a Sparkfun Arduino Pro Mini. It sports an Atmega 328 and runs 5V just like the big guys, but it is truly tiny. I mean magnifying glass and tweezers to solder tiny.

I got hold of a nice Serpac clear-top enclosure, and proceeded to defile it by drilling holes in the top. I then began to plug those holes up with some nice banana jacks from mouser (p/n 108-0906-001). They are the nicest looking banana jacks I could find. I then began to solder leads from a 25-pin male d-sub connector attached to a notch I cut into the side:

When drilling holes in clear plastic material, I like to use a backing of scrap wood to prevent drilling holes into my workbench. If bits of plastic work their way underneath, I dust it away so as not to scratch the material. When I began to drill, I stubbornly set out to do it with the final size large drill bit. That was a mistake, as the large bit tends to skate a bit before it gets a bite, causing major inaccuracy. You can see the results of my first attempt here.

Not pretty. I'm going to use a coping saw to cut out a rectangle from here and just slap a nice piece of thin walnut on top for sort of a more sophisticated control panel look to cover up my blunder. For the remainder of the holes, I started a pilot hole with a smaller bit, and then finished with the larger bit. I spaced the holes one inch apart to create an easy working surface on the finished piece. So what about the enhancements that are going to make this more than a mere patchbay? The plan here is to hook up a dual solid state relay breakout board from They make really great stuff. That takes care of the old on-off-on-off. For automating pots I had originally planned to use a 6-channel digital potentiometer (AD5206), but while I was familiarizing myself with the device, the fact that it takes SPI messages posed sort of a problem. I'm using Firmata and Maxuino to communicate with MaxMSP, and this has worked great so far, BUT getting SPI messages to the device has proven to be challenging. I will continue to work on it since the digital pot is really cool. I have heard that Firmata may be updated to support SPI, but it doesn't right now. That will open a whole new and cool world of potential in my opinion. But what does Firmata support? Servos! So I went out and got a couple micro-servos to control slider pots instead. Here is one of the servos posing for a family portait with the Big Knob and the Arduino, all set up in tutorial configuration (fun!):

To continue with the modularness of the patch bay, I was hoping to incorporate some more tactile elements into the design, such as a slide ribbon pot, and perhaps some conductive doodahs with which a moistened fingertip may interact. I am also toying with the idea of adding switches and pots directly to patch cables so they can be moved about as needed (uh, you can tell I was running out of room on this patch bay, eh?). Finally, I have elected to use stackable banana plug test leads, to provide more possible combinations of bend connections. In messing with the current configuration to see how it bends, I discovered that resistor values of over 5K are not particularly effective. It's quite a small range until the device just begins to function properly, although that changes once you get into a good crash state. The SK-1 does seem to be quite stable through quite an array of abuse. One last point, the beauty of setting up bent devices with d-sub connectors is that your whole bending experience becomes modular. I can unplug my SK-1 and plug in a Speak-and-Math, or a Yamaha PSS-140 (which would be an excellent candidate for connecting to RoboGlitch). Not to mention using MaxMSP/Max for Ableton Live will offer a multitude of versatile options for incorporating bent instruments into future tracks.

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My Monome

I am on the home stretch! All of the soldering is finished. I dropped off my faceplate to be powder coated with a nice black semigloss, and it should be ready this week. I picked up a piece of walnut at Rockler in Seattle, and plan to build a box jig following these instructions. Cheaper than buying a jig if you happen to have a piece of plywood (um, and a table saw). I got some of that thar Danish finishing oil in "Dark Walnut". I'm holding off on the woodworking until my faceplate gets back, because I want physical evidence that everything is going to fit the way I have planned it. So more on that later.

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