Dorkbot Roundup

Chris — Mon, 03 Mar 2008 09:56:53 -0800

Mercury-bound space craft, adding MIDI to everyday objects, and the software running ludicrously-complicated automated painting machines. Dorkbot DC doesn't fail to bring interesting stuff. Tom and I had a great time seeing these projects.

It started off with a talk about the MESSENGER probe. Katie Bechtold is a software developer who works on the X-Ray Spectrometer, some other sensors I can't remember the name of, and some day to day behind-the-wheel space probe driving. She brought along a 1/10 scale model of the probe and did her best to point out where the various sensors and crucial parts are. The model was probably two feet tall, if you want an idea of how big it is.

Her explanation of everything was great for those lacking a background in astrophysics (hint: me). I won't say much about the actual workings of the probe, as I don't think it's appropriate to do so until Echoditto is in the business of slinging extremely complicated computers off to distant planets. Here's what was really neat to me:

I really liked that movie Sunshine. Mercury is pretty darn close to the sun, and MESSENGER has to be protected from it at all times. That means there's a big sunshade the majority of the craft lives behind. It isn't even to Mercury yet and it already hits 700 degrees Fahrenheit on the surface of the shade! Bonkers.

Another big point was her talking about the operating system the craft runs. Apparently a lot (most?) spacecraft run vxWorks, ironically a closed-source operating system that may also be running your router right now. She spoke of a quiet push for open source in space, as there have been times where bugs in vxWorks confounded engineers when time was tight. Considering how precise and efficient everything needs to be on an ultra-low power and distant machine, it sounds a little silly not to have complete control over the software. Maybe we'll see Linux in space some day.

Last, the NASA Deep Space Network sounds awfully cool and impressive. She explained that that's how they actually communicate back and forth with MESSENGER. Turns out it takes 12 minutes for messages to be exchanged! At the speed of light! Anyway, the DSN has massive radio antennas in California, near Madrid, and somewhere in the middle of Australia. The idea is that no matter what time it is, one of those radio antennas will point in the direction of whatever needs talking to off in space. Cross-globe communication is impressive in its own right.

Thanks, Katie. That was really neat.

Next up was Dingo, explaining what MIDI is and how it can be added to just about anything. He started by explaining that MIDI is a widely-used protocol for sending event messages (normally) to musical instruments. It hasn't changed at all since 1983. A quick redux: each message says at least "note-on" or "note-off" and a value from 0-127 mapping to pitch values (C, C#, D, E, F, etc). It works over 5 pin DIN, although only three pins are actually used. Lastly, it works at 31500 baud (I don't know why). There are some other parts too, like velocity (note volume) and aftertouch, but that's basically it.

Dingo then pulled out an Arduino and showed us all how to send MIDI to any program/module that'll accept it. Here he is with a child's accordion he added an infrared sensor to to detect the movement of the bellows, and switches to each of the keys.

Sending MIDI is extremely easy. I highly recommend playing around with Todbot's spooky arduino projects. Based on reading his stuff, I built a little trigger that sends MIDI note data along with velocity from the outputted voltage of a piezo element. I have a little drum machine whose triggers only act as "on" and "off" buttons, meaning the force you hit them with doesn't affect the volume of the sample. That makes everything sound really robotic. However, it accepts MIDI, and will take velocity (note volume) via MIDI. So by wacking that piezo, the little drum machine sounds a lot more human. Here's a photo of the result. The drum machine is under the table.

The Arduino program that runs this is about 20 lines long. I'm happy to show you if you're interested.

Back on track though!

The final presentation was from Alberto Gaitán on the software he wrote to run Remembrancer. Remembrancer was at Curator's Office last year. Anyway, it was essentially a trio of automated painting robots. It looked like this:

Alberto designed the system to drop little blobs of paint based on the output of some Yahoo Pipes searching for keywords from news RSS feeds. The words were things like birth, death, disease, etc. The three panels focused on news from DC (local), the US (regional), and the world (global). Each day the arms would move from left to right for (I believe) six hours. If you look at the red panel, you'll see a huge red triangle. That's when the Virginia Tech shooting happened.

Anyway, Alberto powered this all with patches written in Max/MSP and Jitter. Max/MSP is a visual programming language which passes messages from top to bottom, and is most commonly used by media artists. Max/MSP programs are called patches and look like Rube Goldberg machines. He did his best to explain some of how Max works, but to the uninitiated it really just looked like boxes and lines. Basically, the output of Pipes was parsed to simple strings which then told the paint dropper how much paint to drop as a stepper motor moved it at a constant (very slow) speed . I think the results were really beautiful. If you have interest in using a graphical programming language that is VERY close to Max, check out Pure Data. It was written by the same guy.

Come next month! and say hi to us. Tom and I will almost certainly be there.

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