20100228

Drop-Day 2010 Tech

I figured I'd start writing this up on the return flight from Drop Day, so I'm typing here at an odd, cramped, angle from my flight back from LA to Pittsburgh.

Drop-Day was a fine production, a victory for both hobbyist physical computing, and the forces of democratic freedom. I was impressed with the stark giant white cube dance floor with the, as Biff describes, lovecraftian monolith as a centerpiece. Something about the smaller size and the fog machine made people actually want to dance this year. The sensory rooms were excellent, although some of the code running the party never got off the ground. There is something uniquely appealing about a party that crashes, and requires rewriting of computer code and recompiliation on the fly. In addition to projected visuals ( Kanada, Perceptron, Cortex, Live and recorded video feeds, and other trippy renderings ), we had a few Alumni constructed blinkylights. Keegan completed a most excellent glowing octahedron, Suresh completed a rather nice modification of a commercial lamp, and I constructed several more pairs of goggles. I have spent most of my time travelling ( and very little sleeping ) this weekend, and it was well worth it. However, I doubt I'll be traveling back any time in the next five years. Others travel from much further away (London, Fairbanks) to go to this party, which should give you an idea of how important this party is to Dabney alumni.
RGB controlled diffuse illumination lamp :
Suresh successfully modified a modern style diffuse diffuse illumination lamp for controllable RGB color. He even designed and ordered a custom multi-layer board for the thing. I will try to track him down and see if designs and photographs are available anywhere.

CCFL octahedron :
This project was a wire-frame octahedron, approximately two feet on each edge. An octahedron can be viewed as 3 intersecting squares, once for each of the x, y, z, axes. In this design, each axis was assigned a specific color. The octahedron was constructed using two standard cold cathode fluorescent lighting tubes per edge, driven by black-box driving hardware that is powered by 12V DC. 12V is switched to the various edge drivers using darlington arrays controlled by an AtTiny2123(?), with 12V pulled from a modified desktop computer power supply. The skeleton of the octahedron itself was build by cutting wooden dowels to size, drilling a hole through each end, and joining the ends with zip-ties. The lights and driving hardware was also secured to the skeleton via zip ties. A great effect of the hue rotation on tie-dye style patterns is to cause the location of edges to appear to shift as the color changes and alternatively illuminates different parts of the pattern.

Revised goggles :
The goggles you see in these photographs still use the same old LEDs in ping-pong ball design, stripped down and controlled by an AtTiny13a. I would not recommend this design, as technically the chip is unable to source more than 60mA, where the goggles may require up to 120mA. Offhand the AtMega(4,8,16)8 chips are the only ones I can think of that can source sufficient current, and since they can hold more elaborate programs might be a better choice for future designs. Additionally, although the AVR micro-controllers can function at a range of voltages, the nonlinear V-I curve of the LEDs means that attempts to balance the white-point using resistors must be in the context of a well defined voltage ( preferably a constant 20mA current source, but that takes up board space ). Additionally, I was surprised that the internal resistance of coin-cell Cr2023 batteries limits them to approximately 0.3mA continuous draw. Although the much higher mean current draw of ~20mA for the goggles can be supported, this will cause the battery voltage to drop during operation and the LED white-point to drift. Eventually the voltage falls below the operating voltage of the AtTiny. The coin-cells will recover after about ~30 minutes of rebound. We're still seeing some problems with party-durability but hopefully refining the PCB board design and construction can improve on this. Building the goggles is incredibly annoying and I doubt I shall be constructing any more by the old methods for some time. I'm still a bit baffled as to how someone magically managed to repair solder connections and rebuild the connector on one of the goggles in the middle of the party, but ... thats Dabney house for you.

Laser Spirographs and Monolith-Monitor tower with EL wire :
I don't have good documentation on this at the moment, other than this system crashed a lot during the party, but was still super awesome.

Thanks to everyone who made this happen, it was great to see you all again.


p.s. : rumors are that "weird parties" are associated with the large neuroscience conferences.
p.p.s : These airline headphones state that they will not work outside the airplane. Since I am using them in my laptop and all technology for remote activation/disable is much much more expensive than replacing cheap headphones, we can reasonably assume that United Airlines is lying to us (about so many things)


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