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Kicking it off

A project log for Wide Area Light Grid

Control per-pole LED lighting in a grand space

ethan.dicksethan.dicks 08/21/2014 at 05:270 Comments

Two years ago, the members of the Columbus Idea Foundry got our first glimpses of what has become our new home: a 65,000 multi-level former shoe factory at the edge of downtown Columbus, two blocks from the Center of Science and Industry (where we hold the Columbus Mini-Maker Faire).  Over the next 18 months, we made our plans, secured funding to build out the first floor, packed our shop, and moved into the new space.  The first floor holds our metal shop, wood shop, laser and 3D printer room, welding room, classroom space, studio space, and more.  The second floor is still largely the same as when we first saw it, wooden floors, high ceilings, and support posts every 15 feet in a big, open, empty space.  Down the middle of this space is a 45' x 140' clerestory.  In time for our open house in May, we received a surplussed motorized projection screen that I installed near one end of the clerestory.  For now, we mostly use the upstairs for overflow classroom space, for presentations, and movie night.  The lighting upstairs is somewhat absent, and with my experience making computer-controlled LED lamps and displays, I thought the layout of the space cried out for more than simple illumination, it needed to be dynamic and multipurpose.

With the geometry of the clerestory and the placement of the screen in the middle of a forest of tall posts, the arrangement that seemed to fit best is an intellegent controller for each post driving about 2 feet of passive LED strip, interconnected with power and serial.  The nodes all tie back to a central machine with application code to send out the color control commands.  There are eight sets of pillars down the axis of the clerestory, and with a left-side and right-side of the central aisle, that's sixteen nodes with three colors each for 48 controllable channels.

Fortunately for my design, I had 18 ATmega168-based boards from a prototype run for an LED clock ripe for reuse.  It was a quick matter to remove the parts of the clock board that were only needed for the clock and add in a few parts and connections needed for the new role.  So far, that mod is three TO-220 N-Channel MOSFETs, seven wires, an RS485 driver chip (75176 or equivalent), and 6 wires to connect it.  The firmware is centered around Matthias Hertel's DMXserial library https://github.com/mathertel/DmxSerial (available under the BSD license).

So the lights themselves are pretty uncomplicated, just larger than most lighting rigs (1800 red, blue, and green LEDs in 48 color channels over 6,000 sq ft).  The other aspect of this is the input controller.  To inject a little theater into the rig, I'm borrowing from the ThinkGeek Technomancer Hoodie to build an accelerometer-based gestural controller - a battery-powered AVR, a MEMS accelerometer, and Xbee or Bluetooth to send the processed gestures back to the Linux DMX master box.  

Prototyping has begin.  The PCBs for the controllers are already made and awaiting assembly.  LEDs have arrived.  Code snippets are already working independently.  The next few weeks will see the elements come together in epic bursts of light.

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