The Lights of LIGHTBAR

February 22nd, 2011

Brightness

It takes energy to create light — just ask The Sun, which burns four million tons of hydrogen every second to produce the wide, smooth spectrum of electromagnetic radiation that earthlings crave.

But I’m a normal guy; I do not own even one million of tons of hydrogen. Instead, I’ve borrowed several of LIGHTBAR’s ever-shifting palette of fixtures from well-lit friends, and scrounged the rest from thrift stores and junk shops. Some of these needed repair, rewiring, better housings or nicer diffusion. I love electricity and tinkering in general. LIGHTBAR has made me a bit of a lamp mechanic.

To simulate The Sun in a rainy Portland backyard, LIGHTBAR has traditionally depended on a mixture of tungsten, halogen, high pressure sodium, metal halide, neon and fluorescent lamps — a combined output of about 3000 watts, usually powered by four 20-amp circuits run from my basement.

However, this year’s emphasis on Portability has made things trickier. I have the loan of a pretty good generator when I need it, but I’m no fan of global warming. Anyway, the whole world is moving to new, energy-efficient lighting technologies; some are ghastly, but others are pretty interesting.

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Impressed by such projects as Mark Lottor’s Cubatron, I put out a request in December to the ever-helpful Portland Dorkbot list, asking for a relatively cheap, bus-addressable RGB lighting system that I could spread out over the surface of LIGHTBAR to create animated lightshows of any color. Something a bit like ThingM’s BlinkM, but spannable over longer distances than the I2C bus supports.

General-purpose genius Paul Stoffregen already had a design in mind; my request just pushed him over the edge. The lighting element is the painfully-bright Avago Moonstone tri-color LED, which he chose for its high efficiencies, both energetic (lumens per watt) and financial (lumens per dollar.) A clever PWM-driven switching network reduces component count and saves electrons. Each unit listens on a RS-485 network, so future compatibility with DMX lighting systems is a simple matter of firmware and XLR connectors. But for now, they respond to a simple pidgin of hexadecimal, more than sufficient for our needs.

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At first I was intimidated by these — they’re really dangerously bright! We live in a brave new world of superpowerful light-emiting diodes, but safety standards for these devices are not yet as comprehensive as they are for other bright lights such as lasers, arc-welders and stars. These lights were in bad need of diffusion. Cheapskate that I am, I settled on a combination of dryer duct, plastic zip-ties and paperclips that nicely evokes a hanging Chinese lantern.

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These got their first public showing at LIGHTBAR Blue Night, where they cast a lovely Tardis-blue glow over the proceedings, running all night on a single dry-cell battery. We’ll have them up again on Pink Night, and I hope to find funds someplace for another dozen or so. Meanwhile, I’m working on the software end, just trying to build a framework and grasp the possibilities.

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2 Responses to “The Lights of LIGHTBAR”

  1. Paul Says:

    Actually, nothing was planned before, I just made it all up when I saw your message in January…

  2. mykle systems labs » Blog Archive » RGB OK4U! Says:

    […] Stoffregen, the inventor/genius who built these RGB smart-lights for this year’s LIGHTBAR, has posted in detail about the design and how you can build your […]

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