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First-generation LED project

2009/08/01

I first built LED lighting hardware around 3 years ago, after first reading about the BAM technique from Artistic License.  I ended up building a kit from scratch consisting of a controller and 8 fixtures.  The controller has 2 boards with ATmega8515′s each driving 16x 2N2222′s grouped in 4′s, with RJ-45 connectors.  The fixtures are 4x4x2″ enclosures with PCBs holding a total of 96 LEDs each, 24 each of red, green, blue, and white, again with RJ-45′s.  The first round of 4 fixtures were strictly resistive-ballast, while the second round used LM317′s in constant-current mode.  This coupled with a slightly higher drive voltage allows the fixtures to be strung on anywhere from 3ft to 100ft of standard Ethernet cable.

Last Christmas I decided to go a little overboard on the first tree of my own…  4 of the fixtures are embedded in the tree, while 4 more are behind the curtains as uplights.  Control is via DMX-512 driven by an ENTTEC Open-DMX USB bridge, with a cable running to my computer running custom color-changing code written in Python.

2008 Christmas tree

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