Having somewhat mastered the fading effects with the 5940, I proceeded to scale up to the first visual challenge: Using groups of RGB LEDs to fade through various color schemes in a prototype arrangement.

Immediately I discovered that I could NOT use Sparkfun's RGB led with the 5940. Short explanation: The Sparkfun component has one lead as the Cathode (negative) connection, and the three other leads are Anodes (positive) for each of the colors. The 5940 chip is a "cathode sink" design (I think I'm saying that right) which means that the ports for the LEDs on the chip deliver negative polarity. To uniquely control each color I would need a "common anode" LED, or three separate R G and B leds. Argh.

I went for the separate LED solution, mainly for cost.

Here is the hookup. My arrangement is using 3 rows of 5 RGB groups each, total 45 leds. [Other than for quick testing, do NOT try to run your circuit with a 9v battery like this! This is a really dumb thing I'm doing, because the little battery cannot deliver enough current to run the project for very long at all.]

Hookup for three 5940's driven with Arduino: Notice I like using wire-wrap for connections to the LEDs. The wire is very thin and tough, and no soldering.

First prototype assembly with the circuit

As for diffusion, this layout basically uses the LEDs on their side, projecting across the media in the fabrication.

Top-down view: This shows how the leds, usually in clusters of one red, one blue, one green, are nested. Diffusion materials include wax paper and scotch tape (!) but that's a very temporary solution.

We're using torn paper, fabric, frosted acetate, cotton, and white foam for various effects. You'll notice that for the "sky horizon" I've actually got the LEDs arranged like stage lighting. The separate RGB colors dont blend 100% but the effect is getting to be quite cool.

Detail of the indirect diffusion: These colors slowly cycle through a pre-programmed range.

Another detail of color effects

This very preliminary result looks promising.

For programming and hookup details see http://pixelriot.com/pmatp/node/273

Project Information: "Sampling the Landscape" by Profs. Linda Lauro-Lazin and Peter Mackey. Supported by a Faculty Development Grant, Pratt Institute, 2007.