I have used Arduino in the past during eighth grade exploratory week last year where we were each given one to play around with. I have been using it a bit since then. Arduino is a great prototyping platform for electronics that is very user friendly.
I am currently finishing up a project using RGB LEDs which can change to any color requested by the program. While working on it I acquired a second RGB LED when I connected this one in parallel the first light continued as usual, however the second one was using different colors. I researched it and learned that RGB LEDs are controlled by 4 different pins. Depending on the type the one pin is the constant power input and the other 3 pins have the opposite polarity from the first pin. This way when power is applied the the last three pins the colors will change based on the diffrent pins that are powered the color changes. The concept is pretty close to mixing paint because you are mixing the three primary colors in light form together.
At Science Fair I worked on it some more with Kyle Gagner we came up with a program based off of the original one that I created. This new version has a much smoother color transition between all of the colors of the rainbow. When we tried to upload it to the Arduino the PC couldn't see the Arduino Controller. After many PC reboots and much Google searching we never found a solution because it just started working for no apparent reason. It still dosen't work very well though it seems to be a issue with my PCs COMM ports interfacing with the Arduino and the programming software.
Here is a video of it in action! http://youtu.be/qeUitTTWc2E
The code can be found here:
(Kyle Gagner would like to say this code is horribly messy(Jacob would like to disagree.)
I borrowed a project from Aeryn Johns that he did last year for the Hackers and Makers exploratory class led by John Stanton. What he did was make a cube of green LEDs 3x3x3 that are all individuality controlled by an Arduino so that you can make some very cool patterns with. I don't have a copy of the current code to post but the pattern is very cool and complex.
Video of cube in action! http://youtu.be/c1ov6steexs
Apart of the Hackers and Makers class was a day about 3-D design and printing, Aeryn needed a base for the cube to be built on so he designed one in Google Sketch-Up and printed it out on the 3-D printer we were given access to. We then modified a small cardboard box to hold all the wiring and Arduino and glued the printed base onto the top of the box.
Last robotics season I wanted to use LEDs to make our robot look cool but with all the problems we had with our arm that I never had to work on it. This year is different and I do have time and I want to drive 16 LEDS with the arduino