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Dave over @ PopSci shows you how to build an ambient LED project using an Arduino...

Ambient technology is the current rage for presenting information in a unobtrusive and, sometimes, sublime manner. Information suited for an ambient format ranges from complex number-laden data streams to simple one- or two-digit numbers. The idea here is that you can glean the same information by simply looking at the color of a cube, rather than consulting a sensor's text output.

While this project doesn’t directly take advantage of ambient technology, it does show you a great method for generating a simple color-changing LED that can be integrated into any number of projects. By combining the open-source Arduino microcontroller circuit board with a “smart” LED called BlinkM, you can build a simple mood cube that randomly generates a spectrum of sumptuous colors.

By pairing a sensor with this Arduino-based mood cube to input data, you can create a more ambient-like experience.

Related:

Arduino Diecimila, fully assembled. Arduino is a tool for making computers that can sense and control more of the physical world than your desktop computer. It's an open-source physical computing platform based on a simple microcontroller board, and a development environment for writing software for the board.

ProtoShield for Arduino Kit. An open-source prototyping shield for Arduino NG/Diecimila. It has tons of cool features, to make prototyping on your Arduino easy. Get it at the Maker Store.

Arduino archives @ MAKE.