LED Cube

The Cubatron is the world’s largest true 3D color graphics display (until the BRC is built in August 2006). It is 8×8×8 feet in size. It consists of 729 voxels (3D pixels) arranged in a 9×9×9 matrix, spaced 10 inches apart from each other. Each voxel is a 40mm diameter ball that can be independently set to display a 21-bit RGB color. The entire display can be updated about 30 times per second. The voxels “float” in space so that the viewer can see through the cube and have a view of most of the voxels from any position.
There are 729 voxels. Each one has a microcontroller on it. There are 27 strings of 27 voxels. The voxels on each string have an address of 1 through 27. They are sent commands using a special synchronous protocol which consists of a frame which contains RGB data for each of the 27 voxels on the string. A frame is sent on every string about 30 times per second. The voxels take the last RGB value they got and PWM the RGB LED to display the proper color.
via LLR