The Northern Lights: Demonstrations

Programmability Overview

A major aspect of our project is programmability- it is an interactive display medium, the scope of what can be displayed is limited only by the creativity of the users.

We have prepared demonstrations of two potential programs.

Conway’s Game of Life

Conway’s game of life is a simple cellular automaton, which can be easily visualized in a system like the Lights. Each cell in a grid is either alive or dead (on or off, in our case). If a cell has two or less live neighbors, it is always dead, if it has three, it is unchanged, and if four or more neighbors are alive, it is becomes alive.

When the grid is seeded with a few live cells, complex patterns emerge by following these rules.

Video: Life

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Interactivity

The game of Life is an example of a program that can be run either automatically or interactively: people walking on the grid can cause cells to live or die, or the system itself can randomly seed live cells.

The Ripple-Carry Adder

Another use of the Lights is visualization of data or processes. In this case, we have created a demonstration of a basic logic circuit: a ripple carry adder.

This program is a practical learning tool, and serves to bring the usually invisible processes that information technology is built upon to the human scale.

Ripple-Carry Adder: Technical Details

Cells on the far right of the grid are user-controlled inputs, cells on the left are outputs. Numbers are represented in binary, with the least-significant bits at the bottom of the frame. The adder takes two 3-bit numbers (on the top and bottom), and determines their 4-bit sum. Red colors indicate wires carrying zeros, and blue colors ones. Yellow cells are XOR gates, and magenta cells are AND gates.

In the video, the adder is first set to show 0+0=0, then inputs are adjusted to show 0+2=2 (or 000+010=0010), then 2+2=4 (010+010=0100), then 2+6=8 (010+110=1000).

(if video does not play, load the file adder.avi)

QuickTime™ and a decompressor

are needed to see this picture.

Video: Ripple Carry Adder

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