Light Bulbs and Lighting Systems

This chapter presents some background on the lighting part. Light‐emitting diodes are merely the newest in a long list of different types of lighting devices. Ignoring truly ancient devices such as candles, all of them use electricity. An incandescent bulb works by heating a piece of metal, the filament, until it glows. By adjusting the power level, it can be made to glow different colors. Fluorescent bulbs work entirely differently from incandescent bulbs. They too have a partial vacuum inside a glass tube. To run this complicated device requires a special circuit called a ballast. The chapter considers ballasts for fluorescents and then for LEDs. High‐intensity discharge (HID) lamps are fundamentally similar to fluorescent lamps. The chapter reviews some of the good and bad characteristics of these various light sources. This will help to give some perspective on the prospects for LED lighting.