Flashing lights , screens full of numbers and letters, eerie sounds - these are the stuff of science fiction movies, and except for the letter , they form the subject of lamps and displays .
Small incandescent lapms used to be standard for front-panel indicators, but they have been replaced by light-emitting diodes (LEDs).
The letter behave electrically like ordinary diodes, but with a foward voltage drop in the range of 1.5 to 2.5 volts.When current flows in the forward direction, they light up.
Typically,5ma to 20ma produces adequate brightness.LEDs are cheaper than incandescent lamps, they last forever , and they are even available in multi colours like green, yellow,white,red,blue etc.
They come in convenient panel-mounting pakages;some even provide built-in current limiting.
LEDs are also used for digital displays, most often the familiar 7-segment numeric display you see in calculators.for displaying letters as well numbers (alphanumeric display),you can get 16-segment displays or dot-matrix displays.For low power or outdoor use, liquid-crystal displays are superior.
No comments:
Post a Comment