What is an LED?

LED stands for Light Emitting Diode.   Basically an LED is a diode that when voltage is applied to in the proper manner it emits light.   

A Diode is a two-terminal electronic component that conducts electric current in only one direction.  The most common function of a diode is to allow an electric current in one direction while blocking current in the opposite direction . Thus, the diode can be thought of as an electronic version of a check valve. 

 Diodes are used to regulate voltage (zener diodes), electronically tune radio and TV receivers (varactor diodes), generate radio frequency oscilations(tunnel diodes), and produce light (light emitting diodes).

The discovery of diodes and their crystals’ rectifying abilities was made by German physicist Ferdinand Braun in 1874. The first semiconductor diodes, called cat’s whisker diodes were made of crystals of minerals such as galena. The first known report of a light-emitting solid-state diode was made in 1907 by the British experimenter H. J. Round   Today most diodes are made of silicon.  The first practical LED was invented by Nick Holonyak, Jr., in 1962 while he was at General Electric Company. The first LEDs became commercially available in late 1960s and were red in color.

Today LED’s are commonly available and in wide use in Red, Green, Amber, Blue, and White colors.   LED’s are used in a wide variety applications ranging from voltage indication, lighting, and displays.   They are very energy efficient and  have an extremely long life often exceeding 100,000 hours of operation.

Electronic Message Centers utilize LED’s in a pixel array to convey messages to their intended recipients.  These displays typically use red or amber LED’s for single color or monochrome displays.  A red – green cluster of LED’s make up a tri-color display with the third color being amber when both the red and green are on.  Full color displays use an array of Red, Green, and Blue (RGB) LED’s that can be fired in various combinations to create billions of color combinations.  

Recent breakthroughs in their efficiency and manufacturing costs have led to White LED’s being used in a wide variety of lighting applications.  Although they have a higher initial purchase cost, LED lights last significantly longer with a typical life of over 50,000 hours which at 12 hours/day will lead to at least 10 years of service.  LED lighting also uses significantly less energy and are mostly recyclable making them a “Green” alternative to traditional lighting solutions.   

The low cost of LED’s coupled with their energy efficiency, and their long life make them attractive for a wide variety of commercial and industrial applications.