LED displays, message, are typically commercial or industrial signs. They allow for larger characters and longer viewing distances than digital LED displays. Light-emitting diode (LED) displays are segmented or dot matrix displays allowing for numeric only and alphanumeric character representation. Light emitting diodes (LED) are PN junction devices that give off light radiation when biased in the forward direction. Most light emitting diodes function in the near infrared and visible ranges, though there are now UV LEDs. Light emitting diodes are a reliable means of indication compared to light sources such as incandescent and neon lamps. LEDs are solid-state devices requiring little power and generating little heat. Because their heat generation is low and because they do not rely on a deteriorating material to generate light, LEDs have long operating lifetimes. One of the alternatives, incandescent bulbs, consumes much more power, generate a great deal of heat, and rely on a filament that deteriorates in use. Neon bulbs, on the other hand, rely on excited plasma, which, along with its electrodes, can deteriorate over time.
Choices for display types for LED displays, message, include matrix, line, character, fixed digit, and ticker. A matrix display is composed of an array of LEDs able to form graphics. A line display only displays messages in a line format. A character display is composed of an array of LEDs only capable of displaying characters. On a fixed digit display the digits are fixed and cannot move. On a ticker display the digits can move across the viewing area. LED displays, message can be configured to be used in either an indoor application or an outdoor application. Displays that are configured for outdoors use have weatherproof housings.
Important configuration parameters to consider when specifying LED displays, message, include character height, number of lines, and number of characters, viewing distance, viewing angle, and luminous intensity. The character height may also be called pitch. The number of lines will determine the size of the message display. The number of characters refers to the number of characters per line. Viewing distance is determined primarily by the minimum size requirements for objects that the user must see. The viewing angle is the angle, in degrees, between a line normal to the display surface and the user's visual axis. Luminous intensity is typically given @ 10mA. Also known as pixel brightness. Luminous intensity is luminous flux per unit solid angle, and its unit of measurement is the candela (cd).
LED displays, message, can be mounted in a panel or case, or top mounted, or bottom mounted. Top mounted displays can hang from the ceiling. Case dimensions of height, width, and depth are important to consider. Common features include special effects or animations, programmability, selectable fonts, displaying of countdown time, adjustable intensity, and clock format. Special effects include a variety of scrolling, wiping, twinkling, flashing, images and animations that function in conjunction with text or as stand-alone effects. They are used to provide emphasis on specific textual statements, to simply draw attention to the display, or to provide an additional level of entertainment in conjunction with message presentation. Important environmental parameters to consider when specifying LED displays, message include operating humidity and operating temperature.