7-segment (light emitting diode) or LCD (liquid crystal display) LED displays provide a convenient way to display information or digital data in the form of numbers, letters or even alphanumeric characters.
Typically, 7-segment displays are composed of seven individual color LEDs (called segments) within a single display package. To produce the required numbers or hexadecimal characters from 0 to 9 and A to F respectively, the display must illuminate the correct combination of LED and BCD segments to 7-segment display decoders such as the 74LS47.
A standard 7-segment LED display usually has 8 input connections, one for each LED segment and one that acts as a common terminal or a connection for all internal display segments. Some individual screens also have an additional input pin to display a decimal point in their lower right or left corner.
In electronics there are two major types of 7-segment digital LED display.
• 1. Common cathode (CCD) display - On the common cathode display, all cathode connections on the LEDs are connected to logic "0" or ground. The individual segments are illuminated by applying a logic signal "1" to the individual anode terminals.
• Common Anode (CAD) Display - In the common anode display, all the anode connections of the LEDs are connected to logic "1" and the individual segments are illuminated by connecting the individual cathode terminals to a " LOW "Logic" 0 ".