7-Segment LED Display:
The 7-segment LEDs are the most popular display devices used for single-board
microcomputers (microprocessor trainer kits). The 7-segment LEDs can be either a common anode type or a common cathode type. Each 7-segment LED will have seven Light Emitting Diodes (LEDs) arranged in the form of small rectangular segments and another LED as a dot point in a single package.
In the common cathode type, all the cathode terminals of LEDs are internally shorted and one / two pins are provided for external connection. The anode of the LEDs is terminated on separate pins for external connection.
In common anode type, all the anode terminals of LEDs are internally shorted and one / two pins are provided for external connection. The cathode of LEDs is terminated on separate pins for external connection. The pin configuration and the internal connection of the common anode 7-segment LED are shown in Fig.
In the 7-segment LED a segment will glow or emit light when it is forward-biased. Therefore, a segment can be made to glow, by applying a high (logic-1/+5-V) to the anode and a low(logic-0/0-V) to the cathode. The alphabetic/numeric characters can be displayed on the 7-segment LED by forward biasing the appropriate segments.