Multi Segment LED

A further development of the standard LED package is the seven segment numerical indicator and the sixteen segment alpha-numeric indicator. In these devices, the PN junctions are elongated into a rectangular format and the light is emitted in a bar shape. The letter or number which a multi-segment display is required to produce is formed from a combination of illuminated segments.
Below shows the layout of the constituent light emitting diodes which are used in seven segment displays and  shows the layout for sixteen segment indicators. A sample of the letters or figures which may also be produced by some of the possible combinations of illuminated diodes is also illustrated.

Because these displays are composed of linear segments (that is, there are no curls or twists which can be produced), some anomalies could exist between similarly formed letters or numbers. Any combination which may introduce a misinterpretation is usually not specified in the equipment manual which covers the interpretation of the display.
As an example, the number 1 and the letter I could easily be read one for the other, and the distinction will be shown in the display dictionary.


The diode junctions which form the segments of the display require both an anode and a cathode connection. For a sixteen segment display this would result in thirty two connectors. Fortunately, most situations allow for a common connection to all the cathodes (or, alternatively, all the anodes). The displays are then referred to as common anode connected or common cathode connected and the number of leads reduces to eight or seventeen for the two types of display.