The 7 segment display is the most basic electronic display device that can display digits from 0-9.
They find wide application in devices that display numeric information like digital clocks, radio, microwave ovens, electronic meters etc.
The most common configuration has an array of eight LEDs arranged in a special pattern to display these digits. They are laid out as a squared-off figure ‘8’.
Every LED is assigned a name from ‘a’ to ‘h’ and is identified by its name. Seven LEDs ‘a’ to ‘g’ are used to display the numerals while eighth LED ‘h’ is used to display the dot/decimal.
Generally seven segment displays are available in 10 pin package. While eight pins correspond to the eight LEDs, the remaining two pins (at middle) are common and internally shorted.
The 7 segment display come in two configurations, namely, Common cathode and Common anode.
In Common cathode configuration, the negative terminals of all LEDs are connected to the common pins. The common is connected to ground and a particular LED glows when its corresponding pin is given high.
In Common anode configuration, the common pin is given a high logic and the LED pins are given low to display a number.