7 Segment Pin Assignments

A seven-segment display (SSD) is a widely used electronic display device for displaying decimal numbers from 0 to 9. They are most commonly used in electronic devices like digital clocks, timers and calculators to display numeric information. As its name indicates, it is made of seven different illuminating segments which are arranged in such a way that it can form the numbers from 0-9 by displaying different combinations of segments. It is also able to form some alphabets like A, B, C, H, F, E, etc.

7 segment displays are among the simplest display units to display the numbers and characters. As shown in the above image of a 7-segment display, it consists of 8 LEDs, each LED used to illuminate one segment of unit and the 8thLED used to illuminate DOT in 7 segment display. We can refer each segment as a LINE, as we can see there are 7 lines in the unit, which are used to display a number/character. We can refer each segment "a,b,c,d,e,f,g" and for dot character we will use "h". There are 10 pins, in which 8 pins are used to refer a,b,c,d,e,f,g and h/dp, the two middle pins are common anode/cathode of all he LEDs. These common anode/cathode are internally shorted so we need to connect only one COM pin.

7 Segment Display Pinout

There are two types of 7 segment displays: Common Anode and Common Cathode:

Common Cathode: In this all the Negative terminals (cathode) of all the 8 LEDs are connected together (see diagram below), named as COM. And all the positive terminals are left alone.

Common Anode: In this all the positive terminals (Anodes) of all the 8 LEDs are connected together, named as COM. And all the negative thermals are left alone.

How to Display Numbers on 7 Segment Display?

If we want to display the number “0”, then we need to glow all the LEDs except LED which belongs to line “g” (see 7 segment pin diagram above, so we need a bit pattern 11000000. Similarly to display “1”we need to glow LEDs associated with b and c, so the bit pattern for this would be 11111001. A table has been given below for all the numbers while using Common Anode type 7 segment display unit.

Digit to Display

h g f e d c b a

Hex code

0

11000000

C0

1

11111001

F9

2

10100100

A4

3

10110000

B0

4

10011001

99

5

10010010

92

6

10000010

82

7

11111000

F8

8

10000000

80

9

10010000

90

To learn more about 7 segment display units, read below tutorials which explains the practical applications to use 7 segment displays:

Interfacing 7 segment display with 8051 microcontroller

0-99 counter with AVR mircontroller

Digital Dice using Arduino

A seven-segment display is commonly used in electronic display device for decimal numbers from 0 to 9 and in some cases, basic characters. Use of light emitting diodes (LEDs) in seven segment displays made it more popular, whereas of late liquid crystal displays (LCD) displays have also come into use. Electronic devices like microwave ovens, calculators, washing machines, radios, digital clocks etc. to display numeric information are the most common applications. Let’s take a look at the 7 segment display pinout to have a better understanding.

7 segment display pinout

A 7 segment display is made of seven different illuminating segments. These are arranged in a way to form numbers and characters by displaying different combinations of segments. The binary information is displayed using these seven segments. LED or light emitting diode is P-N junction diode which emits the energy in the form of light, differ from normal P-N junction diode which emits in the form of heat. Whereas LCD use properties of liquid crystal for displaying and do not emit the light directly. These LED’s or LCD’s are used to display the required numeral or alphabet.

Types of 7 segments

There are basically 2 types of 7 segment LED display.
Common Anode: All the Negative terminals (cathode) of all the 8 LEDs are connected together. All the positive terminals are left alone.
Common Cathode: All the positive terminals (anode) of all the 8 LEDs are connected together. All the negative thermals are left alone.

Working on 7 segments

Seven segment devices are generally made up of LEDs. These LEDs will glow when they are forward biased. Intensity of the LEDs depends on forward current. So, sufficient forward current has to be provided to these LEDs to glow with full intensity. This is provided by the driver and is applied to the seven segments.

Numberg f e d c b aHex code
01000000C0
11111001F9
20100100A4
30110000B0
4001100199
5001001092
6000001082
71111000F8
8000000080
9001000090

Table: Display numbers on a seven segment display in common anode configuration

Things change for common cathode configuration.

Numberg f e d c b aHex Code
001111113F
1000011006
210110115B
310011114F
4110011066
511011016D
611111017D
7000011107
811111117F
910011114F

Table: Display numbers on a seven segment display in common cathode configuration

A sample interfacing of the 7 segment display to Arduino uno is provided for reference.

You can find some sample projects to work on involving 7 segment display here.

Saurabh

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