Seven-segment Display – An Introduction

It’s been a long time since display changes our lives. By the help of a display, we can interact with the devices. For example, a mobile phone has a display and, we can see what’s going on our device. If the display is broken, the mobile phone is useless. Today, we have powerful electronic devices with a powerful display like LCD, plasma, HD, UHD and there are lots of different types of them.

What is a Seven-segment Display?

A Seven-segment or simply 7-Segment display is the basic electronic display and, it can show decimal digit or hexadecimal digit. One Seven-segment display can show only a single digit. This display consists of seven segments arranged in a way that decimal numbers can be displayed.

7 Segment Display
Fig 1. Seven-segment Display

All the segments have their unique name a,b,c…. and so on.

How numbers can be displayed?

Assume that all the segments have only two states. The segment is visible or it is not visible. By making suitable segments visible, we can display the numbers. For example, number 1 can be displayed by making segment b and c visible. Similarly, all the numbers can be displayed by using the same method.

Numbers In 7 Segment Display
Digitabcdefg
0OnOnOnOnOnOnOff
1OffOnOnOffOffOffOff
2OnOnOffOnOnOffOn
3OnOnOnOnOffOffOn
4OffOnOnOffOffOnOn
5OnOffOnOnOffOnOn
6OnOffOnOnOnOnOn
7OnOnOnOffOffOffOff
8OnOnOnOnOnOnOff
9OnOnOnOnOffOnOn
AOnOnOnOffOnOnOn
BOffOffOnOnOnOnOn
COnOffOffOnOnOnOff
DOffOnOnOnOnOffOn
EOnOffOffOnOnOnOn
FOnOffOffOffOnOnOn
Table.1 Truth table for displaying numbers

Piratical Seven-segment display

The electronic seven-segment display has two types LCD and LED display. Let’s discuss LED seven-segment display because it’s the most common display used for experiment purpose. The segments are made using LEDs (Light-emitting diodes). In fig 2, we can see that there are eight segments. The additional segment is used to display decimal which is sometimes useful sometimes not.

Seven Segment Display Pinout
Seven Segment Display Pinout

In a single digit seven-segment display, there are ten pins from which, eights pins are for each segments and there are two common pins but both are same pins. You can connect Vcc or Ground pin (depending upon the configuration of the display) to the common pin. Choose only one common pin. It doesn’t matter which pin you choose because both are same pins.

There are two configurations of the seven-segment display

  1. Common anode and
  2. Common cathode

Common Anode Configuration of seven-segment display

There are eight LEDs and all the anode terminals are connected to form this configuration. Because anode is common so, common pin COM should be connected to +Vcc or logic 1. Segments are visible only when pins are connected to the GND terminal or logic 0.

Common Cathode Configuration of seven-segment display

It is opposite of common anode configuration.

All cathode terminals of the LEDs are connected to the same wire or pins. Because cathode is common so, common pin COM should be connected to GND. Segments are visible only when pins are connected to the +Vcc terminal or logic 1.