7-segment Display

_images/7_segment.png

A 7-segment display is an 8-shaped component which packages 7 LEDs. Each LED is called a segment - when energized, one segment forms part of a numeral to be displayed.

  • Each of the LEDs in the display is given a positional segment with one of its connection pins led out from the rectangular plastic package.

  • These LED pins are labeled from “a” through to “g” representing each individual LED.

  • The other LED pins are connected together forming a common pin.

  • So by forward biasing the appropriate pins of the LED segments in a particular order, some segments will brighten and others stay dim, thus showing the corresponding character on the display.

Features

  • Size: 19 x 12.7 x 13.8mm(LxWxH, include the pin)

  • Screen: 0.56’’

  • Color: red

  • Common Cathode

  • Forward Voltage: 1.8V

  • 10 pins

  • Pitch: standard 0.1” (2.54mm)

Common Cathode (CC) or Common Anode (CA)

There are two types of pin connection: Common Cathode (CC) and Common Anode (CA). As the name suggests, a CC display has all the cathodes of the 7 LEDs connected when a CA display has all the anodes of the 7 segments connected.

  • Common Cathode 7-Segment Display

_images/segment_cathode.png

  • Common Anode 7-Segment Display

_images/segment_anode.png

How to Know CC or CA?

Usually there will be label on the side of the 7-segment display, xxxAx or xxxBx. Generally speaking xxxAx stands for common cathode and xxxBx stands for common anode.

_images/7_segment.png _images/7_segment_bs.png

You can also use a multimeter to check the 7-segment display if there is no label. Set the multimeter to diode test mode and connect the black lead to the middle pin of the 7-segment display, and the red lead to any other pin except the middle one. The 7-segment display is common cathode if a segment lights up.

You swap the red and black meter heads if there is no segment lit. When a segment is lit, it indicates a common anode.

_images/7_segment_test.JPG

Display Codes

To help you get to know how 7-segment displays(Common Cathode) display Numbers, we have drawn the following table. Numbers are the number 0-F displayed on the 7-segment display; (DP) GFEDCBA refers to the corresponding LED set to 0 or 1.

_images/segment_code.png

For example, 01011011 means that DP, F and C are set to 0, while others are set to 1. Therefore, the number 2 is displayed on the 7-segment display.

_images/7segment_2.png