Page 143 - CITS - Electronic Mechanic - TT - 2024

ELECTRONICS MECHANIC - CITS

MODULE 8 : Digital panelmeter and Light emitting diode

(LED)

LESSON 77 - 83 : Technician Power Electronics System

Objectives

At the end of this lesson you shall be able to:
• explain seven segment display & its types.

Nowadays, we are using digital displays instead of analog displays such as CRT. This digital display may consist
of seven segments display, LCD display and LED display. Seven Segment display is the combination of seven
LEDs, which are arranged in rectangular fashion. These LED are called the segment of seven segment display.
It is generally used to display numbers and letters on things such as alarm clocks and digital watches etc. LCD
is the combination of solid and liquid states of matter. It uses liquid crystals for producing visible images. LCD is
generally used in optical imaging, LCD thermometer and in medical applications, etc.
Due to some disadvantages, a new technology came into existence, which is light emitting display (LED). It
is a combination of light emitting diodes (LED), which is a semiconductor device that emits incoherent narrow
spectrum light, which is used in LED displays. These are the display components which will be discussed in this
chapter with their applications such as digital panel meter and lighting.
Seven Segment Display:
The seven-segment display is the most common display device used in many gadgets, and electronic appliances
like digital meters, digital clocks, microwave oven and electric stove, etc. These displays consist of seven
segments of light emitting diodes (LEDs) and that is assembled into a structure like numeral 8. Seven segment
displays contain about 8-segments wherein an extra 8th segment is used to display dots. This segment is useful
while displaying non-integer numbers. Seven segments are indicated as A-G and the eighth segment is indicated
as H. These segments are arranged in the form of 8 which is shown in the seven-segment display circuit diagram.

Seven segment displays are generally available in ten pin packages. In those 8 pins relate to the 8 LEDs, the
remaining pins at middle are internally shorted. These segments come in two outlines they are common cathode
and common anode. In common cathode configuration, the negative terminals are connected to the common pins
and the common is connected to the ground. When the corresponding pin is given high, then a particular LED
glows. In a common anode arrangement, the common pin is given to a logic high, and the pins of the LED are
given low to display a number.
Types of 7-Segment Displays

There are two types of seven segment displays available in the market. According to the type of application, these
displays can be used. The two configurations of seven segment displays are discussed below.
Common Anode Display

Common Cathode Display

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