• Home
  • Courses
  • Machines
    • Transformer
    • AC Motors
      • Induction Motor
      • Synchronous Motor
    • DC Motor
    • DC Generator
  • Power System
    • Circuit Breaker
    • Switchgear
    • Substation
    • Control System
    • Measurement
  • Electronics
  • Blog
  • Contact
    • Contact Us
    • Privacy Policy
Have any question?
[email protected]
RegisterLogin
StudyElectrical.Com
  • Home
  • Courses
  • Machines
    • Transformer
    • AC Motors
      • Induction Motor
      • Synchronous Motor
    • DC Motor
    • DC Generator
  • Power System
    • Circuit Breaker
    • Switchgear
    • Substation
    • Control System
    • Measurement
  • Electronics
  • Blog
  • Contact
    • Contact Us
    • Privacy Policy

Basic Electrical

Working of Light Emitting Diode (LED)

  • Categories Basic Electrical, Electronics
working led
working led

A light-emitting diode (LED) is a diode that gives off visible light when forward biased.

Light-emitting diodes are not made from silicon or germanium but are made by using elements like gallium, phosphorus and arsenic. By varying the quantities of these elements, it is possible to produce light of different wavelengths with colors that include red, green, yellow and blue.

For example, when a LED is manufactured using gallium arsenide, it will produce red light. If the LED is made with gallium phosphide, it will produce a green light.

Working Theory of LED

When light-emitting diode (LED) is forward biased as shown in figure below, the electrons from the n-type material cross the pn junction and recombine with holes in the p-type material. 
 
We know that these free electrons are in the conduction band and at a higher energy level than the holes in the valence band. 
Capture
When recombination takes place, the recombining electrons release energy in the form of heat and light. In germanium and silicon diodes, almost the entire energy is given up in the form of heat and emitted light is insignificant. 
 
However, in materials like gallium arsenide, the number of photons of light energy is sufficient to produce quite intense visible light.

The schematic symbol for a LED is shown in the above figure. The arrows are shown as pointing away from the diode, indicating that light is being emitted by the device when forward biased. 

Although LEDs are available in several colours (red, green, yellow and orange are the most common), the schematic symbol is the same for all LEDs. There is nothing in the symbol to indicate the colour of a particular LED. 
Capture

This is a graph between radiated light and the forward current of the LED. It is clear from the graph that the intensity of radiated light is directly proportional to the forward current of LED.

LED Voltage and Current

The forward voltage ratings of most LEDs is from 1V to 3V and forward current ratings range from 20 mA to 100 mA. 

 

Capture
In order that current  through the LED does not exceed the safe value, a resistor Rs is connected in series with it. The input voltage is Vs and the voltage across LED is Vⅆ.
 

 

Capture%2B1

 

 

 

Related Articles

  • Differences between Power Transformer and Distribution Transformer
    Working Principle of Transformer

    A transformer is a static piece of equipment used either for raising or lowering the…

  • DC Motor working 1
    Working Principle of DC Motor

    A DC motor is an electrical machine that converts electrical energy into mechanical energy.  The…

  • working%2Bof%2Bmoving%2Bcoil
    Animated Video - Working of Moving Coil Instruments

    The animated video below explains the working of a moving coil instrument.

  • Automatic Light Controller arduino
    Arduino based Automatic Light Controller

    The automatic light controller offers energy saving and convenience in the areas with a photosensor…

  • ACB Air Circuit Breaker
    Working of Air Circuit Breakers

    What is an ACB? A circuit breaker in which the contacts open and close in…

  • working principle of alternator
    Working Principle of Alternator

    The machine which produces 3 phase power from mechanical power is called an alternator or…

  • Share:
author avatar
Electrical Engineer

Previous post

Core Type and Shell Type Transformers
November 17, 2017

Next post

How Multicolor RGB (Red Green Yellow) LEDs Work?
November 20, 2017

You may also like

Electric current concept
Concept of Electric Charge and Current
22 December, 2021
dc voltage source
What is a Voltage Source? | DC and AC Voltage Sources Explained
20 December, 2021
electrolytic capacitors
Electrolytic Capacitor – Types, Construction, Polarity and Leakage Current
17 July, 2020

    1 Comment

Leave A Reply Cancel reply

Your email address will not be published. Required fields are marked *

Search Here

From Blog

capacitor charging and discharging
Charging and Discharging a Capacitor
29Feb2020
Insulation Resistance Tester Megger
Insulation Resistance Test (IR Test) or Megger Test
16Aug2014
external-characteristic-of-seperately-excited-dc-generator
Characteristics of Separately Excited DC Generators
07Aug2014
How does tesla electric car work
Video : How Does a Tesla Electric Car Work?
12Feb2018

Categories

  • Alternator
  • Arduino
  • Basic Electrical
  • Battery
  • Books
  • Cables
  • Capacitor
  • Career
  • Circuit Breaker
  • Control System
  • DC Generator
  • DC Motor
  • Electric Vehicles
  • Electrical Circuits
  • Electrical Machines
  • Electrical Relays
  • Electrical Safety
  • Electronics
  • Embedded System
  • Exams
  • Generation
  • Guest Post
  • HVDC
  • Instrumentation
  • Interview Questions
  • Locomotives
  • Measurement
  • Microcontroller
  • Objective Questions
  • PCB
  • PLC
  • Power System
  • Projects
  • Signals and Systems
  • Single Phase Motors
  • Substation
  • Switchgear
  • Synchronous Motor
  • Three Phase Induction Motor
  • Transformer
  • Transmission Line
  • Uncategorized

Copyright © 2021 Study Electrical, Inc.

© StudyElectrical.Com 2021

Login with your site account

Lost your password?

Not a member yet? Register now

Register a new account

Are you a member? Login now