LED & LCD

ELECTRONICS AND COMMUNICATION ENGINEERINGPOORNIMA INSTITUTE OF ENGINEERING & TECNOLOGY,

JAIPUR

A PRESENTATION ON

SUPERVISED BY:Mr. Rahul GuptaAssistant Professor

SUBMITTED BY:-Madhusudhan Agarwal

What is LED?

Semiconductors

bring quality

to light! A light emitting diode (LED) is essentially a PN

junction opto-semiconductor device.

It emits a monochromatic (single color) light when operated in a forward biased direction.

LEDs convert electrical energy into light energy.

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How Does An Work?

a.When sufficient voltage is applied to the chip across the leads of the LED, electrons can move easily in only one direction across the junction between the p and n regions.

When a voltage is applied and the current starts to flow, electrons in the n region have sufficient energy to move across the junction into the p region.

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How Does A LED Work?

1.Each time an electron recombines with a positive charge, electric potential energy is converted into electromagnetic energy.

2.For each recombination of a negative and a positive charge, a quantum of electromagnetic energy is emitted in the form of a photon of light with a frequency characteristic of the semi-conductor material (usually a combination of the chemical elements gallium, arsenic and phosphorus)..

Inside a Light Emitting Diode

1. Transparent Plastic Case

2. Terminal Pins

3. Diode

                                                                  

                                                                                                                                                                     

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Driving LEDs

Two type of DRIVING LED

Analog LED Drive Circuits

Digital LED Drive Circuits

                              

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Analog LED Drive Circuit

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Digital LED Drive Circuits

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Bargraph 7-segment Starburst Dot matrix

Some Types of LEDs

Advantage of an LEDEfficiency is highSmall sizeOn/Off time is less .Slow failureLifetime

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Applications of an

• Sensor Applications

• Mobile Applications

• Sign Applications

• Automative Uses

• LED Signals

• Indicators

Liquid-Crystal (LCD) Displays

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1.   What’s Liquid Crystals (LC)

intermediary substance between a liquid and solid state of matter.e.g. soapy water

light passes through liquid crystal changes when it is stimulated by an electrical charge.

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2.   Introduction to Liquid Crystal Displays

A liquid-crystal display (LCD) is a flat panel display that uses the light modulating properties of liquid crystals.

Liquid crystals do not emit light directly It consists of an array of tiny segments (called pixels) that can

be manipulated to present information Using polarization of lights to display objects Common wrist watch and pocket calculator to an advanced

VGA(video graphic array) computer screen

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Different types of LCDs

There are Two type of LCDs available

1.Passive Matrix LCDs

2.Active Matrix LCDs

Active Matrix V/S Passive Matrix LCDs

Active Matrix LCD

Allow very high resolution It isn`t limited to about 50

rows Each sub-pixel is individually

controlled by an isolated thin-film transistor (TFT).

More use in Laptop & TV

Passive Matrix LCD

Allow high resolution It is usually limited to about

50 rows Each sub-pixel is not

individually controlled by an isolated thin-film transistor (TFT).

Less use in Laptop & TV

LCD Display Technology

Technology Enhancements:Better color through corrected CCFLs, LEDsImproved black levels (compensating films)Higher contrast (pulsed backlights)Wider viewing angles (compensating films)Higher resolution (1920x1080)Improved LC twist times

Advantages Very compact and light.

Low power consumption.

Very little heat emitted during operation, due to low power consumption.

No geometric distortion.

Is very thin compared to a CRT monitor, which allows the monitor to be placed farther back from the user, reducing close-focusing related eye-strain.

Can be made in almost any size or shape.

No theoretical resolution limit.

Can be made to large sizes (more than 24 inches) lightly and relatively inexpensively.

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Applications

Thin Film Transistor (TFT) Alpha-numeric displayBack lighting systemsFor brighter displays

Comparison Between LED & LCD

LED Power Consumption is less

Faster response rate time

Sizes Available

17inches and 70inches. 

Color Accuracy is less

Cannot be extremely slim

LCD Power Consumption is more

Slower response rate time

Sizes Available

15inches to 65 inches

Color Accuracy is more

Can be extremely slim

Any

Queries???

AND

SUGGESTIONS

THANK YOU FOR YOUR PATIENCE….