1. LED & LCD SUKHNANDAN COLLEGE MUNGELI A PRESENTATION ON BY:
RAMAKANT CHANDRAKAR

2. Semiconductors bring quality to light!
What is LED?
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.
Semiconductors bring quality
to light!

3. How Does An Work?
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.

4. 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)..

5. Inside a Light Emitting Diode
                                                                                                                                                                                                                                       
Transparent Plastic Case
Terminal Pins
Diode

6. Driving LEDs Two type of DRIVING LED Analog LED Drive Circuits
Digital LED Drive Circuits
                              

7. Analog LED Drive Circuit

8. Digital LED Drive Circuits

9. Some Types of LEDs
Bargraph
7-segment
Starburst
Dot matrix

10. Advantage of an LED Efficiency is high Small size
On/Off time is less .
Slow failure
Lifetime

11. Applications of an Sensor Applications Mobile Applications
Sign Applications
Automative Uses
LED Signals
Indicators

12. Liquid-Crystal (LCD) Displays

13. 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.

14. 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

15. Different types of LCDs
There are Two type of LCDs available 1.Passive Matrix LCDs 2.Active Matrix LCDs

16. Active Matrix V/S Passive Matrix LCDs
Active 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
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

17. LCD Display Technology
Technology Enhancements:
Better color through corrected CCFLs, LEDs
Improved black levels (compensating films)
Higher contrast (pulsed backlights)
Wider viewing angles (compensating films)
Higher resolution (1920x1080)
Improved LC twist times
A liquid-crystal display (LCD) employs transmissive light and a shutter-like mechanism to form grayscale images. Individual liquid crystals within each pixel change their alignment in response to changes in control voltage and will pass or block polarized light to varying degrees. This variation in light intensity, or light shuttering, forms a grayscale image.
LCD monitors are capable of generating very bright images, suitable for viewing under low to moderate ambient light levels. Screens as large as 82 inches have been shown publicly, with resolutions of 1920x1080 pixels. Brightness levels are in excess of 500 nits (over 146 ft-L) on some models. Currently, a LCD monitor or TV requires 10% to 20% less power than a same-size plasma monitor or TV, and weighs about 20% to 25% less.

18. 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. .

19. Applications Thin Film Transistor (TFT) Alpha-numeric display
Back lighting systems
For brighter displays

20. Comparison Between LED & LCD
Power Consumption is less
Faster response rate time
Sizes Available
17inches and 70inches. 
Color Accuracy is less
Cannot be extremely slim
Power Consumption is more
Slower response rate time
Sizes Available
15inches to 65 inches
Color Accuracy is more
Can be extremely slim

21. Any Queries???
AND
SUGGESTIONS

22. THANK YOU FOR YOUR PATIENCE….