VISHVAKARMA GOVERNMENT ENGG. COLLEGE.

LED(light emitting diode)

What is led?• A light emitting diode (LED) is

essentially a PN junction opto-semiconductor that emits a monochromatic (single color) light when operated in a forward biased direction.

• LEDs convert electrical energy into light energy. They are frequently used as "pilot" lights in electronic appliances to indicate whether the circuit is closed or not.

LED & its symbol

LED parts

Function of LED• LEDs convert electrical energy into light

energy.

Working of LED(1)

• The light-emitting section of an LED is made by joining n-type and p-type semiconductors together to form a PN junction.

• When the PN junction is forward-biased, electrons in the n side are excited across the PN junction and into the p side, where they combine with holes.

• As the electrons combine with the holes, photons are emitted.

Working of LED(2)

• The PN -junction section of an LED is encased in an epoxy shell that is doped with light scattering particles to diffuse light and make the LED appear brighter.

• Often a reflector placed beneath the semiconductor is used to direct the light upward.

Types of LED

Bargraph 7-segment Starburst Dot matrix

Applications of LED

• Medical Instrumentation • Bar Code Readers • Color & Money Sensors • Encoders • Optical Switches • Fiber Optic Communication

Application of LED

• Mobile Phone • PDA's • Digital Cameras • Lap Tops • General Backlighting

Application of LED• Full Color Video • Monochrome Message Boards • Traffic/VMS • Transportation - Passenger

Information • Interior Lighting - Instrument Panels &

Switches, Courtesy Lighting • Exterior Lighting - CHMSL, Rear

Stop/Turn/Tail • Truck/Bus Lighting - Retrofits, New

Turn/Tail/Marker Lights

Applications of LED• Traffic • Rail • Aviation • Tower Lights • Runway Lights • Emergency/Police Vehicle

Lighting

Benefits of LEDLEDs offer enormous benefits over

traditional incandescent lampsincluding:

• Energy savings (up to 85% less power than incandescent)

• Reduction in maintenance costs • Increased visibility in daylight

and adverse weather conditions

Presentation by

NisargVishweshVrajeshVijendra

AjayBivinShijin

Abhimanyu

Hope you enjoyed our presentation.

Thank you