BASICS OF LIGHT EMITTING DIODE

                                        BASICS OF LED’S

the new era has begun with the enormous research work. every day new devices came in the market with amazing features. Now a daysLED‘s are becoming more popular and popular and soon would replace old CFL lights and bulbs.LED’s or light emitting diode is the semiconductor devices which produces light when an electric current is allowed to pass through them. The salient characteristic of LED is its low power consumption with bright light, intensity, efficient, durable and long-lasting.

MATERIAL USED IN CONSTRUCTION:-

different colour of  LED’s are manufactured, RED and WHITE being mostly used.  the material used in LED’s manufacturing being gallium arsenide and gallium arsenide phosphide. different materials are used to produce different colours. these days we have bi-colour or even tri-colour LED’s are available which are used in sceneries for creating an illusion of dynamic displays. different materials are responsible for producing different colours.

TECHNICAL FEATURES OF LED’S

LED’s are available in wide voltage range with wattage up-to 10 watts and in a variety of sizes. a simple led requires 2-4 V DC supply and 20-80 milliamperes current to function properly. the intensity of led can be controlled by the amount of current passing through the led. the graph between the voltage and current is non-linear. The voltage drop across led is 1.5V – 2V . By knowing these features you can design basic led circuits

what happens if the voltage above the maximum rating is applied across the LED??

The LED would burn out causing foul smell emitting out of it. so the question arises
HOW TO GLOW LED ON 9V BATTERY OR ON ANY RANDOM VOLTAGE?
 
the solution to this problem is the RESISTOR. It opposes the flow of current and drops out the extra voltage across it. selecting a right value of a resistor is very important. let us now discuss how to select the resistance.
the value of resistor used to glow led is 370 ohms. how this value comes out…
“OHMS LAW”
 we know that V=IR
then the value of resistance is given by
                                          R={( 9 – 1.5)/20}*1000
       R=375 OHMS
choosing the closest value 370 OHMS
In this way, you can design led circuits and extend it using series and parallel combinations.
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