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What is an LED?

Light-emitting diode

Semiconductor

Has polarity

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LED: How It Works

When currentflows across adiode

Negative electrons move one

way and positive holes move

the other way

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LED: How It Works

The wholes existat a lower energylevel than the

free electrons

Therefore when a free

electrons falls it losses energy

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LED: How It Works

This energy isemitted in a formof a photon,

which causes light

The color of the light is

determined by the fall of the

electron and hence energylevel of the photon

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Inside a Light Emitting Diode

! Transparent"lastic #ase

$! Terminal "ins

%! &iode

 

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Kinds of LEDs

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How to Connect a LED:

'e(uires !)*$!)+ and m

To prevent overloading, use resistor

./ 0

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How to Connect a LED:

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Connect LED to BS2

L1& is on when" is high

L1& is on when

" is low

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Connect M!ti"!e LEDs to BS2

2 L1&s are connected to 3S$ each456 pin 7"-"/8 is allowed to sin9:!$)m

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Case Std#: B!inking LED

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Case Std#: B!inking LED

"basic program to ma9e an L1& blin9

ot"t $

Main:!ow $"ase %$$$

high $"ase %$$$goto Main

Make "in$ an ot"t

Loo" &egins here

'rn LED on

(ase for % sec

'rn LED off 

(ase for % sec

)o &ack to &eginning of!oo"

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E*"eriments

;lash an L1&! Single L1&

$!