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8/18/2019 What is an LED
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What is an LED?
Light-emitting diode
Semiconductor
Has polarity
8/18/2019 What is an LED
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LED: How It Works
When currentflows across adiode
Negative electrons move one
way and positive holes move
the other way
8/18/2019 What is an LED
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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
8/18/2019 What is an LED
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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
8/18/2019 What is an LED
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Inside a Light Emitting Diode
! Transparent"lastic #ase
$! Terminal "ins
%! &iode
8/18/2019 What is an LED
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Kinds of LEDs
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How to Connect a LED:
'e(uires !)*$!)+ and m
To prevent overloading, use resistor
./ 0
8/18/2019 What is an LED
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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
8/18/2019 What is an LED
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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
8/18/2019 What is an LED
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Case Std#: B!inking LED
8/18/2019 What is an 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"
8/18/2019 What is an LED
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E*"eriments
;lash an L1&! Single L1&
$!