A light-emitting diode (LED) is a semiconductor device that emits incoherent narrow-spectrum light when electrically biased in the forward direction of the p-n junction. LED is a tiny little bulb. This effect is a form of electroluminescence. We can use LEDs as indicators in electronics devices, say for ON ,led glows and for OFF it doesn't. Life of one led is 100000 hours. The color of the emitted light depends on the condition of the semi conducting material used, and can be infrared, visible, or near-ultraviolet.
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Determining LED Polarity:
LEDs have a positive and negative terminal, also know as the anode and cathode.
The cathode should be connected towards the ground or negative side of the
driving voltage source, and the anode toward the positive side
Calculation of LED resistor Value:
We must put a
resistor in series to
obstruct the current to
avoid burn out.
According to Ohms Law V=IR
or R=V/I, In our case
V=VSupply - VLED
Therefore the resistor
value, R is given by:
R = (VSupply - VLED) / I
VSupply = supply
voltage, VLED = LED
voltage, I = current of
LED
LED Colors
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LEDs are available in
amber, yellow, green,
red, orange, blue and
white. Blue and white
LEDs are much more
expensive than the other
colors. The cost of LED
varies from color to
color because different
semi-conductor materials
are used to make the
different LED colors.
Cost depends on type of
semiconductor used.
White LEDs are the most
expensive because red,
green, and blue are
mixed together to make a
white LED
Advantages of LEDs over others:
- High-levels of brightness and intensity makes it look attractive. See the Open sign , Pizza Sign above.
- High-efficiency and accuracy.
- Low-voltage and minimal current requirements.
- Low radiated heat.
- Resistant to shock , highly reliable.
- No UltraViolet Rays.
- Long source life up to 100000 hours.
- Can be easily controlled and programmed into microcontrollers such as 8051 and 8052.
LED Circuits Links:
LEDs vs Incandescent lamps or Advantages of LEDs
LED Market is growing
day by day & has a
bright future.
LED do not have
filament which makes it
last longer .
Less Heat involved hence
less loss of energy as
compared to Incandescent
lamps.
LED have high efficiency
as compared to
incandescent lamps.
The operational life of
white LED lamps is
100000 hours.
Low Voltage Power Supply