Kitronik 2143K - Page 16

High Power Amp Teaching Resources
www.kitronik.co.uk/2143
LEDs Continued
The Colour Changing LEDs used in the ‘colour’ version of the lamp has the current limit resistor built into the LED
itself. Therefore no current limit resistor is required. Because of this, a ‘zero ’ resistor is used to connect the voltage
supply of 5V directly to the Colour Changing LED.
Packages
LEDs are available in many shapes and sizes. The 5mm round LED is the most common. The colour of the plastic lens
is often the same as the actual colour of light emitted – but not always with high brightness LEDs.
Advantages of using LEDs over bulbs
Some of the advantages of using an LED over a traditional bulb are:
Power efficien
cy
LEDs use less power to produce the same amount of light,
which
means that they are
more efficient. This makes them ideal for battery power applications.
Long life
LEDs have a very long life when compared to normal light bulbs. They also fail by
gradually dimming over time instead of a sharp burn out.
Low temperature
Due to the higher efficiency of LEDs
,
they can run much cooler than a bulb.
Hard to break
LEDs are
much more resistant to mechanical shock
,
making them more difficult to break
than a bulb.
Small
LEDs can be made very small. This allows them to be used in many applications
,
which
would not be possible with a bulb.
Fast turn on
LEDs can light up
faster
than normal light bulbs, making them i
deal for use in car break
lights.
Disadvantages of using LEDs
Some of the disadvantages of using an LED over a traditional bulb are:
Cost
LEDs currently cost more for the same light output than traditional bulbs.
However, t
his
needs to be balanced against the lower running cost of LEDs due to their greater efficiency.
Drive circuit
To work in the desired manner
,
an LED must be supplied with the correct current. This could
take the form of a series resistor or a regulated power supply.
Directional
LEDs normally produce a light that is focused in one direction
,
which is not ideal for some
applications.
Typical LED applications
Some applications that use LEDs are:
 Bicycle lights
 Car lights (break and headlights)
 Traffic lights
 Indicator lights on consumer electronics
 Torches
 Backlights on flat screen TVs and displays

Road signs
 Information displays
 Household lights
 Clocks