Led lightsources

In the fast development of technology LED (light emitting diod) lightsources can not be left without attention.

First LEDs were sold in 1960's. At first three elements were used combined: gallium, arsenic and phosphorus and the colour was red. At first the light output was very weak.

In 1970's the technology was improving and industrial manufacturing started.

Development went from red to yellow, green, blue, that is from longer wavelengths to shorter, because it is harder to produce shorter wavelengths. Due to the low light output the first LED-s were only used as indicators. In 1990 the light output passed regular incandescent lamps and around 1998 halogen. Now scientists are getting closer to the outputs of fluorescent lamps.

Diodes as semiconductors were known to radio technicians long before that.

LEDs are semiconductor crystals where light is generated by the current passing through: electrical effect in the semiconductor where electrons jump from one energy level to another which releases photons at certain wavelength.

LED ensures light in a very narrow specter, which is only a small part of light radiation.

That is why every LED has its own color. Differnet colors are achieved by using different semi-conducting materials. There are two methods for achieving white light with LEDs:'

1.Several different LED-s with different colors (red, green and blue) are used, when mixed produce white light.

2.Blue LED's are used which has inner glowing layer, which can change the blue color to different tones.

LED's have gone through rapid development in the past years and the evolution still continues. Increasingly, LED's are used for lighting, which did not used to be possible due to low light output and no white light. Both problems are fixed today.

All the best known lamp manufacturers deal with developing LED's and creating lightings with them. This very energy efficient lightsource is very different from all the lightsources been in use before and helps create dependable and energy efficient lightings.

LED's field of use is very wide today and manufacturers offer them in different shapes and sizes, including ribbons and chains that can be cut in just the right length.

Thanks to the small sizes of diodes, designer can hide the lightsource in smaller spaces than ever before. With light transferring plastics light emitting sheets are created that seem to glow by themselves. These have LED strips hidden in the sides of plates that scatter the lighte evenly throughout the plate.

With so called RGB method, the LED's can be used in projects where it is necessary to program the changing of light (switching or the change in color) with low maintanace costs and long lifespan of the installation.

The advantages of LED:

+Lifespan of over 100 000 hours, that is at least 11 years. Long lifespan is explained with the simple build. There is no filament or sophisticated electronics like in fluorescent lamps.
+Dependant of colour up to 40lm/W, that is achieved momentarily
+Shockproof and vibration resistant – very suitable for vehicles
+Energy efficient. For example if a regular 60W incandescent works 8hours a day it consumes 175,2kW every year. LED lightsource with 1W consumes only 2,92kW with same working time.
+Does not emit UV radiation, which means no protection is necessary. Light should be smoothened if the lamp is too bright to look at directly.
+Almost no thermal radiation – enables useage of LEDs with flammable materials.
+Can work in a large temperature scale from -40 degrees to +75 degrees.
+Wide variety of colors and the possibility to control different colors.
+Small sizes which give endless playfield for designers and architects.

The main disadvantage so far has been the price of LED components. Recently the interest in LED components has risen and soon LEDs might start pushing today's common lightsources to the background.