When the LED lampor came into use for lighting?
Initially, LEDs were used solely for display. To make them suitable for lighting, it was necessary first of all learn how to make white LEDs, as well as to increase their brightness, but rather light output, ie the ratio of luminous flux to the energy consumed.
In the 60's and 70's were created by LEDs based on gallium arsenide phosphide and emitting in the yellow-green, yellow and red spectral regions. They were used in indicator lights, displays, instrument panels of cars and planes, advertisement screens, different systems of information visualization. LEDs on the light output surpassed incandescent bulbs. For durability, reliability, security, they also surpassed them. One was bad - there were no LED blue, blue-green and white.
What determines the color of the LED lampa?
Exclusively from the band gap, in which electrons and holes recombine, that is the material
of the semiconductor, and the dopants. The "blue" LED lampa, the higher the photon energy, and hence the greater the band gap.
LED lampa reacts as a rise in temperature?
Speaking about the temperature of the LED lampa, it is necessary to distinguish between the temperature at the crystal surface and in the pn-junction. From the first independent life, from the second - the light output. In general, with increasing temperature pn-junction LED brightness decreases, because the internal quantum efficiency is reduced because of the influence of lattice vibrations. Therefore, it is important a good heat sink.
A drop in brightness with increasing temperature is not the same in light-emitting diodes of different colors. It is no longer in AlGalnP-AeGaAs-and light-emitting diodes, that is a red and yellow, and less in InGaN, ie, in green, blue and white.
Is it possible to adjust LED brightness?
The brightness of LEDs very well be regulated, but not by reducing the supply voltage - this is just what you can not do - and so-called method of pulse-width modulation (PWM), which require a special control unit (actually it can be combined with the block Power and converter and the controller controls the color of RGB-matrix). PWM method is that the LED is fed not constant, but the pulse-modulated current, the frequency of the signal must be hundreds or thousands of hertz, and the width of pulses and pauses between them may vary. The average brightness of the LED is driven at the same time, the LED goes out.
A small change in color temperature when dimming LED compares to a similar shift
for incandescent lamps.
Not bad for a LED lampa to the human eye?
The emission spectrum of the LED is close to monochromatic, what it's fundamental difference from the spectrum of the sun or incandescent lamps. Good or bad - It is not known, because as far as I know, serious research in this area has not been anywhere. There are no data on the harmful effects of LEDs on the human eye is missing.
It is hoped that soon the influence of LEDs on the vision will be investigated thoroughly. The
problem of academic interest Mikhail A. Ostrovsky - a prominent specialist in the field of color vision. The theme for the solution of which he started, so called, "Psychophysical perception of LED lighting system of man."
Where today is expedient to use LEDs?
LEDs are used in virtually all areas of lighting, except lighting production area, and there can be used in emergency lighting. LEDs are indispensable in the design due to their light pure color and dynamic lighting in the system. Advantageous as they apply where frequent maintenance is expensive, where it is necessary to save energy and hard with high demands on electrical safety.
In Moscow in early 2004 adopted a three-year program based on energy-efficient lighting LED technology. Coordinating Council headed by Professor JB Eisenberg. This program is offered to use LEDs in the test construction, housing and other areas. For example, the LED lights will be installed in underground passages, doorways, elevators for floors, that is, where do not need much light, but it requires low maintenance and energy costs, as well as important high vandalproof.
