LED lighting manufacturer - GOMAR PLUS - high-tech LED technologies

LEDs - basic informations

Light Emitting Diodes are semiconductor sources of light using the phenomenon of electroluminescence. When a suitable voltage is applied to a p-n junction of diode, it emits light. P-n junctions is not emitting white light itself's, to achieve white light there are various phosphores used. Coating LEDs with phospors in suitable colors gives, as a result various colours including white light.


Spectral power distribution describes a light spreaded into single colors. Colors are described by wavelenght (in nanometers) and corresponding power. Human eye is sensitive to colours from 380nm to 780nm. Wavelenghts under 380nm are UV light, wavelenghts above 780nm are infrared. With spectral distribution we can read the part of power corensponding to particular wavelenght and so, in case of for example blue light the majority of power will be focused in blue part of spectrum. Below we present spectral distribution for particular colors of RGB LED tape.

While talking about colors we should explain a color temperature in Kelvins. Color temperature is related to black-body radiation. As a model of black-body spectral emission we can take a pot full of platinum which, after heating to desired temperature emits a light in designated color temperature. And so, platinum melted to 2046K (Kelvins) temperature emits a light in 2046K color temperature. Candle light emits 2000K, bulb about 2700K. A bulb is nice example of colour temperature model. Tungsten filament reaches a temperature of 2700 - 2800K and emits a light in similar color temperature (example below).

Spectral distribution and color temperature are important things while choosing light for particular application. For example warm white light (3000K) is good choice for living rooms and bedrooms because such light is relaxing and calming. Colder light (5000K) is good for working places because such lighted places are good for working applications and are used for example in production halls, warehouses. But we need to remember, that felling of light is dependent from personal preferences.

An accurate description of light color is available with use of chromacity coordinates. A CIE (International Comission of Illumantion) designed chromacity coordinates presentation. CIE 1931 color space defines precisely color of light with use of x and y coordinates. Below we present example of chromacity color space and charts with data about light color such as: color temperature, Colour Rendering Index, and chromacity coordinates.


Chromacity coordinates

xk

0,3844

yk

0,3848

uk

0,2245

vk

0,3371

Colour temperature [K]

3953

Color rendering index

Iluminant xr

0,3825

Iluminant yr

0,3781

Iluminant ur

0,2260

Iluminant vr

0,3350

Iluminant

Planck's

Jasnoczerwona

R1

80,98

Żółta

R2

87,77

Żółtozielona

R3

94,46

Jasnozielona

R4

83,33

Zielononiebieska

R5

81,37

Jasnoniebieska

R6

84,79

Jasnofioletowa

R7

89,27

Purpurowa

R8

68,15

Głęboka czerwona

R9

13,61

Głęboka żółta

R10

70,41

Głęboka zielona

R11

81,48

Głęboka niebieska

R12

70,34

Oranżowa jasna

R13

82,24

Żółtozielona jasna

R14

96,53

Avg. 8

Ra8

83,76

Avg. 14

Ra14

77,48


Another light characteristics element is a Colour Rendering Index Ra (CRI). Thanks to spectral distribution measurements of light source we can describe how accurate are colours percepted, while lighted with particular light. Range of CRI is from 0 to 100, while the higher index means better perception of objects lighted with talked-about source of light. Commonly used Ra value is an average index of 8 standard colors (R1 to R8) - example above. CIE comision have also added six, standard colours (R9 to R14). We can also use CRI for 14 colours if we want to describe CRI in more accurate way.

Sun light has the highest CRI Ra index - 100. Almost, so high values are available with bulb light - it's a effect of bulb spectral distribution which is "complete", that means there is no gaps in bulb spectrums. LEDs in the context of their design usually have weak R9 index. High quality diodes have a Ra index >80, which is sufficient for most of light applications. Lower Ra can result in weak reading of colors. Higher Ra values (also feasible with LEDs) are necessary in fields, where colours must be seen as they really are, for example is surgery field, hospitals, museum etc. Actually in our offer you can find LED modules designed for high Ra and R9 values. This effect is achieved with mixing spectrums of various LEDs in one COB modules. This example shows, that LEDs are really valuable light sources, which, as a effect of instant modernisation are reaching higher and higher light performance.

Thanks to high lighting effectiveness LED diodes generates savings in electric energy bills, they allow to save up to 90% of energy. Luminous efficiency is defining proportion of light flux emitted by determined source of light to energy absorbed in unit of time. The unit of measure is lumen/wat (lm/W). Exemplary luminous efficiencies of different sources of light:
- light bulb 10 lm/W
- halogen lamp 16-20 lm/W
- fluorescent lamp 50-100lm/W
- LED diodes100-200lm/W

It should be mentioned, that effectiveness of LED diode, or fluorescent light would be different from complete lamp to single diode, or fluorescent light. We should count losses appearing on power systems and optics, nevertheless these sources of light are still the most effective. Below we present a graph showing relations between current of LEDs and luminous efficacy. Example is given for LEDs from various producers, that are used for our products - LED bars and modules:

- OSRAM DURIS E5: L060-050-10-03, L038-120-10-07, L038-240-10-07, L034-063-10-07, L051-061-10-07, LED modules ZH 280mm

- OSRAM DURIS E3: L012-100-10-03, L012-050-10-03, L007-033-10-07, L010-033-10-07, L010-120-10-07, L015-050-10-07

- EDISON: L024-100-10-03, L024-050-10-03, L021-120-10-07, L013-050-10-07

While comparing LED diode with fluorescent light it should be noted, that fluorescent light (also bulbs) are all-round sources of light, while LEDs are lighting directionally, usually at an angle of 120 degrees. The result is higher efficiency of LED lamps than fluorescent lights, in which we loss a part of light on reflection of light flux off the surface. Practicably there are available LED lamps, that let us save up to 50 % of energy in comparison with fluorescent light and up to 90% with regular sources of light.
Another important advantage of LED diodes is their high working life of 30 thousand to 100 thousand hours, while comparing working life of light bulb is about 1 thousand hours, halogen lamp ca. 5 thousand hours, fluorescent light ca. 10 thousand hours. It should be mentioned, that only branded diodes are proving such long working life. Customers should be careful while listening promises of sellers claiming working life of cheap, Far Eastern products on level of 100 thousand hours. Frequently, authentic working life of cheap LED diodes is only several thousand hours. Furthermore LED diode doesn’t blow right away, it loses slowly light flux and it’s working life is given with decrease of light flux to 75%. After that time diode can light further but with weaker light. Durability of diodes brings in savings also while we need to replace sources of light, when access to lamp and replacement of light bulb or fluorescent lamp is giving customers additional work and costs.