Technical

Activity Factor

It is denoted by e, its unit is lm/W. It is the ratio of the total luminous flux emanating from a light source or luminaire to the total power of the source or luminaire. In other words, it is the luminous flux value that the light source or luminaire responds to the 1W power drawn from the network.

Illuminance Level

The average illuminance level is the ratio of the vertical component of the luminous flux per unit area to the area of the surface. Its unit is lm/m2 =lux and it is denoted by lx.

Glare

Glow is most generally dependent on a particular point of the surface and the direction of view. The glitter is denoted by the letter L. Its unit is cd/m2. It is a concept related to the light intensity emitted in a certain direction from the unit area of the surface. The light emitting surface can be a primary light source such as a light-producing lamp or a light-transmitting luminaire surface, or it can be a secondary light source that reflects light from another source. The luminosity of a point of the surface in the y direction is the light intensity emanating from the apparent unit surface in that direction.

Light Generation

The light production of lamps takes place in three different groups as thermal, luminescent and electroluminescent.

Luminescent Light Production

When atoms and molecules pass from the excited state to the ground state, they give back the energy they received as radiation. This happens when the normally insulating gas between two solid electrodes becomes conductive with electric current, and the resulting electron flow excites or ionizes the gas atoms. Electrons flowing from one electrode to the other collide with gas atoms getting in their way. If the velocity of the electrons is large enough to excite the atoms, the electrons excite the atoms and radiation occurs when the atoms pass to their ground state. In luminescent light production, unlike thermal light production, the spectrum of light is not continuous. They emit light at certain wavelengths according to the type of gases used and their partial pressures. Lamps operating on this basis are called high pressure or low pressure according to the pressure of the gas inside. Mercury or sodium gas is generally used in discharge lamps used today.

Electroluminescent Light Generation: LED (Light Emitting Diode)

This process is based on the direct conversion of electrical energy into light energy. LEDs are solid state light sources that allow unidirectional movement of electrons and emit light when an electric current is passed through them. In LED chips, which are formed by the combination of a P-type semiconductor with an N-type semiconductor, electrons combine with the holes as they pass from the negative side to the positive side and emit photons (electro-luminescent). LEDs, whose efficiency has increased rapidly especially after 1999, come to the fore with their high efficiency, good color properties and long lifetime. A typical LED chip consists of the following elements. The types of LED chips commonly available on the market are shown below.

White light with LEDs can be obtained basically in two ways:

• To obtain white light from their combination using tricolor red, green, blue (RGB) LEDs.
  Obtaining white light by covering LEDs emitting short wavelength (blue or ultraviolet) rays with a phosphor layer.

In luminaire designs made with LED chips, the thermal and electrical design of the system, especially the optical design, should be considered. Especially in high power LEDs, intense light comes out from a very small area. Therefore, glare problems should be prevented with a good optical design. The luminous efficiency, which expresses the rate of conversion of electrical energy into light energy of LEDs, varies between 10-40% depending on the type of LED chip. The remaining energy (60-90%) turns into heat. In an LED luminaire with poor thermal design, heat will accumulate and there will be an increase in temperature at the junction (junction) where the light is produced. If the LED junction temperature rises, the luminous efficiency of the LED will decrease and the efficiency factor (lumen/Watt) value, which indicates the amount of luminous flux obtained per unit power, will also decrease. Since LED chips generally work with direct current, they are used with a driver to receive energy from the existing grid. A second task of drivers is to deliver the rated current needed to each LED. LED drivers are generally adjusted to provide constant current and are produced in current stages such as 350 mA, 500 mA, 700 mA, 1050 mA as standard. The efficiency of LED drivers decreases as the load rates decrease.