Street lighting yesterday and today

The basic element in the construction of each radiating source is a radiator, which sends infrared, ultraviolet radiation or placed in a phosphor-coated bubble, it can emit a visible light beam. In addition, there must be power supply elements in addition to the heater in the equipment. Depending on the type of radiator, we can indicate three basic sources of radiation.

1. temperature radiation - tungsten twisted-pair glow light source BULB 
2. fumes of metals or noble gases (neon, xenon, mercury, soda, halides), in which the lighting effect occurs after the discharge phenomenon 
The 3. semiconductor in the form of a LED light-emitting diode

What are the discharge lamps?

As the name suggests, it is a lamp whose light was triggered as a result of an electric discharge. In contrast to the glow or LED, the discharge occurs in metal fumes (mercury) or gases (argon, neon, sodium). Depending on the type of lamp and the discharge environment, the bulb in which it is located can be coated inside with a phosphor - a chemical substance that absorbs UV radiation due to its properties , which could cause permanent and unpleasant effects of burns both on the surface of the human body and and with long-lasting emission on tangible objects. In addition, thanks to the use of phosphor Depending on the thickness of the substance molecules, it is possible to transform the invisible rays into a visible stream. 
Discharge lamps have taken the shape of a tube. They may have standard threads (E27, E40) or be free of them. Depending on the type of lamp in each type there is a different ignition device, as well as a ballast (gland) which limits the discharge current. Both of these elements are mounted directly in the fittings of discharge lamps.

Mercury lamps

A high-pressure mercury lamp is one of the types of discharge lamp used in street lighting. The discharge lamps are the mercury vapor contained in the glass bulb. Mercury discharge occurs in mercury, which, besides lighting, is also used in electric welding.

Low-pressure mercury, in which the electric discharges in the mercury vapor from the inside is covered with a special fluorescent powder (phosphor) in order to convert the emitted UV rays into visible-light radiation. The most common phosphors include calcium or, in the case of narrowband equivalents, clay, and borates 
Due to the high level of mercury vapor emitted and low color rendering index (CRI), the mercury exchange campaign was started slowly from 1935, replacing it with sodium lamps.

Sodium lamp

Sodium lamps, which discharge occurs in sodium vapors, occur in two types - low and high pressure. Inside the glass tube, there are vapors of sodium and auxiliary gases - argon and neon. Feed tubes low pressure is done using transformers with a high degree of dispersion. Produced lamps from 18 to 180W have an efficiency of up to 206lm / W. Due to the gas mixture used, the color temperature does not exceed 2000K, which indicates its yellow-orange shade of light. Due to the low CRI color rendering index, their application was reduced only to roads that do not provide traffic on the side of highways, highways with no pedestrian traffic.

In contrast to low-pressure soda, we can distinguish their high-pressure counterpart. In them, the arc tube is made of ceramic fiber, in which there are vapors of sodium, mercury, and xenon (pressure 2kPa) 
The process of lamp flashing occurs at the moment of evaporation of sodium and mercury. As a result of this process, the pressure inside the arc tube is 2 MPa. As in the case of a low-pressure sodium lamp, the color temperature in this case also does not exceed 2000K but its effectiveness is 150lm / W. Due to the better CRI color rendering index (25-65)have a wider range of applications. Due to the yellow color of light, they work perfectly in the fog, so they are used in environments where the degree of air pollution with various fumes and dust is very high.

Over the years, created sodium lamps, whose color reproduction has exceeded the threshold of 85. Due to the elevated pressure of gas vapors inside the arcade to 95 kPa, the effect of the color temperature is 2500K. In the temperature range, it reached the level of white color, which is why it is called "white soda". Unfortunately, as a consequence of raising the pressure and illumination of the stream, the efficiency of light decreased (up to 40 lm / W), which caused that this type of lamps began to be used as internal lamps for lighting food and meat

Although, as in their case, due to the sodium pressure in the aisle, we can distinguish high-pressure (HPS) or low-pressure (LPS) lamps. Sodium lamps are characteristic and recognizable sources of light, not because of the luminaires they are in, and thanks to the yellow-orange color of the light beam. It was thanks to her that in 2005, the decision was made to slowly replace sodium lamps with lamps emitting a white color - metal halide lamps or currently popularized LED street lights.