Light sources |
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Incandescent bulbs – the symbol of artificial lighting Incandescent bulbs are among the oldest artificial light sources and for now are most well-known among different bulbs. Incandescent bulbs are radiators: in closed gas filled glass flask electrical current makes tungsten spiral smolder. In addition to heat light emits, even though only 5-10% of power turns into light. With the raise of temperature rises luminosity and color temperature, however, the lifespan of lamp shortens, because with higher temperatures the material of filament vaporizes faster. The filament becomes thinner and eventually breaks and this marks the end of bulb. The lifespan of incandescent bulbs are usually around 1000h. There are bulbs with longer lifespan on the market. Pros of incandescent bulbs: +low price Cons of incandescent bulbs: -uneconomic as a light source Regular lamps are general demand lamps that can be economically and versatilely used both at home and in work place. Transparent and frosted lamps both give the same amount of light. Transparent lamps are used in chandeliers and spotlights. The standard cap for incandescent bulb is 27mm cap with turns E27. The standard powers are 15, 25, 40, 60, 75, 100 and 150W. Luminous flux rises proportionally with the rise of power. Small lamps (candle and drop lamps) are smaller compared to regular lamps. Also, the cap is narrower – E14, with diameter of 14mm. These are best suited for ornament lighting, in bathrooms and in many spotlights. E14 camp lamps come in 15, 25, 40 and 60W. They can be both transparent and frosted. Spotlamps' sheaf of light gives the opportunity to spiritfully and lively light rooms and large areas like shop windows, store rooms, reception halls etc. The modern reflective surfaces of these lamps are projected with computers. Front mirror lamp is very similar to regular incandescent with the difference that in the bottom of the flask there is a mirror channeling the light towards cap. The light will be then turned by reflector within the lamp. Active direction gives good lighting of certain areas with rather small power. Since heat and light are first mirrored inside the bulb, the front mirror lamps can not be used in lightings meant for regular lamps. The caps for Front mirror lamps are E27 and E14 and the mirror is silver or golden. Back mirror lamp or spotlamp channels light in front of the bulb. Interior reflecting surface of lamp determines the extent to which light is channeled, usually 20-35°. Outside dimension of lamp is usually in the typesymbol, for example 30mm for R30. E27 cap lamps come in 40, 60, 75 and 100W. E14 cap lamps come in 20 and 40W. While changing the spotlamp it should be noted that the new lamp would have the same extent as the old one had to get same results as before. There are also colorful and plant spotlamps available. Their flask is made of special neodymium glass, which makes the colors more bright and are for that reason often used in interior design. The colors have lush contrast. They are especially suitable for the lighting of flowers, plants and vegetables. Halogens – the next generation incandescents Halogens are basically incnadescents but in the flask there is halogen gas which stops the tungsten emitting from filament precipitate on the inner surface of the flask, channeling it back to the filament. Pros of halogens: +excellent color rendering +bright white light +twice as long lifespan compared to regular incadescents +smaller dimensions +variety of models Useful to know: -Lamp can heat up to 300-600°C. It should not be touched nor put near flammable surfaces or items. For dust and dirt not to melt on the hot surface, first glass lamps or covered lamps can be used -As incandescent bulbs, also halogen lamps turn only modest 10% of energy to light, rest turns to heat. -The lamp lifespan is short when used continually, 2000-3500h. -Low voltage (12V) but powerful halogens cause large currents in the wires. -Voltage alternator is necessary – for each lamp or a group of lamps. Halogens for the grid voltage are made in both E27 and E14 caps. Models are improving and their quantity is increasing. These offer an alternative for the classical incandescent lamps, which are easy to use with the grid voltage without any transformers. They provide bright white light which gives 15% more light as incandescent with the same power and are dimmerable. Halogen spotlamp HaloPAR is a bright alternative for traditional spotlamp. It can easily be powered from the house grid, no transformer necessary. Up to 35% more light compared to traditional spotlamp. Gives 15% energy saving and the lifespan of the lamp is 2000 hours. The models with dicrhoic mirrors enamble to turn 2/3 of thermal radiation backward and are therefor suitable for lighting of heat sensitive objects. Low voltage halogen with aluminium mirrors – HaloSPOT's combreflector ensures the even distribution of the light. Its protective surface reduces glare and facilitates usage. Low pressure integral lamps vary from 12V to 50V. Grately reduced pressur meets the new IEC598 standanrd and can still be used without protective glass. Suitable for highlighting objects even in brighter areas. Choosing a suitable converter Halogen lamp's lifespan is depends of working voltage. Converter is chosen according to the power of lamps. For example, for five 20W lamps a converter with 100VA is used. Converters are usually iron core transformers. Unfortunately their output voltage depends of load, which means after one lamp is destroyed voltage of other lamps rises. Overvoltage will shorten the lifespan of lamps. So, non-working lamps should be replaced as soon as possible. Electron converters keep voltage constant in every situation. In addition, they are smaller and lighter. To minimize and dangers professionals should be consulted when choosing lamps, converters and wires. Fluorescent – energy sufficient light Common fluorescent is 60-150cm long white surfaced glasstube with metal rings with contact legs on both ends. Light is created by fluorescent layer inside the tube that is activated by UVradiation from electrical discharge. Fluorescent lamps can only be used in special lightings, which have the necessary starter to ignite the lamp and a drossel which limits the rise of current after discharge in the tube. Fluorescent is much more luminous compared to incandescent lamps. Luminousity of 100W incandescent is achieved by 18W of fluorescent tube. Lifespan of tube is 8-15 times longer. Color of light Color of fluorescent light depends of the composition of luminence able substance on the inside surface of the tube – luminophore. There are over 10 colors from bright white to warm white. Illumination and the color are dependant of one-another. The more illumination, the colder it seems compared to natural light. Color of the light is determined by the color temperature measured in Kelvins (K). For color 41 it is 2700K and as temperature rises color gets colder. For color 12 it is 5000K. The color of sunlight is 6500K. Different tones of fluorescents are especially distinguishable when the lamps are side-by-side. That is why it is recommended that different tones of fluorescents are not used in the same room. Color rendering Color rendering that is the naturality of colors in lamp light is dependant of the quality of fluorescent. The color of light and color rendering are two different things. Color rendering index (Ra) of different color lights can be the same. Ra=100 means the colors look the same they would in natural daylight and incandescent light. Lifespan of fluorescent Lifespan of fluorescent is 7000 – 15000h which means 5 to 15 years of usage. Lifespan slightly depends on amount of switching. At home you can always turn off the light when light is not needed as the energy saving exceeds the value of alternative. Luminous flux decreases in the end of lifespan. After 8000 -10000 working hours the luminous flux has decreased ca 30%. These lamps should be replaced even though they are still working. Pros of fluorescent: +About 5 times more luminous than incandescent bulbs. Useful to know: -Dimensions limit the use of fluorescent Small fluourscent or compactlamp is small lamp with one socket and 2-4 matt finger tube in which is combined the luminosity and long lifespan of fluorescent and useability and comact sizes of incandescent lamps. Main problem is mounting essential drossel for fluorescent in the lighting. Savings lamp Dulux EL, a small fluourscent lamp, is almost as an incandescent lamp with its electron drossel inside the cap of lamp. Main types of small fluourscnet lamps include two tubes, four tubes and longer with two tubes. Since all the types are technically different they need different interface and are not replaceable with oneanother. To avoid mistakes all the lights have different caps. Also, different colors are available. Compactlamps are energy efficient and last for 6000- 10000 hours. Pros of small fluorescent +4-5 times the luminous flux compared to incandescent lamps Useful to know: -Different types of compactlights are not replaceable with oneantoher Halide lamps – high light output discharge lamps Noticeable improvement of colour and luminousity thanks to the use of metal iodides. Pros of halide lamps: +Very high light output. Halide lamps are mostly used in display windows and sale rooms, presentable general lighting, in exhibitions and museums and also in demanding industrial enterprises as workplace lighting. Four Powerstar HQI TS 150W/WDL can be used to replace thirty PAR 120W. This offers 1500lux, with load of 680W. Merchandise is preserved, work is easier. Lower maintenance costs. Lamps are changed after 6000 hours |
