LIGHTING ILLUMINATION Definition : In general terms, lighting is the process of illumination or applying light to a specific venue or focus. It also the deliberation of application of light to achieve some aesthetic or practical effect. Light is an electromagnetic wave that is visible and travel at 300,000 km/s. Units Light is an electromagnet wave that is visible & tr avel at 300,000 km/s Brightness of light candela (Cd) Brightness of light falling on an object or lux 2 = 1 lm/m2 1 lux = 1 lumen/m LIGHTING NATURAL LIGHTING ARTIFICIAL LIGHTING •
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NATURAL LIGHTING Natural lighting of interiors comes from daylight. It is directly from sun or moon or reflected by them. Daylight (through windows, skylights etc)is often used as the main source of light during daytime in buildings given its high quality and low cost. If a building used only natural lighting during daytime, amount needed depends upon daylight factor ( D.F) Daylight factor (D.F) depends on : 1) Sky condition 2) Size, shape & position of windows 3) Effect of obstructions 4) Reflection
ARTIFICIAL LIGHTING Artificial lighting is the one that man made. Unlike natural lighting, artificial lighting can be control can be said controllable. Design of artificial lighting depends upon: 1. Extent of usage, alone or supplement to artificial lighting 2. Specific task or general 3. Glare & reflection 4. Aesthetic (i.e colour, form & effects) 5. Location 6. Weight of lamp units + components 7. Maintenance (i.e longevity & accessibility) 8. Cost
TYPE OF LAMPS 1. Tungsten Filament or Incandescent uses fine tungsten wire as filament. when filament resists current,temperature rise, light out. rating : 5W – 1500W & last for 1000hrs
2. Discharge Lamps Operated by passing electricity (current) through a gas or vapour. Disadvantages: Disadvantages: take time for full brightness Advantages: last longer & better lights Two types: 1) High pressure mercury discharge lamps Use mercury vapour & 5 mins to full brightness. Orange – yellow. Install at roundabout, road junctions, high risk area 2) Low pressure sodium discharge lamps Use sodium vapour & 15 mins to full brightness White to bluish. Installed as street lighting.
Lamp life of a fluorescent lamps To indicate the life of fluorescent lamps, their useful l ife is defined. It is the time required until the system’s flux is reduced to 80% of its initial value. The system’s decrease in light flux can, however, be tracked back to the following. o a decrease in light flux due t o burning period of lamp(fatigue of fluorescent) o lamp failure o dirt accumulation. 3. Tubular Fluorescent Lamps o uses low pressure mercury vapour o coating will provide various emitting light colours. o available in long tube with straight, oval, compact & circular. 4. Compact Fluorescent Lamp a) CFL with build in ballast. equipped with conventional electric ballast. have higher luminous efficacy, guaranty in immediate, flicker free and weigh less. Mainly used in replace tungsten lamps in restaurant etc. b) CFL with external ballast have thin parallel fluorescent tube, a built in starter and a base. low weight, small size, high luminous efficacy and long life is the advantage of this lamp.
5. High Intensity Discharge Lamp (HID) a)Mercury vapour lamp produce by electric discharged through mercury vapour, resulting in poor quality of greenish hue. addition of phosphor coating in the bulb improve color rendering. b)High pressure sodium lamp manufactured with tube-shaped ellipsoidal bulbs with wattage of between 50 W and 1000 W. extremely high luminous luminous efficacy up to 130 lm/W. radiate a yellowish colour of light a nd achieve bad colour rendering. main application is outdoors for the illumination of streets and car parks c)Low pressure sodium lamp have high efficiency (up to 180 lm/W), quite long life (up to 16000 hours)and reduced running costs. yellow color commonly used for road lighting, parking areas etc can be used in areas where astronomical observations observations take place. d)Metal halides Lamp a further development of high-pressure mercury vapour lamps. the luminous efficacy is about 95 lm/W. suitable for the energy-efficient energy-efficient lighting lighting of offices, salesrooms salesrooms and and window-shops. CONTROL OF ARTIFICIAL L IGHTING i. Switches – cut out current flow by ON-OFF ii. Time control – pre determine ON-OFF iii. Photo-electric – detected intensity intensity of external light to ON-OFF iv. Dimmers – manually or automatically reduce Intensity of lamps v. Presence detector – ON-OFF due to present or movement of life forms.
