Illumination basic and lightning scheme

illumination basics, different types of light bulb ,system and terms used in lightning scheme.

1. Illumination Basic and Scheme

2. Topics Introduction Nature of light Lighting schemes Terms used in illumination Electrical methods of producing light Arc lamps Filament lamps Gaseous discharge lamps

3. 7. Sodium vapour lamp 8. Mercury vapour lamp 9. Fluorescent tube 10. Neon lamp 11. Halogen lamp 12. Compact fluorescent lamp

4. Introduction As we know that almost all human activities depends on light. Sun is a prime natural source of light but artificial lighting plays almost main role in our daily life. These artificial lights are produced by mechanical lamps and electrical lamps . But due to poor performance the mechanical light are totally replaced by electrical lights . The electrical lighting are mainly used for decorative purpose , advertising, traffic control,medical field and street lighting etc.

5. Electrical Lighting Electrical lighting has following advantages : 1. Cleanliness 2. Easy to control 3. Economical 4. Easy to handle 5 . Better reliability 6. Suitable for almost all purposes etc.

6. TERMS USED IN ILLUMINATION 1.Light 2. Luminous Flux 3. Luminous Intensity 4. Illumination

7. LIGHT Light is a form of electromagnetic energy , that part of radiant energy from a hot body which produced the visual sensation on human eye is called light. Light can be of different colours , which depend on the wavelength of radiation causing it.

8. LUMINOUS FLUX To measure light, it is necessary to measure its flux (rate of flow) The total quantity of radiant energy per second responsible for visual sensation from a luminous body is called Luminous Flux. Or Rate of flow of radiant energy M easured in lumens.

9. LUMINOUS INTENSITY Intensity of emission of luminous flux in that direction is the luminous intensity . It is denoted by I and its unit is candela or candle power (CP) . Luminous intensity of source in a particular direction, I = φ / ω

10. ILLUMINATION When light falls on a surface, it becomes visible , the phenomenon is called as illumination . It is defined as luminous flux falling on a surface per unit area . It is denoted by E and measured in lumen per square meter or meter‐ candle. E = Ф / A lux

11. Lighting Schemes Lighting schemes are classified according to the location, requirement and purpose etc. are as under : 1. Direct lighting 2. Indirect lighting 3. Semi direct lighting 4. Semi indirect lighting 5. General lighting

12. Direct Lighting As is clear from the name, in this system almost 90 to 95 % light falls directly on the object or the surface . The light is made to fall upon the surface with the help of deep reflectors. Such type of lighting scheme is most used in industries and commercial lighting . Although this scheme is most efficient but it is liable to cause glare and shadows .

13. Indirect Lighting In this system, the light does not fall directly on the surface but more than 90 % of light is directed upwards by using diffusing reflectors . Here the ceiling acts as a source of light and this light is uniformly distributed over the surface and glare is reduced to minimum. It provides shadow less illumination which is useful for drawing offices. It is also used for decoration purposes in cinema halls, hotels etc.

14. Semi direct Lighting This is also an efficient system of lighting and chances of glare are also reduced . Here transparent type shades are used through which about 60 % light is directed downward and 40 % is directed upward. This also provides a uniform distribution of light and is best suited for room with high ceilings.

15. Semi indirect Lighting In this system about 60 to 90 % of total light is thrown upward to the ceiling for diffused reflection and the rest reaches the working plane directly . A very small amount of light is absorbed by the bowl. It is mainly used for interior decoration .

16. General Lighting This system employs such type of luminaries, shades and reflectors which give equal illumination in all the directions.

17. LAMPS

18. FILAMENT OR INCANDESCENT LAMP

19. Properties of Metal for Filament High melting point : so that it can be operated at high temperature. High specific resistance : so that it produces more heat. Low temperature coefficient : so that filament resistance may not change at operating temperature. Low vapour pressure ; so that it may not vaporize High ductile : so that it may withstand mechanical vibrations

20. SODIUM VAPOUR LAMP

21. Life of such lamps ends when:- Filament breaks or burns out The cathode stops to emit electrons When sodium particles may concentrate to one side of the tube

22. MERCURY VAPOUR LAMP

23. FLUORESCENT TUBE

24. NEON LAMP

25. HALOGEN LAMP

26. COMPACT FLUORECENT LAMP

27. Design of Indoor Light Scheme While designing a good lighting schemes, the following points must be kept in mind : 1. It should provide adequate illumination . 2. It should provides uniformly distributed light all over working plane. 3. It should avoid glare and shadows as far as possible. 4. It should provide light of suitable colours .

28. Factors required for Light Scheme The following factors are required to be considered while designing the lighting scheme : 1. Illumination level 2. Quality of light 3. Co efficient of utilization 4. Depreciation factor 5. Space height ratio

29. Illumination Level Type of work recommended illumination level Offices 100‐400 lumens/ meter square Schools 250‐400 lumens/ meter square Industry 1000 lumens/ meter square Shops 250‐500 lumens/ meter square Hotels 80‐100 lumens/ meter square Hospitals 250‐3500 lumens/ meter square

30. Quality of Light This means that the illumination should not be harmful to the viewers . It should be glare free , shadow less and contrast free . Hard and long shadows can be avoided by using a large number of lamps and adjusting the mounting height.

31. Co – efficient of Utilization Utilization factor = lumens reaching at the working place/total lumens emitted by the source Usually it varies from 0.5 to 0.8.

32. Depreciation Factor The total flux emitted by the source and its fitting may be reduced due to deposition of dust upon the surfaces. Similarly quantity of light reflected from the ceiling and walls also decreases with the passage of time . This is called as depreciation factor. Usually it varies from 1.3 to 1.6

33. Space Height Ratio The ratio of space (horizontal distance ) between the two adjacent lamps to the vertical height of the lamps above the working plane is called space height ratio.