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Lamps & Light Fittings - Coggle Diagram
Lamps & Light Fittings
PRODUCTION OF ARTIFICIAL LIGHTING
Source of the artificial light is the lamp
The lamp converts electrical energy to light energy
There are 3 types of lamps:
1. Incandescent lamp (Tungsten Filament Lamp)
Light is produced when a filament is heated to a very high temperature. This is achieved when the filament is heated by an electric current.
The higher the temperature the more light is produced and the whiter the light.
2. Discharge lamp
Current is passed through a glass tube containing a gas or vapour
As the electrons accelerate towards the positive electrode, they collide with the gas atoms resulting in the emission of light.
Commonly used discharge lamp
:
High pressure sodium
Better colour rendering than the low pressure sodium lamp.
Used in modern street lighting.
High pressure mercury
clear glass or phosphor coated.
Phosphor coating is used to ‘correct’ the missing colour.
Efficacy about 60 lm/W
Lamp life about 16,000 hrs
Efficacy and lamp life of the phosphor-coated lamp is about the same as the clear glass lamp.
The long life, relatively low price and reasonable efficacy makes the lamp suitable for lighting large areas where colour rendering is not of prime importance (e.g. factories).
For better colour rendering phosphor-coated lamps may be used (e.g. shopping malls, airport arrival/departure halls).
Metal Halide
These are high pressure mercury with metal halide added.
Metal halide is a compound between metal and halogen.
The addition of metal halides improve the colour rendition and the efficacy (110 lm/W)
Lamp life is shorter – 10,000 hrs
Used in sports stadium, lower power lamps are used in shop display lighting.
Low pressure sodium
These lamps produce a distinctively yellow light that is monochromatic.
Very poor colour rendering.
High efficacy.
Used for street and garden lightings.
Low pressure mercury (fluorescent lamp)
Produces large proportion of UV.
Phosphor used to convert UV to visible light.
Colour depends on type of phosphors used.
Warm white (3000K), daylight (6500K)
Efficacy 65-105 lm/W
Life 8,000 to 20,000 hours.
Requires starter and ballast.
Available in tubes, circular, compact sizes.
For most indoor areas especially low bay lighting (i.e. mounting height of maximum 6m)
3. LED lamp (Light Emitting Diode)
These lamps produce light by a process of electroluminescence when semiconductor crystals are electrically excited.
Efficacies are improving over the years.
Now it is the most efficient type of lamp.
more than 50,000 hrs.
Cost of lamp initially relatively high but it is getting cheaper now.
Most suitable in areas where lighting have to be left on for long hours. Also used in corridor lightings of HDB estates.
LUMINAIRES (LIGHT FITTING)
A luminaire is the light fitting that holds or contains a lamp.
Luminaires usually absorb and redirect some of the light emitted by the lamps, i.e. it controls the distribution of light.
Provide support, protection and electrical connection.
Have to be safe during installation and operation.
Able to withstand ambient conditions (e.g. corridor light to be splash proof).
MOUNTING POSITION
Recessed into a ceiling
Fixed to a ceiling
Suspended from the ceiling