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Updated on November 11, 2013

What are the basic principles for making lamps?

Lamps (Light Source) are produced by using two principles,  one by converting heat into light and second by discharging the mixture of material and gases. It could be described as under:

(1)     Incandescent Lamp:  Is the first produced light source invented by the great scientist, Mr. Thomas Alva Edison in the year 1879.  These lamps work on the principle of heat.  When the electricity is passed through inside the glass hallow, the tungsten filament gets heated and starts emitting light.  But 80% of the energy is wasted in generating heat and only 20% is used for giving light.  In the era of highly priced Electricity Power, these are now known as power hungry lamps.  Due to their lower price, they are frequently used all over. These include GLS lamps (bulbs), halogen lamps etc.

(2)    Discharge Lamp:  The discharge lamp operates on discharge technology to give high luminous efficacy and long life.  Here electrical discharges between the electrodes cause the filler materials and gases in the pre-coated tube to emit light.  A suitable control gear is invariably used to limit the current and to ensure the light-up of the lamp.  It comprises of low pressure and high pressure type,  based on various applications.  These include Fluorescent Tube Lamps (Tube Light/FTL),  Compact Fluorescent Lamp (CFL), Mercury Vapor Lamps, Sodium Vapor Lamp, Metal Halide Lamp etc. 

(3)    The light sources using the laser beam technology is said to be under development.  

Why CFL is the best replacement for GLS lamp?

The construction of CFL being compact in size and comparable with GLS lamp, hence is considered  to be the best replacement for GLS lamp.  Normal tube lights (FTLs) being longer (4 Ft.)  in size and larger in dia (38 mm) are thus not worth comparing with CFL (12.3 mm dia).

It is therefore advised that CFL must be discussed at all times in reference to GLS lamp only.  It will generate good amount of confidence and interest with the prospects.

What is photometric?

Photometric is the testing measurement involving distance and direction of light by using sophisticated equipment by mounting lamp at an adjustable and measurable distance from the photometer head. It includes measurement of intensity of light, luminance, color temperature, color rendering index etc.  For measurement, accuracy a globe shape halo sphere  is invariably used, which is pre-coated with barium sulphate suspension. .

What is the thumb rule for replacing GLS lamp?

The thumb rule is that a CFL replaces 5 times more wattage GLS lamp to the nearest of standard rating available in the market in terms of light output. It means that similar amount of light output of 100W GLS lamp can be obtained by replacing it with a 20W EL lamp (20W i.e. 1/5th of  100W).

Important: The other thumb rule is neither try nor advise to replace FTL with CFL.  CFL is the best replacement for GLS lamp as explained earlier.

Why there are different base for different CFL lamps?

 These are as per the international design primarily to ensure that lamp concerned is used with the matching fixture including ballast.

What is the CFL?

The CFL (Compact Fluorescent Lamp) is a vacuum discharge lamp and  the latest in the line of revolution in lighting arena. As the name suggests, the CFL is quite a bit like the normal fluorescent lamp, popularly known as tube lights; but necessarily compact in size.  Apart from the size, the other major difference is the lesser amount of energy consumed by CFL.  That’s why it’s truly called the Power Saver lamp, essential for all.  In fact the small size of  CFLs makes it more versatile, usable and acceptable over the traditional lamps.

CFLs are the state-of-the-art energy saver lamps available in two versions: Core and Electronics.  They save 80% energy, have long life and come in wide choice of colors and have high esthetics.

What is the construction of CFL?

The CFL consists of two parts, (1) a gas filled coated tube(s) and (2)  a magnetic or electronic ballast. The gas in the tube glows with ultraviolet light when electricity flows therein through the ballast.   This in turns excites the  triband phosphor coating walls inside of the tube, which emits visible light throughout the surface of the tube.  CFLs are state-of-the-art energy saver lamps who come in two versions (1)  Core/ PL/ Non-Retrofit / Non-Integrated Lamps,  and (2) Self-Ballasted/ Electronic / Retrofit/ Integrated Lamps.

What is triband phosphor?

Triband phosphor is the mixture of various fluorescent elements called activators, essential for the development of luminescence. It helps convert short-wave length ultra-violet radiation into light.

Triband phosphor is the most  superior quality phosphor, capable of emitting red, green and blue wavelengths as against the ‘halophosphor’ with red and blue properties, which is used for ordinary fluorescent lamps (FTLs).  Given the small dia tubes of CFL (12.28 mm) in comparison to FTL (38 mm), the use of triband phosphor ensures better and uniform light output throughout the life of the CFL. Triband phosphor is 10 times more costlier than the halophosphor. The sub-standard spurious CFLs available in the market are largely made of using halophosphor and thus are cheaper in price.

What are the characteristics of 4 Pin CFL?

4 Pin CFL is specially designed for electronic operation to offer the possibility of controllable light output (dimming ), HF (High Frequency) and DC (Direct Current) supply; and a wide range of supply voltages when operated in conjunction with electronic gear.  Electronic gear enables better control of lamp starting characteristics, allowing for instant start which results in longer lamp life.  In view  of its favourable color rendering properties, the 4 Pin lamp is very suitable for use wherever light contributes to the creation of a flicker free and pleasant atmosphere such as in hotels, restaurants, at homes, offices and so on. 

What precautions are suggested for the best results from CFL?

  Do not use in enclosed fittings.
  Do not use in dimming circuits electronic switches.
  Run on stable voltage.
  Fragile-Handle with care.
  Do not expose to water.
  Do not hold from glass.


Low electricity bills:  CFL produces 90% less heat and hence gives more light per watt. It cuts electricity bills by almost 80% in comparison to traditional incandescent lamp ( Popularly know as bulb or GLS lamp), which is considered to be power hungry light source.  Whereas CFL is the most energy efficient light source.  

Higher luminous efficacy: Gives more light output per watt of electricity consumed in comparison to GLS  lamp. An 11W CFL produces around 540-580 lumens compared to 710 lumens by a 60W GLS lamp.  So it is 49 for CFL against 12 of GLS.

Long life: CFLs are available in wide life range of 3000 hours to 12000 hours as compared to GLS lamp’s standard  life range of 960  hours to 1200 hours only.

Available in different color temperatures:  To suit various ambience needs, these are readily, available in Warm White (2700°K) close to GLS lamp, Cool White (4300°K) and Cool Day White (6500°K) similar to tube light.

Enhances color rendering:  The objects are seen in their true and natural colors under CFL lights. Color Rendering Index (CRI) is exceeding  80.

Lower installation cost.  As most of the CFLs are worthy to fit or making it easily fit  in the existing installation itself. 

Lower replacement cost:  Longer life reduces the frequency of replacement and thus keeps the replacement cost low specially, for installation put up at abnormal heights in the  hotels, auditoriums and in developed countries  where labour overhead expenses are innumerous.

Less heat dissipation: Unlike the GLS lamps,  the CFLs by turning more  energy into light than heat helps save on room cooling cost, such as air conditioner, refrigerators etc. 

Universal burning position: More versatile lamp than many others having this constraint like, metal  halide lamp    .  

Enhances esthetics of the installation: Being trendy and compact.

Slim and compact design: makes it suitable for creative luminaires.

Wide range to suit all requirements:  Available in 3, 5, 7, 9, 10, 11, 13, 15, 18, 20, 23, & 26W as compared to restricted usable range of 15, 25, 40, 60, 75, &  100W in  GLS lamps.

Demand side reduction for power: The use of CFLs reduces the energy consumption by 80% and thus helps in better demand side management for power.  The calculation shows that the mere replacement of 100W GLS lamp by 20W CFL generates saving of approximate 800 KW Hrs over CFL lamp’s average life.

Most advantageous for DG set operations:  As CFL consumes lowest wattage per lamp. 

Economical storage and distribution cost: Due to their compact size.

Environment friendly: Power saved is power generated and helps in preventing a great deal of carbondioxide and sulphurdioxide coming from the power generating thermal plants otherwise. Ultimately, enhances the quality of human life and nature around us.


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    • The Engineer profile image

      Ray 5 years ago from USA

      Fantastic explanation. Voted Up and Shared! Thanks for Sharing!