Super NRG Savers

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We are talking about uniform illumination in the room. As a spot light, yes, you can read under 3-5W light.

I have used LED lights and 10W LED light is not sufficient for uniform illumination in a normal size room.

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how many LED Lamps should be used to replace 40 watt Flourecent tube?

A linear light of 20W in 4 feet length or 2 feet length is sufficient to replace a 40W tube light.

Have a look at: Channle Type Linear LED Light

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We are talking about uniform illumination in the room. As a spot light, yes, you can read under 3-5W light.

I have used LED lights and 10W LED light is not sufficient for uniform illumination in a normal size room.

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Well that is an issue, LED lamps need proper reflector. I have seen a LEd 3watt torch and it was more bright that any other (torch except the big one).

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Well that is an issue, LED lamps need proper reflector. I have seen a LEd 3watt torch and it was more bright that any other (torch except the big one).
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LED Lamps, as a matter of fact, don’t need any reflector becuase LED itself is a directional light source with viewing angles available from 15-140 degree. While CFL light sources are omnidirectional and the light going upward or sideways is reflected back (using reflectors) at the point of interest.

The reason why some LED lamps have lens on LEDs to make the beam angle smaller e.g. if a light is made up of LEDs having 120 degree beam angle and you need to make it a spot light, then you use external optics i.e. Lens. A typical example is a surgical light where doctor needs only a small area to be well illuminated.

So LEDs when used in general wide area illumination don’t need to have any Lens. And a reflector would have been needed, should LEDs emit light in all directions which is not the case.

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There are basically two separate parts in energy saver lamp. One is its CFL tube and other is its power supply which of course has capacitors inside.

Both parts have separate life span. Usually the CFL part fails (or degrades) first. It has electrodes inside which have a finite life. Also CFL's performance is highly temperature dependent. In winter, you might have noticed that CFL (energy savers) become very dim. LEDs don't have such problems. They don't have electrodes, they are not ambient temperature dependent.

Power supply failure also occurs in CFL making them dead. It is usually semiconductors in the power supply which fail due to surge / spike. Capacitors can survive more abuse but semiconductors can not. A milli second over voltage surge is sufficent to destry a semiconductor.

Life span of a good quality (not a toy grade) LED is more than 50,000 hours (on 10hr/day usage, it can have more than 10 years life). But to achieve ths life, there are certain conditions most importantly LED should never be over-drived and its heat must be adequately removed.

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