OT: CFL Bulbs

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On Thursday, December 31, 2015 at 7:30:44 PM UTC-8, Doug Miller wrote:

Alas, that's not literally true; no LED is 50% efficient, because the light can come out of the chip, or go the other way (and get absorbed). Fluorescent tubes could conceivably win the efficiency battle some day (because they don't have to include opaque parts).
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wrote:

Not true. LEDs don't absorb 50% of their generated light. In fact the direction of the beam is quite small. Diffusers are used (which do absorb some light) to make the light more omnidirectional. It's no problem to get LEDs that are twice as efficient (measured as getting twice the lumens per watt) as a fluorescent.
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On Friday, January 1, 2016 at 6:35:35 AM UTC-8, krw wrote:

Irrelevant, of course; the light is not formed as a beam inside the bulk of semiconductor, but at glued-on lenses. That's only AFTER the light escapes from the solid semiconductor chip.
You'd have to count up all the quantum jumps that produce a photon, and note that less photons than that are seen to light up the room.
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wrote:

No, it's not irrelevant. There is no rear beam to be absorbed by the emitter. Thats just wrong. THe beam is quite narrow and unidirectional. You do *NOT* lose half the energy immediately as can be easily seen from efficiency numbers.

Not at all true.
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Doug Miller wrote:

--
GW Ross

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wrote:

Put a 15W incandescent bulb in your hand and it will get "uncomfortably warm", too. ;-)
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On 12/31/2015 8:01 PM, Bill wrote:

calories, I would suspect that a 60 watt LED would produce the same heat as a 60 watt tungsten. (For give me if it is no quite right but it has been 50 years since I did this sort of thing)
However I believe LEDs are compared to Tungsten by the lumens they produce (amount of light) and a when you are talking LED you are actually saying they produce the light equivalent to a 60 watt tungsten bulb, not the LED is 60 watts.
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On Thu, 31 Dec 2015 22:28:37 -0500, Keith Nuttle

Yes and no. Since the LED is more efficient, more of the power will go into light (thus less into heat). The light is eventually turned into heat, so yes, in the long run, the heat output is the same but less heat will be dissipated in the fixture.

state the actual wattage but it will be significantly less. Depending on the particular LED, this can vary a lot.
The problem is that LEDs are semiconductor devices so can't tolerate much heat. Every 10C rise in heat will probably reduce its life by 2.5x (or perhaps even more).
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On 12/31/2015 10:28 PM, Keith Nuttle wrote:

Yes, we got used to using watts, but lumen is what we really need to know so you can compare any type of bulb. It will take most of a generation to get used to that.
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You probably are not going to find a 60 watt LED, it would probably be brighter than the sun. LED's marked 60 watt equivalent are just that, equivalent. A 12-14 watt LED is equivalent in brightness to a 60-70 watt incandescent. And FWIW a 15 watt LED bulb hardly feels warm even when left on 24/7. The same said about a 15 watt incandescent will burn you if you touch it.

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LED's are 'effective' watts. They compare the light output vs a standard and mark the bulb. The better LED's have several die that send different color to be more like daylight. Some are warm.
Martin
On 12/31/2015 9:28 PM, Keith Nuttle wrote:

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wrote:

much cooler than incandescent bulbs. Overheating the bulb will *greatly* shorten its life. The issue becomes the bulb, not the enclosure.

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Right - in the bathroom the fan unit wants a 40. And make it darker than without the light almost. I put in a 60w LED (effective) and it is a 16 heat watt unit. Runs cool and won't melt the plastic. Shows more light and my beloved loves it. No brainier on that one.
Martin
On 12/31/2015 7:01 PM, Bill wrote:

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On 12/30/2015 3:40 PM, Meanie wrote:

How do you get them for free?
--
Jeff

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On 12/30/2015 4:24 PM, woodchucker wrote:

Sales rep from work.
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snipped-for-privacy@ghostmail.cc says...

60w-equivalent LED bulbs go for about 2 bucks a shot at Home Depot right now.
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On 12/30/2015 8:13 PM, J. Clarke wrote:

Not here. They are still about $7 ..
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Jeff

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On 12/31/2015 4:35 PM, woodchucker wrote:

6 pack $11.97
http://www.homedepot.com/p/Feit-Electric-60W-Equivalent-Warm-White-A19-LED-Light-Bulb-6-Pack-A800-830-10KLED-6-48/206397936
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Bought two 40-watt equivalent LED bulbs the other day at HD and both were $14 each. Was that a special in your area?
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was heard to mutter:

They're still running in the $5-10 neighborhood here, so maybe the power company was investing some of your hard earned money in making the bulbs appear cheaper to you. Ours did that with the CFLs, we stocked up at something like 4 for 99 cents. Almost wish we didn't, as LEDs are so much better, but they're still not cheap yet.
Puckdropper
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Make it to fit, don't make it fit.

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