LED not that efficient.

[JSH]

Originally Posted by redpoint5

Wait, you said you replaced the 3000k FEIT bulbs with the 5000k Cree. The FEIT are the newer bulbs and the Cree older. But then you said you gave the old bulbs (Cree) to a friend, which would leave you with the newer 3000k FEIT.

Anyhow, the main thing missing is which are more energy efficient.



Is this still the most popular way to produce white light from an LED? The other method, and I believe is more efficient, is to combine RGB LEDs into a single package that gives the illusion of white light.

I replaced 4 year old 3000k FEIT bulbs with new 5000k FEIT bulbs

I still have the 5000k CREE bulbs

I don’t care one bit about any marginal difference in efficiency between the 3000k and 5000k bulbs. I was just happy to get rid of the dingy yellow light from the 3000k bulbs. In both cases the LEDs replaced incandescent.

[oil pan 4]

I'm just going to have to go to the store and open boxes to check efficiency to make sure of what I am getting.

[Stubby79]

Originally Posted by ASV

a lot of white light LED are actually ultra violet LED shining through a micro dot florescent medium.
The medium will burn away over time leaving more and more UV and less white light. the amount of light being generated stays the same.
You just can't see it.
I believe this is caused by the relatively high intensity of UV

I've opened a "burnt out" Feit (or otherwise identical) recently. It was just a bunch of 5630 LEDs fanned out in a circle on a flat piece of aluminum.

Unless the florescent medium is built in to the relatively tiny LED itself, they don't use anything like that.

Maybe the CREE ones do...they tend to have a large hump on top, rather than the totally flat 5630s. (I assued this had to do with spreading the light out)

[oil pan 4]

The phosphorescent white LED were the most common. Don't know if they are falling out of favor.
I think the move away from phosphorescent light emission is the only way LED is going to get a big efficiency jump over tubes.

[Stubby79]

I pulled the bulb off of one of mine (Luminus brand from Costco, not Fiet).



Still works:



Meaning there's no phosphorescent lining to the inside of the bulb, as I was starting to wonder. I can't see there being enough phosphor on top of those tiny chips, either (but correct me if I'm wrong).

Longevity seems ok, in spite of not having a huge heat sink. I've had to replace 1 that I know of in the past ~2 years, on lights that stay on 24/7. Not completely conclusive, but at least comparable to CFLs, which always seem to croak after a couple of years.

I'll re-purpose this bulb. 800 lumens at 9.5 watts (though double that volt-amp wise) for a couple of bucks? Drool!

Edit: They may very well have a phosphor lining built in to each LED...when you cut the power, the LEDs fade to nothing over a half a second or so. (or does the power supply have a capacitor that takes a moment to discharge?) Might explain the yellow you see on modern LEDs? (they used to all be clear just a few years back). Then again, I have red and yellow LED bulbs that are yellow on top.

Welp, I'm now thoroughly confused. Someone enlighten me!

Edit: it inst a persistent glow, like a CFL...I'm going with capacitor discharge.

[jeff5may]

Ok ladies and gentlemen, let me clear up some questions surrounding this new LED light fad.

I didn't know this thread existed until I got a message from somewhere else. I don't know if this thread or the other one on ecorenovator got started first, but they are both headed the same direction. Let me tell you this: there is nothing much different than the path LED lighting is on than the path that fluorescent lighting has already traveled.

Ok, so the thing about Cree is that they have expanded their offering by gobbling up their competition. The market has opened up for them in the downward spiral towards Walmart. They still make firefighter headlamp LED stars and off road vehicle light bars and stadium spotlight modules, but now they make a boatload of thirty eleven brands of COB lights. They pioneered the market and have the rights, so now that it has exploded they are getting their cut. Most of the big knock off brands have been assimilated at the source in China.

As you should know, there is no such thing as "pure white" light. White light is a mixture of a broad spectrum of many wavelengths of light. LED lights are made to produce a narrow output at high efficiency. The only way to produce "white" light from them is to either mix emitters or use scintillating phosphors.

The major innovation in LED lighting came in the mid 90's with the refinement of inexpensive blue emitters. It is the blue LED emitter, combined with a yellow phosphor, that makes it economical to produce a single source "white" emitter. The blend of phosphors used determines the "color temperature" of the observed light. So with all of the white emitters, we have a blue LED and a varying amount of different scintillating phosphors used to render a wide range of color temperatures.

As far as raw efficiency goes, we usually get what we paid for. Why would a manufacturing company stick research grade emitters in a lamp they can only sell for a dollar or two? It's just not economical to do so. Like I said, the market is wide open for them in the flea market direction. Ching chong works for Cree now...

[JSH]

Originally Posted by jeff5may

Ok ladies and gentlemen, let me clear up some questions surrounding this new LED light fad.

Why do you believe LED lighting is a fad? What do you thing will replace it?

[wdb]

I wouldn't be able to stand being in a room with 5000K lights for more than a few minutes. I like 3000K-3500K "halogen" color range; everything higher looks cold and blue to me.

The lights I noticed dropping in intensity were big-box PAR30 long neck replacements. They advertised output rivaling my old halogens, and they delivered it -- for about a month. Now they are putting out far less. They still work, naturally, but I almost wish they'd quit. As to usage, they're in a dark kitchen and are on probably 12 hours/day.

I've resigned myself to paying a premium for Soraa bulbs. So far I'm pleased. They've tended to start out brighter than advertised and then settle into a lower, but still sufficiently high, output. Plus I can pick from a range of color temps and CRI levels.

[samwichse]

Originally Posted by Stubby79

I pulled the bulb off of one of mine (Luminus brand from Costco, not Fiet).



Still works:



Meaning there's no phosphorescent lining to the inside of the bulb, as I was starting to wonder. I can't see there being enough phosphor on top of those tiny chips, either (but correct me if I'm wrong).

Longevity seems ok, in spite of not having a huge heat sink. I've had to replace 1 that I know of in the past ~2 years, on lights that stay on 24/7. Not completely conclusive, but at least comparable to CFLs, which always seem to croak after a couple of years.

I'll re-purpose this bulb. 800 lumens at 9.5 watts (though double that volt-amp wise) for a couple of bucks? Drool!

Edit: They may very well have a phosphor lining built in to each LED...when you cut the power, the LEDs fade to nothing over a half a second or so. (or does the power supply have a capacitor that takes a moment to discharge?) Might explain the yellow you see on modern LEDs? (they used to all be clear just a few years back). Then again, I have red and yellow LED bulbs that are yellow on top.

Welp, I'm now thoroughly confused. Someone enlighten me!

Edit: it inst a persistent glow, like a CFL...I'm going with capacitor discharge.

The yellow part on top of the chip is the phosphor.

But as blue LEDs have become cheaper, UV chips were phased out for blue color with phosphor conversion to the other colors. In filament type bulbs, the phosphor coats the whole stand.

[Stubby79]

Originally Posted by samwichse

The yellow part on top of the chip is the phosphor.

But as blue LEDs have become cheaper, UV chips were phased out for blue color with phosphor conversion to the other colors. In filament type bulbs, the phosphor coats the whole stand.

Interesting. Thanks.

Wondered what was up when my 12v leds started showing up with yellow tops. My older ones were all crystal clear. I take it that different phosphor can put out different colors, not just white?

Hey, whatever works. Gonna have to find an old bulb and compare the light output vs a fresh one.