Brlux said:
So NewBie do you have issues with the Luxeon LED? I think I have seen several less than positive posts about Lumileds products from you. I hope that this is not read wrong. It's not that I am mocking you or anything. If there is someting about them that you think does not hold up to the hype I would be intertained to hear it.
First off, you should notice I purchased them, so issues? No. In fact I've purchased quite a few, many times.
Maybe you just don't understand the hype in their press release.
Lets put it in a simpler mind frame for you.
Lets make 1 Lumen = 10 Horsepower (It isn't, it is for the sake of example.)
I advertise our cars get 230 Horsepower.
So lets substitute:
"A white LUXEON ® III Sportser, for example, is now priced at $3.45 for quantities less than 10,000 units; this delivers an incredible 230 horsepower per dollar."
Now I hand you the cash and you sell me a car. It gets 149 horsepower. So I take it back. We go thru all the cars at the dealership and find one that can do 195 horsepower. None that can attain 230 horsepower. The sales guy says, you have to accept the 145 horsepower car (no you cannot trade it), as this is what we have in stock. But I can assure you that other dealerships have cars that can get 230 horsepower.
So, would you be happy with your car that has 149 horsepower, even though it is advertized as 230 horsepower? If you got really pissed and moaned groaned and you hired a lawyer, and got the best car on the lot that had 195 horsepower, would you be pleased?
How would you feel about the advertizing that stated 230 horsepower?
So, if LumiLEDs claims 23 lumens per dollar in their advertizing and on their Luxeon pages, and they ship parts that are 14.99 to 19.5 lumens per dollar to you, can you see the parallel?
If the dealer sold you the car, and it was missing 35% of it's claimed performance, where would that put you, as far as customer satisfaction?
Would you be any happier if it was missing 15% of it's claimed performance?
Now lets take real world numbers, just so folks can see what really happens:
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What if I told you that the core of the engine block had to be held below 25 degrees Celcius, in order to attain even the 149 horsepower? Then I showed you on a chart, that in typical usage, the engine would reach 80 degrees C, and you'd loose a further 20% of your horsepower?
So now, once your car warms up, you are missing 55% of the claimed horsepower?
For reference, I will further refer you to page 10, the first graph, follow the line for white, to 80 degrees Celcius.
http://www.lumileds.com/pdfs/DS45.PDF
But wait you say, it doesn't reach 80 degrees C. Yes it does.
The top of Page 7 shows you the Thermal Resistance from die to slug. It is 13C/W. Let see, we have a 3 Watt Luxeon, so the temperature will rise by 13 C/W * 3 Watts = 39 degrees Celcius rise.
So, a fella thinks so what...
Ah, lets look at the significance of this 39C rise in the die temperature a little deeper. The ambient temperature is 25 degrees Celcius. The die will
rise by 39 degrees C. So 25C + 39C = 64 Degrees C.
So, there you say, the die didn't rise to 80C.
Ah, but wait...any practical heatsink you have will rise in temperature. If you have ever held a Luxeon LED flashlight in your hand, you will notice how it's gets pretty warm with a little use. Lets just say it gets a little warm and rises by 16 degrees C (which is probably an underestimate).
Well now, we have a heatsink that has risen in temperature by 16C. So we take the ambient temp of 25C, and add the 16C, and you get a flashlight body temperature of 41C (pretty low, we have seen lights that reach 70C...).
So, then a fella thinks, so what.
Well take the Flashlight temperature of 41C, which means the slug of the Luxeon will be no less than 41C (probably hotter in reality), then we add the 39C rise from the Luxeon slug to the die in the Luxeon.
Bingo, there is your 80 degree C rise, and you loose an additional 20% of the output, as shown by the chart on Page 10.
So, now your advertised car that did 230 horsepower, now gets 126.5 horsepower.
(btw, notice how lumens are measured at 25C Tj, which is the LED die junction temperature- Refer to page 4,
http://www.lumileds.com/pdfs/DS45.PDF)
Remember, the beef on the whole deal was only about the shipment of parts that didn't meet their advertising claims. Not about the lumen depreciation due to temperature, that I just talked about.
For those too new to understand what a SX1J emitter is, I will refer you to Page 3, Table 4. This will show you the actual Lumen output of the S bin.
http://www.lumileds.com/pdfs/AB21.PDF
Divide that by the 3W input power that the part is binned at, and you arrive at the lm/W. For the S bin, this works out to 51.7 to 67.2 lumens.
Price was 3.45 ea. So if we take 51.7 lumens, and divide by 3.45, you arrive at 14.985 lumens per dollar. And if we take the top end of the S bin, 67.2 lumens and divide that by 3.45, you arrive at 19.478 lumens per dollar.
