# LED's:power, 5mm, SMT



## gcbryan (Jun 10, 2011)

This is a general question I guess. My interest is in headlamps but it's a LED question so I think this is the best forum.

Which are more efficient in general..."power" LED's or whatever you want to call them such as Cree XP-G for example, or 5 mm LED's or SMT LED's? Is surface mount even a different category or are there XP-G's in surface mount?

It seems as used in headlamps anyway that SMT LED's are much less efficient than power LED's. I'm not sure if this is across the board however (that's why I'm asking here). How do 5 mm LED's compare?

Is it just that power LED's are able to produce more output or are they more efficient as well. Are 5mm LED's more efficient in their lower range? How do SMT LED's fit into all this?


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## LEDninja (Jun 10, 2011)

Power LEDs vary a lot in efficiency.
Early Luxeons about 30 lumens per watt. Later ones 42 lumens per watt.
Cree XP-G about 140 lumens per watt.
Neutral whites that let you see better outside are 10% less efficient. Warm whites are up to 30% less efficient.
You can not just go in a store, pick up a headlamp, and know the efficiency of the LEDs inside.
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5mm LEDs especially the cheap Chinese versions have a nasty of burning out in extended runs. They are usually too blue to let you see clearly.


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## gcbryan (Jun 10, 2011)

What I'm trying to figure out is why in a particular headlamp they would use a Cree XP-E for the main spot beam and have an output of 100 lumens which is fairly efficient as far as current and therefore runtime and then use surface mount LED's for the flood beam and only have a high of 25 lumens and yet the current draw on the flood leds is higher than the main beam at 100 lumens?

I'm guessing it's cheaper but is it necessary for those SMT LEDs to be that inefficient? I also see that some companies use 5 mm LED's for the flood beam so I was wondering if all those headlamps are that inefficient as well or if perhaps 5mm LEDs in general were more efficient (I understand they typically have a blue tint and aren't as pleasant to look at).


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## LEDninja (Jun 10, 2011)

If you go to the superbrightleds LED page:
http://www.superbrightleds.com/cgi-bin/store/index.cgi?action=DispPage&Page2Disp=/leds.htm
Scroll down to the 5050 SMD section, then click on the 1st pure white buy now button. $0.65
Scroll down to the Cree section, then click on the XPE white buy now button. $ 8.95
You get what you pay for.

If the maker of the headlamp use 1 XPE in a reflector for throw and another XPE for flood then the efficiency would be the same but his costs are $8 more and retail prices for the headlamp would be $32 more - by the time manufacturer's profit margin, distributer;s cost and profit margin, retailer's cost and profit margin, import and sales taxes are added in. So to keep prices down the manufacturer uses crud LEDs with clone dies of stuff Nichia came out with in the LAST CENTURY.


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## gcbryan (Jun 10, 2011)

LEDninja said:


> If you go to the superbrightleds LED page:
> http://www.superbrightleds.com/cgi-bin/store/index.cgi?action=DispPage&Page2Disp=%2Fleds.htm
> Scroll down to the 5050 SMD section, then click on the 1st pure white buy now button. $0.65
> Scroll down to the Cree section, then click on the XPE white buy now button. $ 8.95
> ...



I'm now looking at that page and trying to get an idea of the current required to get the figures listed. For the pure white SMD 5050 it was MCD of 6000 and an angle of 120 so using the converter that is 18 lumens. What current was required to produce that? 60 mA?

For the XP-E cool white it shows 100 lumens is this a 350 mA?

If I've understood the specs for the two listed above wouldn't they be roughly equally efficient? 100/18 = 5.5 so 60 * 5.5 = 330 (mA)

Thanks.

By the way I get your point regarding the prices and markups although each part doesn't have to be marked up. Literally all it has to be marked up is $8.00 and they would have the same profit margin on that product. I'm sure they can get XP-E for less than $8 as well but your point is well taken.


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## LEDninja (Jun 16, 2011)

One more point I did not think of at first. You need a lot more light for flood. So even if they use all XPGs at the same efficiency they would use just 1 XPG for throw but 2 for flood cutting your battery life in half.


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## Lynx_Arc (Jun 16, 2011)

One thing I have seen when it comes to headlamps is manufacturers don't tend to take advantage of efficiency to increase runtime but rather use it to bolster higher output claims instead. The newer LEDs of any type tend to be more efficient and at low output levels it matters less if you get an extra 20 hours of runtime if you are already getting 100 hours to begin with. Typically replacing LEDs with more efficient ones doesn't necessarily give you increased runtime but sometimes reduced runtime because of lower operating voltages of newer LEDs make them easily consume more power and use it up faster. So basically designing a light around the LED efficiency and its voltage and current operating characteristics is important too.


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