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Thread: LED Evolution...

  1. #1

    Default LED Evolution...

    Can someone point me to a thread on this website or another website that lists all the different LEDs used in flashlights from an evolutionary standpoint? I am fairly new to dissecting this information, and would like to educate myself. Thanks.

  2. #2
    Flashaholic* AnAppleSnail's Avatar
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    Aug 2009
    South Hill, VA

    Default Re: LED Evolution...

    There are lots of places to read about this on the forum. But LEDs haven't really evolved so much as been redesigned and improved. The main difference between the first Lux1 and the newest Cree/SSC/etc is the ability to work efficiently at higher current.

    Try Flashlightreviews, start with the old ones, to see the effects of LED limitations. And it's not like old LEDs go extinct...
    My biggest light-hog is my camera.

  3. #3
    Flashaholic* bshanahan14rulz's Avatar
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    Jan 2009

    Default Re: LED Evolution...


    ard to navigate, easy to find something interesting.

  4. #4
    *Flashaholic* idleprocess's Avatar
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    Feb 2004

    Default Re: LED Evolution...

    There are two major evolutionary paths of the LED as far as I know:

    Indicator / lamp style
    (3mm/5mm/10mm and the incandescent T-series equivalences I forget)
    The beginnings of the LED packaged it like common incandescent indicator lamps of the time. "Indicator" is an important way to characterize most of these devices since the amount of power they can safely dissipate is pretty minimal (on the order of 100mW or less).

    Related developments:
    So-called "Piranha" or "Superflux" LED's with a rectangular package and 4 legs to attempt to better dissipate heat

    SMD LED's came along with other surface-mount electrical components for backlighting, truly miniaturized indicators, and - with better efficiency and thermal design - general lighting. Some of the SMD LED's on the market bleed into power LED's, described below.

    Power LED's
    Beginning most famously with the Luxeon about 10 years ago, power LED's dissipated entire watts of electrical energy and produced tens of whole lumens of light - making LED flashlights more than just "showerhead" arrangements and paving the way for LED-based general lighting. Power LED's require very careful package design to rapidly and efficiently conduct heat away from the die itself as well as good optical design since they will typically be required to produce a consistent and useful pattern for coupling to optics. The die itself on power LED's is also considerably larger than on indicator LED's.

    Related development:
    Power LED arrays cluster numerous low- to medium-power dies into a single package in a parallel, series, or series-parallel arrangement. Lamina Ceramics devised some of the first big arrays intended for general lighting as panels as opposed to point sources. Some devices that we would consider power LED's are actually arrays - the Luxeon V, the Osram O-Star, the Cree MC-E - but are packaged like power LED's with optical performance good enough to work fairly well with reflectors/optics for point sources. Bridgelux makes some of the better arrays on the market in terms of price/performance, but their intent is clearly for diffuse general lighting.
    I apologize that this letter is so long; I did not have time to write a short letter

  5. #5

    Default Re: LED Evolution...

    I'm curious about this LED evolution myself. I signed up here a couple years back to find a good bicycle light and saw that there were P7s and Q5s. Now there are R5s.

    Clearly, there's an alphabetical evolution going on here, isn't there???

    P -> Q -> R

    I'm assuming that R3 is stronger than Q5, yet an R5 is still stronger than an R3.... but I'm not 100% sure about that just yet.

    Also, there's XPE and XPG and XPL... "emitters", is what they're called??? These also seem to be taking an alphabetical approach.

    Surely, an "evolutionary chart of LEDs" would be rather elementary, wouldn't it?? :P

    I've seen it said that for small, pocket-sized lights (AA, perhaps?)... XPG is actually better than XPL.

    What does it all mean???

  6. #6

    Default Re: LED Evolution...

    Here ya go....

    "The details of LED technology..." -- http://www.candlepowerforums.com/vb/...=1#post3875561

  7. #7
    *Flashaholic* idleprocess's Avatar
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    Feb 2004

    Default Re: LED Evolution...

    P1, Q2, R5 ... for Cree, those are "flux bins."

    What's flux and what's a bin, you say?

    Flux is a generic term for brightness in the LED business.

    Bins are used to categorize performance. As part of the manufacturing process there is normal variation, with some parts performing better than others. During the heyday of the Luxeon Lumileds used to bin for Forward voltage (electrical efficiency), tint, and flux. Cree bins primarily for flux; their forward voltages are pretty consistent and their tints seem tight enough that just going by CCT (Correlated Color Temperature or degrees Kelvin) is tight enough for most applications.

    So a R1 is brighter than a Q2, but a R4 is brighter than a R1.

    Cree has released a steady stream of differing LED chips and packages in recent years. XR-E, XP-G, XM-L, XB-D, etc all define specific packages - many of which share the same LED chip within - with different levels of performance both in terms of flux an optical performance. The XM-L is hailed as being one of the most efficient LED's on the market, but its large chip/phosphor area makes it less-ideal for reflector applications (most flashlights) since that makes it less of a point source.

    There have simply been too many LED's out there to devise a neat chart. Perhaps the DoE has some chart as a result of their L-Prize (or some other semi-neutral organization).

    Companies that come to mind in recent years when it comes to the evolution of LED's (not all of which are terribly important):
    Lumileds (now Philips)
    Seoul Semiconductor
    Lamina Ceramics
    Luminus Devices
    I apologize that this letter is so long; I did not have time to write a short letter

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