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Luxeon Star LED's

Discussion in 'Electronic Design' started by Jason S, Jun 18, 2006.

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  1. Jason S

    Jason S Guest


    I am very interested in those Luxeon Star LED's. I've never used one
    before, but I've read some very interesting things about them, and I am
    thinking about using one in my project.

    I have a few questions about them (info which I can't seem to find on the

    1) For those of you who have used one, are they worthwhile? Are they
    really that bright?

    2) I currently have a high brightness white 12-LED Globe from Jaycar
    Electronics (see link).
    The brightness of this LED globe is quite good, but I want brighter! How
    would the brightness level of this compare to a 1W, 3W and 5W Luxeon? I am
    only used to "MCD" type measurements, not "lumens" per watt.
    The Silicon Chip website shows two projects where luxeons are used outdoors
    at night... Surely they can't be *that* bright?!

    3) If I was wanting to power up a 3W or 5W Luxeon Star, what would be the
    most *simple* power supply I can connect to it that would fit nicely into a
    UB5 Jiffy Box (83L x 54W x 31D mm) - including the luxeon heatsink? I've
    seen some luxeon drivers around on the web but they seem too big in size for
    my project, probably because they include special functions like low battery
    drain, low power cut-off, brightness control, etc (features I don't need
    which take up board space right?).. Note that I will be connecting a *12V
    power adaptor* to it (as opposed to a battery), so I won't need most of
    those features. The smaller the driver circuit, the better =) Any ideas?

    Thanks in advance,

  2. Zak

    Zak Guest

    Lumen is total light output. It is like saying "equivalent to a
    so-and-so many watt lamp". Not that Lumpens match watts, but you get the
    idea. A 10 watt lamp can be in a reflector in which case it is very
    bright in one direction, or it is not and it is rather weak in all

    MCD is millicandela which is candlepower. It is how bright it shines.
    The more directed the higer the MCD or candela rating. That is why
    ultra-bright LEDs hardly can be seen from the side.

    Now back to the Luxeon: compare the power input of the LEDs for
    comparison. You have 12 LEDs now at 30 mA each at 3.something volt each.
    That is just above a watt. You can expect the Luxeon 1 watt to be in
    that ballpark. But the Luxeon will radiate in a wider pattern I think.

  3. Jason S

    Jason S Guest

    Thanks Thomas for answering question 2 for me.
    So what you're saying is a 1W Luxeon would be *about* the same brightness as
    the LED globe I have? Hmmm. I think I'll need to aim for 3W luxeon (would
    that mean up to 3 times brighter than 1W? Sorry, dumb question, lol).

    Now I just need help on question 3 from somebody. =)

  4. Jason S

    Jason S Guest

    I think I found something....
  5. Almost certainly not.
    I have a Jaycar 12led headlamp and a proper Princeton Tec EOS 1W
    The Princeton tec EOS blows the Jaycar out of the water.
    The EOS for example can easily light up a 30m high waterfall at night
    from about 30m away, the Jaycar throws a very dim light by comparison.
    The EOS does have a proper designed reflector though, designed for long
    throw with a mild dispersion pattern. The Jaycar is simply the LEDs on
    their own with a wide pattern, the reflector in it does nothing.
    You can get the Star with or without a built in reflector/lense I
    believe, and that will make a great difference depending on the
    Essentially, yes.

    What do you want to use it for?

    Dave :)
  6. Jason S

    Jason S Guest

    Hi Dave, thanks for your input.

    I want to use it for a disco light - The light beam will just be thrown
    around in a dark room at various speeds (will be used with a pan/tilt module
    I am working on). =) .... with other lighting and party fog, of course!
    I will be using collimating lenses with the star to get a nice, sharp beam.
    I want to adapt LED technology and try and get away from the incandescent

    I can see you can get *coloured* stars! Only seen 1W and 3W ones. I wonder
    if you can get 5W ones as well.

  7. Sounds like fun!
    For indoor use in the dark at close range I'd suggest that the 1W would
    be plenty. The 1W is terribly blinding if you look directly into it, I
    can't imagine what the 3W or 5W would be like. The 1W is much cheaper
    too of course.

    If you are pulsing the LED with a long off duty time then you can
    probably get away with a much smaller heatsink than recommended.

    Now I'm thinking a modified spinning disco ball with a 100 x 1W Stars -
    that would be something!

    Dave :)
  8. The Stars require a constant current supply, so the simplest solution
    would just be an LM317 connected in constant current mode.
    Not the most efficient with 12V input though, as you'd be wasting about
    3W in the regulator.

    Dave :)
  9. Jason S

    Jason S Guest

    That might be true, but I'd rather too bright than not bright enough... I
    will probably go for the 3W. I am thinking 5W would be too bright too.
    Pretty expensive anyway.
    Well, now that you mention it, I wil be using both methods.... steady and
    strobing. Will therefore need to use the recommended heatsink for steady
    LOL! That would be very fiddley!

  10. Jim Yanik

    Jim Yanik Guest

    I was in Wal-Mart yesterday,and they were selling a 3W Luxeon LED
    replacement lamp for Maglite 3-cell flashlights,for $19 USD.

    It didn't look like it had proper heatsinking at all,it looked just like an
    ordinary lamp base.
  11. RHRRC

    RHRRC Guest

    Not exactly a bargain at those prices.

    More than likely it will be running overly hot so output will be a bit
    low and life/degradation seriously affected.

    However bear in mind that the low voltage lamps used in small
    hand-torches have horrible lifetimes (nom lifetimes can be as low as 25
    or 50 hours) but give a usefull life because 'household' torches are
    not used very much at all and even when used - not for very long at a
    Stored away between uses the battery voltage is often well down giving
    a much extended lamp lifetime and a miserable light output.

    The high color temperature of the leds used in these torches leads many
    to assume they emit more light than is the case. The small source
    dimensions also make them appear 'brighter' which is good for marketing
    if irrelevant to their use.
  12. GregS

    GregS Guest

    Right now I am going to try and remove Leds epoxied to copper
    without damage. Wish me luck. I need to reposition the Led's.
    The epoxy is kinda thin since I sprinkled diamond dust in it.

  13. "1 watt" Luxeon when used "as directed" most typically consumes 1.2
    watts. The latest white ones that I know of supposedly typically produce
    45 lumens when used that way when colled sufficiently for chip junction
    temperature of 25 degrees C, which requires heatsink slug surface
    temperature mabe 7-8 degrees C. Expect light output about 6% less with
    temperature 18 degrees C warmer than that.

    The "3 watt" white ones in comparison with the more typical 700 mA drive
    current typically consume 2.6-2.7 watts and produce 65 lumens of light
    when doing so when cooled sufficiently to have their chip junction
    temperature 25 degrees C. requiring the surface of the LED's heatsink slug
    to be cooled to about -9 to -10 degrees C. Expect with temperature 40
    degrees C warmer, light output to be about 14% less.
    80 lumens is typically achievable from white "Luxeon III" at 1 amp, with
    typical voltage drop 3.9 volts so power consumption would typically be 3.9
    watts. Again, this is with cooling sufficient to have the junction within
    the chip at a temperature of 25 degrees C, and the heatsink slug surface
    of the LED needing to be cooled to about -25 degrees C to achieve that.
    At 50 degrees C warmer than that, expect light output about 18% less.

    Based on how I see the DS25 and DS45 datasheets from Lumileds...

    - Don Klipstein ()
  14. They do exist, not for all colors, and price increases more than
    performance for most applications.

    Keep in mind that 3W Luxeon has same chip size as 1W but 5W has a 2x2
    array of same size chips - making any collimated beam up to twice as wide
    (or twice as blurry).

    - Don Klipstein ()
  15. Jason S

    Jason S Guest

    haha, well, good luck! =)
    why are you removing them again?

  16. Jason S

    Jason S Guest

    Thanks for the info Don.
    Hmmm, these things are starting to remind me of the charging of bloody SLA
    batteries when you talk about temperature and heatsinks and stuff! Jaycar
    Electronics have got these 'Heatsink Pin Grid Array with adhesive thermal
    transfer tape' (CAT HH-8580). These wouldn't be sufficient for 3W stars?
    Its says it has a thermal resistance of 5.9 degrees celcius per watt. If
    not, what if I add a small cooling fan as well? Trouble is, all of this
    needs to fit into an ABS box (will be ventilated of course) size approx 83L
    x 54W x 31D, but all the electronics will be in another box close by. What
    do you suggest? I've never used these things before.

  17. GregS

    GregS Guest

    I have them currently spaced so there is no clearance between them.
    I am going to use fiber optic to couple 9 into 1 light source.
    I also use a peltier devive to pump heat out faster from the Led's,
    and from the copper to aluminum CPU heatsink and fan.

  18. GregS

    GregS Guest


    I need 9 or 10 of these ASAP. ???

    I tried taking the things off the sink. Amazing the way they are made.
    I tried heating the sink to 150 F so the epoxy stuff softems.
    Well everything softens. The metal bottom piece is attached to a wafer
    with some kind of glue or epoxy. Some kind of sparkly stuff also, which
    looked like dimonds, but I believe there is no electrical insulation between
    the wafer and sink. This little sink is mated with the larger aluminum
    sink sold as a star. With the little sink and attached wafer on the bottom, a gel
    like material in between the wafer and top clear plastic envelope. The connections are
    made and a plastic outer rim is then attached.

    I have a 6 week 50 min order to make unless I can find a interim supplier.

  19. GregS

    GregS Guest

    I just ran across the Phillips Luxeon K2 series. Anybody know
    anything about these. They seem cheaper than others, but
    I have not mad total comparisons.

  20. RHRRC

    RHRRC Guest

    They do what the datasheet(s) say they do.
    The data from Lumileds is fairly comprehensive on the luxeons

    The K2's are desiged to compete with (particularly) the Cree and Osram
    'power' white leds - maybe Seoul Semi should also now be included.
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