Unique Titanium
Results 1 to 27 of 27

Thread: Luxeon K2 problem

  1. #1

    Default Luxeon K2 problem

    This isn't quite a flashlight project but rather an aquarium lighting project. I figured that some of the brains here may be able to help though.

    I am using the Xitanium 700mA driver ( LED120A0700C24F ) to power six K2's ( LXK2-PW12-R00) in series. In practice, the diver powers 1-3 drivers to full brightness, but after that the LEDs are dim. This driver should be able to drive them all to 700mA.
    LED
    http://www.luxeonstar.com/item.php?i...=LXK2-PW12-R00

    Driver
    http://www.luxeonstar.com/item.php?i...ED120A0700C24F

    Any comments/suggestions?

    Thanks for your help

  2. #2

    Default Re: Luxeon K2 problem

    Sorry, I cant give you any suggestions on the LED Setup. But I am Curious on what type of Fish Tank set-up your doing? I am very new to this whole flashlight thing. But I am no NOOB to Reef Keeping, and im sure that is what you are using the K2's on. I currently have a 55AGA with 2-250 20K MH's, and a 15G AGA with a 150W HQI MH 20K as well. Both are LPS/SPS tanks...
    What can you keep for livestock under the K2's LED lighting?

  3. #3

    Default Re: Luxeon K2 problem

    How many volts does this driver output at 700ma?

  4. #4

    Default Re: Luxeon K2 problem

    700mA constant current
    7.8-24.6V

    Here are the LED's before soldering (I solder together and jumper the two together (each LED side has a non conducting "dummy" leg".

  5. #5

    Default Re: Luxeon K2 problem

    Quote Originally Posted by freerdr17
    Sorry, I cant give you any suggestions on the LED Setup. But I am Curious on what type of Fish Tank set-up your doing? I am very new to this whole flashlight thing. But I am no NOOB to Reef Keeping, and im sure that is what you are using the K2's on. I currently have a 55AGA with 2-250 20K MH's, and a 15G AGA with a 150W HQI MH 20K as well. Both are LPS/SPS tanks...
    What can you keep for livestock under the K2's LED lighting?
    I actually have numerous FW planted tanks.

  6. #6

    Default Re: Luxeon K2 problem

    Looks like each leg is only getting only 350ma?


    Gene

  7. #7

    Default Re: Luxeon K2 problem

    That picture has 2 strings. Each string has an independent 700mA driver.

  8. #8

    Default Re: Luxeon K2 problem

    So how do you change the volts output on that driver?

  9. #9

    Default Re: Luxeon K2 problem

    I don't know how it works electronically, but it is a constant current source. It will adjust the voltage to maintain a constant current within the allowable voltage range.

  10. #10

    Default Re: Luxeon K2 problem

    Gomer,
    I would be suspicious of the high Vf of the K2 LED's and assume that this would approach the max power of the driver prematurely in comparison to the Luxeons that were around when the driver was designed. Your problem with more than 3 in series though sounds too low even for the K2's. Have you measured the voltage across the individual LED's?
    Build Prices .... some mods and builds (not 4 sale) "Nature can be cruel- but we don't have to be."~ Temple Grandin

  11. #11
    Enlightened
    Join Date
    Jun 2006
    Location
    Prague, Czechia
    Posts
    22

    Default Re: Luxeon K2 problem

    Stupid question: The driver and LEDs are drowned in the water?

    Serious questions:
    - Do you have isolated the heatsink and the bottom of the led? With Luxeon K2 you must do that, slug of the device is not electrically neutral.
    - What is the temperature of LEDs? Are they well clamped to the heatsing (over the isolating film), and is the heatsink sufficient?
    - Is the driver connected directly to the 120V AC? Otherwise, check if the source can handle the power of 20W per one driver (6 LEDs).

    I don't know about any other possible issue.
    According to specs, this Xitanium driver can handle 1 to 3 Luxeon V (700mA) LEDs, so it can handle also 2 to 6 Luxeon K2 at 700mA (the Vf is 7V for LuxV and 3.5V for K2).
    Last edited by VoiToi; 10-14-2006 at 03:59 AM.

  12. #12

    Default Re: Luxeon K2 problem

    - Do you have isolated the heatsink and the bottom of the led? With Luxeon K2 you must do that, slug of the device is not electrically neutral.
    Really? I thought the slug was neutral. Is the slug connected to the annode or cathode?

    - What is the temperature of LEDs? Are they well clamped to the heatsing (over the isolating film), and is the heatsink sufficient?
    Thermal Epoxied to the HS, but I can remove them given the info above and rethink the project.
    - Is the driver connected directly to the 120V AC? Otherwise, check if the source can handle the power of 20W per one driver (6 LEDs).
    Yes and yes.

    Thanks for your help. I think you found the reason but now I need to find a solution.

  13. #13
    Flashaholic*
    Join Date
    Oct 2002
    Location
    Baden.at
    Posts
    4,239

    Default Re: Luxeon K2 problem

    if the K2 stats even mention them not being electrically neutral, then it is for sure teh reason.

    I had the same problem with normal 1 Watters some time ago, 3 in Series worked great, 4 was impossible.

  14. #14
    Flashaholic*
    Join Date
    Apr 2002
    Location
    Boise, ID
    Posts
    2,639

    Default Re: Luxeon K2 problem

    Really? I thought the slug was neutral. Is the slug connected to the annode or cathode?
    Neither and both, it is electrically connected to each power lead via a pair of reverse-connected ESD protection diodes.

    Read this thread for a full understanding:
    http://candlepowerforums.com/vb/showthread.php?t=91700

  15. #15

    Default Re: Luxeon K2 problem

    Thanks. That really helps a lot and explains a lot of the problem...now..time to find some thermally conductive, electrically isolating films LOL.

  16. #16
    Flashaholic*
    Join Date
    Dec 2003
    Location
    western Massachusetts
    Posts
    2,287

    Default Re: Luxeon K2 problem

    Quote Originally Posted by Gomer
    Thanks. That really helps a lot and explains a lot of the problem...now..time to find some thermally conductive, electrically isolating films LOL.

    From the K2 datasheet:



    Electrical insulation between the case and the board is required—slug of the device is not electrically neutral. Do not electrically connect either the anode or cathode to the slug.


    Why not just use some thermal adhesive to isolate the slug? The trick is to precoat one surface with a very thin layer, let it thoroughly dry, then join the emitter to the heatsink with the adhesive, being careful to not put so much pressure on the emitter that you drive the slug into the heatsink.



    PhotonFanatic—fanatic@photonfanatic.com
    CPF Custom Builders and Modders
    My Blog

  17. #17
    Flashaholic* 3rd_shift's Avatar
    Join Date
    Mar 2004
    Location
    DFW. TX. U.S.A. Earth
    Posts
    3,338

    Default Re: Luxeon K2 problem

    So K2's have the same issues that the red, red orange and amber Luxeons do?

    Uh-oh.

    I'm glad I only had time to build one light with a K2 thus far.

    I have some electrically isolated stars to try out a few K2's with.

    Member Litemania has electrically isolated stars for sale cheap in the dealers corner part of the forum.

  18. #18
    Flashaholic*
    Join Date
    Apr 2002
    Location
    Boise, ID
    Posts
    2,639

    Default Re: Luxeon K2 problem

    No, they have the same issue that all other luxeon emitters have - that you must isolate the slugs if you're running them in series.

  19. #19
    *Flashaholic* IsaacHayes's Avatar
    Join Date
    Jan 2003
    Location
    Missouri
    Posts
    5,876

    Default Re: Luxeon K2 problem

    3rd, the k2's and luxeons(1,3,5) that are white/green/blue/royalblue/cyan have the same charicteristics on slug isolation. If running in paralell, or single, no problem. They have no problem with one led connected to a negative heatsink. The amber/red/red-orange have a much greater problem since their postive bondwire/lead is connected to the slug, so if the slug touches negative, then it shorts the bondwire and melts it open. The amber/red's don't have ESD diodes AFAIK because their material seems to be more resistant to ESD natrually IIRC.
    Mags: 2C: R/O, True Cyan, UV. 3C:Penta-XR-E Q5, Single SSC P4. Nitecore D10, Fenix LOD-CE, ArcAAA

  20. #20

    Default Re: Luxeon K2 problem

    Where can you get thermally conductive yet electrically isolating films?

  21. #21
    Flashaholic* monkeyboy's Avatar
    Join Date
    Mar 2006
    Location
    UK
    Posts
    2,231

    Default Re: Luxeon K2 problem

    Quote Originally Posted by Gomer
    Where can you get thermally conductive yet electrically isolating films?
    You can just spread a thin layer of Arctic silver thermal adhesive over the metal and allow it to dry beforehand.

    The datasheet for the driver you linked says it can only output up to 17.2Watts. I'd look for a different driver if I were you, K2's can be driven up to 1500mA if heatsinked properly.

    This is what you want:
    http://www.luxeonstar.com/item.php?i...ED120A0024V18F

    With this, you could drive about 6 or 7 K2's at 1500mA which would probably produce more light as 12 K2's at 700mA. Or you could drive 12 at 700mA which would be more efficient.
    Last edited by monkeyboy; 10-14-2006 at 06:14 PM.

  22. #22
    Flashaholic* kevinm's Avatar
    Join Date
    Jun 2006
    Location
    Denverish
    Posts
    846

    Default Re: Luxeon K2 problem

    Quote Originally Posted by Gomer
    Thanks. That really helps a lot and explains a lot of the problem...now..time to find some thermally conductive, electrically isolating films LOL.
    JB Weld, my friends, JB Weld. It conducts heat and not electricity.

    I've been running a reef tank (5.5 gallon nano) for over a year with Luxeon III's . The acropora growth is good as is that of the soft corals, briarium, and hydnophora. This is what got me adicted to LED's in the first place.

    I've heard horror stories with the Arctic Silver. Have any of you tried this? It's a touch expensive...unlike reef tanks which are oh so cheap.

    Kevin

  23. #23
    Enlightened
    Join Date
    Jun 2006
    Location
    Prague, Czechia
    Posts
    22

    Default Re: Luxeon K2 problem

    Quote Originally Posted by Gomer
    Thanks. That really helps a lot and explains a lot of the problem...now..time to find some thermally conductive, electrically isolating films LOL.
    You can try a baking film :-) A big role for about 1$ at every store. It is a very good electrical isolator, and even a very good heat conductor (comparable to special films for isolating from heatsinks). Sometimes I used it to isolate the transistor. In the case od LEDs better way is to use the MCPCB star, but with your strings done, I think you can try this. Then most important is to press the LED with the film to the the heatsing somehow. It that is an issue, then the JB weld or something similar will be better.
    Last edited by VoiToi; 10-15-2006 at 01:09 AM.

  24. #24
    Flashaholic* monkeyboy's Avatar
    Join Date
    Mar 2006
    Location
    UK
    Posts
    2,231

    Default Re: Luxeon K2 problem

    Voitoi,

    Are you talking about greaseproof baking paper or plastic cling film?

  25. #25
    Flashaholic* monkeyboy's Avatar
    Join Date
    Mar 2006
    Location
    UK
    Posts
    2,231

    Default Re: Luxeon K2 problem

    Quote Originally Posted by kevinm
    I've heard horror stories with the Arctic Silver.
    I'm sure Arctic silver only causes problems with circuit boards since it is slightly capacitative. Should be fine on an LED.

  26. #26
    Flashaholic* 3rd_shift's Avatar
    Join Date
    Mar 2004
    Location
    DFW. TX. U.S.A. Earth
    Posts
    3,338

    Default Re: Luxeon K2 problem

    I did lose a red/orange Luxeon3 that was arctic silvered to an osink heatsink.
    I now have an empty black annodized Osink.
    I kinda like the film idea though.

    But.....
    What is that electrically isolated, thermally conductive material that was used on the Luxeon1 stars and the empty pcb stars?

  27. #27
    Enlightened
    Join Date
    Jun 2006
    Location
    Prague, Czechia
    Posts
    22

    Default Re: Luxeon K2 problem

    Quote Originally Posted by monkeyboy
    Voitoi,

    Are you talking about greaseproof baking paper or plastic cling film?
    I mean something like this: http://www.ifyoucare.com/Baking%20products.htm

    I bought one role of this http://www.a1-gastro.cz/DetailPage.a...PG=49515&Nav=1 before years and used it also for baking :-)

    I am studiyng electrical engineering and one teacher showed us results a test - comparing this baking paper with some typical termal-conductive, electrical isolating film, and thermal conductivity of baking paper was only about 20% lower ... and you can buy 5 square meters for 1 $ in almost every store.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •