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Thread: DIY COB LED info

  1. #41

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    I hear you. In this situation the leds could be run without active cooling at all. They will last longer with active cooling but can be run with passive cooling (at least that's my understanding). But I definitely see the benefit in cooling with some type of liquid if needed.

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    Quote Originally Posted by aerogrower View Post
    I hear you. In this situation the leds could be run without active cooling at all. They will last longer with active cooling but can be run with passive cooling (at least that's my understanding). But I definitely see the benefit in cooling with some type of liquid if needed.
    I'll get you a link to the thread when I get onto the desktop.
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  3. #43

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    Quote Originally Posted by Est View Post
    Unfortunately I don't have a convenient way to tap and drill the heatsinks at the moment. Going to do some more looking, but I may go with an option that's pre-drilled for compatibility with an appropriate holder. Worst case, I know you posted some a page or two back. Have you stumbled upon anything else in the meantime?

    Aero, looking good! What're you planning on growing under the lights?
    Est, the cheapest predrilled heatsink for CXB3590 ($27.30), I know, is the Mechatronics Giga, which I mentioned earlier. If it were the smaller CXB3070, there would be cheaper predrilled options. Here is the link:
    https://www.cdiweb.com/ProductDetail...574068/pid=468
    Cutter Electronics carry Mechatronic, too. But I'm guessing that the shipping could be expensive. The sales rep (Mark) there is helpful. I'll ask him if there is an alternative heatsink for CXB3590.

    It should work in passive. Here is a bit of technical details. The capacity of heatsink is rated as thermal resistance. This one has 0.53C/W. Smaller number is better, and this is pretty impressive number (reason for the high price). This means that if the heat generate is 1W, the temperature goes up by 0.53C. With CXB3590 driven at about 50W (700mA for 72V version or 1400mA for 36V version), it releases 24W of heat (using the value calculated here). So the temperature goes up by 24 * 0.53 = 12.8C. This is at the area where you attach COB. If ambient temp is 30C, then it becomes 42.8C. The actual temperature of LED (called junction temperature) is higher, but it should be well below 85C. I haven't measured the temperature of LED, but I touch the heatsink next to the COB, and see if it is too hot, I raise the voltage to drive the fan. So I think this one should work passively, but if it is getting hot, maybe you can attach a fan on the top.

    If drilling is possible, you could use self-tapping screw. With a decent drill bit (and a couple of spares), it isn't too bad. If not, one of the leading COB mobs, SupraSPL, uses thermal compound and Kapton Tape as the main way to attach the COB to the heatsink (scroll down to message #332).
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    It is beyond my comfort zone, but he has been doing it for a long time without problems, and many others follow it. If you go this way, I think you should get the big heat sink from HeatsinkUSA instead of CPU heatsink. There is more space to attach the tape, and it is good to be "semi-passive" in a small chance of fan failure.

    Aero, it looks great! Did you use rivets to attach the angle to the heatsink?
    Last edited by naoki; 01-20-2016 at 04:05 PM.

  4. #44

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    It's true that lower temp influence the longevity and lumen maintenance. With longevity, I have seen some data showing it is a diminishing return. Or I should say that they last long enough below certain temperature of LEDs. I think they use the case temperature, Tc (the temperature you can measure on the access point on the cob) of around 85C, as the standard (they can tolerate much higher temp). The junction temperature (the actual temperature individual LED is experiencing) is higher than this. I haven't measured Tc, but I think that is is less than 60C in our kind of setup (I might be wrong here). So ours should last long enough.

    Active cooling is advantageous to reduce the cost (and weight) without sacrificing the efficiency. Indeed, if I can justify paying lots of money for giant heatsink, simplicity of passive cooling is much more appealing (less things to break).

    I got parts for water-cooled CXA3070 x 2, but I haven't assembled it yet. I want to put them inside of a relatively small enclosure (for cool-intermediate growing orchids in 75/55F range), and pump out the heat. This relocation of heat is a good advantage for this kind of application. The cost is quite a bit higher, though. We'll see how it goes.

  5. #45

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    Naoki..yes I riveted the heatsink to the outer rails. I also like the idea of drilling and using self tapping screws. It was a lot of extra work to drill and tap those little screws that hold down the COB holder. I still would rather have the COB in a holder screwed down rather than the Kapton Tape. I know that those screws aren't going anywhere! These should last a very long time why cut corners?

  6. #46

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    Est, I've been communicating with Matt, and he said that he tested CXB3590 on IceLED Ultra or something similar. The data sheet doesn't specifically say it, but he said there were predrilled holes which matches with 50mm spacing for CXB3590. He was going to confirm this, but I haven't heard back yet (it probably be will be next Mon). He wasn't sure about the model; IceLED Ultra, Xtra Ultra, or Ultra VS (and I'm not sure what are the differences between these models). Here is the link to data sheet.
    Last edited by naoki; 01-22-2016 at 05:47 PM.

  7. #47

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    Quote Originally Posted by Est View Post
    Unfortunately I don't have a convenient way to tap and drill the heatsinks at the moment. Going to do some more looking, but I may go with an option that's pre-drilled for compatibility with an appropriate holder. Worst case, I know you posted some a page or two back. Have you stumbled upon anything else in the meantime?

    Aero, looking good! What're you planning on growing under the lights?
    Est
    Don't know if it would be cost effective or not...if you wanted to order the cpu/fans that I did that are undrilled, and had them sent to me I would be glad to drill and tap them for you. Then for just cost of shipping from me to you you would be all set. Just a thought it would save you paying three times as much for pre-dilled heatsinks. Fans and heatsinks aren't that heavy so shipping shouldn't be to bad.
    Last edited by aerogrower; 01-23-2016 at 04:22 AM.

  8. #48
    War. War never changes. Est's Avatar
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    Est, I've been communicating with Matt, and he said that he tested CXB3590 on IceLED Ultra or something similar. The data sheet doesn't specifically say it, but he said there were predrilled holes which matches with 50mm spacing for CXB3590. He was going to confirm this, but I haven't heard back yet (it probably be will be next Mon). He wasn't sure about the model; IceLED Ultra, Xtra Ultra, or Ultra VS (and I'm not sure what are the differences between these models). Here is the link to data sheet.
    Great, I'll keep my eyes open for his followup. Thanks again for making contact on my behalf!

    Quote Originally Posted by aerogrower View Post
    Est
    Don't know if it would be cost effective or not...if you wanted to order the cpu/fans that I did that are undrilled, and had them sent to me I would be glad to drill and tap them for you. Then for just cost of shipping from me to you you would be all set. Just a thought it would save you paying three times as much for pre-dilled heatsinks. Fans and heatsinks aren't that heavy so shipping shouldn't be to bad.
    That's an incredibly generous of you! I'm going to see how the above turns out and go from there. I may just take you up on your offer.
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