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Thread: DIY COB LED info

  1. #9

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    Great, Mark! I hope you'll give it a try. It did took quite a while to learn about photo-biology and LEDs, but there are lots of good information floating around (it was sometime difficult to filter out the misinformation at first, though).

  2. #10

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    Naoki...perfect timing I actually am building the low light model you described in the beginning of your thread. This is my first time so I wanted to start small and make sure I could do it. I have all the components except the driver which apparently is on the proverbial slow boat from China. May not be here for several weeks. I will post here when I have light! Next will be a full fledged grow light, so your timing is right on. Please check in here as often as you can in case I run into trouble lol.

  3. #11

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    Well did my first build with Naoki kinda holding my hand. I built the 50 watt single COB led. It gives off a very nice pattern of light and has inspired me to build a 200 watt light that will cover most of my grow area. Thank you Naoki couldn't have done it without your help. Has anyone else here started a build? If your on the fence please give it a try and post on here. I will try to post some pics later.

  4. #12
    War. War never changes. Est's Avatar
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    My LEDs are supposed to arrive today. I'll be assembling pieces over the next month and will start putting things together in the start of 2016! I'm sure I'll be in this thread with questions.

    Looking forward to seeing your pictures.
    \(_o)/ ಠ_ಠ
    My Growlist
    NASC Website Come join in on the fun!

  5. #13

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    Est what COB leds are you going with? What drivers etc?

  6. #14

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    Sounds great!

    I was wondering if there are some other heatsink choices. This may be interesting to some people. These Mechatronix heatsinks appear to be predrilled for Zhaga compliance (a standard to mount LEDs). So if you use Ideal LED holders, no need to drill/tap (not difficult, but the most tedious part).

    ModuLED Mega 134100 0.67C/W CXB3070 or smaller $19.06
    ModuLED Giga 152100 0.53C/W CXB3590 or smaller $27.20
    IceLED Ultra 0.25C/W CXB3070 or smaller $14.01

    They are available from cdi. Unfortunately, they don't ship with USPS, so it's not a good option for people in Alaska or Hawaii.

    The lower value of thermal resistance (C/W) is better. ModuLED is passive, and IceLED is active. I didn't look if there is an option to attach a fan to ModuLED (but I'm sure it can be done). Here is some explanation of how to interpret thermal resistance.

    Here is a calculation of COB efficiency:
    COB efficiency Spreadsheets | Rollitup

    So let's say that you drive CXB3070 AB bin at 1.4amp. You can look at "50c diss watt" (dissipated watt (the watt used by LED) at 50C temperature). About 49.83W. Now you can look at the "50C %" column, which says 48.50 %. This is the radiant efficiency (the proportion of electricity converted to light energy). So the rest (51.50%) is converted to heat. This means 49.83 * 0.515 = 25.66245W is released as heat. So with 0.67C/W heatsink, the LED will be ambient (say 25C) + 0.67 * 25.7W + a little bit more (due to the inefficiency of heat from LED to the heatsink, I couldn't find this thermal resistance value for Cree), which is 42.2C + more for the LED temp. I think many manufacturers target the LED (junction) temp of 85C or so, so this would be decent amount of cooling. I'm not sure if this makes sense (or if I'm wrong) since this heat calculation stuff (thermal resistance stuff) is something I recently learned, and I wouldn't say that I understand it fully.

    While I was looking around, I saw something called Synthetic Jet (SynJet), which seems to be interesting, but they are kind of pricey. It's supposed to be more reliable and quieter than fans.
    Last edited by naoki; 11-28-2015 at 06:33 AM.

  7. #15
    nimbulan's Avatar
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    It's too bad Digikey has such a limited selection. Looking through the data sheets, it seems like the 90 CRI parts would produce more useful light (for the plants.) Thanks for all the information, I've been researching LEDs on and off for a long time and this is the best build I've seen.

  8. #16

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    How about a pic?

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