User Tag List

Informational! Informational!:  8
Likes Likes:  3
Page 3 of 14 FirstFirst 123456713 ... LastLast
Results 17 to 24 of 112

Thread: DIY COB LED info

  1. #17

    Join Date
    Mar 2015
    Location
    Fairbanks, AK, USA
    Posts
    120
    Mentioned
    4 Post(s)
    Tagged
    0 Thread(s)
    nimbulan, with availability, KingBrite seems to be the easiest source at this moment. I think aerogrower contacted him.

    Also, generally, you lose the total PAR output with higher CRI. This may not be an accurate description, but it is easy to understand in this way. Phosphor-based white LEDs are basically blue LEDs + phosphors. When phosphors are hit by blue, they fluoresce at a longer wavelength (yellow-red). So different CRI and K are generally done by changing mostly the phosphor layers. So to get warmer color (lower K) or higher CRI, they generally apply more phosphors. The light can be lost at the phosphor layers, so some photons get lost with more phosphors.

    Info below here is probably too much details for most people, but I'm just showing that the above statement isn't based on "myth".

    If you want to see more exact number, here is the calculation done by alesh of RIUp forum (well, I added a bit more calculation and re-implemented it in R by myself). Basically, you digitize the Spectral Power Distribution (SPD) curve, and then you can calculate these conversion factors with R (or a spreadsheet).
    Code:
    ##                                      ler      qer  par.qer par.per.lum ppfd.per.fc ypf.per.lum
    ## Cree.3000K.80CRI               327.26551 4.868716 4.662723  0.01424752   0.1533591  0.01288196
    ## Cree.3000K.90CRI               276.12267 4.915020 4.511533  0.01633887   0.1758702  0.01458771
    ## Cree.4000K.80CRI               322.10079 4.678840 4.533168  0.01407376   0.1514886  0.01230506
    ## Cree.5000K.70CRI               323.42007 4.605715 4.471141  0.01382456   0.1488064  0.01204868
    ## Vero.3000K.80CRI.v1.2          323.10113 4.879973 4.658829  0.01441910   0.1552059  0.01305418
    ## Vero.3000K.80CRI.v2            319.73025 4.944016 4.704169  0.01471293   0.1583687  0.01346317
    ## Vero.4000K.80CRI.v1.2          321.96749 4.730732 4.564988  0.01417841   0.1526152  0.01252857
    ## Vero.4000K.80CRI.v2            323.62228 4.823261 4.619960  0.01427578   0.1536632  0.01281032
    ## Vero.5000K.70CRI.v1.2.2        331.47526 4.614143 4.489774  0.01354482   0.1457953  0.01179274
    ## Vero.Decor                     271.76787 4.977243 4.558739  0.01677439   0.1805580  0.01510056
    Explanation of columns:
    • ler: Luminous efficacy of radiation. Basically how much lumen is given per 1 watt of emitted light (not 1 watt of electric power went into the diode). The unit is lumen/W
    • qer: quantum efficacy of radiation. I'm not sure if this is the correct term, but instead of lumen in LER, we are using number of photon flux (micromol/s). The unit is micromol/s/W = micromol/J. In this, I'm not using PAR, and using all emitted light.
    • par.qer: Similar to QER, but now we are counting the light between 400-700nm (PAR). unit is micromol/J
    • par.per.lum: For a given lumen, how much PAR PPF is there. Companies only gives the lumen output for a given current and temperature. You can multiply the lumen number with this factor to get the PAR PPF. The unit is micromol/s/lumen
    • ppfd.per.fc: If you have only footcandle meter, you can use this factor to get the PPFD. The unit is micromol/m^2/s/footcandle
    • ypf.per.lum: Yield photon flux per lumen. This quantity is similar to par.per.lum. Blue light is about 20-30% less efficient than red light in terms of photosynthesis. While each photon between 400-700nm is counted equally in PPF, each photon is weighted by the photosynthetic efficiency in YPF without limiting the wave lengths to 400-700nm. This difference in photosynthetic efficiency is expressed by Relative Quantum Efficiency (RQE) of photosynthesis. I used the RQE obtained by McCree (1972). See the figure in this wikipedia. A lot of people are familiar with the chloroplast absorption spectrum (top of the same wikipedia page), but many people are not aware that absorption is just a part of the story; some of the light is absorbed by inactive pigments, which don't contribute to the photosynthesis, or released as heat before it initiate the photosynthetic reactions. McCree's RQE is a more relevant curve than the absorption spectrums of chlorophylls. The unit is micromol/s/lumen.


    For the discussion of different CRI, we can focus on par.per.lum column. Then we get the lumen from the datasheet of CXB3070. The value is for 1.9A (higher than I would use) and junction temperature of 85C (higher than what I would target). Forward voltage is 36V, so 68.4W of electric input (not including the loss of power due to AC/DC conversion at the driver). Here are the minimum flux value for the top bin for each.

    3000K 80CRI AD bin: 9000lm = 128.2 micromol/s (PPF) = 115.9 micromol/s (YPF)
    3000K 90CRI Z2 bin: 7390lm = 120.7 micromol/s (PPF) = 107.8 micromol/s (YPF)
    4000K 80CRI BB bin: 9500lm = 133.7 micromol/s (PPF) = 116.9 micromol/s (YPF)
    5000K 70CRI BD bin: 10000lm = 138.2 micromol/s (PPF) = 120.5 micromol/s (YPF)

    So with 3000K where I could compare the different CRI, lower CRI is better as expected (in both PPF and YPF). Basically if you go up in CRI, the bin number goes down a couple steps.

    Now, if you look at PPF values, you may think that 5000K is better than 3000K 80CRI (about 7.8% advantage). From the action spectrum (RQE) of photosynthesis (by McCree 1972 and Inada 1976), one photon of blue light is 20-30% less efficient in terms of photosynthesis than one photon of red light. Although LEDs with lower K have lower PPF, it contains more red light. So the difference in terms of YPF, which incorporates the difference in photosynthetic efficiency, become smaller among different K (4.0% advantage).

    Another point is that the PAR efficiencies of these COBs are pretty high. Assuming that we lose about 10% during the AC/DC conversion, so the actual input electricity in this example would be 68.4/0.9 = 76W. With 4000K, 133.7 micromol/s / 76W = 1.76 micromol/J. The top commercial grow light is around 1.6-1.7 micromol/J for both LED and HPS. See table 3 of this paper. To make the output similar to the commercial grow light, you can use 4-5 of these. So the total cost of <$400 can beat the $1000 top LED fixture.

    If we use lower current and better heatsinks (to lower the junction temperature), the efficiency improves. Also if we go with CXB3590, the efficiency goes beyond whatever available grow lights. My newest one is CXB3590 at 50W each, which I think gives >2 micromol/J.
    Last edited by naoki; 12-04-2015 at 12:29 PM.

  2. #18
    War. War never changes. Est's Avatar
    Join Date
    Apr 2004
    Location
    Champaign, IL
    Posts
    3,935
    Mentioned
    3 Post(s)
    Tagged
    1 Thread(s)
    Quote Originally Posted by aerogrower View Post
    Est what COB leds are you going with? What drivers etc?
    I hopped on the CXB3590 deal that Naoki linked earlier in this thread and went all-in for four! That means I'll be going with the driver from the same post unless I happen to find something else that fits the bill better or more cheaply.

    I'll be looking into those Mechatronix heatsinks for sure. Not needing to buy and drill several cpu heatsinks would be great. I'm still looking at alternatives though, so if any of you have suggestions, do let me know!
    \(_o)/ ಠ_ಠ
    My Growlist
    NASC Website Come join in on the fun!

  3. #19

    Join Date
    Mar 2015
    Location
    Fairbanks, AK, USA
    Posts
    120
    Mentioned
    4 Post(s)
    Tagged
    0 Thread(s)
    Est, with CXB3590, it has to be ModuLED Giga, which is quite pricey.

    I talked about this earlier with aerogrwer, but many people use Extruded Aluminum Heatsinks from HeatSinkUSA. They have different profile, and will cut it for your custom length. 40" of 5.886" profile width should be enough for 4x CXB3590 to do passive cooling without fans. $70 + shipping etc, which is slightly more expensive than CPU fans (cheaper than ModuLED), but it isn't too bad. With passive cooling, you don't have to worry about the fan breaking down. CPU fans are fairly reliable, but there is a chance of break (so I'm adding a thermal protection now). You could add 1x fan in the middle of the big heat sink if you want to go further with efficiency. A small amount of air flow can decrease the temperature of heatsink quite a bit. It would give fairly dense light, maybe similar to 6-8 bulb version of 4' T5HO. If this is too dense (too much light), you could make it to 2x 20".

    Here is a related RIU thread, which I got the information from.

  4. #20

    Join Date
    Apr 2014
    Location
    Michigan
    Posts
    375
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    After all the discussion we had I decided to go the active cooling route with the computer type fans. I have access to a high speed milling machine that makes short work of the drilling and tapping. I am going to build a 4" x 4' long frame out of aluminum angle, welded at the corners. The heat sinks will fit inside the frame and be screwed to the frame. That way I have a neat way to secure all the wires and a sturdy mounting surface to hang it up when im done.
    I will be ordering the COB leds today and im not sure if im going with the CXB3590's or the CXB3070's. So depending on which way I go will determine which driver I get.
    Thanks for keeping up on this thread and thanks for all your help Naoki!

  5. #21

    Join Date
    Mar 2015
    Location
    Fairbanks, AK, USA
    Posts
    120
    Mentioned
    4 Post(s)
    Tagged
    0 Thread(s)
    That's great to hear you have access to nice machines! CPU heatsink works well.

    If you go with HLG-185H-C1400, you can drive 4x CXB3590 or CXB3070. Slightly more light (with the similar input wattage) with CXB3590. It doesn't have enough voltage for 4x CXA3070, though.

    From calculation based on data sheet, CXB3590 appear to be worth getting. But the PPFD measurement done by one person, CXB3070 seems to be not far behind from CXB3590 at the low current. So it's difficult to say the extra $13.50 is justifiable. There appear to be more choices of LED holders, reflectors, and pre-drilled heatsink with the smaller CXB3070.

  6. #22
    nimbulan's Avatar
    Join Date
    Feb 2014
    Location
    Oregon
    Posts
    1,359
    Mentioned
    12 Post(s)
    Tagged
    0 Thread(s)
    Well that is certainly more information than I was expecting! I didn't realize that there are no high bin high CRI parts available. I'll certainly be keeping an eye on how things go in here since I won't be ready to build one until next year sometime.

  7. #23

    Join Date
    Apr 2014
    Location
    Michigan
    Posts
    375
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Got all of the parts ordered and should be building a new light after the new year! Went with the cxb3070 and the appropriate driver HLG-185H-C1400. I also decided to go active cooling with a CPU fan and heat sink for each cob led. Found the CPU/fans for 9.00 each. I will incorporate everything into a frame and away we go! Anyone else close to taking the plunge?

  8. #24
    War. War never changes. Est's Avatar
    Join Date
    Apr 2004
    Location
    Champaign, IL
    Posts
    3,935
    Mentioned
    3 Post(s)
    Tagged
    1 Thread(s)
    Any update?

    I'm looking at pricing out a power supply and cooling now!
    \(_o)/ ಠ_ಠ
    My Growlist
    NASC Website Come join in on the fun!

Page 3 of 14 FirstFirst 123456713 ... LastLast

Tags for this Thread

Posting Permissions

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