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Thread: DIY COB LED info

  1. #49
    nimbulan's Avatar
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    Has anyone tried using a lens or reflector with these COBs? The 115 degree viewing angle seems a bit large to me.

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    I haven't tried them yet but I'm going to on my next build. The 115 angle of view seems to give a nice pattern of light. I'm going to use them on new build to use occasionally to protect them when I foliage spray or spray for pest, to protect the cobs. Then I will remove them for regular use. I also read somewhere that they have found that the lens trap gases given off from the coating on the cobs and diminish there life some? Please take this with a grain of salt as I can't quote said article right now. But it warrants looking into. Maybe Naoki has more input on lens and reflectors.

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    LEDiL has Angelina line of reflectors which works with CXB3590 or CXB3070. I think it is around $10.

    Led lighting - Products | Ledil

    With Ideal COB holder, you need 1 extra piece, which connect the LEDiL to the COB holder. For CXB3590, you need 50-2300AN , for CXB3070, you need 50-2100AN. These are about $1.
    Chip-LokŪ LED Reflector Adaptor

    KingBrite recently made a something similar (copy of Ledil F13838_ANGELINA-XW). It is very cheap ($0.80 ea), but the shipping is not, so you'll need to buy quite a few. Again, you can connect to the Ideal COB holder with the adapter I mentioned above.

    They also have some glass lens for CXB3590 ($5.60). I don't know the details about this lens, though. So from KingBrite, you can have two options for CXB3590:
    Led glass lens: led + Ideal holder 50-2303CR + LED glass lens KB-HB100-80 (diameter 100mm, 80degree).
    Led reflector: led + Ideal holder 50-2303CR + Ideal connector 50-2300AN + Reflector KB-D82-90RF (diameter 82mm, 90degree).

    As aerogrower mentioned, heat might get trapped, but I have seen that others have used the lens.

    Early on, I made DIY reflectors from tin cans (e.g. from chopped tomato) and small yogurt containers. But I'm not using them now. I grow plants in reflective tents, so the light get bounced back somewhat onto the plants (reflection does lose some light, though).

    If you reduce the beam angle, the lower leaves get shadowed more. This isn't a big issue with rosette type plants like Drosera. Without the reflector, it can reach to the lower leaves. This is a big advantage for me. Indeed, the main issue of COB is that it is more of point source light, and it's not diffused enough. So I don't want to make highly directional light. In other words, if you have a big grow area, it may make sense to use reflectors around the edge of the grow area, but in the middle, you might not need the reflectors. Or if you have to set up the light really far away, then the narrow beam with reflectors are good.

  4. #52
    nimbulan's Avatar
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    I was reading a bit about the Kingbrite lenses last night. It sounds like the light transmittance isn't great on them and I'm not really sure how you'd wire the COB up with the lens on.

    Thanks for the information about the Ledil reflectors, it sounds like that might be a better way to go. My main interest in narrowing the beam angle is specifically to be able to raise the light up to grow taller plants than I can right now. I don't really have a good enclosed space to set up reflectors so narrowing the viewing angle of the light source seems like a better option for me.

    Is there a particular website you would recommend buying one of these from? Newark and Digikey appear to require orders of 50+ units.

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    Pm sent.

  6. #54
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    Currently, I would like to build a single COB grow light to test out and to expand my grow area. I'm trying to decide between the CXB3070 and CXB3590. I would like to cover approximately a 2'x2' area for full sun plants like sundews and for germinating Sarracenia seeds. I'm thinking that I may not purchase a reflector now, since I don't know exactly what angle would be best so I will likely build my own to test.

    My current setup is a 2x2' T5HO fixture which produces about 4000 lumens for a 1'x2' area. This seems like about the right amount of light, though I don't have any reflectors set up so I do lose some of it.

    So if anyone can offer me some advice: Which one of these COBs would be ideal for my setup and how many watts should I run it at? Which color temperature/bin offers the highest PAR efficiency?

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    If you can have enough room above plants, you can basically use any reflectors with a narrower beam pattern (i.e you can move the light far away to make sure the plants don't get too much light). You could try something like 60-90 degree beam angle, but you can add the reflector later, too. 90 degree means 45-degree in both side, so from 2 feet distance, the circle diameter is around 2 feet.

    I would say that try CXB3070. You'll gain a bit more output from CXB3590 (for the same watt), but I'm not sure if it justifies the price difference (unless you are a efficiency-number freak like me).

    CXB3070 4000K BD bin (1.4A, 50W, 50C Tj) gives 7989 lumen according to:
    Cree Product Characterization Tool
    Since it is directional (unlike T5HO), you'll get more than 2x light over your current T5HO setting, so it should cover 2'x2' area. One glitch is that the coverage area is not as even as T5 (high light area in the center).

    From my calculation, lowest CRI and higher color temp gives more PAR in general. But in terms of yield photon flux (YPF; i.e. after putting weight representing that red light is more efficient than blue light for photosynthesis (PS)), the lower color temp isn't so far behind (i.e. color temp doesn't matter too much). Higher bin is always better if you can find them.

    Here are the relevant values if you want to calculate by yourself.
    Code:
    ##                   ppf.per.lum ppfd.per.fc ypf.per.lum   ypfd.per.fc
    ## Cree.3000K.80CRI   0.01424752   0.1533591  0.01288196   0.1386603
    ## Cree.3000K.90CRI   0.01407376   0.1514886  0.01230506   0.1324506
    ## Cree.4000K.80CRI   0.01407376   0.1514886  0.01230506   0.1324506
    ## Cree.5000K.70CRI   0.01382456   0.1488064  0.01204868   0.1296909
    [Edit: oops, I posted this info in p.2 of this thread. I have forgotten about it, so this is just a subset of the previous table.]

    Basically, you can get the lumen (or lumen per watt) for each CRI/K model from the Cree datasheet. Note that higher K generally have higher lumen values (and higher bin numbers). Then you can convert the lumen value to PAR photosynthetic photon flux (PPF; use the multiplier in par.ppf.um) or to YPF (use ypf.per.lum column). The value calculated has the unit of micromol/s. The other 2 columns can be used to convert the foot-candle reading from light meter to PPFD or YPFD (unit will be micromol/m^2/s). PPF"D" and YPF"D" represent "D"ensity. So PPF and YPF are the total output from the fixture, PPFD and YPFD are the density of these light on the leaf (i.e PPF per m^2). This is similar to lumen (total output) vs lux/fc (density).

    Now, one thing to note is that PS is not everything. I'm not completely familiar with the physiology of CP, but red light is likely to be important for phytochrome related phenomena. I'm guessing that day length influences the seed and plant dormancy of Saracenia. So red and far red ratio becomes relevant. I have been using 3000, 4000, and 5000K, and all seems to work well for orchids. I subjectively (i.e. without strong scientific support) choose that 4000K is the default for me (it just seems to be a good balance).

    Something like this:
    Cutter Electronics, Supplier of lowest cost leds on the internet
    I think that their coupon is still effective (I think I posted earlier in this thread), but you need to see if it is cheaper domestically once you consider the shipping cost. cutter seems to have top bin frequently, which is difficult to get domestically.

    With regard to the driving current, you'll probably need at least 1400mA (50W) if you want to get that much of light from 1x COB. Maybe LPC-60-1400 is a choice: LPC-60 datasheet

    If you want to get more light (sacrifice a bit of efficiency) you can go with LPC-100-1750: LPC-100 datasheet
    It gives 1750mA (63W), and you'll get 9599 lumen.

    These drivers are not dimmable nor highest efficiency, but they are cheap (and good quality).

    If you want to go dimmable (1.17-1.95A = 40-70W), HLG-80H-42 is one of the best: HLG-80H datasheet
    I personally would go with the cheaper LPC for a single driver + single COB, though. If you are going to connect multiple COB LEDs to a single driver then HLG could be a good choice.
    Last edited by naoki; 02-16-2016 at 01:13 AM.

  8. #56
    nimbulan's Avatar
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    Thank you very much naoki. It certainly is a lot of information to take in for someone as new to LED lighting as I am but this gets me one step closer to taking the plunge.

    Two more quick questions:
    I've noticed that people seem to stick with <5000K lighting for LEDs, yet bulbs as high as 6500k are common with fluorescent lighting. Why is that?
    What does Cree's two-step, three-step, and five-step binning mean? They have multiple "steps" for some color temperature/bin combinations but don't understand the chart at the end of the spec sheet about it.

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