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Thread: Actual, factual, for real LED lighting

  1. #1
    farmertom's Avatar
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    Actual, factual, for real LED lighting

    Okay, so I bought a new LED light- I've been doing some research and talking with folks at the indoor farming store (god bless you berkeley), but it was definitely an impulse buy. Still I think I did it right, though I'd appreciate some knowledgeable feedback.

    It's a four foot fixture for my growshelf, which is currently in a south facing window in coastal northern california. The illuminated shelf is actually only 3 feet wide by 1 foot deep, so the fixture hangs over the sides a little. The sides that aren't facing the window or the room have a (wrinkly) Mylar reflector stapled on. The new fixture's mostly for supplemental lighting- the plants along the window side (HL nepenthes, U. Alpina, H. Heterodoxa x minor, all in 3+ inches living sphagnum) get pretty okay light, but those on the room side get less. I've set the new light up more on that side of the shelf, the side you can view the plants from.

    So. The light is actually for aquariums, but I think the specs are in the correct range: it's a 'Fluval AquaSky LED' fixture: 84 LEDs, 2400 lumens, 35 watts, with adjustable (remote control!) color temp from 3,000 k to 25,000 k. It says it's waterproof, rated for 50,000 hours, has 120 degree dispersion, and that it pairs 6500 k white LEDs with tri-colored RGB LEDs to create an adjustable spectrum. The spectral distribution doesn't have much red (it's at less than 50 out of 100 around 620 nm orange, but close to 100 around 440 nm blue- I'll try to get a picture on here), but if I can fully dim the white LEDs, and since it is only supplemental, will it have been worth the purchase?

    The remote lets you add or subtract as much red, green, or blue as you like, plus a dimmer for adjusting the white LEDs- so I can set it to be all red and blue, or add white and green to make it a little easier on the eyes. It also has six pre-set color combinations (biased red, blue, purple, indigo, yellow, and full white), 4 memory buttons for storing custom color settings, three "natural" effects for replicating moonlight, a sunrise/sunset effect, four types of cloud cover intensities, and 3 storm effects- which include flashing lightning. I don't think I'll make much use of most of these effects (except maybe for parties), but it's pretty fun, and I hope the versatility will help me to dial it in for CP growth.

    If you've made it this far, thanks for bearing with me! How does it all sound? My main questions are: am I gonna cook my plants by accidentally setting this thing to 25,000 k? Is it sufficiently powerful and within a feasible spectral range to grow tropical CPs? How close to my plants should I put it- can I raise the Heliamphora closer and settle the Nepenthes lower to get the best of both worlds? They've been growing without it, everybody pitchering and leaf jumping all over the place since spring, but I can tell they want more.

    I read the equation for lux online- and I am totally boggled by it. I'm a smart guy I promise but I have a math problem.. So 1 lx = 1 lm/1m sq. The new lamp provides 2400 lm for a 1/3 of 1 square meter grow space. So 2400 lm / .33 m sq = 7272.72 lx? The chart online says that falls in the mid range of intensity, and 'will be okay' for Neps. What kind of intensity would it have if I dim the 6500k white LEDs all the way down, just using maximum red and blue? Would it be stressful to the plants to have it on a 'moonlight' setting at night while the humidifier's running?

    I'm gonna (attempt to) make and (attempt to) use that ingenious DIY spectrometer from PublicLab- I hope this light works well for my needs, but I'm also just really fascinated and totally confused by the science (did you see the recent visual representation of light as both a particle and a wave??)- any ideas or ways of thinking to help me understand and apply it all would be greatly appreciated! Thanks!

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    Ah the old LED nightmare is back! You can find a few discussions on this forum, about power, wavelenght, etc. I know we had at least some on this thread.

    Technically, for plants, you don't really need any of the lux, lumens or others metrics, they don't really make sense. Only PAR is important.

    Still overall I'm deeply suspicious of the efficiency of the light you describe, 35W seems very low, and probably not accurate. First step would be to use a Kill a Watt or a cheaper alternative and check the real power usage. Efficiency of LEDs is variable but at least it will give you a starting point.

    This is a gross estimate, using only power usage as it's the easiest to measure. I tried to do it the proper way as you did, but I gave up.
    T8 tubes are ~45W each, I personally count ~30W of white LED = 1 T8 tube. If your LED are purple (or blue+red mixed), you could go ~20W of purple light = 1 T8 tube.

    So now, back to your 35W fixture. If with the white LEDs fully ON and your RGB LEDs full Red+Blue you are ~35W of power usage (unlikely) it may be sufficient as additional lighting but that's about it.
    Depending on the price of your light fixture, you may want to just add a couple of CFL or LED bulbs from Home Depot. 100W equivalent 6500k bulbs (13-14W in LEDs, 1200-1400 lumens) cost ~$20 each and fit nicely in the clamp reflectors they also sell over there.

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    nimbulan's Avatar
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    I would say that 2400 lumens is quite low for the area covered. I use a 4000 lumen T5 fixture for a 2'x1' shelf and a 8000~9000 lumen COB LED for a 2'x2' (I'm probably stretching it closer to 2.5'x2.5' table.) I think ~7200 would be appropriate for low light plants like U. calycifida, though I expect Neps and other plants will want more. My LED is 4000k, and CP growers generally aim for the 3000-6500k range so I wouldn't go higher than that with your fixture.

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    Quote Originally Posted by emc2 View Post
    Ah the old LED nightmare is back! You can find a few discussions on this forum, about power, wavelenght, etc. I know we had at least some on this thread.

    Technically, for plants, you don't really need any of the lux, lumens or others metrics, they don't really make sense. Only PAR is important.

    Still overall I'm deeply suspicious of the efficiency of the light you describe, 35W seems very low, and probably not accurate. First step would be to use a Kill a Watt or a cheaper alternative and check the real power usage. Efficiency of LEDs is variable but at least it will give you a starting point.

    This is a gross estimate, using only power usage as it's the easiest to measure. I tried to do it the proper way as you did, but I gave up.
    T8 tubes are ~45W each, I personally count ~30W of white LED = 1 T8 tube. If your LED are purple (or blue+red mixed), you could go ~20W of purple light = 1 T8 tube.

    So now, back to your 35W fixture. If with the white LEDs fully ON and your RGB LEDs full Red+Blue you are ~35W of power usage (unlikely) it may be sufficient as additional lighting but that's about it.
    Depending on the price of your light fixture, you may want to just add a couple of CFL or LED bulbs from Home Depot. 100W equivalent 6500k bulbs (13-14W in LEDs, 1200-1400 lumens) cost ~$20 each and fit nicely in the clamp reflectors they also sell over there.
    The bolded part is the most important thing.

    As for LEDs, please keep in mind not all LEDs are created equally. I have one of those LED fixtures you are talking about and they are no where near the light output as the CREE ones I'm using in my main rack.

    I have used a Killawatt meter on my DIY LEDs and they run at 1.25-1.5W per hour. So lighting a 12" X 24" area with 14 CREE LEDs costs me 17.5-21W per hour. The numbers were so low I would have needed days to weeks of gathering data to get a better number.

    From my last research... You want reds spiking in the 660nm range and blues spiking in the 430nm range with white to fill in the rest of the spectrum.

    When you start digging into the technical #'s for the LEDs you get a lot of useless information like Luminous flux, why is this useless? Its a measurement of light visible to the human eye so if you look at the RED LEDs its .720 while the warm white LED with the same power is 93.9....130X brighter to the human eye, but which LED is actually producing more usable light to the plant?, visible to the human eye or not? I was not able to find that information but as I've said before I only understand about 1/3 of what I'm reading with this stuff. i've been running a Red/Blue LED test for a while now and they look just as good as the others under white lights given the same power input.

    Here is what that amount of power can do. Feel free to check out Its time to build a Cephalotus grow space, would love input! it is almost everything I've wrote about LEDs. I'm no expert thou.


    DSC_0940
    by randallsimpson, on Flickr

    DSC_0075
    by randallsimpson, on Flickr

    As for the specific questions, yes you can cook you plants. I did....check the thread Start slow a few hours a day for a week then up it a few more hours ect.

    Spacing plants higher/lower to give them more light works wonders, LEDs generally produce there heat away from the lighting area due to the heatsink placement so that allow you to place plants closer to the LEDs. Just make sure and check the temp after it has been running for 5 hours or so.

    Hope some of this is helpful.

  5. #5
    Decumbent Fanatic Jcal's Avatar
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    beautiful plants rss. at first I thought that was a single tray of cephs!

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    Farmertom. there is a thread in this section of the forum called DIY COB LED info. This thread is one of the best I have run across here concerning LEDs. It has loads of info about what PLANTS want as far as light goes. Its all about par. I used to supplement t5s with an aquarium led light like you describe. As soon as I was able to build my own COB leds I did and never looked back. Check the thread out, cant hurt.

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    Never Knows Best gill_za's Avatar
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    RSS,

    How long does it take for a pitcher to turn this dark color? I do not have the LEDs yet but ive recently switched the bulbs to those that peak in PAR region. Curious if this will be any improvement.

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    The changes happened pretty fast maybe 1-2 weeks.

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