Self-made LED panel general discussion

Here is the spectral distribution for Cree MCE LEDs. They seem interesting but their efficiency is way inferior to the single colors taken separately, so I don't know. I would prefer going with single-color LEDs instead.

Gastanker said:

kWh? Really?

Fucking brilliant.

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Yep, this is some serious efficiency right there. http://www.ledgrow.eu/test9.html

puffenuff said:

The only drawback I've heard of for white leds is that flowering takes a bit longer than with the r/b combos. Not sure if it takes longer to induce or finish, the details from the one report were second hand info, so perhaps it could have been strain or growing condition dependent.

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I had no problems with my white LEDs slowing down flowering time. I know that's only one random person's personal observation (which is not exactly scientific), and I also had CFLs (very not scientific when we're interested in how well LEDs do!!), but I'd be willing to bet that they're no slower to flower than matching-wattage HPS or RGB mix.
I'm pretty certain I never saw quicker results under my old 400W HPS. (even with some really short flower indica strains).

Of course as you probably know, I haven't finished my grow yet, so maybe I'm a little early to start wading in just yet But them amber trichs seem to be starting to multiply a little now...

Let's just call it a hunch for now...

Oh...and just to throw this in the ring. Despite the fact that I love my little DIY white LEDs, I'm also going to hang back from buying more for a year or two. They just aren't cost effective at present. I'm going to keep using them of course...they will very nicely boost the spectrum range when I get my HPS back on-line.

And they're just great for veg..

"I would prefer going with single-color LEDs instead."

Right Pat, but they only takes up one slot on your panel to do the job of three or four single LEDs, so it may be worth it in some cases. And you could overdrive them if you choose, but color and stated performance could go out the window. Another nice thing is if you order enough of the LEDs from LedEngin they tune them to any spectral output you want, within reason of course. This to me shows the future of RGB LEDs, especially if the Chinese get their shit together about cooling. Still I'll only use whites now for my blue spectrum. I think most blue diodes are just too stressful for most plants to be under for long periods during flower and if you do use blue, you need to select the correct amount/ratio from what I can tell. Here's the spectral analysis from the white "Epis" in my latest 5x60 from LED Star. To me I think I've got enough blue from these:


4500K 10000K

I've no reason to doubt that they are Epis. Whether they came from a S. Korean factory or a Chinese factory is another thing.

If they aren't efficient, overdriving them certainly won't help hehe.

What is LED Star ? Could you link to the manufacturer or to a retailer ? Thank you

Does this change the game? April 2012 Electronic Products magazine/Product Update: Cree is using silicone carbide as a substrate to grow GaN LEDs. Said to provide a better lattice match (more light in less space) ... compatible with most XP family secondary optics. In cool white (6000K) can deliver up to 139 lm/W @ 350 mA and 85^C. Samples now available

Also have any of you investigated RapidLED? DIY solder & solderless kits, pre-drilled heat sinks, pick your own diodes...

patrikantonius said:

If they aren't efficient, overdriving them certainly won't help hehe.

What is LED Star ? Could you link to the manufacturer or to a retailer ? Thank you

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Hey Patrik, here's their Alibaba site where I found them;
http://led-star.en.alibaba.com/

and here's their site:
http://www.ledstar-lighting.com/en/

Nothing special, but they know their lighting. The trick is to know what questions to ask . I just like their 5x60 panel since it fits the bill for my SoG, though I'm trying it out right now on a couple of plants in 3 gallon bags to get a better feel for it. This is Blackstar grade stuff so my expectations are realistic, though so far so good. Actually I prefer this company's panels over BS.

Ed R speaking about LED spectrums and NASA study on Green LEDs (Nov 2010) http://www.youtube.com/watch?v=P31l6tImo0A&feature=related

Of course green is amply covered in newst generation Cree Warm/Cool Whites, as are other important spectrums, like yellow and orange

There is something big missing here, NASA does not study the growth of marijuana
And if it may be true for some plants, I don't believe that marijuana necessarily needs green light.

patrikantonius said:

I've found two studies, one which is analyzing tomato transplants and the other one, lettuce.

The results show that adding green spectrum actually improves the grow of lettuce but for tomato plants, it is the opposite, it decreases their growth compared to only red & blue spectrum. It is therefore not as obvious as you stated; what would be really useful for us is a comparison on mj plants or figuring out whether mj is biologically closer to lettuce or to tomato plants.

http://www.lzi.lt/tomai/97(2)tomas/97_2_tomas_str10.pdf
http://hortsci.ashspublications.org/content/39/7/1617.full.pdf

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Edit: just found out that the second link is most definitely what Ed R is referring to, so you see it is about lettuce.

Photosynthesis is tightly linked with total amount of photons absorbed:

Note that although the higher reflection is of green (around 550nm), and thats why see the plant green, just a small fraction of green is reflected back, as 15%, and not all as you can read many times on the net.That plants reflect back all the green light is a false statement.

This false statement is found very often linked to other false one, that plants dont use green photons for photosynthesis. Plants reflect back more green photons than of other wl, as they use them with lower efficacy, but as max its used at half the efficacy of red ones. Lower efficacy of green, yes, but its not wasted at all. That green light is wasted is another false statement.


(This is from the master knna "Needed lighting concepts to develop LED grow lights") check it out

jubiare said:

Photosynthesis is tightly linked with total amount of photons absorbed:
Note that although the higher reflection is of green (around 550nm), and thats why see the plant green,
just a small fraction of green is reflected back, as 15%, and not all as you can read many times on the net.
That plants reflect back all the green light is a false statement.

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Looks like your right, I for one thought that the green light was reflected much more than 15-20%

From: http://www.controlledenvironments.org/Light1994Conf/1_1_Geiger/Geiger text.htm
International Lighting in Controlled Environments Workshop - T.W.Tibbitts (editor) 1994 NASA-CP-95-3309


Fig. 1. Absorption, reflection and transmission of light by a typical soybean leaf.

Fig. 2 Comparison of action spectrum and quantum yield for photosynthesis with the chloroplast absorption spectrum.

But how much green do you really need though? Green seems to be a conduit for getting photons deeper into a plant's cellular structures from what I've read and alone or at low levels barely stimulates a plant. Look at all the folks gardening in green light under lights out. Having green to me is important in a way like if you woke up tomorrow and Nature removed almost all the nitrogen in the air, you'd probably be able to breathe but it wouldn't "feel" right.

If someone removed all the N from the air the atmosphere would burn off in a fairly impressive explosion. Green might be more important than we give it credit for. But then again people are growing without it.

You seem to be convinced that green light is mandatory by saying that manufacturers sell us a bill of crap. What I don't understand is why, because there is nothing that actually proves that green light is needed in the growth of marijuana. Plus, I've never seen exceptional yields under white or white + red light.

patrikantonius said:

You seem to be convinced that green light is mandatory by saying that manufacturers sell us a bill of crap. What I don't understand is why, because there is nothing that actually proves that green light is needed in the growth of marijuana. Plus, I've never seen exceptional yields under white or white + red light.

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I agree

You don't build this " World's largest Indoor Vertical Farm! "
http://www.youtube.com/watch?v=5MfcsCyHbYI
without knowing what works, and the purple/pink color of there light is the same as ours.

If I build a DIY panel tomorrow then I would use 90% of the energy on the spectrum outside 500-600nm
and 10% on UV - 10% on far red - 10% on white(green).

Looking at www.illumitex.com/led-horticulture-fixtures/
There is a selection of available spectra's I find interesting.

Is Anybody gonna give these illumitex panels a run???? They are pricey, but seem very well built.....so what's the conclusion here go straight with F3 spectra or mix and match(custom); probably will drive the price way up though..........

Edit........thanks jubiare, so Thebongmater is gonna give it a go...........gonna definitely check that out