Self-made LED panel general discussion

Originally Posted by puffenuff

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.

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:

5W 4500K - Copy.jpg 5W 10000K - Copy.jpg
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...

Originally Posted by patrikantonius

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

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=P31l6...eature=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.

Originally Posted by patrikantonius

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/.../1617.full.pdf

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