LED grow lights... input please.

[SnSstealth]

YO,

Havent read the whole post but heres a guy w/ the "14w" kit. he had 660's added. etc. but seems like hes doing ok. any opinions?
Cannabis and Marijuana seeds :: HomeGrown420 - 140w LED Grow (660/630/470/420)

Db:smokin:

SnSstealth Reviewed by SnSstealth on 02-28-2008. LED grow lights... input please. Hello guys, I'm exchanging eMails with a representative from a LED company. I asked him if they could produce a custom light for growing, and here's what he told me: Our options are as follow: 940nm, 850nm, 660nm, 630nm, 610nm, 590nm 570nm, 530nm, 510nm, 470nm, 460nm, 400nm and a total of 64 LEDs in the bulb. Rating: 5

[physicsnole]

Looks like the 660 and 420nm made a big difference. The buds look decent size, especially for an LED grow.

[Opie Yutts]

I don't want to seem negative, but they look a little sparse to me. Maybe it's just the variety. I don't understand why the arrays are so far away. You need about 3 off those panels per plant to do anything, and they need to be right next to the plant.

[SnSstealth]

I agree opie, theyre a bit small but, like you said there is not enough/bad placement problems.

Have we seen a grow w/ these kits minus the 420/ 660?

db:smokin:

[Gilfaethwy]

Hey guys,

I am fascinated by the whole subject of LED grows. I've been reading SnSstealth's log, and my theory is that the reason why he has been successful where others have met with such difficulty is this: Lumens.

Most of the products out there marketed as "LED Grow Lights" have no light output ratings at all. Most of them are also garbage.

Please bear with me on this post, I know its pretty long, but I am going somewhere with it

I wish the Procyon 100's used had a lumen rating. It would make comparisons and calculations so much simpler. Because I don't know exactly how much current is driving each of the Cree X-lamps, I can only guess at the light output. Based on their specs (as available from the manufacturer) they put out anywhere from 80 to 200 lumens, depending on how much current is used to drive them.

If one assumes an average value of 140 lumens / lamp that gives a total output for a single Procyon 100 = 140 * 56 = 7,840 lumens. Call it 8,000 lumens to simplify math. My guess is that the true value is no less than 6,000, and no more than 10,000.

Now, given SnSstealth's 8*2 = 16 square feet grow room we have seen that 3 * 8,000 = 24,000 lumens seems to be adequate for that area. That gives us an average of 24,000 / 16 = 1,500 lumens/ square foot.

That's where I was going. It looks like 1,500 lumens/sq. ft. is a good baseline for planning a LED lighting system.

Of course that's all assuming that the output is in the right frequencies. Basically I'm saying one needs to have a lighting set-up put out the frequencies, in the right proportions, reaching at least the intensity calculated here.

Does anyone have any critiques or thoughts on this reasoning? And thank you again SnSstealth for providing numbers that I could base my theorizing on!

[Opie Yutts]

Your reasoning sounds fine to me.

[brownthumb]

lumen and PAR are defined terms
an led array designed on a PAR basis will have very low measured lumens

I agree that SnS is doing better than most (all ?) and it is due to the intensity.

FWIW
a Sunmaster 600W MH conversion bulb has 50,000 lumens and 195 PAR watts, ~ 1/3 of its output is of use to us

[Gilfaethwy]

Sorry guys, I just noticed a very significant flaw in my logic. It's a really silly goof.

I've been thinking about the possibility of White LEDs as grow lights, which seems reasonable if one looks at the activity spectra of Green Plant Photosynthesis and compares it to the emission spectra of most White LEDs. They are quite similar, with peaks in roughly the same places.

As such, I goofed and substituted lumen ratings using the data for the white Cree XR-E lamp in the calculations for the light output of the Procyon 100's. And of course, the Procyon's use the Colored Xlamps, and they have different specs, and different lumen ratings.

Brownthumb, I know what lumens are, they're the SI unit of luminous flux, equal to 1 candela * steradian. But what do you mean by PAR? Do you mean Photosynthetically Active Radiation? Or something else? PAR is used as name for too many things in lighting

As for what my goof implies about the numbers, I think it means that the lumen numbers are far too large, which seems astonishing. Trouble is, I'm reading through Cree's spec sheets, and they don't specify lumen output at high driving current for the color parts, just at the relatively pedestrian 350mA.

I'm currently working on researching more and trying to post revised calculations.

Hmm, based on most specs, the lumen output seems to double when going from 350ma to 700ma with minimal increase when going up from 700ma to 1000ma.

[Opie Yutts]

Nothing wrong with white in my opinion. Everyone keeps telling me I'm crazy, but white light seems to work pretty well for fluoros and HID. Just as with those, LED's have many different whites. Just make sure you use the right ones for the individual stages of growth.

[bonzo00420]

what does everyone think about a 250w-hps supplemented by 2(maybe 4-all conceptual) of the 14w's kits along with 80w of fluorescents for a closet grow where heat would be a problem? i heard the 14w's are equivalent to about 50w-if compared to hps- so that should all work out to about 430w give or take some... you think that it would produce like a 400w-hps- or do u think its all a waste? but heat is really the main issue and why i would have to supplement the other light into the grow if i were to do so-- cause the 250 alone would keep the temp in the high 70's...so a 400 would be out of the question..
:rastasmoke:
let me know what you think stealth /opie/anyone else with any thoughts on this -- would really appreciate it...

:stoned: