Self-made LED panel general discussion

[jubiare]

I think what Knna meant is that the energy of each photon is not relevant and what's relevant is the total number of photons hitting the plant.

Yes most likely

I hate to say this but it seems to have become common knowledge that a majority of red light is more beneficial to the plant than a majority of blue. I have not seen successful growths of marijuana using only blue light while the opposite is true.

you'll never see one Only blue or most blue stunt the f*** out of the ladies!

 

[Rasser]

Wanted to bump on this post, in this study : http://www.lzi.lt/tomai/97(2)tomas/97_2_tomas_str10.pdf, done in 2010 with LEDs on tomato plants, the results are the following:
for dry weight, from best to worst:
1) uv + red + blue
2) red + blue
3) red + blue + green
3) red + blue + yellow
4) red + blue + orange
I like to think that UV has little to no effect on marijuana (I cannot source this, but I think I remember reading that from a forum where knna did post, plus UV has several downsides and good reasons not to be used) so if the first result is removed the best efficiency is made with only red and blue LEDs.

UV and cannabis is close related as far as I know.

http://cannabisculture.com/articles/2159.html
Pot potency - Forget big colas and stinky buds: it's all about the resin.
"It takes high quality genetics to produce high quality marijuana, but genetics is only half of the equation.
The genetic structure (genotype) only plays 50% of the role in determining the appearance and quality (phenotype) of a given plant.
The other half is determined by environmental conditions such as light, temperature, humidity and soil nutrition.
All these factors play a role in both the physical and chemical nature of marijuana's trichomes.

The best way to take a look at how environment affects THC production is to look where on the planet
cannabis has naturally adopted a high THC profile. As cannabis has spread around the world it has taken
on many different traits to help in its adaptation to varied areas. The best drug varieties have always been
found at equatorial or high altitude locations. The one thing which both of these variables have in common
is high light intensity and a large amount of ultraviolet (UV) light in the spectrum.

Recent Swiss trials in outdoor plots of clones grown at different altitudes have
shown that there is correlation between higher altitude and increased potency
(although there seems to be a trade off in yield).

This likely means that THC-rich resins act to protect the plant and its seed from both higher light
intensities and ultraviolet presence. It's no surprise that cannabis has developed a chemical to protect
itself against the Sun's damaging UV rays, as they can be injurious to all forms of life."


http://www.cannabisculture.com/articles/2833.html
Metal halide for flowering?
"Third, the lamps emit more UVB light than HPS lamps, although still in very small amounts.
The amount of UVB light plants receive is directly related to the quality of the buds. The more UVB, the higher the quality."

 

[Rasser]

perhaps better to use something like this? the article (thread) is Needed lighting concepts to develop LED grow lights

Those to different kind of curves have puzzled me from the beginning.
Finally a search got me this:

http://www.icmag.com/ic/showthread.php?t=166203
"Those two graphs ^^^ are wrong, it's also a common misunderstanding.
That is the so-called absorption spectra of chlorophyll A/B and carotenoids,
but that was found in vitro with an extract of a leaf inside a "spectrophotometer",
and it's not at all accurate to what plants use to drive Pn (rate of photosynthesis).

You/we should be using the "Photosynthesis Action Spectra" (PAS) as created by K.McCree in the early 1970's,
that is the accurate response of in vivo leafs to photons in PAR (i.e., PPFD), but McCree used monochromatic LEDs
to make his PAS and that is not accurate because green light offers more photosynthesis then red light and more
than blue light too. His PAS was updated last year to reflect the synergy of the whole PAR range not via.
monochromatic lighting. See the second link in my sig for LOTS of info on this and a great explanation of why
the old biology and botany books are wrong, as is those two graphs you uploaded. Ideally a great lamp would
match the updated PAS which would offer a lot of green, red and blue."

 

[jubiare]

the one I uploaded is the PAS created in the '70, that's what's best to use as a general reference (not because I say so, it's just the best to use with solid scientific background, to date)

 

[Rasser]

the one I uploaded is the PAS created in the '70, that's what's best to use as a reference

It sure looks like it, if the other is made by putting green leaf in a blender and measure the chlorophyll juice's reaction to light.

And I think I found the thread you where talking about by Knna.
http://buymarijuanaseeds.com/community/threads/needed-lighting-concepts-to-develop-led-grow-lights.117599/

I wonder what panels hi is using these days.

 

[patrikantonius]

UV and cannabis is close related as far as I know.

http://cannabisculture.com/articles/2159.html
Pot potency - Forget big colas and stinky buds: it's all about the resin.
"It takes high quality genetics to produce high quality marijuana, but genetics is only half of the equation.
The genetic structure (genotype) only plays 50% of the role in determining the appearance and quality (phenotype) of a given plant.
The other half is determined by environmental conditions such as light, temperature, humidity and soil nutrition.
All these factors play a role in both the physical and chemical nature of marijuana's trichomes.

The best way to take a look at how environment affects THC production is to look where on the planet
cannabis has naturally adopted a high THC profile. As cannabis has spread around the world it has taken
on many different traits to help in its adaptation to varied areas. The best drug varieties have always been
found at equatorial or high altitude locations. The one thing which both of these variables have in common
is high light intensity and a large amount of ultraviolet (UV) light in the spectrum.

Recent Swiss trials in outdoor plots of clones grown at different altitudes have
shown that there is correlation between higher altitude and increased potency
(although there seems to be a trade off in yield).

This likely means that THC-rich resins act to protect the plant and its seed from both higher light
intensities and ultraviolet presence. It's no surprise that cannabis has developed a chemical to protect
itself against the Sun's damaging UV rays, as they can be injurious to all forms of life."


http://www.cannabisculture.com/articles/2833.html
Metal halide for flowering?
"Third, the lamps emit more UVB light than HPS lamps, although still in very small amounts.
The amount of UVB light plants receive is directly related to the quality of the buds. The more UVB, the higher the quality."

Thank you for the reading, it is quite interesting but I don't think we can relate this to LEDs so much. It's a wild guess but as we are in a perspective where we try to find the best efficiency, I don't think it really applies.
The sun provides the plants with an insane a amount of light and if the objective was to mimic the sun, we would have multiple thousand-watt panels with very low efficiency. And if it is already difficult to have the right amount of UVB with the sun, I cannot imagine how much power it would take to replicate it with LEDs. And rather than putting only a few LEDs which would have basically no effect, I would prefer putting more reds or eventually some whites instead to boost the real usable light.

This graph from knna's thread sums up how I see sunlight vs. LEDs

The lower the lighting power, the better the efficiency so that's basically the aim of LED lights: sacrificing power for efficiency. And putting UV lights is kinda against this logic.

Anyway, that's pure speculation and there's the possibility that UVB has as much effect on cannabis as it has on tomato plants which would be awesome; but that's not what your article seems to suggest.

 

[patrikantonius]

Shit, when reading what I wrote it sounds like negativism, please excuse me for that I do not master the language yet

There's one thing that we know for sure; there's surely not enough studies studying the efficient growth of marijuana, but it does make sense as it is a bit slippy hehe

 

[Rasser]

Thank you for the reading, it is quite interesting but I don't think we can relate this to LEDs so much. It's a wild guess but as we are in a perspective where we try to find the best efficiency, I don't think it really applies.
The sun provides the plants with an insane a amount of light and if the objective was to mimic the sun, we would have multiple thousand-watt panels with very low efficiency. And if it is already difficult to have the right amount of UVB with the sun, I cannot imagine how much power it would take to replicate it with LEDs. And rather than putting only a few LEDs which would have basically no effect, I would prefer putting more reds or eventually some whites instead to boost the real usable light.

This graph from knna's thread sums up how I see sunlight vs. LEDs

The lower the lighting power, the better the efficiency so that's basically the aim of LED lights: sacrificing power for efficiency. And putting UV lights is kinda against this logic.
Anyway, that's pure speculation and there's the possibility that UVB has as much effect on cannabis as it has on tomato plants which would be awesome; but that's not what your article seems to suggest.

I can't see how that chart relate to efficiency, but it looks like it could relate to this saturation effect in plants.

http://en.wikipedia.org/wiki/Photosynthetic_efficiency
Photosynthesis by D.O.Hall & K.K.Rao says that photosynthesis increases linearly up to about
10,000 lux or ~100 watts/square meter before beginning to exhibit saturation effects.
Thus, most plants can only utilize ~10% of full mid-day sunlight intensity.

 

[Rasser]

Shit, when reading what I wrote it sounds like negativism, please excuse me for that I do not master the language yet

There's one thing that we know for sure; there's surely not enough studies studying the efficient growth of marijuana, but it does make sense as it is a bit slippy hehe

Same with me what I write.

I usually forget to say thanks for something, and go straight for the core of the stuff I don't understand.

 

[bassclef]

I remember seeing somewhere that these graphs aren't exactly accurate representing the peaks of each wavelength in ratio. It's also different for each plant, so these PAR graphs are more of a general guide rather than a rule. I don't think there is a definitive one for cannabis. I remember reading a study where they tested a number of plants and the red peak was greatest around 600-660nm in most of them. The blue peaks were there, but much lower. I'll try to find it.

Now I remember where I had read this. Don's LED faq does a good job addressing it. Check the links to the study where they tested 33 flowering plants, about halfway down the page. Here are the files.



You can see the wavelength graph is weighted toward the red. But what is interesting to take from his analysis is this:

These curves have peak wavelength anywhere from 645 to 690 nm in the red. The plant with the narrowest red peak had peak wavelength around 660 nm. Most plants had photosynthetic action near or over 90% of peak at all wavelengths from 610 to 680 nm, and near or over 80% of peak from 590 to 685 nm. Photosynthetic action for most plants was around 22-30% of peak at 700 nm.

For most of the 33 plants shown, photosynthetic action was down to about half of peak from about 450 nm to about 520 nm, and mostly in the 50-70% of peak range at a secondary peak around 435 nm. At 400 nm, depending on plant species, photosynthetic action was anywhere from less than 10% of peak to about 50% of peak.

One more datapoint is that high pressure sodium lamps have been used for growing plants. The spectral content of those is mostly in the range from 580 to 620 nm, mid-yellow to orangish red. High pressure sodium lamps have a significant very yellowish green spectral emission feature around 568-569 nm, but that one is not as well utilized by plants as red and blue wavelengths are - that wavelength is mainly useful for usefulness to human photopic vision.

Although stimulating only one photopigment is sufficient for photosynthesis, many plants have some requirement of stimulating more than one photopigment or at least one other than the red utilization of Chlorophyll A for proper growth regulation, flowering and fruiting. Proper growth regulation, flowering and fruiting often requires significant blue light.

 

[MajorCoco]

This link is pretty interesting, and talks about the variation of action spectrum between species, as well as discussing the differences between photon flux and luminous intensity on the curve.

http://www.photobiology.info/Gorton.html

Here's a relevant excerpt:
One can see the resultant effect of structural organization on action spectra by comparing an action spectrum for photosynthesis in a green alga with that for a leaf (Figure 9b). The algal specimen is thin; green photons, which are not absorbed strongly by chlorophyll and carotenoids, pass through the thallus and out the other side without being absorbed. Absorptance, and hence action, is low for green light. In contrast, in the leaf, red and blue light are mostly absorbed in the first layer of photosynthetic cells, but green light can penetrate into the leaf interior, gaining chances to be absorbed as it travels a longer pathlength with multiple reflections at cell wall/air interfaces. Green light penetrates further into the leaf, but little escapes. The photosynthetic action spectrum for a leaf thus shows much more action in the green region of the spectrum than the corresponding action spectrum for an alga.

I don't get too hung up about it. Until someone does a proper study of the action spectrum of a few strains of cannabis none of us can know what the action spectrum actually is. The fact that weed seems to have slightly unusual reflective properties in IR wavelengths suggests that it might have a slightly different spectrum than most plants previously tested.

 

[PetFlora]

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.



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

IMHO, the thing to be skeptical about is high PK bloom boosters, not whether green is important, and it's not JUST green.

Another example of where small missing difference are extremely meaningful is in music reproduction: digital v analog. If you examine an analog sign wave it is perfect, but a digital (any digital version) is notched like foot steps + clipped off flat at the top. Even the most exotic expensive reconstruction filters do not quite recover the missing bits. Now many may not hear it, but the fact is digital is inferior

Again, look at the SDG from a quality hps bulb; it's loaded with G/Y/O, and the results speak for themselves: so why reinvent the wheel?

 

[bassclef]

Again, look at the SDG from a quality hps bulb; it's loaded with G/Y/O, and the results speak for themselves: so why reinvent the wheel?

HPS is successful not only because it's loaded with green/yellow, but because of the intensity of the red/orange spectrum. It's not optimal, but the plant still uses it for bud production. According to the study I posted on the previous page, all those flowering plants use well any light from the high 500s to the high 600s, then it drops sharply off. I would assume cannabis would fit in with those graphs too, more or less. Going from 600nm to 660nm is only going to net you around a 10% in efficiency, but we don't have a definitive PAR graph for cannabis, so even that is debatable.

The more important debate is thermal management; we surely lose more that 10% light output, especially on red LEDs, when driving the junction temperature too high. When driven beyond spec this is easy to do. Most of the cheap Chinese LEDs don't have datasheets so we don't even know how bad they are to begin with, but we know bad thermal management can make them much worse.

 

[Gastanker]

This study unfortunately only tested a few spectrum but this data is specific for cannabis and might be slightly helpful http://www.revagrois.ro/PDF/2011/paper/2011-54(1)-7-en.pdf
FOLIAR PIGMENTS AND THEIR DYNAMICS DURING DIFFERENT VEGETATION PHENOPHASES IN FIVE CULTIVARS OF CANNABIS SATIVA L.

 

[Gastanker]

This one is interesting as well - fuck growth rates lets look at cannabinoid production based on spectrum -

Abstract: Plants of a drug strain of Cannabis sativa L -grown 33 days under daylight, shaded daylight conditions, filtered green, blue, and red light, and darkness-were analyzed by gas-liquid chromatography for their cannabinoid content. The highest content of cannabinoids, predominantly Δ9-tetrahydrocannabinol (Δ9-THC) in this strain, occurred in the youngest leaves of daylight-grown plants Leaves at successively lower nodes of this control condition and all treated plants subsequently grown in daylight contained progressively lower levels of cannabinoids Leaves from plants grown under filtered green light and darkness contained significantly lower levels of Δ9-THC than those from plants grown in daylight However, the Δ9-THC content of leaves from plants grown under shaded daylight and filtered red and blue light did not differ significantly from the Δ9-THC content in daylight controls, indicating that these conditions did not alter the synthetic rate of this cannabinoid The cannabichromene (CBC) content of plants grown under filtered red and green light and darkness differed from the CBC content in plants grown in daylight, indicating that the formation of this cannabinoid was independent of Δ9-THC Leaves from plants grown under filtered red and green light and darkness recovered the capacity to synthesize typical levels of Δ9-THC and CBC when placed under daylight conditions Plants from all light and dark treatments, when subsequently placed under daylight conditions for 66 days, attained levels of cannabinoid synthesis comparable to the daylight controls

Effect of Light Quality on Cannabinoid Content of Cannabis sativa L. (Cannabaceae)

Paul G. Mahlberg and John K. Hemphill
Botanical Gazette
Vol. 144, No. 1 (Mar., 1983), pp. 43-48

Not that we're discussing UV but here a blurb anyways -

Abstract

The effects of UV-B radiation on photosynthesis, growth and cannabinoid production of two greenhouse-grown C. sativa chemotypes (drug and fiber) were assessed. Terminal meristems of vegetative and reproductive tissues were irradiated for 40 days at a daily dose of 0, 6.7 or 13.4 kJ m[SUP]-2[/SUP] biologically effective UV-B radiation. Infrared gas analysis was used to measure the physiological response of mature leaves, whereas gas-liquid chromatography was used to determine the concentration of cannabinoids in leaf and floral tissue.

There were no significant physiological or morphological differences among UV-B treatments in either drug- or fiber-type plants. The concentration of Δ[SUP]9[/SUP]-tetrahydrocannabinol (Δ[SUP]9[/SUP]-THC), but not of other cannabinoids, in both leaf and floral tissues increased with UV-B dose in drug-type plants. None of the cannabinoids in fiber-type plants were affected by UV-B radiation.

The increased levels of Δ[SUP]9[/SUP]-THC in leaves after irradiation may account for the physiological and morphological tolerance to UV-B radiation in the drug-type plants. However, fiber plants showed no comparable change in the level of cannabidiol (a cannabinoid with UV-B absorptive characteristics similar to Δ[SUP]9[/SUP] THC). Thus the contribution of cannabinoids as selective UV-B filters in C. sativa is equivocal.


UV-B RADIATION EFFECTS ON PHOTOSYNTHESIS, GROWTH and CANNABINOID PRODUCTION OF TWO Cannabis sativa CHEMOTYPES

1. John Lydon[SUP]2,*[/SUP],
2. Alan H. Teramura[SUP]1[/SUP],
3. C. Benjamin Coffman[SUP]3[/SUP]

Article first published online: 2 JAN 2008
DOI: 10.1111/j.1751-1097.1987.tb04757.x

 

[itskosherbro]

You all are very smart. I hope to be able to contribute in the future.

Super newbie question.... I have a flowering room that is 4x8.... i want to light it as best as possible . Money isnt an object since if i bought these fabricated i would be blowing lots of it. ... I can follow instructions , I was hoping to build 4 units to fill this space>? If somewhere there was a diagram and parts it would be so helpful thanks.

 

[SnotBoogie]

I have no idea how you came to be in this thread kosher, its over a year old

Take a peek round the LED section, theres plenty of DIY guides but sadly its not as easy as just following instructions (sourcing parts, LED selection, etc) unless you want to do a "pseudo-diy" assembly from a bought kit (pointless imho)