Building LED lights from facts, no theories

I have decided to reduce module wattage to under 10 watts down from 13 to 15, driving at 350ma (max.400ma) I will have to add 4 more modules to compensate.
This will give me better top coverage, longer LED life and easier to regulate with a resistor. Of course I give up some brightness that would help with penetration.

My LED selection is based on what I have on hand, instead of what is truely optimal.
Each module will have
4 red K2s, R (second) bin.
1 k2 royal blue, Q (top) bin
1 SSC cool white, top bin
1 SSC blue, top bin.
Resistor to drop 1 to 2 volt.
I plan on using this for vegging to replace a 350 watt CFL array.
I will be playing around trying to flower. I will be adding a couple additional 2.5 foot long strips of red and far red LED during the budding period only.

I don't have high hopes for the budding and don't think it will replace HPS, but I would really like to trash the vegging CFLs and save a couple hundred watts if possible.
Do you guys think the LED color selection is close to optimal for vegging? I might be able to squeeze an extra red LED in, if real Vf's are lower then spec sheet.
I would like to start wiring LED modules this week.

Once I get things going and have unit in operation, I will probably replace resistors with regulator. I will look for one with a lower drop out voltage. With LM317s they use a much power as an LED. I hate to give up that much wasted power.

I did decide not to initially go with fans on top of each module, but instead will be blowing air across the tops of the heat sinks. Fins will be aligned in direction of air flow.

It looks like warm white and farred are providing the mechanics that are needed in early and efficient flowering within cannabis and most likely many short day flowering plants.

2 Warm white (3000k) led with red x6 630 and red 660 x 10 and farred 730 x1, blue 455 x1, blue 470 x1 with 25deg lenses on the reds and 40deg lenses on the blue are giving the results that all are after. If I could only find a good 440nm blue to replace the 455!
If cree would make a 660 and 440 :-(.

The lenses are making a huge difference. even though you loose roughly 12-15% of the lux, the luminous intensity is focused much more efficiently with little or no light scatter. :thumbsup:

I have not been able to try results of near UV {400-425nm}
Thats next. W00T!

Billyjo :pimp:

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Originally Posted by billyjojimbob11

It looks like warm white and farred are providing the mechanics that are needed in early and efficient flowering within cannabis and most likely many short day flowering plants.

2 Warm white (3000k) led with red x6 630 and red 660 x 10 and farred 730 x1, blue 455 x1, blue 470 x1 with 25deg lenses on the reds and 40deg lenses on the blue are giving the results that all are after. If I could only find a good 440nm blue to replace the 455!
If cree would make a 660 and 440 :-(.

The lenses are making a huge difference. even though you lose roughly 12-15% of the lux, the luminous intensity is focused much more efficiently with little or no light scatter. :thumbsup:

I have not been able to try results of near UV {400-425nm}
Thats next. W00T!

Billyjo :pimp:

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:postgood:


Aloha BJJB

I'm sold on lenses.
They give me penetration I wanted,
and the lensed 5 watters are outperforming the un-lensed w/reflectors almost 2:1
IMO, 160 degree/lambertian is a waste of watts.

ciao,
Weezard

Weezard, I'm planning to homebrew a version of your 4+1 x 15w. light. :thumbsup:Looks like the Ledengin LED's have a 90-110 degree beam, though. Would you recommend additional optics or did the 15's work okay for you unmodified?

Also, MPJA has a 28v. / 5.5A power supply (the 24v. is out of stock for awhile). I was thinking getting one to power 2 parallel legs of (2) 15w. 660's, with an LM317 on each leg. Am I just making extra work for myself by not running a 24v. supply into a single LM317 and parallelling (4) 660's off the 317? Seemed like a bit of current to push through a single 317, but I don't really know.

I would like to underdrive the LED's slightly, and have some extra headroom in the build. Thanks!

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Originally Posted by Crunchypants

Weezard, I'm planning to homebrew a version of your 4+1 x 15w. light. :thumbsup:Looks like the Ledengin LED's have a 90-110 degree beam, though. Would you recommend additional optics or did the 15's work okay for you unmodified?

Mine are mounted in a deep aluminum cake pan which serves as a reflector.
Didn't find lenses for the ledengins but the 5Watt leds that I lensed are clearly better than the same configuration without the lenses.
Would call it proof if the red leds were identical.
The lensed set is 660nm., the un-lensed are 625nm.
Perhaps the difference in efficiency compensates.
Ah dunno.
I just ordered more lenses.
Will install them on the 625nm lamp and start taking pictures
of the progress.
If you find, say, 40 degree lenses that fit the 15W ledengin lens, please drop me a line.

Also, MPJA has a 28v. / 5.5A power supply (the 24v. is out of stock for awhile). I was thinking getting one to power 2 parallel legs of (2) 15w. 660's, with an LM317 on each leg. Am I just making extra work for myself by not running a 24v. supply into a single LM317 and parallelling (4) 660's off the 317? Seemed like a bit of current to push through a single 317, but I don't really know.

LM317 has a absolute maximum of 1.5A!
You might want to use an LM138 - 338 instead.

Driving an approximately. 12V led from a 28V supply will work well if you run the 2 parallel sets in series.
That will give you 4V headroom but would have to pass 2.1A.
That would require a pass transistor, etc.

So the LM138 series with a max of 5A. would probably serve better for ease of design.
Google the LM138 series for a quick and easy schematic.

The problem then is the blue led which uses closer to 15V, for peak efficiency.
I use 2 separate supplies because dissapating "excess" energy just rubs me the wrong way
My next ledengin lamp will have 2 Blues.
The goal here is to waste as little power as possible in the regulator.

I would like to underdrive the LED's slightly, and have some extra headroom in the build. Thanks!

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Good idea!
I limit mine and use a thermal switch in series with the fan to keep everything under 50C.
Better Photons:Watts = less waste heat to deal with as well.

Easy lamp to build and it will work for flowering.
Mine covers app. 2 sq ft. and takes 2 or 3 weeks longer, start to finish, than HPS.
But the quality?
Wicked good!:stoned:

Let me know if I can help.

Aloha,
Weezard

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Google the LM138 series for a quick and easy schematic.

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Okay, glad I asked.

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The problem then is the blue led which uses closer to 15V, for peak efficiency.
I use 2 separate supplies because dissapating "excess" energy just rubs me the wrong way
My next ledengin lamp will have 2 Blues.
The goal here is to waste as little power as possible in the regulator.

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Yes, I think I've read everything you've offered on this board (and Steve F.'s as well) and had already planned using a 19.5v Dell PS for the blue(s) as you have mentioned. I am still deciding whether to add a second blue to my plan, or a warm white instead. I realize the white is a crippled blue, so to speak, but I might like the WW just so I can view my hobby better. Not so sure I need all the blue 2 x 15w. would provide. I have a Procyon and although it is probably the best thought-out compromise of ratios for overall use, it's a bit blue-heavy for mid-late flowering, IMO. (Works great as for transition into 12/12 from veg, though.)

Anyway, thanks. I have read a lot of posts, and of the many knowledgable folks contributing on this subject your explanations are by far the clearest to me.

Yes, the lenses are far more efficient than without IMO. Also, the light is culminated which, from what I understand, makes absorbing the photons more efficient. I think lenses will be an absolute must when building a highly efficient array, unless the emitters use a very narrow angle already.

I've been researching LED's for a couple of weeks now. Reading everything I can on the subject mostly from this forum but from others as well. This thread is the most comprehensive on the subject of what LED's (and their various qualities) to use and how to use them. Really good stuff.

But what I haven't been able to find is a clear picture of exactly how to build a proper, efficient, and effective LED lamp or strip or board or square. Whatever you would call it.

What I'm talking about is some instructions on how to put together your own LED grow light from parts easily available on the internet or your local Hardware/Electronics store. But I'm not asking for a beginner guide such as.

"Hook up a 12v power supply to your LED's with this resistor."

I want something that will actually work and work well.

If I had the option of requesting such a guide I would ask that it contain the following:

A guide where you actually build or explain how you would build a decent size array of high powered LED's such as the Cree LED's that would function in the real world of a grow room.

A brief explanation on Power Supplies and why you are using this particular Power Supply and which ones work best for LED's and why.( I realize this may depend on your setup and how large or small it is. But answering the question for the array you are building and then giving a small tidbit on what might work for smaller or larger LED's arrays would be helpful to everyone whatever kind of LED grow light they are trying to adapt to their current setup.)

An brief explanation on LED drivers and how to apply them to your LED grow light.

How to pulse LED's using cheap and easy to program micro chips such as the Picaxe Micro Controllers ( PICAXE ).

The best way to limit current without using a bunch of resistors that burn power and create heat. I've heard allot of technical names thrown around such as "transistors" and many others. And many good explanations and threads are out there on what these things are but not so many on how to apply them to your LED grow light.

How to put the Power Supplies, LED Drivers, and Micro Controllers all together to do advanced techniques such as the "Martian Method". Whereby you might have a string of Far Red LED's continue to pulse for a predetermined amount of time into your Dark Period or Lights out Period of your grow.

Touching on things such as Pulse Width and Variable Frequency(for different types of LED's)

How to string LED's together and a brief explanation on stringing LED's In Series and Parallel and how doing this affects the final results as well as the voltage/amperage/wattage/current and the pros and cons of each.

What to mount your LED's to. And how to string them together.( As in the actual material for connecting them.)

How to apply proper cooling methods such as mounting your LED's to cooling fins.

And anything else that would come up in the building of an LED grow light.


I realize that many of these questions have been answered before, some even in this thread but none of them have been put together in an easy to understand practical format that even beginners can start to grasp.


Now I'm not asking for everything to be handed to me on a silver platter.
I've personally started my quest for building a LED grow light by picking up some cheap LED's, a power supply and I even ordered a Picaxe micro controller to start playing around with. And I have no dout I might eventually figure it all out. But that will take quite some time and many people won't make it through the journey, choosing instead to give up on LED's and stick with HPS/MH or buying LED Lights such as the UFO or Pyrcon. Never being able to realize the benefits of building your own custom arrays and spectrum's in a way that fits your own grow room and style.

I believe even a small guide to building a basic LED grow lamp that covers all the material above would improve the communities understanding of LED's and bring LED's down to a level that everyone could get involved with. What could spring from this is more people using LED's and more and better styles and techniques being developed. With a large enough community behind building their own LED's group buys could be organized such as those going on at the Spanish forum that Knna is apart of. Making top notch LED's such as Cree more affordable for everyone. Even those looking into smaller projects.

If this is beyond the scope and discussion of this thread then I ask that someone create a new thread dedicated to showing people how to build LED's and answering questions they may have along the way.

Thanks for reading.

" I ask that someone create a new thread dedicated to showing people how to build LED's and answering questions they may have along the way."

Aloha Nodestar

You might want to look at;
"Calling out to Weezard for led advice"
In the indoor lighting forum.
Sounds like it's just what you are looking for.:cool:

If not, tell us why.
We aim to please.
Regards,
Weeze

Thank you for the reply Weezard. I've actually already read through that thread. And it is very informative. But it shares problems that almost all threads on the subject share. The information is to spread out(not huge but still problematic for beginners) and it's to complicated for beginners. For instance.

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A sense resisror is so called because it hooks to the sense input of a regulator.

Here's how the LM317 CCR circuit works;

The lm317 is designed to be a variable voltage regulator
and it "wants to see" 1.25Vdc between the output pin and the ADJ/Sense pin. before it will begin regulating anything.
We take advantage of those facts for our current regulator.
We tie a restor to the output pin and draw the current to our load through that resistor.
If we run a wire from the load side of the resistor to the adjust pin, that pin will sense the voltage drop across the resistor.
So, ohm's law.
If we want a 1 ampere current limit, we use a resistor value that will drop 1.25V at 1 amp.
Once the adjust pin senses 1.25v.it regulates voltage to keep that voltage drop, and thus the current, constant.
1 A. X 1.25 V. = 1.25 W.
While a 2 watt resistor would suffice, a 5 or 10 watt resistor will run cooler and thus regulate tighter.
I had some 10 Watt, 1 ohm power resistors laying around so I thermal glued them to the heatsink.
Overkill? Perhaps,. But overkill is a good thing in this case .
Gives me about 1.2A. which is exactly what I wanted.
Seems to be the sweet spot in photons per watt.

What is this R2 you speak of?
The current limit configuration only requires one resistor.

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And then you end with.

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It's very simple.

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Hehe. It probably is very simple in the context of building an LED Grow Light. But separated from allot of other facts and all out on it's own it's complicated to the beginner. Or at least it's complicated to me. I didn't understand most of it and what I did understand was just stand alone information. I don't know how to apply it properly.

That's why I think a full guide would be very helpful. I will reread that thread and try and digest some more information. Thank you for bringing it back up.

I will tread lightly on posting to much more about this subject in this thread unless you guys want to steer the discussion in that direction.

Thanks for the help.

But, your point is well taken.
"That's why I think a full guide would be very helpful. I will reread that thread and try and digest some more information. Thank you for bringing it back up."
Reading it over, I have to agree.
Guess we were having too much fun.;):stoned:

I was talking directly to DH by request.

He's got skills and knows electronics so we were able to shortcut a lot of the basics.
Never occured to me that we were probably confusing some folks.

OK, I'm about to construct a new light.
Soon as I have my excrement gathered, I'll try to get organized and just do a straightforward fabrication.

Plenty of pictures.
No techie talk, :( unless asked.
Insert tab A into slot B sort of thing.
That what you're looking for?

Wait a minute, who am I kiddin'?:wtf:
There's no way I'm gonna suddenly get "organized".
That thread is about as lucid as I get.:jointsmile: Sorry.

Perhaps Dreadedhermie will volunteer to translate.
Or, re-render my ramblings into a more readable style.:)

We now return this thread to it's rightful owners.
Aloha,
Weeze

Quote:

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That thread is about as lucid as I get. Sorry.

Perhaps Dreadedhermie will volunteer to translate.
Or, re-render my ramblings into a more readable style.

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I'll help however I can. :thumbsup:

I can't promise to keep a straight face any better than Weezard, though. :D

Hey guys I've been researching this topic from an amateur's perspective.

I like all the info on this site it is amazing what a bunch of stoners can come up with when there's money to be made ;)

In regards to the color spectrum, specifically UVA vs UVB requirements, Click Here

I am very interested in Knna's quoted spectrum requirements. They do not appear to match the standard photosynthetic action spectrum. Any info on specific requirements for herb? Perfect led grow light thread was mentioned but I can't seem to find it...

Knna: can you tell me the exact LEDs you'd recommend currently given your spectrum suggestions? Price is not much of an object on initial purchase, but I want maximum efficiency.

Hurray! My first post!:rastasmoke:

"Hurray! My first post!:rastasmoke: "

And a darn good one too!:D

Welcome.
Weeze

Hey not to beat a dead horse, but why is the McCree spectrum different than this one? I searched for photosynthetic action spectrum. This is also the spectrum from my photosynthesis book. Kinda important when selecting LEDs...

The spectrum action curve you have posted, and that you may find on most botanic books, is just a sum of the absortion of the different pigments present in the higher green plants.

But it notably differ from what is observed actually on live plants, that uses green way better than that, along with other differences.

There is some things that explain that difference:

-Pigments arnt distributed homogeneously along leaves, but stratified.

-They arnt present of the same relation, and almost never at the 1:1:1 (Chl a: Chl b: carotenoids) that is used to obtain the action curve. It varies with the tipe of light, for plant specie, light intensity that they receive on the long term...

-And the most important: absortion of lab's extracted pigment on solution is very different to absortion of those same pigment in vivo. The process is still very unkown, but the fact is same pigment molecule may absorb the better light of a given wavelenght depending of its orientation (into the leave) and depending to the protein its binded. For example, the central Chlorofill a molecules on the Photosynthetic Reaction Center have a max of 680nm (Photosystem II) and 700nm (Photosystem I), while its the same molecule. Max absorbance from 650 to 720nm of the same molecule has been reported.

So the action spectrum curve you posted is a virtual creation, from unrealistic lab's extractions, while McCree and Inada curves were obtained measuring the photosynthetic response of in vivo plants.

Ok, so I've been researching action spectra and quantum yields of in vivo photosynthesis. I can't seem to find exactly what I'm searching for:

Is there a spectrum which indicates the maximum amount of each wavelength which can be absorbed in vivo?? Also I need to know the relative lumens/einsteins/intensity or whatever per meter squared so I have a rough idea not only of the appropriate spectrum to construct, but the irradiance necessary for each bit of plant...

I'm also capable of searching for academic papers if you've got any citations.

After this, I will find the most efficient LEDs in the proper amounts and wavelengths. Any choice picks?:angelsmiley:

Good luck in the search, Im on it since 4 years ago.

There are many studies about it, but with limitations. The most known are those written by McCree and Inada, along the 70 and 80's of past century. You can fin the same curves for individual specias and strains of commercial crops in agronomic studies. Differences with the averaged curves are small, anyway.

But these studies all have three main limitations:

-They are measurements of usually sun growth plants performed under not saturating photosynthesis irradiances. Efficacy of each wavelenght has proven to be dependent of the irradiance level, specially on the long term, after plant's acclimatation.

-Plants adapt their photosynthetic systems to both the intensity (irradiance) and light's quality they receive, in order to do the best with it.

-All studies concentrate on the effect of isolated wavelenghts. But its different when plants receive all wavelenght at a time. There are sinergies between wavebands that modulate the response. The most known is the Emerson Effect, that is universal (related to the electron flow between photosystems), but there are many unkown ones that are specie especific. Each plant specie have somewhat different liking in their light's quality preferences.

Photosynthetic response is something that is not fixed at all. If there is something remarkable about plants is their adaptation ability in the way to use resources. And light is their main resource.

:thumbsup:Thanks for all the help Knna, you really know what you're talking about!

I've downloaded all the McCree and Inada journal articles I could find. Here's what I learned:

Enhancement (Wavelength modulations such as the Emerson Effect) seems to only be about 7% different from the action spectrum.

McCree has some great data in the 1971 paper, "Action Spectrum, Absorptance and Quantum Yield of Photosynthesis in Crop Plants". On Page 206 species #13 is a tomato plant. From this you can see the quantum yield of 16 key wavelengths in vivo.

Also, according to McCree's article in Plant Physiology vol. 49(5) pg 704, the difference in photosynthesis between the action spectra taken from the sum of each individual wavelength and that of the white light combination was within +/- 7%.
I find this close enough, especially if the emmerson effect is accounted for. I believe this will be my starting point.

Now, the question of photosynthesis saturation must be explored. What are the maximums? I understand that this is a sliding scale, because of the variables of temperature, humidity, nutrients, soil moisture, and CO2 content in the air. What conditions are ideal here? Temp? CO2? Humidity? Given these ideal parameters, I can begin running experiments.:cool:

You can find details of photosynthetic perfomance of cannabis at varying irradiance, temperature and CO2 levels in the study "Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions", by Suman Chandra, Hemant Lata, Ikhlas A. Khan and Mahmoud A. Elsohly. Its a very complete study, again with the limitation of studying responses on the short term, and not on after long term acclimatation.

The study reveals that cannabis can handle very efficiently up to 500-600 uE/m2 at ambient CO2, with optimal day temperature near 30ºC (but strongly dropping over it!), and the best range being 25-30ºC. There is no clear photoinhibition point, with photosynthesis still increasing (although little) at 1500 uE/m2 (not at low temps), so that point at optimal temps and ambient CO2 is over that figure

You must take into account than that 7% of margin error refers to white lights sources, broad band ones with limits on the saturation of a given waveband.

On the LED growing research, we are working with relative narrow wavebands strongly saturated, in the look for the highest photosynthesis but accomplishing the most positive sinergies, trying to achieve way highest photosynthetic efficacies than a white light can do.

We are actually getting very nice enhancements on the spectral efficacy (yield/mol of photons PAR) using this approach when refered to white light sources, of near 200%. So its possible to go way ahead. Its not exactly photosynthetic response, but how carbon efficiently fixation is used, that is related to more factors. But the difference is so huge that sure that a significant part is achieved by enhanced photosynthetic response.

A group of grower are performing experiments with standarized measurements in order to find the optimal spectrums (different according to irradiance used?) for cannabis. If you want to join us, you are welcome. Stadistical analysis of experiments may strongly fasten the research, so sharing our results benefits all.

I was thinking about and experiment for photosynthetic spectral analysis for a given plant. Since some of the wavelengths are codependent, you could not just examine them one by one. You would need to have all of them on at once, and reduce the amount of just one until the O2 output of the plant decreased. Then you would know you'd gone below the max. If you had the right equipment, this would be extremely simple. Though, you'd need an O2 meter to quantify photosynthesis, and you'd need exact amounts of light for every wavelength running simultaneously.

Do you have 200 lasers we could calibrate? :D



Maybe trial and error would be a better way to go...

Hmmmm...but its a very good idea, at the end. Equipment that measures instant O2 flux from a leave is not so expensive....

It would be needed to use a dark period of 30min between each light quality, but using large steps, like 20% for each waveband, we may identify the bext mixes in a rough way and then work in fine tuning it.

Using the same irradiances of differnt SPD needs some work, but its doable. A single testing array with 1 or 2 LEDs of each color and current adjustement for each color is all we need.

I think its a very good idea. At least in order to identify the best photosynthetic respones. Long term (whole grow under a given quality and irradiance) would be still needed to study which matter at the end, the carbon fixation, morphology traits, to understand the final relation between light and yield. But it would be experimenting in far narrower settings.

So, what's that gizmo that instantly measures O2 flux called? :wtf:

CID Bio-Science, Inc.: Portable Photosynthesis, Plant Canopy, Root and Leaf Measurement and Analysis: CI-340

Qubit Systems: Photosynthesis and Transpiration

:wtf: Only $4,000... Maybe I can barrow one. I'll see if my university has one. Might have to test tomatoes instead. that could be as close as I can get. Think it's similar? Would tomato results be remotely useful?

I wish I understood this.......:( I wanna build my own LED so badly:D

Let me start off by saying... I appreciate the interesting reading and feel free to remove or bash this post at will, it's probably deserving.

By comparison, this question will be elementary at best, maybe even ridiculous, but since I know nothing about LED's I'm just gonna throw this out there.

Has anyone ever heard of, or is it even possible to use a large flat panel t.v. to grow marijuana? With the new LED and/or Laser t.v.'s I was just curious as to whether or not it's even possible. Is there similar technology involved that may potentially crossover?

I realize the cost, both initially and while in operation, would be impractical, among any number of other things, I just thought it would be interesting to try. I assume the major problem would be, that I'm confusing color with spectrum or lumens.? Hell, I don't know, you're the smart ones.

Anyone got $10,000 they can loan me for a test.

Peace

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Originally Posted by mrmarbles

Let me start off by saying... I appreciate the interesting reading and feel free to remove or bash this post at will, it's probably deserving.

By comparison, this question will be elementary at best, maybe even ridiculous, but since I know nothing about LED's I'm just gonna throw this out there.

Has anyone ever heard of, or is it even possible to use a large flat panel t.v. to grow marijuana? With the new LED and/or Laser t.v.'s I was just curious as to whether or not it's even possible. Is there similar technology involved that may potentially crossover?

I realize the cost, both initially and while in operation, would be impractical, among any number of other things, I just thought it would be interesting to try. I assume the major problem would be, that I'm confusing color with spectrum or lumens.? Hell, I don't know, you're the smart ones.

Anyone got $10,000 they can loan me for a test.

Peace

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There are LEDs designed to be viewed, and LEDs designed to give light.

Of course those designed to be viewed gives light too, but its way less than required for plant's growing. Plants requires a lot of light, and the only practical way to give it with LEDs is using high power ones.

Think that HID growers uses in 1 sq meter (11 sq ft) what streetlights uses for 50X times that area. That is a lot of light.

I was walking next to a po-po car the other day and was thinking that its lights would be awesome to grow with. The new LED ones are the 7mm(i think, they are def big) and they are bright as balls, I bet you could get some sort of harvst from using popo lights. Just another thought triggered by the post above.

hmmm... red and blue... Cop lights might work...

Let's get some Maui Wowie and try it. We could call it Hawaii 5-0!!!:rastasmoke:

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Originally Posted by knna

A group of grower are performing experiments with standarized measurements in order to find the optimal spectrums (different according to irradiance used?) for cannabis. If you want to join us, you are welcome. Stadistical analysis of experiments may strongly fasten the research, so sharing our results benefits all.

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Hey knna, I'd like to join you and may be I can interest others also.

I only heard the clock tick and don't know what time it is ;), but I have some ideas on how measurements should be taken and better spectrums can be found that I would like to discuss.

Hi, Bubbleblower ,

glad to find people interested.

Light measurement is the most complicated part without expensive equipment. What I do is calculate how many micromols of photons equals to a given number of lm for a given spectrum. I obtain the spectrum of LEDs used using an spectroscope, a camera and some sofware.

Having the amount of uE emitted, at least we can know the average light density in the grow. In order to obtain irradiance data, I use the same procedure than to calculate the absolute uE, so it leads to have a correction factor between uE and lux (measured with a light meter). Only problem is only works for each separated spectrum, so I need to do a measurement for each color used and then add up all them. I use a grid to build a irradiance map for a given distance from lamps.

Consuption of LEDs alone and full system is measured using a voltmeter and amperimeter.

About yields, I suggest to record as many info as possible. Both fresh and dry weight, and unprocessed yield and manicured one. I suggested to weight all the plant weigth (without roots) is fresh, later manicure and weight stems and manicure's rest (better if separately). After drying, report the bud's dry weight and stems and manicure's rest dry weight. I know its too much work weighting, but I think its necessary to eliminate the large differences induced by how each grower process its yield. With such data for each grower, at least for one time, it would be possible to normalize weight reports in a meanglifull way.

Im really interested on any suggestion on how to standarize measurements.

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Originally Posted by knna

Im really interested on any suggestion on how to standarize measurements.

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I know so little that I have many.

To find better spectrums and PPFD levels of course we need photons per nm.
Some use SPD's to convert and others spectrometers to measure the irradiance and they get a -normalized- spectrum, the amount of photons per nm and total irradiance per m2 or so.

But one bulb could give its energy per cm2 on 10 times more surface than another so the sweetspot should be taken into account..
Also the normalized spectrum would be very inaccurate, because different wavelengths loose their energy in a different pace. That effect is big.
So spectrums change depending on the distance from the bulb and we are not really giving the spectrum we think or the amount of photons.

May be we can use 3-dimensional top down measurements and normalize the spectrum once more for every wavelength/distance from the bulb.
That will give a better indication of the real amount of photons and give us like an average spectrum.
We could take measurements with 10cm increments horizontal and vertical.

Yeah, thats why I say to calculate both the "theoretical" average irradiance, meaning the absolute photon emission divided by the surface area of the grow (footage) and or/ volume area.

And aditionaly take measurements using a standard light meter (a 20-30$ one) and convert it to photons/m2 using an Excel sheet. This is a true, actual measurement of the light reaching leaves (the main measurement is taken at top of canopy level).

There is no differential absortion of different wavelenghts in air (when talking about 1, 2 or 3 meters as most, and mostly distance is way below 1m). Another thing is how light quality changes below canopy due the differential transmision of leaves, but I always claim to use undercanopy lighting as the most efficient one, that apart of it, largely avoids this problem. So irradiance measurement using LEDs is usefull both at top canopy and undercanopy.

It would be nice people has spectrometer or spectrorradiometers, but I wouldnt expect it. Its necessary to find ways of measurent that any grower interested may do it if he has the will, having a limited equiptment, as a standard light meter. My purpose is to build a database of the spectrums of LEDs most used, so all people has to do is measure with a light meter and then convert lux or fc into uE/m2.

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Originally Posted by knna

Yeah, thats why I say to calculate both the "theoretical" average irradiance, meaning the absolute photon emission divided by the surface area of the grow (footage) and or/ volume area
And aditionaly take measurements using a standard light meter (a 20-30$ one) and convert it to photons/m2 using an Excel sheet. This is a true, actual measurement of the light reaching leaves .

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That should give very interesting -and surprising- results.

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Originally Posted by knna

There is no differential absortion of different wavelenghts in air (when talking about 1, 2 or 3 meters as most, and mostly distance is way below 1m). .

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May be I put it wrong. I noticed for example a much bigger difference in mW/m2 output relative to distance (below 1 meter) in UVB as in longer wavelengths. Also I saw this graph on page 7 which is very interesting.

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Originally Posted by knna

Another thing is how light quality changes below canopy due the differential transmision of leaves, but I always claim to use undercanopy lighting as the most efficient one, that apart of it, largely avoids this problem.

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I like the idea of intra/under canopy lighting a lot, it was next on my list.
Since no more than 15% (?) of the light penetrates through the canopy this should boost yield per m2 (I obviously like m3 better:)) and only little light is needed to get significant results.

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Originally Posted by knna

Its necessary to find ways of measurent that any grower interested may do it if he has the will, having a limited equiptment, as a standard light meter.

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Lux at certain distances from the bulb, both horizontal and vertical would be easy. I think many people are willing to take these measurements if they understand why that is important and how these data will be used. Everybody -on forums like these- should know where they can find and send this information.
We should get them with the program.
I will ask in a few forums that have thousands of growreports and do many tests.

Let me go further down my list.
Just check this pic and you understand the potential implications for cannabis.

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May be I put it wrong. I noticed for example a much bigger difference in mW/m2 output relative to distance (below 1 meter) in UVB as in longer wavelengths. Also I saw this graph on page 7 which is very interesting.

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Very useful article, thanks.

But that graph refers to how angle of viewing affect the spectrum. And its not related to how light transmit, but to the LED source itself. This difference is caused in white LEDs by how the phosphor layer is added. LED manufacturers had improved it strongly on the last years, but is imperfect yet.

Standard LEDs dont emit almost any UV, and less specifically UVB.

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I like the idea of intra/under canopy lighting a lot, it was next on my list.
Since no more than 15% (?) of the light penetrates through the canopy this should boost yield per m2 (I obviously like m3 better) and only little light is needed to get significant results.

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Purdue University is working hard on this, and in general all researchers involved on the development of grow areas for NASA missions.

Planophills plant's species strongly benefit for intracanopy lighting. Average improvement in yield is being 35% for the same amount of light used, but some species has increased it by 100%, doubling yield with same amount of light.

Percentages of IC lighting generally varies from 25 to 50% of the total light.

Due undercanopy areas are mostly underlit, and many times severely underlit, very little light (compared to the amounts of light used overcanopy) transform lower leaves from sinks to sources of energy and resources. Bottom leaves arnt discarted, as happen when there is only top lighting, due the arey are a ballast for the plant. This mean undercanopy lighting achieve a way better use of plants resources and allows to use optimal irradiances for all the leaves of the plant, strongly improving photosynthetic efficacy.

We are getting excelent bottom buds using very low irradiances undercanopy, below half of used overcanopy (on uE/cubic feet basis).

I believe Ive linked it before, but check here the Excel spreadsheet

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Originally Posted by knna

Very useful article, thanks.

But that graph refers to how angle of viewing affect the spectrum. And its not related to how light transmit, but to the LED source itself.

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Unfortunately there is a lot I don't understand correctly, also because I got much disinformation. May be I did something wrong, I compared a light-distance chart of 5 HPS bulbs with measurements of UV output from 8 other lamps.
uW/m2 was -relatively- lost faster than foot-candles. The graph seemed to confirm what I read in all the why plants are green articles.

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Originally Posted by knna

Standard LEDs dont emit almost any UV, and less specifically UVB.

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For my UVB I use Philips medical grade UVB broadband. It seems somehow the most "extreme" wavelengths within extended PAR are most important to the plant.

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Originally Posted by knna

Planophills plant's species strongly benefit for intracanopy lighting. Average improvement in yield is being 35% for the same amount of light used, but some species has increased it by 100%, doubling yield with same amount of light. Percentages of IC lighting generally varies from 25 to 50% of the total light.
Due undercanopy areas are mostly underlit, and many times severely underlit, very little light (compared to the amounts of light used overcanopy) transform lower leaves from sinks to sources of energy and resources. Bottom leaves arnt discarted, as happen when there is only top lighting, due the arey are a ballast for the plant. This mean undercanopy lighting achieve a way better use of plants resources and allows to use optimal irradiances for all the leaves of the plant, strongly improving photosynthetic efficacy.

We are getting excelent bottom buds using very low irradiances undercanopy, below half of used overcanopy (on uE/cubic feet basis).

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Great. So what I need for my room is at least 8 rings of about 25 watt of leds in the correct combination.
It is for 1.4m2 where I have 2 induction -electrodeless- lamps of 300 watt* plus the 2 x 40 watt UVB (and 2 x 50 watt HPS but only as signaling light).
My idea is also to "finish" my spectrum with red leds most of all.

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Originally Posted by knna

I believe Ive linked it before, but check here the Excel spreadsheet

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Darn, homework :thumbsup:

* Here is a testreport of the 6500K version of it with an accurate SPD. I should still get this for my 2700K.

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Originally Posted by knna

I believe Ive linked it before, but check here the Excel spreadsheet

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Mmm, I still don't get the privilege to access that page, do you have it somewhere else?

Hey Bubbleblower,

Just saw the spectrum graph you got there, I would like to point out to you to be very carefull, it may or maynot be accurate. The chinese have a tendency to lift spectrum graphs from american companies, and thier diodes don't actually meet those graphs.

The first large DIY LED light I built was going to be based on reds and white LEDs, since the whites (I had looked at) had plenty of blue spike (driving the phosphor) and then covered green, yellow and some orange/red. When finished the light sucked, it lacked the needed blue. I took a white diode sent it to someone to spectrographed it's output was a lot different. The blue spike was there but way to the left missing the needed wavelenght. The rest never reached orange/red. After looking around I found an identical spectorgraph, like the one they sent me, for a luxeon white. I have not trusted the chinese since, I thought they would saved me money but in the long run a costly lesson.