Discussion of the pragmatic application of LED's

[guest456mpy]

knna,
Please, continue with any explanations you feel are needed. As you have correctly stated background theories are needed before discussions begin and practical applications formulated. I think that we are in agreement with all of this. Pragmatism doesn't discount theories and science. It only asks that they be tested by experience.

How do you feel about the wording of rule 1, what (if anything) would you change?

H.G.

 

[Weezard]

2 cents from the math impaired.

2 cents from the math impaired.

...

So in my estimation, these are the situations which can benefit by the higher beam concentration to enable a taller growing plant. In my humble opininion technology should not dictate the style of cultivation, by the nature of the strain and the style of the grow accommodated by the choice of supporting technology.

What do you think?

The only other point I wish to comment on is from the previous post:

And the magic word is...

LED light is not actually directional, it only appears to be as an artifact of the way it is emitted. Light is emanated from the face of the device so it is a quasi-collimated light source. The light is not coherent like a laser, nor is it actually collimated, so it does spread out with distance. My empirical measurements with a meter have shown that the concentration or strength of the beam falls nicely with the inverse square law.

"And the duck comes down with a hundred dollars" -Groucho Marx

Discussion?

Again, I don't dispel what you say, merely bringing out some finer points for practical application. As a retired engineer specializing in X-ray and imaging design and implementation for a very large German engineering firm I have had a fair amount of both theoretical and practical applications. I very much enjoy this type of interchange with you as I seldom have an opportunity to converse with someone with the same background and education.

None the less, we must bring these things down to a language and context where "everyman" can understand and use the fruits of our discussion.

"Yes please, math makes me sneeze." -Everymang

Once again, thanks for your timely and valuable input, please continue to do so, my friend.

H.G.

LCD for me,
tends to be.
Whip out a tool
and den we'll see.

First, an 18" sq. array of 12 emitters with a Lambertian pattern.
(180 degree, approximately)



Then a lensed array of 14 emitters at ~ 90 degrees.



Pretty much what I expected to see.
And this is with app. 98% reflective walls.

That got me into testing reflective surfaces.

I'm lining 5 gal. buckets with different materials.
I just set the sensor for my light meter in the bottom, centered. Then place a led array on the top.

Round bucket = no corners.

Same bucket for each test keeps distance and size variables constant.
And I calibrate the light with a flat black lining, before each reading.
Will publish photos when I finish, but preliminary says, the more reflective, the mo' betta.

Not a big surprise, but it does make a bigger difference than I had imagined.

Excellent thread H.G. It's an honor to be a part of it.

Aloha, Y'all
Weezard

 

[guest456mpy]

Thank you weezard, I'm just trying fill an obvious gap in cannabis cultivation, and I am honored to be in the company of such open and productive minds.

Now, after re-reading this thread I feel I may be "over-moderating" the direction where I'd really don't have the right to, so I'm gonna step back and let the natural flow of discussion resume now that "hot button" topics are are no longer in play and the thread seems to be on a good course. If I have anything meaningful to say, I certainly will; but the floor is open for totally open discussion.

Have at it guys,
H.G.

 

[joe4444]

Very Educational

Very Educational

When is the next class, professors? I'll be in the front row!

 

[knna]

If we want to check how is the light density drop with distance due the spreading of light, its a must to do it on a black painted area to eliminate reflection, and of course, with nothing blocking light.

On the other hand, measuring with the reflective walls we use is the best to have a good idea of actual atenuation with distance, due the loss at reflection.

But always be aware than measuring just on a line, directly below the light source may be tricky. We are measuring local irradiance here, only valid for that single point at which we measure it. If we measure just along the optical axis, for sure a narrow optic will get a lower drop with distance, because its intensity is higher, but coverage, less. The higher reading on the optical axis is compensated for the lower reading off axis: lighting is more uneven.

But as I explained, this happen because you are measuring results from just a single panel. So light spreads from it, but on a conical pattern, so light density on the axis falls at lower rate than off it. But if you put 4 panels as that on the 4 corners, you realize that past the distance at which beams joins, drop of light density is way lower, as light going out the beam is compensated from light from the other panels going into it, producing an even lighting. It happen the same if instead of panels, we place LEDs along all the top area lighting downwards.

So, what are the benefits of narrow optics (beam angle) and wide ones?

Narrow optic:

Pros:

-Lower light losses (less light goes to side walls)

-Light more focused, being able to send more light through a hole in canopy of a given size

-Work very well when placed at some distance of plants (typically, more than 1ft)

Cons:

-More uneven lighting. In the case of using LEDs separated to the next instead of crowded panels, difficulties mixing light spectrum.

-Dont work fine at short distances. Need some distance to get light distributed evenly, and, more as narrower optics used, exist the risk of excessive local irradiances when plants are too close. But in general, they can be used at short distances without deleterious effects, apart of reduced efficacy.

-Shadowing may be an issue.

In general, narrow optics is a good idea when k and/or LAI are low (low k:leaves mostly in angle, not horizontal; low LAI: leaves not too abundant, there is enough holes in the canopy) as it allows to use just top lighting.

So light losses are lower (good), but lighting obtained, less even (bad).

Wide optics:

Pros:

-Very even lighting with excelent spectrum mix still at short distances. Increased efficacy of the light, especially at short distance of the lamp.

-Produces a kind of diffuse lighting: light comes from almost all directions, being able to enter any hole in the canopy, independent of leave's angle

-Shadowing is never a problem.

Cons:

-More light loss due more photons goes to the side walls. Worse as larger is the distance from lamp to plants and walls less reflective.

So this option only have a drawback, but its an important one. I choosed to go this way and use very reflective walls to overcome the problem, as apart of it, IMHO, wide optics are way more versatile. I tend to use side lighting always that is possible, and for side lighting for sure that narrow optics arnt a good idea.

Wide beam angles are very useful on side lighting and where k is high, as there is little shadowing and light enters for all the holes in the canopy, "looking" for them on a 3D fashion, and not by brute force vertically. Two leaves separated 1" vertically may block fully space looking from top, but have a wide hole between them. Wide optics works better here.

But I admit than 90º beam angles are generally enough to get the advantages of "wide optics". I use larger ones simply because LEDs I like for efficiency/price arnt avalaible on it. If I could get good LEDs with 90º optics, I would use them. Using secondary lens on larger beam angle LEDs is not a good solution because they have their own losses.

My ideal LED setup would use 90-120º beam angles on the center, and 30-45º ones on the edges, in order to get the lowest light losses but the more even lighting and more diffuse light. And with LEDs distributed along all the grow area, not all in a central panel.

On the other hand, on side lighting, 120-170º beam angles are ideal. The wider the better in this case.

I am working with optical films, that may overcome all the cons for a relativelly low cost in light. Just changing the curvature of the film, it is possible to get a very wide beam angle and a colimated column of light with high intensity from the same LED string.

The debate between brick panels and LEDs evenly distributed along all the grow area is very similar to narrow/wide optics, but both pros and cons are very extreme. While narrow optics on LEDs result on a more uneven light distribution a short distance, if LEDs are not together in the top center of the grow area, at 1ft from the lamp or less there is already an even lighting. But when all LEDs are in the center, it happen very similar to HIDs, that need relatively long distance to lit effectively all the space, and always producing a very uneven lighting that seriosly drop efficacy of the light.

Using multiples sources of light is all advantages, both if considered for single LEDs or full panels: better 2 panels of 50W instead of 1 of 100, and 4 of 25 better than 2 of 50. There is disminishing results here, past a number of light sources there is little gain, but from 1 to 2 or 4, there is a very noticiable difference. Light distribution is always way evenly this way, and evenly lighting result on increased efficacy. On the other hand below a brick panel penetration is increased because intensity is higher, but it only happen below the lamp, while at the sides, penetration is lower, because the light intensity does.

Hempyguy, I dont like rules at all. They only exist to be broken

And I have noticed along the years on the growing boards that there is many different types of growers with different priorities. Its almost impossible to find rules that fits all on almost any thing related to growing. If we narrow the conditions of our "rules", as for example, efficacy of light being target nº1, I would rephrase rule as:

"Use wide angle LED on the center, and narrow on the sides (except if your lamps is going to work always at more of 1 1/2ft of canopy, in which case use narrow optics, and very narrow on sides)."

Or better yet, change the emphasis to:

"If your plants are taller than 2 ft, use side or intracanopy lighting"

 

[smokefrogg]

the narrow versus wide

this is what most intrigued me about the kessil approach

they are using an array of leds in a single lense that is focused and doesn't spread anything at all like your typical panel with individual leds does

/me goes back to lurking and reading here

 

[Weezard]

That's food for thought.

That's food for thought.

Good points Knna!

My worry with side lighting is phototropism.
I appears that hemp phototropism is triggered by the shorter wavelengths.
I mount the blue leds in the center of the array for that reason.
Played around with a monochrome sources and found that my girls "like" blue.

On the strength of that, I can see using distributed red on all sides with the blue leds mounted top-dead-center for classic terminal bud production.
Kinda like sunlight at noon.


I love to read your precision oriented theory.
That's what drives my hands-on futzing around.
Thank you for the time and effort.
I do not ignore any of it.

However this quote has served me very well.

"In theory, theory and practice are the same thing.
In practice, they are NOT!"

High precision is great for pure knowledge and setting up experiments.
But, it does not mean squat to a tree.

For actually keeping my medicine chest stocked, I have found that, within reason, "half-assed is more than good enough." <-(Our state motto.)


We have a great team here and we're jus' gettin started.

Keep the actual facts and information coming, and I'll do my best on the practical application side of leds.


@Joe:
Mahalo fo' da kind words brah!
Professional, I ain't.
Never finished highschool.
So, I do spend a lot of effort trying to understand the science of it.
(Stay in school kids.)


But, I almost define amateur.
I do dis 'cause I love doing dis.


Aloha nui and "thanks for all da fish", guys

Weezard

 

[Weezard]

Ooh!

Ooh!

the narrow versus wide

this is what most intrigued me about the kessil approach

they are using an array of leds in a single lense that is focused and doesn't spread anything at all like your typical panel with individual leds does

/me goes back to lurking and reading here

Are you saying they use a single Fresnel lens on the array?
Hmmm, never occured to me.
I gotta look into this, thanks.


Aloha,
Weeze

 

[one Q]

if I may get in here about LEDs. I have a question not about the LEDs themselves as a good option, but about leaks.

One day the fans were turned off, therefore the scrubbers where not running either. In about 30min the whole area smelled of Canna. This is not safe.

The reason this is my question is that one of the PROs of LED is that you dont nee to run that fan/filter... but IME even with LEDs you still have to keep them going just to keep the scent at bay. Granted, you can get a smaller fan and scrub and this will save, you still have to GET THEM. for some ppl this adds to the conversion cost. I have to toss good equipment and replace them with similar equipment and keep them running still.

i guess my question is if you guys run you fans/filters all the time and if odor leaks out. adding to the discussion Ventilation in an LED grow. Is there a CFM per watt yet??? then growing in the cold months too, add heater? what up with that?

I dont mind crossing over but need a strong "argument" on these points first.

(i am very PRO LED fwiw)

 

[Weezard]

Da Kessil report.

Da Kessil report.

Aloha Smokefrogg.

I'm back.
Mahalo fo' da tip.
Not a fresnel lens.
Much mo' betta dan dat.

I'm very impressed with the engineering of those lights.
But, at app. $9.25 USD per Watt!

Way over my budget.
Guess we hafta wait a while longer. <sigh>

Aloha, Weeze

 

[knna]

Very true, Weezard, what matter is putting things in practice. But some background is required to do the trials with some direction and to extract conclusions that serves to improve after the experiments. But Im all with this thread mostly focused on practical approach and experimental results.

About that, we have used extensively blue LEDs on side lighting, and none has had any problem of phototropism. Plants continue growing aswell, mainly upwards. Yep, some more branching was induced, but that was all (and we thought its a desiderable effect).

On the other hand, lately Im advicing to use just white+red on side panels, with strong red percentage. But because higher efficacy, not because blue caused any problem.

Of course, we always keep blue fraction low in respect the total light, either on top or side lighting. I dont know if using larger percentages may have deleterious effects (photomorphism related or others, as closure of stomatas or something like that), but for sure that there is no any need to use more blue.

Fot our experiments I can state that lighting on bottom part of leaves works perfectly, is not detrimental (at least as far as its not very intense) and allows plants to process higher irradiances optimally than when most of the light only hits on upper part of leaves.

In fact, now I would like to experimentally try how works placing LEDs in the bottom, lighting upwards.

The possibility of using higher irradiances by using both sides of leaves (targetting about double uE/m2 on upper than bottom side, 300 vs 150uE/m2) is potencially an excelent way of incease production per surface/volume unit while keeping efficacy of light (g/uE) near constant.

The Kessil unit is a 35W matrix array of chips with a dome less than 1" and a 60º beam angle. Thus a very strong lighting. I think the minimun distance at which a plant may be of it is 1ft, and that is for obtaining irradiances about the photoinhibition point of cannabis. Likely it would be very useful when LEDs must be at large distance of plants (>2ft). I believe its not on the right direction of development for horticulture and I told them so, but maybe Im wrong. Maybe people demand very intense LED lamps or Kessil are thinking on greenhouses that put lamps very high, but need to block as less sunlight possible.

But i think that at least on actual configuration is very little useful for most indoor growers. Apart of it, its very, very expensive right now.

OneQ, you should not mix the active cooling of a LED panel, when its used, with the required air renovation of the cab or with the need of exhaust air to ride off the heat.

HID growers needs to exhaust a lot of air in order to get rid of heat, thus thinking on the need of air renovation is irrelevant for them, as its covered more than enough.

On the other hand, if you not have a heat load to evacuate, still you need to renove the CO2 of the cab (one of the three main requeriments of plants), thus you need to exhaust air. And always you exhaust air, if you dont want it smell, you need to use a filter.

You can exhaust continuosly (better) or on a temporized way. But if you dont want smalls, its a must to use a filter, whatever the lighting you use. I dont understand why you think that fans of LEDs must be involved on any way to air renovation of the cab.

 

[guest456mpy]

one Q

I run my scrubber fan 24/7.
General grow rule number 3 - no smell - trumps any energy savings by cycling carbon filter fan off.

H.G.

knna, I hope that mooning person was aimed at rules and not me. LOL



H.G.

 

[smokefrogg]

thanks guys for taking a peak at it

the kessil idea seems like it could be a good one, current price point and configuration puts me off...but it makes me think about the future

i am seeing this in a similar vein as cpus, there was a push for single core cpus to be very fast and powerful which got us great results, as multi core cpus began to hit the scene we noticed that the push for raw speed decreased, now there is a push for more and more cpus on a die...this kessil led array makes me think of just that. sure they are at 21 leds per array and the price point is high, if they stay in business it's only a matter of time before we see higher number of leds in an array at a much more attractive price point, hopefully with more configuration options as well, time will tell

 

[treefrog]

A while back, I noticed a post by VerdantGreen in his "205 LED" thread. He said he had changed his ventilation configuration since converting to LED's. Instead of pulling from the bottom and venting out the top, which is, of course, the classic HID method, he reversed it, in an attempt to keep the air-flow congruent. For those not familiar, LED fans blow downward, onto the array and out the sides of the LED housing.

Prior to that post, I had had a conversation with LEDGirl about that very thing. I asked her if the LED's cooling fans could be reversed, so they wouldn't be fighting against the vent fan (classic HID, bottom to top setup) She said the fan's ability to cool the LED's would be compromised if they were flipped. I wonder how true that is, but don't want to risk ruining my light (205) to find out!

Anyways, I'm currently designing a new cab with that in mind. I plan on pulling air into the cab from the top (passively) downward and out, into another area, through some carbon, through the fan and out, keeping the air-flow congruent. Wouldn't that be a practical, dare I say pragmatic application of LED ventilation?

Also, in the midst of my first run with that light, I've noticed a few things. Ridiculous vegetative growth, mostly as it pertains to density. A stronger smell, with a more complex, intricate bouquet, and the plants need more potassium for some reason. These are cuts and a mix that I'm very familiar with.

 

[Weezard]

Potassium, you say?

Potassium, you say?

A while back, I noticed a post by VerdantGreen in his "205 LED" thread. He said he had changed his ventilation configuration since converting to LED's. Instead of pulling from the bottom and venting out the top, which is, of course, the classic HID method, he reversed it, in an attempt to keep the air-flow congruent. For those not familiar, LED fans blow downward, onto the array and out the sides of the LED housing.

Prior to that post, I had had a conversation with LEDGirl about that very thing. I asked her if the LED's cooling fans could be reversed, so they wouldn't be fighting against the vent fan (classic HID, bottom to top setup) She said the fan's ability to cool the LED's would be compromised if they were flipped. I wonder how true that is, but don't want to risk ruining my light (205) to find out!

<sigh> It's true only if you need to maximize a profit margin.

Makes much more sense to draw the air in through the sides of the heatsink and then up through your filter.
That's what I do. It works very well.

Disclaimer:
(You might have to get a li'l drastic to make that work on a commercial light .)

On a commercial unit it's only a couple bucks more per unit to do it right. Alas, it's all about max profit.

On a DIY, it's the only way to fly.
I M pragmatic O.

Anyways, I'm currently designing a new cab with that in mind. I plan on pulling air into the cab from the top (passively) downward and out, into another area, through some carbon, through the fan and out, keeping the air-flow congruent.

Not sure I follow you here brah.
Could you elaborate?

Wouldn't that be a practical, dare I say pragmatic application of LED ventilation?

Also, in the midst of my first run with that light, I've noticed a few things. Ridiculous vegetative growth, mostly as it pertains to density. A stronger smell, with a more complex, intricate bouquet, and the plants need more potassium for some reason. These are cuts and a mix that I'm very familiar with.

Now that's excellent information about the Potassium needs.
How did you sus that out?

Aloha,
Weeze

 

[treefrog]

Now that's excellent information about the Potassium needs.
How did you sus that out?

Aloha,
Weeze

Thanks Weezard ~ The plants started to show the classic signs, that is, crispy and yellowing on the outer edges. This was shortly after being transplanted. I knew there was no way it was nitrogen, because the mix has plenty. Didn't really look like that anyway. Then I thought it was magnesium, because it's such a common issue with MJ, but it didn't actually look like that either. I figured I'd try to treat it that way though, because it's hard to overdue mag. I watered them with a good strong dose of calmag, but it didn't change anything. The next watering, I gave them a strong dose of EJ Meta K and the problem went away. Same mix I've been using for years under HPS and never had a K deficiency. Strange, eh? I'm not saying it's the light, but I'm not saying it isn't either, lol.

I've had the unit apart. Reversing the fans would be an easy deal.
You suck the heat out the top on yours, instead of blowing air on them?

 

[treefrog]

Also, as far as the new cab's ventilation.. I was thinking I'd pull air in (passively) from the top, so it would flow downward, with the LED cooling fans (as they are now) and out the bottom, though I suppose it's a non-issue if I can flip the fans around and keep my vent fan the way it is and has been forever. Does that make sense?

 

[smokefrogg]

hmmm...reverse airflow, you might have something there... =)

 

[Weezard]

Oh.

Oh.

Also, as far as the new cab's ventilation.. I was thinking I'd pull air in (passively) from the top, so it would flow downward, with the LED cooling fans (as they are now) and out the bottom, though I suppose it's a non-issue if I can flip the fans around and keep my vent fan the way it is and has been forever. Does that make sense?

Yes, now I get it

Mahalo fo' da quick reply.

YMMV.

I have not disassembled one of those lights, yet.
So, can not say if it would work well.
Basically, you need airflow through the fins of the heatsink before you drag the warmed air out and dispose of it.
I did it this way:


Since I already had convection currents in the direction of up, I decided to go with the flow.

Only downside is possible dirt buildup on the fan and 'sink.
Round here we get that in either direction, so, I made it easy to take apart and clean.

But, I digress.
This is not a DIY thread.
My bad.

Aloha,
Weezard

 

[alkalien]

Hi all,

from my, very limited, view I can confirm most of your points.

1. Plants under LEDs grow wider, with more branches, less vertical groth.
2. During veg I have to add Mg to the rez to fight huge problems. Could be connected to the leaves beeing ways greener and darker compared to plants under every otherlight in and outdoors.
3. While flowering I have to add a lot of K to again cope with big problems. Lost a lot of lower leaves to a K deficiency.

I'm running a recirculating hydro setup with a commercial 155W Panel. At first I assumed it was me who failed finding the right dose of the Hesi nutrition I'm using but now I'm pretty sure it's because of the LEDs. Still this is my first go at a LED setup plus the first hydro system, so feel free to doubt my input and show me wrong

greets