Bars vs Boards

DankaDank said:

Below is a dialux simulation I made of 8 V22's positioned in 2 groups of 4 cobs centered per 2x2ft area in a 2x4ft area. 330 total watts, 2.5μmol/w 90% reflective walls and an 18inch hanging height.

Despite cramming 2 groups of 4 cobs together, it has better coverage than most strip lights at 6 inches above plant canopy.

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Yes if you hang the light height enough you can get pretty much any level of uniformity. That was never in question. It comes at a cost though. The higher you need to hang the light the more light you will lose on the walls.

The result is that the average PPFD from the strips at 6" will be higher than from the boards/clumped COBs at 18". With both producing the same amount of umol/s.

Uniformity itself is not the problem. That's simply a function of height.

Getting as many as possible of the emitted photons on the plants at that desired level of uniformity is the challenge. Lower hanging heights achieve this.

wietefras said:

Yes if you hang the light height enough you can get pretty much any level of uniformity. That was never in question. It comes at a cost though. The higher you need to hang the light the more light you will lose on the walls.

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Different light configurations lose light at different rates with height increase due to radiation patterns and positioning of LES's.
Strip lights may have an average uniformity at 6 inches but have a much better uniformity at say 12 inches and therefore lose more light on walls than a non strip styled light at 18 inches. Non strip styled lights with a higher hanging height may suffer greater wall losses than strips at 6 inches but will have a better uniformity resulting in better photosynthetic efficiency.

i where never able to achieve a as uniform spread of light using several cobs vs using several boards or many strips in the tents i grow in.
the 3x3 i compared in simply wont allow the hanging height the cob light would need for the uniform spread.

cobshopgrow said:

i where never able to achieve a as uniform spread of light using several cobs vs using several boards or many strips in the tents i grow in.

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Well as just shown above. Even clumping together the COBs gave a perfect uniformity. At 18"height, but still.

Besides a board or a COB at 18" barely have a different uniformity. A board is pretty much a bigger COB. A COB at 18" spreads the light over the full 3x3 tent. The board would only spread it a few inches further due to the larger size. It's really barely noticable in a PPFD matrix

all good, therefore i wrote.
"the 3x3 i compared in simply wont allow the hanging height the cob light would need for the uniform spread. "

i could not work with 18" distance form the canopy, i always had huge gaps in between my cobs at working distance easy to mesure and even see on a picture.
ah and i think you misunderstood, i wasnt comparing the cobs to one board, i used 6 x 288 boards, more or less a wall to wall config, like uisng tons of strips.
that 6 boards had a clearly measurable advantage in uniformity over the cob setup used before (had been 5 cobs, its stupid i know).

DankaDank said:

There is a reason that Fluence has had the Vyper for as long as they have had the spyder.
Strip lights are actually designed and best utilized for multi tier growing where there is no reflective walls and light needs to be concentrated in a certain area without the use of lenses due to height restrictions.

When it comes to large rooms with a single canopy and minimal or no walk ways it really doesn't make sense to use low hanging rack lights as the shape of the light is barley important when hanging multiple lights at higher heights to create a photon blanket.

When it comes to grow tents things get complicated.
Strip lights are almost always going to lack diode density at the corners and sides when hang at their optimal hanging height. when lifted to try even out spread, wall loses are more sever due to many diodes being positioned close to the walls of the tent thus more of the light hits the sides and more importantly from the "power band" 0-60 degree radiation angle.

Like others have said in a tent you want little LES in the middle and more LES to the sides and corners but not to close to the sides/corners as to interfere with the radiation pattern. People don't understand that LEDs emit different amounts of light at different angles from the center of the emitting surface.
Below is a dialux simulation I made of 8 V22's positioned in 2 groups of 4 cobs centered per 2x2ft area in a 2x4ft area. 330 total watts, 2.5μmol/w 90% reflective walls and an 18inch hanging height.
View attachment 4613384
Despite cramming 2 groups of 4 cobs together, it has better coverage than most strip lights at 6 inches above plant canopy.
Regarding penetration I think GM and GG touched on it well at 2:22:45 in the vid below.

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In that section of video the inverse square law example mirrors what I describe in post #23.

So maybe growers should consider depth of canopy and type of lighting? Especially if they're following forum and internet trend grow styles. Got to fatten up those lower buds, defoliate and get the light in.

So smaller fixture set higher above canopy. More chances for light energy to be lost bouncing off stuff. Dependant on fixture, better depth of "penetration" through a central zone. Suggested grow style, lower planting density. Larger plants. Longer turnover period between taking cuttings and harvest.
Larger fixture set close. More even spread. Less chance for light energy to be lost bouncing off stuff. Less depth of "penetration" of useful light levels. Suggested grow style, higher planting density. Smaller plants. Quick turnover period between taking cuttings and harvest.
Again with the 27" high racks.

If people want to get funny, could always take a rack fixture and plonk lenses on it. Narrow down those beam angles and now hang a bit higher.

All with the caveat that results will differ, dependant on leaf area index (LAI). Be careful here, because different grow styles might have vastly different LAI's even though using identical floor space area.

We can go around in circles discussing this, and throwing up examples. Growers can hang high and compact fixtures or hang low and wide fixtures, but they are not going to reap the benefits if applying only one style of growing. Think growers have to try find a middle ground. Will be wasting or losing something if not taking all factors into consideration.

Can have your cake and eat it. Chocolate or Coffee, not Mocha. Inverse square law. Cognitive dissonance. You makes your choices, you pays your money.

Mrgoodsusa said:

Is that 4x4 fixture? Is that enough red to cover a 4x4

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Its for an 0.8m square tent, 2.5x2.5' approx but id happily put sometthing similar in a 1m tent, just add a few inches all-around.

end_of_the_tunnel said:

In that section of video the inverse square law example mirrors what I describe in post #23.

So maybe growers should consider depth of canopy and type of lighting? Especially if they're following forum and internet trend grow styles. Got to fatten up those lower buds, defoliate and get the light in.

Click to expand...

But inverse square law has nothing to do with light penetration. I know GrowLightBullshit or one of his many other nicks that got booted off the forum was always proposing this idea, but it's simply not true.

The reason he saw more penetration in his chart with the light very high is because if ISL (as he calls it) actually applies he forgot to mention how much light you'd really need to achieve that..

So his chart looks like this:


However when you then work back to the amount of light you'd need to start with you get this:


So this is comparing a light that's producing 32000umol/s to get at 500umol/s from high up. Versus one that produces 500umol/s and then this determines that the 32000 gives you better penetration. Ehm yeah, well of course it does since its a much stronger light.

Don't worry though, in reality 'ISL' does not apply like this at all. Obviously you don't lose 98% of your light over a 40"distance.

So to be perfectly clear these tables are complete nonsense. Both left and right column. There is zero value to these numbers. Light does not disappear at that rate in your grow tent/room relative to height.

Instead light intensity goes down due to wall losses. That has a linear relation to the height of the fixture. ie hang the light twice as high and you have twice the amount of wall lit up and therefore you have twice the amount of light lost on the wall. No ISL there.

Once the light hits the canopy LAI is what comes into play. If the photon hits a leaf then it's absorbed (or reflected). The more leaves the less light passes through. If it passes through the upper canopy it just keeps going until it gets absorbed either by the wall, by the plant, the floor or whatever.

Neither of those two have anything to do with inverse square law. Luckily because we'd have massive issues getting light to our plants if it actually disappeared over such short distances.

hmmmm i think both prawn and weitfras are closer in their thinking than this argument shows.

i think it all comes down your style of growing and the power budget you are prepared to allocate for the returns you get on your crop. if we boil it down to the basics the general idea is to get the largest amount of mass/flower within the least amount of space and use the least amount of power possible.

take two polar opposite examples, number one the unlimited option - you have unlimited space and unlimited power budget ie fields and fields of fertile soil and the sun. the sun acts like a really big cob running at approx 380 yotta watts or 380,000,000,000,000,000,000,000,000 watts (dont worry your not paying the bill!), luckily the sun is hung far enough away that you dont get a hot spot and all your fields are bathed in an unmeasurably even light (forget about clouds ect for this). you can have fields of 2 ft tall plants and fields of 10ft tall plants, it doesnt matter they all get the same intensity (inverse square law to small to measure), LAI doesnt matter, power consuption doesnt matter (its free), this method is always the most productive but not the most efficiant, after all the sun is also lighting the rest of our solar system (wall losses, but again we are not paying the bill so fuk it).

example number two, the very limited option (ie how we all do it) - you now have very limited space and a limited power budget ie under stairs cupboard, grow tent or spare room and artifical lighting with a power budget that costs £$£$ (you are paying the bill now). so now every square foot counts and every watt counts, so a single light point doesnt make sense anymore its just not the most efficiant way of evenly lighting your canopy. even if you had the height in your space you have to hang the light too high(and ran harder) to get an even spread on the canopy resulting in wall losses and wasted watts. in this secanario plant height definitely matters, LAI definitely matters, wall loses definitely mater ect...its all about getting your flower to grow in the goldilocks zone of that even photon saturation.

i think like this - start with grow area, say a 4 x 4 tent then allocate a power budget lets say 37.5 watt/sq ft so that gives us an overal budget of 600watts. the best use of that 600watts is to get as much of it as possible converted into photons and then get them photons spread as evenly as possible over that goldilocks zone.
so with led leading in the efficancy/photon genaration per watt catergory we pick them, so say a samsung lm301b. now we can work out how many we need, for the budget concious grower he will want to spend less on the lights(ie fewer diodes/boards/strips) and run them hard.

at max curent a 301b is 200ma at around 2.95 volts so watts= .2 x 2.95 = 0.59 watts, so with our 600watt budget we need around 1000 diodes, you then have to shop around and see what boards/strips are on the market that fits your budget/diode count. this normally is roughly 4 288 "quantum" boards or 10 strips with around a 100 diodes each. then you have to spread the boards/strips over the canopy to get the most even coverage at your desired intensity for as least waste as possible, for this above scenario strips will always win, lower hanging height, less loss better spread.

now for someone where budget isnt a concern (talking light cost not watts used) they can go for more diodes and run them softer. (and we will take this to the extreme budget£$/and diode count) so we take the 301b again and run it at 65ma at around 2.76 volts, = 0.18 watts so now we want around 3300 diodes. of we go shopping and now we can get around 11 "quantum" boards or 33 strips for our budget. in this scenario and at the extreme i think boards probs give a more even spread of light. at this diode intensitity(number of, not brightness) the average strip build has too many diodes too closely grouped all in vertical lines, i think the boards win here...

but... if you take a double row or even tripple row strip with the diodes spaced a bit farther apart vertically, well i think the strips probs edge back out the boards???.

so to recap the sun is free and the best lol.

and id say say strip builds beat board builds for the average grower 80% of the time untill you get crazy then its probs a draw....but strips for the win

Just my very newbie $.02

Why only boards / strips / COBs?

They each have slightly different POU (Philosophy Of Use).

Why not:
Boards in the center - spaced for even distribution.
Strips at the edges - a point or two lower and tilted a few points inwards to account for edge loss on the boards
COBs on the corners - a point or two lower and reflected to account for corner losses.

I can understand one tech. for simplicity & budget concerns - I'm throwing borrowed burples in my tent for flowering later today; pools of different levels and spectrums all over my tent - I don't care much on this round, but I'm looking towards designing for the next grow.

But if I'm concerned strictly about coverage, I'd be looking at products or methods to mitigate edge / corner losses.

That said - I drool on the keyboard a little over those full ceiling board / strip builds!

wietefras said:

Instead light intensity goes down due to wall losses. That has a linear relation to the height of the fixture. ie hang the light twice as high and you have twice the amount of wall lit up and therefore you have twice the amount of light lost on the wall. No ISL there.

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The higher you hang a light above a 2x2 reflective area, the more centered, consolidated and point source you want the LES to be.
The Lower you hang a light above an 2x2 reflective area, the more decentralized, sparse and perimeter dense you want the LES to be.
It is much more difficult to achieve even uniformity at lower heights. An even diode spread over a 2x2 at 6 inches is not going to produce uniformity and will suffer greater wall losses when lifted to achieve better uniformity, than a point source would.

Lockedin said:

Just my very newbie $.02

Why only boards / strips / COBs?

They each have slightly different POU (Philosophy Of Use).

Why not:
Boards in the center - spaced for even distribution.
Strips at the edges - a point or two lower and tilted a few points inwards to account for edge loss on the boards
COBs on the corners - a point or two lower and reflected to account for corner losses.

I can understand one tech. for simplicity & budget concerns - I'm throwing borrowed burples in my tent for flowering later today; pools of different levels and spectrums all over my tent - I don't care much on this round, but I'm looking towards designing for the next grow.

But if I'm concerned strictly about coverage, I'd be looking at products or methods to mitigate edge / corner losses.

That said - I drool on the keyboard a little over those full ceiling board / strip builds!

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there is definitely more than one way to skin this cat thats for sure.

i think you answered your question on why you dont see more strip/board/cob combos, its the ramp up in complexity. often boards/strips and cobs often have different forward voltages and different max amp ratings leading to more and more drivers to complete the build, thats not including the extra more complex frame needed to accomadate individual fixtures at different height and angles.
its definatly doable its just a well thought out strip build suits 80% of circumstances with pretty even coverage at minimum complexity...ie its good enough.

DankaDank said:

It is much more difficult to achieve even uniformity at lower heights. An even diode spread over a 2x2 at 6 inches is not going to produce uniformity and will suffer greater wall losses when lifted to achieve better uniformity, than a point source would.

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i think you have to define diode count in this "even diode spread". if you have 1000 diodes per 2 x 2 evenly spread, run soft to hit the intensity required the uniformaty at 6 inch will be great. but if you have 100 diodes per 2 x 2 evenly spread but run really hard to hit your required intensity then obviously its not gona be as uniform at 6 inch. raising the light will give better uniformaty at the cost of intensity.

grotbags said:

hmmmm i think both prawn and weitfras are closer in their thinking than this argument shows.

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Yes , he agrees that we need to spread the light sources. He just doesn't want to admit that another product but his own can achieve that better at the same component count (and then still cheaper).

Why not use strips with 144 diodes? You'd need only 2 strips per board? That's already killing the boards without going overboard on "extra wiring".

For a 4x4 you'd actually use 4'strips and then it would be one strip per board.

grotbags said:

if you have 100 diodes per 2 x 2 evenly spread but ... then obviously its not gona be as uniform at 6 inch.

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If you spread 100 diodes uniformly over a 2'x2' space then each diode would only have to illuminate a 2.4"x2.4" square. So it would actually do that from 1.7" up already. Radius = sqrt(1.2^2 + 1.2^2).

For a 120 beam angle the led achieves uniformity when the height is at or greater than the radius of the circle it needs to light up.

wietefras said:

If you spread 100 diodes uniformly over a 2'x2' space then each diode would only have to illuminate a 2.4"x2.4" square. So it would actually do that from 1.7" up already. Radius = sqrt(1.2^2 + 1.2^2).

For a 120 beam angle the led achieves uniformity when the height is at or greater than the radius of the circle it needs to light up.

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yer i didnt even think about doin the maths i was just freestyling! just the general concept i was trying to get across.

and you couldnt really only run 100 301b per 2 x 2 cause to get to 75 watts (37.5wattsq/ft) they would have to run 20%+ over max amps. well you could run them like that but its not the norm, you would drastically shorten their life. that and the fact that no one makes a 2 x 2 pcb with 100 diodes on it

DankaDank said:

The higher you hang a light above a 2x2 reflective area, the more centered, consolidated and point source you want the LES to be.
The Lower you hang a light above an 2x2 reflective area, the more decentralized, sparse and perimeter dense you want the LES to be.
It is much more difficult to achieve even uniformity at lower heights. An even diode spread over a 2x2 at 6 inches is not going to produce uniformity and will suffer greater wall losses when lifted to achieve better uniformity, than a point source would.

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have you seen migro's new aray, 6" height 4 bars 240wats for 2x4 what do you think?

grotbags said:

and you couldnt really only run 100 301b per 2 x 2 cause to get to 75 watts (37.5wattsq/ft) they would have to run 20%+ over max amps. well you could run them like that but its not the norm, you would drastically shorten their life. that and the fact that no one makes a 2 x 2 pcb with 100 diodes on it

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lol made a right mess of that!, you would need 150 watts for a 2 x 2 so the diodes would need to be ran at 300%, its obv impossible...

grotbags said:

i think you answered your question

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LOL I did while I was typing - helps sometimes to think things through in type!

Now I have a fun planning, wiring and rigging project to draw up and consume time with - my Wife is gonna hate you guys!