My path from outdoor to COBs - Help/advice appreciated

First of all, Hi there!

I've been lurking around for the past 6 months, soaking up knowledge and envy at equal parts. You guys are awesome and I thank you all so much for, as always, sharing.

So... I haven't grow indoor in a while. The last few years I had outdoor sativas, and for the last few months I've been thinking about skipping this season and going COB. At least as a test. I'll give it a try and go from there.

I bought the most basic without being stupidly small setup: 4 x CXB3590 CD 3500K and HLG-185H-1400B.
Here is where I could use some advice:

• It'll be better 2x2 COBs in a 2x2(60x60cm) space, or 1x4 COBs in 1x4(30x120cm)?
• I have an entire room for it, and I dont really want to have to buy a tent, so I have thought of just hanging 4 white plastic strips from the ceiling. Does that sound as a stupid idea, and I should do it right?
• I'm going to go simple, pots and soil. I know that might be too boring for you fancy gentlemen with your very fine hats and your cocos , but as it's a test I dont want to add any new variables. So: I'll need anything extra apart from the usual feeding, being under LED?
• Any advice on what and how many to grow? For this first one I'm going for quantity.

Thats pretty much it for now. The lights should be here mid next week.

J.

A 2'x2' space would suffer less loss to walls than a 1'x4'. (8 ft of perimeter vs 10 ft)

Make sure you hang it on something secure.

Nothing wrong with soil. I prefer a water only organic grow myself.


Depends on your style, but that's enough light for a 3'x3' or 2'x4'. If you've got mkre space, that's an easy way to get more yield. I like SoG and auto flowers myself, so I stick one per square foot. And some people like to grow one giant plant in a 4'x4'.

Generally if not limited by plant count, SoG would yield more. Less overall grow time needed for the same yield.

you could cover up to 6q ft with 200w at that efficency easily

depending on how many plants u wanna run and how big they r smth like a 50x100 for 2 plants ?

Atulip said:

A 2'x2' space would suffer less loss to walls (8 ft of perimeter vs 10 ft)

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Makes sense. I'll go square.

weed-whacker said:

you could cover up to 6q ft with 200w at that efficency easily

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Yep, thanks.
I'd looked into that and found out the numbers are with you: https://www.rollitup.org/t/cxb-3590-36v-or-72v.878016/#post-11770091

4 CXB3590 3500K CD bin 49W, 56.3% efficient = 196 dissipation W = 110 PAR W *.9 losses = 99.3 PAR W into the canopy and 85.7W of heat into the heatsink
in a 2X2 = 24.8 PAR W/ft² or 1235 PPFD averaged (very high intensity maybe too high unless dimmed)
in a 2X3 = 16.6 PAR W/ft² or 823 PPFD

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So I'm thinking 4 plants in 70x70cm (2.25x2.25') that would be around 973 PPFD.

Desmond J said:

Makes sense. I'll go square.


Yep, thanks.
I'd looked into that and found out the numbers are with you: https://www.rollitup.org/t/cxb-3590-36v-or-72v.878016/#post-11770091


So I'm thinking 4 plants in 70x70cm (2.25x2.25') that would be around 973 PPFD.

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I'm running around 940 PPFD in a 3.3' x 3.3' and my girls love it...

actually 1x4 and 2x2 is literally exactly the same....exact.....assuming it is enclosed at those dimensions 4sqft is what it is no matter how you spread it....
to me 1x4 is more linear and easier to create a light for....all you need is 2x 42" pieces of angle aluminum.....space the cobs 12" apart center point to center point and 2 piece for your width and drop them on the frame
that bar will also light a 2x4 area as it is pretty powerfull

1'x4' has a larger perimeter than 2'x2'. More light will be lost to the walls.

1+1+4+4 = 10

2+2+2+2 = 8

In a 1x4 with 4 cobs, 1 per square foot, the 2 cobs on the end have a portion of light reflected off 3 walls, the middle reflected off 2 walls each. A 2'x2' in the same 1 per square foot, 2 walls of reflection for each. More efficiently uses the light, unless you were in a 100% reflective room(impossible?)

Wisher2 said:

actually 1x4 and 2x2 is literally exactly the same....exact

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Ye I know 4ft2 are 4ft2. I meant it terms of light propagation, and how to better use the overlapping.

ie. in 1x4 there are only 3 overlapping areas, each of them between 2 COBs. Tho I guess they would be bigger.
While in 2x2 are 4 areas, each of them between 2 COBs, plus a center hotspot between the 4 of them.

I guess my original question about shape would be better put like this: Does it matter at all?

rectangular or square will be more uniform in lumens and watts per SF. I prefer 2x2. I use the 2x2 as the basic module and build on that. Don't forget about supplemental lighting, i.e. Far Red, Deep Red, IR, and Royal Blue to name a few. welcome to indoors. peace

are we forgetting that cob/led are semi directional.....where if you are running 1 cob per sqft it dosnt matter what config you are using and you actually dont really need reflection as 1 cob covers 1 sqft period...without reflection....so more perimeter wall really dosnt mater.....wall reflection only catches the small amount of light [email protected] isnt really throwing that much light around....even without optics....but with optics....all light will go to canopy ...
just my 2 pennies

Wisher2 said:

but with optics....all light will go to canopy ...
just my 2 pennies

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90° reflector at 6" height puts 50% output at 6" from the center of the source. There is still light beyond this point, optics merely adjust this point based on beam angle, and may adjust spread pattern. The only way to send all light to the canopy would be to have the canopy large enough that the edge received 0 light.. and at that point it's not growing so it's not a canopy.


Loss to walls is always something to consider when designing your space. It's why we like Mylar and panda film and even white paint. Reflective walls to capture the light we lose.

agreed although........in reality......running hps I love my reflective walls......
with cobs....with the naked eye....when I close my door...no light reflects off the door to the plants even though the plants are inches away from the door....because my cob....@12" away from canopy with 90degree reflector....only covers that sqft of space and not beyond....and by raising the light to say 18" the beam may go beyond but do to the reverse square law.....light become diminished so becomes a mute point for reflectivity......I am willing to bet anyone if they set up an identical grow with 1 cob per sqft with reflect and without...they will both net the same
because we are not talking multidirectional lighting such as HID we are talking directional....and reflectivity beyond the beam is serving no purpose unless your lights beam is beyond the canopy in which case you should then spread your canopy to fit the beam or lower your lights to fit the canopy
JMO for the sake of argument....all in good knowledge to further gain

If you have a cob over a square foot edge at 12" height with 90° reflectors, then you have lighting hitting the walls/floor. At 12" from 12" under the cob, output will be roughly half that of the center, or 6" past the edge of your canopy as described.

Like I said before, you would need to stretch your canopy to the zero point of light to actually capture all of it with the canopy. The beam angle is merely determining the point where half the center value would fall.



This point can also be calculated.

http://www.mathportal.org/calculators/plane-geometry-calculators/right-triangle-calculator.php

Where angle beta would be 1/2 the beam angle, side a the height, side b the distance to 1/2 center value.

Atulip said:

If you have a cob over a square foot edge at 12" height with 90° reflectors, then you have lighting hitting the walls/floor. At 12" from 12" under the cob, output will be roughly half that of the center, or 6" past the edge of your canopy as described.

Like I said before, you would need to stretch your canopy to the zero point of light to actually capture all of it with the canopy. The beam angle is merely determining the point where half the center value would fall.
View attachment 3710624


This point can also be calculated.

http://www.mathportal.org/calculators/plane-geometry-calculators/right-triangle-calculator.php

Where angle beta would be 1/2 the beam angle, side a the height, side b the distance to 1/2 center value.

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I agree in theory
the problem is real world where theoretical values dont hold as much weight
I promise that my 3590's at 12" above canopy with 90degree lens are not throwing any usable photons past a sqft
remember reverse square law
so the problem is are those photons usable....as in will they actually ad a + to growth rates
same may argue any photons are +
IMO larf is born

Just want to get the facts out there and correct any misinformation that may be thrown about. In theory, and practice, anyone with a lux/par meter can confirm.

How much needs to be reflected from walls is important to consider. Unless you prefer 16 individual 1'x1's to a single 4'x4'. Everything beyond that square foot cob is for larf right?


Me personally? I'm gonna try to utilize all the light I can as evenly as I can. And limiting reflection loss to walls aides in that.

Atulip said:

Just want to get the facts out there and correct any misinformation that may be thrown about. In theory, and practice, anyone with a lux/par meter can confirm.

How much needs to be reflected from walls is important to consider. Unless you prefer 16 individual 1'x1's to a single 4'x4'. Everything beyond that square foot cob is for larf right?


Me personally? I'm gonna try to utilize all the light I can as evenly as I can. And limiting reflection loss to walls aides in that.

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as evenly as you can would yes be 1 cob per sqft at that low of a amp draw
700ma on a 36v cob is roughly 25 watts
effecient....yup but not intense.....with that in mind I would probably be running them at 8" to canopy just to get light on the sqft itself....
we arent talking a 300 watt cobb sitting 36" above canopy....we are talking 25 watts which is about 15 par watts....
real world stuff
par/lux meter status
what does that equal..for plant growth??
of course things change as the intensity goes up.....but not with those values
not misinformation.....reality
if you are runnng 25watt per cb you have to be running per sqft

Wisher2 said:

700ma on a 36v cob is roughly 25 watts

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No. Mine will be running @1.4mA

Wisher2 said:

we arent talking a 300 watt cobb

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Indeed, we are not. We are actually talking 200W, and at 50W each.

Wisher2 said:

real world stuff

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Yes, please. Real, and stick to the point whenever possible. Thanks.

@50watts per cob it still wont matter what config
2x2 or 1x4 you will net the same results

I feel I owe this place a follow up to my first indoor in 10 years, so here it goes...
These ones are alive thanks to you people:

(Critical+2 in the left, Critical Kush in the right)

Day 1


Day 8


Day 15


Day 22


I've been ramping up the light from 100W at first to 180 now (out of 210). They were going to be four plants, but 75x75cm is damn claustrophobic and I didn't wanted to end up with an incontrolable jungle, so I went small this first run.

Cheers,
J.

Day 29

Cr+


Cri


And a couple freebies (Jack Herer x Afghani) were added just to help fill up the space



Cheers,
J.