Need help with COB setup.

G

GrowingAbroad

Active Member
Hi guys,
I'm new here and after reading a lot before without posting it's time to get started myself as well.
I'm already growing for a while under HPS and now decided to start using COBS as well on the side.

So the basic thought i have is this.

I usually tend to grow under 1200 watts HPS light which equals around 120.000 effective lumens total taking away the light that gets lost from the reflector and wall.

The plan is to build a 2,5 square meter room using 16 Cree cobs at 36v x 1.4 amps = 804 watts @ 182.5 lumens per watt which should equal around 146.764 lumens at 806 watts. This should give me more Lumens using a lot less power.

There's a few things i still haven't made my mind on which are:

1. Should i only use 3500K cobs or should i mix it up using 3000k and 4000k? I read mixed things so i would like to hear some more opinions about it.
2. Am i correct with the calculations that i made regarding lumens having more grow power with the 800 watts cobs as to 1200 watts HPS?
3. What layout would be best for me to use?

Option 1 -mixed 3000k en 4000k 2 rows of 8
3000 - 4000 - 3000 - 4000 - 3000 - 4000 - 3000 - 4000
.................................................. .............................................. 16 COBS
4000 - 3000 - 4000 - 3000 - 4000 - 3000 - 4000 - 3000
================================================== ===
Option 2 - Only 3500k 2 rows of 8
3500 - 3500 - 3500 - 3500 - 3500 - 3500 - 3500 - 3500
.................................................. .............................................. 16 COBS
3500 - 3500 - 3500 - 3500 - 3500 - 3500 - 3500 - 3500
================================================== ===
option 3 - mixed 3000k en 4000k 3x5
3000 - 3000 - 3000 - 3000 - 3000 - 3000
.....4000.....................4000...................4000..... .......15 COBS
3000 - 3000 - 3000 - 3000 - 3000 - 3000
================================================== ===
Option 4 - just 3500k cobs 3x5
3500 - 3500 - 3500 - 3500 - 3500 - 3500
.....3500.....................3500...................3500..... ........15 COBS
3500 - 3500 - 3500 - 3500 - 3500 - 3500

I look forward to you're advice and comments on this setup.

Thanks in Advance.
 
Kenpark

Kenpark

Well-Known Member
hello I have done various experiments in a 4x4 starting from 10 cob 500watt up to 800watt in my opinion a right compromise is 12 cob 600 watt then 416 watt / m.
As for the color I have always used 3500k .......
same genetics in 4x4 (clone in soil)
500 watts 680 g
600 watts 735 g
800 watts 777 g
 
G

GrowingAbroad

Active Member
Kenpark said:
hello I have done various experiments in a 4x4 starting from 10 cob 500watt up to 800watt in my opinion a right compromise is 12 cob 600 watt then 416 watt / m.
As for the color I have always used 3500k .......
same genetics in 4x4 (clone in soil)
500 watts 680 g
600 watts 735 g
800 watts 777 g
Click to expand...
Thanks for the reply.
While using 800 watt on such an area do you use scrog of something or just let it grow all natural? I will be using scrog to get a full even field using every square inch.
 
G

GrowingAbroad

Active Member
FastFreddi said:
Mix the two.
FF
Click to expand...
Ok and what configuration would you recommend? The room is 1.2m x 2.10m, that won't change.

Option 1 -mixed 3000k en 4000k 2 rows of 8
3000 - 4000 - 3000 - 4000 - 3000 - 4000 - 3000 - 4000
.................................................. .............................................. 16 COBS
4000 - 3000 - 4000 - 3000 - 4000 - 3000 - 4000 - 3000

or

option 3 - mixed 3000k en 4000k 3x5
3000 - 3000 - 3000 - 3000 - 3000 - 3000
.... .4000..................4000...................4000..... .......15 COBS
3000 - 3000 - 3000 - 3000 - 3000 - 3000

Thanks :)
 
FastFreddi

FastFreddi

Well-Known Member
GrowingAbroad said:
Ok and what configuration would you recommend? The room is 1.2m x 2.10m, that won't change.

Option 1 -mixed 3000k en 4000k 2 rows of 8
3000 - 4000 - 3000 - 4000 - 3000 - 4000 - 3000 - 4000
.................................................. .............................................. 16 COBS
4000 - 3000 - 4000 - 3000 - 4000 - 3000 - 4000 - 3000

or

option 3 - mixed 3000k en 4000k 3x5
3000 - 3000 - 3000 - 3000 - 3000 - 3000
.... .4000..................4000...................4000..... .......15 COBS
3000 - 3000 - 3000 - 3000 - 3000 - 3000

Thanks :)
Click to expand...
I run 3000 and 3500 Timber 3vl's...
I have two...each has a 3000 in the center, and 3500 on both ends.
My plants never complain.
I grow freely, no Scroggins. I like to be able to move them around as required.
Topping, fimming, lst and supercropping are my go to plant control.
I use a variety of lights, but my Timbers are #1.
I am personal, and by no means a pro.
Been growing maybe 5 years.
20210407_075252.jpg
20210408_075825.jpg
FF
 
G

GrowingAbroad

Active Member
FastFreddi said:
I run 3000 and 3500 Timber 3vl's...
I have two...each has a 3000 in the center, and 3500 on both ends.
My plants never complain.
I grow freely, no Scroggins. I like to be able to move them around as required.
Topping, fimming, lst and supercropping are my go to plant control.
I use a variety of lights, but my Timbers are #1.
I am personal, and by no means a pro.
Been growing maybe 5 years.
View attachment 4873814
View attachment 4873815
FF
Click to expand...
Thanks for you're opinion.
They sure do look great.
So in your personal opinion you would recommend it like this right?

3500......3500......3500......3500......3500......3500
........3000.........3000...............3000..........3000........
3500......3500......3500......3500......3500......3500

I won't be using any lenses so by havng more diffuse light the 3000' will also reach the ends as well i guess.
 
FastFreddi

FastFreddi

Well-Known Member
GrowingAbroad said:
Thanks for you're opinion.
They sure do look great.
So in your personal opinion you would recommend it like this right?

3500......3500......3500......3500......3500......3500
........3000.........3000...............3000..........3000........
3500......3500......3500......3500......3500......3500

I won't be using any lenses so by havng more diffuse light the 3000' will also reach the ends as well i guess.
Click to expand...
No reflectors for sure.
Sounds good.
Good luck and have fun.
FF
 
B

Bookush34

Well-Known Member
If you want to mix cob color.
Why not have 1750 or 2700 in the mix. And some 4000k

Mixing 3000 and 3500 is too close to really matter. IMO
 
G

GrowingAbroad

Active Member
Bookush34 said:
If you want to mix cob color.
Why not have 1750 or 2700 in the mix. And some 4000k

Mixing 3000 and 3500 is too close to really matter. IMO
Click to expand...
This does kinda make sense actually.
Would this influence the gram per wattage in anyway during flowering you think using the 4000 or would it be neglectable?
 
pulpoinspace

pulpoinspace

Well-Known Member
Bookush34 said:
If you want to mix cob color.
Why not have 1750 or 2700 in the mix. And some 4000k

Mixing 3000 and 3500 is too close to really matter. IMO
Click to expand...
GrowingAbroad said:
This does kinda make sense actually.
Would this influence the gram per wattage in anyway during flowering you think using the 4000 or would it be neglectable?
Click to expand...
Because of hot spots. higher CCT LEDs are more efficient and thus produce more PPFD. They are not far enough away to mix and produce an even spectrum so you will have hot spots under the 4000k. Mixing cobs is generally not a good idea in my opinion. 3500k and 3000k is one thing. I would not mix 1750k and 4000k.

The differences in "yield" and "quality" between 3000k and 4000k are minute and will only be noticed in a side-by-side done by a grower with every other aspect of his grow dialed in.

The prettiest, most potent buds i've ever grown were under 3500k 90cri... yield was more than adequate.

The cri makes a difference. A 3500k 80cri will have almost no far red, while a 3500k 90cri will have a more balanced spectrum.
 
Last edited:
Kenpark

Kenpark

Well-Known Member
GrowingAbroad said:
Thanks for the reply.
While using 800 watt on such an area do you use scrog of something or just let it grow all natural? I will be using scrog to get a full even field using every square inch.
Click to expand...
sometimes I use the scrog other times the sog depends I like to change but the results are roughly similar it depends a lot on the genetics ...
another piece of advice that I can give you and to keep the temperature and humidity under control ....
common problems with LEDs are low temperature and high humidity.
I recommend 26/27 degrees C
other advice consider adding cal mag to your diet from the second week of growth if you use atami cal mag 0.5 ml / l until the end you should be fine
 
G

GrowingAbroad

Active Member
pulpoinspace said:
Because of hot spots. higher CCT LEDs are more efficient and thus produce more PPFD. They are not far enough away to mix and produce an even spectrum so you will have hot spots under the 4000k. Mixing cobs is generally not a good idea in my opinion. 3500k and 3000k is one thing. I would not mix 1750k and 4000k.

The differences in "yield" and "quality" between 3000k and 4000k are minute and will only be noticed in a side-by-side done by a grower with every other aspect of his grow dialed in.

The prettiest, most potent buds i've ever grown were under 3500k 90cri... yield was more than adequate.

The cri makes a difference. A 3500k 80cri will have almost no far red, while a 3500k 90cri will have a more balanced spectrum.
Click to expand...
Thanks for the advice.
The setup will be 3500k and 3000k mixed together.
12x3500k and 4x3000k in the middle.
 
G

GrowingAbroad

Active Member
Kenpark said:
sometimes I use the scrog other times the sog depends I like to change but the results are roughly similar it depends a lot on the genetics ...
another piece of advice that I can give you and to keep the temperature and humidity under control ....
common problems with LEDs are low temperature and high humidity.
I recommend 26/27 degrees C
other advice consider adding cal mag to your diet from the second week of growth if you use atami cal mag 0.5 ml / l until the end you should be fine
Click to expand...
I read about the lower temperatures using cobs yeah so i will keep a close eye on that. Like i said before i'm already growing for some time using HPS and always try to keep my temps around 26-27C with light on and 19-20C with lights out and 60% humidity for seeds, 50% for vegging and 40-45% during flowering so that won't be a real issue i guess (hope).
The only real thing that i was worried about is the light strength but i will be buying a flux meter as well to keep that in check to determine the right height and power consumption during the grow.

Am i correct that around 5000-7000 for seedlings, 15000-45000 for vegging and 60.000-75000 for flowering is the right amount of lux give or take?
 
OSBuds

OSBuds

Well-Known Member
GrowingAbroad said:
I read about the lower temperatures using cobs yeah so i will keep a close eye on that. Like i said before i'm already growing for some time using HPS and always try to keep my temps around 26-27C with light on and 19-20C with lights out and 60% humidity for seeds, 50% for vegging and 40-45% during flowering so that won't be a real issue i guess (hope).
The only real thing that i was worried about is the light strength but i will be buying a flux meter as well to keep that in check to determine the right height and power consumption during the grow.

Am i correct that around 5000-7000 for seedlings, 15000-45000 for vegging and 60.000-75000 for flowering is the right amount of lux give or take?
Click to expand...
Cannabis LED Grow Guide .png
 
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