Custom COB light setup

What's going on fellas. I'm going to start building my first COB light. I'm buying a gorilla 3x3 tent. I plan on growing 4 plants using the manifold method where I top my plants to get 8 colas and LST them so each branch is at equal level. That's 32 colas per grow.

My plans for my light setup is a bit overkill for a 3x3 tent but I'm very confident I will be able to keep the heat down and I'll have up to 9ft of height to work with in the tent which will be plenty of space to keep the lights at a safe distance and also will allow the heat to travel higher up and away from the plants.

My plan is using 9 Vero 29 50v COBs running at 1400ma which will run each COB at 70w. I will place them in 3 rows of 3 and I will space them out using a light meter in the tent to see what spacing gives me the best light coverage. I'm going for 1 COB per sqft as a starting point.

I'm wondering what color lights I should go with. Is 5000K 70cri for veg and 3500K 90cri for flower seem like good choices?

All opinions are welcome. I know there are many of you with lots of experience with COB lights so I'm all ears to any advice. I alsp know many of you will think using 9 COBs in a 3x3 tent is overkill and will put out too much heat but I've done the heat calculations and I feel I will be able to keep the tent at or under 85°.

Sounds good and will work for sure and you have the abillity to switch in a bigger tent without building a new one!
I'd only advice you to use dimmable drivers.

Marky Bluntz said:

What's going on fellas. I'm going to start building my first COB light. I'm buying a gorilla 3x3 tent. I plan on growing 4 plants using the manifold method where I top my plants to get 8 colas and LST them so each branch is at equal level. That's 32 colas per grow.

My plans for my light setup is a bit overkill for a 3x3 tent but I'm very confident I will be able to keep the heat down and I'll have up to 9ft of height to work with in the tent which will be plenty of space to keep the lights at a safe distance and also will allow the heat to travel higher up and away from the plants.

My plan is using 9 Vero 29 50v COBs running at 1400ma which will run each COB at 70w. I will place them in 3 rows of 3 and I will space them out using a light meter in the tent to see what spacing gives me the best light coverage. I'm going for 1 COB per sqft as a starting point.

I'm wondering what color lights I should go with. Is 5000K 70cri for veg and 3500K 90cri for flower seem like good choices?

All opinions are welcome. I know there are many of you with lots of experience with COB lights so I'm all ears to any advice. I alsp know many of you will think using 9 COBs in a 3x3 tent is overkill and will put out too much heat but I've done the heat calculations and I feel I will be able to keep the tent at or under 85°.

Click to expand...

9 cobs on 70 watts each all on full is overkill for a 3x3, 630 watts of led is more like a 4x4. But if you want to mix spectrums it could be cool, especially if you can dim the veg/bloom spectrum individually and keep the lights high for more even coverage.
Id go 5x 3000k 90cri for bloom, and set them up so they are like an x, 1 cob in each corner and 1 in the middle, the remaining 4 5000k in a square with one cob to each side of your tent. Does this description make sense?

You could use a meanwell hlg 320c1400 and hlg480c1400 for powering vegg and bloom fixtures individually but make sure you get the right version for dimming.
@Malocan has a pretty cool light with similar spec, but he is using vero decor, 1700k for bloom.

I use the Vero29 COBs but run them on a dimmable 2100mA Meanwell driver. I use 12 in a 4'x8' enclosure right at tree top level. Set to max for flower. Can use them also in VEG all the way up at ceiling and turned down less than 1/2 way.
I never tried any of the cooler colors. The 3K is GREAT for flowers and OK for VEG. My plants that I vegged then also ran in flower mode 12/12 all did VERY well. In VEG the plants really got big fast and in flower finished early say 5-7 days earlier than expected. The only reason I'd got up to 5K would be for VEG only.

IF I was to expand and get some more COBs I'd add a few 3500K... really the 3k is great even for VEG. My VEG plants are actually growing too fast under them, I had to pull some back away from the lights to see if I could slow them down a little. I guess my point is you will get better use out of the warmer spectrum's over the long haul.

bobrown14 said:

My VEG plants are actually growing too fast under them, I had to pull some back away from the lights to see if I could slow them down a little. I guess my point is you will get better use out of the warmer spectrum's over the long haul.

Click to expand...

Give them a weekly kelp foliar feed, that way you can use the light intensity with less stretch. When fed foliar at short intervals it interferes with the stretching mechanism

I do use rehydrated kelp meal ground up added to my IPM routine .. haven't sprayed this is round yet tho...

Cause lazy and no bugs .

I wasn't aware that kelp interfered with stetch. I use kelp meal in my soil mix.

Has to be foliar

ANC said:

Has to be foliar

Click to expand...

I add it to my IPM routine.... so yes I use it for a foliar along with Horsetail Fern tea (gets rid of mold), Monterrey, Pro-tekt & Ful-power.

How does it work to slow down stretch??

It interferes with the hormones I think. It is fine if you use it once every 2 or 3 weeks, anything more than that, it reduces stretch. It is a well-known property.

Marky Bluntz said:

What's going on fellas. I'm going to start building my first COB light. I'm buying a gorilla 3x3 tent. I plan on growing 4 plants using the manifold method where I top my plants to get 8 colas and LST them so each branch is at equal level. That's 32 colas per grow.

My plans for my light setup is a bit overkill for a 3x3 tent but I'm very confident I will be able to keep the heat down and I'll have up to 9ft of height to work with in the tent which will be plenty of space to keep the lights at a safe distance and also will allow the heat to travel higher up and away from the plants.

My plan is using 9 Vero 29 50v COBs running at 1400ma which will run each COB at 70w. I will place them in 3 rows of 3 and I will space them out using a light meter in the tent to see what spacing gives me the best light coverage. I'm going for 1 COB per sqft as a starting point.

I'm wondering what color lights I should go with. Is 5000K 70cri for veg and 3500K 90cri for flower seem like good choices?

All opinions are welcome. I know there are many of you with lots of experience with COB lights so I'm all ears to any advice. I alsp know many of you will think using 9 COBs in a 3x3 tent is overkill and will put out too much heat but I've done the heat calculations and I feel I will be able to keep the tent at or under 85°.

Click to expand...

That will put your PPFD at around 1800 at full power. You will likely need to dim them which isn't a bad thing since it will increase the efficiency. Better to get too much than not enough.

If you switch the B cobs for C cobs at 1050mA it will increase your efficiency by around 5% for the extra $45 it will cost. You don't need the extra light but ultimately whatever light level you dim to will use less wattage, put off less heat. Seems like a good deal for $45 especially if you're trying to build an ultimate rig.

If you're running mixed cobs and one of them is going to be 5000K 70CRI you might want to consider using 2700K 90CRI for the other color temp.

I can't say for sure because I haven't done the math or the grow comparison but you might get more vegetative mass from 4000K 80CRI which could also be paired with 2700K 90CRI.

With the wattage you're planning on using you can't really go wrong no matter what you do, but those are the things I would consider tweaking.

Randomblame said:

Sounds good and will work for sure and you have the abillity to switch in a bigger tent without building a new one!
I'd only advice you to use dimmable drivers.

Click to expand...

Yes I plan on using a meanwell dimmer driver. And I do plan on upgrading to a 4x4 eventually so that's one of the reasons I'm building a bigger fixture than I need for my current grow space. Thank you!

Rocket Soul said:

9 cobs on 70 watts each all on full is overkill for a 3x3, 630 watts of led is more like a 4x4. But if you want to mix spectrums it could be cool, especially if you can dim the veg/bloom spectrum individually and keep the lights high for more even coverage.
Id go 5x 3000k 90cri for bloom, and set them up so they are like an x, 1 cob in each corner and 1 in the middle, the remaining 4 5000k in a square with one cob to each side of your tent. Does this description make sense?

You could use a meanwell hlg 320c1400 and hlg480c1400 for powering vegg and bloom fixtures individually but make sure you get the right version for dimming.
@Malocan has a pretty cool light with similar spec, but he is using vero decor, 1700k for bloom.

Click to expand...

I understand what you mean about the mixture of COBs. I'm thinking about sticking with 80cri for flower since I've seen some grows with 90cri flowering and the plants were lighter in weight and some plants even became stressed. The plants seemed to grow faster though which saves time. I was thinking of using 3000k and 3500k mixed for flower at 80cri. Is there any benefits of mixing 5000k COBs during flower? I thought those were more for veg. My plan is to use one set of COBs for veg and another set for flower. I will swap them out of the light frame I'm going to build during each grow phase. So that would be using all 5000k COBs for veg and then using a mix of 3000k and 3500k COBs for flower. If adding 4000k or 5000k COBs in the mix during flower will help my grow then I'm all for it. I'm def going with dimming drivers so I can control the lights. Thank you!

bobrown14 said:

I use the Vero29 COBs but run them on a dimmable 2100mA Meanwell driver. I use 12 in a 4'x8' enclosure right at tree top level. Set to max for flower. Can use them also in VEG all the way up at ceiling and turned down less than 1/2 way.
I never tried any of the cooler colors. The 3K is GREAT for flowers and OK for VEG. My plants that I vegged then also ran in flower mode 12/12 all did VERY well. In VEG the plants really got big fast and in flower finished early say 5-7 days earlier than expected. The only reason I'd got up to 5K would be for VEG only.

IF I was to expand and get some more COBs I'd add a few 3500K... really the 3k is great even for VEG. My VEG plants are actually growing too fast under them, I had to pull some back away from the lights to see if I could slow them down a little. I guess my point is you will get better use out of the warmer spectrum's over the long haul.

Click to expand...

Thank you for the input!

Rahz said:

That will put your PPFD at around 1800 at full power. You will likely need to dim them which isn't a bad thing since it will increase the efficiency. Better to get too much than not enough.

If you switch the B cobs for C cobs at 1050mA it will increase your efficiency by around 5% for the extra $45 it will cost. You don't need the extra light but ultimately whatever light level you dim to will use less wattage, put off less heat. Seems like a good deal for $45 especially if you're trying to build an ultimate rig.

If you're running mixed cobs and one of them is going to be 5000K 70CRI you might want to consider using 2700K 90CRI for the other color temp.

I can't say for sure because I haven't done the math or the grow comparison but you might get more vegetative mass from 4000K 80CRI which could also be paired with 2700K 90CRI.

With the wattage you're planning on using you can't really go wrong no matter what you do, but those are the things I would consider tweaking.

Click to expand...

I was thinking of getting the 68v C model COBs and running them at 1050ma as you suggested. I just thought at 1050ma the 68v version would run at 71w each which is the same as the 50v version running at 1400ma. Wouldn't that output the same amount of heat since they'll both operate at 70w? Or is it more efficient because the 68v COBs will be ran at a lower current than the 50v COBs? If I can get a better photon/heat ratio with the 68v at 1050ma then I'm all for it.

I'm only interested in mixing COBs during flowering if it benefits the plants. I was thinking of using a mix of 3000k and 3500k at 80cri for flower and 5000k 70cri for veg. You say 4000k 80cri would be a better veg light for me?

What I plan on doing is using one set of COBs during veg and then swapping those COBs out for another set for flowering. So I'll basically disassemble my fixture during each phase to remove and add different COBs. I plan on building a frame using 90° angle aluminum. It's cheap and easy and will allow me to modify it easily between grow phases.

The wattage will be similar for B at 1400mA and C at 1050mA but the C is a better chip and will put out more light for the same wattage.

Stats for 3000K 90CRI spectrum: (efficiency ratio will be similar for other K samples)
B version at 1400mA: 70.7 watts and 9473 lumens
C version at 1050mA: 69.6 watts and 9952 lumens

It all turns to heat at some point so same heat, more photons. OR, if you dim the Cs to the level of light you would get from the Bs, same photons less heat/electricity.

Either way you're looking at about 1800 PPFD at full power so you can turn off 4-5 of those cobs and still have a kick ass veg lamp. Use the higher K only during veg and kick on the low K during flower. No need for separate cobs being switched out. I see you want 5000K 70CRI for veg, but unless your tent is really short I don't see the logic in going over 4000K. Opinions may differ but the thing is, above 4000K the "red peak" has turned into a greenish yellow peak. The 5000K spectrum might be a little more efficient and might grow the plants a tad shorter but since you're missing out on all the orange and red it doesn't necessarily translate into more plant bulk. 4000K 80CRI contains a heavy dose of blue and maintains reasonable levels of orange/red and is what I would choose for a veg only lamp.

So 4 cobs 4000K 80CRI and 4 cobs 2700K 90CRI, just the 4000K in veg and all 8 in flower. The reason I mention only 8 is that your center will be the hot spot whether you use 8 in a square or 9 in a 3x3 grid. And since your average PPFD with 9 will be 1800 it will be even higher in the center. Also that would allow you to run each set of 4 on an HLG-320H-C1050 driver if you use the C cobs. Going from veg to flower becomes as easy as flipping a switch.

PPFD with 8 of them at 70 watts each is around 1600 so you'll still be maxing out your 3x3 tent and may still need to dim them. PPFD with 4 at 70 watts will be around 800 which I would consider excessive for a veg lamp. 800 PPFD and your plants will grow like crazy if everything else is good.

Food for thought.

i concur 4000k 80 is as good as it gets for veg

Rahz said:

The wattage will be similar for B at 1400mA and C at 1050mA but the C is a better chip and will put out more light for the same wattage.

Stats for 3000K 90CRI spectrum: (efficiency ratio will be similar for other K samples)
B version at 1400mA: 70.7 watts and 9473 lumens
C version at 1050mA: 69.6 watts and 9952 lumens

It all turns to heat at some point so same heat, more photons. OR, if you dim the Cs to the level of light you would get from the Bs, same photons less heat/electricity.

Either way you're looking at about 1800 PPFD at full power so you can turn off 4-5 of those cobs and still have a kick ass veg lamp. Use the higher K only during veg and kick on the low K during flower. No need for separate cobs being switched out. I see you want 5000K 70CRI for veg, but unless your tent is really short I don't see the logic in going over 4000K. Opinions may differ but the thing is, above 4000K the "red peak" has turned into a greenish yellow peak. The 5000K spectrum might be a little more efficient and might grow the plants a tad shorter but since you're missing out on all the orange and red it doesn't necessarily translate into more plant bulk. 4000K 80CRI contains a heavy dose of blue and maintains reasonable levels of orange/red and is what I would choose for a veg only lamp.

So 4 cobs 4000K 80CRI and 4 cobs 2700K 90CRI, just the 4000K in veg and all 8 in flower. The reason I mention only 8 is that your center will be the hot spot whether you use 8 in a square or 9 in a 3x3 grid. And since your average PPFD with 9 will be 1800 it will be even higher in the center. Also that would allow you to run each set of 4 on an HLG-320H-C1050 driver if you use the C cobs. Going from veg to flower becomes as easy as flipping a switch.

PPFD with 8 of them at 70 watts each is around 1600 so you'll still be maxing out your 3x3 tent and may still need to dim them. PPFD with 4 at 70 watts will be around 800 which I would consider excessive for a veg lamp. 800 PPFD and your plants will grow like crazy if everything else is good.

Food for thought.

Click to expand...

Awesome post man. Thank you for all the info!

I honestly didn't think about making a square with 8 COBs. I always visualized grids for some reason. What kind of mixture do you feel would work best with the 4000k and 2700k COBs in a 8 COB square during bloom? Like what order would you place the COBs? And is that the ideal mixture for bloom? I really have no problem swapping out COBs for each grow phase if using 3000k and 3500k during bloom is more optimal than 2700k and 4000k. I'll be using 4000k for veg for sure.

And say I do go with the 8 COB square, what size frame would be about right? With the 3x3 grid I planned on doing a 30"x30" frame.

A 24 inch square would center the cobs over each square foot so that's what I would try. Probably do the 400w on the corners and the others on the sides.

Regarding 3000/3500 or 4000/2700 it's not exact but close to say they will average out to 3250 and 3350 so they would be similar and I would go with 4000/2700 just so you don't need to switch cobs out.

Rahz said:

A 24 inch square would center the cobs over each square foot so that's what I would try. Probably do the 400w on the corners and the others on the sides.

Regarding 3000/3500 or 4000/2700 it's not exact but close to say they will average out to 3250 and 3350 so they would be similar and I would go with 4000/2700 just so you don't need to switch cobs out.

Click to expand...

good choice 4000/2700 but which CRI, 80 or 90

80CRI on the 4000Ks to inhibit stretch a bit and 90CRI on the 2700Ks to fill the deep red back in. I don't have the data to illustrate the final flowering spectrums but I think they would be similar.

Rahz said:

A 24 inch square would center the cobs over each square foot so that's what I would try. Probably do the 400w on the corners and the others on the sides.

Regarding 3000/3500 or 4000/2700 it's not exact but close to say they will average out to 3250 and 3350 so they would be similar and I would go with 4000/2700 just so you don't need to switch cobs out.

Click to expand...

Thank you! You've been a great help.

Should I use one of those angelina reflectors or lenses for the COBs?

Regarding heat sinks, will the 140mm pin passive heatsink be sufficient? I'm looking at the one that most growers use from rapidled.

Instead of 400w I meant to say 4000K but I think you got that.

I would use reflectors.

I haven't used them but the website says 70-80 watts so it should be sufficient.

I use the angelina reflectors with my setup.... focus the lighting down instead of in my eyes!