Questions on COB configuration, PPFD and more

Criminal_Med_Grower

Criminal_Med_Grower

Member
Hello all. I'm just getting back into growing my own meds after many years of buying over-priced, lower quality product. I used to grow HID, but in doing some reasearch I have decided to try a COB setup to get started again. Until recently, I'd never heard of COBs or PPFD. I always setup my rooms buy watts per square foot and didn't worry about efficiency or heat. Too hot, add AC. Not enough product, add another light. It was a horrible balancing act. I'm a little older now, a little wiser and am starting small this time around. So, here we go.
I am going to start with 3 or 4 plants in a tent. I've decided on going with what seems to be popular with most, the CXB3590. I am thinking 8x COBs on 2x 1.4a drivers. These configs should pull a little over 400w at the wall and low 200s in PAR watts:

LED Configs.jpg Thoughts?

Also, I am fuzzy (extremely) on the concept of PPFD. How do you figure it, optimum range, etc. I've read a bit and have gotten even more confused. A little help?
 
Airwalker16

Airwalker16

Well-Known Member
There's no reason to use 1.4amp drivers. Use HLG-240h-c1750b. They run 4 cobs and give you 64watts each rather than just 50.
 
D

Dankistino

Well-Known Member
Crim, how much overhead space have you got. @64w you will need maybe 18-24" canopy clearance, in my experience. Also your case or frame should match the shape of your garden. I use a frame that is ~48" x12 and uses 8 cobs.my grow space is ~26 x 50". My structure is similar to your second illustration. You cant figure ppfd unless the target area for illumination is known.
 
Criminal_Med_Grower

Criminal_Med_Grower

Member
@AirWalker - What are the drawbacks of using the 1750 over 1400? I see 25% more heat to deal with. I've never grown in tents, but I imagine heat will be a factor for me at some point? Although I could dim if heat becomes a problem. What about efficiency? 56% at 1.4a vs 51% at 1.75a right? So, 36v * 1.4a = ~50.4 watts per COB @56% efficency is 28.2 PAR watts per COB. 36v * 1.75a = 63 watts per COB @51% efficiency is 32.1 PAR watts per COB. That's roughly a 13% increase of PAR watts for a 25% heat increase? Is my math right?

@Dankistino - I plan on starting with a gorilla grow tent, so they are 79" tall and can be extended. I'll be scrogging my girls so height can be managed somewhat.
 
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CobKits

CobKits

Well-Known Member
if youe looking for efficiency both citizen and vero are more efficient than cree and substantially cheaper

watts per square foot still works fine as a rule of thumb just shoot for 35-40 with COB instead of 50 for HID
 
V

VegasWinner

Well-Known Member
I like your 36x36 layout. Connect the inner four COB's to one drive and the corner COB's to the other driver, that way you can dim independent the inner and out er core of light. Nice design. . I also use C1400B drivers and they are fine for me. I did the same and heat with a good inline fan is no problem. Should keep you busy growing for some time. enjoy.
namaste
 
Danielson999

Danielson999

Well-Known Member
I think you nailed it. I like your 2'x4' idea simply because it's easier to build another and add it into a 4'x4' whereas a 3'x3' doesn't fit into another area without rearranging it. Also, 1400ma is overkill for that space. Don't waste your money on a larger driver imo. With 8 cobs in 8 sq ft you are already at overkill with 50w per sqft which translates into as much ppfd as you will ever need. I actually did the exact build you're talking about and will be building another just like it to fill my 4'x4' space. I wouldn't worry about heat but I guess that depends on where you live. I actually had to raise my light higher and turn the wattage up just to keep my tent at the temps I wanted.
 
Criminal_Med_Grower

Criminal_Med_Grower

Member
@CobKits - Just took a look at your site. The 1825 - 80CRI look interesting.

@VegasWinner - That's a great idea for connecting inner and outer lights to different drivers. I've put a little thought into supplementing the COBs, but I'll run them by themselves first grow to get a baseline. I'll be running genetics I've used before and want to see how they come along vs what I remember under HID.

@Danielson999 - That's exactly what I was thinking for a 2x4. What does that rig weigh?
 
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Danielson999

Danielson999

Well-Known Member
The heatsinks (SST120) weigh about 1lb each. The drivers weigh about 2lbs each. The 1/16" (3/4") square tubing is about 6lbs (.30lbs per ft).
So...8lbs, 4lbs, 6lbs = 18lbs plus a few more pounds for hardware, wiring and junction boxes. Probably about 25lbs but I didn't weigh it. Definitely not stressing the 1/2" tent poles.
 
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Rayne

Rayne

Well-Known Member
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Criminal_Med_Grower

Criminal_Med_Grower

Member
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Criminal_Med_Grower

Criminal_Med_Grower

Member
I'm putting together a shopping list and I want to get this thing dialed in before I scale. Are there any recommendations for PAR meters at a decent price from a reputable site?

Thanks in advance.

Criminal

bongsmilie
 
MildGro

MildGro

Member
Rayne said:
To help make your decisions some what easier...

(Previously started threads with some useful information)
DIY COB LED Calculator
Recommended PPFD for Cannabis
Max PPF/PPFD with and without CO2
COBs distance from canopy

Since you are used to HID and HID gives off some ultra violet as well as some Infrared...
Expect to need to add UV to your grow space.

Personally speaking... I will not start a grow without some UV a/b supplementation.
Click to expand...
Thanks for this. I can never find these bloody threads when I'm looking. Is it just me or does the search suck on this site lol
 
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