Spacing between COBs

I have been searching and cant find a simple answer to this. How far apart should COB lights be spaced apart. I keep finding a wide range of results. I kinda want to get the frames done this weekend.

My space is 5 feet wide by 3 feet deep and 80 inches tall.

I have three Timber 200w lights that are 4 COBs each. My plan is to make these into single row bars going the width of the tent. So that would make three rows with 4 lights per row. This should provide me with the ability to shut a row off when not needed or raise and lower for different plant heights.

My current idea is to space the front and back rows spaced 16 inches on center apart. The center row spaced 12 inches on center apart.

Will this provide adequate coverage for this area?

Any other suggestions on spacing?

I plan to do 4 to 6 plants under this light.

I did 12" OC on my (16) COBB light but I heard a lot of people say closer to 16" OC. I get really nice coverage at 12" OC with no reflectors and reflectors with my LUX meter.

Depends on the model and at which current you are driving them. There is a ppfd calculator on the forums; https://www.rollitup.org/t/diy-cob-led-calculator.890214/
I've heard anything above 1000ppfd is useless without CO2.

Took a while to get the file to work. But here is my data. It doesnt do much to tell me how far to space them apart. I decided to split the difference though and mounted them 14" OC.

Citizen.1212C4.3000K 12 COBS @1.4A ON 1.813 PROFILE HEATSINK
15 SQ.FT. CANOPY 93.5% EFFICIENT DRIVER @.202285 CENTS PER KWH
Total power watts at the wall: 648.13
Cobs power watts: 606
Total voltage forward: 433
Total lumens: 88476
Total PAR watts assuming 10% loss: 243
Total PPF: 1180.98
PPFD based on canopy area: 847.46
PAR watts per sq.ft.: 16.2
Cob efficiency: 44.51%
Power watts per sq.ft.: 40.4
Voltage forward per cob: 36.1
Lumens per watt: 146.0
Heatsink riser thickness / number of fins / fin's length: 0.3in/6/0.95in
Heatsink area per inch: 100.94 cm^2
Total heat watts: 336
umol/s/W / CRI: 4.86 / 80CRI
Heatsink length passive cooling @120cm^2/heatwatt: 399 inches
Heatsink length active cooling @40cm^2/heatwatt: 133 inches
COB cost dollar per PAR watt: $0.62
Electric cost @12/12 in 30 days: $0.97
Electric cost @18/6 in 30 days: $1.21
Cost per cob: $12.55
Heatsink cost per inch cut: $0.66
Total cobs cost: $151
Total heatsink passive cooling cost: $263
Total heatsink active cooling cost: $87

Checking the programs math I believe the Electric cost @ is off.

Manually calculating the total watts/600, multiply by 12 hours a day, multiplied by my energy costs/.202285 KWH, the multiplying by 30 I come up with $43.69 each month.

462Juvat said:

Checking the programs math I believe the Electric cost @ is off.

Manually calculating the total watts/600, multiply by 12 hours a day, multiplied by my energy costs/.202285 KWH, the multiplying by 30 I come up with $43.69 each month.

Click to expand...

Does the calculation in the data say .202285 cents per kwh? Surely you cant be only paying 0.20 cents per kwh. Wouldn't it be 0.20 dollars per kwh?

It asks what my charge is per KWH. I pull up my electric company rates, add all the fees per KWH together. We have a two tier system and I used the most expensive fee.

coreywebster said:

Does the calculation in the data say .202285 cents per kwh? Surely you cant be only paying 0.20 cents per kwh. Wouldn't it be 0.20 dollars per kwh?

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He works it out into dollars, cents would of just been a written mistake since the maths is correct.

Thats way better rate then I get.
Mines .3855 heavy grid usage rate and .3325 off peak per KWH.

Only time I get off peak usage is 1am to 5am

Regardless I can calculate that easily. The calculator is good for the PPPF calculations though. But it still doesn't help determine how far to space these. The raw data doesn't account for spread, meaning I can achieve the same PPPF numbers in the calculator and group all 12 lights together at one corner of the tent leaving the rest with no direct light.

I guess it will be trial and error.

But watching @Growmau5 videos I do believe I am at the limit for this tent. Anything more would need some reds and probably CO2.

I love watching that guys videos. Pretty advanced stuff but its easy for me to follow. So well spoken and presented too!

462Juvat said:

But watching @Growmau5 videos I do believe I am at the limit for this tent. Anything more would need some reds and probably CO2.

I love watching that guys videos. Pretty advanced stuff but its easy for me to follow. So well spoken and presented too!

Click to expand...

Yeah he's a good egg is growmau5, when I watched his vids I couldn't help but think of him as the David Attenborough of the COB world, he has a good voice for narration.

When I use the calc I input 11 pence per hour because that's my rate.
The calc data on your post shows
15 SQ.FT. CANOPY 93.5% EFFICIENT DRIVER @.202285 CENTS PER KWH ( I assumed you ment 20cents because 0.2 cents per kwh is crazy cheap)
The decimal point, or am I just too stoned to get whats going on.

If I input my data on the calc as 11p per kwh the calc gives me the correct figure for my bills.

Yea, upon further scrutiny it looks to be based off 100, not 1 so the decimal would be over 2 spots. We see it as .22 per hour but based off a 100 scale, it would be 20.

For spacing, spread them evenly over the area you've input in the calculator, and allow half that spacing around the edges of your canopy. A square array provides the most even coverage.

Wall reflection makes a good difference around the edges. Maybe consider hanging some white material around the canopy, if it's in an open area, as opposed to using the reflectors, which just end up wasting light. From what I gather, they don't help at all, even for canopy penetration.

Spacing your cobs I would suggest 8"-10" apart 12" is ok but to me you need them a little closer. I am running 24 of the citizen 1818 @ 1.4A and 24 luminus 22 and they are 12" apart. I will be adding a few more to my setup.

Did you build the lights? I would think 6 bars of 2 cob's spaced 10-12" would be your best option in this case. Very easy to adjust and add to later. Curious as to what you came up with anyway. Imo, covering 60" with 4 cob's will leave some holes in your canopy if you go with 3 bars. Although you could probably stagger the bars and be ok.

I settled on 14" OC (w) in order to reach the tents width, 9" OC (d). I have constructed them as 3 separate bars though in hindsight after seeing how intense they are I could have probably gotten by with 2 bars, 200w wall each and or construct as one large frame. I have had to raise these lights to 30" and turn them down 20%.

My middle bar has the reflectors removed from all 4 COB's, the two center ones are 3500.

let me tell you, inside that reflective tent these lights are like looking into the sun!