SupraSPL
Well-Known Member
Hey man sounds like an awesome build! Here is what I get:@SupraSPLI've been lurking in your high efficiency threads and grow journals for a while now and think I'm finally ready to make the jump to COB, in large part thanks to you.
The grow room is a dedicated room. 6' x 7' x 7'. Planning on having a 5x5 canopy with walkways on for sides. I've ordered the CXB3590 (25) and the holders.
CXB3590 - CD - 36V - 3500k
HLG - 185H - C1050(A)
Ideal 50-2303CR
Planning on running 5 cxbs per heat sink. With one driver. Seems to be the correct ratio on cobs per the driver COB efficiency chart.
Planning on running 1 COB per square foot. 25 cobs. Is this too much light? I'm afraid I may be above the 850-950 PPFD I was shooting for.
I'm having trouble determining the PPFD. I keep coming up with an answer off by a factor of ten, but nonetheless wrong.
I'm wondering if the above driver would be a good choice and how large would the heatsink need to be for passive cooling. I'm thinking of 60" length so I can run 5 COBs per driver. I was looking at the 5.886" at heatsinkusa. I just want to make sure I'm not way overshooting it.
35.5W * 25 = 887.5W dissipation
887.5 * .612% efficiency = 543 PAR W
543 * .9 lens/reflector/wall losses = 489 PAR W
489/25 sq ft = 19.5 PAR W/ sq ft
19.5 * 4.65 umol/s/PAR W * 10.7 = 973 PPFD averaged, when adjusted to 1050mA (driver is capable of up to 1150mA)
973 is assuming a 2D canopy and since your colas are 3D they will be getting less than 973 on average so that should give you great results but if the intensity is too much to keep up with you could dim it, remove on pabel, or spread the lights further apart and add more canopy at the end of the walkways.
Each group of 5 COBs will put 70 W of heat into the heatsink so for passive you could use something like 4.9"X50" (good for 100W of heat) or you could use the 3.5" if you add a 80mm fan at 5-9V. The 5.88"X50" would cost the same and have more surface area (good for 108W) but it has a thinner base and thinner fins so I am not sure which would perform better in practice.