Trying to design an LED all purpose (veg/flower) solution for a room that's 24 inches by 40 inches wide by 5.5 feet high. That's 6.66sqf of floor space. I have it almost figured it out but I want to run my thoughts past you experts and get some opinions.
I think all the parts will come from Jerry at kingbrite. Since his minimum cob order is 5 I think cree cxb3597 36v CD bin 3500k on a dimmable driver (dim them for veg, crank them for flower).
Where im not sure is how hard to drive them and how to place them.
Question One: Placement:
Since the room is 2 feet deep and 3.3 feet wide the easy solution would be to run them in a line with even spacing between their centers and the walls. This means 6.6 inches between each cob and then 6.6 inches from to the side of the room wall to the last cob at the end of the fixture. This will also put 12 inches from all of the cobs to the back of the room and to the front of the room.
Will this be okay? Im worried most about the 12 inches from the cobs to the front and back of the room. Will there be enough light?
Question Two: Driving Them
I am also wondering how best to drive them. This fixture will be used sporadically and won't be going 12 months of the year (1-2, tops 3 grows a year) so I am leaning less to efficiency and more to sheer photon output design.
I think the minimum they should be run is at 1400ma, this puts them at the sweet spot of efficiency and output but given sporadicness of their use I think they could be driven a little harder at 1750ma and they can always be dimmed if too hot or in veg. Driving at 2.1a would be nice but Jerry does not have anything in 2.1a and im not sure how i could drive the 5 cobs at that. It may be overkill.
At 1.4amps would the HLG-240H-C1400 work?
250watts/1.4a = 178.4v/5cobs = 35.7 v for each of the cobs. Is this sufficient to power the 36v cobs considering wires and connections?
Using 250watts driving @ 1.4 amps cob efficiency is 56.2% there should be 141.62 PAR watts over 6.66 sqf giving 21.2 PAR / SQF which is what you aim for to flower.
But for only a few more dollars up front cost it could be driven at at 1750ma.
Would a HLG-320H-C1750 work?
320watts/1.75amps = 182.8v/5cobs = 36.57 v for each of the cobs. This should be more than enough volts.
Efficiency should still be about 51% there should be 5cobs * (36v*1.75a) = 315 watts = 160.65 PAR watts. This gives 24.12 PAR / SQF
Unless my math is wrong. The increase of draw at the wall of 70 watts (28%) going from the HLG240 to the HLG320 only brings an additional 2.92 PAR / SQF. This does not seem worth the added upfront cost and operational cost. Does anyone agree?
UPDATE: i just realized there is an HlG-240 that runs 2.1 amp. Two two of these could be used. One would power 3 cobs and the other could power 2. This would create 27.8 PAR/sqf which is appealing. I would require two dimmer dials which isn't ideal but acceptable. Any caveats with this setup?
Lastly. I haven't seen anyone stick an analogue amp meter inline. I think it could be helpful with the dimming option to know what you are running. Is there a problem putting one at the end of the LED chain?
Thanks in advance for any advice.
I think all the parts will come from Jerry at kingbrite. Since his minimum cob order is 5 I think cree cxb3597 36v CD bin 3500k on a dimmable driver (dim them for veg, crank them for flower).
Where im not sure is how hard to drive them and how to place them.
Question One: Placement:
Since the room is 2 feet deep and 3.3 feet wide the easy solution would be to run them in a line with even spacing between their centers and the walls. This means 6.6 inches between each cob and then 6.6 inches from to the side of the room wall to the last cob at the end of the fixture. This will also put 12 inches from all of the cobs to the back of the room and to the front of the room.
Will this be okay? Im worried most about the 12 inches from the cobs to the front and back of the room. Will there be enough light?
Question Two: Driving Them
I am also wondering how best to drive them. This fixture will be used sporadically and won't be going 12 months of the year (1-2, tops 3 grows a year) so I am leaning less to efficiency and more to sheer photon output design.
I think the minimum they should be run is at 1400ma, this puts them at the sweet spot of efficiency and output but given sporadicness of their use I think they could be driven a little harder at 1750ma and they can always be dimmed if too hot or in veg. Driving at 2.1a would be nice but Jerry does not have anything in 2.1a and im not sure how i could drive the 5 cobs at that. It may be overkill.
At 1.4amps would the HLG-240H-C1400 work?
250watts/1.4a = 178.4v/5cobs = 35.7 v for each of the cobs. Is this sufficient to power the 36v cobs considering wires and connections?
Using 250watts driving @ 1.4 amps cob efficiency is 56.2% there should be 141.62 PAR watts over 6.66 sqf giving 21.2 PAR / SQF which is what you aim for to flower.
But for only a few more dollars up front cost it could be driven at at 1750ma.
Would a HLG-320H-C1750 work?
320watts/1.75amps = 182.8v/5cobs = 36.57 v for each of the cobs. This should be more than enough volts.
Efficiency should still be about 51% there should be 5cobs * (36v*1.75a) = 315 watts = 160.65 PAR watts. This gives 24.12 PAR / SQF
Unless my math is wrong. The increase of draw at the wall of 70 watts (28%) going from the HLG240 to the HLG320 only brings an additional 2.92 PAR / SQF. This does not seem worth the added upfront cost and operational cost. Does anyone agree?
UPDATE: i just realized there is an HlG-240 that runs 2.1 amp. Two two of these could be used. One would power 3 cobs and the other could power 2. This would create 27.8 PAR/sqf which is appealing. I would require two dimmer dials which isn't ideal but acceptable. Any caveats with this setup?
Lastly. I haven't seen anyone stick an analogue amp meter inline. I think it could be helpful with the dimming option to know what you are running. Is there a problem putting one at the end of the LED chain?
Thanks in advance for any advice.
Last edited:
