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PPFD of DIY CXB3590

R

rossta18

Member
Good Evening ICMag,
Long time lurker first time poster. I built myself a DIY COB Light for my 2x2 Tent and wanted to make sure I wasnt over/under powering. The tent is only about 63" so I am a bit height restricted but I have good airflow so no heat issues. The light I built is 4 Cree CXB3590s 3000k with an HLG240-C1400A. I wanted to know what the calculated PPFD is and if I am maybe stressing the plants by running at 100%. Thank you for the input
 
Desert Hydro

Desert Hydro

Active member
Veteran
sorry i was trying to plug your info into the DIY COB calculator but it wouldnt let me select you wattage. this may be a close estimate but probably a little bit off......

i tried at 1.4 amp but it said watts at the wall was near 400 and you are only getting about 250ish from that driver i believe.

CXB3590CD72V3000K 4 COBS @0.7A ON 5.88 PROFILE HEATSINK
4 SQ.FT. CANOPY 94% EFFICIENT DRIVER @13 CENTS PER KWH
Total power watts at the wall: 207.45
Cobs power watts: 195
Total voltage forward: 279
Total lumens: 32746
Total PAR watts assuming 10% loss: 91
Total PPF: 424.06
PPFD based on canopy area: 1141.13
PAR watts per sq.ft.: 22.75
Cob efficiency: 51.67%
Power watts per sq.ft.: 48.75
Voltage forward per cob: 69.78
Lumens per watt: 167.93
Heatsink riser thickness / number of fins / fin's length: 0.27in/14/1.0in
Heatsink area per inch: 260.01 cm^2
Total heat watts: 94
umol/s/W / CRI: 4.66 / 80CRI
Heatsink length passive cooling @120cm^2/heatwatt: 43 inches
Heatsink length active cooling @40cm^2/heatwatt: 14 inches
COB cost dollar per PAR watt: $2.04
Electric cost @12/12 in 30 days: $10.21
Electric cost @18/6 in 30 days: $15.06
Cost per cob: $46.5
Heatsink cost per inch cut: $1.74
Total cobs cost: $186
Total heatsink passive cooling cost: $75
Total heatsink active cooling cost: $24
 
R

rossta18

Member
Forgot to add that the COBs are 36V. Also do you have a link for the DIY COB Calculator did not come up with the Search engine.
 
Dion

Dion

Active member
id say you have about 1200ppfd
thats a bit intense I think, you could dial it back 20% or so

also ur driver is a 250w driver and you are only using 198 or whatever so u can fit another cob on it, not that you need it just saying.
 
Koondense

Koondense

Well-known member
Veteran
With such ppfd you'll need some kind of CO2 supplementation, so maybe back off a bit the current(to 1050mA) or just change your driver.
 
M

mugenbao

Koondense said:
With such ppfd you'll need some kind of CO2 supplementation, so maybe back off a bit the current(to 1050mA) or just change your driver.
Click to expand...

What would you recommend as a good target PPFD for people who are not running CO2? For instance, I'm currently at 850 and had been considering adding another DIY module, but now I wonder if I should rethink that.
 
habeeb

habeeb

follow your heart
ICMag Donor
Veteran
I recently came across two research papers, both show gains to 1500, even to 2000 on another but wasn't sure if that's enriched as it's a graph, but I would say looking at the chart 1200-1300 seems to be sweet spot for power in, and output production, as the higher you go the less plant output production you achieve so...


another thing apparently while I've been away is finding higher room temp is beneficial for LED, so with these two variables, I say a lot to consider before you go enriched
 
Dion

Dion

Active member
habeeb said:
I recently came across two research papers, both show gains to 1500, even to 2000 on another but wasn't sure if that's enriched as it's a graph, but I would say looking at the chart 1200-1300 seems to be sweet spot for power in, and output production, as the higher you go the less plant output production you achieve so...


another thing apparently while I've been away is finding higher room temp is beneficial for LED, so with these two variables, I say a lot to consider before you go enriched
Click to expand...

yup, super correct and also interesting point


I assume we read the same journal(as there has only been 1 peer reviewed scientific study on this topic)

unfortunately this data only tells us biomass, not bud mass, so its unsure if there was more stem/leaf/larf or whatever just that there is more biomass at higher ppfd

also consider the rate of increased photosynthesis vs increased light, its not linear, so 50% more light doesn't equal 50% more bud
800ppfd is good value between photosynthesis and watts

finally the 1500ppfd was at 29c with co2 enrichment of i think 1500....cant remember exactly but it was hotter and co2er for sure


but its all about rate on return, 700-800 is the sweet zone
 
wildgrow

wildgrow

, The Ghost of
Veteran
mugenbao said:
What would you recommend as a good target PPFD for people who are not running CO2? For instance, I'm currently at 850 and had been considering adding another DIY module, but now I wonder if I should rethink that.
Click to expand...



I just recently saw 800-1000 w/o CO2. You could try squeezing in more driven softer, but youre in the target zone now.
 
Koondense

Koondense

Well-known member
Veteran
mugenbao said:
What would you recommend as a good target PPFD for people who are not running CO2? For instance, I'm currently at 850 and had been considering adding another DIY module, but now I wonder if I should rethink that.
Click to expand...

You already got the answer to that by Dion and wildgrow, I think the same. If your lights are eavenly spread there's no need to change anything; it's good though to have the dimming option for early veg stages, if you run full grow cycles.
Cheers
 
J

Jofo1

New member
4x36V COBs in series is 144V load on the power supply, yours is a 179V max supply so you actually can add another 36V COB to fully utilize the power supplied. Each 36V COB run at 1.4A will yield 23W of PAR and 107 PPF. Your setup produces 428 PPF with the four COBs according to the calculator. PPFD is simply 428/(4ft2/10ft2/m2) = 1070 PPFD, measured in square meters.

I would argue that PPFD isn't really a great metric for a small grow area. It seems to me more important to focus on the intensity of the light source relative to what actually hits the plant. A small space has more optical challenges than a large grow room; a large % of the light reflecting off of walls for example. If your COBs have reflectors / lenses to focus most or all of the light onto the canopy or if the area was large enough to ignore the 'end effects' (like where light hits the walls and is reflected) then PPFD makes more sense. The reflective surfaces are at best 80% efficient in practice, probably less. COBs have a 120deg field of view, so in a small grow space, with the COB at a reasonable height from the canopy, a lot of the light will hit the wall first, with a portion reflecting to the plant. My point is simply that if you want to use PPFD as a common metric, to compare to what others are doing successfully, then the configuration of the application matters a lot. As always ymmv.

goof

Personally I use 5x 36V 3590's at 1.4A (3 @3000K and 2 @ 5000K) in a 2'x3' cabinet, lights at about 20" from the top of the canopy (could go lower as heat is not really an issue, and often the plants finish closer), no reflectors or lenses, so some light hits the wall first. If I focused that light onto the canopy only, minimizing what hits the wall first, the plants certainly will get more light intensity and a higher PPFD; didn't add any light, just provided it more effectively to the canopy.
 
G

Guest

Interesting thread.
I'm in a similar situation. My gorilla tent is 2.5 feet by 2 feet by 7 feet tall.
My light is a 4 COB 300 watt kit from Timber. Not pimping just listing the equipment.

Can I ask why you fellows are using the light specs to calculate the light at the plant instead of using a par meter to calculate the DLI based on your grow light schedule of hours on and off?

Using an apogee meter I try to maintain a DLI of around 22-25 in flower.
Without going over my notes I know the ppfd is part of the equation but I just made myself a reference sheet for 12/12 and 18/6 and incriments of par levels to get from a DLI range from 20-30.
Maybe I'm mistaken but I thought the actual light at the plant is what needs to be measured.
I know I burned my last grow some before I got a meter and figured this part out.
 
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