Help me understand Cob Lenses and Reflectors

K

kaivorth

Active Member
I'm planning a DIY Cob light, that will have 8 Citizen 3500k 1212's running at 700ma. At this low amperage for efficiency, I'm worried about light penetration. Will reflectors or lenses help with this? If so what ones should I be looking at?

Grow room is 2'x4' COBs will be evenly spaced.

Also will pin fin heatsinks with pre tapped holes for cxb3590's fit the 1212's as well? Was looking at the Ideal 50-2204CT holders.
 
Millsie

Millsie

Well-Known Member
@CobKits

Personally I wouldn't be running lenses/reflectors on cobs at such low wattage - however if you've got the spare money for 8 lenses/reflectors I'd probably go for it (you're probably looking at 80-90degree)

Most people with low watt bare cobs seem to keep them 8-12" away from the canopy to minimize light throw and modifying their grow to be a sea of green (SoG)

Just depends on how you want to spend your money / time
 
K

kaivorth

Active Member
I mean it looks like they're only $2 a piece, if it helps efficiency, yield, or anything I might as well.

90 degree lenses it is, I suppose these are better than reflectors? Any particular brand I should be looking at, or get whatever is cheapest on alibaba?
 
CobKits

CobKits

Well-Known Member
kaivorth said:
At this low amperage for efficiency, I'm worried about light penetration.
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use more or run them harder. penetration is a function of overall power and you wont magically get more output by putting reflectors on.

24W/SF is really pushing the low end of light intensity. id run at 1050 and dim as needed
kaivorth said:
Also will pin fin heatsinks with pre tapped holes for cxb3590's fit the 1212's as well? Was looking at the Ideal 50-2204CT holders.
Click to expand...

no the 3590s are a different size. the 2204CT holders are great (if you can find them- everybody has been out of stock for mos i hope to have some in a few weeks). the mounting holes are 35 mm apart and i believe the reflector mounting holes are 39.5 mm apart
 
CobKits

CobKits

Well-Known Member
kaivorth said:
I mean it looks like they're only $2 a piece, if it helps efficiency, yield, or anything I might as well.

90 degree lenses it is, I suppose these are better than reflectors? Any particular brand I should be looking at, or get whatever is cheapest on alibaba?
Click to expand...
depends on your setup. all optics are lossy (as is bouncing photons off a wall)
 
K

kaivorth

Active Member
CobKits said:
use more or run them harder. penetration is a function of overall power and you wont magically get more output by putting reflectors on.

24W/SF is really pushing the low end of light intensity. id run at 1050 and dim as needed



no the 3590s are a different size. the 2204CT holders are great (if you can find them- everybody has been out of stock for mos i hope to have some in a few weeks). the mounting holes are 35 mm apart and i believe the reflector mounting holes are 39.5 mm apart
Click to expand...
What would you consider optimal W/SF? Trying to make some good stuff for this grow. I don't mind sacrificing a little efficiency for optimal buds :) I appreciate the advice you've been giving me on a couple other threads too
 
CobKits

CobKits

Well-Known Member
depends how hard you run your cobs.

20PAR W/SF is a good target

at 50% efficiency thats 40W/SF
at 60% efficiency thats 33W/SF
at 40% efficiency thats 50W/SF
 
Abiqua

Abiqua

Well-Known Member
Penetration is light [read: photon] density.

If you fill up a room with 1400mA to 1500ppfd
The same room just requires twice from a 700mA setup.

A light set at 12" putting out 1500ppfd will "penetrate" better than a same light @750ppfd for instance.
 
K

kaivorth

Active Member
You just said 24 PAR W/SF is on the low end, then you said 20 PAR W/SF is a good target?

Maybe I should start really learning the math behind the COBs. How are you calculating PAR W/SF by the amperage I'm running the COBs?
 
R

rhygin77

Member
kaivorth said:
You just said 24 PAR W/SF is on the low end, then you said 20 PAR W/SF is a good target?

Maybe I should start really learning the math behind the COBs. How are you calculating PAR W/SF by the amperage I'm running the COBs?
Click to expand...
There's a distinction. 24 watts/ft2 is the total electrical useage. The measure he used is PAR watts/ft2 (i.e. the amount of electricity that is "converted" to light, which is a portion of the total electrical useage that does not include the heat generated by the LEDs or the driver, etc.).
 
K

kaivorth

Active Member
Ahhhh there we go I just misread something. So are lenses worth using then if they won't help with penetration?
 
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