COB choice for small space DIY

HI! I am in the process of making an LED lamp with COBs for my growcab. Should I go with 3 cxa3070 run at 700mA or another smaller cob? (I'm thinking light spread here, first, efficiency 2nd) suggestions would be welcome as to which ones.

additional questions:

How many watts should I be aiming for in this small space?
Can there be too much light?

also I have already made a DIY LED lamp some years ago and it consists of 9x10w LedEngin LEDs, 2x blue, 4x red, 3x deep red. Those LEDs will preferably be a part of the new lamp. They are run at 700mA. So I already have two meanwell 700-35 I believe.

my details:

cab dimensions
H: 25.6"
W: 29.5"
D: 17.7"

Square feet: 3.6

How bout, 8-12 Vero 10 3500k's on 2 pieces of 2,08" from HeastsinkUSA [16-18"] with either

1 of these : Phillips Xtitanium 350ma 400v+
or 4 of these: Fasttech 300ma 120v

Cooled with 2 or 3 of these per heatsink 50mm Ballbearing Fans


I have a cab of similar dimensions [little bit taller] and I am running into the same complications. Even with just 3 Cree Cxa running @ 700ma, I don't think the spread will be even enough in your cabinet, the penetration where light is most concentrated will be awesome though. But you might have a few "weaker" spots inside....especially when you run a lower height on the plants......

With the Vero's you have superior coverage [for the price] and almost as much efficiency and just about the right amount of penetration for your height.....

Trade-off's or options I guess, I would feel more comfortable going at least 4x the Cree Cxa's and running them soft and as high in the cabinet as possible.....this way you have complete coverage along with penetration


[edit: or maybe 4x Vero 18's with your 700ma Drivers]
[Ideally you want to aim for at least 25 watts sq. ft for the LED's, 35-40 probably being the max you want to run.....]

8/10 said:

HI! I am in the process of making an LED lamp with COBs for my growcab. Should I go with 3 cxa3070 run at 700mA or another smaller cob? (I'm thinking light spread here, first, efficiency 2nd) suggestions would be welcome as to which ones.

additional questions:

How many watts should I be aiming for in this small space?
Can there be too much light?

also I have already made a DIY LED lamp some years ago and it consists of 9x10w LedEngin LEDs, 2x blue, 4x red, 3x deep red. Those LEDs will preferably be a part of the new lamp. They are run at 700mA. So I already have two meanwell 700-35 I believe.

my details:

cab dimensions
H: 25.6"
W: 29.5"
D: 17.7"

Square feet: 3.6

Click to expand...

Does any one else think this cabinet sounds a little short?

Dloomis514 said:

Does any one else think this cabinet sounds a little short?

Click to expand...

Cutting it a little too close for CXA's imho.

Go with some cxa1304 120lm/w you can get them for $1.50 each. Run them at 600 ma or 700 ma so you can use your current drivers and you can usually fit 4 cobs per driver and they give amazing light spread and are one of the most efficient led.

Where do you get them for $1.50? Digikey is selling the CXA1304 3500K B2 bin for $2.64 ea. If you drive it at half power (5W) it is 108 lm/W (33% efficient) and cost $1.63/PAR W.
For comparison, if you went with the Vero10 3000K and drive it at half power (9W), it is 119lm/W (37% efficient) and cost $1.47/PAR W.

wow, thanks for the great advice! First of all, the cab is indeed pushing it height-wise. I am struggling with pot height, plant/light distance and coverage. The latter has turned out to be the biggest problem. BUT it is doable, and I am definitely making progress on the technique side of things, and the next grow I'll be REALLY getting things going (I always say this) with a scrog from seed, topping and LST'ing in a highly controlled fashion.

I'll be checking out your suggestions and return with more questions, probably.

Oh, what do you think about implementing my LedEngin 10w's? The thing is I don't want to mess up the color ratio with too much red. I read that cxa has more blue than the vero's so I initially thought that would be the better alternative.

I am definitely liking your suggestions! cxa3070 seems crazy now. But I've got a noob question. I have always looked at the forward current/ test current as the recommended rating, and I thought that going over this value would be overdriving the LED for shorter life span and lower efficiency?

But, if running the vero 10 at half power yields 9w, that would mean running it at 350mA which is half the I-max and also the forward/test current... Did I mess this up or did I just learn something?

Yes I kind of picked those colors temps randomly. The CXA does have more blue and the Vero has redder red. You could go with 3000K Veros and add a few blue Luxeons during the veg cycle. Or you could go with 3500K or even 4000K Veros.

You are correct, the numbers I mentioned were at half of max current. As long as you can keep up with the cooling, you can drive the Veros harder with no worries. It reduced efficiency slightly, reduces cost/PAR W, but also reduces the evenness of the spread.

Once cxa3070 up high with couple veros ringing around it slightly lower? Even out the red and blue ends?

My cab is 32" tall and had a 3.5" tall chinese led and I was having trouble. I made a wicking bed in the bottom to reduce pot height. Lets the roots spread out rather than down, without root binding too much. LST or Scrog is a must. Even the chinese lamp was light bleaching or burning any bud that got close or touching respectively

Okay, so I think I've got this narrowed down to ~10 vero10's 3500K at 350mA.

The cxa is highly praised but definitely more expensive.

The light-design I am thinking of is a flat aluminum slab just a tad smaller than the grow area with all LEDs spread out evenly on the same plane. Hopefully I'll be able to mount heatsinks and fans on this slab in a way that it hangs as close to the roof as possible. Thanks for the advice, again. this is going to be awesome.

Oh, and Voidling, do you have any threads that show the wicking tray? sounds like a good idea.

The plants I have vegging under 4000k Vero 29 are looking super nice so far

I am extremely happy with the Vero LEDs I have used so far.

Depending on what your cab is made out of, you could save some height by drilling some holes in the roof for the emitters to poke through and mount the heatsink(s) externally.

A 28" piece of this profile will hold 3-4 vero 10's, but temps could be on the high side for passive cooling. However it's the cheapest profile available per watt displaced. If you actively cool one with a 50mm fan you could probably run up to 5 vero 10's at 9watts. Though for the price of the fan and it's driver it would almost be better to just buy more heatsink.
http://www.heatsinkusa.com/2-079-wide-extruded-aluminum-heatsink/

A 28" piece of this profile would be overkill. However it's the next cheapest profile available from HSUSA and would run 18 vero 10's at 9 watts if actively cooled.
http://www.heatsinkusa.com/4-850-wide-extruded-aluminum-heatsink/

You can get the cxa1304 on ebay for 1.5 each shipped. Run them at 600 ma or 700 ma with 4 on a normal driver and it becomes the cheapest option while still giving amazing performance. I'm just recommend these since you already have 700 ma drivers so you can use those and save some cash.

Another option is to get a 1/2 thick aluminum plate you can get 12x24 inches half inch thick for $30 then get a large 200 mm fan for under $10 and run soft since a fan isn't 100% needed but greatly improved cooling. Very cheap and effective way to go.

for everything 20 cxa1304 aluminum fans it comes to $70 total if you use your current drivers.

95'ZR1 said:

You can get the cxa1304 on ebay for 1.5 each shipped. Run them at 600 ma or 700 ma with 4 on a normal driver and it becomes the cheapest option while still giving amazing performance. I'm just recommend these since you already have 700 ma drivers so you can use those and save some cash.

Another option is to get a 1/2 thick aluminum plate you can get 12x24 inches half inch thick for $30 then get a large 200 mm fan for under $10 and run soft since a fan isn't 100% needed but greatly improved cooling. Very cheap and effective way to go.

for everything 20 cxa1304 aluminum fans it comes to $70 total if you use your current drivers.

Click to expand...

nice analysis!

@8/10 here you go. I'll post later about what I would change if you're interested in this method

https://www.rollitup.org/t/voidlings-wicking-bed.623923/

wow, that is something new for me. several plants in the same container and a very shallow one at that... I believe I have been told that two or more plants in the same container wouldn't work cause one plant would dominate and starve the others. that myth is busted. Also I thought that shallow containers would restrict the plants cause they naturally want to grow downwards... another myth busted!

I was planning to go with a wider shallower pot the next grow but I had serious doubts if it was a good idea. I am much more confident about that move now. This will make a lot of new room for my next grow.

But back to the LEDs:

I'm looking at cree's website and the cxa's is listed with different voltages at the same model...? For example, cxa1304 is listed with 9, 18 and 37 Volts...? might be a noob question but I thought the Voltage was more or less static.

http://www.aliexpress.com/item/CREE-XLamp-CXA1304-Warm-White-37V/32254971326.html

This cxa1304 is listed as 37V...? I thought they were ~9V no matter the current.

[email protected], [email protected] or [email protected]. The listing is for the 37v. You would want to drive them at .250ma.
I don't see any order code numbers so how would you know what the bin is?

Ellydee i think you have that wrong. The vf does change but not that much a few numbers at most. The 9v 18v and 37v are different models. It depends what kind of driver you want.

wait i just read it again I'm unsure if that's what you meant, three different models.

95'ZR1 said:

Ellydee i think you have that wrong. The vf does change but not that much a few numbers at most. The 9v 18v and 37v are different models. It depends what kind of driver you want.

wait i just read it again I'm unsure if that's what you meant, three different models.

Click to expand...

Yes, you have a choice of voltages depending on what part number you order.