DiY LED - Cree CXA3070

Another important thing LED builders have to do is choose their drive current. You can use the exact same metrics, electrical efficiency and $/PAR W. For the CXA3070 3000K AB bin, if you are willing to pay $4 /PAR W, you can drive it at 700mA and get 49% efficiency. This can reduce your heatsink cost and will create less heat to get the same job done so you may get AC/ventilation savings.

On the other hand if you want to drive it at 2.1A, your cost drops to $1.60/PAR W and efficiency drops to 36% (will be lower in practice due to increased junction temp from internal thermal resistance of the COB). 36% is still a very respectable number and much higher than the best commercially available lamps. The downside is the drivers cost $30 each so that make 1.4A a better deal in this case.

hmmmmm okay.... soooooo, say I wanna replace a 1000 watt MH for veg, how many of the CXA3070 or CXA3590 would I need? I've been reading this forum for 3 days straight and there is just too much to read and I'm still pretty confused haha... I'm thinking of building something similar to what Mr X had.... just a single aluminum heatsink that's like 48" x 6"

What is the foot print for your veg??

tenthirty said:

What is the foot print for your veg??

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5' x 5'

That is some very good low hanging fruit as far as heat and electric savings. If you grow stocky indica leaning you could veg with 4000K CXA3070s and if you run stretchy sativa leaning you could use 5000K CXA3590s. The amount on wattage per sq foot is up to you, higher wattage will veg them up faster. I currently use about 10W/sq ft and some of them end up 4 foot tall bushes before the flip. So if you built a 250W system for a 5X5 and use the 4000K CXA3070, it would take 5 of them at 1.4A and 5 of these drivers.

If you went for the CXA3590 5000K and ran them at 1050mA, 4 of them would give you 320W although you could dim them as needed. You would need a pair of these drivers HLG-185H-C1050A or HLG-185H-C1050B and you would be dealing with high voltage strings on the DC side in this case (140v)

Another option, you could run the 4000Ks with some deep blues added on a separate string.

I ran all of my lights at 800mA for one complete flowering run on 2 Cali Jacks and for 5 of 7 weeks on two white widows. Production was down too much for me, lost at least an ounce a plant or close to it. Here is some pics of a Strain Hunter Money Maker at 5th day of 12/12 back to 2 CXA 3070 lights at 1400mA. I am vegging with CXA5000Ks at 800mA, seems to do quite well. This Money Maker may be a good strain from reviews I have read. Only problem was only 1 seed out of 3 took. It look's like it could be a real monster under the right conditions, it is impressing me and it's only 22 inches, nodes are tightly grouped and not too much stretch. I have been keeping up with the newer cobs and drivers but will have to live with what I have now, which isn't bad. I already have too many extra parts around. Also have 3 26w 10.0 lizard lights on it for flowering.

medicinehuman said:

View attachment 3263852 I ran all of my lights at 800mA for one complete flowering run on 2 Cali Jacks and for 5 of 7 weeks on two white widows. Production was down too much for me, lost at least an ounce a plant or close to it. Here is some pics of a Strain Hunter Money Maker at 5th day of 12/12 back to 2 CXA 3070 lights at 1400mA. I am vegging with CXA5000Ks at 800mA, seems to do quite well. This Money Maker may be a good strain from reviews I have read. Only problem was only 1 seed out of 3 took. It look's like it could be a real monster under the right conditions, it is impressing me and it's only 22 inches, nodes are tightly grouped and not too much stretch. I have been keeping up with the newer cobs and drivers but will have to live with what I have now, which isn't bad. I already have too many extra parts around. Also have 3 26w 10.0 lizard lights on it for flowering.

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So production was down...
What light(s) and wattage were you using, and what are you using now(how many CXA watts)?

How do you like the UVB? Do you notice much difference in trichs?

I'm using DIY CXA 3070Z4 3000K, I have 8 of those Cobs and 2 same thing in 5000K. I think it is running 32w a cob on 800mA and about 52w a cob on 1400mA drivers. I used UVB all through only once ( only one light) and there was a little noticeable improvement but I don't think they give quite as much at harvest, I don't think you lose too much though. The amount I used last time wasn't much but this time I should be able see for sure what will happen. Oh yeah, that Money Maker is 16 day's old in flower age not 5. I &%*ked up on dates.

medicinehuman said:

I'm using DIY CXA 3070Z4 3000K, I have 8 of those Cobs and 2 same thing in 5000K. I think it is running 32w a cob on 800mA and about 52w a cob on 1400mA drivers. I used UVB all through only once ( only one light) and there was a little noticeable improvement but I don't think they give quite as much at harvest, I don't think you lose too much though. The amount I used last time wasn't much but this time I should be able see for sure what will happen. Oh yeah, that Money Maker is 16 day's old in flower age not 5. I &%*ked up on dates.

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I asked so we could get a reference like 8 cxa@800ma=256w was just short of...?? Before the CXA's you were using how may watts and what type and brand light(s)?Hps, led, T5??

Greengenes707 said:

I asked so we could get a reference like 8 cxa@800ma=256w was just short of...?? Before the CXA's you were using how may watts and what type and brand light(s)?Hps, led, T5??

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I was using t-5's and HPS , 1-96W T-5 AND A 150 HPS WAS REPLACED by 2 CXA3070Z4 3000K's @ 1400mA. So I traded 246w for 104w that I am running on each plant. Lot less power even with drivers and fans than before. Heat is about the same( STILL MANAGABLE) only because I added 2 more closets to grow chambers when I went LED. I don't count a couple of Chinese lights I tried.

SupraSPL said:

That is some very good low hanging fruit as far as heat and electric savings. If you grow stocky indica leaning you could veg with 4000K CXA3070s and if you run stretchy sativa leaning you could use 5000K CXA3590s. The amount on wattage per sq foot is up to you, higher wattage will veg them up faster. I currently use about 10W/sq ft and some of them end up 4 foot tall bushes before the flip. So if you built a 250W system for a 5X5 and use the 4000K CXA3070, it would take 5 of them at 1.4A and 5 of these drivers.

If you went for the CXA3590 5000K and ran them at 1050mA, 4 of them would give you 320W although you could dim them as needed. You would need a pair of these drivers HLG-185H-C1050A or HLG-185H-C1050B and you would be dealing with high voltage strings on the DC side in this case (140v)

Another option, you could run the 4000Ks with some deep blues added on a separate string.

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thanks Supra! I'm going with the CXA3590 for sure.... I have just a few more questions please if you don't mind... if I build them 2 CXA3590 5000K per heatsink to space them out kind of in a square, would say a 48" x 6" aluminum heatsink from HSUSA be enough for passive cooling? or is that overkill? I'm planning on doing something similar to what MR X has here, but just 2 with 2 LED each all spaced out evenly...




Also, what is the range of drivers I can use with the CXA3590 in terms of mA and watts? I don't think I want anything thats dimmable. Is it the watts that gets divided and the current stays at 1050 mA or 1750 mA if I run 2 LED in series or parallel? I think the electrical stuff is what is confusing me the most at this point... thanks again for the help!

hmmm actually I wanna do 3 CXA3590 on a 48" x 6" heatsink 16" apart from eachother .... can I power all 3 from a single driver? and then I'll build 2 of them... so 6 CXA3590 total

Bueno Time said:

I was going to harvest both the Sugar Jones last night and I could only harvest one, took up over 75% of the drying tub. I pulled the Sugar Jones out that was in the front row in the tent and I was blown away by the amount of bud and weight on this thing every single branch snapped over at a 90 degree angle, I couldnt stand it up to take pictures so I layed it down in the bath tub on its side and started chopping branches off and hanging them in the drying tote. The pics do no justice for size and amount of buds, there are colas laying on top of colas in the pictures so you cant even see whats all there, again I am beyond impressed with the yield from one lady in 3L of coco and just Floranova Bloom the whole grow for nutes.

Cant wait to see how much yield and the how the smoke is on this cut with this growing method vs organic.

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The first Sugar Jones I harvested is dried, trimmed and de-stemmed at 60% humidity in jars yielded 74g of unseeded bud and 9.7g of seeded buds that I hit with a little OX and PB pollen. Pretty crazy yield for 2.75L coco, I could fit 4 of them in my tent and would theoretically yield just shy of 12oz from 190w led dissipation or 220w at the wall.

Cant wait to see the yield on the other Sugar Jones that was just as big I believe, each took up a 1/4 of the tent the two were on the right side half of the tent. Shes drying a bit more should be able to trim tomorrow night possibly or the next day. And some OXs and a PK Bubba that will be harvested in about 4 more days. Should be a healthy yield, will update when all is weighed.

Does anyone have any links to help calculate the effectiveness of a heatsink? I was using the calculator on this website (http://www.heatsinkcalculator.com/) which was previously available for free, but now requires a subscription.

I was wondering if a 32" long piece of the 1.813" or the 2.079" profile heatink available on heatsinkusa would be adequate to passively cool about 50-60 watts of vero 10 and 3w emitters?
http://www.heatsinkusa.com/1-813/
http://www.heatsinkusa.com/2-079/

Thanks in advance.

Imaulle said:

if I build them 2 CXA3590 5000K per heatsink to space them out kind of in a square, would say a 48" x 6" aluminum heatsink from HSUSA be enough for passive cooling?

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The HeatsinkUSA 6" profile is very efficient for active cooling because of the long channels between fins and because a 140mm fan cools every channel. So yes you could use passive cooling but it would require about 110cm sq/W. With active cooling you could use 40cm sq/W. CaliWorthington has 24" lengths and at 12V it blows plenty of air through the channels. He bumped it up to 15V to get even more airflow until he got an AC in there.

So to passively cool (3) CXA3590s running at 700mA (51W each) you would need 16830cm sq which is 65" of heatsink. If you added a 140mm fan you could fit that same wattage on 24". The downside though, is less spread between COBs and that could be a real problem since we are building a vegging light and we do not need high intensity. Reflectors might be able to help with that issue. Another option is, you could put each COB on its own CPU cooler.

Imaulle said:

or is that overkill? I'm planning on doing something similar to what MR X has here

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With all due respect to MR X, pioneer LED grower, from eyeballing it that design looks like it would be running VERY hot, especially if those LEDs are generics. The design you are contemplating could be more than 3X as efficient, maybe 4X

Imaulle said:

Also, what is the range of drivers I can use with the CXA3590 in terms of mA and watts?

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The 700mA driver (HLG-185H-C700) is good up to 286V (3 COBS at 700mA or 4 COBs at 600mA)
The 1050mA driver (HLG-185H-C1050) is good up to 190V (2 COBs at 1050mA)
They are both dimmable but they are the cheapest drivers that I know of that would work.

Very impressive numbers BT! I require about 16L of soil (settles to 13) to get the same yield you got with 3L of coco. And it looks like you could reach above 1.5 g/W!

bicit, a spreadsheet makes surface area calculation pretty easy. Just add the measurements of the perimeter (cross section) and then multiply that by the fin length.

Here is what I have for the 2.079" profile:


Other than surface area, the other things to take into consideration are distance between fins and baseplate thickness. A large distance between fins makes for better passive cooling ability. Thick baseplate allows the heat to spread to the fins faster which is very helpful if your heat load is concentrated in one area, example COBs. Thicker baseplate adds weight and material to the heatsink so it increases the cost without increasing the surface area. That can make it harder to compare the cost of one heatsink to another.

bicit said:

Does anyone have any links to help calculate the effectiveness of a heatsink? I was using the calculator on this website (http://www.heatsinkcalculator.com/) which was previously available for free, but now requires a subscription.

I was wondering if a 32" long piece of the 1.813" or the 2.079" profile heatink available on heatsinkusa would be adequate to passively cool about 50-60 watts of vero 10 and 3w emitters?
http://www.heatsinkusa.com/1-813/
http://www.heatsinkusa.com/2-079/

Thanks in advance.

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Not that it wouldnt work but I dont think that is enough sink for 50-60w, probably would run a bit hot unless you put a small pc fan or two blowing in the fins down the length of the heatsink or maybe if you had really good air movement in the grow area to help cool the heat sinks more efficiently.

Just for example Im using the 2.079" profile on my veg and r/b bars for flower.

2x 23" long for 14 XML2 for veg (7 per bar) with really little air movement in the veg cab the bars run a fairly warm but not hot at ~30w (half driver power)
2x 24" long for 18 red/blue LEDs (9 per bar) with lots of air movement in the flowering tent the bars stay pretty cool at ~30w

Both are passively cooled setups but the air movement in the grow area seems to make a substantial difference in cooling.

I agree BT, I would put it at about 25W for passive cooling.

bicit said:

Does anyone have any links to help calculate the effectiveness of a heatsink? I was using the calculator on this website (http://www.heatsinkcalculator.com/) which was previously available for free, but now requires a subscription.

I was wondering if a 32" long piece of the 1.813" or the 2.079" profile heatink available on heatsinkusa would be adequate to passively cool about 50-60 watts of vero 10 and 3w emitters?
http://www.heatsinkusa.com/1-813/
http://www.heatsinkusa.com/2-079/

Thanks in advance.

Click to expand...

a quick simulation with my tools kicks the 1-813 out of the race. and this is the better one.