DiY LED - Cree CXA3070

Much thanks to SUPRASPL, MrFlux and all the people posting knowledge in these LED threads. I have read for several hours a day for the past week researching, learning, and looking at grow journals with COBs to make a decision and purchase some parts for a DIY led.

I Got all my parts in and rigged everything up so I could test the heatsink's ability to cool the single cxa3070 running at 1400mA with a 120mm pc fan blowing through it at 5v. Ran it for about 20 minutes and was happy to see the heatsink was barely warmer than ambient. The base of the heatsink near the COB is thick and that area was staying surprisingly very cool as well. Id call the heatsink/fan combo a success.

Ive got some better thermal paste coming on Monday so Im going to clean the cheap paste off and put the new stuff on when it gets here and solder the wires for the 5v phone charger to the 120mm fan to finalize that connection.

Im trying to decide if I want to build a small cab for the single cob or if I should just get another matching heatsink, cob, and driver for $80 and run both in my current tent replacing the 150w hps next run. They would be run at 1400mA each on the meanwell lpc-60-1400 drivers so about 100w for the two and I believe they could replace or even surpass the 150w hps that is in there now.

Im thinking about getting another cob and running a pair in the tent. But at the same time if I keep the 150w hps tent setup and build a small cab for the cob, I can have more quantity from both setups and more variety. Tough decision Ill have to think about.

JavaCo said:

You might want to check this thread out https://www.rollitup.org/led-other-lighting/733157-cree-cxa3050-100w-custom-led.html. He has about the same growing space as you. He is using two of cxa3050

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Thanks for the reply! Wouldn't there be somewhat of a disadvantage in using the cxa3050s over the 3070s? I want to get as much from the area designated as possible (obviously ) and have 5' (160cm or even more with some modifications) of height to work with.

Letitgrow, I think 5000K would be great for vegging, you wouldnt need to run it very hard in a space that size.

Bueno Time glad to hear you got it running cool! If you want to take it up a notch while you are waiting for your thermal paste, you can flatten the heatsink. Unfortunately CPU heatsinks suffer from the same problem as every aluminum heatsink I have ever tested, they are not flat at all. They tend to have a "dent" in the middle right where the COB would sit. Cree recommends taking it down to 1000 grit but 90% of the improvement happens in the 60/80 grit range. You can get away wet sanding with a simple hand sanding block or if you have a lot of heatsinks to work on an electric palm sander works great.

SupraSPL said:

Bueno Time glad to hear you got it running cool! If you want to take it up a notch while you are waiting for your thermal paste, you can flatten the heatsink. Unfortunately CPU heatsinks suffer from the same problem as every aluminum heatsink I have ever tested, they are not flat at all. They tend to have a "dent" in the middle right where the COB would sit. Cree recommends taking it down to 1000 grit but 90% of the improvement happens in the 60/80 grit range. You can get away wet sanding with a simple hand sanding block or if you have a lot of heatsinks to work on an electric palm sander works great.

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Yeah I probably will try to flatten the mounting surface there are a couple imperfections where 2 of the 4 corners of the cpu were touching the heatsink.

Also if anyone is wondering, this is a picture of the same heatsink as I am using. I measured and calculated the heatsink surface area at ~170 sq in and it feels pretty hefty too for its size, like a pound maybe. I dont have a scale that weighs that small.

I ended up taking your recommendation to resurface the heatsink. It was indeed concave or "dented" like you said in the center of where the chip mounts. I couldnt tell at all until I started sanding with a block and it became apparent it was really not even close to flat. I just used what I already had in the garage for sand papers and it turned out pretty well I think. Much smoother and flatter than before and should give a lot better contact with the COB. I started with 60 grit, then 100, 150, it was not flat yet still so I went back to 60, 100, 150, 220, 400, it still didnt look quite flat but I kept going with the 400 for a while longer, then 2000, 2000 wet, wasnt quite happy with it yet so went back to 400 for a while, then 2000 briefly, then 2000 wet again for a while, and finally some rubbing compound to polish it. Took me a solid hour or a hair more to get it flattened and polished well. Turned out pretty good.

SupraSPL said:

Letitgrow, I think 5000K would be great for vegging, you wouldnt need to run it very hard in a space that size..

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Such a helpful community thank you! Do you think it would still be best to use 2 3000k's for flower then? Could run them low but it sounds like 2 would give best results - once again no engineer!

Edit: also, what drivers are you using Supra? I see you said they were "chinese cheepos" earlier and prices near me aren't pretty...

Nice work bueno, that grit pattern sounds about the same as my first experiences, it was a lot of work! What I eventually realized is that I needed to do 90% of the work in the 60 grit range. I go lengthwise for awhile and then sideways for awhile. Each time you switch you will be able to tell if it is flat yet.

Once it appears flat, you go sideways one more time, THEN progress to the next grit which will be a piece of cake. At that point all you are really doing is removing the scratches from the large grit and it goes very quickly. 60->150->320->600->1000 Something along those lines although you could probably skip a few.

For those who have not seen it, here is an example of the depression in the middle of every aluminum heatsink. I did this by hand with 60 grit 3M pro grade from Home Depot.

Let it grow, if the 1.5X3' is your only grow space then I will assume you want to veg them dense and fast, so I would suggest running the 5000K at 650mA with this $6. It will run at 47% efficiency and dissipate about 22.5W. If you want to run it at 900mA you could use this $11. There are lots of alternatives on eBay and you could run it harder if you need to. But those links are a few that I have tested myself. If you prefer an enclosed UL listed driver check out the Meanwell LPC-60 1050 or LPC-60-1400 ~$25.

Another alternative would be to use XML2 U2 4C. It is 4500K and if you run them at 650mA with those same drivers they will run at 49% efficient and each will dissipate 1.9W. This would be a more complex build but would give you a better spread. You would need a minimum of (8 ) XM-L2 to run with that driver and you would need a few short fin heatsinks to spread them across the canopy. You could use passive cooling at 100cm²/W.


When it comes time to flower you could use two more of those 650mA for the 3000K or you could increase to these 900mA drivers. At 900mA the CXA3070 Z2 3000K will run at 41% efficient and each will dissipate about 32W. The Meanwell LCP-60-1050 does actually put out 1050mA and works with the CXA3070 so that is a great option too. The Meanwell LPC-60-1050 does actually put out 1050mA and it works with the CXA3070 so that is a great option too.

Here's a Spyder 600 that I chose spectrums for- mixing mostly whites, with 2 reds. Data is computed in real time, so it can be changed/adjusted on the fly

http://www.bmlcustom.com/custom-report-details/?partNo=PS3690S101GHTHFGCACGFHTHG

SupraSPL said:

Cool link PF Ill have to look read into their design more.

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I love how they give honest data, but 22% efficiency yipes!

If you DIY a 3000K CXA3070 at 1.4A you can get 52W at 37% efficient for about $67. ($45 for COB, $13 for driver, $9 for heatsink/fan)

The Onyx grow is another 3000K option that is about 30% efficient and relatively cheap. 210 dissipation Watts for $450 = $2.14/W impressive for a commercial lamp.

Is the 22% efficiency based on my spectrum selection, Osram diodes, or...? Not cast in stone yet

SupraSPL said:

I love how to give honest data, but 22% efficiency yipes! The Onyx grow is another 3000K option that is about 30% efficient and relatively cheap.

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I am not sure how they determine it, but they admit it is only 12 PAR Watts and 54.5 dissipation watts so 22% is the radiometric efficiency.

The way I see it, very few manufacturers have mastered the process of making high efficiency white LEDs. It all starts with an extremely high efficiency blue and a very high quality phosphor. Luckily for us Cree has mastered that and they are available for purchase in small quantities, so when it comes to growing LEDs it seems there is no competition for them yet. The Onyx Grow uses Cree XM-L2 3000K T4 bin and the CXA3070 takes it up a notch from that.

Thanks.

I would have thought OSRAM had much better whites, or maybe BML isn't yet using them.

In tele conversation, he is not up to speed on mj or whites for growing

SupraSPL said:

I am not sure how they determine it, but they admit it is only 12 PAR Watts and 54.5 dissipation watts so 22% is the radiometric efficiency.

The way I see it, very few manufacturers have mastered the process of making high efficiency white LEDs. It all starts with an extremely high efficiency blue and a very high quality phosphor. Luckily for us Cree has mastered that and they are available for purchase in small quantities, so when it comes to growing LEDs it seems there is no competition for them yet. The Onyx Grow uses Cree XM-L2 3000K T4 bin and the CXA3070 takes it up a notch from that.

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Good info tnx PF

Supra,

What are your thoughts on high CRI levels vs a high light saturation level?

I recently found the 3590 with a CRI of 95 on the datasheet with a performance group of Z2 which got me thinking. But cannabis is a weed correct, in a plant defining sense? So would it benefit more from more light being in the weed category? Or is quality of light always important?

Which brings me to the CMH. It has a CRI over 90 and does very well with cannabis. Could this be due to CRI alone?

My goal is to grow the best quality I can. Would quality differ from 80 CRI to 90+ CRI?

Canna

CannaBare said:

Supra,

What are your thoughts on high CRI levels vs a high light saturation level?

I recently found the 3590 with a CRI of 95 on the datasheet with a performance group of Z2 which got me thinking. But cannabis is a weed correct, in a plant defining sense? So would it benefit more from more light being in the weed category? Or is quality of light always important?

Which brings me to the CMH. It has a CRI over 90 and does very well with cannabis. Could this be due to CRI alone?

My goal is to grow the best quality I can. Would quality differ from 80 CRI to 90+ CRI?

Canna

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Cannabis is not a weed. It is considered a flowering plant. People call MJ weed , but it is just a nic name.

SupraSPL said:

I love how they give honest data, but 22% efficiency yipes!

If you DIY a 3000K CXA3070 at 1.4A you can get 52W at 37% efficient for about $67. ($45 for COB, $13 for driver, $9 for heatsink/fan)

The Onyx grow is another 3000K option that is about 30% efficient and relatively cheap. 210 dissipation Watts for $450 = $2.14/W impressive for a commercial lamp.

Click to expand...

Do you have a link to the $13 1.4A driver?

SupraSPL said:

Let it grow, if the 1.5X3' is your only grow space then I will assume you want to veg them dense and fast, so I would suggest running the 5000K at 650mA with this $6. It will run at 47% efficiency and dissipate about 22.5W. If you want to run it at 900mA you could use this $11. There are lots of alternatives on eBay and you could run it harder if you need to. But those links are a few that I have tested myself. If you prefer an enclosed UL listed driver check out the Meanwell LPC-60 1050 or LPC-60-1400 ~$25.

Click to expand...

Wow, you just saved me a fair bit of money thanks! Is there some wiring I'm going to have to do to plug them into AC when they arrive?

letitgrowson said:

Wow, you just saved me a fair bit of money thanks! Is there some wiring I'm going to have to do to plug them into AC when they arrive?

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Yep you just have to wire the power cord to the driver. Basic soldering skills would get it done in no time.

Supe/other spectral geniuses,

This is my current spd with the 860w CDM


I would like to supplement this with perhaps more 660nm? I have a 5 x 5 bare vert with around 12" behind plants. I can go above, behind, or a little both with the supplementing LEDs. With the limited 'back' space in vert...would you guys just go with stars or ram em with cobs?

Think I've asked this before and never received an answer. Any advice would be appreciated!