DiY LED - Cree CXA3070

SupraSPL

Well-Known Member
I was looking over the data on that link you referenced (thank you for that) and it is (.037 vs .055 C/W). Also, they are basing their results on a rise of 60C over ambient. Our heatsinks may be as little as 2C over ambient (CPU cooler) or 5-10C for passive cooling. Although I am not sure exactly how much or if that would affect the thermal resistance numbers. I am surprised how well the 9800 seems to perform with only convection cooling. It looks like it would require forced air?
 

zangtumtum

Well-Known Member
the 9800 it's better with active cooling, or at least heatsinks with this type of architecture require active cooling place in the extrusion direction.
I'm testing high power aluminum heat sinks and I'm waiting to test them identical, but entirely of copper.
Theoretical calculation copper earn 2/3 degrees in the same system in the same conditions with the same power, but with a higher weight.
Varying the parameters I have not yet calculated.
 

pepperdust

Well-Known Member
DAMN supra that is bright.. even in a pic I'm squinting...

Thanks for the previous info you gave me.. I appreciate it as I learned to increase the efficiency just drive them a little lower, so it reminded me to tone them down a bit in veg.. less electric, still good lumen output.. wish I still had my kill a watt meter.. I have all these meters around me but not some cheap simple one... go figure

I was talking about some veg color testing... I've done some more, and what I say.. yes it's kinda hard as they are all good at veg, but the combo that is winning by a little is half CW 6,500k / half NW 5,000k with 4 2,700 WW added in.. I'm going to test it against a half 3,000k / half 6,500k lamp I have.. maybe its more blue or the more red??? I am a believer.. well cannot say yet if it's the blues in the red / blue store bought lights, but these veg so well, that it might have some play with the reds in it, as I have heard there is some pure blue veg led lights?? but my instinct says red can boost veg plants also... wasn't the very old NASA led info that lettuce was grown best at 90% red / 10% blue???? also taking this lightly I have a couple ( 3x ) CDM philips bulbs one being the veg lamp and some agros.. the veg lamp does VERY VERY well, and has a lot of red / orange / yellow , so just saying...... it's not a predominant blue bulb and the veg growth rates were very good.

I know people are going to say it's dumb, but I build a 2,700k / 3,000k bar to test against an all 3,000k bar.. we'll see how it goes.. well maybe I did test it un-intentionally as I don't know what bars got put into the flower tent yet..

who knows with this all, but I do think some fine tuning is still in order.. but to just have the simplicity of whites is very easy and good for everyone.. lot alone on the eyes...

Thanks again
 

Kuifje76

Well-Known Member
Hello Kuif :) That is a nice sized closet I am sure you can make some magic happen in there. If cost is no object you can run them soft and significantly reduce the heat that needs to be removed, making the grow ventilation very quiet. You could panasonic bath fans that are near silent. If you can scare up some 3000K CXA3070 ABs and run them at 700mA, they are 49% efficient minimum and dissipate 24.5W ea. So that is only 12.25W of heat per COB, relatively easy to handle, especially with active cooling. Cost is about $4/PAR W.

Regarding the copper plate, although it would spread the heat away from the COB very quickly, it does introduce another thermal interface between the copper and aluminum and it is very expensive in terms of man hours to prepare those surfaces correctly, unless it is machined with precision like high performance CPU heatsinks. So I think the best approach is to use a heatsink with a reasonably thick base plate of pure aluminum, all the way to the fins and to make sure you have sufficient surface area to dissipate the heat into the air (30-40cm²/W for active cooling)

That said, if you run the CXA3070 at 700mA and use active cooling, there will be virtually no gains to be had by overbuilding the cooling system beyond the levels we normally recommend. The reason is because modern whites and blue stand up very well to heat (temp droop) and tend to suffer mostly from current droop instead. So it would be most effective to spend your resources running them softer rather than overbuilding the cooling system. For example, when I tested a CXA3070 at 2.1A on a basic solid aluminum 100W CPU cooler with the fan running at 12V, the decrease in light output as it warmed up was only 2%. Based on that test, I expect there to be virtually no decrease in output from ambient to thermally to warm, when running at 700mA and actively cooling. That is awesome for us!

Everything I said above does not apply to the Cree XPE and XPE2 reds, they really suffer from temp droop and not so much from current droop. However, our standard heatsink recommendations are effective at keeping them cool, especially if the stars are flattened.

So if you want to push the envelope to new territory of efficiency, you could simply run even softer than 700mA and use twice as many COBs. At 300mA the 3000K CXA3070 AB bin is 54.9% efficient minimum (Tj 50C), but Tj would be much lower than 50C in this case, so you could reach 56.5% efficiency minimum, 58% typical. That is about 190lm/W of warm white! The downside is the cost, about $9/PAR W, 4X-5X more than some DIYers are paying for 40% efficient lamps. You could push it even further by running them at 270mA. Driver cost would be negligible, plenty of cheap 270, 300 and 350mA drivers available.
Hey Supra, thanks for the explanation.

First plan was to use 8x cxa3070 in that closet @700 to 1050mA, then 8x cxa3590 @350 to 700mA, but since they are still too expensive 77€/ a piece (I calculated 6-7 years to get the difference in electricity back),
so i'm back to 8x cxa3070, 700mA to 1050mA :) and probably 3x 5000k or 6500k in the middle, since I wanna grow Durban Poison (100% sativa). Happy75 is helping me with those cobs, thumbs up for happy75 !

The idea was a 1 time investment for heatsinks and drivers, and to update cobs every 3 years (more efficient along the way).

I know the numbers you're giving me, i have them in an excel sheet, they come from you :razz:

Like i said, work is no problem. I would buy the copper plate to lower the Tj, I don't understand that 'thermal interface between the copper and aluminium, wouldn't it be better (if they're completely flat and polished), or is it that 2 different materials don't exchange heat that easily)
Max. per cob would be 40W, so maybe it's not necessary...

What do you think of those 2 heatsinks ? any preference ?

I've seen some copper bases for single leds too : here, they probably have them for cree xp-e too ! So I'll buy copper bases for the red lights :) to deal with temp droop :razz:
 

SupraSPL

Well-Known Member
Yes as long as they were flat and polished with a good thermal paste, the additional thermal interface should be a non issue. But it can expensive to do it right (unless the manufacturer did and it you get them second hand) and you are correct with a 40W setup it would make almost no difference compared to straight aluminum. So that is why I advise to channel those funds toward running soft. Good call on the copper stars, might help the XPE reds. Also, I have noticed that copper stars tend to be much flatter than aluminum stars for whatever reason. I plan to do some testing on the red to see how much their output decreases as the heatsink warms up. It will be interesting to see how they do compared to the whites and blues.
 

Tazbud

Well-Known Member
Hi Supra, can I ask what heatsink that is above? with its solid area fit CXA3070?
I was looking for a round heatsink to stick in the end of a 100mm sewer pipe (to run a low powered cob.. )...
I was thinking Vero 10 size from those i'd seen.
 

SupraSPL

Well-Known Member
Hello Taz. It is 3.5" or 89mm diameter if you cut those four mounting posts off. With the mounting posts max width is 4 5/8" or 118mm. The mounting surface is just barely big enough for CXA3070, there is nothing behing the solder points because the copper pad is elevated. This is a common heatsink I got a bunch of them second hand from eBay. They are nice because they are cheap and the copper pad is truly flat.
 

Tazbud

Well-Known Member
I thought it looked a bit cramped on there... what I can see of it.. Ok, yeah, think iv'e seen them similar on ebay with the bolt hangers and smaller (rated) without.. and some round ones (just heatsink) made for vero, maybe they were copper face. I like the mechatronix heatsink design of their fan/heatsink here / they go to 134mm for passive CXA 30 ( here )

open, heavy fins. Visions of some low current cobs in 90* bends and T pieces, joined to vent at the end (for our greenhouse). I don't think my cabinet design is the most efficient but it doesn't seem to take much air over the sinks at all with 700mA, wasn't too sure of the wisdom of plastic a few weeks ago. thanks supra.
 
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Kuifje76

Well-Known Member
I was looking over the data on that link you referenced (thank you for that) and it is (.037 vs .055 C/W). Also, they are basing their results on a rise of 60C over ambient. Our heatsinks may be as little as 2C over ambient (CPU cooler) or 5-10C for passive cooling. Although I am not sure exactly how much or if that would affect the thermal resistance numbers. I am surprised how well the 9800 seems to perform with only convection cooling. It looks like it would require forced air?
Yeah, didn't know what to think about 60° rise over ambient, I'm also surprised of the low numbers with the 9800 and convection cooling, the size (122x122) makes it perfect to slam 2 ventilators on it.
Still undecided between the 2.
 

SupraSPL

Well-Known Member
Hi Supra, can I ask what heatsink that is above? with its solid area fit CXA3070?
I was looking for a round heatsink to stick in the end of a 100mm sewer pipe (to run a low powered cob.. )...
I was thinking Vero 10 size from those i'd seen.
Found them for $10 at Newegg and Amazon, I count 69 fins and a nice hunk of thermal mass in the middle, copper base and core.

http://www.newegg.com/Product/Product.aspx?Item=N82E16835200034&cm_re=RCX-Z300-_-35-200-034-_-Product

http://www.amazon.com/gp/product/B003WLZ1XA/ref=ox_sc_imb_mini_detail?ie=UTF8&psc=1&smid=ATVPDKIKX0DER
 
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Tazbud

Well-Known Member
They might work well + with a bit of space around the outside (thanks for the measurement). Those fans are much quieter also. Cheap enough (well.. $25-30 here) to hack into place. Use the fans where they are needed but I'm guessing they wouldn't be trusted with more than 5-10w if the fan stopped.
 
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Voidling

Well-Known Member
Hey Supra, long time. I saw your name on another thread and thought it looked familiar. Went back looking for my old diy threads from icmag and it turns out the one I was looking for was yours showing the kapton tape and all.

Anyways...I'll have to read through the new light build. I just dropped the money I had for a new led on seeds thanks to some black friday sales going on. Dropped way too much on seeds for not having a good option of light.

My small flower cab is 16" x 28" x 30" tall. I had a chinese light that partially failed. My 400w hps is too hot at 200w. I have a ballast I can remove from my produce growing if I have too in order to run 4 55w pll lights, but they all put off good bit of heat too. What would be an estimate cost for a diy option to cover this footprint if you don't mind me asking.

I have a mother/clone side too under cfl I'd eventually make one for too.

Plus I want to make a white only panel for a miniature rose mantle piece I have in mind.

Thanks
 

Voidling

Well-Known Member
Sure thing, if you can run an iron you can build a sweet lamp. I think it is a great idea to make a simplified guide to make it more accessible.

Bill of materials for a 50W 42.6% efficient lamp something along these lines:
CXA3070 X 2 = $82
Heatsink 10.08" X 6" X 2.8" = $43 ($171 shipped for 4, heatsink USA)
700mA driver X 2 = $24

Misc materials:
Prolimatech PK3 or similar (eBay)
Kapton tape (eBay)
Zinc chain (Walmart or Amazon)
50V hookup wire for LED string 18ga (or use 600V wire from old xmas lights) (elecdirect)
600V wire for AC connections 18ga (elecdirect)
slide connectors .25" (bare, crimp on) (elecdirect.com)
heatshrink tubing .25" (elecdirect.com)
Solder 63/37 lead (amazon)
Solder flux gel syringe - MG chemicals ($10 eBay/Amazon) (this really helps)

tools needed:
cordless drill (harbor freight $15)
heavy duty crimper/cutter/stripper (walmart ebay amazon)
soldering iron (60w eBay $10)

recommended:
GFCI (eBay $7)
sand paper to lap heatsink surface (3M home depot)
Is this running 50 watts or like led manufactures call it what it would be if running full power but have it dialed back? Just trying to figure out what I need for my tiny cab. thanks
 

SupraSPL

Well-Known Member
At 7000mA, the COBs would be dissipating about 24.5W each, but the power draw would be about 28W for each COB.

Since I made that post, we have discovered better heatsink options. These CPU coolers are a great choice for smaller builds. 1 CPU cooler/COB used.

http://www.newegg.com/Product/Product.aspx?Item=N82E16835186070&nm_mc=KNC-GoogleAdwords-PC&cm_mmc=KNC-GoogleAdwords-PC-_-pla-_-CPU+Fans+&+Heatsinks-_-N82E16835186070&gclid=CMi6h_nrmsICFSho7AodKFYAEg

Also, since that post we have gained access to higher efficiency bins. So now if you run at 700mA you get a 49% efficient lamp (minimum). If you run at 1.4A you get 42% efficiency. We have found very good (and cheap $12.99) 1.45A drivers on eBay. They are currently sold out (restock in 18 days) but you can get them from China if you think that would be faster.

From California
http://www.ebay.com/itm/181578939219?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649

From China
http://www.ebay.com/itm/171401815098?var=470444964984&ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649
 

Voidling

Well-Known Member
Thanks Supra, I can wait until they restock.

Is there a list of bin numbers in order so I can learn what bins are better than others, or just point me to a link with the best available at the moment?

How many cobs would you put to flower in that tiny cab?

My card got declined on the international order when I tried buying seeds yesterday so I have money for a light. I was having buyers remorse on spending so much on seeds without a light to grow them. I just really want some cbd genetics.


It's good to see you're still around and tinkering. Happy Thanksgiving
 

SupraSPL

Well-Known Member
The CXA3070 3000K comes in Z2, Z4 and AB brightness bins. The Z2 is available from Digikey, the Z4 bin is available from Aliexpress and the AB bin is occasionally available from Arrow, Ali and sometimes available from RIU members.

Happy TDAY!
 

kkman

Member
Hey KK sorry to hear about the COB but the Alpine 11 will take care of you. Regarding the thermal shutdown protection, maybe something along these lines on the AC power wire?
http://ac-rc.net/catalog/product_info.php?cPath=27&products_id=70&osCsid=hn85urr92h14oncttqurrcvp56
Sorry to bother you again Super, but I ordered a few of the items you mentioned and they just arrived.

So my first question is, looking at the diagram they provide I cant figure if you can connect it to either ac line.
Next how should I connect the thermal switch sensor to the cob TC point?
Lastly I can see how I can connect the switch to a driver when it runs one cob, but how could I connect two switches to two cobs running off the same driver.

If you can help, it would be great.

One last question if I may, Mouser has the ab cxa3070 97 in stock now for £44.53 and the z2 big at £27.44, since the AB bin is almost twice as much as the Z2 bin, would it be worth buying one AB and running it at 1400ma 20-25cm from the canopy or buying two Z2 bin and running them at 700ma 15cm from the canopy.
 
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