DIY LED with COBs - small medium and large grows

[Dawn Patrol]

Second batch turned out 1.17g/W. Third batch still drying but I am expecting 1.1g/W as a minimum.

I'm really impressed by your results - thanks so much for all you help and contributions around the interwebs, it's greatly appreciated!!!

 

[SupraSPL]

THNX DP, the batch turned out MUCH better than estimated, 1.39g/W and a record yield for that space (4'X5' canopy). So 611W of LED far outperformed my 2 X 600W HPS setup, very encouraging. Granted, it took 9 weeks to finish and my HPS results have never been very good relative to the claims of some growers. So for my system HPS got the job done but COB got the job done X 3

 

[OPM]

5 6k and 5 3k cobs all 100w, one bad driver. easily enough room to add more. should push around 600w on a 2x5.5 light bar.

 

[SupraSPL]

Wow that is one of a kind! How hot is the metal next to the COBs and what drivers are you using? How much is it drawing from the wall?

 

[OPM]

They are not getting too hot, china parts so idk how long they will last. I don't have a meter to test the draw. but they are all 100w cobs and drivers. cheapos from ebay. they should draw 60%, so i guesstamate 600 watts draw. they do have heat sink on other side. plus I'll be adding 2 box fans on either side drawing air up thru the system.

 

[Toaster79]

You've got way too little heat sinking surface! You need approx. 4sqr"/W so do the math. Those box fans aren't gonna help much either. You are gonna need some serious heat sinks for this. I'd suggest somenthing like this plus some serious fans to remove the heat. You really want those COBs to run as cool as possible otherwise they'll loose their output really soon. Another thing! Those cheap chinese COBs are really crappy. Extremely low efficiency. You should really consider some Cree or Bridgelux modules for this application. Cree even got some new module in 450nm and 640nm peak in one module. Give it a thought. And those drivers are unreliable. Ditch them and get yourself some Meanwell ore other knonwn quality drivers.

 

[OPM]

It's my first light build. I wasn't planning on spending a ton of money on something that may or may not work. cost me $100 for this one, it'll get me by a grow or two. then I can invest. if not, I'm not really out a hole lot of cash. the next build will be much better.

 

[OPM]

1.5 x 3 x 5 heatsink on the back. + all the other parts are aluminum. I'll have to finish the build b4 I can really say how it's working with heat, fan, ect..

 

[mirdad]

Amazing thread and results Supra.

Myself , ever since I 've been using the Cree CXA3070 AB ( 3000K - 80 CRI ) ,
the average yield per W ,is most of times around 1,2 - 1,3 gpw .

Better with those cobs ,to use more of them and driven at low currents ,
than few of em & 'hard driven' ,right ?

And the cooler they kept ,the more light they output ,also right ?

I have acquired an 'underground DIY fixture ' . With thermal control on it .
Made somewhere in southern Europe.Kinda a 'high-endish ' design ;).

COB leds ( specially the Cree cxa3070 3000K ) ,is definately the wildest artificial lighting ,ever ..
And the best part of it is that the future is right now !

Cheers.
:cool:

 

[SupraSPL]

Awesome lamp MD! it does look familiar haha. Yes my final numbers from my first all-AB bin run turned out 1.39g/W, blew my expectations away. Next batch is coming down now, looks great and finished on time 7.5-8.5 weeks depending on the variety. Running them at about 800mA now and the red/blue strings at 650-700mA.

 

[OPM]

Cobs get hot, but a few inches from them it's warm to the touch. I know I should use real cobs n drivers, the wallet just don't yield enough for that yet. The plants seem to love it. I'll just keep adding what I have till I run out of china made junk. They also mess with the TV on the other side of the house.
Those box fans pull enough air to move the plants under them. airflow is up, not down.

 

[Toaster79]

That's my setup: 3x Cree XP-G2 6500K, 3+3x Cree XP-E 6500K, 3x Cree XT-E 4500K running off one 60W Meanwell driver @1400mA, XP-Es are wired 3S2P (700+700mA) and 2x Bridgelux 25W wired parallel off Meanwell 60W driver also 700+700mA. Extra adjustable power supply for fans, 5-13.5V. Heatsinks for tripplets are 145mm OD, and two CPU hetsinks for the Bridgelux modules (2700K, 95+ CRI).

 

[rick ratlin]

Congrats on your harvest, very impressive! Do you have any pics of your cloner light? Particularly, what size heat sink would you recommend for the Cree XM-L2 4500K for clones. This is gonna cover a 18" x 36" cloner, so I figured I'd use two leds, but was unsure if I mounted these like the larger cobs. I was going to use this driver
http://www.fasttech.com/products/1612/10002422/1178001
Also, what leds are in your veg set-up and what heatsinks/fans as well. Glad everything is going great in the garden, and thanks again for the knowledge.

 

[Toaster79]

Congrats on your harvest, very impressive! Do you have any pics of your cloner light? Particularly, what size heat sink would you recommend for the Cree XM-L2 4500K for clones. This is gonna cover a 18" x 36" cloner, so I figured I'd use two leds, but was unsure if I mounted these like the larger cobs. I was going to use this driver
http://www.fasttech.com/products/1612/10002422/1178001
Also, what leds are in your veg set-up and what heatsinks/fans as well. Glad everything is going great in the garden, and thanks again for the knowledge.

Look, XM-L2 is rated up to 3000mA and that driver is only 350mA so you'd be wasting a lot of money on a quality LED and run it with a cheap crappy unreliable Chinese driver way underpowered. It's like driving a Hummer with a Toyota Yaris engine. Also 3w is way to little light for such area especially coming from a single small source like this. I'd go with at least 7-10 LEDs driven at 500-700mA. For cooling would be an aluminum plate of about 4"x30" sufficient without any fans considering there is a good thermal path between LED and heat sink.

 

[SupraSPL]

Toaster you are correct it is very significantly underpowered, but there is a nice efficiency bonus in this case unlike the hummer with the yaris engine which would suffer from poor load matching. When it comes to cloning we are not looking for photosynthesis, just trying to keep the plant in the vegetative state and we do not want it to respirate too much until the roots are established. At 300mA, the XML2 and XPL can reach above 180 lm/W and will last a lifetime with zero lumen depreciation and almost no electricity consumption (~1.6W). So I clone with 1W in a 12"X18" space and have for a few years now. It works great even with large clones. I also use this method for my headlamps to make them lightweight and batteries last an entire day of use.

That little driver is very cheap but it is all you need to do the job. I have dozens of them all around the house and have never had one fail yet. They come in 300mA 450mA and 600mA sizes. Under the right conditions they are up to 80% efficient.

As far as cooling, if you are running at 300mA you can use these:
http://www.fasttech.com/products/1506/10001927/1163600

and for 600mA you can use these:

 

[SupraSPL]

Since the XP-L became available, I would recommend that above the XML2 because the XPL is available in top bins with a cooler color temp, perfect for cloning.:
http://www.fasttech.com/products/16...e-xp-l-v5-2a-1186-05lm-5700-6000k-led-emitter

 

[Toaster79]

I'm familiar with all the numbers to well. I've also built countless numbers of bike lights flashlights and headlamps. Just didn't know that clones survive near darkness. That XP-L is actually XM-L2 in XP package(3.5x3.5mm instead 5x5mm). And I really have bad experience with cheap Chinese drivers. If you're shooting for even higher efficiency look into Cree MK-R

 

[SupraSPL]

$9 fasttech dimmable headlamp (100mA-600mA) modified with 4000K XML2 and panasonic lithium 18650


assortment of cheapo AC LED drivers covered in shrink wrap. The slide connectors makes it quick and easy to swap them in any circuit. The very worst perfomer in the bunch is also the most expensive one on the left. I will not go above 50% efficiency no matter what load it try on it.


XPE green and XTE warm white on the fasttech 1W heatsink. I sanded these heatsinks smooth to 1000 grit before mounting. At 1W they are barely warm to the touch and even cooler with an XPl or XML2. (These are not carelessly soldered, the flux gel I used ate away at the surface layer for some reason.)


XPE green at 600mA, this would get warm on this sized heatsink.


A pair of 400nm UVA LEDs on the 3W heatsinks. Running these at 300mA, the heatsink are slightly warm to the touch (90f).

 

[SupraSPL]

At 1W the XPL could reach 180 lumens. That is very bright in a 12"X18" box, the clones stay very happy. Some of my friends use 40W of fluoro over their clone domes, but I believe that they could get the same job done with 1W and put those 40W to work elsewhere.

I have analyzed the MKR because of its claims of 200lm/W, but I honestly have no idea where that press release got those figures because it does not reach those numbers. I calculate 180lm/W at Tj 50C 250mA (2.8W). That is for the brightest listed in the PDF 65cri 6200K. Maybe it was an honest mistake?

The only LED I have ever examined that can reach near 200lm/W is the CXA3590 CD 5000K. It is about 200lm/W at .25A (17W) and cost $5.56/PAR W. As far as my knowledge goes, that is the most efficient LED for sale anywhere in the world. I have one in my veg room and it is running at 290mA (20W), powered by this 88% efficient $2.41 driver:

 

[SupraSPL]

All that said tho, I did find a burned out driver the other day. It was powering a CXA3070 at 900mA and it just died for no apparent reason. No biggy to swap out and it was the first dead driver out of dozens, but worth mentioning. I am just glad it did not harm the COB when it died. It was this driver, 90% efficient:
http://www.fasttech.com/products/0/...5v-30w-high-power-constant-current-led-driver