DIY LED with COBs - small medium and large grows

Buddy Brain · Jul 1, 2015

Toaster - thank you for the suggestion on the Meanwell driver, I will check it out.

I re-posted the pictures as jpegs. The entire housing acts as a heat sink. I misspoke, it's actually a channel - not a pocket. The photo shows an extrusion with black anodize, but we have a lot of this stock that is simple silver (mill finish - no anodize). I am using a thermal adhesive paste, so the flat stock for the spacer is plenty flat enough as the paste fills in any gaps. I agree that it would be slightly preferable to have the channel shallow enough to not need the spacer plate, but as mentioned it was designed originally to be an LED light bar housing. The spacer is easy, just takes 5 minutes for the thermal adhesive to dry, I have the standoff pieces and can provide the spacer plate with the standoffs already attached. I could attach the spacer plate w/standoffs to the to the The other nice thing is that it has t-slots on the top, so (4) t-nuts can be used with eye-bolts to hang it, I have those too. The housing extrusion comes from the factory cut at 12' long, so I can have them cut to any length shorter than that. so if someone want a 48" or 60" light bar no problem

Toaster79 · Jul 1, 2015

You need to add vent (or two) on one side and cover both top sides of sink to push room temp air over both COBs. What you have now is gonna cook your driver. Both COBs are heating it with whatever it's putting out and it's not gonna last long this way and until then, efficiency is gonna really suck. I'd also mill away tat first side rib, maybe even two depending on how deep that pocket. Those are also dead air pockets with hot air escaping sideways (heat travels vertically). With some work those could be useful. Have you got any side shots and dimensions?

What would you charge for a 2' extrusion shipped to Europe?

beep7886 · Jul 28, 2015

New Poster here, learning a ton from you guys!!! Could I utilize this same setup above(posted by supraSPL). I have a 1.5 x 2 foot grow cabinet(6 foot tall sterilite cabinet). Could I make one of the above DIY fixtures using a CXB3590 and a Mean Well NPF-120D Power supply. Would this one COB with the 42V @2.9A (121W I believe) be enough for the whole cabinet. I have been contemplating between the new Area51 W90, and the Hans 80W but now after reading all these posts from you guys it seems that DIY COB's are the way to obtain the best results for the buck.
Appreciate the help, thanks

beep7886 · Jul 28, 2015

Or would I be better off going to http://heatsinkusa.com as SupraSPL suggested, and getting say a 8" x 14" heat sink and adding two of the CXB 3590's run around 60W and 10 or so deep red and 5 royal blue led's from steve's led's. The square footage of the room is exactly 3 feet, so I wanted approx 150W (50W per sq ft). I am leaning towards this route as it seems most are running these COD's at a much lower power. I have a few questions,
Would I want a separate driver for each COD and than a third driver for the steve's led's?
Is the surface area mentioned above enough for 150W(I would also ass a pc fan to the top of the heat sink)??
Am I going way to overkill on lighting and should I use maybe vero29's instead??
Sorry if I am asking to many questions, and/or not making much sense. This is my first grow and I am still a rookie
Thanks again!!

beep7886 · Jul 30, 2015

Ok, I am starting to understand the efficiency aspect of running these COB's at lower Amperage. Below is what I have in mind for my 2' x 1.5' grow space (6ft tall). Not including the pc fans or wall wart for the top of the heat sink as I already have those(plan on putting two pc fans on top of this heat sink).
- 8.5 x 18 inch heat sink from heat sink USA.
- I plan on running two CXB3590 80 CRI 3000k
- 9 CREE XTE led's (6 photo deep red, 3 royal blue)
I plan on powering both COB's and the 9 XTE's with ONE MeanWell HLG-120H-C700
Everything will be connected in series, running at 700mA will pull about 120W. Since the power supply has a dimming function I was thinking of maybe running @75W during veg and @120W for flower. Maybe even run it at 600mA during flower for about 110W. The power supply is rated for up to 150W, so running at 110W would still be using 75% of the power supply which still runs above 90% efficiency. Let me know what you guys think, thanks!!!

seaslug · Aug 6, 2015

LOL, I've literally spent hours reading over data sheets of LEDs and drivers, heatsinks, etc.

The original post is from over a year ago. The Cree CXB3590 series is the "best" right now and comes in 36Vf and 72Vf flavors. Mean Well HLG drivers are the "best". (Seems to be the concensus)

Lenny Gray · Sep 21, 2015

Greetings,

I'm about to start building a few DIY COB LEDs, having ordered an assortment of parts, and want to get some clarity on questions of efficiency. SupraSPL wrote "You can get up to 49% efficiency if you can find the top bins and run them soft (700mA). You can get 36% efficiency with the mid bin running hard (1400mA)."

So, does "hard", then, connote HALF power (ie: 1/2 of 100W at 36v = 1389ma) with "soft" actually being one QUARTER power (1/4 of 100W at 36v = 695ma)?

That would explain another datapoint I've gleaned, noticing that commercial panels tend to universally choose 1/2 power, though SupraSPL, again, said that, one year ago, good commercial panels of the time only ran 30% efficient. So, presumably, those good panels were running hotter, more like 2/3 power?

Also, other than general agreement about the downside of running the COBs too hot, I've encountered conflicting opinions about running at actual FULL power. One party cited the conventional wisdom that full power always causes rapid deterioration, even when well cooled, while another, seemingly expert in his own right, said that white COBs are pretty good about that, these days.

Can anyone point to answers to these ideas stated as FACTS?

- Lenny Gray -

seaslug · Sep 21, 2015

Lenny, search terms would be LM-80 and TM-21. I saw some Cree CXA data on my phone but now I can't find it. The CXB are too new for tests to be completed, I think.

"In addition, most of the LEDs in the CXA family have 6,000 hours of LM-80 data published and are able to support TM-21 reported L90 lifetime of over 4 years, even at 105°C."

Edit: found the CXA LM-80 data:

Lenny Gray · Sep 25, 2015

beep7886 said:
Ok, I am starting to understand the efficiency aspect of running these COB's at lower Amperage. Below is what I have in mind for my 2' x 1.5' grow space (6ft tall). Not including the pc fans or wall wart for the top of the heat sink as I already have those(plan on putting two pc fans on top of this heat sink).
- 8.5 x 18 inch heat sink from heat sink USA.
- I plan on running two CXB3590 80 CRI 3000k
- 9 CREE XTE led's (6 photo deep red, 3 royal blue)
I plan on powering both COB's and the 9 XTE's with ONE MeanWell HLG-120H-C700
Everything will be connected in series, running at 700mA will pull about 120W. Since the power supply has a dimming function I was thinking of maybe running @75W during veg and @120W for flower. Maybe even run it at 600mA during flower for about 110W. The power supply is rated for up to 150W, so running at 110W would still be using 75% of the power supply which still runs above 90% efficiency. Let me know what you guys think, thanks!!!

View attachment 526209

When you say "everything running in series", you are, I hope, noticing that you're talking about 170V. Beyond the driver being able to supply that, are you sure you want that high a voltage appearing across your lights?

Toaster79 · Sep 25, 2015

Lenny Gray said:
When you say "everything running in series", you are, I hope, noticing that you're talking about 170V. Beyond the driver being able to supply that, are you sure you want that high a voltage appearing across your lights?

Why would 170V DC be a problem?

Lenny Gray · Sep 27, 2015

Toaster79 said:
Why would 170V DC be a problem?

I was merely thinking about the susceptibility of the flesh. Manufactured lights are boxed up to keep us out. A DIY will invariably not be.

seaslug · Sep 27, 2015

LOL, I was thinking earlier today--don't touch 170VDC with your dick in something wet!

A DIY design with glass lenses can be electrically safe.
https://www.thcfarmer.com/community/threads/my-plan-for-a-cree-cxb3590-light-bar.72868/page-2

SupraSPL · Sep 29, 2015

Lenny Gray said:
Greetings,

I'm about to start building a few DIY COB LEDs, having ordered an assortment of parts, and want to get some clarity on questions of efficiency. SupraSPL wrote "You can get up to 49% efficiency if you can find the top bins and run them soft (700mA). You can get 36% efficiency with the mid bin running hard (1400mA)."

So, does "hard", then, connote HALF power (ie: 1/2 of 100W at 36v = 1389ma) with "soft" actually being one QUARTER power (1/4 of 100W at 36v = 695ma)?

From the LM80 data seaslug posted, the CXA3590 run hard and hot loses 20% of its output after about 9 years of 12/12. But the primary reason for running soft is to increase efficiency by reducing current droop. The main advantage to higher efficiency is to reduce waste heat in the grow space.

We normally run growing LEDs much cooler and softer than CREE expects them to be used so there is little data that would apply to our aplication (LM99) In this example (CREE XPG) there was negligible depreciation after 2 years of 12/12 and may have actually increased output in some cases:

I would not recommend running an LED at full power if it is to be used as a growing lamp. The longer hours/day a lamp is run, the more important efficiency becomes. If you are using the LED in an application where it only runs for short duration, you can run it at 200% full power if you need to, as long as it is sufficiently cooled.

Current droop refers to the decreasing efficiency of an LED as dissipation power is increased. Some LEDs experience much more current drooo than others, but it may come at a cost of lower efficiency to begin with or greater sensitivity to temp droop.

The orange line represents where output would be if there were no current droop (Vero 29):

SupraSPL · Sep 29, 2015

Another data point, Luxeon run at Tj 74C, 1% depreciation after 1 year of 12/12. Estimated 5% depreciation after 10 years of 12/12

Cree Xlamp, Tj 65C, 10 years of 12/12, 3% depreciation

Lenny Gray · Sep 30, 2015

SupraSPL said:
From the LM80 data seaslug posted, the CXA3590 run hard and hot loses 20% of its output after about 9 years of 12/12. But the primary reason for running soft is to increase efficiency by reducing current droop. The main advantage to higher efficiency is to reduce waste heat in the grow space.

We normally run growing LEDs much cooler and softer than CREE expects them to be used so there is little data that would apply to our aplication (LM99) In this example (CREE XPG) there was negligible depreciation after 2 years of 12/12 and may have actually increased output in some cases:
View attachment 539282

I would not recommend running an LED at full power if it is to be used as a growing lamp. The longer hours/day a lamp is run, the more important efficiency becomes. If you are using the LED in an application where it only runs for short duration, you can run it at 200% full power if you need to, as long as it is sufficiently cooled.

Current droop refers to the decreasing efficiency of an LED as dissipation power is increased. Some LEDs experience much more current drooo than others, but it may come at a cost of lower efficiency to begin with or greater sensitivity to temp droop.

The orange line represents where output would be if there were no current droop (Vero 29):
View attachment 539284

So, I'm a little confused over your use of terms. In the original text I cited, you apparently referred to 1/2 power as "hard" and 1/4 power as "soft", and I've been orienting myself to that reality. But in this recent response you say "the CXA3590 run hard and hot loses 20% of its output after about 9 years of 12/12". Is this use of "hard" still referring to 1/2 power?

SupraSPL · Oct 2, 2015

@Lenny Gray It is really a matter of opinion. The manufacturer suggests "nominal" current which is about 75% power. I would consider that running hard because at 75% there is significant current droop in a Cree CX series. I run mine at 15-25% and consider that soft which allows Cree COBs to reach very high levels of efficiency, but that could be considered overkill unless your yield is directly restricted by heat.

For most DIYers, assuming modern top bin Crees, I recommend 50% power which is a good compromise IMO.

ofbyah · Oct 3, 2015

Greetings, I am new to the forum, getting lots of awsome information here. Thanks for sharing everyone.
I am planning on building some lights using 3590's at 36v. I have meanwell 500w & 750w 24v power supplies now.
It would seem to me that this boost converter would be very effective as a dimming power supply at a reasonable cost.

I've allready ordered a couple to try out. If anyone knows why this is a bad idea, I'd love to learn from someone else's
mistakes for a change.

cheers

Toaster79 · Oct 4, 2015

You have a driver that runs at about 90% efficiency and you want to add a step up converter which efficiency is much worse. You'll be turning 25% of your pover into heat before it even comes to be turned into light.

DcBig bud · Oct 12, 2015

I'm thinking about building one of these for a 2 ft x 2-1/2 x 8ft closet space. The plan is to use four cxa3070 cree chips running at 50 watts. This is my only space so my thought is to use as much light as possible. Does this sound like overkill? Will four cobs give me heat problems in this little space? and last but not least, should I use a combination of warm and cool white? By the way, I should mention I plan to grow autoflower in this area. Any help would be much appreciated. Thank you.

Lenny Gray · Oct 13, 2015

DcBig bud said:
I'm thinking about building one of these for a 2 ft x 2-1/2 x 8ft closet space. The plan is to use four cxa3070 cree chips running at 50 watts. This is my only space so my thought is to use as much light as possible. Does this sound like overkill? Will four cobs give me heat problems in this little space? and last but not least, should I use a combination of warm and cool white? By the way, I should mention I plan to grow autoflower in this area. Any help would be much appreciated. Thank you.

When you ask about the 4 x 50W COBS and heat, you may be missing the importance of airflow. (I underestimated it when I first started.) In addition to getting the heat out, you need to recycle the "air" so fresh CO2 comes in while your light's shining. As for how much heat your 2'x2' closet can handle, actually test it by pushing 200 Watts into the closet set up as you expect it to be used. You can probably borrow a couple of incandescents from someone (there are still lots of neo-Luddites around). But it's really about the (heat) energy. If energy (power) flows out of the wall, and can't escape into the world, it builds up in your grow-space. Also, for the 12-hour dark cycle, consider photo-darkroom louvers that let air in without light. Make sure you also let the air out.

DIY LED with COBs - small medium and large grows

DIY LED with COBs - small medium and large grows

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Lenny Gray

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