DiY LED Grow Lights with CREE CXA3070 COBs and CPU Coolers

JoeyV

JoeyV

Well-Known Member
nomofatum said:
When balancing up front cost, performance, and ease of construction I picked these:

http://www.aliexpress.com/item/Wholesale-10pcs-of-lot-30W-LED-Chip-for-Floodlight-Flood-light-Warm-Cool-white-6000k-6500k/2011319079.html

http://www.aliexpress.com/item/400W-S400W-36V-11A-LED-Switching-Power-Supply-36V-11A-85-265AC-input-CE-ROSH-power/1544392301.html

Add a piece of flat stock aluminum, thermal adhesive, a lamp cord, and 2 splice connectors per chip and you have a very high power light strip, perfect for making a grid for optimal distribution. I don't over power them, I run 15 on 400w.

I'm actually waiting on my second order of these now.
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Got a pic of your light strip? Also, how did you wire them up? Series or parallel?

I've been looking at the specs on that power supply, and what's pictured isn't what's specified in the ad. There must be a 36vdc version that isn't listed on the page.

Also, you say you're running fifteen 30w COBs off of that one supply. They must've listed the specs incorrectly on the COBs as well. It's listed at 1500mA.

34vdc(fVmax) * 1500mA = 51w.

1 - 30w COB @ 34vdc = 30w/34vdc = 882mA.

15 COBS @ 882mA = 15 * .882A = 13.23A.

The supply is rated at 36vdc @ 11A = 396w. It has an efficiency rating of (approximately) 82%. So at full load it's drawing 483w. It appears that you'd be losing 87 watts to heat, assuming the supply actually delivers the full 400w output.

The stock strip of aluminum will likely get hot, depending on it's length and thickness. Cooling fins help dissipate the heat by giving more surface area for air to heat up around. But it doesn't sound like you've got any on your strip. You could attach heatsinks behind the COBS on your strip. That should help keep the strip and the COBs cooler. They don't have to have fans. Though a fan blowing over the strip will also help cool things down.

If you're running in parallel, the COBs furthest from the supply will be seeing a drop off in voltage, depending on the gauge of wire your using. Using 18 awg wire would result in a 2% drop down to 33.32vdc @ 1 meter away from the power supply. 12 or 14awg wire will reduce the drop off to below 1%. Placing the supply in the middle of the strip will also reduce the % of loss as would using stranded wire. How much I don't know, but some for certain.

I could be wrong in my calculations however... I'm using basic Ohm's Law and some wire gauge calculators online. I have no experience with these new high powered LEDs. It's all just theoretical for me right now.

I'm still learning about COBs and have a bunch of cheap Chinese stuff for experimenting on order.

To anyone, please feel free to correct me if I'm wrong about any of my calculations. And by all means, expound on anything I might have gotten right or wrong.
 
nomofatum

nomofatum

Well-Known Member
JoeyV said:
Got a pic of your light strip? Also, how did you wire them up? Series or parallel?

I've been looking at the specs on that power supply, and what's pictured isn't what's specified in the ad. There must be a 36vdc version that isn't listed on the page.

Also, you say you're running fifteen 30w COBs off of that one supply. They must've listed the specs incorrectly on the COBs as well. It's listed at 1500mA.

34vdc(fVmax) * 1500mA = 51w.

1 - 30w COB @ 34vdc = 30w/34vdc = 882mA.

15 COBS @ 882mA = 15 * .882A = 13.23A.

The supply is rated at 36vdc @ 11A = 396w. It has an efficiency rating of (approximately) 82%. So at full load it's drawing 483w. It appears that you'd be losing 87 watts to heat, assuming the supply actually delivers the full 400w output.

The stock strip of aluminum will likely get hot, depending on it's length and thickness. Cooling fins help dissipate the heat by giving more surface area for air to heat up around. But it doesn't sound like you've got any on your strip. You could attach heatsinks behind the COBS on your strip. That should help keep the strip and the COBs cooler. They don't have to have fans. Though a fan blowing over the strip will also help cool things down.

If you're running in parallel, the COBs furthest from the supply will be seeing a drop off in voltage, depending on the gauge of wire your using. Using 18 awg wire would result in a 2% drop down to 33.32vdc @ 1 meter away from the power supply. 12 or 14awg wire will reduce the drop off to below 1%. Placing the supply in the middle of the strip will also reduce the % of loss as would using stranded wire. How much I don't know, but some for certain.

I could be wrong in my calculations however... I'm using basic Ohm's Law and some wire gauge calculators online. I have no experience with these new high powered LEDs. It's all just theoretical for me right now.

I'm still learning about COBs and have a bunch of cheap Chinese stuff for experimenting on order.

To anyone, please feel free to correct me if I'm wrong about any of my calculations. And by all means, expound on anything I might have gotten right or wrong.
Click to expand...
Looks like they have half the specs from a 30w and half the specs from a 50w in there, lol.

I gave my last version away when I moved, I'm expecting to receive the parts to build the new light setup any time. My room will be setup and running within the next 3 weeks, you will have to wait at least 1 or 2 to see the light setup.
 
JoeyV

JoeyV

Well-Known Member
nomofatum said:
Looks like they have half the specs from a 30w and half the specs from a 50w in there, lol.

I gave my last version away when I moved, I'm expecting to receive the parts to build the new light setup any time. My room will be setup and running within the next 3 weeks, you will have to wait at least 1 or 2 to see the light setup.
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No prob... not going anywhere.
 
O

obviously

Well-Known Member
So , all I need is : 10x COB , 10x Arctic coolers , 10x Mean Well drivers and silver thermal paste for cpu. Which one you recomand and how many grams for 10 COB ?
PS : I already made my shopping list :)
 
nomofatum

nomofatum

Well-Known Member
obviously said:
So , all I need is : 10x COB , 10x Arctic coolers , 10x Mean Well drivers and silver thermal paste for cpu. Which one you recomand and how many grams for 10 COB ?
PS : I already made my shopping list :)
Click to expand...
Why 10 drivers? Can't you get something that can power more than one? 10 drivers will create more waste heat and cost you more than 1 or 2 that can power you whole setup. If the cooler clips on just use paste, but otherwise get the thermal adhesive version. You don't need much, 5 grams should cover you.

Arctic Silver Arctic Alumina 5g Thermal Adhesive or Paste
 
O

obviously

Well-Known Member
Thank's for replying. What did you think about ? Which driver can support all COB ? And what driver you recomand for Alpine11 plus collers ? Some people said that prolimatech pk-3 is better.
 
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Dloomis514

Dloomis514

Well-Known Member
nomofatum said:
Why 10 drivers? Can't you get something that can power more than one? 10 drivers will create more waste heat and cost you more than 1 or 2 that can power you whole setup. If the cooler clips on just use paste, but otherwise get the thermal adhesive version. You don't need much, 5 grams should cover you.
Arctic Silver Arctic Alumina 5g Thermal Adhesive or Paste
Click to expand...
There needs to be a recycle system for thermal paste. The usual purchase Is a few grams, usage is hardly any. For the price of a postage stamp some one could get the stuff for free. Anyone want mine? On loan?
 
O

obviously

Well-Known Member
Why would I need to get the COB off ? Do you think that prolimatech pk-3 is better than Arctic Silver Arctic Alumina 5g Thermal Adhesive ? And which driver you recomand instead 10 mean well drivers ? Thank you guys :)
 
nomofatum

nomofatum

Well-Known Member
obviously said:
Why would I need to get the COB off ? Do you think that prolimatech pk-3 is better than Arctic Silver Arctic Alumina 5g Thermal Adhesive ? And which driver you recomand instead 10 mean well drivers ? Thank you guys :)
Click to expand...
No idea why you would want to take it off. Arctic Silver is already crazy overkill, really if you were going with paste, a tub of lithium grease would do just fine. Lithium grease was what we originally used in the 90's for heatsinks, at least until we went nuts overclocking and needed the best heat transfer possible.
 
Dloomis514

Dloomis514

Well-Known Member
Voidling said:
I can't get the link to the exact post on mobile, but scroll down to supraspl 's comment here.

https://www.rollitup.org/t/building-up-for-bigger-grow.852683/

Someone used the adhesive but then needed to get the cob off. He either couldn't or it became very difficult. I forget if he managed to without destroying everything
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i think that was me, i used ADHESIVE, not paste. Adhesive is an epoxy, a 2 part mix, that cures as hard as a rock. Dont do that
 
nomofatum

nomofatum

Well-Known Member
Voidling said:
Yeah, was just a reason for someone else not to use the epoxy in the future.
Click to expand...
As long as there is a clip or something to keep it on, you shouldn't need/want the adhesive. I don't have fans or clips on my setup. I adhesive the LED chip to an aluminum strip that is attached to an aluminum rack that holds all the lights. I have the vent fan above and a wall fan to spin the air in the room. My rack serves as a large heatsink.

Just make sure it's not possible for the heatsink to fall off. Would be a shame to burn up all your LEDs because one heatsink falls off. (depending on how you wired)
 
Voidling

Voidling

Well-Known Member
Back in my thread supra posted the thermal coefficients of several thermal pastes.

I know on computer processors to heat sinks is said to use about a pea size I believe. One syringe is a lot of peas worth.
 
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