DiY LED - Cree CXA3070

SupraSPL

SupraSPL

Well-Known Member
I just ran a quick test like the one I described. A CXA3070 Z4 bin powered at 2.2A and mounted onto a heavy duty CPU cooler with fan running at 12v. It has a very smooth copper thermal pad and I used Prolimatech PK3 thermal paste. The driver was pre-warmed up and ambient is 21C. I made sure not to move the COB or flux meter even slightly during the tests.

The COB and heatsink started off at ambient. It measured 40.02Vf and 735 flux (this part can be tricky to measure) you need an instant reading before the junction has time to warm up at all)
Then I let the heatsink get very hot (no fan running) the flux fell to 675 (8%) and Vf fell to 39.55.
Then I kicked on the fan and waited for the flux to stabilize. It measured 722flux and 39.835Vf.
So Vf fell by only .185V and flux decreased by about 2%. The Tj that this implies (39.5C) is amazing considering the COB is dissipating 89W (59W heat). Either the thermal coefficient I am using is wrong (.01V/C) or the CXA3070 package and thermal interface has a much better total thermal resistance that I suspected(.313C/W). Maybe there was some other error in this test. Even a very slight resistance in your connections can affect the Vf in a test with this precision. For example if you wiggle your connections during the test you can see very tiny changes in the Vf of the string. I checked and rebuilt all my connections to try and remove this variable.


Then I did the test again using a 5V fan to try and get a better understanding. These are the numbers:
Starting off 40.02vF and 864 flux (moved COB closer to meter)
fan off, hot heatsink (38C): 39.5Vf 790 flux
fan off, heatsink really HOT (50C): 39.32Vf 732 flux
fan on, stabilized at 39.8Vf and 839 flux

So in summary, with the 12V fan, TJ was 39.5C and flux fell by 2%. With the 5V fan, the Tj was approx 43C and flux dropped by 3%. When I turned the fan off and let the heatsink get hot (38C), Tj was approx 73C and flux dropped by 9%. When the heatsink was really hot (50C), Tj was approx 91C and output fell by 15%. This has some very interesting implications for us LED growers, I will do some testing at 1.45A.
 
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SupraSPL

SupraSPL

Well-Known Member
Tested with the Vero 18 3000K 97CRi on the 2.25A driver. Bridgelux sheet says thermal resistance of the package itself @ 1.05A = .29C/W and @ 2.1A = .38C/W. With the the 5V fan I measure total thermal resistance as .488C/W and with the 12V fan .172C/W. Is this caused by an over achieving cooling system decreasing the overall thermal resistance of the system?

Thermal coefficient, from PDF: .012V/C
Ambient temp 22C
Starting Vf: 31.82
Starting flux: 663
COB dissipation ~ 71W (58W heat)

12V fan (2.5W) - heatsink temp stable at 24C: 625 flux, 31.7Vf = Tj 32C, 5.8% decrease in flux
5V fan (1W) - heatsink temp stable at 28C: 581 flux, 31.48, Tj 50.3C, 12.5% decrease flux
no fan - heatsink temp rising at 46C: 517 flux, 31.17, Tj 76C, 22% decrease in flux
 
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medicinehuman

medicinehuman

Well-Known Member
medicinehuman said:
I have a question about a heatsink that I just picked up, it is 8x12x1-1/4" Will it work for 2- Z4 3000K's. Maybe someone with more smarts than me can figure it out.View attachment 3289614 I'm going to put it in a nice box, with a fan on top if it's feasible.
Click to expand...
DSCF0064.JPG Got the heat sink sanded and have a piece of 1/8" aluminum for the top. Will measure and cut hole for fan later. I have the holes for the cob holders drilled and tapped. The driver came today, it's the dimmable one http://www.meanwell.com/search/hlg-120h-C/HLG-120H-C-spec.pdf. I just need to know what to get and how to install it and whatever it is to make it dimmable. I need instructions on dimming for a dimwhit.:dunce:
 

Attachments

SupraSPL

SupraSPL

Well-Known Member
Nice setup MH! Did you get the A version or the B version of the driver? If my memory serves, I asked Guod to hold my hand on how to make a dimmer for the B version. I used a 100K dimmer and it worked great. I have an extra one if you need. If it is the A version the dimmer is an internal pot.
 
medicinehuman

medicinehuman

Well-Known Member
SupraSPL said:
Nice setup MH! Did you get the A version or the B version of the driver? If my memory serves, I asked Guod to hold my hand on how to make a dimmer for the B version. I used a 100K dimmer and it worked great. I have an extra one if you need. If it is the A version the dimmer is an internal pot.
Click to expand...
It's the B version, thank's I'll take you up on that.
 
SupraSPL

SupraSPL

Well-Known Member
On its way :). You can also add a lower limit resistor (10K I think) but it is not necessary if you avoid dimming it all the way down. The idea is with a 10K resistor, it can never go lower than 10% output to protect the driver. Will send an 18K along with it in case you want to use it.
 
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indianajones

indianajones

Well-Known Member
so my friend who lives in a legal state has this cab he wants
to fill with LEDs. thing is pretty slick, controlled buy a cooler
guys digital temp monitor that cycles the exhaust on and off
as needed.

dresser.jpg

monitor
dresser2.jpg

it used to run a 250w HPS, cab's inner dimensions are
32"w x18"d x48"h, so exactly four square feet. he asked me to
build a LED for it, and i'm debating between 4 or 5 vero 18 at
1050 mA. 4 would probably do better in terms of grams per
watt, but he would get more out of the cab with 5. he typically
yielded 5-6 oz from the 250 per cycle, which would be ~150w
worth of lighting @ gram per watt yields. here are some old pics
of her fired up and budding.

dresser3.jpg
dresser4.jpg
 
AquariusPanta

AquariusPanta

Well-Known Member
indianajones said:
so my friend who lives in a legal state has this cab he wants
to fill with LEDs. thing is pretty slick, controlled buy a cooler
guys digital temp monitor that cycles the exhaust on and off
as needed.

View attachment 3293348

monitor
View attachment 3293349

it used to run a 250w HPS, cab's inner dimensions are
32"w x18"d x48"h, so exactly four square feet. he asked me to
build a LED for it, and i'm debating between 4 or 5 vero 18 at
1050 mA. 4 would probably do better in terms of grams per
watt, but he would get more out of the cab with 5. he typically
yielded 5-6 oz from the 250 per cycle, which would be ~150w
worth of lighting @ gram per watt yields. here are some old pics
of her fired up and budding.

View attachment 3293350
View attachment 3293351
Click to expand...
How many plants is he planning on hosting inside the little hut? @1050mA, you can expect around 30W output per V18, while the CCT will determine the efficiency. My 4000K V18's run (~ 1037mA) around 37% efficient, 40% on good days ;).

With 5x COBs operating in that hut, you may face some heat-related issues depending on how you craft the LED fixture, otherwise try for 5x.
 
indianajones

indianajones

Well-Known Member
AquariusPanta said:
How many plants is he planning on hosting inside the little hut? @1050mA, you can expect around 30W output per V18, while the CCT will determine the efficiency. My 4000K V18's run (~ 1037mA) around 37% efficient, 40% on good days ;).

With 5x COBs operating in that hut, you may face some heat-related issues depending on how you craft the LED fixture, otherwise try for 5x.
Click to expand...
i was counting on 30w output per v18, he will also be using the 4k model
because that's what i've got around to build for him :P

i think he's going to run 4 or 6 plants, depending on variety. the run i showed
a picture of was six plants. if he runs 5 COBs, that puts his watts dissipation
at ~37.5w /sq ft. add in the fans and total power draw should be somewhere
around 180-190w.

i would think that the previous 250w setup would have generated more
heat than 5x vero 18s. even though those look like computer fans for the
exhaust, those little things pull some air. the total volume of the cab is 16
cu ft, and the fans exhaust about 94 CFM. they kept it nice and cool even
with the previous open fixture HID.

for mounting, either a heatsink USA or arctic 11 plus. the 11 plus is just so
convenient it's hard to say no, and they really perform well.
 
AquariusPanta

AquariusPanta

Well-Known Member
indianajones said:
i was counting on 30w output per v18, he will also be using the 4k model
because that's what i've got around to build for him :P

i think he's going to run 4 or 6 plants, depending on variety. the run i showed
a picture of was six plants. if he runs 5 COBs, that puts his watts dissipation
at ~37.5w /sq ft. add in the fans and total power draw should be somewhere
around 180-190w.

i would think that the previous 250w setup would have generated more
heat than 5x vero 18s. even though those look like computer fans for the
exhaust, those little things pull some air. the total volume of the cab is 16
cu ft, and the fans exhaust about 94 CFM. they kept it nice and cool even
with the previous open fixture HID.

for mounting, either a heatsink USA or arctic 11 plus. the 11 plus is just so
convenient it's hard to say no, and they really perform well.
Click to expand...
I'd consider 6x COBs, one for each plant :eyesmoke:. I spoil my lady with 2x V18's and a BlackStar V2 240W (Flower) :blsmoke:
 
Chigur

Chigur

Member
AquariusPanta

AquariusPanta

Well-Known Member
Chigur said:
Amazing thread, Deep to thanks to the Supra and the other key growers here... HATS OFF!

Where i live the power is 220v. ....Seems you are mostly in N America @ 110

Will i need different drivers than the Ebay 50w many of you use?
http://www.ebay.com/itm/50-W-Watt-High-Power-LED-Driver-AC90V-265V-50-60HZ-Waterproof-/181578939219?pt=LH_DefaultDomain_0&hash=item2a46f2bb53

Says 90-265v but i want to be 100% sure.

Also any info on all how will my current would change things?

Cheers
Click to expand...
Yeah the electric potential here in United States is around 120V.

If your outlet is discharging anything between 90-265V, then the driver will do it's job.

As for your last question, the DC output will be somewhere around what is posted on the driver.
 
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