# PAR data for Cree XML at 3.0amps, Satistronics 3w at 650mA



## jcgd (Feb 18, 2004)

I used O2Surplus' Driver design. It's nice because you can gang the drivers together to get whatever current you want and it puts out 24v so you can run 6-7xml. I decided to use four boards and ganged together two of the four drivers on each board so I can drive the xml at 2000mA.


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## redfishsc (Aug 29, 2010)

Good idea. That's a LOT of light!


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## redfishsc (Aug 29, 2010)

I assume you can combine Meanwells (ELN60-48 types) to get around 3,000mA, since I know for a fact they can be tuned to put out 1500mA by adjusting the SRV2 screw.


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## jcgd (Feb 18, 2004)

As far as I can tell, you should be able to do it with any identical driver. You are simply paralleling them, so the voltage stays the same and the current stacks. 

From what I can gather, most people think the heat produced with over 1000mA will be too much to handle. I don't really expect it to be a problem myself, given that nobody using a proper heatsink is even getting them more than warm to the touch, but I figure they should stay warm at best. Even if they are hot to the touch, nobody should worry. As long as you can hold the headsink while the XML are running full blast everything should be fine. Sure the expected life of the LEDs may drop from 12 years to 7, but even then I wouldn't be concerned. The longest I've used a fixture so far is 5 years with a Nova power compact fixture. The technology, even moving slowly, advances fast enough these LEDs will be cheap at the least and completely outdated at the worst.

What did you notice for the heat the XMLs were given off? I'm really wondering if I will have an issue.


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## vim (Jun 29, 2011)

redfishsc, VERY cool data. Thanks for sharing.

I'm running the same 3W LEDs and drivers you've tested and with 10 square inches of hardware store heatsink (aluminium angle) per W they don't get much above ambient. (they're underdriven at 650, so this in no surprise)
"beefy aluminum heatsinks" raise the price considerably, so it would be nice to know if the same W/surface area principle applies when trying to move more heat from each LED.

Sadly 20 no-brand LEDs (using 12) and two drivers still cost less than a single Meanwell driver in my part of the world. 
Still, I think you've shown that as far as LEDs go you really can get less than you pay for, and I'll be keeping an eye out for inexpensive XML drivers.
Thanks roud:

ps. what are the $5 drivers? if they'll run off 12V...


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## redfishsc (Aug 29, 2010)

vim said:


> ps. what are the $5 drivers? if they'll run off 12V...



Here ya go. 12v input is just fine. 
http://www.dealextreme.com/p/6-18v-3000ma-3-mode-circuit-board-for-xm-lt60-emitters-57779




The XML was mounted on a 1" thick, 4" diameter star shaped heatsink from Satistronics, and the 4 Satis white LEDs were mounted to a (roughly) 4X4 CPU-type heatsink.

After running for an hour, neither of them got more that just "barely warm", in case anyone wondered.


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## vim (Jun 29, 2011)

redfishsc said:


> in case anyone wondered.


I did, repeatedly :tongue:

If my current setup works I think it may be worth moving to the XML, not only because of efficiency, but because I think it may be easier to make some nice pendants out of them (current setup needs some serious hiding)

Thanks again for the info.


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## redfishsc (Aug 29, 2010)

I wouldn't say that the two heatsinks on the two different arrays I just compared are "equal", but "similar". 



I don't really think the XML is a total heat demon like some LEDs can be. That's part of the benefit of efficiency:---- less energy is being converted to wasted useless heat. 

They definitely need beefy heatsinking, and I personally would NOT consider running them at 3000mA on a heatsink that wasn't a minimum 1/4" thick with some 1" fins. Better safe than sorry. 3000mA is an incredible amount of current to run through such a small emitter. They're quite the wonder. 



I also think that small clusters of XML's over larger tanks will do a LOT to producing a more pleasant light shimmer instead of they psycho-disco multi-source shimmer that arrays using lots of smaller LEDs can do.


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## vim (Jun 29, 2011)

I've always thought the problem with a relatively small area light source would be hotspots in the tank.

It turns out it's not as bad as I'd thought. Provided most of the light falls within the top of the tank there should be considerable brightening around the edges due to reflection (not shown).

edit: data in %, not PAR.
shows bottom of tank.
circles are 1/2 angle of optic, which is about 50% intensity for optic modeled.


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## redfishsc (Aug 29, 2010)

Excellent charts! They definitely seem to agree with readings/variations I've taken with a PAR meter over my tank.


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## sink (Jun 11, 2011)

vim said:


> I'm running the same 3W LEDs and drivers you've tested and with 10 square inches of hardware store heatsink (aluminium angle) per W they don't get much above ambient. (they're underdriven at 650, so this in no surprise)
> "beefy aluminum heatsinks" raise the price considerably, so it would be nice to know if the same W/surface area principle applies when trying to move more heat from each LED.


My feeling here is that people tend to overestimate the amount of heatsinking required for a given setup. I'm using 28" of 1/8" aluminum angle (probably same as you) for 6 CREE 3W LEDs run at 1A. No fans and very little air movement, and they merely get very warm.

The ability to heat transfer from your die/star to the heatsink makes a difference too. Scaling this contact area up with increasing heat sink area (and making sure to get excellent thermal contact) probably matters a lot.


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## redfishsc (Aug 29, 2010)

sink said:


> My feeling here is that people tend to overestimate the amount of heatsinking required for a given setup. I'm using 28" of 1/8" aluminum angle (probably same as you) for 6 CREE 3W LEDs run at 1A. No fans and very little air movement, and they merely get very warm.


And your feeling would be right. Overkilling the heatsink and using good thermal bonding gives us complete confidence that heat isn't going to be an issue.

I'm glad you are getting such good results with so little heatsinking but I must emphasize that not everyone has this same result. 


I was running 6 XRE and 6 XPG at 1A on a heatsink from heatsinkusa.com that is 2" wide, 12" long, 3/8" thick at the base, with some 1" tall fins. 

The entire heatsink, with no fans, got quite uncomfortably hot, even though it had considerably more mass and passive cooling capabilities that 1/8" angle can. 

So folks who replicate this need to monitor the LEDs, particularly in the spots each LED is located.


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## sink (Jun 11, 2011)

redfishsc said:


> And your feeling would be right. Overkilling the heatsink and using good thermal bonding gives us complete confidence that heat isn't going to be an issue.
> 
> I'm glad you are getting such good results with so little heatsinking but I must emphasize that not everyone has this same result.


Totally agreed! I just meant to convey that people who are making fairly "standard" setups in terms of LED density and power shouldn't overly fret about having to source an expensive heatsink. With some care in design and construction it is entirely possible to get by with aluminum you can get at the hardware store, which is cheaper and easier to use. This is especially true if you add fans.

To get a little bit more on topic, my concern with the XM-Ls wasn't the power output--I'm sure they can replace a lot of smaller emitters just fine in terms of both raw output and value. My issues were:

(1) Hard time finding optics

(2) Placement to avoid dark spots in the aquarium obviously becomes trickier with fewer emitters and fewer optics choices.


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## redfishsc (Aug 29, 2010)

sink said:


> my concern with the XM-Ls wasn't the power output--I'm sure they can replace a lot of smaller emitters just fine in terms of both raw output and value. My issues were:
> 
> (1) Hard time finding optics
> 
> (2) Placement to avoid dark spots in the aquarium obviously becomes trickier with fewer emitters and fewer optics choices.



Yeah it can get tricky. LEDgroupbuy.com carries optics for the XML's. Fortunately for tanks under 20", optics really aren't needed as long as you stick to 1 or 2 rows of LEDs centered in the tank, closer to the surface. 


Over a deeper tank, you'd have to fiddle with the sweet spot of the right optic angle and right suspension height. 


Fortunately you can figure out the light footprint of an LED using basic geometry, or perhaps using an online triangle calculator. 

For a 60 degree optic, every inch away from the optic makes roughly a 1-inch diameter footprint. 20 inches away makes a 20 inch footprint, etc. 

As long as we remember that the inner half of this footprint will be more intense, regarding PAR.


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## silvawispa (Oct 11, 2011)

@Redfish, is the XML data you published µmol/m² or µm/ft² (i'm guessing ft²)

Thanks for your time in doing this


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## Hoppy (Dec 24, 2005)

silvawispa said:


> @Redfish, is the XML data you published µmol/m² or µm/ft² (i'm guessing ft²)
> 
> Thanks for your time in doing this


The standard measurement of PAR is in micromols per square meter per second. That is what PAR meters are calibrated to read.


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## silvawispa (Oct 11, 2011)

Thanks Hoppy, I've seen you use µm/ft² in some conversations, hence my confusion...


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## redfishsc (Aug 29, 2010)

Yeah I'm glad he clarified that, because if it's not actually marked on the PAR meter (I haven't looked yet) then I'd have no clue.


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## redfishsc (Aug 29, 2010)

Actually it is marked on the PAR meter and Hoppy is right, which I never doubted .


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## WingoAgency (Jan 10, 2006)

Do you have BridgeLux or Epi to test with?

Also do you have the Satis cool white instead of pure white that you tested with? What color temperature the Satis pure white is rated at? It's kind of surprising that pure white is similar to the cool white that Cree is outputting.

Pure white usually is around 4000K and is very yellow and dim
6,500-8,500K(such as cool white of Cree) is much bluer and brighter.


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## Hoppy (Dec 24, 2005)

silvawispa said:


> Thanks Hoppy, I've seen you use µm/ft² in some conversations, hence my confusion...


If I used micromols per square foot I was making a mistake. Probably the first one ever:icon_cool


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## redfishsc (Aug 29, 2010)

WingoAgency said:


> Do you have BridgeLux or Epi to test with?
> 
> Also do you have the Satis cool white instead of pure white that you tested with? What color temperature the Satis pure white is rated at? It's kind of surprising that pure white is similar to the cool white that Cree is outputting.
> 
> ...



I have a friend who is ordering some of the (supposedly) Bridgelux stuff from Aquastyleonline ---- a 4500K, a 10K, and a royal blue. 

I'll compare them to the Cree when they arrive but it will take an uber long time most likely.

Now, you mentioned how odd it is that the Satis pure white looks like a Cree cool white. Here's what many people have found---- Chinese LEDs are notoriously horrible at bin labeling and actual selection of proper colors. Sometimes they look greenish, sometimes yellow, sometimes orange/amber, and it doesn't always matter what color temp you order. They vary, one batch from the other. 

Then... you might get 100 LEDs in 10 different orders that match very closely. It's a total crap shoot.

The graphs comparing the Satis pure white to a bunch of Cree cool and neutrals is uploaded here.

Notice how this particular Satis has a very nice spectral output, but is substantially weaker in output. blaaaaaah.


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