300w DIY LED Light - Cree Multichips

A&W · Mar 14, 2014

Hello folks! I plan on building a 300w LED light comprised of 5 Cree XML chips. I hope to reach ~300w goal via 60w drivers. I have read up quite a bit on the Cree CXA3050 & 3070, following bbspills and SupraSPL's builds, among others.

My question to the community is to whether my planned method of heat dissipation will suffice. For visual reference I made a model, and I will also list my parts.

Components
2 x CXA3050 (2700K)
3 x CXA3070 (3000K)
5 x LCP-60-1750 (to me it seemed to fit both chips well enough)
2 x 120mm case fans, to be chosen...
1 x Heatsink 7.28" x 24" x 1.3"

I got lazy on modeling the actual fan, but everything else is to scale.

I appreciate any feedback, thanks!

A&W

SupraSPL · Mar 15, 2014

Welcome A&W I like your design! Your heatsink will have a total surface area of 1324in² or 8540cm² and it will be handling about 243W of heat plus some of the heat from your drivers. That works out to be 35cm²/Watt of heat. For reference I use 5453cm² to handle 71W of heat (77cm²/Watt) and the heatsink stays about 2 degrees C above ambient with active cooling. Whether or not you could get away with half as much surface area and still get good junction temps I cannot say, it would be experimental

If you go for the 8.46" profile you could fit a pair of 200mm case fans. Should be quieter and will hit every fin.

Here are some numbers from my spreadsheet.The CXA3050 2700K will be about 27% efficient $0.55/watt and the CXA3070 3000K will be about 33% efficient $0.62/Watt.

SupraSPL · Mar 15, 2014

Just looked over the LPC-60-1750 and it looks like the vF range is just a bit low for the CXAs. It says max 34vF and the CXAs at 1800mA are about 39vF. The LPC-60-1400 might be a better fit (42vF max). From the chart I posted above you can see in the last column there isnt much of a cost advantage by running at 1750 vs 1400.

smokey the cat · Mar 15, 2014

Welcome A&W -

great looking build, just you'll need to get the right voltage range for the Cree as per Supra's suggestion.
BTW - how accurate are these requirements? Has anyone the skills to test how the volt range of the CXA matches real world performance?

I was a PC fan nerd years ago, but haven't kept up with anything this decade. That said, Corsair do make a lovely looking high-pressure 120mm PC fan designed specifically for heatsinks - I've yet to test it, but the packaging and writeup on the box convinced me last time I when I went shopping a few weeks back.

Supra, gotta say that you are a rockstar of knowing you're way around the cooling capacity of the heatsink. My gut feeling is that 300W as well as the drivers - is going to make for a rather warm experience if not enough airflow.

Expect about 5W of heat per driver

SupraSPL · Mar 15, 2014

Haha tnx smokey. I ll hafta check out that Corsair. In use my CXAs forward voltage is a bit lower than the datasheets predictions but not by much.

Some drivers allow you to go above their vF range and they will reduce current output. Others will stop you in your tracks if you try to go above or below it. I have an LPC-60-1050 hanging around, I will test its limit (48vF) and see how it reacts.

A&W · Mar 15, 2014

SupraSPL said:
Welcome A&W I like your design! Your heatsink will have a total surface area of 1324in² or 8540cm² and it will be handling about 243W of heat plus some of the heat from your drivers. That works out to be 35cm²/Watt of heat. For reference I use 5453cm² to handle 71W of heat (77cm²/Watt) and the heatsink stays about 2 degrees C above ambient with active cooling. Whether or not you could get away with half as much surface area and still get good junction temps I cannot say, it would be experimental If you go for the 8.46" profile you could fit a pair of 200mm case fans. Should be quieter and will hit every fin.

Here are some numbers from my spreadsheet.The CXA3050 2700K will be about 27% efficient $0.55/watt and the CXA3070 3000K will be about 33% efficient $0.62/Watt.
View attachment 3023370

Thanks for recommendations Supra, I'm glad I decided to run this by you all before I started building! I'm with you on the driver suggestion, and I also agree with more heatsink. A 10" x 24" heatsink should provide nearly double the surface area for proper heat dissipation, hopefully that will do.

A&W

A&W · Mar 15, 2014

smokey the cat said:
Welcome A&W -

great looking build, just you'll need to get the right voltage range for the Cree as per Supra's suggestion.
BTW - how accurate are these requirements? Has anyone the skills to test how the volt range of the CXA matches real world performance?

I was a PC fan nerd years ago, but haven't kept up with anything this decade. That said, Corsair do make a lovely looking high-pressure 120mm PC fan designed specifically for heatsinks - I've yet to test it, but the packaging and writeup on the box convinced me last time I when I went shopping a few weeks back.

Supra, gotta say that you are a rockstar of knowing you're way around the cooling capacity of the heatsink. My gut feeling is that 300W as well as the drivers - is going to make for a rather warm experience if not enough airflow.

Expect about 5W of heat per driver

Thanks for having me Smokey! I've been lurking for a while now, it's about time I dropped by. I'm a Corsair junky and those SPs do look powerful, I feel like I'm building my PC again, looking for the most power and least noise. Now that I'm going with a 10" wide heatsink I have a few more fan options.

Do you think the 3050s will help or hinder me? I am sacrificing lumens for another spectral range, think it's worth it?

A&W

SupraSPL · Mar 15, 2014

Thats a darn good question. The 2700K spectrum should be more efficient in terms of photosynthesis but it is harder (less efficient) to make a blue LED into a very warm white. If you run at 1400mA the 3000K 3070 will be 36.24% efficient vs the 3050 2700K which will be 29.15%. That may not sound like much but another way of saying it is the 3000K is 24.3% more efficient.

I suspect that increase in efficiency is so large that the 2700K spectrum is not worth it in this case. If you want to add deep red you could use Luxeon ES which is 38% efficient but it adds complexity to the build and may not even be necessary.

That 10" heatsink would definitely take care of you!

A&W · Mar 15, 2014

I appreciate you doing the math on this Supra

The relevance of the 2700k's had me questioning their value.

I suppose I'll go with 5 x 3070s, unless a 2700k 3070 would be beneficial/available, do you know if they would be?

A&W

SupraSPL · Mar 16, 2014

Cannabare has (100) CXA3070 2700K top bin on order. Hopefully the supplier can actually deliver. We don't have the curve so I am guessing on the LER, but at 1.4A efficiency should be about 35%.

A&W · Mar 16, 2014

Thanks Supra, I'd like to test a 2700 out in the future. I went ahead and pulled the trigger on 5 x CXA3070-0000-000N00Z230F. Heatsink and drivers ordered as well, can't wait to get this baby together!

A&W

SupraSPL · Mar 16, 2014

Awesome can't wait to see it lit up and in action!

300w DIY LED Light - Cree Multichips

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