DiY LED - Cree CXA3070

It was a very hard decision ended up with a set of drivers that range from 680mA to 740mA. They are 84% efficient and power factor corrected. I really wanted to use the fasttech 650mA but once they warm up some of them are as low as 630mA at 34vF which really underutilizes the heatsink and the COB because there isnt much efficiency to be gained by running that soft.

Got a big delivery of heatsinks and started building the driver boards. Not going to lap the heatsinks this time too much work to do and I am not even sure it will affect the Tj which is already down to 44C anyway. So within a few weeks I can go 100% led and get some useful testing.
 
Can I ask an weird electrical question in my opinion about conversion. Basically I have built a 4x4 with 16 crees over 1 sqft each. I asked a friend of mine who builds a ton and tinkers just like me. The question is how do you convert from dc amps to ac amps? Like if I have 12v 1.5A dc how much is it on 120v ac? My friend told me that you just add the amps which means my 20 amps breaker is screwed around 9 LED's. I surfed the web and came to nothing but thought that the 38v led at 1.5A is 57 watts. and 57 watts divided by 120 is almost 0.5. My kill-a-watt meter is coming monday but I like to learn before.


For those who do not want to read!
How do I convert 12v 1.5A DC to 120c AC amps?

Thanks!
 
So on the DC side we have 12v * 1.5A = 18W. If we assume 100% efficiency and perfect power factor, on the AC side that would be 18W/120V = .15A.

But of course the AC-DC conversion is not 100% efficient and if it is not power factor corrected it might have pf of .5

If we assume the adapter is 75% efficient with a power factor of .5, we get 48VA on the AC side or 48VA/120V = .4A.

If you use a bunch of low power factor devices on one circuit, the power factor tends to improve. Your kill-a-watt will show you the power factor. Power factor does not affect your electric bill (Watts), but it does affect how much you can load up a particular circuit (the amount of heat in your wiring). Weird stuff.
 
SupraSPL said:
It was a very hard decision ended up with a set of drivers that range from 680mA to 740mA. They are 84% efficient and power factor corrected. I really wanted to use the fasttech 650mA but once they warm up some of them are as low as 630mA at 34vF which really underutilizes the heatsink and the COB because there isnt much efficiency to be gained by running that soft.
Click to expand...

Supra, can we go back to this? Do you have any links for the drivers that you settled on? Any further info, such as whether this is one driver per COB, etc. would be great. If I try a DIY LED it'll be a copy/paste of something you made!
 
I'm really excited to see this all coming together Supra. I have to admit, that huge tray of 3070's made me really jealous :D Can't wait to see those pigs fly.
 
Mello, I decided to use my weakest drivers (650-680mA) to power the RWB modules (since they max out at 700 and 1000mA) and the strongest drivers (700-740mA) to power the COBs since they max out at 3A. These are the drivers I was referring to. They vary from 680-740mA but their output is stable no matter the vF load and no matter the driver temp. The have a hard cap at 40vF. They are power factor corrected and run at about 84% efficient. Most drivers' output decreases as their temp rises and as you load them up with more vF.

I am using one driver per COB and if I decide later on I can add a few Luxeon ES deep reds to widen the 3000K spectrum because the reds do alright at 700mA.
 
Haha yea OXC since I am running them soft it is not as much bang as it could be but maybe later on down the road I will swap out the drivers for 1A and add some fans to the heatsinks. So far 8 COBs are in use (200W). The modules are staggered with the RWBs (400W) and a pair bare 600HPS that I turn on from week 3 til week 7. Looking forward to scrapping those but it will be a slow process. I have 12 huge heatsinks to sand down, 2 driver boards to build, 200W of RWB to sand down and install onto heasinks, 400W of COB to install onto heatsink and then all the wiring to install for 600W.

But I really enjoy the process and I have a bunch of brand new stinky ladies to motivate me. Darkstar, LA Chocolate, Green Poison, OG18, CC Original Sour D, Stacked Kush and HSO Blue Dream are all at week 3. 2 batches after that some more new stuff HSO Desert Diesel, HSO Amherst Diesel, HSO Green Crack, HSO Bubba Kush, HSO Trainwreck, HSO Lost Coast OG, Delicious Cotton Candy, and G13 Labs Pineapple Exprress. Discovering new flavors and frosty varieties is what its all about for me. I never saw any of this stuff growing up, nothing even remotely close.
 
Your comment about not seeing any of this stuff when you were younger - that made me smile. In the '70's we bought ounces of Mexican weed for $10. Full of seeds and stems. Buds were something we heard about but we never saw one in real life.

EDIT: While googling around I stumbled onto this .pdf from SemiLEDs. I thought it was interesting and might be helpful to others. Especially the parts about handling COB LED's.
 
5000K, 9000 luminous flux

Good thing I'm rockin' two monitors... I pulled up Cree's 3070 .pdf on one screen, and Mouser's 3070 page on the other screen. Scratched my head for a while, then started applying filters. I asked for 5000K, then highest luminous flux, which was 9000.

Here's what I came up with. Mouser appears to stock - well, not stock, but available on order supposedly - 4 that meet those criteria. If any of the LED experts have got a minute, are all four of those good choices?

In 2700K, the highest lm available appears to be 7390 (?) Here's that page. Same question I guess - are those good choices for covering the warm end of the spectrum?

Here's the spectrum chart from Cree:

spectrum.jpg
To my untrained eye, a mix of 5000K and 2700K oughta do the trick?
 
Mellodrama said:
5000K, 9000 luminous flux

Good thing I'm rockin' two monitors... I pulled up Cree's 3070 .pdf on one screen, and Mouser's 3070 page on the other screen. Scratched my head for a while, then started applying filters. I asked for 5000K, then highest luminous flux, which was 9000.

Here's what I came up with. Mouser appears to stock 4 that meet those criteria. If any of the LED experts have got a minute, are all four of those good choices?

In 2700K, the highest lm available appears to be 7390 (?) Here's that page. Same question I guess - are those good choices for covering the warm end of the spectrum?

Here's the spectrum chart from Cree:

View attachment 2995033
To my untrained eye, a mix of 5000K and 2700K oughta do the trick?
Click to expand...

Literally 2700k alone works wonders. Get the same as bbspills did and you will not be disappointed. growth by the hour :)
 
You wouldn't even mess with the "cool" end of the spectrum, eh? The 5000K has a huge bump in the 440 to 450nm range. I went back to the first post of this thread, which made little sense to me a week ago, and found the Z230F in Cree's .pdf. It's a mid-bin 3000K. The Z430F is the next bin (and the best bin) for the 3000K. But Digi-Key doesn't have any of the Z430F's. Neither does Mouser.

Hey, I'm startin' to talk like you guys! Some of your knowledge is rubbing off
 
Mr Flux did the calculus to show us the % blue in a variety of white tints. The Cree CXA 3000K has 10% the 4000K has 19% and the 5000K has 24%. My goal, based on KNNAs recommendation is 15-20% blue for flowering. So technically 3000K could be a bit on the low side but I am currently testing them. The problem with 4000K and 5000K is that their red peak is more like an orange or yellow peak, which I suspect contributes more toward leaves than buds (like HPS).

2700K has a solid peak in red and includes decent amount of deep red, but it suffers an efficiency penalty and is not available in the CXA3070 so it suffers another efficiency penalty. I am not saying that a 2700K Vero or CXA3050 is bad by any means, just that I am trying a different approach.
 
You know what keeps messing me up? Switching back and forth between talking about Kelvin and spectrum. One goes left to right, the other goes right to left, and the wavelength charts we all look at are backwards to boot. Right?

View attachment 2995506

Here's a Cree chart again. The smaller number, 380, is to the left. The larger number, 780, is to the right. If we were to map out the entire electromagnetic spectrum, which typically goes from the largest wavelength to the smallest (radio waves to gamma rays), 780 nm would be to the left and 380 to the right. So that messes with my head.

A light source that is considered "cooler" on the Kelvin scale, such as 3000K, makes more red. A much "hotter" bulb on the Kelvin scale makes more blue. Who doesn't think of red as being hotter, and blue cooler? That messes me up too.

Every time I think I'm maybe starting to understand this, someone comes along and says something that trips me up and I feel like I'm startin' all over again.

I appreciate your guys' patience and knowledge.

EDIT: Supra, you state that 2700K is not available in the CXA3070. Cree's .pdf shows three of them. CXA3070-0000-000N00Y227F, -000N00Y427F, and -000N00Z227F. Do you mean they're just not available to the retail buyer?
 
I apologize Supra if it seems like I'm taking over your thread. I figure if I've got questions then others do too, but they don't want to sound dumb. I ask dumb shit stuff all the time so it's no big deal.

I'm hesitant to use thermal adhesive. Have you experimented with any LED holders? The Molex ones look cool but they're not making any for the CXA30's yet. Ideal makes one for the CXA30's but I don't get it. They're metal. How would you avoid shorts? Maybe the soldered terminals go under the little nylon fingers?
 
I'd be super worried about the thermal properties of that Ideal holder. If you look at the datasheet they show a picture of how it mounts. The COB ends up atop the holder, leaving what looks like a pretty large air gap between the LED and whatever surface you attach the holder to.
 
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