DiY LED - Cree CXA3070

ellydee

ellydee

Well-Known Member
WDIK said:
Any thoughts on spacing for a 3 COB panel?
Click to expand...
Good question.
Love to see a shootout; 3050 vs 3070 at different drive currents. Just like more, smaller panels spread out seems better, would more, smaller cobs be better.
And soon we will have the 3590s, so a lot of options.
 
WDIK

WDIK

Active Member
ellydee said:
Good question.
Love to see a shootout; 3050 vs 3070 at different drive currents. Just like more, smaller panels spread out seems better, would more, smaller cobs be better.
And soon we will have the 3590s, so a lot of options.
Click to expand...
No reason to get complicated. :) I was just wondering about spacing between the COBs. :-P

ETA: I hope I am using that term correctly. COB = Module, correct? What Do I Know?
 
Mellodrama

Mellodrama

Well-Known Member
Yeah, WDIK -
COB just means "Chips On Board". From what I've read on here, a lot of guys think this is the way we're headed. More light with less (or none if you employ holders) soldering and less wires hanging all over the place, etc. Instead of dealing with single emitters, then trying to figure out how many you need to wire in series to each driver, with COB it's very simple - "one driver per COB". Not that you HAVE to do it that way, but "one driver - one COB" sure makes it straightforward.

It seems to me like COB is an easier way to get started with DIY. Once you've built a little bit of confidence you could delve into single emitters and/or groups of emitters on stars for customizing your spectrum.
 
PetFlora

PetFlora

Well-Known Member
Spacing depends on wattage. The higher the wattage, the more distance between to minimize overlap and hot spots

I like these because they can be staggered in rows to provide more homogenous light

I just ordered 2 of the '75' watt singles to put on each side of my 90w ufos (3500/5000K)

http://www.ebay.com/itm/Free-Shipping-200W-LED-Grow-Light-3W-LEDs-Flower-Veg-Integrated-COB-Lamp-Panel-/191034691912?pt=US_Hydroponics&hash=item2c7a8e1148

WDIK said:
Any thoughts on spacing for a 3 COB panel?
Click to expand...
 
Gaius

Gaius

Active Member
These things any good for 3070s? They're about $6 each on eBay. Not sure if they're worth the extra expense or not.

The reflector is the only part I'd probably use, as I read that the glass just reduces efficiency.

 
SupraSPL

SupraSPL

Well-Known Member
Nice reflectors, does the ad give the angle and dimensions?

Got a shipment of drivers and started wiring them up.
DSC06952a.jpg
 
Gaius

Gaius

Active Member
midgetaus said:
Can I play devils idiots here and ask why so many drivers?
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With COBs, you need 1 driver per chip due to the high vF(Forward Voltage) required. You can maybe power 2 with a single driver, but it's a lot more expensive and a bit more dangerous.
 
Gaius

Gaius

Active Member
SupraSPL said:
Nice reflectors, does the ad give the angle and dimensions?

Got a shipment of drivers and started wiring them up.
Click to expand...
Supra, there's a ton of different ones that all look similar. This one shows 30-130 degrees. This one is 90-120. And this one is 60-80. I think the angle varies depending on the distance it's mounted from the chip. I usually stick to US sellers only, but for something this cheap I'm not too concerned.

Kinda also wondering if the bare COB is better left without the reflector though.
 
SupraSPL

SupraSPL

Well-Known Member
They range from 688mA to 748mA. Their output stays steady no matter the vF and no matter the temp of the driver. There is a hard cap at about 40vF. Efficiency is 84-85%. Perfect power factor. Cost is about $13 each shipped.
 
SupraSPL

SupraSPL

Well-Known Member
Yes midget quite a lot of drivers but that board will control about 300W of dissipation. Total drivers in the system is currently 27. Once these next batches are installed it will be 51 (3 in the veg room).

At some point down the road I might consider using active cooling on the COB modules and swap out these drivers for 1A fasttech drivers. I just have to figure out how to get it done efficiently (~2% loss is acceptable to me). I tested a few power supplies today and the best I found was 60%. Maybe if I invest in a pair power supplies with 80+ gold or better I could get it done right. So if one module is dissipating 74 watts and the fan (including power supply losses) was consuming 1.5W that would be 2%.
 
SupraSPL

SupraSPL

Well-Known Member
WDIK I wonder how many lumens a lighthouse puts out....

Gaius I agree going without the lens and using just the reflector. A lens penalizes all the photons while a reflector only redirects and penalizes the wayward photons.
 
WDIK

WDIK

Active Member
SupraSPL said:
Yes midget quite a lot of drivers but that board will control about 300W of dissipation. Total drivers in the system is currently 27. Once these next batches are installed it will be 51 (3 in the veg room).

At some point down the road I might consider using active cooling on the COB modules and swap out these drivers for 1A fasttech drivers. I just have to figure out how to get it done efficiently (~2% loss is acceptable to me). I tested a few power supplies today and the best I found was 60%. Maybe if I invest in a pair power supplies with 80+ gold or better I could get it done right. So if one module is dissipating 74 watts and the fan (including power supply losses) was consuming 1.5W that would be 2%.
Click to expand...
Am I correct that you are currently using a heatsink with no fan?
 
SupraSPL

SupraSPL

Well-Known Member
Yessir 110 sq cm /W. That ends up being 6 pounds of aluminum for each 50W and almost as expensive as the LEDs. So at this point I have to recommend that most sane DIYers use active cooling.
 
Gaius

Gaius

Active Member
SupraSPL said:
Yessir 110 sq cm /W. That ends up being 6 pounds of aluminum for each 50W and almost as expensive as the LEDs. So at this point I have to recommend that most sane DIYers use active cooling.
Click to expand...
You got that "bling" factor going for ya, Soop ;D
 
SupraSPL

SupraSPL

Well-Known Member
Ya it has its advantages for now. If I make the jump to active cooling the COBs will jump from ~600W to ~900W with a hit in efficiency that I think the drivers might make up for anyway.
 
PetFlora

PetFlora

Well-Known Member
I can't wait for your next project.

Looking at the reflector you posted, wouldn't a mufti-faceted parabolic reflector do a better job f dispersing the reflected light?

FYI, I order 2 of the 75w flowering cobs

They won't arrive in time for this go-round, but I am excited to play with cobs and large reflectors

SupraSPL said:
Ya it has its advantages for now. If I make the jump to active cooling the COBs will jump from ~600W to ~900W with a hit in efficiency that I think the drivers might make up for anyway.
Click to expand...
 
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