Seeking Help - Building Custom-Designed DIY LED Grow Lights using CREE CXA3070 COBs

SupraSPL

SupraSPL

Well-Known Member
Yep it was a DC constant voltage -> DC constant current driver and if I recall it was surprisingly not very efficient (~80%). I assume that is because of stepping the voltage up from 12 to 34.

For those diyers that use 12V DC power supplies to run the LEDs they get an efficiency penalty from the AC-DC conversion and then again from the DC constant voltage to DC constant current conversion. Or if they try to run the LEDs on constant voltage they end up with each emitter dissipating a significantly different amount of power (unless it is just 1 COB on each string). So the most efficient approach (84-88%) is 120V AC->DC constant current conversion in one step (unless you have a way to run off a solar or wind powered battery bank).
 
Gaius

Gaius

Active Member
SupraSPL said:
Yep it was a DC constant voltage -> DC constant current driver and if I recall it was surprisingly not very efficient (~80%). I assume that is because of stepping the voltage up from 12 to 34.

For those diyers that use 12V DC power supplies to run the LEDs they get an efficiency penalty from the AC-DC conversion and then again from the DC constant voltage to DC constant current conversion. Or if they try to run the LEDs on constant voltage they end up with each emitter dissipating a significantly different amount of power (unless it is just 1 COB on each string). So the most efficient approach (84-88%) is 120V AC->DC constant current conversion in one step (unless you have a way to run off a solar or wind powered battery bank).
Click to expand...
Thanks for this Supra. So if I run a single chip on each of the 45-watt outputs from the fan controller, then can I just bypass any additional hardware? I'll need a second controller to do that for all 9 lights, but I just bought one for now to test out the concept first. I can always return this stuff if it doesn't end up working out.

If the PC PSU ends up a failed idea, I may try and use 50-watt dimmable drivers for each chip (seems pricey!). If I do this, I'll design the panels such that the dimmable drivers are actually mounted onto them. Now I'm aware that having the driver near the heatsink is bad, but since these will be actively cooled, I'm pretty sure it'll work out -- plus they'll look much cleaner and be easy to move around.
 
smokey the cat

smokey the cat

Well-Known Member
Ignoring electrical efficiency for a moment (stop reading now Supra lol),


I do like the builds of the small DC-DC drivers. One big AC power supply and add a board like this: http://www.ledgroupbuy.com/coralux-5up-ldd-driver-board/ with a bunch of the Meanwell LDD series. As for efficiency - Meanwell claim it's pretty high (95%+) with outputs over 30V, so most of the losses should occur with the ac-dc power supply. Meanwell LDD limited to 1000mA though - the StevesLEDs drivers look really nice with output up to 2000mA, but Stves output V too low for COB use.


In terms of physically putting an array together the small modular approach looks great.

Need more juice? Get a another bigger power supply. Need more lights? Plug in another tiny driver onto your board.

The other thing is the really wide voltage that the LDD-H series cover. Output of 2V-52V gives you a lot of flexibility to run either high voltage cobs or small complementary strings of 1-2 deep blues. Flexibility you don't get with a single ac-dc driver.


Anway, I went for single ac-dc drivers for my cobs. 93% efficiency. But inflexible.
 
SupraSPL

SupraSPL

Well-Known Member
Good info Smokey, I can understand the appeal especially when it comes to dimming. On the other hand I think those use pwm style dimming which adds a third efficiency penalty. Its a tough decision, 1st world problems are the best kind though :)
 
Observe & Report

Observe & Report

Well-Known Member
The MeanWell drivers have a PWM controlled dimmer but they operate by limiting the current on the output and not PWM'ing the output at max current. The issue is your PWM control needs to have frequency and voltage within the limits of the driver. The controllers I was looking at did not. Setting up an arduino to do it is not as simple or cheap as wiring up a pot or adjustable DC voltage source.
 
M

mtnstream

Active Member
I agree with you and Smokey below.

I decided to stick with the same design as my 3050 array, 1500 mA - 36v. That is, running individual constant drivers to each chip, and a pc fan controller running 4-6 fans connected via 3-pin/molex to AC-DC adapter. Clean, simple and relatively efficient.

I am going to drive the 3070's @ constant 1800 mA - 36v and keep them running ambient temps.


SupraSPL said:
Yep it was a DC constant voltage -> DC constant current driver and if I recall it was surprisingly not very efficient (~80%). I assume that is because of stepping the voltage up from 12 to 34.

For those diyers that use 12V DC power supplies to run the LEDs they get an efficiency penalty from the AC-DC conversion and then again from the DC constant voltage to DC constant current conversion. Or if they try to run the LEDs on constant voltage they end up with each emitter dissipating a significantly different amount of power (unless it is just 1 COB on each string). So the most efficient approach (84-88%) is 120V AC->DC constant current conversion in one step (unless you have a way to run off a solar or wind powered battery bank).
Click to expand...
 
Gaius

Gaius

Active Member
mtnstream said:
I agree with you and Smokey below.

I decided to stick with the same design as my 3050 array, 1500 mA - 36v. That is, running individual constant drivers to each chip, and a pc fan controller running 4-6 fans connected via 3-pin/molex to AC-DC adapter. Clean, simple and relatively efficient.

I am going to drive the 3070's @ constant 1800 mA - 36v and keep them running ambient temps.
Click to expand...
You happen to have a photo of the wiring you did for this? I'm curious to see how you did it.

I still don't think I understand the issue with the PC PSU. I assumed that since these are 50-watt COBs, that a 45-watt per-channel fan controller would be perfectly suited to power 6 chips. However after re-reading the spec sheet for the 3070s, it mentions something about 38.5V forward voltage. The output of the PSU I believe is only 12V, which may be why others are saying I need a upconverter.

This is all pretty new to me, so I'm a bit lost now.

What parts do I still need to convert the 45-watts from the fan controller to the appropriate output for the COB? Is that even possible? Should I just return the PSU/Controller and go with the pricey dimmable drivers? Seems like buying 9 dimmable drivers would cost an arm and a leg.
 
M

mtnstream

Active Member
Sorry, I can't post pictures need to remain stealth although I might in the future. My pc controller is for fan connection only.

I would get a constant driver (<$20), copper bottom pc heatsink w/ fan ($15) and mockup up a one chip module. Test it. You could also order one of those dimmable drivers caretakr posted and try it.

Even though your PC PSU might work, personally I wouldn't do it. The answers of why have already been spoken. You might want to research the reefers diy for additional ideas. That's where I learned to build the 1-3 watt arrays driven by meanwells way back when for my tanks. But I decided to wait on new technology before anymore builds.

As Supra said above, "1st world problems are the best kind though"

Gaius said:
You happen to have a photo of the wiring you did for this? I'm curious to see how you did it.

I still don't think I understand the issue with the PC PSU. I assumed that since these are 50-watt COBs, that a 45-watt per-channel fan controller would be perfectly suited to power 6 chips. However after re-reading the spec sheet for the 3070s, it mentions something about 38.5V forward voltage. The output of the PSU I believe is only 12V, which may be why others are saying I need a upconverter.

This is all pretty new to me, so I'm a bit lost now.

What parts do I still need to convert the 45-watts from the fan controller to the appropriate output for the COB? Is that even possible? Should I just return the PSU/Controller and go with the pricey dimmable drivers? Seems like buying 9 dimmable drivers would cost an arm and a leg.
Click to expand...
 
Positivity

Positivity

Well-Known Member
Wow..didn't know efficiency took such a hit with dimmers. Think I still like having dimmers..if nothing else just so I can dim when I'm working in the area.

Do the inventronics with built in dimming suffer from the same efficiency loss?
 
SupraSPL

SupraSPL

Well-Known Member
I believe the inventronics directly adjusts current so it should not affect efficiency. Same goes for the satisled adjustable drivers.

I have some similar dimmable drivers I bought from KNNA years ago that I still use and they are up to 93% efficient. They are not power factor corrected though no biggy.
 
Positivity

Positivity

Well-Known Member
That's good to know, thanks. I'd hate to spend top dollar on inventronics and end up with bad efficiency numbers.

gotta wonder though how many drivers live up to their numbers when tested. I'm surprised a big name like meanwell would be so far off when measured.
 
Gaius

Gaius

Active Member
I'm going back to square-one and re-reading all the materials people have linked to earlier in the thread. Right now I'm feeling way-in over my head, so I need to hit the brakes and study a bit more. I misunderstood earlier about how Supra was doing it, and mistakenly thought I could just run the chips directly from the 12V out of a PC PSU. Looks like I need to use voltage step-up bunks to do this, which maybe isn't a good option?

What I'm really just looking for is the simplest and most cost-effective solution to power these panels over the lifetime of the chips. Since efficiency is pretty important for saving $$$ over the long-run, it looks like dimmable drivers aren't the best way to go here.

Remember I'm trying to power three panels-- each with three CXA3070s. Add to that 6 PC case cooling fans.
Outer chips on each panel will be in the reddish range for flowering:
6x CXA3070-0000-000N00Z230F-ND
Center chip on each panel will be in the blueish range for vegetative growth:
3x CXA3070-0000-000N00Z230F-ND - $38ea($114 total)
Click to expand...
Can these 9 chips be powered within a budget of $200 and still be close to 90% efficient?

With constant drivers, do I need step-up bunks?

1 driver per chip, 1 driver per panel (3 chips), 1 driver for all 3 panels?

Do I buy drivers rated for 50 watts, or lower like 30-40watt?
 
AeroDonkey

AeroDonkey

Member
Might wanna check out luxeon star leds too. May save ya an assload of cash. I use their leds for other projects. They are blinding bright and spectrum specific. Few bucks each instead of 40 and different wattages. NASA uses them as well.
 
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