Questions for the DIY CXA COB experts

alesh

alesh

Well-Known Member
diggsta said:
Hello, I've been following this thread and others dealing with the 3590 chip and would like to ask something, but maybe it's the wrong thread... Looks like a couple subthreads are already open, but if not, please give me a hint and/or shift it to the proper thread...

Anyway, great info here and it's amazing what effort some people (like supra) put in to help others! Thank you :D

So I already ordered

http://www.leds.de/High-Power-LEDs/Chip-On-Board-LEDs/Cree-CXA3590-warmweiss.html
http://www.ebay.de/itm/Orginal-HP-CPU-Kuhler-fur-d530-USDT-Vollkupfer-326170-001-/201467426837?hash=item2ee864f815:g:Ji4AAOSwsFpWSFnE
http://www.voelkner.de/products/825692/Mean-Well-LED-Treiber-Schaltnetzteil-LPC-150-1400.html

because I'm in germany, and I'm pretty sure that it should work at or around a good efficiency. Only later I saw the dimmable hgl-series, oh well.

Now I've come across this video http://freevideos.diyhq.net/video/8WjYmuUcvXo/LED-Tutorial-Light-a-100W-LED-from-12V-Simple-Cheap.html that uses something like this
which made me wonder if the whole thing could have been much cheaper (of course the actual power supply is needed in his case). But probably also less efficient and more insecure due to less quality of the led and also the power supply? if a similar 100w-setup could cost maybe 40$ instead of 120, would it also mean a noticeable efficiency in real terms, i.e. g/w? Or are these threads here like the search for the holy grail of efficiency, no matter what the cost?

EDIT: this seems to be explained here https://www.rollitup.org/t/your-cxa3590-mission-should-you-choose-to-accept-it.827693/page-6 as too inefficient.

I'm basically asking because I already plan to replace or at least reinforce my old fluroescent lamps with a panel of xm-l2's.

And I've seen power supply's being used with 300 or 500 or 700 ma on leds that seem to need more like 1400 ma to get to about half or 2/3 of their max wattage, like the cxa3590. That would mean at 700 this one could only get about 50w maybe? And that would mean that i would need to buy 3 cxa3590 to have the same wattage like one 3590 @ 150w, which would of course be much less efficient. But cost-wise it should be less $$/w, right?

Please excuse my ignorance, I've soldered a lot of audio gear from scratch already, but never actually understood the whole electrical thing. The main thing I'm confused by is how the 3590 "chooses" to use either 72v at ~1200ma or rather 36v at ~2400, as specified in its data sheet... Does it take whatever voltage it gets and then you can adjust the current? Or since the current is fixed in my case, it should just take whatever voltage it can get.. :s

And do I assume correctly that the cxa3590 would break if one would put in maybe 20v at 5 amps?
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My advice is to cancel your order for the old low bin CXA3590 and get top bin CXB3590. They're also cheaper.

There are two versions of the COB - 36V and 72V. Take them as different models if you want.

Voltage determines the current. If you apply 20V to the COB, it will draw (almost) zero current. The more voltage is applied the more current the circuit will draw (exponentially).
 
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diggsta

Member
thanks for the prompt answer! It cleared up almost everything for me :) much appreciated :)

so I just looked for the cxb3590 and couldn't find many in germany. the ones i found were 10 EUR more expensive, or even 25 EUR more (80 EUR). I already paid 55 EUR (which would be ~0,5 EUR/w running at 111w, which is just 3% less efficient than the 36% mentioned here on the forum i think by supraspl in a excel-table as being the most efficient. 3070 were about 0,8 EUR/w).

And I ordered the 72v as it seems, which is about right for the driver.

Anyway, the cheapest setups I could think of with leds (like this one) are around 1.2 EUR/w (just the paper-wattage). probably same with $$. The fasttech xm-l2s seem cheap but considering they can probably only run efficiently at ~6w it's not a big difference.

So is there any way to keep the costs down except with a crappy driver or crappy leds?

And is a led diy with meanwell driver and cree led possible for under 1 EUR/w?

So do you think the cxb3590 is really a must? For me the cxa is probably already a quantum leap, as I used cfls until now... Do I really need it?

And where do you see them cheaper? Only place I saw was cutter for 44 EUR, which is 10 eur cheaper than the cxa, and that's in australia. So the customs fees would eat that up.
 
alesh

alesh

Well-Known Member
diggsta said:
thanks for the prompt answer! It cleared up almost everything for me :) much appreciated :)

so I just looked for the cxb3590 and couldn't find many in germany. the ones i found were 10 EUR more expensive, or even 25 EUR more (80 EUR). I already paid 55 EUR (which would be ~0,5 EUR/w running at 111w, which is just 3% less efficient than the 36% mentioned here on the forum i think by supraspl in a excel-table as being the most efficient. 3070 were about 0,8 EUR/w).

And I ordered the 72v as it seems, which is about right for the driver.

Anyway, the cheapest setups I could think of with leds (like this one) are around 1.2 EUR/w (just the paper-wattage). probably same with $$. The fasttech xm-l2s seem cheap but considering they can probably only run efficiently at ~6w it's not a big difference.

So is there any way to keep the costs down except with a crappy driver or crappy leds?

And is a led diy with meanwell driver and cree led possible for under 1 EUR/w?

So do you think the cxb3590 is really a must? For me the cxa is probably already a quantum leap, as I used cfls until now... Do I really need it?

And where do you see them cheaper? Only place I saw was cutter for 44 EUR, which is 10 eur cheaper than the cxa, and that's in australia. So the customs fees would eat that up.
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There's some difference. Not that much as between CFL and CXA3590.
Try Kingbrite (http://rollitup.org/t/kingbrite-rocks.866244/). I paid about $51 a piece for 3500K/80CRI CD bin. I'm from the Czech Republic so I guess your cost would be very similar. CXB also match drivers better.
 
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diggsta

Member
thank you. then I guess I'll just stick to the cxa for now. 51$ is just a few bucks less than I paid, and if efficiency didn't rise by more than 10%, i can live with that. also I can't wait to build the thing! ;)
 
HockeyBeard

HockeyBeard

Well-Known Member
diggsta said:
thank you. then I guess I'll just stick to the cxa for now. 51$ is just a few bucks less than I paid, and if efficiency didn't rise by more than 10%, i can live with that. also I can't wait to build the thing! ;)
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I wouldn't scoff at even a 7% difference even on a cheaper chip
 
alesh

alesh

Well-Known Member
diggsta said:
thank you. then I guess I'll just stick to the cxa for now. 51$ is just a few bucks less than I paid, and if efficiency didn't rise by more than 10%, i can live with that. also I can't wait to build the thing! ;)
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Well, efficiency is 34% higher (relatively; absolutely it's 14 percentage points) at about 50W,
 
alesh

alesh

Well-Known Member
diggsta said:
damn.. its already on the way and from china it will cost customs and take a month. always those hard decisions:???:
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Yeah the shipping took a month in my case but I didn't pay customs and/or VAT. Should be similar in Germany if sent by China/NL post. Read first, order second:) The CXAs won't disappoint you. They're high CRI so they might provide some advantage over 3500K/80CRI.
 
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diggsta

Member
really thinking about 2x cxb3590 now... would this hlg-185h-c1050a be an efficient driver for the 2? or this
HLG-120H-C1400A or this HLG-120H-C1050A? I'd like to be a little flexible when it comes to light versus efficiency.

and do i need the 36 or the 72v then?! Is it right to say that both current and voltage are divided into 2 when the cobs are put in serial? I'm pretty bad with electronics ;)

is there a table like in this thread https://www.rollitup.org/t/diy-led-vegging-cree-xm-l2-vs-cree-cxa3070.802790/ in the first post for the cxb3590 somewhere?
 
alesh

alesh

Well-Known Member
diggsta said:
really thinking about 2x cxb3590 now... would this hlg-185h-c1050a be an efficient driver for the 2? or this
HLG-120H-C1400A or this HLG-120H-C1050A? I'd like to be a little flexible when it comes to light versus efficiency.

and do i need the 36 or the 72v then?! Is it right to say that both current and voltage are divided into 2 when the cobs are put in serial? I'm pretty bad with electronics ;)

is there a table like in this thread https://www.rollitup.org/t/diy-led-vegging-cree-xm-l2-vs-cree-cxa3070.802790/ in the first post for the cxb3590 somewhere?
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The only difference between 36V and 72V versions is that dies in the 72V version are put in half as many twice as long string. You need to choose your driver accordingly, though.

When you put 2 COBs in serial, they'd need twice as high voltage to pull the same current through.

I'd advise to run CXB3590 at around 50W, which means that you need 1400mA driver for the 36V version or 700mA driver for the 72V one. HLG-185H-C1400 is good for (4) 36V CXB3590s at 50W, HLG-120H-C1400 or ELG-150-C1400 is good for (3) and ELG-100-C1400 is good for (2). 700mA versions of these drivers are good for 72V version of CXB3590.
 
M

miggsta

Active Member
wow thanks, you're a real help! if there's a thank-button to up your thanks-meter I'd click it :)

now it's thinking and reading again and then ordering :lol:

damn those far away shops. it seems that minimum order at kingbrite is 4 or 5 pieces, but I'm kind of limited because I don't have much room neither in terms of space nor do I want more than 2 or 3 plants to keep the penalty low if they catch me. The risk of being caught doesn't get smaller with more plants. And 5 pieces in just one color would limit me to autoflowers in a way. Which would be ok, considering

Just read on of your other threads, this one https://www.rollitup.org/t/cree-cxa-3590-drivers.872825/

Should have read that first. I didn't even consider any height issues.

Considering this, what would you recommend for a 1.3m high x 60cm x 60cm grow box and 1-3 plants? I hope the upcoming cxa3590 will do the job for the time being.

But this is only my second grow box, my first was really improvised, with a carton and 4 cfl ring lamps. Worked ok, but it was fun so I want more ;) I'll keep experimenting a bit with the 3590 which arrives today i hope and I'm sure I'll have more questions soon and I hope you're still around then !)

Btw, your avatar looks pretty much like my grow box. Is it a carton as well?
 
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D

diggsta

Member
alesh said:
When you put 2 COBs in serial, they'd need twice as high voltage to pull the same current through.
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Hey, thanks for all the answers... I used some other account of mine to post the last post, sry about that and spamming you with questions ;)

I now assembled the cxa3590 with a cpu heatsink and a lpc-150-1400 and of course it gets much too warm. What would happen if I put a second cxa3590 in serial with the first? Just asking because I dont know if the shop will take back the lpc driver...
 
alesh

alesh

Well-Known Member
diggsta said:
Hey, thanks for all the answers... I used some other account of mine to post the last post, sry about that and spamming you with questions ;)

I now assembled the cxa3590 with a cpu heatsink and a lpc-150-1400 and of course it gets much too warm. What would happen if I put a second cxa3590 in serial with the first? Just asking because I dont know if the shop will take back the lpc driver...
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The COB or the driver is getting too warm?
 
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diggsta

Member
The cob. It's on a copper cpu heatsink which weighs maybe 800g and has 45 fins on it... But it gets too hot to touch in a minute. It's already glued on so I'd rather keep it there and not break it off, and use the second same heatsink for another cob, which should reduce the heat-wattage per cob by about 2/3 if i run it not at 110w, but at 50w, i hope. Just don't know if I need another driver.
 
alesh

alesh

Well-Known Member
diggsta said:
The cob. It's on a copper cpu heatsink which weighs maybe 800g and has 45 fins on it... But it gets too hot to touch in a minute. It's already glued on so I'd rather keep it there and not break it off, and use the second same heatsink for another cob, which should reduce the heat-wattage per cob by about 2/3 if i run it not at 110w, but at 50w, i hope. Just don't know if I need another driver.
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I see. You can connect the COBs to the driver in parallel, it will definitely help you with temps and get you at around 50W a COB. The heat sink is cooled passively, right? Too many fins too close are not optimal for passive designs. A slight breeze over the HS should help you, too.
 
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diggsta

Member
Thanks a lot! I almost thought so (to put them in parallel), so that means I can still use the lpc driver. I heard that there are disadvantages of using them in parallel, like irregularities in the current leading to a shorter life span. Oh well, it's not all optimal anyway. I already have a pc fan ready to be part of the set. I'll post a picture soon, looks kind of weird already.
 
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diggsta

Member
So I glued the second COB onto the second sink. Now it's probably a little brighter than before, and with the fan it's just cool enough to touch. After half a minute or so it becomes unpleasant, but not impossible. My only means of measuring temperature is a oven thermometer, which shows ~50°C. Looks a bit flimsy still, which I might fix in the future.

So thanks Alesh, you've been a big help!! If I can buy you a beer, I will ;) But only in btc...
 

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