COB Talk

PurpleBuz said:
look at the charts perf diffs between 32 an 45 C. i'm not looking to be in spec, i'm looking for more dollars/lumen/watt.

and btw you didn't answer my question how much heatsink (COST) will it take to bring temps to 32C to match the fans ?
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Can you copy n paste the chart on the thread, so we can reference it?
 
Greengenes707 said:
My point is that it is not as big a gap as you think when you measure the actual Tc.
And if you were to take the fan cost(fan+power) and put it towards sinks...you would lower your passive Tc more for the same price as active. In your situation you are only removing the fan...and not adjusting sink size.
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I see what your getting at, but your nitpicking. I designed the first iteration of the unit as passive (with hope) and found that it was running too hot (>50C). so I redesigned for Version 2 and have shown that it runs passively ok mid 40s.

BUT if I add a few watts of fan it runs 10 degrees C cooler. Your right we are not that far apart, I really was designing for passive. But that 10 degrees seems important to me and it is cheaper to add a bit of active cooling, to get it.

The heat sink thickness is only 0.098", so we have the thermal paste resistance plus the heat sink resistance. making my test point really not far from the Tj, since all measurements were made consistently at the same point, the point is moot.

with extruded heaatsinks from heatsinkusa the cost to lower the temps to the same level is MUCH higher. With the better anodized black pin fin heatsinks the cost is much closer. BUT have you seen the difference in cooling power between active and passive for a state of the art pin fin heatsink ? I recently tested a small 60 mm square sparsely populated pin fin with and without fans and got a 3X increase in performance with a minimal active air flow. pleasantly surprised me at just how well the pins perform.
 
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Speaking of cheap and efficient, I started a thread about the CLU048 here, but here's a sweet snippet from the 1212 version's datasheet:

image.jpg

Full stats here, and a Citizen spreadsheet/simulator right here.

Running at 14.1W like @PurpleBuz, the CLU048-1212 would see 184lm/w for the 4000k 80 CRI version at Tc=25C. I don't think 25C is realistic in a grow room, but thats how Bridgelux advertises it's lm/w.

Anybody have a ballpark on the LER of Citizen COBs? I suppose these could still be less than impressive for eff %. That's where my head starts to hurt a little.
 
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Evil-Mobo said:
You guys are making me want to return my heat sinks to HSUSA and order the round pin models for my light build lol.........
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Just depends on how you're using it and how much of it you're using. It's possible to keep temps at the test point 10C and less over ambient using fans. The emitter closest to the exhaust on my T2-2100 runs about 7C over ambient. That's just under 4 watts of fan power split between two emitters, 2 additional watts per emitter. If we split the cost of the fan, heat sink and fan driver ($14, $31.5 and $5) the cooling cost per emitter is $25.25
 
Rahz said:
Just depends on how you're using it and how much of it you're using. It's possible to keep temps at the test point 10C and less over ambient using fans. The emitter closest to the exhaust on my T2-2100 runs about 7C over ambient. That's just under 4 watts of fan power split between two emitters, 2 additional watts per emitter. If we split the cost of the fan, heat sink and fan driver ($14, $31.5 and $5) the cooling cost per emitter is $25.25
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How is it $25.
 
What do you fellas think about this strategy.

Use the hlg-185h-c1400b running 4 COBs for now until next round of upgrades then get another hlg-185h-c1400b running 4 more COBs in the same space but now I can dim both down to 700ma and have the extra efficiency. 67%

Seems like using the hlg-185h-c1400b can give you the higher output when you need it or you could double them up and run them both low at 700ma at get the efficiency when you want it.

hlg-185h-c1400b Is pretty versital drivers then get the best of both worlds with one driver.
 
Gonna play with this a bit.
5f6efc3c004febafcd772e7e7a35fbdd.jpg



Sent from my iPhone using Tapatalk
 
GrumpyToker said:
What do you fellas think about this strategy.

Use the hlg-185h-c1400b running 4 COBs for now until next round of upgrades then get another hlg-185h-c1400b running 4 more COBs in the same space but now I can dim both down to 700ma and have the extra efficiency. 67%

Seems like using the hlg-185h-c1400b can give you the higher output when you need it or you could double them up and run them both low at 700ma at get the efficiency when you want it.

hlg-185h-c1400b Is pretty versital drivers then get the best of both worlds with one driver.
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The only way you get that efficiency number is if you keep your Tj at 25C.
 
ttystikk said:
Last pearl, then I give up; WTF is so great about passive if it lets the chip run hot?
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I run most of my stuff actively. But if I can run passively with the airflow in my space that's constantly running, its seems like less less parts is less work and leaves less room for equipment failure. It's was more likely a fan fail than an LED that's effectively cooled passively.

In a sense it will still be actively cooled. It will just be cooled using my whole setups cooling rather than a 90mm fan.
 
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