PAR test of cree vs citi vs cutter

OneHitDone

Well-Known Member
3000K has about the same amount of far red. I really like these ratios:

View attachment 3718218
Not quite sunlight, but not bad. Probably good enough to prevent gross developmental problems in most plants, including the devil's weed. Maybe some UV would be good.

Anyway, that's where I'm heading I think. Over my lettuce, and everything else.
Be sure to share with us how lettuce develops under this spectrum ;)
 

JorgeGonzales

Well-Known Member
true understand all of what you said.

But don't we want to know how it performs under realistic operating conditions ? Otherwise its just theoretical potential.
Sure, it's just not this test. Go back and look at SupraSPL's tests. I was afraid I'd be embarassed and that's not how his spreadsheets were measured, but it was. Whew. 75F pulsed.
 

JorgeGonzales

Well-Known Member
Besides we have this data which we can apply with reasonable certainty:

image.jpg

It's a lot harder to make these charts, but current droop is relatively easy, and numbers seem chronically pessimistic with the manufacturers. Cree, Bridgelux, and Citizen all seem to do better than the tools, data sheets, and simulators indicate. How much better is the question.

Still waiting on that sphere data from PLC.
 

ttystikk

Well-Known Member
Who cares what the performance is at 25C ? Does anybody run with a Tj at 25C ?

Isn't it more important to test closer to actual real world operating temps, like 50 C ?
Lol you have hit the nail on the head!

Everyone likes to brag about their light's performance at Tj=25C=77F, but who actually achieves it? Even active cooling is top of the grow tent ambient plus, and passive is hotter than that.

Show me the guy running his chips at 25C or below. I wanna meet him.
 

JorgeGonzales

Well-Known Member
Lol you have hit the nail on the head!

Everyone likes to brag about their light's performance at Tj=25C=77F, but who actually achieves it? Even active cooling is top of the grow tent ambient plus, and passive is hotter than that.

Show me the guy running his chips at 25C or below. I wanna meet him.
But we aren't chasing performance numbers at 25C, we are trying to plot current droop curves.

So, yeah. And the only guys bragging are running Bridgelux. -ducks-

Seriously though Tj=Tc=25C makes it much harder to compare their numbers to everybody elses, and certainly causes confusion around here Christ knows. Luckily they perform well.
 

ttystikk

Well-Known Member
But we aren't chasing performance numbers at 25C, we are trying to plot current droop curves.

So, yeah. And the only guys bragging are running Bridgelux. -ducks-

Seriously though Tj=Tc=25C makes it much harder to compare their numbers to everybody elses, and certainly causes confusion around here Christ knows. Luckily they perform well.
I mean this with the utmost respect; speak for yourself.
 

JorgeGonzales

Well-Known Member
Anyway, for 50C, a good repeatable test would be Ta=Tj=Tc=50C, let temps equalize and do a quick pulsed measurement at different currents.

Measuring the case or Tj is much more difficult to do accurately than the ambient temperature.
 

tomate

Well-Known Member
I disagree; this temperature was chosen by the manufacturers to put their chip's performance in the best possible light, as opposed to it being a good temperature for measurements.
Won't disagree on that, you are absolutely right.
50C is much more realistic, and achievable under steady state conditions with even passive cooling, thus making comparisons much more straightforward.
Then tell us how BOBBY_G can achive those steady state conditions at 50°C with different cobs at different amperages.
That would be far from easy.

And again, we don't need to measure under operating/real life conditions to make a simple comparsion. This would only make everything more complicated and harder to implement.
And you can still extrapolate the data using the case temperature charts from the data sheets.
 
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tomate

Well-Known Member
o_O

Ok, last try. If you want to see PAR measurements under real life operating conditions, then you are wrong here. :peace:
 

JorgeGonzales

Well-Known Member
bad assumption. just one example thermal resistance isn't linear.
It's not, but it's yet another variable linked to temperature, along with forward voltage, and best controlled.

Nice that you get this though. Heat sink discussions can be difficult around here. Wattage specs are arbitrary, and C/W discussions hard without knowing at what temp they are quoted at. Usually higher than we run.

But moving from 25C to 50C might result in a flux drop of 10%, and thermal resistance is a fraction of that, and the amount it varies by temp is a fraction of that.
 

JorgeGonzales

Well-Known Member
Also, I want to point out that what I'm talking about isn't theoretical for me. I've spent way too much time comparing different solid state devices to one another, to match this or that parameter, and if there's one thing I've learned is that it's a hell of a lot easier to normalize comparisons to your ambient temperature, than measure your Tc or Tj and try to normalize to that.
 

BOBBY_G

Well-Known Member

JorgeGonzales

Well-Known Member
Just pulse everything at the same ambient temp like Supra. For manufacturer to manufacturer
comparisons, I mean. A real world test is definitely warranted as well.

Remember, and I should have said this before when people brought up 25C, the end game here isn't figurimg out PPFD/W at 12" and 25C, it's finding the current droop curve SO WE CAN HAVE REAL EFFICIENCY NUMBERS for these new cobs.

Broke out the caps yo.
 

ttystikk

Well-Known Member
Just pulse everything at the same ambient temp like Supra. For manufacturer to manufacturer
comparisons, I mean. A real world test is definitely warranted as well.

Remember, and I should have said this before when people brought up 25C, the end game here isn't figurimg out PPFD/W at 12" and 25C, it's finding the current droop curve SO WE CAN HAVE REAL EFFICIENCY NUMBERS for these new cobs.

Broke out the caps yo.
If you want to use current droop data, why wouldn't you want to use temperature droop data as well, for the same reason?
 
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