OK so I don’t know where to post this so I’ll just post it here and let the mods move it if need be. Are my comments in this thread wrong? Koito's new red phosphor | Candle Power Flashlight Forum Just be aware that my username over there is Magio.
Like everytime we do a runtimes test with a flashlight there is a rather sharp drop in output during the first 30 seconds or so and after that the output tends to level off. That is the drop Im refering to in that thread.
Wow, what a generally nasty tone in that thread… Everyone’s got a stick up his bum like that?
I’d rather have monochromatic red LEDs behind red lenses, regardless their efficiency. White LEDs behind red lenses just look washed-out. I’ve seen people who swear by “brighter” white LEDs in their taillights, and they look hideous, a pale sickly orange.
Nb: you need orangey-red for “red” automotive lamps, called “traffic red” or “Portland Orange”.
That said, if mono-red LEDs have more luminous-fade with increasing heat, just use more chips and spread out the heat. Looks like Peterson wants to use fewer chips pushed harder to get the same luminous output.
Now, if they use a red equivalent of PCA (phosphor-converted amber), I could see that, as PCA chips are a bit more efficient then true amber-emitting LEDs. But if actually white light filtered to red? Ewww.
So, yeah, okay, it’s “lose” not “loose”. Kinda bugs, me, too, I confess. But when someone starts turning into Grammar Nazi or Spelling Nazi rather than addressing the issues, you kinda know he’s losing the argument, or feels as if he is. (Thus, attack the messenger instead of the message.)
All that said, not sure what you’re asking about your comments being “wrong”. They’re legitimate questions. If the written or unwritten rule is to just sit down, shut up, and don’t question what’s posted, then yeah, I guess they’re wrong. 
This +1
I guess the real question is, if you introduce any amount of current to an LED and hold it there, as the led heats up, will it always lose some of its brightness as it heats up? Or will the led only start to lose brightness once it reaches a certain temperature?
As temperature increase’s lumen’s decrease per a watt making it less efficient per watt.
Which is exactly what I had always suspected but those guys on CPF and Peterson themselves are claiming something else.
I would check out that thread, but right now, all I'm getting is the all-too-common . . . .
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Simple look at the cree xpl datasheet.
They bin the led according to how many lumen’s each will make at 1050ma with a temp of 25c and 85c.
I got as far as post #18 when I realized the mods berating you were probably wannabe English grammar/spelling teachers with major superiority complex’s.
At that point I couldn’t follow the discussion further as the berating distracted from the subject matter. I also became sickened by it and had to close the page. :confounded:
They’re two different things.
First, LEDs are generally more efficient at lower temperatures, period. If you can chill them, they’ll glow brighter for a given current.
Second, there’s derating them as they heat up. Beyond a certain point, they’ll lose luminous efficienty and just start heating up with no more light, or worst, with less light. As a function of current and a fixed heatsink, that’s sort of an inverted parabola. Rather than increasing linearly on a 1:1 scale (eg, 1mA = 1lm, 2mA = 2lm), the slope will decrease more and more, flattening out to a peak value, then start dropping.
The first is just a function of the crystal. The second is more related to pent-up heat and how it can kill efficiency.
Ah, here’s a good one…
http://www.lrc.rpi.edu/programs/nlpip/lightinganswers/led/heat.asp
This also shows how red/yellow LEDs are more sensitive to the first, whereas blue/green LEDs are less sensitive.
You can complicate this even further by the fact that phosphors will “saturate” at a certain point. There just ain’t enough atoms jingling around to maintain a linear increase in flux. Too many people trying to go home from work, and just not enough buses to carry them.
So I’m “reading between the lines” what Peterson wanted to do, is use the fact that blue LEDs don’t suffer as much from increased heat as red LEDs do, and would rather phosphor-convert blue light into red.
Blue into monochrome red I can understand, like “PCR” instead of PCA. But if actually white (ie, mixed spectrum of converted light), that’d probably look yicky.
I just don’t see how Peterson can legitimately make this claim at any drive current. The “don’t lose intensity part”
No matter what kind of thermal management you have without going to extremes with liquid cooling or something, when the led is switched on, its temperature will begin to rise. Assuming the current stays the same as when it’s initially switched on the output will drop as the die heats up. So how can Peterson legitimately claim their Leds don’t lose output?
They should’ve added “as much”…
Thank you for that link. Thats what I had always thought but the mods on CPF and Peterson seem to be suggesting there is a way to increase tempature without loss of lumens. Im not convinced that’s true.
Another regular thread in CPF……
After one thread which I started I gave up to follow this crap, I’m happy here
Haha “pale sticky orange ” is the perfect description. I don’t like white LEDs behind red lenses either. Sometimes it’s best to follow the crowd and in this case red LEDs behind red lenses is the way to go haha.
I did mix up the words “lose” and “loose” . But I’m typing all this on my phone and its hard to proofread long paragraphs on a phone.
Automotive lighting has always interested me a lot and this forum doesn’t have an automotive section so I still post there from time to time. Very difficult to have a friendly meaningful conversation though as the most benign comments get shot down by the mods.
That’s what I figured they probably meant but the mods sure didn’t think so. “Nah you trying to act like you know more than the lighting engineers”… Lol
Don’t let a couple a cranks ruin your time over there. I have learned a lot there, and for the most part, most of the folks there are pretty civil. On the other hand, the auto section is highly uninviting with the usual moderator shenanigans from those two. I have lots of respect for the knowledge and courtesy I’ve seen from many other moderators over there. That being said, I hardly ever go there anymore, because BLF is better in almost every way I can think of, not to mention the molasses slow loading at best. I mean come on, is there server on dial up or what?
Either way, I see your questions as valid and worthy of a straight answer, without all the judgmental and condescending attitude. Is it so hard to just say that it seems you are overlooking thermal management? I think not. Now I have no idea other than an educated guess, but thermal management aside, if current is passing, heat must be generating, thereby warming the led. If output goes down as heat goes up, and heat is going up with current, there must be a loss. I think the reality is that you are right that white leds just don’t lose as much intensity.
Sorry for the long post. It was either that, or a long rant over there about manners and goodbye, but what would that change? Bottom line in my eyes is that some people just can’t grasp the concept of not being a jerk. Sorry to see you were treated with so little respect. Cheers to you for not sinking to their level!
yes .
Every LED has a thermal resistance. This tells you how much hotter the DIE (junction) is compared to the solder pad on the bottom per Watt of heat. Manufacturers can drastically improve this value(see Luminus CFT-90), but it will always be there.
In addition there is also the droop effect of LEDs. With higher current density the efficiency drops even when the LED is perfectly cooled.