K2 LEDs - brighter/more efficient?

Is it true that the new K2 LED are going to be brighter and use less juice that the luxeon 1/3/5 LED we are now buying?

If this is the case, am I wasting my money accumlating luxeon flashlights? How soon before flashlights with K2s will be readily available?

The K2's are well past a year late in getting out and from what I have seen, they have a good ways to go before they dethrone a good LuxIII. Just MHO.

When they do catch up, I would expect they might incrimentally pass the LuxeonIII's as time goes on. I have an old ArcLS that still works the same with my eyeballs as it did when it was new. It has been surpassed in terms of efficiency and efficacy but it still suits the same purposes it did back then.

I suggest you buy a light when the need or desire arrises. If you can hold off and want to wait for something better then do so. I would not suggest you jump on the first K2 flashlights unless you have it on authority that they are better than a LuxIII light.

Many many thanks Mr. Gizmo for the reply. Coming from you makes the info. all the more valuable.

Did you say "need" another light I long ago gave up even trying to justify my flashlight habit. I see you added "desire" another flashlight - I suppose just in case I was a true flashaholic

The big thing about them is that they can handle higher junction (ie. die) temperatures and the Lumen reduction from high temps is reduced. This is good news for the lighting industry since they can skimp on heatsinks, run them hotter and still get a fair bit of light from the. For flashlights with decent heatsinks at normal drive levels this isn't a big deal. But it will help when overdriving or cheap flashlights with minimal heatsinking.

Greg

Before you think of using the K2 LED you should test the new SSC LEDs.
According to the article on ledsmagazine (http://www.ledsmagazine.com/press/12172) they are much more efficient than the Lumileds LEDs.

/ opto-king

Thanks for the link Opto

The SSC LEDs look good and 98 lumens per watt sounds good. It leads to the obious when, how much and is the die the same size for reflector compatibility. Interesting but when?

From what I understand, the K2 is less efficient than a similar binned Lux III. The latter is rated at 700ma for a certain flux range while the K2 needs 1000ma for the same flux range.

Brighter and heavier-overdriving potential, higher heat tolerances yes, but efficiency a little less at this point, it appears.

I think I'll wait until all of this is settled before I drive myself nuts trying to decide I need one of these K2 LEDs...

but in the meantime, would someone explain the use of the word "die" here? To what does that refer?

Thanks,
-Jeffrey

I'll ditto LED candle's comment - my understanding is that they are not as efficient - big difference being that you can drive the snot out of them so theoretically you can get them to be significantly brighter than premium lux I and III's but with a signficant drop in runtime.

My understanding is that All LED's are less efficient when overdriven and are most efficient when slightly underdriven.

The die is the little piece of semiconductor inside that emits the light.

The K2 still needs it's heatsinking. At it's drive level, it needs it more. If you cut back on the heatsinking, the die temp will rapidly rise, resulting in reduced light output.

If you don't heatsink it, sure, you can run the die up at 185C, but the light output will drop dramatically.

The great thing about the K2, is it's internal thermal resistance is reduced to 9C/W. This helps a person keep the die slightly cooler. The Luxeon III was 13 C/W. If one were to run both at 4W, the K2's die would be 16 degrees C cooler.

If you don't keep the K2 cool, and you were using the 140 lumen V bin, at let the die rise to 185C, you'd be looking at only 91 lumens for it's output. So it is still important, in the end.

The K2 parts so far have had a rather high forward voltage (voltage across the LED), and as such, when putting say, 1500mA thru them, you end up with nearly 6.5W of heat you have to get rid of. If the forward voltage had been kept lower, the total amount of heat would be less.

Hopefully the production parts will have lower forward voltages, as many of the samples folks have been getting have been on the high end of the scale.

Why is forward voltage important?

Forward Voltage * Current = Watts (heat)

Can some one PLEASE tell me why you are looking at the K2 LED due to that it "can stand" +185degree Celsius? When the important thing sould be the light out put.
:huh2:

For example; if the SSC LED is 98lm/1.2W then that LED will "produce" very little heat due to that it is only 1.2W (with 8 or 9 C/W in thermal resistance depending on type of LED P1 or P3).

When using this LED you do NOT need the 185degree C tollerance.

The only reason for the need of 185degree C is when the LED is to poor in lm/W and there for "produce the extra heat".

What do you think will happen with the plastic 2nd lens when used in extreme heat?

And for you all that are driving the LEDs with batteries, the lm/W should absoulutely be the no 1 issue...or?

AAAAARRRRRRRRRRR!!!!!!!
I hate having to wait for new products to come out. K2's must have been announced over a year ago and its only now they are beginning to hit the market in small quantities and they're not even that good. We'll probably have to wait another year before K2 products become widely available.

When Intel announce a new processor, we don't have to wait 2 years before buying a new computer that uses this processor. Why should LEDs be any different?

Now there's a whole heap of manufacturers claiming better efficiencies. How long do we have to wait for these?

Opto-King said:

Can some one PLEASE tell me why you are looking at the K2 LED due to that it "can stand" +185degree Celsius? When the important thing sould be the light out put.

Click to expand...

Because I would try to overdrive that SCC LED. After all, like you said, it's all about the light output. The problem is, that SCC may not be able to take the heat. I'll get a K2 UWOJ (wishful thinking) and drive it at 1500mA. It should be able to take it due to its junction temperature tolerance. That will give it MAX lumens! Screw the efficiency!

Don't believe me? Read my sig line!
Bernie

Okay, I hear you...BUT why sit and wait for something that seems to never be comming?

That is like quitting you job just because you might win a milion on the lottery some day...

FirstDsent said:

Because I would try to overdrive that SCC LED. After all, like you said, it's all about the light output. The problem is, that SCC may not be able to take the heat. I'll get a K2 UWOJ (wishful thinking) and drive it at 1500mA. It should be able to take it due to its junction temperature tolerance. That will give it MAX lumens! Screw the efficiency!

Don't believe me? Read my sig line!
Bernie

Click to expand...

Opto-King said:

Before you think of using the K2 LED you should test the new SSC LEDs.
According to the article on ledsmagazine (http://www.ledsmagazine.com/press/12172) they are much more efficient than the Lumileds LEDs.

/ opto-king

Click to expand...

The SSC LED's are just vapor ware at this point as far as I know. The K2's are just hitting the streets. That SSC press release reads like the K2 press release sent out over a year ago. Its hard to compare vapor to vapor but by god CPF will try, won't they?

K2's are available to anyone who wants to order them now.

Anyone can order them from Future Electronics, and have them shipped next day if they'd like.

They are fully stock with the regular production parts now.

My first two orders resulted in UWON bins.

If I run them at 1000mA, the Vf should be 4.23 - 4.47V.

If I run them at 1500mA I'm well over 4.5 volts easy, and for that extra 500mA, I only gain 30 extra lumens, or what would be slightly above just noticeable to my eyes. Sounds definitely like a loose-loose proposition.