# Replacement for K2 TFFC?



## kevinm (Apr 7, 2010)

With the death of the K2 TFFC, I'm wondering what LED I should use. The headlamp I'm upgrading has a plastic body and little heatsinking. The K2, at 1A, was fine for hours. The SSC-P4 lasted 10 minutes before the dreaded shift to blue!

Has anyone tried the XP-G in high heat conditions? What about Rebels?

Help?

Kevin:tinfoil:


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## Cuso (Apr 7, 2010)

The death of what? enlighten me...


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## John_Galt (Apr 7, 2010)

Luxeon discontinued production on the K2 LED. He's asking if there is a durable replacement for the minimal heat sinking capabilities of his light housing.


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## kevinm (Apr 7, 2010)

Correct Sirs! The K2 TFFC is no longer being produced. They are still available to some limited extent, but that's it.


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## vaska (Apr 7, 2010)

kevinm said:


> With the death of the K2 TFFC, I'm wondering what LED I should use. The headlamp I'm upgrading has a plastic body and little heatsinking. The K2, at 1A, was fine for hours. The SSC-P4 lasted 10 minutes before the dreaded shift to blue!



I can see only one reason why an old ineffective Luxeon could overcome P4: constant voltage power supply. Are you sure the current was the same with either of the LEDs?
To reckon which LED produce less heat at equal light output, just look at efficiency index. Efficiency of K2 at 1A is about 46 lm/W, that means dissipating 2.9W in heat at 160 lm light output. In case of using XP-G R5 at 1A (107 lm/W) heat dissipation comes to 1.25W while light output rises to 350 lm. The more energy it turnes into light, - the less heat is produced.


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## fyrstormer (Apr 7, 2010)

The K2 TFFC is not old and ineffective, at least not moreso than the P4. Its development was contemporary with the Cree XR-E die, which the P4 uses, and it has a more heat-resistant phosphor coating than the P4, which is why you can run it at an amp and a half without any blue-shift.

The Cree XP-G die is more power-efficient, yes, but it achieves that via a larger die and a lower power-to-area ratio, which is great, but its emission pattern is less point-like as a result, which makes it harder to focus. There is always a tradeoff.


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## jeffosborne (Apr 7, 2010)

Hey, there are plenty of K2 LEDs still available to buy today:

http://www.futureelectronics.com/en...tters/white/Pages/1192327-LXK2-PWC4-0200.aspx

Also, have you thought about adding some aluminum inside the light, to add more heatsink?






Cheers,
Jeff


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## vaska (Apr 8, 2010)

fyrstormer said:


> at least not moreso than the P4.



No one is against  They have equal efficiency at 1 A. But according to examinations carried out by* jtr1962 *Vf of K2 is higher than that of P4, and it means that with equal constant current supply K2 utilises more power and dissipates more heat than P4. With constant voltage supply it's vice versa.



fyrstormer said:


> Cree XR-E die...has a more heat-resistant phosphor coating than the P4, which is why you can run it at an amp and a half without any blue-shift.



As a headlamp manufacturer I used P4 SVO-bin till late 2008 in my lamps with 1.5 A overdrive in turbomode and can witness quite a yellowish tint even at overdrive.



fyrstormer said:


> XP-G...is less point-like as a result, which makes it harder to focus.



Up to my experience XP-G is easier to focus compared to P4, and K2 is rather equal to P4 from the point of optics.


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## HarryN (Apr 8, 2010)

There are two really nice things about the K2 IMHO. 

One - it is the pick up truck of the LED world. They can take abuse like nobody else and just keep running.

Two - they are relatively immune to light output droop from heating compared to many other LEDs. In a plastic body light, this is very useful.

Given the choice for a simple retrofit, I would still use a K2 TFFC and just buy the best one you can find, either through Photon Fanatic or Future, or others, there are plenty still around right now.

The Rebels are handy, but don't have the output (lumens) yet of a K2 IMHO. The do have a very small emission surface though, which can help with focus sometimes.


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## fyrstormer (Apr 8, 2010)

There's another nice thing about the K2, while we're listing advantages  -- their "cool" tint is comparable to or warmer than the P4's "neutral" tint, or else I got really lucky with the small batch I ordered. I put one in my McLuxIII-T, because I'd already put a neutral K2 in my Arc6, and I was expecting the sort of tint I've seen on Chinese-made Cree Q5 lights, but what I got reminded me of morning sunlight instead. Very nice surprise.


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## kevinm (Apr 9, 2010)

jeffosborne said:


> Hey, there are plenty of K2 LEDs still available to buy today:
> 
> http://www.futureelectronics.com/en...tters/white/Pages/1192327-LXK2-PWC4-0200.aspx
> 
> ...



Thanks, Jeff. Future has not given me good tint bins in the past. When I asked about selecting the bin, they said I could for a largish fee. Has that changed?

No room for a better heat sink; the headlamps are small!:naughty:

Kevin


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## kevinm (Apr 9, 2010)

vaska said:


> As a headlamp manufacturer ...



Tell me more about the headlamps. I spend a lot of time caving; anything useful there?

Also, have you tried XP-G's at high temperatures? I like the efficiency, but am worried about destroying the LED.

Thanks,
Kevin


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## vaska (Apr 9, 2010)

kevinm said:


> Tell me more about the headlamps. I spend a lot of time caving; anything useful there?
> 
> Also, have you tried XP-G's at high temperatures? I like the efficiency, but am worried about destroying the LED.
> 
> ...



I don't think my lamp is good for caving. It's designed for professional sportsmen in XC-skiing, night orienteering, rogaining, multisport, and is more for throw than flood. The only useful thing for a caver may be its headgear. If you like I can send the pattern of it in any vector mode you prefer: CorelDraw, AutoCad, Illustrator...

As for XP-G at high temperatures - it's an SMD component that requieres 260C of stove soldering. In my design I never let LEDs to reach temperatures higher than 80C. The light bulb you can see at my picture has 3 XP-Gs in series with the highest consumption of 1.5 A in turbomode. As far as its shape is a good heatsink, I can say nothig of what could happen if the die temperature was really destructive.


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