My Cree Experience - get yourself a welding helmet

In my rush to see what the Cree XR-E had I decided to throw it across a well used Surefire CR123 battery directly. Just a touch for a split second to see what she has. Have you ever started a weld with a Mig welder but forgot to pull your helmet down? That's really what this experience reminded me of as I was close in to the LED to touch some fine point V.M leads to the small contacts (which were hooked up to the CR123). I counted on probably an Ohm or two for the leads so no resistor. I'm still seeing SPOTS.... These LED's are truly BRIGHT. So put on your shades or welding goggles before firing one up You just may need it.

I did the same thing but with 700mA with my bench power supply, just long enough to read the Vf.

BTW the Vf was 3.60v

matrixshaman said:

In my rush
.....
I'm still seeing SPOTS.... These LED's are truly BRIGHT. So put on your shades or welding goggles before firing one up You just may need it.

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Doh!

Reminds me of some song from awhile ago?

Something about shades.

"The future's so bright, I gotta wear shades."

Hmm. You know it is a good idea to bring my sunglasses down with me when I mod.

I don't blind myself too much anymore because I lay a folded up peice of paper over the leds!! Even then though you still see spots!!

Cant' wait to fire mine up.. I gotta wait for a heatsink to come in!!! argh!

Ok I'm going downstairs to mount my Cree on a heatsink for testing. CPF is keeping me from modding!

matrixshaman said:

In my rush to see what the Cree XR-E had I decided to throw it across a well used Surefire CR123 battery directly. Just a touch for a split second to see what she has. Have you ever started a weld with a Mig welder but forgot to pull your helmet down? That's really what this experience reminded me of as I was close in to the LED to touch some fine point V.M leads to the small contacts (which were hooked up to the CR123). I counted on probably an Ohm or two for the leads so no resistor. I'm still seeing SPOTS.... These LED's are truly BRIGHT. So put on your shades or welding goggles before firing one up You just may need it.

Click to expand...

My experience was quite the opposite. The XR-E I hooked up to a 123 was not brighter than the Lux I was comparing it to (same setup, just wires, no opticalware; I did wall and ceiling bounce comparisons). I'm still trying to figure out what the deal is. With all the hype building around these new LED's I was really expecting something spectacular. Prepare yourselves to be disappointed (maybe).

I hear you IH - I've gotten too sucked in here lately As they say 'Step away from the Computer....' Computers - also known as the Black Hole of Time

matrix: Yeah never let a computer know your'e in a hurry!

greenpunk: perhaps you'res has a higher VF and wasn't getting much current.

greenLED - hmmmm - that's the first I've seen any indication of less than spectacular but I wonder a couple things. If you were direct driving a Lux off a battery and that Lux had a considerably low Vf is it possible it might have been brighter as it was being drastically overdriven? Is it possible the XR-E just happen to have a higher Vf? Did you switch back and forth between the LED's a couple times ? I ask that wondering if it is possible the battery was nearing a dropoff point such that the first test depleted it enough that the second LED was left with only a little current. Having the correct voltage input for a particular LED as I understand it is fairly critical to it running at full brightness. I'm sure these are all things you know well but I'm just looking for some logic behind your results. Hopefully more testing or getting it in some optics may produce better results.

Darn - did it again. I just got the old greenish LED pulled out of my Longbow capsule and laid the Cree in there - it sat on the wires that were exposed just right to catch the voltage from where the previous emitter had been. Flash! Fortunately I was squinting a bit more as I expected it this time but still super bright. I put in my other Longbow capsule with nothing on it - bare LED and it seems bright in this bare mode but really no comparison. Now if I only had some AA epoxy I'd have a LongboXR-E. The Cree sat at just about the same height after I took out just enough of the black stuff to see the wires and get out the old emitter. It looks good to go with just a little soldering and some AA I think. I'm not sure what LED was in this but the open circuit voltage on this Longbow driver with no LED was 5.53 volts. I don't know if that's going to be too high but I don't believe these Longbow's were being driven very hard current wise.

careful no load on some drivers will make them go poof!

I had wondered that but fortunately no magic smoke has escaped yet and it's still working. I don't think there is any place locally I can find any artic alumina so I'm trying to think of something else to put under the emitter in this little crater I have before soldering in the Cree. Or I'll wait and order some if needed. But it's a real tease at the moment as I can almost get the LB optic over this without even soldering the Cree as it will come on just laying on top the contact points. I know I could not run it more than a second that way without probable heat troubles but it would be nice to see how the optic does on this. I've also got a Longbow reflector I can try with this setup if the optic doesn't look good.

if just using thermal grease, then any computer shop should have some or radiosnatch. It may not be as good, but will work just fine.

Permatex anti-seize lubricant (the kind made with powdered aluminum) makes a pretty decent substitute for thermal grease - It's cheap, and available at most hardware and auto parts stores.

IsaacHayes said:

Hmm. You know it is a good idea to bring my sunglasses down with me when I mod.

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Yep, I regularly do that already, specially when you are testing on the bench supply

Will

heck my Oakley sunglasses cant block out my surefires i still see spots good thing i got a 200 dollar miller welding helment with auto shading

There was a cute cartoon in a magazine. Sign on the door says "Solar Cell Research" and on the work bench is a little cell hooked up to welding leads and the guy has just slagged a 6" piece of pipe using it.

A guy in a suit is walking in on this with the caption "So what is all this about a breakthrough?".

I can image the same thing for LEDs. All the researchers standing around with welding helmets on to test the new LED.

my 1x a19 xr is just about like my lux lottery win U-2, on high thats all i got to say about it, other the my light meter says the same thing ,it and the u-2 are the same, or damn close in my eyes.

Reminds me of my days as a welderer