LED voltage required-

I thought that white LED required 3V to run, such as the MJLED running off 2 AA cells on my miniM-G. But the little pocket lights like Photon or the one's KevinL sells on CPF runs on two 3V cells and there are no circuits at all. They are driven directly by two button cells for 6V.

What is correct voltage to run white LED. Are they all spec. differently?

This is all a little new to me. /ubbthreads/images/graemlins/help.gif /ubbthreads/images/graemlins/help.gif

Yes, the voltages required are a little higher. This is where "binning" comes into play. Binning is the 4 character code used with luxeons. For the white Luxeons the first character is the output in lumens. The 2nd and 3rd chars are for color tint, and the last code is for the vf of the lamp.

common vf values
lux 3
H 3.03-3.27
J 3.27-3.51
K 3.51-3.75
L 3.75-3.99
M 3.99-4.23

Lux V
R 5.43-5.91
S 5.91-6.39
T 6.39-6.87
U 6.87-7.35

hope this helps!
/ubbthreads/images/graemlins/grin.gif

the photons might have 6v of battery, but check the voltage when the led is on. the draw on the tiny batteries is to high to keep 6v going to the led (cept for mabey a milisecond)
basically its the current (the flow) that goes through it.

the blue & white leds are higher voltage than the red red ornage and yellow .
like the white leds are (basically) a 3.6 type of voltage
and the red leds are (basically) a 2.2 type of voltage

the luxV has series configuration, so 2x3.6 (basically)

current is more important when totally controlling what is going to them, but the above is basically what i learned about the voltage stuff.

if you take a "photon" led out, and run it on 6V of D cells it wont run for long

although the led electronics are very highly voltage critical (the "junction" operates at specific voltages)
white 5mm leds will put out some sort of light at 3v.

...and current too!
This stuff is still hazy to me as well as I've neglected learning the math and electrical theory yet.
I was gonna' make a post about this, but since Nell beat me to it, I'll ask here and include another related question or two. Hopefully this isn't hijacking, but adding to Nell's questions.
Take the MJLED for example. Vf of 3V - 3.6V, and it's happy at around 100 ma. 130 ma is overdriving it. I've tried using 1 AA alky and obviously it doesn't light up at all. I also tried a 14500 with no resistor and almost killed the MJ in under 10 seconds. It's now permanently damaged. This is basically a 3.6V battery, but comes hot off the charger at more like 4.1 - 4.2V depending on your charger. Being a li-ion, it can dump a lot of current.
So all this leads to some basic questions:
What does all this voltage and current stuff mean in general? I've seen analogies used to explain it and all, but still having trouble making all the connections (pun not intended this time).
What's worse (or better) for frying an LED... too much voltage or current?
What are the formulae to calculate some of these basic things, so the EE newbies (like me) know what resistors to get when we run down to Radio Shack?
I don't have a DMM or anything (yet). We can figure out on paper what resistors to use without equipment, as long as one knows all pertinent properties of both the LED and battery being used, right?
Thanks to all who help answer this stuff.

An informative thread about what exactly Vf is:

http://www.candlepowerforums.com/ubbthreads/showflat.php?Cat=&Number=898309&page=&view=&sb=5&o=&vc=1


More info about Vf, resistors, etc.

http://www.candlepowerforums.com/ubbthreads/showflat.php?Cat=&Number=838615&page=&view=&sb=5&o=&vc=1


Maybe I should write a book or something /ubbthreads/images/graemlins/tongue.gif

Evan - thanks to those two threads of yours, I just took a couple steps forward in understanding this stuff. You should write a book. /ubbthreads/images/graemlins/bowdown.gif
Of course, you've now opened yourself to being invited to the thread I'm about to create, since I need some more pieces of the puzzle.