LuxIII or LuxV, NGBB917 or ???

I'm designing a mod for one of my favourite flashlights and I've kind of hit several snags. It has a 6V power source which can be reduced to 3V if necessary.

Firstly, the NexGen stuff from Sandwich Shoppe says max Vout from the module is 6V or Vf, whichever is lower. But electrical characteristics of LuxV, according to the LumiLEDs datasheet, says that at 700mA, typical Vf is already 6.8V.

Does it mean that if I hook up a LuxV to a NGBB917, I will not achieve 917mA in to the Led until the LED heats up and its I/V characteristics change? (Sort of like thermal runaway begins but is halted at 917mA.)

Will I be overpowering the NGBB module by using 4 C-cell alkalines, and can the module handle it without damage or degradation?

Also, I'm deciding whether to use LuxV or LuxIII. I naturally want this to be as bright as possible. I'm making provision to swap out the emitter when the luminous flux degrades. The focusing and beam spread is not under my control, as I've already decided to use the 2deg optics. Heat dissipation is probably as good as it gets with a solid Al head and cooling fins, but will be the same regardless of emitter used.

Looking at 700mA specs, the typical luminous flux of LuxV is twice that of LuxIII. Even at 1A going in to the LuxIII, a 700mA LuxV is still 1/3 brighter and the nominal specs suggest that the LuxV still has slightly better luminous flux efficiency (lumens/watt). (Am I right?) However, we all know that heat generation will skew those specs quite a great deal.

So, at nominal 700mA, which package runs hotter? What about at 917mA?
Will the amount of heat generated result in the relative efficiencies to change such that the LuxIII is now more efficient than the LuxV? Remember that the heatsink does not change.

And in your opinion, is the extra cost of the LuxV over the LuxIII worth it for the extra brightness? What about when the severely reduced lifespan (500hrs vs 50,000hrs to 50% brightness) is considered?

Thanks.

Argh... Posted right on the change to midnight, so it won't so up as a current post. /ubbthreads/images/graemlins/banghead.gif /ubbthreads/images/graemlins/banghead.gif /ubbthreads/images/graemlins/banghead.gif

So.... /ubbthreads/images/graemlins/bumpit.gif /ubbthreads/images/graemlins/grin.gif

Hi, Steelwolf!

As a friendly reminder--IIRC, in McGizmo's site about Adeph FAQ, it had stated that it was a no go for Lux V with BB NG...but it should be ok with BB. So you might want to investigate more before making that purchase.

At one time, I did make a BBNG 1A with a power source of 2 x 123 (over 6V if freshed) to power a Lux III--although some might say it is ok because of the voltage sag and it is bright, it is indeed at the edge of overdriving/buring the lux(it does get warm rather quickly after 10+ minutes).

But at 3.7v(Pila), BBNG 1A with a Lux III J bin hardly generate any heat in a pelican M6 mod.

Given the current and optics, I would say that the Lux III probably will give more intense spot beam(more throw) vs Lux V will give more light, but the hotspot will not be as intensed.

The difference is due to the construction of the Lux led, and I think you will be the best judge as what will suit your need more--more throw/intense hotspot or more light but less intense hotspot.

Btw, what host do you plan to use for the convertor/Lux? That might help to determine whether it will be enough material/heatsink for the combo.(for ex, one might well more warmth with a Minimag vs Mag 2D for BBNG 750 Lux III mod)

Good luck! /ubbthreads/images/graemlins/smile.gif

the luxV from my understanding is a series Pair.
so when you compare the AMPs, you gotta remember the volts is X2. so you need about 7V to get a good drive to the thing. if you want to make Output vs power comparisons, it should be based on calculating the Watts (total power) you will run it at.

I think the life would be extended on a V , if it was underdriven.

a current controlling curcuit can sometimes have higher VOLTAGES applied to it at that driver current.
like i ran a trio of 1w and a quad of 1w off of that slim puck thing when i had 13V of input.

there is 1A puck driver things, i dont know diddley about them, but because i am not seeing big huge outputs on the ones that people discuss, it would be good to point out this buck puck thing here.

http://www.ledsupply.com/led-drivers.html
i think most of this stuff dont fit in leetel flashlights.

you aint gonna get doodly thermal runaway voltage lowering capacity, look at the charts, this thermal change is not wild, its minor. and its based (often) on bench supplies, not batteries that would get lower under that kinda pressure.

stick in 3 ni-mhys and a dummy, and run a 3W easy.

2X3W would be at least as bright, and would last long.

anyways those are some ideas, and a poor start on some of your questions.

OK, so maybe the NexGen won't work. I'm checking out the older BB. I'm told that they aren't as efficient though.

The mod is for a dive light. I kinda like the tight beam that you get from a Carclo 50mm 2deg optic. According to the pictures in the review, there doesn't seem to be much difference to the beam spread regardless of whether you use a single-die LED or a 4-die LED. Of course, using the 5W gives a squarish hotspot. But it still looks tight and intense, so I don't think the beam spread really differs.

But I want it bright, hence my concern with total lumens, and the LuxV seems to win. I was comparing lumens/watt. (All quoted values are nominal and as stated in the pdfs from lumileds.)

LuxIII: 1A x 3.9V = 3.9W for 80 lumens (20.51lumens/watt)
LuxV: 0.7A x 6.84V = 4.8W for 120 lumens (25 lumens/watt)

So the LuxV seems more efficient. Of course, I'm willing to go with a LuxIII if necessary, such as needing to find a suitable driver. BTW, are there other drivers available that power a LuxV from 6V input? What about from 12V?

Space constraints suggest that I use only 1 emitter. But I'm basically designing the entire head, so I could bump up the size to fit more emitters, but then it would look so inelegant. This is also the reason why I say dissipation of heat is not a major concern as there should be more than enough material and surface area. The only question then is concentration of heat. It is obvious that the LuxV, being 4 dies in 1 package would have a very high concentration of heat. Spread out the same 4 dies over the normal space it would take to put 4 LuxIII and it seems obvious that the generated heat is more spread out. Junction temperatures should be lower, especially since the LuxIII is supposed to have a package that transfers heat better.

So, is the LuxIII package more efficient than the LuxV (after thermal derating is considered)? If not, are there drivers suitable to power a LuxV with 6V input?

Or else, what reflector or optic can I use so that I can fit 3 LuxIII emitters on the head without it looking like and oversized monster and yet get a beam almost as tight as the Carclo 2deg?