Can I run a Lux III on one pila 168s?

I am not sure if this is the right forum for this, but I couldn't really think where to ask this. I am wondering if I could run a t rank lux III on one pila 168s direct drive. It should work in theory as the voltage on the pila is almost exactly what the lux III wants, but I am not sure about the current. Would it burn up the led? Thanks! /ubbthreads/images/graemlins/grin.gif

I suspect you really want the 'electronics' forum?

Anyway, yes, it could no doubt be made to work. FWIW, LEDs are best driven in terms of current, not voltage. DD, while 'rock simple' has some serious drawbacks.

But, in as much as Vf matches the source at the current you want, yes it works.

Doug Owen

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bwcaw said:
I am not sure if this is the right forum for this, but I couldn't really think where to ask this. I am wondering if I could run a t rank lux III on one pila 168s direct drive. It should work in theory as the voltage on the pila is almost exactly what the lux III wants, but I am not sure about the current. Would it burn up the led? Thanks! /ubbthreads/images/graemlins/grin.gif

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It would really help to know what the forward voltage of your particular LED is. -That 4th letter is the important one. As in TWOK..in this example the forward voltage is around 3.6 -I don't recall exactly, but H,J,K,L,M,N represent higher forward voltages ascending the letters of the alphabet.

In your case a higher forward voltage (like L or M) is very desirable, so that a freshly charged Li-ion isn't pushing so much amperage into the Luxeon. I personally prefer 700-900mA.

In my particular case for instance, the K rated Lux3 that I'm using will draw 1.2A if I put a freshly charged (4.2v) cell. A little too much for my liking.

YMMV

Thanks guys. What harm will be done if I overdrive it? Will it shorten the life of the led significantly? And it is a TVOK Lux III I am running. BTW I looked on my ab21 and it says forward voltage for a K bin luxeon is 3.5 to 3.75v at 700-1000ma. So it is overdriving the led slightly. But leds are only about $20, so it is easy enough to replace even if it only lasts a couple hundred hours.

bwcaw,

I getting ready to build just such a light. vcal is right on with his data. I also get right at 1.2A with a fresh Pila 168S. I drops quickly though. The good thing about the Pila though, is that it doesn't drop voltage as it drains, like 123's do. You'll have good, bright useable light until the batt's protection circuit kicks in.

If you'd like, you could go ahead and build it and see what happens, or you could wait for me and see if I cook anything. The last time I tried this, it was with a Q3J and that thing self destructed in about 3 hours, but I was using a KL1 as a host.

The only thing you'll gradually lose is the superior brightness.

I'm guessing here..over a few hundreds of hours...
Lumileds calls that phenomenon "luminance maintenance".-or lack thereof.. /ubbthreads/images/graemlins/tongue.gif

Done it! Not a problem at all. Heatsink it properly and you'll be fine. /ubbthreads/images/graemlins/smile.gif

Chop, I only get about 1.1A fresh off the charger on my TWAK. Still pretty close to yours. /ubbthreads/images/graemlins/smile.gif

Well, here is my light assembled: It seems to work quite well with the pila in there. It is a k bin led, so hopefully it will last a little longer than 3 hours! But I am hopefully going to get some m bin III's and those should be about perfect. I also posted a thread about my light here: link Thanks for your input guys! /ubbthreads/images/graemlins/grin.gif

You know, I've often wondered why it is that I even bother with circuits. I just took delivery of half a dozen BadBoys today. I got them to use with Pilas in 3W lights. I've also been discussing the properties of Pilas with CM via PM lately. It seems that CM has confimed what I have seen in practice over the past few months. The Pilas (li-ion rechargeables) are current supplying beasts. Even if you ran a DD light from fresh off of the charger to safety shut down, it should all be at a level of light that is pretty darned bright. The Pilas don't drop voltage as they drain like other batts do and they can be topped off at will. The only downside to a Pila DD light is that you can't use 123's in a pinch.

Yes, that is kinda a bummer if you run your pila down and don't have a spare. But I think that is compensated by the ease of assembly and the simplicity of it. After all, you are baisically taking another thing out of the loop that could possibly fail. (this is nothing against Waynes' boards, but any electronic device is susceptible to failure esp one assembled by me! )

bwcaw,

I know what you mean. I don't know how many BadBoys I've gone through, but I have four dead ones sitting on my bench right now. This is a small percentage of the total that I've used, but it does happen.

I still have 6 BB's to use up, but I'm gonna build a DD soon.