Overdriving Lux3 : how many mA is "safe"?

Overdriving Lux3 : how many mA is \"safe\"?

I've been wondering about this for a while. I'm planning to use a Lux3 on a 6V alkaline or 4.8V NiMH (realistically, NiMH puts out more like 5.2V! At least until you've run them down quite a lot.).

How many mA would you consider a realistic figure to drive a Lux3 at for maximum brightness? LumiLEDs says 1000mA absolute max, but I read so many stories about people living dangerously with DD'ed Lux3s at 1.5 amps and then some. Kinda hard to make up my mind whether I should play by the rules and stick to the "spec" or give the Lux3 an opportunity to be everything it can be (including roasted /ubbthreads/images/graemlins/banghead.gif)

Re: Overdriving Lux3 : how many mA is \"safe\"?

Heat is what kills LEDs - including Luxeons.
If your heatsink is large and effective, you can get away with pumping 1,500mA into one of those things like some of the modifiers ("modders") do.

Re: Overdriving Lux3 : how many mA is \"safe\"?

craig how far can ya go with that.can ya go even figer if ya keep led cool. ive been toying with some ideas.

Re: Overdriving Lux3 : how many mA is \"safe\"?

You will encounter several problems when exceeding 1000ma (1 amp).

1) The temperature of the semiconductor junction will excced design limits, leading to early death of the LED. This death may be at 10 hours or it may be at 1000 hours, but it will be faster than normal.

2) The LED will dim quicker. The excess heat will cause the phosphor to break down, making the light dimmer quicker.

3) The heat management will become critical. At 100ma, you do not need a heat sink. At 350ma you need a metal surface to help disipate the heat. At 700ma you need a heat sink. At 1000 ma you need a good heat sink and moving air or other method to remove the heat from the heat sink.

4) At some point, no matter how good your heat sink, the hair-like wires that connect to the LED's die will melt apart. The exact amount of current that causes this will vary from LED to LED.

5) The LED gets less efficient as the current (and temperature) rise above the design maximums. Running at 1500 ma will not be 1.5 times the light of 1000 ma.

So if you keep it to less than 1.5 amps you'll probably have a real screamer that will last for many hours. It won't be any better than a bright incan bulb, and will be much more expensive, but the "wow" factor is there. It will not be more reliable either.

Daniel

Re: Overdriving Lux3 : how many mA is \"safe\"?

Yea what Daniel said!

Laws of deminishing returns apply here. I would rather have a light run 10%-20% under than 10%-20% over. although I'm sure i could see the difference on a wall, it wouldn't be enough to make a real life difference to me. I've popped my share of LED's.

GregR

Re: Overdriving Lux3 : how many mA is \"safe\"?

lol i want over

Re: Overdriving Lux3 : how many mA is \"safe\"?

I'm planning to use the Hotlips in the OAD body, that should take care of some of the heat issues. I'm actually trying to decide whether I should use a 1 ohm or 1.2 ohm resistor, while trying to maximize light output. I'm aware that regulation is the way to fly for sustained light output, but I'm choosing to go with the resistor route.

Preliminary calculations indicate that 1 ohm will give me ~1167mA, and 1.2 will give me 1050mA on fresh cells. That, plus the battery falloff should quickly bring the current under the 1 amp spec. Actually, it falls a lot. For most of the LED's life it will be driven way under spec.

I'd like decent LED life, maybe not the 20000 hours quoted by Lux3 datasheets but 1000 hours would be good. Think I'll risk 10% over for short periods of time /ubbthreads/images/graemlins/smile.gif

Re: Overdriving Lux3 : how many mA is \"safe\"?

You'll need a resistor or circuit. 6v is too much, and on NiMH it will fry quickly. NiMH doesn't have a voltage drop like alks do under load. My luxIII 3C DD pulls 1.5amps and quickly falls to 1.2amps steady for a while on fresh alks.

One thing I've noticed is luxIII's don't seem to gain much brightness in overdriving as do 5W's. Well I take that back, I haven't overdriven my 5w green yet, infact with fresh alkalines it's only 600something ma draw, but ungodly bright. At 400ma my 5w green blows away my luxIII at 1000ma!

But I did not notice any significant increase in brightness from 1.5am to 1amp on my luxIII's. In fact 800ma is pretty close to 1amp in brightness unless your're watching a light meter...

I'm starting to like 5W's as my favorite again. They are so bright even way underdriven. I can't stare at the reflection from a white wall!! I can't wait until I buy a recharger and put my NiMH in there, to get over 1amp of power to it!! muahha

Re: Overdriving Lux3 : how many mA is \"safe\"?

i like 5 watts but ive heard they are not throwers.and i adore throw

Re: Overdriving Lux3 : how many mA is \"safe\"?

Another thing, heat is a main factor in what harms leds, but also current is the other one that degrades. So even if you could super chill it, and run a lot of current, it still would degrade faster than if run at specs. (in theory of course)

Re: Overdriving Lux3 : how many mA is \"safe\"?

Thanks, being able to run at 800mA will greatly expand the acceptable operating range of the light I plan to build. My Excel spreadsheet (just simple calculations, doesn't take into account increasing battery resistance over lifecycle, only falling voltage) indicates that I might best be served with a 1 ohm 2W. Of course, I guess I'll find out only AFTER I build it /ubbthreads/images/graemlins/tongue.gif

How are you driving your 5Ws? It takes close to 7V to light them up, something which will not be available to me on 4 D cells, alkaline or NiMH.

Re: Overdriving Lux3 : how many mA is \"safe\"?

raggie, my 5w green is a thrower! hehe. it's got a wider beam but goes just as far as my white luxIII 3C mag. I don't know how a 5w white would do though... I'm almost going for wider beams now, I don't like the "tunnel" vision effect. It's nice to spot something far away, but I don't do that very often, unless I was sniping something at night! I'm going to build my tri-lens w/3LuxIII's next, hopefully it will be wide beam, but still bright to shine far and I'll be a happy man! Nothing gets someone's attention like lighting up a huge area with bright white light!

I love 5W's and how much light they put out, but man I wish there were easier ways to power them. 6AA's go by too fast. Perhaps a 3D mag w/4C NiMH and a boost circuit would be the best easiest solution!

Back on topic: either a 1 ohm or 1.2 should be fine. Just check it before you finalize the light to make sure it is indeed at the right current you want.

Re: Overdriving Lux3 : how many mA is \"safe\"?

Notice how Lumileds leans slightly towards 700mA in the spec sheets on the LuxIII - and how much longer the emitter lasts when driven at 700.

Personally, I don't understand the appeal of direct-driving LEDs. If you're going to hook up the emitter to batteries with some nominal resistant inline, you're just displacing an incadescent bulb with something more expensive...

...but that's a begged question.

Re: Overdriving Lux3 : how many mA is \"safe\"?

My 5w green is driven off of 6AA batts, but I have a .5 ohm 5w resistor in there for safety, so alks aren't overdriving it so much. I plan to use NiMH which have a lower voltage (1.2v) but they deliver a ton of current so it should be close to an amp. I designed it for NiMH anyways because AA's don't hold much power, so recharable was the way to go.

Re: Overdriving Lux3 : how many mA is \"safe\"?

Just for fun, I took a 4-cell NiMH pack (5.4V fresh off the charger) and DD'ed my ONE WATT Q4H..

Warning: I do not recommend you do this unless you are prepared to sacrifice the Luxeon. The reason why I do it and I post about it is that others may spare their LEDs from such ABUSE /ubbthreads/images/graemlins/crazy.gif

I bet it hates me now, but I was trying to get some data to extrapolate about the nature of 3W Luxeons. There has been talk about S-bin Lux3s being Qs in disguise, and T-bins being Rs.

The DMM indicates a staggering 1.5 amps blasted through it for 30 seconds at a time, and the lumen output is just unbelievable. I did it a few times, and no angry blue color, which suggests process technology has improved to the point where these could easily have been 3W LEDs. I am aware that I should not count on it though, worst come to worst, I would probably use the LED's demise to order more. Still, I think it's done a heroic job. The light output is fantastic, I'd say it lights the room more effectively than my SF 6P. I just changed the cells in the 6P to boot!

The Q4H is still very much alive and kicking, probably because of the heatsinking I used. Thermalloy ThermalCote grease as the interface material between it and a 5W computer board chipset sink. The sink got nasty hot though, I'd say close to 50degC. But it is just *AMAZING* to see what these little beasts can do when you ask a little more.. actually, 5X overspec. I never had THAT kind of luck when overdriving computer parts.

Thanks to it, I now have an idea of how much a S-bin Lux3 may give me, that, and how hot it gets. Now I understand the need for *SERIOUS* heatsinking.

Now, the question is, S-bin or T-bin Luxeon 3? Or not get too hung up on the bin codes?

Re: Overdriving Lux3 : how many mA is \"safe\"?

I have 2 ledlenser v2 turbos with what were supposed to be 1 watt luxeons, scarfing down 1.3 - 1.6 amps from 3 500mah N cell www.battlepack.com nimh batteries. /ubbthreads/images/graemlins/icon15.gif /ubbthreads/images/graemlins/ooo.gif
A bit of overdrive with a lot of heatsinking should be A-O-K with it.

Re: Overdriving Lux3 : how many mA is \"safe\"?

I don't get this stuff. So am i living dangerously by using 2 AA 2300 mah NiMH batterys to run a VIP 2AA tube (which I don't have yet). Help.
Rich

Re: Overdriving Lux3 : how many mA is \"safe\"?

[ QUOTE ]
scrappy said:
I don't get this stuff. So am i living dangerously by using 2 AA 2300 mah NiMH batterys to run a VIP 2AA tube (which I don't have yet). Help.
Rich

[/ QUOTE ]

No, since that's what the 2AA tube was made for. It should be fine. Even on High it would not exceed maximum factory recommended spec.

Re: Overdriving Lux3 : how many mA is \"safe\"?

Mr. Bulk -- thats all I needed to know, ignore the pm. Thanks alot

Rich.

Re: Overdriving Lux3 : how many mA is \"safe\"?

This is why I've opted to go with incandescent xenon lights for longer throw applications.. LED lights just haven't reached the level (yet) to provide the brightness and throw for the longer distance outdoor applications with increased efficiency and LED life. Another few years yet. If I screw up and overdrive an LED and burn it out in a mod I'm out more money and it's more of a hassle then just changing a $5 surefire xenon bulb... and for short to medium range applications.. LED all the way.. bring up that modded arc ls. /ubbthreads/images/graemlins/smile.gif

With that said, there are some pretty good luxeon throwers out there, like the Electrolumens FT-3C