how hard can you drive a LV? (fixed!)

I just finished my third "D" size M*g LED project. The first two were U bin LIII in DD (L voltage bin) which drive anywhere from 700-1000mA depending on the type of battery (11000mAH NiMH are best!). I am using the O-sinks, Artic Alumina epoxy for the LED and a light coat of Artic Alumina (non-epoxy) between the O-sink and the M*g body.

This 3rd one is a V bin (T voltage bin) LV also DD but from 6 AA NiMH (2200mAH) using a 6AA-2D adapter (from CPF's, of course!) in a Black 2D body with an UCL lens (what else!).

When I first turned it on was like: holly cow! - this thing is REALLY bright /ubbthreads/images/graemlins/buttrock.gif. I have a nice "W" bin with a 1000mA downboy in a M4 with a Turbo Head and the LED adaptor and a KL6 modded for 1A and this "V" bin simply blows them away easily.

Worrying that something might be out of wack I decided to then measure the voltage/current reaching the LED: voltage at the LED was right around 6.9-7.0 volts and the current was about 1650-1700mA!. No wonder this thing was so bright - I am overdriving the heck out of it!. 7 volts times 1.7A is 11.9 watts !!! /ubbthreads/images/graemlins/naughty.gif

Now, from all of my reading on the Space Needle II (SNII), the SNII typically uses a a "W" or "X" bin LV direct driven by 3 CR123 cells, which is a nominal 9 volts or so. That should be even higher voltage and current (I though), so I felt safe with the 6xAA's until I saw the 1.7A draw.

No-load voltage at my pack was right around 8volts so I was not expecting this high current value. I did notice the body of the M*g near the head getting warm after 10-20 seconds of use, but I am afraid of running longer times at this point /ubbthreads/images/graemlins/str.gif

So how much current does the SNII draws on fresh cells? Why is my lower voltage pack delivering such a high current?

Am I about to kill my "V" LV by keeping it on a 1.7A draw? /ubbthreads/images/graemlins/mecry.gif

Will

Re: how hard can you drive LV?

[ QUOTE ]

Am I about to kill my "V" LV by keeping it on a 1.7A draw?


[/ QUOTE ]

Yep. Expect the Vf to drop too, causing current to easily exceed 2A.

You are definitely exceeding the maximum junction temperature. Add some resistance, or better yet, a regulator of some sort.

Personally, I wouldn't exceed 1A on a Luxeon V (both of my Lux V Mags have 750mA current regulators)

Re: how hard can you drive LV?

That's what I though /ubbthreads/images/graemlins/crazy.gif

Now, how much current does the SNII draw?

Will

Re: how hard can you drive LV?

It depends on the Vf of the Lux, but I think it was supposed to be around 1.7A. Though, no two SNIIs will be the same. Nor will things be the same a few 10s of hours down the road.

Re: how hard can you drive LV?

I thought on average SN was 1.2amp. I could be wrong though... Mr-X was driven at 1.5amp.

Re: how hard can you drive LV?

So if the SNII's and MrX's were around 1.5-1.7 amps, then although hard, I am not driving mine harder than others, right?

Do the SNII's or MrX's use a different heat sink perhaps?

Will

Re: how hard can you drive LV?

I would not exceed 1.5amps. Anything more than that it is not making any more light just more heat. Wasted power and harder on the LED. And it might be making less light if it gets too hot.

The 5watts have even less lifespan when driven at normal levels than other luxeons.

Re: how hard can you drive LV?

IsaacHayes,

Thanks. I will use a regulator then - I certainly like how bright this light is but don't want to kill it just yet /ubbthreads/images/graemlins/wink.gif

Will

Re: how hard can you drive LV?

I have a U3U in a 2D mag which I originally had powered by 6AA's in 2x3 to D adapters.
In this config, with cells freshly charged the emitter used to draw 850ma.

Changed battery carriers to one of fivemega's 6AA to 2D holders (Beautiful piece of work BTW). Charged the cells and fired it up. 2500ma !!! /ubbthreads/images/graemlins/ooo.gif /ubbthreads/images/graemlins/ooo.gif /ubbthreads/images/graemlins/ooo.gif
Immediately removed battery pack and drained the freshness off with a car headlamp bulb for a minute or so.

Still it draws 1700ma. But WOW - it's impressive. Thumps out a wall of light similar to my TSP.

Don't use it for extended periods of time, sufficient to get the thing too warm. It's a great show piece and talking point as is.

I'm gonna keep on spanking it at this level until it dies - hopefully by then Lumileds will have their 1400ma capable LuxIII's available which i'll drive via a step-down converter.
Should be like a white laser in a maglite. /ubbthreads/images/graemlins/grin.gif

Tim

Re: how hard can you drive LV?

I'm surprised you didn't melt the bond wires at 2.5amps!!! must have been very breif!!

Re: how hard can you drive LV?

Yes.. Very brief.
That was the first and only time I ran that voltage, routed through my DVM. Only on long enough for me to do a 'double take' at the reading, then disconnect immediately, counting my lucky stars I didn't see smoke /ubbthreads/images/graemlins/grin.gif

Tim

Re: how hard can you drive LV?

besides voltage to luxeon, you also need to factor potential amps to delivered to luxeon.

when direct driving there is almost no burden in your circuit. Luxeon is only device limiting current.

beware of using large li-ion cells like 2x 18650's. voltage may be within limits, but potenial current from 2x 18650 could be 50+ amps.

will kill your five watt very quickly.

Re: how hard can you drive LV?

The perfect setup for a Lux V like you are hoping to drive with a 3 x 123 (short of a true current regulator) is with approx. 2 ohm resistor in series. REALLY bright, good run time, and the Lux V will actually last longer than the batteries.

If you look around for the proper resistor ( using P = IxIxR = 2 watts), these are usually fairly large. I have some specially made, aerospace grade, 10 + watt resistors in SMT 1206 that I were made for this purpose. I had to have way more than I need made to get these special built.

A word of caution, 1206 is pretty small, and many people are frightened off by their small size (really about the size of a Lux lead base). If you are interested in some, send me a PM.

Harry

Re: how hard can you drive LV?

OK I "fixed" my 5watt 2D monster /ubbthreads/images/graemlins/blush.gif. I added a 0.2-0.3Ohm 1watt resistor in series and got about 1.4A max now /ubbthreads/images/graemlins/clap.gif

Here are my before values:
Voltage at LED: approx 7-7.1V
Current at LED: approx 1.7A - yeah, too high /ubbthreads/images/graemlins/whoopin.gif

and after values:
Voltage at LED: approx 7V
Current at LED: approx 1.38A - much better /ubbthreads/images/graemlins/grinser2.gif
Voltage at resistor: 0.39V (power at resistor approx 1/2 watt - well within the 1watt rating)

Still bright, but not as hot/warm as before. Still brighter than my M4 & Turbo Head and 5W "W" bin /ubbthreads/images/graemlins/grin.gif

Thanks to all for the guidance and suggestions /ubbthreads/images/graemlins/happy14.gif

Will

Re: how hard can you drive LV?

Just keep in mind the Vf of the luxeon will drop over time and stabalize at a lower number, so it could end up pulling more in the future. Just something to watch out for!

Re: how hard can you drive LV?

Thanks dude - you have been most helpful. I will keep an eye on it and check the current from time to time /ubbthreads/images/graemlins/grin.gif

Will

Re: how hard can you drive LV?

No problem! /ubbthreads/images/graemlins/smile.gif

Re: how hard can you drive LV?

Gee, I felt guilty/ubbthreads/images/graemlins/evilgrin07.gifbecause I am beating up my Lux V's with one amp regulators. You guys know the max rated current on that Lux V is 750mA, right?

Re: how hard can you drive LV?

Yes, but why live in the "safe" zone /ubbthreads/images/graemlins/naughty.gif

Will