Luxeon Star VS Krypton: Luxeon WINS!!!

Just tried this:

Hooked up 2 LS(with optics) in series (and heatsinked additionally using 2 aluminum extrusions and thermal grease) and powered them directly by a fully-charged 8.4V Nimh. No resistors.

Guess what? In terms of sheer light output, the 2 LSs beat the crap out of:

- My Princeton Tec 40 using a KPR113 + Lithiums(!)

- A 12V/10W Osram decostar, also hooked up directly to the same 8.4V Nimh (yes, its underdriven, but just a case-in-point where efficiency is concerned)

- And yes - completely overwhelmed my twin-versalux.

I've NEVER seen so much light coming out of anything powered by a 9 Volt (or 8.4V rechargeable)battery before! I don't know if I'm harming my LSs, but they didn't get too hot to touch even after 5 mins. Just warm. I *do* know I'm overdriving 'cos of a change in light color(shifts towards blue). Has anyone else witnessed this? My PT40 will still throw farther, but at 50 feet, those 2 LSs win hands down for floodlighting.

Gotta admit - when I first got my bare LS emitter and hooked it up - Blah. It wasn't even brighter than 2 ganged Versalux 20-LED modules. How, I wondered miserably, could LEDs ever beat incandescents? I'd even posted a question earlier elsewhere about their efficiency, compared with halogens and the replies were not as optimistic as I had hoped. But my simple tests above have restored my faith! I'd encourage anyone to try them out and see if they get similar results. Wow - I'm still reeling...

How are you achieving the 8.4V NiMH? AA battery pack?

Nope. Just using a single 150mAh GP 8.4V NimH. Same form factor as a regular 9V battery. I know, runtime will suck, but I could always run a parallel config with 4, maybe even 5 more batteries to multiply runtime accordingly. I'm now trying a runtime test.

UPDATE: The twin LS even matched the 10W Osram halogen decostar when it was run at spec ie. 12V.

UPDATE:

Stopped the runtime test at 12 minutes because light output dipped to about 70% (not *by* 70%). Even at 70% brightness, the twin-LS was still casting crisp shadows at 50feet. Very plenty bright, but not incandescent crushing performance anymore.

All throughout, the heatsinks were cool enough to be touched against my lips. FYI, our ambient room temperature at night here is about 25-26 degrees celsius. The black finned aluminium heatsinks I used measure about 1.5"x1.5"x0.5". Just cheap silicone thermal grease was used to bridge the LSs to the heatsinks. For safety, the LSs were cooled by a desktop fan blowing at them from about 1 foot distance for the first 4 minutes of the runtime test. The rest of the test was conducted with the LSs in still air.

Will post pix soon.

Here are the pix of my test rig:

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by ake:

Eventhough the light from LS is much more evenly than the MAG, at distance (around more than 10-15m) MAG beats the hell out of the LS. Especially when focusing the beam on the MAG.
Ake<HR></BLOCKQUOTE>

You should try the Luxeon MagLite D cell mod; if you really want to compare the two, ditch the plastic lens and use the Mag reflector to focus a real nice spot from a Luxeon (also smooth, like no incandescent can). How about a four to five foot spot at 50 ft, and useable light out to 300+ feet. Driven at hight currents (500 - 700+ma) the Luxeon gets very bright. It also MUST be properly heatsinked, like you've done.

I've made many Mag mods, and they are really a decent replacement for an incandescent; for general use, a much better light source due to the color rendition and eveness of light, and quite bright.

Lambda,

I've seen your mods and I think they're fantastic. But they're still flashlights. I guess I did this little experiment in an effort to see if LEDs really could whoop (relatively) big-gun incandescent ***. That's why the 10W/12V Osram was there - its normally used in household/shopfront decorative or accent spotlights!

It was really nice to see the overall output of 2 overdriven luxeons, for most intents and purposes, match that of the Osram driven at spec. Each luxeon is supposed to put out the equivalent of about 1W of light, right? So 2 luxeons = about 2, maybe 3 watts equivalent, since they're overdriven. But thats still only less than a third of the Osram, which is rated at 10W, yet just as bright! Makes me drool to think what could be achieved with the up and coming 2W and 5W LEDs. *shudder*

I got a differrent result from a single LS VS 2D Maglight though.

I hooked up th LS/O with 2.7 ohm resistor and 3 fresh from the charger Maha AA 1550mAh NiMh vs the 2D Maglight with almost 4 years old D cells (barely use it).

Eventhough the light from LS is much more evenly than the MAG, at distance (around more than 10-15m) MAG beats the hell out of the LS. Especially when focusing the beam on the MAG.

I also check the runtime of LS with 3 AA cells by left it run over night. Start from 10:30pm. I turn it off aound 7:30am next morning. The light 's still usable eventhough much dimmer. When I got home that evening I hook it up again to see how long it can go. Only about an hour past, it's much dimmer, even dimmer than my Infinity.
Interestingly, next day I measure the voltage of battery w/o load, and still get 3.4V! (almost 1.1V left each) Still not sure why it can't drive the LS any more.. Maybe it just runs out off juice over the load.

So I guess my total usable run time from 3AA NiMh is about 10hrs. Not so bad for driving it straight w/o the DCD/DC convertor.

Ake

Interesting, ake. I normally tend not to compare focusing incandescent flashlights with LEDs in general because they always win in terms of perceived brightness and actual throw, thanks to that very concentrated hotspot.

To be fair, whenever I eyeball compare any LED light to an incandescent, I try to find a way to normalize things like focus as much as possible, like by removing the focusing heads and reflectors/collimators for both types of lights, or adjusting the incandescent's beam focus to a medium-setting to mimic the LS+optics.

I am somewhat confused here about the Osram that you were comparing to the LS. Was it being run at full power or at reduced power?

When you attempted to run the lamp with the 8.4V 150mAh battery, I am certain that the lamp was tremendously underdriven; as a rough estimate the battery voltage was probably sucked down to about 7V by the current, the power consumption of the lamp would be around 4W, and the light output would be about 14% of nominal. (These numbers are from some rule of thumb equations for halogen lamps.)

Elsewhere you reported that you had run the lamp at the full rated 12V, and I was wondering what sort of power supply you used to get the 12V.

Regards,
Jonathan Edelson

Jonathan, wonder no more. See my latest post:
http://www.candlepowerforums.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=3&t=001986

The Osram was driven under 2 conditions:
1) 8.4V NiMH (same as the Luxeons)
2) 12V (via a regulated AC-to-DC power supply - 2.5amps max)

Pix of the power supply I used are in that new post. Its just a common general purpose AC/DC regulated multi-voltage power supply for CD players, camcorders...etc. I was simply trying to illustrate(to myself primarily) the efficiency of LEDs.

Granted, not the best choice, but all I had available at the time, and definitely enough to get an idea of the potential of the Luxeons relative to similarly sized halogen lighting appliances.

Are you trying out something similar? I'm keen to compare notes


cheers...