Preview of updated K2: testing of "new" K2 sample

[mofiki]

I got my K2's form Future also. No bin codes on mine either. Something else I noticed though, product must be mounted within a certain period of time upon openning the bag. What!... Why?

 

[SemiMan]

I got my K2's form Future also. No bin codes on mine either. Something else I noticed though, product must be mounted within a certain period of time upon openning the bag. What!... Why?

Standard procedure for surface mount LEDS. You have to run them through a reflow oven within a given amount of time from opening the moisture sealed bag or rebake them to get the moisture out. If you order from one of the large distributors, they will follow the proper handling procedures. You tend not to get that from the smaller dealers.

 

[blesbok]

I just received six K2 -0180s and tested one for Vf at 10mA increments up to 1A. These were labeled SVNG bin (180 lumen, VN color, 3.75-3.99V). This sample measured 3.85V @ 1A, just below the middle of the specified range.

 

[mofiki]

I've got my tripple K2 light pod lit right now. I have it hooked up to a BK Precisson regulated power supply with no resistors or driver. I'm pushing exactly 500mA into it and my voltage meter is showing a wee bit under 10v DC. The amount of light is wowing, no way to measure actual lumens, but I'm pleased. I really don't see the need to burn this thing any brighter. It's been running for about twenty minutes and it's lightly warm. I made a donut shaped aluminum heat sink appoximately 1 5/8" diameter by 3/8" thick which fits perfectly inside aluminum tubing and I got a tripple lense from Future. The color makes this light seem brighter than the tripple Cree XR-E I built a few weeks ago. I guess it's because it's more of a cool white and the Cree's seem more warm. I'm going to get myself some more equipment to measure the light and other tools for Christmas.

 

[Gryloc]

Here are my updated findings. I also updated/edited my original post, which this post is similar to.

LXK2-PWC4-0180

Current   Voltage
  (mA)      (V)             <Update:>
         #1       #2       #3       #4
  50   3.149    3.089    3.055    2.88
 100   3.28     3.222    3.184    3.011
 150   3.38     3.30     3.26     3.102
 200   3.456    3.37     3.33     3.176
 250   3.52     3.42     3.38     3.236
 300   3.57     3.48     3.44     3.27
 350   3.62     3.52     3.48     3.31
 400   3.66     3.56     3.53     3.35  
 450   3.70     3.60     3.56     3.39 
 500   3.73     3.63     3.60     3.42
 600   3.79     3.70     3.67     3.48
 700   3.84     3.77     3.73     3.53  
 800   3.90     3.82     3.78     3.58  
 900   3.95     3.84     3.84     3.62  
1000   3.99     3.89     3.88     3.66  
1100   4.03     3.93     3.93     3.70  
1200   4.09     3.96     3.97     3.73

So, after too many days, I got around to testing the other two. Just a reminder, these are fresh from the cut reel packaging. Vf may drop, but maybe for just a select few of the K2 emitters and only a small fraction of a volt. Emitter #3 was used for more than 30 minutes over the last week in the test rig, and I found that the Vf did not drop one bit since the initial testing. Too bad.

I was rather amazed by the low (or maybe normal) Vf of emitter #4. At 1500mA, I measured a Vf of 3.83V (this is the only emitter out of the four so far that I went to 1500mA since I do not want to ruin my only test rig). This Vf is close to the Vf of the first K2 0180 emitter at 700mA!!! Wow! Good thing that these will be used in series in an application where heat and efficiency is not the most important. As I find anything more about these emitters from my testing, I will post somewhere in this thread. I ordered another K2 0180 with another Future order, so I may get some more variety of color and Vf due to the good 'ol "Luxeon Lottery".

 

[Lightingguy321]

What was the bin code on your K2-0180s?

 

[mofiki]

Today is my lucky day. I just figured out more functions of my tripple power supply from BK. If I switch it to parallel I get double the current, so I can run led's at 1 amp now. I also found that I don't have to buy a new multimeter because I forgot that my Fluke 73 has an upgraded board which makes it a 77. I can measure current. So I had to play to see what the Seoul P4 I built would do. :twothumbs I'm impressed. Looks like about a third more light output. I ran the tripple K2 setup I built to use as a helmet light at 1000mA and the voltage drop across the led's started off at 11.8volts then as it warmed up, about ten minutes, the voltage droped and leveled off at 10.8 volts. I stuck an ice pack under the housing and the voltage worked it's way back up a couple of tenths of a volt but that's about it. At least I can do accurate calculations on run time and battery options without having to guess now.

Would one of you guys recommend a light meter for me now so I can get data. I need data.

 

[SemiMan]

Today is my lucky day. I just figured out more functions of my tripple power supply from BK. If I switch it to parallel I get double the current, so I can run led's at 1 amp now. I also found that I don't have to buy a new multimeter because I forgot that my Fluke 73 has an upgraded board which makes it a 77. I can measure current. So I had to play to see what the Seoul P4 I built would do. :twothumbs I'm impressed. Looks like about a third more light output. I ran the tripple K2 setup I built to use as a helmet light at 1000mA and the voltage drop across the led's started off at 11.8volts then as it warmed up, about ten minutes, the voltage droped and leveled off at 10.8 volts. I stuck an ice pack under the housing and the voltage worked it's way back up a couple of tenths of a volt but that's about it. At least I can do accurate calculations on run time and battery options without having to guess now.

Would one of you guys recommend a light meter for me now so I can get data. I need data.

Was just reading this and I think you may want to check your numbers/heat sink. If you started out at 11.8 cold, then dropped to 10.8 warm, and there was no long term voltage shift, then these LEDS are running a good 100-110 celsius above ambient. In my triple-K2 implementation at 700mA, my LEDS only drop by about 0.4V and that is after hours. I think you may still be in the K2 spec for long term at 110C over ambient (with 25C ambient), but it cutting things thin.

Did you check the voltage again once they were cold?

Semiman

 

[mofiki]

I'm a bit worried about the heat too. Let me run these again tonight at 700mA and see what happens. The housing did get so hot I couldn't handle it and had to wait for it to cool.

 

[mofiki]

Tripple K2 still running after 30 mintutes at 700mA. It started at 10.9 volts and is down to 10.5 volts.

 

[SemiMan]

Looking at your enclosure, you do not have a lot of surface area. That could create some troubles for getting the heat out. You would do better if you could cut some grooves into it to increase the surface area. I have a significant amount of fin surface area on my set up.

Semiman

 

[mofiki]

There's a big difference in the heat between running at 1amp verses 700mA. I can handle the enclosure at 700mA. It burned me at 1amp. It's cooler than the halogen setups I was building with the same encloser. I pushed 20W bulbs 20% and you could smell em. The internal heatsink is almost 1/2" thick. I'd be interested in seeing how you heatsinked your setup and if you could tell me how you calculate area verses heat.

 

[SemiMan]

For my "playing" ... not work, I use CPU heat sinks which are cheap and have lots of surface area. They are perhaps a bit of overkill, but they work, do not way a ton and keep the LEDS nice and cool. For work we have thermal modelling software which fortunately I do not have to run...we have someone for that. Y

On the coolers, you used to be able to buy round ones (that were small, not like the monsters they make now) that were great for making LED lights, but you can not get them any more. Have you seen "tube" coolers, these are used for cooling vacuum tubes, they fit around the tubed. I wonder if you could use that with your set up?

The problem I see with what you have is even with airflow, you do not have a lot of surface area to take advantage of it.

I am looking at your set up which you indicated 700mA, but I only see one of the power supply outputs connected which I think will give you only 350mA will it not?

 

[mofiki]

If you look at the power supply above right corner, the switch for parallel, series, and independent, the supply switches internally. I have it set to parallel so the current meter display is actually double but voltage is the actual. Just to be as sure as I can be I set the current using my Fluke DMM first for accuracy. It was supplying 700mA. Again just to be sure of the voltage reading I connected the Fluke to the outputs of supply to get the voltage drop of the leds.

That program sounds interesting but unless I was to make a business of selling lights I think best guessing will do for heatsinking. I'm currently sourcing suppliers of copper stock. That other little light you saw in the picture has a Seoul P4 installed and runs cool at 1000mA I think because I used a solid copper fabricated heatsink.

I think I'm going to build another housing for the next set of K2's only this time make it about one inch longer and use copper for the heatsink. I know the output of light at 1000mA won't be much more but it will be more and it will be safer from accidental 1amp settings when driven with a Maxflex or bFlex driver board.