hey gang - good to see the forum is still alive and active! i've been dormant in the electronics engineering arena for quite a while now. I'm not sure where my time has gone, but I don't seem to have any left for working on projects. The fact my lab is a complete pig-sty doesn't help matters.
lately the weather has been getting nicer, and I bought a new pedal bike to play around on and give the dog and I a little exercise. The dog prefers to run off-leash, so I prefer to ride at night when there's less "distractions" in the neighborhood, ie people and pets for him to visit with. So i needed some light to see with and be seen by.
I started with a pair of prototype Luxeon K2 "neutral white" stars, which I had epoxy mounted to a heatsink some time ago. I rigged them up with a few lenses and a 1amp buck-puck and they worked fairly well; I calculate I got about 160 lumens from the pair at 1amp. But on especially dark areas of the bike trail, they just were not enough light. So I ordered some SSC P4's (z-power leds, U bin). Rated 100lm at 350ma, and 200+ lm at 1a, these lights kick a lot of ass. I also ordered a compound optic with three spot-lenses in one package. I glued three of the leds to a big xeon cpu heatsink and gave the epoxy a day to cure, and then it was time for a little field test.
First I calibrated my camera using a MaxStar 5 led upgraded maglight. This thing is supposedly a pretty bright luxeon k2, it is much brighter than the stock halogen bulb.
http://projects.dimension-x.net/pictures/bikelite/nite_MAX5.JPGOnce I had the cam settings locked in, I proceeded to test the lights. First came the k2's, running at 1a and IIRC have 25 deg flood optics mounted:
http://projects.dimension-x.net/pictures/bikelite/nite_2xK2_1.0A.JPGNext up is the new p4 light running off a pair of AA batteries at a 500mA micropuck, which is some sort of boost converter. However, the micropuck is limited to 8v out, which is less than the 10-11vF of the led string, so I'm not really sure what current the leds are running on in this picture.
http://projects.dimension-x.net/pictures/bikelite/nite_3xP4_0.35A.JPGNote the much tighter concentration of light. The new optics really project a good spot rather than a flood. Lastly, here is the new p4 light running off a 1a buck-puck and a freshly charged 12v sla battery. I have a bit of a problem here with run time. As the battery voltage drops under 13, the buck-puck's overhead starts cutting into the amount of current it can provide to the leds. I need either build a converter with less overhead, a better topology such as sepic / inverting, or build a higher voltage battery pack.
http://projects.dimension-x.net/pictures/bikelite/nite_3xP4_1A.JPGAll in all, I still respect the output of the K2's and with tighter optics they would make a decent light. But compared to the 600+ lm output of the new light, they're pretty dim. I just received a new four lens compound optic, so as soon as I find a decent heatsink and a suitable driving method, I'll have even more light to play with.
Oh, here's a shot of the P4 light lying on my work bench. I'm going to make a plexiglas sheild which I will mount on those studs pressed into the heatsink. I also need to come up with some sort of baffle to put around the optic, to cut down on the glare I get from leakage around the collaminators.
http://projects.dimension-x.net/pictures/bikelite/3v_test.JPG
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