DealExtreme is one of my favorite online stores. It's a distributor of inexpensive electronic gadgets based in China. I'm always finding something new there. The latest treasure is this little-but-very-bright bare LED:
DealExtreme lists it as a 10 watt LED (SKU 5876). Unbelievably it's just under $12 with shipping included!
Looking at the die shows that it is 9 discrete high-powered white LEDs in a single package. DealExtreme is bad about specs, but the comments in the DX forum seem to suggest that 700 mA at 12 volts is a reasonable spec for this LED. This would yield 8.4 watts.
(I'm wondering though if it isn't 3 x 350 mA @ 3.5 serial LEDs in a 3 parallel strings, which would be 1050 mA @ 10.5 volts. But for now, I'll run it at 700 mA).
DealExtreme lists it as 500-600 lumens @ 6500K color temperature.
As with most LEDs, you need a good current regulated driver circuit since you can't just run these things off a resistor. I decided that the easiest and simplest driver would be one based off the amazingly versatile LM317 chip.
Plugging my values (700 mA) into them yielded the need for a 1.8 ohm resistor with my LM317. Here's the schematic that I designed around those figures (courtesy of ExpressPCH):
Bodged together and plugged into a li-ion pack from my model helicopter and voila, an amazing amount of light. I'm thinking of using it on the headlight of my Piaggio (which currently uses a 3-watt LED) or to replace the bulb on my old 15-watt Niterider headlight, which has seen happier days.
(More photos and photometric testing after the jump)