All right, since the parts arrived this morning, I decided to slap together the 10 watt LED with it's heat sinking and Constant Current driver made from an LM317 Voltage regulator. Note that this is a VERY inefficient method of providing regulated current, but it does work, and is cheap...
Ghetto LM317 - based Constant Current Driver with 10w Power LED... this dang thing is BRIGHT... rated 900-1000 Lumens... somewhere in the range of a 65watt incandescant bulb's output- except the LED emits that over 160 degrees rather than 360, so the apparent intensity is even higher. By eyeball, I'd compare it to a 75 watt incandescant floodlight, maybe a bit more, except for the very cool light color- the LED is 6500K. For reference, Xenon flashtubes operating at their theoretical ideal of 6600K can produce approximately 90 Lumens per Watt, but that of course is only in extremely short pulses. If we can get 900-1000 Lumens (rated output) from the LED, it will be performing as efficiently (if not more so) than a standard short-arc strobe tube. Once the switching circuitry is in place, I can then start experimenting with pulse width and actual minimum illumination time. At least at low power levels, it would appear that these power LED's will be giving Xenon a run for it's money as a light source... but only if the flash duration can be manipulated well.
Cost of build so far:
10 watt LED - $1.00 on eBay auction from Hong Kong - I got a deal, but normally like $7 now
LM317T 1.5A adjustable Voltage Regulator $ .36 (mail order.. 20 for 6.99)
1 Ohm and .5 Ohm 2 watt resistors $ Free Salvaged from a printer circuit board, if bought, maybe $2 total
CPU Heatsink $ Free Salvaged. Just about any chunk of metal (Al or Cu) will do
So, even paying full prices of $7 for LED and $1 each for the resistors (outlandish!), for under $10 you can assemble a BLINDING regulated Power LED, set up for typical voltages found in an automobile or some wall warts. I've managed to cobble this together so far for a grand total of under two dollars ;)
Metered out the resistors to 1.5 Ohm, so that provides for (1.25/1.5) = 833mA regulated. This should be right in the slot in terms of keeping the LED/Regulator relatively cool while giving relatively close to rated output. There's likely to be a little resistance drop with heating, so I'm okay with this power level given the crudeness of the circuit! I may eventually reduce the resistance to 1 Ohm, which would give 1.25A (25% over rated max) when using it as a photo flash.. as the short duration of use will take away most of the heat dissipation concerns. I've used no heatsink compound (none in the bins), but the component's heatsink tabs are screwed tightly against the Aluminum CPU heatsink and this seems to be enough. A loop of uninsulated copper wire also holds the two resistors firmly against the heatsink to help keep them cool also. After ten minutes of operation at 13.5v from a car battery, the heatsink was only mildly warm to the touch and the components themselves were comfortable to hold a finger on.
I do however have a question.. when I meter the LED, I see only 9.3v across it when connected to a 12v wall wart that meters to 17v with no load and 13.6v with the led circuit connected. thoughts?
Now to add a logic-level switching circuit. I've got a few power transistors around, only need something rated for like 2A @ 20v, I'm sure I can find something in the bins that will work..