There are other current souces out there, the LM317 is one of the easier ones. I just got through with a thread in the chat area where someone was asking about constant current sources, it just so happens that transistors are excellent for the function.

The LED voltages are a bit high, they are worst case. Reading the specs (I looked them up after looking stupid) nominal is 3.6V, with a large variation, so the likelier voltage is 7.2.

I would go with the design you have, do heatsink the LM317. It will protect the diodes if the voltage does go above whatever the miminum is, and can't hurt otherwise. It beats a plain resistor, and you don't HAVE to drive those part to absolute max, it will be very close to your designed target in any case.

Just curious, how comfortable are you when we talk about heat sinking the part (LM317). It isn't a big deal, but for someone who isn't familiar it might seem intimidating.

 

Just curious, how comfortable are you when we talk about heat sinking the part (LM317). It isn't a big deal, but for someone who isn't familiar it might seem intimidating.

I just assumed to use an epoxy with a good thermal coefficient (articsilver or such) to a small heat sink. I have built many (20+) computers and am familiar with thermal management solutions. My current computer is a homebuilt watercooled machine.

It looks like the case of the LM317 will have the same potential as as Vout, so I will need to make sure it doesn't ground out on the project case.

 

Yes, the LM317K (TO-3) has the case as the output.

If you don't mind SMT/SMD, you might consider using them. Just leave a good-sized copper-filled area on your PCB for a heatsink. In that case, you'll probably get much better heat dissipation if you mount the PCB vertical due to convection currents.

If you're tight on space, consider using the TO220 case and mounting them vertically. That'll keep the heat away from your PCB.

 

Is this a better design? The guys over at candlepower have been giving me input as well and suggested something like this (I'm not sure about the transistor orientation.)

 

Looks like my circuit is going to be something like this:

I just put an order in at futurelec. Now I just need to secure my LEDs

 

Will these:
http://www.led-tech.de/en/High-Powe...for-Luxeon-K2-and-emitters-LT-951_106_81.html
work with the stock K2 emitters and optics found on luxeonstar.com? Particularly, with the L2 3° Spot Base Module For Luxeon K2 LEDs.

It looks like it will be substantially less expensive for me to make my own stars (even though the soldering is sure to drive me crazy) and then bond my DIY stars to the aluminum c-channel that will be the housing of the project.

Does this seem adequate?