jrz126 said:
Anyhoo, What exactly do the collimating optics do? is it just for focusing the beam? and are they really needed?
now which collminator will I need and can I order it (the collminator) directly from this site?
Collimator optics are necessary since without it the radiation pattern is quite unfocused and thus it is not a useful flashlight. If you'll look at the Lambertian and Batwing radiation patterns on the Luxeon spec sheets you'll see just how broadly they throw light. Compare that to some common T1 3/4 LED pkgs which focus tightly over 20 deg or less.
Those optics are designed to best utilize the Luxeon emitter's output spread, cast it all forward and in focus. Yes you can order it from the same site:
http://www.lumiledsfuture.com/products/optics.cfm
Which one? First off obviously you need a collimator labelled for "Batwing" with a Batwing emitter and vice versa. But have a look at this spec sheet comparison: **broken link removed**
Note that Batwings (with a Batwing optic) focuses significantly better than a Lambertian with a Lambertian optic. Thus I would recommend you select a Batwing rather than Lambertian part. For a flashlight, I'd generally say tighter focus is better. Note you will need a ring spacer or heat stake to fit these lenses in place, make sure you get one with the lens or order one separately.
Be aware a 3W LED, even mounted on a Star, does
not have enough cooling to operate at 3W inside a flashlight without overheating the junction. 3W and 5W devices need to have a signficant thermal connection to a sink with a larger thermal dissipation. In the case of a flashlight this will need to be the case.
Many have noted the Star is very ill designed to fit into a cylinder and make this kind of thermal contact. Sucks since everyone wants to make flashlights! What I think a lot of people do is make a thick slug out of aluminum bar stock, mount the Luxeon emitter itself (not a Star) to it, and mate it up inside an aluminum cylinder. The difficulty is the back of the emitter is
not electrically neutral and usually flashlights ground the case. You can either not ground the case- use an insulated separate wire for the batt negative and route it up to the front- or use insulating heatsink epoxy and be very careful to maintain isolation when attaching it. I've been able to do that ok. Arctic Silver works great. You mix it up, apply a dab to it, and apply the emitter carefully without pressing down too hard. The Arctic stuff is an insulator but if it's squished too hard out of the way the metal will still touch. You can check your results with an ohmmeter and you go to make sure you maintain isolation.