Originally Posted by Ghost_Mutant
Thanks for posting that Instructables link. I'm building my own dual sport kit for my second XR and I was planning on using some more "luxeon" LEDs again. After seeing this info, I'm reconsidering my strategy
My present LEDs on my already dual sported XR are 3 watt turn, and 5 watt brake/tail. The 3 watt/1156 are adequate in the daytime. But the 5 watt brake light is plenty bright and I would say about equal to the original incandescent.
The first set of regular type LEDs I bought were not bright enough for daytime use in my opinion. So the luxeon types are worth the extra $$ to be sure other drivers see my signals. Only problem I had with the "cheap" luxeon is that vibration eventually separated the heat sink from the housing, breaking two of my lights. They were put together with some kind of super glue that failed. I ended up using some JB weld on my still working lights to prevent the heat sink/housing separation. Now I may be able to save the broken ones by using the simple circuit featured in the Instructable.
Speaking of heat sinks, the LEDs you linked to at Mouser look similar to the luxeon that I have; but are you going to heat sink the LEDs somehow? I didn't see any extra heat sinking in the fog light photo.
I'd suggest you post a separate thread on your work and then announcing the link here. Probably be other riders who would want to know this info.
Quoted to copy relevant info from XRL thread to here.
You're welcome for the link. The parts to build your own constant current supply are only a few dollars, and can be very easily customized to a particular need using his provided formulas. This circuit would readily drive the Luxeons as well.
Heat sinks - definitely a must for full power operation. After much research, it seems that standard JB Weld is thermally but not electrically conductive (at least not enough to cause shorting, etc). I can confirm that it does not transfer enough electricity to light an LED, as I accidentally experimented with that during this build... Probably a great option for attaching to heatsinks in a pinch, though I suggest that Arctic Alumina
is a better epoxy for that application long term, being ceramic based and designed for heat transfer.
The Avago LED's are very similar to Luxeons, being slightly more expensive and brighter than Luxeon I, while being only slightly dimmer and much less expensive than Luxeon III. Also, their peak light output requires only 700mA vs 1400mA for the Luxeon III. In the previous picture, I'm running them at 151mA. Going over the spec sheet, I don't anticipate a need for much heatsinking under those conditions. I have a thin aluminum plate JB'd to the plastic, then the LED's JB'd to that.
Word of caution about the Avago LED's - the red does not seem to be available with an electrically isolated slug, so if you mount directly to a metal surface, all the anodes will be linked resulting in a fixed 100% parallel configuration. Be very cautious about forward voltage!
My LED's for the bike however, will have appropriate heatsinks, and I'll take more pictures along the way. Naturally, the brake will need the best heatsink, as it will be an always on (albeit at low power) application. They put off a nice glow at 20 mA.