dynamo taillight led and optics choices

[unterhausen]

I want to build a taillight for my dyno hub system. I didn't see too much recent discussion about this. I'll probably still run a blinky, but I would like a dyno powered light too.

I was looking on Digikey for the highest power red Cree I could get. I found the XP-C. On Cutter, there were two optics that caught my eye: the 10204 and the 10203.

http://www.cutter.com.au/proddetail.php?prod=cut692

http://www.cutter.com.au/proddetail.php?prod=cut691

Any comments on this?

 

[rickson]

You can run a bare emitter in the rear. Focusing is not needed.

 

[Steve K]

I believe that there is a benefit in using a lens. You are able to make the best use of the available light and put it where you want it.

These Carclo lenses would do well enough. I think that the 10 degree beam width is more than adequate for the vertical width. The horizontal width is wider than I use, but would offer an advantage for urban riding where you have more traffic approaching from the sides. Urban riding is also tough, since you are usually competing for peoples attention with a lot of other cars. It's not easy to stand out from the crowd, although flashing lights do seem to help.

Steve K.

 

[markus_i]

While you can run a bare emitter in the rear and that would be plenty bright, I wouldn't recommend it, the visible emitting area is simply too small. I'm using a red LED in combination with an elliptical beam optic and it works great.
Just one thing: don't power it at the full 500 mA. Or at least limit this level to bright daylight riding. Riding in the dark, 20...30 mA are sufficient.
For our new bikes, I'm building two rear lights, each with four red rebels and elliptical beam optics. The LEDs/optics are angled at (roughly) +-30 and +-15 degrees to the axis of the bike, so I get a wider coverage angle in the horizontal plane. First tests show that 4*18 mA are plenty in the lighted room (almost too bright to look at on-axis within the room). I'll still have to check outdoors (once the weather gets a bit better) if I should leave it at that or go down to ~10 mA per LED...

Bye
Markus