Originally Posted by cbr2702

I put a light together for a roadster six months ago, and I had good results with lazyness. That is, I decided I didn't really need everything I thought I wanted at first.

I thought I wanted a dynamo tail light. Then I realized that LED taillights take so little power that I could run a rear stand alone with on an enclosed non-rechargeable battery for six months to a year. So no wires to the rear.

I thought I wanted something to smooth the beam so it wouldn't flicker. That is, a dynamo hub puts out power in a sine wave of increasing frequency. If you rectify with just a little bridge recitifier, you get flicker at low speeds. To get the nicest output you can make moderately complex rectifier that uses capacitors to smooth this. When I actually put the light together, though, I found that there was no flicker unless I was walking the bike or going insanely slowly.

I thought I wanted a standlight. But with the complexity of batteries and charging circuits, and running a rear battery powered light, I decided the benefits were quite small.

I thought I wanted several emitters. Then I realized that with a single cree XR-E (R2, WH tint) (I'm sure there are better ones now) I had more light output than people with 20W halogens had been riding on five years ago.

I thought I wanted a switch. I even chose an enclosure with one. But after setting it all up, I realized I couldn't feel whether it was on or off, and I liked that drivers would see me better with it on. So I leave the switch on 'on'.

So you can certainly make something complex that meets all your criteria, but you may decide it's not worth it. If you do, and just want something like I made, all you need is:

1 White power led
1 heatsink for led
1 elliptical (10/40) lens for led
1 bridge rectifier

Connect the two outputs of the dynamo to the two pins marker ~ on the rectifier. Connect the rectifier + to the led +, the rectifier - to the led -. Attach the led to the heatsink with thermal glue. Attach the lens to the led as appropriate. Put in housing. Done.

If you want a switch, it can go anywhere.