using B&M tail light with Supernova? Also, DIY Cree X-RE tail light?

I have a supernova and don't really want to pay for a tail light when I have a stack of B&M sitting in a drawer. I have seen hints that people have done this. I'm also thinking about DIY'ing a light using one of my cree XRE red LED's for this. I am curious how Supernova does their circuit. Seems like they just have a limiting resistor and 3 Vf to limit the current. I probably would just use one XRE, otherwise it seems like it would be blinding.

might as well try just running a resistor in series with the XRE. Can't hurt, right?
The downside is that whatever current you put through the taillight is being take from the headlight, so you might be limited to 100mA or so, just like with incandescent taillights. Also, you're wasting the power lost in the resistor, which is a shame.

A better arrangement would be a current regulated buck converter for the XRE. 100mA through the XRE would only take 50mA or so from the headlight.

Why not just use 2 X red power LEDs in series with a simple bridge rectifier in parallel with the front light? If you are just using a single front LED I reckon you'd have plenty of current to go around and you'd overcome the vf mismatch...

Savvas

2x emitters seems like it might be blinding. Since this is my off-road (-ish) bike, maybe that will not be a problem. Not sure if the supernova headlight has limiting in it, I don't really want to take the taillight apart to see what's in there. I've seen a picture of a disassembled supernova taillight on someone's (Peter Weigel?) flickr stream, not sure if I can find it right now

Found it, even commented on it link

Still wondering what that surface mount thing is, it's not like any other device I have seen.

that photo isn't much to work with. Might be a resistor..... it certainly doesn't look like a diode or other semiconductor.

and off-topic a bit... JP Weigle does amazing work! I love to just browse his Flickr photos. So many cool bikes!

it reminds me of a resistor pack, but I'm not sure if there are similar looking diode packs.

So as I proposed, for the OP's alternative DIY proposal, would it not be easier to simply try to balance the vfs of the front Supernova and a very simple rear DIY light? Unless the SN is putting DC out of its aux. output, I would imagine that the SMC is a tiny bridge diode. By using 2 x XRE red diodes in series with a similar bridge diode you'd get a vf of around 4.2 volts which seems pretty close to the likely vf of the SN. Personally I'd give it a go. XREs are very cheap and you're not going to do any harm. If you're worried about it being too bright just put a translucent bottle top or similar over it!
Savvas.

Does anyone know how the SuperNova behaves? i.e. how it is wired; what the relation is between its current and voltage? Seems like you would want to have some insight into that before you could really do a proper job of designing a taillight. My general assumption is that it is designed to have roughly the characteristics of a "standard" incandescent light, and thereby is compatible with a taillight having the standard characteristics. However.. assumptions have their limitations!