Could it be done ?
Don't know if the dynamo produces enough voltage to power directly, my DX P7 torch uses a single 18650 rechargable which is 3.7v, 4.2v full charge, 2.75v discharge, but there could well be a way of using the dynamo to maintain a charge into a battery pack or some sort of capacitor for keeping the light on when stationary. I'm no electrician, but there must be a way.
Dynamos are 6V 0.5A (3W) max
IIRC the DX like is 10W, that would slow you down a fair amount!
IIRC some folk on candlepower forums have run a led from a dynamo - its not straightforward as the dynamo needs a different control circuit to get the right voltage and current. I think it was running a single cree 3 w but might have been a triple less than flat out.
You can alter the control circuitry of a dynamo to get more or less any voltage you wnat - the higher the voltage required the faster the dynamo needs to turn to start producing current.
check on candlepower - it out geeks STW by a factor of 4.7
Dynamos are 6V 0.5A (3W) max
No they're not, they're only limited to 0.5a, the voltage can go as high as you like. I've run 6W of lights off mine no problems, and there are triple LED lights that are available that use more than that.
I don't think you can run the p7 torches off them easily, as they are wired up for 2.8A, you'd get rubbish power at 0.5A current.
I do have a plan at some point to make up a light using the Cree MC-E LED (similar to the P7), with half the LED run forward, half run backwards, and just powered directly off the dynamo current - I reckon it would almost certainly work okay, and it'd give a tiny, very bright LED light (it could be a bit smaller than the head of the P7 torch alone), which could actually be pretty efficient, more so than rectifying the current properly.
Joe
Scmidt (makers of really nice hub dynamos) do an LED light called the Edelux [url= http://www.sjscycles.co.uk/product-Schmidt-Schmidt-Edelux-High-Power-LED-Headlight-with-Standlight-and-Senso-17283.htm ]see here[/url], so it's theoretically possible.
maybe have a look at some of their tech specs, to see what info you can glean.
Cheers for the info.