I know rachel is attempting her own bicycle lighting project, so I am hoping that by putting notes on the wiki we can share ideas. Rigel
rigel's dynamo lighting system
This will be based around the Shimano DH-3N71 Dynamo hub. It outputs 3W at 6V. I'm not sure how the voltage or current changes as speed increases, but I am under the impression that it is fairly well-regulated internally.
Currently, I have it wired directly to a rectifier, whose output is a 220uF cap and a Cree XR-E LED. This produces light adequate to ride in the dark and avoid most obstacles. None of this is regulated in any way, so at low (slightly faster than walking) speeds it begins to flicker. This might be a problem for long steep climbs in the dark.
What I would like, ideally, is to have the ability to draw current from a li-ion battery pack when it begins to flicker. In addition, I would like to be able to charge the batteries, and additionally a cellphone if feasible, from the dynohub when i am riding in daylight. I have not found the drag to be noticeable from one LED, but presumably if drawing more current this could become a problem.
Since I am a n00b, I dont know the first thing about implementing this, but i have been led (ha!) to believe that i need the following modules:
- voltage regulator
- battery charging circuit
- led driver circuit
- 5V usb output for alternative uses
The cree LEDs are brightest, i'm told, when drawing 600-700mA. The voltage drop, i believe, is 3.3v per LED, and they are best wired in series to avoid thermal runaway (not sure why this happens, but it's been talked about on several forums i've seen, so i think it best to avoid it altogether) I would probably start with 2, but may use as many as 4 li-ion cells for this purpose.
What voltage regulator should i use? do i need a multiple output voltage regulator or should i step up the voltage in the battery charger module itself? what battery-charger IC should i use? what kinds of interconnects (i would like this to be modular for the working design) are waterproof (and cheap!), as i will be using this in potentially foul weather?