alt.energy.homepower

"(PeteCresswell)" wrote in message
news:c5ijs39mg1hg6flkr4upf6ioev26g267jm@...
> Posted here bco the obvious expertise of group members in matters
> electrical.
>
> Bicycle-mounted front wheel generator (alternator?) hub - puts
> out AC.
>
> Numbers on the hub say 6 volts, 4 watts.
>
> Putting a volt meter on it, I get 3v at walking speed ( mph),
> 6v at 5 mph, and more as speed increases. With me on it, I
> don't see it ever getting up to 20v, but 10-12v could be fairly
> common.
>
> From what I've heard, there is a problem with using bulbs wired
> direct. You get a bulb that won't burn out at the higher
> voltages, and it's dim where most of the riding happens - at 5-10
> mph. It also goes out when the bike goes really slow or stops.
>
> I'm basically clueless re/electrical stuff, but what I've gleaned
> so far is this:
> ------------------------------------------------------------------
> 1) Something called a bridge rectifier will convert AC to DC.
>
> 2) If I put a couple of NiCad batteries end-to-end, but
> across the rectifier's output, they'll be charged when the
> output exceeds 3 volts and supply 3 volts when the output is
> less than 3 volts - limiting the voltage that any bulb or
> LED emitter is subjected to about 3 volts.
>
> 3) There are myriad 3-volt LED lights out there that I can choose
> from for the lighting part. Red, white, steady, flashing....
> you name it, somebody's selling it.
> ------------------------------------------------------------------
>
> Bottom line, I want maximum brightness when just noodling along
> at 3-7 mph, but don't want tb burning out bulbs if/when I go down
> a hill fast.
>
> My primary concern is the lighting that's visible to closing
> traffic from my back. I avoid roads with any significant amounts
> of traffic, but even in the quietest neighborhoods and parking
> lots there's some exposure.
>
> The more light and the more attention-getting on the rear the
> better, since I'm competing with cell phones, text messages,
> email, and navigation screens.
>
> I use a hand-held flashlight for the front lighting and it works
> well. (Lowe's TaskForce 4w LED... one *brave* little flashlight)
> .. but I also want a token front light attached to the bike and
> wired into the system in case some cop wants to get technical or
> the hand-held fails when I still have to get back to my home.
>
> Am I on the right track? Seems like the capacity of the
> rectifier would be a half amp max (4w/20v + fudge factor).
>
> One more time: I'm clueless about electrical stuff.
> --
> PeteCresswell

You could make a bridge rectifier with four very small diodes and use an
adjustable voltage regulator (LM317 Radio Shack). You would only need to
add a couple of capacitors and resistors, one being adjustable, and the
whole thing would be not much bigger than a book of matches. You could then
choose 3 volts or 6 volts (3 would be easier) as long as the bulb does not
use more than amps. If necessary you could use the bicycle for a heat
sink. The Radio Shack regulator has the circuit diagram on the back of the
blister pack.