| (PeteCresswell) 2008-03-01, 5:25 pm |
| 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 (2.5 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:
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1) Something called a bridge rectifier will convert AC to DC.
2) If I put a couple of 1.5v 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.
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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.
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PeteCresswell
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