On Wed, 28 May 2003 17:43:04 +0200, Walter Mitty <
[email protected]> wrote:
>Yeah, but thats what rectifiers & smoothers are for. The other gizmos still nede adapters to plug
>into the wall. The schmidt is a lower power wall socket.
Hmmmm.. Basically, you'd need to make a flexible AC-DC converter circuit which ends up with the
correct voltage whenever you're going faster than x km/hr. The voltage and wattage a bike generator
is designed for is 6V/3W, or in other words 6V, and .5 A. I've been told that hub dynamos, at least,
pretty much act like a current source, as long as the speeds are there. So you'd need to determine
first how much your cell phone draws when charging. The (non-extra-fast) charger for my Nokia 3310
says it's 3.7 V at 355 mA, or 1.7 VA.. holy ****, it only draws about half of a standard bike
lighting setup.
Okay, given the low voltages, I think it's probably safe to say that the regulation and smoothing is
gonna take up a fair amount of the power, at least a quarter if not more. I think I'd "Keep It
Simple, Stupid", and just do rectifier > smoothing cap > low drop regulator. The electronics could
easily fit in a small housing attached to a carkit style holder for your phone. You might want to
look at a regulator that switches off when it drops out of regulation, rather than just passing the
lower voltage.
It's not impossible that using this setup, when you're going fast, voltages spat out from the hub
would go up far enough to damage the regulating electronics (not (usually) the phone itself, unless
the regulator shorts, which remains a possibility). I'd be very careful about this stuff and first
try rifing withg a dummy load and a voltmeter in operation, and see what transpires.
Jasper