Schmidt hub dynamo : any "add ons"?

Discussion in 'Cycling Equipment' started by Walter Mitty, May 25, 2003.

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  1. Walter Mitty

    Walter Mitty Guest

    Since the Schmidt Original Nabendynamo is so damn efficient (I have one), I was wondering if anyone
    in this group might know about transformers/smoothers in order for the Schmidt to power a portable
    radio or walkman or even charge a mobile phone while on the road.

    I don't think it should be impossible. Should it? Is it done?

    --
    Walter Mitty.
     
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  2. Carl R

    Carl R Guest

    I use a rectifier from a 9V 1A dc power adapter similar to the ones that come with cordless phones
    etc... Use the small board inside with the capacitor and connect the schmidt in place of the
    transformer connection (AC). You could use a DC voltage regulator on the output or a rechargeable
    battery pack to control the voltage. I use 4 AA rechargeable NiMh batteries in a backup light in
    parallel with 4 AAA NiMh batteries external that I use for my MP3 player. I have had no problems
    with overcharging/overheating the batteries with this setup. The charge voltage for 4 cells is very
    close to 6V so it acts as a voltage limiter for your light also. With the light on very little
    current will flow to the batteries unless they are totally drained. "Walter Mitty" <[email protected]> wrote
    in message news:[email protected]...
    >
    > Since the Schmidt Original Nabendynamo is so damn efficient (I have one),
    I
    > was wondering if anyone in this group might know about transformers/smoothers in order for the
    > Schmidt to power a portable radio or walkman or even charge a mobile phone while on the road.
    >
    > I don't think it should be impossible. Should it? Is it done?
    >
    > --
    > Walter Mitty.
     
  3. Walter Mitty <[email protected]> wrote in message news:<[email protected]>...
    > Since the Schmidt Original Nabendynamo is so damn efficient (I have one), I was wondering if
    > anyone in this group might know about transformers/smoothers in order for the Schmidt to power a
    > portable radio or walkman or even charge a mobile phone while on the road.
    >
    > I don't think it should be impossible. Should it? Is it done?

    No idea. You might check on the BikeCurrent list, which is hosted on http://www.topica.com

    I see one problem, however. On top of voltage regulation, you would have to deal with the fact the
    Schmidt and other dynamos produce alternating current whereas most chargers and electronic gizmos
    need continuous current.

    Regards,

    Michel Gagnon
     
  4. Walter Mitty

    Walter Mitty Guest

    [email protected] (Michel Gagnon) brightened my day with his incisive wit when in
    news:[email protected] he conjectured that:

    > Walter Mitty <[email protected]> wrote in message news:<[email protected]>...
    >> Since the Schmidt Original Nabendynamo is so damn efficient (I have one), I was wondering if
    >> anyone in this group might know about transformers/smoothers in order for the Schmidt to power a
    >> portable radio or walkman or even charge a mobile phone while on the road.
    >>
    >> I don't think it should be impossible. Should it? Is it done?
    >
    >
    > No idea. You might check on the BikeCurrent list, which is hosted on http://www.topica.com
    >
    > I see one problem, however. On top of voltage regulation, you would have to deal with the fact the
    > Schmidt and other dynamos produce alternating current whereas most chargers and electronic gizmos
    > need continuous current.
    >
    > Regards,
    >
    > Michel Gagnon
    >

    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.

    --
    Walter Mitty.
     
  5. 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 crap, 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
     
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