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Generator Project

Discussion in 'General Electronics Discussion' started by thecombover, Nov 19, 2012.

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  1. thecombover


    Nov 19, 2012
    For my high school pre-engineering class, a friend and I decided to build a generator type device that would charge a cell phone using power generated by pedaling a moving bicycle. We made a poor decision when choosing the project as neither of us has annnnny electronic experience. We produced a design that generated power using a spinning magnet in a coil of wire. However, we need a way to turn the AC current to DC current and also limit the voltage so the charger/battery is not blown out. Any ideas? Thanks!
  2. Miguel Lopez

    Miguel Lopez

    Jan 25, 2012
    You will possibly need to increase the number of turns up to get an AC voltage higher than that DC value of the cell phone battery. Then rectify it using a simple diode (or a bridge rectifier for full wave) and add a resistor in series, to limit the charging current. Don't need to limit the voltage as the charger is a current source, not a voltage source.

    CDRIVE Hauling 10' pipe on a Trek Shift3

    May 8, 2012
    We need particulars from you.

    RMS AC Voltage (No Load)
    RMS AC Voltage (Load Current = 200mA)
    Photo of the generator system.

    This information will give us the basic capabilities of this generator.

    FYI, you could have used a factory made DC brush motor from Radio Shack and used it in reverse. It will generate better than your home brew model and would output pulsating DC.

  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    The simple answer is:

    Rectifier, filter, regulator.

    Everything said above also applies.

    Rectification produces pulsing DC from AC, A filter converts that to a smoother DC, and finally a regulator prevents the voltage from exceeding some set value.

    Much of what has preceded deals with the practical aspects of ensuring you have a sufficiently high DC voltage and power for this to work.
  5. thecombover


    Nov 19, 2012
    Thanks guys! I don't have the generator built yet but it will basically be a box with a spinning magnet inside of it that is wrapped in coils of wire. Can those parts be purchased and combined easily. If it was unclear, this is meant to be a portable device so it would be great if the parts were small.
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Yes, it's called a motor.

    If I were you, I'd use a DC motor because that is pretty much guaranteed to work. Some AC motors can be used, but you may have to go to additional effort.

    Rectifiers, filters and regulators (the last is *essential* if you're charging a phone battery either directly or through the charger socket) can also be bought, but you'll have to solder them into a circuit.
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