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need to convert 12 volts to 6 volts @ about 4-6 amps

Discussion in 'Electronic Design' started by [email protected], Aug 21, 2007.

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  1. Guest

    I don't know if I am in the right category - if I am not somebody
    please direct me there. What I am looking to do is to use a 12volt
    car battery to run 6 volt electrical motor. It used to use 6volt 4
    amp/h battery. I wold like to find out if there is a way of convering
    the power from car battery without waisting any juice. I think I can
    just take some wire and wrap it into a coil and run my positive
    through that, but then I will be loosing the juice. It might not be
    enough to worry about, but, I would like to know the specifics. there
    might also be another way - which I don't know about. I would also
    like to keep it cheap if possible.
    please if you have any ideas -let me know. thanks
  2. Nobody

    Nobody Guest

    The standard mechanism for efficiently controlling power to DC motors is
    pulse width modulation (PWM). IOW, you turn the current on and off rapidly.

    The alternative (dropping voltage across a load resistor) is going to
    waste 50% of your power. If the motor draws a lot of current, you would
    need a high-power resistor, which may well cost more than the components
    required for PWM.

    Essentially, you need:

    1. A transistor (bipolar or MOSFET) which can take the motor current.
    2. A diode with the same current rating.
    3. A square wave oscillator, typically running at a few KHz (for a fixed
    ratio, a 555 is the obvious choice).

    Connect the motor between the +12V supply and the collector or drain of
    the transistor. Connect the emitter or source to the ground (0V) line.
    Feed the square wave to the base or gate (for a bipolar transistor, via a
    resistor). Connect the diode across the motor with the *cathode* to the
    +12V supply.

    If you can provide the specifications of the motor (preferably the
    current; failing that, the power), someone may be able to recommend
    specific components.
  3. John B

    John B Guest

    This question should be in sci.electronics.basics.
  4. If you are needing something in a 12 volt system, but need to pull 6
    volts off to power something else, couldn't you just use two 6 volts
    batteries wired in series to run the 12 volt stuff, but then tap
    directly into one of the 6 volt batteries to power the 6 volt motor?
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