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Brushed DC motor driver

Discussion in 'Electronic Design' started by lmcgill2, Jan 5, 2009.

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  1. lmcgill2

    lmcgill2 Guest

    Hello all,
    I have a 24VDC 1A brushed DC motor, but I have a 28V power supply. I
    was wondering if I could use zener diodes to regulate the voltage down
    to 24V. This seems doable until I consider changing the polarity to
    switch the motor direction. Does anyone know of a creative design
    that uses zeners that would allow me to still switch motor direction?

    Any help would be great.. Thanks, Lucas.
  2. You could put 4 diodes and a bridge in series with the motor:
    (view with fixed-width font)

    | |
    .-----. | V
    A -|~ +|---+ -
    B -|~ -|---+ |
    '-----' | |
    | V
    | -
    | |
    | |
    | V
    | -
    | |
    | |
    | V
    | -

    Diode rating depends on the motor specifications (including stall
  3. Jasen Betts

    Jasen Betts Guest

    3.1 3.1 motor
    5W 5W

    seems crazy to me.
  4. lmcgill2

    lmcgill2 Guest

    Thanks for the replies, the issue we're having is that the polarity
    switching must happen "before" the voltage step down. So the
    circuitry must be able to work independent of the polarity. See below

    | | ________
    (+28)------| |-----(+24)-----| |
    | Voltage Regulation | | Motor | CW Rotation
    (Gnd)------| |-----(Gnd)-----|-------|
    | |

    | | ________
    (Gnd)------| |-----(Gnd)-----| |
    | Voltage Regulation | | Motor | CCW Rotation
    (+28)------| |-----(+24)-----|-------|

    We need to place the voltage regulation circuit "between" the 28V and
    the motor knowing that the 28V may switch in order to switch the
    direction of the motor. Does this make sense?

    Again, any idea would be great. We're trying to keep the number of
    parts to a minumum (due to PCB size requirements) thats why I thought
    zeners would be the easiest.

    Thanks again, Lucas.
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