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? Soft start dc motor (poor man)

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  • JaysonW
    I m the neighborhood toy fixer with a dangerous knowledge of electronics. My neighbors power wheel car died, and I ve tracked the problem to the control
    Message 1 of 3 , Mar 10, 2013
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      I'm the neighborhood toy fixer with a dangerous knowledge of electronics. My neighbors power wheel car died, and I've tracked the problem to the 'control' unit.

      Through research, the control unit handles the high/low/reverse settings and soft starts the dc motors. My sons very similar power wheels does the high/low/reverse selection through a relay network that I can duplicate in the dead car. But I don't know how to easily soft start the motors.

      The motors can run in parallel (high speed), series (low speed) or series reverse polarity (reverse). Theres a 30a fuse in the power system.

      Would a big cap in parallel with the drive load work as a soft start? Or any other simple discreet component solution? I could probably get away with just putting the soft start in the "high power" mode.

      Jay W
    • Larry Beaty
      Simply, put a resistor in series with the high start and use a time delay relay to short it out. Resistor may be a length of steel wire that can handle the
      Message 2 of 3 , Mar 10, 2013
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        Simply, put a resistor in series with the high start and use a time delay
        relay to short it out. Resistor may be a length of steel wire that can
        handle the current.



        Best wishes,



        Larry



        From: Electronics_101@yahoogroups.com
        [mailto:Electronics_101@yahoogroups.com] On Behalf Of JaysonW
        Sent: Sunday, March 10, 2013 1:29 PM
        To: Electronics_101@yahoogroups.com
        Subject: [Electronics_101] ? Soft start dc motor (poor man)





        I'm the neighborhood toy fixer with a dangerous knowledge of electronics. My
        neighbors power wheel car died, and I've tracked the problem to the
        'control' unit.

        Through research, the control unit handles the high/low/reverse settings and
        soft starts the dc motors. My sons very similar power wheels does the
        high/low/reverse selection through a relay network that I can duplicate in
        the dead car. But I don't know how to easily soft start the motors.

        The motors can run in parallel (high speed), series (low speed) or series
        reverse polarity (reverse). Theres a 30a fuse in the power system.

        Would a big cap in parallel with the drive load work as a soft start? Or any
        other simple discreet component solution? I could probably get away with
        just putting the soft start in the "high power" mode.

        Jay W





        [Non-text portions of this message have been removed]
      • Jan Kok
        Larry s solution sounds workable. Another possibility would be to use a delay relay (or 555 timer chip, etc.) to require the car to run in slow mode for 1
        Message 3 of 3 , Mar 10, 2013
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          Larry's solution sounds workable. Another possibility would be to use a
          delay relay (or 555 timer chip, etc.) to require the car to run in slow
          mode for 1 second before switching to fast mode.

          The capacitor idea won't work for several reasons:

          - The capacitors would have to be huge to be effective. (Think of those
          1-farad capacitors you see in car stereo shops!)

          - If they were large enough to be effective, they would also look like a
          momentary short circuit across the motors, causing relay contacts to weld
          shut, fuses to blow, etc.

          - The caps would continue to supply power to the motors after you take your
          foot off the "gas".

          - The cars probably stop by shorting the motor terminals together, so you'd
          also have to figure out how to discharge the caps quickly without welding
          contacts shut.

          - Also need to avoid getting reverse polarity on the caps when running the
          car in reverse.

          The "cool" way to get soft start (and continuously variable speed, if you
          like) is to supply battery power to the motors with a variable duty cycle.
          You can do it with a 555 timer and some power MOSFETs.



          On Sun, Mar 10, 2013 at 11:33 AM, Larry Beaty <lbeaty@...> wrote:

          > Simply, put a resistor in series with the high start and use a time delay
          > relay to short it out. Resistor may be a length of steel wire that can
          > handle the current.
          >
          >
          >
          > Best wishes,
          >
          >
          >
          > Larry
          >
          >
          >
          > From: Electronics_101@yahoogroups.com
          > [mailto:Electronics_101@yahoogroups.com] On Behalf Of JaysonW
          > Sent: Sunday, March 10, 2013 1:29 PM
          > To: Electronics_101@yahoogroups.com
          > Subject: [Electronics_101] ? Soft start dc motor (poor man)
          >
          >
          >
          >
          >
          > I'm the neighborhood toy fixer with a dangerous knowledge of electronics.
          > My
          > neighbors power wheel car died, and I've tracked the problem to the
          > 'control' unit.
          >
          > Through research, the control unit handles the high/low/reverse settings
          > and
          > soft starts the dc motors. My sons very similar power wheels does the
          > high/low/reverse selection through a relay network that I can duplicate in
          > the dead car. But I don't know how to easily soft start the motors.
          >
          > The motors can run in parallel (high speed), series (low speed) or series
          > reverse polarity (reverse). Theres a 30a fuse in the power system.
          >
          > Would a big cap in parallel with the drive load work as a soft start? Or
          > any
          > other simple discreet component solution? I could probably get away with
          > just putting the soft start in the "high power" mode.
          >
          > Jay W
          >
          >
          >
          >
          >
          > [Non-text portions of this message have been removed]
          >
          >
          >
          > ------------------------------------
          >
          > Please trim excess when replyingYahoo! Groups Links
          >
          >
          >
          >


          [Non-text portions of this message have been removed]
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