Auto reversing circuit

Discussion in 'The Projects Forum' started by nigsbro, Mar 1, 2013.

  1. nigsbro

    Thread Starter New Member

    Mar 1, 2013
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    Hi everyone just wondered if anyone can Help I need a 12v dc 10a auto reversing circuit, with 2 limits using magnetic switches.
    so when power switch is pressed the motor will move from limit number 1 to number 2 and stop untill the power switch is released and then the motor will reverse and return from limit 2 to limit 1 and stop. :confused:
     
  2. nigsbro

    Thread Starter New Member

    Mar 1, 2013
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    or if anyone knows if there is a circuit board to do this already it would be a great help to get my old press working again.
     
  3. #12

    Expert

    Nov 30, 2010
    16,298
    6,809
    auto-reversing or, "move to number 2 and stop"? and you have to hold the button until it gets to number 2, and then it returns to 1 after you release the switch?

    I need you to get real clear about this.
     
  4. nigsbro

    Thread Starter New Member

    Mar 1, 2013
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    as long as the button is pressed the motor will move forward from stop 1 to stop 2 once it reaches stop 2 it will stay there untill button released.
    the motor needs to reverse at any time the button is released aswell as a safety messure.
     
  5. BillB3857

    Senior Member

    Feb 28, 2009
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    See the attached circuit.
     
  6. nigsbro

    Thread Starter New Member

    Mar 1, 2013
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    I followed the circuit Bill but both the magnetic switches started to get hot after only a few cycles,
    any ideas?
     
  7. BillB3857

    Senior Member

    Feb 28, 2009
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    My fault. I missed the 10A current draw of the motor. Your limit switches probably can't handle that much current. You could add two relays to increase their capacity. The limit switches would feed the relay coil and the relay contacts would then be inserted in my drawing where the switches are now.
    Sorry I missed the high current factor. You also need to make sure your relay contacts can handle the current.
     
  8. nigsbro

    Thread Starter New Member

    Mar 1, 2013
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    will try again once i get 2 more magnetic switches as cant seem to get it work now with these 2 old ones.
     
  9. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    If reversing a DC motor instantaneously when it is moving the peak current will be very high, higher than a short circuit current!

    You need at least a big resistor in series with the motor, or better still use a current limited PSU, that will actually give some accel/decel like behaviour and be much kinder to the motor, PSU and mechanicals.
     
  10. nigsbro

    Thread Starter New Member

    Mar 1, 2013
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    I was planning on using a 12v 14 amp old xbox 360 psu that already has overload protection built in .
     
  11. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    How many amps does the motor actually draw when moving (not startup)?

    Do you have a photo of the motor or more info on the load inertia etc (ie; what is the motor driving)?
     
  12. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    From what I'm reading, the behavior is like that of a garage door opener?
     
  13. BillB3857

    Senior Member

    Feb 28, 2009
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    I don't need to hold the button to keep my garage door open. OP wants to run one direction as long as the button is held, until it hits limit and stay there as long as the button is held. Upon release of button, drive returns to starting point and stops. He also wants return to starting point if button is released before full stroke is achieved.

    At lease that's the way I understand it. Maybe the OP can clarify.
     
  14. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Thank you, that was my mistake I thought he was instantly reversing the motor direction without a pause. :oops:

    In any case, using a constant current driver for the motor gives a lot of startup safety and end-of-travel stall safety.
     
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