Automatic change of rotation on dc motor

Discussion in 'Electronics Resources' started by 00024, Feb 13, 2014.

  1. 00024

    Thread Starter New Member

    Feb 10, 2014
    3
    1
    I hope someone may be able to offer me assistance.

    I’m working on a project that requires an advertising sign to rock back and forth when displayed .The add sign is mounted on a post. I’m using a 12 volt 10 rpm dc motor connected to a 12 volt battery. The battery is connected to a 10 watt solar panel. How can I make the 12 volt dc motor change direction of rotation automatically? And continuously?

    I was going to use a servo motor to provide the rocking action required however, the servo motor controller requires AC power and this gets more complicated and costly.

    Can I connect some kind of relay to automatically switch motor direction? Rotate shaft 90 degrees, change direction, rotate shaft back 90 degrees, etc.

    Thank you very much,

    00024
     
  2. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    Should be able to do that with a couple relays and limit switches if the motors can tolerate reversing instantly.

    Have you thought of a bell crank?
     
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  3. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,544
    2,370
    The most efficient option may be to arrange a reversing mechanism such as a rotary to linear mechanism, this way the motor can run continuously in one direction and also save on power due to the start current being eliminated every oscillation.
    Probably similar to what Inwo has in mind?
    Max.
     
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  4. 00024

    Thread Starter New Member

    Feb 10, 2014
    3
    1
    Hey thank's allot, I'm looking into the bell crank aspect which I was unaware of. I'm new to this site and should have looked for other similar posts before submitting mine, but thank's again.

    00024
     
  5. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    I agree with Max.
    And he explains better.:D

    If locked into the electrical method.
    A limit switch on each end of stroke and two TD relays will cycle between two points and brake to a stop at each end.
     
  6. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    It can be as simple as a disk on the motor shaft with a hole in it.

    A connecting rod from the hole to a lever on the sign.
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,544
    2,370
    The flywheel-crank con-rod idea?;)
    Max.
     
  8. 00024

    Thread Starter New Member

    Feb 10, 2014
    3
    1
    Hey, I used your idea and it's working, although I still need to iron out the details of my final design. I mounted a round metal electrical conduit with the center of the conduit connected to the motor shaft. I connected an aluminum arm mounted on a pivot to one end of the conduit [as far from center as possible]. Then I have a screw that impedes the arm each time it passes causing my add display to rock back and forth just like I need it to.

    Thank you so much for your input. It made all the difference.

    Al
    00024
     
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