Servo motor used as a stepper motor

Discussion in 'General Electronics Chat' started by Manmeet Singh, Dec 21, 2010.

  1. Manmeet Singh

    Thread Starter Active Member

    May 21, 2008
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    Hello all I have been working on a project in which I would like to minimize cost and have found that the stepper motor is accounting for a large portion of that cost. What im wondering is can I achieve the same functionality using a servo as I would a stepper motor? My needs are I want to be able to rotate with 45 degree increments 360 degrees nothing more both clockwise and counterclockwise. Any thoughts on the topic would be appreciated

    Thanks
     
  2. #12

    Expert

    Nov 30, 2010
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    You will have to devise a system to tell the driver when to stop (because you have arrived at 45 degrees etc). That's about all I can think of.
     
  3. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    What type of servo motor are you considering? Most hobbyist servo motors will only rotate 180 degrees, without modification. They can be modified for full rotation, but then you lose positional control, i.e. either rotate clockwise, stop, or rotate conterclockwise.
     
  4. Manmeet Singh

    Thread Starter Active Member

    May 21, 2008
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    I was intending on using a cheap hobbyist servo motor and modifying it but wasnt sure about if I would lose positional control. Lets say positional control is not critical could I still effectively use a hobbyist servo to rotate 360 degrees and turn with 45 degree increments?

    As a seperate question if I stop issuing the PWM signal to the servo does it swing back to neutral position?
     
  5. Markd77

    Senior Member

    Sep 7, 2009
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    You could add gears to make the 180 into 360. It wouldn't be able to rotate continuously but it could point in any direction.
     
  6. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    No, if you stop sending the PWM signal, the servo will NOT swing back to its neutral position. It will basically be uncontrolled and may be moved by any external forces. Here is some information on hobbyist servos:
    http://www.lynxmotion.com/images/html/servo01.htm.

    Markd77's suggestion of adding additional gearing has been done. Just remember that even with that solution, you can only rotate 360° in one direction, then 360° back - no continuous rotation.
     
  7. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Gearing is one solution. You might also consider one of the newer servos that uses a rotary encoder. They are claimed to be extremely precise, and since there is no pot, there is no theoretical reason they cannot rotate 360° or more. I have not seen ads for ones that go more than 360°, but here are links to ones that will move 360°.

    http://www.shanghaiinspection.com/D...recision-High-Torque-Metal-Gear-Servo-p-24683

    http://www.ltair.com/en/productlist.php?intClassID=50

    As mentioned, the signal to a model servo needs to be continuous.

    John
     
  8. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    Are you using a microcontroller in your current design?
     
  9. shortbus

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    Sep 30, 2009
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