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Stepper Motor Positioning Question/Brainstorm

Discussion in 'Robotics & Mechatronics' started by michrod1234, Jul 16, 2013.

  1. michrod1234

    michrod1234 New Member

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    Hi all!

    So I am new to this forum and this question may or may not be answered already or in the incorrect spot. Please let me know if either of those are true :)

    Okay...so I'm starting a project and will be using a stepper motor for the first time. Problem is...I didn't realize that stepper motors can't give feedback and tell me their position? I thought about switching to a servo, but it doesn't quite fit the needs of my project.

    But I DO need some kind of way to know the position of the stepper I'll be using. I need to add 'something' to it. I thought about using a compass, but I'm wondering if anyone with more experience has any better ideas? A friend of mine suggested an encoder...but I'm not really sure how that would work and couldn't find a detailed enough resource on the internetz.

    Any ideas?

    Appreciated!
     
  2. Pommie

    Pommie Well-Known Member Most Helpful Member

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    Normally, whatever the stepper is driving has a home position with a microswitch. For example, a cnc miller would have a lead screw and would initially be driven to the home position and that would be used as the zero position.

    You'll get a much better idea after reading a few threads over at http://www.cnczone.com

    Mike.
     
  3. alec_t

    alec_t Well-Known Member Most Helpful Member

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    What angular resolution do you need? How many steps per rev does your motor have?
     
  4. dave

    Dave New Member

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  5. shortbus=

    shortbus= Well-Known Member

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    If your motor has a double ended shaft, an encoder or resolver can be fitted to it.
     
  6. Mr RB

    Mr RB Well-Known Member

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    You "know" the position of a stepper motor by keeping track of what step you have moved it to previously. Unless there is a massive fault load the stepper motor will not "lose steps".

    If you also need to know the starting position you can use a single sensor like an optical or hall effect sensor. In some applications they just juse a mechanical endstop, and on startup just move the stepper motor as far as it can go (which hits the endstop) then after that its position is known.
     

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