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Regarding NEMA-17 Pan-Tilt Head

Discussion in 'General Talk' started by Nazmus Sakib, Jul 7, 2019.

  1. Nazmus Sakib

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    Hi All.

    I am doing a project for Remote Control Pan-Tilt for DSLR Camera. Attached is the Module I made using 2 NEMA-17 14:1 Stepper Motor. The unit working Ok so far when I moving both of the Axis using Stepper Driver. But my application is Timelapse and where I am facing a problem.

    As I said when I am moving the Motor continuously then its working. But when I am doing Timelpase of small Moves then I observed sometime works and sometimes not. After testing few days I think I get the problem which is ... the Motor shaft is free to rotate by hand with a very small degree (I think its 0.5 to 1 degree). That means ... I can move the shaft by small hand force this small degree. Now when I am doing a Timelapse ... say total move of 45 degree for 300 frames i.e. Per frame needs only 0.15 degree move then most of the time Motor missed to do the Move. As this Timelapse Move of 0.15 degree is less than the Shaft Error of 0.5 - 1 degree. If I try the same 45 degree Timelapse for less frame like 10 frames then it works Ok as each frame move is 4.5 degree.

    But another observation is ... If I do this 45 degree of 300 frame Timelapse with no Camera mounted then it works.

    I am not sure of its a normal behavior of Stepper Motor that it have a free shaft Move of this 0.5 - 1 Degree? Or for this small moves the Motor not able to give enough torque when Camera is mounted? As I directly connected the Pan and Tilt with Shaft so 1 Shaft Revolution gives my Camera 360 Degree Move. So I need the Shaft very tight and no moves happens normally.

    Can anyone advice any solution? Do I need to change the Stepper Motor with high Gear ratio like 27:1 or even 100:1?

    Thanks. Looking forward your reply.

    Regards.
     

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    #1 Nazmus Sakib, Jul 7, 2019
    Last edited: Jul 7, 2019
  2. Kevon Ritter

    Kevon Ritter Master
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    Are the stepper drivers constantly energized? See Quote
    There is also the great possibility of backlash. This is what would let you turn the output shaft ever so slightly, but you should not be able to actually turn the motor through the gearbox.

     
  3. Nazmus Sakib

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    Hi Kevon.

    Thanks for reply.

    I checked it more ... and yes, I also think its backlash problem. My motor driver is constantly powered ON.

    Is there any way to fix this backlash problem? More gear ratio motor like 50:1 or 100:1 will be better choice for this Pan Tilt application?

    Regards.
     
  4. Kevon Ritter

    Kevon Ritter Master
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    Backlash comes from tiny gaps between components. In this case, it's created by the tiny spacing between each gear in the gearbox. The more gears you add, the more that backlash will increase. I have no clue how stepper planetary drives are assembled. With that said, going to a higher ratio may decrease the overall part count, but it may also increase it as well. I wouldn't worry about backlash at all though. Your application isn't a bouncy or vibration rich environment. There shouldn't be any external forces causing the camera to rock back and forth through the range of backlash. The issue here is stepping.

    What stepper driver are you using?
    What is your micro stepping set to?
    Do you have more info on the stepper?
    With a 14:1 ratio, you have 2800step/rev (for a 200 step) or 5600step/rev (for a 400 step).

    I doubt I'll be able to really help you, but I'm hoping that this info is seen by someone who may have ideas.
     
  5. Gary Caruso

    Gary Caruso OpenBuilds Team
    Staff Member Moderator Builder

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    To counter the backlash keep the system loaded with a spring or rubber bands, just strong enough to keep the gear teeth all contacting on one side.
    Cheers
    Gary
     
    Kevon Ritter likes this.

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