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Incremental rotary encoder motor help

  1. Jan 14, 2016 #1
    1. The problem statement, all variables and given/known data
    Hi please see the image that I have attached. The text colored in red is the data I need to calculate.

    2. Relevant equations


    3. The attempt at a solution
    The encoder has 128 counts per revolution
    So to calculate corresponding angle change this I what I did
    I divided encoder count in decimal number by 128 which gave the number of revolutions, I then multiplied it by 360 to find the angle change

    So for example I did
    6350/128 = 49.61 revolutions
    49.61 * 360 = 17859.34 degrees

    Is this method right?

    To calculate no load speed RPM, I divided the revolutions by (time*60) to get it to RPM

    So for the 6350 encoder count which gave 49.61 revolutions

    I did

    49.64/(5.25*60) = 0.1575 RPM

    Is this RPM calculation right?

    For me it looks as if the RPM is well below and so I must have made a mistake somewhere but I don't know specifically where
     

    Attached Files:

  2. jcsd
  3. Jan 14, 2016 #2

    Hesch

    User Avatar
    Gold Member

    That's correct.

    To calculate the speed, you must know the sample frequency. Say it is 1Hz. Then you will have 6350 counts per second.
    Convert to RPM. ( 128 counts per rev, 60 sec/min ).

    The result is close to 3000 RPM.

    If the sample frequency were 2Hz, the motor speed would be the double ( ≈ 6000 RPM ).
     
    Last edited: Jan 14, 2016
  4. Jan 15, 2016 #3
    Hi can you please tell me where RPM came from?
    I know that it took 5.25 sec for the angle change and so frequency would be 1/T = 1/5.25 = 0.1905Hz

    But I don't really know how to find RPM
     
  5. Jan 15, 2016 #4

    Hesch

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    Gold Member

    So 49.61 rev. within 5.25 sec, which gives 9.449 rev./sec ≈ 567 rev/min. = 567 RPM. ( 1 min = 60 sec ).

    The RPM's in #2 is just an example, not knowing your mentioned 5.25 sec.
     
  6. Jan 16, 2016 #5
    Ok thanks I understand it now
     
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