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How to fix SG90 servo motor jitter on BeagleBone Black with PWM?

Hey guys, am developing a robotic arm control system using a BeagleBone Black running Embedded Linux using `AM335x ARM Cortex-A8`. The system needs to control the position of a servo motor(SG90) using `PWM`. I have ensured that the `Adafruit_BBIO` library is correctly installed and imported in my script, adjusted the duty cycle range if the servo motor does not reach the full range of motion (0-180 degrees).

But am getting the error 

`warning: SG90 Servo motor jitter detected`

   


   import Adafruit_BBIO.PWM as PWM

   import time


   # Define PWM pin and servo parameters

   PWM_PIN = "P9_14"

   PWM_FREQUENCY = 50  # Servo motors typically use a 50Hz frequency


   # Initialize PWM

   PWM.start(PWM_PIN, 7.5, PWM_FREQUENCY)  # Start with 7.5% duty cycle (neutral position)


   def set_servo_angle(angle):

       # Convert angle to duty cycle

       duty_cycle = (0.05 * angle) / 18 + 2.5

       PWM.set_duty_cycle(PWM_PIN, duty_cycle)


   try:

       while True:

           for angle in range(0, 181, 10):  # Sweep from 0 to 180 degrees

               set_servo_angle(angle)

               print(f"Servo Angle: {angle} degrees")

               time.sleep(0.5)


           for angle in range(180, -1, -10):  # Sweep back from 180 to 0 degrees

               set_servo_angle(angle)

               print(f"Servo Angle: {angle} degrees")

               time.sleep(0.5)


   except KeyboardInterrupt:

       print("nExiting...")


   finally:

       PWM.stop(PWM_PIN)

       PWM.cleanup()

   
  1. Boss lady#0000

    0servo1.png

  2. ZacckOsiemo#0000

    Really wanna dig into this albeit I don’t have elinux exp

  3. ZacckOsiemo#0000

    I am also tuning the same motor

  4. Boss lady#0000

    @superbike_z This are the materials I studied along with BeagleBone Black documentation for this project

    https://www.electronics-tutorials.ws/blog/servo-motor.html

    https://www.learnrobotics.org/blog/pwm-basics/

    https://www.packtpub.com/product/advanced-robotics-projects-with-beaglebone-black/9781788627907

    You can learn bash scripting on YouTube from

    To get an extensive level of Linux experience

  5. ZacckOsiemo#0000

    I am doing it on stm32 not on embedded linux

  6. Boss lady#0000

    Ooh okay, I also came across these materials during my research but didn’t bother to go through them, they might be helpful to you

    https://controllerstech.com/stm32-pwm-tutorial/

    https://stm32-base.org/guides/servo-control

    https://www.st.com/content/st_com/en/applications/industrial/motor-control-and-drives.html

  7. ZacckOsiemo#0000

    Oh lovely thank you, yes currently paused because I haven’t wired up my power supply 😦

  8. ZacckOsiemo#0000

    I should add I am not stuck with the same issue you are with, jitter could be caused by imprecise pwm

  9. Boss lady#0000

    What do you suggest I do to fix this

  10. superbike_z#0

    Hey @bosslady0299 might be a bad motor do you have another sample to test?

  11. superbike_z#0

    There is a few things

  12. superbike_z#0

    either your timing is off

  13. superbike_z#0

    or your motor is bad

  14. ZacckOsiemo#0000

    Lets explore a bit are you using an external power supply?

  15. Boss lady#0000

    Yes, A 4xAA alkaline battery

  16. medic4950#0

    If I remember correctly the beegleone Black as a very poor software

  17. medic4950#0

    Sometimes the PWM does not work at all

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