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Arm built and almost there...... couple of small issues though.

Hey guys.

I have my arm built and electronics installed.
I have gotten all of the steppers to work on the arm via the controller.
I do have an issue with the base rotation motor (1) It seems to be stuck in permanent motion in one direction.
I can stop it by moving the appropriate stick on the control just enough in the right direction.... a little more and it goes the other way. I release the stick and off the motor goes again.
Could this be that the control was not in its neutral position when the software was installed? or a dodgy control possibly?

Only one other thing.... the gripper seems to move on startup but not via the controller.
Is this indicative of any particular obvious cause I am not seeing?

Cheers guys.


  • Hey Razz,

    The motor issue is most likely happening at the controller. It has some threshold values that it looks for and will not move the arm. We have found that these values are not consistent so you may have to increase them in

    The gripper should just work with assuming the right libraries are installed. You can try the below on its own and see what happens. The GPIO that controls the stepper is directly connected to an IO on the raspberry pi.

    GPIO.setup(18, GPIO.OUT)
    pwm = GPIO.PWM(18, 100)
  • Thanks for the info... greatly appreciated.
    can you point me toward a "how to" to modify the thresholds for the controller?
    and the above code is pasted into the terminal after running the initialization for the arm to test the gripper correct?
  • edited December 2017


  • Anyone able to help me to adjust the threshold values in the script?
    Just a simple point to where I can learn myself how to do it would be great. :-)

  • Ok I think I have the area I need to adjust for the base rotation motors....
    Would it be advisable to change the -1500 and 5000 to -3500 and 3500 to stop the base wanting to continually rotate in one direction?

    if event.code == 'ABS_X':
    value = event.state
    if value < -1500:
    if not joints[0].isBusy(): joints[0].run(1, 35)
    elif value > 5000:
    if not joints[0].isBusy(): joints[0].run(0, 35)
    if not joints[0].isBusy(): joints[0].softStop()

    Or am I reading this wrong?

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