Hi. I’m a mechanical engineer needing some electronic engineering input for stepper motor system design. My motors rotate an observatory dome at home.
The motors are controlled by a Python program on a Raspberry Pi connected via DRV8871 drivers powered by a 9V transformer. I have attached a diagram of my setup and listed below what I think are the relevant specs for the electronic components.
The motors all run well in air (unconnected to the dome) and so I think the wiring and programming side is all ok. I’m sure that I’ve selected the correct motor torque, power and number of motors to drive the dome (with a generous overdesign on the number of motors based on the measured breakaway torque to get the dome moving).
My issue is that, although the motors rotate the dome most of the time, the motors frequently and randomly stall ('chatter'), where the motor shafts just stop turning and oscillate clockwise and anticlockwise a fraction until I turn the power off or give the dome some assistance to get it moving again. The number of drive motors installed makes no obvious difference to the stalling issue.
As I'm now sure I have ruled out all the potential mechanical issues that could have been preventing the dome from turning, I'm suspecting it's my lack of knowledge on the selection of the electronic components I’m using.
Spec for Stepper Motors 17HS15-1684S-PG5:
Amps / Phase 1.68A
Spec for the DRV8871:
6.5V to 45V motor power voltage
3.6A peak current
Spec for DC transformer
9V, 22A
I would be grateful if anyone out there who understands stepper motors better than me could cast an eye over my setup and point out any obvious issues / improvements I could make.
Also, any idea what the chattering is a symptom of?
Thanks for reading
Alastair
The motors are controlled by a Python program on a Raspberry Pi connected via DRV8871 drivers powered by a 9V transformer. I have attached a diagram of my setup and listed below what I think are the relevant specs for the electronic components.
The motors all run well in air (unconnected to the dome) and so I think the wiring and programming side is all ok. I’m sure that I’ve selected the correct motor torque, power and number of motors to drive the dome (with a generous overdesign on the number of motors based on the measured breakaway torque to get the dome moving).
My issue is that, although the motors rotate the dome most of the time, the motors frequently and randomly stall ('chatter'), where the motor shafts just stop turning and oscillate clockwise and anticlockwise a fraction until I turn the power off or give the dome some assistance to get it moving again. The number of drive motors installed makes no obvious difference to the stalling issue.
As I'm now sure I have ruled out all the potential mechanical issues that could have been preventing the dome from turning, I'm suspecting it's my lack of knowledge on the selection of the electronic components I’m using.
Spec for Stepper Motors 17HS15-1684S-PG5:
Amps / Phase 1.68A
Spec for the DRV8871:
6.5V to 45V motor power voltage
3.6A peak current
Spec for DC transformer
9V, 22A
I would be grateful if anyone out there who understands stepper motors better than me could cast an eye over my setup and point out any obvious issues / improvements I could make.
Also, any idea what the chattering is a symptom of?
Thanks for reading
Alastair
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