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I am new to the electronics hobby so any help is appreciated. For my application I need a quiet motor that can provide high torque at low speed.

I purchased a NEMA 17 stepper motor (model is 17HS4401s) and I am using the DRV8825 driver chip and a PIC microcontroller to drive it. I've connected the circuit as in the diagram below with a 12 V, 2 A motor power supply.

enter image description here

Now, after getting the motor to work, mounting it using screws, and attaching the load, the motor itself is stable, but the shaft vibrates and causes the load to vibrate with it. I've tried the following:

  1. Microstepping the motor to 1/32 steps -> Reduced the vibrations a lot but the load still vibrates
  2. Limiting the current to 1.4 A -> Did not make a difference
  3. Limiting the current to 1 A -> Again reduced the vibration a bit but the load still vibrates
  4. Different step frequency values (0.5 ms, 1 ms and 2 ms) but no significant change happened

Is there a way to get a smooth stable motion from the motor and stop the shaft from vibrating? Would switching to a different driver like the TMC2100 SilentStepStick make a difference?

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  • \$\begingroup\$ What is the motor part number (or if you don't have it, how many degrees per step), and how fast is the shaft rotating when it is vibrating objectionably? \$\endgroup\$
    – TimWescott
    Commented Jan 9, 2021 at 22:35
  • \$\begingroup\$ The motor is 200 steps (1.8 degree) stepper with 1/32 microstepping so so 6400 steps per rotation. and I send a new step signal every 0.5 ms \$\endgroup\$
    – moaz Samy
    Commented Jan 9, 2021 at 23:03
  • \$\begingroup\$ Can you post a picture of the mechanical setup? My stepper vibrates when not mounted solidly. \$\endgroup\$
    – Mattman944
    Commented Jan 10, 2021 at 0:15
  • \$\begingroup\$ if you have a scope and a cheap current sense transformer, stick it on one of the motor wires, you can learn a lot. there are many potential reasons \$\endgroup\$
    – Pete W
    Commented Jan 10, 2021 at 2:22
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    \$\begingroup\$ Ultimately, stepper motors step. You can't get smooth motion from something that moves in discrete steps. Would you be better off with a geared conventional motor, with position feedback if your application needs it? \$\endgroup\$
    – Simon B
    Commented Jan 13, 2022 at 11:40

2 Answers 2

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  1. Only use full steps for max torque. Use appropriate pulley ratios on belt to increase torque as required.
  2. motor noise while moving is due to mechanical resonance, which is dependent on lack of stiffness and lack of damping and bearing slop exciting frame resonance.
  3. Motor noise while idle should not occur but if you hear a squeal noise , it is because of electrical resonance , which depends on supply noise and cable characteristics which transfers motor inductance to the driver.
  4. Ensure at if 2A=24W that the motor has a miniature fan for cooling and same for electronics.
  5. Your motor coil specs are 1.7A and 1.5 Ohms.
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  • \$\begingroup\$ I would think it is perfectly possible for torque variations to cause vibration. Stepper motors are not known for smooth torque. Do you think it is impossible that the vibration is caused by torque variations during rotation? \$\endgroup\$
    – user57037
    Commented Jan 9, 2021 at 22:54
  • \$\begingroup\$ @Tony I don't mind the noise as much I mind the vibration. and I don't know the reason r the fix for that vibration \$\endgroup\$
    – moaz Samy
    Commented Jan 9, 2021 at 23:04
  • \$\begingroup\$ @mkeith I have considered that, but I found people on videos and the internet using stepper motor and never complaining about vibration so maybe it is something wrong with my config? I need to drive the load from the motor directly and avoid belts or gears or something similar \$\endgroup\$
    – moaz Samy
    Commented Jan 9, 2021 at 23:06
  • \$\begingroup\$ I was talking to Tony. He seems to be dismissing the idea that the steps are causing the vibration. I note you say that microstepping helped, so I wonder if torque pulses are causing vibration. In my experience, vibration usually IS caused by mechanical issues. But I would think that with a stepper motor it could also be caused by torque vibrations. \$\endgroup\$
    – user57037
    Commented Jan 9, 2021 at 23:18
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You have not stated it, and in some respects you contradict it, but I'll assume that

"the motor itself is stable, yet the shaft vibrates and causes the causing the load to vibrate with it."

refers to the motor shaft being stationary.

Since you don't have position or velocity feedback, the only likely source of vibration is the PWM frequency used to regulate the current level. This suggests that the driver is faulty, and the PWM frequency is too low, so you can actually see the shaft/load respond.

I'd recommend trying another driver.

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