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I have a BLDC motor and I am keen to know if there is a controller out there that can allow BLDC to be used as stepper motors with (holding torque and accuracy in step size) I know BLDC motors are built for smooth drive experience while stepper motors are built to perform accurate steps (however is there a way to make BLDC motor perform with with the accuracy of stepper motor?

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    \$\begingroup\$ BLDCs have much less poles than steppers, so the control of the magnetic field orientation is much less fine-grained. Also the holding torque in a position where the poles are not aligned will be much weaker than in the positions where it is aligned. \$\endgroup\$ – Eugene Sh. Feb 24 at 20:46
  • \$\begingroup\$ is there a way to make BLDC motor perform with with the accuracy of stepper motor? No. \$\endgroup\$ – Bimpelrekkie Feb 24 at 20:54
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    \$\begingroup\$ It can work in a stepper type mode, but with much larger steps and with lower holding torque. There is a reason that they make both types of motors. \$\endgroup\$ – Aaron Feb 24 at 21:03
  • \$\begingroup\$ @EugeneSh. alright i believe it depends on the exact type of motor to know how many poles are there.. but having that said is there a way to determine how weak holding torqure would be like roughly 50% less or 80% less, I want to get some idea, also for accuracy, are we talking couple of degrees or less? \$\endgroup\$ – BiologyEnthusiast Feb 24 at 21:09
  • \$\begingroup\$ @Aaron, it is understandable, so for me to get intuition of "much larger steps" how much larger are we taking about and how much lower holding torque ~ roughly? \$\endgroup\$ – BiologyEnthusiast Feb 24 at 21:11
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YES

But you would have to add pulleys and belts made for steppers to reduce the ratio like 64:1 because a stepper may have 64 poles /rev as full steps while a BLDC might be 2 or 3. Then you may have to adjust holding-current to limit heat rise.

The gearing ratio depends on diameter ratio but can be cascaded and made to standard loops of belt or any linear length with end stop switches added.

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  • \$\begingroup\$ can you please expand on the " you may have to adjust holding-current to limit heat rise" part? Also what about the holding torque as I want to use BLDC as a servo motor to hold a robotic arm in place. I know the specifics depend on motor size so roughly any idea of both the motors rated for same wattage which could be potentially difference in holding torque.. \$\endgroup\$ – BiologyEnthusiast Feb 24 at 21:24
  • \$\begingroup\$ It depends on size but it’s common to have muffin fans on the end for moving air fast with heat transfer since it’s not rotating air or use a CNC bridge with an adjustable current limit. One could also use variable or thermal controlled fan. Thus the holding torque vs maximum acceleration torque and heat are trade offs with gear ratio \$\endgroup\$ – Tony Stewart EE75 Feb 24 at 21:45
  • \$\begingroup\$ You want a DC servo system. Some of these may use a bldc motor. The associated controllers will usually allow step and direction like a stepper motor. RMS torque is the spec you want to pay attention to. \$\endgroup\$ – Kartman Feb 25 at 0:48
  • \$\begingroup\$ Yes by using a rotary encoder you can increase torque to load disturbance ratio and reduce idle current according to the feedback ratio of target vs actual position error \$\endgroup\$ – Tony Stewart EE75 Feb 25 at 0:55

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