Stepper Motor: Difference between revisions

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=Arduino Tutorial=
=Arduino Tutorial=
Good description. Bottom line:
Good description. Bottom line [https://forum.arduino.cc/index.php?topic=284828.0]:
*Voltage of stepper is low, say 5V, but must be driven at 12-48V due to back emf
*Voltage of stepper is low, say 5V, but must be driven at 12-48V due to back emf
*Inductance and resistance slow down the motor. The lower these quantities, the faster it can rotate.
*Inductance and resistance slow down the motor. The lower these quantities, the faster it can rotate.
*A motor draws a constant current - control electronics work by limiting this current
*A motor draws a constant current - control electronics work by limiting this current
*If a motor draws 3A at 5V - what current does it draw when driven with 48V? Clearly it must be much lower or it would overheat from dissipated heat. [https://electronics.stackexchange.com/questions/313880/understanding-how-much-power-a-stepper-motor-draws] indicates that the drive is a chopper drive- ie, a switching power supply that handles power and probably at 20% energy loss.
*If a motor draws 3A at 5V - what current does it draw when driven with 48V? Clearly it must be much lower or it would overheat from dissipated heat. [https://electronics.stackexchange.com/questions/313880/understanding-how-much-power-a-stepper-motor-draws] indicates that the drive is a chopper drive- ie, a switching power supply that handles power and probably at 20% energy loss.
Here is a second very useful response [https://electronics.stackexchange.com/questions/313880/understanding-how-much-power-a-stepper-motor-draws]:
*Each phase takes the same power in a bipolar (2 phase) motor
*What is the relationship of number of phases to number of windings?
*What is the relationship between number of phases and number of wires?
*Power dissipated by a stepper is I2R - and the actual current out of a power supply is simply P=IV. V_supply >> V_stepper, so current for a high power supply will be lower.


=Voltage=
=Voltage=

Revision as of 23:23, 18 April 2019

Overview

Stepper Motor

A stepper motor (or step motor) is a brushless, electric motor that can divide a full rotation into a large number of steps. The motor's position can be controlled precisely without any feedback mechanism (see Open-loop controller), as long as the motor is carefully sized to the application.

How Stepper Motors Work

  • Basic animation on Wikipedia - 4 poles, multiple teeth - advance of 1/4 tooth per phase - so the resolution is number of teeth*number phases =25*4=100 in the example - [1]
  • See good overview. Note that steppers are typically made of 2-rotors of opposite polarity - [2]
  • Microstepping
  • Difference between 2 phase and 5 phase stepper motors - [3]
  • Comparison of stepper motor to brushless DC motor - [4]
  • Note that the combination of poles and phases determines the full step resolution. If you have many poles and 2 phases, you can advance in a number of steps proportional to the product of number of poles and number of phases. You can have many poles and 2 phases, or many poles and many phases - and each can give the same resolution. The ultimate resolution is determined by the number of poles and microstepping - where microstepping is activating the 2 rotors out of phase
  • https://www.motioncontroltips.com/faq-what-are-stepper-drives-and-how-do-they-work/

Holding Torque vs Moving Torque

  • 125 oz in hold for nema 17, example - [5]

Arduino Tutorial

Good description. Bottom line [6]:

  • Voltage of stepper is low, say 5V, but must be driven at 12-48V due to back emf
  • Inductance and resistance slow down the motor. The lower these quantities, the faster it can rotate.
  • A motor draws a constant current - control electronics work by limiting this current
  • If a motor draws 3A at 5V - what current does it draw when driven with 48V? Clearly it must be much lower or it would overheat from dissipated heat. [7] indicates that the drive is a chopper drive- ie, a switching power supply that handles power and probably at 20% energy loss.

Here is a second very useful response [8]:

  • Each phase takes the same power in a bipolar (2 phase) motor
  • What is the relationship of number of phases to number of windings?
  • What is the relationship between number of phases and number of wires?
  • Power dissipated by a stepper is I2R - and the actual current out of a power supply is simply P=IV. V_supply >> V_stepper, so current for a high power supply will be lower.

Voltage

Running steppers at higher voltage produces more torque. 20x rated voltage is ok. [9]

Lifetime

The typical lifetime for a stepper motor is 10,000 operating hours. This approximates to 4.8 years; given the stepper motor operates one eight-hour shift per day. The lifetime of a stepper motor may vary in regards to user application and how rigorous the stepper motor is run.[10]

See Also

Torque Tests

Test 1

This test used Nema17 stepper motors driven by A4988 driver boards http://reprap.org/wiki/Stepper_torque

M vs n.PNG

Summary: All motors perform well at speeds < 100 revs/min. Dynamical torque starts to drop off at speeds higher than 300 rev/min. The higher the rated current and the lower the inductance, the better the performance at high speeds.

inside a stepper motor

Types of Stepper Motors

  • 17PM-K402 - Hybrid 2 and 4 phase - 6 volts rated - [12] - RAMPS wouldn't run it.
  • 12 V rated - [13] - RAMPS wouldn't run it

Sourcing

NEMA 34

  • 360 in lb - 0.6" shaft, 6x planetary gear - $84 - [14]
  • 75 in lb - $77 - Ebay - [15]

Driver

  • 5A TB6600 driver - $14 each - [16]
  • 4A TB6600 driver is typically $8 - [17]

Small

  • 3A - $6 each - [18]
  • 4A - $9 each for 5 - [19]
  • 4A - Single - $11 - [20]

By Origin

Links

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