Stepper Motor

Introduction

A stepper motor is an electromechanical device that converts electrical pulses into discrete mechanical movements. Unlike conventional DC motors, stepper motors move in precise steps, allowing exact control of position and speed without feedback in many cases. They are widely used in CNC machines, 3D printers, robotics, and automation systems for high-precision tasks.

Types of Stepper Motors

• Bipolar Stepper Motors: Two coils, require H-bridge drivers, offer higher torque and better efficiency.
• Unipolar Stepper Motors: Usually have center-tapped coils, simpler drivers, slightly lower torque.
• Hybrid Stepper Motors: Combine features of permanent magnet and variable reluctance motors for higher precision.
• Linear Stepper Motors: Convert rotational motion to linear motion directly.

Working Principle

Stepper motors operate using a sequence of electrical pulses applied to their coils. Each pulse moves the rotor a fixed angle, called the step angle. By controlling the number and frequency of pulses, you can control position, speed, and direction precisely.

• Full-step mode: moves one complete step per pulse.
• Half-step mode: alternates between full and half steps for smoother motion.
• Microstepping: divides each step into smaller increments for higher resolution and reduced vibration.

Main Components

• Rotor: Rotating part, often contains permanent magnets or teeth for magnetic interaction.
• Stator: Stationary coils energized in sequence to move the rotor.
• Shaft: Connects rotor to mechanical system.
• Bearings: Reduce friction and support smooth rotation.
• Housing: Metal frame that protects motor and helps dissipate heat.

Electrical Characteristics

• Step Angle: 1.8° (200 steps per revolution) is common; can range 0.9°–7.5°.
• Rated Voltage: 2–12V typically, depends on the motor.
• Rated Current: 0.5–2A per phase.
• Holding Torque: Torque when the motor is energized and stationary.
• Phase Configuration: Bipolar (2 wires per coil) or Unipolar (center tap).

Applications

• 3D printers for X, Y, Z axis movement
• CNC machines and laser engravers
• Camera sliders and robotic arms
• Automated valves, textile machinery, and conveyor systems

Advantages

• Precise positioning without feedback (open-loop)
• High torque at low speeds
• Reliable and simple control using pulses
• Durable with long service life

Limitations

• Resonance at certain speeds can cause vibration and noise.
• Limited high-speed torque compared to servo motors.
• Requires proper current setting to avoid overheating.
• Microstepping adds smoothness but reduces torque slightly.

Connection with MKS Board

Stepper motors connect to stepper driver modules, which are then connected to the MKS board. The MKS board sends STEP and DIR pulses:

• STEP Pin: Each pulse moves the motor one step (or microstep).
• DIR Pin: Determines rotation direction.
• Enable Pin: Turns the driver output on/off.
• Current limits must be set on the driver according to motor specifications to prevent overheating.

Proper wiring ensures smooth motion without missed steps or vibrations.

Maintenance Tips

• Keep the motor and driver cool; check heat sinks and fans.
• Inspect wiring for loose connections or shorts.
• Clean mechanical couplings and shafts for smooth operation.
• Check for unusual noises or skipped steps — may indicate resonance or overcurrent.