How to Use Stepper Motor (Unipolar): Examples, Pinouts, and Specs

A unipolar stepper motor is a type of electric motor that divides a full rotation into a series of discrete steps. It is called 'unipolar' because of the way the coils are wired, allowing for simpler driving circuitry. Stepper motors are commonly used in precision positioning devices like 3D printers, CNC machines, and robotics due to their ability to accurately control motion.

• Precision control in robotics
• Positioning in 3D printers
• Movement control in CNC machines
• Automated equipment in manufacturing

• Step Angle: The angle covered in one step (e.g., 1.8 degrees)
• Voltage Rating: The rated voltage for optimal performance (e.g., 5V)
• Current Rating: The maximum current per phase (e.g., 500mA)
• Resistance: The resistance per phase (e.g., 100 ohms)
• Number of Phases: Typically 4 for unipolar motors
• Holding Torque: The torque when the motor is stationary and powered (e.g., 0.3 Nm)

1. Connect the Coils: Connect the coil start and end pins to the motor driver outputs.
2. Power Supply: Ensure the power supply matches the voltage rating of the motor.
3. Control Signals: Use a microcontroller to send control signals to the motor driver.

• Current Limiting: Use a current-limiting driver to prevent damage to the motor.
• Microstepping: For smoother motion, use a driver that supports microstepping.
• Heat Dissipation: Ensure adequate cooling if the motor is operated near its maximum ratings.

#include <Stepper.h>

// Change these values based on your motor's specifications
const int stepsPerRevolution = 200;  // typically 200 steps for a 1.8 degree step angle
const int motorPin1 = 8;             // Coil 1 Start (A)
const int motorPin2 = 9;             // Coil 1 End (A')
const int motorPin3 = 10;            // Coil 2 Start (B)
const int motorPin4 = 11;            // Coil 2 End (B')

// Initialize the stepper library
Stepper myStepper(stepsPerRevolution, motorPin1, motorPin3, motorPin2, motorPin4);

void setup() {
  // Set the speed in RPMs
  myStepper.setSpeed(60);
}

void loop() {
  // Step one revolution in one direction:
  myStepper.step(stepsPerRevolution);
  delay(500);

  // Step one revolution in the other direction:
  myStepper.step(-stepsPerRevolution);
  delay(500);
}

• Motor Does Not Rotate: Check wiring and ensure the power supply is correctly rated.
• Motor Vibrates but Does Not Turn: This could be due to incorrect sequencing. Check the control signals.
• Motor Gets Hot: Ensure the current is not exceeding the motor's rating. Improve cooling if necessary.

• Check Connections: Verify that all connections are secure and correct.
• Test Power Supply: Use a multimeter to ensure the power supply is delivering the correct voltage.
• Review Code: Ensure the stepping sequence in the code matches the motor's requirements.

• Q: Can I run a unipolar stepper motor with a bipolar driver?

  • A: It is possible by not connecting the common wires, but it's not recommended as it may not utilize the motor efficiently.

• Q: How do I know if my stepper motor is unipolar or bipolar?

  • A: Unipolar motors typically have 5 or 6 wires, while bipolar motors have 4 wires.

• Q: What is the purpose of the common wires in a unipolar stepper motor?

  • A: The common wires are used to power the coils and are connected to the positive supply voltage.

Remember to always refer to the specific datasheet of your stepper motor model for precise information and ratings.