How to Interface Stepper Motor with PIC18F4550

Introduction

Stepper Motor

A stepper motor is a brushless DC motor that divides a full 360° rotation into a series of equal steps. The motor rotates by following a specific sequence of control signals, and the rotation speed can be adjusted by changing the rate at which these signals are applied. Stepper motors come in various step angles and torque ratings to suit different applications.

Using a microcontroller, different control signals can be sent to the motor to achieve the desired rotation for a given application.

For further information on stepper motors and their usage, refer to the Stepper Motor topic in the sensors and modules section.

Interfacing of Stepper Motor with PIC18F4550

Stepper Motor Interface with PIC18F4550

Here’s the step-by-step process for interfacing a 6-wire unipolar stepper motor with the PIC18F4550 controller:

1. Step 1: Identify Wires
   The stepper motor has six wires, but only four are required for control.
2. Step 2: Connect Common Wires
   Connect the two common wires of the stepper motor to a 5V supply.
3. Step 3: Use ULN2003 Driver
   Use the ULN2003 driver IC to drive the stepper motor.
4. Step 4: Identify Winding Coils
   To identify the winding coils and their center-tap leads, measure the resistance between the leads. The center-tap leads will show half the resistance value of the corresponding winding.

This setup allows the PIC18F4550 to control the unipolar stepper motor using the ULN2003 driver IC.

Example

Let’s program the PIC18F4550 to rotate the stepper motor 360° clockwise using a half-step sequence and 360° anticlockwise using a full-step sequence.

Stepper Motor Control Code for PIC18F4550

/* 
 * Stepper Motor Control using PIC
 * http://www.electronicwings.com
 */

#include <pic18f4550.h>
#include "Configuration_header_file.h"

void MSdelay(unsigned int val)
{
     unsigned int i,j;
        for(i=0;i<val;i++)
            for(j=0;j<165;j++);
}

void main(void)
{
	int period;
    
    	OSCCON = 0x72;		/* Use Internal Oscillator 8MHz */
	TRISD = 0x00;		/* Make PORTD as output */
	period = 100;		/* Set period in between two steps */
	while (1)
	{
		/* Rotate Stepper Motor clockwise with Half step sequence */
		for(int i=0;i<12;i++)
		{
			LATD = 0x09;
			MSdelay(period);
			LATD = 0x08;
			MSdelay(period);
			LATD = 0x0C;
			MSdelay(period);
			LATD = 0x04;
			MSdelay(period);
			LATD = 0x06;
			MSdelay(period);
			LATD = 0x02;
			MSdelay(period);
			LATD = 0x03;
			MSdelay(period);
			LATD = 0x01;
			MSdelay(period);
		}
		LATD = 0x09;	    /* Last step to initial position */ 
		MSdelay(period);
		MSdelay(1000);

		/* Rotate Stepper Motor Anticlockwise with Full step sequence */
		for(int i=0;i<12;i++)
		{
			LATD = 0x09;
			MSdelay(period);
			LATD = 0x03;
			MSdelay(period);
			LATD = 0x06;
			MSdelay(period);
			LATD = 0x0C;
			MSdelay(period);
		}
		LATD = 0x09;
		MSdelay(period);
		MSdelay(1000);
	}
}