1. Basic Knowledge of Stepper Motor

The main control modes of stepping motors are as follows:

 

 

Single-phase drive: It controls the motor to rotate by only one step angle at a time (only one phase winding is energized in each operation), which is applicable to relatively simple motion control, yet features low precision and small torque.

Two-phase drive: It only controls the motor to rotate by a half step angle at a time (two phases of windings are energized in each operation), which delivers relatively high torque but features slightly complex structure and control logic.

Half-step drive: It controls the motor to rotate by a half step angle each time (via the alternate power-on mode of single-phase and double-phase), so as to achieve higher control accuracy.

2. Application Experiment

Here, we use the single-phase drive mode to drive the stepper motor. Simply put, the principle of the single-phase drive mode is as follows:

 

4-phase winding structure: The 28BYJ-48 stepper motor has 4 independent winding phases, which are controlled by the four pins IN1, IN2, IN3 and IN4 respectively.

Sequential power-on drive: By energizing these four phase windings in sequence, the stepper rotation of the rotor can be achieved. Each time the on-off state of one phase winding is switched, the rotor will move by one step angle.

Hysteresis Structure: The rotor adopts a hysteresis structure, that is, the rotor is composed of a ring of permanent magnets, while the stator consists of 4 electromagnet windings. When a certain phase winding of the stator is energized, a magnetic pole will be generated to attract or repel the magnetic pole of the rotor, thus driving the rotor to rotate.

Deceleration mechanism: The 28BYJ-48 has a built-in deceleration mechanism, which reduces the step angle from the motor's inherent 7.5° to 0.0625°, thus greatly improving the angular resolution.

# Python env   : MicroPython v1.23.0
# -*- coding: utf-8 -*-
# @Time        : 2024/7/27 上午10:23
# @Author      : 李清水
# @File        : main.py
# @Description : GPIO类实验，通过GPIO控制步进电机转动

# ======================================== 导入相关模块 ========================================

# 硬件相关模块
from machine import Pin
# 时间模块
import time

# ======================================== 全局变量 ============================================

# 初始化 GPIO 引脚元组，每个元素为 Pin 对象
pins: tuple[Pin, ...] = (
    Pin(2, Pin.OUT),
    Pin(3, Pin.OUT),
    Pin(4, Pin.OUT),
    Pin(5, Pin.OUT)
)

# ======================================== 功能函数 ============================================

def control_step_motor(step: int) -> None:
    """
    控制步进电机的步进逻辑。

    按照当前步进索引，将对应引脚电平拉高，其余引脚电平拉低，
    实现步进电机的顺序控制。

    Args:
        step (int): 当前步进索引，取值范围为 0 ~ 3。

    Returns:
        None
    """
    for index, pin in enumerate(pins):
        # 索引等于当前步值的引脚拉高，其他引脚拉低
        pin.value(index == step)

# ======================================== 初始化配置 ==========================================

# 上电延时 3 秒
time.sleep(3)
# 打印调试消息
print("FreakStudio: Using GPIO to control step motor")

# ======================================== 主程序 =============================================

while True:
    # 遍历 0 ~ 3 共 4 个步进值
    for step in range(4):
        # 调用步进控制函数
        control_step_motor(step)
        # 每步延时 4 毫秒
        time.sleep_ms(4)