**Introduction to Stepper Motors**
A stepper motor is an electromechanical device that converts electrical pulse signals into angular or linear displacement. The input to the motor consists of a sequence of pulses, and the output is a corresponding incremental movement or stepping motion. In normal operation, it has a fixed number of steps per revolution. When performing continuous stepping motion, its rotational speed is directly proportional to the frequency of the input pulses, and it remains unaffected by voltage fluctuations or load changes. Due to its ability to accept digital control, it is particularly well-suited for use with microcomputers.
**(1) Types of Stepper Motors**
There are three main types of stepper motors:
(1) **Variable Reluctance (VR)** – These motors have a simple structure, low cost, and small step angles, but their dynamic performance is relatively poor.
(2) **Permanent Magnet (PM)** – These motors offer higher torque and better dynamic performance, but they have larger step angles.
(3) **Hybrid (HB)** – Combining the advantages of both VR and PM motors, hybrid stepper motors feature smaller step angles, higher torque, and excellent dynamic performance. They are considered the most advanced type of stepper motor and are sometimes referred to as permanent magnet induction stepper motors.
**(2) Working Principle of Stepper Motor**
Figure X1 shows a schematic diagram of a three-phase variable reluctance stepper motor. The stator has six evenly spaced magnetic poles, each with a 60° angle between them. Coils are wound around these poles and connected to A, B, and C phase windings. The rotor has 40 small teeth, with a pitch of θE = 360° / 40 = 9°. Each stator pole also has five small teeth, matching the rotor’s tooth spacing. Because the number of teeth on the stator and rotor differ (30 vs. 40), there is a "tooth misalignment."
When the A-phase winding is energized, the rotor aligns its teeth with those of the A-phase pole. When the B-phase is energized, the rotor rotates by 3° due to the reluctance torque until the B-phase teeth align with the rotor. This process continues with each phase being energized in sequence, resulting in a regular step of 3° per pulse. By changing the sequence of pulses, the direction of rotation can be reversed.
The step angle θb for a single three-phase operation is calculated using the formula:
θb = 360° / (N × Er)
Where N is the number of phases and Er is the number of rotor teeth.
**(3) Characteristics of Stepper Motors**
- Stepper motors require pulse signals to operate. Without pulses, they remain stationary.
- They can start and stop instantly, making them ideal for precise control.
- The direction of rotation can be easily changed by altering the pulse sequence.
**L298N Drive Motor Operation**
The L298N is a dual H-bridge driver chip commonly used for controlling DC and stepper motors. It features optocoupler isolation for noise immunity and includes built-in protection circuits. The L298N allows for forward and reverse motor control, and supports both full-step and half-step modes. It can drive up to 2A continuously, with a peak current of 3A, and is suitable for a wide range of voltages (5–35V).
Key features include:
- Dual H-bridge configuration for driving two DC motors or one bipolar stepper motor.
- Built-in flyback diodes for inductive load protection.
- LED indicators for power and operational status.
- Compact PCB size (4.4 x 5.0 cm).
- Supports motor reversal and speed control via pulse input.
**L298N Stepper Motor Program**
The L298N is often used in conjunction with microcontrollers such as Arduino to control the stepping motion of a motor. The program typically involves setting up the motor's direction, step mode, and timing. By sending specific pulse sequences to the L298N, the motor can rotate in either direction with precise control over speed and position. The circuit may generate heat during prolonged operation, so proper cooling is recommended for optimal performance.
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