Unipolar stepper motor and bipolar stepper motor
According to the different connection mode, the stepper motor can be divided into single-pole stepper motor, and bipolar stepper motor.
Unipolar stepper motor driver circuit
In a single-pole stepper motor, a lead is connected to the central point of the coil. The advantage of this connection is that the direction of the current can be controlled with a relatively simple circuit.
If the switch is active, current flows from one place to another, creating a magnetic field in the opposite direction.
The benefits of this approach is that the drive circuit can be simplified, because only need two semiconductor switch, but the drawback is a use only half of the motor coil, this means that if the same current flows in the coil, magnetic field intensity will be reduced by half, in addition, due to the lead must connect more, so this kind of motor is more difficult to construct.
In a bipolar stepper motor, each coil has only two leads, and to control the direction, a circuit must be used. This wiring scheme has the disadvantage of requiring more complex driving circuits, but the advantage is that it can achieve the maximum torque of the motor. Compared with the single-pole stepper motor, this connection can improve the torque by 40%, or twice as much as the single-pole stepper motor.
Stepper motor full step, half step, and micro step drive
Stepper motor has three driving modes, namely full step, half step, and micro step drive.
(1) Full step drive
Full step drive, is a step at a time, this is a common drive. According to the number of energized phases, the full step drive is divided into two types, one is single-phase energized drive, the other is double connected electric drive.
Single - phase and double - phase full - step drive concept
(2) half-step drive
A half-step drive is a half-step drive at a time.
The advantage of half-step drive is to improve the resolution, but the disadvantage is that the torque is only 70% of the full step drive. Of course, you can also improve the half-step drive torque by optimizing the current in the coil.
Single - phase and dual - phase alternating power, realize the concept of half - step drive. When a single phase is energized, the coil generates a magnetic field, and the magnet points to the energized coil because of the attraction of the magnetic field. When both coils are connected, the combined magnetic field puts the rotor in an intermediate equilibrium position because both coils generate magnetic fields.
Single - phase and dual - phase alternating power, realize the concept of half - step drive. When a single phase is energized, the coil generates a magnetic field, and the magnet points to the energized coil because of the attraction of the magnetic field. When both coils are connected, the combined magnetic field puts the rotor in an intermediate equilibrium position because both coils generate magnetic fields.
(3) Micro step drive
Because the current size is different, will lead to the coil generated magnetic field strength is different, resulting in the balance position of the rotor changes, this is the principle of micro step drive.
Micro-step driving principle: One coil has the maximum current at the beginning, while the other coil has zero current at this time, and the stator points to a coil. One coil slowly DECREASES the current, the OTHER coil slowly increases the current, because the magnetic field balance position changes, the stator slowly turns to the other coil. Macroscopically, the current change in one coil is close to the curve, the current change in the other coil is close to the curve, until the current in one coil decreases to zero, and the current in the other coil reaches the maximum value, and the stator points to the other coil.
