What is a Stepper Motor Driver?

The stepper motor driver is a drive circuit that enables the stepper motor to operate according to its function. For example, a stepper motor needs enough energy and controls the voltage of each phase in a precise sequence. Therefore, stepper motors are considered to be more accurate than traditional classic DC motors.

The stepper motor driver is a driver circuit that controls the working mode of the stepper motor. The working principle of the stepper motor driver is to send current to the stepper motor in the form of pulses in each phase. There are four types: wave driver, two-phase driver, one-two-phase driver and microstep stepper motor driver.

The waveform stepper motor driver can only excite one phase at a time. When the stepper motor driver energizes the green pole A (south pole), it will attract the north pole of the stepper motor rotor. Then, when the stepper motor driver energizes B and de-energizes A, the rotor will rotate 90 degrees and continue to rotate as the stepper motor driver energizes each phase once.

A complete process usually requires two orthogonal rectangular pulse signals. Depending on the leading phase, the shaft of the stepper motor will rotate clockwise or counterclockwise. The speed is proportional to the clock frequency of the control pulse. This is the GND and + signal mentioned earlier. Therefore, according to the DIP switch set by the step resolution, the stepper motor will move from one position to the next. For example, if you set it to full-step mode, the entire step will be executed, if you set the stepper motor to half-step mode, it will execute half a step, and so on.

Due to inertia, the pulse must be adjusted to synchronize with the magnetic field. Otherwise, the stepper motor may stall. The pulse ramp must also remain smooth and have almost no movement to prevent the stepper motor from stalling and shaking.

The sine wave of the current has fine serrations on the edges. Microstep does not necessarily improve accuracy, but compared with other drive modes, it has higher resolution and accuracy, and is especially suitable for stepper motor applications under no-load conditions. During operation, the stepper motor may lose step. However, the microstep setting will disperse the applied energy, which can reduce the vibration of the stepper motor and reduce the possibility of out-of-step.

For all these driving methods, stepper motors can have different windings. Unipolar motors only accept positive voltage. Unipolar stepper motors require an extra wire in the middle of each coil to match the current flowing from one end to the other. The bipolar stepper motor uses both positive and negative voltages. Bipolar stepper motors have greater torque because they generate a stronger magnetic field, but their structure also determines the demand for more outlet ports.

Driving a stepper motor does not have to be too complicated

Although the process of setting up a stepper motor may seem complicated, it requires precise control and the process may be very simple. Using a microstep controller is an effective way to drive a stepper motor, because the stepper motor driver only needs a few signals. It is also easy to pair a stepper motor with a driver. Through the establishment of continuous working phase current, the rated current of each phase coil, and the drive pulse signal can drive the stepper motor to work.

External links and reference

1. Wikipedia: Motor controller

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