Three Modes of Stepper Motor Drivers

The stepper motor drive system consists of the stepper motor and stepper motor drivers. The performance of the system not only depends on the performance of the motor but also based on the quality of the driver.

The stepper motor driver has three basic drive modes: full-step, half step, and subdivision. The main difference between the three is the control precision of the coil current in the motor(namely, excitation mode).

Full Step Drive

In the full step operation, the stepper motor can equip with full step, half step, and subdivision drive, but the operation effect is different. According to the pulse/direction command, the diver cyclically energizes the two coils of the stepper motor. The pulse in this mode will make the motor move a step angle, which is a 1.8 degree(the standard two phases has 200 step angles in one revolution).

Half Step Drive

In single-phase excitation, the motor shaft stops to the full step position. After the driver receives the next pulse, if another phase is excited and remains in the original state of excitation, the motor shaft will move half step angle and stop in the middle of the two adjacent positions. In this way, the two-phase coil is cyclically single-phase and two-phase excitation, the stepper motor will rotate in half step(0.9 degrees per pulse). Compared with full step mode, half step mode has higher precision, lower vibration at low speed.

Subdivision Drive

The subdivision drive mode has low vibration at low speed and high precision. For the application that requires low-speed operation(the speed of the motor shaft is below 60rpm) or the position, accuracy is less than 0.9 degree, the subdivision stepper motor driver has a wide application. The basic principle is that according to sine and cosine steps, the two coils of the motor are controlled by precision current, which will complete the distance of a step angle by dividing it into several subdivision steps. For example, the 16 subdivision drive mode can make the 200 standard steps per revolution stepper motor reach up to 200*16 = 3200 running accuracy per revolution(namely, 0.1125°).

Conclusion

In a full step state, the angular displacement of the motor shaft is a step angle in a pulse. In half step state, the angular displacement of the motor shaft is a half step angle. It is better not to use full step mode, due to high vibration.