SPMD250STP

Bipolar stepper motor basics

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5.3

Half step drive

This sequence halves the effective step angle of the motor but gives a less regular torque

being one winding or two windings alternatively energized.

Eight steps are required for a complete revolution of the rotor.

The sequence is:

AB ; AB & CD ; CD ; CD & BA ; BA ; BA & DC ; DC ; DC & AB

as shown in fig. 8.

By the configurations of fig. 6, 7, 8 the motor would have a step angle of 90 ° (or 45 ° in half

step). Real motors have multiple poles pairs to reduce the step angle to a few degrees but

the number of windings (two) and the drive sequence are unchanged.

Figure 6.

One-phase-on (wave mode) drive

Figure 7.

Two-phase-on (normal mode) drive