Biomedical Engineering Reference
In-Depth Information
FIGURE 3-29
Schematic of a
standard unipolar
stepper motor drive
configuration.
[Adapted from
(Alciatore et al.,
2003)].
Unipolar configurations use a single voltage rail but can still drive in both direc-
tions because of the way that the windings are configured, as seen in Figure 3-29. The
conventional color codes for these stepper motors are indicated in the diagram.
To implement the appropriate magnetic configurations of the stator shown in Fig-
ure 3-28, each pole pair must be wound with a pair of complementary windings (bifilar
windings), as shown in Figure 3-30. A useful result of this configuration is the ability
to half-step, where only one pair of windings is excited. The switch sequences for full
stepping and half-stepping are listed in Table 3-4.
In the half-step mode, the resolution, or number of steps, is twice that of the full-
step mode. In this case it increases from 4 steps (90
◦
) per revolution to 8 steps (45
◦
) per
revolution.
FIGURE 3-30
Operation of a
unipolar stepper
motor with bifilar
windings.
