Hardware Reference
In-Depth Information
Bipolar Stepper Modes
Before we look at the schematic and software, let's review how the bipolar stepper motor
works. There are three basic modes of operation for a
bipolar
stepper motor:
•
Wave drive, one-phase-on drive
•
Wave drive, two-phase-on drive
•
Half-step drive
One-Phase-On Mode
Figure
7-4
shows the first two of four possible drive states for wave drive, one phase on.
Each winding is energized in turn for the first two steps. The final two steps energize
the same two windings in sequence except that the current polarity is reversed. In other
words, the south pole of the rotor follows the positive input polarity (as wired in the
figure). In this mode, there are a total of four steps.
Figure 7-4.
Wave drive, one phase on
This simple mode of operation suffers from the loss of precision that the half-step
drive has and lacks the torque of two-phase-on mode.
Two-Phase-On Mode
Wave drive, two-phase-on mode energizes both windings for each step. This is where the
extra torque comes from. Figure
7-5
shows two of the four possible steps for this mode.
Notice how the south pole centers itself between two poles, as it follows the two positive
polarities. Like the one-phase mode, there are only four possible steps.
