TABLE OF CONTENTS Chapter 8 introduces the stepper motor, and shows how to drive both unipolar and bipolar steppers in full step, half step and wave modes. It also covers the fundamentals of motor speed up through L/R drive methods.
This chapter covers two more advanced topics; microstepping and a general-purpose serial-controlled stepper driver program. Both topics are illustrated with programs that blend MBasic with assembler language for time-critical routines. If you haven't read Chapters 8, 10, 13, 14 and 15 yet, now is a good time to do so.
One final note; this chapter focuses on bipolar stepper motors, but as you know from Chapter 8, unipolar motors work with same program by simply changing the driving hardware from a bipolar H-bridge to one aimed at unipolar motors. And, you may even use the same bipolar H-bridge driver to drive a unipolar motor, operating in bipolar mode.
Let's go back to the conceptual bipolar stepper motor introduced in Chapter 8. As illustrated in Figure 19-1 if the currents through windings A-C and B-D are equal, the rotor orients itself at an angle halfway between the two stator poles, in our simple four steps per revolution motor, at 45 degrees. We'll say our imaginary motor has 1 ampere flowing through both windings A-C and B-D. Suppose we maintain windings B-D at 1 ampere, but reduce A-C's current to 0.5 ampere. Intuitively, you should see that the rotor will shift to being more closely aligned with winding B-D. If we maintain windings...
