Stepper motors can be energized in two ways. One is by energizing a single coil at a time. Other is by energizing two coils at a time. In the latter case more torque is obtained. In the previous examples we used single coil excitation. By combining two above two ways of excitations, stepper motors can be operated in two modes.
- Full step mode.
- Half step mode
In full step mode stepper motor will be rotating by a specific angle specified by the manufacturer. But in half stepping mode, it will take only half steps. Thus we could increase the resolution of the stepper. Here a program for working stepper motor in half stepping mode is written in Turbo C++. Algorithm is as follows.
Initially a single coil is exited and rotor gets locked with coil. Next keeping the current coil excited the adjacent coil is also excited. Thus the rotor cannot get into lock with any single coil, instead it will be held in a position between the coils. This makes a half step. Now the first coil is de energized keeping the second coil energized. Like wise when this is looped the stepper makes half steps.
Again interface circuit is same as in the previous examples.