Inputs of the Motor

The Switec stepper motor that is used in this project has four inputs, associated with two coils. When referring to the inputs of the motor, the naming ‘contacts’ will be used in this document. The four contacts will be called: Contact 1, Contact 2, Contact 3, and Contact 4.

Figure 1. Contacts of the Motor

The movement of the rotor is caused by a voltage applied to the coils. Depending on the number of the contacts and the constructive details of the motor, the voltages might have different waveforms. The driving diagram can be found in the motor data sheet.

For the Switec stepper used in this project, the waveforms associated with its contacts are shown in the figure below.
Figure 2. Waveforms Associated with the Contacts of the Motor

These waveforms are periodical square signals with a duty cycle of 50%. The period of each signal is divided into six sequences, defined as partial steps.

In order to drive the motor, the voltage levels associated with each partial step must be applied on its contacts, in the order presented in Figure 2. The rotation can be reversed immediately and at any point.

Figure 3. Position of the Rotor

A period of each signal represents a complete rotation (360°) of the rotor. Because the Switec stepper used has a gear train with a reduction ratio of 1/180, a complete rotation of the rotor is transposed in a 2° rotation of the shaft.