Stepper motor

Stepper motors can very generally be divided into unipolar and bipolar steppers. Unipolar stepper motors are characterized by their centre-tapped windings, which divide two coils into four. Stepper motors have neither built-in brushes nor internal electronics, meaning that all commutation must be performed externally. The most common commutation type is the open-loop mode: the motor driver energizes the coils following a certain pattern, but uses no feedback. Steps can be missed in case of motor shaft torque overload. Missed steps cause inaccurate positioning. Bipolar stepper motors usually have four wires and two separate coils inside; they have many features similar to those of unipolar steppers. Unipolar stepper motors can be run as bipolar stepper motors, but not vice versa.

Table of stepper motor windings.

Table of stepper motor drive signals from ATmega128 to the actuator board.

1. Make sure all power is off.
2. Connect the actuator board and main board with a 26-pin cable.
3. Connect the stepper to the actuator board, as shown in Figure 3.

Note: The unipolar motor cable must be properly connected (wires a and b, according to figure 1, connects to pin 1 and 2 on connector UNI1 or UNI2).

1. Connect the JTAG converter with the ATmega128 main board and the PC.
2. Finally, connect the power to the main and actuator boards.