Continuous coil excitation sequence

The timed switches from the previous model have been replaced with the DC part set to PULSE every 4ms for each coil. Total period for 4 coils is 16ms.

Graph showing all four stepper coils exciting in sequence
Note: No attempt has been made to model the motors magnetic characteristics in this simuation.

Conclusion
While it is difficult to model the actual torque and load present in a stepper, using these example circuits it is possible to alter the parameters and simulate the driving circuit of a unipolar stepper motor.