Aaron Michelle's Homepage

Western Washington University EET

Stepper Motor Control Board




The objective of this project is to gain simple control of a servo motor. Forward/Reverse single step and continuous step and variable speed.



First I acquired a Superior Electric Slo-Syn stepper motor. 1.65V 4.7A. This motor controls a simple, single axis stage which had to be completely disassembled and cleaned then reassembled. The next step was to control the motor. I started by researching stepper motors and found that the motor was a unipolar stepper with 200 steps per revolution which comes out to 1.8 degrees per step. I used the 9S12DG128 microcontroller and wrote a program in assembly to energize the four coils in sequence either forward or reverse with a variable delay between coil energization (variable speed).Then I designed and built a board to interface between the microcontroller and the motor.

The schematic for the interface between the controller and motor.

This is the board layout in Eagle CAD. This shows the components and trace routing. the LEDs are to indicate which coil is being powered.

The next step is to generate the necessary CAM files in Eagle CAD and then import these files into Circuit CAM. Circuit CAM will generate a .cam file that Boardmaster will then read and use to control the mill.

This is the finished product with components

The bottom with the traces and LEDs to indicate coil energization.

The top at a different angle.

The board serving as an interface between the microcontroller and stepper motor.


The whole set-up. The single axis table can now be controlled from a terminal window on the pc communicating to the microcontroller. The microcontroller then activates the coils in the stepper motor through any of the 4 Mosfets.

The board works great and the LEDs help to visualize the speed and direction of the motor. I may end up putting this board in a project box when I also create a power supply that is capable of meeting the hight current that the motor draws.