Unipolar Stepper Motor Driver Circuit

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This page presents a circuit for driving high-power unipolar stepper motors. Here you will find all the information needed to make your own. This circuit allows step-level control and can be easily modified for other modes of operation.

What you need

Circuit Schematic and Photo

The L297 has several inputs that can be generated by a PC/104 stack or other controller. This circuit allows you to control each step, in full-step mode. Meaning: You can tell it to move one step in either direction (of course you can make it move fast and it will continuously rotate). The two inputs are a direction and a pulse. In the next section you will find a program to control this using xPC.

Unipolar stepper circuit schematic.png

Here is the CircuitMaker file: Unipolar Stepper Driver Circuit

Unipolar motor driver.jpg Unipolar motor circuit photo.jpg

You may find the following diagrams useful when constructing this circuit:

L297 pinout.jpg NPN pinout.png Stepper wire colors.png

xPC Code

The program below is the simplest program for controlling the circuit above. The Pulse block dictates the speed of the stepper and the constant (1 or 0) sets the direction.

Xpc stepper controller.png


An alternative method for building this circuit is using the DS2003 darlington array. It is lower power, but will save some space and is easier to construct. The circuit is exactly the same as above, except the transistors and half the diodes are inside the IC.

Unipolar driver circuit ds2003.png
Unipolar circuit ds2003 photo.jpg