Driver for bipolar stepper motor based on 74LS194

In this article we will see how to build a single economic driver for stepper motors is not unipolar. This driver can be used with engines of low power and requires no microcontroller.

The assembly is based on an integrated circuit 74LS194. It is designed to provide the basic control functions such as advance (forward), reverse (Reverse), Stop (Stop) and adjusting the speed to 100 steps per minute.


This is not a complex project, and all parts used are easy to find. The method used to change the direction of rotation is a key, but you can easily change this to control the system through the parallel port of a PC.

Speed ​​control is via a potentiometer, but it could also be used for devices such as those mentioned above.

NOTE: This circuit should not be used for applications requiring high precision in the control or positioning.

Basic circuit of the driver
The following figure shows the basic circuit used. (Blue line shows the CLOCK).



Schematic representation of the printed circuit board
The following diagram shows the position of each component on the PCB and the function of each terminal connection.






Component List
* 1 x 74LS194
* 1 x 74LS74
* 1 x ULN2003AN
* 1 x NE555N
* 1 x L7805ACV
* 2 x 2N3904
* 1 x 512-1N4001
* 1 x 470uF/35V
* 1 x 10uF/25V
* 1 x 4.7uF/25V
* 1 x 1uF/25V
* 1 x 3mm GREEN LED
* 3 x 10K 1/4W
* 2 x 3.3K 1/4W
* 1 x 470 ohm 1/4W
* 2 x 2 POS. TERMINAL BLOCK
* 3 x 3 POS. TERMINAL BLOCK