Stepper Motor Driver by SN74194

This page features an inexpensive stepper motor driver that could be used to power slow speed projects on the layout or other hobby applications.

Based on the SN74LS194 - Bidirectional Universal Shift Register the circuit is designed to drive UNIPOLAR type stepper motors and provides only basic control functions - Forward, Reverse, Stop and Speed adjustment.

The only step angle for this driver is the design step angle for the motor.

The circuit is not complex and is cheaper than many dedicated driver/controller devices and the parts are reasonably easy to find.

For the purposes of this page the direction control function is selected by an ON-OFF-ON type toggle switch. This could be easily replaced by another method such as transistors controlled by a PC’s parallel output port.

Speed control is by means of a potentiometer but the circuit could accept pulses or controls from other sources such as a push button or a simple computer interface. The direction could also be controlled by a computer interface.
The following diagram is for the main circuit of the motor driver.

A testing version is shown near the end of this page. It is laid out differently and shows the SN7474 in logic block form and LED’s are used to indicate the motor coils being switched.
The blue line on the drawing is the path that the CLOCK pulses that drive the circuit follow.

The stepper motor would not be connected as shown on the schematic as the motors usually have a common and four coil leads.

Also, the filter capacitor at the power supply to the circuit would not be connected as shown.

Read More Source:
http://home.cogeco.ca/~rpaisley4/Stepper.html
Thank you.

This entry was posted on Friday, November 9th, 2007 at 10:13 pm and is filed under Electronic Control, motor speed controller. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.