Stepper Motor Driver | Electronic Project Circuits

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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.

Stepper Motor Driver using L298 and L297

This Step motor controller uses the L297 and L298N driver combination; it can be used as stand alone or controlled by microcontroller. It is designed to accept step pulses at up to 25,000 per second. An on-board step pulse generator can be used if desired (40-650 pps range). Single supply operation is standard

All eight inputs are pulled up to +5V by RP1 (4.7K) and are buffered by 74HC244. The output driver is capable of driving up to 2Amp into each phase of a two-phase bipolar step motor. The motor winding current is limited by means of a 35KHZ-chopper scheme. The potentiometer (R6) is for varying the winding currents. The nature of the chopping scheme eliminates the need for external current limiting resistors on the motor windings; this simplifies connections and increases efficiency.

A useful of this design is the “idle” current reduction mode. The amount of reduction is fixed at approximately 50% from whatever the running current is set at. Similarly, the motor current can be commanded to shut entirely off.

The internal +5V voltages required for operation are derived from the stepper motor supply. The motor supply voltages should be at least 9V, but must never exceed 32V.

Read More Source: http://www.wzmicro.com/projects.htm