Discrete Motor Driver

Development of a TTL stepper motor driver

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This project was spurred on by the work completed for the NASA Nebraska Fellowship.  I wanted to build an analog version of the digitally driven motor driver designed for the 3D Scanner Arm, shown in another project.  

The main specifications for this project are:

  1. Drive a unipolar stepper motor,
  2. Drive the stepper motor in both forward and reverse directions,
  3. Be driven purely by analog circuitry.

At the time of the start of this project, there weren't any circuits that met these specifications that were found.  So, here's my design for the circuit.

The first revision of this board did not have the decoder, so the stepper's movement is choppy.  The next revision will incorporate the decoder to fix this issue.

sch - 849.83 kB - 01/19/2020 at 00:18


brd - 112.81 kB - 01/19/2020 at 00:18


  • Motivation and Research

    Walker Arce01/19/2020 at 00:11 0 comments

    This project was inspired by the development of a control board for a 3D scanning apparatus for prosthetic socket design.  I wanted to design an analog version that could drive a stepper motor similarly to the overpowered design that previously worked.  

    Looking through other existing options, there were unipolar and bipolar stepper motor drivers that had been implemented using similar analog ICs.

    These circuits shown above drive the stepper motor in a single direction, but the motor needs to be driven in both directions.  To do this, an up/down counter was found, specifically a CD4019, which has binary and BCD variants.  

    This would then need to be paired with either a binary-to-decimal, or BCD-to-decimal, converter to drive the stepper motor, with the counting system being reset at the count of "4".  

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