Projects

Unistep2

A non-blocking Arduino library for controlling 28BYJ-48 stepper motors.
Github: https://github.com/reven/Unistep2

Rationale

28BYJ-48’s are little inexpensive 5v geared stepper motors that are particularly pesky in terms of what’s needed to drive them. They are halfstep steppers and require an 8 step control signal to drive them efficiently. They usually come with (equally inexpensive) ULN2003 driver boards that make connecting them to the Arduino much easier.

I had no success driving them with the standard stepper libraries (Stepper or AccelStepper). There was always resistance and stutter, resulting in increased heat and noise. I finally came across two libraries that worked: Tyler Henry’s CheapStepper, which I couldn’t get to drive two steppers simultaneously without issues; and Matthew Jones’s Unistep, which drove two or more steppers perfectly but in a blocking fashion.

So I decided to create a non-blocking version based on Unistep and added some extra functionality, but I wanted to recognize the contributions made by others.

Features

  • Non-blocking
  • Can manage 2 or more steppers
  • Extra functions to control state of steppers
  • More energy efficient
  • Precise timing avoids noise, heat, stutter, stalling, etc.

Installation

Download the zip in Releases on github and use the library manager to add it to your libraries. Alternatively you can install manually into your Arduino library folder.

Use

Just call

#include <Unistep2.h>

at the begining of your sketch and construct the stepper objects with the following call in your setup() function:

Unistep2 stepper(p1, p2, p3, p4, stepsPerRev, stepDelay);

where p1 to p4 are the pins you’ve connected your ULN2003 to, stepsPerRev are the steps that your stepper takes to do one revolution (4096-ish in the 28BYJ-48’s) and stepDelay is the delay between each step in microseconds (900 is the fastest that seems to work without issues).
Then you must call

stepper.run()

in your loop. Delaying functions will interfere with the stepper movement.

Function descriptions

  • move(int steps): Moves the stepper the indicated amount of steps. If steps is negative movement will be counter-clockwise.
  • moveTo(unsigned int pos): Moves the stepper to an absolute position between 0 and stepsPerRev.
  • currentPosition(): Returns the current absolute position of the stepper.
  • stepsToGo(): Returns the amount of steps remaining for the stepper to complete the assigned movement. Negative will mean counter-clockwise.
  • stop(): Stops the current movement and powers down the pins to save energy and avoid heat generation. Is called automatically after each movement, but is available to be called by the user.

To-do

  • Create examples
  • Add metadata and library info
  • Repackage as plugin zip

Tip jar

If you find this useful in any way, feel free to leave a tip in my bitcoin address if you feel so inclined:

bc1qn7zrnkk47fzwkf5uqyaqu9dzl7mtyrh5h2ef33

License

This library is released into the public domain.

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