An introduction to stepper motors

If you’ve been reading Hack a Day for long enough, you know about our infatuation with stepper motors. These precious little devices put the oomph into our CNC routers, 3D printers, robots, and other miscellaneous projects. Steppers aren’t your run-of-the-mill motors, though. [Steaky] posted a great introduction to stepper motors that lets you hit the ground running building any moving project you could imagine.

Apart from identifying a stepper and figuring out if it works, [Steaky] goes over how to make these motors turn. The theory behind an H-bridge is easy enough, but theory isn’t something often presented in schematics or stepper driver datasheets.

We’ve pulled more than our fair share of steppers from flatbed scanners and old printers. There’s nothing wrong with scavenging old parts, and whether you’re making a robot band to play your kid’s birthday party, robochess, or one of the many 3D printers or CNC machines, there’s going to be a stepper motor in your future.

17 thoughts on “An introduction to stepper motors

  1. I took apart two printers a few weekends ago and the paper and printer head control was done using brushed DC motors with optical encoders reading clear plastic with markings on it. I felt so ripped off.

      1. There was a single small stepper in the bigger printer, I think it had something to do with cleaning the printing heads. But its a little too small for my Drawbot needs. At least I got some good belts and stuff out of it. I can probably re-use a lot of the parts I got.

      2. I’m planning on doing a CNC machine at some point in the future – but threw all the bests etc out as I figured a threaded rod design would be less complicated (hopefully that wasnt a stupid idea)

  2. I just had a heureka moment.
    (new to steppers)

    im building a pan/tilt camera Rig with a couple of 5v geared stepper motors.
    and have been fearing that my motors
    where not up to the task…

    they barely run off 5v as it is..
    (ULN2003A) darlington driver as “unipolar”

    running them off a L293D “Bipolar”
    probably about doubled my Torque,
    by using the whole coil..
    as described in the writeup..

    saved my week!
    Thanks

  3. I just had a Eureka moment.
    (new to steppers)

    im building a pan/tilt camera Rig with a couple of 5v geared stepper motors.
    and have been fearing that my motors
    where not up to the task…

    they barely run off 5v as it is..
    (ULN2003A) darlington driver as “unipolar”

    running them off a L293D “Bipolar”
    probably about doubled my Torque,
    by using the whole coil..
    as described in the writeup..

    saved my week!
    Thanks

    1. dooweeno, I meant acme screw but couldnt remember the name. also, gotta remember to use anti-backlash screws.
      plus, I havent had much experience with servos (and in my experience they are much fewer variations in design)

      1. I use servos where ever I can and avoid steppers like the plague. There are lots of options out there for servo drives now. Just as cheap, in general, as a good stepper drive like a gecko.

    2. I was always under the impression that accuracy wasn’t the issue when choosing between normal threaded rod and ACME. I believe that normal threaded rod is very accurate but that the shape of ACME threads, while harder to manufacture, is much more efficient at transferring power between the rod and the nut. This means you can run the motors cooler; put more force on the tool head; and/or run the head faster. Also, it means less wear and tear on the parts over time. Of course, the next step up past ACME rod is ball-screws which are even more expensive but even more efficient.

      1. Normal threaded rod is awful. In finish and in accuracy. Also 60 degree v-threads are designed to lock where acme does not.

        Even the cheap Nook acme threaded rod is accurate to something like .003″ in a foot.

  4. so… quick question.

    my unipolar steppers, the center of
    the two windings are connected together
    but as im only energizing one at a time
    i “suppose” it doesnt matter?

    do i need to seperate the two windings
    for best performance?

    1. If you are doing half step you will be energizing two winding at a time. But it still does not matter if you are running it unipolar. You can not run these motors bi-polar though. And you can not separate the windings. The junction will be internal and you can not disassemble a stepper motor without messing it up. Alignment will be messed up and removing the rotor without a keeper over the magnets will severely reduce the power of the motor. Just pick up some good motors, lots of places have cheap chinese ones and you can find nice Pacific Scientific or Vexta’s used on ebay for cheap.

      1. Minebea hybrid stepper motors are a good choice as well. Ive dealt with them in automated lighting fixtures such as Intellabeams. Check’em out on ebay. As for servos, Maxon makes some good servo motors.

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