A Brushless Motor On A PCB, Made From PCB

At Hackaday, we really appreciate it when new projects build on projects we’ve featured in the past. It’s great to be able to track back and see what inspires people to pick up someone else’s work and bring it to the next level or take it down a totally new path.

This PCB brushless motor is a great example of the soft collaboration that makes the Hackaday community so powerful. [bobricius] says he was inspired by this tiny PCB BLDC when he came up with his design. His write-up is still sparse at this point, but it looks like his motor is going to be used to drive a small robot. As with his inspiration, this motor has the stator coils etched right into the base PCB. But there are some significant improvements, like increasing the stator coil count from six to eight, as well as increasing the overall size of the motor. [bobricius] has also done away with the 3D-printed rotor of the original, opting to fabricate his rotor from stacked PCBs with cutouts for 5-mm neodymium magnets. We like the idea of using the same material throughout the motor, and it also raises the potential for stacking a second stator on the other side of the rotor, which might help mechanically and electrically. Even still, the prototype seems to hold its own in the video below.

This is [bobricius]’ second entry in the 2018 Hackaday Prize so far, after his not-a-Nixie tube display. Have you entered anything yet? Get to it! Prizes, achievements, and glory await.

33 thoughts on “A Brushless Motor On A PCB, Made From PCB

    1. Totally doable by using coils excited by small BJTs or Mosfets driven by Hall sensors. they should be wired so that the detection of the reach of a position would switch off power to the corresponding coil and turn on the one in immediate vicinity according to the desired direction.
      Those coils should be made of more turns of real wire though so that their inductance can be increased; I believe this motor even though working doesn’t have a good efficiency.

      1. I’ve seen that as well. A long time ago I was taking apart a dead floppy, hoping to salvage steppers, and was confused a long time ago, until I figured out that it was very similar to this. (This looks far nicer.) It was a 3.5 that used PCB traces for it. I wish I’d kept it now, but it was purged a few moves ago.

  1. It’s a little deceiving to call this a brushless motor in the title. Maybe I’m just being pedantic, but this is really a stepper motor. The title isn’t wrong, but I think most of us probably expected to see the kind of brushless motor that you’d find in a quadrocopter.

    It’s still a very cool project! Once we can make a PCB stepper with more torque, RepRaps may be able to do something interesting with the concept.

    1. No, it is a brushless motor, just a two phase brushless motor. They are kind of rare, some high speed spindles use them and some turbo pumps.

      What makes a stepper motor a stepper motor is the design of the rotor and stator with the teeth that causes it to move one step per pulse.

    2. Lucian: no deception a all. Every brushless DC motor is a stepper motor. Both steppers and BLDCs come in different numbers of phases – I’ve seen many floppy drive steppers with three-phase drive – so even that isn’t a distinguishing characteristic. The main difference between the two is that a stepper usually has a whole lot more poles. But also, stepper motors have the same number of stator poles as rotor poles, while BLDCs use different numbers. Note that the example shown uses eight stator and six rotor poles. So this is closer to most BLDC motors than it is to most steppers. So you’re not just being pedantic, you’re also being wrong.

      Furthermore, in what way do you think this couldn’t do the work of a quadcopter motor? If your tripping point is that it uses two-phase drive, and therefore couldn’t be used with a a hobby electronic speed controller, what part of the principles demonstrated do you think wouldn’t translate trivially to three phase? I’m guessing that the maker wanted to save a little money on the drivers, since two-phase requires only two H-bridges, while three-phase requires three.

    1. I’m not sure that would be the best thing, mechanically. A single thick rotor or stator is much stronger than a number of thinner rotors and stators totaling the same thickness.

      They could also complete the magnetic circuit by using ferrous plates on the exposed sides of the stator and the rotor (or the stack of stators and rotors). This would reduce the reluctance greatly, with a corresponding increase in torque.

      Another way to do this is with a Halbach array in place of the simple arrangement of magnets in the rotor (see https://en.wikipedia.org/wiki/Halbach_array and https://hackaday.com/2017/05/08/powerful-professional-brushless-motor-from-3d-printed-parts/), which confines the magnetic field to within the motor using magnets instead of iron.

      This still leaves the PCB as a high-reluctance element in the magnetic circuit, but the whole point of a pancake motor is that by making the coils very thin but covering a large area, the reluctance of a coil can be kept low without incorporating a magnetic core.

    1. I’m not sure what sort of audience this is aimed at, eight year olds perhaps?

      I turned the sound off after about 20~30 seconds but that only made it worse. By the time it got to showing off the pcb (1:51), I simply couldn’t stomach any more.

      Which is rather unfortunate as it looks like a very good piece of engineering from what I did see.

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