[HN Gopher] A home made PCB stepper motor
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A home made PCB stepper motor
Author : nvalis
Score : 230 points
Date : 2022-02-03 11:48 UTC (11 hours ago)
(HTM) web link (kevinlynagh.com)
(TXT) w3m dump (kevinlynagh.com)
| jcims wrote:
| Very cool. Might make for a fun chess board or model train/model
| city layout.
|
| Edit: Glad he mentioned Carl Bugeja's youtube channel, this
| instantly brought Carl's work to mind.
| nvalis wrote:
| The model city application is indeed currently developed [0] at
| the Miniaturwunderland [1] in Hamburg, Germany.
|
| [0] https://www.youtube.com/watch?v=xPUEOhMBpUw (in German)
|
| [1] https://www.miniatur-wunderland.com/
| jacquesm wrote:
| That first video is amazing, what a dedication. And they got
| it working in the end. Super impressive.
| amelius wrote:
| How many robots can you move independently though (all moving
| in different directions or staying in place)?
| jcims wrote:
| Seems like any magnets on the same coil will move in the same
| direction. So it boils down to how well you can isolate the
| coils and/or orchestrate their motion so they aren't sharing
| a coil when you don't want them to be.
|
| I wonder if you could use induced currents in the pucks
| instead of permanent magnets to create the opposing force.
| Then you could tune the PCB coil to target specific elements.
| So 212kHz moves puck A, 241kHz moves puck B, etc
| jacquesm wrote:
| Once you get rid of the permanent magnets though you'd need
| to power the pucks somehow. With permanent magnets you
| don't need any kind of active element on the pucks for
| movement alone.
| amelius wrote:
| You could let the pucks make contact with the PCB, and
| power them like that. If the pucks are pulled towards the
| PCB, then it is easy to let them make contact.
| jacquesm wrote:
| That would cause the whole thing to wear out in no time.
| I don't think any contact scheme would work for this kind
| of application you'd get all of the headaches of motors
| with brushes but on a tiny scale. Spark erosion would
| destroy the traces. Part of the elegance of this design
| is that it is non-contact.
| amelius wrote:
| You could power inductively, perhaps. So create a
| fluctuating magnetic field to deliver power to a coil
| (which is on the puck), then let a microprocessor on the
| puck control the flow of current to different coils (also
| on the puck) which are then pulled towards permanent
| magnets in the PCB.
| jacquesm wrote:
| Hm. You got me thinking about this: another layer below
| that can send a 'charge' pulse to a coil on the puck to
| charge a super cap. Bonus points if you can turn that
| into a levitation mechanism.
| jcims wrote:
| This is along the lines of what I was thinking initially
| but more by reacting to the instantaneous current induced
| in the coil rather than a charge/discharge action.
|
| Basically a small version of the ring launcher -
| https://www.youtube.com/watch?v=V690VphqTwg
|
| Where the ring launcher works by counter emf that evolves
| in the conductor, a tuned emf (like for RFID chips) could
| be made with specific properties. Eg. it might only
| respond to certain frequency bands and possibly (?) allow
| for both repulsive and attractive forces by either
| maintaining or inverting the exciter phase in the board.
| amelius wrote:
| You could let a microcontroller on the puck control the
| allowed currents. If you do this sufficiently fast, you
| can multiplex over different pucks on the board.
|
| Creating a tuned oscillator could be interesting too, but
| could also turn out to be too heavy, in terms of
| component weight.
| jacquesm wrote:
| I'm absolutely itching to give this a shot but I really
| should be concentrating on other things right now.
| _Microft wrote:
| Have through hole vias everywhere and turn your PCB into
| the surface of a tiny airhockey table?
| jacquesm wrote:
| Neat! Not too much pressure though or you'll be peeling
| your robots off the ceiling :)
| prox wrote:
| Would you need to if they can move at 36cm/s ?
| jacquesm wrote:
| Wow, actual innovation. Amazing stuff. And that video is from
| 2014!
| agumonkey wrote:
| Man magnetic fields are so fun to experiment with. These, or
| magnetic locks, so "magical"
| jacquesm wrote:
| If you have a bunch of magnets lying around have a look at
| Halbach arrays.
| buescher wrote:
| Wow; I knew something like this was possible since we've all
| held refrigerator magnets and such that obviously had oddly
| arranged fields, but I only had the vaguest idea. Thank you.
| jacquesm wrote:
| Halbach arrays and some correction coils can be used to
| make a passive magnetic bearing (long sought after holy
| grail). They are super interesting.
| agumonkey wrote:
| I've seen that a few years ago, for denser motors. Do they
| have any other use ?
|
| Thanks for the suggestion nonetheless
| jacquesm wrote:
| Levitation through forward motion, passive magnetic
| bearings, what's not to like?
| jcims wrote:
| My eyes weren't cooperating with the illustration from the Theory
| section, animated it here (author is free to use of course) -
| https://imgur.com/a/hVYWBB2
|
| (note that i reverse a few frames in the loop to be less jarring
| visually, the current is probably not correct when the puck is
| moving left)
| nvusuvu wrote:
| Incredibly helpful to conceptualize what is going on. Thanks!
| a9h74j wrote:
| Helpful. Another thing to notice: You don't necessarily need a
| pcb. For small demo purposes you could close-pack one layer of
| serpentine insulated wire, then a second layer of a second
| serpetine wire. There would be a height difference, but perhaps
| not more than with a two-layer pcb.
| convolvatron wrote:
| the Sri demo shows 2d motion. pcbs make it pretty straightforward
| to have an X and a Y array, but for some reason it doesn't seem
| to me like you can just easily drive both axes independently.
| could you really tune a 'step' to be on an arbitrary slope?
| jacquesm wrote:
| I'd say that depends more on how much you are willing expend on
| hardware to drive it. You could slice your coils into tiny
| segments (essentially: just the tops) and then use the back of
| the PCB to drive them. They'd be magnetic pixels. Maxels?
| convolvatron wrote:
| good idea - but that's alot* of drivers
| jacquesm wrote:
| You _might_ be able to do something here along the lines of
| row and column addressing of DRAM.
| klyrs wrote:
| With 4 layers, it would be a trivial extension to drive a y
| axis
| HeyLaughingBoy wrote:
| If you move X,Y separately but with a small enough step, it
| would be virtually indistinguishable from moving along the
| slope.
| jacquesm wrote:
| Interesting challenge, can you 'microstep' along two axis at
| once without losing sync? That would be neat. I think I've
| worked out a way to rotate them as well!
| HeyLaughingBoy wrote:
| I would imagine so; it should be the same problem as
| helical interpolation, but confined to two axes. https://in
| fosys.beckhoff.com/english.php?content=../content/...
| amelius wrote:
| Different principle, but it reminds me of OpenDrop:
|
| https://www.youtube.com/watch?v=pSls9L_h3Q0
| phkahler wrote:
| I have wanted to do exactly this concept controlled via RPi with
| voice recognition to make a real ouija board. I only mention it
| because I will realistically never get around to it myself.
| [deleted]
| hwillis wrote:
| Pedantic: this isn't a stepping motor, it's just a plain linear
| motor.
|
| Stepper motors have multiple teeth per pole:
| https://en.wikipedia.org/wiki/Stepper_motor#/media/File:Step...
|
| The rotor has slightly fewer teeth than the stator, such that one
| "electrical rotation" (each coil being switched on in sequence)
| causes the rotor to advance by the number of missing teeth. That
| is what makes a stepper so precise; it gets 4+ divisions per
| tooth.
| jhallenworld wrote:
| More pedantry: it's a PM (permanent magnet) stepper motor,
| whereas I think most common stepper motors are hybrid VR
| (variable reluctance) / PM type..
| marcosdumay wrote:
| If you can lock the movement into a specific position and it's
| repeatable because of the geometry of the motor, it's a
| stepper.
|
| Yeah, of course it doesn't have the same design of the steppers
| you buy around. That's obvious from the title alone. That
| doesn't make it not a stepper. And yeah, it's less precise than
| the ones you can buy1. That should be expected too.
|
| 1 - Although, that conclusion is way too simplistic to make. It
| has a different kind of imprecision, so depending on how you
| compare, you may as well conclude that it's more precise.
| jacquesm wrote:
| Equally pedantic: it functions as a linear stepper motor,
| therefore it _is_ a stepper motor. That it doesn 't have a
| platen is not relevant. Being a stepper is not a statement of
| precision, it is a matter of principle, does the movement occur
| in discrete steps or does it occur by continuous movement
| through a magnetic field? This is a stepper by any practical
| definition.
| amelius wrote:
| You could make it move continuously by using an infinite
| number of microsteps.
| jacquesm wrote:
| The same holds for a rotating stepper.
| tommiegannert wrote:
| > Next steps: Levitation / sliding enhancements
|
| I wonder if vibration would help reducing friction. I.e.
| superimposing a low-power high-frequency component in the field
| to avoid static friction.
| amelius wrote:
| It also reminds me of:
|
| https://www.youtube.com/watch?v=9k7zywli4Vg
| cushychicken wrote:
| This is _incredibly_ cool. The research video showing the little
| "robots" placing drops of glue to assemble carbon fibers is
| AWESOME! I haven't been this excited by an internet video in
| months.
|
| My immediate thought: how could this be used to make a really
| cheap desktop pick-and-place system?
| goodpoint wrote:
| > pick-and-place system
|
| Most likely not, but bio/chemical experiments yes.
| gww wrote:
| There's a YouTuber named Stephen Hawes[1] whose made his own
| pick and place machine.
|
| [1] https://youtu.be/6Sa9jNhaRbg
| cushychicken wrote:
| Yeah, but Index prices out at like $500 plus labor to put it
| together.
|
| This has the potential for:
|
| * way less material cost
|
| * way less assembly, and
|
| * way higher reliability due to fewer moving parts
| jacquesm wrote:
| And potentially higher repeat accuracy because you don't
| have the rotational joints to deal with. Those are pretty
| lousy when you get further out from the axis of rotation.
| jacquesm wrote:
| Get it to make more little robots!
|
| Even smaller ones...
| nynx wrote:
| There'd have to be some way to temporary bond components to the
| bots. Regular pick n' place machines use suction.
| jacquesm wrote:
| Put the whole thing in the dark, small solar cells on top and
| then short circuit them through a coil, that could power a
| tiny gripper whenever they are lit up.
| cushychicken wrote:
| I imagine having two little microbots working like tweezers.
| Theoretically, it's possible to manipulate the field to make
| one of the robots rotate. Two magnets rotating in tandem
| could make something like a tiny pair of tweezers.
| jacquesm wrote:
| Or have them be asymmetrical, one has the half-tweezer at
| the left side the frame, the other at the right.
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