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Sorry I am asking a mechanical question here, but, after all, where else people have experience with using motors? If there is a better forum for this, please do guide me.

enter image description here

Everywhere I've seen online, the stepper motor 28BYJ-48 is used in tutorials, to rotate on its own, or, at most, to spin a clothes pin attached to it. I am trying to get Arduino to work for my 10 year old kid. He's got the motor rotating, now what? How does he attach anything to it?

Don't laugh, I made him a wheel out of a raw potato. He is happy with it now. Where can I find any guidance as to what to do next?

KERR
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Ruby
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  • Do you mean one of these: http://robocraft.ru/files/datasheet/28BYJ-48.pdf It looks like a 9mm diameter shaft with two flats. One technique is to get a plastic wheel with a smaller hole, and a very old, unloved soldering iron. Heat up the iron, push it into the hole, and while the plastic is hot, push it onto the shaft. Otherwise a wheel with a 9mm hole with two grub screws screwed against the flats might work. –  Sep 25 '14 at 19:51
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    +1 for "a wheel out of a raw potato" :-) and for your educational work with your kid! Projects with my dad is how I got started in electronics. What to do next? ... Find a way to preserve the potato. – Tut Sep 25 '14 at 19:55
  • @gbulmer, Yes, one of these. Thank you for your response, the word "shaft" along with the words "grub screw" (a.k.a. set screw apparently) got me some much needed search results. – Ruby Sep 25 '14 at 19:58
  • Where can I buy the parts I need? Both on- and offline – Ruby Sep 25 '14 at 19:59
  • Of course, the modern answer is 'use a 3D printer'. That's how we do stuff. Failing that, has his school got a laser cutter? The problem isn't just making a hole the right shape, it also needs to be in the centre. –  Sep 25 '14 at 20:00
  • I am not sure many elementary schools have laser cutters. If they did, where would it be? 3D Printer - yes, I am exploring it now, found 3dhubs.com (or are there better places to print? Not quite ready to invest in a 3d printer just yet). – Ruby Sep 25 '14 at 20:07
  • The next question is, which 3D editor to use. Tried FreeCAD, but it does not seem to allow to create shapes from scratch. SketchUp (formerly b Google, now Timble) freezes on my Win8 horribly, so horribly in fact I can't kill it short of rebooting - an unrelated question. What do people use? – Ruby Sep 25 '14 at 20:08
  • If there is a clay or putty lightweight and strong enough to be used in amateur robotics, that would be wonderful – Ruby Sep 25 '14 at 20:09
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    Would polymorph do? –  Sep 25 '14 at 20:10
  • And please, avoid adding other questions to existing ones. It is a rule to maintain searchability for future visitors. –  Sep 25 '14 at 20:17
  • Yes @venny! Polymorph!! It'd make a good adapter for a large enough hole. Hot glue works too, and maybe easier to get. We use Sketchup, but run it on older Windows. –  Sep 25 '14 at 20:21
  • @venny, about avoiding asking new questions (I presume, you mean in comments) - I just don't want to flood the electronics forum with non-electronics questions. Or do you feel this is a bona fide electronics question? – Ruby Sep 25 '14 at 20:30
  • Polymorph seems very nice, but priced near the cost of 3d printing, no? The kids are doing a school project for Destination Imagination on a very limited budget. – Ruby Sep 25 '14 at 20:31
  • Maybe there is a cheaper light clay, something to make a large "creature" o0ut of. Although, durable things that, for instance, withstand high torque, like this one.. yes, that should work! – Ruby Sep 25 '14 at 20:32
  • Possibly a short piece of stiff hose (fuel line?) and a couple hose clamps? – Tut Sep 25 '14 at 20:55
  • @NickAlexeev, yes, thank you, it would be nice to migrate that question to Robotics.SE. – Ruby Sep 25 '14 at 22:11
  • I don't mean to ask too many questions, but I'd really like to make a quadriped with this. – Ruby Sep 25 '14 at 22:12

7 Answers7

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You can drill a hole to match the shaft into whatever it is and either fix it with a setscrew against the flat or glue it. Or you could glue a brass tube (hobby shop) to the shaft if you can find one that fits. The shaft is 5mm diameter, as venny says.

Of course it's easier if you have access to a small lathe (such as Sherline or one of the small Chinese ones).

If you need to allow for misalignment between shafts it's better to buy or make a shaft coupler such as these helical style ones:

http://www.ebay.com/itm/Flexible-Coupling-Motor-Shaft-Coupler-3mm-X-5mm-/220977869760

There are other types (some of which have a bit of backlash). You can also use a collar with setscrews, but the shaft on that motor is a bit stubby and that type of coupler allows for almost no shaft misalignment so it would jam easily (and the motor is not very powerful). The kind with backlash generally has a bit of flexible material such as urethane rubber sandwiched between two interlocking sets of fingers.

I made a sky tracking drive using one of these cr*p motors and I just drilled out the center of a standard gear (from Stock Drive) a bit to get a slip fit and used the grub screw to secure it. The shaft is pretty stubby so it's hard to get something secured to it unless it fits very tightly or is a clamp or collet-style fixing. In my case, the gear drives a nut that works on a leadscrew.

BTW, you might find the robotics SE useful in this kind of thing. I've not looked at it once, but those folks run into this sort of thing regularly.

Spehro Pefhany
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The diameter of the shaft is 5mm, it sould be possible to use a 5mm propeller collet commonly used on RC airplanes, like this one:

pic
(source: hobbyexpress.com)

Tightening the nut secures the attached object and at the same time it clamps the collet to the shaft.

The shaft should be inserted fully into the clamp, to grip also the non-flattened portion to provide good stability.

Glorfindel
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I found, that carefully filing the shaft down to 2mm will make it a perfect fit for lego gears. You will have to file the flat sides. You can check uniformity of your work by light reflection. The shaft indentation in the front works as center guide, so you take off from both sides evenly. You also might have to slightly round the edges.

If you don't like that, try an adapter: check whether your local library has a 3d printer (some are setting up science labs for kids). There are a handful adapters for this motor (lego, round axis, servo,..) which you can download and print on a 3d printer.

formfeed
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From RobotShop.com

You can use the Actobotics 5mm Bore 0.77'' Set Screw Hub

Given that part, you then have lots of options.

sempaiscuba
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Z223I
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As others have already stated, the shaft in a 28byj-48 is a "5mm diameter round shaft with 2 drive flats".

(Just for reference, the shaft diameter on a 28BYJ-48 is the same as on Nema 11, Nema 14 and Nema 17 stepper motors in case you ever want to upgrade your stepper motor!)

One option that has already been suggested is to use a "5mm mounting hub" (also known as a "set screw hub"). Pololu make an "all-metric" item (both the mounting holes and the grub screw/set screw are metric.) (Web Archive link) You can buy these from ebay - in the UK, a pack of 2 is approximately 8 GBP.

An alternative is to look for a "5mm flange coupling". These are also available on ebay and start at approx 4 GBP. (I have just received mine and it's perfect for my project.)

28BYJ-48 with attached flange coupling

jaimet
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It is amazing that there are so few solutions for power transfer for such a common motor. I have looked at ebay and amazon. Gears are available in a wide range of prices, none that are in the same scale as the price of this cheap motor. There is a gear generator at http://woodgears.ca/gear/help3/index.html for wood gears. This or 3d printing gives you the flexibility of gear ratios and shaft sizes. I just wanted to be able to connect a programmable motor to a drive that would actually do something.

Armando Garcia
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The simplest, most versatile, and cheapest method I found is explained in this ebay page.

Basically you can get a Lego Technic axle (part #6538), remove 2 thin flaps, and it fits perfect. This allows you to connect the DYJ48 stepper motor onto any Lego Technic wheel (there is a range of them), gear, or any other Lego Technic part.

UndergroundCoding
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  • Originally suggested by formfeed. Due to my low reputation level, I am unable to comment his answer to add the link, so I decided to post another answer that might be able to help other people who get stuck in this same boat. – UndergroundCoding Feb 05 '18 at 20:49
  • Please don't use links to eBay pages. eBay Links rot very quickly and the pages are not archived, so answers which rely on them become useless when the eBay auction expires. If you add more context from the link, it is more likely that people will find your answer useful. – Mark Booth Feb 06 '18 at 11:23