Motor out of stock #16
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Yeah, I'm hoping this is just a temporary out of stock issue, but the seller actually has another listing that looks essentially identical (though a tiny bit more expensive) and is still in stock (for now) - https://www.aliexpress.com/item/4001356858801.html I've ordered a handful of those myself and will confirm whether they're the same in ~2 weeks when they arrive 😛 Probably worth snagging a few now regardless since they're pretty cheap. I prefer hard-coded AliExpress links, because of scam sellers (so I like to find a reliable one and stick with that) and also I've been burned by different sellers sending different quality products under the same part number before -- for my splitflap project, I have an entire page dedicated to finding good 28byj-48 stepper motors among the sea of bad clones. My fear is that they may just be selling off "new old stock" from some short-lived product and the motors are not actively being manufactured any longer, in which case the interest in this project could quickly consume what's available. 🤞 Hopefully that's not the case though, as there are basically zero other cheap options for hollow shaft BLDC motors with low KV and zero cogging torque that I could find... |
Add notes about artifacts being auto-generated and untested. Also add link to potential other motor listing. Updates #16
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Your update on March 24th seems quite discouraging, does this mean the project is dead? Seems like one of the coolest ones I've seen in ages. |
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It gets worse, the other listing that @scottbez1 linked to is gone now too. I had an order for a couple of those and that order was simply cancelled earlier this morning, so that double listing seems to have been an oversight. The motors from that seller (and two other sellers as well) that looked similar by had wires running through the hollow shaft already, those have also been removed. Well not removed, I created two orders from separate sellers last night and both of those items have been changed into a completely different item. I haven't been able to find a replacement motor yet. I'm not sure what other motors @scottbez1 has bought to test, but I would love to know. It would be very helpful to know which motors we should avoid specifically. |
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Responding from my phone, so pardon the brevity.
I don't want to call the project dead quite so soon, but it's certainly not
looking very good at all...
Regarding other motors, I basically ordered every single small BLDC from
that AliExpress seller (which is most of the cheap motors I could find on
AliExpress in general) and there's not good news there, unfortunately. All
of the other hollow-shaft motors had noticeable or substantial cogging,
making them poor candidates.
I'll follow up with more details when I have some time this weekend,
including a list of all the motors I've personally checked.
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I certainly wouldn't call it dead in the water, just needs some adjustments for a more widely available motor. I'm tempted to grab a more common 2804 or maybe 2204. Lots of varieties though and not a whole lot that either have an diametrical magnet or room for one. |
You mention cheap, is it a prerequisite that it is really cheap or are there other motors that might fit the bill but are more expensive? |
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@scottbez1 would be helpful to know what sort of BLDC motor you're using at the moment. From what I understand the majority of cogging is a result of the type and size of magnets used in the rotating part. In an effort to generate as much torque as possible, most manufacturers opt for neodymium magnets which are significantly more powerful compared to ferrite magnets. |
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I don't know a lot about motors, but I did find this:
https://store.cubemars.com/ from a company called Tmotors (
https://uav-en.tmotor.com/).
Again, no idea if the specs match anything you need.
…On Fri, Mar 25, 2022 at 8:13 PM C44Supra ***@***.***> wrote:
@scottbez1 <https://github.com/scottbez1> would be helpful to know what
sort of BLDC motor you're using at the moment. From what I understand the
majority of cogging is a result of the type and size of magnets used in the
rotating part. In an effort to generate as much torque as possible, most
manufacturers opt for neodymium magnets which are significantly more
powerful compared to ferrite magnets.
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Seconding what @C44Supra said, perhaps logging here the specs of your currently best-performing motor so the group can help hunt down a replacement, especially once the AliExpress pages disappear. I'm thinking these are important: Critical dimensions, Kv, electrical specs (ex. maybe max torque can indicate something else useful), keywords. Others? In the future, the move is probably a redesign for the more common outrunner motors on hobby RC websites. Considering tackling part of this myself. |
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It looks like newegg has the motor but only with a slipring installed. removing that wouldnt be a problem, but the 50$ pricetag is. i think the best way going forward would be using a standard gimbal motor and putting on a diametrical ringmagnet from mcmastercarr or so. something like those 2804, 2805or 3413 look more common and could propably be used |
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@LeonBentrup that listing on Newegg is from a chinese reseller as well. It was listed by at least 3 different vendors on AliExpress but all three have removed the exact same listings at the same time. I'd say there's good chance it's one and the same vendor, just active under a couple of different names. That said, I did get a reply from the AliExpress seller earlier today:
The other item they are referring to is https://www.aliexpress.com/item/1005003751799249.html It looks somewhat similar but is missing the diametrical magnet. There's also not enough shaft protruding to stick a magnet onto so that would be a no good either. It's also quite problematic that their motor numbers seem to reference the outer diameter and height of the entire motor, where as other suppliers generally reference the internal dimensions of the actual motor parts. The 3413 for instance is pretty much the same as a 2804. I did "some" looking around on AliBaba last night / this morning ( / what day is it again?), and found a supplier that has a motor that shows potential. They're not too expensive, have a 7mm diameter protruding shaft on the bottom and looks to be good design. I've contacted them and are waiting for a reply with more data about that specific motor. A quick search on Amazon led me to some 10x3x7 (outer diameter x thickness x inner diameter) diametric magnets. I think thinner ones would work, too, though. |
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@C44Supra Does it have to to be a motor with a stick out shaft? for example the mks servo42 just uses superglue and two of those are running fine on my 3d printer. its not a hollow shaft there but those cheap 2804 look like you could glue it on there directly. Sticking a 6mm rod with some paper(to not glue the rod in there) down the hollow shaft you could even get it centered pretty good. and since its not turning with 2000 rpm i wouldnt be afraid of the glue giving up |
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@LeonBentrup it'd have to stick out of the bearing at least a little bit, otherwise there's nothing to glue onto without interfering with the motor. I was considering that too. The motor you linked to is a 20-24V BLDC motor though, I haven't dug into the schematics too far just yet, but I suspect the motor in the current design is driven at 5V, which would likely not be very impressive to a 24V motor. The motor I linked to earlier would probably be a safer bet (a 3413), but I'm somewhat hesitant to place an order with that vendor again, considering it took him 10 days to just cancel my order with zero feedback. |
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@C44Supra the linked motor was just an example but thanks to usb c even 20V isnt a problem. the pcbs look quit empty so there should be enough space for a ip2721 or ap33771 to get what ever usb-c pd voltage you want just with the IC and some resistors and buck it down to the 3.3v the esp32 needs. And looking at the linked motor you could propably get away with glueing a 8x6x3 magnet directly on to it. but you could also print a little spacer and glue it in to get the stickout. or use a off the shelf 6x0.5mm steel pipe. this would propably be the simplest solution assuming you dont need the full 6mm space in there. even the 5mm should be enough for spi,power, rst and backlight. |
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@LeonBentrup USB-C could indeed provide higher voltages. However the TMC6300 driver only does up to 11V so you'd likely have to account for that too. Not too hard, but something to keep in mind. |
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@C44Supra And there could be a problem. at the moment you cant really get any normal to high power BLDC ICs. i looked at most of the common ones for other projects. But with USB-C PD you could also get 9V which is also the lowest voltage a 3S LiPo should get. so BLDCs that work with 3S batterys should also work with that. that also makes it possibile to still use a linear regulator cause it only needs to drop 5.7Vx I and not 16.7Vx I when using 20V which is basicly impossible without a heatsink. For motors that would mean you could use a standard t-motor GB2208 but those are pretty thick but propably have a good availability. or something like those MiTooT/Flycat/whatEverRandomName 2805 motors. |
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3D printed BLDC motors exist. Could we design the perfect one for this project? |
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I shot a message to Carl at Flexar to see if there's any opportunities here. |
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Some specs and photo from the inside of the original motor in case it's helpful identifying an alternative:
(for reference, the diametric magnet is a ceramic ring and appears to have been glued onto the rotor, so leverage is not the best way to remove it in one piece... 😬 but it's necessary to remove to access the retaining ring)
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@scottbez1 Ok this is starting to make sense. Those look like compressed ferrite material, which will have a lower flux density than the little bar neodymium magnets, and so lower max torque output but also lower cogging torque. I think. Searching for this might be challenging. Maybe looking for motors with lower than normal max torque hints toward ferrite magnets? |
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Other motors I tested previously and decided against:
On the left:
On the right:
But even if those motors did fit the bill, I think they still wouldn't be a good option since they'd likely go out of stock immediately as well. I think the challenge will be to find a good motor (hollow shaft, low cogging, low kv) that's still actively manufactured rather than leftover "new old stock" like these. |
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That would indeed be a ferrite magnet in the rotor. Usually manufacturers put neodymium magnets in instead to increase motor torque at the cost of top speed. I'd say it's probably hard to determine which type of magnet a motor contains if you don't have a clear visual of it or take it apart. The last motor you added a screenshot of lists the neodymium magnet type in the title at least (NdFeB). That said, even if it was a ferrite magnet I wouldn't trust that particular seller to deliver anything. Was the board as is able to drive the 20-24V motor at all? In other news, the manufacturer I've been in touch with has only sent me dimensional drawings so far. Still waiting to hear back what sort of magnets and arrangement there is in the motor. |
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Did someone wrote the manufacture of the original link for the motor why all these listings got taken down? Maybe they could tell or provide a clear data cheat to manufacture them. But I think that they are only the sellers. |
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@18Markus1984 see one of my earlier replies. They claim that a local buyer bought out their entire lot of motors and someone just forgot to pull down the listing. |
@C44Supra Could a starting point for trying to identify motors with ferrite magnetics be to look for ones of a certain size that have a significantly lower maximum torque than others? Just applying this as a pre-filter to try and narrow down on options quicker. |
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Possibly. The original motor listing didn't have a torque spec, so no reference there. But you can obviously compare different motors to each other, significantly lower torque ratings could mean ferrite magnets. Or typos. Or intentional misrepresentation. AliExpress / eBay and genuine parts specifications generally don't go hand in hand unfortunately 😆 |
Hi, @C44Supra do you have any contact information of the seller? It will be easier for me to talk to them from here China. |
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The best motor was that one with the ridiculous shafts of metal sticking
out the back. Type a or whatever. They are like four bucks on
aliexpress. I bought seven of them. They use so called ring magnets.
They appear to be great, I don't think you could possibly notice the
cogging they exhibit. If you search the forum posts you will find
pictures.
…On Sun, Mar 19, 2023, 15:59 LukasHNZ, ***@***.***> wrote:
Hey guys, is there any availability for a suitable motor in Europe?
Sparkfun from the US seems to be permanently out of stock, also I think 29$
for these motors that usually go for low single digits is a bit of a rip
off.
One Idea that I had while reading some of the issues regarding cogging is
using a completely different motor. Afaik the cogging is from the induction
in the coils from the magnet. (please correct me if I am wrong) Why not
just ditch the magnets altogether and use another set of coils to create
the magnetic field that is needed? While no power is supplied there
shouldn't be any forces and when powered on they can still generate the
haptic feel (maybe even better with more current?)
Has anyone thought about something like that or is it even possible to
construct or buy a motor like that?
I'd love to build a smartknob myself without having to sell a kidney or
having to try 100 motors in the hopes of one fulfilling all the
requirements xD
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Also that's not what causes cogging, your suggested approach would also
suffer from cogging, although it could be more or less depending on the
details.
…On Sun, Mar 19, 2023, 15:59 LukasHNZ, ***@***.***> wrote:
Hey guys, is there any availability for a suitable motor in Europe?
Sparkfun from the US seems to be permanently out of stock, also I think 29$
for these motors that usually go for low single digits is a bit of a rip
off.
One Idea that I had while reading some of the issues regarding cogging is
using a completely different motor. Afaik the cogging is from the induction
in the coils from the magnet. (please correct me if I am wrong) Why not
just ditch the magnets altogether and use another set of coils to create
the magnetic field that is needed? While no power is supplied there
shouldn't be any forces and when powered on they can still generate the
haptic feel (maybe even better with more current?)
Has anyone thought about something like that or is it even possible to
construct or buy a motor like that?
I'd love to build a smartknob myself without having to sell a kidney or
having to try 100 motors in the hopes of one fulfilling all the
requirements xD
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Oh okay, do you know what exactly causes the cogging? Im curious about the problems and the causes. |
Do you still have a link for that shop? |
Are they a drop in replacement from an electrical standpoint or does that require changes to the pcb? |
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I know nothing about your PC, sorry.
…On Fri, Mar 24, 2023, 20:06 Tuege, ***@***.***> wrote:
The ring magnets don't have gaps between the magnets, thus they have much
smoother motion. One by JDpower is called the DC-3515C . I have obtained 3
of them and they have nearly non detectable motor cogging, when moved by
hand. You can feel it a bit but I think you are never going to notice it.
They can be obtained in consumer quanites through the jdpower website,
they sell retail, they should be about $30 USD each or something.
Are they a drop in replacement from an electrical standpoint or does that
require changes to the pcb?
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Uhm what? PCB = Printed Circuit Board. I take it you haven't checked compatibility then. |
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Motors are on Sparkfun!!! |
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@gregory353a link? |
Mentioned in #16 (comment), first link
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Any Information about when they will be back in stock at SparkFun? |
they disappear quickly, so if you want some you should probably sign up for backorder. |
I was waiting for them since September last year till last month. It will be more than 6-7 months. I think it depends how much backorders there are. 😉 Be patient |
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i guess i got lucky, as i only had to wait two months (february to april). |
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Motors are in stock on Sparkfun |
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Motors are in stock on DigiKey |
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Day X of suggesting the amazing DIY PCB motor work of @CarlBugeja |
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Day Y of suggesting you look at the torque and power of those motors and working out why they aren't a good motor for this.Sent from my Galaxy
-------- Original message --------From: Josh ***@***.***> Date: 4/7/23 1:14 am (GMT+10:00) To: scottbez1/smartknob ***@***.***> Cc: zyeborm ***@***.***>, Comment ***@***.***> Subject: Re: [scottbez1/smartknob] Motor out of stock (Issue #16)
Day X of suggesting the amazing DIY PCB motor work of @CarlBugeja
https://youtu.be/PsZszv4qHu4
https://youtu.be/NX7GHqq28uU
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@zyeborm agreed the current motors are not a good fit. I believe that it has a solid chance if the design principles were used with the goal of making a motor that’s specifically tuned for the smart knob. What makes this especially interesting is that it’s easily iterable while other motors are unattainable. |
Add notes about artifacts being auto-generated and untested. Also add link to potential other motor listing. Updates scottbez1#16
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Makerbase3D released a gimbal motor targeted at SimpleFOC that might be a viable replacement BLDC motor. It looks like it meets most of the minimum viable specs? It comes with the AS5600 encoder but it looks like the hollow shaft might be obstructed by the magnet they've attached to the rotor though it should be removable. The hollow shaft measures 8.6mm in diameter, so it could be a good bet for this project. |
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https://aliexpress.ru/item/1005001968864724.html |
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Wondering if there is any desire for these to be produced as a kit. I'm an Operations Manager at a Contract Manufacturer in Toronto, Canada (https://www.engineeringcpr.com/). If the BOM cost is roughly 200 we could proably sell them for around $400-$500 to cover our labour. Happy to give Scott something back for his work too. If there is reasonable interest I would quote it out and get a hard unit cost before moving forward. |
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100% I’d be up for a kit or two…at a reasonable price. Thank you. |
Where did you get these outrageous estimate for BOM? |
Have you considered Nano_D? :P |
Just from the read me. Do you have a more accurate BOM cost? |
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I am not sure if you know, but there is two (least what I know of) dev kits
available based on this smart knob:
- seedlabs <https://store.seedlabs.it/products/smartknob-devkit-v0-1>
- binaris <https://store.binaris.io/>
jdworona ***@***.***> ezt írta (időpont: 2024. máj. 18., Szo,
1:31):
… Wondering if there is any desire for these to be produced as a kit.
I'm an Operations Manager at a Contract Manufacturer in Toronto, Canada (
https://www.engineeringcpr.com/). I had a look through the demo and this
looks like something I could whip up in our downtime pretty easily if we
have a large enough interest (min maybe 50 orders).
If the BOM cost is roughly 200 we could proably sell them for around
$400-$500 to cover our labour. Happy to give Scott something back for his
work too.
If there is reasonable interest I would quote it out and get a hard unit
cost before moving forward.
Where did you get these outrageous estimate for BOM?
Just from the read me. Do you have a more accurate BOM cost?
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and others
Not a major issue as you've said you've got several others on the way for testing, but the link to the motor you used is now out of stock: AliExpress
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