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Author Topic: Brushless motor  (Read 21998 times)

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LX

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Brushless motor
« on: August 11, 2013, 12:47:43 PM »
Hi all,

I have been reading the very interesting and well-explained information on this site about brushless motors.  I have even watched the youtube video about how fan motors are built, which was very enlightening.  Thanks so much for taking the time to put this instructional info on the net.  Even I can understand it! ;D  The reason for all of this research is that I have a brushless motor coming next week, and I would like to understand how it works.

It is a sweet little Chinese motor that and there were not many specs there so I had to track down more information myself.  This brushless DC motor has six leads, and the wiring diagram on the label of the motor shows that the motor must be connected like this :



This is pretty clear to me.  But I am curious about the potentiometer wires.  Is there a microprocessor and a driver on a pcb already hidden away in the motor housing, and the potentiometer wires go to the internal microprocessor?

Also, the wiring diagram shows how the green and blue wires are connected to the potentiometer.  What would happen if the green and blue wires were swapped on either side of the wiper?  Would it damage the motor at all?  The reason I ask this is that someone else I know has the same motor, and if it is wired as the diagram shows, the 0 on the pot is on the lefthand side, when normally you would expect to see 0 on the righthand side.

I hope these questions aren't too ridiculous and trivial.  I just wondered, so I thought I would ask.

Thanks,
Candice

PS I am having a devil of a time with your kaptcha :(

kam

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Re: Brushless motor
« Reply #1 on: August 11, 2013, 14:15:57 PM »
This is pretty clear to me.  But I am curious about the potentiometer wires.  Is there a microprocessor and a driver on a pcb already hidden away in the motor housing, and the potentiometer wires go to the internal microprocessor?

Definitely! There is a built-in driver

What would happen if the green and blue wires were swapped on either side of the wiper?
It will work different. If for example the potentiometer controls the speed and the motor runs faster by turning the pot right-wise, switch the cables and the motor will run slower by turning the pot right-wise


PS I am having a devil of a time with your kaptcha
I had a big-time attack from spammers, my site was closed several times, the server kicked me out, i had to transfer all the site to other servers, i had to break the forum appart for security reasons, i lost the old forum attachments, and i had several days nightmares with chinese hackers breaking into my room only to place ads and banners around my room.... I'm sorry for the hard captcha, but i those nightmares were awful!



LX

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Re: Brushless motor
« Reply #2 on: August 11, 2013, 14:54:38 PM »
Hi Kam,

Thanks so much for your reply.  I won't swap the wires on either side of the wiper when I get my motor then!  I realized after I posted that I had given the info about the pot wiring back-to front.  If you wire the pot as per the diagram,  the "0" is on the right, so to increase motor speed you have to turn the pot dial to the left, which is strange, but I can live with that.  :)  I'll just do what the diagram tells me to do.

About the internal driver in the motor housing...  The microprocessor would have an analog pin, and this is that the pot is connected to?  Or would it work some other way?  Apologies if this is a dumb question.

Thanks,
Candice

PS Yes, I was reading other posts on the forum about the spammers. :-(  I hope they have been deterred.  I'm happy to deal with the kaptcha if it is keeping those idiots from spamming.  :D


kam

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Re: Brushless motor
« Reply #3 on: August 12, 2013, 12:08:47 PM »
Quote
The microprocessor would have an analog pin, and this is that the pot is connected to?
Yes indeed, most likely there is a microcontroller with an A/D.

Why you got a motor witha built in controller? What are you planning to make?


Quote
I was reading other posts on the forum about the spammers. :-(  I hope they have been deterred
So far i had 0 problems. The forum is hosted on a different server (thanks Cheerio for this) and it has a different URL also (notice its "pcb.teenio.de" and not "pcbheaven.com"). So even if i get spam attacks again, at least the rest of the site will remain safe.

LX

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Re: Brushless motor
« Reply #4 on: August 12, 2013, 20:46:15 PM »
Quote
Yes indeed, most likely there is a microcontroller with an A/D.

Why you got a motor witha built in controller? What are you planning to make?

Well Kam, I am only interested in this motor because it is relatively quiet.  :)  I am making something like this, and I have so far been through 2 brushed DC motors one of which is not suitable beacuse it's too noisy.  The brushless motor is very quiet, but whereas I can control my brushed motors with my arduino via an h-bridge, it seems I cannot with this lovely quiet brushless motor (unless I get rid of the pot and do some kind of digital to analog conversion with my arduino eg use a digital pot).

cheerio

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Re: Brushless motor
« Reply #5 on: August 13, 2013, 02:24:52 AM »
Just use a digital poti with spi or i2c interface

LX

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Re: Brushless motor
« Reply #6 on: August 13, 2013, 02:55:24 AM »
Quote
Just use a digital poti with spi or i2c interface

Hi cheerio,

Thanks, yes that was what I wanted to do, mainly because I want to do some sort of hands-free speed control, like with a footswitch or something else.  But I think there might be problems with using a digital pot - I have to do some reading there. Thanks for your input - makes me feel less insane. :D

Sir N

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Re: Brushless motor
« Reply #7 on: August 15, 2013, 02:43:02 AM »
Hi,

It is a sweet little Chinese motor that and there were not many specs there so I had to track down more information myself.  This brushless DC motor has six leads, and the wiring diagram on the label of the motor shows that the motor must be connected like this :
I've never seen any (chinese made) small BLDC motors with a built in controller, so it sounds odd to me (but then, new product hits the market all the time). The main reason for not placing a controller inside the motor is the heat that both the motor itself and its controller generates.
So, could you include a link to the motor  (and if possible to whatever specs you found)?

Sadly, there are plenty of shady businesses in China and you can't always count on what the sales description said - Electronics components and batteries are sometimes mislabelled and sometimes even contain something else entirely :(

I wouldn't be surpriced if this 6 lead motor was actually just having the wires to each of the three phases (ment for an external controller), but drop a link and we may get closer to an answer.


[...] But I am curious about the potentiometer wires.  Is there a microprocessor and a driver on a pcb already hidden away in the motor housing, and the potentiometer wires go to the internal microprocessor?
As said, it would be foolhearty to place the controller in thermal connection with the motor. That said, the amount of heat it needs to get rid of depends on motor power, expected load and overall mechanical design.

Did you just choose a random motor or did you make some estimates on what power and RPM you need?
Hopefully, it comes with a gearbox, as BLDC's are high RPM - 10,000 RPM is entry level, 50,000 RPM or more is not rare and I have spend endless hours chasing down BLDC outrunners with a sufficient low RPM and kV (kV is the RPM increase per volt) coupled with enough torque to make them useable for a few automation/robotics projects in the past.

If you can answer a few quesions, I may be able to give you further ideas...
What maximum speed do you need for your spinner (for the bobbin itself)?
Have you got any idea of the torque needed to spin it at that speed (even just a guesstimate)?
Any particular restraints on size?

Did you consider butchering an old sewing machine or similar (or is that too noisy)?


Also, the wiring diagram shows how the green and blue wires are connected to the potentiometer.  What would happen if the green and blue wires were swapped on either side of the wiper?  Would it damage the motor at all?
Not the least (assuming there IS a controller present).
A potentiometer is just a circular track of either a carbon composition or conductive plastic, creating a resistor, where the wiper (middle pin) is swept over, so only the direction you need to turn it is reversed, as kam told you.

Although unlikely for a speed control, if a non-linear pot is used (like a logarithmic taper as used for audio amplifiers or any of the other non-linear tapers), things would be different, as the resistance change per degree turn is different over the entire track, so be sure you get a linear potentiometer (whether a turning or a sliding type).

I assume you'll want a speed control pedal and a CW/CCW switch as well for your spinner(?) Did you consider how to implement that?

Just for the heck of it, you might consider an electronic version of a drop spindle as well ;D

LX

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Re: Brushless motor
« Reply #8 on: August 15, 2013, 22:16:35 PM »
Hi Sir N,

Someone who knows about drop spindles!  Yay! :D  I can't imagine a motorized drop spindle, but it would be very very cool.

Re your questions... I'm building this spinner for a spinning competition, so I'd like to keep a lot of specific information to myself for now, but I'll try and share some details.  I actually have my brushless motor now and I posted a couple of questions last night but they don't appear here, so maybe i forgot to hit the 'post" button  ::).  The motor does work as the wiring diagram shows and I don't think it could do that if there wasn't a motor driver and controller in the housing.  I think it would be something like the brushless motor fan controllers/drivers described here http://www.pcbheaven.com/wikipages/How_PC_Fans_Work/ except that instead of just 3 or 4 wires, there are 6 wires and for that you get cw/ccw rotation plus a pot connection for speed variation.

But OK.  My current spinner is in it's second iteration right now (and my project is now forking as I am still persuing motor control with my brushed DC motor - eeek).  In the first prototype I had a geared brushed motor that I randomly picked based soley on RPM because I had to start somewhere and knew what kind of speed I was looking for based on the highest rpm that my spinning wheel does and the rpm I wish it did.  That first DC motor was the most horrible noisy thing I have ever had the misfortune to hear.  Also, the gearbox clattered.   :'(  That put me off geared motors.

The spinner I linked to in the video above is the current "best" motorized spinner on the market, and it uses a geared coreless DC motor which I believe is a relatively small Faulhaber motor.  It is controlled by a pic board. :D But I have read some comments about that spinner which suggest to me that that motor also has gearbox issues. Also it doesn't have a great RPM range because it's been geared down enormously.  There are faster spinning wheels, and spindles than this spinner, but it is very quiet, does what it's supposed to do, and that's why everyone loves it.  From everything I have read, I really believe that for these kind of spinners, small 12V DC motors are the way to go.  It's just a matter of finding the right motor, and I think I'm pretty close.  The more I work on my project, the more I think of new ideas which would make my spinning experience even nicer, and then I have to think about whether the motor I have chosen will be suitable.

Sewing machine motors?
1) They are AC motors, and I'm too young to die  ;D
2) too noisy
3) too big. 

I know there are men out there making these sewing machine motor-based spinners for their wives.  All I can say is that they really must wish their wives dead or something! :o  The number of times I have read forum posts by women saying "My husband made me a spinner from a sewing machine motor.  It's getting hot, and so is the pedal.  What could be wrong?" :o OMG!!!  There is no reason in this day and age of micro DC motors that we girls should be subjected to sewing machine motors for spinners!  For sewing, OK, but not for spinning!  :D 

After my first motor, I got another small brushed motor (not geared) which comfortably does just over 2000rpm, but it's not as fast as I would like.  That little thing is lovely and quiet though.  I'm won't mention specific torque figures either because it took me a lot of trial and error to figure that stuff out for myself, and again, it's for a competition where practically everybody will be using the spinner linked to in the video above ;). Mine is different and has a couple of features that commercial spinners don't have but which are really important to me.

At the moment I am looking at brushless motors, but not RC motors - those are too fast and too noisy for this sort of application.  For guys with their quadcopters and planes it's fine because those things are way up in the sky and quite a distance from their ears.  But for a spinner, who is sitting about a meter from the motor, it would be too annoying. Plus for an RC motor you need an ESC and that would have to be housed, which would make the spinner build bigger (and small and cute is better in that case  :P).  I'm also not too keen on the idea of  LiPo batteries which could unexpectedly explode inside the my spinner :( ).  I'm really just looking for a little 12V DC motor that I can connect with an adapter in my living room.

In terms of motor specs (RPM, torque), the brushless motor fits the bill.  And so does my little brushed motor (even if it's a little slow for my liking).

Re Chinese products, yes they can be shonky.  ;D Only time will tell if this is the case with my new motor.  ;D

Sir N

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Re: Brushless motor
« Reply #9 on: August 16, 2013, 05:46:31 AM »
Someone who knows about drop spindles!  Yay! :D  I can't imagine a motorized drop spindle, but it would be very very cool.
I'd think that a hollow bell shape or similar, with a battery, a small motor and a flywheel would do. Just hold it to stop rotation.

It's sort of funny... You wouldn't have been surprised, had I been female I gatherr (?) - Ought I be surprised that you, as a woman, play around with motors?  :P
To really throw you off your rockers, I could tell you that my present (third) sewing machine is utter crap, but I wouldn't like to be without it anyway ;D

Sorry, but I'm just a little confused about how you are obviously rooted deeply in rock hard gender roles AND breaking them at the same time ;D
Wasn't them womenfolk that invented the sewing machine and similar machinery in the first place either ;)

Yet another paradox is, that you ask for assistance, but are reluctant to give the needed info?
If you're afraid of your competition getting wind of your super spinner, you're welcome to drop the numbers and such in a PM, if you feel comfortable with that, but engineering works on numbers, not adjectives, so I won't be much help without this info - it'd be like if I asked you to knit me a sweater tight enough to show my abs but not too tight either and then not reveal my measures.

Those Hansen spinners are ridiculous expensive (and look like something that a 14yrs old kid made in wood shop class) - shouldn't be hard to make it under a third the price and 3 times as purdy.

Brushless PC fans are very small and weak motors, but the same techniques are used in fans that could take off an arm and about noise... it's not the motor in itself that makes the noise, it's bad balance, bad bearings and in the case of a fan, wind noise when the blades disrupts the air flow. Noise in a gearbox is likewise a matter of too sloppy engineering, bad materials, too wide tolerances and such - professional minigrinders (the pro version of a Dremel) doesn't vibrate in your hand when going 40kRPM (or faster) and it is barely audible until you start grinding at something.
I have gearhead motors that are so silent and well balanced, that you have to touch the spindle to know if they're turning.

With a good motor, I'd think a reasonably well build spinner could be made to max out at around 30dBA (perhaps less), if your mechanical provess is up to it. Mind you, I have no hard and fast idea of the power it takes to spin or what speed/torque you need, as I have never had any hands on, but I'd think that the Hansencraft never really used all of its 17W - I'm just guessing here though, based on spinning stuff like string and metal wire.

A stepper motor with enough power would be fairly silent, although quite bulky, but why not do away with old thinking and use direct drive, rather than a "belt" drive?
You might wanna look into pancake motors, they're quite powerfull for their size, but need a driver like any other BLDC motor.
I don't know if the Hansencraft motor is indeed coreless. I see no need for using a coreless motor (quite the contrary actually), as the main feature of coreless types is that they respond very quickly to speed changes, as their core is "just" some copper wire on a light plastic drum, so the (moving) core don't have the inertia of a conventional iron core motor. Spinning probably needs rather slow/smooth speed changes I'd guess.

The control electronics of the Hanencraft is very simple as well - anyone with a Robotics 101 under their belt should be able to make a similar control in their half sleep.


[...] I'm building this spinner for a spinning competition,
I imagine the spectators jumping up and making the wave, chanting encouraging and similar ;P
How much are the tickets... Hehe ;)


Sewing machine motors?
1) They are AC motors, and I'm too young to die  ;D
Ain't we all?
Happens anyway, my best friend, from days past, bought the ticket a month after his 18 year birthday.
But to die from a properly encapsulated AC motor, takes a Darwin Award nominee so...


2) too noisy
Most of the noise in a modern sewing machine, comes from the mechanical actions happening downstream from the motor.


3) too big. 
Sorry, didn't know you were running out of space, since you didn't post any numbers  :P


I know there are men out there making these sewing machine motor-based spinners for their wives.
Uh oh, back in the predefined gender roles *G*

All I can say is that they really must wish their wives dead or something! :o  The number of times I have read forum posts by women saying "My husband made me a spinner from a sewing machine motor.  It's getting hot, and so is the pedal.  What could be wrong?" :o OMG!!!
Come now... Nobody ever died from a little heat (Indian wives and kitchen furnace "explosions" is another thing though).

I think that a more realistic gender differentiator is noise... Men like machinery to be loud - the guy with the loudest toy wins - while women are like... "You don't need those large speakers and could you please turn that ghastly music down to -6dBA immediately" - I bet that's why there's so many broken marriages  ::)


There is no reason in this day and age of micro DC motors that we girls should be subjected to sewing machine motors for spinners! 
One reason I can think of is, that you girls aren't telling us primitive Neanderthals what you need, so we just have to guess and our Martian reptile brain will always prefer a just over-kill over just a kill, just to be on the safe side - women everywhere have heard it numerous times, I'm sure, but they still think men are mindreaders (primitive, but with a superior ESP  :-\) - If women actually told their men how they wanted it, in measurable units, I'm sure the men would step up to it :)


[...] I got another small brushed motor (not geared) which comfortably does just over 2000rpm, but it's not as fast as I would like.
If you use a belt drive, it will have a gearing worth the difference of the driving and driven "wheels" diameters.
Say the pulley on the motor axle is 20mm and the one on the bobbin is 100mm, you'll have a 5:1 gear reduction and the 2kRPM is down to 400RPM (which I'd think would be pretty fast when you have to feed the fleece in a steady flow, but what do I know).
Telling what you'd like, rather than what you don't might spur a more helpful response and the same with pulley diameters and such.


I'm won't mention specific torque figures either because it took me a lot of trial and error to figure that stuff out for myself, and again, it's for a competition where practically everybody will be using the spinner linked to in the video above ;). Mine is different and has a couple of features that commercial spinners don't have but which are really important to me.
As I said, you could PM me with the figures and I promise you that I won't leak a word.


[...] for an RC motor you need an ESC and that would have to be housed, which would make the spinner build bigger
ESC stands for Electronic Speed Control, just like there is an ESC in the Hansencraft.


I'm also not too keen on the idea of  LiPo batteries which could unexpectedly explode inside the my spinner :( ).  I'm really just looking for a little 12V DC motor that I can connect with an adapter in my living room.
You don't need to use LiPos with a BLDC, any battery or a mains adapter is fine, as long as the voltage and current is matched - and the dangers of LiPos are greatly exaggerated - just think of the billions of cell phones in use world wide - how often do you hear of someone getting their head blown of by their phone? ;D
You can always use LiFe cells if you decide to make a portable spinner, they're considerd the safest of Lithium cell chemistries :)


In terms of motor specs (RPM, torque), the brushless motor fits the bill.  And so does my little brushed motor (even if it's a little slow for my liking).
So, your problem is solved with the brushless? Great, happy construction then and please post some photos of the finished version (when you've won the gold and the competition is left behind) :)

I'd still like a link if you could be persuaded, as I both use a lot of motors myself and does a fair bit of consultant work on motors as well, so I'm allways interested in new stuff.