Reply by Tim Wescott ●January 11, 20172017-01-11
On Wed, 11 Jan 2017 21:01:17 -0600, Tim Wescott wrote:


> On Wed, 11 Jan 2017 14:23:36 -0800, robert bristow-johnson wrote:
> 
>> On Tuesday, January 10, 2017 at 1:38:07 AM UTC-5, Tim Wescott wrote:
>>> Normally it takes me a while to get a video out.  This one came to me
>>> and practically pushed it's way out of my brain and into the camera.
>>> 
>>> I hope y'all like it:
>>> 
>>> https://www.youtube.com/watch?v=E9zM07v1vWk
>>> 
>>> 
>> Tim, would the words "rotor" and "stator" be useful?
> 
> Probably.  But it's too late.
> 
>> is the coreless motor one where the basket of wires is stationary and
>> the permanent magnets move?
> 
> AFAIK there's no motor where a basket of wires stays stationary and the
> magnets move.  However, with brushless motors the armature (complete
> with iron) is usually stationary with the magnet section moving.
> 
>> of do the baskets of coils move just like before but without iron
>> cores?
> 
> I wish I could have gotten that damned coreless motor apart, or brought
> myself to take the other one apart.  The basket of wires move just like
> before, just without the iron cores.  The point is to get as much mass
> out of the rotating assembly so that it'll have low inertia.
> 
>> or can you have baskets of coils for *both* the rotor and the stator?
>> 
>> will you be doing a vid soon showing the electric model of a DC motor
>> (for the purpose of control applications)?  like where applied current
>> gets mapped to torque and where rotor speed gets mapped to back e.m.f.?
> 
> I plan on doing just that, yes.  I also plan on explaining sources of
> torque ripple (cogging torque and varying motor constant, although I
> don't know if there's a better name for the latter).  Cogging torque
> reduction is the other reason that coreless motors are good, although
> there are ways to reduce it in a motor that's wound on an armature.


I'm not sure that "soon" is a good word to use, though -- I just had a 
buttload of work dumped in my lap: I'll be giving a talk that needs a lot 
of prep in the next four weeks or so, on top of some other work I've got 
promised.

-- 
Tim Wescott
Control systems, embedded software and circuit design
I'm looking for work!  See my website if you're interested
http://www.wescottdesign.com
Reply by Tim Wescott ●January 11, 20172017-01-11
On Wed, 11 Jan 2017 14:23:36 -0800, robert bristow-johnson wrote:


> On Tuesday, January 10, 2017 at 1:38:07 AM UTC-5, Tim Wescott wrote:
>> Normally it takes me a while to get a video out.  This one came to me
>> and practically pushed it's way out of my brain and into the camera.
>> 
>> I hope y'all like it:
>> 
>> https://www.youtube.com/watch?v=E9zM07v1vWk
>> 
>> 
> Tim, would the words "rotor" and "stator" be useful? 


Probably.  But it's too late.


> is the coreless
> motor one where the basket of wires is stationary and the permanent
> magnets move? 


AFAIK there's no motor where a basket of wires stays stationary and the 
magnets move.  However, with brushless motors the armature (complete with 
iron) is usually stationary with the magnet section moving.


> of do the baskets of coils move just like before but
> without iron cores? 


I wish I could have gotten that damned coreless motor apart, or brought 
myself to take the other one apart.  The basket of wires move just like 
before, just without the iron cores.  The point is to get as much mass 
out of the rotating assembly so that it'll have low inertia.


> or can you have baskets of coils for *both* the
> rotor and the stator?
> 
> will you be doing a vid soon showing the electric model of a DC motor
> (for the purpose of control applications)?  like where applied current
> gets mapped to torque and where rotor speed gets mapped to back e.m.f.?


I plan on doing just that, yes.  I also plan on explaining sources of 
torque ripple (cogging torque and varying motor constant, although I 
don't know if there's a better name for the latter).  Cogging torque 
reduction is the other reason that coreless motors are good, although 
there are ways to reduce it in a motor that's wound on an armature.

-- 
Tim Wescott
Control systems, embedded software and circuit design
I'm looking for work!  See my website if you're interested
http://www.wescottdesign.com
Reply by robert bristow-johnson ●January 11, 20172017-01-11
On Tuesday, January 10, 2017 at 1:38:07 AM UTC-5, Tim Wescott wrote:

> Normally it takes me a while to get a video out.  This one came to me and=

=20

> practically pushed it's way out of my brain and into the camera.
>=20
> I hope y'all like it:
>=20
> https://www.youtube.com/watch?v=3DE9zM07v1vWk
>=20


Tim, would the words "rotor" and "stator" be useful?  is the coreless motor=
 one where the basket of wires is stationary and the permanent magnets move=
?  of do the baskets of coils move just like before but without iron cores?=
  or can you have baskets of coils for *both* the rotor and the stator?

will you be doing a vid soon showing the electric model of a DC motor (for =
the purpose of control applications)?  like where applied current gets mapp=
ed to torque and where rotor speed gets mapped to back e.m.f.?

just curious.

r b-j
Reply by Tim Wescott ●January 10, 20172017-01-10
On Tue, 10 Jan 2017 11:23:32 +0000, piglet wrote:


> On 10/01/2017 06:38, Tim Wescott wrote:
>> Normally it takes me a while to get a video out.  This one came to me
>> and practically pushed it's way out of my brain and into the camera.
>>
>> I hope y'all like it:
>>
>> https://www.youtube.com/watch?v=E9zM07v1vWk
>>
>>
> I like it, nice style and not too long. How did you do the graphic?
> 


Thank you.  Finding subjects that are a nice fit to a 15-20 minute video 
is actually a bit of a chore.  90 minute lectures would be easier, but 
far more tedious to watch.

The graphics were generated in Scilab.  Its graphics abilities are pretty 
crude but it can do the math behind the motion simulation quite easily.  
I just did it as stop-motion animation, generating still for each frame 
in the video, then put it all together with ffmpeg.

I would like to do nicer-looking graphics in something like Blender, but 
my experiences with that are that (A), it takes time to get things 
looking good, (B), I'm never going to be much of an artist, (C), I'd have 
to bend over backwards to either simulate stuff accurately in Blender, or 
import position information, and (D), it's a rabbit hole into which I'm 
afraid that I would jump, and then not come out of for a very very long 
time.  So it'd be lots of time lost for not a lot of gain.


> If ever you redo I thought a little more explanation of the
> brushes/commutator switching action and reason for odd number of rotor
> segments would answer the kind of question that a young mind leaps to.
> 
> I am going to show your video to my kid!


If it's a hit, there's a bazzilion "build your own motor" vids.  I was 
considering doing that as part of the video, but I had the sense to check 
first; both of the ones that I looked at were winners, so I figured I 
didn't need to add anything.

(I did not check to see how many "this is how a motor works" videos there 
might be -- I wanted to do this one regardless.)

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I'm looking for work -- see my website!
Reply by Otmar Bradsky ●January 10, 20172017-01-10
On 10.01.2017 07:38, Tim Wescott wrote:

> Normally it takes me a while to get a video out.  This one came to me and
> practically pushed it's way out of my brain and into the camera.
>
> I hope y'all like it:
>
> https://www.youtube.com/watch?v=E9zM07v1vWk
>


OMG but SCNR, cut your fingernails!
Reply by piglet ●January 10, 20172017-01-10
On 10/01/2017 06:38, Tim Wescott wrote:

> Normally it takes me a while to get a video out.  This one came to me and
> practically pushed it's way out of my brain and into the camera.
>
> I hope y'all like it:
>
> https://www.youtube.com/watch?v=E9zM07v1vWk
>


I like it, nice style and not too long. How did you do the graphic?

If ever you redo I thought a little more explanation of the 
brushes/commutator switching action and reason for odd number of rotor 
segments would answer the kind of question that a young mind leaps to.

I am going to show your video to my kid!

piglet
Reply by Robert Baer ●January 10, 20172017-01-10
Tim Wescott wrote:

> Normally it takes me a while to get a video out.  This one came to me and
> practically pushed it's way out of my brain and into the camera.
>
> I hope y'all like it:
>
> https://www.youtube.com/watch?v=E9zM07v1vWk
>

   Your presentation is becoming more professional.
   Be careful..Hollywood may be watching...
Reply by Tim Wescott ●January 10, 20172017-01-10
Normally it takes me a while to get a video out.  This one came to me and 
practically pushed it's way out of my brain and into the camera.

I hope y'all like it:

https://www.youtube.com/watch?v=E9zM07v1vWk

-- 
Tim Wescott
Control systems, embedded software and circuit design
I'm looking for work!  See my website if you're interested
http://www.wescottdesign.com