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Video: DC Motor Basics

Started by Tim Wescott January 10, 2017
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
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...
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
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!
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!
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
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
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