Video: DC Motor Basics

Your presentation is becoming more professional. Be careful..Hollywood may be watching...

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

Hi Tim,

if you need to make detail parts of the video appear brighter, instead of adjusting brightness and contrast in the editor, try adjusting GAMMA. If your editor does not have gamma adj, find one that does and try it.

keep em, coming,, now I'm looking forward to the next one...

:-)

mark

Me too... well I'll send him the link. (you can lead a horse to water....)

George H.

I'm not sure I did adjust the brightness and contrast in the editor. There was a clip where I did that, but I'm pretty sure it's one that I ended up not using.

But -- I shall remember that.

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 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.)

Yes... but there is a way you could get the audience more involved. Demonstrate winding inductance by holding the motor wires as you disconnect the battery :)

NT

Sno-o-o-ort >:-} ...Jim Thompson

Some things are far more interesting experienced from the inside than viewed from the outside.

I could grab a honkin' big coil from the junkbox and show the spark when you disconnect it from the battery.

In high school electronics we made "engravers" that were just buzzers whose contact points worked on the material being engraved. The spark did the engraving. I remember it being kewl.

As a youngster, maybe 12 years old, I put several D cells in a paper towel cardboard and tried to run a record player motor. I didn't learn the why, but I learned what the effect it had on my hands.

Mikek

For another video, explain the operation of a 3 speed fan motor. I think I'm stuck on the rotating field, but that's why I want the video.

Mikek

If I ever get to the point where I understand one, I sure will!!

Series capacitor reduces current thus torque. The result is greater slip in the motor.

Another way is to select from tappings on the motor winding. There are other ways too of course.

NT

I see you've not volunteered to recreate the experiment for him :)

NT

Is that it? Doesn't it make the squirrel cage overheat?

Can I make one slow down even more by using a lower-value cap (I have a need for a mild, quiet fan in my office in the winter, to stir the air just enough so that the warm are isn't all by the heater).

The motors are squirrel cage variants that can cope with it. But the details of the variation I don't recall.

Yes, but there's a reason capacitor speed controls don't go very low. They're bad news for starting torque, and the lower you go the more the risk of fire rises.

NT

yes, but at reduced stator voltage the rotor currents are reduced too :)

should work, or you can get electronic fans speed controls that work somewhat like thyristor dimmers. you can turn ceiling fans down to like 10 rpm.

When I was a kid I could get mild (120V) shocks and not notice. Now, if it's enough to make my arms twitch I can feel a tightness in my chest for ten minutes or so.

It gives me an idea that maybe I've exceeded my lifetime maximum of such things, and should avoid any further ones.

Did you have to whip out your tiny Johnson in this video?