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Yes this was a useful lecture I learned something (allways a positive)

Sunny and Cool in Albany NY

No I havent used non iron core motors

Thanks for the archive. And thank you Paul for the wonderful and informative lecture.

Iron

My attendance schedule got bumped a bit, so I appreciate the archives.

Iron

thank you paul for the wonderful section

Platinum

Build simple dc motor as a toy

Thanks Paul.  But My slide #2 did not render all of the text/symbols and in the bottom section I do not understand how the measurement of "0.555 x 10 _ _ ounce" factors into the definition.

Iron

Thanks Rob, Design News and Digi-Key.

Iron

Thanks Paul. Thanks everyone in attendance. This concludes our radio show and the following chat. We're looking forward to the program tomorrow. Tune in at the same time.

Blogger

OK for today.  See you all tomorrow.

Thanks for joining us. Bye now.

Blogger

Back EMF is minimized firstly by winding style.... Then by

winding gauge, winding count, and winding inductance.

High speed motors will often have low back emf..... this is

both a blessing and a curse.  Blessing because motor goes

fast, curse because low inductance makes for very high PWM

currents in standard 20KHz PWM controllers.  A low back emf

motor could require high PWM frequencies to properly and efficiently

drive them.

Blogger

Thanks, Paul. Great lecture and excellent pictures

What are some of the ways to reduce/minimize back emf in DC motors?

I know that I went over the selection criteria fast.

What I did not say was about the load aspect of the

selection process.  One must apply one's known load

to the speed-torque-hours-of-operation, etc. and bake

all that in when selecting a motor.

Blogger

Torque is proportional to winding current.

Do not forget free-wheeling currents when

making measurements.  More on that on

Wednesday I believe.

Blogger

Could you go over again the criteria to consider when selectiong a motor? You went over them rather quickly earlier in the presentation.

Great lecture! Thanks!

 bcopsey

 

 

Blogger

I don't think that the motor in the photos was actually

a bad one.  The lighting may not have been good as I

believe we took apart a working unit.

Blogger

Is torque directly proportional to winding current?

It is OK with me if you re-use the material that I have

presented.  I don't know if UBM (the publisher) feels that

way though

Blogger

?? It looks like a defect on one of the commutator wire welds on slide 13 and 9.  Is this a common failures area?

Craiglab

 
Blogger

I have a small bibliography on day 5,

however there are some great app notes

on Freescale, Microchip, and NXP web sites.

Perhaps I will cite these tomorrow.

Blogger

Can we reuse this material? I mentor a competitive high school robotics team, where we use several types of brushed dc motors. Would like to use this materail to teach them about brushed dc motors, motor selection, etc

Iron

Will you go in to series field motors as welol as permanent magnet ?

NormanVutz

 
Blogger

Yes it is possible to start a motor with very large torque.

That is exactly what a DC motor is best at.  Picture this:

The motor is stopped, its held by a high load.  Now we

apply energy to it.  Current goes way up, torque builds, but

we are not turning.... An AC motor will slip because the phased

AC must move on.... But a DC motor will just keep pushing until

(if the motor is very large) the load moves with very large torque.

Blogger

Think of a motor as a gear.  The farther the magnetic interface from the center of the shaft the more lever arm.  So a "pancake" motor will have more power with the same energy than a small cyl.  Theoretically... right.

 

Iron

Hi Paul, are there any  DC Motor design references you may recomend  ? Thanks nice presentation.

edeanda

 
 

 

Blogger

Question on motor efficiency: Is this calculated as mechanical work out divided by electrical power in?

Is it possible to have a small motor with very large touque?

aykc88

 

 

Blogger

@pauln  The magnets are important. In one application the magnet was being slowly demagnetized because we were increasing the drive current too quickly while the motor was under load. It was a low cost motor.

Iron

Good question about the wide brushes.... I meant to comment

on that during the talk and forgot, thanks for asking:
Yes, the brushes are wider because they are designed to short

windings as well as guide current through windings.  This is the

black magic of motor winding design.  All with the purpose to

keep sparking down and torque as smooth as it can be.

Blogger

Question: What is the benefit of DC motor over and above ac motor, once we know brushes have limited life, it requires more maintenance?

 Dsraipal

 

 

Blogger

The really good motors are using Neodyineum composites ... This is the current strongest state of the art

Iron

Our next three days' discussion will be

more about the control electronics.  We will NOT

be talking about planetary gears cause we just

don't have this time during this go...

Blogger

The brushes seem wider than the contacts on the commutator. Are more than one widing excited at the same time?

 Sariimarcosa

 
Blogger

Can we get the curves for all DC motors ? If I a am to choose a DC motor, having the maximum efficiency point matters a lot to me !

Good question about the magnets, I don't

know how they are made... Anyone?

Blogger

Stepper motors are great for tight control.

They can be thought of as a high-pole-count

DC motor where commutation is fractionally

performed.  New Field Control Motor techniques

could rival these for performance.

Blogger

Are the permanent magnets now used all rare earth like cobalt samarium? Are the old style magnets pretty much obsolete?

Anyone have a suggestion for an encoder vendor? I recently order a couple of encoders from CUI, inc., but haven't received them yet.

 

 

Blogger

AC motor control differs from DC motor

control in that AC motor control requires

phasing of the waveforms to move the motor.

 

Blogger

@pauln, A majority of our applications use stepper motors because of the tight control.  And in our particular applications we don't require a lot of torque, but do require a fair amount of speed.  Can the same level of control be achieved with a brush DC motor and, if so, is there any particular advantage to going that route?

Iron

Some DC motors have integral planetary gear boxes. Will you be discussing those types?

Now brushless motors offer greater

precision in control and potentially longer

life, however it comes at some cost to the

motor and drive ciruitry.  Brushless motors

require hall sensors to start un-ambiguously.

The brush motor will start un-ambiguously without

any need for hall sensors or all the electronic

commutation ciruitry that goes with them.

Blogger

The best thing about brush motors

is their simple drive circuitry.  Brush motors

will never be obsolete cause of this.  In many

applications, motors can last for years of intermittent

use, have low cost drive circuitry and be quite useful

even as brush motors.

Blogger

DC motors are easier to control than AC motors.

Iron

Thanks. Will look up the information.

 

Iron

What is the benefit of using DC motors in place of ac motors? What special application for which DC brush motors are being used where we can not use3 ac motors?

 

Iron

Could you go over again the criteria to consider when selectiong a motor? You went over them rather quickly earlier in the presentation.

Great lecture! Thanks!

 

Iron

Excellent presentation Paul.

Iron

Nice presentation ! Thanks

 

Nice refresher course. Thank you PN!

do you also teach the DC brushless motor? I am more interested in that...

Iron

Made a motor many, many years ago in 6-7th grade. I used transformar laminations for the core. It ran well, but the "brushes" (20 gauge wire) burnt up a lot. Otherwise ran well, fast even.

Iron

Will you go in to series field motors as welol as permanent magnet ?

Iron

Hi Paul, are there any  DC Motor design references you may recomend  ? Thanks nice presentation.

Iron

Very good class, thanks

 

Thank You. Can't wait for tomorrows lecture!

Great - looking forward to more....

Iron

Is it possible to have a small motor with very large touque?

Iron

?? It looks like a defect on one of the commutator wire welds on slide 13 and 9.  Is this a common failures area?

Iron

Thanks Paul, a lot of good info

Iron

Thank you Paul. I'm going to love this class. It's one I've been wanting to take for a while now.

Iron

Thanks again Paul.

Iron

Excellent.  Thanks.

 

Thanks, Paul and company.

Thank you Paul, good information

Iron

Very useful Paul. Thanks.

Iron

thanks Paul and Rob

Iron

Thank you for the presentation

 

never used dc motors for any of my projects

Iron

We're now on slide 22.

Blogger

We're now on slide 21.

Blogger

We're now on slide 20.

Blogger

We're now on slide 19.

Blogger

We're now on slide 18.

Blogger

I've worked with some industrial motors 300+ hp that are used in heavy fabrication operations

On slides 15 and 16, should the speed arrow be vertical?

Gold

We;re now on slide 17.

Blogger

mixing chambers, pumps, micro-injector, focus laser focus servo etc.

Iron

DC motors are very easy for speed control and positioning as opposed to AC. Also you might use DC if AC is not available. In a car or to run on betteries, etc.

Iron

DC motors have the advantage of increasing torque with decreasing speed over AC mtors

Secondary drive motor for an assembly operation, trying to decide between dc brush or dc brushless servos.

Iron

We're now on slide 16.

Blogger

APPS: HO & G Scale Railroad crossing gates; animatronics; mechanized effects; and many, many more.  :)

Servos for autopilots

Iron

DC motors for propulsion

Pan and tilt systems

 

Iron

Industrial Feeding equipment

Iron

fluid pumps for electro-chemistry and ore refining -- ac control

Iron

@dsrajpal, "servo" (position and speed control) is easier to accomplish wtih DC motor.  Position and variable speed control with an AC motor is more complex.

 

Valve train applications, automotive

 

I have used DC motors and speed controllers for test benches for gear reducers and pick and place equipment. Easy speed control set up.

 

Iron

lab equipment, automotive (varied)

Iron

Used for use in a small glue removal fixture.

Iron

use motors for positioning things

Gold

Valve train applications

To operate high voltage switches

Iron

I have never selected motors for any application. I'm here to learn.

Iron

We're now on slide 15.

Blogger

Your hand-drill is probably a universal motor.

Dc may be preferred in certain applications.

Iron

For what applications have you selected motors?

Blogger

I supposed the Torque that might get from AC, than DC can't offer.

 

Iron

your hand drill probably has one.

 

Iron

Question: What is the benefit of DC motor over and above ac motor, once we know brushes have limited life, it requires more maintenance?

 

Iron

We're now on slide 14.

Blogger

There's one in my electric motor powered RC model but they're brushless using a eMotor speed controller.

We're now on slide 13.

Blogger

What's the life span of motor brushes?

Iron

The brushes seem wider than the contacts on the commutator. Are more than one widing excited at the same time?

 

Never used one without iron core.

Iron

We're now on slide 12.

Blogger

Thank you, I must be blocked, will try again another day

I believe all of the ones I've used had iron cores

Iron

We're now on slide 11.

Blogger

Besides the one I built for my daughter :-)  Nope.

Iron

No that i remember

Iron

I have used a hollow wound core motor 

Iron

I've seen "planar" or "pancake" motors, but never actually used one...

 Has anyone listening used motors built without iron cores?

Blogger

DFS_Praxair, you have to click play button on the audio bar below the class title.

Gold

Try pulling one out of a 28 foot long PMM motor.

 

Iron

We're now on slide nine.

Blogger

should I expect to hear audio somewhere with downloaded slides?

We're now on slide eight.

Blogger

Yup 40 years ago. The rotor was a nail.

Iron

Hello from Milwaukee!

Iron

I couldn't get it to work decades ago

Iron

Whe I was kid my father also gave me a motor kit.

Iron

We're now on slide seven.

Blogger

Yes!  Made a "half pole" motor as a demonstration to students.  (The engineers at work were MUCH more interested than the students were...)  Works great!

 

yes more years ago than I can count.

 

Iron

No, I've never built a paper-clip Brush DC motor.

Iron

Yes, built several small motors like this a kid. Some worked, some didn't. 

Iron

Most definitely! When I was somewhere between 5 and 10 years old.

Iron

I built the exact same thing for my daughter.

Iron

If you do not see the audio bar above, please refresh your browser. It may take a few tries. The audio bar should appear at the top of the page. Then, press the play button. Note however that some companies block live audio streams. If that's the case with yor company, the class will be archived immediately following the live show and no one seems to have a problem listening to it on demand.

Has anyone listening built something like this?  Did it work?

Blogger

I can't see or hear you at all. Where's the audio/visual?

Has anyone listening built something like this?  Did it work?

Blogger

hello from Timisoara, Romania

Iron

We're now on slide six.

Blogger
@MazianLab: Try using FF or Chrome as your browser. Many people experience audio interruptions with IE. Also, make sure that your flash browser is the current version.

Me also can not hear any audio

 

Iron

We're now on slide five.

Blogger

I do not hear any audio

Steve

Iron

I have audio, but I think necause of trafic it gets on and off all the time.

Iron

We're now on slide four.

Blogger

Does the lecture begin automatically or we need to click any link?

 

Iron

We're now on side three.

Blogger

MazianLab, try refreshing your browser window. 

Blogger

Hi, this is Devendra from Siemens Industry, North Carolina

 

Iron

Also a current flow of one coulomb/sec

 

Audio is live, but disconect all the time.

Iron

Well, the folding water bed was fun, but rather hazardous especially on fine hardwood flooring.

@claudiuleahu, click the play button on the audio bar below the class title.  If not there, refresh your brower.  Also click on Today's Slide Deck for slides

Gold

Good afternoon from Shrewsbury PA. I love motors!

Hi all - Audio is live!

Theres a slide deck under special educational materials

Good Afternoon, everyone

Iron

Hello from Toronto, ON

Iron

Invent something great and give me a fun job.

 

Iron

Glendale, CA says Hi

 

Iron

are here any video or audio materials?

Hi from Pretoria - South Africa

I worked 30 years making other people rich. I decide to stop doing that.

Hello from Miami of Ohio.

Iron

Sounds like more fun than working for a living.

Iron

Good afternoon from Minneapolis

Iron

Oh goody -- a topic I know nothing about!

Hello from cloudy SE Lake Simcoe, Ontario Canada

Iron

No I don't work for Gagemaker. I'm a retire loafer that builds robots, etc. and am a garage inventor of sorts.

 

Hello from Pennsylvania.

Iron

hello from Mishawaka

Iron

Good Morning from Sunny Valdez

johnwolf do you work for Gagemaker?

 

Iron

Hello from Montana

Gold

good moring from SoCal

Iron

Greetings from Midland Tx

Iron

That picture of the 'Paper-clip Brush DC Motor' (slide 6) looks very similar to one my son made from one of those electric experimenter kits (the picture doesn't show the permanent magnet).  And it actually worked.

Iron

Anyone have a suggestion for an encoder vendor? I recently order a couple of encoders from CUI, inc., but haven't received them yet.

Greetings from Colorado Springs.

Iron

Hello from SW Michigan

 

Iron

@johnwolf.lobo, I THINK that spiral cut spreads out the rotor poles for smoother motor rotation.  If the poles were straight (lining up in parallel with the stator poles) then I think the motor tends to "cog" to those positions making for "jerky" rotation.  (I am not a DC motor expert!  It will be interesting to hear the experts' responses.)

Why is the rotor laminations (and coils) cut in a spiral verse cut in parallel with the turn axis?

 

-The streaming audio player will appear on this web page when the show starts at 2 PM Eastern time today. Note however that some companies block live audio streams. If when the show starts you don't hear any audio, try refreshing your browser. If that doesn't work, try using Firefox or Google Chrome as your browser. Some users experience audio interruptions with IE. If that doesn't work, the class will be archived immediately following our live taping.

Blogger

Greetings from Chicago.

Iron

Good morning. Hello from Maryland. Looks like its going to be a good class..

Iron

-Be sure to click 'Today's Slide Deck' under Special Educational Materials above right to download the PowerPoint for today's session.

Blogger

-Please join our Digi-Key Continuing Education Center LinkedIn Group at http://linkd.in/yoNGeY

Blogger

The day 4 slidedeck is posted now.

Blogger

Good afternoon, everyone

Iron

Hi from Albuquerque, New Mexico

 

Blogger

day 4 seems to be missing slides downloads . All other days are there.

-Be sure to follow @designnews and @DigiKeyCEC on Twitter for the latest class information. We encourage you to tweet about today's class using the hashtag #CEC.

Blogger

Hi from chihuahua, mexico

Iron

Good morning from Memphis...

Iron

 

Hello From Morgan Hill, CA

 

Good morning from California.

Iron

hello from maryland

Iron

Good morning from Mobile, AL

Hello from Beaverton, Oregon.

Iron

Good morning from Titusville,Fl.

Iron

Morning from Panama City, FL

Iron

San Diego, CA is checking in this morning!

Iron

Good morning from Scottsdale, AZ

Iron

Good morning from NY.

Iron

Good morning from Edmonton, AB

Iron

I'm caring the market developing of brush DC motors, due to the brushless motors have more advantages and sharing more and more market, the brush motors were going down. Is that true? What's the better aspect of brush motors than brushless motors?

Iron

The DC motor technicaly its informations dose not change more But we hope to learn more ideas

thank you

Iron


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