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'[OT] PWM and coreless motors'
1999\05\04@233113 by Shahid Sheikh

picon face
Hi all,

A quick OT question. What is the minimum safe PWM frequency for small
coreless DC motors. The manafacturer doesn't specify one. From what I
understand, using a low PWM frequecy causes the coils in the motor to
loosen up because of vibration.

Also, what are the advantages of using a coreless motor over an iron core
one? I'm talking about small DC motors maybe upto 6 watts at 18 volts.

Shahid

1999\05\05@061242 by Stefan Sczekalla-Waldschmidt

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face
Hi,

Still in Model-Railroading ?

I think about 20KHz is the PWM frequency used for coreless Motors
like the Faulhaber one.

Shahid Sheikh wrote:
{Quote hidden}

1999\05\05@144842 by Shahid Sheikh

picon face
Yep. Dont tell me you've quit :)

19.somthing is the max I can generate with the Atmel chip I'm planning on
using so I think that will work.

Anyone knows the benefits of using coreless over a iron core motor (or did I
already ask that)?

Also I was wondering how pronounced is the back emf of a coreless motor Vs.
a iron core motor. It should be better than an iron core motor right?

Shahid

-----Original Message-----
From: pic microcontroller discussion list
[spam_OUTPICLISTTakeThisOuTspamMITVMA.MIT.EDU]On Behalf Of Stefan Sczekalla-Waldschmidt
Sent: Wednesday, May 05, 1999 7:16 AM
To: .....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU
Subject: Re: [OT] PWM and coreless motors


Hi,

Still in Model-Railroading ?

I think about 20KHz is the PWM frequency used for coreless Motors
like the Faulhaber one.

1999\05\05@145942 by Mario I. Arguello

picon face
In a message dated 5/5/99 3:48:58 PM SA Eastern Standard Time,
sheikhspamKILLspamEROLS.COM writes:

<< Anyone knows the benefits of using coreless over a iron core motor (or did
I
already ask that)?

I have used coreless motors in my micro helicopter designs. They are
excellent for applications requiring high efficiency, low resistance means
very low current draw. However, they are very delicate since the construction
is different than iron core.

Depending on the application.  I have gone back to using iron core simply
because of cost and maintenance.

If you want to see my helis visit my web pages:

http://members.aol.com/miachper/miasportt.htm

1999\05\05@192733 by Brian Kraut

picon face
I clicked on your URL and AOL could not find it.  Is the address correct?

Mario I. Arguello wrote:

{Quote hidden}

1999\05\06@015313 by Mario I. Arguello

picon face
My URL ... sorry folks that was misspelled..Here is my correct URL.

http://members.aol.com/microchper/miasportt.htm\

Mario

1999\05\06@042234 by Stefan Sczekalla-Waldschmidt

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face
^Hi,

Shahid Sheikh wrote:
>
> Yep. Dont tell me you've quit :)

How could I ....

Did you heard of the Danish Guys who made a Motorola-Protocol
decoder for maerklin based on a PIC 16C84 ?

http://hjem.get2net.dk/formula.micro/indexeng.html

>
> 19.somthing is the max I can generate with the Atmel chip I'm planning on
> using so I think that will work.

AFAIK the higher the better but also 12 KHz may be ok, I think 20 KHz
is just choosed because of being outside the audible range.

The high frequency pwm versus iron-core motors is necessary because
the coreless motor has just a cooper-network glued tho the shaft.
the forces acting on this network will be smaller if more short
pulses of power are applied than only some long.

>
> Anyone knows the benefits of using coreless over a iron core motor (or did I
> already ask that)?

one main difference is the mass of the rotor (inertia). also coreless
motors
has virtually no "Rastmoment" - means if you just take both kind of
motors,
and try to turn them manually you will notice that there is some "force"
necssary
to turn the iron core motore whereas much less "force" is necessary to
turn the
coreless motor.

- oh, I forgot the real difference: Price. :-)

>
> Also I was wondering how pronounced is the back emf of a coreless motor Vs.
> a iron core motor. It should be better than an iron core motor right?

I'm sorry, but this need to be answered by someon else - never tested
this.

Kind regards,

       Stefan

1999\05\06@052555 by Seyler Jean-Yves

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face
There is a big problem with "high frequency" PWM like the 12 kHz you propose
: you can hear it ! unless it is more than #20 kHz (and at this frequency, a
poor 4 MHz PIC is a bit poor :-) ...
So, a railroad application isn't much convenient !!!

Hope this help

Jean-Yves
{Quote hidden}

1999\05\06@081224 by Russell McMahon

picon face
>I have used coreless motors in my micro helicopter designs. They are
>excellent for applications requiring high efficiency, low resistance
means
>very low current draw. However, they are very delicate since the
construction
>is different than iron core.
>
>Depending on the application.  I have gone back to using iron core
simply
>because of cost and maintenance.
>
>If you want to see my helis visit my web pages:
>
>http://members.aol.com/miachper/miasportt.htm



Seems not to work

Perhaps files at http://members.aol.com/miadsgns/
was what was meant - neat stuff.

1999\05\06@135642 by Mario I. Arguello

picon face
In a message dated 5/6/99 9:12:44 AM SA Eastern Standard Time,
@spam@apptechKILLspamspamCLEAR.NET.NZ writes:

<< >I have used coreless motors in my micro helicopter designs. They are
>excellent for applications requiring high efficiency, low resistance
means
>very low current draw. However, they are very delicate since the
construction
>is different than iron core.
>
>Depending on the application.  I have gone back to using iron core
simply
>because of cost and maintenance.
>
>If you want to see my helis visit my web pages:
>
>http://members.aol.com/miachper/miasportt.htm >>
try this link I goofed on above link

http://members.aol.com/microchper/miasportt.htm

Cheers,
Mario

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