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Re: CDROM Spindle Stepper motor

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WRONG !!!!

What makes you think a 'brushless DC motor' is any smoother than a
'stepper motor' ? How many poles does a 'brushless DC motor' have ?
What is the size of the 'step' for a 'brushless DC motor' (they don't
actually work with just DC, do they ?)
How many poles does a' stepper motor' have ?
Neither type has commutators, so any 'smoothness' is entirely due to the
design of the drive electronics, and is ultimately limited only by the number
of poles, isn't it ?    

You clearly do not understand the construction of these types of motor.
There is really fuck-all difference between what is called a 'stepper motor'
and what is called a 'brushless DC motor'.
Mechanically, they are virtually identical. The differences lie mostly in the
drive electronics (for the application), and the way the stator coils are
terminated.
A 'brushless DC motor' usually (but not always) has Hall-effect devices
mounted to sense the rotor position and control the phase of the (typically)
3-phase coil drivers, while 'Stepper motors' usually don't have rotor sensors,
but have more poles in the rotor.. ...

Have a look at the May 2008 issue of Silicon Chip, page 16.
Leo Simpson argues that 'In reality, there is no such thing as a brushless
DC motor', and I totally agree that the terminology is misleading.






Re: CDROM Spindle Stepper motor

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Correct.
Some people do not understand that there is no fundamental difference
between 'stepper motors' and ' brushless DC motors'. They both will move
to a fixed position and stop when their coils are driven by DC, to make them
spin  
continuously requires sequential coil drive, which is really AC not DC, isn't it
?

Have a look at the May 2008 issue of Silicon Chip, page 16.
Leo Simpson argues that 'In reality, there is no such thing as a brushless
DC motor', and I totally agree that the terminology is misleading.





 



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Re: CDROM Spindle Stepper motor

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Why not ?
Commmon stepper motors have 1,8 degree steps, while a typical
commutator DC motor has only 3 or 5 commutator segments being
discretely energised per revolution, is that any smoother ????
It all depends on the drive electronics, with the right timing a
'stepper motor' will be far smoother than a commutator motor.

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You clearly do not understand the construction of these types of motor.
There is really fuck-all difference between what is called a 'stepper motor'
and what is called a 'brushless DC motor'.
Mechanically, they are virtually identical. The differences lie mostly in the
drive electronics for the application, and the way the stator coils are
terminated.
The 'brushless DC motor' usually (but not always) has Hall-effect devices
mounted to sense the rotor position and control the phase of the (typically)
3-phase coil drivers, while 'Stepper motors' usually don't have rotor sensors.

Have a look at the May 2008 issue of Silicon Chip, page 16.
Leo Simpson argues that 'In reality, there is no such thing as a brushless
DC motor', and I totally agree that the terminology is misleading.




Re: CDROM Spindle Stepper motor

"fritz"
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** You clearly are a narcissistic, nit picking idiot who cannot take being
corrected.

Brushless DC motors and stepper motors are the  NOT the SAME  -    each type
is suited to particular applications and they have very different
characteristics.

See:

http://en.wikipedia.org/wiki/Brushless_DC_electric_motor

The see:

http://en.wikipedia.org/wiki/Stepper_motor


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** Completely irrelevant.



......   Phil



Re: CDROM Spindle Stepper motor

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ROTFLMFHO !!!
You are obviously describing yourself there, Philthy !!!!!


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They both have a multi-pole rotor and several stator coils, both will move
the rotor to a fixed position when a coil is energised by DC. They have far
more in common than you realise.


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QUOTES from YOUR link above :
'Brushless DC electric motor......'
'Two subtypes exist:
The stepper motor type may have more poles on the stator.
The reluctance motor. '


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Re: CDROM Spindle Stepper motor

"fritz the fuckhead "


 ** You clearly are a narcissistic, nit picking idiot who cannot take being
 corrected.

Brushless DC motors and stepper motors are the  NOT the SAME  -  each type
 is suited to particular applications and they have very different
 characteristics.

http://en.wikipedia.org/wiki/Brushless_DC_electric_motor




......   Phil



Re: CDROM Spindle Stepper motor

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QUOTES from YOUR link above :
'Brushless DC electric motor......'
'Two subtypes exist:
The stepper motor type may have more poles on the stator.
The reluctance motor. '


Re: CDROM Spindle Stepper motor


Why have you got 'steper motors' stuck in your 'brain' ?

CD players and CD-ROMs do NOT use stepper motors. None. Never.

geoff



Re: CDROM Spindle Stepper motor
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    Thanks Geoff. I used to repair CD players which at that time mostly
used DC commutator spindle motors.
    One of the most common problems was the commutator becoming slightly
erratic, causing increased rotational speed variations which caused the
data from the disc to overflow/underflow the buffer.
    When you turn an unenergised stepper motor's shaft by hand, it jumps
from one magnetically-held step to the next. Normal motors move smoothly
and stop wherever you stop turning them.
    Leo Simpson's a good bloke, but I kinda doubt that he's an expert on
the characteristics and applications of motors. Stepper motors and small
linear-rotation motors all have magnets and coils but they don't all
behave in the same way.



Re: CDROM Spindle Stepper motor

"Bob Parker"

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 **  ??????????

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** All he said was that the name " Brushless DC "  ( invented by the
Japanese as a marketing title ) is a  * misnomer * -  which it is.  Cos they
are all really AC motors.

A better name might be  " Electronically Commutated Motors "  -   but that
has no mass market appeal.


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**  For sure.


......  Phil



Re: CDROM Spindle Stepper motor
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     Well he's been nice to me in the past.



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     When I get a new SC I just skim through it for 15 minutes then give
it to a mate who collects them, so I don't even remember seeing anything
about motors (or anything much else in it).




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    Exactly!




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    That's what I call them. :-)



Re: CDROM Spindle Stepper motor
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Well, with respect Geoff, I have disassembled probably far too many and
an awful lot of them use a stepper to move the laser sled. As to the
definition of the spindle motor, I don't really see the difference
between a stepper and a brushless but I admit I'm not sure how you
define the two types to see the difference, maybe you can clarify that?
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--
Clint Sharp

Re: CDROM Spindle Stepper motor
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Are you sure ?  How can a stepper motor, with it's "quantised' discrete
stepped positions track a continuous spiral groove ?  My understanding is
that all CD spindle motors are servo-controlled , to enable accurate
tracking.

Could it be that people are not aware of what stepper-motors are.  They are
NOT the same as a multi-pole DC motor, as the OP seems to think, from his
description ...


geoff



Re: CDROM Spindle Stepper motor

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You don't understand what a spindle motor does, obviously.
It just spins the disk, it has nothing to do with the tracking of the laser,
which I
have already explained. The spindle motor has feedback to spin the CD at
the right speed, usually with Hall effect sensors. The coarse tracking is
controlled
by a separate motor with position feedback, and fine tracking is controlled with
a 'voice coil' suspension connected to the laser lens.


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Actually they are very similar in construction and theory.
They both have a multi-pole rotor and a number of stator coils.
They both will move to fixed position and stay there when a coil is energised
by DC. To get either type to spin requires a controller to drive the coils
in the correct sequence. The main difference is the coil terminations, steppers
bring out all coils separately while so-called 'DC brushless' motors usually have
the coils connected in star or delta (for 3-phase types).


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Re: CDROM Spindle Stepper motor
" fritz the fuckhead "


** You clearly are a narcissistic, nit picking idiot who cannot take being
corrected.

Brushless DC motors and stepper motors are the  NOT the SAME  -  each type
is suited to particular applications and they have very different
characteristics.

http://en.wikipedia.org/wiki/Brushless_DC_electric_motor


Then  FOAD.


......   Phil




Re: CDROM Spindle Stepper motor

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QUOTES from YOUR link above :
'Brushless DC electric motor......'
'Two subtypes exist:
The stepper motor type may have more poles on the stator.
The reluctance motor. '




Re: CDROM Spindle Stepper motor
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Have you ever seen a CD drive with a stepper motor ?

geoff



Re: CDROM Spindle Stepper motor
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Dude, I think I know eactly what a spindle motor does - I fix Denon, Sony,
and Nad ones every week and have don for decades. Also DVD and
DVD/CD-ROM/RWs.

None of these contain stepper motors, and I can't see how any other CD
could, given the pusly buzzy motion that a stepper can only supply.  I have
never seen a CD with a spindle motor or a sled motor, that is a stepper.  I
have seen stepper motors in telex machines,printers, and iindustrial process
machines.

Stepper motors move one discrete finite 'step' (surprisingly ?) for each
discrete DC pulse that is sent to drive it.  All CD motors I have ever seen
are driven by a continuous DC, the voltage of which is finely varied to
control the speed of the spindle, or the position of the sled.

Grateful you specify which make/model CD contains a stepper motor.

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So now you are trying to fudg the distinction between stepper motors and the
type you really mean. OK, I concede the I can therefore never 'win'.....


geoff



Re: CDROM Spindle Stepper motor
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Sorry - slip of the keyboard.  The Denon, Sony, and NADs are not, of course,
stepper motors but CDs and DVDs....

geoff



Re: CDROM Spindle Stepper motor

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Maybe you just have a problem with expressing technical English clearly......

geoff wrote...
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So what has the tracking of the 'groove' (sic) got to do with the spindle motor,
which always was the obvious subject ?










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