CDROM Spindle Stepper motor

Has anyone tried using a stepper motor from a CDROM ?

I have one, it was used to drive the spindle i.e. spin the disk
of a Sony CDROM.
It has 9 windings (coils) on the stator and 6 magnetic poles on the rotor.
(North poles only - 12 N+S in total)
The 9 stator windings are connected to only 3 terminals.

 

"fritz"

** They are all " brushless DC " motors.

** Google will supply you countless sites about how to modify and use a CR
rom motor in model aeroplanes.

The three wires go to a dedicated, variable frequency speed controller.



....... Phil

 

You'll find a lot of information about controlling them in the RC aero
modelling groups, they modify them for flight. Other than that, look out
for hard disk motor control and brushless dc motor control.

 

The one I have is clearly a stepper motor. You could say all stepper motors
are 'brushless DC' motors if you think about it.....
You apply a current to the motor terminals and it moves to a fixed position.

I haven't had much luck in searching for such sites using Google. (including groups)
Perhaps you could post a few relevant URLs, I must be using the wrong
search terms

 

I haven't had much luck in searching for such sites using Google. (including groups)
Perhaps you could post a few relevant URLs, I must be using the wrong
search terms

 

Thanks for that.

 

cd rom motor rc were the search terms I used...

 

Look up 'spindle'. i.e. it spins the disk
The motor I was talking about isn't part of the laser groove tracking system at all.....

 

Thanks for the help.

 

Strange - that's exactly what I was thinking too. I always had the
idea that the disc rotates at a very constant velocity, which stepping
motors don't do.

Bob

 

In message

CD-ROM spindle motors are generally brushless hall effect sensor types
(at least all the ones I've seen recently are) but isn't that just a
variant of stepper motor? Not trying to be argumentative, I'm just not
sure where the lines are drawn.

 

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.

You clearly do not understand the construction of these types of motor.
There is really ****-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.

 

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.

 

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 ****-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.

 

"fritz"

** 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

** Completely irrelevant.



....... Phil

 

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.

 

"Bob Parker"

** ??????????

** 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.

** For sure.


....... Phil

 

Well he's been nice to me in the past.

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).

That's what I call them.

 

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?

 

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.

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).