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CDROM Spindle Stepper motor

Discussion in 'Hobby Electronics' started by fritz, May 11, 2008.

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  1. fritz

    fritz Guest

    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.
     
  2. Phil Allison

    Phil Allison Guest

    "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
     
  3. Clint Sharp

    Clint Sharp Guest

    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.
     
  4. fritz

    fritz Guest

    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 :(
     
  5. fritz

    fritz Guest


    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 :(
     
  6. fritz

    fritz Guest

    Thanks for that.
     
  7. Clint Sharp

    Clint Sharp Guest

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

    fritz Guest

    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.....
     
  9. fritz

    fritz Guest

    Thanks for the help.
     
  10. Bob Parker

    Bob Parker Guest

    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
     
  11. Clint Sharp

    Clint Sharp Guest

    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.
     
  12. fritz

    fritz Guest

    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.
     
  13. fritz

    fritz Guest

    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.
     
  14. fritz

    fritz Guest

    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.
     
  15. Phil Allison

    Phil Allison Guest

    "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
     
  16. Bob Parker

    Bob Parker Guest

    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.
     
  17. Phil Allison

    Phil Allison Guest

    "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
     
  18. Bob Parker

    Bob Parker Guest

    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. :)
     
  19. Clint Sharp

    Clint Sharp Guest

    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?
     
  20. fritz

    fritz Guest

    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).
     
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