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CDROM Spindle Stepper motor

Easily if the multiple CD/DVD-ROM drives I own are anything to go by, they all seem to manage fine.

So what? Do you think you can't achieve high enough resolution with a stepper?

Well, I'm fairly sure I know what a stepper motor is and how it works, I'm also fairly sure I know what a brushless DC motor is and how that works. Where I'm unsure is in what the difference between the two types is because they both operate in the same way, albeit one has far less poles than the other (which may be the difference!).

OK, so define a multipole DC motor and let's see where the difference lies. AFAIK the type of motor you think is exclusively used in CD and CD-ROM devices is a multipole brushed DC motor but I could be wrong, please enlighten us.

FWIW, the only brushed DC motor I have seen in a CD-ROM drive for a very long time is the one used to open and close the tray.

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Clint Sharp
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Clint Sharp
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Easily, the multiple CD-DVD-ROM writers and readers in my PCs are fine examples.

Umm, yes, as far as I know they are. So is the sled, so are the focus coils on the lens assembly. What, exactly does that have to do with the type of motor?

I raised that subject I'm afraid, lots of CD/DVD-ROM drives use a stepper to position the sled. I am still no more enlightened as to what the difference between a brushless DC motor and a stepper is though. Apart from a 'traditional' stepper motor having many more poles I see no differences in terms of operation.

I think he is generally correct in stating that domestic CD players don't use stepper or brushless motors for the spindle and laser sled but almost all the CD-ROM/DVD-ROM drives I have ever disassembled do. Indeed if he were to do a little research on CD/DVd drive spindle motors he will find a *huge* amount of information about their operation and drive.

Another mistake Geoff makes is that he assumes that a stepper has to have jerky motion, using phase drive on a stepper you can achieve very smooth motion and the rotating mass of the driven parts makes a nice flywheel. He appears not to understand how a worm driven sled can have a much higher resolution than the discrete steps would suggest.

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Clint Sharp
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Clint Sharp

In message , Clint Sharp writes

And having said that, I gutted a *very* old Toshiba XM-5401 SCSI CD-ROM drive today to find three brushed DC motors, one for the spindle, one for tracking and one to open the tray.

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Clint Sharp
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Clint Sharp

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