I have not needed and figured out this yet. GND Other useful components from disk drives Disk drives are also quite nice source for other components also. When you take the motors out of the disk drive, you can easy take other components also. Usually there are optical sensors or microswiches in disk drive to sense the write protect tab. Those components are useful sensors in you stepper-motor controlled robotics circuits.
Many direct drive rotating motors use hall-sensors for sensing rotating speed.
This can be quite useful component if you can figure out how it is connected. Many modern disk drive drive motors use voice-coil control systems, which makes another story. You can use those differents componens at their own or use the controlling electronics provided by the hard disk drive electronics. The control connector carried all disk drive control information and data connector carries the data. All control connector signals are TLL level signals.