Motor found while parts mining.

[dr pepper]

As per usual I've been parts mining, this time a scrap pc from work, I've aquired lots of chokes and low esr caps etc.
The cd rom drive is similar to a laptop type drive, even though the pc was a desktop.

I've robbed steppers from cd roms before and used them in other projects, such as a clock I made from a 40's aircraft guage, the stepper replaced the movement and had the pointer attached to the shaft.

Anyway this drive has a dc motor to position the head, I've never seen that before, how would the drive get positional feedback, would the controller chip use some kind of armature pulse feedback?
The motor is deffo dc, it runs nicely from 5v on my bench supply, excuse the magnifier on the pic, the 'driver has a 3mm tip.

 

[ronv]

Most of the optical drives I have seen use the lands and grooves from the disk for the position feedback.

 

[dr pepper]

Sort of like the servo track on a hard drive then.
I've also pulled to bits a lexmark printer, the head has a dc motor shifting it side to side, it must use some sort of commutator feedback for position.