Thanks to all. I don't have it in front right now, but it is from a 3'rd generation old Dell Optiplex GX1 (or GXa) that was in a fire. But this solves my curiosity that the connections are for feedback for speed or position. I guess a CD ROM drive needs to run at a regulated speed or that the drive needs to know just where it is in the spin phase. Actually I'm scavenging for things for robots, maybe a BEAM robot, but I'm still new at this all. How do you normally figure these things out? I see one way is to try to figure it out from the physical characteristics of the motor and from what it is connected to on the board. I had a stepper motor from a thrown away PC's 5 1/4 floppy. I figured it out by reading about steppers on the net and taking two 5v wires and I found when I simply raked one wire across the leads it would step! I managed to program a Pic to control it, then I connected the Pic to my PC's serial where I could send it commands to step forward and backwards. That was cool! I felt like I'd really done something then. (-: -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of Richard.Prosser@powerware.com Sent: Wednesday, March 30, 2005 22:50 To: Microcontroller discussion list - Public. Subject: Re: [EE] Help Understanding DC Motor from CD Player Lindy, The CD spindle motors in front of me have only 2 terminals directly on the motor. The ribbon cables (12 way in my case) are connected to the laser head assembly. Yours could well be different as I guess there are a large number of variations. The previous answer relating to hall sensors sounds feasible. Do you have the rest of the CDrom that you could trace the connection back to a likely looking driver chip or discrete transistor. The rotational speed is often measured from the optical output so motor speed sensors are not always required. Richard P "Lindy Mayfield" r.sas.com> cc: Sent by: Subject: [EE] Help Understanding DC Motor from CD Player piclist-bounces@mi t.edu 30/03/05 21:12 Please respond to "Microcontroller discussion list - Public." Hi Group, Can anyone help me figure out a DC motor that I took from an old CDrom drive? It seems to be a brushless DC motor and was the one used to spin the CD. It is mounted on a small PC board attached to a narrow ribbon cable. The question is that this ribbon cable that attaches to the PC board has 11 leads. My question is what are all those leads for? I've googled for answers but haven't found any. Stepper motors, yes. But this one not yet. Thanks, Lindy -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist