CD ROM Motors.

[Dwayne]

Hello Folks,

Here is the situation... I have been taking apart some OLD CDROM's. They have a 9 Pole brushless motor in them.

I would like to use that motor and its current windings. Thus, with a PIC, hopefully write a program to turn this motor.

1. Does anyone know how those motors are wound? Star? Delta? or some other configuration? I am suspecting some other configuration, because their seems to be 6 solder joints that are attached to some kind of wires, and 3 more than are attached to some SM chips.

2. Does anyone have any experience with these little motors?

If i cannot do the above, I will end up taking all the windings off, and winding them myself...Which I do not really want to do, but will give me exactly what I want, a star wired motor, with known wire leads.

Dwayne

[mister_e]

mmm as a start i would look on the CD-Rom controller PCB and trace wich chip control it. If findable and if it's not a microcontroller, it could reveale some interesting results IMHO.

What brand and model of CDROM you play with? Maybe i can help on this one.

[Macgman2000]

I have been making brushless motors for RC airplanes / helicopters. I started out modifying CDROM motors....save yourself the disappointment and wind your own. Your best bet is to rewind it with fewer turns and thicker wire in a wye configuration for medium (15 - 20KRPM) and high torque. For under $20 there are brushless kits being sold now....they come with super strong rare earth magnets, spools of enamel wire and dual sealed bearings.

I spent a while getting a PIC to work for the electronic commutation. One word of advice........ASSEMBLY CODE!!!!!! PBPro...was a futile attempt for me, never worked well in this application. Especially when you are dealing with 10,000RPM with variable speed.

Best regards,
Nick

[Dwayne]

Hello MisterE,

First of all, its darn good to have you back and well. You shouldn't be givnig us scares like you did. Just happy that you are not injured to bad.


M>>mmm as a start i would look on the CD-Rom controller PCB and trace wich chip control it. If findable and if it's not a microcontroller, it could reveale some interesting results IMHO.<<

That is just it, I do not know the model or anything. I was give about 4 old CD roms, and just ripped the motors out of them. There was a ribbon that went to the motor with about 10 different leads on it. I did figure out that 3 of the connections went to wires on the motor. Tracing the circuit is litterly impossible without completely destroying the Circuit board. I don't know how they have those 9 poles mounted on that board, but they are so close, that I can't figure out where and how it is mounted. Another thing that puzzled me, is the "apparent" way it is wound. Instead winding one pole, skipping two winding the forth, skipping two and winding the 7th, it looks like they wound two beside each other. (They could have done three beside each other, but I can't see where the wire is wrapping on the 3rd one)...probably failing eye sight...<g>.

I thought about using the existing wire that is so beautifully wound for me <g>. The only thing I will have to watch for is the EMF coming from the coils that could spike me.

I have a friend that is into electric airplanes, and he gave me the plans to a plane. It is a Spitfire, and he said a CD ROM would fly it extremely well. So...I got ahold of a CD ROM motor and started puzzling over it. Most people rewind them. But I look at it and say to myself... If it is already wound....why not? Personally I think I am probably making a mountain out of a molehill. <g>.

Dwayne

[Dwayne]

Hello Mac,

Yes Mac, that is what I was planning on doing... Getting a PIC chip to work with these little motors. I figured since it was already wound, why not attempt to use their work for my behalf.

It may come down to rewinding that motor myself...but that will be one tough job. Not much room between that Rotor pole and the circuit board.

Dwayne

[Macgman2000]

Hello Dwayne,

Are you going to try using PBpro? If you get something that works would you post it? Check out gobrushless.com. They have a lot of information and motor kits.

Things to keep in mind..

1). starting the motor: step throgh a 6 step table to rotate the motor in open loop. Assume at this time that it is spinning > 1K RPM.
2). after doing #1 go to the BEMF sync detection routine. Step through the table based on the BEMF sense to trigger the next in sequence.
3). Use PWM to vary the duty cycle per table increment
4). do all of the above while taking in speed commands from a radio receiver

Best Regards,
Nick