Hello, i have an Seagate ST318406LW SCSI HDD, who has 1.7% bad sectors and operates very slowly. I have decided to scrap it and keep the motor and the housing.

I always wanted to mess around a bit with the stepper motor inside it. Ive read some things online, and it seems i need some sort of a controller, but those vary from the models, and what not.

If any one can assist me with information about this, it will be greatly appreciated.

 

as you disassemble the unit, trace cable or wire back to PCB and lookup datasheets for chips near the connector or point where wires attach to PCB. you will find your driver right there.

 

I see, it says:

SH6950
24A0EJTA

Ive searched for SH6950, but i cant seem to find anything about it. Can you help me?

Here are 2 pictures:
http://dl.dropbox.com/u/54462712/hddelec/IMG_1933.JPG
http://dl.dropbox.com/u/54462712/hddelec/IMG_1932.JPG

 

Any one? Bump.

 

HDD's are made by the hundreds of thousands and it's highly likely the chip you're after is custom made and not available for the hobbyist unless you're prepared to buy a few thousand?

 

I always wanted to mess around a bit with the stepper motor inside it.

What stepper? Are you sure it is a stepper?

 

I dont know, is it? Looks exactly like every other HDD motor.

 

I dont know, is it? Looks exactly like every other HDD motor.

What do you want to use this motor for? Most newer ones are a form of switched reluctance motor, and have very little torque. After all they are only spinning the disks at a high speed. And the heads don't touch the disk, so they don't need much power only speed. Don't think they are useful for much more than the original purpose.

 

Well, this SCSI drive is definitely not new. Its old, id guess from early 2000.

I saw a video where a person made a grinder, just for a project, out of an old hard drive. He glued sanding paper onto the discs and go him self a pretty interesting grinder.

So i thought i could do the same as a project, since i have a few broken, old, hard drives. And since i know SCSI drives have a huge RPM speed, i guessed this drive would be the best choice.

 

Any one? Bump.

 

If the main platter motor isn't actually a stepper, look for the motors that control the flying heads. I'm not very familiar with HDD internals, but I think those motors are steppers.

After you find actual steppers, you can get alot of information by counting the number of wires, and then using a continuity checker to determine which wires are connected to common internal coils. The web has lots of information about how to determine the type of motor using this method. Next will be to figure out what votages they run at. I have no good guidance for doing that. Maybe someone else....?

 

If the main platter motor isn't actually a stepper, look for the motors that control the flying heads. I'm not very familiar with HDD internals, but I think those motors are steppers.

Most modern HDD's use "voice coil" type 'motors' to move the flying heads. A coil with a magnet mounted on the arm of the flying head. They allow the heads to move faster than any other type motor.

The platter motors are usually a switched reluctance "pancake" motor. About the only type motor that will tun fast enough for the high speed needed.

Both the platter and flying head motors are low in torque/force because of the low amount of energy needed, only good for what they are made for.

 

Most modern HDD's use "voice coil" type 'motors' to move the flying heads. A coil with a magnet mounted on the arm of the flying head. They allow the heads to move faster than any other type motor.

Didn't know that. Thanks.

 

I have taken apart many IDE hard drives the motor appears to be a stepper of some sort i think probably unipolar type because if you look at the wires on the motor normally there are 4 leads. 3 of these are single wires and the other one is made up of 3 joined together to one lead. From my experience all that is needed to spin them up is to apply power to it. I believe SCSI is the same way. I have a system with SCSI drives I had one disconnected for a bit and it still spun up. That could vary by standard though I am using SCSI ultra 2 68 pin cabling but I d be surprised if it did. I would think if you say it operates slowly then the rpm is probably 10000 or less rpm or is failing. I made a grinder of sorts out of one but it isn’t going to be very powerful. The platters will stop with a Fairley light resistance is sensed. If it doesn’t spin up try pinouts.RU they have many pinout diagrams for many devices, and standards. (I use this site a lot especially for USB diagrams.)
Also if your going to make a grinder be careful if it’s an IBM deakstar (deathstar) this is because the platters in those drives are made of glass (appears to be tempered though. I had one die pulled it apart I was working on it I dropped the screw driver and then a chunk of the platter busted out just from the handle hitting it. it seems pretty hard but not that hard. I would wonder if putting more load on it if it would fly shatter from the forces acting on it. Like gravity centrifugal centripetal the resistance of a object being ground.
Is this a hot swap because then your data, power, control signals all use one port you could be able to find a pinout and solder leads for power to it if it is a hot swap.
i have almost an identical model it looks like it is just molex for power in the segate pdf so it should just need power to spin up.

 

It will be a Y configuration. Forget about the chip in the drive because you would also need the dsp and the code to run it. You will need a chip that comutates using back emf because it has no sensors.

 

The motor moving the head in 5" drives is/was always a stepper.

Very hard, in my experience, to have it doing something useful.

 

The motor moving the head in 5" drives is/was always a stepper.

Very hard, in my experience, to have it doing something useful.

Why is that? Steppers should be very useful.

 

The motor moving the head in 5" drives is/was always a stepper.

Very hard, in my experience, to have it doing something useful.

The SRM is a form of stepper but is capable of much, much faster speed. Most steppers have permanent magnets in them and "cog" when turned. A SRM has no magnets and doesn't cog when turned by hand. I know of no way you could spin a stepper motor at 7200-10000 RPM like a HDD platter does.

When you say 'head' in a 5" drive I assume you mean a floppy disk drive. They mostly used a linear step motor to move the head. But they didn't run near the speed that a HDD drive does.

 

Here's what Circuit Celler (Sept 2009) says about CD and DVD positioning motors:

A typical CD or DVD drive has two different head positioning systems. The first is a coarse positioner that moves a carriage or sled containing the entire optical pickup assmebly....It can be a linear voice coil actuator or it can be a DC or stepper motor.... In addition to the sled positioner, the optical pickup head always contains two miniature electromagnetic voice coil acutators...

So, at least in the case of CD/DVD, there are possibly several motors for salvage, some might be steppers.