On Thu, 2006-01-12 at 00:27 +0800, John Hennessy wrote:
> Hi, I have a box full of Hard Disk Drive spindle motors recovered from IBM 
> (Sun) 4.2Gig Hard Disk Drives. They have 4 connections. My question is: 
> Are they Bipolar Stepper Motors ?
> 
> It appears that 3 connections are active and the 4th does nothing. I 
> didn't think there was a 3 wire stepper motor. Anyway I can use an L293 
> motor drive IC and sequentially power each of the 3 connectors. I get a 
> clean evenly spaced step requiring 12 steps for a complete rotation. This 
> may double when I wire up to a PIC and energise 2 connectors at once. 
> Reversing the sequence of applying power reverses the step.
> 
> I'm a little surprised they worked in this configuration. I expected to 
> need 4 wires to ensure that two coils where connected. If they are not 
> Bipolar steppers what are they ?

Most drive motors for the last while have been basically 3 phase motors.
I wouldn't really call them "steppers" since steppers generally stop at
specific positions, these motors are designed to spin at an exact rate
as smoothly as possible.

TTYL

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