William Chops Westfield wrote:
> I take apart old disk drives with my kids, mostly for the magnets.  (Cool
> magnets in the head positioner.)  Seems a shame to waste the spindle motors,
> though...  Now, a spindle motor is a brushless multiphase (usually 3phase)
> motor, not unlike a DC fan, right?  Except that fan motors have a simple
> little one-or-two transistor circuit to drive them, while the disk motor
> probably has at least one dedicated IC, a bunch of power transistors, and
> probably the direct involvement of a microprocessor, so that the speed can
> be aequately regulated...  If I don't CARE about speed accuracy, is there
> a simple circuit I can use to drive a spindle motor?

Sure, but the fan's are two phase drive, the disk motors are three.

To get an idea of what waveforms you need you probably should look
at the drive signals from a spinning drive. Look at CURRENT too (small
sense resistors are usually found in the source leads of the drive FETs.

Use a 12c508 to generate 3 square waves with 120 degree offsets for
the 3 leads your motor likely has. You'll also have to ramp the
frequency so that the motor will track the drive rate and not slip.

The problem will be that to get any kind of torque out of the motor
you'll need to buffer the outputs with push-pull drivers (all those
power transistors are there for a reason. Spinning several hundred
grams at 3600/5400/7200RPM takes POWER).

If you want a non-PIC solution you asked the wrong list <G>.