Thank you all for your response to my query regarding hard disk motor.

A few more observations may be of interest.

I have another hard disk. This is of 1.2GB capacity (Seagate ST51270A). In
this hard disk also, the head assembly has been removed. When I connect it
to the power supply (again, the 40 pin connector not used), the motor runs
continuously! I tested it for half an hour and switched it off. Does this
mean that the safety feature that shuts down the motor after 20 seconds is
not functional in this hard disk? In that case, how do I disable that
feature in the other hard disk?

In the 40 pin connector of the 1GB hard disk, pin 39 is initially high. When
the motor stops spinning, this pin briefly goes low and then goes high
again. But connecting this pin to Gnd or +5V through a 1K resistor did not
make the motor spin continuously.

In both the disks, there are 4 wires coming from the coils of the motor.
There is of course the possibility of using a PIC and additional hardware to
make the motor work. But I feel, when the onboard drive electronics which
are particularly designed for the motor are fully functional, why waste a
PIC for this purpose?

Any new thoughts on the matter?

Regards,
Bala

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