Stepper Motor; Operation - IBM 5280 Maintenance Information Manual

Information is written on tracks located on the diskette.
A track is a circular path on the diskette surface.
Information is magnetically written on or read from a track
by a read/write head as the diskette turns.
There are 77 tracks on each side of a diskette. Track
DO,
which is the outside track, is reserved as a label track and
is not used for data. Tracks 75 and 76, which are the two
innermost tracks, are reserved as replacement tracks and
are only used for data if another track becomes damaged
or defective. There are a total of 74 data tracks on one
side of a diskette
1
and on each side of a diskette 2 and
diskette 2D.
A sector is a portion of a track set aside for one record.
A cylinder consists of the tracks on a diskette that can be
read from or written on without repositioning the
read/write heads.
Sector
~~~~-
------- ------------__ Si de 1 }
/~/~ ----~Track
00
/ / _ ; Side 0 Cylinder
-"----Track 00 0
Side 1 }
Track 76
Cylinder
Side 0 76
Track 76
---------------------~~~
STEPPER MOTOR
The stepper motor consists of a permanent magnet rotor
(armature) and pairs of two-phase stator windings. The
motor is a sealed unit that has no gears or commutators
and requires no maintenance.
During assembly, the rotor is magnetized at the plant of
manufacture. Disassembly of the motor reduces the
magnetic flux of the rotor. This causes a reduction in the
torque produced by the motor. For this reason, you should
not disassemble the motor.
60 Theory
With the power on the rotor can not be easily turned by
hand. With the power off, any residual detenting is felt
as a drag or roughness, and might cause a clicking sound
as the shaft is turned.
Operation
For ease of understanding, the· motor used in this example
turns
gO per step. The actual motor turns 1.8° per step.
This simplified motor consists of eight coil-wound stator
poles on a ten-pole permanent magnet rotor.
o
Stator Pole Winding
I n put A _____
+--....
Common Source
Stator Poles
_-1~"''''''''
Input A