Apparatus for positioning a transducer with respect to a track

Claim 2

In a signal reproducing apparatus of the type wherein at least one transducer scans a selected one of a plurality of parallel tracks on a record medium on which signals may be recorded, wherein a stepper motor is used to control the position of said transducer with respect to said plurality of parallel tracks, wherein said stepper motor has a plurality of windings and wherein each step of said stepper motor is defined by a particular current present in each of said plurality of windings, wherein the number of said plurality of parallel tracks exceeds the number of said particular steps of said stepper motor, wherein control means controls the movement of said transducer relative to said plurality of parallel tracks by moving said transducer a selected number of said tracks by providing a sequence of currents to said plurality of windings to effect a movement in said stepper motor, the apparatus further characterized by a physical stop positioned near one of said plurality of parallel tracks designated a home track, said physical stop for restricting the movement of said transducer from moving beyond said home track; and current selection means coupled between said control means and said plurality of windings for selecting either a set of high amplitude currents or a set of low amplitude currents to said plurality of windings; wherein the position of said transducer may be initialized at said home track by stepping said stepper motor at least the number of said plurality of parallel tracks with said set of low amplitude currents and by ending the stepping of said stepper motor with the particular currents present in said windings associated with the particular step of said stepper motor associated with said home track.

Claim 3

An apparatus as in claim 1 further characterized in that said parallel tracks are concentric.

Claim 4

An apparatus as in claim 2 further characterized in that said home track is located at one edge of said plurality of parallel tracks.

Claim 5

An apparatus as in claim 1 further characterized in that said current selection means has a control latch having a plurality of bit positions for storing movement commands from said control means to said stepper motor and having at least one bit position adapted to hold an initialize command; and an analog multiplexer having an output coupled to said stepper motor, having a first set of data inputs each coupled to a selected control voltage for producing said set of high amplitude currents and a second set of data inputs each coupled to a selected control voltage for producing said set of low amplitude currents and having a set of selection inputs for selecting of one of said first set of data inputs and said second set of data inputs; said set of selection inputs being coupled to said control latch such that when said control latch holds said initialize command, that said second set of data inputs is selected ; whereby said set of said low amplitude currents may be selected when said one bit position of said latch holds said initialize command.

Claim 6

An apparatus as in claim 4 further characterized in that said control voltages are each provided by a set of voltage division resistors coupled between a voltage source and a ground potential.

Claim 7

An apparatus as in claim 5 which is further characterized by a first resistor coupled in series between said output of said analog multiplexer and said stepper motor; an offset latch having a plurality of bit posftions each having an output coupled through an offset resistor to said stepper motor for controlling said stepper motor position by an appropriate offset determined by the contents of said plurality of bit positions; and a bias resistor coupled from said stepper motor to a voltage source for providing bias to said offset resistors.

Claim 8

An apparatus as in claim 6 further characterized in that said offset resistors differ in value from each other by multiples of two.

Claim 9

An apparatus as in claim 1 further characterized in that said transducer is mounted in a moveable arm, in that said stepper motor is coupled to said moveable arm, and in that said physical stop limits the movement of said moveable arm such that when said moveable arm contacts said physical stop that said transducer is positioned approximately over said home track.

Claim 10

In a signal reproducing apparatus of the type wherein at least one transducer scans a selected one of a plurality of parallel tracks on a record medium on which signals may be recorded, wherein a stepper motor is used to control the position of said transducer, with respect to said plurality of parallel tracks, wherein said stepper motor has a plurality of windings with each step of said stepper motor being defined by a particular current present in each of said plurality of windings, wherein the number of said plurality of parallel tracks exceeded the number of said particular steps of said stepper motor, wherein control means controls the movement of said transducer relative to said plurality of parallel tracks by moving said transducer a selected number of tracks by providing a sequence of currents to said plurality of windings to effect a movement in said stepper motor, wherein a physical stop is positioned near one of said plurality of parallel tracks, designated a home track, said physical stop for restricting the movement of said transducer from moving beyond said home track, and wherein current selection means selects either a set of high amplitude currents or a set of low amplitude currents to be supplied to said plurality of windings, a method for initializing the position of said transducer at said home track characterized by selecting said set of low amplitude currents to be supplied to said plurality of windings; stepping said stepper motor at least the number of steps corresponding to the number of said plurality of parallel tracks; and completing the stepping of said stepper motor with the particular currents present in said plurality of windings, associated with the particular step of said stepper motor associated with said home track.

Claim 11

In a signal reproducing apparatus of the type wherein at least one transducer scans a selected one of a plurality of parallel tracks on a record medium on which signals may be recorded, wherein a stepper motor is used to control the position of said transducer, with respect to said plurality of parallel tracks, wherein said stepper motor has a plurality of windings with each step of said stepper motor being defined by a particular current present in each of said plurality of windings, wherein the number of said plurality of parallel tracks exceeded the number of said particular steps of said stepper motor, wherein control means controls the movement of said transducer relative to said plurality of parallel tracks by moving said transducer a selected number of tracks by providing a sequence of currents to said plurality of windings to effect a movement in said stepper motor, wherein a physical stop is positioned near one of said plurality of parallel tracks, designated a home track, said physical stop for restricting the movement of said transducer from moving beyond said home track, and wherein current selection means selects either a set of high amplitude currents or a set of low amplitude currents to be supplied to said plurality of windings, a method for initializing the position of said transducer at said home track characterized by selecting said set of low amplitude currents to be supplied to said plurality of windings; stepping said stepper motor at least the number of steps corresponding to the number of said plurality of parallel tracks; and completing the stepping of said stepper motor with the particular currents present in said plurality of windings, associated with the particular step of said stepper motor associated with said home track.