Step motor control circuit

Claim 2

A circuit responsive to current derived from a D.C. source for driving a step motor having excitation winding means and a permanent magnet rotor comprising voltage responsive switch means including a control electrode for selectively controlling a conducting path of the switch means to closed and open circuit conditions, a pair of contacts selectively connected together for selectively controlling bias voltage applied to the control electrode to control the conducting state of the switch means, and means for connecting in circuit with each other said contacts, the switch means conducting path, winding means and D.C. source so that in response to the contacts not being connected together the switch means conducting path is closed and current flows from the source through the switch means conducting path to the winding means in a first direction and in response to the contacts being connected together the switch means conducting path is open circuited and current flows from the source through the contacts to the winding means in a second direction, whereby the rotor is stepped each time the state of the contacts is changed.

Claim 3

A circuit responsive to current derived from a D.C. source for driving a step motor having excitation winding means and a permanent magnet rotor comprising voltage responsive switch means including a control electrode for selectively controlling a conducting path of the switch means to closed and open circuit conditions, a pair of contacts selectively connected together for selectively controlling bias voltage applied to the control electrode to control the conducting state of the switch means, and means for connecting in circuit with each other said contacts, the switch means conducting path, winding means and D.C. source so that in response to the contacts not being connected together the switch means conducting path is closed and current flows from the source through the switch means conducting path to the winding means in a first direction and in response to the contacts being connected together the switch means conducting path is open circuited and current flows from the source through the contacts to the winding means in a second direction, whereby the rotor is stepped each time the state of the contacts is changed.

Claim 4

A circuit responsive to current derived from a D.C. source for driving a step motor having excitation winding means and a permanent magnet rotor comprising voltage responsive switch means including a control electrode for selectively controlling a conducting path of the switch means to closed and open circuit conditions, a pair of contacts selectively connected together for selectively controlling bias voltage applied to the control electrode to control the conducting state of the switch means, and means for connecting in circuit with each other said contacts, the switch means conducting path, winding means and D.C. source so that in response to the contacts not being connected together the switch means conducting path is closed and current flows from the source through the switch means conducting path to the winding means in a first direction and in response to the contacts being connected together the switch means conducting path is open circuited and current flows from the source through the contacts to the winding means in a second direction, whereby the rotor is stepped each time the state of the contacts is changed.

Claim 5

A circuit responsive to current derived from a D.C. source for driving a step motor having excitation winding means and a permanent magnet rotor comprising an electric discharge device including a control electrode and a pair of output terminals, said control electrode being selectively forward biased in response to the conducting state of a pair of selectively open and closed contacts, whereby high and low impedance paths exist through the discharge device between the output terminals while the contacts are respectively closed and open, means for connecting said winding means and said closed contacts in series circuit with the output terminals and D.C. source so that current flows from the D.C. source through the winding means in a first direction while the low impedance path exists, and means for connecting the winding means in series circuit with the D.C. source and closed contacts so that current flows from the D.C. source through the winding means in a second direction while the high impedance path exists.

Claim 6

A circuit responsive to current derived from a D.C. source for driving a step motor having excitation winding means and a permanent magnet rotor comprising an electric discharge device including a control electrode and a pair of output terminals, said control electrode being selectively forward biased in response to the conducting state of a pair of selectively open and closed contacts, whereby high and low impedance paths exist through the discharge device between the output terminals while the contacts are respectively closed and open, means for connecting said winding means and said closed contacts in series circuit with the output terminals and D.C. source so that current flows from the D.C. source through the winding means in a first direction while the low impedance path exists, and means for connecting the winding means in series circuit with the D.C. source and closed contacts so that current flows from the D.C. source through the winding means in a second direction while the high impedance path exists.

Claim 7

In combination, a step motor having a permanent magnet rotor, a magnetic core for coupling magnetic flux to said rotor, winding means on said core, circuit means for sequentially feeding oppositely directed currents to said winding means to induce oppositely directed fluxes in said core and rotor, means in at least one of the core or rotor for stepping the rotor in response to each change in the direction of the fluxes in said core and rotor, said circuit means including two position switch means having first and second contacts selectively open and short circuited for controlling a D.C. current continuously fed in only one direction to the winding means while the first and second contacts are open circuited and for controlling a D.C. current continuously fed in only the other direction to the winding means while the first and second contacts are short circuited, said D.C. currents being maintained until each change in the current direction occurs and of sufficient magnitude to induce a flux in the core and rotor to electromagnetically brake the rotor, said D.C. currents reversing the flux direction each time the current direction is changed, said circuit means further including means for supplying a current of greater amplitude to the winding means while the rotor is being stepped than the D.C. current supplied to the winding means to brake the rotor.

Claim 8

In combination, a step motor having a permanent magnet rotor, a magnetic core for coupling magnetic flux to said rotor, winding means on said core, circuit means for sequentially feeding oppositely directed currents to said winding means to induce oppositely directed fluxes in said core and rotor, means in at least one of the core or rotor for stepping the rotor in response to each change in the direction of the fluxes in said core and rotor, said circuit means including two position switch means having first and second contacts selectively open and short circuited for controlling a D.C. current continuously fed in only one direction to the winding means while the first and second contacts are open circuited and for controlling a D.C. current continuously fed in only the other direction to the winding means while the first and second contacts are short circuited, said D.C. currents being maintained until each change in the current direction occurs and of sufficient magnitude to induce a flux in the core and rotor to electromagnetically brake the rotor, said D.C. currents reversing the flux direction each time the current direction is changed, said circuit means further including means for supplying a current of greater amplitude to the winding means while the rotor is being stepped than the D.C. current supplied to the winding means to brake the rotor.

Claim 9

The combination of claim 3 wherein said current supplying means includes: a voltage controlled impedance having a control electrode responsive to the condition of said switch, and resistance capacitance charging circuit means controlling the voltage magnitude applied to the control electrode.

Claim 10

In combination, a step motor having a permanent magnet rotor, a magnetic core for coupling magnetic flux to said rotor, winding means on said core, circuit means for sequentially feeding oppositely directed currents to said winding means to induce oppositely directed fluxes in said core and rotOr, means in at least one of the core or rotor for stepping the rotor in response to each change in the direction of the fluxes in said core and rotor, said circuit means including two position switch means having first and second contacts selectively open and short circuited for controlling a D.C. current continuously fed in only one direction to the winding means while the first and second contacts are open circuited and for controlling a D.C. current continuously fed in only the other direction to the winding means while the first and second contacts are short circuited, said D.C. currents being maintained until each change in the current direction occurs and of sufficient magnitude to induce a flux in the core and rotor to electromagnetically brake the rotor, said D.C. currents reversing the flux direction each time the current direction is changed, said winding means including first and second segments, said circuit means further including: means for feeding a current in one direction to only said first segment during a first time interval and means for feeding a current in a direction opposite to the first direction to only the second segment during a second time interval.

Claim 11

In combination, a step motor having a permanent magnet rotor, a magnetic core for coupling magnetic flux to said rotor, winding means on said core, circuit means for sequentially feeding oppositely directed currents to said winding means to induce oppositely directed fluxes in said core and rotOr, means in at least one of the core or rotor for stepping the rotor in response to each change in the direction of the fluxes in said core and rotor, said circuit means including two position switch means having first and second contacts selectively open and short circuited for controlling a D.C. current continuously fed in only one direction to the winding means while the first and second contacts are open circuited and for controlling a D.C. current continuously fed in only the other direction to the winding means while the first and second contacts are short circuited, said D.C. currents being maintained until each change in the current direction occurs and of sufficient magnitude to induce a flux in the core and rotor to electromagnetically brake the rotor, said D.C. currents reversing the flux direction each time the current direction is changed, said winding means including first and second segments, said circuit means further including: means for feeding a current in one direction to only said first segment during a first time interval and means for feeding a current in a direction opposite to the first direction to only the second segment during a second time interval.

Claim 12

The combination of claim 5 wherein the core includes a pair of pole faces on opposite sides of the rotor, and further including a low resistivity strap fitting over both said pole faces and intercepting leakage magnetic flux flowing from one pole face but not into the other pole face, said strap having slot means so that current is induced therein by the intercepted leakage flux, said strap interfitting with the pole faces so the current induced in the strap has a tendency to substantially equalize fluxes in the pole faces.

Claim 13

The combination of claim 6 wherein said winding means comprises a pair of coils, each wound on a different leg feeding flux to the pole faces on opposite sides of the rotor.

Claim 14

The combination of claim 6 wherein said winding means comprises a single coil wound on a leg feeding flux to the pole faces on opposite sides of the rotor, the magnetic reluctance of the core from the coil to the two different pole faces being different.

Claim 15

The combination of claim 6 wherein the circuit means further includes resistance capacitance network means in a bias circuit for control electrodes of both transistors of one of the pairs of switches, said resistance capacitance network means varying the impedance of the transistor of said one of said switches so that the current supplied between said ends is greater while the rotor is being stepped in response to current flowing between said ends than the current supplied between said ends while the rotor is braked by the current flowing between said ends.

Claim 16

The combination of claim 5 wherein the circuit means includes a single voltage controlled switch having a control electrode responsive to the condition of the switch means and a pair of terminals connected in series between a D.C. source and one of the winding segments.

Claim 17

The combination of claim 5 wherein the other winding segment is connected between one of the terminals and a control electrode of the voltage controlled switch and in series between the D.C. source and a control switch, said control switch being connected between the control electrode and other terminal of the voltage controlled switch.

Claim 18

The combination of claim 6 further including a resistance capacitance circuit in a bias network for the control electrode of the voltage controlled switch, said resistance capacitance circuit varying the impedance of the voltage controlled switch between said terminals so that the current supplied to said one winding segment is greater while the rotor is being stepped in response to current flowing through said one winding segment than the current supplied to said one winding segment while the rotor is braked by the current flowing through said one segment.

Claim 19

In combination, a step motor having a permanent magnet rotor, a magnetic core for coupling magnetIc flux to said rotor, winding means on said core, circuit means for sequentially feeding oppositely directed currents to said winding means to induce oppositely directed fluxes in said core and rotor, means in at least one of the core or rotor for stepping the rotor in response to each change in the direction of the fluxes in said core and rotor, said circuit means including two-position switch means having first and second contacts selectively open and short circuited for controlling a D.C. current continuously fed in only one direction to the winding means while the first and second contacts are open circuited and for controlling a D.C. current continuously fed in only the other direction to the winding means while the first and second contacts are short circuited, said D.C. currents being maintained until each change in the current direction occurs and of sufficient magnitude to induce a flux in the core and rotor to electromagnetically brake the rotor, said D.C. currents reversing the flux direction each time the current direction is changed, the circuit means including: a first pair of voltage controlled switches for feeding current in one direction from a D.C. source between said first and second ends, and a second pair of voltage controlled switches for feeding current in a second direction from the D.C. source between said first and second ends; and control means for enabling both switches of the first pair while disabling both switches of the second pair or for disabling both switches of the first pair while enabling both switches of the second pair, each switch of said first pair of switches comprising a transistor of a first conductivity type, each switch of said second pair of switches comprising a transistor of a second conductivity type, said first and second conductivity types being opposite from each other, said control means including said two-position switch means for selectively connecting control electrodes of said transistors to be responsive to voltages of opposite polarities derived from the D.C. source, one contact of said switch means being directly connected to the control electrodes of all of said transistors.

Claim 20

In combination, a step motor having a permanent magnet rotor, a magnetic core for coupling magnetIc flux to said rotor, winding means on said core, circuit means for sequentially feeding oppositely directed currents to said winding means to induce oppositely directed fluxes in said core and rotor, means in at least one of the core or rotor for stepping the rotor in response to each change in the direction of the fluxes in said core and rotor, said circuit means including two-position switch means having first and second contacts selectively open and short circuited for controlling a D.C. current continuously fed in only one direction to the winding means while the first and second contacts are open circuited and for controlling a D.C. current continuously fed in only the other direction to the winding means while the first and second contacts are short circuited, said D.C. currents being maintained until each change in the current direction occurs and of sufficient magnitude to induce a flux in the core and rotor to electromagnetically brake the rotor, said D.C. currents reversing the flux direction each time the current direction is changed, the circuit means including: a first pair of voltage controlled switches for feeding current in one direction from a D.C. source between said first and second ends, and a second pair of voltage controlled switches for feeding current in a second direction from the D.C. source between said first and second ends; and control means for enabling both switches of the first pair while disabling both switches of the second pair or for disabling both switches of the first pair while enabling both switches of the second pair, each switch of said first pair of switches comprising a transistor of a first conductivity type, each switch of said second pair of switches comprising a transistor of a second conductivity type, said first and second conductivity types being opposite from each other, said control means including said two-position switch means for selectively connecting control electrodes of said transistors to be responsive to voltages of opposite polarities derived from the D.C. source, one contact of said switch means being directly connected to the control electrodes of all of said transistors.

Claim 21

The combination of claim 13 wherein the core includes a pair of pole faces on opposite sides of the rotor, and further including a low resistivity strap fitting over both said pole faces and intercepting leakage magnetic flux flowing from one pole face but not into the other pole face, said strap having slot means so that current is induced therein by the intercepted leakage flux, said strap interfitting with the pole faces so the current induced in the strap has a tendency to substantially equalize fluxes in the pole faces.

Claim 22

The combination of claim 14 wherein said winding means comprises a pair of coils, each wound on a different leg feeding flux to the pole faces on opposite sides of the rotor.

Claim 23

The combination of claim 14 wherein said winding means comprises a single coil wound on a leg feeding flux to the pole faces on opposite sides of the rotor, the magnetic reluctance of the core from the coil to the two different pole faces being different.

Claim 24

The combination of claim 14 wherein the slot means includes a first slot extending longitudinally of the strap between the pole faces to divide the strap into first and second segments extending for the entire distance between edges of the two pole faces, said first and second segments being joined after passing the edges of the two pole faces to form a pair of joining segments, said pair of joining segments being separated by a second slot in the strap.