US3794864A

US3794864A - Galvano-magneto effect apparatus

Info

Publication number: US3794864A
Application number: US00262182A
Authority: US
Inventors: N Masuda
Original assignee: Denki Onkyo Co Ltd
Current assignee: Denki Onkyo Co Ltd
Priority date: 1967-12-09
Filing date: 1972-06-13
Publication date: 1974-02-26
Anticipated expiration: 1991-02-26
Also published as: JPS4824289B1

Abstract

A galvano-magneto effect apparatus in which a parallel T circuit consisting of resistors and capacitors is employed as the positive feedback circuit of an active element. A magnetism sensing element the resistance of which varies with the intensity of a magnetic field applied is employed as the resistance component, and an AC signal is supplied from the AC signal generating source to the input side of said active element. The center frequency of said parallel T circuit is varied in reference to the frequency of said AC signal by varying the intensity of said magnetic field, and the output to be supplied to a load is increased or decreased by varying said center frequency.

Description

[ 1 Feb. 26, 1974 United States Patent 1191 Masuda FOREIGN PATENTS OR APPLICATIONS 1,060,933 4/1954 France............

[ GALVANO-MAGNETO EFFECT APPARATUS 330/144 Germany 338/12 Primary ExaminerRudolph V. Rolinec Assistant ExaminerB. P. Davis [73] Assignee:

[22] Filed: June 13, 1972 Attorney, Agent, or Firm-Armstrong & Wegner 21 Appl. No.: 262,182

ABSTRACT A galvano-magneto effect apparatus in which a paral- [30] Foreign Application Priority Data Dec. 9, 1967 42-73930 lel T circuit consisting of resistors and capacitors is employed as the positive feedback circuit of an active [52] US. 307/309, 333/75, 338/12,

element. A magnetism sensing element the resistance of which varies with the intensity of a magnetic field applied is employed as the resistance component, and

307/254 H0lv 5/00 333/75; 330/109, 103, 86;

[51] Int. 1

Field 01 Search an AC signal is supplied from the AC signal generating source to the input side of said active element. The center frequency of said parallel T circuit is varied in 1 References Cited reference to the frequency of said AC signal by vary- UNITED STATES PATENTS ing the intensity of said magnetic 11 to be supplied to a load is increas varying said center frequency.

eld, and the output ed or decreased by 2,173,427 9/1939 Scott 3,405,368 10/1968 Howe..... 3,017,586 Dersch... 3 395,333 Aiken 7 Claims, 12 Drawing Figures PATENTED FEB 26 I974 SHEEI 1 0f 3 FIG1 PATENTED FEBZ 6 I974 1 llml GALVANO-MAGNETO EFFECT APPARATUS BACKGROUND OF THE INVENTION The present invention relates to a galvano-magneto effect apparatus employing a galvano-magneto effect device the impedance of which varies with the intensity of a magnetic field to be applied.

Recently, various types of contactless switches have been developed as the galvano-magneto effect apparatus of this type. These switches employ said galvanomagneto effect device as the bias resistor of the switching element such as, for example, the transistor.

The present invention provides a galvano-magneto effect apparatus which can be employed as the switching apparatus, utilizing that the frequency response of the CR circuit varies with variation of the resistance value of the galvano-magneto effect device.

SUMMARY A galvano-magneto effect apparatus (hereafter referred to as the apparatus) comprises: a signal generating source which generates an AC signal; at least one active element such as, for example, a transistor to which said AC signal is supplied at its input side; a feedback circuit including of a parallel T circuit has a pair of input terminals and a pair of output terminals one of which is short-circuited to one of said input terminals, two resistors which are series-connected across the input terminal and output terminal which are not short-circuited, a capacitor which is connected between the connecting point of both resistors and said terminals which are short-circuited, two capacitors and which are series-connected so that these seriesconnected capacitors are connected in parallel with the series resistors and a third resistor, which is connected between the connecting point of the two capacitors and said terminals which are short-circuited at least one of said resistors is formed with a magnetism sensing element such as, for example, a magneto resistance effect device the resistance of which is varied with the intensity of the magnetic field to be applied. The output of said active element is supplied to the input terminal of said parallel T circuit and the output of the parallel T circuit is positive-fed back to the input side of the active element the apparatus further includes a magnetism applying means such as a mechanism which is provided with a rotary yoke made of a magnet and a fixed yoke made of a magnetic material at a position opposed to said rotary yoke so that the magnetic field is applied to said magnetism sensing element at a specified rotation angle of the rotary yoke, the center frequency of said parallel T circuit is varied by varying the intensity of the magnetic field applied to the magnetism sensing element and the output of the entire apparatus is increased or decreased by varying said center frequency.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is illustrated in detail by the accompanying drawings wherein.

FIG. 1 is a block diagram illustrating the outline of the apparatus according to the present invention,

FIG. 2 is a connection diagram illustrating the parallel T circuit to be employed in the apparatus of the present invention, I

FIGS. 3 and 4 show an embodiment of a magnetism applying means to be employed in the apparatus, and FIG. 3 is a cross sectional front view as seen along line YY in FIG. 4 and FIG. 4 is a cross sectional plan view as seen along line XX in FIG. 3.

FIGS. 5, 11 and 12 are respectively cross sectional plan views of another embodiment of said magnetism applying means,

FIG. 6 is a circuit connection diagram of the embodiment of the apparatus according to the present invention, and

FIGS. 7 to 10 are connection diagrams of another embodiment of parallel T circuit.

DETAILED DESCRIPTION Referring to FIG. 1, there is shown a block diagram of the apparatus according to the present invention.

Signal generator 1 generates an AC signal of a specified frequency and the output of this signal generator is supplied to the input side of the active element such as, for example, transistor 21.

The output from the collector of said transistor is positively fed back to the base by feedback circuit 3.

Said feedback circuit 3 comprises of parallel T circuit 4 consisting ofresistors and capacitors and is provided with a pair of input terminals T and T and a pair of output terminals T and T Input terminal T of the parallel T circuit is connected to the collector of the transistor, input terminal T to the emitter of the transistor, and output terminal T to the base of the transistor. Load L is connected to the output side, that is, output terminals T and T of the parallel T circuit 4.

Referring to FIG. 2, there is an embodiment of parallel T circuit 4. Two T circuits, that is, T circuit 41 consisting of series-connected resistors R and R and capacitor C series-connected to one of these resistors and T circuit 42 consisting of series-connected capacitors C and C and resistor R series-connected to one of these capacitors are parallel-connected so that the circuit of series-connected resistors R and R and the circuit of series-connected capacitors C and C are parallel-connected, thus forming the parallel T circuit.

Resistor R is made up by series-connecting fixed resistor R and a magnetism sensing element such as, for example, magneto resistance effect device R the impedance of which varies with variation of the intensity of the magnetic field. Furthermore, resistance value r of resistor R is set so that it becomes equal to the sum of the resistance values of resistors R and R when a specified intensity of the magnetic field is applied to device R by the magnetism applying means.

Magnetism applying means 5 is designed such that projections 511 and 511' which are opposed each other are provided at the inside surface of circular fixed yoke 51 fixed in outer frame 53. Device R is provided at the surface of one of projections and moving yoke 52 which is formed as a disc and radially magnetized is housed in the space in fixed yoke 51 so that its poles S and N are respectively opposed to projections 511 and 511', as shown in FIGS. 3 and 4.

Shaft 521 is fixed coaxially passing through moving yoke 52. The lower end of shaft 521 is rotatably secured at the bottom of outer frame 53 which covers said fixed yoke and the upper end is projected outside fixed yoke 51 to form knob 522. In the magnetism applying means thus constructed, magnet 52 is rotated by manually rotating knob 522, the positions of magnetic poles S and N'vary in reference to

projections

511 and 511 to open or close the magnetic path, thus varying the intensity of magnetic field applied to device R As shown in FIG. 5, both sides surrounding both projections 51 1 and 511' of fixed yoke 51 are formed with permanent magnets512 and 512 the same magnetic poles of which are respectively opposed while moving yoke 52 is formed with a magnetic material which is not magnetized, and a plural number of projections 523 can be radially provided at the side edge of moving yoke 52 so that said projections are opposed to projections 511 and 511' of fixed yoke 51.

The closed magnetic path is formed when projection 523 of the moving yoke is opposed to projection 511 of the fixed yoke and a strong magnetic field is applied to device R As known, the center frequency of the parallel T circuit is determined by the resistance value of the resistors and the capacity value of capacitors. If the resistance value of resistor R, is r,, that of resistor R is r,, that of resistor R is r the capacity value of capacity C, is c,, that of capacitor C is c, and that of capacitor C is e the filtering selectivity becomes highest in the relations denoted by r,=r =r /2 and c,=c =2c In this case, center frequency f0 is given below as known.

f ll 212K 9 According, if said capacitors and resistors are set to the values described above and an AC signal from signal generator 1 is not applied to transistor 21, transistor 21 the output of which is positively fed back by feedback circuit 3 having parallel T circuit 4 generates a signal of frequency f0. lf resistance value p of magneto resistance effect device R is varied by varying the intensity of magnetic field applied to device R and resistance value r, of resistor R is consequently varied, the oscillation frequency varies, and thus the output attenuates.

Actually, signal S of frequency fs from signalgen erator 1 is applied to said transistor 21 and the output voltage and current to be supplied to load L become the maximum when frequency fs and oscillation frequency f coincide, hsrsbyj sputpu pltasc n current is greatly reduced when the center frequency f0 is varied from the above condition. Accordingly, if the apparatus is set in advance so that the components of the parallel T circuit satisfy said relative equation and center frequency f0 coincides with signal frequency fs of signal generator 1 when the specified intensity of magnetic field is applied to device R by the magnetism applying means and the intensity of magnetic field is varied by operating magnetism applying means 5, the output voltage and current supplied to load L suddenly increase when the intensity of magnetic field reaches 'said specified level and suddenly decrease when the intensity of magnetic field varies from the specified level, thus performing the switching.

Referring to FIG. 6, there is shown the circuit diagram illustrating an embodiment of the apparatus of the present invention.

The output of AC signal generator 1 is applied to the primary coil of transformer 11 and the input side of oscillation circuit 2 is connected to secondary coil terminals l2 and 12' of transformer 11.

Oscillation circuit 2 corresponds to transistor 21 and feedback circuit 3 and is comprised of a pair of parallel-connected transistors 61 and 62, transistor 63, parallel T circuit 4 connected between the bases of both transistors 62 and 63, positive and negative feedback circuits from transistor 63 to transistor 62 and DC power supply 64.

Secondary terminal 12' of transformer 11 is connected to the positive electrode of DC power supply 64 by common line L, the other secondary terminal 12 is connected to the base of transistor 61, and the collector of transistor 61 is connected to the negative electrode of DC power supply 64 by common line L The emitters of transistors 61 and 62 are connected each other and are connected to common line L, through bias resistor 65 and the collector of transistor 62 is connected to common line L through resistor 66. The emitters of mutually connected transistors 61 and 62 are connected to the collector of transistor 63 through the series circuit of variable resistor 68 and ca pacitor 67, whereby the series circuit forms the negative feedback circuit from transistor 63 to transistor 62. Furthermore, the base of transistor 63 is connected to common line L, through biasresistor 69 and to com mon line L, through bias resistor 70 and the emitter of transistor 63 is directly connected to common line L,. The series circuit consisting of said parallel T circuit 4 and capacitor 71 are connected between the bases of transistors 62 and 63 and variable resistor 72 is connected between the connecting point of parallel T circuit 4- and capacitor 71 and the collector of transistor 62. ariable resistor 72 forms the positive feedback circuit from transistor 63 to transistor 62.

In this embodiment, parallel T circuit 4 is the same as shown in FIG. 2. Series capacitors C, and C and series resistors R, and R are parallel-connected between transistor 62 and capacitor 71. The sides of capacitor C and resistor R, which are not connected to said both resistors and capacitors are connected to common line L].

As described above, resistor R is the series resistor of magneto resistance effect device R and fixed resistor R and device R is built in magnetism applying means 5. In other words, the intensity of magnetic field is varied by rotating the moving yoke.

Load L is connected between common line L at the negative pole side of the DC power supply; and the colllector of transistor 63.

The circuit of the embodiment shown in FIG. 6 functions as described below. When moving yoke 52 is in a position shown in FIG. 4, that is, a position where the magnetic pole of moving yoke 52 is opposed to device R the maximum intensity of magnetic field is applied to device R and therefore device R provides a large resistance corresponding to the intensity of magnetic field.

It is assumed that the resistance value when the resistance of device R is maximum is r the sum of resistance value r,, and resistance value r of fixed resistor R that is, resistance value r of resistor R is set as r,=r,=r ,/2, the capacitors are set so as to satisfy the relations of C =Cz=2C with respect to the capacity, and the components of parallel T circuit 4 are set so that center frequency f0 is equal to signal frequency fir of signal generator 1.

If signal S is supplied from signal generator 1 to transformer 11, the alternating signal corresponding to signal S is applied to the base of transistor 61 through the secondary side of transformer 11. When the base of transistor 61 is negatively biased by this alternating signal, transistor 61 turns on and the current from DC power supply 64 flows through resistor 65 and the emitter and collector of transistor 61.

This current accompanies the voltage across both ends of resistor 65, transistor 62 connected to resistor 65 turns off and, the collectorpotential drops, a negative voltage is applied to the base of transistor 63 and transistor 63 turns on. Furthermore, because the collector potential of transistor 63 rises, the voltage is applied to the emitter of transistor 62 through variable resistor 68 and capacitor 67, thereby transistor 62 is turns on and transistor 61 permits a larger current to pass while the collector potential of transistor 62 is applied to the base of transistor 63.

Under this condition, the positive voltage from signal generator 1 is applied to the base of transistor 61 and therefore transistor 61 turns on and transistor 62 turns on. When the positive potential occurs at the collector of transistor 62, this potential is applied to the bases of transistors 62 and 63, transistor 63 turns on the collector potential of transistor 63 drops. The drop of this collector potential causes the emitter potential of transistors 61 and 62 to drop and causes transistors 61 to turn on transistor 62 to turn off.

At this stage, the subsequent negative signal is applied to the base of transistor 61 and accordingly, the circuit repeats said functioning. Because load L is connected to the collector of transistor 63, the current flows in the load when the negative voltage is applied to the base of transistor 61 and the value of this current is controlled by the parallel T circuit as the filter. In other words, the output current of oscillation circuit 2 is extremely large when the center frequency of the parallel T circuit between the base of transistor 62 and transistor 63, that is, oscillation frequency f0 of oscillation circuit 2 is synchronized with signal frequency fit of signal generator 1 and the current supplied to the base of transistor 63 is extremely low when center frequency f0 is varied from signal frequency fir. Moreover, the resistance across the emitter and collector of transistor 63 approximates the maximum and the current flowing in load L through transistor 63 is extremely small.

If the intensity of magnetic field applied to device R is reduced by turning moving yoke 52 from the position shown in FIG. 4, the resistance of device R is lowered, the center frequency is varied, the circuit constant is unbalanced and the output to input ratio of the filter is thereby reduced.

Accordingly, the current applied to load L is reduced and therefore the switching operation for load L can be performed. While the maximum intensity of magnetic field is applied to device R the resistance value of device R need not satisfy the balancing condition of the parallel T circuit. For example,'the apparatus can be designed to satisfy the balancing condition of the parallel T circuit when the intensity of magnetic field applied to device R is minimum, that is, device R has the minimum resistance value.

. Any one of resistors R R and R of parallel T circuit 4 can be formed with device R and a plural number of resistors can be formed with the devices.-

As shown in FIG. 7, for example, resistor R, can be formed with the series resistor consisting of devices R and fixed resistor R and resistor R, can be formed with the series resistor consisting of devices R and fixed resistor R And a fixed resistor can be used as resistor R As shown in FIG. 8, resistors R, and R, can be respectively formed with combination of the devices and fixed resistors and resistor R, can be formed with the series resistor consisting of device R and fixed resistor R31;

As shown in FIG. 9, resistors R, and R are made using device R with three terminals and capacitor C can be connected to intermediate terminal 81. When device R with three terminals is employed, resistor R, can be formed with device R as shown in FIG. 10.

Each resistor need not be combined with the fixed resistor and can be formed with a single device.

In cases described above, the component values of each resistor and capacitor are set so that the abovementioned balancing condition is satisfied when the specified intensity of magnetic field is applied to the device.

As shown in FIG. 7, if two devices are employedin the parallel T circuit, the devices can be provided at both end surfaces of both

projections

511 and 511 of fixed yoke 51 of magnetism applying means 5 as shown in FIG. 11. When more than three devices are employed, the magnetism applying means can be constructed as described above.

Said'magnetism applying means is made up by modifying the mechanism shown in FIG. 4. As shown in FIG. 12, many projections 511 are provided at the internal surface of fixed yoke 51 along the circumferential direction, each projection is provided with magnetism sensing device R and each of devices is provided with respective circuit shown in FIG. 6. Thus, the magnetism is applied to the devices in sequence along with rotation of moving yoke 52 and the output is applied to many loads in sequence; accordingly, one rotary switching mechanism can be employed as the mechanism which permits continuous switching.

The apparatus according to the present invention can be used as a contactless switching apparatus. It is useful for various types of electronic equipment.

What is claimed is: a 1. A galvano-magneto effect apparatus comprising a. a signal generating source which generates AC signals, b. at least one active element coupled to said AC signal source, c. a feedback circuit having a parallel T circuit comprising 1. a pair of input terminals,

2. a pair of output terminals one of which is shortcircuited to one of said input terminals,

3. first and second resistors which are seriesconnected between the input terminal and output terminal which are not short-circuited,

4. a first capacitor which is connected between said short-circuited terminals and the connecting point between said first and'second resistors,

ec .aaqthi d ap i s, ar i connected said series-connected capacitors being parallel-connected with said first and second resistors, and I 6. resistance means connected between said second and third capacitors and said short-circuited terminals, said resistance means including a magnetism sensing means the resistance of which is varied in accordance with the intensity of a magnetic field applied thereto wherein the output of said active element is applied to the input terminal of said parallel T circuit and the output of said parallel T circuit is positively fed back to the input of said active element, and

d. a magnetism applying means for applying the magnetic field to said magnetism sensing means, wherein the magnetic field applied to said magnetism sensing means is varied by said magnetism applying means thereby varying the center frequency of the parallel T circuit whereby the output of the entire apparatus is varied.

2. An apparatus according to claim 1, wherein said parallel T circuit is adjusted such that, when a predetermined magnetic field is applied to said magnetism sensing means, the resistance of said resistance means is equal to two times the resistance value of said first resistor, the capacity of said second and third capacitors are equal and the capacity of said first capacitor is equal to 1/2 the capacity of the second capacitor, and the center frequency of said parallel T circuit coincides with the signal frequency of the AC signal generating source, wherein said center frequency is varied in reference to the frequency of said AC signal by varying the intensity of the magnetic field applied to said magnetism sensing means thereby varying the output of the entire apparatus.

3. An apparatus according to claim 2, wherein the center frequency of said parallel T circuitcoincides with the frequency of a signal generated from said AC signal generating source when the intensity of magnetic field applied to said magnetism sensing means is maximum.

4. An apparatus according to claim 2, wherein the center frequency of said parallel T circuit coincides configured such that a magnetic path is formed be tween both said yokes when said rotary yoke'is positioned at a specified rotation angle, wherein the magnetic flux applied to said magnetism sensing means is varied by rotating said rotary yoke.

6. An apparatus according to claim 5, wherein said rotary yoke comprises a magnet.

7. An apparatus according to claim 5, wherein said fixed yoke comprises a magnet. V t

Claims

1. A galvano-magneto effect apparatus comprising a. a signal generating source which generates AC signals, b. at least one active element coupled to said AC signal source, c. a feedback circuit having a parallel T circuit comprising 1. a pair of input terminals, 2. a pair of output terminals one of which is short-circuited to one of said input terminals, 3. first and second resistors which are series-connected between the input terminal and output terminal which are not short-circuited, 4. a first capacitor which is connected between said shortcircuited terminals and the connecting point between said first and second resistors, 5. second and third capacitors which are series-connected said series-connected capacitors being parallel-connected with said first and second resistors, and 6. resistance means connected between said second and third capacitors and said short-circuited terminals, said resistance means including a magnetism sensing means the resistance of which is varied in accordance with the intensity of a magnetic field applied thereto wherein the output of said active element is applied to the input terminal of said parallel T circuit and the output of said parallel T circuit is positively fed back to the input of said active element, and d. a magnetism applying means for applying the magnetic field to said magnetism sensing means, wherein the magnetic field applied to said magnetism sensing means is varied by said magnetism applying means thereby varying the center frequency of the parallel T circuit whereby the output of the entire apparatus is varied.

2. a pair of output terminals one of which is short-circuited to one of said input terminals,

3. An apparatus according to claim 2, wherEin the center frequency of said parallel T circuit coincides with the frequency of a signal generated from said AC signal generating source when the intensity of magnetic field applied to said magnetism sensing means is maximum.

3. first and second resistors which are series-connected between the input terminal and output terminal which are not short-circuited,

4. a first capacitor which is connected between said short-circuited terminals and the connecting point between said first and second resistors,

4. An apparatus according to claim 2, wherein the center frequency of said parallel T circuit coincides with the frequency of a signal generated from said AC signal generating source when the intensity of magnetic field applied to said magnetism sensing means is minimum.

5. An apparatus according to claim 1, wherein said magnetism applying means comprises a rotary yoke of a magnetic material and a fixed yoke opposite said rotary yoke, wherein at least one of said yokes is a magnet configured such that a magnetic path is formed between both said yokes when said rotary yoke is positioned at a specified rotation angle, wherein the magnetic flux applied to said magnetism sensing means is varied by rotating said rotary yoke.

5. second and third capacitors which are series-connected said series-connected capacitors being parallel-connected with said first and second resistors, and

6. resistance means connected between said second and third capacitors and said short-circuited terminals, said resistance means including a magnetism sensing means the resistance of which is varied in accordance with the intensity of a magnetic field applied thereto wherein the output of said active element is applied to the input terminal of said parallel T circuit and the output of said parallel T circuit is positively fed back to the input of said active element, and d. a magnetism applying means for applying the magnetic field to said magnetism sensing means, wherein the magnetic field applied to said magnetism sensing means is varied by said magnetism applying means thereby varying the center frequency of the parallel T circuit whereby the output of the entire apparatus is varied.

7. An apparatus according to claim 5, wherein said fixed yoke comprises a magnet.