JP3011619U - Portable magnetic sensitive alarm device - Google Patents

Abstract

(57) [Abstract] [Purpose] The purpose of the present invention is to easily detect a strong magnetic field by carrying it, especially strong magnetism generated from a ferromagnetic material such as a permanent magnet whose magnetic polarity does not change or a magnetic diagnostic apparatus for medical use. Another object of the present invention is to provide a portable magnetically sensitive alarm device that issues a warning. [Structure] At least two detection coils cross-arranged as magnetic sensors, a drive circuit to which a detection output from the detection coils is input, and an alarm means that is driven by the drive circuit to issue an alarm Is.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a portable magnetic sensitive alarm device.

[0002]

[Problems to be Solved by Prior Art and Invention]

 Magnetic cards, which have become extremely popular in recent years, are always carried around because of their convenience, and many accidents have been reported in which information is accidentally exposed to strong magnetism and information is lost. Since this magnetic card, floppy disk, etc., records information with extremely weak magnetization, the information can be easily erased by the magnetism whose polarity is fixed in one direction like a permanent magnet. It has been known. For this reason, it was reported that magnetic card, floppy disk, etc. records were lost on a daily basis among people involved in magnetic diagnostic equipment in medical institutions, various research facilities, experimental equipment, and various electrical equipment. It has even been reported that there is a danger of developing into a serious accident involving property and life. An object of the present invention is to provide a portable magnetic responsive alarm device which easily outputs a warning by detecting a strong magnetic field, especially only a strong magnetism generated from a permanent magnet whose polarity does not change or a magnetic diagnostic device for medical use. To do.

[0003]

[Means for Solving the Problems]

 A portable magnetic sensitive alarm device according to the present invention comprises at least two detection coils arranged as magnetic sensors, a drive circuit to which a detection output from the detection coils is input, and a drive circuit driven by the drive circuit. It is equipped with an alarm means for issuing an alarm. The detection coils are arranged so as to cross each other in the X-axis and Y-axis directions. Further, three detection coils may be provided and may be arranged so as to cross each other in the X-axis, Y-axis and Z-axis directions. The detection coil is a general-purpose choke coil.

The drive circuit includes a low-pass filter that passes only the extremely low frequency component of the detection output from the detection coil. The drive circuit further includes an amplifier that amplifies the output of the low-pass filter, a detector that converts the output of the amplifier into a direct current, a Schmitt trigger circuit to which the output of the detector is input, and a Schmitt trigger circuit. An electronic switch controlled by an output and an oscillator whose operating power is turned on / off by turning on / off the electronic switch are provided. The alarm means is a speaker and / or a light emitting element.

[0005]

[Action]

 When a person carrying the portable magnetic sensitive alarm device approaches a strong magnet such as a permanent magnet or a magnetic diagnostic device for medical use, the detection coil performs magnetic detection, and the detection output is input to the drive circuit. When the detection output exceeds a certain level, the driving circuit generates the driving output for a certain period of time and drives the alarm means for a certain period of time to issue a sound and / or light alarm. Therefore, if the magnetic sensitive alarm device you carry gives an alarm, move to a place where this alarm will not be issued, and the recorded information on the magnetic recording medium such as your magnetic card or floppy disk will disappear. Will disappear.

[0006]

【Example】

 An embodiment of a portable magnetic sensitive alarm device according to the present invention will be described below with reference to the drawings. 1 is a block diagram of an embodiment of a portable magnetically sensitive alarm device according to the present invention, and FIG. 2 is a waveform diagram of each part of FIG. In FIG. 1, 1 and 2 are detection coils as a magnetic sensor for detecting magnetism, 4 is a low-pass filter for preventing malfunction due to unnecessary magnetism, and 5 is an induced voltage due to magnetism detected by the detection coils 1 and 2 ( (Detection output) to a certain amount, 6 is a detector that converts the output of the amplifier 5 to DC, and 7 is a Schmitt trigger that sends an ON signal when a magnetism above a certain set reference level is detected. Reference numeral 8 is a circuit, 8 is an electronic switch that is turned on / off by an ON signal of the Schmitt trigger circuit 7, 9 is an audio frequency oscillator, 10 is a speaker, 11 is a light emitting diode, and 12 is a power supply.

In the present invention configured as described above, the detection coils 1 and 2 are used as the magnetic sensor, and the reason is as follows. That is, as a general magnetic sensor, a semiconductor element (Hall element, magnetoresistive effect element, etc.) can be cited. However, these semiconductor elements require a large bias current, and also have the drawback that the characteristics change greatly depending on the operating temperature. Therefore, it is not suitable for use as a portable device.

Therefore, as the magnetic sensor, detection coils 1 and 2 such as a general-purpose choke coil that consumes no power are used, and the detection coils 1 and 2 are each a plane orthogonal axis as shown in FIG. Cross-arranged on (X-axis and Y-axis). The detection coil 1 has a directional characteristic that spreads in the Y-axis direction as shown in FIG. 4A, for example, and the detection coil 2 also has a directional characteristic (not shown) that spreads in the X-axis direction. Therefore, by arranging the detection coils 1 and 2 so as to cross each other as shown in FIG. 3A, the respective directivities are crosswise expressed on the X axis and the Y axis (FIG. 4B). By adding 1 and 2, the induced voltage can be efficiently generated for the magnetism on the plane, and the dead zone can be eliminated.

Further, it is apparent that omnidirectional detection can be performed by adding another detection coil 3 as shown in FIG. 3 (B) to give directivity in the Z-axis direction. The synthetic directional pattern in this case is shown in FIG.

It is well known that the induced voltage is not generated unless the magnetic flux crossing the detection coils 1, 2 and 3 is changed every moment, and the induced voltage e is expressed by the formula 1.

[Equation 1] Here, N is the number of turns of the coil, t is time, and dφ / dt is the amount of change in the amount of magnetic flux with respect to time. In the present invention, the moving speed of a human being with respect to a fixed ferromagnetic material, the walking behavior, etc. are used as the changes, so that only the ultra-low frequency component of the induced voltage is detected and amplified. That is, in a daily environment, a huge amount of AC leakage magnetic flux is emitted from various electric equipments. Therefore, in the detection output of the detection coils 1, 2 and 3, that is, the induced voltage (FIG. 2 (A)), this AC leakage magnetic flux is generated. The frequency component due to the magnetic flux is also included. Therefore, in the present invention, as a measure for preventing malfunction due to the influence of the AC leakage magnetic flux, a low-pass filter having a steep cutoff characteristic and removing the frequency component due to the AC leakage magnetic flux and passing only the above-mentioned ultra-low frequency component is passed. The filter 4 is provided to eliminate the above influence.

Next, the ultra-low frequency component (FIG. 2 (B)) that has passed through the low-pass filter 4 is amplified to a sufficient amplitude by the amplifier 5 (FIG. 2 (C)) and then supplied to the detector 6. There, it is converted into a DC voltage (Fig. 2 (D)). The detection output of the detector 6 is supplied to the Schmitt trigger circuit 7, and the Schmitt trigger circuit 7 outputs an ON signal (FIG. 2 (E)) when the output of the detection circuit 6 exceeds a certain reference level. The constant reference level is set to a safe magnetic detection level at which there is no risk of loss of recorded information on a portable magnetic recording medium. The Schmitt trigger circuit 7 has a time constant circuit that can arbitrarily set the time constant and a circuit that has a hysteresis characteristic, and must always operate for a specified time (about several seconds) for one detection coil output. The ON signal is configured to continue (FIG. 2 (E)), and the control signal to the electronic switch 8 is surely output.

The ON signal of the Schmitt trigger circuit 7 is applied to the electronic switch 8, and the electronic switch 8 is turned on for the duration of the ON signal of the Schmitt trigger circuit 7. When the electronic switch 8 is turned on, the power source 12 is supplied to the audio frequency oscillator 9 via the electronic switch 8 so that the audio frequency oscillator 9 starts the oscillation operation and outputs the audio frequency signal (FIG. 2 (F)). Output. When this audible frequency output is supplied to the speaker 10, an alarm sound is emitted, and a caution warning action for being in a strong magnetic field environment is realized. At the same time, the power source 12 is supplied to the light emitting element such as the light emitting diode (LED) 11 through the electronic switch 8, and the light display by blinking the light emitting element 11 is also possible. Therefore, by confirming the alarm by the sound and / or light from the speaker 10 or the light emitting element 11 and moving to a place where the alarm is no longer issued, the information recorded on the magnetic recording medium such as a magnetic card or a floppy disk that is carried is carried out. Will never disappear.

Since the device of the present invention is a device mainly for carrying, it is natural that the components used are examined so as to have the minimum possible power consumption.

[0014]

[Effect of device]

 According to the portable magnetic sensitive alarm device of the present invention, the following effects can be obtained. (1) A magnetic field without polarity change can be detected, and an alarm (sound and / or light) is issued to prevent loss of recorded information on a magnetic recording medium such as a portable magnetic card or floppy disk. be able to. (2) It is hard to react to the AC leakage magnetic field in everyday environment and does not malfunction. (3) Since the detection coil is used as the magnetic sensor, power consumption is extremely low. (4) It has a simple structure and circuit configuration, and it is small and lightweight, so it has excellent portability. (5) Directivity is small because the crossing arrangement of a plurality of detection coils is used. (6) Since it can be easily realized with general-purpose parts, it can be provided at a very low cost. (7) It is also possible to perform optical display using a light emitting element such as an LED or a lamp, or a combined display of sound and light.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a portable magnetic sensitive alarm device according to the present invention.

FIG. 2 is a waveform diagram of each part in the block diagram of FIG.

FIG. 3 is a schematic view of a crossing arrangement of detection coils.

4A and 4B show directional characteristics of a detection coil, where FIG. 4A is a unidirectional characteristic, FIG. 4B is a planar directional characteristic, and FIG. 4C is a three-dimensional directional characteristic.

[Explanation of symbols]

 1,2,3 Detection coil 4 Low pass filter 5 Amplifier 6 Detector 7 Schmitt trigger circuit 8 Electronic switch 9 Audio frequency oscillator 10 Speaker 11 LED 12 Power supply

Claims (8)

[Scope of utility model registration request] 1. A magnetic sensor comprising at least two detection coils arranged in a crossed manner, a drive circuit to which a detection output from the detection coils is input, and an alarm means driven by the drive circuit to issue an alarm. A portable magnetic sensitive alarm device. 2. The portable magnetic sensitive alarm device according to claim 1, wherein the detection coils are arranged to cross each other in the X-axis and Y-axis directions. 3. The portable magnetic sensitive alarm device according to claim 1, comprising three detection coils, each of which is arranged to intersect in the X-axis, Y-axis and Z-axis directions. 4. The portable magnetic sensitive alarm device according to claim 1, wherein the detection coil is a general-purpose choke coil. 5. The portable magnetic sensitive alarm device according to claim 1, wherein the drive circuit includes a low-pass filter that passes only an extremely low frequency component of a detection output from the detection coil. 6. The portable magnetic sensitive alarm device according to claim 5, wherein the drive circuit further comprises an amplifier for amplifying the output of the low-pass filter, a detector for converting the output of the amplifier into a direct current, and the detector. Portable terminal including a Schmitt trigger circuit to which the output of the above is input, an electronic switch controlled by the output of the Schmitt trigger circuit, and an audio frequency oscillator whose operating power supply is turned on / off by turning on / off the electronic switch. Magnetic sensitive alarm device. 7. The portable magnetic sensitive alarm device according to claim 1, wherein the alarm means is a speaker or a light emitting element. 8. The portable magnetic sensitive alarm device according to claim 1, wherein the alarm means is a speaker and a light emitting element.