JPH0843012A - Distance detecting apparatus - Google Patents

Abstract

PURPOSE:To provide a distance detecting apparatus, which detects the distance between two points without malfunction with regard to distance detecting apparatus for detecting the distance between a transmitter and a receiver based on the strength of magnetic field. CONSTITUTION:Driving circuits 4, 5 and 6 drive coils 1, 2 and 3 with the modulating signals, which are turned on/off with the signal having the second frequency lower than the first frequency that is the frequency of an AC current. A rceiver 9 detects the component of the second frequency from the detected AC magnetic field and detects the fact that the distance to a transmitter 8 becomes a specified value or more when the detected level is less than the specified value. Since the central axes of the coils for generating the magnetic field are arranged in three-dimensional directions, the magnetic field, which is generated by at least one of three magnetic-field generating coils, is most strongly detected with the receiver 9. Therefore, the change in coupling caused by the direction of the transmitter 8 and the receiver 9 is less, and the distance between the transmitter 8 and the receiver 9 can be accurately detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting a distance between two points, and more particularly to a device for detecting a distance between a transmitter and a receiver depending on the strength of a magnetic field.

[0002]

2. Description of the Related Art A method using a measure or the like is generally used to measure the distance between two points. However, this method is a method for measuring the distance to the last, and is not a method for measuring the distance without making other people aware of its existence.

As a method for measuring the distance without making other people aware of the existence thereof, there is a method using radio waves or sound waves. The method using radio waves is that a weak radio wave is emitted from the transmitter, the radio wave is always received by the receiver, and when the radio wave cannot be received by the receiver, it is judged that the distance between the transmitter and the receiver exceeds a specific value. Is the way. Further, as a method of using a sound wave, there are a method similar to the above-mentioned radio wave and a method of observing a time until the sound wave arrives.

[0004]

According to the method described above, the distance can be obtained without being noticed by others. However, the above-mentioned method using radio waves has a problem of malfunction due to the problem of directivity of radio waves. For example, the antenna coil for the receiver has directivity and
Even when using, the reception level drops drastically in a certain specific direction, and the distance between the transmitter and the receiver is wrong. That is, there is a problem that the received level changes depending on the positional relationship between the antenna that emits the radio wave and the antenna that receives the radio wave, and the distance between the two points is erroneously detected.

The same is true of sound waves, and the distance between two points is erroneously detected due to the directivity of the sounding body and the receiving sensor. There is also another method using sound waves, for example, a method of measuring the propagation time of the sound waves to detect the distance, but there is a problem of directivity of the sounding body and the reception sensor as described above.

As described above, conventionally, there has been no method of measuring the distance between two points without being noticed by others, other than measurement by a measurer or the like. Further, for this reason, there has been no method for detecting whether the distance between two points has become a specific value or more without malfunctioning.

An object of the present invention is to provide a distance detecting device which detects a distance between two points without malfunctioning.

[0008]

FIG. 1 is a block diagram showing the principle of the present invention. The invention comprises a transmitter 8 for generating a magnetic field and a receiver 9 for detecting the magnetic field.

The transmitter 8 includes three coils 1, 2, 3 whose central axes are arranged in a three-dimensional direction, and the three coils 1, 1.
2 and 3 are provided corresponding to the above, and an alternating current is passed through the coil 3
It is composed of a number of driving circuits 4, 5 and 6 and a control circuit 7 for sequentially and repeatedly turning on the three driving circuits to control an AC magnetic field flowing to the coil.

The receiver 9 detects the magnetic field generated by the transmitter, and when the magnetic field is below a specific level, it detects that the distance from the transmitter is above a specific value.

[0011]

The driving circuits 4, 5, 6 have a second frequency lower than the first frequency, which is the frequency of the alternating current, for example.
Driving the coils 1, 2 and 3 with a modulation signal that is turned on and off with a signal of the frequency, and the receiver 9 detects the component of the second frequency from the detected AC magnetic field, and the detection level is specified. When the value is less than or equal to the value, it is detected that the distance from the transmitter 8 is equal to or greater than a specific value.

Since the central axes of the magnetic field generating coils are arranged in the three-dimensional direction, the magnetic field generated by one of the at least three magnetic field generating coils is most strongly detected by the receiver. There is little change in the coupling depending on the directions of the transmitter and the receiver, and the distance between the transmitter 8 and the receiver 9 can be accurately detected.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings.
FIG. 2 is a circuit diagram of the transmitter according to the first embodiment of the present invention.
The coils 11 to 13 have the same shape and are arranged so that the axes of the coils are at right angles. The number of turns is also the same. 3 and 4 are diagrams for explaining the arrangement.
In FIG. 3, the central axes of the coils 11, 12 and 13 intersect at a point O, and are also at right angles.
Further, in FIG. 4, the central axis of the coil 12 is the coil 1
1, intersects with the central axis of the coil 13 at right angles. Although the coil 11 and the coil 13 do not intersect, the coil 1
When viewed on the center line of 2, it is a right angle.

One ends of the coils 11, 12 and 13 are connected to the plus side of the power source. The other end is connected to two-input NAND gates 14, 15, 16 which are open collectors. The output of the pulse generator having the oscillation frequency of f1 is added to the input of one end of the NAND gates 14, 15 and 16. The outputs of the flip-flops 18 and 19 and the output of the NOR gate 20 are added to the other end.

The output of the flip-flop is added to the input of the NOR gate, and the output is added to the input D of the flip-flop 19. To the clock terminals CLK of the flip-flops 18 and 19, the output of the pulse generator 21 having the oscillation frequency of f0 is added.

When the outputs of the flip-flops 18 and 19 are at the L level, the output of the NOR gate 20 is at the H level and the NAND gate 16 is turned on. When the NAND gate 16 is turned on, the coil 13 is driven by the pulse of the pulse generator 17. Then, the pulse generator 21
The flip-flop 19 takes in the H level output from the NOR gate 20 in synchronism with the pulse. By this approach, the output of the flip-flop 19 becomes H level,
The NOR gate to which the output is added outputs L level. At this time, the NAND gate 15 is turned on, and the pulse generator 1
The 7 pulses drive coil 12.

Further, when a pulse is output from the pulse generator 21, the flip-flop 18 takes in the H level of the output of the flip-flop 19. As a result, the flip-flop 18 outputs H level, and the OR gate 20 to which it is added outputs L level.

Since the H level output of the flip-flop 18 is applied to the NAND gate 14, the NAND gate 14 is turned on. When the NAND gate 14 is turned on, the coil 11 is driven by the pulse of the pulse generator 17. Then, according to the next pulse output from the pulse generator 21, both flip-flops 18 and 19 output L level. This state is the state described above.

As described above, the sequential coils 13, 12, 1
1 is driven by the pulse of the pulse generator 17,
An alternating magnetic field having a frequency of f1 is generated. The alternating magnetic field generated by the transmitter described above is received by the receiver. FIG. 5 is a circuit diagram of the receiver. The alternating magnetic field described above is applied to the receiving coil 26.
Is converted into a voltage by and is amplified by the operational amplifier 27. still,
A capacitor 28 is connected to the output end of the coil so that the receiving coil 26 and this capacitor resonate at the frequency f1, and only the signal of the frequency f1 is taken in with respect to external noise. There is.

The received signal amplified by the operational amplifier 27 is applied to the level detection circuit 29, and the level detection circuit 29 detects whether the input level is a specific value. Then, the level detection circuit 29 drives the buzzer 30 when the value is equal to or less than the specific value.

The magnetic fields generated by the coils 11, 12 and 13 have directionality but are independent, that is, the coils 11 and 12 sequentially.
Then coil 12, then coil 13. Further, since the coil 11 is further driven, the receiving coil 26 sequentially detects them.

FIG. 6 is a waveform diagram of the reception level. The envelope of level L1 is the envelope of the signal generated from the coil 11, and the envelope of level L2 is the coil 12
The envelope of the signal generated by the coil 13 and the envelope of the level L3 indicate the envelope of the signal generated by the coil 13. The level detection circuit 29 detects the level of this signal. The level detection circuit 29 in FIG. 5 detects whether the power of the input signal is below a specific value. It should be noted that the level detection circuit 29 does not detect the power level, but the instantaneous maximum level, as shown in FIG.
Then, it may be detected whether the level L1 is a specific value or less.

As described above, since magnetic fields are generated in three directions, no matter what direction the transmitter is placed or in which direction the receiver is placed, there is always a gap between the transmitter and the receiver. The magnetic field coupling is high. Therefore, when the detection level in the receiver is equal to or lower than the specific value, the distance between the transmitter and the receiver is substantially equal to or greater than the specific value, and a distance sensor having no directivity can be obtained.

In the above-described first embodiment of the present invention, the AC magnetic field is emitted from the three coils, but the present invention is not limited to this. For example, the AC magnetic field may be modulated by a modulation signal, and the receiving side may receive the modulated wave and obtain the level for recognizing the distance from the peak value of the modulated wave. FIG. 7 is a block diagram of a transmitter that generates the modulated magnetic field. 7, those parts which are the same as those corresponding parts in FIG. 2 are designated by the same reference numerals, and a description thereof will be omitted.

Open collector NAND gates 14 ', 15', 16 'for driving the coils 11, 12, 13'
Has three input terminals, and the signal shown in FIG. 2 is applied to each of two inputs. The frequency is f1> f2
There is a relationship. Further, the output of the pulse generation circuit 32 (generated pulse frequency f2) is applied to the remaining terminals.
For example, when the output of the flip-flop 18 is 1 and the NAND gate 14 'is on, the pulse of the frequency f1 is turned on / off by the pulse of the frequency f2. That is, it is equivalent to AM-modulating the signal of frequency f1 with the signal of frequency f2.

The coils 11, 12, and 13 driven by the above-mentioned signals generate a magnetic field equivalent to or proportional to the above-mentioned driving. The magnetic field is received by the receiver. In the first embodiment of the present invention, the alternating magnetic fields sequentially generated from the three coils are received and the distance between the transmitter and the receiver is detected from the level thereof. However, in the second embodiment of the present invention, Receives the sequentially generated modulated AC magnetic field and detects the level of the modulated wave. FIG. 8 is a circuit diagram of a receiver according to the second embodiment of the present invention.

Similar to the above, the modulated alternating magnetic field is converted into a voltage by the receiving coil 26 and amplified by the operational amplifier 27. A capacitor 28 is connected to the output end of the coil so that the receiving coil 26 and this capacitor resonate at a frequency f1, and the center frequency is f1 against external noise and f2 It is designed to capture only signals that are frequency modulated.

The received signal amplified by the operational amplifier 27 is
The signal is input to the detection circuit 42 including the diode 35, the capacitor 36, and the resistor 36. In this detection circuit 42, the received signal amplified by the operational amplifier is first half-wave rectified by the diode 35. Then, it is smoothed by the capacitor 36. A resistor 37 is connected in parallel with the capacitor 36, and the resistor 37 discharges the electric charge charged in the capacitor 36.

The received signal detected by the detection circuit 42 is input to the band pass filter (BPF) 39 via the capacitor 38. This bandpass filter has a pass center frequency f
2 and only the aforementioned modulated signal passes. The passed signal, that is, the signal of f2 is amplified by the amplifier 40 and input to the level detection circuit 41. The level detection circuit 41 is f2
Is a circuit for detecting a signal having a frequency of, and drives the buzzer 30 when the level is below a predetermined level. In the first embodiment of the present invention, it is directly determined whether the amplitude value of the received signal is less than or equal to the specific value, but in the second embodiment of the present invention, the signal of the transmitter is at the frequency of f2. Since the signal is modulated, the signal from the transmitter can be stably detected by amplifying the signal of the frequency f2 through the bandpass filter after the detection.

In the above-described second embodiment of the present invention, the signals other than the signal of f2 are cut using the bandpass filter, but the present invention is not limited to this. For example, an encoder that outputs a detection signal when a signal component having a specific frequency is input may be used.

Further, in the embodiment of the present invention, three coils are provided on the transmitter side, and an alternating current is applied to these three coils in sequence to generate an alternating magnetic field. It is not limited to. For example, the signal obtained by configuring the transmitting side with one coil, the receiving side coil with three, and switching the coils sequentially in time to receive signals is the first and second embodiments of the present invention. And the same effect can be obtained. Furthermore, in the first and second embodiments of the present invention, the buzzer is sounded when the distance between the transmitter and the receiver reaches a specific value or more, but the present invention is not limited to this. The amplitude may be displayed with a meter or the like.

[0032]

As described above, according to the present invention, it is possible to easily determine whether or not the distance between two points is equal to or greater than the target value with a simple circuit. In addition, by putting the transmitter of the present device in a bag or the like and putting the receiver in a pocket, it is effective in preventing lost items and preventing storage.

[Brief description of drawings]

FIG. 1 is a principle block diagram of the present invention.

FIG. 2 is a circuit diagram of a transmitter according to a first embodiment of the present invention.

FIG. 3 is a layout view of coils.

FIG. 4 is a layout view of coils.

FIG. 5 is a circuit diagram of a receiver according to the first embodiment of the present invention.

FIG. 6 is a waveform diagram of a reception level.

FIG. 7 is a circuit diagram of a transmitter according to a second embodiment of the present invention.

FIG. 8 is a circuit diagram of a receiver according to a second embodiment of the present invention.

[Explanation of symbols]

 1,2,3 coil 4,5,6 drive circuit 7 control circuit 8 transmitter 9 receiver

Claims (3)

[Claims] 1. A magnetic field generating coil having a central axis arranged in a three-dimensional direction, and three driving circuits provided corresponding to the three coils and flowing an alternating current through the coils. The 3
A transmitter having a control circuit for controlling an alternating current flowing to the coil by sequentially turning on the individual drive circuits, and a magnetic field generated by the transmitter, and when the magnetic field is below a specific level, the transmitter A distance detecting device, comprising: a receiver which determines that the distance is equal to or greater than a specific value. 2. The drive circuit drives the coil with a modulation signal that is turned on and off with a signal of a second frequency lower than the first frequency of the alternating current, and the receiver receives the second frequency signal. A distance detecting device, characterized in that a component is detected, and when the detection level is equal to or lower than a specific value, the distance to the transmitter is equal to or higher than the specific value. 3. A coil that generates a magnetic field, a transmitter that includes a drive circuit that causes an alternating current to flow through the coil, three coils whose central axes are arranged in a three-dimensional direction, and a magnetic field that is generated by the transmitter. Is detected by the coil, and it is sequentially and selectively discriminated whether or not the level of the signal detected by the coil is below a specific level, and when the level is below the specific level, it is assumed that the distance to the transmitter becomes a specific value or more. A distance detection device comprising a receiver having a detection circuit.