JP5979548B2 - CURRENT SENSOR TERMINAL WITH WIRELESS TRANSMITTING FUNCTION, WIRELESS TRANSMITTING METHOD, AND WIRELESS TRANSMITTING / RECEIVING SYSTEM - Google Patents

Description

  The present invention relates to a current sensor terminal with a wireless transmission function, a wireless transmission method, and a wireless transmission / reception system suitable for application to, for example, a system for monitoring the power consumption by detecting the amount of current flowing through an electric wire.

  Recently, so-called energy saving has become an important issue due to the problem of the supply and demand situation of electric power energy. For this reason, attempts are being made to monitor power consumption in a detailed manner in factories, commercial facilities, offices, and even ordinary homes to help save energy as a whole. In order to achieve these objectives, not only the power of the entire factory, the entire commercial facility, the entire office, and the entire household, but also the power consumption of each room, terminal, or electrical device is monitored. There is a need to.

  From such a request, a wireless transmission function is added to the sensor terminal that detects the amount of current and power consumption that flows through the wires wired to each room, the wires that supply power to the terminal devices and electrical equipment, and is installed as appropriate. Thus, there has been proposed a wireless sensor network system that wirelessly transmits the current amount and power consumption detected by the sensor terminal to a monitoring center having a reception function.

  A sensor terminal with a wireless transmission function proposed to be compatible with this system is equipped with a battery as a power source and wirelessly transmits transmission data to a monitoring center at certain time intervals. In this case, in addition to the identification information of the terminal itself, the digital value of the measured current amount and the digital value of the power consumption are generally included in the data wirelessly transmitted from the sensor terminal (for example, (See Patent Document 1 and Patent Document 2 below).

JP-A-2005-159532 JP2011-259252A

  As described above, a sensor terminal with a wireless transmission function used in a conventionally proposed wireless sensor network system is equipped with a battery as a power source. Therefore, when this battery deteriorates, it needs to be replaced. There is a problem that there is.

  Therefore, in order to eliminate the need for battery replacement, it is desirable to provide a stand-alone power source without having a battery power source. As a method of satisfying this requirement, a clamp type current sensor that is attached to an electric wire and detects the electromagnetic induction current is used, and the electromagnetic induction current detected by this clamp type current sensor is stored, so that a power supply for wireless transmission is used. It can be considered to be a voltage.

  However, in this case, the electromagnetic induction current detected from the electric wire, particularly a household power line, is at a very small level, but the stored voltage is used as a power source to reliably perform wireless transmission at an appropriate time interval. You must consider making it possible. That is, it is important that a sensor terminal with a wireless transmission function consumes as little power as possible during wireless transmission.

  By the way, the power consumption during wireless transmission is proportional to the total amount of data to be transmitted (total amount of telegrams). Therefore, in order to reduce power consumption during wireless transmission, it is important to reduce the total amount of data to be transmitted as much as possible.

  Conventionally, however, as described above, the data to be transmitted includes measurement data consisting of a digital value of the measured current amount and a digital value of power consumption as it is, so that the total amount of data to be transmitted is large. There is a problem. For this reason, if the stored voltage storing the electromagnetic induction current detected by the current sensor is used as the power supply voltage for wireless transmission, it must be stored for a long period of time in order to obtain the required stored voltage. There is a problem that it can not stand. Or since there is much total data which should be transmitted, there exists a possibility that all transmission of transmission data may not be completed when an electrical storage voltage is made into a power supply voltage. Therefore, conventionally, it has been practically difficult to use a stored voltage obtained by storing an electromagnetic induction current detected by a current sensor as a self-supporting power source for a sensor terminal with a wireless transmission function.

  In view of the above problems, the present invention can wirelessly transmit information on measured current amount and power consumption even when a stand-alone power source is used without using a battery that needs to be replaced as a power source. An object of the present invention is to provide a current sensor terminal with a wireless transmission function.

In order to solve the above problems, the present invention provides:
A current sensor that detects and outputs an electromagnetic induction current based on the current flowing through the wire;
A power storage circuit that rectifies and stores the electromagnetic induction current from the current sensor;
A transmission circuit that wirelessly transmits a predetermined transmission signal that does not directly include data relating to the amount of current flowing through the electric wire detected by the current sensor;
A switch circuit for supplying the transmission circuit with a storage voltage of the storage circuit as a power supply voltage of the transmission circuit;
A determination circuit for determining whether or not a storage voltage of the storage circuit exceeds a predetermined threshold voltage;
Based on the determination result of the determination circuit, from the time when the storage voltage of the storage circuit exceeds a predetermined threshold voltage, for a predetermined time longer than the time to complete wireless transmission of the transmission signal in the transmission circuit, A timer circuit for turning on the switch circuit and supplying the stored voltage as a power supply voltage to the transmission circuit;
With
The transmission circuit repeatedly performs wireless transmission of the transmission signal in the period of the predetermined time that is supplied with a power supply voltage through the switch circuit based on a determination result of the determination circuit, so that the current sensor A current sensor terminal with a wireless transmission function is provided, wherein the transmission interval of the transmission signal is changed in accordance with the detected amount of current flowing through the electric wire.

  In the current sensor terminal with a wireless transmission function according to the present invention having the above-described configuration, the transmission signal does not directly include data relating to the amount of current flowing through the electric wire detected by the current sensor. Instead, the transmission interval of the transmission signal is changed according to the amount of current flowing through the electric wire detected by the current sensor.

  For this reason, in this invention, the electrical storage circuit which detects the electromagnetic induction current based on the electric current which flows through an electric wire, rectifies the detected electromagnetic induction current, and stores it is provided. Then, in the determination circuit, it is determined whether the storage voltage of the storage circuit exceeds a predetermined threshold voltage, and when the storage voltage of the storage circuit exceeds a predetermined threshold voltage, the transmission circuit A predetermined transmission signal is wirelessly transmitted.

  At this time, the switch circuit is turned on by the timer circuit for a predetermined time longer than the time for completing the wireless transmission of the transmission signal in the transmission circuit from the time when the storage voltage of the storage circuit exceeds a predetermined threshold voltage. Then, the storage voltage is supplied to the transmission circuit as a power supply voltage (independent power supply).

  Since the storage voltage of the storage circuit is consumed in the transmission circuit during the wireless transmission period of the predetermined time, the storage voltage is lowered by a certain voltage from the predetermined threshold voltage. When the wireless transmission period ends, the power storage circuit starts to store power using the electromagnetic induction current from the reduced stored voltage. The storage voltage next exceeds the threshold voltage after a time corresponding to the amount of current, which is the time integration of the current flowing through the electric wire. That is, if the current flowing through the electric wire is small, it takes time to increase to the threshold voltage next, and if the current flowing through the electric wire is large, the time until it next increases to the threshold voltage is shortened. That is, the transmission signal is transmitted from the transmission circuit at a transmission interval corresponding to the amount of current flowing through the electric wire detected by the current sensor.

  Therefore, on the receiving side, the transmission interval of the received transmission signal is detected, and the amount of current flowing through the electric wire detected by the current sensor during the transmission interval is calculated from the detected transmission interval. That is, on the receiving side, the transmission interval of the received transmission signal is converted into a current amount. Therefore, in the present invention, it is not necessary to directly include digital data relating to the measured current amount in the predetermined transmission signal wirelessly transmitted by the sensor terminal. Since the ratio of the measured current amount to the transmission signal of the digital data is large, the total data amount of the transmission signal can be greatly reduced. Thereby, the power consumption at the time of transmission can be reduced significantly. Thus, according to the present invention, even when a stand-alone power supply is used, information on the measured current amount and power consumption can be wirelessly transmitted at an appropriate timing.

  According to this invention, the transmission interval of the transmission signal can be changed according to the amount of current flowing through the electric wire detected by the current sensor, and the transmission interval of the transmission data received on the receiving side can be converted into the amount of current. By doing so, the total amount of data to be transmitted can be minimized, and the measured current can be measured even when using a stand-alone power source without using a battery that needs to be replaced. It is possible to provide a current sensor terminal device with a wireless transmission function capable of wirelessly transmitting information on the amount and power consumption.

It is a figure for demonstrating the outline | summary of the structural example of embodiment of the radio | wireless transmission / reception system by this invention. It is a figure which shows the example of an external appearance structure of embodiment of the current sensor terminal with a wireless transmission function by this invention. It is a circuit diagram which shows the structural example of the wireless transmission part in embodiment of the current sensor terminal with a wireless transmission function by this invention. It is a figure which shows the timing chart used for operation | movement description of the circuit diagram of FIG. It is a figure for demonstrating the example of the transmission signal in embodiment of the current sensor terminal with a wireless transmission function by this invention. It is a figure which shows the structural example of the receiver which comprises embodiment of the radio | wireless transmission / reception system by this invention. It is a figure which shows the flowchart for demonstrating the processing operation example of the receiver of the example of FIG.

  FIG. 1 is a diagram illustrating an outline of a configuration example of an embodiment of a wireless transmission / reception system according to the present invention. An area 1 surrounded by a square in FIG. 1 indicates a power supply wiring area in a factory, a store, or a general household.

  In the area 1, a switchboard 2 is provided. The distribution board 2 is connected to the transmission line 3 and a plurality of electric wires 41, 42,..., 4n (n is a positive number) for distributing power from the distribution board 2 to each room or facility in the area 1. Integer). And in this embodiment, in the switchboard 2, the electric wire part which comprises each one part of electric wire 41,42, ..., 4n is current sensor terminal 51,52, ... with a wireless transmission function. , 5n are attached.

  Here, since the current sensor terminals 51, 52,..., 5n with the wireless transmission function have exactly the same hardware configuration, in the following description, the current sensor terminals 51, 52,. When there is no need to distinguish each of 5n, it is described as a current sensor terminal 5 with a wireless transmission function. Similarly, when there is no need to distinguish each of the plurality of electric wires 41, 42,. In the following description, a current sensor terminal with a wireless transmission function is abbreviated as a current sensor terminal.

  As shown in FIG. 2, the current sensor terminal 5 includes a clamp-type current sensor 501 and a wireless transmission unit 502. The clamp type current sensor 501 includes a clamp mechanism unit 503 and a current detection unit 504. The clamp mechanism unit 502 has, for example, a U-shape, and is attached to the current detection unit 504 so as to be rotatable about the hinge unit 505 as illustrated in FIGS. . As shown in FIG. 2B, the current sensor terminal 5 is attached to the electric wire 4 by clamping the clamp mechanism portion 503 so that the electric wire 4 is accommodated in the U-shaped portion. The clamp mechanism unit 503 is locked when the engaging portion 506 of the clamp mechanism unit 503 is engaged with the protrusion 507 provided on the current detection unit 504.

  Thus, in the state where the clamp mechanism 503 is locked to the electric wire 4, in the current sensor terminal 5, a ring-shaped core (see the dotted line in FIG. 2B) is formed around the electric wire 4. A coil is wound around the ring-shaped core, and an electromagnetic induction current is induced in the coil by a magnetic field generated by a current flowing through the electric wire 4. The current detection unit 504 detects an electromagnetic induction current induced in the coil. In this embodiment, the electromagnetic induction current detected by the clamp type current sensor 501 is supplied to the wireless transmission unit 502.

  The wireless transmission unit 502 rectifies and stores the electromagnetic induction current received from the clamp-type current sensor 501 and uses the stored voltage as a power supply voltage for wireless transmission. Then, the wireless transmission unit 502 sends a predetermined transmission signal to the receiving device 6 when the stored voltage becomes equal to or higher than a predetermined threshold voltage equal to or higher than a voltage that can be used as a power supply voltage for wireless transmission. For wireless transmission.

  At this time, in this embodiment, the wireless transmission unit 502 does not include the electronic data (digital data) of the current amount measured based on the current detected by the clamp type current sensor 501 in the transmission signal. Instead, the wireless transmission unit 502 transmits a transmission signal to the reception device 6 at a transmission interval corresponding to the amount of electromagnetic induction current received from the clamp-type current sensor 501.

  In this embodiment, as shown in FIG. 1, the receiving device 6 receives transmission signals from the plurality of current sensor terminals 51 to 5n in common, and thus the receiving device 6 has the current sensor terminals 51 to 51. It is necessary to be able to identify which of 5n is a transmission signal. Therefore, the transmission signal from the wireless transmission unit 502 is a signal that can be identified by the reception device 6 as the transmission signal from the plurality of current sensor terminals 51 to 5n.

  In this case, by including the identification data of each current sensor terminal 5 in the transmission signal, the reception device 6 can identify which current sensor terminal 5 is the transmission signal. However, since the amount of telegram data of the transmission signal increases, in this embodiment, as will be described below, the identification data is not included in the telegram data of the transmission signal, and a plurality of pieces of data are received by the reception device 6. The transmission signal is devised so that it can be identified from which of the current sensor terminals 51 to 5n it is a transmission signal.

  FIG. 3 is a circuit diagram illustrating a configuration example of the wireless transmission unit 502. As illustrated in FIG. 3, the wireless transmission unit 502 includes a power storage circuit 510, a threshold voltage determination circuit 520, a timer circuit 530, a switch circuit 540, and a wireless transmission circuit 550.

  The power storage circuit 510 includes a voltage doubler rectifier circuit 511 and a power storage capacitor 512. The voltage doubler rectifier circuit 511 is connected to the output terminals 501a and 501b of the clamp type current sensor 501, and doubles the AC electromagnetic induction current appearing between the output terminals 501a and 501b. The obtained direct current charges the power storage capacitor 512 for storage.

  The voltage doubler rectifier circuit 511 is for boosting the voltage because the electromagnetic induction current level detected and output from the current flowing through the electric wire 4 by the clamp type current sensor 501 is small. As the voltage doubler rectifier circuit 511, a booster circuit using a charge pump or the like is usually used. However, since the power consumption is large, in this embodiment, only a diode and a capacitor such as a Cockcroft-Walton circuit are used. And a booster circuit with low power consumption is used.

  Since the storage capacitor 512 is charged by an electromagnetic induction current corresponding to the current flowing through the electric wire 4 detected by the clamp type current sensor 501, the storage voltage VC of the storage capacitor 512 is the time of the current flowing through the electric wire 4. It rises according to the amount of current that is the integral value.

  The storage voltage VC stored in the storage capacitor 512 is supplied as a power supply voltage for the threshold voltage determination circuit 520 and the timer circuit 530, and is also supplied as a power supply voltage for the wireless transmission circuit 550 through the switch circuit 540. The switch circuit 540 forms a power supply voltage supply control circuit that controls whether or not the storage voltage VC stored in the storage capacitor 512 is supplied to the wireless transmission circuit 550 as a power supply voltage.

  The threshold voltage determination circuit 520 determines whether or not the storage voltage VC stored in the storage capacitor 512 exceeds a predetermined threshold voltage Vth. In this example, the threshold voltage Vth is set to a voltage value sufficient to drive the wireless transmission circuit 550, for example, 3 volts.

  The threshold voltage determination circuit 520 in the example of FIG. 3 includes an operational amplifier 521 that constitutes a comparison circuit. In the threshold voltage determination circuit 520, a series circuit of a resistor 522 and a resistor 523 is connected in parallel with the storage capacitor 512. At the connection point between the resistor 522 and the resistor 523, the divided voltage obtained by dividing the storage voltage VC, which is the voltage across the storage capacitor 512, according to the resistance values R 1 and R 2 of the resistor 522 and the resistor 523. Vd is obtained, and this divided voltage Vd is supplied to the non-inverting input terminal of the operational amplifier 521 constituting the comparison circuit. On the other hand, the reference voltage for comparison Vref is supplied to the inverting input terminal of the operational amplifier 521.

  In this embodiment, as the operational amplifier 521, the one having a built-in band gap reference circuit and capable of outputting a reference voltage based on the band gap reference is used. The reference voltage based on the band gap reference is a stable reference voltage that does not depend on variations in elements in the IC constituting the operational amplifier 521, power supply voltage, and temperature, and is, for example, 1.25 volts. In this embodiment, the reference voltage based on the band gap reference of the operational amplifier 521 is supplied to the inverting input terminal of the operational amplifier 521 as the reference voltage for comparison Vref.

  In the operational amplifier 521, when the divided voltage Vd at the connection point between the resistor 522 and the resistor 523 exceeds a predetermined voltage larger than the reference voltage Vref for comparison, the output signal SU1 obtained at the output terminal becomes high level. Sometimes the output signal SU1 becomes low level. In this embodiment, the divided voltage Vd at the connection point between the resistor 522 and the resistor 523 is a predetermined voltage higher than the reference voltage Vref for comparison when the storage voltage VC of the storage capacitor 512 is 3 volts as described above. In this example, the resistance values R1 and R2 of the resistor 522 and the resistor 523 are selected so as to be a voltage.

  As is clear from the above description, the output signal SU1 of the operational amplifier 521 is obtained when the stored voltage VC of the storage capacitor 512 is sufficient to drive the wireless transmission circuit 550, in this example, 3 volts. High level signal.

  Therefore, the output signal SU1 of the operational amplifier 521 is directly supplied to the switch circuit 540 as a switch control signal, and the switch circuit 540 is turned on in the high level section of the output signal SU1, and the wireless transmission circuit 550 is connected to the storage circuit. It is conceivable to supply the storage voltage VC of the capacitor 512 as the power supply voltage.

  However, in such a configuration, when the switch circuit 540 is turned on and the stored voltage VC is supplied as the power supply voltage to the wireless transmission circuit 550, power is consumed in the wireless transmission circuit 550. The voltage value of the storage voltage VC of the storage capacitor 512 decreases. Then, since the divided voltage Vd at the connection point between the resistor 522 and the resistor 523 becomes lower than a predetermined voltage higher than the reference voltage Vref for comparison, the output signal SU1 of the operational amplifier 521 becomes low level, and the switch circuit There is a problem that the power to the wireless transmission circuit 550 is turned off before the wireless transmission of the transmission signal in the wireless transmission circuit 550 is completed.

  In order to avoid this problem, in this embodiment, the timer circuit 530 is provided between the output terminal of the threshold voltage determination circuit 520 and the switch circuit 540. In this example, the timer circuit 530 includes a charge / discharge circuit 531 that forms a time constant circuit, and an operational amplifier 532 that forms a comparison circuit.

  The charge / discharge circuit 531 includes a diode 533 whose anode is connected to the output terminal of the operational amplifier 521 of the threshold voltage determination circuit 520, and a parallel circuit of a capacitor 534 and a resistor 535 connected to the cathode of the diode 533. Then, the voltage across the capacitor 534 is supplied to the non-inverting input terminal of the operational amplifier 532 constituting the comparison circuit. A reference voltage based on a band gap reference of the operational amplifier 521 is supplied to the inverting input terminal of the operational amplifier 532 as a comparison reference voltage Vref.

  The switch circuit 540 is provided between the timer circuit 530 and the wireless transmission circuit 550, and the output signal SU2 of the operational amplifier 532 of the timer circuit 530 is supplied to the switch circuit 540 as its switch control signal.

  In the charge / discharge circuit 531 constituting the time constant circuit of the timer circuit 530, when the output signal SU1 of the operational amplifier 521 of the threshold voltage determination circuit 520 becomes high level, the diode 533 is turned on, and a charging current flows through the capacitor 534. The voltage across the capacitor 534 instantaneously increases to 3 volts. Then, the output signal SU2 of the operational amplifier 532 becomes a high level, whereby the switch circuit 540 is turned on, and the storage voltage VC of the storage capacitor 512 is supplied as the power supply voltage to the wireless transmission circuit 550.

  In this way, when the switch circuit 540 is turned on and supply of the power supply voltage to the wireless transmission circuit 550 is started and power is consumed in the wireless transmission circuit 550, the storage voltage VC of the storage capacitor 512 decreases. The output signal SU1 of the operational amplifier 521 of the voltage determination circuit 520 is at a low level. For this reason, charging of the capacitor 534 of the charge / discharge circuit 531 of the timer circuit 530 is stopped, and a discharge current starts to flow from the capacitor 534 through the resistor 535. At this time, the diode 533 is reverse-biased and turned off, and the discharge current flows only through the resistor 535. Therefore, the voltage across the capacitor 534 decreases with a discharge time constant determined by the capacitance of the capacitor 534 and the resistance value of the resistor 535.

  When the voltage across the capacitor 534 becomes lower than the comparison reference voltage Vref, the output signal SU2 of the operational amplifier 532 becomes low level, and the switch circuit 540 is turned off. Therefore, the switch circuit 540 is turned on for a certain time Tx determined by the discharge time constant of the charge / discharge circuit 531 from the time when the storage voltage VC of the storage capacitor 512 reaches 3 volts, and the wireless transmission circuit 550 The storage voltage VC of the storage capacitor 512 is supplied as a power supply voltage.

  In this embodiment, the wireless transmission circuit 550 completes the wireless transmission of the transmission signal for the fixed time Tx determined by the discharge time constant of the charging / discharging circuit 531 of the timer circuit 530, that is, the length of the period during which the switch circuit 540 is turned on. To be long enough to do. That is, the capacitance of the capacitor 534 and the resistance value of the resistor 535 are selected so that the fixed time Tx determined by the discharge time constant is sufficient to complete the wireless transmission of the transmission signal.

  In this example, the wireless transmission circuit 550 includes an MCU (Micro Controller Unit) 551 composed of, for example, a microcomputer, and a wireless IC (Integrated Circuit) 552 constituting a high-frequency wireless transmission circuit. Here, the MCU 551 and the wireless IC 552 are assumed to operate at a power supply voltage of 3 volts in this example. Therefore, when the storage voltage VC of 3 volts stored in the storage capacitor 512 is applied to the MCU 551 and the wireless IC 552 through the switch circuit 540, the wireless IC 552 receives the control of the MCU 551 and transmits the transmission signal of this example. Wireless transmission.

  In this embodiment, different wireless transmission frequencies are assigned to the wireless ICs 552 of the current sensor terminals 51 to 5n, and the wireless IC 552 transmits a frequency signal of the wireless transmission frequency as a transmission signal based on the control of the MCU 551. As wireless transmission.

  For example, the transmission signal is a signal having a preamble section, a data section, and an error detection section as shown in FIG. 5A, and only in the high level period of the transmission signal as shown in FIG. 5B. ASK (Amplitude Shift Keying) signal to which the assigned frequency signal is transmitted. That is, the transmission signal is an intermittent signal of the frequency signal of the radio transmission frequency assigned to each of the current sensor terminals 51 to 5n in the preamble section and the error detection section, and in the data section, in this example, a time corresponding to 1 bit. It is a continuous signal of the frequency signal in a long section.

  In the example of FIG. 5, the data interval is provided between the preamble interval and the error detection interval. However, in this embodiment, since the transmission signal does not need to include digital data of the current amount, the minimum interval is set. The data section can be 0-bit data, and the data section need not be provided.

  If the number of current sensor terminals 5 provided in the system is too large and the number of frequencies allocated to be different for each current sensor terminal is insufficient, the identification information of the current sensor terminal is added to the data section of the transmission signal. It may be included. Further, a temperature sensor or the like may be connected to the wireless transmission unit 502 in addition to the current sensor 501 so that temperature data measured by the temperature sensor is included in the data section.

  The receiving device 6 determines which of the plurality of current sensor terminals 51 to 5n has received the transmission signal by determining the frequency of the received transmission signal. That is, in this embodiment, the frequency of the transmission signal is identification information of each of the current sensor terminals 51 to 5n.

  Further, as is clear from FIG. 5, the transmission signal does not include the digital data of the current amount of the current detected by the clamp type sensor 501 as the telegram data. Then, the current amount detected by the clamp type sensor 501 is determined from the transmission interval of the received transmission signal.

  An example of the operation of the current sensor terminal 5 will be described with reference to FIG. When the current sensor terminal 5 is attached to the electric wire 4 as shown in FIG. 2B by the clamp mechanism 503 of the clamp type sensor 501, the storage voltage VC of the storage capacitor 512 of the wireless transmission unit 502 is As shown to 4 (A), it rises gradually according to the electric current amount which flows into the electric wire 4. FIG.

  At time t1 in FIG. 4, when the storage voltage VC of the storage capacitor 512 exceeds the threshold voltage Vth (= 3 volts), this is determined by the threshold voltage determination circuit 520, and the output signal SU1 ( (See FIG. 4B). Therefore, the capacitor 534 of the charge / discharge circuit 531 of the timer circuit 530 is instantaneously charged to 3 volts, the output signal SU2 (see FIG. 4C) of the operational amplifier 532 becomes high level, and the switch circuit 540 is turned on. Become.

  When the switch circuit 540 is turned on, the 3-volt storage voltage VC of the storage capacitor 512 is applied to the MCU 551 and the wireless IC 552 of the wireless transmission circuit 550, and the frequency assigned to the current sensor terminal 5 described above from the wireless IC 552. Is transmitted wirelessly to the receiving device 6 (see the shaded area in FIG. 4D).

  By starting the wireless transmission, the storage voltage VC of the storage capacitor 512 is lower than the threshold voltage Vth, so that the output signal SU1 (see FIG. 4B) of the operational amplifier 521 of the threshold voltage determination circuit 520 is set to a low level. Become. However, the charging voltage of the capacitor 534 of the charging / discharging circuit 531 of the timer circuit 530 decreases with a discharge time constant corresponding to the resistance value of the resistor 535, and at this point in time, is larger than the reference voltage for comparison Vref. The output signal SU2 (see FIG. 4C) maintains a high level.

  When the time Tx corresponding to the discharge time constant of the charge / discharge circuit 531 of the timer circuit 530 after the wireless transmission of the transmission signal indicated by the hatched portion in FIG. Since the charging voltage is lower than the comparison reference voltage Vref, the output signal SU2 (see FIG. 4C) of the operational amplifier 532 becomes low level. When the output signal SU2 of the operational amplifier 532 becomes low level, the switch circuit 540 is turned off, and the supply of the power supply voltage to the MCU 551 and the wireless IC 552 of the wireless transmission circuit 550 is cut off. However, at this time t2, as described above, the wireless transmission of the transmission signal from the wireless IC is completed.

  At this time t2, the switch circuit 540 is turned off, so that the supply to the wireless transmission circuit 550 to the storage voltage VC of the storage capacitor 512 is interrupted. Storage is resumed by charging with current, and the storage voltage VC gradually rises as shown. At time t2, the storage voltage VC of the storage capacitor 512 does not become zero volts, but becomes a voltage value OFS that is lower by an amount corresponding to the power consumed by the wireless transmission circuit 550.

  Here, the transmission signal wirelessly transmitted from the wireless transmission circuit 550 is a fixed transmission signal as shown in FIG. 5 that does not include message data corresponding to the measured current amount. The power consumed for transmission is constant. Therefore, the storage voltage VC remaining in the storage capacitor 512 after the wireless transmission operation in the wireless transmission circuit 550 is always a value obtained by subtracting a certain amount of power consumed by the wireless transmission from the threshold voltage Vth. Is a constant value.

  The power storage capacitor 512 starts power storage from this voltage value OFS. Then, when the storage voltage VC of the storage capacitor 512 exceeds the threshold voltage Vth again at time t3, for example, during the time Tx from the time t3 to the time t4, in exactly the same manner as after the time t1 described above. Performs wireless transmission of the transmission signal. And from time t4, the electrical storage according to the electric current of the electric current which flows through the electric wire 4 in the electrical storage capacitor | condenser 512 is restarted. Thereafter, in exactly the same manner, every time the storage voltage VC of the storage capacitor 512 exceeds 3 volts, which is the threshold voltage Vth, during the time Tx from time t5 to time t6, and further from time t7 to time t8 During Tx, the wireless transmission of the transmission signal is repeatedly executed.

  Then, the time lengths P1, P2, P3,... From the end time t2, t4, t6... Of the previous transmission period Tx to the start time t3, t5, t7. Is the time length until the storage voltage VC of the storage capacitor 512 reaches the threshold voltage Vth from the voltage value OFS, and Vth−OFS = constant, so that the time lengths P1, P2, P3,. .. is a time corresponding to the amount of current flowing through the electric wire 4.

  Therefore, the amount of current detected by the clamp type current sensor 501 can be detected by detecting the time lengths P1, P2, P3. Since the time length Tx of the transmission section is constant and known, the receiving device 6 starts the time Tx of the current transmission section from the start time of the time Tx of the previous transmission section (transmission signal reception start time). The time lengths P1, P2, P3,... Can be calculated by subtracting the time length Tx from the time length up to the time point (the reception signal reception start time point).

  Next, a configuration example of the receiving device 6 will be described with reference to the block diagram of FIG. As shown in FIG. 6, the receiving circuit 6 includes a receiving circuit 61, an A / D conversion circuit 62, an FFT (Fast Fourier Transform) circuit 63, a processing processor 64, a frequency corresponding terminal ID table memory 65, a watch A unit 66, a terminal ID reception time memory 67, a terminal ID reference data memory 68, and a terminal ID current amount memory 69.

  In the frequency corresponding terminal ID table memory 65, a correspondence table of each terminal ID (Identification; identification information) of the plurality of current sensor terminals 51 to 5n and the frequency assigned to each of the current sensor terminals 51 to 5n. Is remembered.

  The terminal ID reception time memory 67 is a memory in which the reception time of the transmission signal received by the receiving device 6 is stored in association with the terminal ID of the current sensor terminal 5 that wirelessly transmits the transmission signal.

  In the reference data memory 68 for each terminal ID, the time length of the transmission interval of the transmission signal measured in advance for each of the current sensor terminals 51 to 5n, and the wires 41 to 4n between the time lengths of the transmission intervals, respectively. Is stored in association with each terminal ID.

  Each time the terminal ID current amount memory 69 receives a transmission signal from each of the current sensor terminals 51 to 5n, the current amount calculated as described later from the time difference from the previous reception time, respectively, Is stored in association with the terminal ID.

  The processing processor 64 has a function of a conversion circuit that calculates the transmission interval of the received transmission signal from the demodulated data from the FFT circuit 63 and converts the calculated transmission interval into a current amount in the transmission interval.

  Next, the processing operation of the receiving apparatus 6 of this example will be described below with reference to the flowchart of FIG. 7 mainly showing the processing flow in the processing processor 64.

  In the reception device 6, the transmission signal from the current sensor terminal 5 is received by the reception unit 61, converted into a digital signal by the A / D conversion unit 62, and supplied to the FFT circuit 63. The FFT circuit 63 converts the received frequency signal into a frequency spectrum signal and supplies it to the processing processor 64.

  The processor 64 acquires the frequency spectrum signal from the FFT circuit 63 as demodulated data (step S101 in FIG. 7), and a peak that can be considered significant at a specific frequency position in the demodulated data of the frequency spectrum signal. It is determined whether or not a transmission signal from the current sensor terminal 5 has been received depending on whether or not is standing (step S102).

  If it is determined in step S102 that the transmission signal from the current sensor terminal 5 has not been received, the processing processor 64 returns the processing to step S101 and takes in new demodulated data.

  When it is determined in step S102 that the transmission signal from the current sensor terminal 5 has been received, the processing processor 64 determines the frequency of the received transmission signal based on the frequency at which the frequency spectrum signal from the FFT circuit 63 has a peak. Determine. Then, the processor 64 recognizes the terminal ID of the current sensor terminal to which the frequency is assigned from the determined frequency by referring to the correspondence table of the frequency corresponding terminal ID table memory 65 (step S103).

  Next, the processing processor 64 acquires the time information of the clock unit 66 at this time as the reception time Rt of the received transmission signal, and associates it with the terminal ID certified in step S103, and receives the reception time for each terminal ID. 67 (step S104).

  Next, the processor 64 reads the previous reception time R (t−1) for the terminal ID recognized in step S103 from the terminal ID reception time memory 67 (step S105). Then, the processing processor 64 uses the current sensor terminal 5 of the terminal ID as a time length obtained by subtracting the time length Tx of the transmission section from the difference between the previous reception time R (t−1) and the current reception time Rt. The current transmission interval Pt (= Rt−R (t−1) −Tx) of the transmission signal from is calculated (step S106).

  Next, the processing processor 64 calculates a correspondence table between the time length of the transmission interval of the transmission signal and the current amount for the terminal ID recognized in step S103 stored in the reference data memory 68 for each terminal ID in step S106. By referring to the transmission interval Pt (step S107), the corresponding current amount is calculated, and stored in the terminal ID current amount memory 69 in association with the terminal ID certified in step S103 (step S108). After step S108, the processor 64 returns the process to step S101, and repeats the processes after step S101.

  In step S108, when the value corresponding to the transmission interval Pt calculated in step S106 does not directly exist in the correspondence table between the time length of the transmission interval of the transmission signal and the current amount, the correspondence table Current corresponding to the transmission interval Pt calculated in step S106 by performing interpolation calculation processing using the correspondence data between the time length of the transmission interval before and after the transmission interval Pt calculated in step S106 and the current amount. The amount is calculated.

  As described above, in this embodiment, the current sensor terminal 5 includes the power storage circuit 510 that rectifies and stores the electromagnetic induction current based on the current flowing through the electric wire 4, and the power storage voltage VC of the power storage circuit 510 is predetermined. Since the transmission signal is wirelessly transmitted to the receiving device 6 every time the threshold voltage Vth is reached, the transmission interval of the transmission signal can be changed according to the measured current amount.

  Then, the receiving device 6 detects the corresponding current amount by detecting the transmission interval of the transmission signal received from the current sensor terminal 5. Therefore, the current sensor terminal 5 does not need to use the digital data of the current amount to be measured as the telegram data of the transmission signal, can greatly reduce the transmission data amount, and reduce the power consumption for wireless transmission. be able to.

  For this reason, the current sensor terminal 5 can use the storage voltage VC of the storage circuit 510 as a power source for wireless transmission. That is, the storage voltage VC by the electromagnetic induction current can be used as the independent power supply voltage without mounting the battery. In addition, in this embodiment, the timer circuit 530 is provided so that the storage voltage VC is supplied to the wireless transmission circuit 550 as the power supply voltage until the wireless transmission in the wireless transmission circuit 550 is completed. There is an effect that radio transmission can be performed reliably.

  The timer circuit 530 is composed of a charge / discharge circuit (time constant circuit) having a simple circuit configuration including a diode, a capacitor, and a resistor, and has an effect that power consumption can be suppressed by the configuration.

[Other Embodiments or Modifications]
The reference voltage Vref supplied to the operational amplifier 521 and the operational amplifier 532 constituting the comparison circuit is the reference voltage based on the bandgap reference as in this embodiment, but the comparison reference voltage Vref is the bandgap. It is not limited to the case where a reference voltage by reference is used. For example, in order to further reduce the power consumption of the wireless transmission unit 502, an output voltage such as a silver oxide battery having a flat output voltage change characteristic may be used as the reference voltage for comparison Vref.

  Further, in the above-described embodiment, in the receiving device 6, the transmission interval is changed from the start time of the time Tx in the previous transmission section (start of reception of the transmission signal) to the start time of the time Tx in the current transmission section (transmission signal). It is calculated as time lengths P1, P2, P3... Obtained by subtracting the time length Tx from the time length until the reception start time). However, the time length from the start time of the time Tx of the previous transmission section (transmission signal reception start time) to the start time of the time Tx of the current transmission section (transmission signal reception start time), that is, the time length P1. , P2, P3... And a certain time length Tx may be calculated as a transmission interval. In that case, the receiving device 6 stores a correspondence table between the transmission interval and the amount of current, each of which is the sum of the time lengths P1, P2, P3... And a certain time length Tx. It is stored in the reference data memory 68 for each ID.

  In the above-described embodiment, in the receiving device 6, the reference data memory 68 for each terminal ID stores a correspondence table between the transmission interval of received transmission signals and the amount of current, and converts the transmission interval into the amount of current. I tried to do it. However, by storing a correspondence table between the power consumption corresponding to the current amount and the transmission interval in the reference data memory 68 for each terminal ID, the reception device 6 sets the transmission interval to the power consumption instead of the current amount. You may make it memorize | store in conversion.

  In the above-described embodiment, the transmission signal is an ASK signal having a frequency assigned to each current sensor terminal. However, other modulation methods such as FSK (Frequency Shift Keying) can be used.

  In the above-described embodiment, the frequency assigned to each current sensor terminal is used as the transmission signal that enables the reception side to identify the transmission terminal. However, the present invention is not limited to this. A transmission signal consisting only of data may be wirelessly transmitted. Alternatively, transmission signals having different transmission rates (baud rates) may be used for each current sensor terminal, and each of the current sensor terminals may be identified by detecting the baud rate of the transmission signal on the reception side.

  In addition, the transmission signal does not necessarily have a preamble section and an error detection section as in the above-described embodiment. In short, a signal that can identify each of the current sensor terminals on the receiving device side. Any signal may be used.

  4, 41 to 4n, electric wire, 5, 51 to 5n, current sensor terminal, 6 ... receiving device, 501 ... current sensor, 502 ... wireless transmission unit, 510 ... power storage circuit, 520 ... threshold voltage determination circuit, 530 ... timer circuit 540 ... Switch circuit, 550 ... Wireless transmission circuit

Claims (10)

A current sensor that detects and outputs an electromagnetic induction current based on the current flowing through the wire;
A power storage circuit that rectifies and stores the electromagnetic induction current from the current sensor;
A transmission circuit that wirelessly transmits a predetermined transmission signal that does not directly include data relating to the amount of current flowing through the electric wire detected by the current sensor;
A switch circuit for supplying the transmission circuit with a storage voltage of the storage circuit as a power supply voltage of the transmission circuit;
A determination circuit for determining whether or not a storage voltage of the storage circuit exceeds a predetermined threshold voltage;
Based on the determination result of the determination circuit, from the time when the storage voltage of the storage circuit exceeds a predetermined threshold voltage, for a predetermined time longer than the time to complete wireless transmission of the transmission signal in the transmission circuit, A timer circuit for turning on the switch circuit and supplying the stored voltage as a power supply voltage to the transmission circuit;
With
The transmission circuit repeatedly performs wireless transmission of the transmission signal in the period of the predetermined time that is supplied with a power supply voltage through the switch circuit based on a determination result of the determination circuit, so that the current sensor A current sensor terminal with a wireless transmission function, wherein the transmission interval of the transmission signal is changed according to the detected amount of current flowing through the electric wire. The current sensor terminal with a wireless transmission function according to claim 1, wherein the predetermined transmission signal is a signal that enables the reception side to identify the transmission terminal. 3. The wireless transmission function according to claim 2, wherein the transmission circuit wirelessly transmits a signal having a frequency assigned to each of the current sensor terminals as the transmission signal that enables the transmission terminal to be identified. Current sensor terminal. The determination circuit includes a first comparison circuit that is a power storage of the power storage circuit but has an output terminal at a high level when the threshold voltage is exceeded.
The timer circuit is configured to discharge in accordance with a diode that is conductive when the output terminal of the first comparison circuit is at a high level, a capacitor that is charged by a current through the diode, and a charging voltage of the capacitor. It comprises a resistor and a second comparison circuit that compares the charging voltage of the capacitor and the threshold voltage, and the on / off of the switch circuit is controlled by the output of the second comparison circuit. The current sensor terminal with a wireless transmission function according to claim 1 or 2.   The current sensor terminal with a wireless transmission function according to claim 1, wherein the power storage circuit includes a booster circuit. A power storage step of detecting an electromagnetic induction current based on a current flowing through the electric wire with a current sensor and rectifying and storing the detected electromagnetic induction current;
A determination step of determining whether or not the storage voltage stored in the storage step exceeds a predetermined threshold voltage;
When it is determined in the determination step that the storage voltage exceeds a predetermined threshold voltage, the storage voltage is longer than the determination time by a predetermined time longer than a time for completing the wireless transmission of the transmission signal. A wireless transmission step of performing wireless transmission of a transmission signal that does not directly include data relating to the amount of current flowing through the wire detected by the current sensor, as a power supply voltage;
Have
After the wireless transmission step, the process returns to the power storage step and repeats from the power storage step to the wireless transmission step, and sets the transmission interval of the transmission signal according to the amount of current flowing through the wire detected by the current sensor. A wireless transmission method characterized by being changed. The wireless transmission method according to claim 6, wherein the transmission signal is a signal that enables the reception side to identify a transmission terminal. In a wireless transmission / reception system comprising a current sensor terminal with a wireless transmission function for wirelessly transmitting an amount of current flowing through an electric wire, and a receiving device for receiving a transmission signal from the current sensor terminal with a wireless transmission function,
The current sensor terminal with the wireless transmission function is:
A current sensor that detects and outputs an electromagnetic induction current based on the current flowing through the wire;
A power storage circuit that rectifies and stores the electromagnetic induction current from the current sensor;
A transmission circuit that wirelessly transmits a predetermined transmission signal that does not directly include data relating to the amount of current flowing through the electric wire detected by the current sensor;
A switch circuit for supplying the transmission circuit with a storage voltage of the storage circuit as a power supply voltage of the transmission circuit;
A determination circuit for determining whether or not a storage voltage of the storage circuit exceeds a predetermined threshold voltage;
Based on the determination result of the determination circuit, from the time when the storage voltage of the storage circuit exceeds a predetermined threshold voltage, for a predetermined time longer than the time to complete wireless transmission of the transmission signal in the transmission circuit, A timer circuit for turning on the switch circuit and supplying the power supply voltage to the transmission circuit;
With
The transmission circuit repeatedly performs wireless transmission of the transmission signal in the period of the predetermined time that is supplied with a power supply voltage through the switch circuit based on a determination result of the determination circuit, so that the current sensor The transmission interval of the transmission signal is changed according to the amount of current flowing through the detected wire,
The receiving device is:
Each time the transmission signal is received, a storage circuit that stores information at the time of reception;
A conversion circuit that calculates a transmission interval of the transmission signal from a time difference between temporally adjacent reception times of the transmission signal stored in the storage circuit, and converts the calculated transmission interval into a current amount or power consumption;
A wireless transmission / reception system. The transmission signal is a signal that enables the reception side to identify a transmission terminal,
The receiving device is:
An identification circuit for identifying the transmission terminal from the received transmission signal;
The storage circuit stores the reception time point of the transmission signal for each transmission terminal by associating with the identification information of the transmission terminal identified by the identification circuit,
The wireless transmission / reception system according to claim 8, wherein the conversion circuit converts the calculated transmission interval into a current amount or power consumption for each transmission terminal. The conversion circuit is
For each transmission terminal identified by the identification information, a storage circuit that stores correspondence information between a transmission interval and a current amount or power consumption,
For each of the transmitting terminal, no line transceiver system of claim 9, the amount of current or power consumption corresponding to the transmission interval and the calculated, and calculating by referring to the correspondence information that the storage .

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