JP6434095B1 - Wireless terminal, control method, and control program - Google Patents

Abstract

An object of the present invention is to provide a wireless terminal that can use an optimum SF value according to the amount of power that can be used. A wireless terminal (2) according to the present invention includes a power generation element (21), a storage element (23) charged by the power generation element (21), and a voltage for detecting an output voltage of the storage element (23). A detection circuit (26), an SF value selection unit (276) for selecting an SF (diffusion rate) value based on an output voltage, a sensor (25) for detecting a physical phenomenon, an output voltage, and an SF And a transmission module (29) that applies the value and transmits data based on the detection result of the sensor (25) by a spread spectrum method. [Selection] Figure 4

Description

  The present invention relates to a wireless terminal, a control method, and a control program.

  As a communication method for realizing IoT (Internet of Things), a communication method generally called LPWA (Low Power Wide Area) that realizes long-distance communication with low power consumption has attracted attention in recent years.

  For example, Non-Patent Document 1 introduces a communication method called LoRa (registered trademark) as a kind of LPWA. In this communication system, the terminal side can set a spread factor (hereinafter referred to as “SF”), and long distance communication is possible by increasing the spreading factor.

Ministry of Internal Affairs and Communications Information and Communication Council Information and Communication Technology Subcommittee Land Radio Communication Committee, “Information and Communication Council Information and Communication Technology Subcommittee Report Advisory No. 2009“ Technical Conditions Necessary for Advancement of Low-Power Wireless Systems ” "Technical conditions for advanced 920MHz band low-power wireless system" "[online], [Search July 7, 2017], Internet <URL: http://www.soumu.go.jp/main_content/ 000477030.pdf>

  Non-Patent Document 1 describes a communication class assuming battery drive for a small terminal that transmits sensor data and the like. However, a guideline on how such a terminal, particularly a terminal having a power storage element, should determine the SF value has not been disclosed.

  The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a wireless terminal, a control method, and a control program that can effectively use the change of the SF value.

  A wireless terminal according to the present invention includes a power generation element, a storage element charged by the power generation element, a voltage detection circuit that detects an output voltage of the storage element, and an SF value selection unit that selects an SF value based on the output voltage. A sensor that detects a physical phenomenon, and a transmission module that operates by an output voltage and transmits data based on the detection result of the sensor by a spread spectrum method using an SF value.

  In the wireless terminal according to the present invention, when the output voltage is less than the predetermined voltage, the SF value selection unit preferably selects a smaller SF value than when the output voltage is equal to or higher than the predetermined voltage.

  In the wireless terminal according to the present invention, it is preferable that the SF value selection unit further selects the SF value based on the data size.

  The radio terminal according to the present invention preferably further includes a data determination unit that determines data to be transmitted based on the SF value and the output voltage, and the transmission module transmits the data determined by the data determination unit. .

  The wireless terminal according to the present invention further includes a storage unit that stores data based on the detection result of the sensor, and when the SF value selection unit cannot select an SF value that can be applied to data transmission, It is preferable that the data is stored until the next transmission, the SF value selection unit newly selects an SF value, and the transmission module applies the newly selected SF value to transmit the stored data.

  Moreover, in the radio | wireless terminal which concerns on this invention, when an SF value selection part selects SF values other than predetermined | prescribed SF value, it is preferable to further have a display part which displays that.

  A method of controlling a wireless terminal having a power generation element, a power storage element, and a sensor for detecting a physical phenomenon according to the present invention is characterized in that the power storage element is charged by the power generation element, the output voltage of the power storage element is detected, and SF is Select a value, operate with the output voltage, and apply the SF value to transmit data based on the sensor detection result in a spread spectrum manner.

  A control program for a wireless terminal having a power generation element, a power storage element, and a sensor that detects a physical phenomenon according to the present invention charges the power storage element with the power generation element, detects an output voltage of the power storage element, and performs SF based on the output voltage. The wireless terminal is made to select a value, operate with the output voltage, and apply the SF value to transmit data based on the detection result of the sensor in a spread spectrum method.

  Since the radio | wireless terminal which concerns on this invention can select SF value according to the output voltage of an electrical storage element, it became possible to utilize optimal SF value according to the electric energy which can be used.

6 is a diagram illustrating an example of a processing outline in a wireless terminal 2. FIG. 1 is a diagram illustrating an example of a schematic configuration of a wireless communication system 1. FIG. 2 is a diagram illustrating an example of an external view of a wireless terminal 2. FIG. It is a figure which shows an example of the external view of the automatic door 6 which installs the radio | wireless terminal 2. FIG. 2 is an example of a schematic configuration diagram of a wireless terminal 2. FIG. It is a table | surface which shows an example of the relationship between the output voltage of the electrical storage element 23, the transmission data size, and SF value which the memory | storage part 272 memorize | stores. It is a figure which shows an example of the data memorize | stored in the buffer 272a. It is a state transition diagram which shows the transition of the electric supply state of the radio | wireless terminal 2. FIG. 5 is a flowchart illustrating an example of data storage processing by a control unit 273. 5 is a flowchart illustrating an example of data transmission processing by a control unit 273. 6 is a graph showing an example of the operating status of the wireless terminal 2. It is a flowchart which shows an example of the method of determining the data transmitted based on SF value and an output voltage in a 1st modification.

  Hereinafter, various embodiments of the present invention will be described with reference to the drawings. However, it should be noted that the technical scope of the present invention is not limited to these embodiments, and extends to the invention described in the claims and equivalents thereof.

<First Embodiment>
FIG. 1 is a diagram illustrating an example of processing outline in the wireless terminal 2.

  The wireless terminal 2 can be used, for example, as an open / close sensor having a communication function in an IoT system that detects open / close of a door and uses open / close information in a remote place. In the following, an outline of processing until the SF value is selected based on the voltage of electricity generated and stored by the wireless terminal 2 and data is transmitted by the spread spectrum method by applying the selected SF value will be described.

  The SF (spreading rate) is a ratio of a spreading code rate (chip rate) to a transmission data rate (bit rate) when wireless communication is performed by a spread spectrum method. In the LoRa standard, the SF value can take 6 levels from 7 to 12, and the larger the value, the higher the noise resistance of communication and the longer the communicable distance. However, the larger the SF value, the longer it takes to transmit data of the same size, so the power consumption of the wireless terminal 2 increases.

  The wireless terminal 2 receives sunlight to generate power and stores the generated electricity (S1). Next, the wireless terminal 2 detects the open / closed state of the door on which it is installed, and generates data based on the detection result (S2). Next, the wireless terminal 2 measures the voltage of the stored electricity (S3), and selects the SF value corresponding to the measured voltage (S4). Next, the wireless terminal 2 applies the selected SF value and transmits the data by the spread spectrum method (S5).

  As described above, the wireless terminal 2 according to the present invention can measure the voltage of the stored electricity and apply the SF value corresponding to the voltage to transmit the data by the spread spectrum method. For this reason, the wireless terminal 2 can select the SF value according to the stored voltage of electricity, that is, the amount of electricity that can be used by the wireless terminal 2.

  FIG. 2 is a diagram illustrating an example of a schematic configuration of the wireless communication system 1.

  The wireless communication system 1 includes wireless terminals 2, 2 ′, 2 ″, a gateway 3, a network server 4, and application servers 5, 5 ′. The wireless terminals 2, 2 ′ and the gateway 3 are spread spectrum systems. The gateway 3, the network server 4, and the application server 5 are connected via a communication network such as the Internet, etc. As an example, the wireless communication system 1 conforms to the LoRaWAN standard, and the wireless terminals 2, 2 are connected. It is assumed that the modulation method of communication between “2” and the gateway 3 conforms to the LoRa standard.

  The wireless terminals 2, 2 ′, 2 ″ transmit data to the gateway 3. The gateway 3 transmits LoRa format data used for communication between the wireless terminal 2 and the gateway 3 between the gateway 3 and the network server 4. The data is converted into an IP data format used for communication between the data and transmitted to the network server 4. One gateway 3 can receive data from a plurality of wireless terminals 2, 2 ', 2 ".

  The network server 4 transfers the data transmitted from the wireless terminal 2 to the gateway 3 to each application server 5, 5 '. The application servers 5 and 5 ′ execute processing using data transmitted from the network server 4, that is, data of the wireless terminal 2 and the like.

  3A is a diagram illustrating an example of an external view of the wireless terminal 2, and FIG. 3B is a diagram illustrating an example of an external view of the automatic door 6 on which the wireless terminal 2 is installed.

  An example of the wireless terminal 2 is a wireless terminal having a magnetic sensor that detects opening and closing of a door. A power generating element 21 and a display device 28 are disposed on the surface of the wireless terminal 2. The power generation element 21 is an element that generates power by environmental power generation, and is, for example, a solar cell for photovoltaic power generation, a piezoelectric element for vibration power generation, a thermoelectric conversion element for temperature difference power generation, or the like. The display device 28 is a device for displaying the operation status of the wireless terminal 2, and is, for example, an LED (Light Emitting Diode), a small light bulb, or the like. In the present embodiment, an example in which the power generation element 21 is a solar cell and the display device 28 is an LED is shown.

  As shown in FIG. 3b, the wireless terminal 2 is disposed at a fixed portion of the automatic door 6, and the magnet 7 is disposed at a position near the wireless terminal 2 when the automatic door 6 is open in a movable portion of the automatic door 6. Is done. When the automatic door 6 is opened, the magnet 7 approaches the wireless terminal 2 so that the wireless terminal 2 detects that the magnetic flux has exceeded a predetermined amount and determines that the automatic door 6 has been opened. When the automatic door 6 is closed, the magnet 7 moves away from the wireless terminal 2, so that the wireless terminal 2 detects that the magnetic flux has become less than a predetermined amount, and determines that the automatic door 6 has been closed.

  FIG. 4 is an example of a schematic configuration diagram of the wireless terminal 2.

  The wireless terminal 2 detects a surrounding physical phenomenon and transmits the detected physical phenomenon as data to the gateway 3. For this purpose, the wireless terminal 2 includes a power generation element 21, a power supply IC (Integrated Circuit) 22, a power storage element 23, a first voltage detection circuit 24, a sensor 25, a second voltage detection circuit 26, a microcomputer 27, The display device 28 and the transmission module 29 are provided.

  The power supply IC 22 is a converter that boosts the electricity generated by the power generation element 21 and supplies the boosted electricity to the power storage element 23, and is a DC-DC converter in the present embodiment. The power storage element 23 is a capacitor that stores the boosted electricity by the power supply IC 23 and supplies the stored electricity to a load circuit such as the microcomputer 27 and the transmission module 29. A secondary battery can be used instead of the capacitor.

  The first voltage detection circuit 24 and the second voltage detection circuit 26 are circuits that detect the output voltage of the storage element 23. The first voltage detection circuit 24 is connected to the storage element 23 and a load circuit (sensor 25, second voltage detection circuit 26, microcomputer 27, display device 28, and transmission module 29) that operates according to the output voltage of the storage element 23. A switch 24a for switching between. In an example of this embodiment, the minimum voltage Vmin at which the load circuit of the wireless terminal 2 can operate is 3.0V, and the maximum voltage Vmax is 3.6V. The minimum voltage Vmin and the maximum voltage Vmax can be set to other values.

  The sensor 25 is a device that detects a surrounding physical phenomenon and converts the detected physical phenomenon into an electrical signal. In an example of this embodiment, the sensor 25 is a magnetic sensor for detecting opening / closing of the automatic door 6. The sensor 25 may be any device as long as it can detect a target physical phenomenon, such as a magnetic sensor, an optical sensor, a temperature sensor, a current sensor, an ultrasonic sensor, an acceleration / vibration sensor, or a contact sensor.

  The microcomputer 27 comprehensively controls the overall operation of the wireless terminal 2 and is, for example, a microcontroller. For this purpose, the microcomputer 27 includes an input / output unit 271, a storage unit 272, and a control unit 273.

  The input / output unit 271 includes GPIO (General Purpose Input / Output), UART (Universal Asynchronous Receiver / Transmitter), and the like. The input / output unit 271 inputs electric signals from the sensor 25 and the second voltage detection circuit 26 to the control unit 273, and outputs data supplied from the control unit 273 to the transmission module 29 and the like.

  The storage unit 272 includes a semiconductor memory such as a ROM (Read Only Memory) and a RAM (Random Access Memory). The storage unit 272 stores a driver program, an operating system program, an application program, data, and the like used for processing by the control unit 273.

  For example, the storage unit 272 stores a communication device driver program that controls the transmission module 29 as a driver program. In addition, the storage unit 272 stores a connection control program using a communication method such as LoRa as an operating system program. The storage unit 272 includes a buffer 272a (not shown) for storing data based on the detection result of the sensor 25.

  The control unit 273 includes one or a plurality of processors and their peripheral circuits. The control unit 273 controls the overall operation of the wireless terminal 2 and is, for example, a CPU (Central Processing Unit). The control unit 273 controls the operation of the transmission module 29 and the like so that various processes of the wireless terminal 2 are executed in an appropriate procedure according to a program or the like stored in the storage unit 272. The control unit 273 executes processing based on programs (driver program, operating system program, application program, etc.) stored in the storage unit 272. Further, the control unit 273 may be able to execute a plurality of programs (such as application programs) in parallel.

  The control unit 273 includes a data generation unit 274, a voltage value calculation unit 275, an SF value selection unit 276, a display unit 277, a data determination unit 278, and the like. Each of these units included in the control unit 273 is a functional module implemented by a program executed on a processor included in the control unit 273. Alternatively, these units included in the control unit 273 may be mounted on the wireless terminal 2 as independent integrated circuits, microprocessors, or firmware.

  The transmission module 29 has a wireless communication interface circuit such as LoRa. The transmission module 29 applies the SF value or the like set by the control unit 273, and transmits data to the gateway 3 or the like by spectrum communication wireless communication. In addition to transmission, the transmission module 29 may be a transmission / reception module that can receive data transmitted from the gateway 3 or the like and supply the data to the control unit 273.

  FIG. 5 is a table showing an example of the relationship among the output voltage of the storage element 23, the transmission data size, and the SF value stored in the storage unit 272.

  In the storage unit 272, Vdd that is the output voltage of the storage element 23, the size of data based on the detection result of the sensor 25 transmitted by the transmission module 29, and the SF value that the transmission module 29 applies when transmitting data are mutually related. Is stored in association with. The data size indicates the size of the payload in the frame of the MAC layer of the LoRaWAN standard. When the data transmitted by the wireless terminal 2 has a fixed length, a correspondence table between Vdd and SF values obtained by deleting the data size column from the table of FIG. 5 can be used.

  The top row of (1) in FIG. 5 indicates that when the output voltage Vdd is greater than 3.5V and less than or equal to 3.6V and the data size is less than 10 bytes, SF value = 12 is selected. Show. The second row from the top of (1) in FIG. 5 selects SF value = 11 if the data size is 10 bytes or more and less than 25 bytes when Vdd is greater than 3.4V and less than 3.5V. Indicates to do.

  In the last line of (6) in FIG. 5, there is a line in which the SF value “none” is described. This indicates that when the output voltage Vdd is as low as 3.1 V or less, the output voltage Vdd falls below the minimum voltage Vmin (3.0 V) during the data transmission even if the SF value is set to 7 as the minimum. When the output voltage Vdd falls below the minimum voltage Vmin, the switch 24a is switched to the OFF state, and the supply of electricity to the transmission module 29 and the like is stopped, so that the data transmission is stopped. In this case, since there is no SF value applicable to data transmission, the column of SF value is described as “none”.

  FIG. 6 is a diagram illustrating an example of data stored in the buffer 272a.

  The buffer 272a temporarily stores data based on the detection result of the sensor 25. The buffer 272a stores information on “open” or “closed”, which is the open / close state of the automatic door 6, and the elapsed time (seconds) from when the most recent open / close state was detected. The example of FIG. 6 indicates that the oldest data has an order of “1”, the state is “open”, and the time interval from the most recent closed state detection is 10 seconds. The second oldest data has an order of “2”, and indicates that the time interval from detection of data having a state of “closed” and an order of “1” is 30 seconds.

  The leftmost column ("Order" "1" ... "4" column) and the top row ("Order", "State", and "Time interval" rows) in the table of FIG. As described above, it is not stored in the buffer 272a. The maximum number of data that can be stored in the buffer 272a is not limited to four, and may be one or more.

  FIG. 7 is a state transition diagram showing the transition of the electricity supply state of the wireless terminal 2.

  First, since the storage element 23 is not stored, the output voltage Vdd is lower than the maximum voltage Vmax at which the load circuit can operate. At this time, the wireless terminal 2 is in an electric supply stop state (S101). When the storage element 23 is charged by the power generation element 21 and the output voltage Vdd increases until it becomes equal to the maximum voltage Vmax, the first voltage detection circuit 24 switches the switch 24a to the ON state. When the switch 24a is switched to the ON state, the electricity stored in the storage element 23 is supplied to the load circuit, and the wireless terminal 2 enters the electricity supply state (S102).

  In the electricity supply state (S102), when the load circuit uses electricity and the output voltage Vdd of the storage element 23 decreases to the minimum voltage Vmin at which the load circuit can operate, the first voltage detection circuit 24 turns off the switch 24a. Switch to state. When the switch 24a is switched to the OFF state, the electricity stored in the storage element 23 is not supplied to the load circuit, and the wireless terminal 2 enters the electricity supply stop state (S101). As described above, the wireless terminal 2 takes either the electric supply stop state (S101) or the electric supply state (S102) according to the change in the value of the output voltage Vdd of the power storage element 23.

  FIG. 8 is a flowchart illustrating an example of data storage processing by the control unit 273. This process is executed when the wireless terminal 2 is in the electric supply state (S102), and is not executed when the electric supply stop state (S101). Note that the operations described below are executed in cooperation with each element of the wireless terminal 2 by the control unit 273 mainly including a CPU or the like based on a program stored in the storage unit 272 in advance.

  First, the sensor 25 detects a change from the closed state to the open state of the automatic door 6 or from the open state to the closed state, and outputs an electrical signal (detection signal) corresponding to the change to the microcomputer 27. The control unit 273 is in a state of waiting for detection of the electrical signal output from the sensor 25, and when detecting the electrical signal (S201), the data generation unit 274 generates data corresponding to the detected electrical signal (S202). . Next, the data generation unit 274 stores the generated data in the buffer 272a of the storage unit 272 (S203). Next, the control unit 273 returns to a state of waiting for detection of an electric signal output from the sensor 25. The control unit 273 executes this process every time an electrical signal output from the sensor 25 is detected.

  If the buffer 272a is full of data in S203, the data generation unit 274 may delete the oldest data and store new data in the buffer 272a, or delete new data without storing it in the buffer 272a. May be.

  FIG. 9 is a flowchart illustrating an example of data transmission processing by the control unit 273. This process is executed when the wireless terminal 2 is in the electric supply state (S102), and is not executed when the electric supply stop state (S101). This process is preferably executed in parallel with the data storage process shown in FIG. Note that the operations described below are executed in cooperation with each element of the wireless terminal 2 by the control unit 273 mainly including a CPU or the like based on a program stored in the storage unit 272 in advance.

  First, the control unit 273 reads one oldest data from the buffer 272a (S301). When there is no data in the buffer 272a, the control unit 273 waits until new data is stored in the buffer 272a, and reads out after the data is stored.

  Next, the voltage value calculation unit 275 calculates the output voltage Vdd of the storage element 23 from the electrical signal (voltage signal) output from the second voltage detection circuit 26 (S302). Next, the SF value selection unit 276 uses the correspondence table shown in FIG. 5 to select the SF value based on the size of the data read from the buffer 272a and the output voltage Vdd calculated by the voltage value calculation unit 275. (S303). Hereinafter, the SF value selected in S303 may be referred to as SF1. When the data size is a fixed length and the correspondence table between the output voltage Vdd and the SF value is used as the correspondence table, the SF value selection unit 276 calculates the voltage value calculation unit 275 without referring to the data size. The SF value can be selected based on the output voltage Vdd.

  For example, when the output voltage Vdd of the storage element 23 is less than a predetermined voltage, the SF value selection unit 276 can select a smaller SF value than when the output voltage Vdd is greater than or equal to the predetermined voltage. As a result, when the output voltage Vdd is low, the wireless terminal 2 can communicate by applying a small SF value to reduce the amount of electricity used. In addition, the SF value selection unit 276 can select the largest SF value among the SF values applicable to the transmission of data of that size when the output voltage is Vdd in order to improve the noise resistance of the transmission. . Further, the SF value selection unit 276 places importance on low power consumption, and can select the smallest SF value among the SF values applicable to transmission of data of that size when the output voltage is Vdd.

  Next, when the SF value selection unit 276 can select an SF value applicable to transmission (Y in S304), the control unit 273 sends the selected SF value and the data stored in the buffer 272a to the transmission module 29. Then, the transmission module 29 is controlled to transmit data. The case where the SF value selection unit 276 can select an SF applicable to transmission corresponds to a case where the SF value column in the table of FIG. 5 corresponds to a case other than “None”.

  Next, the transmission module 29 applies the input SF value and transmits the input data to the gateway 3 (S305). Next, after the data transmission is successful, the control unit 273 deletes the transmitted data from the buffer 272a (S306).

  Next, the display unit 277 determines whether or not SF1 selected by the SF value selection unit 276 is a predetermined SF value (S307). The predetermined SF value is 12, for example, when importance is attached to noise resistance and the length of communication distance. The predetermined SF value may be a value having a width such as 10-12. Also, a value instructed from the network server 4 may be used.

  When SF1 is a predetermined SF value, the display unit 277 controls the display device 28 to display that the data transmission state is normal, and the display device 28 performs the display (S308). When SF1 is not a predetermined SF value, the display unit 277 controls the display device 28 to display that the data transmission state is abnormal, and the display device 28 performs the display (S309). For example, when the predetermined SF value is set to 12 and SF1 is 11 or less, the display device 28 displays that the data transmission state is abnormal, whereby the user of the wireless terminal 2 can It can be known that the amount is insufficient or the amount of data transmission is larger than expected.

  When the SF value selection unit 276 cannot select an SF value applicable to transmission (N in S304), the control unit 273 does not control the transmission module 29 to transmit data. Next, the display unit 277 controls the display device 28 to display that the transmission is impossible, and the display device 28 performs the display (S310). Next, after waiting for a predetermined time (S311), the control unit 273 performs the processing from S301 onward. As a result, since the data that has not been transmitted (the data read in S301 one time before) is stored in the buffer 272a, the SF value selection unit 276 enters the state after the output voltage Vdd of the storage element 23 increases. A corresponding SF value can be newly selected. The transmission module 29 can transmit data that has not been transmitted (data stored in the buffer 272a) by applying a newly selected SF value, that is, an SF value corresponding to the latest output voltage Vdd.

  If the switch 24a is switched from the ON state to the OFF state while the transmission module 29 is transmitting data in S305, the supply of electricity from the power storage element 23 to the microcomputer 27, the transmission module 29, etc. is stopped and the transmission is performed. Module 29 interrupts transmission. As a result, the gateway 3 fails to receive data. In order to cope with this, a non-volatile memory is used as the buffer 272a, and the control unit 273 performs control to retransmit the data transmitted when the switch 24a is switched to the ON state and then to the OFF state. You may go.

  Specifically, after the switch 24a is switched to the ON state again, the control unit 273 executes the data transmission process shown in FIG. 9 from S301. Thereby, data transmission leakage can be prevented. Further, since the SF value is selected in S303 based on the output voltage Vdd newly calculated in S302, data can be transmitted by applying the SF value suitable for the latest situation.

  FIG. 10 is a graph showing an example of the operation status of the wireless terminal 2.

  FIG. 10 shows the relationship between the ambient brightness that affects the amount of power generated by the power generation element 21 that is a solar cell, the SF value at the time of data transmission, the state of the switch 24a, and the output voltage Vdd of the power storage element 23. The horizontal axis of the top graph in FIG. 10 indicates time, and the vertical axis indicates the output voltage Vdd of the storage element 23. The time required for charging the storage element 23 is several hours to several days, and the time required for data transmission by the transmission module 29 is about several tens ms to several seconds. However, in order to make it easy to grasp the tendency of the change in the output voltage Vdd. The scale of the horizontal axis is appropriately changed and described. Hereinafter, main operations of the wireless terminal 2 will be described with reference to this graph.

  Initially, the graph of the time t1-t3 shows the example at the time of the radio | wireless terminal 2 starting operation | movement and transmitting data. Until the time t1, the place where the wireless terminal 2 is arranged is dark, and thus electricity is not stored in the power storage element 23. Since the place where the wireless terminal 2 is arranged becomes bright at time t1, the power generation element 21 starts power generation. Since the generated electricity was stored in the storage element 23, the output voltage Vdd of the storage element 23 increased.

  When the output voltage Vdd increases to Vmax at time t2, the first voltage detection circuit 24 that detects this increases the switch 24a from the OFF state to the ON state. By switching the switch 24a to the ON state, electricity is supplied from the power storage element 23 to the sensor 25, the microcomputer 27, the transmission module 29, and the like, and the operations of the flowcharts shown in FIGS. 8 and 9 are started.

  Almost simultaneously with the start of the operation of the microcomputer 27 or the like at time t2, the sensor 25 detects a change in the open / close state of the automatic door 6, and the data generation unit 274 generates data corresponding to the change in the state and stores it in the buffer 272a. (S201 to S203 in FIG. 8). Next, the SF value selection unit 276 selects the SF value = 12 having high noise resistance because the output voltage Vdd is the maximum voltage Vmax and sufficient electricity is stored in the storage element 23 to transmit data. (Y in S302 to S304 in FIG. 9). Next, the transmission module 29 applied the SF value = 12, and transmitted data (S305 in FIG. 9). Since the transmission module 29 used electricity for data transmission, the output voltage Vdd decreased from time t2 to time t3.

  Next, the graphs at times t3 to t5 show an example in which the wireless terminal 2 detects a change in the open / close state of the automatic door 6 and transmits data before the output voltage Vdd reaches the maximum value Vmax. When the transmission module 29 finishes data transmission at time t3, the control unit 273 enters a data reception waiting state based on the detection result of the sensor 25 (S301 in FIG. 9). In this state, the electricity used by the circuits such as the sensor 25, the microcomputer 27, and the transmission module 29 is less than the electricity supplied from the power generation element 21 to the storage element 23. For this reason, from time t3 to t4, electricity was stored in the storage element 23, and the output voltage Vdd increased.

  When the sensor 25 newly detects a change in the open / closed state of the automatic door 6 at time t4, the data generation unit 274 generates data based on the detection result of the sensor 25 as in the time t2 to t3 (FIG. 8). S201 to S203). Since the output voltage Vdd did not reach the maximum voltage Vmax, the SF value selection unit 276 selected 8 smaller than 12 as the SF value (S303 in FIG. 9). As a result, the data transmission process is the same as the process at times t2 to t3, except that the transmission time (t4 to t5) is shorter than the previous transmission time (t2 to t3).

  Next, the graphs at times t5 to t7 show an example when the wireless terminal 2 detects a change in the open / close state of the automatic door 6 immediately after the output voltage Vdd reaches the maximum value Vmax and transmits data. In the process between time t5 and time t7, the output voltage of the power storage element 23 at time t5 is Vmax, and as a result, the SF value selection unit 276 selects SF value = 12. It is the same as the process between.

  Next, the graph of time t7-t10 shows the example at the time of the quantity of the electricity which the electric power generation element 21 generate | occur | produces changing with the surrounding brightness changes. Data transmission was completed at time t7, and the location where the wireless terminal 2 was placed changed from a bright state to a dim state. Due to this change, the electricity used by the load circuit such as the sensor 25, the microcomputer 27, the transmission module 29, and the like to the time t8 is more than the electricity supplied from the power generation element 21 to the storage element 23, and as a result, the output voltage Vdd decreases. did. Thereafter, the power generation amount of the power generation element 21 and the output voltage Vdd of the power storage element 23 increased as the place where the wireless terminal 2 was placed changed to a bright state at time t8.

  Next, the graph after time t10 shows an example when the output voltage Vdd reaches the minimum value Vmin during the transmission of data by the wireless terminal 2. From time t11, the transmission module 29 applied the SF value = 10 and transmitted data, but used more electricity than expected when the SF value selection unit 276 selected the SF value. By using this electricity, the output voltage Vdd dropped to Vmin during the transmission of data by the transmission module 29 at time t12. The first voltage detection circuit 24 that has detected the decrease in the output voltage Vdd controlled the switch 24a from the ON state to the OFF state. By controlling the switch 24a to be in the OFF state, the transmission module 29 stops transmitting data until the output voltage Vdd reaches Vmax after time t12.

  As described in detail above, by operating according to the state transition diagram of FIG. 7 and the flowcharts shown in FIGS. 8 and 9, the wireless terminal 2 selects the SF value according to the output voltage Vdd of the storage element 23. It is possible to change the noise resistance of communication according to the amount of power that can be used.

<First Modification>
Hereinafter, a first modification will be described with reference to FIG. In the first modification, data to be transmitted is determined based on the SF value and the output voltage.

  In the first embodiment, the wireless terminal 2 transmits one data at a time. However, in the first modification, the wireless terminal 2 can transmit two or more data at a time. The configuration and other processing flow of the wireless terminal 2 in the first modified example are the same as those in the first embodiment except that the processing of S401 to S403 is executed between Y and S305 of S304 in FIG. . Description of the same contents as those in the flowchart of FIG. 9 is omitted.

  First, when the result of S304 corresponds to Y, the data determination unit 278 checks whether or not the next data is stored in the buffer 272a (S401). If the next data is not stored in the buffer 272a (N in S401), the process proceeds to S305.

  When the next data is stored in the buffer 272a (Y in S401), the data determination unit 278 sets the maximum data size that can be transmitted based on the SF value SF1 selected in S303 and the output voltage Vdd. Determine (S402). Next, the data determination unit 278 selects the data to be transmitted from the data stored in the buffer 272a within the range equal to or smaller than the data size determined in S402, in the order of storage in the buffer 272a, and determines the transmission target. (S403). In S403, the data determination unit 278 may select the maximum number of data within a range that fits in the maximum data size, or may select a smaller number of data than the maximum number. After the data determination unit 278 performs the process of S403, the process proceeds to the process of S305.

  By executing the processing of S401 to S403, the wireless terminal 2 can transmit a plurality of data at a time by applying the same SF value as the SF value used when transmitting one data. Compared with the case where transmission is performed in divided times, overhead such as a frame header can be reduced. As a result, it is possible to reduce the time for transmitting data of the same size, and it is possible to reduce the power consumption of the wireless terminal 2.

  In the first modification, when the data determination unit 278 determines the data to be transmitted based on the SF value and the output voltage, the data is stored in the buffer 272a in the order in which the data is stored (that is, FIFO (First In First Out)). To determine the data to be transmitted. The data determination method is not limited to this. For example, when a plurality of data is stored in the buffer 272a, the data determination unit 278 selects data to be transmitted with respect to data stored at intervals of one or more predetermined numbers. You may decide. The data determination unit 278 may determine data to be transmitted in the reverse order of the order in which the data is stored in the buffer 272a. The control unit 273 may delete the data excluded from the transmission target according to these rules from the buffer 272a.

  In the first modification, the number of data that can be transmitted by applying the same SF value as the SF value in the case of one data is used as the transmission data. The data determination method is not limited to this. For example, the data rate may be increased by reducing the SF value, and more data may be used as transmission data.

  The present invention is not limited to this embodiment. For example, in the present embodiment, the wireless communication system 1 conforms to the LoRaWAN standard, and the modulation scheme of communication between the wireless terminal 2 and the gateway 3 conforms to the LoRa standard, but the wireless terminal 2 has an SF value. Any other communication method may be used as long as it can be changed.

  It should be understood by those skilled in the art that various changes, substitutions and modifications can be made thereto without departing from the spirit and scope of the present invention.

2 wireless terminal 21 power generation element 23 power storage element 25 sensor 26 second voltage detection circuit (voltage detection circuit)
29 Transmission Module 272 Storage Unit 276 SF Value Selection Unit 277 Display Unit 278 Data Determination Unit

Claims (8)

A power generation element;
A power storage element charged by the power generation element;
A voltage detection circuit for detecting an output voltage of the storage element;
An SF value selection unit that selects an SF (diffusion rate) value based on the output voltage;
A sensor for detecting a physical phenomenon;
A transmission module that operates according to the output voltage and applies the SF value to transmit data based on the detection result of the sensor in a spread spectrum manner;
A wireless terminal characterized by comprising:   The radio terminal according to claim 1, wherein when the output voltage is less than a predetermined voltage, the SF value selection unit selects a smaller SF value than when the output voltage is equal to or higher than the predetermined voltage.   The radio terminal according to claim 1, wherein the SF value selection unit further selects the SF value based on a size of the data. A data determination unit for determining data to be transmitted based on the SF value and the output voltage;
The wireless terminal according to claim 1, wherein the transmission module transmits data determined by the data determination unit. A storage unit for storing data based on the detection result of the sensor;
When the SF value selection unit cannot select an SF value applicable to the transmission of the data,
The storage unit stores the data until the next transmission,
The SF value selection unit newly selects an SF value,
The wireless terminal according to any one of claims 1 to 4, wherein the transmission module transmits the stored data by applying a newly selected SF value.   The radio | wireless terminal as described in any one of Claims 1-5 which further has a display part which displays that when the said SF value selection part selects SF value other than predetermined | prescribed SF value. A method of controlling a wireless terminal having a power generation element, a storage element, and a sensor that detects a physical phenomenon,
Charging the power storage element with the power generation element;
Detecting the output voltage of the storage element;
Select SF (diffusion rate) value based on the output voltage,
Operating with the output voltage, and applying the SF value to transmit data based on the detection result of the sensor in a spread spectrum manner;
A control method characterized by that. A control program for a wireless terminal having a power generation element, a storage element, and a sensor for detecting a physical phenomenon,
Charging the power storage element with the power generation element;
Detecting the output voltage of the storage element;
Select SF (diffusion rate) value based on the output voltage,
Operating with the output voltage, and applying the SF value to transmit data based on the detection result of the sensor in a spread spectrum manner;
A control program for causing the wireless terminal to execute the above.