Battery-free wireless sensor device

Abstract

The invention relates to the technical field of energy collection technology and low-power-consumption electronic products, and discloses a battery-free wireless sensor device which comprises a solar power supply circuit, a thermoelectric generator (TEG) circuit, a 3.3 V power supply circuit and a single-chip microcomputer peripheral circuit. The 3.3 V power supply circuit comprises a multi-path power supply multiplexer with a priority function and a 3.3 V synchronous boost converter, and the single-chip microcomputer peripheral circuit comprises a single-chip microcomputer radio frequency module, a sensor and a USB interface circuit. Limitation of a lithium battery can be overcome, permanent self-power supply can be achieved, and due to the fact that the lithium battery is not needed, the technology can reduce maintenance cost, enable equipment to be more reliable and reliable, can achieve long-time self-power supply, is suitable for the environment with permanent temperature gradient and light transmission and internally comprises a solar power supply circuit and a thermoelectric generator (TEG) circuit. And the two energy channels are complementary, so that the overall reliability and availability can be improved.

Description

Technical Field

[0001] The invention relates to energy collection technology and the technical field of low-power electronic products, in particular to a battery-free wireless sensor device. Background Art

[0002] Wireless sensor technology is a technology that uses wireless transmission to collect and transmit data from physical or environmental sensors. These technologies are widely used in various fields, including environmental monitoring, health monitoring, smart homes, industrial automation and agriculture.

[0003] Wireless sensor networks are an important part of wireless sensor technology. They consist of a large number of distributed sensors that can sense, process and transmit information through wireless channels. They are mainly composed of wireless sensor nodes, which are usually powered by batteries with limited capacity, but the battery lasts for a short time, and lithium batteries are highly active, flammable and explosive, and have high maintenance costs. In order to overcome these limitations and achieve permanent self-power supply, a dual-source complementary energy acquisition technology using thermoelectric generators, solar power generation and supercapacitor energy storage is proposed for greenhouse environments. Summary of the invention

[0004] The present invention provides a battery-free wireless sensor device to solve the problems raised by the above background technology.

[0005] The present invention provides the following technical solution: a battery-free wireless sensor device, comprising a solar power supply circuit, a thermoelectric generator (TEG) circuit, a 3.3V power supply circuit, and a single-chip peripheral circuit, characterized in that: the 3.3V power supply circuit comprises a multi-channel power multiplexer with a priority function and a 3.3V synchronous boost converter, and the single-chip peripheral circuit comprises a single-chip radio frequency module and a sensor and a USB interface circuit;

[0006] The solar power supply circuit includes a P1 element and a capacitor C4, wherein the P1 element is a solar power supply interface, wherein the P1 element includes P1-1 and P1-2, wherein the P1-2 pin is connected to the positive pole of the solar 12V output, and the P1-1 pin is connected to the negative pole of the solar 12V output, wherein the two pins of the capacitor C4 are respectively connected to the P1-1 pin and the P1-2 pin and are simultaneously connected to the chip BQ25173DSG, wherein the BQ25173DSG includes BQ25173DSG-1, BQ25173DSG-2, BQ25173DSG-3, BQ25173DSG-4, BQ25173DSG-5 and BQ25173DSG-6, wherein the BQ25173DSG-1 pin is a DC power input port, the BQ25173DSG-2 pin is connected to a resistor R6 (6KΩ), and the BQ25173DSG-2 pin is a programmable charging current.

[0007] As a preferred technical solution of the present invention, the BQ25173DSG-3 pin is a charging enable pin with a low level being effective, and the BQ25173DSG-3 is connected to the RAK3172-16 pin of the single-chip wireless communication module, and the single-chip microcomputer can control whether the supercapacitor is charged or not according to actual needs. The BQ25173DSG-4 pin is GND, and the BQ25173DSG-5 pin is an output pin. A high level represents charging, and a low level represents that the output voltage has reached 98% VREG, VREG is a programmable adjustable voltage, i.e., the supercapacitor charging voltage. The BQ25173DSG-5 pin is connected to the RAK3172-25 pin of the single-chip microcomputer for monitoring the charging status, and the BQ25173DSG-5 pin is connected to a resistor R25 (10KΩ), and the other end of R25 is connected to the cathode of the light-emitting diode D1, and the anode of the light-emitting diode is connected to the VCC_5.6V network, and the light-emitting diode is used to indicate charging. When the supercapacitor charging value is 98% VREG, the BQ25173DSG-5 pin becomes low level, and the light-emitting diode D1 is on. If the charging voltage is less than 98% VREG, the light-emitting diode D1 is off. The R25 is a current limiting resistor. The BQ25173DSG-6 pin PG is connected to the resistor R5 (750Ω), and the other end is connected to the cathode of the light-emitting diode D3. The anode of D3 is connected to the VCC_5.6V network, which is used to indicate whether the input voltage is normal. When VIN>VIN_LOWV and VOUT+VSLEEPZ<VIN<VIN_OV, PG becomes low level and the light-emitting diode D3 is on. Otherwise, the light-emitting diode D3 is off, wherein VIN is the input voltage, VIN_LOWV is the input start charging voltage of 3.05V, VOUT is the output voltage, VSLEEPZ is the output sleep mode threshold of 95mV, and VIN_OV is the input overvoltage threshold of 18.1V.

[0008] As an optimal technical solution of the present invention, the thermoelectric generator (TEG) circuit includes a thermoelectric generator TEG and a power generation sheet. The thermoelectric generator TEG interface is a P2 port. The thermoelectric generator uses 2441G-7L31-10CX1. The positive electrode of the power generation sheet is connected to the negative electrode of the 3.0V Zener tube D2. The positive electrode of the power generation sheet is connected to the DC input pin of BQ25504RGTT-2. The positive electrode of the power generation sheet is connected to a 22uH inductor, and the other end of the inductor is connected to the BQ25504RGTT-16 pin (boost charging switch node inductor connection end). The positive electrode of the power generation sheet is connected to a 10uF capacitor to GND, which acts as an energy storage filter. The positive electrode of the power generation sheet is connected to a 10MΩ resistor R11, and R11 is connected in series with a 10MΩ resistor R12 to GND. The series node is connected to the BQ25504RGTT-3 pin (MPPT network sampling pin), and the maximum power point tracking technology (MPPT) is used.

[0009] As a preferred technical solution of the present invention, the BQ25504RGTT-7 pin is a resistor divider bias voltage, which is simultaneously connected to a 6.2MΩ resistor R13, a 4.32MΩ resistor R14, and a 2.67MΩ resistor R15. R13 is connected in series with a 3.74MΩ resistor R17 and finally connected to GND. The series node is connected to the BQ25504RGTT-6 pin (battery overvoltage threshold setting pin), R14 is connected in series with a 5.76MΩ resistor R18 and finally connected to GND, the middle series node is connected to the BQ25504RGTT-8 pin (battery undervoltage threshold setting pin), the R15 is connected in series with a 3.24MΩ resistor R19, the R19 is connected in series with a 4.12MΩ resistor R20 and finally connected to GND, and the R15 / R19 middle node is connected to the BQ25504RGTT-9 pin (battery OK hysteresis threshold ), the middle node of R19 / R20 is connected to the BQ25504RGTT-10 pin (battery OK threshold), the BQ25504RGTT-14 pin is connected in parallel with two 15F / 5.6V super capacitors, the positive pole of C13 / C14 is connected to the BQ25504RGTT-14 pin, and the negative end is connected to GND, the BQ25504RGTT-11 pin is the battery OK output pin connected to the microcontroller RAK31772-26 pin for indicating that the energy storage element voltage is OK, the BQ25504RGTT-15 pin is the power output end connected in parallel with two capacitors C10 (10uF) / C11 (0.1uF) and the other end of the capacitor is connected to GND, and a 0Ω resistor R10 is connected in series, and then a 10uF capacitor C12 is connected in parallel to GND, and the other end of R10 is connected to TPS2121RUXR.

[0010] As a preferred technical solution of the present invention, the 3.3V power supply circuit includes a multi-way power multiplexer with priority function and a 3.3V boost converter. The multi-way power multiplexer circuit portion includes a TPS212x device. The TPS212x is a dual-input, single-output power multiplexer (MUX). The device will automatically detect the input source, select and seamlessly switch between available inputs. Priority can be automatically assigned to the highest input voltage or manually assigned to a lower voltage input. If the solar power supply and temperature difference power generation circuits work properly, stable two-way power supply voltages VIN1=5.6V and VIN2=4.98V can be generated.

[0011] As a preferred technical solution of the present invention, the 3.3V boost converter is TPS610994YFFR with a fixed output of 3.3V, an input voltage range of 0.7V to 5.5V, and has undervoltage / overvoltage protection functions. When the input voltage is less than 3.3V, the converter works in a boost conversion mode and outputs to 3.3V. When the input voltage is close to or higher than the output voltage, TPS61099x has a buck mode and a pass-through operation function. In the drop mode, even if VIN>VOUT, the output voltage will be adjusted to the target value of 3.3V. The rated capacity of the selected solar power supply CR=8.925C, two parallel connections are 17.85C, and the conversion efficiency of TPS6100994 is 85%, so 3.3V / 100 The effective capacity of the mA power supply is CR_solar=2*0.85*CR=15.1725C. According to the formula Q=IT, the time it takes for the supercapacitor to be fully charged and continuously discharge 100mA is tsolar_3.3V=151.725s. If a thermoelectric generator (TEG) is selected, if VTEG>0.4V, VSC>2.2V, ITEG>0.1mA, the efficiency of BQ25504 is 80%, and the effective capacity of 3.3V / 100mA is CR_TEG=2*0.8*0.85*CR=12.138C. According to the formula Q=IT, the time it takes for the supercapacitor to be fully charged and continuously discharge 100mA is tTEG_3.3V=121.38s.

[0012] As a preferred technical solution of the present invention, the single-chip microcomputer peripheral circuit includes an STM32WLE5CC microcontroller, an AHT20 temperature and humidity sensor, a LoRaWAN gateway, and a TTN server. The STM32WLE5CC microcontroller performs data processing and LoRa communication. The AHT20 temperature and humidity sensor is connected to the RAK3172 module through an I2C interface to monitor the ambient temperature and humidity in real time and send the data to the LoRaWAN gateway. The LoRaWAN gateway forwards the data to the TTN server. The CH340E chip is connected to the RAK3172 serial port 2 and is connected to an external device through a miniUSB interface.

[0013] As a preferred technical solution of the present invention, the single-chip microcomputer starts to enter the peripheral configuration (serial port / GPIO / IIC / Sub-GHz configuration) when it is powered on, and then performs the LoRaWAN node configuration, including the device EUI (DevEUI), which is the unique identifier of each LoRaWAN node, the application EUI (AppEUI) LoRaWAN network identifier, and the application key (AppKey) used as a security key for the node to communicate with the network, and then enters the OTAA network access stage: the node sends a network access request, the network server responds, and the node will perform network access verification after receiving the server response. If the security parameters are configured in the node, the network access is completed. If the network access is successful, it enters the RTC sleep mode. This state is managed by the single-chip microcomputer ultra-low power consumption RTC timer. If 10 minutes are up, the single chip will be automatically woken up. The microcontroller reads the AHT20 sensor data through the IIC interface, and then uploads the data to the server. If the upload fails more than 10 times, the system is reset. If successful, it returns to the RTC sleep mode. If the preamble code is received to wake up, the Sub-GHz enters the receiving state to receive data, then processes the data and finally returns to the RTC sleep mode. If it is in sleep mode for 2 minutes, it starts to detect the 2-way voltage and whether the solar energy is full or not. If the BQ25173DSG-5 pin is low, it means that the charging voltage has reached 98% VREG. At this time, the microcontroller controls the BQ25173DSG-3 pin to output a high level to turn off solar charging; if the charging voltage does not reach 98% VREG, the BQ25173DSG-3 pin remains low and continues to charge, and then the two tasks are completed and return to sleep mode.

[0014] The present invention has the following beneficial effects:

[0015] 1. This battery-free wireless sensor device can overcome the limitations of lithium batteries and achieve permanent self-powering by using supercapacitor energy storage technology. Since no lithium batteries are required, this technology can reduce maintenance costs and make the equipment more reliable and dependable.

[0016] 2. This battery-free wireless sensor device can achieve long-term self-powering and is suitable for environments with permanent temperature gradients and light transmission. It includes a solar power supply circuit and a thermoelectric generator (TEG) circuit. The two energy channels complement each other to improve overall reliability and availability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the internal process structure of the present invention;

[0018] Figure 2 This is a schematic diagram of the solar power supply circuit structure of the present invention;

[0019] Figure 3 This is a schematic diagram of the circuit structure of the thermoelectric generator of the present invention;

[0020] Figure 4 It is a schematic diagram of the threshold voltage structure overview of the present invention;

[0021] Figure 5 This is a schematic diagram of the voltage structure of the BQ25504RGTT charging process of the present invention;

[0022] Figure 6 This is a schematic diagram of the structure of a 3.3V power supply circuit of the present invention;

[0023] Figure 7 This is a schematic diagram of the VCOMP priority source structure of the present invention;

[0024] Figure 8 This is a schematic diagram of the structure of the single-chip microcomputer peripheral circuit of the present invention;

[0025] Fig. 9 It is a schematic diagram of the structure of the single-chip computer program running process of the present invention;

[0026] Fig. 10A , 10B It is a schematic diagram of the overall circuit structure of the present invention. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] See also Figure 1-1 0, a battery-free wireless sensor device, comprising a solar power supply circuit, a thermoelectric generator (TEG) circuit, a 3.3V power supply circuit, and a single-chip peripheral circuit, characterized in that: the 3.3V power supply circuit comprises a multi-channel power multiplexer with a priority function and a 3.3V synchronous boost converter, and the single-chip peripheral circuit comprises a single-chip radio frequency module and a sensor and a USB interface circuit;

[0029] The solar power supply circuit includes a P1 element and a capacitor C4. The P1 element is a solar power supply interface. The P1 element includes P1-1 and P1-2. The P1-2 pin is connected to the positive pole of the solar 12V output, and the P1-1 pin is connected to the negative pole of the solar 12V output. The two pins of the capacitor C4 are respectively connected to the P1-1 pin and the P1-2 pin and are also connected to the chip BQ25173DSG. The BQ25173DSG includes BQ25173DSG-1, BQ25173DSG-2, BQ25173DSG-3, BQ25173DSG-4, BQ25173DSG-5, and BQ25173DSG-6. The BQ25173DSG-1 pin is a DC power input port, the BQ25173DSG-2 pin is connected to the resistor R6 (6KΩ), and the BQ25173DSG-2 pin is a programmable charging current.

[0030] In a preferred embodiment, the BQ25173DSG-3 pin is a charging enable pin with a low level being effective, and the BQ25173DSG-3 is connected to the RAK3172-16 pin of the single-chip wireless communication module. The single-chip microcomputer can control whether the supercapacitor is charged or not according to actual needs. The BQ25173DSG-4 pin is GND, and the BQ25173DSG-5 pin is an output pin. A high level indicates that the charging is in progress, and a low level indicates that the output voltage has reached 98% VREG. VREG is a programmable adjustable voltage, i.e., the supercapacitor charging voltage. , BQ25173DSG-5 pin is connected to the microcontroller RAK3172-25 pin for monitoring the charging status, BQ25173DSG-5 pin is connected to the resistor R25 (10KΩ), the other end of R25 is connected to the cathode of the light emitting diode D1, and the anode of the light emitting diode is connected to the VCC_5.6V network. The light emitting diode is used to indicate the charging status. When the supercapacitor charging value is 98% VREG, the BQ25173DSG-5 pin becomes low level, and the light emitting diode D1 is on. If the charging voltage is less than 98% VREG, the light emitting diode D1 is off. The diode D1 is off, R25 is the current limiting resistor, the PG of the 6th foot of BQ25173DSG- is connected to the resistor R5 (750Ω), and the other end is connected to the cathode of the light-emitting diode D3, and the anode of D3 is connected to the VCC_5.6V network, which is used to indicate whether the input voltage is normal. When VIN>VIN_LOWV and VOUT+VSLEEPZ<VIN<VIN_OV, PG becomes low level and the light-emitting diode D3 is on, otherwise the light-emitting diode D3 is off, where VIN is the input voltage, and VIN_LOWV is the input start charging The voltage is 3.05V, VOUT is the output voltage, VSLEEPZ is the output sleep mode threshold of 95mV, VIN_OV is the input overvoltage threshold of 18.1V, and the BQ25173DSG-7 pin is used to adjust the charging voltage of the supercapacitor. The supercapacitor adjustment voltage counting formula is: VREG=VFB_REF*, where VREG is the charging adjustment voltage, VFBREF=0.8V is the feedback reference voltage, RFBT is _R1(604K), RFBB is R3(100K), and VREG=5.6V is obtained. One end of resistor R1 is connected to BQ25173DSG-8 pin, and the other end is connected to R3. The other end of R3 is connected to GND. The middle point of the series connection is connected to BQ25173DSG-7 pin. BQ25173DSG-8 pin is the voltage output end connected to the positive pole of two parallel 15F / 5.6V supercapacitors C2 / C3. The negative pole of C2 / C3 is connected to GND. The two supercapacitors are used as energy storage elements to power the back-end circuit. The total capacity is 30F / 5.6V. C1 is a filter capacitor with a value of 0.1uF. One end is connected to the output end of BQ25173DSG-8 pin, and the other end is connected to GND.Resistors R26 / R27 are used as a voltage divider circuit. One end of R26 is connected to the output terminal of BQ25173DSG-8, and the other end is connected to R27. The other end of R27 is connected to GND. The middle series node of the two resistors is connected to the microcontroller RAK3172-3 pin to monitor the supercapacitor charging voltage. Solar power supply circuit function: 2W / 12V solar panel generates electricity to charge two parallel 15F / 5.6V supercapacitors through supercapacitor charging management chip BQ25173DSG. The microcontroller detects that the BQ25173-5 pin is low, indicating that the charging voltage has reached 98% of the regulated output voltage VREG, and detects that the BQ25173-8 pin outputs the regulated voltage VREG of 5.6V, indicating that the supercapacitor is fully charged. The microcontroller RAK3172-16 pin outputs a high level to stop charging the supercapacitor. When VREG drops to the termination discharge voltage U2=4.4V, the microcontroller RAK3172-16 pin outputs a low level to continue charging the supercapacitor and so on. Supercapacitor charging and discharging calculation, charging current setting IIN=50mA, discharge current ID=15mA, capacitor rated voltage UR=VREG=5.6V, capacitor capacity C=15F, starting voltage U1=5.4, termination discharge voltage U2=4.4V[2]. Then the actual available rated capacity CR of the capacitor is counted according to the formula:. According to Q=IT, the discharge current ID=10mA, then the discharge duration tR=8.925C / 0.01A=892.5s; the charging current IIN=50mA, then the time required for full charge is tC=8.925C / 0.05A=178.5s.

[0031] In a preferred embodiment, a thermoelectric generator (TEG) circuit includes a thermoelectric generator TEG and a generator sheet. The interface of the thermoelectric generator TEG is the P2 port. The thermoelectric generator uses 2441G-7L31-10CX1. The positive electrode of the generator sheet is connected to the negative electrode of the 3.0V Zener D2. The positive electrode of the generator sheet is connected to the DC input pin of BQ25504RGTT-2. The positive electrode of the generator sheet is connected to a 22uH inductor, and the other end of the inductor is connected to the BQ25504RGTT-16 pin (the boost charging switch node inductor connection end). The positive electrode of the generator sheet is connected to a 10uF capacitor to GND, which acts as an energy storage filter. The positive electrode of the generator sheet is connected to a 10MΩ resistor R11, and R11 is connected in series with a 10MΩ resistor R12 to GND. The series node is connected to the BQ25504RGTT-3 pin (MPPT network sampling pin), and the maximum power point tracking technology (MPPT) is used.

[0032] In a preferred embodiment, the BQ25504RGTT-7 pin is a resistor divider bias voltage, which is simultaneously connected to a 6.2MΩ resistor R13, a 4.32MΩ resistor R14, and a 2.67MΩ resistor R15. R13 is connected in series with a 3.74MΩ resistor R17 and finally connected to GND. The series node is connected to the BQ25504RGTT-6 pin (battery overvoltage threshold setting pin), R14 is connected in series with a 5.76MΩ resistor R18 and finally connected to GND, the middle series node is connected to the BQ25504RGTT-8 pin (battery undervoltage threshold setting pin), R15 is connected in series with a 3.24MΩ resistor R19, R19 is connected in series with a 4.12MΩ resistor R20 and finally connected to GND, the R15 / R19 middle node is connected to the BQ25504RGTT-9 pin (battery OK hysteresis threshold), and the R19 / R20 middle node is connected to the BQ25504RGTT- Connected to BQ25504RGTT-10 pin (battery OK threshold), BQ25504RGTT-14 pin is connected in parallel with two 15F / 5.6V super capacitors, the positive pole of C13 / C14 is connected to BQ25504RGTT-14 pin, and the negative end is connected to GND, BQ25504RGTT-11 pin is the battery OK output pin connected to the microcontroller RAK31772-26 pin to indicate that the energy storage element voltage is OK, BQ25504RGTT-15 pin is the power output end, two capacitors C10 (10uF) / C11 (0.1uF) are connected in parallel, and the other end of the capacitor is connected to GND, and a 0Ω resistor R10 is connected in series, and then a 10uF capacitor C12 is connected in parallel to GND, and the other end of R10 is connected to TPS2121RUXR. The function of capacitors C10 / C11 / C12 is to filter the energy storage and smooth the voltage. The 17 / 12 / 1 / 13 pins of the BQ25504RGTT are connected to GND. The working principle of the supercapacitor charging management chip BQ25504RGTT, BQ25504 is an ultra-low power boost converter with battery management function, designed for energy harvesting applications. It is capable of extracting energy from extremely low input voltage sources (such as 0.1V to 3.0V) and storing it at a higher voltage level, such as in a supercapacitor. The working principle of this chip is based on the following key functions: Boost converter / charger stage: BQ25504 has a boost converter that can operate in the range of 0.13V to 3V for the input voltage VIN_DC. When the input voltage exceeds 600mV, the cold start circuit can be started to start charging VSTOR. When the VSTOR voltage reaches 1.8V, the cold start operation ends and the normal charging operation begins. Battery Management: The chip has built-in battery management functions, and the overvoltage (VBAT_OV) and undervoltage (VBAT_UV) thresholds, as well as the threshold of the battery good (VBAT_OK) indicator can be programmed.These thresholds are used to protect storage elements from damage by overcharging or discharging. The following are the various threshold settings: the undervoltage protection voltage is set to 2.1V, the calculation formula VBAT_UV = VBIAS, where VBIAS = 1.25V from the data sheet, VBAT_UV = 1.25V (1 + R14 / R18) = 2.1875V, the overvoltage protection voltage is set to 4.98V;.

[0033] Calculation formulaVBAT_OV=3 / 2*VBIAS(VBAT_OV=1.5*1.25V(1+R13 / R17)=4.98VBattery OKOutput voltage is set to 2.5V;

[0034] Calculation formulaVBAT_OK_PROG=VBIASVBAT_OK_PROG=1.25V*(1+R19 / R20)=2.5VBattery OK hysteresis output voltage is set to 3.0V;

[0035] Calculation formulaVBAT_OK_HYST=VBIASVBAT_OK_HYST=1.25V(1+(R15+R19) / R20)=2.9VWhen the input voltage exceeds 600mV, the cold start circuit can be started to start charging VSTOR. When the VSTOR voltage reaches 1.8V, the cold start operation ends, the internal VBAT is connected to VSTOR and normal charging operation begins. When the voltage is detected to reach VBAT_OK_HST=2.9V, the system load switch is turned on and connected to VSTOR. When the charging voltage reaches VBAT_OV=4.98V, the charging is turned off. Boost conversion MPPT mode: The boost DC / DC converter is placed between the TEG and the storage stage. If the VSTOR voltage does not reach the minimum threshold of about 1.8V, the boost will operate in degraded mode with poor conversion efficiency (between 10% and 50%). When the threshold 1.8V is reached, the boost switches to normal operation. For VSTOR between 1.8V and VBAT_OV = 4.9V, the converter operates in maximum power tracking mode (MPPT mode), and every 16 seconds and for 256 milliseconds, the TEG is disconnected, allowing the BQ25504 to measure the open circuit voltage (VOC). After that, the DC / DC operates by regulating the TEG voltage to a set point voltage equal to VMPP =. If the capacitor is fully charged, that is, when VSTOR reaches VBAT_OV, the DC / DC converter is turned off to avoid overload. Simulation test, such as Figure 5.BQ25504RGTT charging process voltage VS current characteristics, 5 thermoelectric generators 2441G-7L31-10CX1 are connected in series to the P2 port, the hot end is 30 degrees, the cold end is 20 degrees, the open circuit voltage of each is 0.4V, and 5 are 2V. The test results are shown in the figure below, with a total of 4 stages. Stage 1: In the "cold start stage", VSTOR changes from 0V to 1.8V. Once VSTOR reaches 1.8V, the next stage begins. Stage 2: The boost converter operates in MPPT mode. The current of the TEG increases significantly to 55mA. The TEG voltage is close to, that is, 1.05V. The internal transistor between VBAT and VSTOR is turned on, but the supercapacitor is charged by the current flowing through the internal diode of the transistor. Stage 3: Once VSTOR is higher than 2.2V, the internal transistor remains off and the supercapacitor continues to charge. Before VBAT_OV, Boost is in MPPT mode. The TEG open circuit stage is repeated every 16 seconds; ITEG current drops to zero, and the TEG voltage (not visible in this figure due to the low sampling rate of the device) briefly rises to 2.1V. From the figure, we know that the single charge capacity C = (180-30)s*0.055 = 8.25C; the supercapacitor is two 15F / 5.6V in parallel, so it takes 15 / 8.25 = 1.8 times to fully charge the two capacitors, so it takes about 2 cycles.

[0036] In a preferred embodiment, the 3.3V power supply circuit includes a multi-way power multiplexer with priority function and a 3.3V boost converter. The multi-way power multiplexer circuit portion includes a TPS212x device. TPS212x is a dual-input, single-output power multiplexer (MUX). The device will automatically detect the input source, select and seamlessly switch between available inputs. Priority can be automatically assigned to the highest input voltage or manually assigned to a lower voltage input. If the solar power supply and the temperature difference power generation circuit work properly, stable two-way power supply voltages VIN1 = 5.6V and VIN2 = 4.98V can be generated.

[0037] In a preferred embodiment, the 3.3V boost converter is TPS610994YFFR with a fixed output of 3.3V, an input voltage range of 0.7V to 5.5V, and has undervoltage / overvoltage protection functions. When the input voltage is less than 3.3V, the converter works in a boost conversion mode and outputs to 3.3V. When the input voltage is close to or higher than the output voltage, TPS61099x has a buck mode and a pass-through operation function. In the drop mode, even if VIN>VOUT, the output voltage will be adjusted to the target value of 3.3V. The rated capacity of the selected solar power supply is CR=8.925C, and two parallel connections are 17.85C. The conversion efficiency of TPS6100994 is 85%, so the effective capacity of the 3.3V / 100mA power supply is CR_solar=2*0.85* CR=15.1725C, according to the formula Q=IT, the time tsolar_3.3V=151.725s for the supercapacitor to discharge 100mA after it is fully charged. If a thermoelectric generator (TEG) is selected, if VTEG>0.4V, VSC>2.2V, ITEG>0.1mA, the efficiency of BQ25504 is 80%, and the effective capacity of 3.3V / 100mA is CR_TEG=2*0.8*0.85*CR=12.138C, according to the formula Q=IT, the time tTEG_3.3V=121.38s for the supercapacitor to discharge 100mA after it is fully charged can be obtained. The power supply of the entire device can be supplied through the miniUSB interface or through an external battery to meet different application requirements. Through the above design, a low-power, long-distance communication LoRaWAN temperature and humidity monitoring node can be realized, which is suitable for monitoring sensor data such as temperature and humidity in greenhouses. Basic functions: Upload temperature and humidity data every 10 minutes (time is adjustable), sleep at other times, and realize wake-up timing function through the ultra-low power wake-up counter of the STM32WLE5CC microcontroller.

[0038] In a preferred embodiment, the single-chip microcomputer peripheral circuit includes an STM32WLE5CC microcontroller, an AHT20 temperature and humidity sensor, a LoRaWAN gateway, and a TTN server. The STM32WLE5CC microcontroller performs data processing and LoRa communication. The AHT20 temperature and humidity sensor is connected to the RAK3172 module through an I2C interface to monitor the ambient temperature and humidity in real time and send the data to the LoRaWAN gateway. The LoRaWAN gateway forwards the data to the TTN server. The CH340E chip is connected to the RAK3172 serial port 2 and is connected to an external device through a miniUSB interface.

[0039] In a preferred embodiment, the MCU starts to enter the peripheral configuration (serial port / GPIO / IIC / Sub-GHz configuration) when it is powered on, and then performs the LoRaWAN node configuration, including the device EUI (DevEUI), which is the unique identifier of each LoRaWAN node, the application EUI (AppEUI) LoRaWAN network identifier, and the application key (AppKey) used as the security key for the node to communicate with the network, and then enters the OTAA network access stage: the node sends a network access request, the network server responds, and the node will perform network access verification after receiving the server response. If the security parameters are configured in the node, the network access is completed. If the network access is successful, it enters the RTC sleep mode. This state is managed by the MCU ultra-low power RTC timer. If 10 minutes are up, the MCU will automatically wake up. The AHT20 sensor data is read through the IIC interface, and then the data is uploaded to the server. If the upload fails more than 10 times, the system is reset. If successful, it returns to the RTC sleep mode. If the preamble code is received to wake up, the Sub-GHz enters the receiving state to receive data, then processes the data and finally returns to the RTC sleep mode. If 2 minutes are passed in the sleep mode, the 2-way voltage and the solar energy fullness status are detected. If the BQ25173DSG-5 pin is low, it means that the charging voltage reaches 98% VREG. At this time, the microcontroller controls the BQ25173DSG-3 pin to output a high level to turn off solar charging; if the charging voltage does not reach 98% VREG, the BQ25173DSG-3 pin remains low and continues to charge, and then the two tasks are completed and return to sleep mode.

[0040] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0041] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A battery-free wireless sensor device, comprising a solar power supply circuit, a thermoelectric generator (TEG) circuit, a 3.3V power supply circuit, and a single-chip microcomputer peripheral circuit, characterized in that: The 3.3V power supply circuit includes a multi-channel power multiplexer with a priority function and a 3.3V synchronous boost converter, and the single-chip microcomputer peripheral circuit includes a single-chip microcomputer radio frequency module and a sensor and a USB interface circuit; The solar power supply circuit includes a P1 element and a capacitor C4, wherein the P1 element is a solar power supply interface, wherein the P1 element includes P1-1 and P1-2, wherein the P1-2 pin is connected to the positive pole of the solar 12V output, and the P1-1 pin is connected to the negative pole of the solar 12V output, wherein the two pins of the capacitor C4 are respectively connected to the P1-1 pin and the P1-2 pin and are simultaneously connected to the chip BQ25173DSG, wherein the BQ25173DSG includes BQ25173DSG-1, BQ25173DSG-2, BQ25173DSG-3, BQ25173DSG-4, BQ25173DSG-5 and BQ25173DSG-6, wherein the BQ25173DSG-1 pin is a DC power input port, the BQ25173DSG-2 pin is connected to a resistor R6 (6KΩ), and the BQ25173DSG-2 pin is a programmable charging current.

2. A battery-free wireless sensor device according to claim 1, characterized in that: The BQ25173DSG-3 pin is a charging enable pin, which is valid at a low level, and the BQ25173DSG-3 is connected to the RAK3172-16 pin of the single-chip wireless communication module. The single-chip microcomputer can control whether the supercapacitor is charged or not according to actual needs. The BQ25173DSG-4 pin is GND, and the BQ25173DSG-5 pin is an output pin. A high level represents charging, and a low level represents that the output voltage has reached 98% VREG. VREG is a programmable adjustable voltage, i.e., the supercapacitor charging voltage. The BQ25173DSG-5 pin is connected to the RAK3172-25 pin of the single-chip microcomputer for monitoring the charging status. The BQ25173DSG-5 pin is connected to a resistor R25 (10KΩ), and the other end of R25 is connected to the cathode of the light-emitting diode D1. The anode of the light-emitting diode is connected to the VCC_5.6V network. The light-emitting diode is used to indicate the charging status. When the super When the capacitor charging value is 98% VREG, the BQ25173DSG-5 pin becomes low level and the light-emitting diode D1 is on. If the charging voltage is less than 98% VREG, the light-emitting diode D1 is off. The R25 is a current limiting resistor. The BQ25173DSG-6 pin PG is connected to the resistor R5 (750Ω), and the other end is connected to the cathode of the light-emitting diode D3. The anode of D3 is connected to the VCC_5.6V network, which is used to indicate whether the input voltage is normal. When VIN>VIN_LOWV and VOUT+VSLEEPZ<VIN<VIN_OV, PG becomes low level and the light-emitting diode D3 is on, otherwise the light-emitting diode D3 is off, wherein VIN is the input voltage, VIN_LOWV is the input start charging voltage of 3.05V, VOUT is the output voltage, VSLEEPZ is the output sleep mode threshold of 95mV, and VIN_OV is the input overvoltage threshold of 18.1V.

3. A battery-free wireless sensor device according to claim 1, characterized in that: The thermoelectric generator (TEG) circuit includes a thermoelectric generator TEG and a generator sheet. The thermoelectric generator TEG interface is a P2 port. The thermoelectric generator uses 2441G-7L31-10CX1. The positive electrode of the generator sheet is connected to the negative electrode of the 3.0V Zener D2. The positive electrode of the generator sheet is connected to the DC input pin of BQ25504RGTT-2. The positive electrode of the generator sheet is connected to a 22uH inductor, and the other end of the inductor is connected to the BQ25504RGTT-16 pin (boost charging switch node inductor connection end). The positive electrode of the generator sheet is connected to a 10uF capacitor to GND, which acts as an energy storage filter. The positive electrode of the generator sheet is connected to a 10MΩ resistor R11. The R11 is connected in series with a 10MΩ resistor R12 to GND, and the series node is connected to the BQ25504RGTT-3 pin (MPPT network sampling pin), maximum power point tracking technology (MPPT).

4. A battery-free wireless sensor device according to claim 3, characterized in that: The BQ25504RGTT-7 pin is the resistor divider bias voltage, which is simultaneously connected to a 6.2MΩ resistor R13, a 4.32MΩ resistor R14, and a 2.67MΩ resistor R15. R13 is connected in series with a 3.74MΩ resistor R17 and finally connected to GND. The series node is connected to the BQ25504RGTT-6 pin (battery overvoltage threshold setting pin), R14 is connected in series with a 5.76MΩ resistor R18 and finally connected to GND, the middle series node is connected to the BQ25504RGTT-8 pin (battery undervoltage threshold setting pin), the R15 is connected in series with a 3.24MΩ resistor R19, the R19 is connected in series with a 4.12MΩ resistor R20 and finally connected to GND, the R15 / R19 middle node is connected to the BQ25504RGTT-9 pin (battery OK hysteresis threshold), the R19 The / R20 intermediate node is connected to the BQ25504RGTT-10 pin (battery OK threshold), the BQ25504RGTT-14 pin is connected in parallel with two 15F / 5.6V supercapacitors, the positive pole of C13 / C14 is connected to the BQ25504RGTT-14 pin, and the negative end is connected to GND, the BQ25504RGTT-11 pin is the battery OK output pin connected to the RAK31772-26 pin of the microcontroller to indicate that the energy storage element voltage is OK, the BQ25504RGTT-15 pin is the power output end, and two capacitors C10 (10uF) / C11 (0.1uF) are connected in parallel. The other end of the capacitor is connected to GND, and a 0Ω resistor R10 is connected in series, and then a 10uF capacitor C12 is connected in parallel to GND, and the other end of R10 is connected to TPS2121RUXR.

5. A battery-free wireless sensor device according to claim 1, characterized in that: The 3.3V power supply circuit includes a multi-way power multiplexer with priority function and a 3.3V boost converter. The multi-way power multiplexer circuit part includes a TPS212x device. The TPS212x is a dual-input, single-output power multiplexer (MUX). The device will automatically detect the input source, select and seamlessly convert between available inputs. Priority can be automatically assigned to the highest input voltage or manually assigned to a lower voltage input. If the solar power supply and temperature difference power generation circuits work properly, stable two-way power supply voltages VIN1=5.6V and VIN2=4.98V can be generated.

6. A battery-free wireless sensor device according to claim 5, characterized in that: The 3.3V boost converter is TPS610994YFFR with fixed output of 3.3V, input voltage range of 0.7V~5.5V, and undervoltage / overvoltage protection. When the input voltage is less than 3.3V, the converter works in boost conversion mode and outputs to 3.3V. When the input voltage is close to or higher than the output voltage, TPS61099x has buck mode and pass-through operation functions. In the buck mode, even if VIN>VOUT, the output voltage will be adjusted to the target value of 3.3V. The rated capacity of solar power supply is CR=8.925C, and two in parallel is 17.85C. The conversion efficiency of TPS6100994 is 85%, so the effective capacity of 3.3V / 100mA power supply is The value is CR_solar=2*0.85*CR=15.1725C. According to the formula Q=IT, the time for the supercapacitor to be fully charged and continuously discharge 100mA is tsolar_3.3V=151.725s. If a thermoelectric generator (TEG) is selected, if VTEG>0.4V, VSC>2.2V, ITEG>0.1mA, the efficiency of BQ25504 is 80%, and the effective capacity of 3.3V / 100mA is CR_TEG=2*0.8*0.85*CR=12.138C. According to the formula Q=IT, the time for the supercapacitor to be fully charged and continuously discharge 100mA is tTEG_3.3V=121.38s.

7. A battery-free wireless sensor device according to claim 1, characterized in that: The single-chip microcomputer peripheral circuit includes an STM32WLE5CC microcontroller, an AHT20 temperature and humidity sensor, a LoRaWAN gateway, and a TTN server. The STM32WLE5CC microcontroller performs data processing and LoRa communication. The AHT20 temperature and humidity sensor is connected to the RAK3172 module through an I2C interface to monitor the ambient temperature and humidity in real time and send the data to the LoRaWAN gateway. The LoRaWAN gateway forwards the data to the TTN server. The CH340E chip is connected to the RAK3172 serial port 2 and is connected to an external device through a miniUSB interface.

8. A battery-free wireless sensor device according to claim 7, characterized in that: The MCU starts to enter the peripheral configuration (serial port / GPIO / IIC / Sub-GHz configuration) after powering on, and then performs LoRaWAN node configuration, including device EUI (DevEUI), i.e., each LoRaWAN node unique identifier, application EUI (AppEUI), LoRaWAN network identifier, application key (AppKey), a security key used for node-network communication, and then enters the OTAA network access phase: the node sends a network access request, the network server responds, and the node performs network access verification after receiving the server response. If the security parameters are configured in the node, the network access is completed. If the network access is successful, it enters the RTC sleep mode. In this state, the MCU ultra-low power consumption RTC timer is managed. If 10 minutes are up, the MCU is automatically awakened through the IIC interface. The AHT20 sensor data is read through the port, and then the data is uploaded to the server. If the upload fails more than 10 times, the system is reset. If successful, it returns to the RTC sleep mode. If the preamble code is received to wake up, the Sub-GHz enters the receiving state to receive data, then processes the data and finally returns to the RTC sleep mode. If 2 minutes are passed from the sleep mode, the 2-way voltage and the solar energy fullness status are detected. If the BQ25173DSG-5 pin is low, it means that the charging voltage reaches 98% VREG. At this time, the microcontroller controls the BQ25173DSG-3 pin to output a high level to turn off solar charging; if the charging voltage does not reach 98% VREG, the BQ25173DSG-3 pin remains low and continues to charge, and then the two tasks are completed and the system returns to the sleep mode.

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