Low-power-consumption Internet of Things sensing system based on thermoelectric power generation and energy supply

Abstract

The invention belongs to the technical field of Internet of Things sensing systems, and particularly relates to a low-power-consumption Internet of Things sensing system based on thermoelectric power generation and energy supply, which comprises a power generation module, an electric energy management module, a data collection module and a wireless transmission and storage module. The power generation module comprises a heat dissipation unit, a thermoelectric power generation unit and a heat pipe heat conduction unit. The energy management module comprises a low-power-consumption low-voltage boosting unit, an electric energy collecting unit, an energy storage unit and a discharging voltage stabilizing unit. The data collection module comprises a microprocessor main control chip unit with a built-in Wi-Fi module, a serial port communication circuit unit, a temperature and humidity collection unit, a sound loudness collection unit and a working state warning unit. The wireless transmission and storage module comprises an MQTT wireless transmission network server unit, an equipment client unit, a WEB client unit and a database client unit. The problem of power supply of the wireless sensor working outdoors is solved, power consumption of system operation is reduced, and long-term effective operation of the system is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of passive Internet of Things sensor systems, and specifically relates to a low-power Internet of Things sensor system based on temperature difference power generation. Background Art

[0002] The Internet of Things (IoT) technology is a hot topic in the field of science and technology in recent years. It uses the Internet to connect various things in the physical world to achieve data exchange and communication. IoT technology has a wide range of application scenarios in intelligent manufacturing, intelligent inspection and maintenance, and intelligent transportation. However, there is still a significant bottleneck in the development of IoT technology, that is, the demand for uninterrupted energy. In recent years, the application of wireless sensor networks has become more and more common. Since the IoT sensor system itself consumes a lot of power and needs to be consumed continuously, and relies on limited battery capacity, and large-capacity batteries are huge in size, the development of wireless sensor networks has been greatly restricted.

[0003] The MQTT protocol is a message protocol based on the publish / subscribe paradigm under the ISO standard. It works on the TCP / IP protocol family and is a publish / subscribe message protocol designed for remote devices with low hardware performance and poor network conditions. The protocol is event-driven and uses a publish / subscribe model to connect devices. Unlike the traditional client / server model, it is a messaging model in which the sender (publisher) does not send messages directly to a specific receiver (subscriber). Instead, the publisher classifies messages into different topics, and subscribers subscribe to the topics they are interested in. When a publisher sends a message to a topic, the MQTT agent routes and filters all incoming messages and then passes them to all subscribers who have expressed interest in the topic. Publishers and subscribers are decoupled from each other and do not need to know the existence of each other. The only connection between them is based on a predetermined message protocol. The publish-subscribe model supports flexible message communication because subscribers and publishers can be dynamically added or removed as needed, while also making it easier to implement message broadcasting, multicasting, and unicasting. Therefore, the MQTT protocol is expected to simplify IoT sensor circuits.

[0004] Furthermore, energy harvesting technology is an effective solution to the power demand and service life of wireless sensor nodes. Various clean energy sources such as piezoelectric, photovoltaic, geothermal, hydropower, and wind power generation show that renewable energy can generate enough power for wireless sensors. Among them, thermal energy has the characteristics of sufficient resources, convenient collection, and simple principle, and is a very attractive solution. Thermoelectric conversion technology is generally implemented using thermoelectric sheets, which use the first thermoelectric effect, that is, the thermoelectric phenomenon of the voltage difference between two substances caused by the temperature difference between two different electrical conductors or semiconductors. One end of the thermoelectric device is the cold side and the other end is the hot side. However, when using thermoelectric sheets to collect environmental thermal energy, it is difficult to artificially create a temperature difference between the cold and hot ends in a single environment, which makes it difficult to collect thermal energy and it is difficult to maintain the power demand of the IoT sensor system. Therefore, it is necessary to start from the IoT sensor circuit and thermoelectric conversion efficiency to provide a low-power IoT sensor system based on temperature difference power generation to overcome the problems of complex wiring, limited battery capacity, and high cost of existing sensors. Summary of the invention

[0005] The purpose of the present invention is to provide a low-power Internet of Things sensor system based on temperature difference power generation. Through the optimization of the energy management module, the effective collection of electric energy is achieved, while the power consumption is reduced, so that the Internet of Things sensor system can operate continuously at low cost.

[0006] To achieve the above object, the present invention provides a low-power IoT sensor system based on temperature difference power generation, comprising:

[0007] Thermoelectric power generation module, used to convert thermal energy into electrical energy;

[0008] An energy management module, used for stabilizing and boosting the output voltage of the temperature difference power generation module, as well as storing and releasing electric energy;

[0009] A data collection module, used for collecting and storing environmental sensor data;

[0010] A wireless transmission and storage module, used for wireless transmission and communication of sensor data and local storage of data;

[0011] Among them, the energy management module includes a low-power low-voltage boost unit, an energy collection unit, an energy storage unit and a discharge voltage stabilizing unit; the input end of the low-power low-voltage boost unit is connected to a capacitor and an inductor, the capacitor is used to preliminarily store the energy input by the temperature difference power generation unit, and the inductor is used to maintain the stability of the input current; the energy collection unit is used to control the collection and release process of the electric energy collected by the capacitor to the energy storage unit; the discharge voltage stabilizing unit is connected to the energy storage unit, and a voltage stabilizing capacitor is respectively arranged at its voltage input end and output end to maintain the stability of the output voltage of the energy storage unit.

[0012] Furthermore, the low-power low-voltage boost unit and the energy collection unit include a BQ25504 ultra-low-power boost converter, and the undervoltage threshold is set to 4.3V through the VBAT_UV pin; the overvoltage threshold is set to 5.1V through the VBAT_OV pin; the normal working voltage threshold of the energy storage unit is set to 4.7V through the OK_PROG pin; and the normal working hysteresis voltage threshold of the energy storage unit is set to 4.9V through the OK_HYST pin;

[0013] The capacitor at the input end of the low-power low-voltage boost unit is connected to the VSTOR pin of the BQ25504 ultra-low-power boost converter.

[0014] Furthermore, the VREF_SAMP pin of the BQ25504 ultra-low power boost converter is also connected to a 0.01μF voltage reference capacitor. The BQ25504 ultra-low power boost converter interrupts operation for 256 milliseconds every 16 seconds, and stores the open-circuit voltage of a preset proportion collected by the VIN_DC pin as a reference voltage on the VREF_SAMP pin, which is used to adjust the input voltage to be close to the reference voltage, thereby realizing the maximum power point tracking function of the temperature difference power generation module.

[0015] Furthermore, the discharge voltage stabilization unit includes a TPS73633DBVR linear regulator, whose voltage input end is connected to the VBAT interface of the BQ25504 ultra-low power boost converter, and the input voltage range is 1.7 to 5.5V; the EN pin of the TPS73633DBVR linear regulator is connected to the VBAT_OK pin of the BQ25504 ultra-low power boost converter, and starts to output voltage after receiving a signal that the energy storage unit can work normally.

[0016] Furthermore, the energy storage unit includes a plurality of lithium-ion button batteries connected in series; the capacitance of the capacitor connected to the input end of the low-power low-voltage boost unit is at least 4.7 μF, and the connected inductor is a 22 μH inductor; the capacitor and the inductor are both connected to the VIN_DC pin of the BQ25504 ultra-low power boost converter;

[0017] The VSTOR pin of the BQ25504 ultra-low power boost converter is also connected to a capacitor for collecting the boosted electrical energy.

[0018] Furthermore, the temperature difference power generation module includes a temperature difference power generation unit, a heat dissipation unit and a heat pipe heat conduction unit; the heat dissipation unit is bonded to the cold end of the temperature difference power generation unit through thermal grease, so as to achieve heat dissipation of the cold end of the temperature difference power generation unit; one end of the heat pipe heat conduction unit is bonded to the hot end of the temperature difference power generation unit, and the other end is in contact with the ambient heat source, so as to provide a continuous and stable heat source for the hot end of the temperature difference power generation unit, so as to achieve long-distance heat energy transmission.

[0019] Furthermore, the data collection module includes a microprocessor main control chip unit with a built-in WiFi module, a serial port communication unit, a temperature and humidity collection unit, a sound loudness collection unit, and a working status warning unit;

[0020] The serial communication unit is connected to the TX and RX pins of the microprocessor main control chip unit, and is used to download and communicate with the computer through UART communication;

[0021] The data interface of the temperature and humidity collection unit is connected to the microprocessor main control chip unit for transmitting the measured environmental data;

[0022] The sound loudness collection unit is connected to the analog signal input terminal of the microprocessor main control chip unit, and is used to compare and amplify the voltage signal input by the sound-to-electric conversion device, and output an analog voltage signal;

[0023] The working status warning unit is connected to the microprocessor main control chip unit and is used to indicate whether the low-power Internet of Things sensor system is connected to the wireless transmission network, whether to upload data, and whether to enter a deep sleep state.

[0024] Furthermore, the microprocessor main control chip unit includes an ESP32-C3 module chip with a built-in Wi-Fi module and an onboard PCB antenna, and its power supply voltage is 3.0V to 3.6V;

[0025] The IO4 pin of the ESP32-C3 module chip is connected to the DATA pin of the temperature and humidity collection unit for receiving the collected temperature and humidity data, and the IO3 pin is connected to the analog signal output port of the sound loudness collection unit for receiving the sound loudness analog signal.

[0026] Furthermore, the ESP32-C3 module chip is provided with a deep sleep mode, which is used to regulate the low-power IoT sensor system to enter the deep sleep mode after completing a data collection cycle to reduce power consumption.

[0027] Furthermore, the wireless transmission and storage module includes:

[0028] A device client, used to publish the sensor data collected by the data collection module;

[0029] WEB client, used to monitor the status of each device;

[0030] A database client, used to store the published sensor data;

[0031] MQTT wireless transmission network server, used to build MQTT Broker, acting as a central hub to establish connections, disconnect, subscribe and unsubscribe with various clients;

[0032] The device client is downloaded into the ESP32-C3 module chip. After the microprocessor main control chip unit is started, it automatically connects to the MQTT server and publishes the collected sensor data in JSON format.

[0033] In general, the above technical solution conceived by the present invention has the following technical advantages compared with the prior art:

[0034] 1. The low-power Internet of Things sensing system based on thermoelectric power generation provided by the present invention can initially store the energy input by the thermoelectric power generation unit through the low-power and low-voltage boost unit of the energy management module, thereby improving the energy management effect, enabling continuous energy conversion and supply, while maintaining the stability of the input current through the inductor; and then controlling the storage and release process of the electric energy in the capacitor to the energy storage unit through the energy collection unit, thereby realizing the effective collection of electric energy, and preventing the damage to the battery caused by overcharging and undervoltage conditions, so that the Internet of Things sensing system can continue to operate at low cost.

[0035] 2. The present invention realizes low-current circuit design for the energy management module and the data collection module through a specific chip circuit design. At the same time, the deep sleep mode of the data collection module realizes low-power operation of the system, overcoming the problems of complex wiring, limited battery capacity, and high cost of existing traditional wired sensors.

[0036] 3. The present invention provides a continuous and stable heat source for the hot end of the thermoelectric power generation unit through a heat pipe heat conduction unit to achieve long-distance heat energy transmission, thereby alleviating the problem of small temperature difference between the cold and hot ends of the thermoelectric power generation under a single environment.

[0037] 4. The present invention uses an environmental data collection system based on the MQTT transmission protocol to solve the problems of high cost and large deviation caused by traditional artificial environmental data monitoring, and can achieve large-scale, multiple environmental indicators, and 24-hour uninterrupted detection. The circuit is self-powered and shows great application potential in the Internet of Things.

[0038] 5. The low-power IoT sensing system constructed by the present invention can generate a stable input voltage under a constant temperature difference. The energy management module can realize automatic charging and discharging switching and successfully operate the wireless sensor module, thereby solving the power supply problem of wireless sensors working outdoors and reducing the power consumption of the system operation, thereby ensuring the long-term and effective operation of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic structural diagram of the low-power Internet of Things sensing system based on temperature difference power generation of the present invention.

[0040] Figure 2 This is a block diagram of the low-power Internet of Things sensing system based on temperature difference power generation of the present invention.

[0041] Figure 3 This is a schematic diagram of the structure of the power generation module of the low-power Internet of Things sensor system based on temperature difference power generation of the present invention.

[0042] Figure 4 This is a schematic diagram of the principle of the energy management module of the low-power Internet of Things sensor system based on temperature difference power generation of the present invention.

[0043] Figure 5 This is a schematic diagram of the principle of the data collection module of the low-power Internet of Things sensor system based on temperature difference power generation of the present invention.

[0044] Figure 6 This is a schematic diagram of the principle of the sound loudness collection circuit of the low-power Internet of Things sensor system based on temperature difference power generation of the present invention.

[0045] Figure 7 This is a curve of environmental data variation over time of the low-power Internet of Things sensing system based on temperature difference power generation of the present invention in an outdoor environment, powered by a battery, with a deep sleep time of 20 seconds.

[0046] Figure 8 The low-power Internet of Things sensor system based on temperature difference power generation of the present invention places one end of the heat pipe of the temperature difference power generation unit on a heating table at 90°C. When charging the energy storage unit, the battery voltage changes with the charging time.

[0047] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0048] 1-heat pipe heat conduction unit, 2-temperature difference power generation unit, 3-heat dissipation unit, 4-low voltage boost unit, 5-energy collection unit, 6-discharge voltage stabilization unit, 7-microprocessor, 8-sensor module, 9-temperature and humidity sensor, 10-sound loudness sensor, 11-WiFi module, 12-MQTT transmission network, 13-WEB terminal, 14-MQTT server, 15-database terminal. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0050] like Figures 1 to 5 As shown, the present invention provides a low-power Internet of Things sensing system based on temperature difference power generation, which mainly includes:

[0051] Thermoelectric power generation module is used to convert the thermal energy generated by the heat source into electrical energy that can be used and stored.

[0052] The energy management module is connected to the power generation module and is used to achieve voltage stabilization and low-power boosting of the output voltage of the power generation module, while achieving storage and release of electric energy.

[0053] The data collection module is connected to the energy management module and is used to realize the collection, storage and transmission functions of environmental sensor data.

[0054] The wireless transmission and storage module is used to realize the wireless transmission of sensor data, wireless communication and local storage of data.

[0055] Among them, the thermoelectric power generation module includes a heat dissipation unit 3, a thermoelectric power generation unit 2 and a heat pipe thermal conduction unit 1. The thermoelectric power generation unit 2 is used to convert heat in the environment into electrical energy. One end of the heat pipe thermal conduction unit 1 is bonded to the hot end of the thermoelectric power generation unit 2 to provide a continuous and stable heat source for the hot end of the thermoelectric power generation unit 2. The other end of the heat pipe thermal conduction unit 1 is in contact with the environmental heat source to achieve efficient heat energy transmission over a long distance. The heat dissipation unit 3 is bonded to the cold end of the thermoelectric power generation unit 2 through thermal grease to achieve heat dissipation at the cold end of the thermoelectric power generation unit 2. Such a configuration can increase the temperature difference between the hot and cold ends of the thermoelectric power generation unit, thereby increasing the power generation.

[0056] See also Figure 3In some preferred embodiments, the heat pipe heat transfer unit includes 16 copper 20cm heat pipes for long-distance heat conduction. The temperature difference power generation unit includes 8 SP1848-27145 thermoelectric sheets with a volume of 40mm*40mm*3.4mm. Heat pipe technology uses phase change to achieve efficient heat transfer, and relies on the vapor and liquid phase change heat transfer of the working fluid internally, with high thermal conductivity and consistent isothermal properties. Therefore, heat pipes are very suitable for transferring heat from a distant heat source environment, and provide a continuous and stable heat source for the hot end of the thermoelectric sheet while ensuring that the cold end of the thermoelectric sheet is relatively cold.

[0057] The energy management module includes a low-power low-voltage boost unit 4, an energy collection unit 5, an energy storage unit and a discharge voltage stabilizing unit 6. The energy collection unit can store the collected electrical energy in the energy storage unit. When the energy storage unit reaches the specified energy storage voltage, it stops energy collection, releases a signal to the subsequent circuit, and switches to the mode in which the energy storage unit outputs electrical energy (discharge mode). When the supply voltage is less than the specified minimum voltage, the battery power supply is cut off to prevent the data collection module from entering an undervoltage state. In order to ensure that the energy storage unit has sufficient supply voltage to power the data collection module in non-deep sleep mode, the energy storage unit is quantitatively calculated according to the time setting and power consumption of the deep sleep mode and non-deep sleep mode of the ESP32-C3 module chip, so as to charge the energy storage unit in time through the energy collection unit.

[0058] See also Figure 4 In some preferred embodiments, the low-power low-voltage boost unit continuously collects energy from a low-voltage input source (thermoelectric power generation unit). The low-power low-voltage boost unit and the energy collection unit include a BQ25504 ultra-low-power boost converter. The input VIN_DC pin of the BQ25504 ultra-low-power boost converter is connected to a minimum 4.7μF capacitor, which is directly connected to the thermoelectric power generation unit for preliminary storage of energy input by the thermoelectric power generation unit. Its voltage is consistent with the low voltage generated by the thermoelectric sheet of the thermoelectric power generation unit and changes with the change of the voltage of the thermoelectric power generation unit. At the same time, the input VIN_DC pin is connected to a 22μH inductor to maintain the stability of the input current. The VREF_SAMP pin of the BQ25504 ultra-low power boost converter is connected to a 0.01μF voltage reference capacitor. The BQ25504 ultra-low power boost converter interrupts its operation for 256 milliseconds every 16 seconds, and stores the preset proportion of the open-circuit voltage collected by the VIN_DC pin as a reference voltage on the VREF_SAMP pin, which is used to adjust the input voltage to be close to the reference voltage, thereby realizing the maximum power point tracking function of the temperature difference power generation module.

[0059] The BQ25504 ultra-low power boost converter can cold start at a minimum of 600mV and continuously collect energy at a minimum of 130mV. The undervoltage threshold is set to 4.3V through the VBAT_UV pin; the overvoltage threshold is set to 5.1V through the VBAT_OV pin; the normal operating voltage threshold of the energy storage unit is set to 4.7V through the OK_PROG pin; and the normal operating hysteresis voltage threshold of the energy storage unit is set to 4.9V through the OK_HYST pin.

[0060] In some preferred embodiments, the BQ25504 chip first stores the collected boosted electric energy in the capacitor of the VSTOR pin, with a voltage of 2 to 5V, which does not change with the voltage of the temperature difference power generation unit. When the VSTOR voltage is greater than the undervoltage threshold, the VSTOR pin is connected to the VBAT pin and starts to charge the energy storage unit. When VBAT reaches the normal working hysteresis voltage, the VBAT_OK pin outputs a high potential to indicate that the energy storage unit can be discharged. When VBAT reaches the overvoltage threshold, the BQ25504 chip stops charging the VBAT pin to protect the battery. When the VBAT voltage is less than the normal working voltage, the VBAT_OK pin outputs a low level to indicate that the energy storage unit enters the charging mode.

[0061] In some preferred embodiments, the energy storage unit includes two rechargeable 3V lithium-ion button batteries connected in series, model ML2032, nominal voltage 3V, capacity 65mAh. Figure 8 As shown, one end of the heat pipe of the temperature difference power generation unit is placed on a heating table at 90°C, and the cold end is connected to a heat dissipation aluminum plate through thermal conductive silicone grease and placed in the air to charge the energy storage unit. The cold end of the thermoelectric sheet is connected to a heat dissipation aluminum plate through thermal conductive silicone grease and placed in the air. It can be seen that the voltage has not reached the discharge voltage at this time, so as the charge amount increases, the battery voltage gradually increases, indicating that the temperature difference power generation unit can achieve good energy storage.

[0062] In some preferred embodiments, the discharge voltage stabilizing unit includes a TPS73633DBVR linear voltage regulator, the voltage input end is connected to the VBAT interface of the BQ25504 chip, the input voltage range is 1.7 to 5.5V, and a 0.1μF voltage stabilizing capacitor is set at the voltage input end and the output end respectively. After receiving the normal working signal of the battery, a 3.3V voltage can be stably output. The EN pin is connected to the VBAT_OK pin of the BQ25504 chip, and an LED indicator is connected at the same time to indicate whether to start working. The high and low level signals of the VBAT_OK pin determine whether to output voltage. When the battery voltage enters the undervoltage state, the discharge voltage stabilizing unit is controlled to shut down the output voltage to prevent the output voltage from being too low to damage components.

[0063] The data collection module includes a microprocessor main control chip with a built-in Wi-Fi module and antenna (used to run programs, receive sensor data, and connect to a wireless transmission network), a serial communication circuit, a temperature and humidity collection circuit, a sound loudness collection circuit, and a working indicator light circuit.

[0064] See also Figure 5 In some preferred embodiments, the microprocessor main control chip of the Wi-Fi module includes an ESP32-C3 module chip, which has a built-in 2.4GHz Wi-Fi module and an onboard PCB antenna, 4MB flash memory, and a power supply voltage of 3.0V to 3.6V. An RC delay circuit is set at the enable pin of the ESP32-C3 chip to ensure normal power supply of the chip. The IO4 pin is connected to the DATA pin of the temperature and humidity collection circuit to receive the collected temperature and humidity data through SPI communication, and the IO3 pin is connected to the analog signal output port of the sound loudness collection circuit to collect the sound loudness analog signal. The ESP32 module chip can enter the deep sleep mode at a fixed time. In the deep sleep mode, only the RTC timer and RTC memory in the ESP32-C3 chip work, and the current is only 5μA to reduce power consumption. A 0.1μF and a 10μF decoupling capacitor are connected to the 3V3 power supply pin at the chip power input end. A BOOT button and a RST button are set to realize manual operation of the main control ESP32-C3 chip. After receiving the enable signal, the microprocessor is started to collect and publish data. After a specific time (after completing a data collection cycle), it enters a low-power deep sleep mode, wakes up again after a specific time of sleep, and repeats the above steps.

[0065] The serial communication circuit is connected to the TX and RX pins of the ESP32-C3 chip, and downloads and communicates with the computer through UART communication.

[0066] The temperature and humidity collection circuit includes a DHT11 digital temperature and humidity sensor, which has a wide voltage supply of 2.7-5.5V and a built-in high-precision 14-bit ADC. It can communicate with the microcontroller through SPI via the DATA pin and output high-precision digital temperature and humidity data.

[0067] See also Figure 6 The sound loudness collection circuit includes a GMI6050P-36db omnidirectional electrostatic microphone, which is used to convert the sound loudness signal into an electrical signal; an SS8050 NPN transistor, which is used to amplify the signal; and a 0.1μF filter capacitor, which outputs the analog signal through the ADC1_CH3 interface. The threshold voltage is set by an adjustable resistor, and an LM393 comparator is set. When the input voltage exceeds the threshold voltage, the DO pin outputs a high configuration.

[0068] In an outdoor environment, the battery of the present invention is used to power the device, and the deep sleep time is set to 20 seconds, that is, each time a data collection cycle is completed, the device can sleep for 20 seconds, and the curve of environmental data changing with time is measured, as shown in FIG. Figure 7 As shown, it can be seen that the low-power IoT sensor system constructed by the present invention can operate well and effectively collect temperature, humidity and sound data of the environment.

[0069] The working indicator circuit includes two LED indicators 1 and 2 with series resistors, which are used to indicate whether the system is connected to the wireless transmission network, whether data is uploaded, and whether it enters a deep sleep state. When waiting for a connection, light 1 flashes at intervals, and when the connection is successful, light 1 flashes twice at intervals. When the data transmission is successful, light 2 flashes once, and before entering the deep sleep mode, light 2 flashes twice in succession.

[0070] The circuit is a circuit module with an area of ​​60cm*70cm.

[0071] The wireless transmission and storage module includes an MQTT wireless transmission network server, a device client, a WEB client, and a database client.

[0072] The device client program is downloaded to the ESP32 chip through the UART serial port. After connecting to the Wi-Fi network, it automatically searches for the MQTT server IP address and connects. After the connection is successful, the data is published on the network in JSON format.

[0073] The WEB client includes a computer connected to the same Wi-Fi network. After entering the URL in the browser, the user name and password can be entered to monitor the number of clients, collected information, data transmission bandwidth and other information.

[0074] The database client includes a computer with a built-in MySQL database. After connecting to the same MQTT server, it subscribes to the published JSON format data information through a Python script file, and links to the MySQL local database to save the data.

[0075] The MQTT wireless transmission network server includes a computer and the EMQX server script file officially provided by MQTT. The EMQX server is deployed on the computer using the command prompt. EMQX is a fully open source, large-scale, elastically scalable, cloud-native distributed IoT MQTT message server. After the EMQX server is deployed, it acts as a central hub for establishing connections, disconnecting, subscribing, and unsubscribing with each client. The MQTT protocol has the advantages of being lightweight, simple, open, low bandwidth occupancy, and easy to implement, providing real-time and reliable message services for continuous remote devices.

[0076] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A low-power Internet of Things sensor system based on temperature difference power generation, characterized in that: include: Thermoelectric power generation module, used to convert thermal energy into electrical energy; An energy management module, used for stabilizing and boosting the output voltage of the temperature difference power generation module, and storing and releasing electric energy; A data collection module, used for collecting and storing environmental sensor data; A wireless transmission and storage module, used for wireless transmission, communication and local storage of the environmental sensing data; Among them, the energy management module includes a low-power low-voltage boost unit, an energy collection unit, an energy storage unit and a discharge voltage stabilizing unit; the input end of the low-power low-voltage boost unit is connected to a capacitor and an inductor, the capacitor is used to preliminarily store the energy input by the temperature difference power generation unit, and the inductor is used to maintain the stability of the input current; the energy collection unit is used to control the storage and release process of the electric energy collected by the capacitor to the energy storage unit; the discharge voltage stabilizing unit is connected to the energy storage unit, and a voltage stabilizing capacitor is respectively arranged at its voltage input and output ends to maintain the stability of the output voltage of the energy storage unit.

2. The low-power Internet of Things sensor system based on temperature difference power generation according to claim 1 is characterized in that: The low-power low-voltage boost unit and the energy harvesting unit include a BQ25504 ultra-low-power boost converter; the BQ25504 ultra-low-power boost converter sets an undervoltage threshold through a VBAT_UV pin; sets an overvoltage threshold through a VBAT_OV pin; sets a normal working voltage threshold of the energy storage unit through an OK_PROG pin; and sets a normal working hysteresis voltage threshold of the energy storage unit through an OK_HYST pin; The capacitor at the input end of the low-power low-voltage boost unit is connected to the VSTOR pin of the BQ25504 ultra-low-power boost converter.

3. The low-power Internet of Things sensor system based on temperature difference power generation according to claim 2 is characterized in that: The VREF_SAMP pin of the BQ25504 ultra-low power boost converter is also connected to a 0.01μF voltage reference capacitor. The BQ25504 ultra-low power boost converter interrupts its operation for 256 milliseconds every 16 seconds, and stores the preset proportion of the open-circuit voltage collected by the VIN_DC pin as a reference voltage on the VREF_SAMP pin, which is used to adjust the input voltage to be close to the reference voltage, thereby realizing the maximum power point tracking function of the temperature difference power generation module.

4. The low-power Internet of Things sensor system based on temperature difference power generation according to claim 2 is characterized in that: The discharge voltage stabilization unit includes a TPS73633DBVR linear regulator, whose voltage input end is connected to the VBAT interface of the BQ25504 ultra-low power boost converter, and the input voltage range is 1.7 to 5.5V; the EN pin of the TPS73633DBVR linear regulator is connected to the VBAT_OK pin of the BQ25504 ultra-low power boost converter, and starts to output voltage after receiving a signal that the energy storage unit can work normally.

5. The low-power Internet of Things sensor system based on temperature difference power generation according to claim 2 is characterized in that: The energy storage unit includes a plurality of lithium-ion button batteries connected in series; the capacitance of the capacitor connected to the input end of the low-power low-voltage boost unit is at least 4.7 μF, and the connected inductor is a 22 μH inductor; the capacitor and the inductor are both connected to the VIN_DC pin of the BQ25504 ultra-low power boost converter; The VSTOR pin of the BQ25504 ultra-low power boost converter is also connected to a capacitor for collecting the boosted electrical energy.

6. The low-power Internet of Things sensor system based on temperature difference power generation according to any one of claims 1 to 5, characterized in that: The temperature difference power generation module includes a temperature difference power generation unit, a heat dissipation unit and a heat pipe heat conduction unit; the heat dissipation unit is bonded to the cold end of the temperature difference power generation unit through thermal conductive silicone grease, and is used to achieve heat dissipation of the cold end of the temperature difference power generation unit; one end of the heat pipe heat conduction unit is bonded and connected to the hot end of the temperature difference power generation unit, and the other end is in contact with the ambient heat source, and is used to provide a continuous and stable heat source for the hot end of the temperature difference power generation unit, so as to achieve long-distance heat energy transmission.

7. The low-power Internet of Things sensor system based on temperature difference power generation according to any one of claims 1 to 5, characterized in that: The data collection module includes a microprocessor main control chip unit with a built-in WiFi module, a serial port communication unit, a temperature and humidity collection unit, a sound loudness collection unit, and a working status warning unit; The serial communication unit is connected to the TX and RX pins of the microprocessor main control chip unit, and is used to download and communicate with the computer through UART communication; The data interface of the temperature and humidity collection unit is connected to the microprocessor main control chip unit for transmitting the measured environmental data; The sound loudness collection unit is connected to the analog signal input terminal of the microprocessor main control chip unit, and is used to compare and amplify the voltage signal input by the sound-to-electric conversion device, and output an analog voltage signal; The working status warning unit is connected to the microprocessor main control chip unit and is used to indicate whether the low-power Internet of Things sensor system is connected to the wireless transmission network, whether to upload data, and whether to enter a deep sleep state.

8. The low-power Internet of Things sensor system based on temperature difference power generation according to claim 7 is characterized in that: The microprocessor main control chip unit includes an ESP32-C3 module chip with a built-in Wi-Fi module and an onboard PCB antenna, and its power supply voltage is 3.0V to 3.6V; The IO4 pin of the ESP32-C3 module chip is connected to the DATA pin of the temperature and humidity collection unit for receiving the collected temperature and humidity data, and the IO3 pin is connected to the analog signal output port of the sound loudness collection unit for receiving the sound loudness analog signal.

9. The low-power Internet of Things sensor system based on temperature difference power generation according to claim 8 is characterized in that: The ESP32-C3 module chip is provided with a deep sleep mode, which is used to regulate the low-power IoT sensor system to enter the deep sleep mode after completing a data collection cycle to reduce power consumption.

10. The low-power Internet of Things sensor system based on temperature difference power generation according to claim 8, characterized in that: The wireless transmission and storage module includes: A device client, used to publish the sensor data collected by the data collection module; WEB client, used to monitor the status of each device; A database client, used to store the published sensor data; MQTT wireless transmission network server, used to build EMQX server, acts as a central hub to establish connections, disconnect, subscribe and unsubscribe with various clients.

Images