Passive sensing brings flexible sensing configurations to IoT
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Passive sensing brings flexible sensing configurations to IoT

Posted Date: 2024-01-30
Electronic Enthusiast Network reports (Text/Li Ningyuan) The global sensor market has shown a trend of rapid growth amid continued technological innovation and demand upgrading. Especially now, the concept of Internet of Things is hot. The Internet of Things and sensors are deeply bound. Internet of Things applications require a large number of sensors to collect various environmental information. For wired or battery-powered sensors, power outages are rarely encountered. Many IoT sensors are deployed over a wide range and over long distances. In these scenarios, it is impossible to use wired connections or battery power. This makes it difficult to use sensors for applications that require long-term monitoring, have batteries that are difficult to replace, or cannot be connected via long-distance wired connections. Passive sensing, conversion energy utilization Sensors can be classified into active sensing and passive sensing. Passive sensors are also called energy conversion sensors. The most obvious feature is that they do not require an external power supply, that is, they do not require an external power supply and can An induction sensor that obtains energy from the outside. Sensors that do not require an external power supply generally focus on vibration, strain, temperature and light. The more representative ones are sensors that use the thermoelectric effect, photoelectric effect, and piezoresistive effect. On the sensor node, the piezoelectric and electromagnetic types collect vibration energy, and the thermoelectric type collects temperature difference energy. The sensor uses these effects to complete energy conversion to support its own work. Vibration energy belongs to kinetic energy, which is one of the energies that exists widely in the environment and is easily obtained. Vibration energy is collected by using a mass block that resonates with the main frequency of vibration of the surrounding environment, such as a piezoelectric force sensor. The energy-collecting diaphragm is used in conjunction with other electrical components and mechanical components to convert the pressure to be measured into electricity through a vibrating rhythm, thereby completing relevant measurement work. Sunlight and electromagnetic waves both belong to radiant energy. Photoelectric conversion is now relatively mature, and the converted current and voltage are relatively stable. Its applications are very common, and it has the advantages of fast response and non-contact. A typical application of electromagnetic waves is the well-known RFID. Passive RFID tags are powered by electromagnetic energy transmitted by RFID reading devices. When a reading device scans a passive RFID tag, energy is transmitted to the tag, allowing the chip and antenna to receive enough power to transmit information back to the reading device. Thermal energy is also a type of energy used by energy conversion sensors, because it requires as large a temperature difference as possible to achieve energy conversion. Huge temperature differences are not likely to occur in normal environments, so this conversion must generate as much power as possible. For example, the application of thermocouples. Energy Harvesting Passive Sensing Expands More Applications The common environmental energy conversion types above usually face the problem of weak power conversion, so now many of these sensors are equipped with energy collection ICs to provide high-efficiency conversion for the energy collected by the sensor. Generally speaking, energy harvesting ICs must be able to efficiently convert the collected energy in the μW to mW range, and their own operating losses must be low enough to support power-self-sufficient nodes. At the same time, wireless energy harvesting technology is also making breakthroughs. Wireless energy harvesting is also called wireless power harvesting, that is, the sensor obtains energy from the interface through NFC. This kind of energy harvesting means that the sensor does not require an external power supply, and the interface obtains energy from the incoming RF radiation power to the sensor interface and RF transmission through NFC during operation. Although the current power consumption is not enough in many scenarios to allow sensors to completely escape the power supply constraints, technical verification in some low-power scenarios is completely fine. With the further development of technology, there is still a lot of space for the application of IoT sensors in the future. In the future, the ability of sensors to obtain energy can be further enhanced through the integration of different energy collection methods, and the efficiency and power of energy conversion can be improved. summary The spread of Internet of Things applications will definitely face many power supply problems. Passive sensing provides a good solution for various sensing configurations in the future. With the advancement of technology, passive sensors with various functions and various energy extraction methods will show their talents in many applications in the Internet of Things era.
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