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This article introduces the relevant knowledge of "what does the technology of the perceptual end include". In the operation of actual cases, many people will encounter such a dilemma. Next, let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

The technology of the sensing end includes: 1, sensor technology, which can help people to complete the automatic detection and automatic control of objects; 2, radio frequency identification technology, which can obtain the relevant information of objects through the principle of electromagnetic coupling without touching objects; 3, two-dimensional code technology; 4, Bluetooth technology; 5, ZigBee technology and so on.

The operating environment of this tutorial: windows10 system, Dell G3 computer.

The key technologies of the sensing layer (end) of the Internet of things include sensor technology, radio frequency identification technology, QR code technology, Bluetooth technology and ZigBee technology. The main function of the perception layer of the Internet of things is to collect and capture the state information of the external environment or objects. When collecting and capturing the corresponding information, the radio frequency identification technology will be used to identify the objects first, and then through the highly integrated micro sensors installed on the objects to sense the environmental information of the objects and the state information of the objects themselves, to achieve real-time monitoring and automatic management of the objects. The realization of this function is inseparable from the coordination and cooperation of various technologies.

Sensor technology

The sensing function of the Internet of things is inseparable from the sensor, and the greatest role of the sensor is to help people to complete the automatic detection and automatic control of objects. At present, the related technology of the sensor has been relatively mature and has been used in many fields, such as geological exploration, aerospace exploration, medical diagnosis, commodity quality inspection, traffic safety, cultural relic protection, mechanical engineering and so on. As a detection device, the sensor will first sense the external information, and then convert the information into electrical signals through specific rules, and finally transmit it to the computer by the sensor network for analysis and use by people or artificial intelligence.

The physical composition of the sensor consists of three parts: sensitive element, conversion element and electronic circuit. The sensitive element can feel the corresponding object directly, and the conversion element is also called the sensing element, and its main function is to convert other forms of data signal into electrical signal; the electronic circuit as the conversion circuit can adjust the signal, and convert the electrical signal into useful electrical signal that can be processed and managed by human and computer.

Radio frequency identification technology

Radio frequency identification is referred to as RFID, which is one of the wireless automatic identification technologies, and it is also called electronic tag technology. Using this technology, the relevant information of objects can be obtained through the principle of electromagnetic coupling without touching objects.

The perception layer of the Internet of things usually establishes a radio frequency identification system, which is composed of electronic tags, readers and intermediate information systems. Among them, the electronic tag is generally installed on the surface of the object or embedded in the inner layer of the article, and the basic information of the object is stored in the tag so that it can be identified by the Internet of things; the reader has three functions: one is to read the information about the item to be identified in the electronic tag, the second is to modify the information about the item to be identified in the electronic tag, and the third is to transmit the obtained information to the central information system for processing. The function of the central information system is to analyze and manage the data information read by the reader from the electronic tag.

QR code technology

Two-dimensional code (2-dimensional bar code), also known as two-dimensional bar code, two-dimensional bar code, is a kind of information recognition technology. The two-dimensional code records the information through the black-and-white graphics, which are distributed on the two-dimensional plane according to the specific law, and the graphics correspond to the binary numbers in the computer. People can input the two-dimensional code into the computer for data recognition and processing through the corresponding photoelectric recognition equipment.

There are two types of QR codes, the first is stackable / row QR codes, and the other is matrix QR codes. The stackable / row-typed two-dimensional code is different from the matrix two-dimensional code in shape, the former is made up of one-dimensional code, and the latter is composed of matrix. Although the two are different in shape, they both adopt the same principle: each QR code has a specific character set, a corresponding width of "black stripe" and "white space" to replace different characters, and a check code.

The QR code has many advantages:

First, the coding density is high and the information capacity is very large. Generally speaking, a QR code can theoretically hold 1850 uppercase letters, or 2710 numbers. If converted into bytes, it can contain 1108; converted into Chinese characters, it can contain more than 500.

Second, the coding range is wide. The basis of two-dimensional code coding can be fingerprints, pictures, text, voice, signature and so on. The specific operation is to digitize these bases first, and then convert them into bar code form to present. The QR code can represent not only text information, but also image data.

Third, it has strong fault tolerance and error correction function. The QR code is partially contaminated with oil and becomes blurred, or the QR code can be read and used normally in these extreme cases because the QR code is partially damaged by sharp penetration. In other words, as long as the damaged area of the QR code does not exceed 50%, the original information can be restored by technical means.

Fourth, the decoding reliability is high. The error rate of QR code is less than 1/10000000, which is ten times lower than that of ordinary bar code.

Fifth, high security and good confidentiality.

Sixth, it is simple to make, low in cost and durable.

Seventh, the scale can be reduced and enlarged at will.

Eighth, can read with a variety of devices, such as photoelectric scanners, CCD imagine equipment and so on. Convenient and easy to use, high efficiency.

Bluetooth technology

Bluetooth technology is a typical short-distance wireless communication technology, which has been widely used in the perception layer of the Internet of things, and is one of the important short-distance information transmission technologies in the perception layer of the Internet of things. Bluetooth technology can be used not only between mobile devices, but also between fixed devices, and between fixed and mobile devices. This technology combines computer technology with communication technology to solve the problem of short-distance information transmission without wire or cable.

Bluetooth integrates time division multiple access, high-frequency hopping and other advanced technologies, which can realize not only point-to-point information exchange, but also point-to-multipoint information exchange. Bluetooth technology standardization has been relatively mature, the relevant international standards have been issued, for example, its transmission band uses the international unified standard 2.4GHz band. In addition, there is a special frequency band with an interval of 1MHz in addition to this frequency band. When Bluetooth devices use different power, the communication distance is different. If the power is 0dBm and 20dBm, the corresponding communication distance is 10m and 100m respectively.

ZigBee technology

ZigBee refers to the IEEE802.15.4 protocol, which, like Bluetooth, is also a short-distance unlimited communication technology. According to the relevant characteristics of this technology, it is between Bluetooth technology and wireless marking technology, so it is not the same as Bluetooth technology.

ZigBee transmits information over a short distance and has low power. Therefore, this low-power communication technology is often used among some small electronic devices in daily life. Like Bluetooth technology, the public wireless band used by ZigBee is also 2.4GHz, as well as frequency hopping and grouping technology. However, there are only three available bands for ZigBee, namely 2.4GHz (Public Radio Band), 868MHz (European usage Band) and 915MHz (US usage Band). The basic rate of ZigBee is 250Kbit/s, which is lower than that of Bluetooth, but it is cheaper and simpler than Bluetooth. The rate of ZigBee is not proportional to the transmission distance. When the transmission distance is 134m, the rate is only 28Kbit/s. However, it is worth mentioning that the transmission reliability of ZigBee becomes higher when it is at this rate. The application system using ZigBee technology can connect hundreds of network nodes, up to 254 at most. These characteristics determine that ZigBee technology can perform better than Bluetooth technology in some specific areas, including consumer precision instruments, consumer electronics, home automation and so on. However, ZigBee can only transmit data over a short distance and of a small order of magnitude because of its low rate and small communication range.

ZigBee components can be embedded in a variety of electronic devices, and can achieve short-distance information transmission and automatic control of these electronic devices. Specifically, it has the following characteristics:

The capacity of ① network is large. Because ZigBee devices can be connected to 254network nodes, each ZigBee network can serve 255devices at the same time. ZigBee network supports not only stars, clusters and other network structures, but also other complex network structures.

② rate is low, close range. The lowest communication rate is 10 Kbit/s, the highest is 250Kbit/s, and the transmission range is between 10m and 134m. If the transmission power of RF between neighboring nodes increases, the transmission range of information can reach about 3km. In the case of routing, the communication range between nodes will be larger.

③ has low cost. The protocol of ZigBee is relatively simple, and the power is as low as 1/10 of Bluetooth. Therefore, ZigBee has low performance requirements for communication controllers, so data measurement can be realized only by using 8-bit microcontrollers with low performance. In addition, the sub-function node code of ZigBee is only 4KB, and there is no need to pay patent fees when using ZigBee protocol, so the cost is low.

④ low power consumption. The working cycle of ZigBee network is short, and the number of communication cycles is small. The devices connected by this kind of network generally have only two states, namely, sleep state and active state. For example, to make a ZigBee device work for more than half a year, it takes only two ordinary No. 5 dry batteries.

⑤ has high reliability. The ZigBee network has an information collision avoidance mechanism, which reserves a special data gap, which can avoid data conflicts and collisions and improve the overall reliability of the ZigBee network.

⑥ short delay. In general, the delay range of ZigBee network is 15~30ms, and some applications which are sensitive to delay can work normally within this delay.

⑦ has high security. The reason why the ZigBee transmission network has high security is that the technology adopts three-level security mode. The first level security mode is no security setting, the second level security mode is the anti-data leakage mechanism based on control list, and the third level security mode is advanced symmetric password setting, such as AES-128 encryption algorithm. In order to ensure the integrity of data, ZigBee also has the function of identifying and checking data.

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