What technologies are included on the sensing side?

Perception-side technologies include: 1. Sensor technology, which can help people complete automatic detection and automatic control of items; 2. Radio frequency identification technology, which can obtain relevant information about items through the principle of electromagnetic coupling without touching the object; 3. QR code technology; 4. Bluetooth technology; 5. ZigBee technology, etc.

The operating environment of this tutorial: Windows 10 system, Dell G3 computer.

The key technologies of the IoT perception layer (end) include sensor technology, radio frequency identification technology, QR code technology, Bluetooth technology and ZigBee technology, etc. The main function of the IoT perception layer is to collect and capture the status information of the external environment or items. When collecting and capturing the corresponding information, radio frequency identification technology will be used to first identify the items, and then sense them through highly integrated micro-sensors installed on the items. Information about the environment where the items are located and information about the status of the items themselves enable real-time monitoring and automatic management of items. The realization of this function cannot be achieved without the coordination and cooperation of various technologies.

Sensor Technology

The Internet of Things can’t realize the sensing function without sensors. The biggest role of sensors is to help people complete the automatic detection and detection of items. Automatic control. At present, sensor-related technologies are relatively mature and are used in many fields, such as geological exploration, aerospace exploration, medical diagnosis, commodity quality inspection, traffic safety, cultural relic protection, mechanical engineering, etc. As a detection device, the sensor first senses external information, then converts this information into electrical signals through specific rules, and finally transmits them to the computer through the sensor network for analysis and utilization by people or artificial intelligence.

The physical composition of the sensor includes three parts: sensitive element, conversion element and electronic circuit. Sensitive components can directly sense the corresponding items. Conversion components are also called sensing components. Their main function is to convert other forms of data signals into electrical signals. Electronic circuits, as conversion circuits, can adjust signals and convert electrical signals into signals that can be used by people and computers. Processing and management of useful electrical signals.

Radio Frequency Identification Technology

The abbreviation of Radio Frequency Identification is RFID. This technology is one of the wireless automatic identification technologies, and people will It's called electronic labeling technology. Using this technology, information about items can be obtained through the principle of electromagnetic coupling without touching the object.

The perception layer in the Internet of Things usually builds a radio frequency identification system, which consists of electronic tags, readers and writers, and intermediate information systems. Among them, electronic tags are generally installed on the surface of items or embedded in the inner layer of items. The basic information of the items is stored in the tags to facilitate identification by IoT devices; the reader has three functions. One is to read the relevant information in the electronic tags. The second is to modify the information of the items to be identified in the electronic tag, and the third is to transmit the obtained item information to the central information system for processing; the function of the central information system is to analyze and manage the information collected by the reader from the electronic tag. The data information read in.

QR code technology

QR code (2-dimensional bar code), also known as two-dimensional bar code and two-dimensional bar code, is a information identification technology. QR codes record information through black and white graphics. These black and white graphics are distributed on a two-dimensional plane according to specific rules. The graphics correspond to the binary numbers in the computer. People can use the corresponding photoelectric recognition equipment to identify the two-dimensional codes. The code is entered into the computer for data identification and processing.

There are two types of QR codes. The first type is stacked/lined QR codes, and the other is matrix QR codes. There are differences in form between stacked/lined QR codes and matrix QR codes. The former is composed of stacked one-dimensional codes, while the latter is composed of a matrix. Although the two are different in form, they both use the same principle: each QR code has a specific character set, with "black bars" and "blanks" of corresponding widths to replace different characters. There are check codes and so on.

QR code has many advantages:

First, the coding density is high and the information capacity is large. Generally speaking, a QR code can theoretically accommodate 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 for QR code encoding can be fingerprints, pictures, text, sounds, signatures, etc. The specific operation is to digitize these basis first and then convert them into barcodes. QR codes can not only represent 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 is partially damaged due to being penetrated by a sharp object. In these extreme cases, the QR code can be read and used normally. In other words, as long as the damaged area of ​​the QR code does not exceed 50%, technical means can be used to restore the original information.

Fourth, the decoding reliability is high. The error rate of QR codes is less than one in ten million, which is more than ten times lower than the error rate of ordinary barcodes.

Fifth, high security and good confidentiality.

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

Seventh, you can reduce and enlarge the scale at will.

Eighth, it can be read with a variety of devices, such as photoelectric scanners, CCD design equipment, etc. Convenient, easy to use and efficient.

Bluetooth technology

Bluetooth technology is a typical short-distance wireless communication technology. It has been widely used in the perception layer of the Internet of Things. It is the Internet of Things One of the important short-distance information transmission technologies in the perceptual layer. Bluetooth technology can be paired between mobile devices, fixed devices, or fixed and mobile devices. This technology combines computer technology with communication technology to solve the problem of short-distance information transmission without wires or cables.

Bluetooth integrates a variety of advanced technologies such as time division multiple access and high-frequency segment hopping, which can realize both point-to-point and point-to-multipoint information exchange. Bluetooth is relatively mature in terms of technical standardization, and relevant international standards have been introduced. For example, its transmission frequency band adopts the internationally unified standard 2.4GHz frequency band. In addition, there are special frequency bands with intervals of 1MHz outside this frequency band. When Bluetooth devices use different powers, the communication distances are different. If the power is 0dBm and 20dBm, the corresponding communication distances are 10m and 100m respectively.

ZigBee Technology

ZigBee refers to the IEEE802.15.4 protocol. Like Bluetooth technology, it is also a short-range wireless communication technology. According to the relevant characteristics of this technology, it is between Bluetooth technology and wireless tag technology, so it is not equivalent to Bluetooth technology.

ZigBee transmits information over a short distance and with low power. Therefore, this low-power communication technology is often used between some small electronic devices in daily life. Like Bluetooth technology, the public wireless frequency band used by ZigBee is also 2.4GHz, and it also uses frequency hopping, grouping and other technologies. However, ZigBee has only three usable frequency bands, namely 2.4GHz (public wireless frequency band), 868MHz (frequency band used in Europe), and 915MHz (frequency band used in the United States). The basic rate of ZigBee is 250Kbit/s, which is lower than the rate of Bluetooth, but it is lower cost and simpler than Bluetooth. The rate of ZigBee is not proportional to the transmission distance. When the transmission distance is expanded to 134m, its rate is only 28Kbit/s. However, it is worth mentioning that the transmission reliability of ZigBee will become higher when it is at this rate. Application systems using ZigBee technology can connect hundreds of network nodes, up to 254. These characteristics determine that ZigBee technology can perform better than Bluetooth technology in some specific fields, including consumer precision instruments, consumer electronics, home automation, etc. However, ZigBee can only complete short-distance, small-scale data traffic transmission because of its low speed and small communication range.

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

① Large network capacity. Since ZigBee devices can be connected to 254 network nodes, and based on its own equipment, each ZigBee network can serve 255 devices at the same time. ZigBee networks not only support star, cluster and other network structures, but also support other complex networks. network structure.

　②Low speed, close range. Its communication rate is as low as 10 Kbit/s and as high as 250Kbit/s, and its transmission range is between 10m and 134m. If the RF transmission power between adjacent nodes increases, the information transmission range can reach up to about 3km. If routing is used, the communication range between nodes will be larger.

　③Low cost. ZigBee's protocol is relatively simple, with power as low as one-tenth that of Bluetooth. Therefore, ZigBee has lower performance requirements for communication controllers. In this way, data calculation can be achieved by using only an 8-bit microcontroller with low performance. . In addition, the ZigBee sub-function node code is only 4KB, and there is no need to pay patent fees when using the ZigBee protocol, so the cost is low.

　④Low power consumption. The ZigBee network has a short working cycle and a small number of communication cycles. Devices connected to this 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 only needs to consume the power of two ordinary AA dry batteries.

　⑤High reliability. The ZigBee network has an information collision avoidance mechanism, which reserves dedicated data gaps to avoid data conflicts and collisions, improving the overall reliability of the ZigBee network.

　⑥Short delay. Under normal circumstances, the delay range of ZigBee network is 15~30ms, and some application software that is sensitive to delay can work normally within such delay.

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

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