Sensor technology
Sensors are the main devices for obtaining information in the Internet of Things, and their biggest role is to help people complete the automatic detection and automatic control of items.
At present, the sensor-related technology has been relatively mature, and common sensors include temperature, humidity, pressure, photoelectric sensors and so on, which are used in many fields, such as geological exploration, intelligent agriculture, medical diagnosis, commodity quality inspection, traffic safety, cultural relics protection, mechanical engineering and so on.
As a detection device, the sensor will first sense the external information, and then convert this information into electrical signals through specific rules, and finally transmitted to the computer by the sensor network for people or artificial intelligence to analyze and utilize.
The physical composition of the sensor includes three parts: the sensitive element, the conversion element, and the electronic circuit.
The sensitive element can directly feel the corresponding items, the conversion element is also called the sensing element, the main role is to convert other forms of data signals into electrical signals;
The electronic circuit as a conversion circuit can be adjusted to the signal, will be converted to electrical signals can be used for people and computer processing, management of useful electrical signals.
Radio frequency recognition technology
Radio frequency recognition (RFID, Radio Frequency Identification), also known as the electronic label technology, the technology is wireless non-contact automatic diagnosis technology.
It can recognize a specific target and read and write related data through radio signal. It is mainly used to establish a unique identity label for each item in the Internet of Things.
The perception layer in the Internet of things usually has to establish a radio frequency recognition system, the recognition system consists of electronic label, read-write and the central information system three parts.
Among them, the electronic tag is usually installed on the surface of the item or embedded in the inner layer of the item, and the basic information of the item is stored in the tag so that it can be recognized by the IoT equipment;
The read-write has three roles
One is to read the information about the item to be recognized in the electronic tag,
the second is to modify the information about the item to be recognized in the electronic tag,
Two-dimensional 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 2-dimensional bar code records information through black and white graphics, these black and white graphics are distributed in the two-dimensional plane in accordance with a specific law, the graphics and the computer binary number corresponds to, people through the corresponding photoelectric recognition equipment will be able to 2-dimensional bar code entered into the computer for the identification and processing of data.
There are two types of QR codes, the first is the stacked/rowed QR code, and the other is the matrix QR code.
Stacked/rowed QR codes and matrix QR codes differ in form, the former being stacked from one-dimensional codes, the latter being composed in the form of a matrix.
Although the two are different in form, they all use the same principles: each QR code has a specific character set, there is a corresponding width of the "black bar" and "blank" to replace the different characters, and there is a check digit, etc.
The blue code is the same as the matrix QR code, but it is not the same as the matrix QR code.
Bluetooth technology
Bluetooth technology is a typical short-range wireless communication technology, which is widely used in the perception layer of IoT, and is one of the important short-range information transmission technologies in the perception layer of IoT.
Bluetooth technology can be used in pairing between mobile devices as well as between fixed devices, and can be used in pairing between fixed and mobile devices.
The technology combines computer technology with communications technology to solve the problem of short-distance information transmission without wires or cables.
Bluetooth is a collection of time-division multiple access, high-frequency band-hopping and other advanced technologies, which can realize both point-to-point information exchange and point-to-multipoint information exchange.
Bluetooth has been relatively mature in terms of technology standardization, and relevant international standards have been introduced, for example, its transmission frequency band adopts the international unified standard 2.4GHz frequency band.
In addition, there are special bands outside of this band that are spaced at 1MHz. 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.
ZigBee technology
ZigBee refers to the IEEE802.15.4 protocol, which is the same as Bluetooth technology, it is also a kind of short-range unlimited communication technology.
Based on the characteristics associated with this technology, it falls between Bluetooth technology and wireless tagging technology, and therefore, it is not equivalent to Bluetooth technology.
ZigBee transmits information over a shorter distance and with lower power, so this low-power communication technology is mostly used between some small electronic devices in daily life.
Like Bluetooth, ZigBee uses the same public **** wireless band, 2.4GHz, and also employs frequency hopping and packetization technologies.
However, there are only three available frequency bands for ZigBee, namely 2.4GHz (the public **** wireless band), 868MHz (the band used in Europe), and 915MHz (the band used in the US).
The base rate of ZigBee is 250Kbit/s, which is lower than the rate of Bluetooth, but less expensive and simpler than Bluetooth.
The rate of ZigBee is not proportional to the transmission distance, and when the transmission distance is extended to 134m, the rate is only 28Kbit/s. It is worth mentioning, however, that the reliability of ZigBee transmission becomes higher when it is at this rate.
Applications using ZigBee technology can realize hundreds of network nodes connected, up to 254.
These characteristics allow ZigBee technology to outperform Bluetooth in specific areas such as consumer precision instruments, consumer electronics, and home automation.
However, ZigBee is only capable of transmitting short-range, low-volume data traffic due to its low rate and small communication range.
ZigBee components can be embedded in a wide range of electronic devices and can realize short-range information transmission and automation control of these electronic devices.