The Internet of Things (IoT) will build a world of all-things interconnection and connect the entire physical world into a network and provide unprecedented technical support through technologies such as sensing, analysis and control. Among these, short-range wireless communications play a crucial role. In particular, the current fastest growing field of IoT smart home, a wide range of wireless technology agreements, the standard battle intensified.
Currently, a variety of short-range wireless transmission technologies are widely used in the field of Internet of Things. The more competitive wireless communication technologies include ZigBee, Bluetooth and WiFi, and new technologies developed based on these technologies. In the current IoT smart home industry, these three kinds of wireless communication technologies have all been applied in the field of smart home, and the market share of the ZigBee wireless communication technology has been gradually increased in recent years. Of course, to build a physical interconnection of all things with the network , in order to present these three wireless communication technology has its own advantages and disadvantages.
In order to adapt to the rapid development of the Internet of Things industry, ZigBee, WiFi and Bluetooth technologies are now improved on their own technical standards, respectively introducing ZigBee3.0, WiFi Halow and Bluetooth 5.0.
WiFi Halow
WiFi is a wireless extension technology of Ethernet and is currently used in smart hardware fields such as a WiFi smart socket, a WiFi camera, and the like. However, in the field of IoT smart home, WiFi is not the most suitable wireless technology in the field of IoT smart home because of factors such as low security factor, high power consumption and device scalability.
In order to meet wireless technology more suitable for the interconnection between devices, the WiFi Alliance released the 802.11ah WiFi standard, "Halow", earlier this year.
WiFi Halow is better suited for low-power, long-distance IoT devices. Halow using the 900MHz band used by WiFi lower than 2. 4G Hz and 5.0GHz bands, which means lower power consumption. At the same time, Halow's coverage reaches 1 km and the signal is stronger.
WiFi Halow Compared to the previous WiFi protocol, improved performance and power consumption in the wall. According to the WiFi Alliance, this technology will not be available until 2018. However, although the wireless transmission performance of WiFi is improved, a new generation of Halow does not mention the security issue of wireless communication, and Halow will also run on an unlicensed band, which means there will be interference between different products . For the IoT smart home devices, security and anti-interference ability are the top priorities in the development of smart home. Therefore, the WiFi protocol needs to be widely used in the field of Internet of Things, and the security and anti-interference capability need to be solved problem.
Bluetooth 5.0
Bluetooth is also a very common wireless communication technology in everyone's life, such as Bluetooth speakers, bracelet devices and car Bluetooth system. In ZigBee, WiFi and Bluetooth these three kinds of wireless communication devices , Bluetooth is one of the shortest point-to-point communication distance.
June 16, Bluetooth Alliance released a new generation of Bluetooth technology standard Bluetooth 5.0. The signal range of Bluetooth 5.0 has been doubled, which means it's longer communication distance, low-power transmission speed is four times the existing standards, but also has accurate indoor positioning.
Bluetooth communication distance has been improved, but this point-to-point communication does not have large-scale network topology capabilities. For example, a perfect smart home solution even needs hundreds of devices, Bluetooth 5.0 can not achieve large-scale networking equipment. At the same time, the power consumption of Bluetooth devices is generally about a month, for the electronic devices and smart hardware, Bluetooth 5.0 performance to better meet the needs of hardware devices, but in the field of smart home, Bluetooth 5.0 also need to be tested.
ZigBee3.0
ZigBee is a low power LAN protocol based on the IEEE802.15.4 standard. It features low power consumption, low complexity, autonomous networking, low speed and high security. It is a very suitable wireless communication protocol for the Internet of Things. Especially in recent years, the market share of ZigBee wireless communication technology in the field of Internet of things has been greatly improved. However, ZigBee has different technical standards based on different application layers, such as ZigBee HA, ZigBee LL and ZigBee BA. Therefore, smart home devices manufactured by different manufacturers do not achieve interoperability. In order to solve the interconnection problem, ZigBee3.0 standard was born.
Based on the IEEE802.15.4 standard and operating at 2.4 GHz (worldwide frequency), ZigBee 3.0 is the first unified, open and complete wireless Internet of Things (IoT) using the ZigBee PRO network, unifying the ZigBee Alliance's market-leading wireless standards Product Development Solutions. It extends from the physical layer to the application layer, including interoperability certification and branding for a growing number of market segments, covering the broadest
The dryer is a kind of mechanical equipment that uses heat energy to reduce the moisture content of materials. It is used to stop the drying operation of objects and vaporize the moisture (usually moisture or other volatile liquid components) in the materials after heating to obtain solid materials with regular moisture content. The purpose of drying is to meet the requirements of material application or further processing.
The future development of dryers will develop and improve dryers under the conditions of deepening the study of drying mechanism and material drying characteristics, and controlling the operation conditions of different materials; In addition, large-scale, high strength, high economy, and improved compliance with raw materials and quality are the fundamental trends of dryer development. Now let's introduce the function, working principle, classification, operating procedures, selection instructions and cleaning methods of the dryer.
The dryer acts as a refrigeration compressor to suck the low pressure (low temperature) refrigerant in the evaporator into the compressor cylinder. The refrigerant steam is compressed, and the pressure and temperature rise at the same time; The refrigerant steam with high pressure and high temperature is pressed to the condenser. In the condenser, the refrigerant steam with higher temperature and cooling water or air with lower temperature stop heat exchange.
The heat of the refrigerant is taken away by water or air and condensed, and the refrigerant vapor becomes liquid. This local liquid is then sent to the contraction valve, which is throttled into a low temperature and low pressure liquid and enters the evaporator; The low temperature and low pressure refrigerant liquid in the evaporator absorbs the heat of the compressed air and vaporizes (commonly known as "evaporation"), while the compressed air condenses a large amount of liquid water after cooling; The refrigerant steam in the evaporator is sucked away by the compressor.
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