In the field of intelligent building and industrial automation, LONWORKS fieldbus technology and RS485 bus technology are widely used. Analysis of the advantages and disadvantages of LONWORKS fieldbus technology and RS485 bus technology is extremely important for their reasonable application in practical engineering. Today we will analyze the relationship between these two technologies.
What is a fieldbus
Fieldbus is a digital, two-way transmission, multi-branch communication network that is used in production sites to connect intelligent field devices and automation control systems.
Fieldbus can transmit digital signals in a variety of media (multiple wired and wireless modes), and can connect up to dozens of self-control devices on two wires, which can save a lot of cables, racks, connectors, and reduce system design. , installation, maintenance workload.
The field bus forms a complete control system that is truly dispersed in the field, improves the reliability of the control system operation, enriches the information content of the control device, and provides information such as the number of valve actions and fault diagnosis, creating control information for entering the public data network. The conditions communicated between the field devices and their networks with higher control management layers, facilitating the integration of management and control.
What is LONWORKS Fieldbus Technology
LonWorks network technology is an advanced fieldbus technology introduced by Echelon in December 1990. LON (Local Operation Network) is a local operation network, with all the characteristics of fieldbus technology, and is widely used in international high-end equipment. The core of LonWorks technology is the neuron chip, transceiver and LonTalk communication protocol. The neuron chip is a very large scale integrated circuit with three CPUs inside to control communication and application execution. The neuron chip can form a control network either directly or through a transceiver.
LONWORKS field network bus technology is actually a kind of measurement and control network technology, which is exactly a kind of industrial control network technology, which can conveniently realize the connection of field sensors, actuators, meters, etc. This kind of network is different from LAN, but An industrial control network because it transmits monitoring information, status information, and control information with a small amount of data.
What is the core of LONWORKS fieldbus technology?
The core technology of LONWORKS is three 8-bit CPU neuron chips, with communication and control functions, and solidified the LONTALK protocol, as well as 34 common I/O control objects. It uses the complete IOS/OSI model. The seven-layer communication protocol adopts an object-oriented design method to simplify the design of network communication into a parameter setting, which not only saves a lot of design workload, but also increases the reliability of communication.
LONWORKS fieldbus technology, mostly used in buildings, is the only protocol that covers the layering of 7-layer networks, and it also enables the interconnection of layers.
What is the device of LONWORKS fieldbus technology?
The majority of the devices in the LONWORKS fieldbus work to detect and control the state of the components of the controlled physical system. They are called control devices or nodes and can have any combination of embedded sensors and output interfaces of the actuators. Apply the detected variables and control logic such as PID loop control, data logging and process editing data processing. (eg linearization, calibration)
Comparison of LonWorks Network Bus Technology and RS485 Bus Technology
Communication distance: The maximum transmission distance of RS485 bus is 1.2km; the maximum transmission distance of LonWorks bus is 2.7 km.
Transmission rate: The transmission rate of the RS485 bus is 300-9.6 kbps; the transmission rate of the LonWorks network is 300-1.25 Mbps.
Network structure: RS485 bus network constitutes a master-slave distributed control system; LonWorks network can form a distributed arbitrary structure form network.
Network capacity: One channel of RS485 bus network can connect up to 255 nodes; LonWorks adopts three-layer structure, namely domain, subnet, and node. There is no limit to the number of nodes in the system. The neuron chip contains a 48-bit ID number, which is the only one in the world.
Communication method: RS485 bus network is difficult to communicate in real time; LonWorks network uses P-CSMA/CD technology for real-time communication.
Communication reliability: The fault tolerance and error detection capability of the RS485 bus network must be set by software; the LonWorks neuron chip consists of three CPUs, two of which are dedicated to communication, and the fault tolerance and error detection capabilities are completed by both hardware and software.
Product interchangeability: RS485 bus network has no unified communication protocol, and the product is difficult to be compatible; LonWorks technology adopts the international standard LONTALK communication protocol, which truly realizes the interchangeability of products.
Network expansion function: The RS485 bus network has limited expansion capability, and has limitations in transmission distance, node capacity, and transmission speed. It is suitable for small systems; the LonWorks network is extremely easy to expand, modify, and maintain.
System Advancement: LonWorks network technology is an international standard formed in the early 1990s and is widely used worldwide.
Remote monitoring and operation: The LonWorks network is seamlessly connected to the Intenet for remote monitoring and remote operation.
The difference between LonWorks fieldbus technology and RS485 bus technology
1) LONWORKS technology is a field bus with a complete control network system, which includes everything from the physical layer to the application layer to the network operating system.
RS485 is just a specification of the physical layer of the network.
2) LONWORKS technology supports multi-media, such as: twisted pair, coaxial cable, power line, fiber, wireless, infrared, etc.
RS 485 communication does not support multi-media.
3) LONWORKS technology has a very good openness, and products from different manufacturers using LONWORKS technology can work together on the same network. It is difficult for different manufacturers' products using RS485 technology to work on one online.
4) LONWORKS technology supports a variety of topologies such as bus, star, and free topology.
RS 485 communication is only available in a bus topology.
5) Each segment of the LONWORKS technology network can be up to 2700 meters in length (without repeaters). There can be 64 nodes per network segment.
Each segment of the RS485 communication network can only reach 1000m, and each segment has only 32 nodes.
6) LONWORKS technology supports complete network structures such as domains, subnets, and nodes. One domain per LONWORKS network supports up to 32,385 nodes.
RS 485 communication is difficult to compare with this.
7) The LONWORKS technology processor has 3 CPUs that can handle complex network communication applications.
The general RS485 communication processor has only one CPU, which is difficult to handle complex network communication and applications.
LONWORKS technology has the ability to withstand common mode interference and can adapt to harsh environments.
RS 485 communication has poor anti-interference ability.
8) LONWORKS technology is a peer-to-peer communication network. Each node has the same status, no master node, high reliability and good real-time performance.
RS485 communication is generally a master-slave structure.
9) LONWORKS technology is easy to maintain and can be loaded and loaded directly from the network.
RS 485 communication is difficult to do this.
Due to the reliability and openness of the LonWorks system, the neuron chip consisting of three single-chip microcomputers will cover all the complex contents of all 7-layer protocols of OSI, and it will be solidified on the hardware, plus 2700 meters of non-relay transmission distance and 32000 nodes. The capacity makes LonWorks more obvious than the traditional bus in dealing with multi-node large-flow real-time control. It has become the mainstream control network of today's intelligent community products, and is also the cell control network recommended by the Ministry of Construction.
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