RS485 is a communication method that is most commonly used in industry, telecommunications, POS, etc. In particular, RS485 is used a lot in noisy environments due to its large transmission range, and too much transmission. too long in noisy environment. Not only stopping there, RS485 is also widely used in computer systems, controls, PLCs or smart sensors…
What is RS485?
RS485, also known by its full name, is the RS485 communication standard or RS485 cable, this is a communication method that connects to computers and other devices. RS485 is not just a single interface but it is a communication complex capable of creating simple networks of many devices.
RS485 communication standard can connect up to 32 devices on a single wire pair and a ground wire system at a distance of up to 1200m.
Structure of RS485
RS485 cable is constructed very simply, only from wires twisted together in pairs. However, this very structure creates a serious drawback, when interference occurs in one pair of wires, immediately another pair of wires will also suffer. This leads to the operating voltage between the 2 wires not having too much difference, the RS485 receiver can still receive the signal because the receiver has eliminated all interference.
What is the working principle of RS485?
The principle of operation of RS485 is quite simple, data will be transmitted through 2 wires when twisted together, this wire is called twisted cable. When the wire is twisted, it gives RS485 high anti-interference ability and better long-distance signal transmission.
RS485 is divided into 2 types of configurations, currently the most used are 2-wire configuration and 4-wire configuration. Let’s find out the working principle of these 2 types of configuration!
RS485 “Cable Construction”
+ 2-wire RS485 pinout
For 2-wire configuration, data will be transmitted in one direction at a given time. With this type of setup, the TX and RX signals will share a single pair of wires, helping users save on installation costs.
Looking at the figure above, we can see that the transmitter and receiver will be connected at each node of a twisted pair. However, the 2-wire configuration limits the nodes to twisted pair so the user must pay attention to the turnaround delay.
+ 4-wire RS485 pinout
The operating principle of the 4-wire configuration is quite different, where data will be transmitted and arrived at the same time from the nodes. Here, 2 wires will take care of transmitting and the other 2 wires will take care of receiving.
Looking at the figure above, we can see that the main gate and transmitter are reconnected to the node system that receives data on twisted pairs. However, you should note that these links will be limited to primary and secondary communication, or simply limited to where nodes cannot receive signals from each other.
Advantages and disadvantages of RS485
+ Advantages of RS485
+ Is the most advanced product today, overcoming the weaknesses left by RS232.
+ RS485 cable is the only communication standard that can connect multiple transmitters and receivers on the same network at the same time.
+ Receivers with input resistance up to 12kΩ RS485 can still connect up to 32 devices. In addition, with other inputs, RS485 can connect up to 256 devices.
+ When RS485 is connecting devices at quite a distance, users can overcome it by installing more repeaters to increase the number of connected devices, making the signal more stable, avoiding line interference.
+ RS485 has 2 signal lines installed, so the signal will be transmitted faster over longer and wider distances.
+ Disadvantages of RS485
+ When transmitting too many devices on the same line, the response time will be slow.
+ Devices need to use the same RS485 standard instead of the existing Analog standard
+ A certain knowledge is required to use RS485 effectively
Difference between RS485 and RS232
As everyone knows, RS485 is an advanced version, overcoming all the disadvantages of the RS232 communication standard. But what is the difference between these two communication standards?
1. Number of Slaves
The first difference between RS485 and RS232 is the number of controls and buttons:
+ RS485: Control 32 devices at the same time
+ RS232: Only 1 driver and 1 receiver can be controlled
2. Distance in Communication
The next difference to mention is the distance in the communication of Rs485 and RS232:
+ RS485: Maximum communication distance reaches 1200m
+ RS232: The maximum communication distance is only 15m
This communication distance reflects that RS232 is not capable of anti-interference at the transmission lines, the signal is often interfered, so it limits the communication distance, reducing the communication speed greatly. Therefore, RS485 is a very suitable communication standard for you to operate devices at long distances.
3. Transfer rate
The next difference between RS232 and RS485 is the baud rate:
+ RS485: Transfer rate 10MBit/s. This speed is achieved because the RS485 cable is twisted in order to increase resistance to interference, allowing magnetic fields to pass through and not disrupting communication, so RS485 communicates at a faster rate.
+ RS232: Transfer rate 20KBit/s
Application of RS485 in Industry
RS485 is widely applied in the industry in general and the automation industry in particular. The outstanding applications of RS485 can be mentioned as applications in remote control of motors VFD or in inverters. RS485 also controls simple PLC and HMI networks, all of which allow remote control of motors in the industry.
+ Practical example: To monitor and check the amount of water pumped in from a pump, you do not need to keep a close eye on it. Instead, when using RS485, you can completely control and monitor the amount of water from a far away place.
+ Example HMI: When the RS485 communication standard connects the system including HMI and PLC, the PLC will also be successfully connected to the VFD via RS485.
+ Example PLC: The PLC system is often used in monitoring and monitoring the water level in the tanks, so when connected to RS485, the PLC can monitor the water level from the control center or can return. control flow, water level manually as needed.
+ Example VFD: The VFD system when connected to RS485 allows controlling the speed of the water pump from a remote center.
