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All about RS485 – How RS485 Works and How to Implement RS485 into Industrial Control Systems?

In short, RS485 is a standard defining the electrical characteristics of serial lines for use in serial communications systems. It is essentially a form of serial communication. It may sound complicated for those who don’t know what is serial communication, so here’s an explanation.

What is Serial Communication?
Serial communication is a way to send data. It is like the Universal Serial Bus (USB) or ethernet that we can find in many of our modern computers. Manufacturing facilities use serial communication to link their devices together. As mentioned, an example of serial communication is RS485.

Now, why don’t companies just use USB or ethernet to transmit data between their devices? Compared to serial communication, USB and ethernet are significantly more complex and expensive. Serial communication also has a deterministic behaviour to avoid collisions of data packets, making it more reliable for a linkage system with many devices. Ultimately, it can be thought in a way that serial communication is more made for this usage as compared to the common USB and ethernet.

There are different serial communication standards such as RS232, RS422 and RS485. The most widely used communication standard is RS232. The main difference between them is in the hardware.

You can find out more about the differences between RS485 and RS232 here.

About RS485
There are many standards in serial communication and RS485, also known as TIA-485 (-A) or EIA-485, is just one of them. This standard is a product of joint efforts by the Telecommunications Industry Association and the Electronic Industries Alliance (TIA/EIA). It is known for being able to be used effectively over long distances and in electrically noisy environments. Due to this and it being able to transmit data over long distances, the RS485 is used commonly as a protocol for POS, industrial and telecom. The RS485 is also common in computers, PLCs, microcontrollers and intelligent sensors in scientific and technical applications.

RS485 is used more industrially where many devices need to be interconnected together for a system. However, Arduino and Raspberry Pi hobbyists also use it for some of their projects when multiple peripherals need to be linked to the board.

Real-world applications of RS485
RS485 is used in many computer and automation systems. Some of the examples are robotics, base stations, motor drives, video surveillance and also home appliances. In computer systems, RS485 is used for data transmission between the controller and a disk drive. Commercial aircraft cabins also use RS485 for low-speed data communications. This is due to the minimal wiring required due to the wiring configuration requirements of RS485.

RS485 is however most popularly used in programmable logic controllers and factory floors where there are lots of electrical noise. RS485 is used as the physical layer for many standards and proprietary automation protocols to implement control systems, most commonly Modbus.

Modbus is the world’s most popular automation protocol in the market. Developed by Modicon, Modbus enables different devices from different manufacturers to be integrated into the main system. Most Modbus implementations use RS485 due to the allowance of longer distances, higher speeds and multiple devices on a single network.”

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