There are many basic ways to connect PLC to computer? How many do you know?

PLC programming is different from other computer software programming. The written program will not run automatically on the computer. It needs to be combined with external circuits and mechanical equipment to realize the value of the program. This is also the characteristic of automation technology. Theory + practice, the combination of software and hardware, is the correct direction of automation development. This article summarizes several basic ways to connect PLC with computer.

1. Serial port

Serial port is the earliest and most convenient way. It uses the computer's own serial port and the PLC's serial port to establish a connection. Early PLCs all adopted this download method. For example, Mitsubishi FX series, Siemens S7-200 and S7-300 series. Even in the new century, many computers have cancelled serial ports, but there are few PLCs without serial ports.

The serial port of PLC is usually used to establish a connection with the touch screen. However, computers nowadays do not have serial ports, and are generally implemented using USB to serial port cables, especially USB to 485 serial ports, which are not only used for PLCs, but also widely used for the connection of various inverters and servo drives. Don't think that inverters and servo drives only have a few parameters to set, and there is no need to connect them to the machine. When dealing with load problems, it is very necessary to monitor the parameters and various states of the inverter online.

USB to RS485 is a common tool for industrial control personnel. For example, when doing serial communication, we can use the serial assistant to monitor data. The early Siemens PLC download cable can be replaced with this cable, and it can also be used for many inverters, servo drives and all download cables that use RS485 communication. Generally, original cables are very expensive. Using a universal USB to RS485 cable can save a lot of money.

The connecting cables of Siemens S7-200, GE PLC series, Danfoss, CT, Fuji, Schneider, Lenze and other drives can be replaced by USB to 485 cables, while their original cables are extremely expensive.

2. USB

Although serial ports have many advantages, they also have many disadvantages, the biggest disadvantage being slow speed. With the advancement of technology, USB has gradually taken over half of the market, and now PLCs all support USB. The most commonly used program is the MICRO USB interface, which is the T-shaped port of old mobile phones and mobile hard disks. Not only PLCs, but also most touch screens and text displays use this interface to download programs.

As shown in the figure above, it is a Mitsubishi FX3 series PLC. Look at the interface in the red circle. Many industrial control products have this interface. Almost all touch screens have this download interface.

There is another interface, which is the square USB interface, which is the interface on the printer. Omron PLC uses this interface, so the printer's connection cable is the download cable of Omron PLC.

As shown in the figure above, the red circle part is the download interface of Omron PLC, which is the same as the interface of the printer.

Serial port and USB are the two most commonly used connection methods, which are not only suitable for PLC, but also widely used in touch screen, servo, inverter, etc. Many PLCs support both connection methods at the same time.

As shown in the figure above, this is the connection option of Mitsubishi PLC programming software GX WORKS2. We can see that it supports two methods.

3. Network cable

With the development of Internet technology, Ethernet is increasingly used in the industrial automation industry, so many PLCs also support network connection, such as Siemens' latest TIA platform, S7-1200 series. Even the low-end S7-200smart series supports network connection.

Summary: In the field of industrial control, some people are very wise: by learning one product, they can draw inferences about other products, and by learning one problem, they can think of solutions to other problems. It is important to know how many brands of products and how many instructions to remember, but the most important thing is to use them flexibly. On the premise of understanding the principles and basic knowledge, understanding the essence of various connection methods will save you a lot of unnecessary trouble and achieve twice the result with half the effort.