3 Communication Methods for PLC to Connect to Computer
PLC programming is different from other computer software programming. The written program will not run automatically on the computer. It needs to combine external circuits and mechanical equipment to give full play to the value of the program. This is also the characteristic of automation technology. Theory + practice, the combination of software and hardware, This is the right direction for the development of automation. This article summarizes several basic ways of connecting PLC with computer.
1. Serial port
The serial port is the earliest and most convenient way. It uses the serial port that comes with the computer to establish a connection with the serial port of the PLC. Early PLCs used this download method. Such as Mitsubishi FX series, Siemens S7-200 and S7-300 series. Even in the new century, many computers have canceled the serial port, but few PLCs have no serial port.
The serial port of PLC is generally used to establish connection with the touch screen. And now the computer has no serial port, generally use the USB to serial cable to achieve, especially the USB to 485 serial port, not only used for PLC, but also widely used in the connection of various frequency converters, servo drives. Don't think that there are only a few parameters for the inverter and the servo drive, and it is not necessary to connect the machine. When dealing with difficult problems of the load, it is necessary to monitor the parameters and various states of the inverter on the machine.
USB to RS485 is a common tool for industrial controllers. For example, when doing serial communication, we can use the serial assistant to monitor data. The download line of the early Siemens PLC can be replaced by this cable, and many frequency converters, servo drives and all download lines using RS485 communication can be used.
2. USB
Although the serial port has many advantages, it also has many disadvantages. The biggest disadvantage is the slow speed. With the advancement of technology, USB gradually occupies half of the country. Now PLCs all support USB programs, and the most used is the MICRO USB interface, which is the T-shaped port of old mobile phones and mobile hard drives. Not only PLCs, but most touch screens and text displays also use this interface to download programs.
There is another interface, which is the square USB interface, which is the interface on the printer. Omron PLC uses this interface. Therefore, the connection cable of the printer is the download cable of Omron PLC.
Serial port and USB are the two most commonly used computer connection methods, which are not only suitable for PLC, but also widely used in touch screen, servo, inverter and so on. However, many PLCs support two connection methods at the same time.
3. Network cable
With the development of Internet technology, Ethernet is more and more used in the industrial automation industry, so many PLCs also support network cable connection, such as Siemens' latest Portal platform, S7-1200 series. Even the low-end S7-200smart series supports network connection.
