Modbus, Kepserver, Siemens PLC Communication

Yesterday in the field to achieve the communication of industrial data, simply write it.

1. In accordance with international practice, first introduce

Modbus Communication protocol sense is a physical level, several terminals in series, by setting each terminal different ID number, to access. Specific hardware implementations have not yet been studied.

The system adopts Modbus RTU mode communication, using and checking, low in front.

For the introduction of Modbus, this article is very good: Geek College Wiki

Kepserver is a service software that provides OPC services, which provides an OPC service that can be called by external programs and written by the client data.

The OPC (OLE for Process Control) is used for process-controlled OLE,

OLE is an abbreviation for object linking and embedding (objects linking and embedding).

OPC uses the client/server structure, and the OPC server, as the central data source, is responsible for providing data from the field devices to various clients.

Siemens PLC, my understanding is the microcomputer, but can be used in more demanding environment.

2. How to Achieve

The data communicates with the computer via Modbus, using USB to R232 and then R485 hardware implementation. This is to prepare the driver in advance, I use Yu Tai Lian UT-8801 usb to serial port, drive.

Modbus has two lines of communication, measuring the two-wire voltage should be around 0.11V

The device data is then read through the Modbus protocol.

Using your own software to pass data into Kepserver, tutorial: Developing OPC clients in C #

The software sends the modbus instruction to get the data, through the binding OPC service, according to the address established in the Kepserver, writes the obtained data to the kepserver.

Kepserver is connected via a network cable to the PLC, using the PLC IP address, and the default port number 102 to communicate.

The name set up in Kepserver is the access address of the software above, and the address of these names is the address of the DB block in the PLC. (later fill in the map)

In this way kepserver can write data to the PLC, the PLC uses WINCC to establish the interface to see the data and data history curve in real time.

3. Minor errors

The computer does not recognize the COM port, the driver is not installed well, next time try a new computer, must bring a driver.

Modbus Line does not know the positive or negative, you can use multimeter test voltage detection.

Modbus data can not be read, the principle is that the ID of the device is duplicated.

OPC software fails to write, attention to various error prompts, and online search, especially the time format of each operating system.

(Follow up map)

Modbus, Kepserver, Siemens PLC Communication