Abstract : This paper uses a Siemens PLC as the master station and an Eurotherm 590P DC speed controller as the slave station, and introduces the specific hardware configuration process and PLC program writing for communication between them via a PROFIBUS network.
1. Introduction:
Fieldbus serves as a bridge for communication between controllers and field devices. With the continuous development of fieldbus technology, its advantages such as high speed, accuracy, and reliability have become increasingly apparent. PROFIBUS-DP, as a type of fieldbus, has been widely used in factory automation. PROFIBUS-DP is an open network that allows products from different manufacturers to communicate. This article uses SIEMENS' SIMATIC S7-300 PLC as an example to illustrate how to achieve communication with a Eurotherm 590P speed controller via the PROFIBUS-DP bus.
2. Hardware configuration section :
Create a project in SIMATIC Manager, configure the network configuration in hardware. The CPU selected for this system is CPU 315-2DP. When inserting the CPU, configure the PROFIBUS network. The default station address is 2, the transmission rate is 1.5 Mbit/s, the line rule is DP, and the PROFIBUS attribute is DP master. Just click OK.
Third-party devices that support the PROFIBUS-DP protocol all have GSD files. When configuring a slave system, the GSD file needs to be manually loaded. Insert the CD that comes with Eurotherm into the computer, and then in the hardware configuration window, click "Options-Install GSD File-Browse (specify to eury1649.GSD)-Install" in sequence. As shown in Figure (1)
Figure (1) Installation of Eurotherm GSD driver
After installation, the installed driver file will be found in the "PROFIBUS DP-Additional Field Devices-Drive" directory on the right side of the configuration screen. Drag the Eurothrem 590+ directly onto the PROFIBUS bus as shown in Figure (2) 1. The system will automatically assign the speed controller address on the bus, or you can manually assign it. The selectable range is 0-125, but addresses 0, 1, and 2 are usually used as master station addresses and should be avoided as much as possible. Add the Process Data Read module according to the amount of data required. This article takes reading current and speed and setting ramp speed value as an example. Two process data reads and one process data write are required, as shown in Figure (2) 2. Double-click the Eurothrem 590+ module to bring up the 590+ properties dialog box and select the Parameter Assignment tab. As shown in Figure (2), in the Value column, the first three groups are reserved by the system and cannot be changed, as shown in Figure (2) 3. The following numbers are hexadecimal values of the markers for the 590+ parameters you need to read or change. Each pair corresponds to one parameter in the Eurotherm database. In the diagram, 012A (HEX) in Figure 4 represents motor current feedback, with marker number 298. Similarly, 5 corresponds to speed feedback, with marker number 207, and 6 corresponds to ramp input, with marker number 5. After configuring the required data, click OK to close the dialog box. Finally, compile and save; the hardware and network configuration is complete.
Figure (2) Hardware Configuration
3. Speed controller settings:
To communicate with a PLC, the Eurotherm 590P only needs to be configured with the communication type and address. The required parameters are shown in Figure (3).
Communication method selection: MENU-SEIRIAL LINKS-TEC OPTION-TYPE-PROFIBUS DP.
Communication address selection: MENU-SEIRIAL LINKS-TEC OPTION-ADDRESS (address range 0-125). The set address must be consistent with the address in the PLC configuration. For example, address 3 is used in this case.
After completing all settings, save the parameters: MENU-PARAMETER SAVE-SAVE
4. PLC Programming Section
In a PLC, network read/write operations can be performed through SFC14 and SFC15, or directly through the MOVE instruction.
The data block corresponding to the PLC in this example is shown in Figure (4), and the program is shown in Figure (5).
5. Conclusion
As described above, based on the PROFIBUS-DP bus, communication between the S7-300 and the Eurotherm 590P speed controller is established through hardware configuration and speed controller parameter settings. Through programming, the status monitoring and control of the device can be realized. This communication method can also realize communication between the PLC and multiple speed controllers. This method is also applicable to Eurotherm's 690 frequency converter.
