How to connect legacy factory automation systems to Industry 4.0 without disruption
Figure 5: Dialog for programming the Weidmüller gateway with PLC tag properties. The tags are names assigned to variables of any type stored in the PLC memory. Image source: Weidmüller
Creating the tag map is again performed from the PC connected to the Ethernet switch via the ‘Add Tag Map’ icon, which initiates the Tag Map Editor dialog (Figure 6). Each PLC connected to the network will need its own tag map. In the dialog, the target device is selected, and each tag to be used as a data source is ‘mapped’ to a data destination. The process is then repeated for all connected devices. The final step in the process is to activate the tag map to initiate communication between the source and destination tags hosted on the network devices. A tag map viewer on the PC allows for a check that the right source data is heading to the right destination.
Industry 4.0 enhances manufacturing productivity and efficiency. However, it requires new Industrial Ethernet infrastructure, which is expensive and disruptive to install.
DIN rail mounted, and they operate over a 0 to 55˚C temperature range using a 12-to-24-volt input. Once configured via a browser, the Weidmüller gateways require no other equipment to transfer serial data formatted for one of the supported RS-232/RS-485 serial protocols into one of the supported Industrial Ethernet protocols, or vice versa. Data can be
connecting the device to an Ethernet switch and then plugging in a PC into the other side of the switch (Figure 4). Once that’s done, the gateway can be connected to the 12-to-24-volt supply. The PC can then be used to log in through a browser window where the main gateway dialog appears. Dialogs then simplify the setup of the Industrial Ethernet network, as well as the addition of Ethernet and serial network devices to the gateway. Finally, the gateway serial ports are set to match the serial port configuration of the connected controller. The key to the gateway’s ability to communicate between devices that use different protocols is the use of ‘tag’ data. The gateway enables the movement of tag data between different connected devices.
Tags are key when programming modern PLCs. They are names assigned to variables of any type stored in the PLC memory. Some examples of tag names are: ‘#DATETIME’, ‘HEARTBEAT’, and ‘Switch_Group1_IP’. The tags are stored in the PLC’s memory in a tag database. In this tag database, all function blocks (for example, relays, timers, and counters) and program variables (for example, a timer value called ‘Transmitter_ RF_ Mute_ Timer’), as well as all other objects, are stored as tagged variables with attributes such as initial value, float, string, integer, Boolean (on/ off), ASCII text, discrete inputs, and discrete outputs. The tag approach allows for a more efficient approach to more complex programming but does require (as with other structured programming languages) that the developer assigns the variable tags as well as the data type in advance of their use in the program. Data arrays can also be defined in the tag database. For each PLC connected to the gateway, the developer must specify the tags from which data will be read and the tags to which that data will then be written. This first requires the tags from each
PLC connected to the gateway to be programmed into the gateway before it can use them for communication across the network. This is done from the PC connected to the gateway via the Ethernet switch. By selecting the ‘Add Tag’ icon in the configuration browser window, a dialog is activated that allows the developer to specify the tag name, data type, address, and other related information if required. It is also possible to speed things up by importing tags from a .csv file (Figure 5). Once the tags for all the connected devices have been entered, the next step is to create a ‘tag map’. The tag map enables the gateway to read the data in the registers of a source PLC and write them to the correct destination device. The data in the registers is effectively the communication payload. The payload is extracted from the source tag using the source PLC protocol, and then delivered to the gateway memory for transmission to the destination tag using the destination device protocol. It’s not critical that the source and destination tags have the same data type.
transferred to and from any port in any combination without the need to edit any PLC code.
protocols and without having to add wiring or multiple gateways. These Weidmüller gateways offer two Ethernet ports and either two (in the 7940124932 model) or four serial ports (7940124933). They support EtherNet/IP, EtherNet/IP- PCCC, ModbusTCP, and S7comm (a Siemens Industrial Ethernet protocol) at up to 10 Mbits/s. The Ethernet ports accept an 8 pin RJ45 connector. On the serial side, the gateways can handle Modbus RTU, Modbus ASCII, DF1-CIP, DF1-PCCC, PPI, DirectNET, CCM, and HostLink serial protocols. Note that while the serial support is for RS-232/ RS-485 standards, the serial input to the gateway is via the Ethernet- style 8-pin RJ45 connector rather than the RS-232/RS-485 type. The gateways are interoperable with PLCs from Automation Direct, GE, Rockwell Automation, Schneider, and Siemens. The gateways can be
Getting started with industrial gateways Configuring the Weidmüller gateway simply requires
Conclusion
Industry 4.0 enhances manufacturing productivity and efficiency. However, it requires new Industrial Ethernet infrastructure, which is expensive and disruptive to install. As shown, industrial gateways allow for a staged introduction of Industry 4.0 by bridging the gap between existing RS-232/RS-485 networks and the phasing in of Industrial Ethernet infrastructure. Using these solutions, equipment and networks can be gradually upgraded over months or years with minimal disruption.
Figure 6: For each connected PLC, the Tag Map Editor enables each tag data source to be mapped to a data destination. The process is repeated for all connected devices. Image source: Weidmüller
we get technical
40
41
Powered by FlippingBook