Planning Ethernet-based automation networks The right switch for any application

Transcription

1 Planning Ethernet-based automation networks The right switch for any application Communication within machines and systems is increasingly based on the Ethernet standard (IEEE 802.3). When designing networks, planners frequently face the challenge of selecting the right infrastructure components for their applications. The Ethernet network functions simultaneously as a modern fieldbus system and a universal communications backbone over which the typical IT services are provided, for example, for transmitting camera data. As structuring elements, the installed switches should therefore make use of the numerous options provided by the standard in the industrial installation environment. At the same time, they must take into account the requirements of the automation protocols used, such as Profinet or Ethernet/IP, in the areas of real-time capability, diagnostic properties, and network redundancy. For the first time, industrial switches are now available with integrated DLR redundancy for Ethernet/IP networks. Economical networking according to the plug & play principle The consistent implementation of the plug & play philosophy of the IEEE standard allows industrial Ethernet switches to network machines and systems easily and economically. To do this, according to the plug & play principle, the switches forward the data traffic, filtered according to destination addresses. A broad product portfolio is available for the different applications and environmental demands that includes switches having a data rate of 100 or 1000 Mbps and various port configurations. Using glass-fibre ports, it is possible to bridge great distances of up to 30 kilometres and more via multimode and singlemode cables. While the glass-fibre ports support a fixed transmission speed of 100 Mbps or Gigabit, depending on their design, the copper twisted-pair ports adjust to the best-possible

2 data rate of the connected communication partner. The port-related automatic auto-crossing and auto-negotiation mechanisms ensure the establishment of a secure link to end devices having a transmission speed of 10, 100, or 1000 Mbps. Thus, the switches allow the combination of devices and segments having different data rates. Direct installation on the machine or system Figure 1 The IP67 switches can be flexibly installed directly in the machine in a space-saving manner. In addition to the conventional RJ45 plug-in connectors that are used within control cabinets, protected variants such as the M12 circular plug-in connector are used for decentralised installation in the field. The fourpin D-coded M12 plug-in connector is standardised for fast Ethernet networking (100 Mbps) using the M12 standard. To connect distributed end devices in the field, Phoenix Contact provides switches having the high IP67 protection rating. The devices in the 1605 series include five M12 ports. Due to their slim 30 millimetre design, they can be installed directly and easily on one of the machine sections. Thus, users can choose the mounting site of the IP67 switches flexibly, in a space-saving manner, and optimised for installation, near the Ethernet end devices to be connected (Figure 1). Automatic priority identification If Ethernet is used for field communication, timecritical I/O data must be transmitted. When selecting suitable switch components, the realtime requirements of the automation protocol used must be taken into account. Here, suitable switches such as the IP67 devices of the 1605 series support the quality-of-service mechanisms used by Profinet IO and automatically evaluate the prioritisation information included in the data telegrams in the VLAN field. The prioritisation of Figure 2 The power-over-ethernet switches in a Gigabit design are connected in the field via M12 plug-in connectors. data packets forms the basis for data traffic having a higher priority, such as time-critical process data, not being slowed down by data traffic with a lower priority during periods of

3 higher data volume. At the same time, the switches include the PTCP (precision time control protocol) filter functions required for unmanaged components in Profinet networks. To simplify the planning of Profinet networks, they are categorised into three application classes. The IP67 devices of the 1605 series represent a Profinet Class A solution. Significant savings in cabling costs The power-over-ethernet (PoE) technology according to IEEE 802.3at in combination with a Gigabit data rate is suitable for connecting cameras and vision sensors in the system area. Corresponding components are generally physically remote control cabinets and are often installed on inaccessible parts of the system. The power-over-ethernet design means that the component installation requires just one cable that is used in parallel for data transmission and power supply. This results in significant savings in the cabling costs. The eight-pin cable design having an x-coded M12 plug-in connector according to CAT 6A is used for Gigabit Ethernet communication (Figure 2). Up to eight power-over-ethernet end devices can be linked directly in the field via the PoE switch in the IP67 protection class. Immediate localisation of faults The network diagnostics contribute decisively to increasing the availability of the system function. Based on the diagnostics information, users can perform maintenance actions before a failure occurs. In order to be able to diagnose the network directly via the controller, the automation switches in the Profinet or Ethernet/IP operating modes are visible via the respective automation protocol. The diagnostics information of the network components is then available directly in the PLC and in the engineering tool of the controller (Figure 3). In Profinet networks, such network components are in Class B. Corresponding switches support the device function of Profinet IO. They are thus visible in the controller as Profinet devices that can be configured and diagnosed by Engineering. Since the switches also include topology recognition via the Link Layer Discovery Protocol (LLDP), it is possible to display the network topology. It is thus possible to localise errors quickly when they occur. Rapid switchover time when errors occur The use of switches allows the implementation of network topologies such as star, tree, ring, or any meshed structures. While star and tree topologies can also be established using unmanaged switches, ring or meshed structures require a special design. If a ring is implemented in an Ethernet topology, the redundant port must be blocked via a redundancy

4 mechanism and may be activated only if the ring is interrupted. This task is performed by the redundancy protocol of each managed switch. All active components in the meshed topology must also support the same redundancy protocol. As a universal solution, the Rapid Spanning Tree Protocol (RSTP) provides switchover times here in the range of one second. Figure 3 The selection aid explains which switches are suitable for Profinet applications of Conformance Classes A, B, and C. In automation networks, alternative redundancy mechanisms are normally used, for example, the Media Redundancy Protocol (MRP) in Profinet networks of Conformance Classes B and C. In addition to a more rapid switchover, these solutions also allow the cable routeminimised integration of two-port field devices. Ethernet/IP networks work using the Device Level Ring (DLR) redundancy technology, which makes possible very short recovery times of three milliseconds. This allows for a virtually seamless switchover of the device communication. Using the DLR technology, it is possible to install controllers, I/O modules, field devices, and drives in a fast redundant ring. Standard components such as PCs, other Ethernet/IP devices that are not DLR-capable, or switches, were previously integrated into the ring by connecting special three-port components upstream. The new Advanced Managed Switches in the FL Switch 7000 product family from Phoenix Contact now provide devices that can be directly integrated into a DLR ring. This results in considerable advantages when installing and implementing Ethernet/IP networks.

5 The world s first switches with DLR support The new Advanced Managed Switches in the FL Switch 7000 product family are particularly suited for use in Ethernet/IP networks (Figure 4). This is because the industrial Ethernet components are equipped for the first time with the Common Industrial Protocol (CIP). This new technology means they can be configured and diagnosed from the Ethernet/IP control system. The FL Switch 7000 switches are also the world s first devices that support the Device Level Ring (DLR) redundancy mechanism. If an error occurs, switchover times of less than three milliseconds are achieved using DLR, thus increasing network availability. Figure 4 The FL Switch 7000 Advanced Managed Switches are the world s first devices to support the Device Level Ring (DLR) redundancy mechanism. The FL Switch 7000 switches allow the integration of up to six devices that are not DLR-capable into the ring topology. The eight-port components are available as pure copper solutions and alternatively having two or three glass-fiber interfaces. Variants having multimode or single-mode glass fibers allow flexible integration into the superordinate network. In addition, the FL Switch 7000 series provides proven functions such as IGMP snooping, multicast source detection, and auto query port for intelligent multicast filtering in order to increase the stability of the network. If you are interested in publishing this article, please contact Becky Smith: marketing@phoenixcontact.co.uk or telephone