Lack of predictability of the timing behaviour was for a long time used as an argument against the use of Ethernet in industrial applications. This reasoning was in most cases based on experience with early network topologies in which the network users were interconnected through hubs. A hub forwards all the packets received at one port to all the other ports. Such networks use the CSMA/CD method (Carrier Sense Multiple Access with Collision Detect) to specify who may transmit and when.
In the CSMA method, the station wishing to transmit listens to the channel (carrier sensing) before it transmits data. A station may transmit only when the transmission medium is not already being used by another station. If the transmission medium is in use, the station waits until it is free before sending its data. Owing to the signal propagation delays, it can nevertheless happen that two devices transmit simultaneously. In order to avoid a loss of data in a collision case, both transmitters must be able to detect the collision (collision detect) and retransmit their data packets after an arbitrarily selected delay. CSMA/CD is the customary standard for 10-Mbit networks with hubs.
Early Ethernet network topologies, some of which are still in use today, use hubs as standard because the complex switches produced in the 1980s and early 1990s were expensive.
Plug & Play switches – ECO Line and WaveLine
The ECO Line and WaveLine from Weidmüller are cost-effective ways of gaining a foothold in the world of Industrial Ethernet. Ongoing adaptation of the products to new technologies and the needs of customers enables users to set up network infrastructures for industrial applications simply and quickly. The ECO Line products require no configuration and for many products even the pin assignment of the connecting cables is flexible with the help of the auto-crossover functionality (Auto-MDI/X). This means that users can use straight-through cables for connections between switches and terminal devices and also for connections between switches, making crossover cables no longer obligatory.
The new WaveLine has a uniform housing concept in which up to eight copper ports and one optional FO connection can be integrated.
Plug & Play switches – AdvancedLine
When the demands are even greater, then iOpen recommend Weidmüller’s AdvancedLine. In addition to the new features of the WaveLine, the switches of the AdvancedLine provide further benefits for applications in tough conditions:
- All AdvancedLine models feature an extended temperature usage range. This allows their use in rooms without climate control and operation outside of the normal temperate zone.
- Separate routes for signal and power cables are not always possible in industrial applications. The optional FO ports ensure trouble-free operation even over long distances through strong electromagnetic fields and are available in multimode or singlemode versions.
- When upgrading networks, the uniform component width enables existing units to be exchanged for new ones with more ports without having to shift all the other components on the rail or having to extend the switching cabinet.
- The products of the AdvancedLine provide users with 6 to 24 ports and two optional FO ports in compact aluminium housing.
- The extremely wide voltage supply range guarantees stable operation even if the majority of terminal devices connected may have already shut down.
- The plug-in power supply connections, which also include a redundant power supply option, enable quick connection and disconnection of the power supply when working on the network.
- An MTBF time in excess of 60 years makes these switches ideal for robust and reliable Industrial Ethernet networks.
Weidmüller ECO Line and WaveLine switches are available from iOpen .