July/August 2019

30 n COMMUNICATIONS July/August 2019 www.drivesncontrols.com Single-pair Ethernet: the future for factory comms? E thernet has successfully made the transition from the office environment to the factory floor where the eight-conductor cables and their RJ-45 connectors are a now a familiar sight. But an alternative version of Ethernet is now emerging that promises to be simpler, cheaper, lighter and easier-to-install. Instead of the four pairs of conductors found in a traditional Ethernet cable, the new transmission medium uses just one pair – and can even re-use existing cables. Although it is not offering any breakthroughs in terms of transmission speeds or distances, the new format is being designed to meet the needs of the modern factory that may contain hundreds, or even thousands, of IoT connections. Known generically as single-pair Ethernet (SPE), demand for the new format was driven originally by the automotive sector which was looking for a high-speed, yet lightweight, transmission technology for applications such as transmitting camera and diagnostic signals in increasingly digitised and autonomous vehicles. But SPE has many potential attractions in other areas such as building and factory automation. “To be able to replace existing fieldbus systems, we will need components that are more cost-effective, more miniaturised, and more standardised. Here, single- pair Ethernet cables are playing a key role,”explains Berry Medendorp, Belden’s director of global industrial marketing.“The easy set-up, smaller sizes, significant reduction in weight, and simple connection technology make this technology an interesting option in automation engineering, building cabling, railway engineering, and also in many other applications.” On the shopfloor, the new technology could help to eliminate the confusing variety of serial communications systems that have emerged in recent decades, many of them requiring proprietary connections, and not being able to interoperate with each other. A quarter the weight The potential advantages of single-pair Ethernet are significant. The cables, for example, weigh about a quarter as much as traditional eight-core Ethernet cables. They will also ease cable congestion and open up more routing options. SPE will bring continuous IP-based communications to the field level, allowing simple devices such as sensors and RFID readers to be equipped with Ethernet interfaces, and helping to make the vision of almost seamless Ethernet communications from the shopfloor to the cloud a practical reality.“Single-pair Ethernet is the technology on which we will build the road to the future success of the industrial IoT,”declares Eric Leijtens, global product manager for industrial communications at TE Connectivity. Although it is already possible to send Ethernet signals via twisted pairs, existing wiring and application standards (such as 100Base-T1 and 1000Base-T1) limit the number of devices that can be connected to such cables, and restrict their transmission range to 100m or less. To address the emerging market for IoT technologies – predicted to be worth $6.2 trillion by 2025, with almost 40% of this coming from manufacturing applications – the IEEE set up a task force (802.3cg) to work on a twisted-pair Ethernet technology that would enable transmissions beyond 100m. The group drafted a standard that defines a single twisted-pair cabling system capable of transmitting Ethernet signals at speeds of up to 10Mb/s – and potentially up to 1Gb/s in the future – over distances of at least 15m or (with lower transmission rates) up to 1km. The IEEE defines two versions of its system. One, called 10Base-T1S, and has a range of 15m and a data rate of up to 10Mb/s; the other, called 10Base-T1L, can carry data at the same rate over a distance of up to 1km and will support up to ten inline connections. 10Base-T1S operates at 200Mhz, while the long-haul version operates at 20MHz. SPE can operate over generic cabling and could re-use the vast installed base of existing cables (such as those originally installed for 4– 20mA and Profibus applications), cutting costs dramatically. A new Ethernet cabling technology is eerging that promises to make factory communications cheaper and easier, as well as saving space and weight. Using simple two-conductor cables, this new version of Ethernet could replace proprietary serial communications and support links from the shopfloor to the cloud. Tony Sacks reports. Photo: Harting