Single Pair Ethernet (SPE) is the catchword when it comes to the network infrastructure for the Industrial Internet of Things (IIoT). Users hope it will allow them to implement a consistent communication architecture in all applications where data is present. This is based on the concept of extending Ethernet connection right down to sensor level, i.e. wherever there are no data highways but where users need compact data transmission with a long reach.
Industrial-Ethernet networking is used in industrial applications and offers a range of benefits thanks to its real-time transmission. However, the technology is too complex for simple sensor applications. "At sensor level, we are still using bus architectures. We now want to create an IP-based communication infrastructure with a uniform communication protocol, reaching from the sensor to the cloud", explains Simon Seereiner, Head of Product Management SAI & IE at Weidmüller.
Adjusting data transmission rates
Single Pair Ethernet does not require excessive data-transmission rates and can span larger distances, while also having a more compact design. Unlike cabled Ethernet connections, it requires just one pair of wires rather than two or four pairs. This was originally developed in the automotive sector, where space and weight savings are of utmost importance, to have an infrastructure that has as few cables as possible, yet deliver the high performance required due to the increasingly autonomous driving characteristics. "This is why automotive construction companies started to develop a protocol for Single Pair Ethernet together with the IEEE standards association right back in 2012", Seereiner explains. Likewise, in the industrial sector sensors increasingly need to be integrated into machines and systems, so the cabling needs to be compact and designed for industrial use. Single Pair Ethernet is the key technology that makes it possible to implement IoT applications in the industrial sectors: transfer rates of 10 Mbits/s with a transfer length of 1000 m up to 1 Gbit/s with a transfer length of 40 m are completely adequate even for complex sensor systems. Scanners and cameras for monitoring or for detecting a component's type and location can also be continuously integrated into the network via Ethernet.
Data and power supply in one
Power over Data Line (PoDL) technology means that Single Pair Ethernet can also ensure the power supply to the connected components. Up to 60 W can be guided to an interface during simultaneous data transmission of 100 Mbit/s. "This makes it possible to supply a sensor with both power and data using just one two-wire cable. And this is all done with a small and compact design", Seereiner explains. There is no need for an additional power supply cable, which is beneficial when spatial conditions are tight. Power supply with simultaneous data transmission is set out in the relevant standards. The IEEE has defined a classification into different power classes for this purpose. Since classes 1–9 are already assigned to Power over Ethernet (PoE), the power classes for PoDL start at 10. Weidmüller's product range already includes two plug-in connectors for Single Pair Ethernet technology; one variation in protection class IP20 and one variation in protection class IP67. Both variations are part of the series of standards IEC 63171, which defines the plug-in connectors for Single Pair Ethernet. Due to the sturdy locking mechanism, the extraction force of at least 50 N and an industrial dielectric strength of 2.25 kV DC, the new SPE plug-in connectors have the perfect properties for industrial use. The high density means that up to 50% less space is required compared to RJ45 plug-in connectors in the IP20 environment. Furthermore, the SPE plug-in connectors can be quickly and easily assembled in the field and are suitable for cabling in the AWG 26 to AWG 22 range.
Pooling experience and expertise
To promote the development of Single Pair Ethernet for industrial applications, many experts from the fields of plug-in-connector technology, connection systems, automation technology, and the cable industry, have got together to develop internationally applicable standards for this technology. “Weidmüller has been involved in this type of technology partnership right from the start. And everyone is working together to pool their competences and exchange information", says Seereiner about the partnership. The experience of other companies can prove really beneficial, such as in the implementation of new products", says Seereiner. “The aim of this technology partnership is to guarantee a coordinated infrastructure for devices, plug-in connectors, cables and measurement technology”. This type of uniform and consistent infrastructure is based on international standardisation. With a technology of this importance, this involves an extremely wide range of organisations such as the IEEE. For the IEEE 802.3 cg project, plug-in connectors and their electrical properties were defined for the first time in the IEEE environment. All plug-in connectors can be used if they meet the electrical properties set out in the standard. The connectors for Single Pair Ethernet are defined in the IEC 63171-X series of standards. The design of the mating faces and the mechanical requirements of the connectors are described in the subordinate series of standards. Weidmüller's SPE plug-in connectors are examples of IEC 63171-2 variations for the IP20 environment and IEC 63171-5 variations for the IP67 environment. Weidmuller will be shortly introducing two new connector solutions for Single Pair Ethernet where the two mating faces, ie. for IP20 and IP67, are mutually compatible. This is particularly beneficial in field measurement technology, where users can easily connect devices with IP67 interfaces using an IP20 measurement connector and vice versa", reveals Seereiner. And that's not all: "There are also plans for a 4-chamber version in addition to the single connectors". This would allow for the cabling of four SPE systems via a single interface and with a compact design: the housing is smaller than the conventional RJ45 housing. Weidmüller is also working flat out on additional solutions to create an infrastructure for SPE technology.