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Written by: Guadalupe Chalas, Senior Marketing Data Specialist, Device Connectors, Phoenix Contact
As application areas transition to Ethernet protocols and field devices continue to require increased transmission capacities, single pair Ethernet (SPE) is becoming an attractive option. It delivers fast and gigabit Ethernet combined with power over a simple two-wire interface. In addition, SPE can be used with standard industrial grade housings designed for the harshest environments.
Standards now exist for Ethernet transmission, SPE transmission channels and application-specific Ethernet transmission and cabling. Before transitioning existing systems to SPE, system integrators and component manufacturers must learn about the connectors, network cables, and switches available for use.
Single Pair Ethernet has the Potential to Revolutionize the Industrial Ethernet Infrastructure.
Industrial Ethernet is used for factory, building and process automation applications. It differs from standard Ethernet because it allows for deterministic and real-time data exchange. Although today’s Industrial Ethernet infrastructure is effective, it has limitations.
For example, Ethernet connectivity isn’t seamless to the field device level. Fieldbus networks must be used to enable data flow from field devices. In addition, gateways are required to bridge the fieldbus and Ethernet networks, adding complexity and expense.
Single pair Ethernet has the potential to enhance the Industrial Ethernet infrastructure. SPE is a miniaturized two-wire Ethernet solution that enables direct connectivity and power delivery to field devices. It eliminates the need for a gateway and brings Ethernet all the way to the field devices.
The benefits of an Industrial Ethernet infrastructure with SPE include:
- Increased efficiency. Organizations experience fewer down-time instances and shorter down-time durations.
- Smarter devices. With enhanced communication to devices, organizations can collect data from devices and tell devices exactly what to do.
- Real-time manufacturing data. This supports cloud computing and higher levels of analytics.
- More robust capabilities. SPE supports higher data speeds than protocols previously used at the field device level. In addition, SPE supports greater cabling distance at lower speeds than any other protocol—up to 10Mbps over a distance of one kilometer.
A Smaller Footprint and Reduced Cabling Requirements Compared to Traditional Industrial Ethernet Technologies
Historically, Industrial Ethernet infrastructures have been built with Fast Ethernet and Gigabit Ethernet technologies. Fast Ethernet is half duplex, meaning that one pair of wires transmits and receives data. Gigabit Ethernet needs four pairs of wires to support higher speeds.
In contrast, SPE needs only one pair of wires for data and power, leading to reduced cabling. It also has a reduced footprint, due to less wire and two contacts instead of four or eight. SPE can support 10Mbps, 100Mbps, and 1Gps with a single interface. In addition, SPE has M8 and M12 interface compatibility.
See below for characteristics of different types of SPE:
- 10Base-T1S. This is used for short distances and can support up to eight nodes. Work is underway to expand to 16 or 32 nodes.
- 10Base-T1L. This is used for long distances, up to one kilometer.
- 100Base-T1 and 1000-BaseT1. These are used for Gigabit SPE.
Leveraging Power Over Data Lines (PoDL) Minimizes Size, Weight and Cost Requirements, in Addition to Reducing Cabling
Unlike traditional Power of Ethernet (PoE) technology, Power over Data Lines (PoDL) enables power and data over a single pair of cables. PoDL requires less cabling, which reduces the size, weight and cost of equipment. Short-reach SPE, which is 15 meters, provides up to 50 watts of power. Long-reach SPE allows for approximately 7.7 watts of power at 1,000 meters.
Standards Exist for Ethernet Transmission, SPE Transmission Channels and Application-Specific Ethernet Transmission and Cabling
SPE standards are defined at three different tiers: (1) requirements for Ethernet transmission, (2) requirements for the SPE transmission channel and (3) requirements for application-specific Ethernet transmission and cabling. Different organizations handle each of these tiers of standards.
The Institute of Electrical and Electronic Engineers (IEEE) has created committees, subcommittees and working groups to address Ethernet standards.
- LAN/MAN Standards Committee. This group is responsible for IEEE 802, which addresses local area network (LAN) and metropolitan area network (MAN) standards. This standard serves as an umbrella for all other Ethernet standards.
- Ethernet Subcommittee. This group is responsible for the IEEE 802.3 standard.
- Working Groups and Released Ethernet Standards. These groups are responsible for IEEE 802.3XX standards.
Standards that are relevant to SPE include IEEE 802.3cq which relates to PoDL or PoE, IEEE 802.3cg which relates to the physical layer specification for management parameters for 10MB/s operation and power delivery over a single pair and IEEE 802.3da which is working to expand the nodes supported by SPE.
The International Electrotechnical Commission (IEC) defines connector interface standards. As outlined in Figure 5, several relate to SPE. Phoenix Contact is working on the IEC 63171-2, the IEC 63171-5 and the IEC 63171-7 standards.
IEC 63171-2 and IEC 63171-5 Connectors Offer Miniaturization, Ease of Integration and Industrial Reliability
There are three significant advantages associated with IEC 63171-2 and IEC 63171-5 SPE connectors:
- Miniaturization. The IEC 63171-2 connector interface is much smaller than a standard RJ45, allowing for double the packing density. It is also the smallest interface for the entire series of IEC 63171 standards.
- Ease of integration. Connectors can be integrated into a standard M8 housing and connector. IEC 63171-2 and IEC 63171-5 connectors have the same internal interface.
- Industrial reliability. The IEC 63171-2 and IEC 63171-5 connectors offer mechanical robustness, vibration safety, EMC compatibility and features designed for industrial environments.
SPE is a Future-Proof Technology.
SPE provides higher speeds over longer distances, supporting up to 1Gbps over 40 meters and 10Mbps over 1,000 meters. For comparison, the maximum reach for Profinet is 100 meters at 100Mbps and the maximum reach for I/O Link is 20 meters at 230Kbps.
In addition, SPE includes broad technology competence from leading companies coming together and representing key markets. Through collaboration, industry players have developed a solution that works for everyone. Thanks to M8 compatibility, SPE allows for easy integration and installation within existing systems.
Prices are Falling and SPE Will Soon be More Economical Than RJ45
Today, SPE is more expensive than RJ45—primarily because production volumes are low. In the near future, however, the average market price for a one-meter SPE patch cable is expected to be much lower than a comparable RJ45 patch cable. In addition, SPE uses less copper cabling which makes the technology a more cost-effective solution than RJ45.
Phoenix Contact Offers IP 20 and IP 67 SPE Connectors and Network Cables, with Switches Coming in 2022
Phoenix Contact currently sells a variety of IP 20 and IP 67 SPE connectors and network cables (see Figure 9 for additional details). With regard to switches, Phoenix Contact is currently testing switch installations together with sensors and device manufacturers to ensure interoperability of SPE and PoDL. The company plans to launch its first SPE switches in 2022 and will continue to expand its product portfolio based on market needs in 2022.
Phoenix Contact participates in the Single Pair Ethernet System Alliance which includes players from all levels of the Industrial Ethernet ecosystem. This collaboration leads to easier implementations from sensors through to cables and the cloud.