Ethernet Connectivity - Fit for Industry

Ethernet, a driving force in industrial automation technology, has made itself synonymous with innovation. Slogans such as "vertical integration", "network convergence", "PC-based control" or "homepage for every field appliance" characterise the discussion. Behind it all is the idea of taking successful technology from the office world and exploiting it for the industrial world as well. Driving this innovation on the one hand is the pressure on costs and on the other the requirement to give the manufacturing industry access to global networks.

However, network convergence does not automatically lead to the convergence of ambient conditions! Convergence should not be a one-sided process, but should rather reflect the demands of industrial automation. Economic benefit from new technology is only possible if it is used in technically appropriate solutions.

In industrial environments, most new developments are made based on the basis of 100 BaseT, in other words Fast Ethernet. Cabling for Fast Ethernet is based on a CAT 5 installation in compliance with DIN EN 50 173. It is recognisable by its RJ 45 connectors. The cables contain 4 core pairs with optional screening. Two pairs are required for Fast Ethernet. A distinction is made between UTP and STP cables depending on whether the cable has no screen or a complete screen. Offices are normally fitted with so-called star wiring: a separate cable goes to each desk from a central storey distribution board. This wiring system is ideally suited to office buildings.

Applicability to industrial conditions

Applicability to industrial conditions

However, if you compare the situation in an office with conditions in an industrial environment, the weaknesses of an office network can be quickly identified: A star configuration is a complete non-starter in field cabling. Field bus systems such as AS Interface are based on linear configurations. Issues such as mechanical stability, EMC protection as well as ease of handling and assembly raise further questions. The Ethernet idea remains a good one, but will scarcely be successful in the rough industrial environment without paying attention to the particular requirements involved.

Making Ethernet fit for industry

Making Ethernet fit for industry

Using its expertise in the field of industrial connectivity and based on practical experience, HARTING has produced a specification for industry-proof networks that is closely aligned with proven solutions for field bus systems.

The thing which holds modern, worldwide networks together is compatibility. Only when the unfettered exchange of data is ensured, can our communication society function. If continuous communication is required, it must not break down at the connector interface. Today's RJ 45 is without doubt the standard for communication. There is simply no way around it. Recognising this was the impetus for developing a new industrial Ethernet connector system at HARTING.

If RJ 45 is viewed not as a connector, but rather as a simple piece of interface geometry, an opportunity opens up. HARTING has more or less reinvented the RJ 45. The aim in developing the new product family was to fully meet the requirements for industrial application of 100 Mbit Fast Ethernet, and at the same time bring Ethernet to the field by means of very simple termination technology.

In contrast to the office, decentralised peripheral equipment in IP 67 environments requires hybrid cabling in order to supply power to 24 V actuators, i.e. as well as connecting signal wires, power transmission also has to be maintained.

This interface solution for hybrid networks enables Ethernet and power supply, properly separated, to be housed in one connector, thereby drastically reducing installation costs. Two locking mechanisms have been developed for different types of application and location. The standard locking mechanism for the RJ 45 which is standardised to IEC 60603-7, is designed to take a maximum strain of 50 N. For applications in industrial environments which place higher demands on locks, HARTING supplies an additional 4-point lock over the outside of the housing. IP 67 types are achieved with the Han® 3A locking lever which is known as an industry standard. The modular construction of the data connector in this family allows the same insert to be used in IP 20 and in hybrid and non-hybrid IP 67 connectors.

Making Ethernet fit for industry

The data module has four HARAX quick connection contacts which provide gastight connection for flexible, industrial CAT 5 cables (AWG 22 - 24) as well as for massive cables up to AWG 22 - 23. The four contacts in the hybrid version which can take loads of up to 16 amps, have the same quick connection design, and allow the connection of flexible wires up to a diameter of 1.5 mm².

The consistency of the quick connection design is also shown in the industrial screening of the connector which does not require the usual crimping of the cable braid to the screen. Simply slotting the two screens together with an audible click is enough to achieve 360° screening. The appliance side of the connector can either be designed as a panel feed-through or directly implemented in the appliance. The consistent use of SMD connection technology for the RJ 45 data connector and the hybrid contacts also ensures low manufacturing costs on the appliance side.

Quick connection technology minimises installation costs

Ethernet offers enormous potential for rationalisation. This approach can only be successful if it is the symbiosis of communication and installation benefits. The short-sighted transference of office solutions to machines will result in considerably greater installation costs for the user. An industrial connector has to be assembled regardless of whether it is a power connector or a communications connector. This is why HARTING relies on quick connection technology which can be performed on-site without special tools and which has proved itself in industrial applications.

The few, simple steps needed to assemble a hybrid cable can be described as follows:

  • Strip away cable sheath and place data wire in the splicing element
  • Press the splicing element together with the insert
  • Align and lock the screens with the insert and connect the cable screen
  • Feed in the power cable and press the guiding pockets together to terminate
  • Lock the housing with the inserts

This work sequence can be carried out by a fitter on site in less than two minutes without any special tools, and the simple data version can be completely connected in one minute.

The IP 20 versions for data can be installed at 21 mm intervals which guarantees maximum packing density on the appliance side. For the hybrid IP 67 version, we have succeeded in reducing the fitting length by 30% over the industry standard housing, Han 3A. By widening the creepage distances, HARTING has developed a connector which is compatible with the RJ 45 and which meets the insulation co-ordination required in IEEE 802.3 AF even in industrial environments. This modification permits "power over MDI", i.e. the 48 volt power supply via the data interface.

Compatibility requires standards

Compatibility requires standards

After a decade spent arguing about the subject of field buses, a solution was only reached through the power of the market. The number of bus systems in use is now limited. However, no common standards have been found either for the protocol or for transmission technology. Every field bus organisation has pursued its own process of standardisation. This has led to a situation where the different connectors used today especially in decentralised systems with a lot of IP 67 appliances, still represent a barrier which can only be overcome at some expense. One result of this is the low distribution of decentralised IP 67 assemblies. Automation without control cabinets has not caught on as yet.

HARTING has set itself the goal of setting a broad standard from the very beginning with Ethernet in an industrial environment by offering a consistent connector solution. By working in the PNO (PROFIBUS User Organisation), the IAONA (Industrial Automation Open Networking Alliance), the DKE (German Electrotechnical Commission) and also the IEC (International Electrotechnical Commission), it is possible to establish a broad base to prevent the kind of proliferation which has happened with field buses. For example, at the beginning of the year the PNO decided to use the HARTING solution as a uniform design for ProfiNet. Furthermore an international standard has been proposed as the HARTING approach is an open solution and not a proprietary system.

Compatibility requires standards

From connector to an Ethernet system component

From connector to an Ethernet system component

The connector fulfils its classic function of making an electrical connection at the beginning and end of a cable. However, HARTING has taken this classic connection function a step further. After all, there are different network configurations to be achieved, and a transition from IP 20 to IP 67 has to be found. With InduNet, the HARTING system family for connectivity in the automation network, entry to the Ethernet age is made easier. The user can make any kind of connection in the network in a totally flexible manner: installation is guided by the application.

Andreas Huhmann
HARTING Deutschland GmbH & Co. KG

Market Manager Industry

THE SIEMENS VIEWPOINT: Industrial Ethernet more relevant than ever

If the 80s were the decade of the Personal Computer, the 90s are the decade of local networks. New automation concepts based on modularity, accompanied by increasing rationalisation, require sophisticated network solutions in industry with its special demands in terms of reliability and strength.

Industrial Ethernet has had a definite role to play in industrial communication at Siemens since 1985. Since then it has proved itself as a reliable network for transmitting large volumes of data between control units, PCs, workstations, etc., in manufacturing plants. Today Ethernet is the number one in local, industrial networks (LANs) with a share of 80%.

The basic idea behind Industrial Ethernet is to use the existing Ethernet standards and to add on the necessary, beneficial details for industrial communication. In this way products are created for the special conditions which exist in the manufacturing and process environment. These are completely compatible with existing Ethernet products, but with regard to their permissible temperature range, mechanical construction and EMC stability, for example, they meet the higher requirements of the industrial environment. Specially designed components for use in rough environments – starting with special, robust electronics, twisted pair cables with optimum screening all the way to robustly designed connectors – permit the construction of safe network connections even where interference levels are high.

It is no wonder, therefore, at a time when control intelligence is being decentralised, that Industrial Ethernet is not only the basis for the IT world, but is also bringing more and more IT functions into the field. This is because the industrial environment is becoming more and more dominated by intelligent field appliances which have to exchange extensive volumes of data. For example, small, industrial switch modules allow a linear network construction as required for field bus systems, with a correspondingly high data throughput.

With the pace of these developments, Industrial Ethernet will remain highly relevant in the next few years, and it will result in positive, customer-friendly changes in the world of automation.

The Electrical Lean Switches from Siemens allow robust twisted pair cables to be directly connected using Fast-Connect technology which saves both time and money.