Friday, 18 March 2011

Industrial In/Out Connectors

Industrial USB Connectors from In2Connect UK Ltd

Industrial applications from the simplest hand held data logger to a fully blown industrial Ethernet system have carried the world’s best loved I/O connectors into a harsher and less tolerant environment. Industrial connectors face numerous environmental stresses. In order to support transportation, communications, networking, IT, medical systems, etc. they must match the level of product technology and the rapid development and growth of the sector and must combat temperature and humidity; exposure to liquids, oils and chemicals; shock or vibration and RF/EMI interference. Above all, whatever the specific application, they must provide absolute fail safe reliability.

In most industrial applications, waterproofing of components is arguably the first major add-on to the features required of an indoor interconnect and it has become very clear that many engineers and designers don’t want to reinvent interconnects for the sake of it, they want manufacturers to adapt products that they’ve already got built into BOMs.

As a prime example of this, whilst the D-sub I/O connector is a very mature product it remains extremely popular in instrumentation and industrial contexts and with the acceleration of rugged computers, hand held data loggers, etc. the connector manufacturer has seen an accelerating demand for more robust
D-sub designs both waterproof and filtered against RF or EMI. One only has to consider the extreme variety of applications demanding computerised control/communication systems to see what is driving this ~ everything from robotics systems in wet manufacturing; wash-down areas like milking parlours, food preparation plants, car washes; and networking technologies for automating discrete and process manufacturing plants.

As a consequence of this demand, EN 60529 an international classification system for the sealing effectiveness of enclosures for electrical equipment against the intrusion of foreign bodies and moisture was developed by the International Electrotechnical Commission. It isn’t specific to connectors, but they form an integral part of most entering or exiting most enclosures. This system utilizes the letters "IP" ("Ingress Protection") followed by two or three digits. The first digit indicates the degree that persons are protected against contact with moving parts and intrusion: 6 = No ingress of dust; and complete protection against contact.
The second digit indicates the degree of protection of the equipment inside the enclosure against the harmful entry of various forms of moisture (e.g. dripping, spraying, submersion, etc.): 7 = No ingress of water in harmful quantity when immersed in water under defined conditions of pressure and time (up to 1 m of submersion), i.e. temporary immersion. 8 = Suitable for continuous immersion in water under conditions which shall be specified by the manufacturer but is usually taken to cover depths say between 1 and 3 metres. It doesn’t cover the pressures associated with deep sea exploration, etc.

If one takes the ubiquitous D-sub connector, the aim has been to reduce the number of components that make up the connector, hence remove all possible leakage paths and manufacturers have generally produced an IP67 rated connector by adding a mounting plate with a silicone O-ring to create a watertight seal at the panel interface and back potting screw machined contacts to prevent water ingress through the connector body. These are now available in pretty much all of the standard d type configurations excepting crimp. Backpotting of the contacts has to be done once the contacts are embedded in the insulator, so the concept of a truly waterproof crimp d-sub would arguably cost too much to achieve?

Cost of course is amongst the leading drivers, thus the design concept for I/O connectors will always be limited by it ~ so in order to save space and reduce equipment size the industry needs to get more and more signals, such as common signals, microwave signals, optical signals, high voltage signals, power signals into a single connector whilst maintaining circuit or signal separation. This has been achieved with the IP67 mixed layout d-sub.

MIL-C circular connectors like the D38999 range provide waterproofing and environmental sealing; EMI/RFI shielding; shock and vibration proofing, but at a relatively high cost. So what does the electronic tap-ware industry do when not fitting baths into fighter aircraft? In2Connect was set this question when asked to develop low cost, functional waterproof connectors and the resulting Pintail circular range is an IP68 rated indoor/outdoor interconnect solution for industrial and electronics applications. These multi-pin, threaded coupling connectors will provide IP68 integrity when mated or when fitted with a waterproof end cap.

The connector bodies are moulded from glass filled nylon and are available in free plug, cable end receptacle and fixed jam nut receptacle formats, all with dust caps to suit. Contacts are interchangeable between plug and socket to allow design flexibility and polarisation. They were designed to be light weight, corrosion resistant and RoHS compliant with additional improved product features over competitive products; such as ~ planform contact identification by raised numbering for easy identification of circuits to save time and money when soldering or repairing incoming cables. Contacts are solder cup and are an integral part of the insulator, so less piece parts or crimp contacts to lose and no need for expensive crimp tools. To simplify the field assembly process, the dual O ring sealing means that the integral backshell can be easily removed in two sections to allow accurate soldering of the incoming cable. The threaded bodies provide a quick and easy connection to reduce installation and service time and have inbuilt key/keyway orientation with good cable waterproofing and retention by virtue of a rear compression nut. Not rocket science like the aluminium bodied MIL-Ccircular connectors, but then the proximity sensing electronic taps in our bathrooms aren’t for rocket fuel.

Ethernet has long been the standard communications protocol in the office, but the transition to Industrial Ethernet for shopfloor networks has meant reinforcement to the Ethernet and other similar connectors.  Office or shopfloor are built on the same standards-based networking platform, the Ethernet local area network (LAN) standard IEEE 802.3. The key advantage of industrial Ethernet is that it allows manufacturers to deploy a single platform to enable interoperability in connecting workplace operations to corporate and office networks. However, there is a huge difference between installing Ethernet in a sheltered office environment and installing them on the manufacturing floor. If a connector or interconnect fails in a manufacturing system, the cost of parts replacement and repair will be insignificant compared to the indirect costs which could be associated with production downtime.

D-sub and circular multipin in/out connectors are relatively chunky with or without additional protection, but the transition of RJ45, USB, FireWire IEE 1394 and Optical Fibre to the industrial environment has required the application of the type of reinforcement associated with MIL-C circular connectors. For industrial real-time-Ethernet, the industry has gravitated toward an RJ45 connector type with a bayonet latching or screw threaded coupling mechanism according. This robust design with IP67 rating ensures reliable protection and easy connection under harsh environmental conditions.

It could be said that what goes around (the connector), comes around ~ and provides the called for reliability at the same time?

By: Bob Hart

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