I/O Systems Resource Center

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Controls engineers need a variety of information on device connectivity via their input/output, I/O modules and components on topics such as terminal blocks, remote I/O, device and sensor networks, signal conditioning, cabling, wiring, connectors and cordsets.

Terminal blocks, available as spring clamp terminal blocks, screw clamp terminal blocks, and newer insulation displacement terminal blocks (IDC) are the most popular choices.

Remote I/O modules provide an ability to distribute control closer to the components and share the overall control responsibilities.

Machine mount I/O is growing is popularity as it provides flexibility and faster reconfiguration with reliable connection using connectors and cordsets.

As machine data becomes more critical to overall operations, signal conditioners and other signal conditioning devices increase in importance by helping ensure data signals are clean and uncorrupted.

The growing use of digital networks, particularly starting with sensor networks and device networks, provides faster, less expensive, easier to maintain and troubleshoot data transmission.

Timely news, back-to-basics primers, feature articles, technical white papers and descriptions of the latest products all provide valuable insights that can be used in designing and building machine controls.

Machine-Mount I/O Benefits From Recent Changes in Wire Schemes and IP Protection
IP Opens New Doors for I/O: Machine-Mount Modules Benefit From Better Protection in Harsher Environments

Is Redundancy Necessary or Superfluous?
Unnecessary Redundancy?: The Value of the Product or the Critical Nature of the Process Can Warrant It

Smart Analog I/O Gives Better Price/Performance Ratio
Get Smart: Smart Analog I/O Offloads the Main Controller and the Network

Is Safety I/O's Fault Detection and Diagnostics Worth the Price?
Should We Push for Safety I/O?: Does Its Fault Detection and Diagnostics Justify the Cost Hit?

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White Papers: In Depth Research

Redundancy in Technological Systems
Author: Helge Hornis, Ph D, Manager, Intelligent Systems, Pepperl+Fuchs
Posted: 03/10/2010
Redundancy is a concept frequently applied in technological systems. When investigating in detail why redundancy is used, one will find that there are many reasons for doing this. Looking at several redundant implementations should make this clear. Still, all aspects of redundancy have one idea in common: increased ability to control a system even when problems occur.

Functional safety systems are probably the most common automation solutions based on redundancy. Here the rationale is to provide a control system that is able to safely shut down a machine in case of emergency. Depending on a detailed safety evaluation, safety solutions of varying complexity can be used to address the particular needs of the application. Safety systems are still designed to comply with EN954, which divides applications into five classes between B at the low end and CAT 4 at the upper end. To show that not all redundant systems are equal, let's focus on two scenarios. Figure 1 shows a safety system where a number of redundant-safe input devices (e-stops and magnetic interlock switches) are connected redundantly in a series. These safety strings are then connected to a safety relay, which is ultimately responsible to shut down motors, drives or other potentially harmful devices. Consider a situation where one of the safe contacts on a magnetic safety switch is welded or simply sticky. Due to the redundant nature of the safety string, the machine will still come to a safe shutdown as soon as the door, evaluated by this magnet, is opened. Even better, the safety relay will not even allow a restart of the system after the door has been closed. The reason for this is that the safety relay demands that as soon as one of its safe inputs shows an open contact, the second input must also go open, clearly a condition not satisfied due to the welded contact. Unfortunately, it is rather trivial to trick the safety relay. All one has to do is open and close another door. As soon as this happens, the safety relay detects its two inputs as open, making this a resettable condition. As soon as this happens, the redundant nature of the system is compromised. All it takes is a second fault at the magnetic door switch, and it will not be able to result in safe system shutdown.

TIA-1005 Industrial Ethernet Cabling Standard
Author: Anixter
Posted: 10/28/2009
The Effect on the 10/100 Industrial Ethernet Switch Performance.

The Anixter Infrastructure Solutions Lab wanted to determine what effect the new TIA-1005 industrial cabling infrastructure standard would have on the data throughput performance of real Ethernet data packets running between SmartBits test cards and various manufacturers' 10/100 Ethernet switches in a real-world simulation. The test included five (5) different IP20-rated switches and three (3) different enterprise rack-mounted switches using various cabling channels made from both Category 5e and Category 6 cabling components and connector pairs that are allowable under the standard. The premise also asserts that the effect of the cabling channel interference will also vary from port to port and switch to switch because of the variable transmitter and receiver functionality.

How to Design a Low–Power Wireless Sensor Network
Author: Wim De Kimpe, CTO GreenPeak
Posted: 05/21/2009
Driven by the demand for “green” technology and better use of power, a new generation of extreme low power wireless networks is being developed for use in machine to machine networks, for industrial and control applications, as well as for health, security and other purposes. This article is about this new approach towards truly wireless networks – without any network cables or power lines.

By using systems that require very little power, it is possible to develop wireless networks that can last longer than their batteries and therefore require little or no maintenance over the life of the device, or a device that does not require any batteries at all, instead, using energy harvesting to provide the power required.

Before the era of wireless sensor communication, low-power was synonymous to low current consumption. The lower the milli-amp figure, the better the device was at low-power operation. It was all about how many or rather how few milli-amps the electronics consumed. Furthermore, when the device did not need to communicate, it was turned off, to be awoken when an alarm situation was raised or a periodic status update was called for. This technique is called duty cycling.

Overcoming Concerns about Wireless PACs and I/O in Industrial Automation
Author: Opto22
Posted: 04/23/2009
Industrial Automation Flirts with Wireless
The automation industry increasingly finds wireless attractive, and for several reasons.
- Running a wired network incurs significant labor and material costs, while wireless networks cost far less.
- Wireless offers connectivity for remote areas or areas not currently served by wired networks.
- Wireless controllers and I/O can manage devices and processes even in inaccessible areas, or areas where network wiring is difficult or impossible to install.
- And wireless can offer a way to provide proof-of-concept for a new project before incurring the expense of a wired network.

For all these reasons, automation engineers are beginning to seriously consider wireless solutions (specifically WLAN, wireless Ethernet, or Wi-Fi) for all or part of their applications.

But with all these good reasons to use wireless, several concerns remain. Among them are security, network performance and reliability, availability and cost of I/O components, and the necessity of choosing between wired and wireless solutions up front.

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