I/O Devices Increasingly Distributed

By Gary A. Mintchell June 1, 2002
Trends in I/O Devices
  • I/O devices are more distributed

  • Industrial networks increasingly popular

  • Ethernet use growing for I/O communication

  • Special function modules flourish

Extra Products Online

‘Give me enough time and enough money, and I can build a machine to solve any automation problem,’ once said application engineers in the automation special machine industry. Well, they were probably overly optimistic, but automation suppliers are responding to the pain felt by control engineers needing to do more in less time while reducing cost. One response is development of increasingly distributed I/O devices.

Many factors had to converge to provide distributed I/O devices. Among them are robust industrial networks, increasing computer power in smaller silicon packages, and powerful control algorithms. Networks allow I/O modules to be located close to field devices, resulting in labor and material savings for wiring. Increasing computing power in smaller packages makes I/O modules smaller, and embedded control algorithms can also incorporate onboard processing for applications like PID and motion control.

OEM and user engineers alike should realize reduced wiring, programming, and labor costs using these new products and architectures.

Are Control Engineering’s readers adopting these new offerings? Are they moving toward a distributed architecture? What intelligent I/O devices are they adopting?

Control Engineering and Cahners Research polled 10,000 readers during January 2002. Results are based on 540 respondents who answered the online questionnaire and were involved in the evaluation, specification, recommendation, installation, and/or purchase of I/O devices. Among these, 77% do so for in-plant requirements and 42% for OEM requirements. Some do so for both in-plant and OEM, thus the value greater than 100%.

One indicator of how new technologies are being adopted lies in an analysis of the question, ‘how do you apply I/O devices?’ As might be expected, 84% are applied in PLC systems , but 50% of those responding are implementing distributed I/O systems. By comparison, a 2001 telephone survey of 100 readers revealed only 6% implementing distributed I/O systems. While this is not a scientific survey, the trend is clear. CE readers have discovered the benefits.

Readers vote for open

Proponents of open networks and architectures have advocated enabling engineers to find the best solution regardless of manufacturer. A case in point from this survey is that 34% of respondents say they install DIN-rail-mounted I/O modules using a different manufacturer from their PLC supplier, while 48% buy those modules from their PLC supplier. Automation suppliers have provided choices for users, and users in turn are taking advantage.

Speaking of networks, readers revealed how they are connecting I/O modules. As one might expect, 4-20 mA still holds the top ranking. Perhaps surprisingly, Ethernet came in as the next-most-used network, followed by DeviceNet. ControlNet, HART, and Profibus follow.

Significantly, looking at what these readers plan to implement in the future, Ethernet overtakes 4-20 mA as top dog. In fact, not only will Ethernet usage grow, but also will DeviceNet, ControlNet, Profibus, FOUNDATION fieldbus, Optomux, Lonworks, and Seriplex. Control Engineering readers look to be serious about implementing open networks.

I/O device products

To request information on these products, visit www.controleng.com/freeinfo . For more manufacturers of these products, visit Control Engineering Buyer’s Guide at. www.controleng.com/buyersguide

OPC I/O server

Cumming, Ga. -KEPDirect EBC I/O server, a 32-bit application connects Microsoft Windows client software to AutomationDirect Ethernet I/O, using Ethernet Base Controllers (EBC) from AutomationDirect. The server interfaces to Ethernet EBC I/O using OPC (OLE for Process Control). With the server, any industrial HMI/SCADA, data historian, MES, or ERP software package that includes an OPC driver can connect directly to DL205, DL405, or Terminator Ethernet I/O. www.automationdirect.com AutomationDirect

VME I/O modules for Series 90-70 PLCs

Charlottesville, Va. -High-density discrete and analog I/O modules provide rapid data transfer to Series 90-70 PLCs over a VME backplane, increasing control flexibility. Each module can contain 64 discrete I/O points or analog channels. Discrete modules include 24 V dc input, 24 V dc output, and 64- or 32-point relay output. Compatible with all Series 90-70 CPUs and racks, the VME I/O is integrated using a configuration tool supplied with each module. Modules with cable connections can be terminated using a DIN Rail Transition Module, which provides a high-density screw terminal block with universal mounting. www.gefanuc.com GE Fanuc Automation

Strain gauge module for distributed measurements

Austin, Tex. -Engineers and scientists now can take distributed strain measurements with FP-SB-140 strain gauge module, part of the FieldPoint product family. The module has 16-bit resolution and interfaces with a wide variety of transducers, such as load cells and pressure sensors. Each of its eight channels can be programmed with a different excitation level of 2.5, 5, or 10 V. Each analog input channel has a software-enabled comb filter that users can set to reject frequencies above 15, 60, or 240 Hz. www.ni.com National Instruments

Simplify I/O wiring connections

Harrisburg, Pa. -Fieldline machine mountable I/O solutions have an IP67 environmental rating and can be implemented on a number of fieldbus protocols including DeviceNet, CANopen, Interbus, and Profibus DP. Integrated diagnostics provide local indication of bus error states and I/O device status. Bus specific parameters, i.e. address and bit rate, are set externally to the module with a standard screwdriver. Sensor/Actuator devices and network cabling are connected to I/O modules through industry standard M12 connectors. www.phoenixcon.com Phoenix Contact

Mixed I/O base

North Andover, Mass. -Momentum 170 ANR 120 91 Mixed I/O Base connects to analog and discrete I/O modules. It eliminates the need for multiple I/O bases and communications ‘tophats’ when both discrete and analog inputs and outputs are required at a single location. This 24 V dc power base contains eight discrete inputs, eight discrete outputs, six analog inputs, and four analog outputs. Analog modules feature 14-bit resolution for both input and output and a range of -10 to +10 V dc. www.schneiderautomation.com Schneider Automation

Data logging module

Temecula, Calif. -Snap Data Logging Module (DLM) provides a non-volatile file system for the Snap Ultimate I/O system. Previously, the 16 MB of RAM on the brain provided the only data storage for the system. This removable, postage stamp sized multimedia card can store up to 256 MB of data gathered from any mechanical, electrical, or electronic devices connected to the I/O system for the purposes of industrial automation and control, enterprise data acquisition, or remote monitoring. It has a FAT file system, allowing users to remove the card and plug it into a PC to view the files. The product is available with multimedia cards with 16, 32, 64, 128, and 256 MB of RAM. www.opto22.com Opto 22

Embedded zone control I/O cards

Mayfield Heights, O .-Zone Control I/O (ZCIO) cards allow for conveyor multi-zone control. 1799-ZCIOV (sinking output) and 1799-ZCIOB (sourcing output) modules introduce Zone Interlocking Parameters (ZIP), a parameter-based technology that allows one card to consume data directly from up to four other ZCIO cards. This eliminates the need to route information between the cards through a scanner or use hardwiring. Embedded I/O modules can also perform local control using DeviceLogix Smart Component Technology. www.rockwellautomation.com Rockwell Automation

Decentralized approach to I/O device wiring

Schaumburg, Ill. -CPM2C-S-DRT combines local control, remote I/O, and a DeviceNet intelligent slave. The result is a shirt-pocket-sized device that can connect up to 362 I/O points, act as an I/O pass through in a DeviceNet system, and provide 2 msec program execution time for local control. Local expansion options include digital, analog, and temperature, as well as a standard 20 kHz pulse-input capability, and an HMI port. The built-in remote I/O capability supports a total of 32 I/O modules and offers up to 256 I/O points over twisted-pair wiring. www.info.omron.com Omron Electronics

Extra Products Online

To get more information on these extra products, visit the company website or go to

Carlisle, PA – Compact, DIN-rail mountable Logic Signal Inverter provides a solution for connecting sensors and controllers with incompatible dc signals. It converts sensor signals from positive logic (PNP) to negative logic (NPN) and vice versa. It is packaged in a housing less than 0.5-in. wide for assembly with standard IEC DIN-rail-mount terminal blocks. Automation Systems Interconnect

48-channel digital I/O board reduces processor overhead

San Diego, CA – Model 104-DIO-48S is a 48-bit parallel digital input/output card designed for PC/104-based data acquisition. The 48-channel board features Change of State (COS) Detection on selected ports, allowing the card to generate an interrupt port by port. Each port can be software configured to function either inputs or latched outputs. Each I/O line is buffered and capable of sourcing 15 mA or sinking 24 mA. Included is a 1 MHz on-board clock and three 16-bit down counters, which can be configured for event counting, frequency measurement, or generating frequency or pulse outputs.

Access I/O

Germantown, WI – Programmable Field Controller allows an engineer to store and execute a control program locally, and still communicate with the network. Program execution continues, even if the fieldbus connection is lost. The Wago Programmable Field Controller is compatible with the classic Wago I/O system. It is programmed through an IEC 61131-3 compatible programming tool and simple logic control can be downloaded into each I/O node. Wago