11650 pages

PC-Based I/O Control Systems
Why PC-Based Control?
Automation engineers have argued for years over the place of PC-based control
in the industry. Even as hardware controllers have become more PC-like and PCs
have become more reliable, differences still remain.

up a new system, how many points of I/O do you need to control? Options vary in
terms of the network used for communicating with I/O, and networks vary in
terms of how many I/O points or I/O units they can support.

Your choice to use PC-based control depends on the needs of your specific
situation. Here are some reasons you may want to choose PC-based control:

Protocol—Like the network (and related to it), a specific protocol may be
necessary for your application. Ethernet-based SNAP I/O uses the open
OptoMMP protocol. Older serial-based I/O may use mistic or Optomux. Or
perhaps you need high-speed Pamux for digital I/O. Check the options for the
protocols they support, too.

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Direct access to standard computer networks and communication
interfaces, such as Ethernet

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Ability to use standard programming languages you may already know,
such as C++, VB.NET, or another object-oriented programming tool

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Easier integration with a variety of systems, including company computer
networks, manufacturing, business, and facility systems

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Lower cost due to use of commercial off-the-shelf technology

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Better performance in applications that require rapid reading or writing to
files, or complex calculations

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Extensive storage capacity for applications that accumulate large quantities
of data

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Protection of intellectual property, such as control algorithms

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Ability to run the control program and the human-machine interface (HMI)
on the same hardware

Options for PC-Based Control
So you’ve decided PC-based control is the way to go. What hardware and
software do you need to make it work?
This document shows examples of system architecture for PC-based control,
followed by detailed tables listing the hardware and software you can use for
each example. Here are some things to think about as you look at the options.
Programming language—If you already know one or more programming
languages (like flowchart-based PAC Control, or C#, or a .NET language), or have a
specific one you need to work in, look for the options that support that language.
Network—Have an existing serial I/O network? Need to connect with devices on
Ethernet? Need the speed of a direct connection to digital I/O? Or if you’re setting
Form 1165-130114

Distributed control—An Opto 22 I/O unit consists of I/O modules and an I/O
processor (brain), mounted on a rack. Brains provide distributed control for many
functions, including counting, latching, thermocouple linearization, ramping, and
much more—even PID loop control. Any option that uses brains lets you take
advantage of this distributed control, so that these functions continue even if the
I/O unit loses communication with the PC.
If you don’t want distributed control, look for the option that provides direct
control of I/O without brains.

Contents
Ethernet: PC-based Control using SoftPAC
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System example, page 2
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Details, page 3
Ethernet: PC-based Control using OptoMMP Protocol
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System example, page 4
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Details, page 5
Direct Control of I/O—No Brain (I/O Processor)
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System example, page 7
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Details, page 8
Serial: PC-based Control via Brain (I/O Processor)
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System example, page 9
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Details, page 10
Pamux: PC-based Control via Brain (I/O Processor)
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System example, page 12
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Details, page 13

© 2012–2013 Opto 22. All rights reserved. Dimensions and specifications are subject to change. Brand or product names used herein are trademarks or registered trademarks of their respective companies or organizations.

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