How to select a controller

Think Again: Applications and controller options vary widely. Take care in selection, especially in the overlapping areas. Functionality matters more than a name. Do you need a programmable logic controller (PLC), programmable automation controller (PAC), industrial personal computer (IPC), or distributed control system (DCS)?

11/17/2015


AutomationDirect, which provided the photo, upper left, said that IPCs and PC-based controllers have the most programming options and best opportunities for integrating motion, vision, and human-machine interface (HMI). Shady Yehia provided a six-questionController options vary almost as widely as the applications they control. More than one type of controller often can serve any particular application. Is the application best suited for a programmable logic controller (PLC), programmable automation controller (PAC), industrial personal computer (IPC), or distributed control system (DCS)? Names are less important than functionality. Experts can help sort it out. 

Table of options

PLCs "continue to be a popular choice for machine control and for simple process control applications," explained Jeff Payne, automation controls group product manager at AutomationDirect. "Their ladder logic programming is well-suited for control simple and complex automated sequences, but is lacking when it comes to control of analog variables and data handling," Payne said. In a table comparing PLC, PACs, IPCs, and PC-based control capabilities, Payne said IPCs and PC-based controllers have the most programming options and best opportunities for integrating motion, vision, and human-machine interface (HMI). 

Flowchart helps

For the process industries, "Manufacturers of PLCs are promoting an idea that the combination of PLC and supervisory control and data acquisition (SCADA) can deliver the same functionality that a DCS provides," said Shady Yehia, the instrumentation, control, and automation proposals and engineering manager in a process technology integration company. Yehia's six-question flowchart helps select between the PLC-SCADA combination versus a DCS. 

Criteria matrix

There is no clear cut fast rule about when to use a PAC, PLC, or IPC; factors include "budget, size, support, complexity, and future expansion," said Ryan Williams, project manager at Stone Technologies, a system integrator. "Selection factors may include existing programming licenses owned, maintenance and engineering training and familiarity, and regional contractor support for the system." When unclear, "create a selection matrix with weighted criteria and grade each." 

Ability to change

Easier access to control logic is important. Daniel B. Cardinal, an electrical engineer with more than 30 years of experience designing control systems and working as a control system integrator, said that manufacturers can reduce costs with "improved abilities to change design information to affect actively running PLC programs. The real value to manufacturers comes from minimizing chaos, by having support personnel understand how to interact with all control system applications." They "must have the ability to change logic circuits by interacting with rules, design specifications, and table-based configuration information." 

Less integration

Programmable controllers are a better fit for applications where extremely fast scan times, very large input/output (I/O) counts, or high performance redundancy are critical, said Vibhoosh Gupta, product management leader, GE Intelligent Platforms. "But for low- to mid-range applications that require a dedicated OI, all-in-one automation panels provide a simplified architecture with easy remote connectivity options and lower total cost of ownership, thereby enabling the Industrial Internet age for new levels of productivity, insight, and user experience," Gupta said. 

24-core processing

PC-based controls have much more flexibility in form factor, said Reid Beilke, who is a product specialist at Beckhoff Automation. With advanced chip designs, a 24-core control platform is available, a 36-core version is available soon, and programming software can optimize that power to upgrade functions and capabilities. Think again about controller selection: Six articles in this issue, pages 26-44, offer details, and each article has more information in its online version.

- Mark T. Hoske, content manager, CFE Media, Control Engineering, mhoske@cfemedia.com.

ONLINE extra

- See the articles referenced in this story below.



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Salary and Career Survey, IT and OT convergence, robotic standards and safety, secure circuit protection
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John O. Ayuk, PE, CFSE, PMP, CAP
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The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by Control Engineering subscribers. Vote now (if qualified)!
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The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
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Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
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April 2018
Cybersecurity best practices, artificial intelligence, robotic additive manufacturing, embedded systems, IIoT integration, energy efficiency
March 2018
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This article collection contains several articles on how today's technologies heap benefits onto an edge-computing architecture such as faster computing, better networking, more memory, smarter analytics, cloud-based intelligence, and lower costs.
IIoT: Machines, Equipment, & Asset Management
Articles in this digital report highlight technologies that enable Industrial Internet of Things, IIoT-related products and strategies.
PLCs
Programmable logic controllers (PLCs) represent the logic (decision) part of the control loop of sense, decide, and actuate. Featured articles in this digital report compare PLCs and programmable automation controllers (PACs), industrial PCs, and robotic controllers.
SIDB

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

April 2018
ROVs, rigs, and the real time; wellsite valve manifolds; AI on a chip; analytics use for pipelines
February 2018
Focus on power systems, process safety, electrical and power systems, edge computing in the oil & gas industry
December 2017
Product of the Year winners, Pattern recognition, Engineering analytics, Revitalize older pump installations
John O. Ayuk, PE, CFSE, PMP, CAP
Automation Engineer; Wood Group
Doug Baker
System Integrator; Cross Integrated Systems Group
Jose S. Vasquez, Jr.
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Fire & Life Safety Engineer; Technip USA Inc.
Data Centers: Impacts of Climate and Cooling Technology
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
Safety First: Arc Flash 101
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
Critical Power: Hospital Electrical Systems
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
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