PLCs, DCSs & Controllers

Selecting the right PLC

June 2019 PLCs, DCSs & Controllers

Automation projects, big or small, start with a specification. Here are five factors to consider when choosing a PLC vendor.

Broad range of devices

The selected brand must have a complete product range to meet the requirements of customers. PLCs must be available with sufficient memory to support I/O, and log and manipulate historical data in addition to executing the control program. Where execution speed is critical, the CPU processing speed must be considered as well. Some additional questions to ask are: What are your sector’s standards? Do applications need to comply with hazardous environment standards, CFR-21.11, or the spray-and-wipe standards of the food and beverage sector?

Influenced by the mobile industry, customers expect HMI colour touch-panels to provide the communication window between operator and system. In cases where space is at a premium, PLC + HMI all-in-one controllers have distinct advantages. Some PLC manufacturers even provide PLC + HMI controllers with on-board I/O modules, which in addition to saving space, also reduce wiring requirements.

Data communication

Flexibility is key. The selected brand of PLC should support multiple protocols to ensure interoperability with existing and future applications, as well as third-party devices. Important industrial protocols include Modbus, CANopen and EthernetIP. Some brands also support protocols, such as SNMP and FTP. Check to see if your PLC manufacturer provides software utilities that enable you to implement proprietary third-party protocols, whether serial RS-232/485 or TCP/IP.

Users can also benefit through increased visibility of operating data and diagnostic information. The ability to access a PLC via Web browser and VNC support are excellent methods of remotely accessing a PLC, while SMS messaging and email are handy for notification via mobile devices.

Intelligent software

Saving time is the primary benefit of intelligently-designed software. There are two particularly important factors to consider.

Ease of use: ergonomic design eliminates the need to search for elements while programming. In addition, logical, consistent construction saves time, since the programmer intuitively knows what to do even when programming a particular task for the first time.

Re-usability: whether programming in ladder or C functions, designing HMI screens and Web pages, or creating custom controls, the ability to reuse work across projects saves time.

Service and support

Look for PLC manufacturers that offer a high level of customer care. Make certain that support, whether technical or sales, is easily available and prompt. Personal support – meaning from people not automated systems, which is available 24/7 is extremely valuable.

This is what can make a difference when meeting tight project deadlines. Support documents, specifications and guides, should be readily available. Select a company that provides support and documentation at no additional charge.

Total cost of ownership

Development and future maintenance costs can affect profit margins. Therefore, when purchasing a PLC, select a company committed to supporting it over the long term. This can have a major impact on the success of an industrial automation project.


Share this article:
Share via emailShare via LinkedInPrint this page

Further reading:

Powerful controller for high safety requirements
Phoenix Contact PLCs, DCSs & Controllers
Thanks to its 8-core processor, high-level language and open-source software such as Docker or even Matlab Simulink can run simultaneously with the control program.

New user-friendly modular controller
Allpronix PLCs, DCSs & Controllers
Novus has released its N20K48 controller family. This new concept is based on a compact, powerful core controller plus a growing family of micromodules that enable it to meet a wide range of application requirements.

ABB white paper explores the future of DCS technology
ABB South Africa News PLCs, DCSs & Controllers
The company foresees a modular automation architecture that will evolve to address customer needs, becoming more open, interoperable and flexible.

Introducing Commander S and Marshal
PLCs, DCSs & Controllers
Control Techniques is launching a new member to the Commander family of drives and a revolutionary app named Marshal. Commander S provides a solution for applications that require plug-and-play control convenience straight from the box, while Marshal revolutionises how the user interfaces with the drive.

Left-alignable extension modules for PLCnext Control devices
Phoenix Contact PLCs, DCSs & Controllers
As the left-alignable modules communicate with the controller via PCIe, the standardised interface can also be used by third-party devices.

Manufacturer-independent device management and update service
Phoenix Contact PLCs, DCSs & Controllers
In the industrial environment, solutions for Device and Update Management (DaUM) often use a specific process called a vendor to distribute files to proprietary devices and install them based on the manufacturer. ...

Redundant PLC for maximum availability
Phoenix Contact PLCs, DCSs & Controllers
Integrating IO-Link-capable sensors and actuators is especially popular with suppliers of machines or skids for the food and beverage industry.

Hotel sets new energy efficiency standard
Beckhoff Automation PLCs, DCSs & Controllers
Steigenberger Alsik Hotel & Spa in Sønderborg is not only the largest hotel in southern Denmark, but also one of the most sustainable and climate-friendly hotels in northern Europe. High-tech solutions ...

Easy recording of weather data
Phoenix Contact PLCs, DCSs & Controllers
Phoenix Contact’s pre-installed solution with PLCnext Control records the values of wind speed and direction, temperature, irradiation, humidity and the amount of precipitation.

Controller for robotic systems
Omron Electronics PLCs, DCSs & Controllers
Omron has announced the launch of its first ‘Robotic Integrated Controller’, based on its leading NJ series of machine controllers for industrial automation.