A specialized computerized device called a Programmable Logic Controller (PLC) is utilized in industrial automation and control systems. It is intended to execute control logic programs that regulate the behavior of machines or processes in an industrial context in order to carry out certain tasks.
PLCs are frequently used to track sensor inputs, process that data using the control logic that has been programmed into them, and provide outputs to drive actuators or other devices. Various industrial operations, including production, electricity generation, water treatment, and transportation networks, are controlled and automated in real time by them.
When selecting a Programmable Logic Controller (PLC) for your industrial automation needs, there are several important factors to consider. First, evaluate the specific requirements of your application. Consider the number of inputs and outputs (I/O) needed, the complexity of the control logic, and any special functions or capabilities required.
Considerations when you are selecting a PLC
Which brand or kind would be "best suited" for a certain project out of the many PLCs that are readily accessible for practically any application?
To assist reduce the alternatives for a given application, there are numerous factors that should be considered:
CPU speed – How big is the system, and what kind of reaction time is needed for the process?
Memory capacity – When is enough memory enough? Do you need an external memory card?
Redundancy – Is there a need for any amount of redundancy
I/O – How many devices must it manage or control? Is working with external or remote I/O interfaces necessary?
Communication protocols – What devices and protocols will it need to connect with?
Compatibility – Does the system need to communicate with already installed hardware and software, or is it being developed from the ground up?
Scalability – Is it possible to scale the system up or down to meet system changes?
Environment – What kind of environmental circumstances will it encounter? Do you need to take any particular measures, such as using conformal coated components or a more durable choice for hostile environments?
Actions performed - Does it have to be capable of any special tasks, such motion control, robotics, or security?
Reliability – Is it anticipated that the system would function for months or perhaps years with little to no downtime?
Cost – what is the budget? Have factors such the procurement of hardware, software licences, programming, installation, ease of interface with current plant/systems, maintenance, and backup support, as well as any future upgrade requirements, been taken into account collectively as a "system"?
PLC brands: what’s the difference?
There are several brands that offer programmable logic controllers (PLCs), each with its own characteristics and strengths. Here are some of the popular PLC brands and an overview of their differences:
Allen Bradley
In addition to its primary flagship platform ControlLogix, Allen Bradley also provides the smaller CompactLogix and MicroLogix PLC systems.
The modular ControlLogix and CompactLogix systems provide a variety of processor alternatives based on memory sizes, on-board communication needs, redundancy, safety integration, and environmental factors (extended temperature, conformal coating, etc.).
A separate base chassis, often known as a rack, a CPU, an I/O module, and a communications module make up the ControlLogix platform. several configuration choices are available, ranging from modest single-processor systems with little I/O to big redundant systems with a high I/O count and several distant I/O drops. All of these options are scalable.
The cost of a ControlLogix system is the highest in the Allen Bradley PLC family, however this is justified by the system's demonstrated longevity, dependability, and large-scale control system capabilities. ControlLogix is the chosen platform in situations where dependability or criticality are crucial.
With or without on-board communications, CompactLogix consists of a separate power supply, CPU, and I/O modules that are all DIN rail mounted. CompactLogix is frequently utilised in situations where cost or a smaller system are factors, even if it is still built with long life and expandability possibilities.
The MicroLogix is a compact "brick"-style PLC with an integrated power supply, CPU, and I/O that may be expanded using available extension modules. The MicroLogix system may be connected into a larger CompactLogix or ControlLogix system and is intended for minor process and automation control tasks.
All new products have strong backward compatibility and legacy support, ensuring there is a migration route from earlier versions for anyone seeking to update an existing Allen Bradley system. When a new product is released, the software is also upgraded to guarantee that any new hardware features are supported.
General Electric
General Electric, sometimes known as GE, has a long history of creating PLC hardware and software. The 90-30 and 90-70 heritage series are being combined and replaced by the RX3i series from PACSystems.
Industrial Internet connectivity is built on the RX3i controller. It is a strong, flexible Programmable Automation Controller with a high availability focus. A single control engine and a common programming environment are included in the RX3i to enable application portability across various hardware platforms.
RX3i improves system performance and flexibility with integrated essential control platforms, logic, motion, HMI, process control, and high availability based on GE Reflective Memory technology. The RX3i platform is equipped with a variety of processors, ranging in price from very inexpensive models to extremely powerful redundant systems with real hot standby capabilities.
In comparison to practically every other PLC on the market, the RX3i CPE400 is the flagship CPU and has an astounding amount of power, including a 4-core processor and 64MB of built-in RAM. The Achilles Level 2 certification is one of a number of sophisticated security features that are integrated into the CPE400 to help reduce operational and security threats to the control system.
The Versamax Micro and Nano controllers, which provide a low-cost entry point option, make up the tiny line of GE PLCs. Prior to the RX3i taking over for bigger systems, the Versamax standard range is geared at small to medium systems.
GE PLCs were automating the procedures that produce half of the world's power as of the time of writing.
Siemens
From simple controllers to massive redundant platforms used on some of the biggest and most complicated engineering projects in the world, Siemens offers a wide range of PLC solutions.
The S7-1500 advanced controller, which has a 1ns "bit processing time" in the CPU and features like built-in Profinet, 4-Level security, an integrated display, and native OPC UA accessibility, is now the top model in the Siemens PLC line. One of the PLC systems with the greatest features available today is the S7-1500.
Siemens also offers the well-known S7-300 and S7-400 controllers, the latter of which offers a complete redundancy option, in addition to the sophisticated S7-1500. One of the capabilities of its S7 PLC line is the ability to provide two safety runtime groups, allowing for the division of the infrastructure into two sections, each with its own set of control settings, such as priority and time cycles. This has the advantage that operators may edit the programming blocks and download them to the PLC without having to interrupt any activities.
The latest Total Integrated Architecture (TIA) software suite offers a wide range of programming options that make it easier than ever to configure and set up not only PLCs but also HMIs, drives, and other related Siemens equipment. Historically, the Siemens S7 PLC programming environment could be challenging for the uninitiated. Siemens also provides free basic technical help.
Schneider Electric
Modicon, the primary PLC line from Schneider Electric, offers a variety of platforms in all sizes, from tiny brick-style controllers up to the redundant M340 and M580 systems and several historical systems like Quantum, Premium, and Momentum. PLCs, PACs, and specialised controllers from Schneider Electric are simple to programme, commission, maintain, and are IIOT ready.
As Ethernet/IP standards have been included, enabling deterministic distributed I/O, this range is particularly useful in situations where hot redundancy is required. The Schneider Electric Unity software is liked by many engineers because it makes PLC to PLC communications very simple. Large offices may be found in most major locations, providing significant local assistance inside Australia.
