PLC Architecture: Types, Benefits , Differences, & More
The use of Programmable Logic Controllers (PLCs) has revolutionized the automation industry by providing a reliable and cost-effective platform for a wide range of industrial processes. They are in huge demand, making the value of the PLC industry stand close to $36 billion. PLC architectures help maximize performance while reducing maintenance costs associated with automated systems, making them an attractive option for many businesses.
What is a PLC Architecture?
Programmable Logic Controllers (PLCs) are industrial computers designed to control and monitor processes in automated systems. PLC architectures refer to the different types of hardware components used in a PLC system, such as controllers, input/output modules, communication modules, and power supplies.
Each type of component has its own specific function in the automation process. Choosing the right architecture for your application maximizes performance while reducing maintenance costs associated with automation systems. To learn more about PLC architecture, you can pursue a PLC programming course.
Types of PLC Architecture
There are three distinct types of architecture of PLC. They are as follows:
1. Fixed Architecture
Fixed PLC architecture is the most basic type of architecture. This arrangement has a single central processor that controls all inputs and outputs. It can be used in applications with only a few input signals and output commands to control.
The main advantage of this setup is its simplicity; however, it limits the scalability of the overall system as additional I/O points must be added with an external module or expansion board. In addition, these systems are usually more expensive than modular architectures due to their fixed nature.
2. Modular Architecture
Modular PLC architectures consist of multiple individual modules connected through a common bus or network connection like Ethernet or Modbus TCP/IP. This allows each module to act independently while still being able to communicate with other modules within the system.
It provides enhanced flexibility when constructing an automation system from scratch or attempting to adapt an existing one for different purposes. Modules can range from simple digital I/O cards to complex motion controllers capable of easily controlling sophisticated robotic arms and other robotic devices.
3. Distributed Architecture
Distributed PLC architecture involves several separate components distributed around a facility that work together as part of an overall automation solution without having one centralized location for all elements involved in the process control scheme.
Examples include wireless communications between various sensors located throughout a production line that feed information about machine performance, such as temperature readings, pressure levels, etc. This allows operators at remote locations (such as offices) access real-time data without needing physical access to them on-site at any given time, which helps promote efficiency.
Also Read: Different Types of PLC
PLC Comparison Table
The following table provides a comparison of all three PLC types.
| Parameters | Fixed PLC | Modular PLC | Distributed PLC |
|---|---|---|---|
| CPU Performance | Low | Medium – High | High |
| Program & Data Memory Size | Low | Medium – High | High |
| Power Supply | Embedded | Module | Module |
| Input Interface | Embedded | Module | Module |
| Output Interface | Embedded | Module | Module |
| Communication Interface | Embedded | Module | Module |
| Mounting System | Single Unit | Rack, Backplane, Rail, or Chassis. | Rack, Backplane, Rail, or Chassis. |
| Physical Size | Small | Medium to Large | Medium to Large |
| Flexibility | No | Yes | Yes |
| Customizable | No | Yes | Yes |
| Applications | Basic applications with a small number of inputs and outputs. | Medium to high-end applications with a large number of inputs and outputs. | High-end applications and plant-wide control with a very large number of inputs and outputs. |
| Cost | Low | Medium | High |
How Does Architecture of Programmable Logic Controller (PLC) Work?
The CPU (Central Processing Unit) is the brain of the PLC system. It consists of a control module and a processor. While the CPU processor does all of the number crunching and program execution, the CPU control unit controls how the various PLC hardware components interact with one another.
The CPU processor receives data from the input devices, processes it, and sends it to the output devices. It also communicates with the data and program memory to exchange data. Once all the data has been collected, the program is cycled through for processing. The output interface processes the generated data and sends it to the output devices for execution.
The diagram given below shows the PLC architecture.
Benefits of PLC Architecture
Some of the benefits of the architecture of PLC are:
1. Increased Performance
By choosing the right architecture for your particular application, you can ensure optimal operation and reduce downtime associated with troubleshooting issues or dealing with malfunctions in the system.
Modular architectures allow users to easily expand their systems as needed, allowing companies to quickly adapt to changing market conditions.
2. Less Maintenance Cost
PLC architectures also offer reduced maintenance costs when compared to traditional control systems such as hardwired relays or contactors. Modular designs are easier to troubleshoot than their hardwired counterparts since each component can be replaced individually if necessary instead of replacing an entire system.
This helps reduce both repair time and money spent on repairs, which ultimately leads to improved operational efficiency and higher profits for businesses utilizing these types of automation solutions.
3. Compatibility
Another great advantage that comes with using PLC architecture is its wide range of compatibility across different vendors’ products, due to its adherence to open standards like CANopen or Ethernet/IP protocols.
Therefore, most of the third-party components can be added to existing installations easily, saving time during initial setup stages as well as future expansions.
Also Read: Advantages of PLC
Challenges of PLC Architecture
Some of the challenges of the architecture of PLC are:
1. High Cost
One of the biggest challenges associated with PLC architectures is their relatively high cost compared to other industrial automation systems. As these are often used in highly specific applications, such as those found in manufacturing and industrial processes, they require specialized components that can be expensive to purchase and maintain.
Additionally, most PLCs use proprietary software for programming, which are not compatible with existing hardware or other systems, more costly upgrades and modifications are necessary when expanding or changing a system’s capabilities.
2. Security Concerns
Since these systems are responsible for controlling critical processes within factories and production lines, they must have secure access controls to prevent unauthorized users from accessing them remotely or altering any of their settings without permission.
This requires additional resources that need to be allocated towards implementing reliable security measures, such as firewalls, encryption protocols, etc. This increases costs further while also posing technical issues due to the complexity of integrating different elements properly.
3. Inflexibility
One major challenge concerning PLC architecture is its inflexibility when it comes to modifying programs once they have been written and uploaded into the system’s memory banks.
This means any changes must involve writing new code from scratch rather than simply adapting existing code, which can lead to significant delays during development cycles.
Conclusion
Despite having a few drawbacks, PLC architecture remains an essential component within modern automated factories and production lines due to its reliability and scalability. This makes it a must-have technology for businesses looking to remain competitive in today’s ever-evolving marketplaces. You can test your knowledge of PLC through these PLC interview questions guide and increase your chances of landing a better job in this industry.
FAQs
The PLC block diagram is a graphic representation of the working of the PLC system. It consists of the various components of PLC architecture, such as the I/O interface, power supply, CPU, memory, indicator lights and switches, and communication interface.
The four main components of a PLC are the I/O interface, processor, communication interface, and power supply. The processor contains both the CPU and system memory.
There are three different types of PLC architecture in industrial control systems – fixed, modular, and distributed architecture.
