PLC Selection 101: Tips and Tricks for a Successful Choice

The choice of PLCs is a crucial component of automation and control systems. Choosing the best programmable logic controller (PLC) to meet the needs of a particular application is involved. It can be difficult to select the best alternative when there are so many accessible. But the process may be made a lot easier and clearer with the correct knowledge and direction. The variables that should be taken into account while choosing a PLC including its compatibility with existing systems, performance capabilities and the total cost will be thoroughly examined in this article.

PLC Selection Parameters

Factors that should be considered when selecting a PLC include:

1. Input and Output (I/O) requirements

The number of inputs and outputs required as well as their type (digital or analog) will determine the size and capability of the PLC. Digital inputs and outputs can be used for discrete control tasks while analog inputs and outputs are used for tasks that require measurement and control of continuous variables such as temperature or pressure. The specific requirements of a particular application will dictate the appropriate type and number of inputs and outputs needed and thus the appropriate PLC to use.

2. Processor speed

The processing speed of the PLC will impact how quickly it can respond to changes in the system. If the processing speed is slow, it may not be able to keep up with the demands of the system leading to delays in responses and potential system malfunctions. A faster processing speed can help ensure that the system operates smoothly and efficiently.

3. Memory capacity

The amount of memory required will depend on the complexity of the program and the amount of data storage needed. The more complex the program and the larger amount of data storage needed, the more memory the program will require to run efficiently. However, the amount of memory required can also vary based on the programming language, the operating system and the hardware on which the program is running.

4. Programming language

Different PLCs may use different programming languages which will impact the ease of programming and the ability to interface with other control systems. PLCs may use different programming languages such as ladder logic, structured text, function block diagrams and sequential function charts. The programming language used will affect the ease of programming and the ability to interface with other control systems. For example, ladder logic is commonly used in industrial control applications and is relatively easy to learn and understand while the structured text is more powerful and flexible but requires more programming experience. The choice of programming language should be considered when selecting a PLC for a specific application.

5. Communication protocols

It is important to select a PLC that supports the necessary communication protocols to interface with other control systems such as HMI (Human Machine Interface) and SCADA (Supervisory Control and Data Acquisition) systems.

6. Brand reputation

Consider the reputation of the PLC manufacturer and the support provided in terms of training, technical support and product warranties. A reputable manufacturer can offer a better-quality product and their products may have been thoroughly tested to ensure reliability and durability. A reputable manufacturer also may provide technical support and product warranties.

Technical support is also important and it is important to consider the level of support offered by the manufacturer. Support should be available when needed and the manufacturer should be responsive and knowledgeable in addressing any issues that arise.

Product warranties are also an important consideration. A manufacturer that offers a good warranty can provide peace of mind and may be more likely to stand behind their product. The warranty should be comprehensive and cover any potential issues that may arise.

7. Cost

The cost of the PLC should be evaluated in relation to the requirements and benefits of the specific application. It is essential to understand the overall cost and potential return on investment (ROI) before deciding to invest in a PLC. Factors that should be considered include the complexity of the control system, the number of inputs and outputs, the required processing speed and the expected lifespan of the equipment. The ultimate goal is to ensure that the cost of the PLC is justified by the benefits it provides such as increased efficiency, improved productivity and reduced downtime.

8. Expansion capabilities

Consider the future expansion needs of the system as well as the availability of expansion modules for the selected PLC. This will help ensure that the system can accommodate any future changes or upgrades that may be required. Additionally, it is important to ensure that the selected PLC has a variety of expansion modules available to allow for flexibility in the system’s design and functionality.

9. Environmental conditions

The environment in which the PLC will be installed plays a crucial role in its performance and longevity. Factors such as temperature, humidity and dust levels can affect the PLC’s functionality and cause it to malfunction or fail. It is important to consider these environmental factors when selecting and installing a PLC to ensure its proper operation and reliability.

10. Compliance with industry standards

It is important to select a PLC that complies with relevant industry standards such as UL, CE or CSA. They ensure that the device has undergone rigorous testing and meets safety, performance and quality standards. Compliance with these standards can also help ensure that the device can be legally sold and used in various regions and markets.

11. Ease of use and maintenance

Consider the ease of programming and troubleshooting as well as the availability of technical support and replacement parts.

12. Integration with other systems

The PLC should be able to integrate seamlessly with other control systems and devices such as sensors and actuators. By seamlessly integrating with other control systems and devices, a PLC can help improve efficiency, accuracy and productivity in various industrial applications.

13. Data logging and reporting

Consider the data logging and reporting capabilities of the PLC including the ability to store data and generate reports for analysis and trend analysis. These capabilities are often used to monitor and control various industrial processes and improve their efficiency and productivity. PLCs can record various types of data such as temperature, pressure, speed and production rates and store them in a local or remote database for further analysis. Reports can be generated in various formats including charts, graphs and tables and provide valuable insights into the performance of the system over time.

In conclusion, selecting the right programmable logic controller (PLC) is a crucial aspect of automation and control systems. The process of selecting a PLC can be made simpler by considering several factors such as input and output requirements, processor speed, memory capacity, programming language, communication protocols, brand reputation, cost, expansion capabilities, environmental conditions, compliance with industry standards, ease of use and maintenance, integration with other systems and data logging and reporting. By understanding and considering these factors, one can ensure that the selected PLC meets the requirements of a specific application, operates efficiently and provides benefits such as increased productivity and reduced downtime.