Connectivity in manufacturing industries: PLCs communication protocols
Copyright: ST-One
PLCs (Programmable Logic Controllers) were developed in the 1960s in the United States to replace control systems based on electromechanical relays. The last one was widely used in the automobile industry. However, the need for frequent maintenance and the complexity of interconnections were turning points for developing new technologies. In this context, General Motors was the first company to implement PLC system, seeking a more flexible and less failure-prone solution. Historically, the first commercially available PLC was the Modicon 084, which allowed engineers to modify the control logic without changing its structure. Since then, these controllers have been significantly improved, upgrading in hardware and software to meet the growing demands of industrial automation.
The main characteristic of PLC is its programmability, allowing quick adjustments due to its operating logic defined by a computer program. Its main components include the CPU, which is responsible for executing the program instructions stored in memory. Because of this, it has a high capacity for processing and executing complex tasks quickly. In addition, PLC input and output modules facilitate simultaneous data collection and allow precise control of external devices. It also has power supplies that ensure continuous and reliable operation, even in harsh conditions. Finally, its different communication interfaces support the integration of multiple devices and systems, increasing flexibility and scalability.
Finally, although it is commonly associated only with industrial automation, this technology is also used in other areas. PLCs can assist in the control of lighting in buildings, agricultural irrigation systems and even in theme park attractions.
Diversity of machines and protocols in manufacturing industry
The ability to communicate with various communication protocols is crucial for factories that use a variety of machines and, consequently, PLCs. This diversity is due to several reasons, one of them being technological evolution. It is possible that new machines purchased for the production line will come with more modern protocols, such as OPC-UA or MQTT, for example. These protocol types offer greater flexibility and integration capability than older models such as Modbus or RS232.
The use of specialized machinery is also another cause of this diversity. Different machines, which are designed to perform specific tasks, can be optimized with the protocols that best suit their needs. As an example there’s precision machines, which can use protocols such as Fanuc CNC, to ensure accuracy and control. In addition, some manufacturers develop their own protocols to ensure compatibility with their products, such as Mitsubishi Melsec.
However, in the same industrial plant, different machines must communicate, even if they often use different protocols. Among the advantages of communication flexibility are:
- Interoperability: Factories can choose the best equipment for their specific needs without having trouble with compatibility;
- Systems expansion: Allows the implementation of new devices without the need for major reconfigurations, making systems more scalable;
- Adaptation to new technologies: Allows the integration of new technologies and IoT devices, facilitating the continuous evolution of industrial systems;
- Integration with corporate systems: Integration with Historian systems, for example, improves management and operational efficiency;
- Security: The diversity of protocols includes advanced security features, ensuring data protection and the integrity of industrial operations;
How does communication with the PLC happen in practice?
Communication protocols allow PLCs to connect with a variety of devices and systems, such as actuators, human-machine interfaces (HMI), and other PLCs. They function as a set of rules that define how data is transmitted and received between devices. The steps of this communication are:
- Protocol selection: First, the industry need to choose the appropriate communication protocol for the application. The most common ones include Modbus, Profibus, Ethernet/IP, among others;
- PLC configuration: The PLC is configured to use the chosen protocol. This may involve installing specific communication modules and setting parameters in the PLC software;
- Sensor reading: The PLC collects data from sensors and input devices connected to it. This data can include information such as temperature, pressure, position, etc;
- Data processing: The PLC CPU processes this data according to the installed program, making decisions based on the defined control logic;
- Data formatting: The processed data is organized according to the specifications of the communication protocol. This ensures that the data is understandable to other devices on the network;
- Transmission: Data is transmitted through the PLC’s communication module to the network or directly to other devices. On an Ethernet network, for example, data can be sent to a SCADA server or Historian system;
- Reception of commands: The PLC can also receive commands from other devices or control systems. These commands can instruct the PLC to change the control logic, adjust parameters, or perform specific actions;
- Update: The PLC updates its internal states and also the states of connected devices based on the feedback received;
Copyright: ST-One
Communication and data collection across different industry sectors
Connecting all the machines in the same industrial site is essential for making complete OEE analyses, for example. Despite its remarkable importance, carrying out this process is still a challenge. As a result, implementing solutions that integrate data from all sources is essential for manufacturers that integrate the latest technological era. Within each manufacturing industry sector, there are more common PLC models, chosen according to some requirements such as operating environment, complexity and cost. The most used in each of them are:
Automotive
- CANopen (Controller Area Network): These are used due to their low latency and high reliability, which are essential for real-time control systems such as brakes and motors;
- DeviceNet: Uses the CAN structure, recommended for connecting industrial devices in machine control systems;
Food and Beverage
- Ethernet/IP: Ethernet-based protocol, allows fast and efficient communication, essential for processes that require high data speed;
- Profinet: Used for real-time communication, ensuring accurate synchronization of critical processes;
Chemical
- Profibus: Used for communication in chemical plant control processes, due to its robustness and reliability. They are also resistant to harsh environments and electromagnetic interference;
- Modbus: It is ideal for communication between sensors and controllers in industrial environments due to its simplicity and robustness;
Pharmaceutical
- Modbus: Used for communication between laboratory equipment and process control systems;
- Ethernet/IP: Allows the integration of real-time control and monitoring systems, essential to ensure product quality and compliance;
Pulp and Paper
- Profinet: Used for real-time communication, essential for the synchronization of production processes;
- Profibus: Its robustness is ideal for environments with challenging conditions, such as pulp and paper mills;
Connectivity applied in practice
To exemplify the importance of this protocols, consider an industry in the automotive industry. An automobile factory, like other industries, has a complex production line that includes various equipment and control systems. In this case, it is possible that each piece of machinery uses a different communication protocol. For example, assembly robots can use the EtherCAT protocol for communication. Temperature and pressure sensors, Modbus, while motor controllers use CAN. Finally, there are quality inspection systems, which use the Profibus protocol.
Within this scenario, the industry needs hardware that supports multiple communication protocols. This device is installed and configured to communicate with all these mentioned machines. After that, the collection of data from the devices in real-time begins, regardless of the protocol used. Subsequently, all data is centralized in a production management system. This allows for a comprehensive view of the production line, and the identification of problems such as temperature deviations or failures in the assembly robots.
In this way, the factory can take corrective actions based on the analyzed data, such as adjusting motor controllers and predictive maintenance. This example makes it clear how flexibility in terms of communication protocols is a differential, resulting in many benefits.
Copyright: ST-One
Importance of compatibility with various protocols
The various communication protocols that exist in the industry allow PLCs to connect and communicate with sensors, Human Machine Interface (HMI) and other devices. This is indispensable for the integration and interoperability of automation systems.
This connectivity is important, as the data generated by the machinery can reveal valuable insights into the day-to-day operations of the industry. In addition to real-time production monitoring, widely used in analyses such as performance and productivity, the storage of historical data is also indispensable. Thanks to this visibility, it is possible to unlock numerous results for the industry, such as:
- Improved operational efficiency: Access to data allows for optimized resource usage, reduced downtime, and increased productivity;
- Predictive maintenance: Helps prevent unplanned downtime, reduce repair costs, and increase equipment life;
- Increased product quality: Reduces the number of defective products and improves customer satisfaction;
- Cost reduction: Analyzing the data collected helps to identify areas where costs can be reduced, such as energy consumption and raw material usage;
- Assertive decision-making: Improves responsiveness to changes in operating conditions;
The trend for the future is for Ethernet-based protocols to gain even more popularity due to their high speed and simultaneous communication capabilities. This, combined with the integration with IoT solutions, which allow for scalable cloud data storage, can shape the industrial landscape in the coming years. These innovations increase efficiency, safety, and the ability to respond quickly to operation adjustments. Learn more about us.
