Choose the right system architecture – save costs, stay flexible

In industrial automation, choosing the right system architecture determines efficiency and costs and provides scope for future development. Smart communication between the PLC and automation components such as drives, sensors and valve terminals can not only significantly reduce overall costs, but also ensure the flexibility and expandability of a system. Today, users have a wide range of design options at their disposal: from discrete wiring and fieldbus systems with Remote I/O to centralized and decentralized pneumatic connections. In this blog post, we take a look at the areas of application, advantages and disadvantages of the various architectural approaches with a focus on costs and flexibility.

Discrete wiring: Cost-effective solution for small machines

With discrete wiring, each individual component, such as sensors and actuators, is connected directly to the central control unit in the control cabinet. Each input and output requires its own line. Although this eliminates the need for expensive and complex communication protocols and bus nodes, the architecture quickly reaches its limits and, with increasing size, leads to high cabling costs and takes up a lot of space in the control cabinet. The system quickly becomes extremely complex and error-prone when expansions are made. However, this system is sufficient for small machines or systems with manageable inputs and outputs, as long as costs and space requirements are kept within limits.

Fieldbus systems: For relatively complex automation tasks

Fieldbus systems are digital networks that connect several devices to the control unit via a single communication line. Examples are ProfiNET, EtherNET/IP or EtherCAT. These are relevant for medium to large systems with a large number of inputs and outputs. This is because a fieldbus significantly increases the flexibility and scalability of a system: fewer cable lines are required, as a single data line now reduces the number of discrete connections. New devices can be easily integrated into the network and different components can communicate via the same bus. Diagnostics are also made easier, as faults can now be identified more easily.

At the same time, the necessary fieldbus nodes are very cost-intensive and compatibility is becoming an important issue: after all, not every device can communicate with every fieldbus. The architecture is dependent on the fieldbus protocol used in the PLC.

Remote I/O: Out of the control cabinet

Remote I/O relocates I/O modules from protection class IP65 to remote locations close to sensors and actuators. These modules communicate with the central control system via fieldbus systems. Remote I/O is essential for large and extensive systems if the modules are to be placed outside the control cabinet and close to the components. The wiring effort is further minimized, the data rates increased and the control cabinet capacity significantly reduced. Installation on the plant floor also makes it much easier and cheaper to scale the machine while simplifying servicing, because faults can be diagnosed and rectified directly on site.

The use of Remote I/O has become an integral part of modern automation architecture and represents a major benefit for automation. However, this technology is initially the most expensive to purchase. The system is much more dependent on a stable network connection and requires a great deal of expertise in planning and integration.

Pneumatics and electrical automation perfectly connected

The integration of valve terminals and pneumatic components into an automation system offers great potential, but also harbors the risk of oversizing due to long and complex tubing, and high costs due to additional interfaces being required. However, with the right components and a communication language that is as uniform as possible, a decentralized or hybrid (modular and decentralized) connection can be implemented. This reduces the number of bus nodes and IP addresses while simplifying diagnostics.

Network Interface Controllers and Remote I/O Solutions for Industrial Automation

Reliable data flow is the backbone of modern automation. Network interface controllers and remote I/O solutions ensure seamless communication between machines, sensors, and actuators—transforming isolated components into an integrated, responsive system. This connectivity enables real-time decision-making, improved process visibility, and scalable control architectures tailored for demanding automation environments.

This communication typically happens via electrical bus cables—often simple two-core cables—that connect field devices and other components to form a robust network. These devices, also known as network participants, may include everything from sensors and actuators to switches, signal lamps, or even push buttons. Though simple, each participant becomes an intelligent node once connected to the network.

These remote control components are powered through the bus cable and can transmit and receive data packets with addressing and control information. Think of this process as sending digital letters, where each packet is like an envelope addressed to a specific device, ensuring the correct recipient receives the intended command or data.

What Are Fieldbus Devices?

Fieldbus devices are industrial components designed to communicate over a digital network known as a fieldbus. This type of communication protocol connects sensors, actuators, controllers, and other equipment within an automated system—replacing traditional point-to-point wiring.

By sharing a common network, these devices can efficiently exchange data, commands, and status updates. This not only simplifies installations but also increases system flexibility and scalability.

Common types of fieldbus devices include:

1. Sensors: Fieldbus-enabled sensors, such as temperature sensors, pressure sensors, flow meters, and proximity sensors, provide data about the process variables they are monitoring. They transmit this data over the fieldbus network to controllers or other devices for analysis and control.

2. Actuators: Fieldbus-enabled actuators, such as valves, motors, and drives, receive control signals over the fieldbus network to perform specific actions. These signals can include commands for opening or closing valves, starting or stopping motors, or adjusting speed and position.

3. Controllers: Fieldbus controllers, also known as programmable logic controllers (PLCs), receive data from sensors and issue commands to actuators to control and automate industrial processes. They serve as the central intelligence for the fieldbus network, coordinating communication and making decisions based on the received data.

What Is a Fieldbus Protocol?

A fieldbus protocol is a defined set of rules that govern how devices communicate within a fieldbus network. It establishes how information is transmitted, interpreted, and acted upon—ensuring reliable and consistent communication across the system.

Core components of a fieldbus protocol include:

• Physical Layer: Defines the electrical and mechanical aspects of the network (e.g., cables, connectors, voltage levels, and transmission speed).
• Data Link Layer: Manages reliable data transfer by handling error detection, frame structure, and addressing.
• Network Layer: Oversees device addressing and message routing across the network.
• Application Layer: Specifies the structure and content of exchanged data, enabling devices to interpret commands and values correctly.

Several fieldbus protocols are widely used, each with its own strengths and application areas:

• PROFIBUS: Popular in both process (PA) and discrete (DP) automation environments.
• Modbus: Known for its simplicity and compatibility, especially in serial communications.
• Foundation Fieldbus: A digital protocol used in process automation with support for two-way, multi-drop communication.
• DeviceNet: Common in factory automation, especially for linking sensors and actuators with PLCs.
• CANopen: Based on the CAN bus, widely used for control applications in machinery and industrial systems.

The right protocol depends on system requirements such as speed, data types, and device compatibility.

The Role of Remote I/O in Industrial Systems

Remote I/O modules are essential for distributed control systems, serving as intermediaries between field devices and central controllers like PLCs. By enabling localized data acquisition and signal control closer to the source, they reduce wiring complexity and installation time, simplify maintenance and diagnostics, support scalable architectures for future expansion, and integrate seamlessly with Industry 4.0 systems. This setup enhances flexibility and improves data visibility, particularly in large-scale automation environments.