Choosing the right system architecture to save costs, stay flexible
In industrial automation, choosing the right system architecture determines efficiency, costs and future viability. 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 system is flexible and easy to expand. Nowadays, users have a wide range of design options at their disposal: from discrete wiring and fieldbus systems with remote I/O to a centralised and decentralised pneumatic installation. In this blog post, we take a look at the application areas and the advantages and disadvantages of the various architectural approaches while focussing 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 as the size increases, cabling costs go up and more space is needed in the control cabinet. Once it gets extended, the system quickly becomes extremely complex and error-prone. 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 more 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 cables are required, as a single data cable now reduces the number of discrete connections. New devices can be easily integrated into the network and different components can communicate through the same bus. Diagnostics are also simplified, as malfunctions can now be identified more easily.
At the same time, the necessary fieldbus nodes are very cost-intensive and compatibility becomes an important issue, since 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 IO relocates IO modules with protection class IP65 and higher to remote locations close to sensors and actuators. These modules communicate with the central controller through 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 work is minimised even further, the data rates increased and the control cabinet capacity significantly reduced. Placing the machine in the field also makes it much easier and cheaper to scale and simplifies servicing, as 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 comes with the highest initial price tag. The system becomes much more dependent on a stable network connection and requires a great deal of expertise in planning and integration.
A perfect combination of pneumatics and electric automation
Integrating valve terminals and pneumatic components into an automation system offers great potential. Yet it also poses the risk of oversizing as tubing tends to be long and complex, while the need for more interfaces pushes up costs. However, a decentralised or hybrid (modular and decentralised) connection can be created with the right components and a communication language that is as uniform as possible. This reduces the number of bus nodes and IP addresses and simplifies diagnostics.
