Relays and PLCs (programmable logic controllers) are two popular tools for automating control processes. However, they have different advantages and limitations, and you need to take these into account when deciding which is right for your application.
Relays are among the oldest control devices and are still popular for simple applications. Understandable: relays areeasy to use, reliable and cheaper than PLCs. But we must note that the limitations of relays include their limitedfunctionality and the difficulty of expanding the system.
PLCs are controllers specifically designed for industrial applications, offering greater functionality and greater expandability than relays. PLCs can be used to control more complex processes, its use will simplify system expansion, and allow for troubleshooting and diagnostics and data collection. However, PLCs are more expensive and require specialised skills for installation and maintenance.
So when planning which control device to choose, the following aspects should be taken into account:
- Functionality: the first and most important consideration is the number and complexity of functions that the system needs to handle. For simpler applications, such as controlling switches and lights, relays may be sufficient. However, if the system needs to handle more complex functions, more complex control, PLCs offer more functionality.
- Extendability: the extensibility and scalability of the system. If the system is projected to beexpanded, PLCs offer more opportunities for expansion because they have a number of expansion modules and interfaces.
- Cost: Relay-based systems are generally cheaper, while PLCs can be more expensive. However, if the system needs more functionality and expandability, PLCs will more economical in the long run.
- Maintenance and troubleshooting: relays are generally easier to maintain and repair due to their simpler design, while PLCs require specialised skills for maintenance and troubleshooting: the latter will require advance planning if PLC is the right choice for your project.
Overall, when planning which control device to choose, you need to consider the complexity of the application, the functionality required, the extensibility and the price. For simple applications, relays may be appropriate, while for more complex process control, PLCs are necessary. PLCs may be preferable for more complex functions and allow for easier and more cost-effective expansion.