The key differences between relay-based and PLC-based control systems are:
| Parameters | Relay-Based Control System | PLC-Based Control System |
|---|---|---|
| Technology | For switching there is the use of physical relays. | Uses microprocessor-based controllers |
| Flexibility | Limited, changes require rewiring | Moderate, made through alteration of the software’s code. |
| Complexity | Ideally, for use in basic control processes. | It is used in the management of the complex logic and processes. |
| Space Requirement | Large and comparatively heavy, thus occupies more space bigger, takes up more space | Compact, integrates multiple functions |
| Maintenance | Time-consuming, involves manual labor | Easier, mostly software-driven |
| Cost | Less costly to install, more expensive in the long-run | Higher installation cost, lower operation and maintenance cost |
| Speed | It takes significantly longer time than direct path routing as it follows a mechanical switching. | Faster with faster response times |
| Reliability | Susceptible to breakdown after some time | More dependant with lesser componentry |
| Programming | No programming required | Requires programming knowledge |
| Scalability | With high levels of customization, it becomes hard to scale the product or add more features. | It only requires a small addition in software for it to be scaled up. |
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