# What are the key differences between relay-based and PLC-based control systems?

**URL:** <https://forumautomation.com/t/what-are-the-key-differences-between-relay-based-and-plc-based-control-systems/12440>\
**Category:** Electrical\
**Tags:** plc, controlsystem, relay\
**Created:** [August 14, 2024, 9:46am UTC](https://forumautomation.com/t/what-are-the-key-differences-between-relay-based-and-plc-based-control-systems/12440 "2024-08-14T09:46:37Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Rabert](https://forumautomation.com/user_avatar/forumautomation.com/rabert/32/6784_2.png) [@Rabert](https://forumautomation.com/u/Rabert)\
**Post date:** [August 14, 2024, 9:46am UTC](https://forumautomation.com/t/what-are-the-key-differences-between-relay-based-and-plc-based-control-systems/12440/1 "2024-08-14T09:46:37Z")

</div>

The key differences between relay-based and **[PLC](https://forumelectrical.com/plc-timer-and-their-types/)**-based control systems are:

 ![image](https://cdn.forumautomation.com/original/2X/6/60e68a25dfc36fb0b6ff8529e56f4c4bce78ea4e.jpeg)

| 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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