What are PLCs replacing?

What are PLCs replacing?

• A. Electromechanical relays
• B. Digital signal processors
• C. Microcontrollers
• D. Solid-state relays

Answer: (A)

Programmable logic controllers replace electromechanical relays in many control systems. Before PLCs, control logic was built with banks of relays wired together to implement conditions, timers, and interlocks. A PLC stores the same logic in software, scanning inputs and producing outputs, which makes it easy to modify the sequence, expand the system, and diagnose faults without rewiring. This also reduces panel space and mechanical wear, and minimizes arcing that can occur with moving relay contacts. Solid-state relays are often used as the power switches controlled by a PLC, but they don’t replace the control logic itself. Digital signal processors handle intensive signal processing tasks, and microcontrollers serve different, typically smaller-scale control roles.

Programmable logic controllers replace electromechanical relays in many control systems. Before PLCs, control logic was built with banks of relays wired together to implement conditions, timers, and interlocks. A PLC stores the same logic in software, scanning inputs and producing outputs, which makes it easy to modify the sequence, expand the system, and diagnose faults without rewiring. This also reduces panel space and mechanical wear, and minimizes arcing that can occur with moving relay contacts. Solid-state relays are often used as the power switches controlled by a PLC, but they don’t replace the control logic itself. Digital signal processors handle intensive signal processing tasks, and microcontrollers serve different, typically smaller-scale control roles.