Relaislogik

Relaislogik, or relay logic, is a method of implementing logical control using electromechanical relays. A relay is an electrically driven switch comprising a coil and one or more contacts. When the coil is energized, the contacts change state, typically moving from normally closed to open or from normally open to closed. By wiring multiple relays and their contacts in series and in parallel, engineers can perform basic logical operations such as AND and OR, enabling complex control circuits without semiconductor devices.

Relaislogik interfaces were foundational in early industrial automation and control systems, including machinery, process lines, and early telecommunications equipment. The approach gave rise to ladder logic, a graphical programming style that imitates electrical ladder diagrams and is designed for technicians to read easily. Components such as latching relays provided memory, while interlocking circuits supported safety and sequencing requirements. The robustness and visibility of relay circuits made them a staple in environments where electronics were still developing.

In modern practice, relay-based logic is largely superseded by transistor- and microcontroller-based logic and by programmable logic controllers (PLCs). Nevertheless, relay logic remains relevant in legacy installations and in niche applications where rugged, fail-safe, or high-current performance is desirable. It also serves as an educational tool to illustrate fundamental switching concepts, logic design, and the historical evolution of automation and computing.