What is the purpose of a relay in PLC circuitry?

The purpose of a relay in PLC circuitry is to control a high voltage circuit using a low voltage signal. Relays are electrically operated switches that allow one circuit to control another circuit. When a low voltage signal is applied to the relay's coil, it energizes the coil, which then closes or opens the relay contacts. This change in state allows the relay to control a high-power circuit, making it possible for a PLC to safely interact with devices that operate at higher voltages or currents. This is crucial in automation systems where control must be maintained while protecting the control circuitry from the effects of high voltage or current spikes. Relays serve as a vital interface between the low voltage control systems of PLCs and the high voltage loads they govern.