PLC does not replace relays

PLC will replace some of the function of the relay, but for now, it is impossible to completely replace.

Information

Nowadays, PLC working voltage 12V mostly, it is impossible to directly replace the relay to control 220V or even higher motor. Nowadays, the majority of relays are used as a logic control, and then control the relay, which controls the motor, so that, of course, the LED signal lamps do not need intermediate relays.

PLC refers to programmable logic controller, which uses a class of programmable memory for its internal storage program, performs logical operations, sequential control, timing, counting and arithmetic operations, such as user-oriented instructions, and through digital or analog input/output control of various types of machinery or production processes.

Relay (English name: relay) is a kind of electric control device, is when the change of input quantity (excitation quantity) reaches the stipulated requirements, in the electrical output circuit to make the controlled quantity happen a predetermined step change of a kind of electrical appliances. It has an interactive relationship between the control system (also known as input circuit) and the controlled system (also known as output circuit). Usually used in automated control circuits, it is actually a kind of "automatic switch" that controls the operation of large currents with small currents. Therefore, it plays a role in the circuit of automatic regulation, safety protection, switching circuits and so on.