Logic Gates in PLC Ladder Logic: A Beginner’s Guide

Logic gates are an electronics circuit which makes logical decisions based on the combination of digital signals present on its inputs. clickhere to read Introduction to PLCs.

OR gate

Y=A + B

An OR gates produces a HIGH on the outputs when any of the inputs is HIGH. The outputs is LOW when all the inputs are LOW.

In this ladder program, the output Y1 is HIGH when either X1 or X2 is HIGH, and vice versa.

AND gate

Y=A.B

An AND gate produces a HIGH output only when all the inputs are HIGH. The output is LOW when any one input is LOW.

In this ladder program, the output Y1 is HIGH when both inputs X1 and X2 are HIGH; otherwise, output Y1 is LOW

NOT gate

The inverter (NOT circuit) performs the operation called inversion or complementation. The inverter changes one logic level to the opposite level

The Y1 is on when power is supplied to it, and Y1 will turn off if X1 is triggered.

XOR gate

An XOR gate produces a HIGH output only when one of its inputs X1 OR X2 IS HIGH. The output is LOW in any other condition.

The output Y1 is only set to HIGH in two specific conditions: when X1 is ON and X2 is OFF, or when X1 is OFF and X2 is ON. In all other scenarios, Y1 remains at a LOW state.

NAND gate

The NAND gate is like a digital detective that reveals falsehood. It takes multiple inputs and declares ‘false’ only when every input is ‘true.’ In this sense, it’s the mirror image of an AND gate, constantly seeking out the truth in a sea of possibilities.

Y1 shines its light in every scenario, except when both X1 and X2 join forces to dim its glow.

The video showcases the design of all the Previously mentioned logic gates within the Mitsubishi GXWorks 2 software