From the course: Learning PLC Ladder Logic: 1 The Basics

Multiple inputs - Ladder Logic Tutorial

From the course: Learning PLC Ladder Logic: 1 The Basics

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Multiple inputs

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- [Narrator] In one operation, we are going to learn how to program letter logic when we have more than one inputs. Inputs are placed in the left side of the letter logic, so depending on how many inputs and the logic of a program all need to be placed in the left side. There are two methods to program multiple inputs. AND, OR. The AND is similar to the function of the AND gate where you can have any number of inputs, but only one output. The truth table that you can on the screen shows you that the output is only turned on when all inputs are true, so if both inputs are zero, output is zero. If one of the inputs is zero, the output is zero, as well. The only time that the output is equal to one, when both inputs are one. If you have multiple inputs that you need them all to be on in order to activate a certain output, then use AND. AND inputs are added in series. Just two or more normal instructions side by side. Using OR. If you have multiple inputs that you want any input to trigger at the same output, then use OR. The OR is similar to the function of the OR gate where you can have any number of inputs, but only one output. Here is the truth table of the OR gate. Notice that if any of the inputs is true, the output is true, as well. The way to add OR inputs is to add them in parallel. This is how the OR instructions are placed. So, think about it as another route to the output. Another option; OR. So depending on the logic, AND, OR are added to the letter logic in order to activate the output.

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