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

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Latch/unlatch output

Latch/unlatch output - Ladder Logic Tutorial

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

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Latch/unlatch output

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- [Instructor] Latch and unlatch output. Output latching and unlatching are used together. They are types of output instruction they used in ladder logic. So, when latching an output, we need to unlatch it within the same program. So, what latching instruction actually means. An output latching instruction is an output instruction used to maintain or latch an output on, even if the input condition changes. So, if any run has a latching instruction, this means that the output reference to the latching instruction is turned on and remain on even if the run logic or the PLC power is lost. Latch, to latch an output on, output stays on until unlatch instruction becomes true. Unlatch instruction, to unlatch a latched on instruction with the same address. Let's see what this means. This is a regular output instruction. We have a pushbutton in order to start a motor. Since we're using a regular output, once I press on the pushbutton, the motor starts, but once I let go, the motor turns off…

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