A Programmable Logic Controller (PLC) is an industrial digital computer specialized for manufacturing processes, such as assembly lines, robotic devices, or any activity requiring high-reliability control. They were first developed in the automobile industry to provide flexible sequencing and process control. Early PLCs were expensive and difficult to program, but their use has spread because programming can be done quickly with ladder logic diagrams. Ladder logic is a graphical language that resembles a ladder with two vertical rails between which rungs containing switches are strung. When current flows through the switch contacts at the top of each rung, it energizes coils located further down the rung on one of two… Read More
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The XIC (Examine if Closed), a normally open switch or pushbutton, instruction is a fundamental instruction for working with Programmable Logic Controllers (PLCs). The XIC instruction performs the function opposite to the XIO (Examine if Open) instruction. When the input is closed, the output of the XIC will be ON. If the input is open, then the output of the XIC will be OFF. The main purpose of using this type of instructions is to check status or condition of an equipment before allowing PLC to take any further action. For example, in a production line where machines are triggered by sensors to start operation, it is important to make… Read More
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