IsaGraf IEC 1131-3

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Hi all, Does anyone know much about the following standard? IEC 1131-3 Apparently, there are six ways that you can develop RTU sequences: - Ladder Logic - Instruction List - Structured Text - Functional Block Diagram - Sequential Function Charts I don't really get ladder logic. I haven't been able to find a simple resource that explains how it works. The only rules I know are: - There is a left/right power rail - Programs start from left to right, all ladders simultaneously Not much else. Can anyone provide further explanation???

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Since you ask about ladder logic, let's take a step back. Ladder diagrams are a universally-understood description of a control circuit. You'd be hard-pressed to find an electrician anywhere that wouldn't recognize one. They're found everywhere from your household furnace, clothes dryer, etc. all the way up to the largest manufacturing line, from the oldest piece of electrical machinery to the newest. PLCs were introduced into the electrician's world, not the computer programmer's. So in order for them to gain acceptance and keep the learning curve (for plant electricians) short, they had to give them something close to what they were already comfortable with. Essentially, ladder logic is a computer simulation of an electrical ladder diagram. If you want to learn more, start by reading this: http://forums.mrplc.com/index.php?autocom=downloads&showfile=156

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I also did this power point presentation years ago as a brief to PLC;s if tha also helps http://forums.mrplc.com/index.php?autocom=downloads&showfile=206