Lecture13AProgrammable_Logic_Controllers

Lecture13AProgrammable_Logic_Controllers -...

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Programmable Logic  Controllers From www.plcs.net
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http://www.plcs.net/ Table of Contents Starters    What is a PLC?    PLC History Theory of Operation    The Internals   How it Works   Response Time   Effects of Response Time Creating Programs    Relays   Replacing Relays   Basic Instructions   Basic Program Example   PLC Registers   A Level Application ANIMATED   How a Ladder is Scanned Main Instruction Set   ANIMATED   Latching Instructions ANIMATED   Counters ANIMATED   Timers   Timer Accuracy ANIMATED   One-Shots ANIMATED   Master Controls ANIMATED   Shift Registers ANIMATED   Moving Data Numbers    Math   Number Systems   Boolean Math Wiring    DC Inputs   AC Inputs   Relay Outputs   Transistor Outputs Communications    Communications History   RS-232 Comm (hardware)   RS-232 Comm  (software)   Using RS-232 (Ladder Diagram) Manufacturers Links    Links   Manufacturers Y2K Pages
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What is a PLC? A PLC (i.e. Programmable Logic  Controller) is a device that was invented  to replace the necessary sequential  relay circuits for machine control. The  PLC works by looking at its inputs and  depending upon their state, turning  on/off its outputs. The user enters a  program, usually via software, that gives  the desired results. 
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Where are they used? PLCs are used in many "real world" applications. If there is industry present, chances are good that  there is a plc present. If you are involved in machining, packaging, material  handling, automated assembly or countless other  industries you are probably already using them. If you are not, you are wasting money and time. Almost any application that needs some type of  electrical control has a need for a plc. 
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Example For example, let's assume that when a switch turns on we want  to turn a solenoid on for 5 seconds and then turn it off  regardless of how long the switch is on for. We can do this with a simple external timer. But what if the  process included 10 switches and solenoids? We would need  10 external timers. What if the process also needed to count how many times the  switches individually turned on? We need a lot of external  counters.  As you can see the bigger the process the more of a need we  have for a PLC. We can simply program the PLC to count its  inputs and turn the solenoids on for the specified time. 
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PLC History In the late 1960's PLCs were first introduced. The primary reason for designing such a device was 
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Lecture13AProgrammable_Logic_Controllers -...

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