Siemens SIMATIC S7-200 - PLC Fundamentals; Basic PLC Operation

Getting Started - Advanced
Training Documents, 09/2007, A5E01469795B
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Table of contents
Preface................................................................................................................................................... 3
1 Quick review........................................................................................................................................... 7
1.1 A Few Words of Review ............................................................................................................. 7
1.2 Here are the Bits......................................................................................................................... 8
1.3 Power flow in a ladder diagram................................................................................................... 9
1.4 Finding information about ladder instructions ........................................................................... 10
1.5 The PLC scan cycle: Reading the inputs .................................................................................. 11
1.6 The PLC scan cycle: Writing the outputs .................................................................................. 12
1.7 The PLC scan cycle: Program logic..........................................................................................13
2 Latching................................................................................................................................................ 15
2.1 Introduction............................................................................................................................... 15
2.2 Normally Closed (NC) Contact.................................................................................................. 16
2.3 Inserting a normally-closed contact .......................................................................................... 17
2.4 Testing your circuit.................................................................................................................... 18
2.5 A faster way to create logic state latches.................................................................................. 19
2.6 Making a Set/Reset network..................................................................................................... 20
2.7 Safety Tip: How to control a machine shutdown when a wire breaks........................................ 21
3 Pulse Operated Switch.......................................................................................................................... 23
3.1 Introduction............................................................................................................................... 23
3.2 Solution Overview..................................................................................................................... 24
3.3 Edge detection.......................................................................................................................... 25
3.4 Examples of edge detection ..................................................................................................... 26
3.5 Bit memory (M addresses)........................................................................................................ 27
3.6 Pulse-operated switch .............................................................................................................. 28
3.7 Solution Description and Test................................................................................................... 29
3.8 Time to Show What You Know .................................................................................................30
4 Off Delay Timer..................................................................................................................................... 31
4.1 Introduction............................................................................................................................... 31
4.2 Save As... ................................................................................................................................. 33
4.3 Solution Overview..................................................................................................................... 34
4.4 Solution - Enter the Program .................................................................................................... 35
4.5 Solution Description.................................................................................................................. 36
4.6 Entering comments................................................................................................................... 38
4.7 Time to Show What You Know ................................................................................................
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