conversations.from: human
conversations.value: a title for a book about PLCs, PLC, Computing with the genre: Engineering & Transportation, Engineering
conversations.from: assistant
conversations.value: A title for this book could be 'Programmable Logic Controllers'
conversations.from: human
conversations.value: Give me a description for a book titled Programmable Logic Controllers about PLC, PLCs, Simatic with the genre: Engineering & Transportation, Engineering.
conversations.from: assistant
conversations.value: An easy-to-read alternative to the expensive and jargon-filled manual sets, this reference describes how to set up and troubleshoot a PLC in general, and covers implementation in specific leading proprietary PLC systems: Allen-Bradley (PLC-5 and SLC 500), Siemens (Simatic S5 and Simatic S7), and OMRON (all, but specifically CQM1). It includes, but goes beyond, simple Boolean logic enabling readers to use all of the power of a modern PLC. Complete coverage of capabilities of modern PLCs; extensive troubleshooting coverage; full instructions (for Boolean logic, timing and counting, data manipulation, process control, and communication) -- with at least one instruction of each type described in detail and similar instructions described in terms of what they do differently; setup and configuration requirements of all PLCs. For anyone interested in programming and configuration of Programmable Logic Controllers (PLCs) for industrial control.
conversations.from: human
conversations.value: Give me the first five paragraphs for this book.
conversations.from: assistant
conversations.value: Programmable Logic Controllers
  As an illustration of the use of these terms in specification, the following were included in the specification of a MX100AP pressure sensor (see later in this chapter, Section 2.1.8, for an explanation of this sensor):
  A mechanical switch generates an on/off signal or signals as a result of some mechanical input causing the switch to open or close. Such a switch might be used to indicate the presence of a workpiece on a machining table, the workpiece pressing against the switch and so closing it. The absence of the workpiece is indicated by the switch being open and its presence by it being closed. Thus, with the arrangement shown in Figure 2.3a, the input signals to a single input channel of the PLC are thus the logic levels:
  With the arrangement shown in Figure 2.3b, when the switch is open the supply voltage is applied to the PLC input; when the switch is closed the input voltage drops to a low value. The logic levels are thus:
  Switches are available with normally open (NO) or normally closed (NC) contacts or can be configured as either by choice of the relevant contacts. An NO switch has its contacts open in the absence of a mechanical input and the mechanical input is used to close the switch. An NC switch has its contacts closed in the absence of a mechanical input and the mechanical input is used to open the switch. Mechanical switches are specified in terms of number of poles, that is, the number of separate circuits that can be completed by the same switching action, and number of throws, that is, the number of individual contacts for each pole.
  A problem with mechanical switches is that when a switch is closed or opened, bounce can occur and the contacts do not make or open cleanly. Because they involve an elastic member, they bounce back and forth like an oscillating spring. This "bounce" may produce amplitudes that change logic levels over perhaps 20 ms, and so a single switch change may give rise to a number of signals rather than just the required single one. There are a number of ways of eliminating these spurious signals. One way is to include in the software program a delay of approximately 20 ms after the first detected signal transition before any further signals are read. A possibility for a single pole/double throw (SPDT) switch is to use two NAND logic gates (see Chapters 3 and ), as illustrated in Figure 2.4a. When the switch is in position A, the output is a logic 1. When the switch moves to position B, the output becomes logic 0 and remains latched at this spot, even when the switch bounces. Figure 2.4b shows how a D flip-flop (see Chapter 3 for a discussion) can be used to debounce a single pole/single throw (SPST) switch. The output of the D flip-flop does not change until a position-edged clock signal is imposed, and if this is greater than the bounce time, the output is debounced.
conversations.from: human
conversations.value: Give me five more paragraphs.
conversations.from: assistant
conversations.value: Figure 6.5a shows Mitsubishi notation. With such a situation, Mitsubishi uses an ORB instruction to indicate "OR together parallel branches." The first instruction is for a normally open pair of contacts X400. The next instruction is for a series set of normally closed contacts X401, hence ANI X401. After reading the first two instructions, the third instruction starts a new line. It is recognized as a new line because it starts with LDI, all new lines starting with LD or LDI. But the first line has not been ended by an output. The PLC thus recognizes that a parallel line is involved for the second line and reads together the listed elements until the ORB instruction is reached. The mnemonic ORB (OR branches/blocks together) indicates to the PLC that it should OR the results of the first and second instructions with that of the new branch with the third and fourth instructions. The list concludes with the output OUT Y430. The instruction list would thus be entered as:
  Figure 6.5b shows the Siemens version of an XOR gate. Brackets are used to indicate that certain instructions are to be carried out as a block. They are used in the same way as brackets in any mathematical equation. For example, (2 + 3) / 4 means that the 2 and 3 must be added before dividing by 4. Thus with the Siemens instruction list we have in step 0 the instruction A(. The brackets close in step 3. This means that the A in step 0 is applied only after the instructions in steps 1 and 2 have been applied.
  The IEC 61131-3 standard for such programming is to use brackets in the way used in the previous Siemens example, that is, in the same way brackets are used in normal arithmetic. This enables instructions contained within brackets to be deferred until the bracket is completed. Thus the IEC instruction list program:
  Figure 6.6 shows a circuit that can be considered as two branched AND blocks. Figure 6.6a shows the circuit in Mitsubishi notation. The instruction used here is ANB. The instruction list is thus:
  Figure 6.6b shows the same circuit in Siemens notation. Such a program is written as an instruction list using brackets. The A instruction in step 0 applies to the result of steps 1 and 2. The A instruction in step 4 applies to the result of steps 5 and 6. The program instruction list is thus:
conversations.from: human
conversations.value: Reverse the sentences.
conversations.from: assistant
conversations.value: The program instruction list is thus:. The A instruction in step 4 applies to the result of steps 5 and 6. The A instruction in step 0 applies to the result of steps 1 and 2. Such a program is written as an instruction list using brackets.6b shows the same circuit in Siemens notation. The instruction list is thus:
  Figure 6. The instruction used here is ANB.6a shows the circuit in Mitsubishi notation. Figure 6.6 shows a circuit that can be considered as two branched AND blocks. Thus the IEC instruction list program:
  Figure 6. This enables instructions contained within brackets to be deferred until the bracket is completed.
  The IEC 61131-3 standard for such programming is to use brackets in the way used in the previous Siemens example, that is, in the same way brackets are used in normal arithmetic. This means that the A in step 0 is applied only after the instructions in steps 1 and 2 have been applied. The brackets close in step 3. Thus with the Siemens instruction list we have in step 0 the instruction A(. For example, (2 + 3) / 4 means that the 2 and 3 must be added before dividing by 4. They are used in the same way as brackets in any mathematical equation. Brackets are used to indicate that certain instructions are to be carried out as a block.5b shows the Siemens version of an XOR gate. The instruction list would thus be entered as:
  Figure 6. The list concludes with the output OUT Y430. The mnemonic ORB (OR branches/blocks together) indicates to the PLC that it should OR the results of the first and second instructions with that of the new branch with the third and fourth instructions. The PLC thus recognizes that a parallel line is involved for the second line and reads together the listed elements until the ORB instruction is reached. But the first line has not been ended by an output. It is recognized as a new line because it starts with LDI, all new lines starting with LD or LDI. After reading the first two instructions, the third instruction starts a new line. The next instruction is for a series set of normally closed contacts X401, hence ANI X401." The first instruction is for a normally open pair of contacts X400. With such a situation, Mitsubishi uses an ORB instruction to indicate "OR together parallel branches.5a shows Mitsubishi notation.Figure 6
conversations.from: human
conversations.value: Give me the last five paragraphs.
conversations.from: assistant
conversations.value: Every step can have an associated action. An action describes the behavior that occurs when the step is activated. Each action can have a qualifier: N indicates the action is executed while the step is active. If no qualifier is indicated it is taken to be N.|  
  IF... THEN... ELSE is used when selected statements are to be executed when certain conditions occur.
  The FOR... DO iteration statement allows a set of statements to be repeated, depending on the value of the iteration integer variable.
  The WHILE... DO iteration statement allows one or more statements to be executed while a particular Boolean expression remains true.
  The REPEAT... UNTIL iteration statement allows one or more statements to be executed and repeated while a particular Boolean expression remains true.