Introduction to Industrial Automation

4.3.7   Sequential Automation Systems

A category of simple automation circuit design problems are the so-called sequential logic automa-

tion problems. The simplicity refers to the difficulty of the state diagram synthesis, which offers 

a standard design procedure. Chapter 7 will present that for these specific types of systems, a 

specific programming language has been developed for PLCs, which is called the sequential func-

tion chart (SFC) and has been adopted by the Standards IEC 61131-3. Let’s illustrate this type of 

application in more detail by the following example.

N

A

R

A

Stop (s) 

e

1

e

2

T

M

1

B

T

B

B

B

B

Start (x) 

T

A

A

A

B

B

A

M

2

Figure 4.30  Automation circuit for Example 4.10 based on the system state diagram of Figure 4.29.

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Logical Design of Automation Circuits 

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