Introduction to Industrial Automation

Figure 4.5  State diagram for the direct on line starting motor.

N

C

C

R

 

b

0

b

1

Figure 4.6  The automation circuit extracted from the state diagram of Figure 4.5.

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  Introduction to Industrial Automation

By applying the logical expression (1) according to Step 4 for the C variable, we obtain that:

 

C e b

f b f C

= + +

+ +

⋅

0

0

1

1

(

)

or

 

C e b f b f C

= ⋅ ⋅ ⋅

+ +

0

0

1

1

(

)

where the automation circuit shown in Figure 4.8 can be extracted.

4.3.2   State Diagrams with Sensors

The introduction of the electrical latch and the related operation through sensors (two-wire com-

mand), via the state diagrams approach, will be presented in the following example. In general, 

the electrical latch can be considered as a signal that “stops” the operation of a motor, identically 

to a STOP button. On the other hand, the operation of a motor through a sensory command 

means that as long as the corresponding NO contact of the sensor is closed, the motor will also be 

in operation. Since this command signal is not instantaneous, it is not required to have a memory 

element to store it, and thus this is equivalent to the fact that in the logical expression (1) of 

Step 4, the last term of the current state has to be omitted.