Introduction to Industrial Automation

10.19   Working Time Monitoring of a Machine 

under a Three-Shift Schedule

An industrial plant operates in a three-shift schedule. A complex machine of the production pro-

cedure operates intermittently due to the kind of process performed. Its operation also depends 

on the mood of the machine operator for its working time. Therefore, it is desired to know (e.g., 

weekly) the total hours of the machine’s operation. For this reason, there are three control panels, 

one for each shift work, and three hour-meters that record the hours of the machine operation per 

shift work, as shown in Figure 10.19. Each operator can start up the machine only from the control 

panel corresponding to his shift work if:

  a. The operator turns on the switch with a key

  b. The corresponding START button is pressed

Then the machine operates and the hour meter records the time of operation. Any handling 

from the other two control panels must cause no action. The machine operation stops either by 

the operator by pressing the STOP button, or by a sensor detecting a critical temperature. After 

defining the I/O devices and their connections to a PLC, write the required program. Examine 

also, if it is possible to have the same operation with only one pair of START-STOP buttons com-

mon for the three shift works.

PS

1

PS

2

M

PC

H

0

Indication of

non-closed door

b

0

 Open

b

1 

Close

b

2 

Emergency

STOP