Introduction to Industrial Automation

10.13   A Machine with Three Operational States 

and an Acknowledgement Signal

A complex machine has three operational states: stoppage, preheating, and operation. If the 

machine is in stoppage state, the pressing of a START-STOP button energizes the message 

“Preheating-Wait” and the output of heating resistors. By pressing the START-STOP button for a 

second time and if the time interval of three minutes has passed, the motor C is energized, while 

the message indication and the resistors are de-energized. If during the preheating phase the cancel 

button is pressed, the message indication and resistors are de-energized. If during this operation 

the cancel button is pressed, nothing happens, while the START-STOP button is pressed the 

motor stops immediately. Write a PLC program to satisfy the desired operation specifications 

(Figure 10.13).