Copyright Goodheart-Willcox Co., Inc. 114 Programmable Logic Controllers: Hardware and Programming To change the parameters of the save instructions, such as AutoSave and Program Backup, use the Tools menu. From the Tools menu, click Options to open the System Options dialog box, Figure 6-37. In the Save Time Interval (minutes) option in the AutoSave section, enter the time interval at which you want the program to automatically save the project files. For example, type in “10” if you want the program to automatically save the project files every 10 minutes. To specify the number of copies of the project files you want the program to keep, enter the desired number in the Number of Backups text box that is located in the Program Backup section. Specify that you want the system to keep only one copy of the project. This copy is called the backup file. 6.11 Using the LogixPro Simulator to Create Ladder Logic Diagrams This section provides examples of how to use the LogixPro simulator to perform many of the tasks described in this chapter. Review and practice with these examples to increase your understanding of basic PLC programming. The diagram in Figure 6-38 shows the use of normally open (NO) and normally closed (NC) switches. As in relay ladder diagrams, Switch-1 is open and Switch-2 is closed. Closing the NO Switch-1 at address I:1/0 turns on the red pilot light (R-PLT) at address O:2/0. Opening the NC Switch-2 at address I:1/1 turns off the red pilot light. Normally Open (NO) and Normally Closed (NC) Switches. 000 001 O:2/0 I:1/0 End Switch-1 Switch-2 R-PLT I:1/1 Goodheart-Willcox Publisher Figure 6-38. PLC ladder logic diagram for Example 6-1, showing NO and NC switches. Example 6-1 Goodheart-Willcox Publisher Figure 6-37. System Preferences SLC 500 Program tab in the System Options dialog box.