When you're using counters in your PLC program, if the PLC goes into the stop mode or the power cuts off, you'll lose all of the counter values and these values cannot be restored after running the PLC again.
There are some programming tools and setups in the "STEP 7" that can be used to protect these types of data in the event of a power failure. In this lesson, you're going to learn how to use these tools so that you will not lose the counter values when the CPU stops or the power fails.
Previously, you learned that you can use S7 timers for the purpose timing in your programs. The maximum time value you can have for these timers is 2 hours and 46 minutes. But in some projects you may need longer time values. One way to increase the time value for timing is to use a combination o...
The time value for the timer is currently 5 seconds and the counter value is 3. With these numbers, the fan should stay running for 5 seconds three times or 15 seconds. Now let's test the program one more time.
Whether you’re testing a PLC program with an actual PLC or with a simulator, by default the CPU executes the program in continuous scan mode. However, the PLC simulator in STEP 7 is capable of executing the program in single scan mode as well.
Now, you may be asking, “What is the difference b...
10 Comments