In some projects you need a PLC output to be energized when a group of PLC inputs are all true at the same time. To write such a PLC program there are two ways:
1. Writing the PLC program using what I call the "bit logic" approach
2. Writing the PLC program Using the comparator operations
In this lesson I will write a PLC program using both methods and then test them in the online mode.
As you know, the maximum amount of time that you can use on S7 or SIMATIC timers for timing is 2 hours 46 seconds. If you need larger timing values, one of the options might be using the IEC timers.
If you're not interested in using IEC timers, the other option is to build your own customized t...
So far I've inserted a timer and a counter in the first network and also a flip-flop in the second network to turn on the fan. Now I'm going to show you how these programming elements should work together to be able keep the output energized continually for 15 seconds.
The problem with this program is, when I press the start switch, the timer times the 5 seconds once but I need the timer to time the 5 seconds 3 times in a row. Let's fix this by adding some additional code.
12 Comments