Keyword Sequential Function Chart single branch structure
The debugger when the first step in debugging found
TO timer may find the timing can normally closed but not the set time M0.1 1. The reason is because
Post 1 because the program will continue to scan the RESET M0.0 is so M0.1 becomes an instruction within a cycle. .
A latch circuit is provided to maintain the
Note need to use SET command
Exercises Page 132 Page 3 small problems
At first I lack a deep understanding of control design methods do not know the problem of dual-coil sequence.
Sequential Function Chart I draw the following
Timer T0 regular time
The figure above state transition diagram is no problem, but first, you think so, think is relatively simple, does not take into account the work of the PLC, a single scan. The cycle of problems.
In a scan cycle program, after the instruction has been executed, the last scan cycle to update the output values.
I.e. the output value in the current scan cycle unchanged, if the next scan cycle if an input is disconnected, the output will be cleared
A status output to a scan sustain period.
Output port status will be updated at every scanning period. But in a cycle it is constant, latched, unless you use a set of instructions
So I think the ladder program structure should look something like this
The output circuit of the above figure is incorrect, resulting in the phenomenon of double coil, there is no way to be understood that the implementation of PLC scan cycle.
The correct procedure is
See program
Program on the Baidu network disk S7_Pro36
Video shot into the video link address
Finally, the overall experience:
Before you write the log, they may just some knowledge, as this summary as you can while reading, and writing log records (you might compare discrete knowledge, there is no network) Finally you do not have after-school exercise you may feel good that you have mastered the knowledge. For example, you will not be a deep understanding of the process PLC scan cycle, dual coil phenomenon.
And you do after-school exercise, and put a question with a single branch sequential function chart and parallel branch can achieve a deeper understanding of the apparently. This summary is significantly better way, summed up all arise out of knowledge with a question. Establishment of a network.
2 only a question, and very streamlined, this learning method is better.