In many engineering applications, people always hope that the system can have the time reminder function, no need for man to timing. Nowadays many PLCs already has this function.But the timer timing time is still limited, sometimes it can not meet the requirement for a long period of time. Therefore we need to write a simple program to meet this higher requirement, the following is a long-time timing reminder program case of Haiwell PLC.
2. Theprogramming thought and programs
Scheme 1: Four counters are used,first counter represents seconds, the second counter represents minutes, the third counter represents hours and the fourth counter represents days.When the first counter count60 times (that is 60 s), it automatically gives a connection signal to the second counter whose count value is changed to one simultaneously, then the first counter reset at the same time. The rest can be done in the same manner to realize the long-time timing function.
Scheme 2: Adopt the INC instruction to replace the function of the counter.
Compare between the count value of the counter with the set value. when the count value is greater than or equal to the set value, then the timing reminder outputs.
The program for Scheme one:
The program for Scheme two:
The program can realize the long-time timing function. By adding scheme one Network 6 (or scheme two Network 2), the Multi-segments long-time timing reminder fucntion can be realized. Between the two schemes,it can be obviouslyseen that scheme 2 is more simple and practical, because the number of counters that can be used in a program is limited. While INC instruction can replace the counter to achieve the same effect.