PLC basic question

Karoly

Member
Join Date
May 2012
Location
Doha
Posts
24
o_O I am a newbie trying PSIM and am facing difficulty with a counter in the Batch program. I observe that there is significance in the order of the rungs in this case.

Please see this picture

The pump 1 (O:101) trigger flow meter I:105
The pump 2 (O:102) trigger flow meter I:106

Both flow meters are used to increment a counter C1

Pump 1 works till counter = 35, and afterwards pump 2 works

Now when I give counter before inputs (Program 1 in figure) counter is activated by I:105 but not activated by I:106. It just stops at 35.

When I give counter after inputs (Program 2 in figure) counter is activated by I:106 also.

Why?
 
When you stop the pump 1, what ensures that I:105 will be zero thus allowing pulses on I:106 to be seen by the counter?

Either use two separate counters, or edge detection logic for each input to trigger your counter.
 

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