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Old June 24th, 2004, 08:57 AM   #1
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Unhappy Timer ?!?.?!?.

Hello to all,

I’ve go an interesting problem. It’s is about an timer.
We’ve have programmed a “on delay” timer witch waits for an input and after the input (logical 1), the input shows a negative flank (logic 0) the timer starts to run for a period of 1 minute. If the input is a 1 the output of the timer becomes a 1 to until the time has elapsed.
The problem is that after the minute the output signal of the timer still is a 1 and the time starts to count again.
You’ve got something like a endless loop.

The input of the timer is (the SET condition) a valve is open and we’ve got no RESET because the output will be a logical 0 if the time has elapsed. Well normally spoken.

Does anyone have any idea how this is possible and if there is some solution for this (except “use an other timer”)?
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Old June 24th, 2004, 09:09 AM   #2
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Which PLC ?
And please post your code !

I have tried to picturize how you want the timer to work according to your text (but I must say that your text is a little confusing):
Input:   _______--____------------____________

Timer: *----------> *---------->

Output: _____________--------________________


The timer starts at the "*" where you have the negative flank of the input.
The output is ON as long as the input is ON and the timer is running.
Is this way you want it to work ? If not, try to make diagram on how you want it.
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Last edited by JesperMP; June 24th, 2004 at 09:16 AM.
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Old June 24th, 2004, 09:43 AM   #3
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We've got the right timer programed.

input:.. _____----____________

output: _____------------____


It's not that important.
The real problem is that if there is a signal at the input the timer doesn't stop after his time has elasped. Even if the input signal becomes a 0 again.
The output of the timer stays an 1 and doen't change after the time has elasped.

We;ve got an IBHSoftec S7-314 für Windows SoftSPS
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Old June 24th, 2004, 09:50 AM   #4
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Please post your code.
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Old June 24th, 2004, 09:54 AM   #5
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Timer code:

U A16.0
L S5T#1M
SA "T4"
NOP 0
NOP 0
NOP 0
NOP 0

Written in FBD. The timer is only used as an condition by the set of an bit.
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Old June 24th, 2004, 10:09 AM   #6
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If this was a normal S5 PLC then I would think it impossible that the timer would be "defective". But as it is a soft PLC from IBH softech, maybe there is problem (but it is still unlikely).

You have to post the entire code, so we can see how A16.0 is programmed and how that particular code section is scanned.

Maybe A16.0 is reset when T4 is finished and then immediately set again before you can see it.
Maybe A16.0 or T4 is referenced elsewhere in the program.
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Old June 24th, 2004, 01:04 PM   #7
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use a trigger input just before the timer so it will only react when input changes from 0 to 1.
or disable input as long as timer is running.
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