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One shot trigger

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#1 mr_electrician

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Posted 11 January 2008 - 07:46 AM

I am trying to write some logic that will enable me to set a bit(using the set/reset bit) only once untill a certain condition happens. WHat I have is a flow form machine that has some logic that will allow the machine to break the program after the part is formed. I want to add to this logic but I need to pulse the bit one time. Is there not any kind of one shot in Siemens?

J G Ashton - M.E., C.Tech.
Industrial Controls Specialist

Anyone who has never made a mistake, has never tried something new. - Einstien


#2 panic mode

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Posted 11 January 2008 - 08:20 AM

first of all what PLC and software we are talking about? did you try -(P)- instruction?

and you can allways do DIY one shot:

   condition										 aux				 one_shot
----| |-----------------------------------+-------------|\|----------------( )
										  |
										  |								aux
										  +--------------------------------( )


#3 Groo

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Posted 11 January 2008 - 08:35 AM

Is there not any kind of one shot in Siemens?



In S7-300/400 yes, unsure of S7-200, that's the current Siemens range. In the old S5 there was not.

So only S7-200 I'm unsure of.

The above example is as good as any to create a 1-shot if the PLC has none.

#4 Rodney

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Posted 11 January 2008 - 09:02 AM

In S7 200 it is also posible you use the positive or negative transition IPI or INI. This is placed down stream on the rung and when all conditions become true or false depending on which you are using you have a one shot pulse.



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#5 mr_electrician

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Posted 11 January 2008 - 09:22 AM

first of all what PLC and software we are talking about? did you try -(P)- instruction?

and you can allways do DIY one shot:

   condition										 aux				 one_shot
----| |-----------------------------------+-------------|\|----------------( )
										  |
										  |								aux
										  +--------------------------------( )

I am using a 300. What you show is almost the same as what I wrote. I am going to employ the positive rise bit.
Net:1
M40.1(nc running)M42.5(strip blocks missing)M42.6 (Stripper key removed)
------[ ]--------------[P]------------------------------(S)

Net:2
M80.2 - break is active(bit is 1 till end of cycle) M42.6
-----[ ]------------------------------------------------®
You would probably have to see the whole sequence of events or understand the machine to see this work but I am confident it will.
I just have to battle proof it. Too bad there using the machine now! :yes:
Thanks guys.

Edited by mr_electrician, 11 January 2008 - 09:30 AM.

J G Ashton - M.E., C.Tech.
Industrial Controls Specialist

Anyone who has never made a mistake, has never tried something new. - Einstien





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