step 7 question

sayahan2003 · Jun 1, 2007

dear friends,
please excuse me because i am new in step7. i have 2 questions:

1-i have doubt about time value of timers. as you
know, when i use s5t#... then the time valuse is
limited to 2H46Min. if i want to measure more than
this time for example 24 hour, what can i do? i know
that i have to change the time base but i dont know
how. i read the help of step 7 but i couldnt
undrestand.
2- if i want to turn on a bit for just 1 cycle in
every 10 seconds(oneshot), how can i do it?

JesperMP · Jun 1, 2007

1.: Use the IEC timers in stead of the S5 Timers.
The usage is a bit different, so expect to dig into it for some time.
Search for an example with "multiple instance IEC timer".

2.: You have to program a timer that restarts every 10 seconds.
You can use both S5 Timers and IEC timers for that purpose.
For an IEC timer simply put the inverted .Q output to the .EN input.
(You can not use the clock bits because the max cycle time for these are 2 seconds).

sayahan2003 · Jun 1, 2007

what is IEC timer?

PeterW · Jun 1, 2007

sayahan2003 said:
what is IEC timer?

You'll find them in the standard library folders. Its not an instruction, but an block that is already stored in your PLC.

sayahan2003 · Jun 1, 2007

Dear peter,
thank u so much but really there is no simple way to solve these problems?

sayahan2003 · Jun 1, 2007

my dear friends
i am still waiting for your help

R_Stone · Jun 1, 2007

You could just stack timers. In other words, set up a one hour timer. When it times out have it start the next timer and so on. That would be a simple quick and dirty way to do it.

Robert

S7Guy · Jun 1, 2007

sayahan2003 said:
Dear peter,
thank u so much but really there is no simple way to solve these problems?

sayahan2003 said:
my dear friends
i am still waiting for your help

Actually, both methods that were described are quite simple. Have you given it a try?

10BaseT. · Jun 2, 2007

You can use DAYS as the timebase for IEC timers - you aren't trying to tell me that isn't enough ?

manmeetvirdi · Jun 2, 2007

hi

set up a free running timer of 1 hour.
Use the pulse of this timer to increment a counter with desired value at PV of the counter.
or
Use the pulse of this timer to increment a word register.
Keep comparing the word register value with desired value.

manmeet

sayahan2003 · Jun 2, 2007

10BaseT. said:
You can use DAYS as the timebase for IEC timers - you aren't trying to tell me that isn't enough ?

my dear friend,
the problem is i cant find IEC timer in library.

sayahan2003 · Jun 2, 2007

manmeetvirdi said:
hi

set up a free running timer of 1 hour.
Use the pulse of this timer to increment a counter with desired value at PV of the counter.
or
Use the pulse of this timer to increment a word register.
Keep comparing the word register value with desired value.

manmeet

thank u my friend
i will try your suggestion

manmeetvirdi · Jun 2, 2007

sayahan2003 said:
the problem is i cant find IEC timer in library.

Libraries-->Standard Library-->System Function Blocks-->SFB4
SFB4-->on delay iec timer

regards,
Manmeet.

sayahan2003 · Jun 2, 2007

manmeetvirdi said:
Libraries-->Standard Library-->System Function Blocks-->SFB4
SFB4-->on delay iec timer

regards,
Manmeet.

thanks all of my friend

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