Special functions Timer

[PDirac]

Hi !

I'm quite new at programming ladder but I find the
PLC very powerful. I have a vacuum system and
want to measure 3 analog inputs of the course
of 1 hour and put these value in the DM memory.
Since this memory is 4096 byte I have to subdivided
by 3 and record these events at 3 seconds intervals.
How do I go about using the Clk special bit ?

Thanks,

Pdirac

[support]

The "Clk:xxxs" pulses have predefined intervals that cannot be changed.

To create a clock pulse with arbitrary period, use a self-reseting timer as follow:

     T1           Fn_#1
|---||---------{dCusF}
|    T1             T1
|---|/|---------(TIM)


Timer T1 is a self-reseting timer and you can use its contact at any circuit before it as a clock pulse to trigger the custom function. Make sure that the place the self-resetting circuit last. In your case, T1 should have a preset value of 30 to get 3 seconds interval.

[PDirac]

Hi !!!
Thank you so much.
I'll try it and I'm sure it will work out.

Bob

[griz]

I need to have three of these timers in my circuit one for 1 sec one for 3 sec and one for 5 sec. Only one would run the circuit at a time being picked by the input switches. Is this possible with this type of circuit? I am new to ladder and am trying to do my first project. Also is there a way to make a sequence run only once? Basically I am causing 10 solonoids to open in a sequence based on the selected time delay. Any help would be appreciated.

[support]

Your case is different, the simplest way is to use 3 normal timers predefined with SV of 10, 30 and 50 and depending which which sequence step the appropriate timer is used.

If you have powerful PLC such as the T100MD+ then you can even use a single timer and trigger it by assigning its present value to a new value and clearing its contact:

   E.g
     CLRIO T1           ' clear Time "T1" contact
     TIMERPV[1] = 50  ' preset value loaded onto timer.

The timer with label name "T1" will start timing down from 50 (5.0 seconds) to zero when the above TBASIC statement are executed (this is not available on E10 or H-series PLCs).