20 pid´s in siemens

[darkest_shade]

how can i program or make an arrange to manipulate 20 or more pid´s in siemens s-7, remember a thread of NICK B & KEN M but dont understand at all, can i make an acumulator on ob35? for trigger pid´s individual?

ROGER

 

[dchartier]

Hello shade;

In one project we did 25 temperature loops in a S7-313C-2DP processor, all in OB35, set at 100ms. Of course the rest of the program was as compact as we could make it (we used the available technological functions to control heating SCRs), and we used multi-instance DBs to limit the amount of memory we needed to process the whole project. But the OB35 call was not a problem.
Your main limitation will be the work memory available on your CPU, not the cyclic OBs.
Hope this helps,
Daniel Chartier

 

[darkest_shade]

thanxs for your reply D.Chartier

all at the same time? ill need to check the specifications of your cpu vs mine, im using a cpu 417-4h. ill try for trigger the pid´s at diferent times, i dont know if 2 or 4 at a time will be fine.

 

[Nick B]

A 417 is a lot of Horsepower...and thus would not worry about it. You have a lot of Interrupt OB's (OB30~38). On a small 300 with only OB35 to play with I would probably build a mux and break the calls into 4 to keep the jitter done.

Nick

 

[Manglemender]

As Nick B says, "A 417 is a lot of Horsepower!"

When setting up your timed interrupts for processing you PID loops, bear in mind the process. There is no point running your PID loops faster than the the feedback is likely to change. i.e. a temporature control loop will run acceptably at a relatively low update time but a position control loop would want to run much faster!

Nick

 

[darkest_shade]

thanx nick´s!!

is great to know that

i´m using a filter level control, for a gas refinery. think i need low update 500ms 1sec maybe.
so if i do a 24 pids with this proccesor, Nick you think i need to make interrupts???

if yes
can you please give me some small explanation how can i do that any example will be great.

else
just for curiosity, can you please give me some small explanation how can i do that any example will be great.

////////////THANX!!!!!

end.

 

[darkest_shade]

damn i have troubles, i can make one of the pids work fine, but i cannot make 2 work simultaneously, or switch them, there only works the first one, the second stays into zeros.

does any one have any solution????

i know, it must be simple, but i cant see the answer, i need my 23th coffee cup,

 

[Manglemender]

Timed interrupt OBs are configured in the hardware config for the processor and are executed at a regular interval e.g. OB35 every 100mS.

If you post the code the doesn't work for you, someone may be able to offer advice on what's wrong with it.

Nick

 

[darkest_shade]

SORRY MY MISTAKE

I´m using a 412-1 for tests right now, cuse the 417-4h is on instalation, alrready manipulate 3 pid into ob35, they don´t worked cuse i dont toggle the setpoint input, when i toggle the inputs they start to work! is that normal??? isn´t COM_RST that for¡???