S7 - problem parameterising FB58 TCONT_CP

I'm trying to use FB58 for a temperature control loop for the first time and I can't persuade it to accept an input for the CYCLE and CYCLE_P parameters.

I'm calling the block in OB35 and CYCLE should therefore be 100 ms. According to the Help file this parameter is a REAL (which strikes me as a bit odd) so I tried entering 1.000000e+001 but no joy the input data remains red. I've also tried 0.1 s, as shown in the Help file as being the default, as well as S5T#100ms. No joy, all remain red.

Can some kind soul please show me how this input needs to be formatted!

Cheers

Roy

Edit: Just had a look in the IDB and sure enough the default values of 0.1s for CYCLE and 0.2s for CYCLE_P are present as REALS. So I highlighted the 0.1s value and copied it into the CYCLE parameter of FB58 - no change, as before it remains red.

I guess if the worst comes to the worst, I can change the value directly in the DB, but it seems a bit odd!

They are INOUT's which means you cannot address them as absolute values.

Try a double flag and preload it. edit: I presume internally the block calcs these values

You're right Peter that works. I created a couple of new REALs in my "general" DB and fed the FB58 their address and it swallowed them quite happily. Pity they don't mention it in the Help files!

Thanks

Roy

Now I'm having problems with FC41 CONT_C!

and this time simply pointing at a DB entry entry doesn't solve the problem.

More precisely, it concerns the I and D times, following my problems I created a DB to hold the controller's parameters from the word go, only to find that for these two TIME values (this time the format is clearly described in the Help file, unlike the FB58 help file) the editor won't accet a link to the DB. It will accept the times directly input to the FB-parameter inputs, but that's not exactly what I would call comfortable for tuning the loop on site, because it means you got to go online with the editor rather than being able to do it, for example, from the operator panel.

Can somebody confirm if this really is the case, or is there some way to persuade the editor to accept the link to the DB data.

Cheers

Roy

Do you mean FB 41 and not FC.

If FB and you want to set the parameters via the OP. After calling the FB, it creates your specified IDB.

Leave the IN parameters blank, just open the IDB and enter your presets direct into the words and save the IDB.

Later on the Visual system could write direct to the DB, or write to an interface DB and do a L DBx.etc and T DBy.etc, DBy being your instance DB.

edit: condition the above with an update button. You would have to save the IDB back into the project to ensure its up to date.

Do you mean FB 41 and not FC.

Click to expand...

Yes, my dyslexic fingers again!

I don't know why I didn't think about accessing the IDB directly - after all it's something I do on a regular basis. I guess I must have been too irritated by the fact that it wouldn't accept an input from my controller-DB!

Anyway that's it for today, I'm off for a weeks holiday, but I'll be back on Monday the 9 th, I expect, because my FB41 is sitting there glowing geen at me with it's EN-input valid, SP_INT = 1.5, PV_IN = 0, GAIN = 0.73, I = T#14s and LMN_PER not budging from 0!

See you then!

Cheers

Roy

I created a DB with a time variable at DB2.DBD0 and entered this for parameter "TI" for FB41. The editor accepted this.

SimonGoldsworthy said:

I created a DB with a time variable at DB2.DBD0 and entered this for parameter "TI" for FB41. The editor accepted this.

Click to expand...

I was going to ask what format he was entering, perhaps a word onstead of double.

I created a DB with a time variable at DB2.DBD0 and entered this for parameter "TI" for FB41. The editor accepted this.

Click to expand...

Just tried it again and now it works!

The only thing I can think of is that I had maybe created the DB but not saved it after entering my parameter variables.