Manipulate Siemens SFB4-TON timer

Hi,
Is it possible to manipulate the standard SFB4-TON timer from Siemens in a VAT table? I need to do some qualification tests on a system with a few large IEC timers. With the default timers it is possible to overwrite the actual time with another value but it seems that this is not possible with the SFB 4 timers. The preset time is 72 hours and I would like to test the program by changing the expired time close to the preset time so I only have to wait a few seconds.
Temporary software changes to test the result of the timers are not acceptable, I may only change values through the VAT table. The preset time is also written in the software with an constant value, so I can’t change that either.

Subtract time from STIME in the instance DB to make the timer expire quickly. E.g. if your plc has only been running for a short time, enter t#-71h50m in STIME to make the elapsed time 71h50m + what ever time has so far elapsed.

L D[AR2 said:

Subtract time from STIME in the instance DB to make the timer expire quickly. E.g. if your plc has only been running for a short time, enter t#-71h50m in STIME to make the elapsed time 71h50m + what ever time has so far elapsed.

Click to expand...

Thanks!!
If I enter the value STIME = ATIME – wanted ET, I can manipulate it the way I want.
I was playing with the ATIME and STIME before but I could not figure out how to change them (never thought about entering a negative value).

Wow - I will have to test this!

For some time I have complained about the Siemens timers not paying attention to a change in the preset once they start timing. AB and GE timers don't do this. For example if a timer preset is 5 minutes and the timer is timing, I can change the preset to a value lower than the elapsed time and an AB or GE timer will be DONE. Not so with a Siemens timer. This does present usability problems in the field. Thanks for the thread, I will play with this "in my spare time".

Paul B said:

Wow - I will have to test this!

For some time I have complained about the Siemens timers not paying attention to a change in the preset once they start timing. AB and GE timers don't do this. For example if a timer preset is 5 minutes and the timer is timing, I can change the preset to a value lower than the elapsed time and an AB or GE timer will be DONE. Not so with a Siemens timer. This does present usability problems in the field. Thanks for the thread, I will play with this "in my spare time".

Click to expand...

Better to increment an integer on a timed interval. Compare against a preset.

Yep, that has been my solution so far - make my own timers.