S7-300/Wago Configuration

[malc cope]

Hi I currently have a system which comprises a S7-314C-2 DP which is link to a number of SEW drives & 2 WAGO I/O units this system is now commisioned succesfully and all is fine other than because of time delays between the PLC and the remote I/O I need to speed up the response time of some of the control. To acheive this I have replaced one of the WAGO Fieldbus modules (740-343) with a WAGO Fieldbus controller module (740-833) and I have programmed the controller so that the process can be controlled locally. this in principle appears to work, other than there appears to conflict between the I/O, as far as can establish I beleive this due to how the WAGO hardware is configured, i.e the hardware has to be configured so that the fieldbus controller can control the I/O and not the S7 PLC and then the S7 PLC I/O has to be mapped locally in the WAGO unit to access the local I/O. This all appears fairly straightforward other than the information as how to configure the S7 to communicate with the WAGO is lacking, reading through their manual the only comment is 'In Preparation'. Am I right in thinking that I need to use Siemens FB SFB52 (RDREC) & SFB53 (WRREC) to communicate with the WAGO unit? Any assisitance will be greatly appreciated

[Groo]

I know nothing about WAGO units but why is it too slow, what speed reaction are you looking at and what is the baud rate set to on the (I would presume) profibus?

[malc cope]

Basically I am looking at 2 inputs when both inputs are on after a short time delay typically less than 200ms i need to operate an output for about 120ms, as the process is checking items passing on a conveyor line the timing is quite critical, the baud rate is 1.5Mbps, the program scan time in the plc is typically 250ms, I have had the controls for this in a timed interrupt OB on a 50ms time slot but I do not get consistant enough control, the control is currently in a small local plc which handles the controls quite well, the reason this is no good as a long term solution is because the time variables will need to be changed depending on the conveyor speeds being used, also as the WAGO as a encoder input we may change to an encoder on the conveyor rather than using time for better control, again previous trials using the encoder with the control in the main PLC has not been reliable enough

[JesperMP]

If the WAGO unit is connected to a Profibus on the onbaord DP port on the 314C2DP CPU, then all you have to do is to import the .GSD file from the Wago unit into the HW Config in STEP7. You can the exchange data directly via the i/o image.

[Groo]

I've seen scan times such as that (well not that high) during early commissioning, where not all the I/O is fitted, the diagnostic functions stretch the scan time quite a bit. If its code thats doing it then maybe you should look at faster ways of doing it or perhaps goiung for a better processor.