Profibus configuration

I am relatively new to profibus, and thus not fully aware of its capabilities.

Do the devices as configured in prosoft need to be connected in the same physical order along the cable? Or can I mix up the order, assuming the addresses are set properly on each device? Also, can I have more devices configured than I physically have connected?

My particular situation is that I find myself on occasion needing to send a power supply out for service and the available spare is not always the exact same model. This means a different .gsd file. I have tried just using the same config with the different power supply, and it works most of the time, but sometimes the behavior is a little funny. I want to change the prosoft configuration to include the spare power supply so when required I can unplug the original and plug in the spare with a different address. This way there is always a disconnected power supply in the configuration. I have considered downloading an alternate prosoft configuration file when needed, but to take the machine down to do this should be a last resort.

Thanks!

1) the order shouldn't matter, as long as the addresses are set right. Also, ensure you follow proper cabling guidelines, which are very different from Devicenet. No trunks; everything should be one daisy chain, unless you have repeaters.

2) some Profibus masters (like a siemens PLC) have instructions to activate and deactivate slaves. This allows for extra devices to be configured, which are not physically present, as you suggest. However, I don't know if the Prosoft cards support this feature or not.

Hi,

Your first question, you already got an good answer.

your second question: All Profibus masters I worked with, including several Siemens S5 and S7 cards and molex SST-PB3-VME/SST-5136-PFB-VME cards have no problems with slaves that are configured, but not actualy connected to the bus.
So I think it will not be a problem when you configure a new slave number with the power supply, and only connect it when you need is.
The only thing is that the card will tell you that a configured slave is not on-line.
( in my case, having a red LED indication on the Profibus card ).

Success

John.S said:

your second question: All Profibus masters I worked with, including several Siemens S5 and S7 cards and molex SST-PB3-VME/SST-5136-PFB-VME cards have no problems with slaves that are configured, but not actualy connected to the bus.
So I think it will not be a problem when you configure a new slave number with the power supply, and only connect it when you need is.
The only thing is that the card will tell you that a configured slave is not on-line.
( in my case, having a red LED indication on the Profibus card ).

Click to expand...

You're correct; I should have been more specific. The Profibus masters usually work correctly with a device configured but not present, but they will register an error. In an S7 PLC, this means a Red error LED, an entry in the diagnostic buffer, and possibly an HMI alarm.

The activate/deactivate feature I mention masks the error for a specific device, so that you can make the red light go away. This can be very convenient when you expect to have a device only sometimes attached, like the backup power supply you mention. Most operators get scared when they see a system that always has the error light on/flashing, even while working correctly.

Thank you for your responses! My inclination was that I would be fine, but your confirmation is reassuring. I will need to look into the error light masking you mention. It is a 1756 ControlLogix PLC, in case anyone has experience with this.