CAN Bus

Hello everybody,

Just want to ask is there some major difference between PROFIBUS and CAN Bus cable. This morning we tried to connect to PLC via CP5611 - CANBus cable to the repeter (PROFIBUS network) and we had comunication error and PLC SF was on. I had to reset TP in order to get everything back in order. Later on I tried connection with spare PC and it was OK.
Did the usage of the CAN Bus cable instead of PROFIBUS caused the fault or just mistake when cable was made by electrician?

Thanks

Krcedinac said:

Hello everybody,

I tried connection with spare PLC and it was OK.
Thanks

Click to expand...

Sorry, mistake not PC ... PLC

CANbus cable normally has a lower resistance than Profibus cable. If your cable was very long, or your baud rate was very high, the difference in resistance may have caused the problem. Other than that, I can't think of an obvious reason why CANbus cable couldn't be substituted for Profibus cable.

$

Krcedinac said:

Hello everybody,

Just want to ask is there some major difference between PROFIBUS and CAN Bus cable. This morning we tried to connect to PLC via CP5611 - CANBus cable to the repeter (PROFIBUS network) and we had comunication error and PLC SF was on. I had to reset TP in order to get everything back in order. Later on I tried connection with spare PC and it was OK.
Did the usage of the CAN Bus cable instead of PROFIBUS caused the fault or just mistake when cable was made by electrician?

Thanks

Click to expand...

What Baud rate is the Profibus running at ? If I am not mistaken the max rate for Profibus is 12M. I believe CANbus baud rates are much lower. Could be if the Profibus is at the higher baud rate the CANbus cable is not rated for that

Ian

I have had customers use DeviceNet (CAN based) cable on ProfibusDP applications where they wanted to have power and communications on the same cable, which is not the case with standard ProfibusDP media. They did not have the baud rate running at 12Mb, but more along the lines of 500Kb or 187.5Kb or slower. At first I followed the rules that this wouldn't work, but then people did it, it worked, and I just threw up my hands.

Joe_WaZoo

Hello, thanks for replying

Profibus network baud rate is 1.5 Mbps. I will try to connect again, but next time when machine is stoped... not running like last time. The cable lenght is some 40-50m. As I wrote before, I noticed that the shirm was not attached properly and after we fixed that we tried many time connection with spare PLC and there was no faults.

I can't see how the construction of CANBus cable would prevent it from being used in your application. Sure, there is a difference in capacitance, but it shouldn't cause a problem at only 1.5Mbps.

Sorry, I can't see a problem with the cable.

$

new attempt

Hello again,

On Friday I tried again to connect to PLC via CP5611-CAN Bus cable. I first connected to the MPI/DP port (CP317-2 6ES7 317-2AJ10-0AB0/V2.1) and tested (PG/PC interface) both connections MPI and PROFIBUS and it said that it is OK. Then I tried again to connect to the diagnostic repeater in PROFIBUS network and again I had SF fault on the PLC. Again it made disturbance on the network and I had to rest main touch panel in order to remove fault. Then I put cable back to MPI/DP port. When I tried Test mode (on line) in CFC with MPI it worked and with PROFIBUS it said: "CPU could not be linked on line". Now I more confused than last time. Anyway it is working with MPI slow but it is working.