[Prosoft with ControlLogix] Trying to diagnose Profibus fault

Hi guys,

Some of you may remember me mentioning a backup Profibus connection I have in my project. A quick recap:

1. Existing Profibus connection between Main Control Panel at water treatment plant, and Lake Intake Pump Station (about 0.5 miles away).

2. Profibus wiring is existing, and worked just fine with old PLCs (Siemens S7). So far as I know, it hasn't been touched during the panel swap other than to land it onto surge suppressors (which I've disconnected entirely to reduce variables).

3. I'm using a MVI56-PDPMV1 at the Main Control Panel (address 0) and an ILX69-PBS at the Lake Intake Pump Station (address 10). These are the only things connected to the Profibus network (and were the only things connected previously as well, save that the old system piggy-backed through the Main Control Panel's PG port via a CP5611 for the HMI's access; that's all been removed and now the Profibus is simply a backup for the fiber link between the Main Control Panel and the Lake Intake Pump Station).

4. I have terminating resistors switched "on" at both ends. The connector at the Main Control Panel is being reused from old system, it has a PG port. The connector at the Lake Intake Pump Station is new, and doesn't have a PG port. I've wired Green to A1, and Red to A2 on both sides (no crossover or anything).

5. When I use the Prosoft Configuration Builder to set up the Profibus connection, if I scan the network only the master shows up; the slave has never showed up.

6. If I go to "monitor/modify" in Prosoft Configuration Builder, the slave has a red border around its icon. If I go to its diagnostics tab, the error is that the slave is "not existant".

7. I've re-terminated both sides of the Profibus connection; the old terminations were kind of hammered so I re-stripped the outer insulation, made sure there was a good connection to the shield, and re-stripped both A and B conductors too.

8. If I measure voltage across the A and B conductors in the connector, I get about 0.5-0.6VDC. But according to my ohm's law calcs across the differential, the voltage should be about 1.0VDC (the supply voltage is 5.0VDC).

9. If I go to the diagnostics webpage for the ILX69-PBS it says under the Module Status:
And under the Network Status:
At this point I have no idea what else to do. I have a call in to Prosoft but they're not going to be able to get back to me until tomorrow as the engineer assigned to my call has left for the day.

They seem to believe it is a physical connection problem since the configured slave should show up on a scan, and since it isn't there's not much else to try. We did have surge protectors in line with the connections, but to make everything as simple as possible I have entirely bypassed them and have wired everything directly (to no avail).

If anyone has anything to suggest looking into, it would be amazingly helpful. Thanks a bunch.

Hi,

Maybe an open door, but have you checked baud rate.
Higher baud rates means shorter allowed cabling.
If possible, try a lower baud rate, supported by your slave, and see if you can get a connection.

success.

gr. John

"MVI56-PDPMV1 at the Main Control Panel (address 0) " ..

It is not a good practice to use address 0 as it is reserved for PG / Laptop ... Is there a CP5611 card connected to the same network. this card usually has a default address of 0.

I would change the address of the prosoft gateway and try...

First.. regarding ProSoft support. You tell them that you want another Engineer to help you.

Is there a way you can take the CompactLogix system to the main control panel just to take the cabling out of the equation? For a simple test, a straight-through serial cable works just fine from a master to a slave.

Just like the last couple of gents mentioned, try changing your scanner node #, then try to establish comms at the different baud-rates.

As silly as it sounds, also check the new connector at your scanner to make sure your cable is entering the 'in' end and not the outfeed end or your resistor won't do anything.
GL

Thanks for all the help guys. It turned out to be the baud rate; it was too high for the length of cable and after setting it lower, it worked perfectly. I'm kind of surprised that wasn't the first thing Prosoft's Tech Support suggested, but that's why this forum is so valuable and why I was happy to become a supporting member.

I will also change the Master address to 1 as per best practices, though we'll technically never have anything connected to the PG port.