Communication problems with CI854
i'm currently working on the communication via profibus of different equipement with the PM862 CPU. so basically, i have tow loops.
-the first one is comprised of a number of multimeters (sentron pac4200) communicating at 1.5MBaud.
- the second one is comprised of a number of deported I/Os and 4 abb softstarters communicating at 1.5Mbaud.
at that point everything worked fine. I needed to add to the second loop some GE MM200/MM300 protection relays, the loop started to get long so i had to slow the baudrate to 19.2kbaud, in that moment i started to have communication problems.
- i lost the communication with first loop even though i've changed the baudrate in the CI854 and the sentron pac4200 has a an automatic baudrate detection.
and eventually the RXA/B LED of the CI854 card wouldn't even light.
- i get contradictory readings from the second loop so several of the MM300 relays and ABB softstarters are declared not communicating in CBM even tough their respective communication LEDS are green.
thanks in advance for your help.
Voted best answer
Sounds like your problem.
- Presumably, you've checked all the bus terminating resistors and nothing was left on when it should be off etc. Also conflicting address segments etc.
- Check the AC800M Web server to see if all of the device addresses are appearing in the live list. (Open a web browser to the controller IP address)
- If an electrical Profibus segment is so long that you have to reduce the speed, then really its too long. Make a better design.
- Physically examine the installation - do not assume that everything is installed properly until you have done so. I have seen a Profibus installation where the contractor had coiled 50 meters of "spare" cable under the floor. Needless to say, the bus was unreliable and regularly lost comms with modules.
- If the bus length is well within the limits for 1.5M but the speed still needs to be reduced to overcome the number of errors you have on the bus, then you probably have an installation problem.
- If the bus is too long, replace segments of the electrical bus with fibre. This gives you two benefits .... You isolate sections of the bus from electrical interference AND you get a longer bus length.
- If the bus goes through areas where you find it difficult to avoid electrical noise you can use short electrical segments separated by fibre.
Beg/Buy/Borrow/Steal one of these ... https://procentec.com/products/profit... which can help you track down issues with adding new devices, address conflicts, error rates, cable lengths etc.
In addition to the other answer, here are my comments:
- we have used electrical Profibus segment with length about 700 m and baudrate 187.5 kbit/s and it works fine. Try to increase the baudrate. From the manuals, 187,5 should work for cable length up to 1000 m.
- check if all your slaves support the selected baudrate. Some devices doesn't support all the standard settings and in that case communication is not working
- you didn't provide your network configuration, how the slaves are connected. Also as a first check for the new slaves added, try to connect only them to CI854 and try to establish the connection to them. Then add the existing slaves, which already work
- check all the terminators, try with all terminators open. Carefully check connection inside Profibus connectors, often they could create problems (try with already tested connectors)
- changing of baudrate requires restart of nodes - For CI854, first download the new configuration (in order to execute Autotuning of Profibus parameters) and then reset the module by physical remove of the unit (it is hot swap). For the slaves usually I switch off the power supply for a while. I believe you are using CI854A, not CI854
- read the ControlBuilder manuals about the Profibus (usually c:>Program Files\ABB Industrial IT\Engineer IT\Compact Control Builder AC 800M 5.1\Manuals)