I have a small CIP system that I'm having issues with. Basically, it consists of two ML1400s and a C-More HMI. Switch is located about 5' from the HMI, which is in a large SS enclosure that holds three VFDs and six motor starters. The Ethernet cable from the switch to the first PLC is about 100' long, and about 200' to the second PLC. The furthest PLC "runs the show". The closest PLC only reads the position of limit switches to validate valve position. CIP is started and monitored from the HMI. I read validation signal from the slave PLC every second (MSG over CH1, reading one word)
Here's the problem:
Every once in a while, I lose the validation signal from the PLC, which causes the system to stop. I set up a maintain timer and it works fine (latch currently holds for 7 seconds). The timer tricks the main PLC into thinking that switch position is validated.
I'm not fond of "tricking" the system, because moving a valve while running CIP could be expensive - read PRODUCT LOSS.
I've been trying to diagnose over a VPN connection, and several pumps are starting within a few seconds of each other, so I can't nail down which starter or VFD is causing the signal loss. To make things worse, I was involved in the project only after most of the pumps were wired, so I have no idea which may have ground loops, which wires may be run next to the Ethernet cables, etc.
I know this is a general question, but is there a recommended way to "filter" electrical" interference off the Ethernet cables?
I guess I could set up a serial network, too, but pulling cables isn't going to be fun.
Here's the problem:
Every once in a while, I lose the validation signal from the PLC, which causes the system to stop. I set up a maintain timer and it works fine (latch currently holds for 7 seconds). The timer tricks the main PLC into thinking that switch position is validated.
I'm not fond of "tricking" the system, because moving a valve while running CIP could be expensive - read PRODUCT LOSS.
I've been trying to diagnose over a VPN connection, and several pumps are starting within a few seconds of each other, so I can't nail down which starter or VFD is causing the signal loss. To make things worse, I was involved in the project only after most of the pumps were wired, so I have no idea which may have ground loops, which wires may be run next to the Ethernet cables, etc.
I know this is a general question, but is there a recommended way to "filter" electrical" interference off the Ethernet cables?
I guess I could set up a serial network, too, but pulling cables isn't going to be fun.