raymo (Customer) asked a question.
We are running a P3-550E system with several I/O cards. There is one P3-16TD3P that is connected to the term board via a zip link cable.
One of the outputs, which controls the main air valve to the machine, intermittently drops out causing a fault in the machine.
When this happens the channel (in this case 5) shows a fault and no power comes out of that channel.
I've replaced the module, the zip link cable and checked all connections. The fault stays on until the 24VDC power supplied to the outputs is cycled through an E-stop. When this fault occurs and open the module in the Hardware Configuration it shows a Status bit fault "Missing 24V" on MST-0.1.3.17. This is the third module but it only has 16 outputs. How is there a fault showing on channel 17?
I'm including a screen shot of the module.
Thanks,
Ray
that module was retired in 2022. i would look at a replacement!
MST-0.1.3.17 is a card fault (Missing 24V) bit, not an output point.
As for the original issue, I can offer no help.
Agree, this module is retired, but apparently you have these in your stock parts, and want to use them. You replaced the PLC module and the zip link cable, but not the zip link RTB. I have ran into situations where the RTB was bad. (evidence suggested that they had a short on the zip link RTB circuit and the circuit was not properly protected) When the problem occurs, do you have 24V on the RTB terminals, but the module reports "Missing 24V"? If so, the RTB could be the problem. Possibly more work than replacing the RTB, but you could get a zip link cable to be used for testing, cut open the cable jacket, locate the power wires, strip off the wire insulation, and attach a volt meter to verify if the RTB is at fault.
Thanks for the reply. I've thought about the RTB. When the fault occurs there is no voltage out of the module to the RTB. I did try to move that output to an unused output on the same module. It did the same thing. It's possible that 2 channels are bad but it seems like a long shot. Also, none of the other outputs have failed. This is the only one with any kind of load. (Solenoid at 1.6 Ohms). The rest are solid state relays.
I've since wired this valve to a completely different module that uses a relay base for outputs. The only thing that I can think is that this solenoid is overloading the output for some reason. It is a new solenoid and connector, btw.
"none of the other outputs have failed". So right, cannot be power not getting to module if other outputs are working during the "Missing 24V" error. Strange then that the module gives you this error. If you are directly trying to power this solenoid thru the module, then yes, overloading. "Solenoid at 1.6 Ohms". Assuming 24VDC, I calculate 15A! The module outputs are rated 0.5A per point, and 4A per common, and trips at 1.2-2.4A. I must have something wrong, this high amount of amps should take the whole power supply down. But good, it sounds like you got it working! I like to use separate power supplies for the PLC modules and field output circuits, and protect the individual field output circuits, for example using the DN-SUPP supplementary terminal blocks.