I look around for a few and eliminate the obvious possibilities.I then open up the electrical box that holds my MicroLogix 1500.What do ya know the fault light is blinking I hook up mr.
I dont quite understand. Fault description is as follows.The controller cannot communicate with an expansion IO module. ![]() HMMMMMM. This is a MicroLogix 1500 LRP with a 1769-OV16 connected to the side of the controller, then a 1769-CRL3 connecting to a 1769-PA4 power supply and a 1769-IQ6XOW4. Have to double check it. F.Y.I. When using the Rockwell live chat you are required to select a ChatQue before you can connect. I have noticed that the list is fairly small, with MicroLogix and RSLogix500 not being a choice. I selected ControlLogix HardwareSoftware because it was the closest match. I asked the tech what would be the best selection and he told me that the MicroLogix and RSLogix500 are not currently supported by live chat, but should be sometime in the future and he would do the best that he could to help me out. Not sure how many people use this but I have found Live Chat to be a nice tool to have in my bag. This particular machine has been in service 6 months after a complete rebuild (everything electrical was replaced). Other than the connection theory, what could be causing this Both units have Islatrol line filters feeding any power connected to the PLC and IO cards, also all outputs are isolated with relays. The electrician trys to reseat connectors while the processor is in run mode. When it faults out they call me, and low and behold the electrician is nowhere to be found. I changed the ML1200 and output module with a new spare that I had, and I am having the same problem. If your distribution is at the other end of the plant, your line filters can only do so much. Look carefully at any inductive loads and check them to be sure the snubber circuits are in place and appropriately connected. A big motor starter or solenoid valve can snap a couple hundred volts of back EMF when it opens, which doesnt necessarily cross the backplane but can induce disruption in the 1762 bus. On the MicroLogix 1500, the thing Id look at is the expansion power supply. The power supply itself, or a dip in the power feeding it, would cause that expansion bank of modules to fault. There are no snubbers on the coils, what would you recommend Thanks. When the coil loses its power, the collapse of the flux field can send a DC surge back to the card.
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