FloridaEngineer
Member
Hello everyone,
I am completely new to PLCs no formal training but I work as a process engineer in a plant that uses them and have been trying to teach myself for several months now.
The system was supposed to be set up by a contractor but was never fully finished because funding was cut so the essentials to operate the plant are there. I was tasked with commissioning a 4-20 AO flow meter and adding the reading to our factory talk HMI with a totalizer.
The PLC (Logix5555) that the flowmeter is wired to is only used to receive and send inputs and outputs to the main plc (Logix5575) in the control room. The control room PLC does all the operating logic.
Now, what I did is use RSLogix to first get the Logix5555 to send the input from the flowmeter to the Logix5575 and store it in the tag there. I did nothing new just added it to a previously created list of other inputs that get copied to the PLC that I know already worked. This all went fine.
Then I took that tag and connected it to an analog input function block which I connected to a totalizer function block. I did this based on another flow meter that had already been setup. This seems to work fine too.
I was getting ready to add the graphics to the HMI and I was calibrating the bit data and PVScale when I noticed that the pump I was using was behaving strange in factory talk. All our pumps have HOA switches which can be set to hand, off and auto. The pump ran fine in hand, and turned off, but with the switch in auto, the HMI faceplate still says its running and is in Local mode. So I vent and checked the VFD (connected to Logix5555) and it was on at 0.0% in remote. What I also noticed is that every VFD connected to that PLC was powered on but not running. This is strange behaviour to me and had not seen it before because as far as I know all VFDs are set up to turn off when output is below minimum.
Any thoughts on why this might be happening? or how I could find out what the matter is. I suspect that the changes I made may have something to do with it but I did not alter anything related to the VFD.
Any help is appreciated!
I am completely new to PLCs no formal training but I work as a process engineer in a plant that uses them and have been trying to teach myself for several months now.
The system was supposed to be set up by a contractor but was never fully finished because funding was cut so the essentials to operate the plant are there. I was tasked with commissioning a 4-20 AO flow meter and adding the reading to our factory talk HMI with a totalizer.
The PLC (Logix5555) that the flowmeter is wired to is only used to receive and send inputs and outputs to the main plc (Logix5575) in the control room. The control room PLC does all the operating logic.
Now, what I did is use RSLogix to first get the Logix5555 to send the input from the flowmeter to the Logix5575 and store it in the tag there. I did nothing new just added it to a previously created list of other inputs that get copied to the PLC that I know already worked. This all went fine.
Then I took that tag and connected it to an analog input function block which I connected to a totalizer function block. I did this based on another flow meter that had already been setup. This seems to work fine too.
I was getting ready to add the graphics to the HMI and I was calibrating the bit data and PVScale when I noticed that the pump I was using was behaving strange in factory talk. All our pumps have HOA switches which can be set to hand, off and auto. The pump ran fine in hand, and turned off, but with the switch in auto, the HMI faceplate still says its running and is in Local mode. So I vent and checked the VFD (connected to Logix5555) and it was on at 0.0% in remote. What I also noticed is that every VFD connected to that PLC was powered on but not running. This is strange behaviour to me and had not seen it before because as far as I know all VFDs are set up to turn off when output is below minimum.
Any thoughts on why this might be happening? or how I could find out what the matter is. I suspect that the changes I made may have something to do with it but I did not alter anything related to the VFD.
Any help is appreciated!
