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Old June 30th, 2020, 03:35 PM   #1
mylespetro
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Program in auxiliary PLC

Hey everyone,

Just wanted to see if anyone had any opinions on programming in a PLC that is essentially just being used to store data that's being written to it by another PLC? We have a lift station with a CompactLogix doing the control, but the spec called for a serial radio link back to the water utility, therefore the panel builder put in a MicroLogix 1100 to interface between the CompactLogix and the radio. I have all of the digital and analog I/O being written into the Micro from the Compact and have the I/O labelled, but what would you consider the bare minimum programming (if any) inside the Micro if it's not actually controlling anything? Would you include a comms heartbeat? Or something more elaborate?

Thanks in advance!
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Old June 30th, 2020, 04:11 PM   #2
I_Automation
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Heartbeat - Yes.

As far as other things, I like to put logs in for runtime, pieces count, cycles, etc. Just so next time I get to it I can tell the customer things like "this pump has run 12 thousand hours", "this machine has produced 128 million parts" and other numbers they, and I, am usually impressed with.
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Old June 30th, 2020, 08:27 PM   #3
DwSoFt
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I don't know why you would need an interface PLC unless the radio is serial and the compactlogix is not. I would use a heartbeat yes.
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Old July 10th, 2020, 08:57 AM   #4
mylespetro
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Quote:
Originally Posted by DwSoFt View Post
I don't know why you would need an interface PLC unless the radio is serial and the compactlogix is not. I would use a heartbeat yes.
The radio spec'd by the panel builder was serial only, but what arrived onsite has a digital/Ethernet jack so it may have been unnecessary to use the MicroLogix after all.
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Old July 10th, 2020, 11:18 AM   #5
GaryS
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i would have to rethink the idea of using a PLC to log data they are really not designed for that. They would have limited storage at best.
i would look a computer with real hard drive and maybe even look at writing to a cloud drive it shouldn't be to hard to setup.
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Old July 10th, 2020, 11:24 AM   #6
OkiePC
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Quote:
Originally Posted by GaryS View Post
i would have to rethink the idea of using a PLC to log data they are really not designed for that. They would have limited storage at best.
i would look a computer with real hard drive and maybe even look at writing to a cloud drive it shouldn't be to hard to setup.
From what I interpret from this thread, I don't think it's logging data so much as just acting as a data buffer and serial to Ethernet converter between the Compactlogix and the serial radio network.
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Old July 10th, 2020, 01:47 PM   #7
DwSoFt
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Quote:
Originally Posted by mylespetro View Post
The radio spec'd by the panel builder was serial only, but what arrived onsite has a digital/Ethernet jack so it may have been unnecessary to use the MicroLogix after all.
Just because the radio has an Ethernet port doesn't mean the network supports it.

For example I have a network with MDS SD4 radios mostly but they are all in transparent or 710a mode as some of the radios are MDS 4710. Due to that I cannot use packet with Mac which is the mode that supports Ethernet. I use that port just for the web interface to configure it when on site. That is it.
On a side note. 400mhz is very low bandwidth for Ethernet comms. 900 and above is better but the higher the frequency the shorter the distance and the better the path needs to be (no trees in the way) 400mhz will cut through trees.
I prefer to do modbus when switching to serial comms for the radio network.
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