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Unread October 10th, 2019, 06:55 AM   #1
johnnyboy1852000
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Modbus RTU Issues

Hi Everyone,

I seem to be having issues communicating through Modbus RTU from my Horner XL7e to my Emerson Drives. The Connection is there but the drives are supper slow to respond.

Seems to me like a conflict somewhere but, I can not seem to find what's holding me up. At first I thought it was a bad port on the PLC because I stole a PLC that runs the same program from a currently running machine and everything works fine. So I ordered a new touchscreen and the same thing is happening SLOW responses from the drives.

any help or suggestions would be greatly appreciated.
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Unread October 10th, 2019, 08:52 AM   #2
gclshortt
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https://accautomation.ca/horner-xl4-...-instructions/
The above thread will show the XL4 communicating to a Solo process controller via Modbus RTU (RS485)

A couple of things to check.
- RS485 termination resistor
- Ensure all of the parameters like parity, bit rate, stop bits are the same on all of the devices.
- Increase the baud rate to see if speeds improve.

On the Horner a status register can be programmed into the communications. Does it contain any information?

Just a couple of thoughts.
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Unread October 11th, 2019, 04:46 PM   #3
Gene Bond
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For speed considerations, I map my registers into Menu 0. I usually have 0.060 through 0.063 for my writes (to the drive), and 0.064 to 0.070 for my reads (to the plc).

Also, are you using the CT RTU driver? It's on the Horner web site. Seems to work better than the generic Modbus.
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Unread October 14th, 2019, 01:59 PM   #4
johnnyboy1852000
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Gene Bond,

Where is this CT RTU Driver located on there site? I use there site quite often and can not seem to find it.

I also don't quite understand what you are saying here "I map my registers into Menu 0. I usually have 0.060 through 0.063 for my writes (to the drive), and 0.064 to 0.070 for my reads (to the plc)." can you explain a little more on this.

Thanks
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Unread October 14th, 2019, 09:07 PM   #5
Gene Bond
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https://hornerautomation.com/support-files/
https://hornerautomation.com/downloa...cols/CTRTU.exe

Use Menu 22 to map what you want in menu 0

22.060 = 1.021 for example, so Preset Speed 1 would be in 0.060

You didn't mention which model drive you're using?
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Unread October 15th, 2019, 06:10 AM   #6
johnnyboy1852000
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Gene Bond,

The Drive's we use are Emerson EP204-I... Our setup consist of a Horner PLC then 3 Emerson drives daisy chained together.
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Unread October 15th, 2019, 06:39 AM   #7
Gene Bond
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OK, I was referring to the SK, SP, Unidrive M series (General Purpose through High Performance Drives). The Epsilon series is Servo Only.

The CT-RTU protocol is still appropriate, though. I believe it was developed for the Epsilon series, but works well on the general purpose drives as well.

Also note that Control Techniques is no longer an Emerson Brand. Emerson sold CT to Nidec about 2 years ago...
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Unread October 15th, 2019, 06:45 AM   #8
johnnyboy1852000
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Gene Bond,

So if i do the conversion from Mod bus to CT RTU is there anything i have to adjust or is it a straight forward thing. I have never worked with CT RTU before so unsure.
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Unread October 15th, 2019, 07:37 AM   #9
Gene Bond
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Should be straight forward. The addresses are the same.

If you want to see a different picture of what addresses are what, you may want to play with a project in CTvue Configurator 3

Remember that the Modbus address can be +/- 1 digit... I don't recall which is what, but I seem to remember that CTvue is -1 from the menu address.
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