modbus rtu

Ranjith

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R
Join Date
May 2007
Location
Melbourne
Posts
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Is it possible to communicate to an ABB VSD from Micrologix 1200 using modbus rtu protocol. All I want to do is to start/stop a pump motor controlled by an ABB VSD. If i can get speed/status/current etc from the drive via modbus would be a bonus. What is the limitation of the modbus compared to DeviceNet?
Thanks for your valuable input.
 
I am sure it would help the members of the list to answer your question if you quoted the exact model of ABB VSD you are asking about.

Stu....
 
The MicroLogix 1200 (CH 0) does support Modbus RTU but only as a slave. I don't believe it can be configured as a Modbus RTU Master, which is what would be required to control a VFD or read status information from the VFD.

I would recommend controlling the drive using hardwired signals, and using a communications protocol (Modbus, DeviceNet, etc.) to retrieve any status information available; voltage, current, fault codes, etc.

I have had success controlling across the line starters and VFD's using DeviceNet. Both the MCC and the PLC (ControlLogix) were Allen Bradley, which made the integration a little easier than trying to integrate an Allen Bradely PLC with another brand VFD (ABB, Cutler Hammer, Square D) using DeviceNet.

Hope this helps,

blamb
 
The 1200 with 2 serial ports now has Modbus master capability on Channel 0. We have communicated with Powerflex 4 drives using the NET-AIC as a RS232 -> RS485 convertor.

Actually I see that all the 1200s have Modbus capability but if you changed the port on a single channel 1200 to Modbus you wouldn't be able to program it.
 
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The ACS550 has embedded Modbus capability. Talk to your local ABB rep about how to set it up as your application seems quite simple from the drive end.

I would take you thru it but it's not my strong suit, by any means. And, you need to do it with a person familiar with the Master end to complete the link.

Look at Group 51 in the parameters. That should get you started.
 
We haven't done it with the MicroLogix, but we've done drive control over Modbus RTU to ABB drives - worked great. On our newer systems we have standardized on a hardwired E-Stop and all other control and monitoring functions over Modbus.
 
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Thanks all for your valueable input. I have used DeviceNet/Profibus many times before. Reading through new AB catalog realised that micrologix have the Modbus Master/slave capability. So the hardware is already there for Modbus and do not need to pay for additional comms cards on both sides (PLC and drives). OK after reading all your comments I got the idea of how to get the Master and slaves to talk.
I am planning to use micrologix 1762BWAR which has 2 comm ports and it is cheaper than micrologix 1500. I want to connect a panelview to this system as well. I hope that I can get a panelview to work on Modbus to reserve Ch0 for programming purposes only. Please send me your thoughts.
Thanks
 
Thanks Bernie
When i need to connect my PC to the PLC then I need to disconnect the panelview. Is there a way to get around this? Now i am thinking about using micrologix 1100 with Panelview component touch 10". With this I can use ethernet to program both the PLC and the HMI.
 
Right, you would need to diconnect.

With the 1100 the serial port has RS485 directly implemented. Just get the AB breakout (1763-NC01 using the 1761-CBL-AM00 or the 1761-CBL-HM02 for the cable connection from the 1100 to the breakout).
 
My second post so bear with me.

I am attemtping, 1st time, to use an 1100 with a Panelview Component 600 color screen. Sales rep talked me into it. We are using ethernet and it is working so far. Small program. Monday we will be connecting the first of 3 AB drives via modbus. From what I have learned so far, it should work if I can get through the painstakingly slow process of getting the tags into it.
 

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