Controllogix with Modbus

I have been given a task to get a machine back up and running again that has been sitting for a couple years now. It has two servo motors on it. We use them to drive one way clutches up to 7000-9000 rpm in our test lab. I have been told that the servos are on Modbus. I'm not familiar with Modbus so what all do I need in order to control and communicate to these two servos on Modbus if using Controllogix?

Thanks in advance.

You can learn all you want, and more, at modbus.org.

In my opinion, the best way to do Modbus serial protocol from a ControlLogix is to use the Prosoft MVI56-MCM module. It's more expensive than some other methods, but it's by far the most popular and dependable method.

Yeah, was just looking at that module online. $3000! It's still cheaper than a machine sitting not doing anything I guess.

Eddie Willers said:

You can learn all you want, and more, at modbus.org.

In my opinion, the best way to do Modbus serial protocol from a ControlLogix is to use the Prosoft MVI56-MCM module. It's more expensive than some other methods, but it's by far the most popular and dependable method.

Click to expand...

If you already have Ethernet/IP capability this may be an option:

http://www.rtaautomation.com/products/460/esmm.html

I've used these before, the most recent about 2 weeks ago. They work out pretty well if you only have a few words to communicate or if you can communicate in blocks. If you need to pass 400 parameters you are probably better off with the Prosoft product. But if you only need to pass 10 or 20 parameters you can get 4 of the RTA gateways for what you will pay for the Prosoft module. I don't think the RTA product will be any more difficult to set up than the Prosoft module.

Keith

http://gridconnect.com/industrial-protocols/ethernet-ip/net232-ethernet-ip-to-modbus.html
I used this one three months ago, it only permits to use just one serial modbus unit, it doesn't have gateway or scanner capabilities. They have a good chat support.
My link was between a compactlogix L32E and a power analyzer.

The other option is to use a plc (from a different vendor) that already has modbus (master) built in.
I know this is not likely but it does make for a simple solution

Do you have the manual on the servos....covering ModBus communications? You will need it, to know how to communicate with the servo to get the results you want..

You will it need to know how to change the "ID" of the 2 servos (since by default, they probably have the same ID).

Do you know if ModBus communication with the servos is begin used already (like modbus to display or existing controller)?


rta makes some good stuff and I have found their support top notch.
I recently used 3 of their Modus/RTU-ASCII to Ethernet/IP I gateways. I attempted to program it and tried it , it failed so I ran it again and collected a log file.
I sent my configuration (with the MB comm manual of the device) and and log file to them.
They would inspect the log file, and send me another cfg file to test.
We dialed it in within a couple of emails back and forth. They even took care of the "bit swap".

Another option, depending on how complicated your code is, would be to use a MicroLogix 1400 which has Ethernet and Modbus communications native. They are about $1000 and use RSLogix 500 software for easy programming. I had a ventilation system in my last job that had a bunch of power panel controllers that used Modbus. I was able to communicate with 17 controllers at 9600 baud with outstanding throughput. You WILL need the register map for the servos to know what to write/read when communicating with them.

That might be a better option. I don't think the code of this machine is going to be all that complicated. It was built by Wineman and it was not PLC controlled but rather controlled via their own proprietary hardware. I'm going to gut most of the controls out of it and put a PLC in it. I was going to go with Controllogix but if I can get by with Micrologix, then that would be just as good, especially if it has built in Modbus comms. Would there be anything else I would need to consider with Micrologix as far as interfacing and controlling the servos??

sfindley said:

Another option, depending on how complicated your code is, would be to use a MicroLogix 1400 which has Ethernet and Modbus communications native. They are about $1000 and use RSLogix 500 software for easy programming. I had a ventilation system in my last job that had a bunch of power panel controllers that used Modbus. I was able to communicate with 17 controllers at 9600 baud with outstanding throughput. You WILL need the register map for the servos to know what to write/read when communicating with them.

Click to expand...

That might be a better option. I don't think the code of this machine is going to be all that complicated. It was built by Wineman and it was not PLC controlled but rather controlled via their own proprietary hardware. I'm going to gut most of the controls out of it and put a PLC in it. I was going to go with Controllogix but if I can get by with Micrologix, then that would be just as good, especially if it has built in Modbus comms. Would there be anything else I would need to consider with Micrologix as far as interfacing and controlling the servos??

You will need a 1763-NC01 cable to connect your servos to the PLC. You also have to make sure you have the right settings. Check out this thread:

http://www.plctalk.net/qanda/showthread.php?t=76146

Hope this helps!