Power monitoring unit and control logix

[aec]

Hi all,
I need to communicate with 28 Circutor PMU(Power monitoring unit )using a control logix 1756-L61.

Problem is that these PMU uses MODBUS protocol .

By going through the threads I saw PRO SOFT a product used to convert Ethernet to modbus but it needs 1756-ENET which is not available under communication modules in rockwell website for control logix .
How to proceed any suggestion or help please.

Thanks in advance

 

[Ken Roach]

There 1756-ENET is an old EtherNet/IP module for ControlLogix; the modern 1756-ENBT, 1756-EN2T, and 1756-EN3T can do everything the old one did, but faster.

There are quite a few EtherNet/IP to Modbus bridges on the market, as well as Modbus modules for the ControlLogix chassis.

Are you using RS-232 or RS-485 ? How much data do you need to read, and how fast ?

 

[aec]

Hi Ken ,

Thank you for your time and response

I have selected 1756-EN2T.

There are quite a few EtherNet/IP to Modbus bridges on the market, as well as Modbus modules for the ControlLogix chassis.

Can you point some links for me please .


Are you using RS-232 or RS-485 ?

This PMU CVM 96 has both RS 232 and RS 485 so which one would be better for long distance ???

How much data do you need to read, and how fast ?

Sorry this is my first communication set up for MODBUS how to determine the Data and speed .

I want to connect 28 PMU from which I will need to get the datas like

Ø Busbar voltage (V)
Ø Power Factor Bus 1 AND 2
Ø Current (A) on feeder
Ø Energy (kW) on feeder

Details about the PMU .

http://www.circutor.com/docs/Mn_cvm96ethernet_03.pdf


Thank you :site:

 

[aec]

hi could someone tell me how to determine the data .and speed ?????

 

[Pudden]

Hi Aec,

You will need to use RS485, as it supports multi-drop.(RS232 is peer to peer and max 15 meters)
The normal RS485 supports up to 31 slaves. However, I recommend you to have 10 slaves/RS485 network. So in your case, you would need 3 coneverters/modbus modules. If the data that you need to read is non-time critical, you can connect all 28 PMU to one RS485 network.
For more detailed info on RS485:
http://en.wikipedia.org/wiki/RS-485

Modbus will allow you to either read one register/command or several registers/command. In your case I would advise to read all in one and that should save some "line time".
I have attached a very basic spread sheet, for line time calculation for Modbus RTU.

//Patrick L

 

[Pudden]

If you go for an external EtherNet/IP to Modbus converter, here is one I can recommend:
http://www.anybus.com/support/support.asp?PID=110&ProductType=Anybus Communicator

//Patrick L

 

[BobB]

Second Anybus converters - they just work when set up correctly.