8 posts in this topic

Hello everyone,

I'm a beginner in RS485 communications and i want to control 2 inverter LS iG5A via RS485 from a PLC Mitsubishi FX2N

I really don't understand how i should aproach and start this part of program in Ladder Diagram, to write and read parameters from Inverters.

 Please help me with an example 

 

Thanks.

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So you have the FX2N-485-BD card then? What software are you using to develop the code? Mitsubishi have function blocks for Modbus communication for the FX2N series since the cards do not support ModbusRTU by default.

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This is not a standard product, and may or may not follow the Mitsubishi standards. This leads to a pretty complex situation where it's very hard to help out.

How does this RS485 work? Which instructions do you use to activate it and send/receive data? You should really start by reading the manual, then do some programming, and then when you get stuck in GW2, just post a new topic. We cannot make the program for you, and it certainly makes things more difficult when you are using a product which is not standard...

These are the steps I would normally recommend for someone using a standard Mitsubishi product:

  1. Use "Labels" in the program (or structured Ladder), to enable the use of function blocks
  2. Download the FX Modbus library from Mitsubishi website
  3. Run the program

Here are some basic steps for your situation:

  1. Find the send/receive instructions in the manual for your specific product
  2. Build the ModbusRTU protocol in ladder code (see full spec on: http://www.modbus.org/)
  3. Run the program

It may be that the "built-in" RS485 port on your CPU uses Mitsubishi's RS instruction to send receive data. If that is the case, then you can probably use the function blocks from Mitsubishi's website, but I have no idea!

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Well,  i don't need the whole program between CX2N and iG5A. Can you make me just an example with one parameter, like  RUN Forward? I dont understand how to make this two devices work together.

So, mr. Kaare-t can you help me?

Here is the manual of CX2N: just 30 pages :)

http://www.coolmay.net/kindeditor/attached/file/20160728/20160728115808_0506.pdf

Edited by Liviu Mercutia

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I have no idea how the CX2N works with regards to the Modbus protocol. I briefly looked into the manual you linked, and on page 27 it says that D8120b14 selects Modbus or standard MC. This is not a standard Mitsubishi unit, and the spec for D8120 is not the same, so it's impossible for me to help you out.

However, it says that you can use the RS instruction when setting D8120b14=0, so maybe there's a chance you can use the standard Mitsubishi function block which utilizes RS instructions together with this unit. You should download the function block solution pack for serial Modbus from Mitsubishi's website and do some testing. Maybe it works...

Regarding one parameter, or many parameters, the principal is basically the same: If you have implemented one parameter/setting then all the others are easy, so just start with something simple like "RUN Forward".

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