Modbus issues

Billyboydtr

Member
Join Date
Jan 2020
Location
Helensvale
Posts
2
Hi Guys it as been a while me being on here, i had a issue this morning with a VSD drive which as failed, the issue is that they are on 6 months lead time, the plc talk to the drive with Modbus 485 rtu and the plc is locked up so i can not change the code, so my question is can you get a protocol converter to talk to another VSD, like the man in the middle

So if the PLC output reg 40001 bit 3 and the new drive is reg 40003 bit 4, is the a cover that can do this ?

Regards Dave
 
Hmm that's a tough one.

You might be able to use something like a Red Lion Data Station Plus. You can set up tag mapping from one destination to another.

I'm just not sure if they come with two RS485 ports, or one RS485 and one RS232.

That's a fairly expensive solution though, others might have a better idea
 
The datastation plus DSPSX/GT-A has 2 RS232 & one RS422/485 although one 232 port is for programming it can be used for communication as there is also a USB for programming.
 
If you're trying to translate between devices, my first thought is a Red Lion DSP, PTV, or HMI, but you'll run into the same trouble getting one of them as you're having with the drive. I see some of their stuff on e-bay, but you're taking a small chance that way.


I've set up G3 and Kadet HMIs as well as a DSP to transfer data between AB and Siemens PLCs and between an AB PLC and Eurotherm (or Watlow?) controllers via Modbus, so I know they will do it well. If you can get them.
 
ICC's Mirius gateway can be used to remap Modbus RTU registers. We've had several customers use this gateway to successfully emulate VSD's.

Configuration is performed using the ICC Configuration Studio software where you can add the mappings for both the master side and the slave side and set the register numbers to whatever you want. The gateway also supports database manipulation operations called Database Logic, so if there is any weird scaling or conversions that need to be done, it can be done in the gateway.
http://www.iccdesigns.com/protocol-gateways/66-mirius.html

If you have any additional questions or would like assistance configuring the Mirius for this application, feel free to submit a support ticket on our website.
 
I assume

  • the idea is to leave the existing Modbus Master messaging PLC alone,
  • there are a small number of bits being flipped,
  • there is a 1:1 correspondence between the bits on the failed VSD and those that need controlling or reading on the replacement VSD.

For a short term need this could be done with a python script, a github repo, an RPI or spare laptop, and a couple of RS-485-capable UART setups. The programming would take somewhere between a couple of hours and half a day. It would introduce a slight delay of course, but that might be acceptable.
 
Thanks Guys for your fast response, i Have a brand new Redlion DSPSX000 unit on my shelf which as been there for 4 years which i total forgotten about, looks like i will be firing up the crimson 3.1 software,

Thanks Dave
 

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