Hello, automation fam,
It took quite a bit 😅 to come back and write to our blog, but here we are with another real application and case study.
As our logo states “simplified automation”, for us is not just a marketing slogan but instead is our belief, keep it simple, keep it smooth.
This is the case for this application where we were tasked to make talk a ControlLogix with a pH controller.
As a lot of you know, the most famous and used communication protocol is Modbus, and most of these specialty devices can communicate over Modbus.
But what we were thought to always do, in the case we had to pass information from/to Allen Bradley and other devices via Modbus TCP, was to purchase a piece of equipment such as Redlion or Anybus and use it as a protocol converter.
But a few years ago, Rockwell released this add-on instruction that allows implementing the Modbus protocol to the Ethernet/IP communication. While the first release was a little bit tricky, the latest has been dramatically improved, this resulted in the fastest solution deployment.
After watching one of the Tim Wilborne from TW controls videos, an opportunity just came to happen to use the AOI, and we did it successfully.
As always, you must deal with offsets, pulling rates, and end devices setup, but other than that, we were able to use both read and write commands and control the device (in our case a Walchem W600 pH controller) from the HMI.
Some setups need to happen, to be able to make this work:
- Make sure to place your Modbus add-ons on a subroutine that run at 20 ms periodically
2 – messages can overlap with each other, while we did not experience any loss of data, is always a good practice to set different pulling rates, play with the numbers until the “overlap” bit will go away.
3 – Put the tags you are using to communicate with the HMI on a lower scan routine, this is another good practice, since we are using fast scanning, we want just the Modbus communication to sit in there, while the tags and other manipulation (i.e., 2 words to float), will stay on a slower scanning task.
4 – If You can’t connect with your setup at the first attempt, it’s always good to have in your toolbox software such as Modbus poll and verify that the famous port 502 is enabled via telnet.
Something that we did not mention earlier is that the AOI has the server and the client version, in our scenario we used the client mode, but we do think it would make too much difference to integrate by using the server function.
In conclusion, we are pleased to have found this awesome solution, especially with so many issues we are experiencing with the supply chain, and how difficult is to find devices, this is a great and cost-effective solution to get the customer up and running in little time. Who isn’t for a simplified and quick solution?
As always, we are here to help, if you need any support on this or other related matters, contact us, or drop a comment below, we’d like to talk about this stuff all day long.
Until next time,
Have Fun!
P.S. Committed to making your life easier.