Best way to combine multiple Modbus RTU controllers into a single dashboard

General
1

I have several RPi's (spread out in a large building) each with an RS485 to USB adapter connected to a Modbus RTU temperature controller to read the actual temp and write the setpoint (as part of a program running in v2 dashboard). If the controllers were all located in a row, I would daisy chain the RS485 signal and assign them slave ID's accordingly, but they are physically separated from one another which makes that problematic.

The program I have created using v2 dashboard is great and is accessible via the URL:1880/dashboard/page1

So for example I have 3 RPi's installed (each with a dedicated RS485 to USB adapter)
192.168.8.20:1880/dashboard/page1 is for Oven #20
192.168.8.30:1880/dashboard/page1 is for Oven #30
192.168.8.40:1880/dashboard/page1 is for Oven #40

Instead I would prefer one single dashboard that has all 3 of the above. The only way I can think of doing this is via MQTT whereby the read and write operations are done at each RPi and then that data is sent via MQTT to the nodes running on a separate device that displays the dashboard panels for all 3 ovens.

Is there any other route worth pursuing? Or is MQTT the best way to handle this?

2

You could join the incoming data from the 3 ovens and check every subsequent message. You can then use the joined data to update a single dashboard page.
So I missed the fact that the ui pages are different IP's.
You could set a a http endpoint and serve up a web page, the 3 machines could use websockets to send there data to the page. example flow Simple Web page with live data updates via websocket (flow) - Node-RED

3

That is how I would do it, though you could run mosquitto and the combined dashboard on one of the oven Pis, rather than have another one.

4

Is there a reason you are using a PI at each oven ?? i.e. does it give you some form of local control there are well ? I would just use one of the RS485 RTU/TCPIP gateways that are readily available. I have 4 of them running here and have not had a single issue or failure with them.

Craig

5

We have an ARM64 machine wtih 5 RS485 ports and built-in nodered. So either you choose modbus or MQTT, the machine would be a choice.

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6

We installed a Pi at each oven because we had 120V power at each oven, but no Ethernet (hence each Pi is on wifi), and also did not want to run 2-wire RS485 from oven-to-oven based on some physical barriers in place.

Thanks for this suggestion. I had not thought of that, so looked around and found this, which seems like it would work. If I understand correctly, that will take each my my Modbus RTU devices and make then accessible anywhere via Modbus TCP, correct?

1 Like
7

Yep - although waveshare are the best known devices.

regards

Craig