How to Get a Remote I/O Point into Node_RED


#1

OK Node-RED gurus, here is what I’m trying to do: I have a PAC R2 which is talking to a EB2 over TCP/IP. Attached to the EB2 is an analog input module which reads a pressure transducer. I setup a strategy and added the EB2 and if I look at the points I see data. So far so good. That data point has a tag name.

Here’s the Node-RED part I don’t get. How do I read that data point? I setup up a PAC read node to read the the tag associated with that point but nothing happens. Is there some other node I need to go out and read that tag? From the description of the node I should be able to read any tag in the strategy just by connecting to it using the PAC Read node.

Thanks,

Dave


#2

In node-red the msg object is how you pass the values from one node to the next. Your pac read node gets the value, then the “blocks” or nodes after that are what process your values contained in the msg.

Are you using a debug block after your node-red read blog? (it’ll output the msg object / msg.payload to the debug panel on the right so you can see what value you’re pulling out.) If you are using that and you’re not seeing any output or error messages the next question would be if the flow is enabled and live.

Also something to check is I am pretty sure it is only the PAC that responds to the rest API calls, it sounds like the EB2 is set up as a module from the PAC, make sure you’ve set node-red to talk to the PAC not the EB2. (You should be able to access the tag since the EB2 is a module in the PAC.)


#4

That’s a yes to all of those. It has a debug node attached to it, I’m talking to the PAC not the EB2 and the strategy is running on the PAC.


#5

What are the symptoms again? (in terminal where node-red is started there is often a log, and in the flow you can see errors sometimes, also the debug panel, if you’re not getting messages in any of those places I would wonder if the flow is enabled and deployed.)


#6

Can confirm that this works as you think it should.

I have a PAC S and an EB as remote I/O on it.
I configured the PAC S in Node-RED and put the type as Analog Input and then put the name of the point on the EB.
Every time I click the Inject Node, it gets the (in this case) voltage.


#7

Then difference between yours and mine is the Inject node. If I want to grab that data on a regular basis is that what I should use?


#8

Your flows need to start with an input node (only one little circle on the right), not a processing node (a little circle on both sides). The Inject node as Beno shows is what you want. When you add it, read the instructions in the Info tab on how it works. You can set it up to trigger on a regular interval.


#9

That makes sense. In all our other flows we’re using a Modbus read node and you can set the read intervals. I didn’t see that on the PAC read node but I thought it might work anyway. Still getting used to NR.

Thanks for your help!

Dave


#10

Sorry about forgetting to mention that part, the flow was running but not operating because that inject node is the trigger. Good discussion.