Unable to get gauge readings via Modbus Read / Response

Dashboard
1

Hi all,

I am currently working on a project where I have connected a Brainbox ED-008 to receive pulses from an engine with regards to RPM counting.
Using a Modbus Read, Modbus Response and a Gauge node here.

The engine sends out a pulse two times for every revolution, and is from there converted from a Hz signal to a 24V signal.
My issue is that even thou the Modbus Response node receives counts, it only shows up a total amount of counts received, and not displaying current values as counts per minute:
image
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Does anyone know how I can change it from displaying as total counts over to counts / minute?

Best regards,
Alexander

2

You will need to filter a specific value that you want to use, currently you inject an object.
What does the output of a debug node show ?

3

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The debug node receives a msg payload with constantly increasing values due to registering the ticks. So it is able to receive the information, I'm just uncertain on how I am supposed to specify which values I want to get up on the gauge display.

The engine on which I am working on is counting two pulses per revolution, so I also have to scale it down by 2 to get the actual reading. Say for instance that the engine has a max capacity of 4500 RPM, I would receive 9000 pulses. Also stuck on how to get the true readings instead of the pulses received.

4

You payload is array where value (2 pulses per revolution) is at first position.
Feed this payload to change node to grab the value from array and divide it by 2
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Then feed it to the gauge node.

5

Tried adding a change node with a JSON expression as suggested, but receive this message in debug:
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Tried changing the payload to [1], then i receive this:
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6

I think you can even use

{{msg.payload[0]/2}}

in the value field of the gauge node

7

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Values undefined. Any suggestions for what nodes to use to be able to define the value of the input?

8

Sorry, my bad. I didn't read the first post carefully. You are working with modbus so these are buffers, not the numbers.
I think you'll need to start with get some knowledge from here : https://github.com/BiancoRoyal/node-red-contrib-modbus/wiki