Hi, I have a load cell which a receive the value using MQQT (from my python script), then I would like to save the first 5 value coming from MQTT to compute the offset of my load cell. Then when I will have my offset, I can substract it from my msg.payload to set the load cell to 0. I have tried t…

Couple of things. You could use a for loop rather than while which would be easier to follow and also quicker. Secondly, you are just adding the current msg payload 5 times and then output it. I don't think that is what you meant? If you want to accumulate the last 5 messages from an MQTT topic, y…

Also asked at the same time on Stack Overflow - https://stackoverflow.com/questions/59820595/adding-the-first-5-values-to-compute-offset

Ok thank you, I got it. I have tried to begin, here is what I have in my function node : I saved the value inside an array, but it keeps in memory all the value from my last trials, or I'd like to empty the array at each new run of the code. So I will get the new value for my offset. If I keep all…

Please read the other recent thread on array's. It has the information you need. For example, you haven't written the context variable back so it will never change.

Ok thank you, where can I read that ? I am starting with node-red, trying to learn...

[image] Message queue node that can be indexed General Problem: small screen. Can only display 1 message. Big size of messages to queue I want the node to store/queue messages. If it gets a next command, it shows the next message. If it gets a previous command, it s…

Thank you for this link and your help, I got what I wanted !

So, at the end of the day all you want is to average the first five incoming values and store the result in the context ? If this is the case you could alternatively try using the batch node along with the join node. The batch node would group each 5 messages, without overlap. The join node would …

The node node-red-contrib-calculate looks as if it may do exactly what you want (if that is to average a reading over five samples).

Thank you. Not completly but at least it makes the mean of a number of point, then I need to get only one result to have my offset, but it's useful. Thanks

Node-RED

Node-RED Forum

Adding the first 5 values to compute offset

General

TotallyInformation 20 January 2020 10:37 7

Topic		Replies	Views
Hello all , I want your help in adding two consecutive msg.payload array[] and then finding running average for latest value + stored value General	27	1587	23 April 2022
Extract the same mqtt topic value from 20 devices General	10	1708	11 January 2021
Building the average of the last 5 msg and send it? General function-node	3	843	12 April 2022
Making percentage calculations with two different msg.payload General	7	3272	18 May 2018
Sum up three outputs from mqtt General	21	2664	5 August 2019

Copyright OpenJS Foundation and Node-RED contributors. All rights reserved. The OpenJS Foundation has registered trademarks and uses trademarks. For a list of trademarks of the OpenJS Foundation, please see our Trademark Policy and Trademark List. Trademarks and logos not indicated on the list of OpenJS Foundation trademarks are trademarks™ or registered® trademarks of their respective holders. Use of them does not imply any affiliation with or endorsement by them.

Adding the first 5 values to compute offset

Related topics