Node-RED Temperature flows

Node-RED example flows related to temperature.

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Table of Contents

• Compare two temperatures

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Compare two temperatures

With this flow you can compare the current state of two temperature sensors.

You can download this flow here.

Scenario:

• Open a window open if, in the summer, the outside temperature is lower than the inside temperature.

Explanation of each node:

• [inject node] Every 30 minutes a trigger between 16.00 and 21.00. It’s also possible to use the ‘other temperature’ as trigger for this flow.
  • top flow [get node]* Get the current temperature in a room.
  • bottom flow [get node]* Get the current outside temperature.
  • bottom flow [trigger node] Add a delay of 1 second to force the correct order of input values for the next node.

  Send       nothing
  then       wait for
             1 seconds
  then send  the original message
  

• [join node] Merge the two temperatures together as one value like “26|18”. The second value is always the outside temperature.

    Mode                              Manual
    Combine each                      msg.payload
    to create                         a String
    joined using                      [a-z] |
    Send the message:
      After a number of message parts  2
  

• [function node] Calculate the difference between the two temperatures.

   var temps = msg.payload.split('|');
   var diff = Math.round(temps[0] - temps[1]);
   node.status({text:diff})
   msg.payload = diff;
   return msg;
  

• [switch node] Only continue if the difference is bigger than X degrees.

   Property  msg.payload
   > [0-9] X
  

• [template node] Define the text which will be sent to inform you.

    The temperature in room X is \{\{payload\}\} degrees higher than outside
  

• [debug node] This can be replaced with an output node of your choice. Like Telegram/Whatsapp/speaker/etc

* This get node is part of the additional nodes set, named node-red-contrib-zigbee2mqtt. You must install this first to used it. Via the menu > Manage Palette > Palette

Suggestions for related flows:

• This flow can also be used for controlling a fan in the bathroom, compare humidity in the bathroom with the humidity from somewhere else in the house. During the year the humidity has different values.

Additions to this flow:

• Use the ‘other temperature’ sensor as trigger for this flow;
• You can also check if the window is already open, before running this flow. This can be accomplished by adding a contact sensor on the window;
• If you use the temperature sensor as trigger then the inject node can be removed. And you need to add a filter to only send messages in a specific timeframe and limit the amount of messages.

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Table of Content ^

<< See also my other Node-RED pages

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