Logging MQTT Sensor Data

Data from sensors will need to be stored. But how much do you really need to store? Many sensors like state sensors (ON/OFF), temperature etc will fluctuate very little over the course of a day so does it makes sense to store the same sensor value every x seconds?

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Node-Red Setup and Admin Notes

Note: Working Notes Node red uses a settings file called settings.js located in /usr/lib/node-modules/node-red/ folder by default. You can create your own settings file and customise it either by copying the existing file or using the file available from Github here. To use your own settings file use the -s switch when starting node-red e.g. node-red -s mysettingsfile.js If you place a settings.js in the .node-red folder that will be used by default.

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Storing Data in Node-Red Variables

Node-red nodes pass the msg object between nodes. However this object is replaced by the next msg object. So how do you store data between node calls? Node-Red provides three mechanisms: The context object -stores data for a node The Flow object – stores data for a flow The global object -stores data for the canvas

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Using The Python MQTT-SN Client

There is a Python client included with the RSMB src files. You can download the RSMB ( Really small message broker here here. The client is written in python2.7 and consists of 4 files. The MQTTSN.py handles the packet packing and unpacking, and you don’t need to edit this.

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