DS18B20 Sensor Node-RED node for Raspberry Pi

Node-RED node for working with DS18B20 sensors, inspired in this library, but modified to behave slightly different with dynamically reading DS18B20 sensor id's at run-time in the UI.

It is compatible only with RaspberryPi hardware and it only reads the temperature values from sensors. The base library is a npm module, which handles with the whole 1-Wire protocol with DS18B20 sensors (aka it does the magic).

• NPM site: https://www.npmjs.com/package/node-red-contrib-sensor-ds18b20
• Historic downloads statistics: https://npm-stat.com/charts.html?package=node-red-contrib-sensor-ds18b20&from=2017-01-23&to=2022-01-23

Physical Connection of sensor(s)

The DS18B20 sensors must be connected on GPIO4 (or physical pin #7) because this is the only pin that supports native 1-Wire protocol. The scheme of connection is typically the one on the image below.

Requirements

On the Linux system where your Node-RED is running and where your sensors are connected to, make sure you have loaded all the kernel modules needed for working with 1-Wire devices, what the DS18B20 sensor is. Thus, you need to active or have activated the 1-Wire Interface on the Rpi. To do this just go to the Raspi-Configuration page with:

sudo raspi-config

Go to Interfaces and then to 1-Wire and enable it and reboot the device. You are done.

Installation

Run the following command in the root directory of your Node-RED install

npm install node-red-contrib-sensor-dynamic-ds18b20

Or just use the package manager(or manage pallette) from the Node-Red Interface to search for this module and install it manually.

Features

• Click the "Retrieve sensors" button
• This will hit the http://127.0.0.1:1880/sensors/1wire/ API provided by the underlying DS18B20 module
• Sensor id's will be loaded into the drop-down menu
• The sample flow writes the selected id to a global variable
• This global variable is written to the "msg.sensorid" property of the node-red-contrib-sensor-dynamic-ds18b20 module.
• This then reads the temp value from that sensor
• No more defining temp sensor id's in design mode, you can allocate them dynamically in the UI

Sample flow

''' [{"id":"531a9bf4.bad494","type":"tab","label":"Flow 1","disabled":false,"info":""},{"id":"53695c22.da6614","type":"http request","z":"531a9bf4.bad494","name":"get sensors","method":"GET","ret":"obj","paytoqs":"ignore","url":"http://127.0.0.1:1880/sensors/1wire/","tls":"","persist":false,"proxy":"","authType":"","x":400,"y":120,"wires":[["a4a8c70a.498658"]]},{"id":"a4a8c70a.498658","type":"function","z":"531a9bf4.bad494","name":"","func":"\nvar listArray = [];\n\nmsg.options = msg.payload;\nmsg.payload = global.get('temp_sensorid');\n\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":580,"y":120,"wires":[["c3f032f9.2146c"]]},{"id":"c3f032f9.2146c","type":"ui_dropdown","z":"531a9bf4.bad494","name":"temp sensor","label":"","tooltip":"","place":"Select option","group":"10788b43.59cf15","order":4,"width":0,"height":0,"passthru":false,"multiple":false,"options":[],"payload":"","topic":"","topicType":"str","x":760,"y":120,"wires":[["1cebd71d.7e4829"]]},{"id":"64b1d95c.229e58","type":"sensor-dynamic-ds18b20","z":"531a9bf4.bad494","name":"temp","topic":"","x":470,"y":220,"wires":[["ee57abfa.593ea8","cd85f616.a65b38"]]},{"id":"ee57abfa.593ea8","type":"ui_text","z":"531a9bf4.bad494","group":"10788b43.59cf15","order":3,"width":0,"height":0,"name":"","label":"Current temp","format":"{{msg.payload}}","layout":"row-spread","x":630,"y":220,"wires":[]},{"id":"cd85f616.a65b38","type":"debug","z":"531a9bf4.bad494","name":"DS18B20 output","active":true,"tosidebar":true,"console":true,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":650,"y":260,"wires":[]},{"id":"ba4fa5ac.454938","type":"function","z":"531a9bf4.bad494","name":"","func":"\nvar listArray = [];\n\nmsg.sensorid = global.get('temp_sensorid');\n\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":320,"y":220,"wires":[["64b1d95c.229e58"]]},{"id":"1cebd71d.7e4829","type":"change","z":"531a9bf4.bad494","name":"","rules":[{"t":"set","p":"temp_sensorid","pt":"global","to":"payload","tot":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":990,"y":120,"wires":[[]]},{"id":"a94a9ac2.f233f8","type":"ui_button","z":"531a9bf4.bad494","name":"Retrieve sensors","group":"10788b43.59cf15","order":1,"width":0,"height":0,"passthru":false,"label":"Retrieve sensors","tooltip":"","color":"","bgcolor":"","icon":"","payload":"","payloadType":"str","topic":"","topicType":"str","x":190,"y":120,"wires":[["53695c22.da6614"]]},{"id":"8b835913.b816e8","type":"inject","z":"531a9bf4.bad494","name":"","props":[],"repeat":"5","crontab":"","once":true,"onceDelay":0.1,"topic":"","x":160,"y":220,"wires":[["ba4fa5ac.454938"]]},{"id":"ca27b8f9.6b1628","type":"inject","z":"531a9bf4.bad494","name":"","props":[{"p":"payload"}],"repeat":"","crontab":"","once":true,"onceDelay":0.1,"topic":"","payload":"","payloadType":"str","x":480,"y":180,"wires":[["ee57abfa.593ea8"]]},{"id":"10788b43.59cf15","type":"ui_group","name":"Dashboard","tab":"970798f9.ff53c8","order":1,"disp":true,"width":"6","collapse":false},{"id":"970798f9.ff53c8","type":"ui_tab","name":"Home","icon":"dashboard","disabled":false,"hidden":false}] '''