Module: MMM-temp-ds18b20

Display DS18B20 sensor's temperature on your MagicMirror

Module installation

Dependencies

• An installation of MagicMirror²
• ds18x20
• And of course, have DS18B20 sensor(s) !

Useful commands

List DS18B20 sensors IDs:

find /sys/bus/w1/devices/ -name "28-*"

Get DS18B20 sensors temperatures:

find /sys/bus/w1/devices/ -name "28-*" -exec cat {}/w1_slave \; | grep "t=" | awk -F "t=" '{print $2/1000}'

Installation

Navigate into your MagicMirror's modules folder:

cd ~/MagicMirror/modules

Clone this repository:

git clone https://github.com/thlb/MMM-temp-ds18b20

Navigate to the new MMM-temp-ds18b20 folder and install the node dependencies.

npm install

Configure the module in your config.js file.

Using the module

To use this module, add it to the modules array in the config/config.js file:

modules: [
   {
       module: 'MMM-temp-ds18b20',
       position: 'top_right',
       header: 'Temperature sensors',
       config: {
            refreshInterval: 10, // in seconds
            displayMode: 'x-stack',
            sensors:[
                {
                    id: "28-800000xxxxxx",
                    label: "Inside"
                },
                {
                    id: "28-800000xxxxxx",
                    label: "Outside"
                }
            ]
        }
    },
]

Configuration options

The sensors property contains an array with multiple objects (one per sensor connected the Raspberry). These objects have the following properties:

The following properties can be configured:

DS18B20 Installation

Requirements

• Raspberry
• DS18B20 sensor(s)
• 4.7kΩ resistor (Yellow, Violet, Red, Gold)
• Breadboard (optionnal)
• Jumper wires (optionnal)

Foreword

The DS18B20 communicates with the controlling device via the “One-Wire” communication protocol, a proprietary serial communication protocol that uses only one wire to transmit the temperature reading to the microcontroller. There is differents models :

• DS18B20+ : Genuine
• DS18B20 : Pre-wired and waterproofed version

Technical specifications :

• -55°C to 125°C range
• 3.0V to 5.0V operating voltage
• 750 ms sampling
• 0.5°C (9 bit); 0.25°C (10 bit); 0.125°C (11 bit); 0.0625°C (12 bit) resolution
• 64 bit unique address
• One-Wire communication protocol

DS18B20 Layout

This sensor has three pins :

Hardware installation

1. Power off the Raspberry.
2. Follow this diagram :

Using multiples sensors

Plug multiples sensors on the Raspberry is very easy. With multiples sensors, we still only have three connections to the Raspberry (+3.3V, GND & Data). The single data wire will return the temperature readings from all th sensors. This is possible because each DS18B20 sensor has a unique serial number coded into it which the Raspberry Pi can be used to identify them by.

Raspberry configuration

Edit file /boot/config.txt and add the following line :

dtoverlay=w1-gpio

Load the drivers :

sudo modprobe w1-gpio
sudo modprobe w1-therm

Edit file /etc/modules and add the following lines to auto-load drivers on boot :

w1-therm
w1-gpio

Check that sensors are well recognized by the Raspberry :

find /sys/bus/w1/devices/ -name "28-*"

You should see as many lines as sensors plugged. Note that the part 28-xxxxxxxxxxxx is the ID of the sensor.

Now, if you want to check the temperatures value af all your sensors :

find /sys/bus/w1/devices/ -name "28-*" -exec cat {}/w1_slave \; | grep "t=" | awk -F "t=" '{print $2/1000}'

Finnaly, perform a sudo reboot of your Raspberry to check the proper load of the driver on boot. If the previous command still works, the drivers are correctly loaded.