With the weather getting a little chilly I wanted to monitor the temperature in my kids room.

    I had a Raspbery PI 2 Ver B lying around and I ordered some bits and bobs off trademe for a bit of messing about.

    • DHT11 Temperature sensor
    • OLED display
    • Breadboard and resistors

    Running RASPBIAN JESSIE WITH PIXEL OS

    • Version:April 2017
    • Release date:2017-04-10
    • Kernel version:4.4

    1 Installing updates

    Not 100% sure if updating is totally necessary, however we do need nodejs and npm installed

    sudo apt-get update
    sudo apt-get upgrade
    sudo apt-get install nodejs npm

    1.1 Alternate method is to upgrade Node to version 7 on Raspbian

    curl -sL https://deb.nodesource.com/setup_7.x | sudo -E bash -
    sudo apt-get update && sudo apt-get upgrade
    sudo apt-get install build-essential

    2 Patch v8.h to fix REPLACE_INVALID_UTF8 build issue

    Raspbian 2017-04-10 ships with node version 0.10.29. However in order to build the libraries in this project requires editing the /usr/include/nodejs/deps/v8/include/v8.h file. more info

    1. Open using command ‘sudo nano /usr/include/nodejs/deps/v8/include/v8.h’
    2. Search for WriteOptions
    enum WriteOptions {
        NO_OPTIONS = 0,
        HINT_MANY_WRITES_EXPECTED = 1,
        NO_NULL_TERMINATION = 2,
        PRESERVE_ASCII_NULL = 4,
    };
    1. Add the REPLACE_INVALID_UTF8 = 0 line (note the comma on previous line)
    enum WriteOptions {
        NO_OPTIONS = 0,
        HINT_MANY_WRITES_EXPECTED = 1,
        NO_NULL_TERMINATION = 2,
        PRESERVE_ASCII_NULL = 4,
        REPLACE_INVALID_UTF8 = 0
    };

    3 Blynk

    3.1 Install Blynk libraries

    sudo npm install -g onoff
    sudo npm install -g blynk-library

    3.2 Test Blynk

    export NODE_PATH=/usr/local/lib/node_modules
    blynk-client 715f8cafe95f4a91bae319d0376caa8c

    Project 1 (Easy): Make an LED turn off and on using Blynk

    Hardware requirements

    • LED
    • Resistor 330-500 ohm or there abouts
    • Breadboard
    • 2 x wire connectors Male to Female.

    Project 2: Temperature sensor

    Hardware requirements

    • DHT11 sensor
    • 10K resistor
    • 2 x wire connectors Male to Female.
    1. Follow instructions to wire up the DHT11 to PI
    2. Follow instructions to create Blynk project and install node DHT sensor library
    3. Create temp.js file with contents below set with your AUTH key. Note: The below script has an additional virtual port 2 to display a temp digital readout
        var blynkLib = require('blynk-library');
        var sensorLib = require('node-dht-sensor');
    

        var AUTH = 'YOUR KEY HERE';
    

        // Setup Blynk
        var blynk = new blynkLib.Blynk(AUTH);
    

        // Setup sensor, exit if failed
        var sensorType = 11; // 11 for DHT11, 22 for DHT22 and AM2302
        var sensorPin  = 4;  // The GPIO pin number for sensor signal
        if (!sensorLib.initialize(sensorType, sensorPin)) {
            console.warn('Failed to initialize sensor');
            process.exit(1);
        }
    

        // Automatically update sensor value every 2 seconds
        setInterval(function() {
            var readout = sensorLib.read();
            var temp = readout.temperature.toFixed(1);
            var humidity = readout.humidity.toFixed(1);
            blynk.virtualWrite(2, temp);
            blynk.virtualWrite(3, temp);
            blynk.virtualWrite(4, humidity);
    

            console.log('Temperature:', temp + 'C');
            console.log('Humidity:   ', humidity + '%');
        }, 5000);
    1. Next run the temp script
    sudo NODE_PATH=/usr/local/lib/node_modules node ./temp.js

    Project 3: OLED display

    1. Follow instructions
    2. TODO Display temp and humidity to OLED

    Reference

    Raspberry PI PIN diagram

    The original pin diagram image was lost during the blog migration. The official Raspberry Pi GPIO documentation has the current pinout reference.

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