Raspberry PI

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