Let's Build a Temperature Sensor with a Raspberry Pi Part 1

app.js

const sensor = require('node-dht-sensor');

sensor.read(22, 4, function(err, temperature, humidity) {
  if (err) {
    console.log("AHHHHHHHH error", err);
    return;
  }

  console.log('temp: ' + temperature.toFixed(1) + '°C, ' + 'humidity: ' + humidity.toFixed(1) +  '%');
});

instructions.md

Let's Build a Temperature Sensor with a Raspberry Pi Part 1

Setting Up The Projects

Parts:

• Raspberry pi with built in bluetooth.
• Adafruit DHT22 temperature-humidity sensor

Steps

• Install raspbian...
  • I used the April 2018 image.
• Wire up the pi to the sensor.
  • Use the diagram and instructions on this page https://learn.adafruit.com/dht/connecting-to-a-dhtxx-sensor.
  • Plug the left pin (red pin) into 5v.
  • Plug the right pin (black pin) into ground.
  • Plug the inner left pin (green pin) into a gpio pin, I chose 4.
  • Raspberry pi pins.
• Plug in the pi, connect it to your local network, and enable ssh.
  • I used the following link to do this before I plugged in the pi: Prepare SD card for Wifi on Headless Pi.
• Install node on the pi.
  • I used nvm Node Version Manager to do this.
• Make sure node is working on the pi.
  • npm install -g cowsay
  • cowsay hi
  • You might need to source ~/.bashrc before nvm works.
• Setup the node-dht-sensor
  • The instructions are on the link, here's what I did:
    • On the pi, run the following code:

        wget http://www.airspayce.com/mikem/bcm2835/bcm2835-1.56.tar.gz
        tar zxvf bcm2835-1.56.tar.gz
        cd bcm2835-1.56
        ./configure
        make
        sudo make check
        sudo make install
      

• Write the code.
  • Create a new node project, so just mkdir sensor or something.
  • Inside that directory, npm install node-dht-sensor, might take a while.
  • I've included my code in this gist, you can just copy and paste it.
  • Run the app, node app.js
  • 🤗

open-tabs.md

Open Browser Tabs

• Adafruit DHT22 temperature-humidity sensor
• Adafruit DHT11, DHT22 and AM2302 Sensors
• Adafruit thermistor
• Wikipedia thermistor
• DHTxx family Humidity Sensors
• Quora How do humidity sensors work?
• Wikipedia Capacitance
• Wikipedia Capacitor
• Wikipedia Resistor
• How Capacitors Work
• Khan Academy Capacitors and capacitance
• npm node-dht-sensor
• bcm2835
• Prepare SD card for Wifi on Headless Pi
• nvm Node Version Manager
• GPIO pins image
• Raspberry pi zero pins