---
type: video
yt_id: VVU2YVRMdUlfajQtMHdpRFN6bWFQY3RRLnZhNUpCcDVMVkU0
videoId: va5JBp5LVE4
title: "Let's Build a Temperature Sensor with a Raspberry Pi Part 1"
date: "2018-07-05T15:25:39Z"
slug: "lets-build-a-temperature-sensor-with-a-raspberry-pi-part-1"
image: 
  name: "let's-build-a-temperature-sensor-with-a-raspberry-pi-part-1.jpg"
  alt: "Let's Build a Temperature Sensor with a Raspberry Pi Part 1"
  width: 1280
  height: 720
status: 'published'
description: "I made a temperature sensor using a raspberry pi, now I know the temperature of my apartment 🤗."
tags: ['ble', 'node js', 'raspberry pi', 'temperature sensor']
---


I had a temperature sensor in my box of things, and I wanted to know the temperature.

This is a two-part project. In this part, I connect a raspberry pi to a temperature & humidity sensor so that I can read the current temperature in my apartment.

[In part 2](/lets-build-a-temperature-sensor-with-a-raspberry-pi-part-2), I set up the pi to emit the temperature and humidity data using BLE. I also made an iPhone app that can read that data.

## Hardware

*   Raspberry Pi with built-in Bluetooth. I used a zero w.
*   [DHT22 temperature-humidity sensor](https://www.adafruit.com/product/385)

## How To Do This

Setup the Raspberry Pi with Raspbian and Node.js.

I setup my raspberry pi zero and installed node.js following the same process in that's in my [Raspberry Pi for Developers: Getting Started course](https://sammeechward.com/courses/raspberry-pi-for-developers-getting-started/)

Wire up the pi to the sensor.

The next step was to wire up the temperature sensor to the pi. I used the DHT22 temperature and humidity sensor, which is a super common sensor, so there's a diagram and instructions on [adafruit.](https://learn.adafruit.com/dht/connecting-to-a-dhtxx-sensor) Here's my setup:

*   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. (I origianlly chose 14, but my faulty soldering made that pin unreliable)

[Raspberry pi pins](https://www.raspberrypi.org/documentation/usage/gpio/)

Plug in the pi, and connect to it using ssh.

I used the following link to do this before I plugged in the pi: [Prepare SD card for Wifi on Headless Pi](https://raspberrypi.stackexchange.com/questions/10251/prepare-sd-card-for-wifi-on-headless-pi).

Here's the official documentation on how to connect to a pi using ssh: [https://www.raspberrypi.org/documentation/remote-access/ssh/](https://www.raspberrypi.org/documentation/remote-access/ssh/)

Install `[node-dht-sensor](https://www.npmjs.com/package/node-dht-sensor)`

There's a great library that makes it super easy to connect a raspberry pi to a DHT sensor. Before you can use the `node-dht-sensor` library, you have to install the bcm2835 c library that gives easy access to the gpio pins for libraries like `node-dht-sensor`. You can follow the instructions on npm, but here's the code I ran on the pi to install it:

```c
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
```

Code the app.

Now for the fun part. This app could have been written in 4 lines of javascript, so it's really not complex at all. I just `npm install node-dht-sensor` and wrote the following code.

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

const sensorNumber = 22;
const pinNumber = 4;
sensor.read(sensorNumber, pinNumber, (err, temperature, humidity) => {
  if (err) {
    console.log("AHHHHHHHH error", err);
    return;
  }

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

* The code I wrote in the video: [https://gist.github.com/meech-ward/d7974f565113719ab192e5f6bce3e271#file-app-js](https://gist.github.com/meech-ward/d7974f565113719ab192e5f6bce3e271#file-app-js)
* Open browser tabs at the end of the video: [https://gist.github.com/meech-ward/d7974f565113719ab192e5f6bce3e271#file-open-tabs-md](https://gist.github.com/meech-ward/d7974f565113719ab192e5f6bce3e271#file-open-tabs-md)
