How to Build a Simple Yet Effective DIY Humidity Sensor with an Arduino


Building a humidity sensor can be a fun and educational DIY electronics project. With just a few components, including an Arduino microcontroller, you can create a device that measures the relative humidity in the surrounding environment.

In this guide, I will show you how I built a simple humidity sensor using an Arduino Uno, a DHT11 temperature and humidity sensor module, and a few other basic components. I'll explain how the circuit works, provide a parts list and wiring diagram, and walk through the process of uploading sensor code to the Arduino.

While this humidity sensor is basic, it is accurate enough for most home and hobbyist applications. The whole project can be built in an afternoon with novice to intermediate skills in Arduino and electronics. Let's get started!

Parts and Tools Needed

To build the Arduino humidity sensor, you will need:

You'll also need basic tools like wire strippers, pliers, etc. No soldering is required since this is built on a breadboard.

Circuit Diagram

Here is the circuit diagram showing how to connect the components:

How to Build a Simple Yet Effective DIY Humidity Sensor with an Arduino

The DHT11 sensor, 10K resistor, and LEDs connect to the Arduino as shown. Power and ground rails run along the sides of the breadboard.

Uploading the Code

To get the sensor data into the Arduino, you'll need to upload this example DHT11 sensor code from the Arduino IDE:


include "DHT.h"

define DHTPIN 2 // Digital pin connected to the DHT sensor

define DHTTYPE DHT11 // DHT 11


void setup() {
Serial.println(F("DHTxx test!"));


void loop() {

float h = dht.readHumidity();
float t = dht.readTemperature();

if (isnan(h) || isnan(t)) {
Serial.println(F("Failed to read from DHT sensor!"));

Serial.print(F("Humidity: "));
Serial.print(F("% Temperature: "));
Serial.println(F("°C "));

This initializes communication with the sensor, takes readings every 2 seconds, and prints the results to the Serial monitor.

Building the Circuit

With the code set up, it's time to build the circuit on the breadboard. Follow the wiring diagram closely to make all the correct connections.

Plug the Arduino into your computer via USB to upload the code. Attach the battery pack or wall adapter to provide power.

Once wired up, open the Serial monitor in the Arduino IDE. You should begin seeing temperature and humidity readings print out every 2 seconds once the code starts running!

Adding Indicator LEDs

To take this project a step further, you can add LEDs that visually indicate the humidity level.

Use a red LED to represent high humidity. Connect it through a 220 ohm current limiting resistor to Arduino pin 4.

Connect a green LED and resistor to pin 5 to indicate lower humidity levels.

Then modify the Arduino code to turn the LEDs on and off based on the humidity threshold you want. For example:

if (h > 70){ // Humidity over 70%
digitalWrite(4, HIGH); // Turn on red LED
digitalWrite(5, LOW);
} else {
digitalWrite(4, LOW);
digitalWrite(5, HIGH); // Turn on green LED

Upload this new code and your humidity sensor will now have visual indicators!

Applications and Future Improvements

While this Arduino humidity sensor is very simple, it can form the basis for many useful projects:

There are also ways to improve accuracy and reliability:

Overall, building your own humidity sensor with an Arduino is a super satisfying electronics project. With just a few common components, you can create a useful tool to monitor humidity in any environment. Let me know in the comments if you end up building one!