Exploring Temperature and Humidity Sensing with Arduino

• Arduino
• Lower Secondary (Key Stage 3)

Exploring Temperature and Humidity Sensing with Arduino

By Jonathan Acheson 

Learning Objective

At the end of the lesson you will understand how to use a DHT11 sensor with Arduino to measure temperature and humidity.

DHT11 Module Hardware Overview

Want to keep a log of the climate in your greenhouse, build a humidor control system, or track temperature and humidity data for a weather station project? AOSONG’s DHT11 Temperature and Humidity sensor module could be the perfect fit for you!

The DHT11 module is a sensor that can measure temperature and humidity. It consists of a sensor and supporting circuitry.

DHT11 Sensor

DHT11 can measure temperature from 0°C to 50°C with a ±2.0°C accuracy,  and humidity from 20 to 80% with a 5% accuracy.

Note that the DHT11 has a sampling rate of 1Hz, which 

means it can provide new data once every second.

Inside the DHT11 Sensor

If you remove the sensor’s casing, you will find an NTC thermistor and a humidity sensing component inside.

Inside the DHT11 Sensor

Inside the DHT11 Sensor

1. The humidity sensing component has two electrodes with a moisture-holding substrate (usually a salt or conductive plastic polymer) in between.
   
2. As the humidity rises, the substrate absorbs water vapor, resulting in the release of ions and a decrease in the resistance between the two electrodes.
3. This change in resistance is proportional to the humidity, which can be measured to estimate relative humidity.

Inside the DHT11 Sensor

DHt11 also includes a NTC thermistor for measuring temperature. A thermistor is a type of resistor whose resistance varies with temperature.

Module Pinout

The DHT11 module is relatively simple to connect. There are only three pins:

Module Pinout

+ (VCC) pin provides power to the sensor. Despite the fact that the supply voltage of the module ranges from 3.3V to 5.5V, a 5V supply is recommended. With a 5V power supply, the sensor can be placed up to 20 meters away. With 3.3V supply voltage, the sensor can be placed just 1 meter away; otherwise, the line voltage drop will cause measurement errors.

Out pin is used for communication between the sensor and the microcontroller.

– (GND) is the ground pin.

Wiring DHT11 Module to Arduino

Now it’s time to connect the DHT11 module to 

the Arduino! Connections are relatively simple. 

 

+ (VCC) pin to the Arduino’s 5V output and 

 – (GND) pin to ground. Finally, 

Out pin to digital pin #8.

Installing DHT library

To install the library, navigate to Sketch > Include Library > Manage Libraries… Wait for the Library Manager to download the libraries index and update the list of installed libraries.

CODING TIME

READ SHEET!

Displaying Readings on Serial Monitor

Once the DHT library is installed, you can display temperature and humidity readings from the DHT11 sensor on the Arduino Serial Monitor.

Code Explanation

READ SHEET!

Code Explanation

READ SHEET!

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