Project Hub /IoT & Connected Devices/Environmental & Weather Monitoring/In-Depth: Interfacing HTU21D Temperature & Humidity Sensor with Arduino

Beginner

ARDUINO

₹500 – ₹1,500

3 – 6 Hours

Partial Kit

In-Depth: Interfacing HTU21D Temperature & Humidity Sensor with Arduino

Learn how to connect and use the HTU21D temperature and humidity sensor with an Arduino using the I2C interface.

Originally published on LastMinuteEngineers

View original tutorial

Parts You'll Need

This project is sourced from another site, not written by us — this list is our best match of their components against what we stock, not a verified bill of materials. Always check the original blog (linked above) for the actual parts list before buying.

DHT11 Temperature and Humidity Sensor Module for Arduino Raspberry Pi Rs. 243.00
Jumper Wire 10 Pin Male To Male 20cm Rs. 45.00
Cable for Arduino Nano (USB 2.0 A to USB 2.0 Mini B) 30cm Rs. 69.00
400 Points Mini Solderless Prototype PCB Breadboard High Quality Rs. 89.00
MB102 Adjustable Breadboard Power Supply Module (3.3V & 5V) for Arduino & Raspberry Pi Rs. 139.00
Jumper Wire 10 Pin Male To Female 20cm Rs. 45.00

Selected: Rs. 0.00

We don't carry yet: Arduino (unspecified board)
HTU21D Temperature

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How It Works

This project interfaces an HTU21D digital temperature and humidity sensor module with an Arduino Uno microcontroller to measure ambient environmental conditions. The HTU21D sensor communicates with the Arduino using the Inter-Integrated Circuit (I2C) protocol, which utilizes a two-wire interface consisting of a serial data line (SDA) and a serial clock line (SCL). Connected via jumper wires to the Arduino's designated I2C pins, the sensor receives power and exchanges digital packets with the microcontroller. Software libraries, specifically the Adafruit_HTU21DF library supported by the Adafruit BusIO library, handle the low-level communication protocols and translate raw binary register data from the sensor into readable temperature and relative humidity values. Powered and programmed via a USB cable connected to a computer running the Arduino IDE, the Arduino executes the compiled sketch to continuously poll the sensor over the I2C bus, processing the environmental metrics for display or interactive media applications.

Why Build This

Design automated greenhouse climate control systems by acquiring precise real-time environmental telemetry for coursework or applied laboratory setups.

Implement reliable indoor weather stations and humidor monitoring systems utilizing industry-standard I2C digital sensing hardware.

Gain practical engineering experience integrating specialized digital sensors with microcontroller firmware for interactive environmental monitoring platforms.

Real-World Application

Greenhouse climate control, humidor monitoring systems, indoor weather stations, and HVAC systems.

Skills You'll Learn

I2C communication protocol

digital sensor interfacing

library integration and dependency management

environmental data acquisition

microcontroller programming

Safety Precautions

Prevent liquids, dust, and other contaminants from coming into contact with the exposed polymer sensing film window unless using a filtered version with a PTFE hydrophobic filter.

Technology Tags

ARDUINO

HTU21D

I2C

TEMPERATURE SENSOR

HUMIDITY SENSOR

C++

EMBEDDED SYSTEMS

Frequently Asked Questions

Why are there extra libraries like Adafruit BusIO required for this project?

The Adafruit BusIO library handles underlying hardware communication layers required by the Adafruit_HTU21DF library to properly communicate with the sensor over the I2C bus.

Can I use any pins on the Arduino Uno for the I2C connection?

No, I2C communication requires specific dedicated pins on the Arduino Uno, typically labeled as A4 (SDA) and A5 (SCL), which support hardware-level two-wire communication.

What happens if the HTU21D sensor gets exposed to water or dust?

Direct contact with liquids or dust can contaminate the exposed polymer sensing film window, potentially ruining accuracy unless using a specialized filtered version with a PTFE hydrophobic filter.

Gallery

This page is part of Kitkraft's Project Hub — a curated collection of electronics & robotics projects gathered from the maker community to help students and hobbyists discover and learn to build. Kitkraft does not claim authorship of the original project, and makes no representation as to the accuracy, completeness or safety of third-party source material. The summary and "How It Works" explanation above are AI-generated, rewritten with reference to the original tutorial — not a reproduction of it. Full credit and a direct link to the original source are provided above. If you're the original creator and have a concern about how your work is represented here, please contact us and we'll address it promptly.

Kitkraft Project Hub — curated from the maker community, credited at the source.

PRJ-01419