Temperature Humidity Controller Using Arduino
This temperature humidity controller using Arduino is designed for electronics enthusiasts who want precise control in DIY projects. The temperature humidity controller using Arduino can automatically switch devices like fans, coolers, and humidifiers. With the temperature humidity controller using Arduino, you can maintain stable environmental conditions. This guide explains the working of the temperature humidity controller using Arduino step by step.
Learn how to build your own temperature humidity controller using Arduino for labs, greenhouses, and DIY electronics. The temperature humidity controller using Arduino offers reliability, simplicity, and low cost. Anyone interested in electronics can create this project. Explore the working and setup of the temperature humidity controller using Arduino in detail. Build your temperature humidity controller using Arduino with ease and improve your projects.
Introduction
Maintaining a stable environment is essential for several applications, such as greenhouses, laboratories, storage areas, and even small-scale automation projects. To achieve this, we can build a temperature humidity controller using Arduino.
This project reads real-time temperature and humidity values from a DHT11 sensor and automatically turns connected devices (like fans or humidifiers) on or off through relay modules. The design is simple, low-cost, and very effective for beginners as well as advanced electronics enthusiasts.
In this article, we’ll explore the components required, circuit diagram, step-by-step building guide, and practical uses of this project.
Materials for the Project
| Component | Quantity | Description | Buy Link |
|---|---|---|---|
| Arduino Nano | 1 | Main microcontroller board | Buy Here |
| DHT11 Sensor | 1 | Temperature & humidity sensor | Buy Here |
| 16×2 LCD with I2C Module | 1 | Display module | Buy Here |
| Relay Module (5V) | 2 | To control AC devices | Buy Here |
| BC547 Transistors | 2 | For relay driving | Buy Here |
| 1N4148 Diodes | 2 | Flyback diode protection | Buy Here |
| Resistors (1kΩ) | 2 | For transistor base | Buy Here |
| Push Buttons | 3 | For manual control/settings | Buy Here |
| Two-Pin Terminal Blocks | 2 | For relay output connections | Buy Here |
| Breadboard / PCB | 1 | For circuit assembly | Buy Here |
| Jumper Wires | As required | For circuit connections | Buy Here |
| 5V Power Supply | 1 | To power Arduino | Buy Here |
Useful Tools
| Tool | Quantity | Purpose / Notes | Click & Buy |
|---|---|---|---|
| Soldering Iron Kit | 1 | For making permanent connections | Click & Buy |
| Solder Wire (60/40, 0.8mm) | 1 | Electrical soldering | Click & Buy |
| Wire Stripper & Cutter | 1 | Stripping jumper wires | Click & Buy |
| Mini Screwdriver Set | 1 | For module and relay terminal screws | Click & Buy |
| Multimeter | 1 | Testing voltages and continuity | Click & Buy |
| Hot Glue Gun (optional) | 1 | Securing components in place | Click & Buy |
| Small Pliers | 1 | Holding and bending wires | Click & Buy |
| Heat Shrink Tubing Set | 1 | Insulating exposed wires | Click & Buy |
Circuit Diagram Explanation
The circuit of the temperature humidity controller using Arduino consists of several sections:
Arduino Nano (Main Control Unit):
Reads temperature and humidity data from the DHT11 sensor.
Sends display values to the 16×2 LCD via I2C.
Controls relays through BC547 transistors.
DHT11 Sensor:
VCC → 5V of Arduino
GND → GND of Arduino
Data pin → D2 of Arduino
Relay Control Section:
Each relay is driven by a BC547 transistor.
Arduino digital pins D3 and D4 send signals to control the transistors.
1kΩ resistors are used between Arduino pins and transistor bases.
1N4148 diodes are used across relay coils to protect from back EMF.
The relays’ output terminals are connected to appliances (fan, humidifier, heater).
Push Buttons:
Three push buttons are connected to D5, D6, and D7 with pull-down to GND.
They are used for setting parameters (like threshold temperature and humidity) or manual overrides.
16×2 LCD (with I2C):
VCC → 5V of Arduino
GND → GND
SDA → A4 of Arduino
SCL → A5 of Arduino
Displays real-time temperature, humidity, and system status.
This ensures that the Arduino reads sensor values, compares them with set thresholds, and switches relays accordingly.
Download Circuit Diagram
Step-by-Step Guide to Build the Project
Step 1: Connect the Arduino
Start by placing the Arduino Nano on a breadboard or project setup area.
Power it with a 5V regulated power supply.
Step 2: Connect the DHT11 Sensor
Connect 5V pin to the Arduino VCC pin.
Connect GND to Arduino ground.
Connect the output pin of the DHT11 to pin D2 of Arduino.
Step 3: Build Relay Driver Circuits
Take a BC547 transistor and connect its emitter to ground.
Connect a 1kΩ resistor between Arduino pin D3 and the transistor’s base.
Connect the relay coil between the collector of the transistor and Arduino 5V.
Place a 1N4148 diode across the relay coil (cathode to 5V, anode to collector).
Repeat the same for the second relay with Arduino pin D4.
Step 4: Add Terminal Blocks for Appliance Connections
Connect the relay common (COM) and normally open (NO) terminals to a two-pin terminal block.
This allows easy connection of external devices like fans, heaters, or humidifiers.
Step 5: Connect Push Buttons
Connect three push buttons for user interaction.
First button → D5, second → D6, third → D7 (other side to GND).
These can be used for setting thresholds or manual switching.
Step 6: Connect the LCD Module
Connect LCD VCC → Arduino 5V.
LCD GND → Arduino GND.
LCD SDA → Arduino A4.
LCD SCL → Arduino A5.
This will display the sensor readings and system status.
Step 7: Final Assembly
Recheck all connections carefully.
Connect the Arduino to your computer or external power.
Upload the required sketch (Arduino code).
Power ON and observe the LCD showing live temperature and humidity.
The relays will switch ON/OFF depending on the threshold values set.
Arduino Code
How It Works
The DHT11 sensor continuously measures the room temperature and humidity.
Arduino processes this data and compares it with predefined threshold values.
If the temperature exceeds the set value, the Arduino activates the relay connected to a fan or cooler.
If the humidity drops below the set value, another relay can activate a humidifier.
The LCD module provides live feedback, showing current readings and relay status.
The push buttons allow manual control or adjustment of thresholds (depending on the code).
Practical Applications
The temperature humidity controller using Arduino can be used in various fields:
Greenhouses Maintain the right climate for plants.
Industrial storage Protect sensitive equipment from humidity damage.
Laboratories Ensure stable temperature and humidity for experiments.
Home automation Automatically switch fans, humidifiers, or heaters.
Warehouses Preserve goods by preventing excessive moisture or dryness.
FAQs
1. What is the purpose of this project?
The project is designed to monitor and control temperature and humidity levels automatically using Arduino, DHT11 sensor, and relays.
2. Can I use another sensor instead of DHT11?
Yes, you can use DHT22 for higher accuracy or SHT31 for professional applications.
3. Is Arduino Nano necessary?
Not strictly. You can use Arduino Nano, Mega, or even ESP32 for Wi-Fi-enabled control.
4. How many devices can I control with this project?
This project is designed for two devices (fan and humidifier), but you can extend it with more relays.
5. Can I power the relays directly from Arduino?
Small relay modules can run on Arduino’s 5V, but for reliability, use an external regulated 5V supply.
6. Can I display data on my phone?
Yes, by using an ESP8266 or ESP32 instead of Arduino Nano, you can send data to mobile apps or cloud platforms.
7. Is this project safe for AC appliances?
Yes, but make sure you use relays rated for your AC load and insulate connections properly.
Conclusion
The temperature humidity controller using Arduino is a highly practical project for anyone looking to automate climate control in small environments. It combines sensors, relays, and Arduino programming to create a reliable system that can manage fans, coolers, or humidifiers based on real-time conditions.
This DIY project is affordable, easy to build, and can be extended with IoT for remote monitoring. Whether for home, labs, or industrial applications, this controller provides a solid foundation for automation enthusiasts.