This project utilizes an Arduino Uno CH340G development board paired with a DHT11 temperature and humidity sensor to create a compact yet capable environmental monitoring system. It measures ambient temperature (°C) and relative humidity (%), and based on these, calculates a comprehensive set of derived atmospheric metrics including: Heat Index, Dew Point, Absolute Humidity, Specific Humidity, Mixing Ratio, Vapor Pressure, Saturation Vapor Pressure, Wet Bulb Temperature, Humidex, and Enthalpy.
The main.cpp sketch located in the /src directory of this repository consists of a C++ program that begins by importing the DHT.h library, as included in the platformio.ini config. After defining the sensor type and the corresponding data pin, the sketch initializes serial communication at a 9600 baud rate. A short delay follows to allow the DHT11 sensor to stabilize before data collection begins. Within the loop() function, the program attempts to read temperature and humidity values from the sensor. If either value is invalid (NaN), the system prints a row of "nan" values and waits one second before retrying.
When valid data is received, the program proceeds to calculate multiple atmospheric parameters based on the raw sensor input. Before transmitting the results to the serial monitor, the program calls a function that blinks the onboard LED three times, visually signaling that the data was successfully retrieved from the DHT11 module. The calculated values are then output in comma-separated format at two-second intervals, providing a continuous stream of real-time environmental data.
27.00,43.00,27.02,15.60,11.04,0.21102,0.27,15.29,35.57,18.54,29.94,1124.19
nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nanEach row represents a full sensor readout and computed atmospheric metrics, output every 2 seconds:
| Description | Temp (°C) | RH (%) | Heat Index (°C) | Dew Point (°C) | Abs. Humidity (g/m³) | Spec. Humidity | Mix. Ratio (g/kg) | Vapor Pressure (hPa) | Sat. Vap. Pressure (hPa) | Wet Bulb (°C) | Humidex (°C) | Enthalpy (kJ/kg) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Valid data | 27.00 | 43.00 | 27.02 | 15.60 | 11.04 | 0.21102 | 0.27 | 15.29 | 35.57 | 18.54 | 29.94 | 1124.19 |
| Sensor read failure / invalid | nan | nan | nan | nan | nan | nan | nan | nan | nan | nan | nan | nan |
| Formulas used | T | RH | heatIndex = dht.computeHeatIndex(T, RH, false) | dewPoint = T - ((100 - RH) / 5.0) | absHumidity = 216.7 × (RH/100 × 6.112 × e^(17.62×T / (243.12+T)) / (273.15+T)) | specificHumidity = 0.622 × (RH/100) / (1 + 0.622 × (RH/100)) | mixingRatio = 622 × (RH/100) / (1000 - RH/100) | vaporPressure = RH/100 × 6.112 × e^(17.62×T / (243.12+T)) | satVaporPressure = 6.112 × e^(17.62×T / (243.12+T)) | wetBulb = complex empirical formula (see source code for full expression) | humidex = T + 0.5555 × (vaporPressure - 10.0) | enthalpy = 1.006×T + (2501 + 1.86×T) × RH/100 |
This setup features an Arduino Uno CH340G clone connected to a DHT11 temperature and humidity sensor and a USB-to-Serial adapter (CP2102 module). The DHT11 sensor is connected to digital pin 2 for data, with power (VCC) and ground also wired to the Arduino. The USB-to-Serial adapter is connected with its TX and RX lines wired to the Arduino's RX and TX, respectively (crossed), and GND shared between both devices. The system is powered via USB, and the onboard LED confirms activity.
To process the data output from the Arduino Uno CH340G board into a visual format, the dht11_viewer.py script has been developed. This script functions as a real-time terminal interface that visualizes serial data from the board. It enhances readability using the colorama library for ANSI color formatting, and establishes communication via USB using the pyserial library.
To install the required libraries, use the following commands:
pip install colorama # For ANSI color formatting
pip install pyserial # For USB serial communicationUpon execution via the command python3 dht11_viewer.py, the script imports all necessary dependencies and initializes terminal color settings. It then scans and lists available serial ports, verifying that the user-specified port (e.g., /dev/tty.usbserial-1410) is available. If the target port is not detected, the script exits gracefully with a descriptive error message.
Once connected, the script enters its main loop, continuously reading lines of data from the serial port. Each line is decoded and parsed into 12 expected floating-point values, corresponding to: temperature, humidity, heat index, dew point, absolute humidity, specific humidity, mixing ratio, vapor pressure, saturation vapor pressure, wet bulb temperature, humidex, and enthalpy.
If a read or parse operation fails—due to invalid input or disconnection—the error is logged and displayed in red for clear visibility. Additionally, the script handles keyboard interrupts (Ctrl+C) to terminate the session safely and display a goodbye message along with the total uptime.
╔══════════════════════════════════════════════════════╗
║ Arduino Weather Station Live Feed ║
║ Latest update at 2025-05-12 00:34:37 ║
║ Uptime: 00:00:07
╔══════════════════════════════════════════════════════╗
║ Temp (°C): 25.70 (approx ±2.00)
║ Humidity (%): 48.00 (approx ±5.00)
║ Heat Index (°C): 25.58
║ Humidex: 28.93
║ Dew Point (°C): 15.30
║ Wet Bulb Temp (°C): 18.28
║ Enthalpy (kJ/kg): 1249.28
║
║ Abs Humidity (g/m³): 11.47
║ Specific Humidity: 0.22992
║ Mixing Ratio (g/kg): 0.30
║
║ Vapor Pressure (hPa): 15.81
║ Sat Vapor Press.: 32.94
╚══════════════════════════════════════════════════════╝
║
║ Log & Status:
║ [00:34:34] Waiting for data |
║ [00:34:35] Data received, parsing...
║ [00:34:35] Measurement received and displayed.
║ [00:34:36] Waiting for data /
║ [00:34:37] Waiting for data -
║ [00:34:37] Data received, parsing...
║
╔══════════════════════════════════════════════════════╗
║ Press Ctrl+C at any time to exit the program. ║
╚══════════════════════════════════════════════════════╝
Waiting for data \This method runs entirely on the Arduino Uno, requiring no external Python scripts. It outputs a real-time, human-readable weather dashboard directly to the Serial Monitor at 9600 baud. Every 10 seconds, the Arduino reads data from the DHT11 sensor connected to pin 2 and displays a live environmental summary, including temperature, humidity, system uptime, and over ten calculated metrics—all formatted as a structured table.
Additional features include a rolling log section that shows recent activity (sensor reads, calculations, and output status), a blinking onboard LED to indicate update cycles, and a clear on-screen message prompting users to wait 10 seconds for the next refresh. The entire interface is self-contained within the Arduino sketch, with no libraries or dependencies beyond the DHT11 sensor itself—just upload the code, connect the sensor, and open the Serial Monitor to begin.
+----------------------------------------------------+
| Arduino Weather Station Live Feed |
| Uptime: 00:00:37 |
+----------------------------------------------------+
Temp (C): 25.70 (approx +/-2.00)
Humidity (%): 48.00 (approx +/-5.00)
Heat Index (C): 25.58
Humidex: 28.93
Dew Point (C): 15.30
Wet Bulb Temp (C): 18.28
Enthalpy (kJ/kg): 1249.28
Abs Humidity (g/m3):11.47
Specific Humidity: 0.22992
Mixing Ratio (g/kg):0.30
Vapor Pressure (hPa):15.81
Sat Vapor Press.: 32.94
+----------------------------------------------------+
Log & Status:
[00:00:37] Measurement received from DHT11.
[00:00:37] Calculations for metrics done.
[00:00:37] Parsing data to serial output.
[00:00:37] Successful display to serial monitor.
=== WAIT FOR 10 SECONDS FOR SCREEN TO REFRESH ===
+----------------------------------------------------+
| HexKernel | GitHub Repository |
| github.com/HexKernel/Arduino-DHT11-Weather-Station |
+----------------------------------------------------+No additional software or libraries are needed on your computer—just use the Arduino Serial Monitor or any serial terminal.