Arduino Weather Station with Multiple Sensors
Measure temperature, humidity, rainfall, air quality, atmospheric pressure, and sunlight — all displayed live on a 20×4 I2C LCD. Fully simulated in Wokwi, no hardware needed.
🌡 DHT22
🔵 BMP180
💨 MQ-135
🌧 Rain Sensor
☀️ LDR
🖥 20×4 I2C LCD
🚀 No hardware? Simulate this entire weather station in your browser for free
▶ Open in Wokwi SimulatorProject Overview
6Sensors Used
20×4I2C LCD Display
4LED Indicators
100msRefresh Rate
This advanced Arduino weather station integrates six environmental sensors into a single system. Each sensor feeds data to the Arduino Uno, which processes the readings and displays live values on all four rows of a 20×4 I2C LCD. LED indicators fire automatically when conditions cross alert thresholds.
🎓 Ideal For:
Engineering Mini Projects
STEM Exhibitions
Robotics Competitions
IoT Learning
Environmental Monitoring
Sensors & Components
🌡
DHT22
Temperature & Humidity
🔵
BMP180
Atmospheric Pressure
💨
MQ-135 (Gas Sensor)
Air Quality (AQI %)
🌧
Rain Sensor
Rain Detection YES/NO
☀️
LDR (Photoresistor)
Sunlight Intensity %
🖥
20×4 I2C LCD
Real-Time Display
Key Features
✓
Multi-sensor environmental monitoring✓
Real-time display on 20×4 I2C LCD✓
Air quality % with safety level classification✓
Atmospheric pressure in hPa✓
Rain detection (digital HIGH/LOW)✓
Sunlight intensity monitoring✓
LED-based automatic alert indicators✓
Serial monitor debugging output✓
Fully simulated in Wokwi (free)
📟 Hardware Pin Assignments (Arduino Uno)
D5 — DHT22 Data
D8 — Rain Sensor
A0 — LDR (light)
A1 — MQ-135 (air)
A2 — Pressure pot
A4/A5 — SDA/SCL (LCD)
D1–D4 — LED indicators
Wiring Connections
All sensors connect through a breadboard to the Arduino Uno. Follow each table carefully. Resistors (220Ω) are required for all four LEDs.
DHT22 Temperature & Humidity Sensor
| DHT22 Pin | Arduino Pin | Notes |
|---|---|---|
| VCC | 5V (breadboard+) | Power via breadboard |
| GND | GND (breadboard−) | Ground via breadboard |
| DATA | D5 | With 220Ω pull-up to VCC |
MQ-135 Air Quality Gas Sensor
| MQ-135 Pin | Arduino Pin | Notes |
|---|---|---|
| VCC | 5V | Breadboard power rail |
| GND | GND | Breadboard ground rail |
| AOUT | A1 | Analog concentration reading |
| DOUT | – | Not used in this sketch |
LDR Photoresistor Sensor (Light Intensity)
| LDR Pin | Arduino Pin | Notes |
|---|---|---|
| VCC | 5V | Power rail |
| GND | GND | Ground rail |
| AO | A0 | Analog light reading |
Rain Sensor (Slide Switch in Wokwi)
| Switch Pin | Arduino Pin | Notes |
|---|---|---|
| Pin 1 (VCC) | 5V rail | Power |
| Pin 2 (SIG) | D8 | Digital rain signal |
| Pin 3 (GND) | GND rail | Ground |
Pressure Potentiometer (Simulating BMP180)
| Pot Pin | Arduino Pin | Notes |
|---|---|---|
| VCC | 5V rail | Power |
| GND (signal) | A2 | Mapped 950–1050 hPa |
20×4 I2C LCD Display
| LCD Pin | Arduino Pin | Wire Color |
|---|---|---|
| VCC | 5V (breadboard) | Red |
| GND | GND.3 | Black |
| SDA | A4 | Gold |
| SCL | A5 | Blue |
LED Alert Indicators
Four LEDs (each with a 220Ω resistor) provide instant visual feedback when sensor readings cross alert thresholds. They connect via breadboard to Arduino digital pins 1–4.
Blue LED (D1)
Rain detected — activates when rain sensor reads HIGH
Red LED (D2)
Temperature alert — fires when temp > 35°C
Purple LED (D4)
Air quality warning — fires when air > 60%
Orange LED (D3)
Sunlight alert — fires when light intensity > 70%
Air Quality Classification
0–30%
Safe
31–60%
Moderate
61–100%
GET OUT!!
Step-by-Step Build Guide
1
Open Wokwi & Create a New Arduino Project
Go to wokwi.com, click New Project, and select Arduino Uno as your board template.
💡 Use the Wokwi button at the top of this page to open a pre-loaded simulation if available.
2
Paste the diagram.json
Click the
diagram.json tab and replace all content with the JSON from Step 6 below. This sets up all components — the Arduino, breadboard, all 6 sensors, 4 LEDs, resistors, and 20×4 LCD — with pre-wired connections.💡 You won't need to drag or connect anything manually. All wiring paths are encoded in the JSON.
3
Install Required Libraries
This project needs three libraries. In Wokwi, add them in the Libraries panel. In the Arduino IDE, use Sketch → Manage Libraries:
—
—
—
—
LiquidCrystal_I2C by Frank de Brabander—
DHT sensor library by Adafruit—
Wire (built-in, no install needed)
⚠️ If the LCD stays blank, try changing
0x27 to 0x3F in the code.4
Paste the Arduino Code
Open the
sketch.ino tab and replace all content with the full code from Step 7. Verify that pin numbers (D5, D8, A0, A1, A2, A4, A5, D1–D4) match what's defined in the diagram.json.5
Run the Simulation
Click the green ▶ Play button. The LCD will show the METEOSTAT splash screen for 2 seconds, then switch to live data. Four rows display: sunlight status, temperature, rain state, and air quality. Interact with the Wokwi sensor sliders to change readings in real time.
💡 Drag the slide potentiometer to simulate changing atmospheric pressure between 950–1050 hPa.
6
Monitor the Serial Output
Open the Serial Monitor (baud: 9600) at the bottom of Wokwi. All six readings are printed every 100ms — humidity, temperature, rain state, air quality level, pressure (hPa), and sunlight level with alert text.
7
Test the LED Alerts
In the Wokwi simulation, adjust the gas sensor slider above 60% to trigger the purple air LED. Increase the LDR slider above 70% for the orange sunlight LED. Toggle the slide switch to simulate rain (blue LED). Set the DHT22 temperature above 35°C for the red LED.
Wokwi diagram.json
Copy and paste this entire JSON into the diagram.json tab in Wokwi. It defines all components, positions, and every wiring connection.
📄 diagram.json
{
"version": 1,
"author": "MakeMindz",
"editor": "wokwi",
"parts": [
{ "type": "wokwi-breadboard", "id": "bb1",
"top": 93, "left": 434.8,
"attrs": { "color": "#eeefed" }
},
{ "type": "wokwi-arduino-uno", "id": "uno",
"top": -143.4, "left": 719.4, "attrs": {} },
{ "type": "wokwi-led", "id": "led1",
"top": 174.4, "left": 647.4, "rotate": 180,
"attrs": { "color": "blue" }
},
{ "type": "wokwi-led", "id": "led2",
"top": 174.4, "left": 781.8, "rotate": 180,
"attrs": { "color": "red" }
},
{ "type": "wokwi-led", "id": "led4",
"top": 174.4, "left": 906.6, "rotate": 180,
"attrs": { "color": "purple" }
},
{ "type": "wokwi-led", "id": "led5",
"top": 174.4, "left": 1021.8, "rotate": 180,
"attrs": { "color": "orange" }
},
{ "type": "wokwi-bmp180", "id": "bmp1",
"top": -68.265, "left": -184.791, "attrs": {} },
{ "type": "wokwi-lcd2004", "id": "lcd1",
"top": -166.4, "left": 1080.8,
"attrs": { "pins": "i2c" }
},
{ "type": "wokwi-gas-sensor", "id": "gas1",
"top": 219.4, "left": 493.7, "rotate": 270, "attrs": {} },
{ "type": "wokwi-dht22", "id": "dht1",
"top": -76.5, "left": 465, "attrs": {} },
{ "type": "wokwi-photoresistor-sensor", "id": "ldr1",
"top": 236.9, "left": 388.3, "rotate": 270, "attrs": {} },
{ "type": "wokwi-bmp180", "id": "bmp2",
"top": -58.665, "left": -175.191, "attrs": {} },
{ "type": "wokwi-resistor", "id": "r2",
"top": 167.45, "left": 977.8, "rotate": 180,
"attrs": { "value": "220" }
},
{ "type": "wokwi-resistor", "id": "r3",
"top": 43.2, "left": 383.45, "rotate": 90,
"attrs": { "value": "220" }
},
{ "type": "wokwi-resistor", "id": "r4",
"top": 167.15, "left": 739.2,
"attrs": { "value": "220" }
},
{ "type": "wokwi-resistor", "id": "r5",
"top": 167.15, "left": 864,
"attrs": { "value": "220" }
},
{ "type": "wokwi-resistor", "id": "r6",
"top": 167.15, "left": 604.8,
"attrs": { "value": "220" }
},
{ "type": "wokwi-bmp180", "id": "bmp3",
"top": 18.135, "left": -98.391, "attrs": {} },
{ "type": "wokwi-slide-switch", "id": "sw1",
"top": -34, "left": 627.1, "attrs": {} },
{ "type": "wokwi-slide-potentiometer", "id": "pot1",
"top": 33.8, "left": 1122.2,
"attrs": { "travelLength": "30" }
},
{ "type": "wokwi-bmp180", "id": "bmp4",
"top": -237.493, "left": 384.925, "attrs": {} }
],
"connections": [
[ "bb1:55t.c", "uno:1", "violet", ["v-86.4","h48","v-220.8","h-67.2"] ],
[ "bb1:62t.d", "bb1:tn.50", "black", ["v0"] ],
[ "bb1:43t.c", "uno:2", "violet", ["v-86.4","h-172.8","v-220.8","h249.6"] ],
[ "bb1:50t.c", "bb1:tn.40", "black", ["v-48","h-9.6"] ],
[ "bb1:30t.c", "uno:3", "violet", ["v-76.8","h-57.6","v-240","h249.6"] ],
[ "bb1:37t.d", "bb1:tn.30", "black", ["v0"] ],
[ "bb1:16t.c", "uno:4", "violet", ["v-326.4","h326.4"] ],
[ "bb1:23t.d", "bb1:tn.18", "black", ["v0"] ],
[ "lcd1:GND", "uno:GND.3", "black", ["h-19.2","v192","h0","v9.6","h-134.4"] ],
[ "lcd1:VCC", "bb1:tp.38", "red", ["h-9.6","v211.3","h-19.2"] ],
[ "dht1:VCC", "bb1:tp.16", "red", ["v48","h172.8"] ],
[ "dht1:GND", "bb1:tn.17", "black", ["v28.8","h153.6"] ],
[ "bb1:1t.c", "bb1:tp.1", "red", ["v0"] ],
[ "bb1:2t.a", "bb1:tn.1", "black", ["v0"] ],
[ "bb1:4t.a", "uno:A0", "white", ["v-86.4","h441.6"] ],
[ "bb1:3t.a", "uno:6", "violet", ["v-9.6","h57.6","v-192","h374.4"] ],
[ "bb1:12t.a", "bb1:tn.9", "black", ["v0"] ],
[ "bb1:13t.a", "bb1:tp.10", "red", ["v-19.2","h9.6","v-19.2"] ],
[ "bb1:10t.a", "uno:A1", "white", ["v-124.8","h384"] ],
[ "sw1:1", "bb1:tp.15", "red", ["v0"] ],
[ "sw1:2", "uno:8", "violet", ["v9.6","h144.1","v-86.4","h105.6"] ],
[ "sw1:3", "bb1:tn.15", "black", ["v38.4","h-9.4","v76.8"] ],
[ "pot1:VCC", "bb1:tp.31", "red", ["h-28.8","v-76.8","h-268.8"] ],
[ "pot1:SIG", "bb1:tn.48", "black", ["h-67.2","v37.6","h-38.4"] ],
[ "pot1:GND", "uno:A2", "white", ["v0","h24.4","v-48","h-403.2"] ],
[ "dht1:SDA", "r3:1", "red", ["v9.6","h-57.5","v-38.4","h-19.2"] ],
[ "r3:2", "bb1:tp.16", "red", ["h67.2","v-1.2","h0"] ],
[ "dht1:SDA", "uno:5", "violet", ["v9.6","h316.9","v-86.4","h124.8"] ],
[ "uno:5V", "bb1:tp.28", "red", ["v19.1","h-92.2"] ],
[ "uno:GND.2", "bb1:tn.26", "black", ["v38.3","h-130.5","v28.8"] ],
[ "lcd1:SDA", "uno:A4", "gold", ["h0"] ],
[ "lcd1:SCL", "uno:A5", "blue", ["h0"] ],
[ "led1:A", "bb1:22t.e", "", ["$bb"] ],
[ "led1:C", "bb1:23t.e", "", ["$bb"] ],
[ "led2:A", "bb1:36t.e", "", ["$bb"] ],
[ "led2:C", "bb1:37t.e", "", ["$bb"] ],
[ "led5:A", "bb1:61t.e", "", ["$bb"] ],
[ "led5:C", "bb1:62t.e", "", ["$bb"] ],
[ "gas1:AOUT", "bb1:10t.e", "", ["$bb"] ],
[ "gas1:DOUT", "bb1:11t.e", "", ["$bb"] ],
[ "gas1:GND", "bb1:12t.e", "", ["$bb"] ],
[ "gas1:VCC", "bb1:13t.e", "", ["$bb"] ],
[ "ldr1:VCC", "bb1:1t.e", "", ["$bb"] ],
[ "ldr1:GND", "bb1:2t.e", "", ["$bb"] ],
[ "ldr1:DO", "bb1:3t.e", "", ["$bb"] ],
[ "ldr1:AO", "bb1:4t.e", "", ["$bb"] ],
[ "r2:1", "bb1:61t.d", "", ["$bb"] ],
[ "r2:2", "bb1:55t.d", "", ["$bb"] ],
[ "r4:1", "bb1:30t.d", "", ["$bb"] ],
[ "r4:2", "bb1:36t.d", "", ["$bb"] ],
[ "r5:1", "bb1:43t.d", "", ["$bb"] ],
[ "r5:2", "bb1:49t.d", "", ["$bb"] ],
[ "r6:1", "bb1:16t.d", "", ["$bb"] ],
[ "r6:2", "bb1:22t.d", "", ["$bb"] ],
[ "led4:A", "bb1:49t.e", "", ["$bb"] ],
[ "led4:C", "bb1:50t.e", "", ["$bb"] ]
],
"dependencies": {}
}
Arduino Code (sketch.ino)
Paste this into the sketch.ino tab in Wokwi, or upload to your physical Arduino Uno.
⚙️ sketch.ino (Arduino / C++)
#include <Wire.h> #include <LiquidCrystal_I2C.h> #include <DHT.h> // LCD: I2C address 0x27, 16 cols, 4 rows (20x4 mode) LiquidCrystal_I2C lcd(0x27, 16, 4); // Pin definitions #define DHTPIN 5 // DHT22 data pin #define RAINPIN 8 // Rain sensor (slide switch) #define BARPIN A2 // Pressure potentiometer #define AIRPIN A1 // MQ-135 air quality sensor #define LDRPIN A0 // LDR light sensor #define DHTTYPE DHT22 DHT dht(DHTPIN, DHTTYPE); // LED alert pins #define LedRain 1 // Blue – rain detected #define LedSun 2 // Orange – high sunlight #define LedTemp 3 // Red – high temperature #define LedAir 4 // Purple – poor air quality // Global variables int temperature; int humidity; float lightPercent; float airPercent; float rain; float pressure; int rainState; int barValue; int airValue; void setup() { Serial.begin(9600); lcd.init(); lcd.backlight(); // Splash screen lcd.setCursor(4, 0); lcd.print("METEOSTAT"); lcd.setCursor(2, 1); lcd.print("STEM UMSSN 2026"); lcd.setCursor(4, 2); lcd.print("Team Xenodi"); delay(2000); // Pin modes pinMode(LedRain, OUTPUT); pinMode(LedSun, OUTPUT); pinMode(LedTemp, OUTPUT); pinMode(LedAir, OUTPUT); pinMode(LDRPIN, INPUT); pinMode(AIRPIN, INPUT); pinMode(RAINPIN, INPUT); pinMode(BARPIN, INPUT); dht.begin(); } void loop() { // --- Read all sensors --- int rainState = digitalRead(RAINPIN); int barRaw = analogRead(BARPIN); int pressure = map(barRaw, 0, 1023, 950, 1050); int airRaw = analogRead(AIRPIN); int airPercent = map(airRaw, 0, 1023, 0, 100); int lightRaw = analogRead(LDRPIN); int lightPercent = map(lightRaw, 0, 1023, 0, 100); float temperature = dht.readTemperature(); float humidity = dht.readHumidity(); // --- Serial monitor output --- Serial.print("Humidity: "); Serial.print((int)humidity); Serial.println("%"); Serial.print("Temp: "); Serial.print((int)temperature); Serial.println("C"); Serial.print("Rain: "); if (rainState == HIGH) { Serial.println("YES"); } else { Serial.println("NO"); } Serial.print("Air Quality: "); Serial.print((int)airPercent); Serial.print("%"); if (airPercent < 30) { Serial.println(" Safe"); } else if (airPercent < 60 && airPercent > 31) { Serial.println(" Moderate"); } else if (airPercent < 100 && airPercent > 61) { Serial.println(" GET OUT!!"); } Serial.print("Pressure: "); Serial.print(pressure); Serial.println("hPa"); Serial.print("Sun: "); Serial.print((int)lightPercent); Serial.print("%"); if (lightPercent < 30) { Serial.println(" SAFE"); } else if (lightPercent < 60 && lightPercent > 31) { Serial.println(" MEDIUM"); } else if (lightPercent < 100 && lightPercent > 61) { Serial.println(" TAKE COVER!!"); } delay(100); // --- LCD display --- lcd.clear(); // Row 0: Sunlight lcd.setCursor(0, 0); lcd.print("Sun: "); lcd.print((int)lightPercent); lcd.print("%"); if (lightPercent < 30) { lcd.print(" SAFE"); } else if (lightPercent < 60 && lightPercent > 31) { lcd.print(" MEDIUM"); } else if (lightPercent < 100 && lightPercent > 61) { lcd.print(" TAKE COVER!!"); } // Row 1: Temperature lcd.setCursor(0, 1); lcd.print("Temp: "); lcd.print((int)temperature); lcd.print("C"); // Row 2: Rain status lcd.setCursor(0, 2); if (rainState == HIGH) { lcd.print("Rain: YES"); } else { lcd.print("Rain: NO"); } // Row 3: Air quality lcd.setCursor(0, 3); lcd.print("Air: "); lcd.print((int)airPercent); lcd.print("%"); if (airPercent < 30) { lcd.print(" Safe"); } else if (airPercent < 60 && airPercent > 31) { lcd.print(" Moderate"); } else if (airPercent < 100 && airPercent > 61) { lcd.print(" GET OUT!!"); } delay(100); // --- LED alert logic --- if (RAINPIN == HIGH) { // Blue: rain digitalWrite(LedRain, HIGH); } else { digitalWrite(LedRain, LOW); } if (airPercent > 60) { // Purple: air quality digitalWrite(LedAir, HIGH); } else { digitalWrite(LedAir, LOW); } if (temperature > 35) { // Red: high temp digitalWrite(LedTemp, HIGH); } else { digitalWrite(LedTemp, LOW); } if (lightPercent > 70) { // Orange: bright sun digitalWrite(LedSun, HIGH); } else { digitalWrite(LedSun, LOW); } }
📌 Key Code Notes
map(raw, 0, 1023, 950, 1050)— converts potentiometer to hPa pressure rangemap(raw, 0, 1023, 0, 100)— converts analog reads to 0–100% for air and light0x27— default I2C LCD address; try0x3Fif the screen stays blankdht.readTemperature()returns Celsius by default; passtruefor Fahrenheitdelay(100)— 100ms refresh rate; increase to reduce LCD flicker- The splash screen (METEOSTAT) displays for 2 seconds on power-on before live data starts
🧪 Simulate the Full Weather Station Free
No Arduino, no breadboard, no wiring. Paste the JSON and code from this tutorial and run the entire weather station live in Wokwi.
▶ Launch Wokwi Simulator
✓ Free to use
✓ Adjustable sensor sliders
✓ Real-time serial monitor
✓ No downloads needed
Comments
Post a Comment