🔦 Level 2 – Sensors & IR Control

Project 2.6: "Basic Weather Station"

🚀 Project 2.6 – Basic Weather Station (DHT11 + LCD1602)

🎯 What You’ll Learn

✅ Goal 1: Read temperature and humidity with the DHT11 sensor.
✅ Goal 2: Display values on the LCD1602 screen.
✅ Goal 3: Trigger alerts when values pass thresholds.

Key Ideas

Short definition: Sensors measure the environment, displays show the data.
Real‑world link: Weather stations and smart homes use sensors + displays to monitor conditions.

🧱 Blocks Glossary (used in this project)

Digital input (DHT11): sensor = dht.DHT11(machine.Pin(X)) → Setup sensor.
Measure: sensor.measure() → Take a reading.
Temperature: sensor.temperature() → Get °C.
Humidity: sensor.humidity() → Get %.
LCD setup: lcd = LCD1602(rs, en, d4, d5, d6, d7) → Setup display pins.
LCD print: lcd.puts("text", row, col) → Show text on screen.
Serial print: print("...") → Show values on computer.
Loop: while True: → Repeat forever.
Delay: time.sleep() → Pause between readings.

🧰 What You Need

Part	How many?	Pin connection
D1 R32	1	USB cable
DHT11 sensor	1	Pin 4 (data)
LCD1602	1	RS=14, EN=12, D4=13, D5=5, D6=18, D7=19

🔌 Wiring tip: Connect DHT11 data to pin 4, VCC to 3.3V, GND to GND. LCD1602 uses 6 pins for parallel data.
📍 Pin map snapshot: Pin 4 (DHT11), Pins 14/12/13/5/18/19 (LCD).

✅ Before You Start

print("Ready!")  # Confirm serial is working

🎮 Microprojects (5 Mini Missions)

🎮 Microproject 2.6.1 – Read temperature and humidity

Goal: Show sensor values in serial monitor.
Blocks used: DHT11 setup, measure, print.

Block sequence:

Setup sensor on pin 4
Measure values
Print temperature and humidity
Repeat

MicroPython Code:

# Read temperature and humidity

import machine, time, dht                     # Import pin control, time, and DHT library

sensor = dht.DHT11(machine.Pin(4))            # Setup DHT11 sensor on pin 4

print("DHT11 ready")                          # Serial start message

while True:                                   # Infinite loop
    sensor.measure()                          # Take a measurement
    temp = sensor.temperature()               # Read temperature in °C
    hum = sensor.humidity()                   # Read humidity in %
    print("Temp:", temp, "C  Hum:", hum, "%") # Print values to serial
    time.sleep(2)                             # Delay 2 seconds between readings

Reflection: You can now see live temperature and humidity values.
Challenge: Print “Hot!” if temp > 30, “Cool” otherwise.

🎮 Microproject 2.6.2 – Show values on LCD

Goal: Display sensor values on LCD1602.
Blocks used: LCD setup, LCD print.

Block sequence:

Setup LCD pins
Measure sensor
Print values on LCD

MicroPython Code:

# Show values on LCD1602

import machine, time, dht, lcd1602            # Import pin control, time, DHT, and LCD library

sensor = dht.DHT11(machine.Pin(4))            # Setup DHT11 sensor
lcd = lcd1602.LCD1602(rs=14, en=12, d4=13, d5=5, d6=18, d7=19)  # Setup LCD pins

print("LCD ready")                            # Serial start message

while True:
    sensor.measure()                          # Take measurement
    temp = sensor.temperature()               # Temperature
    hum = sensor.humidity()                   # Humidity
    lcd.clear()                               # Clear LCD screen
    lcd.puts("Temp:"+str(temp)+"C", 0, 0)     # Print temperature on row 0
    lcd.puts("Hum:"+str(hum)+"%", 1, 0)       # Print humidity on row 1
    print("Displayed on LCD")                 # Serial confirmation
    time.sleep(2)                             # Delay

Reflection: The LCD shows both values clearly.
Challenge: Add degree symbol “°C” if library supports it.

🎮 Microproject 2.6.3 – Threshold alert

Goal: Show alert when temperature too high.
Blocks used: if/else, LCD print.

Block sequence:

Measure sensor
If temp > 30 → show “HOT!”
Else → show normal values

MicroPython Code:

# Threshold alert on LCD

import machine, time, dht, lcd1602

sensor = dht.DHT11(machine.Pin(4))            # Setup DHT11
lcd = lcd1602.LCD1602(rs=14, en=12, d4=13, d5=5, d6=18, d7=19)

print("Threshold alert ready")

while True:
    sensor.measure()                          # Measure
    temp = sensor.temperature()               # Temperature
    hum = sensor.humidity()                   # Humidity
    lcd.clear()                               # Clear LCD
    if temp > 30:                             # If too hot
        lcd.puts("HOT!", 0, 0)                # Show HOT message
        print("HOT!")                         # Serial alert
    else:                                     # Otherwise
        lcd.puts("Temp:"+str(temp)+"C", 0, 0) # Normal temp
        lcd.puts("Hum:"+str(hum)+"%", 1, 0)   # Normal humidity
    time.sleep(2)

Reflection: The LCD warns when temperature is high.
Challenge: Add buzzer beep when HOT.

🎮 Microproject 2.6.4 – Humidity alert

Goal: Show alert when humidity too low.
Blocks used: if/else, LCD print.

Block sequence:

Measure sensor
If hum < 40 → show “DRY!”
Else → show normal values

MicroPython Code:

# Humidity alert on LCD

import machine, time, dht, lcd1602

sensor = dht.DHT11(machine.Pin(4))
lcd = lcd1602.LCD1602(rs=14, en=12, d4=13, d5=5, d6=18, d7=19)

print("Humidity alert ready")

while True:
    sensor.measure()
    temp = sensor.temperature()
    hum = sensor.humidity()
    lcd.clear()
    if hum < 40:                              # If humidity too low
        lcd.puts("DRY!", 0, 0)                # Show DRY message
        print("DRY!")                         # Serial alert
    else:
        lcd.puts("Temp:"+str(temp)+"C", 0, 0)
        lcd.puts("Hum:"+str(hum)+"%", 1, 0)
    time.sleep(2)

Reflection: The LCD warns when humidity is low.
Challenge: Add LED ON when DRY.

🎮 Microproject 2.6.5 – Combined weather station (continuación y completo)

Goal: Show both values and alerts for temperature and humidity.
Blocks used: DHT11, LCD, if/else, serial print.

Block sequence:

Measure sensor values
Show values on LCD
If temp > 30 → HOT alert
If hum < 40 → DRY alert
Print alerts on serial

MicroPython Code:

# Combined weather station

import machine, time, dht, lcd1602            # Import pin control, time, DHT, and LCD library

sensor = dht.DHT11(machine.Pin(4))            # Setup DHT11 sensor on pin 4
lcd = lcd1602.LCD1602(rs=14, en=12, d4=13, d5=5, d6=18, d7=19)  # Setup LCD pins

print("Weather station ready")                # Serial start message

while True:                                   # Infinite loop
    sensor.measure()                          # Take measurement
    temp = sensor.temperature()               # Read temperature
    hum = sensor.humidity()                   # Read humidity
    lcd.clear()                               # Clear LCD before writing
    lcd.puts("Temp:"+str(temp)+"C", 0, 0)     # Show temperature on row 0
    lcd.puts("Hum:"+str(hum)+"%", 1, 0)       # Show humidity on row 1
    if temp > 30:                             # If temperature too high
        print("HOT ALERT")                    # Serial alert
        lcd.puts("HOT!", 0, 10)               # Show HOT on LCD at row 0, col 10
    if hum < 40:                              # If humidity too low
        print("DRY ALERT")                    # Serial alert
        lcd.puts("DRY!", 1, 10)               # Show DRY on LCD at row 1, col 10
    time.sleep(2)                             # Delay between readings

Reflection: The LCD shows values and alerts together, making a complete weather station.
Challenge:

Easy: Add buzzer beep when HOT or DRY.
Harder: Blink LED twice when both HOT and DRY happen at the same time.

✨ Main Project – Weather Station with Alerts

🔧 Blocks Steps (with glossary)

Digital input (DHT11): Measure temperature and humidity.
LCD output: Show values and alerts.
Serial print: Log values and alerts.
Logic (if/else): Decide when to show HOT or DRY.
Loop: Repeat continuously.

Block sequence:

Setup DHT11 sensor and LCD pins.
Measure temperature and humidity.
Display values on LCD.
If temp > 30 → HOT alert.
If hum < 40 → DRY alert.
Print alerts on serial.
Repeat loop.

🐍 MicroPython Code (line‑by‑line comments)

# Project 2.6 – Basic Weather Station (Main Project)

import machine, time, dht, lcd1602            # Import pin control, time, DHT library, and LCD library

sensor = dht.DHT11(machine.Pin(4))            # Setup DHT11 sensor on pin 4
lcd = lcd1602.LCD1602(rs=14, en=12, d4=13, d5=5, d6=18, d7=19)  # Setup LCD1602 with pins

print("Weather Station Main ready")           # Serial start message

while True:                                   # Infinite loop
    sensor.measure()                          # Take measurement from DHT11
    temp = sensor.temperature()               # Read temperature in °C
    hum = sensor.humidity()                   # Read humidity in %
    lcd.clear()                               # Clear LCD before writing
    lcd.puts("Temp:"+str(temp)+"C", 0, 0)     # Show temperature on row 0
    lcd.puts("Hum:"+str(hum)+"%", 1, 0)       # Show humidity on row 1
    if temp > 30:                             # If temperature too high
        print("HOT ALERT")                    # Serial alert
        lcd.puts("HOT!", 0, 10)               # Show HOT on LCD
    if hum < 40:                              # If humidity too low
        print("DRY ALERT")                    # Serial alert
        lcd.puts("DRY!", 1, 10)               # Show DRY on LCD
    time.sleep(2)                             # Delay between readings

📖 External Explanation

What it teaches: How to combine sensor input with a display and alerts.
Why it works: The DHT11 provides values, the LCD shows them, and logic decides when to alert.
Key concept: Sensors + outputs = interactive weather station.

✨ Story Time

Your robot is now a tiny meteorologist 🌦️. It measures the air, shows the data on its screen, and warns you when it’s too hot or too dry.

🕵️ Debugging (2 Common Problems)

🐞 Debugging 2.6.A – LCD shows random characters

Problem: LCD prints garbage instead of numbers.
Clues: Wrong wiring or missing lcd.clear().
Broken code:

lcd.puts("Temp:"+temp+"C", 0, 0)  # Missing str() conversion

Fixed code:

lcd.puts("Temp:"+str(temp)+"C", 0, 0)  # Convert number to string

Why it works: LCD requires text, not raw numbers.
Avoid next time: Always wrap numbers with str().

🐞 Debugging 2.6.B – Sensor always reads 0

Problem: DHT11 shows 0 for temp and humidity.
Clues: Forgot to call measure().
Broken code:

temp = sensor.temperature()   # No measure() before

Fixed code:

sensor.measure()              # Take measurement first
temp = sensor.temperature()   # Then read values

Why it works: DHT11 must be triggered before reading.
Avoid next time: Always call measure() before reading.

✅ Final Checklist

I saw temperature and humidity values on LCD.
HOT alert appeared when temp > 30.
DRY alert appeared when hum < 40.
Serial printed values and alerts.
My challenge changes worked (buzzer or LED).

📚 Extras

🧠 Student tip: Try covering the sensor with your hand to see humidity rise.
🧑‍🏫 Instructor tip: Show how str() converts numbers to text for LCD.
📖 Glossary: DHT11, LCD1602, humidity, threshold, alert.
💡 Mini tips:
- Always call sensor.measure() before reading.
- Use lcd.clear() to avoid overlapping text.
- Keep delays around 2 seconds for stable readings.