Project 5.8: "Weather Station with App"

What you’ll learn

✅ Multi-sensor reading: Collect data from DHT11 (temp), soil moisture (analog), and raindrop (digital).
✅ App messages: Send clean “KEY:VALUE” strings the app can display.
✅ Smart alerts: Trigger app notifications when conditions cross thresholds.
✅ History logs: Keep a short memory of recent readings.
✅ Actuator control: Turn a fan or “pump” ON/OFF from the app.

Key ideas

Short definition: Sensors measure the world; we send simple messages so the app can understand and act.
Real-world link: Weather stations and smart gardens report conditions and trigger alerts automatically.

Blocks glossary (used in this project)

DHT11 temperature: Reads air temperature in Celsius.
Analog input (ADC): Reads soil moisture as a number (0–4095).
Digital input: Reads raindrop sensor (1 = wet trigger, 0 = dry).
Serial println: Sends clear text messages to the app.
Variables: Store thresholds, logs, and actuator states.
if / else: Create alerts and control actuators based on conditions.

What you need

Part	How many?	Pin connection
D1 R32	1	USB cable (30 cm)
DHT11	1	Signal → Pin 26, VCC, GND
Soil humidity sensor	1	Signal → Pin 32 (ADC), VCC, GND
Raindrop detection sensor	1	DO (digital out) → Pin 35 (input), VCC, GND
L9110 fan module (optional)	1	IN1 → Pin 23 (actuator control), VCC, GND

🔌 Wiring tip: Pins 34–39 are input-only; use Pin 35 for raindrop DO. Keep the soil sensor signal on Pin 32 (ADC). DHT11 goes to Pin 26.
📍 Pin map snapshot: Using 26 (DHT), 32 (soil ADC), 35 (raindrop DO), 23 (actuator). Other pins are free.

Before you start

USB cable is plugged in
Serial monitor is open
Test print shows:

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

Microprojects (5 mini missions)

Microproject 5.8.1 – Acquisition of data from multiple sensors

Goal: Read DHT11, soil moisture (raw + %), and raindrop (wet/dry).
Blocks used:

DHT11 temperature: Get “temp_c”.
Analog input (ADC): Read soil “raw”.
Digital input: Read raindrop “wet” (1/0).
Serial println: Print all values.

Block sequence:

Setup DHT11 on Pin 26.
Setup ADC on Pin 32.
Setup raindrop digital input on Pin 35.
Read and print all values.

MicroPython code:

import dhtx  # Import DHT11 sensor library
import machine  # Import machine to access ADC and Pin

sensor = dhtx.DHT11(26)  # Create DHT11 on Pin 26
print("Microproject 5.8.1: DHT11 ready on Pin 26")  # Status message

adc32 = machine.ADC(machine.Pin(32))  # Create ADC on Pin 32 for soil sensor
adc32.atten(machine.ADC.ATTN_11DB)  # Set ADC attenuation for full-scale reading
adc32.width(machine.ADC.WIDTH_12BIT)  # Use 12-bit resolution (0–4095)
print("ADC ready on Pin 32 (soil)")  # Status message

rain = machine.Pin(35, machine.Pin.IN)  # Create digital input for raindrop on Pin 35
print("Raindrop input ready on Pin 35")  # Status message

temp_c = sensor.temperature()  # Read temperature in Celsius
print("TEMP(C):", temp_c)  # App-friendly temperature output

raw = adc32.read()  # Read raw soil moisture value
print("SOIL_RAW:", raw)  # Show raw number for calibration

moisture_pct = int((4095 - raw) * 100 / 4095)  # Convert to percentage (higher=wet)
print("SOIL(%):", moisture_pct)  # Show mapped moisture percent

wet = rain.value()  # Read raindrop wet/dry (1=wet trigger, 0=dry)
print("RAIN:", wet)  # App-friendly raindrop state

Reflection: You now have three senses: temperature, soil moisture, and rain—great weather data!
Challenge:

Easy: Print humidity later using DHT11 if available in your library.
Harder: Average the soil reading from 3 samples.

Microproject 5.8.2 – Data transmission to app

Goal: Send clear “KEY:VALUE” strings for app display.
Blocks used:

Serial println: Output TEMP, SOIL, RAIN messages.

Block sequence:

Use the values from Microproject 5.8.1.
Print “TEMP:xx”, “SOIL:%xx”, “RAIN:0/1”.
Keep consistent formats.

MicroPython code:

temp_c = 25  # Simulated temperature value for demonstration
print("Microproject 5.8.2: Send to app")  # Status message

moisture_pct = 42  # Simulated soil moisture percent
print("TEMP:", temp_c)  # App-friendly temperature string

print("SOIL:", moisture_pct)  # App-friendly soil percent string

rain_state = 0  # Simulated raindrop state (0=dry, 1=wet)
print("RAIN:", rain_state)  # App-friendly raindrop state

Reflection: Short labels + numbers are easiest for apps to read and show.
Challenge:

Easy: Add “TIME:ms” using a system counter.
Harder: Add “PLACE:GARDEN_A” to tag your station.

Microproject 5.8.3 – App alerts based on conditions

Goal: Print alert strings when thresholds are crossed.
Blocks used:

if / else: Decide alerts.
Serial println: Output “ALERT:…” messages.

Block sequence:

Set thresholds: temp_high = 32°C, soil_low = 30%, rain_wet = 1.
If crossing → print alerts.
Else → print “STATUS:OK”.

MicroPython code:

temp_c = 33  # Example temp for testing alerts
moisture_pct = 25  # Example soil moisture percent
rain_state = 1  # Example rain state (1 = wet trigger)

print("Microproject 5.8.3: Checking alerts...")  # Status message

temp_high = 32  # Threshold for heat alert in Celsius
soil_low = 30  # Threshold for dry soil alert in percent
rain_wet = 1  # Value indicating rain detected

if temp_c >= temp_high:  # Check temperature condition
    print("ALERT:HEAT")  # Print heat alert
if moisture_pct < soil_low:  # Check soil moisture condition
    print("ALERT:DRY_SOIL")  # Print dry soil alert
if rain_state == rain_wet:  # Check rain condition
    print("ALERT:RAIN")  # Print rain alert

if (temp_c < temp_high) and (moisture_pct >= soil_low) and (rain_state != rain_wet):  # All OK
    print("STATUS:OK")  # Show normal status

Reflection: Alerts help the app react fast—set thresholds that make sense for your place.
Challenge:

Easy: Add “ALERT:COLD” if temp < 15°C.
Harder: Add “ALERT:FLOOD_RISK” if rain_state==1 and soil > 80%.

Microproject 5.8.4 – Historical data in app

Goal: Keep a short log of recent readings and print it.
Blocks used:

Variables (list): Store tuples of readings.
Serial println: Print last few entries.

Block sequence:

Create history = [].
Append (temp, soil%, rain).
Limit to last 5 entries.
Print “LOG:…”.

MicroPython code:

history = []  # Create an empty list for recent readings
print("Microproject 5.8.4: History log ready")  # Status message

def add_reading(temp_c, soil_pct, rain_state):  # Define function to add a reading tuple
    history.append((temp_c, soil_pct, rain_state))  # Append tuple to history
    if len(history) > 5:  # Keep only the last 5 entries
        history.pop(0)  # Remove the oldest entry
    print("LOG:ADDED", (temp_c, soil_pct, rain_state))  # Confirm addition

def print_history():  # Define function to print current history
    print("LOG:CURRENT")  # Header for log
    for item in history:  # Iterate through saved readings
        print("LOG:ITEM", item)  # Print each reading tuple

add_reading(25, 40, 0)  # Add example reading
add_reading(26, 38, 0)  # Add example reading
add_reading(28, 33, 1)  # Add example reading
print_history()  # Print the history entries

Reflection: Small logs make apps more useful—users like seeing trends, not just one number.
Challenge:

Easy: Increase history length to 10.
Harder: Print averages over the history before the list.

Microproject 5.8.5 – Control of actuators from an app

Goal: Turn the fan/pump ON/OFF using app words.
Blocks used:

Digital output: Control Pin 23.
Receive callback: Detect “PUMP:ON/OFF” or “FAN:ON/OFF”.
Serial println: Print the result.

Block sequence:

Setup pump pin on 23.
Define handle_method to read incoming command.
If ON → pin HIGH; if OFF → pin LOW.
Print “PUMP:ON/OFF”.

MicroPython code:

import machine  # Import machine to control the actuator pin

pump = machine.Pin(23, machine.Pin.OUT)  # Create actuator control pin on 23
print("Microproject 5.8.5: Actuator pin ready on 23")  # Status message

def handle_method(key1, key2, key3, keyx):  # Define callback for app control
    msg = str(key1)  # Convert main payload to text
    print("APP->R32:", msg)  # Show incoming message
    if msg == "PUMP:ON":  # Check for ON command
        pump.value(1)  # Turn actuator ON
        print("PUMP:ON")  # Confirm state
    elif msg == "PUMP:OFF":  # Check for OFF command
        pump.value(0)  # Turn actuator OFF
        print("PUMP:OFF")  # Confirm state
    elif msg == "FAN:ON":  # Alternative label
        pump.value(1)  # Turn ON
        print("FAN:ON")  # Confirm state
    elif msg == "FAN:OFF":  # Alternative label
        pump.value(0)  # Turn OFF
        print("FAN:OFF")  # Confirm state
    else:  # Not a known actuator command
        print("CMD:UNKNOWN")  # Explain unknown command

Reflection: Simple words can control real hardware—keep command names clear and safe.
Challenge:

Easy: Add “PUMP:TOGGLE”.
Harder: Add “PUMP:ON:3s” to run for a timed cycle.

Main project – Weather station with app

Blocks steps (with glossary)

DHT11 + soil + raindrop: Read all sensors and map soil to percent.
App messages: Print TEMP, SOIL, RAIN.
Alerts: Print ALERT strings when thresholds are crossed.
History: Keep last 5 readings and print them.
Actuator control: Respond to “PUMP/FAN” commands from the app.

Block sequence:

Setup sensors on 26, 32, 35 and actuator on 23.
Read and print values (TEMP, SOIL%, RAIN).
Check thresholds and print alerts.
Save to history and print it.
Listen for actuator commands and act.

MicroPython code (mirroring blocks)

# Project 5.8 – Weather Station with App

import dhtx  # Read DHT11 temperature sensor
import machine  # Control ADC and Pins
import time  # Provide timing for loops and delays

sensor = dhtx.DHT11(26)  # DHT11 on Pin 26
print("DHT11 ready on Pin 26")  # Confirm sensor setup

adc32 = machine.ADC(machine.Pin(32))  # Soil sensor ADC on Pin 32
adc32.atten(machine.ADC.ATTN_11DB)  # Configure attenuation for full scale
adc32.width(machine.ADC.WIDTH_12BIT)  # Use 12-bit resolution (0–4095)
print("ADC ready on Pin 32 (soil)")  # Confirm ADC setup

rain = machine.Pin(35, machine.Pin.IN)  # Raindrop DO input on Pin 35
print("Raindrop input ready on Pin 35")  # Confirm raindrop input

pump = machine.Pin(23, machine.Pin.OUT)  # Actuator (fan/pump) control on Pin 23
pump.value(0)  # Ensure actuator starts OFF
print("Actuator ready on Pin 23 (OFF)")  # Confirm actuator setup

temp_high = 32  # Temperature alert threshold (Celsius)
soil_low = 30  # Soil dryness threshold (percent)
print("Thresholds -> TEMP_HIGH:", temp_high, "SOIL_LOW:", soil_low)  # Show thresholds

history = []  # Short list of recent readings
print("History log initialized")  # Confirm history setup

def add_reading(temp_c, soil_pct, rain_state):  # Helper to add a reading
    history.append((temp_c, soil_pct, rain_state))  # Append the reading tuple
    if len(history) > 5:  # Keep last 5
        history.pop(0)  # Remove oldest entry
    print("LOG:ADDED", (temp_c, soil_pct, rain_state))  # Confirm addition

def print_history():  # Helper to print history
    print("LOG:CURRENT")  # Header
    for item in history:  # Iterate entries
        print("LOG:ITEM", item)  # Print each item

def handle_method(key1, key2, key3, keyx):  # Callback to control actuator via app
    msg = str(key1)  # Convert payload to text
    print("APP->R32:", msg)  # Show incoming app message
    if msg == "PUMP:ON":  # Turn actuator ON
        pump.value(1)  # Set pin HIGH
        print("PUMP:ON")  # Confirm
    elif msg == "PUMP:OFF":  # Turn actuator OFF
        pump.value(0)  # Set pin LOW
        print("PUMP:OFF")  # Confirm
    elif msg == "FAN:ON":  # Alternative label
        pump.value(1)  # Set pin HIGH
        print("FAN:ON")  # Confirm
    elif msg == "FAN:OFF":  # Alternative label
        pump.value(0)  # Set pin LOW
        print("FAN:OFF")  # Confirm
    else:  # Unknown command
        print("CMD:UNKNOWN")  # Explain

while True:  # Main loop to read sensors and report to the app
    temp_c = sensor.temperature()  # Read temperature from DHT11
    print("TEMP:", temp_c)  # App-friendly temperature output

    raw = adc32.read()  # Read soil raw value
    print("SOIL_RAW:", raw)  # Print raw for calibration

    soil_pct = int((4095 - raw) * 100 / 4095)  # Convert raw to percent (higher=wet)
    print("SOIL:", soil_pct)  # App-friendly soil percent

    rain_state = rain.value()  # Read raindrop (1=wet trigger)
    print("RAIN:", rain_state)  # App-friendly rain state

    if temp_c >= temp_high:  # Check heat alert
        print("ALERT:HEAT")  # Print heat alert
    if soil_pct < soil_low:  # Check dry soil alert
        print("ALERT:DRY_SOIL")  # Print dry soil alert
    if rain_state == 1:  # Check rain alert
        print("ALERT:RAIN")  # Print rain alert
    if (temp_c < temp_high) and (soil_pct >= soil_low) and (rain_state != 1):  # All OK
        print("STATUS:OK")  # Normal status message

    add_reading(temp_c, soil_pct, rain_state)  # Save to history
    print_history()  # Print the last few readings

    time.sleep(2)  # Wait 2 seconds before next reading for readability

External explanation

What it teaches: You built a small weather station that reads sensors, reports to an app, triggers alerts, logs history, and controls a simple actuator.
Why it works: The D1 R32 reads digital and analog signals; mapping the soil value to percent makes it human-friendly; short “KEY:VALUE” prints let apps parse and display data easily; condition checks trigger alerts; a list keeps your last readings.
Key concept: “Sense → report → alert → remember → act.”

Story time

You’ve turned your robot into a tiny meteorologist. It watches the sky (rain), checks the ground (soil), feels the air (temperature), and sends updates like a smart garden station.

Debugging (2)

Debugging 5.8.A – Data loss during transmission

Problem: The app shows missing values or mixed lines.
Clues: Prints are too fast; the app misses some messages.
Broken code:

print("TEMP:", temp_c)  # Rapid prints
print("SOIL:", soil_pct)  # Rapid prints
print("RAIN:", rain_state)  # Rapid prints
# No pacing between messages

Fixed code:

print("TEMP:", temp_c)  # Send temperature
time.sleep(0.05)  # Short pause helps the app read
print("SOIL:", soil_pct)  # Send soil percent
time.sleep(0.05)  # Short pause
print("RAIN:", rain_state)  # Send rain state
time.sleep(0.05)  # Short pause

Why it works: Tiny delays let the app process messages in order and avoid drops.
Avoid next time: Pace your prints or bundle them into one line if needed.

Debugging 5.8.B – Alerts are not being sent

Problem: Conditions cross thresholds, but no “ALERT” appears.
Clues: You see temperature/soil messages, but no alert lines.
Broken code:

if temp_c > temp_high:  # Excludes equal case
    print("ALERT:HEAT")  # Heat alert

Fixed code:

if temp_c >= temp_high:  # Include equal case
    print("ALERT:HEAT")  # Heat alert fires reliably

Why it works: Including equality prevents missing the exact threshold value.
Avoid next time: Decide and code whether equality should trigger an alert.

Final checklist

Temperature, soil percent, and rain state printed clearly
Alerts appeared when crossing thresholds
History showed the last few readings
Actuator responded to “PUMP/FAN” commands
App displayed “KEY:VALUE” messages without confusion

Extras

🧠 Student tip: Add “UNIT:C” or “UNIT:F” to switch temperature units (convert when needed).
🧑‍🏫 Instructor tip: Have students measure raw soil values wet vs dry to set a realistic soil_low threshold.
📖 Glossary:
- Percent mapping: Convert a raw number into 0–100% so humans can read it easily.
- Alert: A message printed when a condition crosses a threshold.
- History log: A short list of past readings to show trends.
💡 Mini tips:
- Use short delays between prints so apps don’t miss messages.
- Keep wiring stable; noisy wires cause bad readings.
- Label your station (PLACE) when using multiple setups.