How to Build IoT Smart Home System with Raspberry Pi Pico W in Wokwi: Complete Tutorial

🏠

Project Overview

This tutorial builds a complete IoT Smart Home Monitoring System using the Raspberry Pi Pico W — all simulated in Wokwi, so no physical hardware is needed. The system integrates multiple sensors and output devices to mimic real-world home automation and security.

Measure distance (security / parking)

Detect intruders via ultrasonic sensing

Monitor light intensity (LDR)

Buzzer alarm activation

LED visual status indicators

WiFi-ready IoT architecture

Night watch & day safe modes

Priority-based security logic

💡 What You Will Learn How ultrasonic echo timing works · ADC on Pico W · Priority-based security logic · PWM buzzer control · Multi-sensor embedded systems · Wokwi IoT simulation · MicroPython code structure

🔧

Components Used

#	Component	Role	Type
1	Raspberry Pi Pico W	Main controller with built-in WiFi	Controller
2	HC-SR04 Ultrasonic Sensor	Distance measurement (2 cm – 400 cm)	Sensor
3	LDR (Photoresistor)	Ambient light detection via ADC	Sensor
4	Green LED	Safe / night watch status indicator	Output
5	Red LED	Intruder alert indicator	Output
6	Buzzer	PWM-driven audio alarm	Output
7	Relay Module	Control high-voltage devices (optional)	Passive
8	Breadboard & Jumper Wires	Circuit connections	Passive

📌

Wiring & Pin Map

All connections at a glance. Wire each component to the corresponding GPIO pin on the Pico W.

Ultrasonic TRIGGP16

Ultrasonic ECHOGP17

Ultrasonic VCC3V3

Ultrasonic GNDGND.7

Red LED (Anode)GP14

Green LED (Anode)GP15

LED CathodesGND.4

Buzzer (+)GP13

Buzzer (–)GND.4

LDR AOGP26 (ADC0)

LDR VCC3V3

LDR GNDGND.6

📐

Circuit Diagram (diagram.json)

Paste this diagram.json into your Wokwi project to set up all parts and connections instantly.

MAIN CONTROLLER

Raspberry Pi Pico W

MicroPython v1.24.1 · Built-in WiFi

📡

HC-SR04

Ultrasonic Sensor

TRIG→GP16 | ECHO→GP17

💡

LDR

Photoresistor

AO→GP26 (ADC0)

🟢

Green LED

Safe Indicator

A→GP15 | C→GND

🔴

Red LED

Alert Indicator

A→GP14 | C→GND

🔔

Buzzer

PWM Audio Alarm

+→GP13 | –→GND

⚡

Power Rails

3V3 & GND

All sensors & outputs

All wires shown in Wokwi simulation · Open simulation to view interactive circuit

{
  "version": 1,
  "author": "MakeMindz",
  "editor": "wokwi",
  "parts": [
    {
      "type": "board-pi-pico-w",
      "id": "pico",
      "top": 0,
      "left": 0,
      "attrs": { "env": "micropython-20241129-v1.24.1" }
    },
    {
      "type": "wokwi-led",
      "id": "led1",
      "top": 92.4,
      "left": -178.6,
      "attrs": { "color": "green" }
    },
    {
      "type": "wokwi-led",
      "id": "led2",
      "top": 92.4,
      "left": -140.2,
      "attrs": { "color": "red" }
    },
    {
      "type": "wokwi-hc-sr04",
      "id": "ultrasonic1",
      "top": -56.1,
      "left": 82.3,
      "attrs": {}
    },
    {
      "type": "wokwi-buzzer",
      "id": "bz1",
      "top": 79.2,
      "left": -94.2,
      "attrs": { "volume": "0.1" }
    },
    {
      "type": "wokwi-photoresistor-sensor",
      "id": "ldr1",
      "top": 127.8,
      "left": 122.8,
      "rotate": 180,
      "attrs": {}
    }
  ],
  "connections": [
    [ "pico:GND.4",     "led1:C",          "black", [ "h0" ] ],
    [ "led2:C",          "pico:GND.4",     "green", [ "v0" ] ],
    [ "bz1:1",           "pico:GND.4",     "green", [ "v0" ] ],
    [ "bz1:2",           "pico:GP13",      "green", [ "v0" ] ],
    [ "led2:A",          "pico:GP14",      "green", [ "v0" ] ],
    [ "led1:A",          "pico:GP15",      "green", [ "v0" ] ],
    [ "pico:GP26",       "ldr1:AO",        "green", [ "h0" ] ],
    [ "pico:GND.6",      "ldr1:GND",       "black", [ "h32.66", "v35.15" ] ],
    [ "pico:3V3",        "ldr1:VCC",       "green", [ "h23.06", "v121.55" ] ],
    [ "ultrasonic1:VCC", "pico:3V3",       "red",   [ "v19.2" ] ],
    [ "ultrasonic1:TRIG","pico:GP16",      "green", [ "v163.2", "h-0.4" ] ],
    [ "ultrasonic1:ECHO","pico:GP17",      "green", [ "v0" ] ],
    [ "pico:GND.7",      "ultrasonic1:GND","black", [ "h0" ] ]
  ],
  "dependencies": {}
}

▶ Open Simulation in Wokwi

⚙️

System Logic Explained

The system uses a priority-based control structure — the same pattern found in professional security automation. Security always takes precedence over environment mode.

🚨 Priority 1 — Intruder Alert

Triggered when distance < 50 cm

Red LED turns ON
Green LED turns OFF
Buzzer activates (PWM @ 1 kHz)
Serial monitor prints alert

🌙 Priority 2 — Night Watch

Triggered when LDR value > 30000 (dark)

Red LED OFF
Buzzer OFF
Green LED blinks (0.5s)
System enters monitoring mode

☀️ Priority 3 — Day Safe Mode

Triggered when light intensity is high

Red LED OFF
Buzzer OFF
Green LED stays ON
Normal operation

💡 How Ultrasonic Distance Works The HC-SR04 fires a 10 µs pulse on TRIG. The sensor sends ultrasonic bursts and the ECHO pin goes HIGH for the duration the sound takes to return. Distance = (echo duration × 0.0343) ÷ 2 (in cm).

🐍

Complete MicroPython Code

Copy and paste this into main.py in your Wokwi project or on your physical Pico W.

from machine import Pin, ADC, PWM
import time

# ──────────────────────────────────
# Hardware Configuration
# ──────────────────────────────────

# Ultrasonic Sensor (HC-SR04)
trigger = Pin(16, Pin.OUT)
echo    = Pin(17, Pin.IN)

# LDR connected to ADC pin GP26
ldr = ADC(26)  # GP26 = ADC0

# LEDs
red_led   = Pin(14, Pin.OUT)
green_led = Pin(15, Pin.OUT)

# Buzzer — PWM for audible tone
buzzer = PWM(Pin(13))
buzzer.freq(1000)  # 1 kHz

# ──────────────────────────────────
# Thresholds (tune as needed)
# ──────────────────────────────────
INTRUDER_DISTANCE = 50     # cm — trigger alert below this
DARK_THRESHOLD    = 30000  # LDR ADC value — higher = darker

# ──────────────────────────────────
# Ultrasonic Distance Measurement
# ──────────────────────────────────
def measure_distance():
    trigger.low()
    time.sleep_us(2)
    trigger.high()
    time.sleep_us(10)
    trigger.low()

    while echo.value() == 0:
        start = time.ticks_us()

    while echo.value() == 1:
        end = time.ticks_us()

    duration = time.ticks_diff(end, start)
    distance = (duration * 0.0343) / 2
    return distance

print("Security System Initialized")
print("──────────────────────────")

# ──────────────────────────────────
# Main Loop
# ──────────────────────────────────
while True:
    distance    = measure_distance()
    light_value = ldr.read_u16()

    print(f"Distance: {distance:.1f} cm | LDR: {light_value}")

    # 🚨 PRIORITY 1: INTRUDER ALERT
    if distance < INTRUDER_DISTANCE:
        print("🚨 INTRUDER DETECTED!")
        red_led.value(1)
        green_led.value(0)
        buzzer.duty_u16(30000)  # Buzzer ON

    # 🌗 PRIORITY 2 & 3: ENVIRONMENT MODE
    else:
        red_led.value(0)
        buzzer.duty_u16(0)      # Buzzer OFF

        if light_value > DARK_THRESHOLD:
            print("🌙 Night Watch Mode")
            green_led.toggle()   # Blink
            time.sleep(0.5)
        else:
            print("☀️  Day Safe Mode")
            green_led.value(1)  # Steady ON
            time.sleep(0.5)

📝

Step-by-Step Build Guide

Open Wokwi and Create a New Project

Go to wokwi.com and create a new project. Select Raspberry Pi Pico W as your board and choose MicroPython as the language.

Add diagram.json

Click the diagram.json tab in Wokwi and replace the contents with the diagram.json code above. This adds all components (Pico W, HC-SR04, LDR, LEDs, buzzer) and their wired connections automatically.

Add the MicroPython Code

Click the main.py tab and paste the complete code from Step 4 above. The code sets up GPIO pins, defines the measure_distance() function, and runs the main monitoring loop.

Run the Simulation

Click the green ▶ Play button. The serial monitor will print distance and LDR readings. You should see "Day Safe Mode" or "Night Watch Mode" messages depending on the simulated light level.

Test the Intruder Alert

In the Wokwi simulation, click on the HC-SR04 sensor and adjust the distance slider to below 50 cm. The red LED should light up, the buzzer should activate, and the serial monitor prints "🚨 INTRUDER DETECTED!"

Test Night Watch Mode

Click on the LDR sensor in Wokwi and drag the light level slider to a low value (simulating darkness). The green LED will begin blinking and the serial monitor will print "🌙 Night Watch Mode".

Tune Thresholds (Optional)

Adjust INTRUDER_DISTANCE and DARK_THRESHOLD in the code to suit your real-world environment. Higher DARK_THRESHOLD values make the system more sensitive to low-light conditions.

Deploy to Real Hardware (Optional)

Flash MicroPython firmware to your physical Pico W using Thonny IDE. Wire the components as per the pin map, copy main.py to the board, and run. The system works identically on real hardware.

▶ Try the Free Simulation More Projects →

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