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High School

Smart Home

Build a scaled-down smart home model that combines sensors, status indicators, and an automated entry barrier into one coordinated system.

Level
Challenger
Time
2 hrs
Parts
6
Hardware-checked
Not yet
Start building
Smart home model with an automated entry barrier, pool, sensors, and exposed control electronics

0 of 5 build milestones complete

What you're building

This capstone build combines multiple sensors, status LEDs, and an automated barrier so several parts of the model can work together as one system.

It introduces the same kind of system integration used in real smart environments, where sensors collect information and automated components respond to changing conditions.

What you'll learn

  • Combine multiple sensors into a single coordinated system
  • Track and update state across several inputs at once
  • Integrate an automated mechanism with status indicators
  • Understand how sensors, code, and physical outputs work together
  • Debug a larger system by isolating one subsystem at a time

Parts you'll need

Microcontroller board × 1

Coordinates the sensors, LEDs, and automated barrier as one system.

Ultrasonic distance sensors × multiple

Detect objects or occupancy in different monitored areas of the model.

Micro servo motor × 1

Raises and lowers the automated entry barrier.

Status LEDs × multiple

Provide visible feedback about what the sensors are detecting.

Breadboard × 1

Holds the electronic connections for the sensors, LEDs, and servo.

Jumper wires × a bundle

Connect the sensors, LEDs, and servo to the microcontroller.

Build it

  1. 1

    Plan the smart-home system

    Decide where each sensor, status indicator, and automated component will be placed before wiring anything.

  2. 2

    Mount the sensors

    Position the ultrasonic sensors so they can reliably detect objects in the areas you want the system to monitor.

    Sensor placement diagram

    Not drawn yet. We only publish a diagram once someone has built this with real parts and checked it — so rather than guess at the connections, we are telling you they are missing. The written wiring notes are accurate.

  3. 3

    Wire the status LEDs

    Connect the status LEDs through current-limiting resistors to the microcontroller so the system can provide visible feedback.

    Status LED wiring diagram

    Not drawn yet. We only publish a diagram once someone has built this with real parts and checked it — so rather than guess at the connections, we are telling you they are missing. The written wiring notes are accurate.

  4. 4

    Attach the automated entry barrier

    Connect the barrier arm to the servo horn and mount the servo securely at the entrance.

    Entry barrier diagram

    Not drawn yet. We only publish a diagram once someone has built this with real parts and checked it — so rather than guess at the connections, we are telling you they are missing. The written wiring notes are accurate.

  5. 5

    Connect the full system

    Connect every sensor, LED, and the servo to power, ground, and the correct signal pins on the microcontroller.

    Full system wiring diagram

    Not drawn yet. We only publish a diagram once someone has built this with real parts and checked it — so rather than guess at the connections, we are telling you they are missing. The written wiring notes are accurate.

  6. 6

    Upload the system code

    Connect the microcontroller to your computer and upload the code below.

  7. 7

    Test each subsystem

    Test the sensors, LEDs, and barrier separately before running everything together.

  8. 8

    Test the complete smart home

    Trigger different sensors and confirm that the system updates its indicators and automated barrier correctly.

Wiring

Smart Home wiring diagram

Not drawn yet. We only publish a diagram once someone has built this with real parts and checked it — so rather than guess at the connections, we are telling you they are missing. The written wiring notes are accurate.

Each ultrasonic sensor connects to power and ground, with trigger and echo connected to digital pins. Each status LED connects through a current-limiting resistor to a digital output. The servo's signal wire connects to an appropriate control pin. Match every connection to the pins defined in your code, and plan your available pins before wiring the full system.

Code

arduino
1#include <Servo.h>2 3Servo barrier;4 5const int servoPin = 9;6 7const int trigPins[2] = { 10, 12 };8const int echoPins[2] = { 11, 13 };9 10const int redPins[2] = { 2, 4 };11const int greenPins[2] = { 3, 5 };12 13const int detectionThresholdCm = 10;14 15int openZones = 2;16 17void setup() {18  barrier.attach(servoPin);19 20  for (int i = 0; i < 2; i++) {21    pinMode(trigPins[i], OUTPUT);22    pinMode(echoPins[i], INPUT);23 24    pinMode(redPins[i], OUTPUT);25    pinMode(greenPins[i], OUTPUT);26  }27}28 29void loop() {30  openZones = 0;31 32  for (int i = 0; i < 2; i++) {33    long distanceCm = readDistanceCm(i);34 35    bool detected =36      distanceCm > 0 &&37      distanceCm < detectionThresholdCm;38 39    digitalWrite(40      redPins[i],41      detected ? HIGH : LOW42    );43 44    digitalWrite(45      greenPins[i],46      detected ? LOW : HIGH47    );48 49    if (!detected) {50      openZones++;51    }52  }53 54  if (openZones > 0) {55    barrier.write(90);56  } else {57    barrier.write(0);58  }59 60  delay(50);61}62 63long readDistanceCm(int index) {64  digitalWrite(trigPins[index], LOW);65  delayMicroseconds(2);66 67  digitalWrite(trigPins[index], HIGH);68  delayMicroseconds(10);69 70  digitalWrite(trigPins[index], LOW);71 72  long duration =73    pulseIn(echoPins[index], HIGH, 30000);74 75  if (duration == 0) {76    return -1;77  }78 79  return duration * 0.034 / 2;80}81
  • Line 13: detectionThresholdCm controls how close an object must be before the system considers it detected.
  • Line 48: The barrier responds to the state created from the sensor readings, connecting sensing, processing, and physical action.

Try it

  1. 1Upload the code and test one sensor at a time.
  2. 2Move an object in front of a sensor and confirm its status LEDs change.
  3. 3Test the servo separately and confirm the barrier can move through its intended range.
  4. 4Run the entire system and confirm the sensor readings, status indicators, and barrier work together.
  5. 5Repeat different combinations of sensor inputs to make sure the system behaves consistently.

Understand

Why this works

  1. Sensing

    The sensors report what is happening in different parts of the model.

  2. Processing

    Your code reads those inputs and keeps track of the system's current state.

  3. Control

    The LEDs and automated barrier respond based on what the sensors detect.

  4. System

    All of the sensing, logic, and outputs run together continuously as one coordinated smart-home system.

Troubleshooting

Common problems and what to check.

A status LED shows the wrong state.
Check that the sensor and its corresponding LED pins use the same array position in the code.
The barrier does not move.
Test the servo by itself first and confirm the servoPin in the code matches the physical connection.
The barrier reacts incorrectly.
Print the sensor readings to the Serial Monitor and confirm the state logic is interpreting them correctly.
Sensors interfere with each other.
Ultrasonic sensors placed close together can interfere with one another. Read them one at a time and add a short delay between measurements if necessary.
The system works one part at a time but fails when everything runs together.
Test each subsystem independently, then reconnect them one at a time until you identify which connection or section of code causes the problem.

Take it further

Small change

Add a live status display

Display the current state of the smart-home system using additional LEDs or another output device.

Add something

Improve the automated entrance

Add more conditions that determine when the entry barrier should open or remain closed.

Add something

Log system activity

Print a message whenever one of the monitored areas changes state or the automated barrier moves.

Design it yourself

Add another automated subsystem

Design another sensor-controlled feature and integrate it into the existing smart-home logic.

You decide how it works. No steps for this one.

Check your understanding

1. What makes this project a system instead of a collection of separate components?

2. What role does the microcontroller play in the smart-home system?

3. Why should you test each subsystem separately when debugging?

What to build next

You now know:

  • Integrating multiple subsystems into one system
  • Reading and comparing multiple sensors
  • Tracking state across a program
  • Driving a status display from program state
  • Debugging a system part by part
  • Combining sensor input with motor output
  • Using conditional (if/else) logic

That is every project in the library. Go back to any of them and take on the harder changes at the bottom — those are the part nobody walks you through. All projects