Radar Guard 8.0

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Kit purchase

Looking for parts? Check out our all-in-one kits below — packed with components, beginner-friendly guides, and tons of fun.

Name	Includes Arduino board	PURCHASE LINK
Ultimate Sensor Kit	Arduino Uno R4 Minima	BUY
Elite Explorer Kit	Arduino Uno R4 WiFi	BUY
3 in 1 Ultimate Starter Kit	Arduino Uno R4 Minima	BUY
Universal Maker Sensor Kit	×	BUY

Course Introduction

In this project, we’ll build a Radar Warning System using an ultrasonic sensor, servo, LCD, stepper motor, and buzzer.

The servo scans the area, and when an object comes within 20 cm, the system enters ALERT mode: the LCD shows a warning, the red LED and buzzer blink, and the stepper motor sweeps back and forth. Once the object leaves, the system resets to normal with the green LED on and “Area is Empty” displayed.

Note

If this is your first time working with an Arduino project, we recommend downloading and reviewing the basic materials first.

Required Components

In this project, we need the following components:

SN	COMPONENT INTRODUCTION	QUANTITY	PURCHASE LINK
1	Arduino UNO R4 Minima/Arduino UNO R4 WIFI	1	BUY
2	USB Type-C cable	1
3	Breadboard	1	BUY
4	Wires	Several	BUY
5	Ultrasonic Sensor Module	1	BUY
6	I2C LCD 1602	1	BUY
7	Digital Servo Motor	1	BUY
8	Passive Buzzer	1	BUY
9	1kΩ resistor	4	BUY
10	LED	4	BUY
11	Stepper Motor 28BYJ-48 ULN2003 Drive Module 5	1	BUY

Wiring

Common Connections:

LED
- Red LED: Connect the LEDs anode to a 1kΩ resistor then to the 3 on Arduino, and the LEDs cathode to negative power bus on the breadboard.
- Green LED: Connect the LEDs anode to a 1kΩ resistor then to the 4 on Arduino, and the LEDs cathode to negative power bus on the breadboard.
Digital Servo Motor
- Connect to breadboard’s positive power bus.
- Connect to breadboard’s negative power bus.
- Connect to 7 on the Arduino.
Buzzer
- Connect to breadboard’s negative power bus.
- Connect to 2 on the Arduino.
Ultrasonic Sensor Module
- Trig: Connect to 6 on the Arduino.
- Echo: Connect to 5 on the Arduino.
- GND: Connect to breadboard’s negative power bus.
- VCC: Connect to breadboard’s red power bus.
Stepper Motor 28BYJ-48 ULN2003 Drive Module 5
- IN1: Connect to 11 on the Arduino.
- IN2: Connect to 10 on the Arduino.
- IN3: Connect to 9 on the Arduino.
- IN4: Connect to 8 on the Arduino.
I2C LCD 1602
- SDA: Connect to A4 on the Arduino.
- SCL: Connect to A5 on the Arduino.
- GND: Connect to breadboard’s negative power bus.
- VCC: Connect to breadboard’s red power bus.

Writing the Code

Note

You can copy this code into Arduino IDE.
To install the library, use the Arduino Library Manager and search for LiquidCrystal_I2C and Stepper and install it.
Don’t forget to select the board(Arduino UNO R4 WIFI) and the correct port before clicking the Upload button.

#include <Servo.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <Stepper.h>

// --------------------- Pins ---------------------
// Ultrasonic
const int trigPin = 6;
const int echoPin = 5;

// Servo (scanner)
const int servoPin = 7;

// LEDs & Active Buzzer
const int redLed   = 3;
const int greenLed = 4;
const int buzzer   = 2;   // Active buzzer: HIGH=on, LOW=off

// LCD
LiquidCrystal_I2C lcd(0x27, 16, 2); // if no display, try 0x3F

// Stepper (28BYJ-48 + ULN2003)  IN1→8, IN2→9, IN3→10, IN4→11
const int IN1 = 8;
const int IN2 = 9;
const int IN3 = 10;
const int IN4 = 11;
const int stepsPerRevolution = 2048;     // typical for 28BYJ-48
const int stepperRPM = 16;
// Phase order (common): IN1, IN3, IN2, IN4; if not working, try IN1,IN2,IN3,IN4
Stepper stepperMotor(stepsPerRevolution, IN1, IN3, IN2, IN4);

// --------------------- Scan settings ---------------------
Servo radarServo;
const int alertDistance = 20;            // cm
const unsigned long updateInterval = 20; // ms per servo tick
int currentAngle = 0;
int increment    = 1;
unsigned long lastServoUpdate = 0;

// Detection threshold
const uint8_t ENTER_HITS = 3;            // Enter ALERT after 3 consecutive hits
int triggerCount = 0;

// --------------------- Beep/Blink (100ms) ---------------------
unsigned long lastBlinkTs = 0;
bool blinkOn = false;

// --------------------- Helpers (decl) ---------------------
float getDistance();
float getDistanceMedian3();
void setNormalState();
void lcdSetEmpty();
void lcdSetWarning();
void doSweepWithBeepBlink(); // Perform 0→180→0 sweep, with LED/Buzzer blinking

// --------------------- Setup ---------------------
void setup() {
  radarServo.attach(servoPin);

  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);

  pinMode(redLed, OUTPUT);
  pinMode(greenLed, OUTPUT);
  pinMode(buzzer, OUTPUT);

  lcd.init();
  lcd.backlight();
  lcd.clear();

  stepperMotor.setSpeed(stepperRPM);

  lcdSetEmpty();
  setNormalState();
}

// --------------------- Main Loop ---------------------
void loop() {
  unsigned long now = millis();

  // Servo scanning (only when not in ALERT mode)
  if (now - lastServoUpdate >= updateInterval) {
    lastServoUpdate = now;

    radarServo.write(currentAngle);

    // Distance measurement every 5 degrees
    if (currentAngle % 5 == 0) {
      float d = getDistanceMedian3();
      if (d < alertDistance) triggerCount++;
      else triggerCount = 0;

      // Enter ALERT after enough hits
      if (triggerCount >= ENTER_HITS) {
        triggerCount = 0;

        // Show warning on LCD, turn off green LED
        lcdSetWarning();
        digitalWrite(greenLed, LOW);

        // Loop: after each full sweep, check distance again
        while (true) {
          doSweepWithBeepBlink(); // Perform 0→180→0 sweep with LED/Buzzer

          // After sweep, check if object is still present
          float d2 = getDistanceMedian3();
          if (d2 >= alertDistance) {
            // No object → exit ALERT
            break;
          }
          // Still detected → repeat another sweep
        }

        // Stop buzzer and LED, restore normal state
        blinkOn = false;
        digitalWrite(redLed, LOW);
        digitalWrite(buzzer, LOW);
        setNormalState();
        lcdSetEmpty();
      }
    }

    // Update scanning angle
    currentAngle += increment;
    if (currentAngle >= 180) { currentAngle = 180; increment = -1; }
    else if (currentAngle <= 0) { currentAngle = 0; increment = 1; }
  }
}

// --------------------- Sweep (0→180→0) with Beep/Blink ---------------------
// Perform one complete sweep 0→180→0 smoothly,
// with LED and buzzer toggling every 100ms during the motion.
void doSweepWithBeepBlink() {
  const int halfTurnSteps = stepsPerRevolution / 2; // 180°

  // Reset blinking state
  lastBlinkTs = millis();
  blinkOn = false;
  digitalWrite(redLed, LOW);
  digitalWrite(buzzer, LOW);

  // Forward half-turn
  for (int i = 0; i < halfTurnSteps; i++) {
    stepperMotor.step(1);
    unsigned long now = millis();
    if (now - lastBlinkTs >= 100) {
      lastBlinkTs = now;
      blinkOn = !blinkOn;
      digitalWrite(redLed, blinkOn ? HIGH : LOW);
      digitalWrite(buzzer, blinkOn ? HIGH : LOW);
    }
  }

  // Backward half-turn
  for (int i = 0; i < halfTurnSteps; i++) {
    stepperMotor.step(-1);
    unsigned long now = millis();
    if (now - lastBlinkTs >= 100) {
      lastBlinkTs = now;
      blinkOn = !blinkOn;
      digitalWrite(redLed, blinkOn ? HIGH : LOW);
      digitalWrite(buzzer, blinkOn ? HIGH : LOW);
    }
  }

  // At the end, ensure LED and buzzer are off
  digitalWrite(redLed, LOW);
  digitalWrite(buzzer, LOW);
}

// --------------------- Distance (median filter) ---------------------
float getDistance() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  unsigned long duration = pulseIn(echoPin, HIGH, 30000UL);
  if (duration == 0) return 9999.0; // Timeout → very far
  return duration * 0.034f / 2.0f;  // Convert to cm
}

float getDistanceMedian3() {
  float a = getDistance();
  float b = getDistance();
  float c = getDistance();
  // Return the median of three readings
  if (a > b) { float t = a; a = b; b = t; }
  if (b > c) { float t = b; b = c; c = t; }
  if (a > b) { float t = a; a = b; b = t; }
  return b;
}

// --------------------- UI helpers ---------------------
void setNormalState() {
  digitalWrite(greenLed, HIGH);
  digitalWrite(redLed, LOW);
  digitalWrite(buzzer, LOW);
}

void lcdSetEmpty() {
  lcd.clear();
  lcd.setCursor(1, 0);  // Centered "Area is Empty"
  lcd.print("Area is Empty");
  lcd.setCursor(0, 1);
  lcd.print("                ");
}

void lcdSetWarning() {
  lcd.clear();
  lcd.setCursor(4, 0); // Centered "WARNING!!"
  lcd.print("WARNING!!");
  lcd.setCursor(2, 1); // Centered "Foreign Body"
  lcd.print("Foreign Body");
}