Arduino Project

Arduino Radar System Project with Ultrasonic Sensor V9

Course Introduction

In this lesson, we’ll build a Radar Warning System using an ultrasonic sensor, a servo, an I²C LCD, LEDs, and a buzzer.

The servo sweeps the ultrasonic sensor across the area, measuring distances in real time. When an object comes within 50 cm, the system enters ALERT mode: the LCD shows a warning, the green LED turns off while the red LED turns on, and the buzzer beeps with a frequency that increases as the target gets closer. Once the object moves away, the system resets to normal mode, showing “Area is Empty” and restoring the green LED.

Note

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

1.1 Install Arduino IDE(Important)
1.2 Introduction of Arduino IDE

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	Passive Buzzer	1	BUY
6	Ultrasonic Sensor Module	1	BUY
7	1kΩ resistor	4	BUY
8	I2C LCD 1602	1	BUY
9	4-Digit Segment Display Module	1	BUY
10	LED	4	BUY

Wiring

6.png__PID:bec3edcb-310a-42f1-87d1-c00cc3105dba

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 11 on the Arduino.
Echo: Connect to 10 on the Arduino.
GND: Connect to breadboard’s negative power bus.
VCC: Connect to breadboard’s red power bus.

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
Build the circuit.
Upload the code to the Arduino board using Arduino IDE.
In the Arduino IDE, check the current Arduino port(COMx).
To install the library, use the Arduino Library Manager and search for LiquidCrystal_I2C and install it.
The ArduinoRadarGUI is used here. You can click here Radar_Guard9.0.zip to download it.
Open ArduinoLidarGUI.pde in the Processing IDE .
Modify the code in line 35 to ensure the correct port number(COMx).
Run the Processing sketch to visualize the radar data.

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

// ---------- Pin Mapping ----------
const int trigPin   = 11;   // ultrasonic trig
const int echoPin   = 10;   // ultrasonic echo
const int servoPin  = 12;   // servo motor
const int buzzerPin = 2;    // buzzer
const int redLED    = 3;    // red LED
const int greenLED  = 4;    // green LED

// ---------- Config ----------
const long BAUD_RATE     = 9600;
const int  thresholdCM   = 50;          // base threshold
const int  minAngle      = 0;           // servo min angle
const int  maxAngle      = 180;         // servo max angle
const int  stepAngle     = 1;           // step size
const uint16_t servoMs   = 20;          // step interval
const uint32_t echoTOus  = 20000UL;     // ultrasonic timeout

// --- Hysteresis & stability ---
const int  thresholdEnterCM = 50;       // enter alert
const int  thresholdExitCM  = 55;       // exit alert
const byte stableN          = 3;        // stable count
byte enterCnt = 0, exitCnt = 0;

// ---------- LCD ----------
LiquidCrystal_I2C lcd(0x27, 16, 2);

// ---------- Globals ----------
Servo scanner;
int  angleCur = minAngle;
int  dir      = +1;

bool alertNow  = false;
bool lastAlert = false;

uint32_t tServoNext  = 0;

// Buzzer scheduler
bool      buzzOn      = false;
uint32_t  tBuzzNext   = 0;
uint16_t  buzzOnMs    = 20;
uint16_t  buzzOffMs   = 200;

long lastDistCM = 9999;

// ---------- Helpers ----------
// Measure distance (cm)
long measureDistanceCM() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  unsigned long dur = pulseIn(echoPin, HIGH, echoTOus);
  if (dur == 0) return 9999;
  long cm = (long)(dur / 58.0f);
  if (cm <= 0) cm = 9999;
  return cm;
}

// Send data to Serial
void sendData(int angle, long dist) {
  Serial.print(angle);
  Serial.print(",");
  Serial.print(dist);
  Serial.print(".");
}

// LED state
void setIdleIndicators() {
  digitalWrite(greenLED, HIGH);
  digitalWrite(redLED, LOW);
}
void setAlertIndicators() {
  digitalWrite(redLED, HIGH);
  digitalWrite(greenLED, LOW);
}

// LCD messages
void lcdSetEmpty() {
  lcd.clear();
  lcd.setCursor(1, 0);
  lcd.print("Area is Empty");
  lcd.setCursor(0, 1);
  lcd.print("                ");
}
void lcdSetWarning() {
  lcd.clear();
  lcd.setCursor(4, 0);
  lcd.print("WARNING!!");
  lcd.setCursor(2, 1);
  lcd.print("Foreign Body");
}

// Update LCD only when state changes
void updateLCDIfChanged(bool state) {
  if (state != lastAlert) {
    if (state) lcdSetWarning();
    else       lcdSetEmpty();
    lastAlert = state;
  }
}

// Stable alert decision
bool computeStableAlert(long dist) {
  static bool state = false;
  if (!state) {
    if (dist <= thresholdEnterCM) {
      if (++enterCnt >= stableN) { state = true; enterCnt = 0; exitCnt = 0; }
    } else enterCnt = 0;
  } else {
    if (dist >= thresholdExitCM || dist == 9999) {
      if (++exitCnt >= stableN) { state = false; exitCnt = 0; enterCnt = 0; }
    } else exitCnt = 0;
  }
  return state;
}

// Buzzer timing
void updateBuzzerScheduler(bool state, long dist) {
  if (!state) {
    digitalWrite(buzzerPin, LOW);
    buzzOn = false;
    return;
  }
  int mapped = map((int)dist, 5, thresholdCM, 60, 300);
  mapped = constrain(mapped, 40, 400);
  buzzOffMs = (uint16_t)mapped;
}

// ---------- Setup ----------
void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(buzzerPin, OUTPUT);
  pinMode(redLED, OUTPUT);
  pinMode(greenLED, OUTPUT);

  Serial.begin(BAUD_RATE);

  scanner.attach(servoPin);
  scanner.write(angleCur);

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

  setIdleIndicators();

  uint32_t now = millis();
  tServoNext = now + servoMs;
  tBuzzNext  = now;
}

// ---------- Loop ----------
void loop() {
  uint32_t now = millis();

  // Servo & distance update
  if ((int32_t)(now - tServoNext) >= 0) {
    tServoNext += servoMs;

    // move servo
    angleCur += dir * stepAngle;
    if (angleCur >= maxAngle) { angleCur = maxAngle; dir = -1; }
    else if (angleCur <= minAngle) { angleCur = minAngle; dir = +1; }
    scanner.write(angleCur);

    // distance
    long d = measureDistanceCM();
    lastDistCM = d;

    // alert state
    alertNow = computeStableAlert(d);
    if (alertNow) setAlertIndicators();
    else          setIdleIndicators();

    updateLCDIfChanged(alertNow);
    updateBuzzerScheduler(alertNow, d);
    sendData(angleCur, d);
  }

  // Buzzer update
  if (alertNow) {
    if ((int32_t)(now - tBuzzNext) >= 0) {
      if (!buzzOn) {
        digitalWrite(buzzerPin, HIGH);
        buzzOn    = true;
        tBuzzNext = now + buzzOnMs;
      } else {
        digitalWrite(buzzerPin, LOW);
        buzzOn    = false;
        tBuzzNext = now + buzzOffMs;
      }
    }
  } else {
    if (buzzOn) {
      digitalWrite(buzzerPin, LOW);
      buzzOn = false;
    }
  }
}

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Arduino Project

Arduino Radar System Project with Ultrasonic Sensor V9

Course Introduction

Required Components

Wiring

Common Connections:

Writing the Code

Arduino Project

Arduino Radar System Project with Ultrasonic Sensor V9

Course Introduction

Required Components

Wiring

Common Connections:

Writing the Code

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