Radar Guard 10.0

Note

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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 lesson, you’ll build an ultrasonic safety scanner using a servo, LEDs, and a buzzer. The servo sweeps the ultrasonic sensor to detect distance, while the LEDs change from green to yellow to red based on how close an object is. In danger zones, the buzzer sounds an alert with different beeping patterns.

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	Buzzer Module	1	BUY
9	Traffic Light LED	1	BUY

Wiring

Common Connections:

Traffic light LED
- R: Connect to 2 on the Arduino.
- Y: Connect to 3 on the Arduino.
- G: Connect to 4 on the Arduino.
- GND: Connect to GND on the Arduino.
Digital Servo Motor
- Connect to breadboard’s positive power bus.
- Connect to breadboard’s negative power bus.
- Connect to 12 on the Arduino.
Buzzer Modudle
- I/O: Connect to 5 on the Arduino.
- GND: Connect to breadboard’s negative power bus.
- VCC: Connect to breadboard’s red power bus.
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.

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).
The ArduinoRadarGUI is used here. You can click here Radar_Guard10.0.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>

// ------------ Pin Definitions ------------
const int trigPin   = 11;    // Ultrasonic Trig pin
const int echoPin   = 10;    // Ultrasonic Echo pin
const int servoPin  = 12;    // Servo signal pin
const int buzzerPin = 5;     // Passive buzzer
const int greenLED  = 2;     // Traffic light - Green
const int yellowLED = 3;     // Traffic light - Yellow
const int redLED    = 4;     // Traffic light - Red

// ------------ Servo Settings ------------
const int minAngle  = 0;     // Servo minimum angle
const int maxAngle  = 180;   // Servo maximum angle
const int stepAngle = 1;     // Servo movement step
int currentAngle    = minAngle;
int direction       = 1;     // +1 for forward, -1 for backward

// ------------ Distance Thresholds ------------
const int thresholdYellowCM = 30;  // ≤30cm = Yellow zone
const int thresholdRedCM    = 15;  // ≤15cm = Red zone

// ------------ Buzzer Control ------------
bool buzzerEnabled = false;
unsigned long nextBuzzTime = 0;
int buzzerFreq = 2000;     // Default beep frequency
int buzzOnMs    = 80;
int buzzOffMs   = 200;
bool buzzing = false;

// ------------ Timing ------------
unsigned long nextServoMove = 0;
const uint16_t servoStepInterval = 20;

// ------------ Servo Object ------------
Servo scanner;


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

  unsigned long duration = pulseIn(echoPin, HIGH, 20000); // timeout 20ms
  if (duration == 0) return 9999;                         // No echo

  long distance = duration / 58.0;
  if (distance <= 0) distance = 9999;
  return distance;
}


// ------------ Update LEDs + Buzzer by distance ------------
void updateStateByDistance(long dist) {

  // ---- Red zone ----
  if (dist <= thresholdRedCM) {

    digitalWrite(redLED, HIGH);
    digitalWrite(yellowLED, LOW);
    digitalWrite(greenLED, LOW);

    buzzerEnabled = true;
    buzzerFreq = 2800;   // Danger tone
    buzzOnMs  = 120;
    buzzOffMs = 120;
  }

  // ---- Yellow zone ----
  else if (dist <= thresholdYellowCM) {

    digitalWrite(redLED, LOW);
    digitalWrite(yellowLED, HIGH);
    digitalWrite(greenLED, LOW);

    buzzerEnabled = true;
    buzzerFreq = 2000;   // Warning tone
    buzzOnMs  = 80;
    buzzOffMs = 250;
  }

  // ---- Green zone ----
  else {

    digitalWrite(redLED, LOW);
    digitalWrite(yellowLED, LOW);
    digitalWrite(greenLED, HIGH);

    buzzerEnabled = false;
    noTone(buzzerPin);
  }
}


// ------------ Non-blocking buzzer scheduler ------------
void updateBuzzer(unsigned long now) {
  if (!buzzerEnabled) {
    buzzing = false;
    noTone(buzzerPin);
    return;
  }

  if (now >= nextBuzzTime) {
    if (!buzzing) {
      tone(buzzerPin, buzzerFreq);
      buzzing = true;
      nextBuzzTime = now + buzzOnMs;
    } else {
      noTone(buzzerPin);
      buzzing = false;
      nextBuzzTime = now + buzzOffMs;
    }
  }
}


// ------------ Setup ------------
void setup() {
  Serial.begin(9600);

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

  pinMode(buzzerPin, OUTPUT);
  pinMode(greenLED, OUTPUT);
  pinMode(yellowLED, OUTPUT);
  pinMode(redLED, OUTPUT);

  // Initial LED state
  digitalWrite(greenLED, HIGH);
  digitalWrite(yellowLED, LOW);
  digitalWrite(redLED, LOW);

  // Servo init
  scanner.attach(servoPin);
  scanner.write(currentAngle);

  nextServoMove = millis();
  nextBuzzTime = millis();
}


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

  // ------ Servo movement control ------
  if (now >= nextServoMove) {
    nextServoMove = now + servoStepInterval;

    currentAngle += direction * stepAngle;

    if (currentAngle >= maxAngle) {
      currentAngle = maxAngle;
      direction = -1;
    }
    else if (currentAngle <= minAngle) {
      currentAngle = minAngle;
      direction = 1;
    }

    scanner.write(currentAngle);

    long dist = measureDistanceCM();

    updateStateByDistance(dist);

    // Send angle + distance to Processing GUI
    Serial.print(currentAngle);
    Serial.print(",");
    Serial.print(dist);
    Serial.print(".");
  }

  // ------ Update buzzer (non-blocking) ------
  updateBuzzer(now);
}