Radar Guard 1.0

Note

🌟 Welcome to the SunFounder Facebook Community! Whether you’re into Raspberry Pi, Arduino, or ESP32, you’ll find inspiration, help ideas here.

✅ Be the first to get free learning resources.
✅ Stay updated on new products & exclusive giveaways.
✅ Share your creations and get real feedback.

👉 Need faster updates or support? Click [here] join our Facebook community
👉 Or join our WhatsApp group: Click [here]

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 ESP32 board	PURCHASE LINK
ESP32 Ultimate Starter Kit	ESP32 WROOM 32E +	BUY
Universal Maker Sensor Kit		BUY

Course Introduction

In this lesson, we will learn how to use the Ultrasonic Sensor Module, Digital Servo Motor, and I2C LCD 1602 with the ESP32 to create a radar defense system.

When the ultrasonic sensor module is running, it emits an audible alarm and flashes the red LED if it detects an obstacle within its sensing range. If no obstacle is detected, indicating a safe state, the green LED stays on.

Note

If this is your first time working with an ESP32 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	ESP-WROOM-32 ESP32 ESP-32S Development Board	1	BUY
2	USB Type-C cable	1
3	Breadboard	1	BUY
4	Wires	Several	BUY
5	1kΩ resistor	4	BUY
6	Ultrasonic Sensor Module	1	BUY
7	LED	4	BUY
8	I2C LCD 1602	1	BUY
9	Digital Servo Motor	1	BUY
10	Passive Buzzer	1	BUY

Wiring

Common Connections:

LED
- Green: Connect the LEDs cathode to the negative power bus on the breadboard, and the LED anode to a 1kΩ resistor then to GPIO14 on the Arduino.
- Red: Connect the LEDs cathode to the negative power bus on the breadboard, and the LED anode to a 1kΩ resistor then to GPIO27 on the Arduino.
Digital Servo Motor
- Connect to breadboard’s positive power bus.
- Connect to breadboard’s negative power bus.
- Connect to GPIO18 on the ESP32.
Passive Buzzer
- ＋: Connect to GPIO25 on the ESP32.
- －: Connect to breadboard’s negative power bus.
I2C LCD 1602
- SDA: Connect to GPIO21 on the ESP32.
- SCL: Connect to GPIO22 on the ESP32.
- GND: Connect to breadboard’s negative power bus.
- VCC: Connect to breadboard’s red power bus.
Ultrasonic Sensor Module
- Trig: Connect to GPIO17 on the ESP32.
- Echo: Connect to GPIO16 on the ESP32.
- 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 ESP32Servo and LiquidCrystal I2C and install it.
Don’t forget to select the board(ESP32 Dev module) and the correct port before clicking the Upload button.

#include <ESP32Servo.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// ----------------- Pin mapping (ESP32) -----------------
const int trigPin  = 17;
const int echoPin  = 16;   // Connected through voltage divider to 3.3V!
const int servoPin = 18;

const int redLed   = 27;
const int greenLed = 14;
const int buzzer   = 25;

// ----------------- LCD -----------------
LiquidCrystal_I2C lcd(0x27, 16, 2);  // If not displayed, change to 0x3F

// ----------------- Settings -----------------
const int alertDistance = 20;             // Alarm if less than 20cm
const unsigned long updateInterval = 20;  // Servo scan step interval (ms)

// Smooth scanning
int currentAngle = 0;
int increment = 1;        // Change by 1° each step

unsigned long lastServoUpdate = 0;

// Consecutive trigger count
int triggerCount = 0;

// State record (to update LCD only on state change)
enum RadarState { EMPTY, WARNING };
RadarState lastState = EMPTY;

// Servo object
Servo radarServo;

void setup() {
  // Servo (set pulse range according to servo spec)
  radarServo.setPeriodHertz(50);  // 50Hz
  radarServo.attach(servoPin, 500, 2400); // Default 500-2400us pulse width

  // Ultrasonic sensor
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);

  // LED and buzzer
  pinMode(redLed, OUTPUT);
  pinMode(greenLed, OUTPUT);
  pinMode(buzzer, OUTPUT);

  // I2C/LCD
  Wire.begin(21, 22);  // SDA=21, SCL=22
  lcd.init();
  lcd.backlight();
  lcd.clear();

  // Initial state
  lcdSetEmpty();
  setNormalState();
}

void loop() {
  unsigned long currentMillis = millis();

  // When not alarming, do smooth scan + periodic measurement
  if (currentMillis - lastServoUpdate >= updateInterval) {
    lastServoUpdate = currentMillis;

    // Update servo angle
    radarServo.write(currentAngle);

    // Measure distance every 5°
    if (currentAngle % 5 == 0) {
      float distance = getDistance();
      if (distance < alertDistance) {
        triggerCount++;      // Consecutive detections under threshold
      } else {
        triggerCount = 0;    // Safe, reset counter
      }

      // Trigger alarm only after 5 consecutive detections
      if (triggerCount >= 5) {
        if (lastState != WARNING) {
          lastState = WARNING;
          lcdSetWarning();
        }
        alertMode();         // Alarm until safe
        triggerCount = 0;    // Reset counter after alarm
      } else {
        // Show normal state
        if (lastState != EMPTY) {
          lastState = EMPTY;
          lcdSetEmpty();
          setNormalState();
        }
      }
    }

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

// Ultrasonic distance measurement (returns cm)
float getDistance() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // pulseIn timeout 30000us (≈30ms)
  long duration = pulseIn(echoPin, HIGH, 30000);
  if (duration == 0) return 9999.0;  // Timeout means very far
  float distance = duration * 0.034f / 2.0f;
  return distance;
}

// Alarm mode: continuous flash/beep until object removed
void alertMode() {
  // During alarm, green LED off
  digitalWrite(greenLed, LOW);

  // Keep alarming while object present
  while (getDistance() < alertDistance) {
    digitalWrite(redLed, HIGH);
    digitalWrite(buzzer, HIGH);
    delay(100);
    digitalWrite(redLed, LOW);
    digitalWrite(buzzer, LOW);
    delay(100);
  }

  // Back to normal
  lcdSetEmpty();
  setNormalState();
  lastState = EMPTY;
}

// Normal state: green LED on, red LED and buzzer off
void setNormalState() {
  digitalWrite(greenLed, HIGH);
  digitalWrite(redLed, LOW);
  digitalWrite(buzzer, LOW);
}

// LCD: show “Area is Empty”
void lcdSetEmpty() {
  lcd.clear();
  // "Area is Empty" = 14 chars, center = (16-14)/2=1
  lcd.setCursor(1, 0);
  lcd.print("Area is Empty");
  lcd.setCursor(0, 1);
  lcd.print("                ");
}

// LCD: show warning
void lcdSetWarning() {
  lcd.clear();
  // "WARNING!!" = 9 chars, center = (16-9)/2≈4
  lcd.setCursor(4, 0);
  lcd.print("WARNING!!");
  // Second line "Foreign Body" starting at col 2
  lcd.setCursor(2, 1);
  lcd.print("Foreign Body");
}