Radar Guard 3.0

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, we will learn how to use the Ultrasonic Sensor Module, Digital Servo Motor, and MAX7219 Dot Matrix Module with the Arduino Board to create a radar defense system version 3.0.

When the ultrasonic sensor module detects an object, it will display the object’s range on the MAX7219 Dot Matrix Module.

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	Digital Servo Motor	1	BUY
7	MAX7219 Dot Matrix Module	1	BUY

Wiring

Common Connections:

Digital Servo Motor
- Connect to breadboard’s positive power bus.
- Connect to breadboard’s negative power bus.
- Connect to 2 on the Arduino.
Ultrasonic Sensor Module
- Trig: Connect to 4 on the Arduino.
- Echo: Connect to 3 on the Arduino.
- GND: Connect to breadboard’s negative power bus.
- VCC: Connect to breadboard’s red power bus.
MAX7219 Dot Matrix Module
- CLK: Connect to 11 on the Arduino.
- CS: Connect to 10 on the Arduino.
- DIN: Connect to 12 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 LedControl and install it.
Don’t forget to select the board(Arduino UNO R4 WIFI) and the correct port before clicking the Upload button.

#include <LedControl.h>
#include <Servo.h>

// hardware pins
LedControl lc(12, 11, 10, 4);   // DIN=12, CLK=11, CS=10, 4 modules
Servo    radarServo;
const int servoPin = 2;         // servo control pin
const int trigPin  = 4;         // HC-SR04 Trig pin
const int echoPin  = 3;         // HC-SR04 Echo pin

// timing
const unsigned long updateInterval = 20;  // ms per step
unsigned long lastUpdate = 0;
int currentAngle = 0;
int increment    = 1;

// thresholds for rows 0..7
const int thresholds[8] = { 32, 28, 24, 20, 16, 12, 8, 4 };

void setup() {
  Serial.begin(9600);

  // init LED matrix
  for (int m = 0; m < 4; m++) {
    lc.shutdown(m, false);
    lc.setIntensity(m, 8);
    lc.clearDisplay(m);
  }

  // init servo
  radarServo.attach(servoPin);
  radarServo.write(currentAngle);

  // init ultrasonic
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
}

void loop() {
  unsigned long now = millis();
  if (now - lastUpdate < updateInterval) return;
  lastUpdate = now;

  // 1) move servo to currentAngle
  radarServo.write(currentAngle);

  // 2) measure distance
  float d = getDistance();
  Serial.print("Angle: ");
  Serial.print(currentAngle);
  Serial.print("°, Distance: ");
  Serial.print(d);
  Serial.println(" cm");

  // 3) map angle -> step -> module & col
  int step   = map(currentAngle, 0, 180, 31, 0);
  int module = step / 8;
  int col    = 7 - (step % 8);

  // 4) always light row 0 at (module,col)
  lc.setLed(module, 0, col, true);

  //    then for each deeper threshold light extra rows
  for (int r = 1; r < 8; r++) {
    if (d <= thresholds[r]) {
      lc.setLed(module, r, col, true);
    }
  }

  // 5) update angle
  currentAngle += increment;

  // 6) at each end clear all before reversing
  if (currentAngle >= 180) {
    currentAngle = 180;
    increment = -1;
    clearAll();
  } else if (currentAngle <= 0) {
    currentAngle = 0;
    increment = 1;
    clearAll();
  }
}

// perform ultrasonic distance measurement (cm)
float getDistance() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  long dur = pulseIn(echoPin, HIGH, 30000);
  return dur * 0.034 / 2;
}

// helper: clear entire display
void clearAll() {
  for (int m = 0; m < 4; m++) {
    lc.clearDisplay(m);
  }
}