DIY radar using Arduino and Processing. For more detail, please refer to Cytron Tutorial page.

ArduinoRadar.pde

/*
  Project: Arduino Radar
  Software: Processing IDE 3.4
  Item used:
  - Maker UNO
  - Analog Distance Sensor (10-80cm)
  - TowerPro MG946R Metal Gear Servo
*/

import processing.serial.*;
import java.awt.event.KeyEvent;
import java.io.IOException;

String Port = "/dev/cu.wchusbserial14120"; // Arduino port
Serial myPort;

int distanceLimit = 40; // Distance limit is set to 40cm

String angle = "";
String distance = "";
String data = "";
String noObject;

float pixsDistance;

int iAngle, iDistance;
int index1 = 0;
int index2 = 0;

PFont orcFont;

void setup()
{
  size(1366, 768);
  smooth();
  myPort = new Serial(this, Port, 9600); 
  myPort.bufferUntil('.');
}

void draw()
{
  fill(98, 245, 31);
  noStroke();
  fill(0, 4);
  rect(0, 0, width, height - height * 0.065); 
  
  fill(98, 245, 31); 
  
  drawRadar();
  drawLine();
  drawObject();
  drawText();
}

void serialEvent (Serial myPort)
{
  data = myPort.readStringUntil('.');
  data = data.substring(0, data.length() - 1);
  
  index1 = data.indexOf(","); 
  angle = data.substring(0, index1); 
  distance = data.substring(index1 + 1, data.length()); 
  
  iAngle = int(angle); // Change string angle to int
  iDistance = int(distance); // Change string distance to int
}

void drawRadar()
{
  pushMatrix();
  translate(width / 2, height - height * 0.074); 
  noFill();
  strokeWeight(2);
  stroke(98, 245, 31);
  
  arc(0, 0, (width - width * 0.0625), (width - width * 0.0625), PI, TWO_PI);
  arc(0, 0, (width - width * 0.27), (width - width * 0.27), PI, TWO_PI);
  arc(0, 0, (width - width * 0.479), (width - width * 0.479), PI, TWO_PI);
  arc(0, 0, (width - width * 0.687), (width - width * 0.687), PI, TWO_PI);
  
  line(-width / 2, 0, width / 2, 0);
  line(0, 0, (-width / 2) * cos(radians(30)), (-width / 2) * sin(radians(30)));
  line(0, 0, (-width / 2) * cos(radians(60)), (-width / 2) * sin(radians(60)));
  line(0, 0, (-width/2) * cos(radians(90)), (-width / 2) * sin(radians(90)));
  line(0, 0, (-width/2) * cos(radians(120)), (-width / 2) * sin(radians(120)));
  line(0, 0, (-width/2) * cos(radians(150)), (-width / 2) * sin(radians(150)));
  line((-width / 2) * cos(radians(30)), 0, width / 2, 0);
  popMatrix();
}

void drawObject()
{
  pushMatrix();
  translate(width / 2, height - height * 0.074); 
  strokeWeight(8);
  stroke(255, 10, 10); 
  pixsDistance = iDistance * ((height - height * 0.1666) * 0.025); 
  
  if (iDistance < distanceLimit) { // Distance range limit
    line(pixsDistance * cos(radians(iAngle)), -pixsDistance * sin(radians(iAngle)), (width - width * 0.505) * cos(radians(iAngle)), -(width - width * 0.505) * sin(radians(iAngle)));
  }
  popMatrix();
}

void drawLine()
{
  pushMatrix();
  strokeWeight(8);
  stroke(30, 250, 60);
  translate(width / 2, height - height * 0.074); 
  line(0, 0, (height - height * 0.12) * cos(radians(iAngle)), -(height - height * 0.12) * sin(radians(iAngle))); 
  popMatrix();
}

void drawText()
{ 
  pushMatrix();
  fill(0, 0, 0);
  noStroke();
  rect(0, height - height * 0.0648, width, height);
  fill(98, 245, 31);
  textSize(15);
  text("10cm", width - width * 0.3854, height - height * 0.0833);
  text("20cm", width - width * 0.281, height - height * 0.0833);
  text("30cm", width - width * 0.177, height - height * 0.0833);
  text("40cm", width - width * 0.0729, height - height * 0.0833);
  textSize(30);
  text("Angle: " + iAngle + " °", width - width * 0.48, height - height * 0.0277);
  if (iDistance < distanceLimit) {
    text("Distance: " + iDistance + "cm", width - width * 0.3, height - height * 0.0277);
  }
  else {
    text("Distance:          ", width - width * 0.3, height - height * 0.0277);
  }
  textSize(25);
  fill(98, 245, 60);
  translate((width - width * 0.4994) + width / 2 * cos(radians(30)), (height - height * 0.0907) - width / 2 * sin(radians(30)));
  rotate(-radians(-60));
  text("30°", 0, 0);
  resetMatrix();
  translate((width - width * 0.503) + width / 2 * cos(radians(60)), (height - height * 0.0888) - width / 2 * sin(radians(60)));
  rotate(-radians(-30));
  text("60°", 0, 0);
  resetMatrix();
  translate((width - width * 0.507) + width / 2 * cos(radians(90)), (height - height * 0.0833) - width / 2 * sin(radians(90)));
  rotate(radians(0));
  text("90°", 0, 0);
  resetMatrix();
  translate(width - width * 0.513 + width / 2 * cos(radians(120)), (height - height * 0.07129) - width / 2 * sin(radians(120)));
  rotate(radians(-30));
  text("120°", 0, 0);
  resetMatrix();
  translate((width - width * 0.5104) + width / 2 * cos(radians(150)), (height - height * 0.0574) - width / 2 * sin(radians(150)));
  rotate(radians(-60));
  text("150°", 0, 0);
  popMatrix();
}

ArduinoRadarGP2Y0A21.ino

/*
  Project: Arduino Radar
  Software: Arduino IDE 1.8.7
  Item used:
  - Maker UNO https://www.cytron.io/p-maker-uno
  - Analog Distance Sensor (10-80cm) https://www.cytron.io/p-sn-gp2y0a21
  - TowerPro MG946R Metal Gear Servo https://www.cytron.io/c-84-dc-motor/c-475-servo-motor/p-mg946r
*/

#include <Servo.h>
Servo myServo;

const int SENSOR_PIN = A0;
const int SERVO_PIN = 9;

long duration;
int distance;

void setup()
{
  pinMode(SENSOR_PIN, INPUT);
  Serial.begin(9600);
  myServo.attach(SERVO_PIN);
}

void loop()
{
  for (int i = 15; i <= 165; i++) {
    myServo.write(i);
    delay(30);
    distance = measureDistance();

    Serial.print(i);
    Serial.print(",");
    Serial.print(distance);
    Serial.print(".");
  }

  for (int i = 165; i > 15; i--) {
    myServo.write(i);
    delay(30);

    distance = measureDistance();

    Serial.print(i);
    Serial.print(",");
    Serial.print(distance);
    Serial.print(".");
  }
}

int measureDistance()
{
  long totalCm = 0;
  int cm = 0;
  for (int i = 0; i < 50; i++) {
    int adc = analogRead(SENSOR_PIN);
    cm = (6762 / (adc - 9)) - 4;
    totalCm += cm;
  }
  cm = totalCm / 50;
  if (cm > 80) {
    cm = 80;
  }
  
  return cm;
}