Sonar — Ultrasonic Sensor HC-SR04

#define trigPin 3
#define echoPin 2

void setup() {
  Serial.begin(9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
}

void loop() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);          // 10 µs trigger pulse
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  long duration = pulseIn(echoPin, HIGH, 30000);  // timeout 30 ms ≈ 5 m
  float distance = duration * 0.0343 / 2;         // cm
  Serial.println(distance);
  delay(200);
}

import processing.serial.*;

Serial myPort;
float distance;

void setup() {
  size(600, 200);
  printArray(Serial.list());
  myPort = new Serial(this, Serial.list()[0], 9600);
  myPort.bufferUntil('\n');
}

void draw() {
  background(255);
  fill(0);
  textSize(24);
  text("Distance: " + nf(distance, 0, 2) + " cm", 50, 50);

  fill(100, 200, 255);                                    // horizontal bar
  rect(50, 100, map(constrain(distance, 0, 200), 0, 200, 0, width - 100), 30);
}

void serialEvent(Serial p) {
  String data = p.readStringUntil('\n');
  if (data != null) distance = float(trim(data));
}

#include <Servo.h>

Servo servo;
bool sweeping = false;
int angle = 0;
int step = 1;

void setup() {
  Serial.begin(9600);
  servo.attach(9);
}

void loop() {
  if (Serial.available()) {
    String command = Serial.readStringUntil('\n');
    command.trim();
    sweeping = (command == "1");      // "1" = START, anything else = STOP
  }

  if (sweeping) {                     // one small step per loop()
    angle += step;
    if (angle >= 180 || angle <= 0) step = -step;
    servo.write(angle);
    delay(10);
  }
}

import processing.serial.*;

Serial myPort;
boolean isSweeping = false;

void setup() {
  size(400, 200);
  myPort = new Serial(this, Serial.list()[0], 9600);
  textAlign(CENTER, CENTER);
}

void draw() {
  background(240);
  textSize(16);
  fill(0);
  text("Servo Control", width/2, 30);
  drawButton("START", 100, 100, isSweeping);
  drawButton("STOP", 250, 100, !isSweeping);
}

void drawButton(String label, int x, int y, boolean active) {
  fill(active ? color(0, 200, 0) : color(180));
  rect(x, y, 100, 40, 7);
  fill(0);
  text(label, x + 50, y + 20);
}

void mousePressed() {
  if (mouseX > 100 && mouseX < 200 && mouseY > 100 && mouseY < 140) {
    myPort.write("1\n");
    isSweeping = true;
  } else if (mouseX > 250 && mouseX < 350 && mouseY > 100 && mouseY < 140) {
    myPort.write("0\n");
    isSweeping = false;
  }
}

#include <Servo.h>

const int TRIG_PIN = 6;
const int ECHO_PIN = 7;
const int SERVO_PIN = 9;
const int DISTANCE_THRESHOLD = 50;   // centimetres

Servo servo;
float duration_us, distance_cm;

void setup() {
  Serial.begin(9600);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  servo.attach(SERVO_PIN);
  servo.write(0);
}

void loop() {
  digitalWrite(TRIG_PIN, HIGH);      // 10 µs pulse
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  duration_us = pulseIn(ECHO_PIN, HIGH);
  distance_cm = 0.017 * duration_us; // = 0.0343 / 2

  if (distance_cm < DISTANCE_THRESHOLD) servo.write(90);
  else                                  servo.write(0);

  Serial.print("distance: ");
  Serial.print(distance_cm);
  Serial.println(" cm");
  delay(500);
}

#include <Servo.h>

Servo myServo;
#define trigPin 9
#define echoPin 10

float measure() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  long duration = pulseIn(echoPin, HIGH, 30000);
  return duration * 0.0343 / 2;
}

void setup() {
  Serial.begin(9600);
  myServo.attach(6);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
}

void loop() {
  for (int angle = 0; angle <= 180; angle += 2) {
    myServo.write(angle);
    delay(50);
    Serial.print(angle);
    Serial.print(",");
    Serial.println(measure());
  }
  for (int angle = 180; angle >= 0; angle -= 2) {   // sweep back too
    myServo.write(angle);
    delay(50);
    Serial.print(angle);
    Serial.print(",");
    Serial.println(measure());
  }
}

import processing.serial.*;

Serial myPort;
int angle;
float distance;

void setup() {
  size(600, 600);
  myPort = new Serial(this, Serial.list()[0], 9600);
  background(0);
}

void draw() {
  if (myPort.available() > 0) {
    String data = myPort.readStringUntil('\n');
    if (data != null && data.contains(",")) {
      String[] parts = split(trim(data), ",");
      if (parts.length == 2) {
        angle = int(parts[0]);
        distance = float(parts[1]);
        float r = map(distance, 0, 100, 0, 250);
        float x = width/2 + r * cos(radians(angle));
        float y = height  - r * sin(radians(angle));
        stroke(0, 255, 0);
        fill(0, 255, 0);
        ellipse(x, y, 5, 5);
      }
    }
  }
}