Ultrasonic Distance System with Real-Time Data Visualization

This smart parking assistant utilizes an ultrasonic sensor and a moving average filter to provide stable distance tracking via an I2C LCD, LED traffic lights, and a reactive buzzer. Optimized with non-blocking code for zero-lag responsiveness and MATLAB integration, the project demonstrates essential principles of signal processing and efficient timing for embedded systems.

Dec 29, 2025

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GPL3+

Devices & Components

16x2 LCD display with I²C interface

40 colored male-female jumper wires

Arduino Uno Rev3

Ultrasonic Sensor - HC-SR04

5V Mini Traffic Light Red Yellow Green 5mm LED Display Module

Battery 5V (PowerBank)

Piezo buzzer

Software & Tools

Arduino IDE

Project description

Code

Arduino IDE Sketch

cpp

You can just copy paste it :)

1// // 1. PIN DEFINITIONS & LIBRARIES
2#include <Wire.h> 
3#include <LiquidCrystal_I2C.h>
4
5// Initialize the LCD at address 0x27 with 16 columns and 2 rows
6// Note: If 0x27 doesn't work, try 0x3F
7LiquidCrystal_I2C lcd(0x27, 16, 2);
8
9// Ultrasonic sensor pins
10const int trigPin = 9;
11const int echoPin = 10;
12
13// Traffic light LED pins
14const int ampelR = 8;  // Red LED
15const int ampelY = 12; // Yellow LED
16const int ampelG = 13; // Green LED
17
18// Buzzer pin
19const int buz = 7;
20
21// // 2. VARIABLES FOR DISTANCE & MOVING AVERAGE
22long duration = 0;
23int distance = 0;
24
25const int numReadings = 5;
26int readings[numReadings]; 
27int readIndex = 0;         
28long total = 0;            
29int averageDistance = 0;   
30
31// // 3. TIME CONTROL VARIABLES (Global)
32unsigned long previousMillis = 0;   // For buzzer timing
33unsigned long lastLCDUpdate = 0;    // For LCD refresh timing
34const int lcdInterval = 200;        // Update LCD every 200ms
35bool buzzerState = LOW;           
36
37// // 4. SETUP
38void setup() {
39  Serial.begin(9600);
40
41  // LCD Initialization
42  lcd.init();
43  lcd.backlight();
44  lcd.setCursor(0, 0);
45  lcd.print("System Ready");
46  delay(1000);
47  lcd.clear();
48
49  pinMode(trigPin, OUTPUT);
50  pinMode(echoPin, INPUT);
51  pinMode(ampelR, OUTPUT);
52  pinMode(ampelY, OUTPUT);
53  pinMode(ampelG, OUTPUT);
54  pinMode(buz, OUTPUT);
55
56  for (int i = 0; i < numReadings; i++) {
57    readings[i] = 0;
58  }
59}
60
61// // 5. MAIN LOOP
62void loop() {
63  unsigned long currentMillis = millis();
64
65  // // 6. SENSOR MEASUREMENT
66  digitalWrite(trigPin, LOW);
67  delayMicroseconds(2);
68  digitalWrite(trigPin, HIGH);
69  delayMicroseconds(10);
70  digitalWrite(trigPin, LOW);
71
72  duration = pulseIn(echoPin, HIGH, 25000); 
73  distance = (duration * 0.034) / 2;
74
75  if (distance <= 0) {
76    distance = 200;
77  }
78
79  // // 7. CALCULATE MOVING AVERAGE
80  total = total - readings[readIndex];
81  readings[readIndex] = distance;
82  total = total + readings[readIndex];
83  readIndex = readIndex + 1;
84
85  if (readIndex >= numReadings) {
86    readIndex = 0;
87  }
88  averageDistance = total / numReadings;
89
90  // // 8. TRAFFIC LIGHT LOGIC
91  if (averageDistance <= 20 && averageDistance > 0) {
92    digitalWrite(ampelR, HIGH); digitalWrite(ampelY, LOW); digitalWrite(ampelG, LOW);
93  } 
94  else if (averageDistance > 20 && averageDistance <= 50) {
95    digitalWrite(ampelR, LOW); digitalWrite(ampelY, HIGH); digitalWrite(ampelG, LOW);
96  } 
97  else {
98    digitalWrite(ampelR, LOW); digitalWrite(ampelY, LOW); digitalWrite(ampelG, HIGH);
99  }
100
101  // // 9. BUZZER LOGIC
102  int pauseInterval = 0;
103  const int beepDuration = 10; 
104
105  if (averageDistance <= 5 && averageDistance > 0) pauseInterval = 1; 
106  else if (averageDistance <= 10) pauseInterval = 100;
107  else if (averageDistance <= 15) pauseInterval = 300;
108  else if (averageDistance <= 30) pauseInterval = 700;
109  else if (averageDistance <= 50) pauseInterval = 1200;
110  else pauseInterval = 0;
111
112  if (pauseInterval == 1) {
113    digitalWrite(buz, HIGH);
114  } 
115  else if (pauseInterval == 0) {
116    digitalWrite(buz, LOW);
117    buzzerState = LOW;
118  } 
119  else {
120    if (buzzerState == HIGH) {
121      if (currentMillis - previousMillis >= (unsigned long)beepDuration) {
122        digitalWrite(buz, LOW);
123        buzzerState = LOW;
124        previousMillis = currentMillis;
125      }
126    } 
127    else {
128      if (currentMillis - previousMillis >= (unsigned long)pauseInterval) {
129        digitalWrite(buz, HIGH);
130        buzzerState = HIGH;
131        previousMillis = currentMillis;
132      }
133    }
134  }
135
136  // // 10. LCD DISPLAY LOGIC
137  // We update the LCD only every 200ms to avoid flickering
138  if (currentMillis - lastLCDUpdate >= lcdInterval) {
139    lastLCDUpdate = currentMillis;
140    
141    lcd.setCursor(0, 0);
142    lcd.print("Distance:       "); // Spaces clear old digits
143    lcd.setCursor(10, 0);
144    lcd.print(averageDistance);
145    lcd.print("cm");
146    
147    lcd.setCursor(0, 1);
148    if(averageDistance <= 20) lcd.print("Status: STOP!   ");
149    else if(averageDistance <= 50) lcd.print("Status: Caution ");
150    else lcd.print("Status: Clear   ");
151  }
152
153  // // 11. OUTPUT FOR MATLAB
154  Serial.println(averageDistance);
155
156  delay(30);
157}

// // 1. PIN DEFINITIONS & LIBRARIES
#include <Wire.h> 
#include <LiquidCrystal_I2C.h>

// Initialize the LCD at address 0x27 with 16 columns and 2 rows
// Note: If 0x27 doesn't work, try 0x3F
LiquidCrystal_I2C lcd(0x27, 16, 2);

// Ultrasonic sensor pins
const int trigPin = 9;
const int echoPin = 10;

// Traffic light LED pins
const int ampelR = 8;  // Red LED
const int ampelY = 12; // Yellow LED
const int ampelG = 13; // Green LED

// Buzzer pin
const int buz = 7;

// // 2. VARIABLES FOR DISTANCE & MOVING AVERAGE
long duration = 0;
int distance = 0;

const int numReadings = 5;
int readings[numReadings]; 
int readIndex = 0;         
long total = 0;            
int averageDistance = 0;   

// // 3. TIME CONTROL VARIABLES (Global)
unsigned long previousMillis = 0;   // For buzzer timing
unsigned long lastLCDUpdate = 0;    // For LCD refresh timing
const int lcdInterval = 200;        // Update LCD every 200ms
bool buzzerState = LOW;           

// // 4. SETUP
void setup() {
  Serial.begin(9600);

  // LCD Initialization
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("System Ready");
  delay(1000);
  lcd.clear();

  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(ampelR, OUTPUT);
  pinMode(ampelY, OUTPUT);
  pinMode(ampelG, OUTPUT);
  pinMode(buz, OUTPUT);

  for (int i = 0; i < numReadings; i++) {
    readings[i] = 0;
  }
}

// // 5. MAIN LOOP
void loop() {
  unsigned long currentMillis = millis();

  // // 6. SENSOR MEASUREMENT
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  duration = pulseIn(echoPin, HIGH, 25000); 
  distance = (duration * 0.034) / 2;

  if (distance <= 0) {
    distance = 200;
  }

  // // 7. CALCULATE MOVING AVERAGE
  total = total - readings[readIndex];
  readings[readIndex] = distance;
  total = total + readings[readIndex];
  readIndex = readIndex + 1;

  if (readIndex >= numReadings) {
    readIndex = 0;
  }
  averageDistance = total / numReadings;

  // // 8. TRAFFIC LIGHT LOGIC
  if (averageDistance <= 20 && averageDistance > 0) {
    digitalWrite(ampelR, HIGH); digitalWrite(ampelY, LOW); digitalWrite(ampelG, LOW);
  } 
  else if (averageDistance > 20 && averageDistance <= 50) {
    digitalWrite(ampelR, LOW); digitalWrite(ampelY, HIGH); digitalWrite(ampelG, LOW);
  } 
  else {
    digitalWrite(ampelR, LOW); digitalWrite(ampelY, LOW); digitalWrite(ampelG, HIGH);
  }

  // // 9. BUZZER LOGIC
  int pauseInterval = 0;
  const int beepDuration = 10; 

  if (averageDistance <= 5 && averageDistance > 0) pauseInterval = 1; 
  else if (averageDistance <= 10) pauseInterval = 100;
  else if (averageDistance <= 15) pauseInterval = 300;
  else if (averageDistance <= 30) pauseInterval = 700;
  else if (averageDistance <= 50) pauseInterval = 1200;
  else pauseInterval = 0;

  if (pauseInterval == 1) {
    digitalWrite(buz, HIGH);
  } 
  else if (pauseInterval == 0) {
    digitalWrite(buz, LOW);
    buzzerState = LOW;
  } 
  else {
    if (buzzerState == HIGH) {
      if (currentMillis - previousMillis >= (unsigned long)beepDuration) {
        digitalWrite(buz, LOW);
        buzzerState = LOW;
        previousMillis = currentMillis;
      }
    } 
    else {
      if (currentMillis - previousMillis >= (unsigned long)pauseInterval) {
        digitalWrite(buz, HIGH);
        buzzerState = HIGH;
        previousMillis = currentMillis;
      }
    }
  }

  // // 10. LCD DISPLAY LOGIC
  // We update the LCD only every 200ms to avoid flickering
  if (currentMillis - lastLCDUpdate >= lcdInterval) {
    lastLCDUpdate = currentMillis;
    
    lcd.setCursor(0, 0);
    lcd.print("Distance:       "); // Spaces clear old digits
    lcd.setCursor(10, 0);
    lcd.print(averageDistance);
    lcd.print("cm");
    
    lcd.setCursor(0, 1);
    if(averageDistance <= 20) lcd.print("Status: STOP!   ");
    else if(averageDistance <= 50) lcd.print("Status: Caution ");
    else lcd.print("Status: Clear   ");
  }

  // // 11. OUTPUT FOR MATLAB
  Serial.println(averageDistance);

  delay(30);
}

MATLAB Visualisation

matlab

Generates a live plot of the distance in cm

1% Script for real-time visualization of HC-SR04 data
2% Important: Close the Arduino IDE Serial Monitor before running this script!
3
4% Serial port configuration
5clear;
6s = serialport("COM3", 9600);
7configureTerminator(s, "LF"); % Set the terminator to Line Feed
8
9% Initialize data arrays
10time = [];
11distance = [];
12
13% Create figure and plot
14figure;
15h = plot(NaN, NaN, 'LineWidth', 2); % Create a placeholder plot handle
16xlabel('Time (s)');
17ylabel('Distance (cm)');
18title('Real-time Distance Data from HC-SR04');
19grid on;
20
21% Start timer for real-time visualization
22tic;
23
24% Read data in a loop
25while isvalid(s)
26    % Try to read a line from the serial port
27    try
28        dataString = readline(s);
29        value = str2double(dataString);
30    catch
31        % Ignore read errors and try again in the next iteration
32        continue;
33    end
34    
35    % Check if conversion was successful and value is within range
36    if ~isnan(value) && value > 0 && value < 400
37        % Append new data points
38        time = [time, toc];
39        distance = [distance, value];
40        
41        % Update the plot data
42        set(h, 'XData', time, 'YData', distance);
43        
44        % Adjust the X-axis dynamically
45        current_time = toc;
46        if current_time > 10 % Show only the last 10 seconds
47            xlim([current_time - 10, current_time]);
48        else
49            xlim([0, 10]);
50        end
51        
52        % Adjust Y-axis range (0-300 cm)
53        ylim([0, 300]); 
54        
55        % Force immediate drawing
56        drawnow limitrate;
57    end
58end
59
60% Close the serial port when the loop is terminated
61delete(s);
62clear s;
63disp('Serial connection closed.');

% Script for real-time visualization of HC-SR04 data
% Important: Close the Arduino IDE Serial Monitor before running this script!

% Serial port configuration
clear;
s = serialport("COM3", 9600);
configureTerminator(s, "LF"); % Set the terminator to Line Feed

% Initialize data arrays
time = [];
distance = [];

% Create figure and plot
figure;
h = plot(NaN, NaN, 'LineWidth', 2); % Create a placeholder plot handle
xlabel('Time (s)');
ylabel('Distance (cm)');
title('Real-time Distance Data from HC-SR04');
grid on;

% Start timer for real-time visualization
tic;

% Read data in a loop
while isvalid(s)
    % Try to read a line from the serial port
    try
        dataString = readline(s);
        value = str2double(dataString);
    catch
        % Ignore read errors and try again in the next iteration
        continue;
    end
    
    % Check if conversion was successful and value is within range
    if ~isnan(value) && value > 0 && value < 400
        % Append new data points
        time = [time, toc];
        distance = [distance, value];
        
        % Update the plot data
        set(h, 'XData', time, 'YData', distance);
        
        % Adjust the X-axis dynamically
        current_time = toc;
        if current_time > 10 % Show only the last 10 seconds
            xlim([current_time - 10, current_time]);
        else
            xlim([0, 10]);
        end
        
        % Adjust Y-axis range (0-300 cm)
        ylim([0, 300]); 
        
        % Force immediate drawing
        drawnow limitrate;
    end
end

% Close the serial port when the loop is terminated
delete(s);
clear s;
disp('Serial connection closed.');

Downloadable files

MATLAB Visualisation

File for the Visualisation

visualHCSR04.m

Arduino Sketch

Code for HC-SR04, traffic light, buzzer, LCD, ...

sketchHCSR04_with_trafficlight.ino

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falzinger

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