Monitoring and Warning System Using Arduino & Ultrasonic Sensor

1#include <LiquidCrystal.h>   // Library for controlling the LCD
2
3// LCD pin connections
4int RS = 12;
5int E  = 10;
6int D4 = 9;
7int D5 = 8;
8int D6 = 7;
9int D7 = 6;
10
11// LED pin definitions
12int redLed    = 4;
13int greenLed  = 5;
14int orangeLed = 11;
15
16// Control variables
17int BuzzTimes = 10;     // Number of warning blinks
18int redBlink  = 10;     // (Declared but not currently used)
19
20// Create LCD object (parallel mode)
21LiquidCrystal lcd(RS, E, D4, D5, D6, D7);
22
23// Ultrasonic sensor pins
24int trigPin = 2;
25int echoPin = 3;
26
27// Variables for distance measurement
28long  TravelTime;        // Time taken for echo to return (µs)
29float TravelDistance;    // Calculated distance (cm)
30int   TravelTarget;      // (Declared but not currently used)
31
32void setup() {
33  Serial.begin(9600);        // Start serial communication
34  lcd.begin(16, 4);          // Initialize 16x4 LCD
35
36  // Set LED pins as outputs
37  pinMode(redLed, OUTPUT);
38  pinMode(greenLed, OUTPUT);
39  pinMode(orangeLed, OUTPUT);
40
41  // Set ultrasonic sensor pin modes
42  pinMode(trigPin, OUTPUT);
43  pinMode(echoPin, INPUT);
44
45  // Display startup message
46  lcd.setCursor(0, 0);
47  lcd.print("System Ready");
48  delay(1000);
49  lcd.clear();
50}
51
52void loop() {
53
54  // Display distance label on LCD (value updated later)
55  lcd.setCursor(0, 0);
56  lcd.print("Distance:");
57  lcd.print(TravelDistance);
58  lcd.print(" cm");
59
60  // Trigger ultrasonic pulse
61  digitalWrite(trigPin, LOW);
62  delayMicroseconds(10);
63  digitalWrite(trigPin, HIGH);
64  delayMicroseconds(10);
65  digitalWrite(trigPin, LOW);
66
67  // Measure echo pulse duration
68  TravelTime = pulseIn(echoPin, HIGH);
69
70  delay(500);  // Measurement interval delay
71
72  // Convert time to distance in cm
73  TravelDistance = (TravelTime * 0.034) / 2;
74
75  // Clear previous warning/status messages
76  lcd.clear();
77
78  // CAUTION ZONE (10–20 cm)
79  if (TravelDistance >= 10 && TravelDistance <= 20) {
80
81    digitalWrite(redLed, LOW);
82    digitalWrite(greenLed, LOW);
83    digitalWrite(orangeLed, HIGH);
84
85    lcd.setCursor(4, 2);
86    lcd.print("BE CAUTIOUS");
87    lcd.setCursor(4, 3);
88    lcd.print("YOU ARE CLOSE");
89  }
90
91  // DANGER ZONE (< 10 cm)
92  else if (TravelDistance < 10) {
93
94    int B = 0;
95    while (B < BuzzTimes) {
96
97      // Blink red LED as warning
98      digitalWrite(redLed, HIGH);
99      delay(50);
100      digitalWrite(redLed, LOW);
101      digitalWrite(greenLed, LOW);
102      delay(50);
103
104      // Re-display distance and warning
105      lcd.setCursor(0, 0);
106      lcd.print("Distance:");
107      lcd.print(TravelDistance);
108      lcd.print(" cm");
109
110      lcd.setCursor(4, 2);
111      lcd.print("WARNING, TOO CLOSE");
112
113      B = B + 1;   // Increment blink counter
114    }
115  }
116
117  // SAFE ZONE (> 20 cm)
118  else {
119    digitalWrite(greenLed, HIGH);
120    digitalWrite(redLed, LOW);
121    digitalWrite(orangeLed, LOW);
122
123    lcd.setCursor(4, 2);
124    lcd.print("SAFE ZONE");
125  }
126
127  // Print distance to Serial Monitor (debugging)
128  Serial.print("Distance: ");
129  Serial.print(TravelTime);   // NOTE: This prints time, not distance
130  Serial.println(" cm");
131}