Parking Sensor Distance Detector

1/*
2  ============================================================
3  Parking Sensor / Distance Alert
4  CS 220: Computer Architecture & Embedded Systems
5  Capstone Project
6  ============================================================
7  COMPONENTS:
8    - Arduino Uno
9    - HC-SR04 Ultrasonic Sensor
10    - LCD 16x2 Display
11    - Potentiometer (LCD contrast)
12    - Green, Yellow, Red LEDs
13    - Piezo Buzzer
14    - 470Ω resistors (LEDs), 220Ω resistor (LCD backlight)
15
16  PIN MAPPING:
17    Ultrasonic → TRIG=7, ECHO=6
18    LCD        → RS=12, EN=11, D4=5, D5=4, D6=3, D7=2
19    LEDs       → Green=8, Yellow=9, Red=10
20    Buzzer     → Pin 13
21  ============================================================
22*/
23
24#include <LiquidCrystal.h>
25
26// ---------- LCD Setup ----------
27LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
28
29// ---------- Ultrasonic Sensor Pins ----------
30const int TRIG_PIN = 7;
31const int ECHO_PIN = 6;
32
33// ---------- LED Pins ----------
34const int GREEN_LED  = 8;
35const int YELLOW_LED = 9;
36const int RED_LED    = 10;
37
38// ---------- Buzzer Pin ----------
39const int BUZZER_PIN = 13;
40
41// ---------- Distance Thresholds (cm) ----------
42const int SAFE_DIST    = 40;   // Green  → far away, all clear
43const int CAUTION_DIST = 20;   // Yellow → getting close
44const int DANGER_DIST  = 10;   // Red    → very close, beep fast
45
46// ---------- Timing for beeping ----------
47unsigned long lastBeepTime = 0;
48int beepInterval = 500;        // ms between beeps (gets shorter as closer)
49
50// ============================================================
51// SETUP
52// ============================================================
53void setup() {
54  // LED pins as OUTPUT
55  pinMode(GREEN_LED,  OUTPUT);
56  pinMode(YELLOW_LED, OUTPUT);
57  pinMode(RED_LED,    OUTPUT);
58
59  // Buzzer as OUTPUT
60  pinMode(BUZZER_PIN, OUTPUT);
61
62  // Ultrasonic pins
63  pinMode(TRIG_PIN, OUTPUT);
64  pinMode(ECHO_PIN, INPUT);
65
66  // Start LCD
67  lcd.begin(16, 2);
68
69  // Welcome message
70  lcd.setCursor(0, 0);
71  lcd.print(" PARKING SENSOR ");
72  lcd.setCursor(0, 1);
73  lcd.print("  Initializing  ");
74  delay(2000);
75  lcd.clear();
76}
77
78// ============================================================
79// MAIN LOOP
80// ============================================================
81void loop() {
82  // Get distance reading
83  long distance = getDistance();
84
85  // Update LCD display
86  updateDisplay(distance);
87
88  // Update LEDs based on distance
89  updateLEDs(distance);
90
91  // Update buzzer based on distance
92  updateBuzzer(distance);
93
94  delay(100);  // Small delay between readings for stability
95}
96
97// ============================================================
98// FUNCTIONS
99// ============================================================
100
101// --- Measure distance using HC-SR04 ---
102long getDistance() {
103  // Send a 10 microsecond pulse to TRIG
104  digitalWrite(TRIG_PIN, LOW);
105  delayMicroseconds(2);
106  digitalWrite(TRIG_PIN, HIGH);
107  delayMicroseconds(10);
108  digitalWrite(TRIG_PIN, LOW);
109
110  // Read the ECHO pulse duration
111  long duration = pulseIn(ECHO_PIN, HIGH);
112
113  // Convert duration to distance in cm
114  // Speed of sound = 343 m/s = 0.0343 cm/µs
115  // Divide by 2 because pulse travels to object AND back
116  long distance = duration * 0.0343 / 2;
117
118  // Cap at 200cm for display purposes
119  if (distance > 200) distance = 200;
120  if (distance < 0)   distance = 0;
121
122  return distance;
123}
124
125// --- Update the LCD with current distance and status ---
126void updateDisplay(long distance) {
127  // Row 1: Distance reading
128  lcd.setCursor(0, 0);
129  lcd.print("Dist: ");
130  lcd.print(distance);
131  lcd.print(" cm    ");   // Extra spaces clear old characters
132
133  // Row 2: Status message
134  lcd.setCursor(0, 1);
135  if (distance > SAFE_DIST) {
136    lcd.print("  ALL CLEAR!    ");
137  } else if (distance > CAUTION_DIST) {
138    lcd.print("  SLOW DOWN...  ");
139  } else if (distance > DANGER_DIST) {
140    lcd.print("  CAUTION!!!    ");
141  } else {
142    lcd.print("   ** STOP! **  ");
143  }
144}
145
146// --- Update LEDs based on distance ---
147void updateLEDs(long distance) {
148  if (distance > SAFE_DIST) {
149    // Far away — green only
150    digitalWrite(GREEN_LED,  HIGH);
151    digitalWrite(YELLOW_LED, LOW);
152    digitalWrite(RED_LED,    LOW);
153  } else if (distance > CAUTION_DIST) {
154    // Getting close — yellow only
155    digitalWrite(GREEN_LED,  LOW);
156    digitalWrite(YELLOW_LED, HIGH);
157    digitalWrite(RED_LED,    LOW);
158  } else if (distance > DANGER_DIST) {
159    // Close — yellow + red
160    digitalWrite(GREEN_LED,  LOW);
161    digitalWrite(YELLOW_LED, HIGH);
162    digitalWrite(RED_LED,    HIGH);
163  } else {
164    // Very close — red only, flashing
165    digitalWrite(GREEN_LED,  LOW);
166    digitalWrite(YELLOW_LED, LOW);
167    digitalWrite(RED_LED,    HIGH);
168  }
169}
170
171// --- Update buzzer beep rate based on distance ---
172void updateBuzzer(long distance) {
173  // No beep when safe distance
174  if (distance > SAFE_DIST) {
175    noTone(BUZZER_PIN);
176    return;
177  }
178
179  // Beep interval gets shorter as object gets closer
180  if (distance > CAUTION_DIST) {
181    beepInterval = 600;        // Slow beep
182  } else if (distance > DANGER_DIST) {
183    beepInterval = 250;        // Fast beep
184  } else {
185    beepInterval = 80;         // Very fast beep (almost solid tone)
186  }
187
188  // Non-blocking beep using millis()
189  unsigned long currentTime = millis();
190  if (currentTime - lastBeepTime >= beepInterval) {
191    lastBeepTime = currentTime;
192    tone(BUZZER_PIN, 1000, 50);  // 1000Hz tone, 50ms duration
193  }
194}