liquid_crystal_i2c_distance_measurement.ino

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);

const int trigPin = 9;
const int echoPin = 10;
const int ledPin = 3;  // PWM pin for LED

// Adjust these values to match your desired range
const float MIN_DISTANCE = 5.0;   // Distance in cm when LED should be brightest
const float MAX_DISTANCE = 10.0;  // Distance in cm when LED should be dimmest
const float MAX_DISTANCE_DISPLAY = 20.0;  // Maximum distance for display purposes

float duration, distance;

void setup() {
  // Ultrasonic sensor init
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);

  // LCD init
  lcd.init();
  lcd.backlight();
  lcd.clear();
  
  lcd.setCursor(0, 0);
  lcd.print("Dist:");
}

void loop() {
  // Get distance reading
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  duration = pulseIn(echoPin, HIGH);
  distance = (duration * 0.0343) / 2;

  // Constrain distance for display
  float displayDistance = constrain(distance, 0, MAX_DISTANCE_DISPLAY);

  // Update numerical display
  lcd.setCursor(5, 0);
  lcd.print(distance, 1);
  lcd.print("cm    ");

  // Update bar graph
  updateBarGraph(displayDistance);

  // Update LED brightness
  updateLED(distance);

  // Print to Serial for debugging
  Serial.print(distance);
  Serial.print("cm, LED: ");
  Serial.println(calculateLEDBrightness(distance));
  
  delay(100);
}

void updateBarGraph(float value) {
  int numBlocks = map(value, 0, MAX_DISTANCE_DISPLAY, 0, 16);
  lcd.setCursor(0, 1);
  for (int i = 0; i < 16; i++) {
    if (i < numBlocks) {
      lcd.write(255);
    } else {
      lcd.print(" ");
    }
  }
}

int calculateLEDBrightness(float distance) {
  if (distance <= MIN_DISTANCE) return 255;  // Full brightness
  if (distance >= MAX_DISTANCE) return 0;    // Off
  
  // Map distance to LED brightness (inverse relationship)
  return map(
    constrain(distance, MIN_DISTANCE, MAX_DISTANCE) * 100,  // Multiply by 100 for better precision
    MIN_DISTANCE * 100,
    MAX_DISTANCE * 100,
    255,  // Maximum brightness
    0     // Minimum brightness
  );
}

void updateLED(float distance) {
  int brightness = calculateLEDBrightness(distance);
  analogWrite(ledPin, brightness);
}