error: 'lcd' was not declared

Projects Programming
1

#include <LiquidCrystal.h> //Include the library of the LCD
#define LDRpin A0 // pin where we connected the LDR and the resistor

int LDRValue = 0; // result of reading the analog pin

void setup() {

pinMode (4, OUTPUT); //Pin connected to the LED
Serial.begin(9600); // sets serial port for communication

LiquidCrystal lcd(7, 8, 9, 10, 11 , 12); // initialize the library with the numbers of the interface pins
lcd.begin(16, 2); // set up the LCD's number of columns and rows:
lcd.setCursor(0,0);
lcd.write("LIGHT: "); // Print a message to the LCD.
}

void loop() {
LDRValue = analogRead(LDRpin); // read the value from the LDR

if(LDRValue >= 200){
digitalWrite (4, HIGH); // Turn OFF LED
Serial.print ("High Density Light -> ");
lcd.setCursor(0,1);
lcd.print (LDRValue);
}
else if (LDRValue >= 70) {
digitalWrite (4, HIGH); // Turn OFF LED
Serial.print ("Normal Density Light -> ");
lcd.setCursor(0,1);
lcd.print (LDRValue);
}
else if ( LDRValue < 70){
digitalWrite (4, LOW); // Turn ON LED
Serial.print ("Low Density Light -> ");
lcd.setCursor(0,1);
lcd.print (LDRValue);
}

Serial.println(LDRValue); // print the value to the serial port
delay(1000); // wait a little
}

2

Look closely at the examples which came with your liquid cyrstal library, and notice where this line appears in the example sketches.

LiquidCrystal lcd(7, 8, 9, 10, 11 , 12);

Is yours in the same place?

3

Thanks for pointing out this sill mistake .

4

In the C/C++ language you can only use what you have declared BEFORE you use it!

So if you want to use "lcd" in the setup function," lcd " must be declared before the setup function.

Put the lcd declaration ABOVE the setup() function:
LiquidCrystal lcd(7, 8, 9, 10, 11 , 12); // initialize the library with the numbers of the interface pins