Turn LED On and Off Through LDR

LDR

An LDR (Light Dependent Resistor) is a component that has a (variable) resistance that changes with the light intensity that falls upon it. This allows them to be used in light sensing circuits. A photoresistor is made of a high resistance semiconductor.

Hardware Required

Arduino Board

LED
220 ohm resistor
LDR
10k ohms resistor

Circuit Diagram

Code

int ldr=A0;//Set A0(Analog Input) for LDR.
int value=0;
void setup() {
Serial.begin(9600);
pinMode(3,OUTPUT);
}

void loop() {
value=analogRead(ldr);//Reads the Value of LDR(light).
Serial.println("LDR value is :");//Prints the value of LDR to Serial Monitor.
Serial.println(value);
if(value<300)
  {
    digitalWrite(3,HIGH);//Makes the LED glow in Dark.
  }
  else
  {
    digitalWrite(3,LOW);//Turns the LED OFF in Light.
  }
}

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