Interfacing of LDR With Arduino

Light Sensor / Light intensity Measurement

Description:

1. A photoresistor or light-dependent resistor (LDR) or photocell is a light-controlled variable resistor. The resistance of a photoresistor decreases with increasing incident light intensity; in other words, it exhibits photoconductivity.

Components:
1. Arduino Board
2. LDR

Connections:

Connect the photoresistor one leg to pin 0, and pin to +5V
Connect a resistor (around 10k is a good value, higher
values gives higher readings) from pin 0 to GND.

Code:

/*

---------------------------------------------------

           PhotoR     10K
 +5    o---/\/\/--.--/\/\/---o GND
                  |
 Pin 0 o-----------

----------------------------------------------------

*/

int lightPin = 0;  //define a pin for Photo resistor
int ledPin=11;     //define a pin for LED

void setup()
{
    Serial.begin(9600);  //Begin serial communcation
    pinMode( ledPin, OUTPUT );
}

void loop()
{
    Serial.println(analogRead(lightPin)); //Write the value of the photoresistor to the serial monitor.
    analogWrite(ledPin, analogRead(lightPin)/4);  //send the value to the ledPin. Depending on value of resistor 
                                                //you have  to divide the value. for example, 
                                                //with a 10k resistor divide the value by 2, for 100k resistor divide by 4.
   delay(10); //short delay for faster response to light.
}

Output:
    See output on terminal