LDRs or Light Dependent Resistors are...
LDRs or Light Dependent Resistors are very useful especially in light/dark sensor circuits. Normally the resistance of an LDR is very high, sometimes as high as 1000 000 ohms, but when they are illuminated with light resistance drops dramatically.
Warning: Last items in stock!
int portaLed = 10; //Port is being used to connect the LED
int portaLDR = A5; //Analog port used by LDR
pinMode(portaLed, OUTPUT); //Sets Led door as output
int estado = analogRead(portaLDR); Read the value provided by LDR
// If the value read from the analog port is greater than
// 800, acende o LED
// Set the value below according to your circuit
if (estado > 800)
else //Otherwise, the LED goes out