Lesson 7- Read a Sensor(Photocell)

 

A photoresistor changes its resistance depending on how much light is falling on it. In the dark, its resistance can be 100K ohm or more; in light, it can decrease to 5K or less.

We will be reading the voltage on pin A0, using the analogRead function.

// the setup routine runs once when you press reset:

void setup() {

// initialize serial communication at 9600 bits per second:

Serial.begin(9600);

}

// the loop routine runs over and over again forever:

void loop() {

// read the input on analog pin 0:

int sensorValue = analogRead(A0);

// Convert the analog reading (which goes from 0 - 1023) to a voltage (0 - 5V):

float voltage = sensorValue * (5.0 / 1023.0);

// print out the value you read:

Serial.println(voltage);

}

Use the Serial Monitor to see the output voltage. Make sure the Baud Rate is the same as in the sketch(typically 9600).