PHOTODIODE

CIRCUIT

We connect two wires to the Arduino board. The first goes to ground from the negative leg of the photodiode. The second goes from our analog pin to the negative leg of the photodiode.  Also we connect our analog pin  through a pull-down resistor (here 4,7 KOhms) to the positive leg of the photodiode

By increasing and decreasing the lightning, we change the current that is prodused by the photodiode. This changes the voltage in the circuite, giving us a different analog input. When the light very dim there are 0 volts going to the pin, and we read 0. When the light is very bright there are 5 volts going to the pin and we read 1023. In between, analogRead() returns a number between 0 and 1023 that is proportional to the amount of voltage being applied to the pin.

Code
(The following code will print in the serial the light measured by the Sensor)

int sensorPin = A0;
int sensorValue = 0;

void setup(void) {
   Serial.begin(9600);
   pinMode(sensorPin, INPUT); 
}
 
void loop(void) {
   sensorValue = analogRead(sensorPin);
   Serial.println(sensorValue);
}

Selects the input pin for the photodiode
Variable to store the value coming from the sensor


Opens the serial gate
Declares the sensorPin as an INPUT



Reads the value from the sensor
Prints in the serial the value the sensor measured