/* Photocell simple testing sketch.
Connect one end of the photocell to 5V, the other end to Analog 0.
Then connect one end of a 10K resistor from Analog 0 to ground
For more information see http://learn.adafruit.com/photocells */
int photocellPin = 0; // the cell and 10K pulldown are connected to a0
int photocellReading; // the analog reading from the analog resistor divider
void setup(void) {
// We'll send debugging information via the Serial monitor
Serial.begin(9600);
}
void loop(void) {
photocellReading = analogRead(photocellPin);
Serial.print("Analog reading = ");
Serial.print(photocellReading); // the raw analog reading
// We'll have a few threshholds, qualitatively determined
if (photocellReading < 10) {
Serial.println(" - Dark");
} else if (photocellReading < 200) {
Serial.println(" - Dim");
} else if (photocellReading < 500) {
Serial.println(" - Light");
} else if (photocellReading < 800) {
Serial.println(" - Bright");
} else {
Serial.println(" - Very bright");
}
delay(1000);
}
Using the above code, I placed a photocell on a breadboard with 1 leg connected to 5v and the other leg connected to analog pin 0 as well as connecting the same leg to ground using a 10k pulldown resistor.
Analog reading = 774 - Bright Analog reading = 754 - Bright Analog reading = 768 - Bright Analog reading = 876 - Very bright Analog reading = 960 - Very bright Analog reading = 943 - Very bright Analog reading = 906 - Very bright Analog reading = 941 - Very bright Analog reading = 694 - Bright Analog reading = 677 - Bright Analog reading = 673 - Bright Analog reading = 677 - Bright Analog reading = 669 ... Analog reading = 62 - Dim Analog reading = 63 - Dim Analog reading = 62 - Dim Analog reading = 62 - Dim Analog reading = 63 - Dim Analog reading = 63 - Dim Analog reading = 62 - Dim
With the room light on, the reading was Bright, and when I shone a torch light into the photocell it registered as Very bright. When I switched the room light off it registered as Dim, and when I cupped both hands over the photocell it registered as Dark.