(Reference) Photoresistors

Photoresistors

Wiring

• Requires analog input pin
  • A0
  • A1
  • A2
  • A5
  • A3 (SDA or D0)
  • A4 (SCL or D1)

Operation

• As light level varies, Photon 2 will measure a voltage change on analog input (due to voltage divider)
• Since this is an analog input, we use analog to digital conversion to read input
• Voltage on pin will varies 0v to 3.v, and Photon 2 will read 0 to 4095

Code

const int PIN_PHOTORESISTOR = A1;

void setup() {
    Serial.begin(9600);
    pinMode(PIN_PHOTORESISTOR, INPUT);
}

void loop() {
	// read analog value (ADC); range 0-4095
    int lightReading = analogRead(PIN_PHOTORESISTOR);

	// if you want to know the actual voltage 
	int voltage = (float) lightReading / 4095 * 3.3;
}

Credit

• Sparkfun
• Sparkfun
• Images created with Fritzing