The Use of Light Sensor

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The Microduino Light Sensor uses a photosensitive resistor to detect the amount of ambient light present. The sensor is effectively a resistor that changes in value as the light intensity surrounding it changes. The sensor will output a voltage value that corresponds to the amount of light detected by the sensor.

Couple the sensor to an LED and you have a smart light that illuminates a room as it gets dark!


  • Electrical Specifications
    • Analog Output Device
    • Analog Output: 0-1023 (with Microduino Core modules)
  • Technical Specifications
    • Bright Resistance(up to 100Lux): 8-20kΩ
    • Dark Resistance: 1MΩ
    • Sensitivity:
      • Given light intensity of 10Lux and 100Lux, with corresponding resistances (R10 and R100), the sensitivity factor is 0.8. This gives you a sense of how resistance changes with a given quantitative change in the amount of light present.
  • Dimensions
    • Board: 20mm x 10mm
    • Connector: 4-Pin interface, 1.27mm-pitch
  • Connection Interface
    • Pins: Signal, VCC (power), GND (ground) and NC (not connected)
    • NOTE: Sensor must be connected to analog capable ports (i.e. A0-A7)



Module Number Function
mCookie-CoreUSB 1 Core board
mCookie-Hub 1 Sensor pin board
Microduino-Light 1 Photosensitive sensor
  • Other Hardware Equipment
    • One USB cable


  • Setup 1:Connect Microduino-Light and the A0 analog port of the Hub.
  • Setup 2:Connect the CoreUSB, Hub and Light to the computer with a USB cable.

Experiment: Detect analog Brightness Value

  • Open Arduino IDE and copy the following code into IDE.
#define  sensorPin  A0

int state;

void setup()
  pinMode(sensorPin, INPUT);
void loop()
  state = analogRead(sensorPin);
  • Select the right board from Tools→Serial Port in Arduino IDE and download the program.
  • After the download, you can open the serial monitor. The displayed value reflects the current light intensity.
  • Result

The stronger the light is, the greater the output value becomes. Therefore, you can build some projects controlled by light intensity change.

Program Debugging

  • “#define sensorPin A0”defines sensor interface.
  • Use“analogRead(sensorPin);”function to read the output analog value of the sensor and therefore, to judge light intensity change.


  • Couple the Light Sensor with an LED and you can automate the intensity of the LED based on how bright or dark it is in a room.