Light Dependent Resistor Module with Arduino

Sense light with your Arduino and this module

Written By: Cherie Tan

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Light-dependent resistors, also known as photo-resistors, are sensors that allow the detection of light. They are not only useful but are small and inexpensive. In this guide, you will learn to use a light-dependent resistor module with the Arduino. We will use a Little Bird Uno R3 board, a mini breadboard, some jumper wires, and the module. You will learn to hook it up to the Arduino board, and measure the relative brightness of the environment.

Step 1   The Light Dependent Resistor Module

  • Let's take a closer look at the light-dependent resistor module as well as the buzzer module. The light-dependent resistor module has four pins: 3.3V : While 'VCC' stands for Voltage Common Collector, we'll connect the VCC pin to 3.3V on the micro:bit GND: In electronics, we define a point in a circuit to be a kind of zero volts or 0V reference point, on which to base all other voltage measurements. This point is called ground or GND. Note: Voltage is the difference in potential between two points. As it is difficult to talk about voltage without a reference point, we need another point to compare it to. DO: Digital Output AO: Analog Output

Step 2   Connect LDR module to breadboard

  • Connect the light dependent resistor onto the breadboard.

Step 3   Connect + to VCC

  • Plug one end of a jumper wire to the breadboard as shown.
  • Connect the other end to the light dependent resistor module.

Step 4   Connect GND to GND

  • Connect a black jumper wire from GND of the module to GND on the Little Bird Uno R3

Step 5   Connect AO to A0

  • Next, connect the analog output pin (AO) of the module to A0 pin on the Little Bird Uno R3

Step 6   Code for Light dependent resistor module

void setup() {
  Serial.begin(9600); //initialise serial monitor


void loop() {
  unsigned int lightVal;
  int lightVal=analogRead(A0);  //assign value of LDR sensor to a temporary variable
  Serial.println(lightVal);     //display output on serial monitor
  • Upload this code to your Little Bird Uno R3
  • This program will read the analog value from the module. The resistance of a light dependent resistor varies by how much light is falling on it. Around bright light, this value will be different to being in complete darkness. Cover the module with a hand and watch what happens to the values shown in the serial monitor! Then expose the module to sunlight and watch the value change again.
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