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Light Sensor (LDR)

Components Needed:

  • 1x ESP32
  • 1x USB Programming Cable
  • 1x Double Width Breadboard
  • 1x 10kΩ Resistor (Brown-Black-Orange)
  • 1x Photoresistor (LDR)
  • 3x Male-Male Jumper Wires

Connections:

Using the breadboard, connect the LDR to the ESP32 as follows:

  • LDR Leg 1 (any leg of the LDR) → ESP32 D34
  • LDR Leg 1 → 10kΩ Resistor → GND
  • LDR Leg 2 (the other leg) → 3V3

Code:

Upload the following code onto the ESP32:

// Define the LDR pin
int ldrPin = 34;  // You can change this to any analog-capable GPIO pin
int ldrValue = 0;

void setup() {
  // Start serial communication
  Serial.begin(115200);
}

void loop() {
  // Read the LDR value
  ldrValue = analogRead(ldrPin);

  // Print the LDR value to the Serial Monitor
  Serial.println(ldrValue);

  // Delay to prevent flooding the monitor
  delay(500);
}

Explanation:

  • The LDR (Light Dependent Resistor) is connected to GPIO34 to measure light levels.
  • In the setup(), serial communication is started at a baud rate of 115200, which is the default for ESP32.
  • In the loop(), the code reads the LDR value using analogRead(ldrPin) and stores it in ldrValue.
  • It then prints the LDR value to the Serial Monitor.
  • The delay(500) adds a 0.5-second pause between readings to avoid flooding the monitor with data.

Results:

You will see a continuous stream of numbers in the Serial Monitor, representing the light levels detected by the LDR. Higher numbers mean brighter light, and lower numbers mean dimmer light. The readings update every 0.5 seconds, giving you real-time feedback on the light intensity around the sensor.

Try for yourself:

  1. Create a light-controlled buzzer using the LDR and an active buzzer. When the light level drops below a certain threshold (for example, when it gets dark), the buzzer should turn on.
  2. Create a day-night sensor using an LDR and an LED to automatically switch the LED on in low light conditions and off during the day.