How to Build an IoT Light Detector with ESP32

The ESP32 is a powerful microcontroller that offers a wide range of applications in the realm of Internet of Things (IoT) and sensor-based projects. One such application is utilizing the ESP32 in conjunction with a Light Dependent Resistor (LDR) to detect changes in light intensity. This combination allows you to create a simple and cost-effective light sensing system, which can be applied in various scenarios such as automated lighting control, security systems, and environmental monitoring. In this article, we will guide you through the process of setting up an ESP32 with an LDR to detect changes in light intensity.

Understanding the Light Dependent Resistor (LDR) 

A Light Dependent Resistor (LDR), also known as a photoresistor or photocell, is a passive electronic component that exhibits a change in its resistance based on the amount of incident light falling on its surface. When exposed to light, the LDR’s resistance decreases, and conversely, when the light intensity decreases, the resistance increases. This property makes LDRs an ideal choice for light sensing applications.

Materials Required

Before we begin, gather the following materials:

• ESP32 development board
• Light Dependent Resistor (LDR)
• 10k ohm resistor (for voltage divider setup)
• Breadboard and jumper wires
• USB cable for programming and power supply
• Computer with Arduino IDE installed

Circuit Connection

Coding the ESP32

Now, let’s write the code to read the analog value from the LDR and interpret it as changes in light intensity. Follow these steps:

Open the Arduino IDE on your computer.

Go to “Tools” and set the board to “ESP32 Dev Module” and choose the appropriate COM port.

Copy and paste the following code into the Arduino IDE:

const int ldrPin = A0; // LDR connected to analog pin A0

void setup() {
  Serial.begin(9600); // Initialize serial communication for debugging
}

void loop() {
  int ldrValue = analogRead(ldrPin); // Read the analog value from the LDR
  Serial.print("LDR Value: ");
  Serial.println(ldrValue); // Print the LDR value for monitoring
  // Add your logic here to interpret the LDR value and take appropriate actions




  delay(500); // Wait for a short time before reading the LDR value again
}

Upload the code to your ESP32 board by clicking on the “Upload” button.

Interpreting the Data

Once the code is uploaded successfully, open the Serial Monitor in the Arduino IDE (Tools > Serial Monitor) to observe the LDR values. You will notice that the values change as you cover the LDR or expose it to different light sources.

To interpret the LDR values effectively, you can calibrate the system based on your specific application. For instance, you might set a threshold value below which the system assumes it’s dark and triggers an action like turning on a light or activating a security alarm.

Experiment and Calibration

To calibrate the system, experiment with different light conditions and note down the corresponding LDR values. This will help you determine the appropriate threshold value for your application. Depending on your use case, you may need to fine-tune the threshold and the corresponding actions the ESP32 should take.

Conclusion

Using an ESP32 with a Light Dependent Resistor (LDR) provides an efficient and versatile solution for detecting changes in light intensity. This simple setup can be integrated into a wide range of projects to enable light-sensitive functionality. By adjusting the threshold values and actions, you can customize the system to suit various scenarios, making it an essential component in your IoT toolkit. So, start experimenting with this setup and unleash its potential in your creative projects!