Light intensity using a photoresistor with ADC Using Arduino

The objective of this project is to measure light intensity using a photoresistor and process the sensor data with Analog-to-Digital Conversion (ADC) via analogRead(). The data is read through an analog input pin on the Arduino and converted into a digital value, which can be processed and displayed.

Fundamental Programming Concepts

• Analog-to-Digital Conversion (ADC): Converts the analog signal from the photoresistor into a digital value (0–1023) using analogRead().
• Variable Scope: Understand the scope of variables (global and local) used to store the light intensity readings.
• Analog Sensors: Measure real-world values, such as light intensity, and convert them into signals that can be read by Arduino.

Requirement Components

To complete this light intensity sensor with ADC using Arduino project, you will need:

• Arduino Uno Board
• Photoresistor (Light Dependent Resistor – LDR)
• 10kΩ Resistor (for voltage divider circuit)
• Breadboard
• Jumper Wires
• USB Cable (for connecting Arduino to your computer)

Circuit Diagram

Circuit Connection

How to Connect the Circuit

1. Photoresistor (LDR): Connect one side of the photoresistor to 5V and the other side to A0 on the Arduino.
2. 10kΩ Resistor: Connect one end of the 10kΩ resistor between A0 and GND to create a voltage divider circuit.
3. Power: Ensure that the Arduino is powered via the USB cable, with 5V and GND connected to the breadboard.

Explanation of Circuit

• The photoresistor (LDR) changes its resistance based on the light intensity: lower resistance with higher light and higher resistance with lower light.
• The voltage divider circuit converts the change in resistance into a voltage signal, which is read by A0 on the Arduino using analogRead().
• The analog signal (0-5V) is converted to a digital value between 0 and 1023, representing the light intensity.

Programming Section for light intensity using a photoresistor

Arduino Syntax

Arduino Code:

Here is the Arduino code to measure light intensity using a photoresistor and display the value on the Serial Monitor:

const int ldrPin = A0;  // Define the pin connected to the photoresistor
int lightIntensity = 0; // Variable to store the light intensity reading
void setup() {
  Serial.begin(9600);  // Initialize serial communication at 9600 baud rate
}
void loop() {
  // Read the analog value from the LDR
  lightIntensity = analogRead(ldrPin);
  // Print the light intensity to the Serial Monitor
  Serial.print("Light Intensity: ");
  Serial.println(lightIntensity);
  delay(500);  // Wait for 500 milliseconds before reading again
}

Steps to Upload Code:

1. Connect your Arduino to your computer using a USB cable.
2. Open the Arduino IDE and select the correct Board and Port.
3. Copy and paste the provided code into a new sketch.
4. Click the Upload button to transfer the code to your Arduino.
5. Open the Serial Monitor to observe the light intensity values as you vary the light falling on the photoresistor.

Check Output

Once the code is uploaded, the Serial Monitor will display real-time readings of the light intensity in the form of digital values ranging from 0 (dark) to 1023 (bright). These readings will update every 500 milliseconds.

Troubleshooting Tips

• Incorrect readings? Ensure that the photoresistor and resistor are connected correctly to form a proper voltage divider.
• Serial Monitor not showing output? Verify that the correct COM port is selected and that the baud rate in the Serial Monitor is set to 9600.
• No change in light intensity readings? Try varying the light levels manually by covering or shining light on the photoresistor to see the changes in readings.

Further Exploration

• Convert to Lux: Convert the raw analog readings into lux (a standard unit of light measurement) by calibrating the sensor with known light levels.
• Add an LCD Display: Instead of using the Serial Monitor, display the light intensity on an LCD display for real-time feedback.
• Multiple Sensors: Add more photoresistors to monitor light intensity in different areas, processing the data from multiple analog inputs.

Note

This project demonstrates how to measure light intensity using a photoresistor with Arduino. The use of analogRead() for Analog-to-Digital Conversion (ADC) and a basic understanding of variable scope will help beginners process sensor data for further use.

FAQ

Q1: How does analogRead() work in this project?
The analogRead() function reads the analog voltage (0-5V) from the photoresistor and converts it into a digital value between 0 and 1023.

Q2: What is a photoresistor, and how does it work?
A photoresistor (LDR) changes its resistance based on light levels: the resistance decreases in brighter light and increases in darkness.

Q3: Can I use this project to measure precise light levels?
Yes, but you’ll need to calibrate the photoresistor by converting the raw analog readings into lux using a mathematical formula.

Q4: Why is a voltage divider circuit needed?
The voltage divider circuit allows the photoresistor’s changing resistance to be converted into a voltage signal that can be read by the Arduino’s analog pin.

Q5: Can I use analogRead() for other sensors?
Yes, analogRead() can be used for any analog sensor, such as temperature sensors, potentiometers, or other light sensors.