LDR 5mm Light Dependent Resistor (LDR)

Wiring Connections:

• The LDR has two terminals (leads):
  • Terminal 1: Connects to one end of a power source or analog input.
  • Terminal 2: Connects to a resistor or ground, depending on the configuration of your circuit.
• Basic Circuit: The LDR is often used in a voltage divider circuit. One terminal is connected to a fixed resistor and then grounded, and the other is connected to a power source ( 5V or 3.3V). The voltage between the LDR and the resistor will vary depending on the light intensity.

Power:

• Operating Voltage: Can operate effectively between 3.3V and 5V, making it suitable for use with various microcontrollers and development boards like Arduino, ESP32, and Raspberry Pi.
• Current: Since it’s a passive component, the current flowing through the LDR depends on the applied voltage and resistance value under different light conditions.

Input and Output:

• Input: The LDR receives input in the form of light intensity. The more light it receives, the lower its resistance becomes.
• Output: The output is the change in resistance. This change can be measured as a varying voltage in an analog circuit, which can then be interpreted by a microcontroller or used to control other components.

Physical Characteristics:

• Diameter: The LDR has a 5mm round sensing area.
• Leads: Two metal leads approximately 25mm long for easy connection to a breadboard or circuit.
• Material: The sensing element is made from Cadmium Sulfide (CdS), which changes resistance based on light exposure.
• Shape: Circular top with a wavy pattern that acts as the light sensor.

Technical Specifications:

• Dark Resistance: ≥1MΩ when exposed to darkness or minimal light.
• Light Resistance: As low as 10kΩ to 20kΩ when exposed to bright light.
• Response Time:
  • Rise Time: 20ms (the time it takes to react to an increase in light).
  • Decay Time: 30ms (the time it takes to react to a decrease in light).
• Temperature Coefficient: The LDR’s performance slightly varies with changes in ambient temperature, but it can operate from -30°C to +70°C without issues.

Additional Features:

• Non-Polarized: The LDR is a non-polarized component, meaning it can be connected in either direction in a circuit.
• Durable: Designed to last for years in most environments as long as it is not exposed to extreme moisture or physical damage.
• Simple Analog Output: When used with an analog pin on a microcontroller like an Arduino, it provides a simple and continuous voltage that changes with the light intensity.

How to Use:

• Connecting to an Arduino:
  • Set up the LDR in a voltage divider circuit by connecting one terminal of the LDR to 5V and the other to ground through a fixed resistor (10kΩ).
  • The point between the LDR and the resistor should be connected to an analog input on the Arduino to read the varying voltage levels.
• Basic Code for Arduino:

int LDRPin = A0; // Connect LDR to analog pin A0

int LDRValue = 0; // Variable to store the value

void setup() {

Serial.begin(9600); // Start serial communication

}

void loop() {

LDRValue = analogRead(LDRPin); // Read the value from the LDR

Serial.println(LDRValue); // Print the value to the serial monitor

delay(500); // Delay for stability

}

• Applications:
  • Automatic Lighting: Use the LDR to turn lights on when it gets dark and off when it’s bright.
  • Light Meters: Create a basic light meter that measures the intensity of the surrounding light.
  • Security Systems: Use the LDR as part of a motion or intruder detection system, where a sudden change in light can trigger an alarm.
  • Solar Trackers: Employ multiple LDRs in a solar panel project to ensure the panels always face the brightest light source.

Applications:

• Automatic Light Control: Used in outdoor lighting or streetlights to turn on during the night and off during the day.
• Light-Sensitive Alarms: Trigger alarms or notifications when there’s a sudden change in ambient light, useful for security systems.
• Solar Energy Systems: Helps in tracking the sun for optimal panel positioning by detecting the brightest light source.

The 5mm LDR Light Dependent Resistor is a practical and cost-effective solution for detecting and measuring light intensity in various environments. With a simple design and easy-to-implement setup, it’s perfect for beginners and professionals alike. Whether you’re automating a lighting system or experimenting with light-based sensors, the LDR provides an intuitive way to interact with the physical world through light detection.