LDR Sensor Module Medium 7mm

LDR Sensor (Light Dependent Resistor) – Medium 7 mm

The LDR Sensor (Light Dependent Resistor) is a passive electronic component whose resistance changes according to the intensity of light falling on its surface. The 7 mm medium-size LDR is widely used in light-sensing and automatic control applications due to its simple structure, low cost, and reliable performance.

Working Principle

An LDR works on the principle of photoconductivity. When light strikes the photosensitive surface, photons energize electrons in the semiconductor material, reducing resistance.

• Bright light → Low resistance

• Dark or low light → High resistance

This resistance variation is converted into a voltage signal using a voltage divider circuit, which can be read by microcontrollers.

Key Features

• Medium size 7 mm sensing area

• High sensitivity to visible light

• Fast response to light changes

• Low cost and easy to use

• No polarity (can be connected either way)

• Long operational life

Electrical Characteristics

• Type: Photoresistor (LDR)

• Diameter: 7 mm

• Resistance (Dark): ~1 MΩ or higher

• Resistance (Bright Light): ~5 kΩ – 20 kΩ

• Operating Voltage: Compatible with 3.3 V and 5 V systems

• Output: Analog (resistance-based)

Applications

• Automatic street light systems

• Light-activated switches

• Smart home automation

• Solar tracking systems

• Day/night detection circuits

• Alarm and security systems

• Arduino, Raspberry Pi, ESP32 projects

• Educational and laboratory experiments

Advantages

• Very simple interface

• Low power consumption

• Affordable and widely available

• Suitable for beginners and professionals

• Works well with analog input systems

Conclusion

The 7 mm LDR Sensor is a reliable and efficient solution for detecting ambient light levels. Its simplicity, flexibility, and compatibility with microcontrollers make it an essential component for automation, IoT, and educational projects where light detection is required.