5mm LDR (Light Dependent Resistor)

A compact 5mm photoresistor that changes resistance based on ambient light intensity - essential for light-sensing circuits, automatic lighting systems, and Arduino/microcontroller projects. Available at The Engineer Store, Bengaluru with fast shipping and full technical support.

Specifications

Key Features

• Analog Light Sensing: Resistance decreases smoothly as light intensity increases - provides a simple analog signal proportional to brightness.
• Wide Resistance Range: From ~10 kOhm in bright light to over 1 MOhm in complete darkness, offering excellent sensitivity across lighting conditions.
• No Polarity: A passive, non-polarized component - connect either lead to either side of your circuit without worrying about orientation.
• Compact 5mm Form Factor: The most popular LDR size, fitting easily into breadboards, PCBs, and enclosures.
• Breadboard & PCB Friendly: Standard through-hole leads plug directly into solderless breadboards or solder neatly onto perfboards and custom PCBs.
• Low Power Consumption: Draws minimal current, making it ideal for battery-powered and low-power IoT applications.
• Fast Response Time: ~20-30 ms response allows detection of rapid light changes for dynamic applications.
• Works with All Microcontrollers: Pairs perfectly with Arduino, ESP32, Raspberry Pi Pico, STM32, and any platform with an analog input or ADC.

How It Works

An LDR is made from cadmium sulfide (CdS), a semiconductor material whose electrical resistance changes with light exposure. When photons strike the CdS surface, they free electrons, increasing conductivity and lowering resistance. In darkness, fewer electrons are free, so resistance climbs to over 1 MOhm. By placing the LDR in a voltage divider circuit with a fixed resistor, you can convert this resistance change into a measurable voltage that a microcontroller's analog-to-digital converter (ADC) can read - giving you a numerical light level in your code.

Basic Wiring Guide

• Voltage Divider (most common): Connect one LDR lead to VCC (3.3V or 5V), the other lead to a 10 kOhm fixed resistor going to GND. Read the voltage at the junction (middle node) using an analog input pin on your microcontroller.
• With Arduino: LDR -> A0 analog pin via voltage divider. Use analogRead(A0) to get values from 0 (dark) to 1023 (bright light).
• With ESP32: Same voltage divider to any ADC-capable GPIO. Use 3.3V supply for accurate 12-bit ADC readings (0-4095).
• Standalone Trigger: Pair with a transistor or comparator (e.g., LM393) to create a simple light-activated switch without a microcontroller.
• Tip: Adjust the fixed resistor value (1 kOhm-100 kOhm) to shift the sensitivity range to match your target lighting conditions.

Project Ideas

• Automatic Street Light: Build a circuit that turns on an LED or relay-controlled lamp at dusk and off at dawn - a classic embedded systems project.
• Smart Plant Monitor: Measure sunlight exposure for indoor plants and alert via buzzer or app when light levels are too low.
• Line-Following Robot: Use multiple LDRs to detect contrast between a dark line and a light surface for basic robot navigation.
• Light-Level Data Logger: Record ambient brightness over 24 hours using Arduino + SD card module for environmental studies.
• Security Alarm: Detect

Frequently Asked Questions

Buy 5mm LDR (Light Dependent Resistor) Online in India

Purchase the 5mm LDR (Light Dependent Resistor) online at The Engineer Store - India's most trusted electronics components store. We deliver across all major cities including Bengaluru, Mumbai, Delhi, Chennai, Hyderabad, Pune, Kolkata, Ahmedabad, Jaipur, and Surat. Get the best price on 5mm LDR (Light Dependent Resistor) with fast 1-5 day shipping from our Bengaluru warehouse. All products are 100% authentic, sourced from authorized distributors with 7-day warranty on manufacturing defects.

Looking to buy 5mm LDR (Light Dependent Resistor) at the best price in India? The Engineer Store offers competitive pricing, bulk discounts for orders of 10+ units, and dedicated technical support via email and WhatsApp. Whether you are a hobbyist, student, or professional engineer, we have everything you need for your electronics projects.