LDR Light Sensor Module 4-Pin

An LDR — light dependent resistor — drops its resistance as ambient light intensity increases. In darkness, resistance is high. In bright light, resistance falls sharply. The LDR Light Sensor Module 4-Pin uses that resistance change to drive an LM393 comparator IC, which compares the LDR voltage against an adjustable reference set by the onboard potentiometer. When light drops below that threshold, the digital output pin flips from LOW to HIGH — giving a clean switching signal that any microcontroller digital input pin can read without ADC hardware.

The ldr module provides both DO and AO on the same four pins. The digital output from the LM393 comparator suits threshold-based triggers — turn a relay on when it gets dark, send an interrupt when a beam breaks. The analog output from the AO pin gives raw LDR voltage proportional to light intensity, which suits ldr sensor module builds that need graduated light level readings rather than simple on-off detection. Operating voltage runs from 3.3V to 5V DC, so the light sensor module connects directly to Arduino 5V systems and ESP32 3.3V systems without level shifting.

The LDR sensor 4 pin interface — VCC, GND, DO, AO — keeps wiring simple for beginners. The ldr sensor price at this specification level makes it one of the most cost-effective ambient light detection options for student and hobbyist builds. Sensitivity adjusts through the onboard potentiometer by turning it until the status LED on the board switches at the desired ambient light level — no code change required. Available at StemVolt, this sensor module for enthusiast and students building light-reactive automation and embedded sensing projects.

Related Products:

• Read More Sensor Module Blog
• Checkout The LDR Sensor Module 3 pin

Features:

• LM393 comparator delivers clean digital switching without microcontroller-side signal processing
• Dual DO and AO output allows threshold detection and graduated light reading simultaneously
• Onboard potentiometer adjusts detection sensitivity without modifying sketch or code
• 3.3V to 5V DC operation suits Arduino Uno, ESP32, NodeMCU, and STM32 builds directly
• Status LED indicator confirms detection threshold crossing visually during calibration

Technical Specifications:

 Applications:

• Use LDR Light Sensor Module 4-Pin to trigger street light relays automatically at dusk and dawn
• LDR sensor module detects beam interruption in conveyor object counting and industrial sorting builds
• Light sensor module controls greenhouse grow light switching based on natural daylight level changes
• Students use LDR sensor 4 pin in Arduino line-following robots for surface reflectance detection builds

Package Includes:

• 1 x LDR Light Sensor Module 4-Pin