Description
The DIY Photoresistor Light Sensing Kit is an entry-level light detection module built around a cadmium sulfide (CdS) light-dependent resistor (LDR). The LDR’s resistance decreases as light intensity increases—typically from several megohms in darkness to a few kilohms in bright light—allowing the module to convert ambient light levels into an electrical signal . This makes it suitable for automatic lighting control, light-seeking robots, brightness monitoring, and educational electronics projects.
The 3-wire design connects to any microcontroller with an analog input (or digital input, depending on module type). If your module is the analog voltage-divider type (KY-018 style), the signal pin outputs a voltage that varies continuously with light intensity, readable via analogRead() . If your module is the LM393 comparator type, the digital output (DO) switches between HIGH and LOW when light crosses an adjustable threshold set by the onboard potentiometer . The module operates from 3.3V to 5V, making it compatible with Arduino, ESP32, and most hobbyist platforms.
Note: This is a relative light sensor, not a calibrated lux meter. Absolute light intensity measurement requires calibration against a reference instrument .
Features
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CdS Photoresistor Sensing Element: Resistance varies inversely with light intensity, from megohms in darkness to kilohms in bright light .
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Wide Operating Voltage (3.3V–5V): Compatible with Arduino, ESP32, Raspberry Pi (with ADC), and other 3.3V/5V systems .
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Compact 3-Wire Interface: Simple VCC, GND, and signal connection for quick prototyping .
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Adjustable Sensitivity (LM393 variants): Onboard potentiometer allows threshold tuning for light/dark detection .
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Fast Response Time: Typical rise/fall times of 20–30ms for GL55-series photoresistors .
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Wide Operating Temperature: Functions from -30°C to +70°C .
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Mounting Holes: Fixed bolt holes for secure installation in enclosures and robot chassis .
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Low Cost and Simple: Ideal for beginners, STEM education, and proof-of-concept projects .
Technical Specifications
| Parameter | Specification |
|---|---|
| Sensor Element | CdS Photoresistor (LDR), GL55 series typical |
| Operating Voltage | 3.3V – 5V DC |
| Output Type | Analog voltage (voltage-divider type) OR Digital HIGH/LOW (LM393 type) — verify your module |
| Light Resistance (10 Lux) | 5–10 kΩ (GL5516 typical) |
| Dark Resistance | 0.5 MΩ typical (GL5516); up to 1 MΩ for other types |
| Spectral Peak | 540 nm (visible light) |
| Response Time | ~20–30 ms |
| Operating Temperature | -30°C to +70°C |
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