The DIYKIT DIY-259 20mm 20528 LDR (Light Dependent Resistor) is a high-sensitivity, large-format photoresistor designed for precise ambient light detection in DIY electronics, robotics, and industrial automation. Featuring a generous 20mm active diameter, this cadmium sulfide (CdS) photoconductive cell captures more incident light than standard smaller sensors, resulting in a more pronounced resistance change and higher signal-to-noise ratio. Whether you are building an automated street light controller, a solar panel tracking system, or an optical barrier, the 20528 LDR provides a robust, analog response to changing environmental light levels. Its simple two-pin interface makes it exceptionally easy to integrate into both microcontroller-based systems and pure analog circuits.
The DIYKIT DIY-259 20mm 20528 LDR (Light Dependent Resistor) is a high-sensitivity, large-format photoresistor designed for precise ambient light detection in DIY electronics, robotics, and industrial automation. Featuring a generous 20mm active diameter, this cadmium sulfide (CdS) photoconductive cell captures more incident light than standard smaller sensors, resulting in a more pronounced resistance change and higher signal-to-noise ratio. Whether you are building an automated street light controller, a solar panel tracking system, or an optical barrier, the 20528 LDR provides a robust, analog response to changing environmental light levels. Its simple two-pin interface makes it exceptionally easy to integrate into both microcontroller-based systems and pure analog circuits.
At the core of the 20528 LDR is a semiconductor track made of cadmium sulfide. When light photons strike the surface of the semiconductor, valence electrons are excited into the conduction band, significantly increasing the material's electrical conductivity. This process causes the sensor's resistance to drop dramatically. In complete darkness, the material has very few free charge carriers, resulting in a high dark resistance state. The spectral response of this CdS cell is optimized to closely match the sensitivity of the human eye, peaking in the green-to-yellow visible light spectrum. Because the resistance change is continuous and non-linear, it is highly recommended to calibrate your software or analog comparator circuit to the specific ambient lighting conditions of your environment. Please note that exact electrical characteristics, such as precise rise and fall response times, can vary by module revision; always check the datasheet for exact curves.
The versatility of the 20mm 20528 LDR makes it suitable for a wide range of applications. In consumer electronics, it is commonly used in automatic night lights, clock backlights, and electronic toys to trigger actions when ambient light drops below a certain threshold. In robotics and renewable energy, it serves as the primary sensing element in solar trackers, allowing dual-axis or single-axis motorized mounts to align solar panels directly with the sun. It is also highly effective in security systems as a simple beam-break detector, in industrial environments for basic contrast sensing, and in educational science kits to teach students the fundamentals of optoelectronics and analog sensor integration.
Integrating the 20528 LDR into your microcontroller project is straightforward. The most common configuration is a voltage divider circuit. Connect one lead of the LDR to your system's VCC (typically 3.3V or 5V). Connect the second lead to an analog input pin (such as A0 on an Arduino) and also to a fixed pull-down resistor (typically 10k Ohms) connected to Ground (GND). As light levels increase, the LDR's resistance drops, causing the voltage at the analog pin to rise toward VCC. In darkness, the LDR's resistance increases, pulling the analog pin voltage down toward GND. This analog voltage can then be read using an Analog-to-Digital Converter (ADC) and processed in your code to trigger relays, LEDs, or motors. For digital threshold switching without a microcontroller, the LDR can be paired with an LM393 comparator integrated circuit or a simple NPN transistor switch.
1 x DIYKIT 20mm 20528 LDR Light Dependent Resistor
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