PR5528 Photoresistor (LDR) – 5mm Light-Dependent Resistor for Light Sensing

The PR5528 is a high-sensitivity light-dependent resistor (LDR), also known as a photoresistor or photocell, designed to detect ambient light intensity in electronic circuits. Its resistance decreases as the light falling on its sensing surface increases, and rises again when the light level falls. This inverse relationship makes the PR5528 a simple and reliable building block for automatic lighting control, light-activated alarms, and any project where a circuit must respond to changes in illumination.

The device is based on the internal photoelectric effect in a semiconductor material, which gives it stable and repeatable performance over time. A practical advantage is that it is polarity-independent: the two terminals can be connected either way, simplifying circuit design and allowing direct integration into DC-powered sensing or switching circuits without worrying about electrode orientation. The PR5528 is supplied in a standard 5mm diameter package and is sensitive to visible light in the 400–700nm range, with a spectral peak around 540nm. In complete darkness its resistance is in the megaohm range (typically above 1MΩ), while under sufficient light it can fall to approximately 1Ω. The sensor operates across a wide temperature range of approximately -25°C to +70°C and is suitable for both indoor and sheltered outdoor environments.

The PR5528 is typically used in a voltage divider with a fixed resistor, and the resulting voltage is read by a microcontroller’s analog-to-digital converter. This makes it compatible with Arduino, ESP32, Raspberry Pi, and other development platforms. Common applications include automatic street lighting that switches on at dusk, security systems that detect light changes, night lights, stairway illumination, solar garden lights, and photography light meters. The component is a bare two-terminal photoresistor; it does not include an onboard comparator, potentiometer, or digital output. A separate module board with those features would be required if a digital (high/low) output is needed.