Light Dependent Resistor (Photoresistor/LDR)
makerA light dependent resistor (LDR) is a resistor whose resistance varies significantly with light intensity.
expanded
An LDR, or photoresistor, is an electronic component that exploits the properties of semiconductors to allow its resistance to change relative to the intensity of light incident on its surface. In practical applications, LDRs are essential for systems requiring light sensitivity, such as automatic lighting controls and alarm systems.
examples
An LDR used in a street lighting circuit that activates lights when ambient light falls below 10 lux.
Commonly used in outdoor lighting systems to automatically turn on lighting at dusk and turn off at dawn based on the surrounding brightness.
An LDR is employed in a simple alarm circuit, where resistance drops below 5 kΩ when more than 200 lux of light is detected.
Applied in security systems to detect changes in light levels, indicating movement or intrusion when light levels change unexpectedly.