4-Way Photosensitive Sensor

Light Dependent Resistor (LDR) Module Description and Working Principle

As widely known, voice-controlled lights in hallways often include an additional sensor known as a photoresistor or Light Dependent Resistor (LDR). The LDR, typically made of cadmium sulfide (CdS), is a variable resistor that changes its resistance based on the intensity of incident light. When the incident light increases, the resistance decreases, and when the incident light decreases, the resistance increases. LDRs are commonly used for light measurement, control, and conversion (i.e., converting light changes into electrical signals). They are widely used in various light control circuits, such as controlling and adjusting lights and light switches.

The LDR module is most sensitive to ambient light and is generally used to detect the brightness of the surrounding environment, triggering microcontrollers or relay modules.

Schematic Diagram