LDR (Light Dependent Resistor) Basics

This page describes LDR (Light Dependent Resistor) basics and lists LDR manufacturers.

Figure: LDR Symbol

As shown in the figure, the LDR’s resistance is sensitive to the presence of light. The resistance of the LDR varies with the intensity of light. The higher the intensity of light, the lower the resistance. Because of this, it’s also known as a photo resistor or a light-activated resistor (LAR).

The resistance range of an LDR typically spans from 5 Ohms to 0.75 MOhm. There are two main types of Light Dependent Resistors: Intrinsic and Extrinsic.

• The dark resistance of an LDR can be as high as 0.75 MOhm.
• LDRs are commonly used in optocouplers.
• Common materials used in their construction are Cadmium Sulfide (CdS) and Selenium (Se).

LDR (Light Dependent Resistor) Manufacturers

Here are some well-known LDR manufacturers:

• EXCELITAS TECH
• ADVANCED PHOTONIX
• LPRS
• Cosmic Devices
• RS Components