eNotes: Mechatronics and Controls

13.11 LIGHT INTENSITY

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13.11.1 Light Dependant Resistors (LDR)

These devices change from high resistance (>Mohms) in the dark to low resistance (<Kohms) in bright light.

The change in resistance is non-linear, and occurs relatively slowly also.

A simple comparator circuit is shown below.

This sensor is relatively easy to design with.