This is low cost LDR (Light Dependent Resistor). Basically it is a light sensitive resistor, the resistance will decrease when the surface is expose to light. It is widely used to detect Day or Night, example in automatic car porch light. It is nonlinear sensor, when it is not expose to light, the resistance can goes up to 500K ohm, but from our testing, in normal room condition, it will be 10 to 20K ohm when the light is not illuminate. When light is activated, the resistance drops to 1K or less.

Features:

• Use as a resistor, just two terminals, no polarity
• Small size LDR
• Resistance decreases when it is exposed to higher light intensity
•Normally use with another Resistor as a voltage divider