The resistance of 20mm GL20528 Light Sensitive Photoresistor LDR changes with the change in the ambient light exposed on the surface of the sensor. As the light on the sensor increases then the resistance across the two leads decreases. Light Dependent Resistor is a type of photocell which finds excellent use in light sensing device application, whether it is automatic outdoor light ON/OFF switch or indoor automatic light switch; moreover, the 12mm LDR or photoresistor sensor works best in both light and dark regions. The photo-resistor is a staple of electronics. If you need a way to sense the level of ambient light, then there is no easier way to do it without an LDR/photo-resistor. Two Cadmium Sulphide PhotoConductive Cells with spectral responses similar to that of the human eye. Cell resistance falls with increasing light intensity. Applications of this product include smoke detection, automatic lighting control, batch counting, and burglar alarm systems. Furthermore, some of the applications are given below.  Analog Applications: Camera exposure control Auto slide focus – dual cell Photocopy machines – the density of the toner Colorimetric test equipment Densitometer Electronics scales – dual cell Automatic gain control – modulated light source Automated rear view mirror Digital Applications: Automatic headlight dimmer Nightlight control Oil burner flame out Streetlight control Absence/presence (beam breaker) Position sensor Other applications: Annunciator Camera automatic photometry Electronic toy Industrial control Light control Light control lamp Photoelectric control Switch To know more about photo-resistor, click here. What is photo-resistor? Features: Coated with epoxy Good reliability High sensitivity Small volume Fast response Good spectrum characteristic Model: GL20528 ( GM20528 ) Size: 20mm Max. voltage: 500 VDC Max. power: 500 mW Spectrum Peak Value (nm): 560 Light resistance ( KΩ) : 10–20 kΩ Dark resistance ( KΩ): 2 kΩ. Υ value : 0.6. Increase response time: 30 mS. Decrease response time: 30 mS. Package Includes : 1 x 20mm GL20528 Light Sensitive Photoresistor LDR. SKU: PGI-00611918 Category: Light/Color Sensor