Electronics portal | Search electronic components online (or old version here) | >20 mln. datasheets | Electronic circuits, schematics, and diagrams | Social network for geeks | Electronics auctions | News about radio electronics | >50k service manuals | Free fonts download | Pinouts collection

Complete list of electronic components suppliers | Complete list of electronic components producers

Dark Detector with LM555

This is a dark detector circuit. This circuit will generate sound if no light source and silence when light falling on CdS.

CdS : Cadmium sulphide or cadmium sulphide (CdS) cells rely on the material’s ability to vary its resistance according to the amount of light striking the cell. The more light that strikes the cell, the lower the resistance. Although not accurate, even a simple CdS cell can have a wide range of resistance from less than 100 Ω in bright light to in excess of 10 MΩ in darkness. Many commercially available CdS cells have a peak sensitivity in the region of 500nm – 600nm. The cells are also capable of reacting to a broad range of frequencies, including infrared (IR), visible light, and ultraviolet (UV). They are often found on street lights as automatic on/off switches. They were once even used in heat-seeking missiles to sense for targets.

VN:F [1.6.9_936]
Rating: 5.5/10 (121 votes cast)
VN:F [1.6.9_936]
Rating: -1 (from 43 votes)

Discuss this article at the forum