LDRvastukset

LDR vastukset, also known as photoresistors or light-dependent resistors, are electronic components whose resistance decreases with increasing incident light intensity. They are typically made from semiconductor materials like cadmium sulfide (CdS) or lead sulfide (PbS). The core principle of operation involves the photoelectric effect, where photons striking the semiconductor material excite electrons, increasing the number of charge carriers available and thus lowering the resistance.

The spectral response of an LDR varies depending on the material used. For instance, cadmium sulfide LDRs are sensitive to visible light, while lead sulfide devices are more suited for infrared detection. The relationship between resistance and light intensity is generally non-linear and can be described by a power law. The darkness resistance of an LDR is typically very high, in the megaohm range, while under bright light, it can drop to a few hundred ohms or less.

LDR vastukset find widespread application in various electronic circuits where light detection is required. Common uses include automatic street lighting systems that turn on at dusk and off at dawn, light-activated alarms, light meters in cameras, and as input sensors in simple robotics projects. They are a cost-effective and simple solution for many light-sensing tasks, though their response time can be slower compared to other photodetectors like photodiodes or phototransistors. Their temperature sensitivity is another factor to consider in precise applications.