valovastukset

Valovastukset, also known as photoresistors or light-dependent resistors (LDRs), are electronic components whose resistance decreases with increasing incident light intensity. They are made from semiconductor materials such as cadmium sulfide (CdS) or cadmium selenide (CdSe). When light strikes the semiconductor material, it excites electrons, increasing the number of charge carriers available for conduction. This increase in charge carriers leads to a decrease in the material's electrical resistance.

The relationship between light intensity and resistance is typically non-linear and varies depending on the specific material used and the manufacturing process. Valovastukset are often used in circuits where a change in light level needs to be detected or as a simple sensor. Common applications include automatic streetlights that turn on when it gets dark, light meters for cameras, and alarm systems that trigger when a light beam is interrupted. They are generally inexpensive and easy to use, making them popular for hobbyist projects and basic electronic designs. However, their response time can be relatively slow compared to other light-sensing technologies, and their accuracy can be affected by temperature and aging. The spectral sensitivity of a valovastus depends on the semiconductor material, meaning they respond differently to various wavelengths of light.