智能照明-人类偏好自动调光

　　智能照明-人类偏好自动调光

　　自动调光是首选的工作环境，如工厂和办公室，以确保最佳照明的工人完成他们的任务，同时最大限度地减少照明的整体能源消耗。环境光传感器（ALS）是有效地帮助确定正确的亮度设置，以实现最佳的照明相结合的电力照明与自然光。

　　ALS Principles

　　ALS suppliers such as Vishay typically tune the spectral response of sensors to mimic the human eye using optical filters. In practice， this enables an electronic dimmer to adjust lamp brightness continuously to ensure the illumination always meets the needs of human workers as natural light levels vary during the day. Other sensor characteristics， however， can depend on factors such as detector size， lot-to-lot manufacturing variations， and whether the sensor has a phototransistor or photodiode output.

　　If the base of a silicon transistor is exposed to visible light， ionization occurs that produces charge pairs which have the same effect as an externally applied base current. If connections are made to the base and collector only， the device acts as a photodiode and a small current will flow depending on the intensity of the incident light and the photosensitivity of the chip. On the other hand， biasing the device as a transistor produces amplification of the photodiode current. In this case， the output current depends on the transistor gain as well as the photosensitivity of the chip.