photo sensor types
They come in different types, each with its own special features and uses. The major varieties include photodiodes, phototransistors,and optocouplers. Current flows from a photodiode in the presence of light, while phototransistors control electronic transitions or amplify electrical signals by shining light on them. Optocouplers propagate electrical signals between circuits with an optical link. The sensitivity, speed, spectral response and operating temperature range of them is all different. Their applications run from automatic door openers for the handicapped through various industrial automatic controls,to medical equipment.