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A photoelectric, or optical smoke detector, contains a source of infrared, visible, or ultraviolet light—typically an incandescent light bulb or light-emitting diode (LED)—a lens, and a photoelectric receiver—typically a photodiode. In spot-type detectors, all of these components are arranged inside a chamber where air, which may contain ...
Optical beam smoke detectors work on the principle of light obscuration, where the presence of smoke blocks some of the light from the beam, [5] typically through either absorbance or light scattering. Once a certain percentage of the transmitted light has been blocked by the smoke, a fire is signalled.
Conceptual through-beam system to detect unauthorized access to a secure door. If the beam is interrupted, the detector triggers an alarm. A photoelectric sensor is a device used to determine the distance, absence, or presence of an object by using a light transmitter, often infrared, and a photoelectric receiver. They are largely used in ...
Photoconductive effect: These detectors work by changing their electrical conductivity when exposed to light. The incident light generates electron-hole pairs in the material, altering its conductivity. Photoconductive detectors are typically made of semiconductors. [5]
Photodiodes are used in consumer electronics devices such as compact disc players, smoke detectors, medical devices [17] and the receivers for infrared remote control devices used to control equipment from televisions to air conditioners. For many applications either photodiodes or photoconductors may be used.
This is often connected to an electrical trigger. The trigger reacts to a change in the signal within the light sensor. An optical sensor can measure the changes from one or several light beams. When a change occurs, the light sensor operates as a photoelectric trigger and therefore either increases or decreases the electrical output.
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