Photocell
A device that detects light. Used for photographic light meters, automatic on-at-dusk street lights and other light-sensitive applications, a photocell varies its resistance between its two terminals based on the number of photons (light) it receives. Also called a “photodetector,” “photoresistor” and “light dependent resistor” (LDR).
The photocell’s semiconductor material is typically cadmium sulfide (CdS), but other elements are also used. Photocells and photodiodes are used for similar applications; however, the photocell passes current bi-directionally, whereas the photodiode is unidirectional.
Photodiode
A light sensor (photodetector) that allows current to flow in one direction from one side to the other when it absorbs photons (light). The more light, the more current. Used to detect light in camera sensors, optical fibers and other light-sensitive applications, a photodiode is the opposite of a light emitting diode (see LED). Photodiodes detect light and let electricity flow; LEDs receive electricity and emit light.
Solar Cells Are Photodiodes
Solar cells are photodiodes that are chemically treated (doped) differently than the photodiode used as a switch or relay. When solar cells are struck by light, their silicon material is excited to a state where a small electrical current is generated. Many arrays of solar cell photodiodes are required to power a house.
Phototransistor
A transistor that uses light rather than electricity to cause an electrical current to flow from one side to the other. It is used in a variety of sensors that detect the presence of light. Phototransistors combine a photodiode and transistor together to generate more output current than a photodiode by itself.
Photoelectric
Converting photons into electrons. When light is beamed onto a metal, electrons are released from its atoms. The higher the light frequency, the more electron energy released. Photonic sensors of all kinds work on this principle, for instance photocell, and photovoltaic cell is an electronic device. They sense light and cause an electric current to flow.
construction
photocell consists of an evacuated glass tube containing two electrodes emitter and collector. the emitter is shaped in form of a semi-hollow cylinder. it is always kept at a negative potential. the collector is in the form of a metal rod and fixed at the axis of the semi-cylindrical emitter. the collector is always kept at a positive potential. the glass tube is fitted on a non-metallic base and pins are provided at the base for external connection.
wokring
the emitter is connected to a negative terminal and the collector is connected to the positive terminal of a battery. radiation of frequency more than the threshold frequency of material of emitter is made incident on the emitter. photo-emission take place. the photo-electrons are attracted to collector which is positive w.r.t the emitter thus current flows in the circuit. if the intensity of incident radiation is increased the photoelectric current increase.
Our others photocontrol application situation
The job of a photocell switch is to detect levels of light from the sun, and then turn on or off the fixtures that they are wired to. This technology can be used in many ways, but one of the most common examples would be street lamps. Thanks to photocell sensors and switches, they can all be turned on and off automatically and independently based on the sunset and the sunrise. This can be a great way to save on energy, have automatic security lighting or even simply to have your garden lights illuminate your pathways at night without having to turn them on. There are many different ways to use photocells for outdoor lights, for residential, commercial or industrial purposes. You only need to have one photocell switch wired into a circuit to be able control all the fixtures, so there is no need to purchase one switch per lamp.
There are many different types of photocell switches and controls, all better suited for different situations and various perks. The easiest switch to mount would be the stem mounting photocells. The swivel controls are also very easy to install but offer more flexibility. Twist-Lock photocontrols are a bit more difficult to install, however they are much more sturdy and are built to withstand vibrations and small impacts without breaking or causing disconnects in the circuit. Button photocells are well suited to outdoor lights, designed to be easily pole mounted.
Findable data source:
1. www.pcmag.com/encyclopedia/term/photocell
2. lightbulbsurplus.com/parts-components/photocell/
3. learn.adafruit.com/photocells
4. thefactfactor.com/facts/pure_science/physics/photoelectric-cell/4896/
5. www.elprocus.com/phototransistor-basics-circuit-diagram-advantages-applications/
Post time: Jul-16-2021