Photoelectric sensor is a kind of small electronic equipment, a key element for photoelectric conversion in various photoelectric detection systems. It is mainly a sensor that uses various properties of light to detect the presence or absence of objects and changes in surface conditions. Photoelectric sensors have the characteristics of non-contact, fast response, and reliable performance, so they are widely used in industrial automation devices and robots. Here is how it works:

1. Working principle
The basic principle of the photoelectric sensor is based on the photoelectric effect, which converts the measured change into the change of the light signal, and then further converts the non-electric signal into the electric signal with the help of the photoelectric element. The photoelectric effect refers to illuminating an object with light, which can be regarded as a series of photons with a certain energy bombarding the object. At this time, the energy of the photon is transferred to the electron, and the entire energy of a photon is absorbed by one at a time. When the electron is absorbed, the state of the electron will change after it gets the energy transmitted by the photon, so that the object irradiated by the light produces a corresponding electric effect.

2. The principle of photoelectric effect
The photoelectric element is the most important part of the photoelectric sensor, and its core working principle is different types of photoelectric effect. According to the wave-particle duality, light is composed of photons moving at the speed of light. When an object is illuminated by light, its internal electrons absorb the energy of the photon and change state, and its own electrical properties will also change. This phenomenon is called For the photoelectric effect. According to the different changes of electrical properties, the photoelectric effect is divided into the following three types:

2.1 External photoelectric effect
The phenomenon in which electrons escape from the surface of an object under the action of light is called the external photoelectric effect. The photoelectric components based on the external photoelectric effect include phototubes, photomultiplier tubes and so on.

2.2 Photoconductive effect
The phenomenon that electrons in a semiconductor cannot jump out of the semiconductor after absorbing a photon, changing the conductivity of the object, or generating a photoelectromotive force is called the internal photoelectric effect. The internal photoelectric effect can be divided into photoconductive effect and photovoltaic effect according to its working principle. Photoelectric components based on the photoconductive effect include photoresistors and phototransistors.

2.3 Photovoltaic effect
Under the action of light, the phenomenon that an object produces a certain directional electromotive force is called the photovoltaic effect. Photoelectric components based on the photovoltaic effect include photovoltaic cells, photodiodes, and triodes.

The above is an introduction to the working principle of the photoelectric sensor. Photoelectric sensors can be used to detect non-electricity that directly cause changes in light quantity, such as light intensity, illuminance, radiation temperature measurement, gas composition analysis, etc.; it can also be used to detect other non-electricity that can be converted into light quantity changes, such as part diameter, surface roughness , Strain, displacement, vibration, speed, acceleration, as well as the recognition of the shape and working state of the object.

(Summarized by Easybom)