The application of photoelectric sensors is very extensive. They can be seen everywhere in the daily life and production automation of modern society. A photoelectric sensor is a device that converts an optical signal into an electrical signal, so its direct use is light metering. It also has counting, automatic control, photography, video recording, and distance measurement. Next Xiaobian introduced the application of photoelectric sensors and the working principle of photoelectric sensors.
Application of photoelectric sensors
1, smoke turbidity monitor
Preventing industrial smoke and dust pollution is one of the important tasks of environmental protection. In order to eliminate industrial smoke and dust pollution, we must first know the amount of smoke and dust emissions, so we must monitor the smoke source, automatically display and exceed the standard alarm. Flue dust turbidity in the flue is detected by the size of the change in light transmission through the flue. If the turbidity of the flue gas increases, the light emitted by the light source is increased by the absorption and refraction of smoke particles, and the light reaching the photodetector is reduced. Therefore, the intensity of the output signal of the photodetector can reflect the change of the turbidity of the flue.
2, bar code scanning pen
When the scanning tip moves on the bar code, if a black line is encountered, the light of the light emitting diode will be absorbed by the black line, and the phototransistor will not receive the reflected light and will be in a high impedance and in an off state. When a white interval is encountered, the light emitted by the light emitting diode is reflected to the base of the phototransistor, and the phototransistor generates a photocurrent and conducts. After the entire bar code is scanned, the phototransistor transforms the bar code into electrical pulse signals. After the signal is amplified and shaped, the pulse train is formed. The signal processing is then processed by the computer to complete the identification of the bar code information.
3, product counter
When the product is running on a conveyor belt, it constantly blocks the light path from the light source to the photoelectric sensor, so that the photoelectric pulse circuit generates one electrical pulse signal. Once the product is shaded once, the photoelectric sensor circuit generates a pulse signal. Therefore, the output pulse number represents the number of products. The pulse is counted by the counting circuit and displayed by the display circuit.
4, photoelectric smoke alarm
When there is no smoke, the light emitted by the light emitting diodes travels in a straight line, and the phototransistor does not receive signals. When there is no output and there is smoke, the light emitted by the light emitting diode is refracted by the smoke particles, so that the triode receives the light, a signal is output, and an alarm is issued.
5, measuring speed
Applying two colors of black and white on the rotating shaft of the motor, the reflected light and the non-reflected light alternately appear when the motor rotates. The photoelectric sensor intermittently receives the reflected signal of the light and outputs the intermittent electrical signal, which is amplified by the amplifier and the shaping circuit. The plastic output square wave signal, and finally the output speed of the motor is output by the electronic digital display.
6. Application of Photocells in Photoelectric Detection and Automatic Control
When photocells are used as photodetectors, their basic principles are the same as photodiodes, but their basic structure and manufacturing process are not exactly the same. Since the photovoltaic cell does not require an applied voltage during operation, it has a high photoelectric conversion efficiency, a wide spectral range, good frequency characteristics, and low noise, and it has been widely used for photoelectric readout, photoelectric coupling, raster distance measurement, laser collimation, and movie playback. , UV light monitors, and flameout protection devices for gas turbines.
The photoelectric sensor works
The physical basis of photoelectric sensors is the photoelectric effect, which means that many of the electrical properties of semiconductor materials change due to exposure to light. The photoelectric effect is generally divided into two major categories, namely the outer photoelectric effect and the inner photoelectric effect. The external photoelectric effect refers to the behavior of a substance to absorb photons and stimulate free electrons. When the metal surface is exposed to a specific light, the metal absorbs photons and emits electrons. The emitted electrons are called photoelectrons. When the wavelength of light needs to be less than a certain critical value (equal to the frequency of light is higher than a certain critical value), electrons can be emitted, and the critical values ​​thereof are the limit frequency and the limit wavelength. From E = hn-W, if the incident photon energy hn is greater than the work function W, then some photoelectrons still have residual energy after leaving the metal surface, which means that some photoelectrons have a certain kinetic energy. Because different electrons need different work to disengage from a certain metal, they absorb the photon energy and the kinetic energy remaining after the metal escapes. Since the work function W is the minimum value of the work to be done to get electrons out of the metal, if E is used to represent the kinetic energy of the photoelectrons with the highest kinetic energy, then there is the following relation E = hn-W (where h denotes the Plank constant ,n denotes the frequency of incident light. This relation is usually called the Einstein photoelectric effect equation.
Editor's summary: The application of photoelectric sensors and the working principle of photoelectric sensors are introduced here, and we hope to help everyone. If you want to know more related information, you can pay attention to this website information.
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