As we all know, nowadays, sensors have been widely used in human production and life. Especially for high-precision products, various sensors are used to monitor and control the parameters in the production process, so that the equipment can work in the normal or optimal state, and the product can achieve the best quality. Therefore, it can be said that without many excellent sensors, modern production will lose its foundation. In medicine, the use of sensors can better analyze the cause of disease and get a good treatment plan. In scientific research, sensors have a more prominent position. In many fields, people's senses and simple sensors can not get accurate data at all. We must use high-precision sensors to achieve analysis and measurement. The light sensors are sensors that use photosensitive elements to convert light signals into electrical signals. Because of the characteristics of nontouch, fast response and reliable performance, it plays a very important role in automatic control and non-electric electronic technology.
Optical sensor is a sensor that converts light signal into electric signal by using photosensitive elements. Its sensitive wavelength is near the wavelength of visible light, including infrared wavelength and ultraviolet wavelength. Optical sensors are not only limited to the detection of light, but also can be used as detection elements to form other sensors to detect many non-electric quantities, as long as these non-electric elements are converted into changes in optical signals. Optical sensor is one of the most productive and widely used sensors. It plays a very important role in automatic control and non-electric measurement technology. There are many kinds of light sensors, such as phototube, photomultiplier tube, photoresistor, photosensitive triode, photocoupler, solar cell, infrared sensor, ultraviolet sensor, optical fiber photoelectric sensor, color sensor, CCD and CMOS image sensor.
Working Principle of Light Sensor
Light sensor is also called photoresistor. Its working principle is based on internal photoelectric effect. The light sensor is equipped with a high precision photoelectric tube. There is a small flat plate in the photoelectric tube which is composed of "needle type two tubes". When a reverse fixed pressure is applied to both ends of the photoelectric tube, the impact of any light on it will lead to the release of electrons. As a result, the current of the photoelectric tube will also be released when the intensity of light is higher. As the current passes through a resistor, the voltage at both ends of the resistor is converted into a 0-5V voltage that can be accepted by the digitalal-analog converter of the collector, and the results are stored in an appropriate form. Simply speaking, the light sensor transmits the analog signal of the light intensity to the robot host based on the principle that the resistance of the photosensitive resistor changes due to the influence of the light intensity.
Photoresistor is a kind of resistor made of photoelectric effect of semiconductor, whose resistance value varies with the intensity of incident light. The greater incidental light intensity, the less electric resistance. And when the incident light is weak, the electric resistance increases. Photoresistors are generally used for light measurement, light control and photoelectric conversion (conversion of light changes to electrical changes).
Principle: It works based on semiconductor photoelectric effect. The photoresistor has no polarity and is purely a resistor element. When used, DC voltage or AC voltage can be added. The working principle of photoresistor: when illuminated, the electric resistance is very small; when it is not illuminated, the resistance is very large. The stronger the illumination, the smaller the electric resistance; when the illumination stops, the electric resistance restores to its original value.
Spectral range: from ultraviolet area to infrared area.
Advantages: high sensitivity, small size, stable performance, low price.
Performance parameters of photoresistors:
The resistance of a photoresistor which is not illuminated is called dark resistance, and the current flowing through it is called dark current. The resistance which is illuminated is called bright resistance, and the current is called bright current. The bigger the dark resistance, the better it is; the smaller the bright resistence, the better it is. In practical application, the dark resistance is about mega-ohm while the bright resistance is about several thousand ohms.