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Miscellaneous Sensors
Published in Clarence W. de Silva, Sensor Systems, 2016
A photoresistor (or photoconductor) has the property of decreasing its electrical resistance (increasing the conductivity) as the intensity of light falling on it increases. Typically, the resistance of a photoresistor could change from very high values (megohms) in the dark to reasonably low values (less than 100 Ω) in bright light. As a result, very high sensitivity to light is possible. Some photocells can function as photoresistors because their impedance decreases (output increases) as the light intensity increases. Photocells used in this manner are termed photoconductive cells. The circuit symbol of a photoresistor is given in Figure 10.7a. A photoresistor may be formed by sandwiching a photo-conductive crystalline material such as cadmium sulfide (CdS) or cadmium selenide (CdSe) between two electrodes. Lead sulfide (PbS) or lead selenide (PbSe) may be used in infrared photoresistors.
Data Acquisition-Sensors and Microcontrollers
Published in Daniel H. Nichols, Physics for Technology, 2019
A photoresistor changes resistance with light level. The brighter the light, the lower the sensor’s resistance; the dimmer the light, the higher the sensor’s resistance (Figure 17.9). Placing the sensor in the bottom half of the circuit results in the output voltage to be high when the sensor is dark, and low when the sensor is illuminated. Placing the sensor in the top half of the circuit results in the output voltage to be low when the sensor is dark, and high when the sensor is illuminated.
Robot’s Sensors and Instrumentation
Published in Jitendra R. Raol, Ajith K. Gopal, Mobile Intelligent Autonomous Systems, 2016
Photoresistor sensors are sensitive to light intensity change. When no light falls on this sensor, it shows maximum resistance, usually called dark resistance. When light falls on this sensor, a decrease in the sensor’s resistance value is observed. The measured change in resistance gives the measure of the light intensity.
Design reviews on a multipurpose power sockets for different applications
Published in Cogent Engineering, 2018
Chin jie Wong, Umar Nirmal, Sharmeeni Murugan
A light sensor contains a major component, a photoresistor or light-dependent resistor (LDR). Photoresistor or LDR is a resistor that is sensitive to light and can be used as switch with based on the intensity of light. The resistance of the resistor will be increased if the light intensity that it received is decreasing. This features is known as photoconductivity. The characteristics of light dependent resistor allows it to be used in light-sensitive detector circuits or light and dark activated switching circuits. Photosensor or photodetector is another type of sensor that operated with the presence of light or other electromagnetic energy (Haugan et al., 2008). P-N junction inside the photodetectors will convert the light photons into current. With the absorbed photons, the photosensors are able to make electron-hole pairs in the depletion region. Temperature compensated solar light sensor, infrared light sensor and ambient light sensor are the types of light sensor that will be discussed.