A photocell is a resistor that changes resistance depending on the amount of light incident on it. A photocell operates on semiconductor photoconductivity: the energy of photons hitting the semiconductor frees electrons to flow, decreasing the resistance. An example photocell is the Advanced Photonix PDV-P5002, shown in Figure 21.2.
A photoresistor or photocell is a light-controlled variable resistor. The resistance of a photoresistor decreases with increasing incident light intensity. A photoresistor can be applied in light-sensitive detector circuits, and light- and dark-activated switching circuits. It's also called light-dependent resistor (LDR).
In bright light, the photocell’s resistance is around 10 kΩ, making an output of about 2.7 V. In darkness, the photocell’s resistance is around 500 kΩ, making an output of about 0.3 V. The sensor output could go to a PIC32 digital or analog input. Kevin M. Lynch, ... Matthew L. Elwin, in Embedded Computing in C with the PIC32 Microcontroller, 2016
(Image courtesy of Advanced Photonix, Inc., advancedphotonix.com.) (Middle) Circuit symbol for a photocell. (Right) A simple light-level-detection circuit. In bright light, the photocell’s resistance is around 10 kΩ, making an output of about 2.7 V. In darkness, the photocell’s resistance is around 500 kΩ, making an output of about 0.3 V.
Photocells are light-sensitive, variable resistors. As more light shines of the sensor’s head, the resistance between its two terminals decreases. They're easy-to-use, and an essential component in projects that require ambient-light sensing. This is a very small light sensor.
A photocell or photoresistor is a sensor that changes its resistance when light shines on it. The resistance generated varies depending on the light striking at his surface. A high intensity of light incident on the surface will cause a lower resistance, whereas a lower intensity of light will cause higher resistance.