Photoresistors, also commonly referred to as light-dependent resistors (LDRs), are a class of variables resistors which change their resistance depending on how much light is hitting the resistor. These types of resistor are made of materials which exhibit photoconductivity and are often used in light-sensitive detector circuits, light-activated switching circuits, and dark-activated switching circuits. In this article, we look at the main classes of photoresistor, namely, intrinsic and extrinsic photoresistors.
When it comes to photoresistors, there is not a great deal of difference between the different types, and most photoresistors would by using the same principles. The main difference between intrinsic and extrinsic photoresistors (the two main types) is in the types of materials which the photoresistors are made of-which can sometimes affect the mechanism of resistance change by slight amounts.
Generally speaking, photoresistors work when light is shone onto the photoresistor. When the photons of light hit the photoconductive materials in the photoresistor, the valence band electrons from this material breaks free, leading to a large number of free electrons in the material (and an equal number of positively charged holes where the electrons used to be). The number of free electrons is also proportional to the amount of light being shone on the photoresistor, i.e. the greater the light intensity, the greater the number of free electrons and holes. It should be noted that most photoresistors only work with certain wavelengths of light, and outside of these ranges, the resistance of the device does not change at all.
0:00 Intro
00:27 What is Photo Resistor/LDR?
00:56 Schematic Symbol
01:12 The Origin of Photo Resistor
01:42 Chemical composition of Photo Resistor
03:05 Category of Photo Resistor/LDR
03:15 intrinsic Photo Resistor
03:35 Intrinsic Photo Resistor
03:58 Advantage & Disadvantage of Photo Resistor/LDR
04:05 Advantage of Photo Resistor/LDR
04:22 Disadvantage of Photo Resistor/LDR
04:44 Actual application of Photo Resistor
🔗Resources:
• www.elprocus.com/ldr-light-de...
• lednique.com/opto-isolators-2/...
• eepower.com/resistor-guide/re...
• www.azom.com/article.aspx?Art...
• www.physics-and-radio-electro...
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Негізгі бет Ano ang PHOTO RESISTOR? at paano ito gawing Sensor? [tagalog]
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