Do you know what is the LDR Full Form? The LDR stands for Light Dependent Resistor. It is a process that calculates the resistance of an LDR from the amount of light falling on the surface of the LDR. LDR is a specific type of resistor.
An LDR, or Light Dependent Resistor, functions similarly to a potentiometer. In comparison, the resistance of a potentiometer can be adjusted by rotating its knob. In contrast, the resistance of an LDR is determined by the amount and intensity of light that falls on its surface. As more light is exposed to the LDR, its resistance decreases; conversely, the resistance increases as less light is present. The LDR can be utilized in various projects and applications, such as dark detectors, automatic street lights, and motor speed control.
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How is LDR made?
An LDR, or Light Dependent Resistor, is an electronic component made from a high-resistance semiconductor material, such as cadmium sulfide (CdS) or cadmium selenide. Unlike traditional semiconductors, LDRs do not have a P-N junction. The manufacturing process of LDR involves depositing a thin layer of the semiconductor material on a substrate, such as glass or ceramic. The semiconductor is then heated at high temperatures to create a crystal structure that forms the active material.
The semiconductors are arranged in a specific pattern, often a zigzag formation and metal contacts are added to both ends to make a connection with the LDR. This allows the LDR to be connected to a circuit and to measure the resistance change based on the amount of light received. Additionally, to protect the semiconductors, which are photosensitive, a coating of a transparent material is applied. This not only protects the LDR but also allows light to pass through and thus, helps in the overall functioning of the LDR.
LDRs are widely used in various projects and applications such as dark detectors, automatic street lights, and motor speed control. They are susceptible to changes in light intensity and respond quickly to even small changes in light, which makes them an ideal component in these types of projects.
Types of LDR
- Intrinsic Photoresistor– An intrinsic photoresistor is a Light Dependent Resistor (LDR full form) made from a pure semiconducting material, such as silicon or germanium. The resistance of an intrinsic photoresistor changes in response to light due to the movement of charge carriers within the semiconductor material.
- Extrinsic Photoresistor– An extrinsic photoresistor is a type of LDR made by doping a semiconductor material with impurities, such as boron or phosphorus. The impurities create an excess or deficiency of charge carriers in the semiconductor, which results in a change in resistance when the photoresistor is exposed to light.
How does LDR work?
The function of an LDR is based on the principle of photoconductivity. When light shines on the surface of an LDR, made of photoconductive material, the energy from the light is absorbed. This causes the electrons in the valence band of the material to become excited and move to the conduction band, increasing the LDR’s conductivity. The effect is directly proportional to the amount of light that falls on the LDR.
For the LDR to work correctly, the energy absorbed from the light must be greater than the bandgap energy, allowing the valence band electrons to become excited.
When the LDR is in darkness, its resistance is at its highest, approximately 1012 ohms. As the intensity of light increases, its resistance decreases.
A hyperbolic graph can represent the relationship between resistance and light intensity in an LDR-
How is LDR (Light Dependent Resistor) tested?
The following is the procedure for LDR testing:
- For the purpose of checking the LDR, a multimeter should be used, and it should be set up properly.
- It is required for the multimeter’s positive and negative terminals to be connected with the LDR’s two portions.
- A torch can be used to illuminate the LDR surface after connecting the wires to the proper terminals. After this, the reading of the meter is verified.
- After verifying the reading in the light, the meter reading is verified by keeping the LDR in the dark.
- In both cases, different resistances of the LDR can be observed. The resistance of an LDR can be seen to be higher in the dark than the resistance of an LDR in the light.
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