LDR Full Form – What Is LDR, Definition, Meaning, Uses

LDR Full Form Friends, in this Artical, we’ll look at the full form of LDR. When the energy of light E = hv falls on the surface of a semiconductor and is greater than the forbidden energy gap between the semiconductor’s valence band and conduction band, electrons rapidly migrate from the conduction band to the valence band. When electrons and holes pair, the material’s conductivity rises, which is proportional to the intensity of the light. Because the resistance of the material reduces and the conductivity increases as the light intensity increases, this device is known as an LDR (light dependent resistor).

LDR Full Form

LDR full form is Light-Dependent Resistor. Light Dependent Resistors, or LDR, are extremely important in light/dark sensor circuits. An LDR’s resistance is typically very high, up to 1000 000 ohms, but it reduces dramatically when it is lighted with light resistance.

LDR: Light-Dependent Resistor

LDR Full Form
LDR Full Form

What is LDR?

The resistivity of a light dependent resistor (also known as a photoresistor or LDR) is a function of electromagnetic radiation. As a result, they are photosensitive devices. Photoconductors, photoconductive cells, and simply photocells are other names for them.

They’re manufactured out of high-resistance semiconductors. A photoresistor or LDR is denoted by a variety of symbols, one of the most frequent of which is depicted in the figure below. The light falling on it is indicated by the arrow.

LDR Working Principle

So, how does a photoresistor (also known as a light dependent resistor or LDR) function? The principle of photoconductivity governs the operation of photoreceptors. Photoconductivity is an optical phenomena in which a material’s conductivity rises when light is absorbed by it.

Electrons in the valence band of the semiconductor material are stimulated to the conduction band when light, or photons, falls on the device. To allow electrons to jump from the valence band to the conduction band in incident light, these photons must have an energy larger than the bandgap of the semiconductor material.

As a result, when the light on the device has adequate energy, more electrons are stimulated to the conduction band, resulting in a larger number of charge carriers. When the circuit is closed and current begins to flow through the device, the resistance of the device is considered to have decreased as a result of this process. This is LDR’s most basic functioning premise.

The LDR construction

A light-dependent barrier is made up of a light-sensitive substance that is placed over an insulating substrate like ceramic. To attain the necessary resistance and strength rating, the material is deposited in a zigzag pattern. The metal deposit locations are divided into two zones by this zigzag zone.

Then, on either side of the region, ohmic connections are created. These contracts’ resistance should be as low as feasible to guarantee that resistance fluctuations are primarily due to the action of light. Cadmium sulfide, cadmium selenide, indium antimonide, and cadmium sulfide are all commonly used compounds. Lead and cadmium are not used because they are detrimental to the environment.

LDR Characteristics – LDR Full Form

Photoresistors are light-dependent resistors (LDR) whose resistance reduces in the presence of light and increases in the absence of light. In the dark, a light-dependent resistor’s resistance is extremely high. Dark resistance is the name given to this type of resistance.

This can reach 1012, and allowing the device to absorb light will considerably reduce its resistance. When a steady voltage is provided to it and the light intensity increases, the current begins to rise. The resistance versus illumination curve for a certain LDR is shown in the diagram below.

LDR Varieties

Based on the materials employed in their fabrication, photoresistors (LDR) can be divided into two groups. There are two types of photoresistors:

Unoptimized Semiconductors (intrinsic photoresistors): These are made of pure semiconductor materials like silicon or germanium. When photons of sufficient energy fall on it, electrons are stimulated from the valence band to the conduction band, and the number of charge carriers increases.

Extrinsic Photoresistors are semiconductor materials that have been doped with dopants, which are impurities. Above the valence band, these dopants produce new energy bands that are filled with electrons. As a result, the bandgap is narrowed and less energy is required to excite. For longer wavelengths, extrinsic photo resistors are typically utilized.

LDR applications – LDR Full Form

Photoresistors (LDR) are commonly utilized as light sensors because of their inexpensive cost and simple form. Photoresistors are also used in the following applications:

  • In the camera’s light meter, detect the absence or presence of light.
  • Can be utilized in the design of street lighting (can be combined with a good Arduino starter kit to act as a street light controller)
  • a set of alarm clocks
  • Circuit for a Burglar Alarm
  • a meter that measures the intensity of light
  • Counting the quantity of items on a moving conveyor belt is one of the activities that a SCADA system can do.

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