Introduction to LDR

The majority of street lights, outdoor lights, and a variety of indoor home appliances are typically operated and maintained manually on many occasions. this is often not only risky, however, additionally, but it also results in wastage of power with the negligence of personnel or uncommon circumstances in controlling these electrical appliances ON and OFF. Hence, we will utilize the sunshine sensor circuit for automatic cut the hundreds supported daylight’s intensity by employing a light-weight sensor. this text discusses in short about what’s a light-dependent resistor, the way to make a light-dependent resistor circuit and its applications.

It stands for Light Dependent Resistor or LDR, which may be a passive electronic component, basically a resistor that features a resistance that varies counting on the sunshine intensity. An LDR is formed of a high resistance semiconductor that absorbs photons and supported the number and frequency of the absorbed photons the semiconductor material gives bound electrons enough energy to leap into the conduction band. The resulting free electrons conduct electricity leading to lowering the resistance of the photoresistor. the amount of electrons depends on the frequency of the photons.


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LDR Symbol

The LDR symbol used in circuits is based around the resistor circuit symbol, but shows the light, in the form of arrows shining on it. In this way, it follows the same convention used for photodiode and phototransistor circuit symbols where arrows are used to show the light falling on these components.

The light-dependent resistor circuit symbols are shown for both the newer style resistor symbol, i.e. a rectangular box and the older zig-zag line resistor circuit symbols.

Working Principle of  LDR

This resistor works on the principle of photoconductivity. it’s nothing but, when the sunshine falls on its surface, then the fabric conductivity reduces and also the electrons within the valence band of the device are excited to the conduction band. These photons within the incident light must have energy greater than the bandgap of the semiconductor material. This makes the electrons to leap from the valence band to conduction.

These devices depend upon the sunshine, when light falls on the LDR then the resistance decreases, and increases within the dark. When an LDR is kept within the dark place, its resistance is high and, when the LDR is kept within the light its resistance will decrease.

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Applications of LDRs

There are many applications for Light Dependent Resistors. These include:

Lighting switch

The most obvious application for an LDR is to automatically turn on a light at a certain light level. An example of this could be a street light or a garden light.

Camera shutter control

LDRs can be used to control the shutter speed on a camera. The LDR would be used to measure the light intensity which then adjusts the camera shutter speed to the appropriate level.

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