LDR (metal) 5mm, 10k, Photoresistor, (Price per 1pec)
Professional Design Remind Phone Watch - 6.5mm Metal Cap LDR – HaiWang Sensor Detail:
How an LDR works
It is relatively easy to understand the basics of how an LDR works without delving into complicated explanations. It is first necessary to understand that an electrical current consists of the movement of electrons within a material. Good conductors have a large number of free electrons that can drift in a given direction under the action of a potential difference. Insulators with a high resistance have very few free electrons, and therefore it is hard to make the them move and hence a current to flow.
An LDR or photoresistor is made any semiconductor material with a high resistance. It has a high resistance because there are very few electrons that are free and able to move - the vast majority of the electrons are locked into the crystal lattice and unable to move. Therefore in this state there is a high LDR resistance.
As light falls on the semiconductor, the light photons are absorbed by the semiconductor lattice and some of their energy is transferred to the electrons. This gives some of them sufficient energy to break free from the crystal lattice so that they can then conduct electricity. This results in a lowering of the resistance of the semiconductor and hence the overall LDR resistance.
The process is progressive, and as more light shines on the LDR semiconductor, so more electrons are released to conduct electricity and the resistance falls further.
Applications
Camera automatic photometry
Photoelectric control
Indoor ray control
Annunciator
Industrial control
Light control switch
Light control lamp
Electronic toy
It is a kind of variable resistor and the resistance depends on the intensity of light falling on it.
In total dark, its resistance is as high as 10 Mega Ohms which reduces to a few Ohms in bright light.
LDR is called as CdS cells because its semiconductor is Cadmium Sulphide.
Its light sensitive area is doped with impurities like Silver, Antimony or Indium.
When the light fall on the semiconductor material, flow of electron- hole pairs occur and electrical conductivity takes place.
In structure, the LDR has a thin Zig-Zag shaped semiconductor line enclosed in a transparent case.
LDR can handle very high current and even AC passes through it without harming the device.
Two leads are arising from the two ends of the semiconductor.
LDR is available in sizes 3mm, 5mm,7mm, 10mm,11mm,12mm, 20mm,25mm etc