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A photocell, also known as a photoresistor or light-dependent resistor (LDR), is a type of resistor whose resistance changes with the amount of light it is exposed to. The basic principle behind how a photocell works is the variation of conductivity in response to light intensity.
HOW DOES A PHOTOCELL WORK?
Here’s a simple explanation of how a photocell (Dusk to dawn sensor) works:
Application of photocell(Dusk to dawn sensor)
Photocells are widely applicable to control outdoor lights(street lighting, passage lighting and door way lighting) automatically in accordance with the ambient lighting level.
Working principle:
Photocell can be used to automatically turn on lights when it gets dark and turn them off when it gets light
In darkness or low light conditions, the resistance of the photocell is high, then assisting in automatic light on.
When light falls on the surface of the photocell, the semiconductor material absorbs photons from the light, causing the electrons in the material to move and increase its conductivity,then the light turn-off.
As a result, the resistance of the photocell decreases as the light intensity increases.
Material Properties:
Photocells are typically made of semiconductor materials.
The most common material used is cadmium sulfide (CdS) or cadmium selenide (CdSe).
Voltage Changes:
As the resistance changes, the voltage across the photocell also changes.
In bright light, the voltage across the photocell decreases, while in darkness or low light conditions, the voltage increases.
Types of light controllers:
The photocell is generally divided into two main categories: NEMA photocells and Zhaga photocells.
NEMA PHOTOCELLS is consist of wire-in photocontrol,twist-lock lightcontrol,NEMA Receptacle and related accessories.
Zhaga PHOTOCELLS are consist of Zhaga socket and Zhaga Sensor.
Limitations:
While photocells are effective for many applications, they may have limitations in accurately reproducing color information compared to more sophisticated sensors.
In summary, a photocell functions by changing its resistance in response to light. This property is utilized in various electronic and electrical systems to control or measure light levels.
