The easiest way to use the LDR is in voltage divider configuration. Hence the voltage across the base junction increases and the transistor conducts switching ON the bulb. When light falls on the LDR, its resistance drops, and so does the voltage across it, however the voltage across R increases. When a LDR is kept in the dark place, its resistance is high and, when the LDR is kept in the light its resistance will decrease. These devices depend on the light, when light falls on the LDR then the resistance decreases, and increases in the dark. The through hole version of an LDR will be added. Navigate to the Sparkfun-Sensors folder and click on ‘PHOTOCELL’. When the LDR is in the dark, its resistance is very large, typically in the M range. It is a resistor with resistance that changes according to the amount of light falling on it. Street lights are designed to switch on automatically when it is dark and switch off when there is light so as to save energy. This is done using LDR which senses the light. It automatically switches on lights when the light goes below ambient light.
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By this system manual works are completely removed. What is meant by automatic street light?Īutomatic street light system is a simple concept which uses transistor as a switch. The resistance of a photo resistor decreases with increasing incident light intensity in other words, it exhibits photo-conductivity.
Hi, LDR stands for Light Dependent Resistor, technically A photo resistor or light-dependent resistor (LDR) or photocell is a light-controlled variable resistor.