![]() ![]() Therefore you need to add a transistor to amplify the current that flows through the CdS cell. Usually, however, a CdS cell cannot draw enough current to activate the relay when light hits it. In an extremely simple circuit, you would wire a CdS cell directly to a relay, so that a lot of light would energize the electromagnet and a small amount of light would not. When no light hits it, it has high resistance - it conducts electricity poorly. When a lot of light hits it, it has almost zero resistance - it conducts electricity very well. A photo-resistor changes its resistance based on the amount of light that hits it. In a modern streetlight, a small circuit replaces the bird and turns the light on when the amount of light falls below a certain threshold.Ī common light-sensing component is the cadmium sulfide photo-resistor, also known as a CdS cell. On the Flintstones, a small bird sits inside the light and turns it on every night before he goes to bed. Many cities already use sensors mounted on light poles to regulate traffic signals, decrease the amount of LED lighting to be emitted at certain times of the day, turn on the lights only when a car or pedestrian appears, sense gunfire, or hold the boxes for small cell technology that enables advanced broadband. By admin Comments Off on How do the Streetlights Turn on Automatically at Night? ![]()
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