How do street lights work?

In a real street light the circuit might be a bit more advanced, but not a lot. It has the CdS cell, the transistor and the relay, but might need more than one transistor depending on the size of the relay. read more

Much like older Christmas tree lights, streetlights are connected in series design; the current to operate five streetlights on the same street flows from light 1 through 2, 3 and so on. In the past, when one light burned out, the streetlights after it would not power on since the current could not cross the dead bulb. read more

A relay is basically an electromagnetic switch; when the electromagnet has a high current (lots of light falling on the photo-resistor – daytime) then it pushes the switch open so no current can fl ow to the streetlight. read more