A street light turns on automatically by way of a photocell switch also known as a dusk to dawn switch.
The dusk to dawn switch or sensor senses the darkness which then activates the switch to complete the circuit to allow the street light to come on.
Street lights that light up the streets at night are on sensors.
Traffic lights on the other hand are on timers as well as sensors that tell the lights when to change colors.
The street lights however just turn on at night and off during the daylight hours through use of a a light sensor.
Dusk to Dawn light switches detect natural light and turn on the lights after sunset.
They also shut everything down when the sun rises, so nothing burns power during the day.
Many photocell fixtures come with motion detectors as well.
Dusk to dawn light sensors, also known as twilight switches are practical, because they automatically turn on the light with the dawn.
As soon as it gets lighter again in the morning, the light switches off again.
So the lighting is controlled based on the actual lighting conditions, regardless of the time of day.
A common reason why dusk to dawn light stays on all the time is because of system override.
This can be caused by power outages as well as small issues in your system.
Moreover, system override can occur if wires are incorrectly placed.
The good thing is that system override is easy to fix.
Some dusk to dawn lights use a photocell as a source of their power.
Photocell technology is used to identify when dusk has fallen, which prompts the lights to turn on.
Similarly, these lights detect natural light and turn off when morning comes.
Photocell lights are activated by the changing of natural light, which means that they automatically shift with daylight changes and adjust when the nights are longer or shorter.
Some photocell outdoor lights also contain motion sensors too.