solar street lamp How do street lights turn on automatically at night? - Working of the simple day and night street lamp controller

Some people may think of a question about how the street light turns on automatically when it starts to darken.There are two ways street lights work.It depends on what mechanism is actually implemented on the street light.Some countries use timers to control street lights, while others use photoelectric detectors to control street lights.
Street lights controlled by timers usually use electronic clocks built into the entire system.According to the timer setting, the clock will automatically turn on the street light at night and turn off the street light automatically in the morning.Some systems have slightly different timers and slightly different daily, thus maintaining longer lighting during the winter months and shorter lighting during the summer months.
Now come to a modern street light using a photoelectric detector, and a small circuit turns on the light when the amount of light falls below a specific threshold.The photoelectric detector is a small electronic element called photoelectric resistance, which is sensitive to light.--xa0The CD-sulfur photoelectric resistor is a commonly used photoelectric detector, also known as a CdS battery.
A photo-The resistance changes its resistance according to the amount of light falling on the resistance.) very well.).When no light shines on it, its resistance increases and reaches the maximum value, thus greatly reducing the current.) directly.The relay circuit is shown in the Red Square in the figure.
Therefore, when a large amount of light falls on the photoelectric detector, the current flows and it powers the magnet while a small amount of light does not.When the light shines on the CdS battery, the amount of electricity flowing through the CdS battery is very small, not enough to activate the relay.Therefore, a transistor amplifier is added to the circuit to amplify the current flowing through the circuit.
The transistor is like a switch.
When the light falls on the photoelectric detector, it turns on the transistor.This will power the magnet and the light goes out.When the day is dark, there is no light on the photoelectric detector, so the transistor goes out and the relay stops working to keep the light on.
Real street lights may have more advanced circuits, which means that together with CdS units, transistors and relays;Depending on the size of the relay, it may have more transistors