In the construction of new rural areas, solar street lights are favored for their environmental advantages. The basic requirement for solar street lights is to charge during the day and illuminate at night. The circuit does not include a separate light sensor and instead uses the output voltage of the photovoltaic panel, which is a common practice in solar systems. So, how do solar street lights charge during the day and remain off while illuminating at night? Below, we will introduce this.
The solar controller contains a detection module, typically employing two methods:
1) Using a photoresistor to detect the intensity of sunlight; 2) Utilizing a voltage detection module to measure the output voltage of the solar panel.
Method One: Using a photoresistor to detect light intensity
Photoresistors are particularly sensitive to light. When the light intensity is low, the resistance is high, and as the light intensity increases, the resistance value decreases. Therefore, this characteristic can be used to detect the strength of sunlight and output it to the solar controller as a control signal for turning the street light on or off. The photoresistor and a simple light-sensitive circuit are illustrated below.
A balance point can be found using a sliding potentiometer. When the light is strong, the resistance of the photoresistor is low, resulting in a high level at the base of the transistor, which is turned off, and the LED does not light up; when the light is weak, the resistance of the photoresistor is high, leading to a low level at the base, turning the transistor on, and the LED lights up.
However, using a photoresistor has certain drawbacks. It has high installation requirements and is prone to miscontrol in rainy or overcast conditions.
Method Two: Detecting the voltage of the solar panel
The solar panel converts sunlight into electrical energy. The stronger the light, the higher the output voltage, and with weaker light, the output voltage decreases. Therefore, the output voltage of the panel can be used as a reference; when the voltage falls below a certain level, the street light will turn on, and when it exceeds a certain level, the street light will turn off.
This method can ignore the impacts of installation and is more straightforward.
The above methods for how solar street lights charge during the day without turning on and illuminate at night have been shared here. Additionally, solar street lights are clean and environmentally friendly, easy to install without the need for laying electrical lines, saving significant manpower and resources. This also improves installation efficiency while providing good social and economic benefits.
